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Summary: In this work, an isolated modular resonant circuit with effective voltage regulation is presented as front‐end for multilevel inverter system to interface renewable sources of energy with micro grid. Inputs of each module of the converter are connected to low‐voltage DC sources. Modular‐structured module outputs may be linked in sequence or parallel to attain the desired DC link capacitor voltage for multilevel inverter. The proposed converter overcomes imbalance in the capacitor voltage of diode‐clamped inverter structure. Interleaved phase shift of 90° is supplied among the gate pulses of all four modules that minimizes the input‐side current ripples. An effective zero voltage switching (ZVS) is achieved over wide load range using duty cycle and frequency‐duty cycle double control method to improve system performance at light load condition. Adopting powder core magnetics and low forward voltage insulated‐gate bipolar transistors (IGBTs) reduces magnetic and conduction loss. A 12‐kW prototype of the designed modular resonant converter was verified by experimentation with a different‐level diode‐clamped inverter structures. [ABSTRACT FROM AUTHOR]

An optimized resonant converter with zero-voltage switching over an extensive range of loading is proposed to integrate renewable energy sources to an onboard charger. In conventional resonant circuit, high-frequency transformer (HF) parasitic components are used as tank circuit, this degrades the performance due to non-optimal magnetic components. Here, the HF transformer is fabricated with optimized resonant tank circuit shunt branch inductance ($L_p$) as magnetizing inductance, hence eliminating the need for shunt branch inductance. The proposed resonant converter circuit design is optimized for minimum kilovoltampere rating and better voltage regulation with both duty cycle and frequency control (mixed control method). Furthermore, the performance of the converter at a very light load is improved using the proposed control method. Incorporating a low- $R_{\text{DS}}(\text{ON})$ silicon carbide mosfet and softly turning off the switches for a wide load variation minimizes conduction and switching losses and improves efficiency. Using powder core for the design of the tank circuit reduces magnetic losses. A 3-kW prototype of the converter is built to verify the performance from no load to full load. The highest efficiency of the proposed converter is 98.6%, attained at 50% full load. [ABSTRACT FROM AUTHOR]

A two-stage grid-tied efficient solar photovoltaic (SPV) system with zero voltage switching (ZVS) and zero current switching (ZCS) at the dc–dc converter stage and adaptive synchronization at the inverter stage is proposed. In the first stage, an improved high step-up boost-integrated flyback converter with quasi resonant voltage multiplier cell is proposed. ZVS turn-on of all mosfets and ZCS turn-off of all diodes of resonant voltage multiplier cell results in high efficient power conversion compared with the conventional boost-integrated flyback converters. Small-sized coupled inductor enhances magnetic utilization in this converter. Second stage consists of a single-phase H-bridge grid interfaced inverter with variable band hysteresis current control technique. Amplitude adaptive notch filter is used to extract fundamental unit voltage vector of grid voltage required for estimation of synchronized reference current for hysteresis controller. A 250 W laboratory prototype is developed and experimentally evaluated. Experimental results demonstrate efficient renewable energy conversion at dc–dc converter stage and quality power injection at dc–ac inverter stage of the proposed grid-tied SPV system under changing solar insulation levels. [ABSTRACT FROM PUBLISHER]