Michael Bland

A 150 kVA vector controlled matrix converter induction motor drive

This paper describes the design, construction, and testing of a 150-kVA closed-loop vector-controlled matrix converter induction motor drive. The primary objective of this research effort is to evaluate the utility of the matrix converter in electric vehicle applications, primarily for motor control. A prototype converter has been built using 600-A 1400-V insulated gate bipolar transistors. Closed-loop vector control has been implemented and tested using a 150-hp induction motor load. This paper presents the design of this converter along with practical test results, representing the largest matrix converter built to date.

Gate drive level intelligence and current sensing for matrix converter current commutation

This paper is concerned with the process of current commutation in matrix converters. The mechanisms involved in the commutation process are described and practical waveforms are presented. A novel commutation strategy is described that uses gate drive level intelligence in the form of a field-programmable gate array. Current direction is determined using device voltages and, therefore, the measurement problems associated with all other commutation methods are overcome. Practical results from an 18-kW matrix converter induction motor drive are presented.

Control Design of a Three-Phase Matrix-Converter-Based AC–AC Mobile Utility Power Supply

This paper describes the control analysis and design of an ac-to-ac three-phase mobile utility power supply using a matrix converter capable of high-quality 50-, 60-, and 400-Hz output voltage and reduced input harmonic distortion. Instead of the traditional structure employing a diode bridge rectifier, a dc link and a pulsewidth-modulated inverter, a three-phase-to-three-phase direct ac-ac (matrix) converter has been used as the power-conditioning core of the system, working in conjunction with input and output LC low-pass filters. An optimizing control design method using a genetic algorithm approach has been used, which yields designs to minimize a cost function, taking into account transient and steady-state output voltage performance targets, together with robustness to different operative conditions and system parameters drift. Simulation and experimental tests have demonstrated that the system meets the power-quality requirements of the application.

Elimination of Waveform Distortions in Matrix Converters Using a New Dual Compensation Method

Matrix converters are becoming a real alternative to traditional topologies for many ac-ac power conversion applications. One of the less well-known advantages is the potential for reduced waveform distortion that arise from device characteristics and commutation delays. This paper describes the origin of distortion effects for a matrix converter with current sign-based commutation and gives a novel approach to the method that can, in principle, eliminate the distorting effects to give a power converter having excellent linear behavior. The effectiveness of compensation techniques are illustrated for both an open-loop matrix converter driving a passive load and a matrix converter as part of a vector-controlled drive.

A Utility Power Supply Based on a Four-Output Leg Matrix Converter

A four-output leg matrix converter and variable-speed diesel generator are integrated to create a three-phase plus neutral utility power supply. The matrix converter is designed to meet tight harmonic and the forth leg provides the facility to supply unbalanced and single-phase loads. This enables the generator to provide stable power over a range of engine speeds and load conditions. Test results for the 10 kW offline power supply are provided to demonstrate system performance.

Comparison of calculated and measured losses in direct AC-AC converters

This paper is concerned with modelling, predicting and experimental measurement of semiconductor losses in direct AC-AC (matrix) converters. All of the commutation scenarios possible in a matrix converter topology using two or four step commutation are identified and studied. A complete loss model for both switching loss and conduction loss for the purposes of comparison with other converter technologies is developed.

A utility power supply based on a four-output leg matrix converter

A four-output leg matrix converter and a variable-speed diesel generator are integrated to create a three-phase plus neutral utility power supply. The matrix converter is designed to meet tight harmonic specification and the fourth leg provides the facility to supply unbalanced and single-phase loads. This enables the generator to provide stable power over a range of engine speeds and load conditions. Two modulation techniques for four-output leg matrix converters have been considered and compared. Test results for a 10-kW offline power supply are provided to demonstrate system performance.

Comparison of bi-directional switch components for direct AC-AC converters

The objective of this paper is to assess the performance of bi-directional switch components for direct AC-AC (matrix) converter applications. Three 2-phase to 1-phase matrix converters will be constructed, each with different bidirectional switch components. The three bi-directional switch structures to be considered are: silicon (Si) diode-Si IGBT, silicon carbide (SiC) diode-Si IGBT and Si reverse blocking IGBT (RB-IGBT). All of the commutation scenarios possible in a matrix converter topology using two or four-step commutation are studied. The improved reverse recovery performance of the SiC Schottky diodes is assessed with reference to measured switching waveforms. The affect of the three different switch structures on the overall performance of the matrix converter with particular attention to power circuit losses is investigated.

A High Power RF Power Supply for High Energy Physics Applications

This paper considers the design of a “long-pulse” modulator supply rated at 25kV, 10A (250kW peak power, duty ratio 10%, 25kW average power, pulse length ≃ 1 – 2ms). The supply is based on direct modulation of a multi-phase resonant power supply, fed by an active rectifier. The objectives of the development are to produce a compact power supply, with low stored energy and with high power quality at the utility supply. The paper provides a brief overview of the technology, followed by a discussion of the design choices.

Extremum Seeking-Based Optimization of High Voltage Converter Modulator Rise-Time

We digitally implement an extremum seeking (ES) algorithm, which optimizes the rise time of the output voltage of a high voltage converter modulator (HVCM) at the Los Alamos Neutron Science Center by iteratively, simultaneously tuning the first eight switching edges of each of the three-phase drive waveforms (24 variables total). We achieve a 50 μs rise time, which is reduction in half, compared to the 100 μs achieved at the Spallation Neutron Source at Oak Ridge National Laboratory. Considering that HVCMs typically operate with an output voltage of 100 kV, with a 60-Hz repetition rate, the 50 μs rise time reduction will result in very significant energy savings. The ES algorithm will prove successful, despite the noisy measurements and cost calculations, confirming the theoretical results that the algorithm is not affected by noise whose frequency components are independent of the perturbing frequencies.