Asymmetric control of HF link soft switching converter for UPS and PV systems with bidirectional power flow

For the purpose of realizing a small site, light weight and low EMI power converter for a UPS or a PV system connected to the AC grid, this paper proposes a new type of power converter characterized by the following features: (1) electrical isolation from the AC system line by using a high frequency transformer, (2) totally soft switched operation using natural commutation principle without using a complicated resonant circuit topology, (3) ability for bidirectional power flow and instantaneous AC current control, and (4) improved power conversion efficiency by means of "asymmetric phase angle control scheme". Operating principles, some technical points to note, control method and operating modes are shown in detail. The experimental results to prove the total soft switching operation and the improved power conversion efficiency are also shown.