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ABSTRACT: The matrix converter is an array of controlled bi-directional semi-conductor switches that allows direct ac-ac conversion without an intermediate dc link. This converter has several attractive features that have been investigated in the last two decades. Multilevel converter technology has become increasingly popular in recent years due to high power quality, high-voltage capability, low switching losses and low EMI issues. This paper is concerned with applying multilevel techniques to direct ac-ac power converters and concentrates on developing the concepts of space vector modulation for a multilevel matrix converter. Results from a small-scale experimental prototype are presented to validate the theoretical findings.
IEEE Transactions on Industrial Electronics 02/2012; · 5.16 Impact Factor
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ABSTRACT: This paper presents first an overview of the well-known voltage and current dc-link converter topologies used to implement a three-phase PWM ac-ac converter system. Starting from the voltage source inverter and the current source rectifier, the basics of space vector modulation are summarized. Based on that, the topology of the indirect matrix converter (IMC) and its modulation are gradually developed from a voltage dc-link back-to-back converter by omitting the dc-link capacitor. In the next step, the topology of the conventional (direct) matrix converter (CMC) is introduced, and the relationship between the IMC and the CMCs is discussed in a figurative manner by investigating the switching states. Subsequently, three-phase ac-ac buck-type chopper circuits are considered as a special case of matrix converters (MCs), and a summary of extended MC topologies is provided, including three-level and hybrid MCs. Therewith, a common knowledge basis of the individual converter topologies is established.
IEEE Transactions on Industrial Electronics 12/2011; · 5.16 Impact Factor
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ABSTRACT: This paper considers the design of a high voltage high frequency power supply for industrial electrostatic precipitator applications. The supply is based on a series resonant series-loaded converter. The main aim of this, university-industry partnership, work is to design and experimentally validate the capability of the proposed configuration in achieving higher efficiency and more flexible transient response when compared with a traditional line frequency based power supply. Closed-loop behaviour of the power supply, during sparking events, is also investigated with a non-linear precipitator model.
Energy Conversion Congress and Exposition (ECCE), 2010 IEEE; 10/2010
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ABSTRACT: This paper deals with the design, control, and implementation of a three-phase ground power-supply unit for aircraft servicing. Instead of a classical back-to-back converter configuration, a three-phase direct ac-ac (matrix) converter has been used as the power conditioning core of the power supply, working in conjunction with input and output LC filters. An optimized control system in the ABC frame employing a repetitive controller has been successfully implemented, taking into account both the transient and steady-state performance targets together with the system effectiveness under extreme unbalanced conditions. Extensive experimental tests on a 7.5-kVA prototype prove the efficiency of the designed system in meeting the high demanding civil and military international standards requirements.
IEEE Transactions on Industrial Electronics 07/2010; · 5.16 Impact Factor
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ABSTRACT: This paper proposes a fault tolerant four-phase matrix converter motor drive. The converter is used to drive a permanent magnet synchronous motor (PMSM) for aerospace applications. The use of a fault tolerant topology improves the availability of the drive system under one phase open-circuit faults. To achieve the satisfactory motor performance under fault conditions, an additional redundant output phase is connected to the neutral point of motor windings. The direct space vector modulation technique used for a conventional three-phase matrix converter can be simply applied to the four-phase matrix converter with minor modifications. Moreover, the modified control strategy is introduced to maintain the good system performances with torque ripple minimization under faulted conditions. Experimental and simulation results are shown to verify the effectiveness of proposed fault tolerant four-phase matrix converter drive as well as the associated modulation and control.
Power Electronics, Machines and Drives (PEMD 2010), 5th IET International Conference on; 05/2010
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ABSTRACT: This paper addresses two types of additional losses in induction motors. One is stray load loss resulting from loss segregation when induction motors operate from a sinusoidal supply voltage and the other is harmonic loss when induction motors operate from inverter-fed supply voltage. Both losses are of concern in machine design and operation but they are difficult to predict accurately without the use of empirical factors. This is due to their complex loss mechanisms and small magnitudes relative to output power for high efficiency machines. Compared to total machine power loss, however, they are a significant source of loss. Investigation into the correlation of the two loss components could enable effective quality control of the manufacturing of machines for use on inverter supplies. With the availability of advanced calorimetric and harmonic injection techniques, it becomes possible for these small loss components to be measured with precision. In this paper, seven induction motors ranging in power through 1.1, 7.5, 15 to 30 kW are tested for experimental comparison. Among these are four 7.5 kW machines. Test results suggest there is a need for induction motors designed specifically for inverter-fed operation.
IEEE Transactions on Industry Applications 03/2010; · 1.66 Impact Factor
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Microelectronics Reliability. 01/2010; 50:1738-1743.
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ABSTRACT: This paper investigates the electro-thermal stress levels and related degradation risk affecting standard technology multichip IGBT modules when used in pulsed power resonant converters. Indeed, these feature fairly unique operational characteristics, which differentiate them substantially from more common power electronics applications (e.g., inverters, dc-dc converters). First, an overview of the converter functioning is provided; then, an a priori minimisation of the electro-thermal stress levels affecting the active switches (IGBTs) is searched for: this is based on an experimental parametric study of the turn-off snubber and of the DC-link capacitance value for which the overall switching power losses can be minimised. Accurate calorimetric measurements of the switching losses and infrared measurements of the IGBTs surface temperature during transient operation are presented. Simulation is used to complement the gained information in the frequency range not covered by the experimental method.
Pulsed Power Conference, 2009 IET European; 10/2009
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ABSTRACT: This paper presents an overview of a modular, multi-cellular converter for flexible power management of future electricity networks. The proposed converter is capable of connecting asynchronous grids together as well as incorporating renewable energy systems into the grid and improving power quality. Target applications are expected to be at power levels of around 10 MW and at a system voltage of 10-30 kV. The prototype described in this paper is rated at 300 kVA. The concept of the modular converter is presented along with an outline of its construction. Verification of the control methods for the converter structure is provided by initial experimental results from the prototype converter connected between two low voltage grid systems.
Energy Conversion Congress and Exposition, 2009. ECCE 2009. IEEE; 10/2009
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ABSTRACT: This paper considers the semiconductor thermal cycling monitoring of high power resonant converters. For the tests a single phase resonant converter rated at 1 kV, 250 A (250 kW peak power, duty ratio 10%, 25 kW average power, pulse length 1 ms) has been developed. This represents one phase of a multi-phase resonant power supply designed for long-pulse modulation (typically 1 ms-2 ms) when equipped with a suitable output transformer. Pulsed operation is obtained by direct modulation of the high frequency power supply. The main aim of the work reported here is developed a physic-based multi-chip IGBT structures and experimentally monitoring the chip temperature using high speed thermal imaging, during the pulse, to identify the limitations and reliability of the modulator technology proposed. The paper provides a brief overview of the prototype test rig. Simulations including multi-chip structures, experimental results and high quality chip thermal images are provided to validate the effectiveness of the proposed approaches.
Energy Conversion Congress and Exposition, 2009. ECCE 2009. IEEE; 10/2009
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ABSTRACT: The paper introduces an advanced multicellular power converter structure for flexible power management in future electricity networks. The power converter structure is analysed and the control approaches required in order to overcome the technical challenges of power flow control in such a structure are presented. The operation of the control is verified by simulations and supported by prototype converter experimental results. The results show that the proposed system control works satisfactorily and thus fulfills expected functionality.
Power Electronics and Applications, 2009. EPE '09. 13th European Conference on; 10/2009
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ABSTRACT: This paper presents a low switching frequency, selective harmonic elimination (SHE) modulation method which may be applied to a cascaded H-bridge active rectifier. The method is based on a decoupled scheme where the modulation index of each H-bridge cell is controlled independently to enable complete control of power flow through the converter. The method utilises a phase shift between the AC side cell voltages to achieve the required cell power balancing but with reduced distortion in the output waveform when compared with previously presented methods. Practical results from a laboratory based prototype converter are presented to validate the analysis. Although presented for a single phase topology the method can be applied to a three phase converter.
Power Electronics and Applications, 2009. EPE '09. 13th European Conference on; 10/2009
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ABSTRACT: This paper presents a method for improving the control design for a high-power induction motor (IM) drive employing rotor-flux-based orientation. An offline genetic-algorithm routine is used to estimate the electrical and mechanical parameters of the machine using only speed transient measurements. This routine is applied to a range of operating conditions to obtain an accurate knowledge of the IM parameters as a function of the d -axis motor current id . The information acquired is then employed, together with an enhanced control design obtained by optimizing speed and current transient responses, to increase the performance of the vector control algorithm. The effectiveness of this design method is demonstrated through a wide range of simulations using Matlab-Simulink and experimental results at power levels up to 230 kW.
IEEE Transactions on Industrial Electronics 06/2009; · 5.16 Impact Factor
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ABSTRACT: This paper describes the development of a high-frequency resonant-power converter for high-energy physics (CW) applications. The proposed converter topology has been demonstrated by the construction of a laboratory demonstrator that produces 25 kV with less than 1% ripple at 1 A (25 kW). The converter is a direct converter topology operating without the use of a dc link, significantly reducing the size and weight of the converter and resulting in a relatively high-energy density converter. A high-frequency (20 kHz) resonant circuit is employed which provides inherent short-circuit protection of the converter from the output, while reducing the turns ratio of the transformer. The transformer is integrated into the resonant circuit and operates at the same frequency as the resonant circuit (20 kHz). To achieve high-frequency and high-flux operation of the transformer, an amorphous (nanocrystalline) core is used, further reducing the physical size of the converter. Use of the resonant circuit also allows for soft switching of the IGBTs. High-frequency operation allows for a reduction in size of both the transformer and output filters, thereby removing the need for operation with a crowbar. All of the techniques implemented in the prototype converter may be extended to higher voltage higher power systems.
IEEE Transactions on Plasma Science 05/2009; · 1.17 Impact Factor
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ABSTRACT: This paper considers the calorimetric measurements of losses and the semiconductor thermal cycling monitoring of high power resonant converters. For the tests a single phase resonant converter rated at 1 kV, 250 A (250 kW peak power, duty ratio 10%, 25 kW average power, pulse length 1 ms) has been developed. This represents one phase of a multi-phase resonant power supply designed for long-pulse modulation (typically 1 ms-2 ms) of RF tubes when equipped with a suitable output transformer. Pulsed operation is obtained by direct modulation of the high frequency power supply. The main aim of the work reported here is to monitor semiconductor losses of the IGBT modules through calorimetry and the device temperature using high speed thermal imaging, during the pulse, to identify the limitations and reliability of the modulator technology proposed. The paper provides an overview of the technology and design of the prototype test rig studied. Experimental results, showing semiconductor losses obtained through calorimetry and high quality chip thermal images are provided to validate the effectiveness of the proposed approaches.
High Power RF Technologies, 2009. IET. Conference on; 03/2009
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ABSTRACT: This paper describes the design, construction and testing of a dual-output power converter concept where only the large components, such as the DC link capacitor and heat-sink, are shared between two actuators which are used sequentially in the deployment of aircraft landing gear. This mutual component approach combines the advantages of dual-use power converters with the flexibility of one power converter per application. Practical results of the converter operating are presented for a range of test conditions in order to validate the simulation study.
Applied Power Electronics Conference and Exposition, 2009. APEC 2009. Twenty-Fourth Annual IEEE; 03/2009
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ABSTRACT: Modulation techniques for multilevel converters can create distorted output voltages and currents if the DC-link voltages are unbalanced. This situation can be avoided if the instantaneous DC voltage error is not taken into account in the modulation process. This paper proposes a feed-forward space vector modulation method for a single-phase multilevel cascade converter. Using this modulation technique, the modulated output voltage of the power converter always generates the reference determined by the controller, even in worst case voltage unbalance conditions. In addition, the possibility of optimizing the DC voltage ratio between the H-bridges of the power converter is introduced. Experimental results from a 5-kVA prototype are presented in order to validate the proposed modulation technique.
IEEE Transactions on Industrial Electronics 03/2009; · 5.16 Impact Factor
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ABSTRACT: Simplified space vector modulation (SVM) techniques for multilevel converters are being developed to improve factors such as the computational cost, number of commutations, and voltage distortion. The feedforward SVM presented in this paper takes into account the actual DC capacitor voltage unbalance of the multilevel power converter. The resulting technique is a low-cost generalized feedforward 3-D SVM method and is particularized for three-phase multilevel diode-clamped converters. This new modulation technique can be applied to topologies where the gamma component may not be zero. The computational cost of the proposed method is similar to those of comparable methods, and it is independent of the number of levels of the power converter. Experimental results using a three-level diode-clamped converter are presented to validate the proposed modulation technique.
IEEE Transactions on Industrial Electronics 02/2009; · 5.16 Impact Factor
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Microelectronics Reliability. 01/2009; 49:1352-1357.
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ABSTRACT: Recently, considerable interest has been shown in direct (matrix) converter topologies as an alternative to conventional motor drives. In general, when compared with existing three-phase motor drives (rectifier-inverter types), these topologies offer advantages, such as reduced space and weight (due largely to the removal of the large electrolytic capacitor), four-quadrant operation, and high-quality current waveforms. Consequently, there is now considerable interest regarding direct converters in areas such as aerospace, where issues such as the size and weight of the converter are important. The work presented in this paper capitalizes on these advantages in power conversion for high-power radio-frequency supplies, such as those used in high-energy physics research and associated applications.
IEEE Transactions on Industrial Electronics 01/2009; · 5.16 Impact Factor
