A efficiency optimization and loss balancing method for hybrid three-level active neutral point clamped inverter
摘要
Three-level active-neutral point-clamped (3L-ANPC) inverters have been widely used in medium and high power photovoltaic systems. But at present, 3L-ANPC inverters still suffer from the problems of complex modulation, difficulty in simultaneous high-efficiency and heat dissipation equalization. Therefore, this paper proposed a Si-SiC hybrid 3L-ANPC inverter circuit topology and modulation strategy. When the output voltage is clamped to the neutral point, the dual-branch continuity method of simultaneous conduction of the upper and lower bridge arms is adopted to effectively reduce the conduction loss; in addition, the introduction of the transition zero state adjusts the drive timing, so that the hard switching losses are concentrated in the two SiC MOSFETs to reduce switching losses and equalize the temperature of each switching tube at the same time. In this paper, the working principle of the proposed Si-SiC hybrid 3L-ANPC inverter is firstly introduced, then its loss model and thermal model are established and theoretically analyzed, and finally a three-phase ANPC experimental platform is built for experimental verification. The experimental results show that the efficiency of the device is improved by 0.8%, the switching tube junction temperature is reduced, and the loss and temperature distribution are balanced compared with the conventional 2-SiC scheme and 4-SiC scheme.