光伏系统中逆功率检测方法分析-控制理论与控制工程专业论文.docxVIP

ABSTRACT Anti-reverse power flow Photovoltaic system can reduce the influence of the Photovoltaic system on the Grid, simplify the design of the system, and can work without storage batteries to reduce costs. The current reverse power detection and control system cannot avoid parts of the reverse power flowing back to the Grid because of a lack of fast reverse power detection method, causing operational safety of the Grid is threatened potentially. So a new algorithm is needed to detect reverse power as soon as possible. Firstly, the generation mechanism of the reverse power and current detecting algorithm is analysed, and a practical and fast reverse power detection algorithm is proposed. Main harmonics of the Grid are filtered out with the help of cascaded delayed signal cancellation algorithm (CDSC), and the parameters of fitting ellipse of voltage and current at the ppc is calculated by the least square-fitting of ellipses algorithm. According to the characteristic of ellipse fitting parameters shows different when the inverse power occurs or the Grid faults, a reverse power detecting and controlling algorithm is proposed. Then a Photovoltaic system and distribution network model is built with a new predictive direct power control strategy for the Photovoltaic inverter to verify the effectiveness of the algorithm. After that, the hardware and software of reverse power detection and control system is designed based on LPC1768 microcontroller and embedded operating system uC/OS-II. Finally, effectiveness of the algorithm is verified by the simulation on the MATLAB software, the simulation results show that the algorithm can detect the reverse power within a cycle distinguishing the reverse power from the Grid fault as well, and the algorithm has a good noise and harmonic robustness. Meanwhile, hardware and software of the reverse power detection and control system is tested, and experiment results have verified the correctness of the system. KEY WORDS：reverse powe