Research On Controllable Half-bridge LCLC Resonant Inverter For High Frequency Power Distribution System

HFAC PDS has been known as the effective alternative of DC PDS because of its excellent advantages as fewer conversion stages, high power density, high efficiency and faster response, which is more qualified for the demands of power distribution system as lower transmission loss, better stability, higher power level, longer distance, more loads and faster response. Single-phase DC/HFAC inverter acts as power side in HFAC PDS, and usually can be classified into two categories: full-bridege and half-bridege. Conventional inverter in SPWM has the following disadvantages: high switching frequency and absence of soft-switching. Conversely, resonant inverter is used in HFAC PDS widely. It is difficult to reach soft-switching for resonant inverter with full-bridge when applied in occasion of high input voltage and low output voltage. Resonant inverter with half-bridge is the efficient supplement for full-bridge, while the adjustable performance of output is limited. Besides, it is common for inverters worked in parallel due to the extension of power capacity and redundancy. In order to control easily, it is necessary to reach the decoupling of the output amplitude and phase.For the reasons above, a controllable half-bridge LCLC resonant inverter with dual-PWM modulation for HFAC PDS is proposed in this paper. The inverter has the following advantages: the adjustability of output voltage, the decoupling of the phase and amplitude in output voltage and soft-switching of switches in proper condition. This dissertation introduces the topology and its twelve operating modals divided as the different on-off state of switches, and analyzes the working processing of the inverter firstly. Then the adjustability of output voltage andthe decoupling principle of the phase and amplitude in output voltage is expounded, as well as the precondition and the processing of soft-switching. Switching network and resaonant netwoek are the essential parts for resonant inverter. This article studies the effects of the resonant network normalization parameters and control angle on the minimum control angle to ensure soft-switching, THD of the output voltage, and voltage regulation ratio by means of listing expression and drawing pictures. The steps and principles to determine the LCLC resonant parameters are summarized too. Lastly, the simulation model and experimental prototype is implemented to verify the features of the proposed inverter: the adjustability of output voltage, the decoupling of the phase and amplitude in output voltage and soft-switching of switches.