交直流混合微电网双向接口变换器模型预测控制

A Model Predictive Control Method for Bidirectional Interfacing Converters in Hybrid AC/DC Microgrids

针对双向接口变换器在交流侧三相不平衡状态下出现的直流侧电压振荡型波动、正序电压相位检测困难、有功功率和无功功率计算不准确的问题,提出了一种直接功率模型预测控制方法。首先,利用瞬时电压、电流向量建立系统瞬时功率向量预测模型,以省略功率计算的锁相环节,避免电压相位检测不准确对控制性能的影响;其次,为功率向量的实部和虚部分别设计参考量,抑制实部中负序分量引起的二倍频功率波动,以避免直流侧电压振荡型波动;最后,以功率向量的实部和虚部作为控制单元,分别设计目标函数,消除两者间的相互影响,同时,在目标函数中设计开关频率约束项,使得被控器件开关频率可调。仿真和实验结果表明,所提控制方法可实现无功功率参考变化时,有功功率不受影响,相比于传统PWM方法,有功功率超调量下降了约74%,且该方法可保证系统全功率因数运行,系统直流侧无振荡型波动。

A model predictive control strategy is proposed to solve the inevitable DC voltage oscillation,inaccuracy phase information of positive voltage,unclear calculation of the active and reactive power of the bidirectional interfacing converters in three-phase unbalanced condition.Firstly,an instantaneous power vector predictive model is built by using instantaneous voltage and current vector to omit the phase-lock-loop and to avoid the effect of inaccurate voltage phase detection;Secondly,power references are designed for the real and imaginary components of the power vector,respectively,to restrain the double-frequency power caused by the negative sequence component and to eliminate the DC voltage oscillation;Finally,objective functions are designed for the real and the imaginary components of power vector,respectively,to avoid the interaction between them,and a switching frequency limitation part is included in objective functions to make the switching frequency tunable.Simulation and experimental results show that the active power is not influenced by the change of reactive power.A comparison with the traditional PWM method shows that the proposed method reduces the overshoot of active power by about 74%,the power factor is regulated to 1,and the DC voltage oscillation is eliminated.