光伏直流升压场站并网整体协同低电压穿越控制策略

光伏直流升压汇集场站中，光伏列阵经DC/DC升压后汇集，再由DC/AC换流站逆变后接入交流电网。对于多个光伏直流升压场站并网系统，并网DC/AC换流站输出无功电流大小受自身容量与端口电压跌落程度影响，在协调机制不明确情况下，无功整定困难，靠近故障的场站存在脱网风险。为此，在分析各DC/AC换流站无功出力对端口电压影响的基础上，提出了光伏直流升压场站并网系统整体协同低电压穿越控制策略。进入低穿后，DC/AC换流站检测本地端口电压，立即向电网注入无功进行支撑；总控站利用通信获知各换流站的端口电压，进而协调各换流站的无功电流输出额度。同时，在分工况细化协调机制的基础上，对DC/AC换流站无功电流输出进行通用化整定。仿真结果表明，所提控制策略在交流电网发生故障时，能有效协调各DC/AC换流站进行无功补偿，提高系统整体低电压穿越能力。

Overall coordinated low voltage ride-through control strategy for grid connection of a photovoltaic DC booster station

In a photovoltaic DC boost collection station, the photovoltaic array is collected after DC/DC boost, and then connected to the AC power grid after being inverted by the DC/AC converter station. For the grid-connected system of multiple photovoltaic DC voltage boosting stations, the output reactive current of the grid-connected DC/AC converter station is affected by its own capacity and the voltage drop degree of the port. Under the unclear coordination mechanism, it is difficult to set the output reactive power, and there is a risk of disconnection of the station near the fault. Therefore, based on the analysis of the influence of the reactive power output of each DC/AC converter station on the port voltage, an overall cooperative low voltage ride-through control strategy of the grid-connected system of the photovoltaic DC voltage boosting station is proposed. After entering the low voltage ride-through, the DC/AC converter station detects the local port voltage and immediately injects reactive power into the power grid for support. The master control station obtains the port voltage of each converter station through communication, and then coordinates the reactive current output quota of each converter station. At the same time, the reactive current output of the DC/AC converter station is adjusted by a detailed coordination mechanism under different working conditions. The simulation results show that the proposed control strategy can effectively coordinate the reactive power compensation of each DC/AC converter station and improve the overall low voltage ride-through capability of the system when the AC power grid fails.