动态电压恢复器控制策略研究

电压补偿策略是关系动态电压恢复器(DVR)有效工作的最重要策略。首先,简述了跌落前电压补偿法、同相电压补偿法、最小能量补偿法等几种补偿方法,然后用相量图的形式详细地分析了上述几种补偿方法的原理。分析表明跌落前电压补偿法能保证跌落前后负载电压的连续性,但输出电压的幅值和功率不受控制;同相电压补偿法输出电压幅值最小、计算简单,但输出电压相角有偏移、功率不受控制;最小能量补偿法能优化输出的功率,但输出电压幅值比较大、相角有偏移。在此基础上提出了一种确定DVR最佳补偿点的方法,结合上述3种方法的优点,在电压跌落的不同的具体情况下寻找最佳补偿点。采用该控制方法的DVR节约了DVR直流侧存储的能量,延长了电压补偿的时间,同时避免了系统侧电压上升时引起能量倒灌导致直流侧过电压的威胁。仿真试验验证了该方法的有效性。

Control strategies of dynamic voltage restorer

As voltage compensation strategy is the main part of DVR(Dynamic Voltage Restorer),several compensation methods,such as pre-sag compensation,in-phase compensation and minimum-energy compensation,are introduced and their principles are analyzed in phasor diagram.Pre-sag compensation ensures the continuity of load voltage before and after voltage sag,but the amplitude and power of output voltage are out of control.In-phase compensation is simple in calculation and its output voltage amplitude is the smallest,but the phase angle of output voltage is offset and the power out of control.Minimum-energy compensation optimizes the output power,but the amplitude of output voltage is bigger and the phase angle offset.The optimal compensation method is proposed,which integrates the advantages of three methods above-mentioned to find the optimal compensation point according to different sag conditions.DVR applying the optimal compensation method saves the energy stored at DC side,extends the compensation time and avoids the danger of over-voltage at DC side caused by the energy feedback to DVR when system voltage rises.Simulation results verify the effectiveness of the presented compensation method.