A single-phase-to-three-phase converter for a low-cost AC motor drive is proposed. The converter employs only six switches and incorporates a front-end half-bridge active rectifier structure that provides the DC link with an active input current shaping feature, which results in sinusoidal input current at close to unity power factor. The front-end rectifier in the converter permits bidirectional power flow and provides for excellent regulation against fluctuations in source voltage, facilitating regenerative braking of the AC motor drive. A control strategy that maintains a near-unity power factor over the full operating range and is easy to implement is described. Suitable design guides for the selection of filter components are presented. Simulation and experimental results that verify the developed theoretical models are also presented. >

A new single phase to three phase converter with active input current shaping for low cost AC motor drives

The performance of the parallel resonant power converter and the combination series/parallel resonant power converter (LCC converter) when operated above resonance in a high power factor mode are determined and compared for single phase applications. When the DC voltage applied to the input of these converters is obtained from a single phase rectifier with a small DC link capacitor, a relatively high power factor inherently results, even with no active control of the input line current. This behavior is due to the pulsating nature of the DC link and the inherent capability of the converters to boost voltage during the valleys of the input AC wave. With no active control of the input line current, the power factor depends on the ratio of operating frequency to tank resonant frequency. With active control of the input line current, near-unity power factor and low-input harmonic currents can be obtained. >

Characteristics of load resonant converters operated in a high-power factor mode

A parallel-resonant DC link (PRDCL) circuit topology is presented as a way to realizing zero-switching-loss, DC-AC high switching frequency power conversion. The circuit is used as an interface between DC voltage supply and the voltage-source PWM (pulse-width-modulated) inverter. It provides a short zero-voltage period in the DC link of the inverter to allow zero-voltage switching to take place in the PWM inverter. The peak voltage stress on the PWM inverter switches is limited to the DC supply voltage. Another significant advantage of the proposed circuit is that the inverter can be controlled by the conventional PWM strategy. The circuit is systematically analyzed, and its operation principle is explained in detail. Design considerations and formulae are also presented. A complete zero-voltage-switching DC-AC converter system consisting of the proposed circuit and the PWM inverter is simulated on computer. >

Parallel resonant DC link circuit-a novel zero switching loss topology with minimum voltage stresses

The performance of the parallel resonant converter and the combination series/parallel resonant converter (LCC converter) when operated above resonance in a high power factor mode are determined and compared for single-phase applications. When the DC voltage applied to the input of these converters is obtained from a single-phase rectifier with a small DC link capacitor, a relatively high power factor inherently results, even with no active control of the input line current. This behaviour is due to the pulsating nature of the DC link and the inherent capability of the converters to boost voltage during the valleys of the input AC wave. With no active control of the input line current, the power factor depends on the ratio of operating frequency to tank resonant frequency. With active control of the input line current, near unity power factor and low input harmonic currents can be obtained. >

Characteristics of load resonant converters operated in a high power factor mode

The main objective of this paper is to summarize the state of the art of power factor correction in off-line power supply systems. The study is only focused on equipment fed from a single-phase line and it covers theoretical aspects, control strategies, power topologies and future trends. The authors cover AC-DC converters, DC-DC converters in resistor emulators, multiplier approach control, average current mode control, variable hysteresis control, one- and several-switch power topologies, and soft switching. >

Jin He

Papers

Input-current shaping in line-rectification by resonant converters.