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传统两电平有源电力滤波器(active power filter,APF)由干功率开关耐压水平和载流能力的限制,难以实现对高压大容量非线性负载的谐波补偿。在高压大容量系统中,二极管钳位型三电平变换器得到了广泛的应用。对三电平APF进行研究,提出一种母线电压闭环数字控制策略。在同步旋转dq坐标系下,将三电平APF母线电压控制系统分为电压外环和电流内环2部分。在电压外环中,采用自适应滤波器求出直流侧电压平均值,采用PI控制器产生有功指令电流维持直流侧电压恒定。在电流内环中,针对三电平APF直流侧中点电位不平衡问题,从空间矢量PWM调制方法的角度出发,对中点平衡问题进行仔细研究,提出一种简单的中点电压平衡控制策略,只需检测各相电流和中点电压波动的方向,对小矢量进行取舍实现APF中点电位平衡控制。实验结果表明了所提出算法的正确性和有效性。
The traditional two-level active power filter (APF) is limited by the voltage level of the dry power switch and the current carrying capacity, so it is difficult to achieve the harmonic compensation for the high-voltage large-capacity non-linear load. In the high-voltage high-capacity system, diode-clamped three-level converter has been widely used. The three-level APF is studied and a closed-loop digital control strategy of bus voltage is proposed. In the synchronous rotation dq coordinate system, the three-level APF bus voltage control system is divided into two parts: voltage outer loop and current inner loop. In the voltage outer loop, adaptive filter is used to find the average value of the DC voltage, and the PI controller is used to generate the active command current to maintain the DC voltage constant. In the current inner loop, in view of the potential imbalance at the mid-point of the three-level APF DC side, from the perspective of space vector PWM modulation method, the problem of mid-point balance is carefully studied and a simple midpoint voltage balance control strategy , Only need to detect the direction of each phase current and midpoint voltage fluctuations, the small vector to choose the APF midpoint potential balance control. The experimental results show the correctness and validity of the proposed algorithm.