Research On The Single-Phase Cascade Inverters

Topology and principle of the single-phase cascade inverters for the modularized ASI is introduced in this paper. Comparing several PWM technologies, the Carrier-Phase-shifted SPWM technology is adopted. The volume of the output filter can be reduced greatly in cascade inverter with Carrier-Phase-shifted SPWM technology which has a high equivalent switching frequency and a good output sine wave. In order to meet the need of stability and dynamic characteristic, a multi-loop closed control strategy, which is the voltage effective value feedback, voltage instantaneous value feedback and inductance current feedback, is adopted. This multi-loop closed control strategy is analyzed and simulated. The implementation strategy is using digital and analogous hybrid control. The voltage effective value loop is realized by DSP, while the voltage instantaneous value and inductance current loops are realized by analogous circuit. The design of CPLD which simplified signal-phase cascade inverter circuit is also introduced in this paper. A experimental prototype is accomplished and validates its stability, external characteristic and dynamic characteristic.To simplify structure of the modularized ASI, a half-bridge DC/DC transformer with zero voltage switching (ZVS) is presented at the end. The converter is characterized by simple structure, ZVS, low switch voltage stress, high efficiency and high reliability. The cascade inverter, supplied by this DC/DC transformer, is analyzed and simulated. Results validate that output sine wave can attain the expected request. However, it makes much more demands for ability of adjusting voltage to control circuit.