火电辅机变频器低压穿越直流电压补偿及其控制

针对火电辅机变频器因厂用电压跌落而触发闭锁,造成发电机组停机的问题,设计了基于变频器直流母线电压补偿的辅助穿越装置。辅机变频器采用直接转矩控制,低压穿越装置主电路采用三重交错并联升压变换器结构,在电压跌落期间维持变频器直流母线电压稳定,同时减小输出电流高频纹波。考虑到并联模块参数差异造成的均流问题,提出在传统电压电流双闭环控制的电压外环加入均流环的解决方法,消除环流,使开关管电流应力更为均衡。由于控制系统具有非线性、强耦合的特点,传统PI控制器存在局限性,所以利用模糊控制算法优化PI控制器参数整定,改善其性能。最后用仿真验证了所提方法的有效性。

DC Voltage Compensation and Control of Low Voltage Ride ThroughDevice of Power Auxiliary Inverter

In view of the problem that power generating unit will shut down due to the drop of the stationservice voltage, low voltage ride through (LVRT) device based on the inverter DC bus voltage compensation was designed. For the auxiliary inverter, direct torque control was adopted. For the main circuit of the LRVT device, ternary staggered parallel boost converter structure was used, which maintained the DC bus voltage stability during the voltage drop and reduced the high frequency ripple of the output current. Considering the current balancing problem of the parallel modules caused by parameter difference, current balancing loop was added to the outer loop of the traditional voltage and current doubleclosedloop control, so that the circulating current was eliminated and the current stress of switch devices was more balanced. Because of the nonlinear and strong coupling characteristics of the control system, conventional PI controller was limited, so fuzzy control algorithm was used to optimize the parameters of PI controller. Finally, simulation was carried out to prove the proposed method.