Dead Zone Generation And Balance Control Of DC Bus Capacitor Voltage Of Single Phase Active Neutral-point-Clamped Five Level Inverter

As consumption of energy growing rapidly,it becomes a common sense that great effort should be put into the developing of new energy,thus distributed photovoltaic generation draws extensive attention.One of the directions of distributed PV power generation is with transformer-less inverter.Works in this paper are carried out with the background of a single phase active-neutral-point-clamped five-level(5L-ANPC)inverter.Dead zone for the switching of output states and their digital control realization are analyzed.The mechanism of DC bus capacitors voltage imbalance is further discussed and the balance control strategy is proposed.Finally,simulation and experiment verification are reached.1.Firstly,operating principle of the selected topology is introduced.Abnormal output states which occur in the dead zone during output voltage switching are introduced.New dead time insertion patterns are given which eliminate the output error through current path control.Lastly,the soft switching introduced by the new method is analyzed.The energy loss of the selected typical active-neutral-point-clamped five-level inverters are analyzed and compared with each other.2.The usual digital generation of driving signals is briefly described,based on which the selecting method of corresponding output sequence and driving sequence is analyzed.Dead time problem between carrier period is analyzed and output sequence transfer diagram is generated.The output error introduced by the intermediate sequence is analyzed.The avoiding method is also given.3.The mechanism of DC bus capacitors' voltage imbalance for half-bridge inverter and its self-balancing capability is analyzed.The capacitor imbalance caused by closed-loop controller and the positive feedback effect are further illustrated.Several active and passive balancing strategies are introduced and a passive balance control strategy is developed.4.The experimental platform is briefly introduced.Experimental verification of control strategy is given.