A study on the DC link voltage balancing for power conditioners based on cascaded H-bridges

In medium and high power field, cascade multilevel converter has been paid more attentions to research and application. When the cascade multilevel converters compensate reactive power and harmonic current, the control of the floating capacitor voltage has been being a hot research topic. So far, DC bus voltage balance control method can be divided into two groups: circuit balance and algorithm balance. The latter one is preferable from both cost and other aspects. Based on layered control algorithm, this paper focus on the voltage balance fundament and analyzes the process of DC capacitor's absorbing active power and releasing active power with the influence of converter's output pulse voltage. Based on this fundament, a new control method, voltage vector trimming in the parallel direction, is introduced. Compared with other DC voltage balance control methods, this method has the advantage of improving efficiency of DC voltage. At last, the simulation based on the tools of matlab/simulink is made. The simulation result results indict that this DC voltage balance control method functions well.