# Hardware Implementation of Composite Control Strategy for Wind-PV-Battery Hybrid Off-Grid Power Generation System

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^{e}Sept-Îles, 175 Rue de la Vérendrye, Sept-Îles, QC G4R 5B7, Canada

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## Abstract

**:**

## 1. Introduction

_{1}and β

_{2}) to achieve high performance.

- Minimizing the number of power converters to reduce the hardware complexity and increase the system efficiency,
- Development of an indirect control for the buck-boost converter to realize many tasks such as achieving high performance from PV without using any MPPT algorithm, facilitating the bidirectional power flow between the ESS and PCC, and ensuring stable operation during the disturbance,
- Effective and efficient, mechanical-speed sensorless operation of variable-speed WT-based permanent magnet brushless DC generator (PMBLDCG) using hybridization of the root-finding algorithm (secant method) with P&O technique,
- Reinforcement of the SRF based control with virtual impedance active damping to improve the power quality at the PCC while eliminating the 5th and 7th order harmonics, along with the prevention of the 6th order-harmonic generation in the rotor of the synchronous generator (SG), as well as to solve the issue of filter resonance.

## 2. System Configuration and Operation

_{WT}), PV (P

_{PV}), and DG (P

_{DG}), depending on if it is greater, equal, or less than load power demand (P

_{L}), and also based on the SoC% of ESS.

## 3. Developed Composite Control Strategy

#### 3.1. Control of DC-DC Boost Converter on WT Side

_{WT}to provide accurate and fast convergence to the optimum operating point during sudden wind speed change. The fundamental equation of the secant method is described in [30,31,32,33].

_{9}) of the boost converter for the WT side.

#### 3.2. Control of DC-DC Buck-Boost Converter for ESS Side

_{7}and S

_{8}) of the DC-DC buck-boost converter for the ESS side.

#### 3.3. SRF Control with Virtual Impedance-Based Active Damping

## 4. Results and Discussion

#### 4.1. Performance at the AC Side under Presence of Linear Load

#### 4.2. Performance at the DC Side at Solar Irradiation and Wind Speed Change

#### 4.3. Generated and Consumed Active and Reactive Powers

_{DG}, Q

_{DG}), load (P

_{L}, Q

_{L}), three-phase interfacing inverter (P

_{inv}, Q

_{inv}), generated active power from WT (P

_{W}), and PV panel (P

_{PV}), and from the ESS (P

_{ESS}), are demonstrated. One observes that the balance in power in the hybrid off-grid system is perfectly achieved, and all generated power in this operating mode (operating mode 2) is provided to the load and to charge the ESS because the SoC% is less than 50%. So, on the AC side, the DG is supplying the load directly and the difference of power is provided to the ESS through the three-phase interfacing inverter, which is why the active and reactive power is with a negative sign. On the DC side, all generated power from the WT and the PV array is used to charge the ESS, which is why the P

_{ESS}is with a negative sign; it is increasing and decreasing based on the variation of the wind speed and solar irradiation. It is observed that the power balance is achieved without any issue, which confirms the robustness of the indirect control developed for the DC-DC buck-boost converter based on the double loop strategy.

#### 4.4. Performance at PCC under the Presence of Nonlinear Loads

_{dc}) and its reference (V

_{dc}

^{*}), currents of the phase ‘a’ of DG (${i}_{DGa}$), load (${i}_{La}$), and inverter (${i}_{inva}$) are demonstrated, and in Figure 9b,c and Figure 10b,c, the harmonic spectrum of load and DG currents are presented. One observes that the interfacing inverter acts as a power active filter under the presence of RL and RC both types of nonlinear loads. It compensates for harmonics and balances the DG current. One observes that the common DC-link voltage is maintained constant and follows its reference, which is equal to 350 V. One sees clearly from the spectra of harmonics shown in Figure 9b and Figure 10b the presence of the 5

^{th}and 7

^{th}order of harmonics in the load current. The total harmonics distortion (THD) of the load current is equal to 26.9% in Figure 9b for RC type nonlinear load and 26.05% in Figure 10b for RL type nonlinear load. The THD of the DG current as demonstrated in Figure 9c and Figure 10c is equal to 2.31% and 1.88%, respectively. This achieves the limit of IEEE Std 519-1992. One observes that the 5

^{th}and 7

^{th}order harmonics are mitigated at the level of DG current in the presence of both nonlinear loads. This proves that the stator of the SG is protected against 5

^{th}and 7

^{th}order harmonics under the presence of all nonlinear loads, which confirms the robustness of the SRF control with virtual impedance-based active damping, which is developed for the three-phase interfacing inverter.

#### 4.5. Experimental Results of the DG under the Presence of Linear Load

_{DGab}and v

_{DGbc}) are sinusoidal and regulated at their rated value, which equals 208 V at the primary of the transformer (element no. 5 in Figure 5 and 50 V at the secondary as shown in Figure 11c. The connected load is supplied with a constant current at a fixed frequency (i.e., 60 Hz). The DC current applied to the rotor winding of SG is constant and is equal to 0.8 A.

#### 4.6. Performance under Load Variation and Presence of Linear Load

_{dc}), output DG current of phase ‘a’ (i

_{DGa}), the generated current from the PV panel and WT (i

_{WT}+ i

_{PV}), load current of phase ‘a’ (i

_{La}), ESS current (i

_{b}), and line PCC voltage (v

_{Lab}) are presented. It is observed in Figure 12a that the load is suddenly connected to the system at t = 0.72 ms, and the DG stabilizes only after t = 0.12 s, and in this period, the ESS provides the difference. One observes that the common DC-link voltage is well regulated, and it is not affected during the transition, which confirms the robustness of the outer control loop of the DC-DC buck-boost converter. It is observed in Figure 12b, that ESS provides the difference of power between t = 0 s to t = 0.2 s, and the current becomes equal to zero when the load is disconnected at t = 0.2 s. In Figure 12c, the ESS current is increased more when the load is suddenly increased at t = 0.2 s. In all the cases, the load is supplied without interruption, and the power is balanced in the hybrid off-grid system. The common DC-link voltage is well regulated without deviation (overshoot and undershoot), which confirms the robustness of indirect control developed for the DC-DC buck-boost converter.

#### 4.7. Performance in Presence of RC and RL Types Nonlinear Loads

_{dc}), load current of phase (i

_{La}), DG current (i

_{DGa}), and the output inverter current (i

_{inva}) of phase ‘a’ in the presence of nonlinear loads type RL and type RC are presented. In Figure 13b,c and Figure 14b,c, the harmonics spectra of the load and DG currents are demonstrated. One observes clearly in Figure 13a and Figure 14a that the DG currents are sinusoidal and balanced in presence of the both type of nonlinear loads, and the common DC-link voltage is well regulated at its set value, which is equal to 120 V. It is observed that the inverter operates as an active filter; it mitigates harmonics and balances the DG current. This confirms the robustness of the proposed indirect control strategy for the DC-DC buck-boost converter and the SRF with a virtual impedance-based-active damping control strategy for the three-phase interfacing inverter. As demonstrated in Figure 13c and Figure 14c, the 5th and the 7th order harmonics are mitigated and THD of DG currents is less than 5% in the presence of both types of nonlinear loads, which confirms that the SG of the DG is protected against 5th and 7th order harmonics and proves the robustness of the developed control strategy for the three-phase interfacing inverter.

#### 4.8. Performance of the WT at Wind Speed Change

_{Lab}), load current (i

_{La}), output WT current at the DC side, and ESS current (i

_{b}) are presented in Figure 15. This test is realized by maintaining a constant load and applying different speeds to the PMBLDCG. One observes clearly that the output DC current, which is measured at the DC side of the WT, varies with the variation of the wind speed. Seeing that the DG is running at this time, the difference of generated power is taken by ESS. The ESS current is increased at t = 1.8 s and increased further at t = 3 s, t = 6 s, and at t = 12.2 s. One sees clearly that perturbation and observation (P&O) with variable steps of DC voltage based on the secant method performs well during wind variation, and all transitions are realized without any overshoot in current or voltage. It is observed that the PCC voltage is well regulated, and load is continually supplied without any interruption during the transition and during rotor speed variation. This proves the effective operation of the MPPT technique without sensing the rotor speed proposed for the variable speed wind turbine based on PMBLDCG.

_{sa}) of phase ‘a’, WT output DC voltage (v

_{WT}) and current (i

_{WT}), and stator current (i

_{sa}) of phase ‘a’ are presented. In Figure 16, (b) the zoomed waveforms of (a) between t = 2.64 s and t = 2.88 s are shown. One observes that experimental results are similar to the simulation results where the output DC voltage of the WT varies slightly with the variation of the wind speed. It is observed that the output stator current and the current measured at the output of three-phase diode-bridge increase at t = 0.8 s and increase more at t = 2.8 s with the increasing of the rotor speed. This validates the desired operation of the MPPT technique without mechanical speed measurement.

#### 4.9. Performance of the PV Panel at Solar Irradiation Change

_{DGa}) of the phase ‘a’, the PV current (i

_{PV}), ESS current (i

_{b}), and the common DC link voltage are shown in Figure 17. This test is realized under solar irradiation change to test the performance of the proposed approach to achieve high efficiency from PV array without using any MPPT technique. One observes that the common DC-link voltage is regulated constant at its rated value, which is equal to the sum of the output voltage of the PVs connected in series. The system is subjected to solar irradiation change at t = 0.4 s, t = 0.72 s, and 1.16 s. One observes that by maintaining the common DC link voltage constant, one can easily extract the maximum of current from the PV panel during solar irradiation change. It is observed that the ESS current increases with the increase of the PV panel current, and V

_{dc}is maintained constant; this proves the desired operation of the outer and inner control loops of the indirect control, which are designed to achieve MPPT from PV and balance the power in the off-grid system.

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## Define Abbreviation

Symbol | Description |

WT | Wind turbine |

PV | Photovoltaic array |

ESS | Energy storage system |

DG | Diesel generator |

PMBLDCG | Permanent magnet brushless DC generator |

i_{sa}, i_{sb}, and i_{sc} | Stator currents of the PMBLDCG |

C_{WT} | The capacitor at the output of the diode bridge |

V_{WT} | DC voltage of the WT |

L_{WT} | The inductor of the DC-DC boost converter for WT side |

i_{WT} | DC current of the WT |

V_{PV} | Output PV voltage |

i_{PV} | Output PV current |

v_{b} | Battery voltage |

L_{b} | Inductor that connects the battery to the DC-DC buck-boost converter |

V_{dc} | Common DC-link voltage |

V_{inva}, V_{invb}, and V_{invc} | Output voltages of the interfacing inverter |

i_{inva}, i_{invb}, and i_{invc} | Output currents of the interfacing inverter |

V_{ca}, V_{cb}, and V_{cc} | Voltages of the output filter |

R_{c} and C_{C} | Resistance and capacitor of the output filter |

i_{cc} | The current of the output filter |

L_{inv} and L_{DG} | Inductors of the output filter |

V_{La}, V_{Lb}, and V_{Lc} | Load voltages |

i_{La}, i_{Lb}, and i_{Lc} | Load currents |

i_{DGa}, i_{DGb}, and i_{DGc} | Diesel generator currents |

AVR | Automatic voltage regulator |

DE | Diesel engine |

P&O | Perturbation and observation technique |

V_{WTmax} | The maximum voltage obtained using the P&O technique |

ΔV_{WT} | Step of ${V}_{WT}$ variation |

V_{WT}* | Reference DC voltage of the WT |

ΔV | WT DC voltage error value |

PI | Proportional integral regulator |

i_{WT}* | Reference DC current of the WT |

Δi_{WT} | WT DC current error value |

d_{WT} | Control signal |

S_{1} to S_{9} | Power electronic switches (insulated-gate bipolar transistor (IGBT)) of the power converters |

PWM | Pulse-width modulation |

V_{dc}* | Reference of the common DC-link voltage |

ΔV_{dc} | Error value of the common DC-link voltage |

i_{b}* | Reference battery current |

Δ i_{b} | Error value of battery current |

d_{b} | Control signal |

f_{s} | System frequency |

f_{s}* | Reference of the system frequency |

l_{Loss} | losses of active power |

d-q | Direct and quadrature axis |

LPF | Low pass filter |

PLL | Phased locked loop |

ωt | Angular frequency |

i_{DGa}*, i_{DGb}* and i_{DGc}* | Reference of DG currents |

G(s) | Transfer function of LCL filter |

## References

- Hidalgo-Leon, R.; Amoroso, F.; Litardo, J.; Urquizo, J.; Torres, M.; Singh, P.; Soriano, G. Impact of the Reduction of Diesel Fuel Subsidy in the Design of an Off-Grid Hybrid Power System: A Case Study of the Bellavista Community in Ecuador. Energies
**2021**, 14, 1730. [Google Scholar] [CrossRef] - Mokhtara, C.; Negrou, B.; Settou, N.; Settou, B.; Samy, M.M. Design optimization of off-grid Hybrid Renewable Energy Systems considering the effects of building energy performance and climate change: Case study of Algeria. Energy
**2021**, 219, 119605. [Google Scholar] [CrossRef] - Dubuisson, F.; Rezkallah, M.; Ibrahim, H.; Chandra, A. Real-Time Implementation of the Predictive-Based Control with Bacterial Foraging Optimization Technique for Power Management in Standalone Microgrid Application. Energies
**2021**, 14, 1723. [Google Scholar] [CrossRef] - Rezkallah, M.; Singh, S.; Chandra, A.; Singh, B.; Ibrahim, H. Off-Grid System Configurations for Coordinated Control of Renewable Energy Sources. Energies
**2020**, 13, 4950. [Google Scholar] [CrossRef] - Rezkallah, M.; Chandra, A.; Singh, B.; Singh, S. Microgrid: Configurations, Control and Applications. IEEE Trans. Smart Grid
**2017**, 10, 1290–1302. [Google Scholar] [CrossRef] - Sawle, Y.; Gupta, S.; Bohre, A.K. Review of hybrid renewable energy systems with comparative analysis of off-grid hybrid system. Renew. Sustain. Energy Rev.
**2018**, 81, 2217–2235. [Google Scholar] [CrossRef] - Upadhyay, S.; Sharma, M. A review on configurations, control and sizing methodologies of hybrid energy systems. Renew. Sustain. Energy Rev.
**2014**, 38, 47–63. [Google Scholar] [CrossRef] - Nehrir, M.H.; Wang, C.; Strunz, K.; Aki, H.; Ramakumar, R.; Bing, J.; Miao, Z.; Salameh, Z. A Review of Hybrid Renewable/Alternative Energy Systems for Electric Power Generation: Configurations, Control, and Applications. IEEE Trans. Sustain. Energy
**2011**, 2, 392–403. [Google Scholar] [CrossRef] - Beleiu, H.G.; Maier, V.; Pavel, S.G.; Birou, I.; Pică, C.S.; Dărab, P.C. Harmonics Consequences on Drive Systems with Induction Motor. Appl. Sci.
**2020**, 10, 1528. [Google Scholar] [CrossRef] [Green Version] - Rezkallah, M.; Chandra, A.; Ibrahim, H.; Singh, B. Implementation of Two-Level Control Coordinate for Seamless Transfer in Standalone Microgrid. In Proceedings of the 2019 IEEE Industry Applications Society Annual Meeting, Baltimore, MD, USA, 29 September–3 October 2019; Volume 75, pp. 1–6. [Google Scholar] [CrossRef]
- Park, B.; Jaehyeong, L.; Hangkyu, Y.; Gilsoo, J. Harmonic Mitigation Using Passive Harmonic Filters: Case Study in a Steel Mill Power System. Energies
**2021**, 14, 2278. [Google Scholar] [CrossRef] - Hoon, Y.; Mohd, A.M.R.; Muhammad, A.A.M.Z.; Mohamad, A.M.Z. Shunt active power filter: A review on phase synchronization control techniques. Electronics
**2019**, 8, 7. [Google Scholar] [CrossRef] [Green Version] - Bielecka, A.; Wojciechowski, D. Stability Analysis of Shunt Active Power Filter with Predictive Closed-Loop Control of Supply Current. Energies
**2021**, 14, 2208. [Google Scholar] [CrossRef] - Bhim, S.; Chandra, A.; Kamal, A.L.-H. Power Quality: Problems and Mitigation Techniques; John Wiley & Sons: Hoboken, NJ, USA, 2014. [Google Scholar]
- Mehmood, S.; Qureshi, A.; Kristensen, A.S. Risk Mitigation of Poor Power Quality Issues of Standalone Wind Turbines: An Efficacy Study of Synchronous Reference Frame (SRF) Control. Energies
**2020**, 13, 4485. [Google Scholar] [CrossRef] - Singh, B.; Sharma, S. SRF theory for voltage and frequency control of IAG based wind power generation. In Proceedings of the International Conference on Power Systems, Kharagpur, India, 27–29 December 2009; IEEE: Piscataway, NJ, USA, 2009; pp. 1–6. [Google Scholar]
- Naderipour, A.; Asuhaimi Mohd Zin, A.; Bin Habibuddin, M.H.; Miveh, M.R.; Guerrero, J.M. An improved synchronous reference frame current control strategy for a photovoltaic grid-connected inverter under unbalanced and nonlinear load conditions. PLoS ONE
**2017**, 12, e0164856. [Google Scholar] [CrossRef] [PubMed] [Green Version] - Benhalima, S.; Miloud, R.; Chandra, A. Real-Time Implementation of Robust Control Strategies Based on Sliding Mode Control for Standalone Microgrids Supplying Non-Linear Loads. Energies
**2018**, 11, 2590. [Google Scholar] [CrossRef] [Green Version] - Lopez-Santos, O.; Urrego-Aponte, J.O.; Lezama, S.T.; Almansa-López, J.D. Control of the Bidirectional Buck-Boost Converter Operating in Boundary Conduction Mode to Provide Hold-Up Time Extension. Energies
**2018**, 11, 2560. [Google Scholar] [CrossRef] [Green Version] - Ramos-Paja, C.A.; Bastidas-Rodríguez, J.D.; González, D.; Acevedo, S.; Peláez-Restrepo, J. Design and Control of a Buck–Boost Charger-Discharger for DC-Bus Regulation in Microgrids. Energies
**2017**, 10, 1847. [Google Scholar] [CrossRef] [Green Version] - Yu, S.Y.; Kim, H.J.; Kim, J.H.; Han, B.M. SoC-based output voltage control for BESS with a lithium-ion battery in a stand-alone DC microgrid. Energies
**2016**, 11, 924. [Google Scholar] [CrossRef] [Green Version] - Zhu, Y.; Kim, M.K.; Wen, H. Simulation and Analysis of Perturbation and Observation-Based Self-Adaptable Step Size Maximum Power Point Tracking Strategy with Low Power Loss for Photovoltaics. Energies
**2018**, 12, 92. [Google Scholar] [CrossRef] [Green Version] - Rezkallah, M.; Hamadi, A.; Chandra, A.; Singh, B. Design and Implementation of Active Power Control With Improved P&O Method for Wind-PV-Battery-Based Standalone Generation System. IEEE Trans. Ind. Electron.
**2017**, 65, 5590–5600. [Google Scholar] [CrossRef] - Jung, Y.; So, J.; Yu, G.; Choi, J. Improved perturbation and observation method (IP&O) of MPPT control for photovoltaic power systems. In Proceedings of the Conference Record of the Thirty-First IEEE Photovoltaic Specialists Conference, Lake Buena Vista, FL, USA, 3–7 January 2005; pp. 1788–1791. [Google Scholar]
- Gunasekaran, M.; Krishnasamy, V.; Selvam, S.; Almakhles, D.J.; Anglani, N. An Adaptive resistance perturbation based MPPT algorithm for Photovoltaic applications. IEEE Access
**2020**, 8, 1. [Google Scholar] [CrossRef] - Pathak, G.; Singh, B.; Panigrahi, B.K. Isolated microgrid employing PMBLDCG for wind power generation and synchronous reluctance generator for DG system. In Proceedings of the 2014 IEEE 6th India International Conference on Power Electronics (IICPE), Kurukshetra, India, 8–10 December 2014; pp. 1–6. [Google Scholar]
- Sharma, R.; Singh, B. MDSOGI-FLL Control for SyRG-PMBLDCG-BES-PV Based Microgrid. In Proceedings of the IEEE Industrial and Commercial Power Systems Europe, Genova, Italy, 11–14 June 2019; pp. 1–6. [Google Scholar]
- Pathak, G.; Singh, B.; Panigrahi, B.K. Control of Wind-Diesel Microgrid Using Affine Projection-Like Algorithm. IEEE Trans. Ind. Inform.
**2016**, 12, 524–531. [Google Scholar] [CrossRef] - Chen, Y.-M.Y.; Liu, C.S.; Hung, C.; Cheng, C.-S. Multi-input inverter for grid-connected hybrid PV/wind power system. IEEE Trans. Power Electron.
**2007**, 2, 1070–1077. [Google Scholar] [CrossRef] - Chun, S.; Kwasinski, A. Analysis of classical root-finding methods applied to digital maximum power point tracking for sustainable photovoltaic energy generation. IEEE Trans. Power Electron.
**2011**, 26, 3730–3743. [Google Scholar] [CrossRef] - Hosseini, S.H.; Farakhor, A.; Haghighian, S.K. Novel algorithm of maximum power point tracking (MPPT) for variable speed PMSG wind generation systems through model predictive control. In Proceedings of the 2013 8th International Conference on Electrical and Electronics Engineering (ELECO), Bursa, Turkey, 28–30 November 2013; pp. 243–247. [Google Scholar]
- Rezkallah, M.; Chandra, A.; Saad, M.; Tremblay, M.; Singh, B.; Singh, S.; Ibrahim, H. Composite Control Strategy for a PV-Wind-Diesel based Off-Grid Power Generation System Supplying Unbalanced Non-Linear Loads. In Proceedings of the 2018 IEEE Industry Applications Society Annual Meeting (IAS), Portland, OR, USA, 23–27 September 2018; pp. 1–6. [Google Scholar]
- Rezkallah, M.; Chandra, A.; Saad, M.; Tremblay, M.; Singh, B.; Singh, S.; Ibrahim, H. Design and Implementation of Decentralized Control for Distributed generation based Off-grid System. In Proceedings of the 2020 IEEE International Conference on Power Electronics, Smart Grid and Renewable Energy (PESGRE2020), Cochin, India, 2–4 January 2020; pp. 1–6. [Google Scholar]
- Bao, C.; Ruan, X.; Wang, X.; Li, W.; Pan, D.; Weng, K. Step-by-Step Controller Design for LCL-Type Grid-Connected Inverter with Capacitor–Current-Feedback Active-Damping. IEEE Trans. Power Electron.
**2014**, 29, 1239–1253. [Google Scholar] [CrossRef] - Liu, F.; Zhou, Y.; Duan, S.; Yin, J.; Liu, B.; Liu, F. Parameter Design of a Two-Current-Loop Controller Used in a Grid-Connected Inverter System with LCL Filter. IEEE Trans. Ind. Electron.
**2009**, 56, 4483–4491. [Google Scholar] [CrossRef]

**Figure 6.**Performance under fixed linear load at the AC side and (

**b**) Zoom of (

**a**) between t = 1.1 s to 1.3 s.

**Figure 7.**Performance at the DC side under wind and solar irradiation change of the common DC-link voltage (${V}_{dc}$) and its reference (${V}_{dc}^{*}$ ); ESS current (${i}_{b}$ ) and its reference ${i}_{b}^{*}$; the state of charge of the ESS (SoC%); the output PV current (${i}_{PV}$ ); the stator voltage of the phase ‘a’ of the PMBLDCG (${V}_{sa}$ ) and the current (${i}_{sa}$ ); and the DC-WT current (${i}_{dc}$ ).

**Figure 8.**Global power demand and generation in the hybrid wind-PV-diesel off-grid system; theactive and reactive powers of DG (P

_{DG}, Q

_{DG}), load (P

_{L}, Q

_{L}), three-phase interfacing inverter (P

_{inv}, Q

_{inv}), generated active power from WT (P

_{W}), and PV panel (P

_{PV}), and from the ESS (P

_{ESS}).

**Figure 9.**(

**a**) Waveforms of the DG, load, and inverter currents under the presence of nonlinear load type RC; (

**b**) harmonic spectrum of load current; and (

**c**) harmonic spectrum of DG current.

**Figure 10.**(

**a**) Waveforms of DG, load, and inverter currents under the presence of nonlinear load type RL; (

**b**) harmonic spectrum of load current; and (

**c**) harmonic spectrum of DG current.

**Figure 11.**Steady-state performance of (

**a**) excitation current (i

_{ex}), SG terminal stator voltages (v

_{DGab}, v

_{DGbc}) at the primary of the transformer and stator current (i

_{DGa}) of phase ‘a’; (

**b**) SG terminal stator voltages (v

_{DGab}, v

_{DGbc}) at primary of transformer and stator currents (i

_{DGa}, i

_{DGb}) of phase ‘a’ and ‘b’; and (

**c**) SG terminal stator voltage (v

_{DGab}) at primary of the transformer and at secondary (v

_{DGab}), excitation current (i

_{ex}), and stator current (i

_{DGa}).

**Figure 12.**Dynamic performance of system: (

**a**) common DC-link voltage (v

_{dc}), DG current (i

_{DGa}) of phase ‘a’, sum of PV current and DC-WT current (i

_{PV}+ i

_{WT}), and load current (i

_{La}) of the phase ‘a’ at sudden switching ON of linear load at t = 0.08 s; (

**b**) common DC-link voltage (v

_{dc}), load voltage of phase ‘a’ (v

_{Lab}), ESS current (i

_{b}), and load current of phase ‘a’ (i

_{La}) under sudden switching off of linear load at t = 0.2 s; and (

**c**) common DC-link voltage (v

_{dc}), load voltage of phase ‘a’(v

_{Lab}), ESS current (i

_{b}), and load current of phase ‘a’ (i

_{La}) under sudden increasing of linear load at t = 0.2 s.

**Figure 13.**(

**a**) Performance in the presence of nonlinear load (RL type), (

**b**) harmonic spectrum of load current, and (

**c**) harmonic spectrum of DG current.

**Figure 14.**(

**a**) Performance in the presence of nonlinear load (RC type), (

**b**) harmonic spectrum of load current, and (

**c**) harmonic spectrum of DG current.

**Figure 16.**Waveforms of WT side for: (

**a**) stator voltage (v

_{sa}) of phase ‘a’, output DC voltage (v

_{WT}) and current (i

_{WT}), and stator current (i

_{sa}) and (

**b**) its zoomed waveform.

**Figure 17.**Waveforms of PCC voltage (v

_{DGa}) at secondary of the transformer of output PV (i

_{PV}), ESS current (i

_{b}), and common DC link voltage (v

_{dc}).

Mode | Conditions | ES | State of ESS |
---|---|---|---|

Mode1 | P_{PV} + P_{WT} + P_{DG} < P_{L}SoC% > 50% | WT, PV&DG | discharging |

Mode2 | P_{PV} + P_{WT} + P_{DG} > P_{L}SoC% < 50% | WT, PV&DG | charging |

Mode 3 | P_{PV} + P_{WT} + P_{DG} > P_{L}SoC% < 100% | WT, PV&DG | charging |

Mode4 | SoC% = 100% P _{pv} + P_{WT} + P_{DG} > P_{L}P _{pv} + P_{WT} + P_{DG} = P_{L} | WT, PV&DG | Stop charging |

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**MDPI and ACS Style**

Rezkallah, M.; Ibrahim, H.; Dubuisson, F.; Chandra, A.; Singh, S.; Singh, B.; Issa, M.
Hardware Implementation of Composite Control Strategy for Wind-PV-Battery Hybrid Off-Grid Power Generation System. *Clean Technol.* **2021**, *3*, 821-843.
https://doi.org/10.3390/cleantechnol3040048

**AMA Style**

Rezkallah M, Ibrahim H, Dubuisson F, Chandra A, Singh S, Singh B, Issa M.
Hardware Implementation of Composite Control Strategy for Wind-PV-Battery Hybrid Off-Grid Power Generation System. *Clean Technologies*. 2021; 3(4):821-843.
https://doi.org/10.3390/cleantechnol3040048

**Chicago/Turabian Style**

Rezkallah, Miloud, Hussein Ibrahim, Félix Dubuisson, Ambrish Chandra, Sanjeev Singh, Bhim Singh, and Mohamad Issa.
2021. "Hardware Implementation of Composite Control Strategy for Wind-PV-Battery Hybrid Off-Grid Power Generation System" *Clean Technologies* 3, no. 4: 821-843.
https://doi.org/10.3390/cleantechnol3040048