A.D. le Roux

Digital control of an integrated series active filter and diode rectifier with voltage regulation

The integration of a series active filter with a 12-pulse diode rectifier can provide a cost-effective and efficient means of supply current harmonic-free AC/DC conversion. Controlling the series active filter as a frequency-selective impedance requires low delays and is not well suited for digital control. This paper suggests a current-mode control strategy to allow full digital control of the active filter. The suggested current-mode control method for supply current balancing and voltage regulation is verified experimentally.

An integrated controller module for distributed control of power electronics

This paper introduces the concept of a module controller. The module controller integrates the control unit, power supply, measurement unit and communications link into the IGBT module, or as a standard add-on module. The benefits of this is both financial, technical and include lower manufacturing and design cost, increased reliability and ease of maintenance of the system as a whole.

Novel Direct Flux and Direct Torque Control of Six-Phase Induction Machine With Nearly Square Air-Gap Flux Density

In this paper, a novel control method for a six-phase induction machine with nearly square air-gap flux density is proposed and evaluated. In this method, the stator phase windings alternately act as either flux- or torque-producing phases. In this way, the flux and the torque of the induction machine are directly controlled with no vector transformation used. Theoretical and finite-element analyses are used to calculate, among other things, the torque and the decouple control constant of the drive. The steady-state measured results of a small six-phase induction machine drive with the proposed control scheme implemented show good agreement with calculated results. The proposed control drive system is also shown to have a fast torque response.

A 1.5-MW Seven-Cell Series-Stacked Converter as an Active Power Filter and Regeneration Converter for a DC Traction Substation

A prototype 1.5 MW series-stacked converter system was built and installed at a dc traction substation. The converter inverts energy generated by slowing an electric train using regenerative braking. The regenerated energy is fed into the local ac network at the dc substation. A secondary function of the converter is to perform active power filtering (APF) while a train is drawing power from the substation. The systems control is based on the instantaneous reactive power theory. An interleaved switching scheme was used to switch the seven-cell series-stacked converter, thus exploiting the natural balancing properties of the series-stacked converter. Results obtained from tests done show that both the APF and regeneration functions of the system were successfully implemented.

Integrated active rectifier and power quality compensator with reduced current measurement

This paper describes a three-phase integrated active rectifier and shunt power quality compensator (IPQC). The measurement of only three currents is required, and the control algorithm can be implemented using a low-cost controller. The IPQC improves the harmonic content of the supply current, displacement power factor, supply current balance, and can serve as a four-quadrant active rectifier for motor drives and other DC-link loads. The operation of the IPQC is experimentally verified using a conventional three-phase insulated gate bipolar transistor voltage-source inverter. A low-cost fixed-point DSP-based controller with fixed-band hysteresis current regulation is used for the implementation of the control algorithms.

DFT-based Repetitive Control of a Series Active Filter Integrated with a 12-pulse Diode Rectifier

This paper considers the transient performance and stability of a recurrent discrete Fourier transform (DFT) based control method for a series active filter integrated with a 12-pulse diode rectifier. The control method targets specific harmonics and/or the negative sequence fundamental component of the supply current, and is intended for use with nonsinusoidal/unbalanced supply voltages. The proposed control method is based on DFTs instead of the dq-method, and a simple approach is used to account for small frequency variations found in practical power systems.

Development of a 1.5 MW, Seven Level Series-stacked Converter as an APF and Regeneration Converter for a DC Traction Substation

A prototype 1.5 MW series-stacked converter system was built and installed at a DC-traction substation. The converter inverts energy generated by slowing an electric train using regenerative braking. The regenerated energy is fed into the local AC network at the DC-substation. A secondary function of the converter is to perform active power filtering (APF) while a train is drawing power from the substation. The systems control is based on the instantaneous reactive power theory. An interleaved switching scheme is used to switch the seven level series-stacked converter, thus exploiting the natural balancing properties of the series-stacked converter. Results obtained from tests done show that both the APF and regeneration functions of the system were successfully implemented

A series-shunt compensator with combined UPS operation

Series-shunt power quality compensators with the ability to function as an uninterruptible power supply (UPS) can solve a variety of power quality problems. This topology consists of two power electronic inverters. The shunt inverter is typically used as a voltage source during UPS operation, requiring a shunt inverter rated for the full load power. The rating of the series inverter is typically minimized to reduce cost, resulting in limited voltage compensation. This paper suggests a topology that enables the series inverter of a series-shunt compensator to assist the shunt inverter during UPS operation. The proposed topology allows the use of a shunt inverter with a power rating lower than the load rating, resulting in a compensator with reduced power rating while maintaining a high capacity for voltage compensation. This paper also suggests an arrangement of passive filters for switching ripple that does not adversely affect series voltage compensation. Practical results are presented, illustrating the operation of the proposed series-shunt UPS and series-shunt compensation for a capacitive nonlinear load.

Digital control of an integrated series active filter and passive rectifier with voltage regulation

The integration of a series active filter with a 12-pulse diode rectifier can provide an effective means for supply current harmonic free AC/DC conversion. Controlling the series active filter as a frequency selective impedance requires low delays and is not well suited for implementation by digital control. This paper suggests two control methods intended for implementation by digital control. The suggested current-mode control method for supply current balancing and voltage regulation is verified experimentally.

Torque Performance of Optimally Designed Six-PhaseReluctance DC Machine

In this paper the principle, basic torque theory and design optimisation of a six-phase reluctance dc machine are considered. A trapezoidal phase current waveform for the machine drive is proposed and evaluated to minimise ripple torque. Low cost normal laminated salient-pole rotors with and without slits and chamfered poles are investigated. The six-phase machine is optimised in multi-dimensions by linking the finite-element analysis method directly with an optimisation algorithm; the objective function is to maximise the torque per copper losses of the machine. The armature reaction effect is investigated in detail and found to be severe. The measured and calculated torque performances of a 35 kW optimum designed six-phase reluctance dc machine drive are presented