Research On Reverse Power Flow Detection Algorithm In PV Power System

Anti-reverse power flow Photovoltaic system can reduce the influence of thePhotovoltaic system on the Grid, simplify the design of the system, and can workwithout storage batteries to reduce costs. The current reverse power detection andcontrol system cannot avoid parts of the reverse power flowing back to the Gridbecause of a lack of fast reverse power detection method, causing operational safetyof the Grid is threatened potentially. So a new algorithm is needed to detect reversepower as soon as possible.Firstly, the generation mechanism of the reverse power and current detectingalgorithm is analysed, and a practical and fast reverse power detection algorithm isproposed. Main harmonics of the Grid are filtered out with the help of cascadeddelayed signal cancellation algorithm (CDSC), and the parameters of fitting ellipse ofvoltage and current at the ppc is calculated by the least square-fitting of ellipsesalgorithm. According to the characteristic of ellipse fitting parameters shows differentwhen the inverse power occurs or the Grid faults, a reverse power detecting andcontrolling algorithm is proposed. Then a Photovoltaic system and distributionnetwork model is built with a new predictive direct power control strategy for thePhotovoltaic inverter to verify the effectiveness of the algorithm. After that, thehardware and software of reverse power detection and control system is designedbased on LPC1768microcontroller and embedded operating system uC/OS-II.Finally, effectiveness of the algorithm is verified by the simulation on theMATLAB software, the simulation results show that the algorithm can detect thereverse power within a cycle distinguishing the reverse power from the Grid fault aswell, 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.