This paper describes how matrix converters (MCs), one at each side of a three-phase open-end-winding ac machine, achieve the following features simultaneously: 1) machine phase voltage up to 1.5 times the input phase voltage in the linear modulation mode, therefore extending the rated torque operation region to 150% of the rated speed of the machine; 2) peak voltage stress across the slot insulation which is limited to the peak of input phase voltage, i.e., a factor of at least √3 lower as compared to the conventional back-to-back converter; 3) controllable grid power factor to be leading, lagging, or unity; and 4) elimination of the instantaneous common-mode voltage at the machine terminals, therefore eliminating the bearing current due to switching common-mode voltage and reduction in the conducted electromagnetic interference. To simultaneously achieve the aforementioned capabilities, a space vector pulsewidth modulation technique is described in which the MCs are modulated using only rotating space vectors. A hardware prototype of the drive system is built. Experimental results from this hardware prototype verify the operation and claims of the drive system.

Direct-Matrix-Converter-Based Drive for a Three-Phase Open-End-Winding AC Machine With Advanced Features

In this paper, the authors attempt to introduce a new modulation algorithm for matrix power converters, with an alternative PWM strategy, regardless of type of input and output (AC or DC), and also the number of input and output phases, by using suitable toggling matrix switches, such that favorable output patterns are achieved (with variable amplitudes and frequency). The switch functions in such a converter ensure that the switches do not short-circuit the voltage sources, and do not open-circuit the current sources, thus yielding continuous currents at output terminals. Also if the number of input-phases are equal or less than the number of output-phases, then continuous current is available at input terminals. The advantage of this approach is that it can be developed for any kind of matrix converter. It is illustrated that, even under unbalanced and highly distorted input voltage waveforms, the output waveforms are reasonably clean and balanced. Here, the topology of a DC to single-phase AC power converter and single-phase to three-phase AC/AC power converter are presented.

A new generalized direct matrix converter

A four-leg-based fault-tolerant matrix converter topology is proposed, along with switching function and space vector approaches for modulation schemes, to improve the reliability of matrix converter drives. The four-leg-based fault-tolerant structure utilizes an additional redundant phase module. Based on the reconfigured hardware topology, fault-tolerant modulation strategies with both switching function and space vector approaches are developed to provide the matrix converter drives with continuous and disturbance-free operation. Pulsewidth-modulated algorithms with closed-form expressions, based on a switching function matrix, are presented to synthesize redefined output waveforms with reconfigured converter structures. Furthermore, a space-vector-based scheme using the indirect equivalent circuit with the fictitious dc link is also developed for the fault-tolerant topology after failures. Experimental results show the feasibility of the proposed four-leg-based fault-remedial approach, along with the developed modulation techniques.

Four-Leg-Based Fault-Tolerant Matrix Converter Schemes Based on Switching Function and Space Vector Methods

Hybrid electric vehicle (HEV) technology has numerous advantages over conventional vehicles, from standpoints of fuel economy, energy independence, and environmental concerns. Effective solutions for HEVs have been expanding their applications over highway vehicles, such as sedans and sport utility vehicles, into a variety of traditional vehicles. HEV systems applied to off-highway heavy-duty vehicles, which are operated by an engine, a generator, and traction motors, are investigated in this paper. This paper explores the use of a direct ac/ac converter for off-highway heavy-duty HEVs, which can directly drive traction motors from the generator with no intermediate dc conversion. In addition, a phase-redundant matrix converter structure with a backup leg and a control scheme is proposed to guarantee reliable and safe vehicle operations by providing continuous disturbance-free operations against converter faults. Fault-diagnosis techniques using line-to-line and phase voltages are presented not only to detect system malfunctions but to locate a failed switching device among 18 switching components as well. Appropriate reconfiguration structure and control actions with accurate knowledge about fault occurrence can avoid propagation of fault, which may lead to a catastrophic system failure.

Phase-Redundant-Based Reliable Direct AC/AC Converter Drive for Series Hybrid Off-Highway Heavy Electric Vehicles

In this paper, a novel wind power generation system is proposed which uses an intermediate high frequency (few kHz) ac link for power conversion. The high frequency ac link is achieved by using a reduced switch-count three-phase power electronic transformer (PET). There are two primary windings and one secondary winding in each phase of the PET. The primary windings are coupled in exact phase opposition. A 3×3 matrix converter is used to convert the high frequency secondary voltage to the desired low frequency voltage to be applied at the generator terminals. Two modulation modes as a part of the PWM of the matrix converter are described. In the first mode of operation, the common-mode voltage is eliminated at the generator terminals however, the output voltage transfer ratio of the matrix converter is limited to 0.75. The other modulation mode has higher output voltage transfer ratio equal to 0.866 with finite high-frequency common-mode voltage at the generator terminals. A method for smooth transition between the two modes of operation is described.

A novel integrated three-phase, switched multi-winding power electronic transformer converter for wind power generation system

Modulation strategies for a matrix structured direct AC to AC converter are developed. In principle, for a given set of input three-phase voltages, any desired set of output voltages can be synthesized by suitable toggling matrix switches. Mathematical proof that the direct AC to AC matrix converter can operate with unity displacement factor is provided by analyses based on the switching matrix approach. A symmetric and antisymmetric switching strategy is developed for synthesizing an output voltage vector from the appropriate combination of input voltage vectors. Unity displacement factor operation is achieved by using the combined symmetric and antisymmetric modulation strategy. This combined algorithm enables unity displacement factor operation without current sensing and current control.

B. Dobaj

Papers

Unity input displacement factor correction principle for direct AC to AC matrix converters based on modulation strategy