基于暂态功率特性调整无功电流的高电压穿越控制策略

传统的光伏并网逆变器高电压穿越控制策略以削减有功功率为代价提高无功输出,难以平衡网侧电流和直流母线电压、抑制故障切除后电流和电压突变带来的暂态冲击。在分析高电压暂态功率特性的基础上,提出一种维持有功功率输出不变、调整无功电流参考值的高电压穿越控制策略。首先,以小信号模型分析高电压暂态功率特性,得出高电压期间有功功率不变、网侧无功冗余是抑制电压恢复的关键;然后,依据电网电压骤升幅度给出一种估算无功电流参考值的方法;在此基础上,结合有功电流控制,讨论3种不同电网电压骤升幅度下并网逆变器的控制能力,分别给出相应的高电压控制策略;最后,仿真和实验验证了所提控制策略的有效性。

Control Strategy of High Voltage Ride Through for Adjusting Reactive Current Based on Transient Power Characteristics

Traditional control strategy of high voltage ride through (HVRT) for photovoltaic (PV) grid-connected inverter (GCI) improves reactive power output at the cost of reducing active power, which is difficult to achieve a balance between grid-side current and DC bus voltage. And it suppresses the transient impact caused by sudden voltage and current changes after the fault removal. Based on the analysis on the transient power characteristics of high voltage, an HVRT control strategy that maintains active power output and adjusts the reference value of reactive current is proposed. Firstly, a small-signal model is used to analyze the transient power characteristics of HVRT, which reveals that the key of suppressing voltage recovery is the constant active power and reactive redundancy on grid side. Secondly, a method for estimating the reference value of reactive current is proposed according to the voltage surge amplitude. On this basis, by combining with active current control, the control capacity of the GCI with three different voltage surge amplitudes is discussed, and the control strategies of HVRT are given respectively. Finally, the simulation and experiments verify the effectiveness of the proposed control strategies.