This paper presents a review of the most popular control and modulation strategies studied for matrix converters (MCs) in the last decade. The purpose of most of these methods is to generate sinusoidal current on the input and output sides. These methods are compared considering theoretical complexity and performance. This paper concludes that the control strategy has a significant impact on the resonance of the MC input filter.

A Review of Control and Modulation Methods for Matrix Converters

Methods and systems for transforming electric power between two or more portals. Any or all portals can be DC, single phase AC, or multi-phase AC. Conversion is accomplished by a plurality of bi-directional conducting and blocking semiconductor switches which alternately connect an inductor and parallel capacitor between said portals, such that energy is transferred into the inductor from one or more input portals and/or phases, then the energy is transferred out of the inductor to one or more output portals and/or phases, with said parallel capacitor facilitating “soft” turn-off, and with any excess inductor energy being returned back to the input. Soft turn-on and reverse recovery is also facilitated. Said bi-directional switches allow for two power transfers per inductor/capacitor cycle, thereby maximizing inductor/capacitor utilization as well as providing for optimum converter operation with high input/output voltage ratios. Control means coordinate the switches to accomplish the desired power transfers.

Universal power converter

In this paper, the concept of an all-dc wind park with series-connected turbines is investigated as an alternative to the classical ac parallel or radial wind park. This paper presents a literature overview of all-dc wind park concepts with series connection. A three-phase conversion system with permanent magnet machine, ac-ac converter, high-frequency transformer, and diode bridge rectifier is suggested in this paper for the series connection of dc turbines. The dc series park with the suggested conversion system is compared in terms of losses, cost, and reliability to the state-of-the-art park configuration which is the ac radial park with HVDC transmission. It is found that the dc series park becomes comparable with the ac radial design for high ratings of the dc turbines. Furthermore, the comparison shows that emphasis must be put on reducing the losses in the conversion system of the dc turbine and, particularly, the ac-ac converter. Therefore, the efficiency of the ac-ac converter is compared for three different topologies: the direct matrix converter, the indirect matrix converter, and the conventional back-to-back converter. The direct matrix converter is found to be the most efficient, suitable for the suggested conversion system.

An All-DC Offshore Wind Farm With Series-Connected Turbines: An Alternative to the Classical Parallel AC Model?

Reduced matrix converter (RMC) is a convenient topology for offshore wind farm due to its potential to reduce the size and weight of the converter, to improve the reliability by removing the electrolytic capacitor, and to increase the efficiency inherent to less stages of conversion. Moreover, it is a very flexible topology which permits different types of operation with a simpler modulation compared with conventional three-phase matrix converter. This paper investigates different modulation strategies applied to RMC for offshore wind farms, focused on efficiency improvement of the entire convention system. Simulation results using a detailed loss model for high-power level are presented. Four cases are investigated according to the modulation strategies (space vector modulation and carrier-based modulation) and the operation principle (current source converter or voltage source converter). Losses in the clamp circuit are also calculated. Different wind velocities are considered in the simulations. Results show that current source operation with space vector modulation presents minimum losses at nominal wind velocity. This operation is suitable for series connection of offshore wind farms which has been reported as the most efficient alternative from the grid losses point of view.

A Study of Efficiency in a Reduced Matrix Converter for Offshore Wind Farms

Market liberalization has significantly changed the energy supply system in Europe, i.e. from a top-down centralized power generation system towards a more decentralized system. In addition, partially due to incentive programs, vast amounts of renewable power generator systems (mostly wind and PV) have been installed. More flexible grid structures are needed to cope with this new landscape of distributed generation. This paper explores the role of state-of-the-art power electronics to realize the required infrastructure. The potential efficiency gains and cost savings that can be realized by using DC-to-DC converters in electronic substations are presented in detail.

Power electronic technologies for flexible DC distribution grids

This paper proposes a novel control strategy and a protection circuit, and also shows the advantage of utilizing (newly developed) reverse blocking IGBT (RB-IGBT), to solve several practical problems of the matrix converter. The proposed control strategy is based on a virtual indirect control method with a virtual rectifier and a virtual inverter. PWM pulses for the matrix converter are obtained by combining PWM pulses for the virtual rectifier and inverter. As a result, the input current and the output voltage can be controlled independently. The advantage of those methods is confirmed by experimental results with a 750 W induction motor drive system. Good sinusoidal waveforms are obtained for the input and output currents, and the T.H.D. of the input and output current are 5.1% and 1.4%, respectively. The conduction loss of the RB-IGBT is decreased to about 2/3 of the conventional AC switch with series connection diode. Thus, the converter is about a half to the conventional PWM rectifier-inverter system with the same capacity. Furthermore, the protection problem is solved by a dynamic clamp method without an electrolytic capacitor. This protection circuit directly dissipates reactive load energy by dynamic clamp operation of an IGBT.

A novel approach to practical matrix converter motor drive system with reverse blocking IGBT

In this paper, simple simulation methods to calculate power semiconductor loss and instantaneous junction - case temperature difference in a power module of a matrix converter are proposed. The validity of the proposed simulation method for loss calculation is confirmed through experiment using a 22 kW test set-up of the matrix converter. By using the simulation method for temperature calculating, the influence of the output frequency on the junction - case temperature difference is investigated. Moreover, the effect of using a novel IGBT (RB-IGBT) that has reverse blocking capability is discussed. It is shown that the efficiency of a matrix converter using the RB-IGBT is higher by 1.3 points than that of a conventional PWM rectifier and inverter system.

Analysis of loss and junction temperature in power semiconductors of the matrix converter using simple simulation methods

This paper proposes a simple control strategy for a high-frequency AC-link AC/AC direct converter The proposed control strategy is based on the virtual converter system that consists of a PWM rectifier part, a high-frequency AC-link part and an inverter part The proposed method realizes wide control range, high performances and low snubber loss The validity of the proposed method is confirmed through the simulation and experimental results

H. Ohguchi

Papers

A novel approach to practical matrix converter motor drive system with reverse blocking IGBT

Analysis of loss and junction temperature in power semiconductors of the matrix converter using simple simulation methods

A novel control strategy for high-frequency AC-link AC/AC direct converter based on virtual converter system