Analysis Study of Fast Dynamic Response for Three-Phase Voltage Source Inverter

Abstract

The power inverter is a crucial device employed within power grids to convert direct current (DC) into alternating current (AC). In the context of high-power grid-connected photovoltaic (PV) power generation systems, three-phase inverters have demonstrated superiority over their single-phase counterparts. Specifically, a three-phase voltage source inverter (VSI) is employed for this application. The VSI operates with a consistent input voltage while ensuring that the output voltage remains unaffected by changes in the load. However, the conventional three-phase VSI has a notable drawback. Continuous voltage and current monitoring in each phase are required to maintain synchronous operation between the power inverter and the PV-power generation system. The conventional synchronous checking procedure is relatively complex, which affects the inverter's dynamic performance. Checking for synchronisation takes time and pushes the inverter to use a more advanced controller. This sophisticated controller is crucial to evaluate the control algorithm’s performance using the dynamic operation. To address these challenges, a current control strategy has been integrated into this project by implementing the synchronous reference frame current control (SRFCC) method with the proportional-integral (PI) controller. Furthermore, a synchronous reference frame phase-locked loop (SRF-PLL) is implemented in grid phase synchronisation to maintain a high-quality regulated current output. The effectiveness of this controller has been evaluated through simulations conducted using the PSIM software, providing insights into its operational behaviours and effectiveness within the project's context. According to the results obtained, it has been identified that the current control strategy with the three-phase grid-connected VSI that has been implemented in this paper is a fast dynamic response compared to the conventional inverter. The fast dynamic response inverter can reduce as much as 7.5% of the time required by the injected current to change from half-rated current to full-rated current and 2.5% of the time required by the injected current to change from full-rated current to half-rated current.