多电平逆变器直流侧电容电压的平衡与控制

多电平逆变器能产生多阶梯、低失真电压波形，特别适合于大功率高电压场合。二极管箝位式多电平逆变器（DCMLI）因无需独立的直流电源来维持每级电压而备受青睐。但该逆变器存在直流侧电容电压的不平衡问题，因而未能在有功功率变换中得到广泛应用。针对这一问题，文中提出一种适用于n电平DCMLI的电容电压动态平衡控制算法，该算法基于空间矢量PWM(SVPWM)法，用电容电压偏差值与各冗余开关状态下的电容电流预测值的乘积作为衡量电容电压偏离其平衡基准值程度大小的准则，通过选取使电容电压偏离程度最小的冗余开关状态来维持电容电压平衡并产生所期望的输出电压波形，但同时要舍去某些导致电容电压本质不平衡的特殊空间矢量。以5电平DCMLI为例，仿真验证了该算法的有效性。

BALANCING AND CONTROL OF DC BUS VOLTAGE IN DIODE-CLAMPED MULTILEVEL INVERTERS

Multilevel inverters that provide more than two voltage levels and less distorted waveform offer many benefits for higher power or higher voltage applications. The Diode clamped multilevel inverter (DCMLI) does not require a separate DC power source to maintain voltage at each level and has been attracting wide industrial interests recently. However, it suffers from problems such as DC bus voltage unbalance and is not widely used in active power transfer. This paper presents a dynamic control algorithm, which can provide a selected output voltage waveform and balance the voltage across the DC bus capacitors in n level DCMLI. The proposed control method based on space vector pulse width modulation (SVPWM) methods uses the product of capacitor voltage deviation and its charging current as a criterion for determination of the switching state to be utilized. Some peculiar space vectors causing the capacitor voltages intrinsical unbalance must be canceled, however. Simulation results about a five level inverter are used to verify the efficiency of the control algorithm