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Single-phase quasi-Z source inverter (qZSI) needs large capacitance, and its switching loss is high when controlled by traditional SPWM. In this paper, a new modulation method for single-phase qZSI is proposed, which combines SPWM and pulse-width-amplitude modulation (PWAM), as a result of hybrid modulation. SPWM is employed at low dc-link voltage to avoid shoot-through state and act switching at...
The double-line-frequency (2ω) power ripple of single-phase quasi-Z-source (qZS) Photovoltaic (PV) inverter highly affects the whole system's design and performance. In this paper, a comprehensive modeling for single-phase qZS PV inverter is proposed, where the 2ω-ripple models of qZS inverter system served by real PV source are established and discussed on cases of with and without PV terminal capacitor...
A six-switch solid state variable capacitor (SSVC) with minimum dc capacitance is proposed. A variable ac capacitor (with capacitance variable from 0 to Cac) is conventionally realized by an H-bridge inverter and a large electrolytic dc capacitor with capacitance of 10 times the ac capacitance value, Cac to absorb the 2ω dc ripple. The proposed SSVC consists of a six-switch converter with two ports...
This paper presents a multilevel modular switched-capacitor dc-dc converter for high voltage gain and high power application with reduced component rating and count. For the traditional switched-capacitor dc-dc converters in high voltage gain application, the switching device or the capacitor has to suffer the high voltage stress. For the topology with reduced device and capacitor voltage stress,...
A new solid state variable capacitor (SSVC) with minimum dc capacitance is proposed. A variable ac capacitor (with capacitance variable from 0 to Cac) is traditionally implemented by an H-bridge inverter and a large electrolytic dc capacitor with capacitance of 20 times the ac capacitance value, Cac to absorb the 2ω dc ripple. The proposed SSVC consists of an H-bridge and an additional phase leg connected...
This paper proposes an analytic model to calculate the double fundamental frequency (2ω) voltage and current ripples for single-phase quasi-Z-source inverter (qZSI). The model enables the exact calculation of the 2 Ω components of the inductor current and the capacitor voltage, which is crucial for designing a single-phase qZSI system. A guideline for selecting the capacitance and inductance in quasi-Z-source...
This paper investigates the resonance issues occurring in an HVAC grid-connected offshore wind farm and then presents an active damping control strategy accordingly. The offshore wind farm composed of wind turbine generators, voltage source converters, step-up transformers and HVAC submarine cables is considered in this study. The entire system is modeled by per unit values and emulated by a scaled-down...
This paper proposes a bidirectional multilevel dc-dc converter for applications that require high voltage gain. Some of conventional multilevel dc-dc converters have diverse voltage or current stresses for the switching devices within the circuit, not suitable for modular configuration or for high efficiency demand; some suffer from relatively high power loss or large device count for high voltage...
A 260 kVA inverter has been developed with a passive soft-switching snubber. The main circuit configuration and prototyping are described. Optimization of the passive soft-switching snubber parameters has been made to control the voltage overshoot across the switches, minimize snubber and inverter losses, and effectively limit dv/dt and di/dt during activation. An efficiency higher than 98.5% has...
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