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链式动态电压恢复器(DVR)作为一种有效的改善电压跌落问题的设备,近年来已经逐步应用于电力系统中,用以改善用户的电能质量。为此,将级联多电平技术与载波移相技术相结合,针对6kV配电系统设计了5MVA无耦合变压器的11电平链式DVR,通过将级联多电平逆变器等效线性化,在传统单闭环控制系统基础上,在电压外环控制的同时,引入了耦合电容器的电流反馈,设计了双闭环控制器。针对任意时刻的电路故障,对其电压跌落做了系统的电压补偿仿真分析。研究表明,链式结构的DVR大大提高了功率单元的开关频率,谐波失真小、电压变化率低,满足了DVR对高电压质量的要求,采用双闭环控制策略,通过调整相应的控制参数可以提高电力系统的阻尼和稳定性,减小补偿电压的稳态误差,提高了DVR的响应速度和电压震荡等性能指标,有较高的实用价值。
Chain dynamic voltage restorer (DVR) as an effective device to improve the voltage drop problem in recent years has been gradually applied to the power system to improve the user’s power quality. Therefore, combining the cascaded multi-level technology and carrier phase shifting technology, a 5-MVA 11-level chainless DVR with no coupling transformer was designed for 6kV power distribution system. By cascading multi-level inverter with equivalent linearity Based on the traditional single closed-loop control system, the current feedback of the coupling capacitor is introduced while the control of the voltage outer loop is designed. The double closed-loop controller is designed. Aiming at the circuit fault at any moment, the voltage sag of the voltage sag was simulated and analyzed systematically. The research shows that the chain structure DVR greatly improves the switching frequency of the power unit, the harmonic distortion is small, the rate of voltage change is low, meets the requirements of DVR for high voltage quality, and the double closed-loop control strategy can be adopted by adjusting the corresponding control parameters Improve the damping and stability of the power system, reduce the steady-state error of the compensation voltage, and improve the performance index of the DVR such as the response speed and the voltage oscillation, which is of high practical value.