基于无差拍控制的光伏电站低电压穿越技术的研究

Research on low voltage ride through of photovoltaic plant based on deadbeat control

随着光伏电站接入电网容量的不断增大,在电网发生扰动或故障情况下,光伏并网系统的脱网会进一步给电网带来不利影响。并网光伏电站应具备低电压穿越(Low Voltage Ride Through,LVRT)能力。在电流无差拍预测控制的基础上,对控制系统进行了改进。在低电压期间,通过发出无功功率支撑电网电压的恢复,采用限幅控制防止电流增大,投入并联卸荷电阻限制直流侧电压的升高,实现光伏电站的低电压穿越。最后采用新能源电力系统国家重点实验室中的光伏系统参数,建立仿真模型并进行了验证。结果表明在电网发生电压跌落时,控制系统能够抑制并网电流的增大并能发出无功功率支撑并网点电压,实现了低电压穿越,且系统在故障切除后能够快速恢复,验证了该LVRT控制策略的有效性,为下一步开展动模实验奠定了基础。

With the increasing of the capacity ofphotovoltaic plant grid integration, the photovoltaic plant＇s off-grid will have a more adverse influence on the grid under the grid disturbance or fault. The low voltage ride through （LVRT） capability is necessary for grid-connected photovoltaic plants. In this paper, the control system is improved based on the current deadbeat predictive control method. During low voltage of the system, the control means that increase reactive power to support the system voltage, use the current limiting control to prevent excessive current and put into shunt resistance to limit DC voltage are adopted to realize the LVRT of the photovoltaic plant. Then based on the photovoltaic system parameters of the State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources of China, the simulation model is founded. The simulation results show that the increase of grid current and DC voltage are effectively restricted and the system voltage is supported by the reactive power from the inverter, when the grid voltage drop occurs. The photovoltaic system can fast recover after fault clearing. The aim of LVRT is realized and the effectiveness of the control strategy is verified. It l^w ~ f,~,,,,,t^t~,,,, ~,,, A ：~ ~~.~~, ：