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                                                                                            Transactions on Industry Applications
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                            Control of Hybrid Wind-Diesel Standalone
                             Microgrid for Water Treatment System
                                          Application
                          Félix Dubuisson, Student Member, IEEE, Miloud Rezkallah, Member, IEEE, Ambrish Chandra,
                           Fellow, IEEE, Maarouf Saad, Senior Member, IEEE, Marco Tremblay, and Hussein Ibrahim


                                                                                                             elements such as energy storage system to compensate their
            Abstract— This paper deals with the control of a                                                  intermittency [2]. Moreover, complex control strategies are
        standalone microgrid based on variable speed wind                                                     needed to ensure a stable operation and clean uninterruptible
        turbine (WT) and fixed speed Diesel Generator (DG) for                                                power supply to the water treatment station as application,
        water treatment application. A Perturb and Observe                                                    which is considered as a critical load.
        (P&O) method is used to achieve the Maximum Power                                                       According to [3], the most of isolated microgrids are
        Point Tracking (MPPT) from the WT without using speed                                                 operating using a droop control strategy. This control
        sensors. Two levels of control are proposed for the three-                                            technique can regulate the voltage and frequency as well as
        phase voltage source inverter for voltage and frequency                                               achieve power sharing. Droop control possesses different
        regulation at the Point of Common Coupling (PCC) and                                                  advantages such as simplicity, robustness and ability to
        power management in standalone and diesel connected                                                   operate without resorting to communication between system
        modes. Furthermore, the battery energy storage is                                                     elements [4]. However, each energy source is independent and
        controlled using simple approach to balance the power in
                                                                                                              adapt its voltage and frequency references based on the
        the system during load variations and wind speed changes.
                                                                                                              powers measured at the PCC. Usually, the frequency reference
        The performance of the proposed system is tested using
        Matlab/Simulink under load and weather variations. In                                                 is regulated with controlling the active power variations and
        addition, the system is tested on a small-scale prototype in                                          the voltage references are regulated by controlling the reactive
        the laboratory under load and wind speed variations.                                                  power variations, that is why this control technique is
                                                                                                              identified as P-f and Q-V droop. It is reported in [5], that
           Index Terms— Diesel generator, perturbation and observation                                        droop control is not perfect and possesses drawbacks, such as
        technique (P&O), power management, SRF, standalone
        microgrid, voltage and frequency regulation, wind turbine
                                                                                                              the high droop coefficients, which can compromise the grid
                                                                                                              stability, by the deviations in voltage and frequency. In
                                                                                                              addition, its implementation is hard due to the complex
                                          I. INTRODUCTION                                                     transformation needed. Many, droop-based control strategies
                                                                                                              are proposed in the literature to compensate these drawbacks
        M         ANY facilities, such as water treatment systems
                                                               are not
              connected to the main electrical grid. They are powered
        only from the conventional DG. As known that this energy
                                                                                                              [6-7]. In [6], an adaptive voltage droop control, is proposed to
                                                                                                              tune the voltage droop coefficients, to compensate the
                                                                                                              mismatch of the different energy sources voltage output, and
        source is costly and responsible for the emission of
                                                                                                              to improve the reactive power sharing. For this technique,
        greenhouse gases especially when it operates at light loads.
                                                                                                              communication is suggested to achieve high performances
        Generating electricity locally in these isolated areas from
                                                                                                              from the adaptive voltage droop strategy and if the
        Renewable Energy Sources (RES), such as wind or solar is a
                                                                                                              communication system is interrupted the controller operates
        good way to answer these drawbacks [1]. However,
                                                                                                              using last tuned droop coefficients. This control technique is
        combination of RES with the existing DG is a complex
                                                                                                              more efficient than conventional droop control system where
        process; it requires advanced control and additional reliable
                                                                                                              the obtained experimental results show that the reactive power
                                                                                                              sharing is done properly, and that the system is not affected by
           F. Dubuisson, M. Rezkallah, A. Chandra and M. Saad are with the                                    delay time caused by communication system. In [7], droop-
        Department of Electrical Engineering, École de Techonologie Superieure,                               based strategy to control the inverter in a microgrid, is
        Montreal, QC H3C 1K3, Canada (e-mail: felix.dubuisson.1@ens.etsmtl.ca,
        cc-miloud.rezkallah@etsmtl.ca;ambrish.chandra@etsmtl.ca,                                              proposed. This control technique is validated in simulation
        maarouf.saad@etsmtl.ca).                                                                              using Matlab Simulink and in real time through hardware
           M. Tremblay is with the SUEZ Treatment Solutions, Montréal, QC H4R                                 prototype. The obtained results under different conditions
        2K9,Canada (e-mail: Marco.Tremblay@suez-na.com)
           M. Rezkallah and H. Ibrahim is with the Cégep de Sept-Îles, Sept-Îles, QC                          show satisfactory performances in terms of power sharing and
        G4R        5B7,      Canada        (e-mail:       miloud.rezkallah@itmi.ca                            voltage as well as frequency regulation at the PCC.
        Hussein.Ibrahim@cegepsi.ca).                                                                            In the same context, authors in [8] proposed Synchronous



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This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TIA.2019.2938727, IEEE
                                                                                            Transactions on Industry Applications
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                                                                       Fig. 1. Configuration of the proposed standalone microgrid

        Reference Frame (SRF) control. This technique is a well-                                              based PMSG possesses various advantages such as no need of
        developed technique for three-phase converters control. It                                            electrical excitation, higher efficiency, higher number of
        controls the current and guarantees a good dynamic                                                    poles, higher power density, also they are easier to control and
        performance, as well as zero steady-state error during                                                no needs gearbox [12] [13]. Moreover, this technology usually
        transitions. The measured current is transformed from the                                             requires power converters to achieve stable operation with
        stationary frame into the rotating frame and can be regulated                                         high efficiency. To achieve high efficiency from WT driven
        using PI controllers. This control technique is used to control                                       variable speed PMSG, Maximum Power Point Tracking
        Active Power Filter (APF) and Unified Power Quality                                                   (MPPT) based control, is required. Many MPPT techniques
        Conditioner (UPQC) as detailed in [9]. Unfortunately, it                                              are proposed in the literature [14-17], such as Tip-Speed Ratio
        requires decisive PLL techniques. However, in grid connected                                          (TSR) technique, Optimum Relation Based (ORB) technique,
        systems, the voltage and frequency are considered as constant,                                        and Perturbation and observation (P&O) technique.
        so, synchronization with PCC is not a big issue but in                                                  According, to [15], these MPPT methods possess advantages
        standalone systems where the DG operates only when needed,                                            and drawbacks, which should be solved. Among these
        a robust technique for the synchronization between the                                                drawbacks, there is the necessity of mechanical sensors.
        inverter and the PCC, is needed.                                                                      Presence of this sensors lead to increase of the cost and
          UPQCs are controlled to manage the power in hybrid                                                  hardware complexity of installation [16]. Generally, P&O
        microgrids and improve the power quality [9]. They are                                                method require only output voltage and current of the WT.
        composed of two back-to-back inverters sharing a DC link.                                             according to [16], it is so hard to find a good step size which
        The first inverter is controlled as a voltage source and the                                          ensures a fast convergence of the control when system is
        second as an active filter. Consequently, one ensures the                                             subjected to the sudden wind variations without any
        voltage regulation at the PCC and delivers power to                                                   oscillation around the MPP. In [17], a P&O technique based
        compensate load variations while the other one improves                                               on integral action, is proposed. A correlation between the
        power quality. Unfortunately, the use of two back-to-back                                             variations of the power and the voltage at the input of the DC-
        inverters increase the number of power converters, which                                              DC boost converter is used, therefore only electrical measures
        leads to an increase the hardware complexity, consequently its                                        are needed.
        cost is increasing as well. In [10], authors proposed a droop-                                          In [18], control of wind–diesel hybrid system for standalone
        based control strategy controlling UPQC to ensure a proper                                            application to reduce the fuel consumption, is proposed, and in
        power flow between the AC and the DC side. The obtained                                               [19], battery storage system is employed to achieve high
        results show good performances under severe conditions, such                                          performances and reduce the fuel consumption in standalone
        as nonlinear load and the reactive power sharing is done                                              microgrid. In [18,19], DG is kept running at all time, which is
        properly, as well as, the AC voltage regulation at the PCC. In                                        not effective, costly and can affect the lifespan of the DG.
        [11], a new SRF based control is proposed for UPQC with an                                             To solve these issues and achieve high performances in
        improved PLL. This method is simpler and easier to                                                    standalone microgrid for water treatment applications, the
        implement, as it needs reduced number of current sensors. In                                          following solutions, which represent the contributions of this
        addition, the reactive power and harmonic compensation are                                            research work, are proposed,
        done properly under presence of unbalanced linear and non-                                              1) Design of a new and simple standalone micro-grid
        linear loads.                                                                                         configuration based on fixed speed DG and WT driven
          Wind Energy Conversion System (WECS) based on                                                       variable speed PMSG for water treatment station without any
        Permanent Magnet Synchronous Generator (PMSG) has                                                     mechanical sensors.
        gained more and more interests in microgrid applications. WT



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This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TIA.2019.2938727, IEEE
                                                                                            Transactions on Industry Applications
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          2) Enhanced power sharing strategy to regulate the voltage
        and frequency at the PCC.
          3) Less fuel consumption by reducing the time running of
        DG and maximizing its efficiency by operating the DG only at
        its rated power.
          4) Robust and simple control strategy for the DC-DC buck-
        boost converter to ease the bidirectional power flow through
        the battery.
          5) Enhanced MPPT technique, which is proposed first in
        [17].
                                                                                                                Fig. 2. Control strategy for the DG
          6) Validation in real time of all proposed concept for water
        treatment system application.
          This paper is organized as follows, in section II the proposed
        standalone microgrid is presented with its operation mode. In
        section III, all developed control strategies are detailed. In
        section IV, simulation and experimental results as well as
        discussion are given, and the conclusion is presented in
        Section V.

                    II. STANDALONE MICROGRID CONFIGURATION
           Fig. 1 shows the proposed standalone microgrid
        configuration. It consists of Diesel Engine (DE) driven fixed
        speed Synchronous Generator (SG) and WT driven variable
        speed Permanent Magnetic Synchronous Generator (PMSG),
        which is connected to the common DC bus through a diode
        rectifier and controlled DC-DC boost converter. A battery
        pack of Nickel Cadmium technology is used to balance the
        power in the system. To protect the battery from overcharging
        a DC dump load, is employed. For a galvanic isolation
                                                                                                                Fig. 3. Two-level control strategy for the three-phase inverter
        between the AC and the DC bus, a delta-star transformer is
        employed. The water treatment system is considered as a load
        and is connected to the AC bus.                                                                                                      III. CONTROL SYSTEM
           In Table 1, different operation modes of the system shown                                             In this section, the developed control strategies of the
        in Fig. 1, are detailed. The operation mode depends on the                                            different elements of the system, are detailed.
        state of charge (SOC) of the battery, the power generated by
        the WT (PWT) and the power consumed by the load (PLOAD).                                              A. Control strategy for the DG
        For each mode, the energy sources are detailed, as well as, the                                          Regarding the control strategy of the DG, it can be seen on
        SOC of the battery.                                                                                   Fig. 2. A governor compares the measured speed with its
           The DG is used as a backup energy source, it starts only                                           reference and the error is fed to Proportional Integral (PI)
        when the SOC of the battery gets lower than 50% and stop                                              controller that decide the amount of fuel required to increase
        when the SOC reaches 70%. The DG charges the battery and                                              or decrease the speed of the engine in order to regulate the
        supply the load at the same time. The battery charges much                                            frequency at the PCC. The Automatic Voltage Regulation
        faster if the WT is delivering power at the same time, but the                                        (AVR) compares the voltage measured at the PCC with its
        DG can supply the load and charges the battery on its own.                                            reference and the error is fed to a PI controller to obtain the
                                            TABLE I                                                           field voltage required to generate the excitation current for
                                     SYSTEM OPERATION MODES                                                   SG.
                                                   Energy                        State of the
             Mode                Conditions
                                                   sources                         battery                    B. Control Strategy for the Three-Phase Inverter
                                PWT > PLOAD
            Mode 1
                                SOC > 50%
                                                     WT                            Charging                      The developed control strategy for the three-phase inverter
                                PWT < PLOAD                                                                   is illustrated in Fig. 3. It consists of two-level control. When
            Mode 2                              WT + Battery                     Discharging
                                SOC > 50%                                                                     the DG is turned on, the inverter is responsible for balancing
                                PWT < PLOAD                                                                   the powers between the AC and the DC side of the microgrid
            Mode 3                                   DG                            Charging
                                SOC < 50%
                                PWT > PLOAD                                                                   and the first level control, is used. The inverter current is
            Mode 4                                DG +WT                        Fast charging
                                SOC < 50%                                                                     converted from the stationary frame to the rotating frame
                                 PWT >PLOAD          WT                            Charging                   using Park transformation.
            Mode 5
                                 SOC>70%
                                PWT > PLOAD                                     Discharging in
            Mode 6                              WT +Battery
                                SOC = 100%                                     the Dump Load




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This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TIA.2019.2938727, IEEE
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                                     2       2  
                          sin  sin    sin    
             id        
                        2
                                         3
                                      2 
                                                   3 
                                                 2   a
                                                          i                  
             i q      cos  cos    cos  
                        3               3    
                                                        i
                                                     3  b                                           (1)
             io       1            1          1
                                                          i
                                                         c                                                   Fig. 4. Control strategy for the DC-DC Buck-boost Converter
                                                       
                          2            2          2    



           The inverter direct current reference (IdINV_ref) is calculated
        using the sensed load current (IdLOAD) and the DG current
        reference (IdDG_ref). Using the DG current reference makes
        sure that the DG operates at its rated power. A PI controller is
        used to compare the sensed direct inverter current to this new
        reference. Regarding the q component of the inverter current,                                           Fig. 5. MPPT strategy for the WT
        it is forced to zero thanks to a PI controller to minimize the
                                                                                                              second level control. The measured voltage at the PCC is
        reactive power exchanges between the AC and the DC side of
                                                                                                              compared with its reference and the error is fed to PI
        the microgrid. The inverter current reference in the rotating
                                                                                                              controller and the current measured at the PCC is subtracted
        frame is fed to a hysteresis controller in order to create the
                                                                                                              from the output of the PI controller in order get the new
        signal switches of the inverter as,
                                                                                                              current references as,


                                                                                                    (2)                                                                                                   (7)


                                                                                                              C. Control Strategy for the DC-DC Buck-Boost Converter
           A PLL is needed to obtain the phase shift (θ) for the
        transformations between the rotating and the stationary                                                 Fig. 4 shows the control strategy for the DC-DC buck-boost
        frames. The phase shift (θ) is calculated using in-phase and                                          converter. A PI controller is used to regulate the DC link
        quadrature unit templates, which are calculated as follows,                                           voltage. The output of the PI controller represents the battery
                                                                                                              current reference and is compared with the sensed battery
                                                                                                              current and the output of the PI controller is the control signal
                                                                                                              which is fed to PWM to get the switches signals of the buck-
                                                                                                    (3)       boost converter.

                                                                                                                                                                                                          (8)
           Where vLa, vLb and vLc are the line to line voltage and VL is                                                                                                                                  (9)
        the amplitude of the AC voltage.
        The quadrature units are calculated as follows:
                                                                                                              D. MPPT Approach for the WECS
                                                                                                                 The control strategy used to achieve MPPT form the WT is
                                                                                                              shown in Fig. 5. As already mentioned, the proposed control
                                                                                                              technique for MPPT from WT does not need speed sensor,
                                                                                                    (4)
                                                                                                              only output voltage and current are used to compute the power
                                                                                                              at nth and (n-1) th instants as,

                                                                                                                                                                                                         (10)
           The frequency is obtained based on the following equations                                                                                                                                    (11)
        as,
                                                                                                                 The sign of the power variation is used to determine the
                                                                                                    (5)       sign of the incremental step to reach the MPP.

                                                                                                    (6)
                                                                                                                                                                                                         (12)

           If the DG is turned off, the inverter supplies the connected
        loads and ensures regulation of the frequency as well as the                                             As detailed in Fig. 5, dD is the incremental step, it is
        voltage at the PCC. These tasks are achieved by selecting the                                         responsible for the speed of convergence but also for the size



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This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TIA.2019.2938727, IEEE
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                                                                                                               Fig. 7. Transfer function of the DC-voltage regulation




        Fig. 6. State flow chart to control AVR, governor and the controlled switch

        of the oscillations. According to [20], the step size dD should
        be 0.5% in order to get a good compromise between speed of
        convergence to the MPP and oscillations around the MPP.                                                Fig. 8. Bode diagrams of the transfer function, PI controller and closed loop
                                                                                                               system.
        E. Control Strategy for the Dump- Load
          The dump load is used to protect the battery from
        overcharging. Its switch is turned off only if the SOC of the                                             Based on (14), one obtains the gains as:
        battery is fully charged.
                                                                                                                                                                                                        (15)
        F. Power Flow Supervisor
                                                                                                                                                                                                        (16)
           A supervisor based on state flow chart is used to turn ON
        and OFF the DG. As one can see on Fig. 6, the DG is turned
                                                                                                                 Selecting, ζ and ω equal to 0.7 and 439.82 rad/s as detailed
        ON only based on the SOC of the battery. Once the SOC of
                                                                                                              in [21], one obtains a good compromise between the static and
        battery becomes less than 50%, the governor and AVR are
        turned ON and once the system frequency and the terminal                                              dynamic performances.
        stator voltage of the DG are equal to the system frequency and                                           The CDC is selected equal to =500e-6F. The optimal gains
        the AC voltage at the PCC, the controlled switch is turned on.                                        that ensure less overrun and fast response time as presented in
        If the SOC of the battery is high or equal to 70%, the                                                Fig.8 are selected as, kp=0.3079 and ki=96.7208.
        controlled switch, AVR and governors, are turned off.
                                                                                                                          IV. SIMULATION AND EXPERIMENTAL RESULTS
        G. Optimal method for PI gain tuning
                                                                                                                To validate the different control approaches presented
           The PI controller have two parameters: kp and ki to tune.                                          above and test the performances of the proposed standalone
        The following technique, which is based on determination of                                           microgrid, many scenarios are tested and validated using
        the transfer function of the control loop, is applied to get the                                      simulations on Matlab/Simulink and in real time through
        optimal gains of the proposed PI controllers. As is detailed in
                                                                                                              small-scale hardware prototype of 2 kW.
        Fig. 7 and 8, the transfer function in open loop of the DC-
        voltage control loop is described as:                                                                 A. Simulation Results under Load and Wind variations
                                                                                                                 Fig. 9 shows the waveforms of the PCC voltage and its
                                                                                                              magnitude, the load current, DG current, inverter current,
                                                                                                 (13)
                                                                                                              battery current, WT current, voltage of the DC bus, SOC of
                                                                                                              the battery, and system frequency. During this test, the wind
            And the closed loop is given as:                                                                  varies as follows: it starts at t=7s and increases until t=8s, then
                                                                                                              it stays constant until t=11s, next it starts decreasing until
                                                                                                              t=15s and stays constant until t=16s, where it increases until
                                                                                                 (14)         t=18s and then it stays constant until the end of the simulation.
                                                                                                              The load is varying between t=7s and t=9s and at t=18s.



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           One can see that the WT current varies with the wind speed                                         load, the DG and the inverter. One can see the exchange of
        variations and that the PCC voltage and frequency are well                                            active power between t=2s and t=10,7s, when the DG is
        regulated at their rated values, which are 460V and 60 Hz. The                                        charging the battery. Also, one can see that the DG is always
        DC voltage oscillates during wind and load variations, but it is                                      producing the same amount of power, which is its rated
        regulated around its rated value, which is equal to 350V. In                                          power. And when the DG is off, the inverter is supplying the
        addition, one can see that the battery is charging very slowly                                        load on its own. Regarding reactive power one can see a small
        from t=2s to t=7s, this is due to the absence of wind. Then,                                          exchange of reactive power between the DG and the inverter.
        from t=7s to t= 10.7s, it starts charging much faster when the                                        These exchanges can reach 500 Var when the load is varying
        DG and the WT are providing power. At t=10.7s, the SOC of                                             but they are about 100 Var is steady state, so one can consider
        the battery is equal to 70% so the DG is turned off. Between                                          they are insignificant.
        t=10.7s and t=18s, the WT is not delivering enough power to                                              To validate the performances of the dump-load another test
        supply the load, so the battery is discharging to help the wind                                       was done. Fig. 11 shows the waveforms of the PCC voltage
        turbine supply the load. At t=18s, the load is reduced, and the                                       and its magnitude, the load current, dump load current,
        WT is delivering enough power to supply the load and charge                                           inverter current, battery current, WT current, voltage of the
        the battery at the same time. Therefore, one can say that both                                        DC bus, SOC of the battery, and the system frequency. As one
        the DG and the WT can charge the battery and supply the load                                          can see, at t=6.65s the SOC of the battery reaches 100% and
        simultaneously. Which leads to say that the battery is helping                                        the dump load is activated to dissipate the power and protect
        the system to maintain its stability by balancing the powers.
           On Fig. 10 one can see the active and reactive power of the




                                                                                                                Fig. 11. Simulation results of the dump load system




        Fig. 9. Simulation results under load and wind variations




        Fig. 10. Active and reactive power of the system under weathered and load
        variations.                                                                                             Fig. 12. Hardware configuration



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        the battery from overcharging. One can see that the load
        voltage, frequency and DC bus voltage are well regulated.
        This confirms that battery is protected from overvoltage and
        system is able to operates in this operation mode without any
        unbalance or frequency deviation.
        B. Experimental Results Under Load and Wind Variations
           Fig. 12 shows the hardware configuration used to validate
        the results obtained with the simulation. It is composed of DG
        (Induction Motor (IM) driven SG), synchronization switch,
        inverter, boost converter, variable voltage transformer, LC
        filter, dSPACE controller, lead acid batteries, WT (IM driven
        PMSG), and loads.
           Fig. 13 demonstrates the performances of the Diesel-Battery                                                                                       (a)
        system under load variations. In Fig. 13 (a) and (b), the




                                                                                                                                                   (b)
                                                                                                                Fig. 15. Dynamic performances of the Battery-WT system under load and
                                                                                                                wind speed variations
                                                      (a)




                                           (b)
        Fig. 13. Dynamic performances of the Diesel-Battery system under load                                                                                (a)
        variations




                                                                                                                                                   (b)
        Fig. 14. Dynamic performances of the Battery system without Diesel under                                Fig. 16. Dynamic performances of the Diesel-Battery-WT system under load
        load variations                                                                                         and wind speed variations




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        waveforms of the DC bus voltage, DG current, battery current                                          developed to operate the DG efficiently at its rated power by
        and load current are shown. One can see that the DG is                                                controlling the three-phase voltage source inverter. The
        producing current even when there is no load and that the                                             obtained results in the presence of severe conditions show
        current charges the battery. Also, one can see that the dynamic                                       satisfactory performance without any saturation of the
        of the DG is slow when the load increases and that the battery                                        controllers and with less overrun and fast response time. The
        delivers or absorb more current during the load variations. So,                                       voltage and frequency regulation at the PCC as well as power
        one can say that the battery helps to keep stable the operation                                       sharing, are achieved at different operation modes and during
        by balancing the powers in the system. One can clearly see                                            transitions. It has been demonstrated that the DG was used as
        that the DC voltage is well regulated in this operation mode,                                         back up energy sources and that the load is supplied at all time
        which confirms the robustness of the developed control                                                with a stable power without any interruption.
        strategy for the DC-DC buck boost converter.
           In Fig. 14, the waveforms of the DC bus voltage, the                                                                                        APPENDIX
        voltage of the PCC, the battery current and the load current are                                                                           TABLE II
        shown. One can see that the battery can provide power to the                                                                        SYSTEM PARAMETERS
        load at any time. It is observed that during absence of load, the                                       Elements                          Parameters and Values
                                                                                                                                  P=50kW, Vdc=288V, ω=12500 rpm, Rs=0.0041 Ω ,
        battery is discharging slowly, this is due to the passive                                             WECS                Ld=8.7079e-05H , Lq=1.4634e-04H, Flux linkage=
        elements of the system. In this operation mode, the DC                                                                    0.07V.s, J=0.089kg.m^2, F=0.005N.Més, Tf=4N.m
        voltage is well regulated, which confirms the robustness of the                                                           nominal voltage=250V, cut-off voltage=187.5V, fully
                                                                                                                                  charge voltage=286V, energy capacity=100KWh,
        developed control strategy for the DC-DC buck boost                                                   Battery
                                                                                                                                  nominal discharge current=80A, internal
        converter.                                                                                                                resistance=0.00625Ω
           In Fig. 15 (a) the voltage measured after the MSAP, the                                                                Sn=52.5kVA, Vn=460V, fs=60Hz, 2P=4, Rs=0.0181Ω,
        load current, the battery current and the DC current measured                                         SG                  Ll=0.0009622 H, Lmd=0.02683H,
                                                                                                                                  Lmq=0.01187H, J=0.3987kg.m2, F=0.031N.m.s
        after the DC-DC boost converter, are presented. In this test,                                         AC bus              VLLrms=460V, Frequency=60Hz
        there is no load and the wind speed are varying. One can see                                          Load                Maximum load=40kW
        that the battery is being charged by the WT. In Fig. 15 (b) the
                                                                                                                                                  TABLE III
        waveforms of the voltage at the PCC, the load current, the                                                               SMALL SCALE PROTOTYPE PARAMETERS
        battery current and the DC current measured after the DC-DC                                            Elements                           Parameters and Values
        boost converter, are shown. In this test, the wind speed is kept                                      DG                  P=2kW, ω=1800rpm, V=208, I=6.8A, fs=60Hz,
        constant, and load varies. One can see that when load is                                              Battery             V=120V
        removed, WT charges the battery. When load increase at                                                WECS                P=2.5kW, ω=1800 rpm, V=280V, I=5,1A
        t=1.2s, the battery stops charging because the current                                                AC bus              VLLrms=40V, Frequency=60Hz
                                                                                                              Load                40kW
        produced by the WT is used to supply the connected load.
        When load is increased more at t=3.2s, battery is discharging
        in order to balance the power in the system. Then one can                                                                                    REFERENCES
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This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TIA.2019.2938727, IEEE
                                                                                            Transactions on Industry Applications
                                                                                                                                                                                                             9

        [8]   Han, Yang, Hao Chen, Zipeng Li, Ping Yang, Lin Xu et Josep M                                    design of microgrids, renewable energy generations and
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              realization with introducing unified power quality conditioner integrated                                           power electronics and system control
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              85, Oct. 2017.                                                                                                      Université, Montréal, Canada., in 2010
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              conditions,“ IEEE Transactions on Industrial Electronics, vol. 58, no 9,                        center on smart grids and energy systems (Inergia Lab) at
              p. 3967-3975, Sept. 2011.                                                                       spet-iles in Quebec and as a research assistant in Electrical
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              varying control of permanent magnet synchronous generators for wind                             and his research interests include control and design of
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              March 2014.
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              controller for variable-speed fixed-pitch wind energy conversion                                                     Montréal since 1999. He received B.E.
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              4899-4908, Aug. 2016.                                                                                                degree from the University of Roorkee
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                                                                                                                                   Calgary, in 1977, 1980, and 1987,
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              54, no 3, pp 1983-91, May 2018.                                                                 Problems and Mitigation Techniques’. He is Fellow of many
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                                                                                                              Institute of Engineering and Technology U.K., Engineering
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                                                                                                              Institute of Canada etc. and registered as a Professional
              experimentation of a voltage source active filter compensating current                          Engineer in Quebec. He is a Distinguished Lecturer of the
              harmonics and power factor,“ in Proceeding of IECON'94-20th Annual                              IEEE Power and Energy Society and the IEEE Industry
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                                                                                                              Application Society. He is the recipient of IEEE Canada ‘P.
                                                                                                              Ziogas Electric Power Award 2018’.


                                        Félix Dubuuisson (S’18) received the
                                        M.Sc. degrees in electrical engineering
                                                                                                                                             Maarouf Saad received a bachelor and
                                        from the École de Technologie
                                                                                                                                             master degrees in electrical engineering
                                        Superieure Montreal, QC, Canada, where
                                                                                                                                             from Ecole Polytechnique of Montreal
                                        he is currently working toward Ph.D.
                                                                                                                                             respectively in 1982 and 1984. In 1988, he
                                        degree. He is currently studying the
                                                                                                                                             received a Ph.D. from McGill University
                                        predictive control for an off-grid system
                                                                                                                                             in electrical engineering. He joined Ecole
                                        using renewable energy sources. His
                                                                                                                                             de technologie superieure in 1987 where
                                        research interests include control and
                                                                                                                                             he is teaching control theory. His research



0093-9994 (c) 2019 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.
This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TIA.2019.2938727, IEEE
                                                                                            Transactions on Industry Applications
                                                                                                                                                                                                           10

        is mainly in nonlinear control and optimization applied to
        robotics and power systems.

                             Marco Tremblay is the R&D Director at
                             Suez Water Technologies & Solutions in
                             Montreal, Canada, developing industrial
                             power electronic and control products.
                             He is a licensed professional engineer
                             with a bachelor degree from McGill
                             University. He later obtained a Master
                             degree from École de Technologie
        Supérieure de Montréal where he is presently a PhD
        candidate. His major contribution has been the development
        of innovative products used to purify drinking water for more
        than fifty million people around the world and to reduction
        industrial pollution. He is presently studying the use of neural
        networks in equipment condition monitoring and diagnostics.




                             Hussein Ibrahim received the PhD
                             degree in engineering from Québec
                             University at Chicoutimi, Canada.
                             Since July 2009, he has research
                             director at Cégep of Sept-iles in the
                             north of Quebec. His research interests
                             include renewable energy sources
                             integration, hybrid energy power
        system, storage energy, heat and mass transfer, fluid
        dynamics, and energy efficiency.




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