Maoh-Chin Jiang

A novel single-phase soft-switching unipolar PWM inverter

A novel single-phase soft-switching unipolar PWM inverter (SSUPI) using a simple auxiliary resonant unit is proposed. All main switches of high-frequency arm operate at zero-voltage-switching (ZVS) turn-on, while the auxiliary switches operate at zero-current-switching (ZCS) turn-off. All main switches of low-frequency arm operate at 60 Hz to greatly reduce switching losses. As a result, commutations of the main power devices occur with low losses. Consequently, higher efficiency is achieved. Moreover, a unipolar PWM scheme is used to reduce the output voltage harmonics. Some experimental results of the proposed SSUPI, rated 500 W and operated at 40 kHz, are presented for demonstration.

Analysis and design of a novel soft-switching three-phase inverter

A novel low cost four main switches and four auxiliary switches power converter configuration of the softswitching three-phase inverter is proposed in this paper. All main switches in the three-phase inverter operate at zero-voltage-switching (ZVS) turn on. The auxiliary switches operate at zero-current-switching (ZCS) turn on and turn off. Since the control circuits and the auxiliary circuits are thereby reduced to two sets, the reduction in the number of main switches can also increase the reliability. Thus, the proposed power converter configuration achieves low cost and high efficiency without changing device rate. The principle of operation, experimental results of the softswitching three-phase inverter, rated 600W and operated at 40kHz, are also provided to demonstrate the performance.

A novel single-phase soft-switching unipolar PWM shunt active power filter

This paper proposed a novel single-phase soft-switching unipolar PWM active power filter (SSUPAPF). The proposed active power filter uses a simple auxiliary resonant circuit. The main switches of high-frequency arm operate at zero-voltage- switching (ZVS) turn-on. Also, the auxiliary switches operate at zero-current-switching (ZCS) turn-off. The main switches of low-frequency arm operate at 60Hz to reduce switching losses. Moreover, a unipolar PWM strategy is used for the proposed SSUPAPF. This strategy results in a better input current waveform than for the bipolar PWM strategy. The advantages of the proposed SSUPAPF are found in efficiency improvement, reduced the voltage stresses, and greatly reduced EMI. Furthermore, the proposed active power filter achieves a unity power factor and a sinusoidal line current. Finally, some experimental results are presented for demonstration.

A ZVS-PWM voltage-doubler rectifier with high power factor

This paper proposes a new single-phase high power factor rectifier, which features regulation by conventional PWM, soft commutation and instantaneous average line current control. A zero-voltage-switching pulse-width modulation (ZVS-PWM) auxiliary circuit is configured in the presented ZVS-PWM rectifier to perform ZVS in the main switches and the passive switches. Furthermore, soft commutation of the main switch is achieved without additional current stress by the presented ZVS-PWM auxiliary circuit. A significant reduction in the conduction losses is achieved, since the circulating current for the soft switching flows only through the auxiliary circuit and a minimum number of switching devices are involved in the circulating current path, and the proposed rectifier uses a single converter instead of the conventional configuration composed of a four-diode front-end rectifier followed by a boost converter. Seven transition states for describing the behavior of the ZVS-PWM rectifier in one switching period are described. A prototype rated at 1 KW, operating 80 kHz, with an input AC voltage of 220 Vrms and an output voltage 400 Vdc has been implemented in laboratory. An efficiency of 96.7% and power factor over 0.99 has been measured. Analysis, design, and the control circuitry are also presented in this paper.

High-power-factor soft-switched DC power supply system

This paper proposes a dc power supply system to give high power factor and low current distortion on the rectifier side and provide stable dc voltage on the isolated dc/dc converter side. The proposed dc power supply system uses a new zero-voltage-switching (ZVS) strategy to get ZVS function. Besides operating at constant frequency, all semiconductor devices operate at soft switching without additional voltage stress. A significant reduction in the conduction losses is achieved, since the circulating current for the soft-switching flows only through the auxiliary circuit and a minimum number of switching devices are involved in the circulating current path, and the rectifier in the proposed dc power supply system uses a single converter instead of the conventional configuration composed of a four-diode front-end rectifier followed by a boost converter. An average-current-mode control is employed in proposed dc power supply system to detect the transition time and synthesize a suitable low harmonics sinusoidal waveform for the input current. A design example of 1000-W soft-switching single-phase dc power supply system is examined to assess the converter performance.

A soft-switching single-phase unified power quality conditioner

A soft-switching single-phase unified power quality conditioner (UPQC) using simple resonant units is proposed in this paper. In the proposed UPQC, all main switches operate at zero-voltage-switching (ZVS) turn-on and all auxiliary switches operate at zero-current-switching (ZCS) turn-off. The proposed UPQC consists of a soft-switching series active power filter and a soft-switching shunt active power filter. The soft-switching series active power filter can compensate the ac source voltage fluctuation. It can be used to regulate both the over-voltage and under-voltage situations. On the other hand, the soft-switching shunt active power filter can compensate the current harmonics and improve the power factor. Finally, some simulation results are presented for verification.

A novel single-phase soft-switching unipolar PWM rectifier

This paper proposed a novel single-phase soft-switching unipolar PWM rectifier (SSUPR) using a simple auxiliary resonant unit. All main switches of high-frequency arm operate at zero-voltage-switching (ZVS) turn-on, while the auxiliary switches operate at zero-current-switching (ZCS) turn-off. All main switches of low-frequency arm operate at 60 Hz to greatly reduce switching losses. Moreover, a soft-switching unipolar PWM strategy is used for the proposed soft-switching rectifier. This strategy results in a better input current waveform than for the bipolar PWM strategy. Furthermore, the proposed rectifier achieves a near unity power factor, sinusoidal input current and a bidirectional power flow capability. Some simulation results of the proposed SSUPR, rated 400 W and operated at 40 kHz, are presented for verification.

Analysis and design of a novel soft-switching single-phase dynamic voltage restorer

A novel soft-switching single-phase three-arm dynamic voltage restorer (DVR) is analyzed and designed. The proposed soft-switching three-arm DVR which can solve the abnormal voltage problems such as voltage swell, voltage sag, over-voltage, under-voltage and harmonics. The proposed scheme is composed of a three-arm topology which operates as a rectifier and an inverter. Rather than the conventional four-arm topology, the proposed three-arm topology not only reduces the number of main switches but also increases the system reliability and simplifies the control circuits. Using simple resonant units, all main switches of high frequency arm are operated at zero-voltage-switching (ZVS) turn-on, while all auxiliary switches are operated at zero-current-switching (ZCS) turn-off. Finally, some simulation results are presented for verification.

A single-phase DVR equipped with a high-frequency isolated soft-switching converter

This paper presents a single-phase dynamic voltage restorer (DVR) equipped with a high-frequency isolated soft-switching converter. The proposed DVR can maintain the load voltage stable and lower the harmonic distortion. Moreover, by using simple resonant units, all main switches are operated at zero-voltage-switching (ZVS) turn-on mode. Simultaneously, other auxiliary switches are operated at zero-current-switching (ZCS) turn-off mode. The advantages of this topology are reducing the switching losses and lowering the electromagnetic interference (EMI). On the other hand, by using a high-frequency isolated soft-switching converter instead of using a low-frequency isolation transformer can significantly reduce the weight and volume of the proposed DVR. And, the power density of the proposed device can be enhanced greatly. Finally, some results of the simulation are provided to verify the performance of the proposed DVR.

A soft-switching three-phase five-arm ac voltage regulator

This paper presents a soft-switching three-phase five-arm ac voltage regulator. It can solve the unusual voltage situations such as under-voltage, over-voltage, voltage sag, voltage swell and three-phase unbalanced source and load. Also, the proposed voltage regulator not only maintains a stable output voltage but corrects the input current to achieve a unity power factor. The proposed scheme combines a three-phase rectifier with a three-phase inverter in a common dc-link. Besides using simple resonant units, all main switches are operated at zero-voltage-switching (ZVS) turn-on. Furthermore, all auxiliary switches are operated at zero-current-switching (ZCS) turn-off. Rather than the conventional three-phase ac voltage regulator, which uses twelve main switches to construct a six-arm topology, the proposed soft-switching five-arm ac voltage regulator can reduce the number of main switches. Moreover, the reduction in the number of main switches not only can simplify the control circuit but also can increase the system reliability. In addition, a simple feed forward controller, based on the energy balance concept, is proposed to control the voltage of energy-storage capacitors. Since the energy change in the energy-storage capacitors can be fast compensated, the transient performance of the proposed voltage regulator can be improved. After all, some experimental results are presented to verify the feasibility of the proposed soft-switching three-phase five-arm ac voltage regulator.