Li Jingxin

Design and experience of grid-connecting photovoltaic power system

This paper researches two photovoltaic power systems. One is 10 kW located in Beijing, the other is 100 kW located in north of Shanpsilaxi province of China. Both the Photovoltaic component array choice and the operations of grid-connecting photovoltaic power system are designed. For 10 kW Photovoltaic power system, this paper gives 3 whole year yield data and their analyses. The single phase transformerless grid-connecting inverters are applied to this system. The inverters have two-stage structure, DC-DC and DC-AC, but they often operates only with last DC-AC stage according to the panel string output voltage. For 100 kW photovoltaic power system, 3 phase transformerless grid-connecting inverters are used. This system is just built in this summer, practical operation data is few. To all systems, the weather is apparently the remarkable influence factor to yield, but other parameter settings can also do same business. The research shows the correlation. The output power quality of one inverter of 10 kW systems is analyzed, too.

An approach to improve efficiency of EV batteries charger under light load

This paper presented an approach to improve efficiency of EV batteries charger under light load. On the basis of analysis on the original charger built upon capacitor-diode-diode clamp circuit, a modified capacitor-diode-switching clamp circuit was designed to replace the original one in the full-bridge phase-shifted zero-voltage and zero-current-switching PWM DC/DC converter. Operating principle was introduced, and the critical condition to judge whether under light load was derived. Circuit simulation and experiment on the prototype were performed under different loads. Both results show that besides the advantages of the original topology, higher efficiency and less stress on switches are achieved under light load.