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作为微电网分布式电源的主要控制方式之一,PQ控制在不平衡电压下运行时会产生有功和无功功率的脉动现象。文中推导出有功脉动幅值和无功脉动幅值之间的关系,并进一步提出了控制功率脉动的微电网二级控制策略。该方案根据最优化理论,以功率脉动幅值为优化目标,以文中定义的功率脉动率和PQ控制的功率给定值为约束建立优化模型。通过拉格朗日乘子法将优化模型转化成非线性方程组求解,从而得到正负序电流的最优给定值,然后利用双电流控制可以达到同时减小有功和无功脉动的目的。仿真结果表明,该方案相对于传统控制向微电网注入的负序电流较小,且有效控制了有功和无功脉动。
As one of the main control methods of microgrid distributed power supply, PQ control can generate pulsations of active and reactive power when operating under unbalanced voltage. In this paper, the relationship between active pulsation amplitude and reactive pulsatile amplitude is deduced, and the secondary control strategy of microgrid to control power pulsation is proposed. According to the optimization theory, the optimization objective is to optimize the power ripple amplitude. The optimization model is established based on the power ripple rate defined in the paper and the power reference given by PQ control. Through the Lagrange multiplier method, the optimal model is transformed into the nonlinear equations to obtain the optimal given value of the positive and negative sequence currents, and then the dual-current control can reduce the active and reactive pulsations at the same time. Simulation results show that the proposed scheme has smaller negative-sequence current injected into the microgrid than traditional control, and effectively controls the pulsations of active and reactive power.