AC Line Conditioner Research Articles

Novel AC line conditioner for power factor correction

A new ac line conditioner is presented for high input power factor and clean ac output voltages for isolating the linear or nonlinear loads. A three-phase two-leg switching mode rectifier with neutral-point-clamped topology is proposed to draw the sinusoidal line currents from the ac mains. The carrier-based current controller is used in the inner control loop to track the line current commands with unity power factor. The dc bus voltage controller is adopted in the outer control loop to regulate the dc-link voltage. A voltage compensator is used to balance the neutral point voltage on the dc tank. A three-phase two-leg inverter with neutral-point-clamped topology is adopted in the system to provide the clean ac output voltages to the critical or sensitive loads. The carrier-based current control scheme is adopted to improve the instantaneous output voltages. Experimental results show the validity and effectiveness of the proposed control strategy.

An eight-switch three-phase VSI for power factor regulated shunt active filter

A three-phase neutral point clamped (NPC) inverter operated as a shunt ac line conditioner is presented. Eight power switches and four clamping diodes with voltage rating vdc/2 are used in the proposed inverter. The presented inverter can compensate current harmonics and reactive power generated from the nonlinear loads, and supply the demanded dc side power of the inverter. If there is no nonlinear load connected to the system, the adopted inverter is operated as a power factor pre-regulator. If there is no output load connected to the dc side of the inverter, the inverter is operated as a shunt active filter. If a nonlinear load is connected to the ac source and a dc load is connected to the inverter, the adopted inverter is operated as an integrated power quality compensator to draw the sinusoidal line currents from the ac mains. To supply the necessary active power for the dc side load and compensate the power losses of inverter, a proportional-integral (PI) controller is used to obtain the active power for the inverter. A space vector pulse-width modulation (SVPWM) is used to track the line current commands. Simulation and experimental results based on a laboratory scale-down prototype are presented to verify the effectiveness of the proposed control scheme.

AC power line conditioner with switch-clamped topology

A new AC line conditioner with high input power factor and clean AC output voltages for isolating the linear or nonlinear loads is introduced. An AC/DC rectifier with switch-clamped topology is adopted to draw the balanced sinusoidal line current from the AC supply system. A three-leg inverter with switch-clamped topology is adopted in the system to provide clean AC output voltages to the critical or sensitive loads. Experimental results show the validity and effectiveness of the proposed control strategy.

Three-phase four wire voltage controlled AC line conditioner with unity input power factor and minimised output voltage harmonics

The paper presents a new high performance AC line conditioner isolating any configuration of nonlinear loads for three-phase four wire applications. The proposed conditioner is composed of a switch mode rectifier (SMR) and a ROM based sinusoidal pulse width modulation (SPWM) inverter. The three-phase half bridge type SMR operates under voltage mode control. No current sensing is required. The inverter is also a half bridge type controlled by a ROM based SPWM modulator. Preoptimised SPWM control patterns rejecting the effects of DC link voltage ripples and dead times are programmed. Owing to the nature of the three-phase scheme, the voltage imbalance problem between the DC link capacitors can be lessened. High quality three-phase AC outputs can be obtained while nearly sinusoidal input currents are drawn.

Design and implementation of a 25-kVA three-phase PWM AC line conditioner

In this paper, an improved version of PWM AC line conditioners is proposed. As compared to previously reported structures, it uses fewer standard switch modules. This, in combination with less stringent gating requirements, improves the overall operating reliability of the system. In addition, it retains the same advantages of a regular force-commutated AC line conditioner, including sinusoidal input-output waveforms, fast dynamic response, and small input-output filters. The operating principle of the proposed structure is discussed, and the voltage feedback loop design is analyzed. Results from a 25 kVA experimental setup are provided for verification. >