Three-phase Matrix Research Articles

STATE SPACE VECTOR BASED ADVANCED DIRECT POWER CONTROL OF MATRIX CONVERTER AS UPFC

This paper presents state space vector analysis for three-phase matrix converters operating as unified power flow controllers (UPFCs). It allows direct ac/ac power conversion without dc energy storage links; therefore, It reduces volume, cost, capacitor power losses, together with higher reliability. The line active and reactive power, together with ac supply reactive power, can be directly controlled by selecting an appropriate matrix converter switching state guaranteeing good steady-state and dynamic responses. This advanced control of MC guarantee faster responses without overshoot and no steady- state error, presenting no cross-coupling in dynamic and steady-state responses. Simulations are carried out, showing the effectiveness of the proposed method in steady-state and transient conditions.

PWM Strategy and Its Output Control Range of Single-Phase to Three-Phase Matrix Converters

PWM Strategy and Its Output Control Range of Single-Phase to Three-Phase Matrix Converters

Analysis and implementation of space-vector-modulated three-phase matrix converter

This study introduces a detailed analysis, design and implementation of a three-phase matrix converter based on space-vector modulation technique. The modulation strategy is described and modelled. All steps of hardware design using discrete semiconductor devices are given. The modulator is implemented using a digital signal processor. The experimental results for passive loading and three-phase induction motor conditions are given. Then the converter performance is discussed.

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

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.

Fuzzy Control Adaptive of a Matrix Converter for Harmonic Compensation Caused by Nonlinear Loads

Since discovered, electrical energy represents one of the most decisive fields in any technological development achieved by man. However, with the expansion of industrial process requiring not only a lot of power but also clean electric power, the distribution systems require effectively and efficiently control strategy. One of the greatest physical phenomena that affects on the quality of electric energy is the harmonics caused by nonlinear loads connected to the grid, which are generally converters based on power electronics components. Indeed, these are the main cause of the deterioration of energy quality.This work presents a topology of harmonic compensation based on a three-phase matrix converter with a fuzzy controller adaptive. The principal adjustment estimates the output currents in order to calculate the optimal rate of modulation. Fuzzy controller adaptive was used to not only improve the control strategy of the converter, but also to improve the quality of energy in accordance with international standards. To evaluate the effectiveness of the work, we conducted tests of numerical simulations on our model based on fuzzy control. The results of simulations will be presented and interpreted.

Harmonic Sequence Impedances: A Tool for the Three-Phase Frequency Scan Technique

In this paper, the harmonic response of an electric system under imbalance conditions is established. Symmetrical harmonic components are proposed to give a new way of interpreting resonance occurrence in three-phase power systems. A three-phase harmonic bus impedance matrix (THBIM) for a simple distribution system is derived using analytical procedures. The development of frequency scans for the THBIM elements in both phase and sequence reference frames is carried out. Simulation results show the benefits of the harmonic sequence components for characterization of the harmonic resonance conditions in unbalanced distribution systems, and for characterizing the effectiveness of the mitigating techniques. This method offers a new way to conduct harmonic analysis and diagnosis in unbalanced power systems.

Fuzzy-based Closed-loop Speed Control of Induction Motor Fed from Matrix Converter

In this study; closed-loop speed control of an induction motor that was achieved by a fuzzy-based slip regulation technique has been performed. As a power source for the motor, a three-phase matrix converter has been used, and the space-vector modulation was adapted for the generation of the switching control signals. Real-time control signals for the matrix converter were generated through MATLAB/Simulink (The MathWorks, Natick, Massachusetts, USA) supported digital signal processor control card. The space-vector modulation technique used in this work is simpler than other control algorithms, both in terms of implementation and the input power factor control. Furthermore, the proposed space-vector modulation technique for the matrix converter reduced “turn-on” number of the switching devices in a switching period, and therefore, fewer switching losses have occurred. Simulation and corresponding experimental results were given for various operating conditions.

Duty Cycles for Three-Phase of Three-Phase Matrix Converters

This paper presents the simple derivation process of duty cycles of a three-phase to three-phase matrix converter. The duty cycles with only four times commutations for all three phases during one control period are derived from the input voltages and the references of the output voltages and input power factor angle.

Matrix Converter-Based Unified Power-Flow Controllers: Advanced Direct Power Control Method

This paper presents a direct power control (DPC) for three-phase matrix converters operating as unified power flow controllers (UPFCs). Matrix converters (MCs) allow the direct ac/ac power conversion without dc energy storage links; therefore, the MC-based UPFC (MC-UPFC) has reduced volume and cost, reduced capacitor power losses, together with higher reliability. Theoretical principles of direct power control (DPC) based on sliding mode control techniques are established for an MC-UPFC dynamic model including the input filter. As a result, line active and reactive power, together with ac supply reactive power, can be directly controlled by selecting an appropriate matrix converter switching state guaranteeing good steady-state and dynamic responses. Experimental results of DPC controllers for MC-UPFC show decoupled active and reactive power control, zero steady-state tracking error, and fast response times. Compared to an MC-UPFC using active and reactive power linear controllers based on a modified Venturini high-frequency PWM modulator, the experimental results of the advanced DPC-MC guarantee faster responses without overshoot and no steady-state error, presenting no cross-coupling in dynamic and steady-state responses.

Fault-tolerant, matrix converter, permanent magnet synchronous motor drive for open-circuit failures

A fault-tolerant matrix converter drive topology, which can be effectively used to drive a permanent magnet synchronous motor for research in critical applications, with particularly emphasis on aerospace applications, is presented. The proposed matrix converter configuration, a four output-phase matrix converter, uses a normally redundant output phase connected between the input supply and the neutral point of the motor in order to provide fault-tolerant capability in the presence of faults. This proposed fault-tolerant matrix converter can deal with open-circuit faults caused by failures in either the power converter or machine windings. Without using any additional connecting devices and without modifying the modulation technique, the satisfactory system performance under faulty operating conditions can be achieved using the developed control strategy. The space vector representation of the direct space vector modulation technique is adaptable so that the technique used for a conventional three-phase matrix converter can be applied to the four-phase matrix converter even in the fault-tolerant mode. The verification of the proposed fault-tolerant matrix converter drive is confirmed using extensive simulation and experimental results.

Direct torque control of six-phase induction motors using three-phase matrix converter

This paper presents a new direct torque control (DTC) method for six-phase induction motor (SPIM). In the proposed method, direct torque and flux control are applied to the SPIM using matrix converter with the conventional three-phase source as its input. The new DTC scheme for SPIM benefits the advantages of both DTC and matrix converter, such as unity power factor and absence of dc-link. The simulation results show the effectiveness of the proposed method in both dynamic and steady state response.

Position Estimation of a Matrix-Converter-Fed AC PM Machine From Zero to High Speed Using PWM Excitation

This paper describes a sensorless position estimation method for a permanent-magnet (PM) motor fed from a three-phase matrix converter using only its space-vector pulsewidth-modulation (SVPWM) sequence. The scheme employs measurements of dii/dt of the motor line currents to construct orthogonal ldquoresolverlikerdquo position signals. In principle, the SVPWM waveforms provide sufficient excitation to extract the position signal from the motor current. However, in order to improve the signal-to-noise ratio of the di/dt signals, a small modification to the SVPWM is required. Sensorless control of the PM synchronous motor at zero and high speeds is demonstrated experimentally. The use of alternative input voltage vectors is also investigated to reduce the current ripple.

Simulation of Inelastic Stress - Strain Response of Nanocomposites by a Network Model

This paper describes the viscoelastic properties of network model. In the first approximation, nanocomposite was modeled as a 3D tetrafunctional network considering entanglements to act as the physical x-links. Nano-sized non-deformable domains of defined shape and size were introduced into the network. The chains in the vicinity of the inclusions were considered immobilized. Hence, the semicrystalline polymer was considered a three-phase system containing flexible matrix bulk phase, immobilized chains near the inclusion surface and rigid crystalline domains. The crystallites were characterized by their Young's modulus and their traction properties were calculated using the Hooke's law. Unlike the model, the real polymer has viscoelastic deformation properties. The components which could cause viscoelastic properties were introduced and their impact on viscoelastic properties of whole network was investigated. The components were for example the reptation motion of chain in entanglements or chain, whose motion was retarded by impact of surroundings. The model enabled to investigate the influence of each component, as well as the influence of distribution of each component. The types of nods, whose influence was investigated in this contribution, were fast knot, free entanglement, one-way entanglement and energy barrier.

High-Performance Nanoscale Composite Coatings for Boiler Applications

In this article, we will show how unconventional nanoscale composite coatings can be formed using conventional wire-arc thermal spray systems. The as-sprayed SHS7170 wire-arc coatings are found to develop an amorphous matrix structure containing starburst-shaped boride and carbide crystallites with sizes ranging from 60 to 140 nm. After heating to temperatures above the peak crystalline temperature (566 °C), a solid/state transformation occurs that results in the formation of an intimate three-phase matrix structure consisting of the same complex boride and carbide phases, along with α-iron interdispersed on a structural scale from 60 to 110 nm. The nanocomposite microstructure contains clean grain boundaries, which are found to be extremely stable and resist coarsening throughout the range of temperatures found in boilers. Additionally, the properties of the coating are presented including the bond strength, hardness, bend resistance, and impact resistance. The sprayability, forgiveness, and repairability of the SHS7170 wire-arc coatings are explained in detail, with an emphasis on field applicability in boiler environments. The performance of the SHS7170 coatings in boiler environments is measured via elevated temperature-erosion experiments conducted at 300, 450, and 600 °C using bed ash from an operating circulating fluidized-bed combustor boiler, and the results are compared with those for existing boiler coatings.

Evaluation of Modulation Schemes for Three-Phase to Three-Phase Matrix Converters

This paper presents a method for evaluating different modulation schemes employed with three-phase to three-phase matrix converters. The evaluation method addresses three important modulator characteristics: the output waveform quality, the input waveform quality and the switching losses associated with the modulation schemes. The method is used to evaluate four different modulation strategies, all based on the direct space-vector modulation approach. Further, regarding the switching losses, the paper proposes a new space-vector approach by which the switching losses can be reduced by 15%-35%, depending on the output load angle. This new modulation approach is applicable whenever the output voltage reference is below half the input voltage and the output voltage quality is then superior to that of the conventional space vector modulation scheme. The functionality of the new modulation scheme is validated by both simulations and experimental results and compared to waveforms obtained by using exiting space vector modulation schemes. The output voltage of the proposed scheme turns out to be comparable to the best of the conventional schemes while the input current is more distorted.

Unity Power Factor Operation Control Method For Single-phase to Three-phase Matrix Converter

This paper proposes a new control method of matrix converter to obtain the unity power factor operation. Source side of the matrix converter is single-phase voltage, and the load side is three-phase ac motor. The number of switching device is six, and the converter does not require a reactor or an electrolytic capacitor. Generally, it is difficult for matrix converter to control both its input current waveform and the output voltage waveform, because the switching devices are connected to both source side and load side. In this paper, applying an algebraic transfer matrix, the control method of single-phase to three-phase matrix converter applies the indirect modulation model. The indirect modulation model treats a matrix converter as a two-stage transformation converter. The rectifier of proposed model consists only diode and small L-C filter. Hence, the switching frequency is lower than the conventional model one. The inverter of the proposed model regulates both the input current waveform and the motor speed. The inverter control scheme for IPM motor is based on direct torque control (DTC). The additional current controller improves its input current waveform. Hence, an optimum switching pattern of the matrix converter realizes quick torque response and unity power factor operation. This paper describes that the proposed method achieves the power factor 97.6% by experimental tests. The experimental results confirm the feasibility of the proposed method for matrix converter.

Matrix converters

This paper deals with the vector-controlled MCT matrix converter induction motor drive with minimized commutation time and enchanced waveform quality. It also deals with the design, construction, and testing of a 10-kVA three-phase to three-phase matrix converter induction motor drive. The converter has been built using discrete 65 A metal-oxide-semiconductor (MOS) controlled thyristors (MCTs). The commutation time has been minimized to avoid any unnecessary waveform distortion, particularly at low demanded output voltages. This minimization gives the matrix converter superior waveform quality in comparison to a conventional inverter and maximizes the available converter output voltage before over modulation is required. The converter is vector controlled and has been tested using a 12-hp induction motor. Full results of these tests are presented.

Matrix converter induction motor drive: modeling, simulation and control

This paper presents a model in Simulink, which consists of a three-phase matrix converter, an induction motor, a field-oriented controller, and a power supply. A simplified Venturini's modulation algorithm is used in the simulation model. This algorithm provides unity fundamental displacement factor at the input regardless of the load displacement factor and can be easily implemented in closed loop operation. Simulation results are presented for both input and output sides of the converter. These results demonstrate a high-performance matrix converter-fed induction motor drive with unity input displacement factor.

Analytically Closed Calculation of the Conduction Losses of Three-Phase AC-AC Sparse Matrix Converters

For three-phase a.c.-a.c. power conversion a conventional matrix converter (CMC) or a d.c. side connection of a current DC link rectifier and a voltage d.c. link inverter comprising no energy storage components in the d.c. link could be employed. The combination of d.c. link converters does show a lower number of turn-off power semiconductors and, therefore, has been denoted as Sparse Matrix Converter (SMC) or Very Sparse Matrix Converter (VSMC). A limitation of the phase displacement of the current and voltage fundamentals at the input and at the output to ± π/6 does allow a further reduction of the system complexity, accordingly the respective topology has been introduced in the literature as Ultra Sparse Matrix Converter (USMC).In this paper a novel concept for the analytical calculation of the current stresses on the power semiconductors of the Sparse Matrix Converter Topologies (SMC, VSMC, and USMC) is proposed. As a comparison to a digital simulation shows, the analytical results do show a very good accuracy in a wide modulation range and for widely varying load current phase angle and widely varying ratio of output and mains frequency. Therefore, the analytical results provide an excellent basis for the dimensioning of the SMC, VSMC or USMC and/or for the determination of the rated output power and efficiency which could be achieved by employing given power transistors and diodes.

Development of a three-phase bus impedance matrix in the complex frequency domain for transient analysis in unbalanced distribution systems

Abstract Untransposed feeders, a combination of single-phase, two-phase and unequal three-phase loads impose imbalance in distribution systems. This paper presents a generalized computer technique to develop the three-phase bus impedance matrix Z bus3 (s) in the complex frequency domain. The method utilizes the phase-frame representation of the network elements. Consequently, the transient response due to line removals or additions, asymmetrical shunt faults, series faults, and capacitor switching can be simulated by modifying Z bus3 (s) . Thus, the proposed method makes it possible to analyze a power system network considering imbalance and the frequency dependence of the feeder parameters, and to obtain the transient response due to fault or capacitor switching conditions in the presence of harmonic distortion.