不平衡电网电压下光伏并网逆变器滑模直接电压/功率控制策略

摘要

不平衡电网电压下，光伏并网逆变器的输出功率和输出电流都将产生波动，给电力系统的稳定运行造成不利影响。根据光伏并网系统的数学模型，提出了光伏并网逆变器基于滑模控制的直接电压/功率控制策略。该控制策略可在电网电压不平衡时有效抑制并网逆变器输出有功功率和无功功率的波动。根据光伏并网逆变器输出功率和正、负序电流的关系，提出了以消除负序电流为控制目标的改进控制策略。此外，为提高系统的运行性能，提出了功率电流协调控制策略。最后，对所提出的控制策略进行了仿真分析，仿真结果验证了所提出控制策略的有效性。%Under unbalanced grid voltage, second order pulsation component will appear in the output power and the output current of the PV grid connected inverter, which will affect the stable operation of the power system. Based on the mathematical model of PV grid connected system, this paper proposes a direct voltage/power control strategy based on sliding mode control (SMC) for the PV grid connected inverter. When the grid voltage is unbalanced, the control strategy can effectively suppress the power oscillation in the active and reactive power. According to the relationship between the output power and the positive/negative sequence current of the PV grid connected inverter, an improved control strategy is proposed to eliminate the negative sequence current. In addition, a power/current coordinated control strategy is proposed to improve the operating performance of the PV system. Finally, simulation analysis is carried out, and the results verify the effectiveness of the proposed control strategy.