Eksperimentalno ponašanje prototipa matričnog pretvarača izvedenog s novim energetskim modulima

This paper describes the design and the solutions adopted for a matrix converter prototype of 10 kW, based on new integrated power modules. The performance of the converter is verified by means of experimental tests.Članak opisuje projekt i rješenja usvojena za prototip 10 kW matričnog pretvarača, izvedenog s novim integriranim energetskim modulima. Svojstva pretvarača provjerena su eksperimentalnim ispitivanjima

Matrix converter open circuit behavior analysis

The matrix converter current recirculating path during an open circuit condition is given in detail with the aim of contributing more expert knowledge to a fault detection system for matrix converter. Simulation results were obtained demonstrating how current recirculates in the matrix converter and the clamp circuit during an open-circuit fault. Healthy output phase currents can be canceled to zero due to current recirculating via the clamp circuit. This result could contribute expert knowledge to a fault detection system to avoid false fault detection and diagnosis

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

Analysis and design of matrix converters for adjustable speed drives and distributed power sources

Recently, matrix converter has received considerable interest as a viable alternative to the conventional back-to-back PWM (Pulse Width Modulation) converter in the ac/ac conversion. This direct ac/ac converter provides some attractive characteristics such as: inherent four-quadrant operation; absence of bulky dc-link electrolytic capacitors; clean input power characteristics and increased power density. However, industrial application of the converter is still limited because of some practical issues such as common mode voltage effects, high susceptibility to input power disturbances and low voltage transfer ratio. This dissertation proposes several new matrix converter topologies together with control strategies to provide a solution about the above issues. In this dissertation, a new modulation method which reduces the common mode voltage at the matrix converter is first proposed. The new method utilizes the proper zero vector selection and placement within a sampling period and results in the reduction of the common mode voltage, square rms of ripple components of input current and switching losses. Due to the absence of a dc-link, matrix converter powered ac drivers suffer from input voltage disturbances. This dissertation proposes a new ride-through approach to improve robustness for input voltage disturbances. The conventional matrix converter is modified with the addition of ride-through module and the add-on module provides ride-through capability for matrix converter fed adjustable speed drivers. In order to increase the inherent low voltage transfer ratio of the matrix converter, a new three-phase high-frequency link matrix converter is proposed, where a dual bridge matrix converter is modified by adding a high-frequency transformer into dc-link. The new converter provides flexible voltage transfer ratio and galvanic isolation between input and output ac sources. Finally, the matrix converter concept is extended to dc/ac conversion from ac/ac conversion. The new dc/ac direct converter consists of soft switching full bridge dc/dc converter and three phase voltage source inverter without dc link capacitors. Both converters are synchronized for zero current/voltage switching and result in higher efficiency and lower EMI (Electro Magnetic Interference) throughout the whole load range. Analysis, design example and experimental results are detailed for each proposed topology

Design control and implementation of a four-leg matrix converter for ground power supply application

The technology of direct AC/AC power conversion (Matrix Converters) is gaining increasing interest in the scientific community, particularly for aerospace applications. The aim of this research project is to investigate the use of direct AC/AC three phase four-leg Matrix Converter as ground power unit to supply aircraft with power during stopover or maintenance in airports. The converter fourth leg is used to provide a path for the zero sequence components when feeding unbalanced or non-linear loads. A high bandwidth controller is required to regulate the output voltage of Matrix Converter with a 400Hz output frequency. However, the controller bandwidth is limited due to the reduced ratio between the converter switching frequency and the fundamental frequency. In this case undesirable, periodic errors and distortion will exist in the output voltage above all in the presence of a non-linear or unbalanced load. Digital repetitive control system is proposed to regulate the output voltage of a four-leg Matrix Converter in an ABC reference frame. The proposed control structure introduces a high gain at the fundamental and its integer multiple frequencies. Using the proposed repetitive controller will reduce the tracking error between the output and the reference voltage, as well as increasing the stability of the converter under balanced and unbalanced load conditions. Simulation studies using SABER and MATLAB software packages show that the proposed controller is able to regulate the output voltage during balanced and unbalanced load conditions and during the presence of non-linear load. In order to validate the effectiveness of the proposed controller, an experimental prototype of a 7.5KW has been implemented in PEMC laboratory using DSP/FPGA platform to control the converter prototype. The steady state and the dynamic performance of the proposed control strategy are investigated in details, and extensive experimental tests have showed that the proposed controller was able to offer high tracking accuracy, fast transient response and able to regulate the output voltage during balanced, unbalanced and non-linear loading

Design control and implementation of a four-leg matrix converter for ground power supply application

The technology of direct AC/AC power conversion (Matrix Converters) is gaining increasing interest in the scientific community, particularly for aerospace applications. The aim of this research project is to investigate the use of direct AC/AC three phase four-leg Matrix Converter as ground power unit to supply aircraft with power during stopover or maintenance in airports. The converter fourth leg is used to provide a path for the zero sequence components when feeding unbalanced or non-linear loads. A high bandwidth controller is required to regulate the output voltage of Matrix Converter with a 400Hz output frequency. However, the controller bandwidth is limited due to the reduced ratio between the converter switching frequency and the fundamental frequency. In this case undesirable, periodic errors and distortion will exist in the output voltage above all in the presence of a non-linear or unbalanced load. Digital repetitive control system is proposed to regulate the output voltage of a four-leg Matrix Converter in an ABC reference frame. The proposed control structure introduces a high gain at the fundamental and its integer multiple frequencies. Using the proposed repetitive controller will reduce the tracking error between the output and the reference voltage, as well as increasing the stability of the converter under balanced and unbalanced load conditions. Simulation studies using SABER and MATLAB software packages show that the proposed controller is able to regulate the output voltage during balanced and unbalanced load conditions and during the presence of non-linear load. In order to validate the effectiveness of the proposed controller, an experimental prototype of a 7.5KW has been implemented in PEMC laboratory using DSP/FPGA platform to control the converter prototype. The steady state and the dynamic performance of the proposed control strategy are investigated in details, and extensive experimental tests have showed that the proposed controller was able to offer high tracking accuracy, fast transient response and able to regulate the output voltage during balanced, unbalanced and non-linear loading

Méthode unifiée de simulation et de conception des convertisseurs de puissance

Le développement des convertisseurs de puissance à haute fréquence est en plein essor grâce à l'émergence des technologies vertes telles que les véhicules hybrides et les énergies renouvelables. Ces nouvelles technologies allient l'efficacité des machines électriques à la puissance brute des moteurs thermiques. Les convertisseurs de puissance qui contrôlent ces machines sont des technologies embarquées qui doivent posséder un rendement élevé ainsi qu'une très grande fiabilité. En plus des applications terrestres, les convertisseurs embarqués se retrouvent maintenant dans l'industrie de l'aéronautique et de l'aérospatiale. En ce sens, leur fiabilité et leur rendement deviennent plus que jamais des caractéristiques recherchées. Encore aujourd'hui, le développement d'un convertisseur de puissance demeure une science qualitative. Malgré le fait que plusieurs techniques de commande soient disponibles pour augmenter la stabilité des convertisseurs, il n'existe pas beaucoup de règles systématiques pour la conception physique de l'unité. La plupart du temps, la disposition des composants physiques du convertisseur est réalisée artistiquement sur la plaquette de circuit imprimé aux endroits les plus commodes. Ce manque de rigueur au niveau des problèmes d'interférences électromagnétiques n'est pas tellement surprenant, car l'analyse de ce type de problème est complexe et coûteuse. Souvent, l'espoir de résolution de ce type de problème passe par la conception de plusieurs générations de plaquette de circuit imprimé. En regard à cette problématique, le but de cette thèse est de fournir des outils simples et validés expérimentalement permettant aux concepteurs des circuits imprimés de régler les problèmes de fiabilité à la base lors de la conception de la plaquette. Plusieurs solutions sont exposées concernant 1' orientation du champ magnétique, 1' identification des éléments parasites, la modélisation des semi-conducteurs de puissance et la modélisation électromagnétique des convertisseurs

Nouveaux mécanismes de commutation pour des structures dédiées aux convertisseurs de puissance de haute efficacité et interrupteurs du futur

Nowadays, the scarcity of cheap energy sources requires a particular effort in optimizing the performance of all conversions. The electric power vector is particulary expected to grow in importance, in conjunction with the development of renewable energy sources. Research in the field of power electronics considers several aspects, including conversion topologies, command strategy as well as the structure and performance of power switches. This work focusses on the power component and the study of dedicated power converting structures. One goal is the use of active switches to replace elements with spontaneous behaviors presenting dissipative phenomena, in order to attempt to reduce switching and conduction losses. Indeed, several works introduce bidirectional monolithic switches adopting new structures, and predict high efficiency components in the near future. On the other hand, the emergence of components without spontaneous properties leads to a redefinition of switching mechanisms in power converters in order to enable the replacement of diodes by active devices. One aspect of this work is the investigation of a close control system including the detection of zero-crossings based on the measurement of both voltage and current in bidirectional switches. A voltage-current representation for the exploitation of experimental results is provided in order to allow for comparison with theoretical behaviors. Several material and internal structure types of components are compared in terms of switching performances. The concept of automatic switching was recently introduced to describe mechanisms based on the detection of non-compliant situations in the switching cell, namely the short-circuit of a voltage source and the opening of a current source. The proposal of applying a new control strategy allows to compensate for the absence of spontaneous extinction. Where sources of a classic switching cell are in a situation of energy exchange or isolation, a third state appears in which source values (converter input/output currents and voltages) are subject to fast changes. The use of passive elements becomes compulsory in order to allow a limitation in the theoretical infinite variations of source values. An intelligent close control system allowing a bidirectional component to switch its state on the basis of measurements of both current and voltage was designed and implemented. An automatic diode with synthesized spontaneous switching functions was studied and experimented for the validation of the proposed self-switching mechanisms model including passive circuits. The use of bidirectional switches allows the extension of conventional converter topologies to new modes of operation. This work presents the modification of a current converter topology traditionally implemented with thyristors, to allow for compensation of reactive power. The spontaneous extinction of thyristors is replaced by a controlled extinction which becomes independent of the polarity of source values. However, the forced opening of the input line inductors current path requires to be absorbed by an input filter whose study is proposed in this work

Contribution to the Active Generator Principle:the Gate-commutated Polyphased Matrix Converter

This work is part of the innovative "Active Generator" (AG) project. AG is a concept that suggests a new arrangement of the turbine-generator line of a high power utility (a few hundred of MW) in order to de-synchronize the rotation speed of the turbine-generator group from the fixed grid frequency (50 Hz or 60 Hz). This de-synchronization has essentially two advantages. First, the variable speed of the group enables the operation of the turbine at its best available efficiency in function of the delivered power. Second, the de-synchronization allows to eliminate the gearbox between the turbine and the generator without losing the important degree of freedom in the choice of optimal nominal rotation speed of the turbine. The latter advantage is particularly interesting for high power utilities, whose prime mover is a gas turbine, because for this power range the gearbox constitutes a heavy burden. The de-synchronization is realized with a static frequency converter which is a power electronics circuit composed of silicon power devices. The converter must ensure the same nominal frequency ratio than the gearbox it replaces, which can go above 50%. For such ratio the converter must be inserted between the stator windings of the generator and the grid. There are numerous different frequency converters. Some of them are available as industrial products and others are still in a development state. Not all of these different frequency converters are well adapted to high power applications. In the AG literature, a few recommendations suggest to use a low frequency commutation sequence, combined with a high number of input phases. The high number of input phases ensures a sufficient resolution of the converter's output voltage. Compared to others, this sequence is supposed to decrease the commutation losses of the converter, avoid the usual overdesign of the nominal power of the generator, and, finally, does not require the converter to include bulky intermediary DC storage components (capacitor or inductor). This sequence is a variant of the "Cosine Waveform Crossing" (CWC) method used for Naturally Commutated Cyclo-converters (NCC) and is named slowCWC. However, up till now, there is no converter that is able to run properly with this sequence. Thus a new converter is needed. This PhD work introduces a new converter that is able to fulfill the slowCWC sequence. It is derived from a slight modification of an existing topology (NCC) and is called "gate-commutated Polyphased Matrix Converter" (PPMC). It is a direct frequency converter with a high number of input phases, generally greater than twenty, and a matrix structure of the valves that allows to connect each of the three output phases to each of the generator (input) phases. The valves are bi-directional in voltage and current and are transistor-based to achieve the turn-off capability required by the commutation sequence. The PPMC requires to add protection circuits across each generator stator winding. These circuits protect the stator windings from overvoltages which appear during some forced commutations. In its first part this PhD work uses an analytical approach and the results are expressed in a per unit system that is also adequate to describe the electrical machines. In this first part, it is about the development of design rules for the components of the protection circuits. In addition the energy losses linked to these circuits are evaluated. Those losses strongly depend on the commutation type, which is itself influenced by the presence of the protection circuits. The expression of the duration of natural commutations in the per unit system is also developed in this first part and it constitutes a key parameter in the determination of the commutation type. These theoretical developments are illustrated with numerical simulations. In its second part this PhD work presents the realization of a small-scale experimental set-up with reduced power (1 kW) but a high input phase number (27). The aim of the experimental set-up is to implement and experiment in real-time the command and control algorithm of the PPMC as well as to verify the theoretical predictions developed in the first part. The results of those developments lead to the quantitative assessment of the efficiency of the PPMC. Besides the key parameters that can help to improve this efficiency are pointed out. In certain cases the efficiency of the PPMC is acceptable under the condition that a generator parameter (its leakage reactance) remains under a given limit. This work ends with a list of suggestions for future works related to the improvement of the PPMC and related to the AG project