具有低开关频率特性的指定谐波抑制预测控制方法研究

Predictive Control of Specified Harmonic Suppression Switching Strategies With Low Switching Frequency Characteristics

为了避免器输出波形中低次谐波对孤岛型微电网的电压质量产生严重影响,需尽可能减少其谐波失真含量。同时,为提高逆变效率,还需降低开关损耗,令逆变器保持在低开关频率的工况下。模型预测控制相较于脉宽调制策略的灵活性更高,动态性能更好,常与其他优化算法结合,以获得所需控制效果。因此,该文提出一种具有低开关频率特性的预测控制指定谐波抑制开关策略,采用该策略可以减少输出电压信号低次谐波含量,有效抑制谐波畸变,同时可以有效降低系统的开关频率。针对未来时刻电压状态谐波提取相互独立的特点,将并行计算方法的思想引入预测控制中,提高系统的在线实时性。在两电平逆变器实验平台上进行测试,验证了该方法的正确性以及控制策略的有效性。相比指定谐波消除脉宽调制策略,所提方法能在线实时生成稳定的逆变器开关序列,证明了该控制策略不仅能在低开关频率工况下有效抑制低次谐波,而且具有良好的动态性能。

In order to avoid the severe impact of low harmonics of the inverter output waveform on voltage quality of the islanded microgrid,the amount of harmonic distortion needs to be reduced as much as possible.At the same time,switching losses need to be reduced in order to increase inverter efficiency and keep the inverter at a low switching frequency.Model predictive control is more flexible and has better dynamic performance than pulse width modulation strategies,and it is often combined with other optimization algorithms to achieve the desired control effect.Therefore,in this paper,a predictive control specified harmonic suppression switching strategy with low switching frequency characteristics was proposed to reduce the low harmonic content of the output voltage signal and effectively suppress harmonic distortion.At the same time,the switching frequency of the system could also be effectively reduced.And the idea of parallel computing method was introduced into the predictive control for the characteristics of mutually independent voltage state harmonic extraction at future moments to improve the online real-time performance of the system.The correctness of the method and the effectiveness of the control strategy could be verified by testing on a two-level inverter experimental platform.Compared with the specified harmonic elimination PWM strategy,the proposed method can generate a stable inverter switching sequence online and in real time,proving that the control strategy is not only effective in suppressing low harmonics at low switching frequency operating conditions,but it also has good dynamic performance.