| Popis: |
As the large amount of new energy accessed to the power system, the transient cut off of the new energy from the grid will have an inevitable influence on the power system, at the same time, various faults of the power system will have bad impact on the new energy system. This paper makes the photovoltaic generation system as the research object, and the research mainly focused on the low voltage ride through ability of photovoltaic station when the grid occurs three-phase short circuit fault and heavy load disturbance, which means the grid-connected inverters can not only keep on operation uninterrupted, but also injects the reactive current into the system, which can provide voltage support for the power system during the period of grid fault. Based on the foundation of traditional control strategy of low voltage ride-through of photovoltaic power station, a new control strategy of low voltage ride-through of photovoltaic inverter based on model current predictive control (MPC) is proposed in this paper. The discrete-time model of the inverter, filter, and load are used to predict the future behavior of the output currents for each of the eight possible switching states. This control method used the cost function to choose a switching state that minimizes the error between the output currents and their references. This control strategy has some advantages, such as, control system design is relatively simple, output currents can follow their references order quickly, so it has a good dynamic characteristic. Finally, three-phase short circuit fault and heavy load disturbance simulations have been carried out on the PSCAD/EMTDC platform, the simulation results show that during the low voltage of the system, the PV plant can support the voltage by providing reactive power. During the heavy load access into the system suddenly, grid-inverters can control the photovoltaic station inject certain reactive current into the power system and provide power for the heavy load nearby according to the orders, which can not only reduce the other reactive equipment investment, but also improve the transient stability of the power system. According to the study in this paper, the proposed method has been proved effective. |
