Solid-state switch-mode rectification converters have reached a matured level for improving power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input AC mains and precisely regulated DC output in buck, boost, buck-boost and multilevel modes with unidirectional and bidirectional power flow. This paper deals with a comprehensive review of improved power quality converters (IPQCs) configurations, control approaches, design features, selection of components, other related considerations, and their suitability and selection for specific applications. It is targeted to provide a wide spectrum on the status of IPQC technology to researchers, designers and application engineers working on switched-mode AC-DC converters. A classified list of more than 450 research publications on the state of art of IPQC is also given for a quick reference.

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A review of single-phase improved power quality AC-DC converters

A power semiconductor device includes trenches disposed in a first base layer of a first conductivity type at intervals to partition main and dummy cells, at a position remote from a collector layer of a second conductivity type. In the main cell, a second base layer of the second conductivity type, and an emitter layer of the first conductivity type are disposed. In the dummy cell, a buffer layer of the second conductivity type is disposed. A gate electrode is disposed, through a gate insulating film, in a trench adjacent to the main cell. A buffer resistor having an infinitely large resistance value is inserted between the buffer layer and emitter electrode. The dummy cell is provided with an inhibiting structure to reduce carriers of the second conductivity type to flow to and accumulate in the buffer layer from the collector layer.

Power semiconductor device

A system and method for combining power from DC power sources. Each power source is coupled to a converter. Each converter converts input power to output power by monitoring and maintaining the input power at a maximum power point. Substantially all input power is converted to the output power, and the controlling is performed by allowing output voltage of the converter to vary. The converters are coupled in series. An inverter is connected in parallel with the series connection of the converters and inverts a DC input to the inverter from the converters into an AC output. The inverter maintains the voltage at the inverter input at a desirable voltage by varying the amount of the series current drawn from the converters. The series current and the output power of the converters, determine the output voltage at each converter.

Distributed Power Harvesting Systems Using DC Power Sources

Selective harmonic elimination pulsewidth modulation (SHEPWM) method is systematically applied for the first time to multilevel series-connected voltage-source PWM inverters. The method is implemented based on optimization techniques. The optimization starting point is obtained using a phase-shift harmonic suppression approach. Another less computationally demanding harmonic suppression technique, called a mirror surplus harmonic method, is proposed for double-cell (five-level) inverters. Theoretical results of both methods are verified by experiments and simulations for a double-cell inverter. Simulation results for a five-cell (11-level) inverter are also presented for the multilevel SHEPWM method.

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Multilevel selective harmonic elimination PWM technique in series-connected voltage inverters

An electric drive apparatus and method for controlling medium-voltage alternating current motors wherein a multi-phase power transformer having multiple secondary windings provides multi-phase power to multiple power cells, each of which have a single-phase output and are controllable by a modulation controller. The primary and secondary windings in the power transformer may be star- or mesh-connected; the secondary windings may be shifted in phase. Because the power cells are connected in series, the maximum output voltage for each cell may be less than the maximum line-to-line voltage. The power cells can have a tri-state output which can be controlled using pulse-width modulation techniques. AC input power is converted to DC output power for each output phase. Output power modulation can be produced by interdigitating a selected number of carrier signals so that harmonic components reflected back to the input are attenuated.

Medium voltage PWM drive and method

A new current source inverter with sinusoidal output voltage and current is presented. Gate turn-off thyristors (GTO's) and pulsewidth modulation (PWM) control techniques are used in the current source inverter to produce the sinusoidal output voltage and current. Three capacitors are connected to the ac output terminals to absorb overvoltages which occur when the GTO current is cut off and to provide a filter function for reducing harmonics in the output current. Voltage spikes, which have been a serious problem in the practical application of this inverter, are suppressed by adding gate pulses which force the inverter into a state of shoot-through. Moreover, this inverter permits the capacitance of an ac output terminal capacitor for absorbing overvoltages to be reduced to one-tenth or less of that of a commutating capacitor in a conventional thyristor type current source inverter. A 3.7-kW induction motor is driven by the inverter. The motor efficiency and noise level are measured and compared with those obtained when the motor is driven by a conventional voltage source PWM inverter. An operating efficiency five or six percent higher and noise level 10 dB lower are obtained for the former. Therefore, this current source GTO inverter is very suitable for ac motor variable speed drives.

A New Current Source GTO Inverter with Sinusoidal Output Voltage and Current

With the application of gate turn-off thyristors (GTO's) and PWM control techniques, a current source inverter capable of producing sinusoidal input/output (I/O) voltages and currents has been developed. The sinusoidally modulated current is fed to the GTO's in the rectifier and inverter sections. The overvoltage-absorption capacitors connected to the ac input and output terminals function as a filter and, consequently, the waveforms of the input/output voltages and currents become sinusoidal. Because the PWM control utilizes the high-speed switching characteristics of the GTO's, the dc link current smoothing reactor and the overvoltage absorption capacitors are greatly reduced. The dc link voltage in the rectifier section is controlled to adjust the ac motor current. This is accomplished by using the firing angle shift method in conjunction with the method involving varying the width of the bypass gate pulses, which put the rectifier section into a bypass state. The current source GTO inverter is used to drive an 11-kW induction motor. As a result, excellent acceleration and deceleration characteristics are obtained, which verifies that the new current source inverter is quite suitable for driving an ac motor at variable speeds.

A Current Source GTO Inverter with Sinusoidal Inputs and Outputs

A large capacity (1-2 MkVA) driving system for variable-speed-driving an AC motor by a power converter (inverter, converter) in which GTO (gate turn-off) thyristors are used as switching devices. In this system, high frequency GTO thyristors are connected in series, power converters are multiplexed, the AC motor is used in its plural phases, instantaneous spatial vector PWM (pulse width modulation) control is performed, vector control for the motor is performed, and a circuit for recovering snubber energy for GTO thyristors and a power factor adjusting circuit are provided. Thus, this driving system provides a torque ripple of 1% or less, speed response of 60 rad/sec or more, efficiency of 95% or more and a power factor of 98% or more.

Large capacity variable speed PWM spatial vector type sub-harmonic system for driving AC electric motor

A power conversion apparatus has a circuit configuration in which a collector voltage of an IGBT is divided. It also has a unit which protects the IGBT against overvoltages applied to the collector by outputting a potential of a voltage dividing point to a gate of the IGBT. A case of a resistor on the high-voltage side of the voltage dividing point is fixed to an emitter potential of the IGBT.

Semiconductor power conversion apparatus

A power converter system includes: a circuit breaker (3a) having one terminal connected to a power system and another terminal connected to a load (20); a transformer (6a) for interconnection; a power converter (30); and a controller (50) for controlling the power converter, wherein, during a return to grid connected operation, the power converter is controlled such that the phase of an output voltage of the power converter matches the phase of the system voltage, and the circuit breaker is closed, so as to prevent an overcurrent during a changeover from the self commutated operation to the grid connected operation of the power converter.

Shigeta Ueda

Papers

A New Current Source GTO Inverter with Sinusoidal Output Voltage and Current

A Current Source GTO Inverter with Sinusoidal Inputs and Outputs

Large capacity variable speed PWM spatial vector type sub-harmonic system for driving AC electric motor

Semiconductor power conversion apparatus

Electric power transformation system and method for controlling power transformer