In high frequency AC (HFAC) distribution system, the resonant inverter is used to improve power quality and keep the stability of the output AC voltage. Aiming at the problems of poor output power quality and slow transient performance caused by unreasonable filter parameter design and load change during inverter operation, a single-phase H-bridge LCLC resonant inverter based on analog circuit controller implement is introduced in this paper for HFAC power distribution system (PDS). In this study, to design harmonic compensator and analyze the responsiveness of the inverter, it is necessary to analyze the output voltage total harmonic distortion (THD) of LCLC resonant inverter and the performance of the open loop system in detail. On the one hand, a proportional-integral-resonant (PIR) controller is designed to maintain the zero static error of the voltage output and suppress the output voltage THD of LCLC resonant inverter. On the other hand, an integral controller combines with phase-shift modulation (PSM) method is presented to effectively improve the transient performance of resonant inverter and provide the fixed frequency of the output voltage. On the basis of the above, the experimental prototype is implemented with the output AC voltage root mean square of 28 V, and the output voltage frequency for resonant inverter is equal to switching frequency. A rated output power of 130 W experimental platform is built to verify the effectiveness of the theoretical analysis, control strategy, and modulation method.

A three-phase three-level transformerless T-type grid-connected inverter system with three-level boost maximum power point tracking converter is introduced in this article for high-voltage high-power applications. First, the mathematical model of grid-connected photovoltaic inverter system is built. Second, a multiloop interleaved control scheme is proposed for three-level boost maximum power point tracking converter to reduce the ripple of the inductor current and balance the capacitor voltage of DC bus. A predictive current control method and a power feedforward strategy are also proposed for the T-type three-level inverter part to reduce the harmonic content of grid-connected current and to improve the dynamic response of the system, respectively. In order to solve complex algebraic computation of traditional space vector pulse width modulation or multi-carrier pulse width modulation method, a single-carrier pulse width modulation method is presented for T-type three-level inverter. Finally, all control strategies and modulation method are implemented on a single-chip digital signal processor. A high conversion efficiency, low cost, and low harmonic current could be obtained on a 23-kW experimental prototype.

Taking two power cells cascaded as an example, a PWM algorithm is proposed for single-phase cascaded H-bridge three-level converter. Rectification operating mode of the three-level converter is described in detail in this paper. In order to lower the switching frequency and balance the capacitor voltage, the output voltage vectors are optimal selected for the rectification operating modes, and the proposed PWM is verified by simulation and experiment, the algorithm is general, simple and easy to digital realization. The simulation and experimental results prove its validity and feasibility.