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Stability Improvement of LCL-Based Fuel Cell Power Quality Enhancement System Utilizing Phase Compensation of Current Regulator
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Majid Hosseinpour *1   , Rasoul Akbari1 , Mahdi Shahparasti2 |
1- Department of Electrical Engineering, University of Mohaghegh Ardabili, Ardabil, Iran, & Department of Electrical Engineering, University of Mohaghegh Ardabili, Ardabil, Iran,
2- School of Technology and Innovations, University of Vaasa, Vaasa, Finland & School of Technology and Innovations, University of Vaasa, Vaasa, Finland |
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Abstract: (441 Views) |
Grid-connected inverters are key devices for transferring power from distributed generation systems and renewable energy sources to the grid. To suppress current harmonics and enhance the quality of the injected power, various filters are employed, among which the LCL filter is widely used. However, due to the inherent resonance of the LCL filter, the variable impedance of weak grids can introduce disturbances at the inverter output, ultimately leading to system instability. The objective of this paper is to improve the power quality of a fuel-cell-based grid-connected system employing an LCL filter, using a control strategy based on grid-current feedback and active damping of the capacitor current. In this study, a grid-connected fuel cell power-conditioning system with an LCL filter is analyzed. The stable and passive behavior of the system is evaluated while considering the influence of current regulator phase delay. Furthermore, the design procedure and simulation results of the system under study are presented in detail.
The system under study is composed of an inverter is employed to connect the fuel cell to the grid. To eliminate the dominant harmonics at the inverter output, an LCL filter is implemented. The inverter control strategy incorporates grid-current feedback and active damping of the capacitor current. The filter parameters L1, C, and L2 correspond to the inverter-side inductor, filter capacitor, and grid-side inductor of the LCL filter, respectively. The grid impedance, which includes the transmission lines, transformer, and power factor correction capacitor, is modeled by an equivalent parallel Lg-Cg circuit. Since the output voltage of the fuel cell is insufficient for direct grid connection, a DC–DC converter is employed to step up the voltage level. Considering the characteristics of the fuel cell, this converter must operate with a continuous input current with very low ripple.In the current control loop, the grid current iL2 is regulated to be sinusoidal and synchronized with the point of common coupling (PCC) voltage. The PCC voltage (vPCC) is measured through a phase-locked loop (PLL) to ensure synchronization, where θ represents the detected grid voltage angle. This angle θ, combined with the reference current amplitude I∗, is used to generate the current reference (iref). The error signal between iL2 and iref is processed by the current regulator Gi. To damp the resonance of the LCL filter, the capacitor current feedback (iC) is fed back with a damping factor kd. Finally, the outputs of the current regulator Gi and the active damping term are combined to generate the modulation signal vM. Using digital pulse-width modulation (PWM), the corresponding gate signals for the power switches are produced. The proportional–resonant current regulator is denoted by Gi.To validate the accuracy of the theoretical analysis and the feasibility of the proposed control strategy, the required simulations have been carried out. The output power of the grid-connected fuel cell power-conditioning system is considered to be approximately 8.5 kW. In the first stage, the fuel cell voltage is boosted by means of a DC–DC boost converter. Subsequently, the DC-link voltage is injected into the grid through a grid-connected inverter equipped with an LCL filter. The inverter control strategy is based on grid-current regulation combined with active damping of the capacitor current. Moreover, to compensate for the phase delay in the control system, a phase-delay compensator is employed to enhance the quality of the injected power. To demonstrate the dynamic behavior of the studied system, the fuel cell input fuel flow is varied dynamically, so that the accuracy and effectiveness of the control strategy in injecting power proportional to the fuel cell’s generated power can be evaluated. Under full fuel flow, the system produces approximately 5.8 kW. When the fuel flow is reduced by 20%, the output power decreases to about 4.65 kW. Once the fuel flow is increased again, the generated power returns to its nominal value with appropriate dynamic performance.
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| Keywords: Grid-connected inverter, Fuel cell, Active damping, Phase compensator |
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Full-Text [PDF 875 kb]
(57 Downloads)
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Type of Study: Research |
Received: 2024/10/3 | Accepted: 2025/08/8 | Published: 2025/08/10
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Hosseinpour M, Akbari R, Shahparasti M. Stability Improvement of LCL-Based Fuel Cell Power Quality Enhancement System Utilizing Phase Compensation of Current Regulator. ieijqp 2025; 14 (2) :29-43 URL: http://ieijqp.ir/article-1-1013-en.html
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