不对称电网下背靠背系统前端整流器的优化控制方法

An Optimal Control Method of Front-end Rectifier in the Back-to-back Systems Based on Asymmetric Grids

当三相电网不对称时,传统双闭环控制策略下直流侧和交流侧将分别产生偶数次和奇数次非特征谐波,从而会严重影响背靠背系统前端整流器的性能。针对这一问题,该文首先建立了电网不对称时背靠背前端脉宽调制(pulse width modulation,PWM)整流器的数学模型和功率模型,并根据瞬时功率理论分析了功率波动形式;然后提出了一种瞬时正、负序分离方法,该算法精度较高,延时较小;其次,考虑所使用功率管电流的限幅值,分析了电网不平衡对整流器带载能力的影响,并提出了PWM整流器优化控制策略,以整流器有功功率波动为零或者最小为控制目标。最后,搭建了实验平台,验证了该控制策略的有效性。

When a three-phase grid is unbalanced, its DC and AC sides contained even-numbered and odd-numbered non-characteristic harmonics based on the traditional double-loop control strategy, which can seriously affect the quality of rectifiers in the front of back-to-back systems. To solve this problem, the mathematical model and power mode of the rectifier in the front of back-to-back systems were established in this paper, and power fluctuations forms were analyzed according to the instantaneous power theory; Then a separation method of the instantaneous positive and negative sequence was proposed, the algorithm＇s accuracy was high, and delay was small; Considering the current limit of the power device, this paper analyzed the impact caused by unbalanced voltages on the rectifier load capacity and proposed a PWM rectifier optimal control strategy which was to maintain a constant or fluctuating minimum active power. An experiment platform was built in the laboratory, and results showed that the strategy was effective.