L. Moran

Design aspects of synchronous PWM rectifier-inverter systems under unbalanced input voltage conditions

The effects of input line voltage unbalance are analyzed, starting with the distortion in the input line currents and extending to the DC bus components and inverter output line voltages and currents. Analytical results are used to obtain system design curves as a function of the input voltage unbalance for all major system components. Key predicted results were verified on a 2 kVA prototype unit.<<ETX>>

A refined PWM scheme for voltage and current source converters

A pulse-width-modulation (PWM) scheme that uses the converter switching frequency to minimize unwanted load current harmonics is described. This results in the reduction of the number of switch communications per cycle. The method is suitable for high-performance variable-speed AC-motor drives that require high-output switching frequencies for near-silent operation. It is also applicable, without change, to voltage or current-source inverters and to two and four-quadrant three-phase PWM rectifiers. Key predicted results have been verified experimentally on a 5 kVA inverter breadboard.<<ETX>>

A solid-state high-performance reactive-power compensator

A high-performance reactive-power compensator is presented and analyzed. The VAR compensator consists of a three-phase current-regulated pulse width modulated voltage-source inverter connected to a self-controlled DC bus. Reactive-power compensation is achieved by forcing the inverter output current to follow a reactive sinusoidal reference waveform at a constant switching frequency. The main advantages of this scheme are that it reduces the stresses on the switching devices (as compared with other current regulated techniques), and it has a fast response time, which allows almost instantaneous reactive current control, and low harmonic distortion in the line currents. In particular, the authors discuss the proposed scheme in terms of principles of operation, power and control system design, and the analysis under transient operating conditions. Simulated results obtained with the Spice simulating package for steady-state and transient operating conditions are presented and validated on an experimental unit. >

A three-phase solid-state voltage compensator system

A three-phase solid-state voltage compensator system which employs a three-phase pulse-width-modulated (PWM) voltage-source inverter is presented and analyzed. This system can compensate for undervoltage, overvoltage and voltage unbalances produced by the AC mains. It also significantly improves the AC mains input power factor and substantially reduces any line-current harmonic generated by nonlinear loads. The paper discusses the proposed voltage compensator system in terms of principles of operation and power circuit design. The predicted results are verified experimentally.

A solid state VAR compensator with fast dynamic response

The performance of a three-phase solid-state reactive power compensator with fast dynamic response is analyzed. The compensator consists of a three-phase pulse-width-modulated voltage-source inverter connected to a self-controlled DC bus. The principal advantage of this scheme is that it can maintain a near-unity source power factor without sensing and computing the associated reactive power component. It can also substantially reduce the harmonic content of the input line current when the load is nonlinear. A mathematical model for the compensator connected across a variable power factor load is derived. The frequency response is obtained for open-loop operation which allows for design of the controller. Predicted results are verified experimentally.<<ETX>>

Analysis and design of a novel 3- phi solid-state power factor compensator and harmonic suppressor system

A three-phase solid-state power-factor-compensation scheme is presented and analyzed. This scheme employs a PWM voltage-source inverter and has two important features: it can maintain a near-unity mains input power factor without sensing and computing the associated reactive power component, and it can substantially reduce any line current harmonics generated by nonlinear loads. The proposed scheme is discussed in terms of principles of operation, power system design, and analysis under unbalanced operating conditions. Predicted results are in agreement with experimental results.<<ETX>>

A solid state high performance reactive power compensator

A high performance reactive power compensator is presented and analyzed. The volt-ampere reactive (VAr) compensator consists of a three-phase current-regulated pulse width modulated voltage-source inverter connected to a self-controlled DC bus. Reactive power compensation is achieved by forcing the inverter output current to follow a reactive sinusoidal reference waveform at a constant switching frequency. The scheme is discussed in terms of principles of operation, power and control system design, and the analysis under transient operating conditions. Simulated results obtained with the PSpice simulation software package for steady-state and transient operating conditions are presented.<<ETX>>

Analysis and design of a 3-phase current source solid-state VAR compensator

A Reactive Power Condensation (RPC) system which employs a three phase current source foræ-conoomutated FWM rectifier is presented and analysed in this paper. Pulse width modulation is also investigated as a means of reducing the size of reactive components. The proposed RPC system can compensate for leading and lagging displacement power factor. Other areas of investigation include selection of rectifier input and output filter components and closing of the loop around the reactive power æmmand signal. Finally, predicted results are verified experimentally.