Design and Development of Novel Matrix Converter Performance Enhancement Technique for Induction Motor Drive

Matrix converter is a direct AC-AC converter topology that directly converts energy from an AC source to an AC load without the need of a bulky and limited lifetime energy storage element. Due to the significant advantages offered by matrix converter, such as adjustable power factor, capability of regeneration and high quality sinusoidal input/output waveforms. Matrix converter has been one of the AC–AC topologies that hasreceived extensive research attention for being an alternative to replace traditional AC-DC-AC converters in the variable voltage and variable frequency AC drive applications. In the present paper an indirect space vector modulated matrix converter is proposed. The basic idea of an indirect modulation scheme is to separately apply SVM to the rectification and inversion stages, before combining their switching states to produce the final gating signals. The paper encompasses development of a laboratory prototype of 230V, 250VA three phase to three phase DSP controlled matrix converter fed induction motor drive. The observations and real time testings have been carried out to evaluate and improve the stability of system under various typical abnormal input voltage condition

Reduction of output common mode voltage using a novel SVM implementation in matrix converters for improved motor lifetime

This paper presents the study of an alternative Space Vector Modulation (SVM) implementation for Matrix Converters (MC) which reduces the output Common Mode (CM) voltage. The strategy is based on replacing the MC zero vectors by the rotating ones. In doing this, the CM voltage can be reduced which in-turn reduces the CM leakage current. By reducing the CM current, which flows inside the motor through the bearings and windings, the Induction Motor (IM) deterioration can be slowed down. The paper describes the SVM pattern and analyses the CM voltage and the leakage current paths. Simulation and experimental results based on a MC-IM drive are provided to corroborate the presented approach

Microprocessor controlled matrix converter connector for power systems

A matrix N×M multiphase converter is a simple structure incorporating N×M bi-directional switches, connecting N input phases to M output phases and able to convert input voltages into output voltages of any shape and frequency. However, commutation problems and complicated control algorithms keep it from being utilized on a large scale. This paper gives a solution to the control system of the multiphase matrix converters for power system application. The practical application of multiphase matrix converters (MC) in power systems involves the study of application requirements, possible converter topologies and the development of new, reliable control algorithms. The MC is working as a connection device between power systems or as an interconnection device within the power system. The proposed tasks performed by the MC in the power system are power flow control and power flow oscillation dumping. The device can be viewed as new FACTS device-series power system connector, based on straightforward energy conversion

A review of model predictive control strategies for matrix converters

Matrix converters are a well-known class of direct AC-AC power converter topologies that can be used in applications in which compact volume and low weight are necessary. For good performance, special attention should be paid to the control scheme used for these converters. Model predictive control strategy is a promising, straightforward and flexible choice for controlling various different matrix converter topologies. This work provides a comprehensive study and detailed classification of several predictive control methods and techniques, discussing special capabilities they each add to the operation and control scheme for a range of matrix converter topologies. The paper also considers the issues regarding the implementation of model predictive control strategies for matrix converters. This survey and comparison is intended to be a useful guide for solving the related drawbacks of each topology and to enable the application of this control scheme to matrix converters in practical applications

Improved space vector modulation with reduced switching vectors for multi-phase matrix converter

Multi-phase converter inherits numerous advantages, namely superior fault tolerance, lower per-leg power rating and higher degree of freedom in control. With these advantages, this thesis proposes an improved space vector modulation (SVM) technique to enhance the ac-to-ac power conversion capability of the multi-phase matrix converter. The work is set to achieve two objectives. First is to improve the SVM of a three-to-seven phase single end matrix converter by reducing number of space vector combinations. Second is to use the active vector of the SVM to eliminate the common-mode voltage due to the heterogeneous switching combination of a dual three-to-five phase matrix converter. In the first part, the proposed technique utilizes only 129 out of 2,187 possible active space vectors. With the reduction, the SVM switching sequence is greatly simplified and the execution time is shortened. Despite this, no significant degradation in the output and the input waveform quality is observed from the MATLAB/Simulink simulation and the hardware prototype. The results show that the output voltage can reach up to 76.93% of the input voltage, which is the maximum physical limit of a three-to-seven phase matrix converter. In addition, the total harmonics distortion (THD) for the output voltage is measured to be below 5% over the operating frequency range of 0.1 Hz to 300 Hz. For the second part, the common-mode voltage elimination is based on the cancellation of the resultant vectors (that causes the common-mode to be formed), using a specially derived active vectors of the dual matrix converter. The elimination strategy is coupled with the ability to control the input power factor to unity. The proposed concept is verified by the MATLAB/Simulink simulation and is validated using a 5 kW three-to-five phase matrix converter prototype. The SVM switching algorithm itself is implemented on a dSPACE-1006 digital signal processor platform. The results prove that the common-mode voltage is successfully eliminated from the five-phase induction motor winding. Furthermore, the output phase voltage is boosted up to 150% of the input voltage in linear modulation range

Finite Control Set Model Predictive Control Of Direct Matrix Converter And Dual-Output Power Converters

Model Predictive Control (MPC) with a finite control set has been successfully applied to several power converter topologies as reported in the scientific literature and research activity on predictive control techniques has increased over the last few years. MPC uses a discrete-time model of the system to predict future values of control variables for all possible control actions and computes a cost function related to control objectives to find the optimal control action. The control action which minimizes the cost function is selected and applied to the system for the next time interval. Different control objectives can be introduced in the user-defined cost function and controlled simultaneously by solving the multi-objective optimization problem. This approach is particularly advantageous for certain power converter topologies, such as Direct Matrix Converter (DMC) and dual-output power converters, for which conventional control techniques require complicated Pulse Width Modulation (PWM) schemes and multi-loop control, incurring high computational burden and complexity. Conversely, since MPC does not need a modulator to generate switching signals, implementation of the MPC technique is simple and intuitive. However, the MPC method also has several drawbacks:1. Real-time implementation of MPC incurs high computational burden2. There is no analytical procedure to adjust the weighting factors for multi-objective optimization problem3. A complete system model must be derived since MPC method uses this model to predict control variables4. MPC implementation is not straightforward for several power converter topologies, such as dual-output power converters. In this dissertation four specific contributions are reported that address these drawbacks. First, a fully FPGA-based real-time implementation of model predictive controller is proposed for direct matrix converter. In conventional real-time implementation of model predictive control method, Digital Signal Processors (DSPs) and Field-Programmable Gate Arrays (FPGA) are both used to ensure fast processing operation and preserve performance of the predictive controller. For the proposed, real-time implementation method, all control calculations and the safe commutation scheme for DMC are fully implemented in the FPGA and the need for a DSP is eliminated. Advantages of the proposed approach are simplicity and the ability to exploit the parallel computation capability of the FPGA to calculate in parallel the predictive state for all switch combination. This translates in a significant reduction of required computation time and potentially in reduced control hardware cost. Second, a novel model predictive control scheme for the three-phase direct matrix converter based on switching state elimination is proposed. The conventional MPC solves a multi-objective optimization problem by minimizing a multi-objective cost function over a one-step horizon. The control performance is strongly affected by the weighting factors used in the cost function and this is problematic. The proposed method solves this difficulty by eliminating the weighting factors and using a state elimination method based on error constraints that have a clear physical interpretation. Third, the model predictive control scheme is proposed for Nine-Switch Inverter (NSI) under an unknown load condition. Nine-switch inverter is a dual-output inverter and the proposed method can control two three-phase load simultaneously by solving single optimization problem. In power electronics applications, control of the power converter must work well under all load conditions and the control method should provide clean power no matter what the load is. In this work, two ac load currents are estimated using full-order observers and converter is controlled by using model predictive control method. Fourth, the model predictive control scheme is proposed for dual-output Indirect Matrix Converter (IMC). Modulation method for this topology is complicated and conventional linear control techniques require tuning of the controller parameters. In conventional control technique, multi-loop control is required to independently adjust the two ac outputs. The usage of multi-loop control techniques increases the complexity of implementation of the controller. On the other hand, proposed method can achieve several control goals by using single control loop and provide good system performance

Matrix Converter Based Open-end Winding Drives

University of Minnesota Ph.D. dissertation. August 2015. Major: Electrical/Computer Engineering. Advisor: Ned Mohan. 1 computer file (PDF); xiii, 172 pages.A significant portion of all electric power generated is consumed by electric motors employed in commercial, industrial, and transportation sectors. Variable frequency drives (VFDs) are desirable, and in many cases necessary, for superior control performance and efficiency. At present, most VFDs use a `line frequency AC' -> `DC-link' -> `variable frequency AC' architecture, where the front-end converter may or may not support bidirectional power flow and input power factor control. In these drives, the load-end converter is almost always a two- or multi-level voltage source inverter (VSI). The front-end converter may be another VSI, or a line-commutated rectifier. This is a robust architecture that has benefited from extensive use; consequently, the inverter design and control methods are quite standard, and the behavior of all components in the drive system is generally understood. VSI based drives need large capacitors to support the DC-link voltage and significant reactance at the drive input to limit the harmonic current drawn from the grid. The switching common-mode output voltage generated by these drives causes bearing currents and ultimately motor failure. Therefore, even though the drive topology is quite robust, the system suffers from downtime and high maintenance costs because of the unreliable capacitors and bearing failure; and large volume because of the large capacitor and line reactor requirement. Matrix converters offer `line frequency AC' -> `variable frequency AC' conversion without an intermediate DC-link, although an actual or implied soft link may exist. These converters use reactive components only for filtering the harmonics of the PWM frequency. Furthermore, when modulated using rotating vectors, the output common-mode voltage is ideally equal to zero. A major limitation of this modulation technique is a poor voltage transfer ratio of 0.50, and therefore modulation using stationary vectors has received more attention, even though the latter generates switching common-mode voltage at the output, and allows input power factor control only at the expense of the voltage transfer ratio. The output common-mode voltage can be eliminated while maintaining a good voltage transfer ratio using a direct matrix converter based open-end winding drive reported in 2010. This drive topology is also capable of input power factor control; and is expected to have significantly lower reactive element requirements compared to VSI based drives. Indirect topologies for matrix converter based open-end winding drives are also possible. These topologies utilize a three-level inverter structure and employ three converters: the front-end converter converts the input voltages to ordered three-level link voltages. The two load-end converters convert the link voltages to variable frequency voltages to be applied at the two sets of motor terminals. The additional advantages of the indirect approach are a more mature structure, clamp circuit elimination, robust and efficient commutation, lower voltage stress on the switches, and lower losses. The indirect topologies also lend themselves to low-voltage-ride-through without any additional switches. This dissertation presents experimental results from two distinct indirect matrix converter based open-end winding drives. The results demonstrate good common-mode performance, high voltage transfer ratio, and input power factor control. Having established the feasibility of the indirect approach for matrix converter based open-end winding drives, the two indirect drives reported here and the direct drive reported in literature are compared on semiconductor requirements, semiconductor losses, and input/output harmonic content. The most promising matrix converter based open-end winding drive is then compared with state-of-the-art systems on the same criteria, as well as on passive elements, control, and instrumentation requirements. To this end, a new filter design procedure with optimal damping for matrix converter applications is also developed in this dissertation. A comparison of the reactive components used by this filter to the reactive components used in back-to-back VSI systems shows that the matrix converters' passive element requirements are in fact lower than the back-to-back VSI based systems. In summary, this dissertation demonstrates the feasibility of two distinct drive topologies with significant advantages using experimental results. The practical questions pertinent to any new design are answered, and the conclusions have been used to identify the best matrix converter based open-end winding drive topology. Qualitative and quantitative comparison with the state-of-the-art systems reveal a clear advantage in the common-mode voltage related effects and the passive components' sizing