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Showing papers in "IEEE Transactions on Industrial Electronics in 2002"


Journal ArticleDOI
TL;DR: The most important topologies like diode-clamped inverter (neutral-point clamped), capacitor-Clamped (flying capacitor), and cascaded multicell with separate DC sources are presented and the circuit topology options are presented.
Abstract: Multilevel inverter technology has emerged recently as a very important alternative in the area of high-power medium-voltage energy control. This paper presents the most important topologies like diode-clamped inverter (neutral-point clamped), capacitor-clamped (flying capacitor), and cascaded multicell with separate DC sources. Emerging topologies like asymmetric hybrid cells and soft-switched multilevel inverters are also discussed. This paper also presents the most relevant control and modulation methods developed for this family of converters: multilevel sinusoidal pulsewidth modulation, multilevel selective harmonic elimination, and space-vector modulation. Special attention is dedicated to the latest and more relevant applications of these converters such as laminators, conveyor belts, and unified power-flow controllers. The need of an active front end at the input side for those inverters supplying regenerative loads is also discussed, and the circuit topology options are also presented. Finally, the peripherally developing areas such as high-voltage high-power devices and optical sensors and other opportunities for future development are addressed.

6,472 citations


Journal ArticleDOI
TL;DR: The state-of-the-art view in the development of this matrix converter is presented, starting with a brief historical review and an important part of the paper is dedicated to a discussion of the most important modulation and control strategies developed recently.
Abstract: The matrix converter is an array of controlled semiconductor switches that connects directly the three-phase source to the three-phase load. This converter has several attractive features that have been investigated in the last two decades. In the last few years, an increase in research work has been observed, bringing this topology closer to the industrial application. This paper presents the state-of-the-art view in the development of this converter, starting with a brief historical review. An important part of the paper is dedicated to a discussion of the most important modulation and control strategies developed recently. Special attention is given to present modern methods developed to solve the commutation problem. Some new arrays of power bidirectional switches integrated in a single module are also presented. Finally, this paper includes some practical issues related to the practical application of this technology, like overvoltage protection, use of filters and ride-through capability.

1,879 citations


Journal ArticleDOI
TL;DR: A PWM method is developed for cascaded and hybrid inverters to achieve the same harmonic gains as phase disposition PWM achieves for diode-clamped inverters.
Abstract: Analytical solutions of pulsewidth-modulation (PWM) strategies for multilevel inverters are used to identify that alternative phase opposition disposition PWM for diode-clamped inverters produces the same harmonic performance as phase-shifted carrier PWM for cascaded inverters, and hybrid PWM for hybrid inverters, when the carrier frequencies are set to achieve the same number of inverter switch transitions over each fundamental cycle. Using this understanding, a PWM method is then developed for cascaded and hybrid inverters to achieve the same harmonic gains as phase disposition PWM achieves for diode-clamped inverters. Theoretical and experimental results are presented in the paper.

1,146 citations


Journal ArticleDOI
TL;DR: This paper comprehensively analyzes the relationship between space-vector modulation and three-phase carrier-based pulse width modulation and shows that all the drawn conclusions are independent of the load type.
Abstract: This paper comprehensively analyzes the relationship between space-vector modulation and three-phase carrier-based pulse width modulation (PWM). The relationships involved, such as the relationship between modulation signals (including zero-sequence component and fundamental components) and space vectors, the relationship between the modulation signals and the space-vector sectors, the relationship between the switching pattern of space-vector modulation and the type of carrier, and the relationship between the distribution of zero vectors and different zero-sequence signal are systematically established. All the relationships provide a bidirectional bridge for the transformation between carrier-based PWM modulators and space-vector modulation modulators. It is shown that all the drawn conclusions are independent of the load type. Furthermore, the implementations of both space-vector modulation and carrier-based PWM in a closed-loop feedback converter are discussed.

1,004 citations


Journal ArticleDOI
TL;DR: In this paper, the Industrial Electronics Laboratory at the Swiss Federal Institute of Technology, Lausanne, Switzerland, has built a prototype of a two-wheeled vehicle with two coaxial wheels, each of which is coupled to a DC motor.
Abstract: The Industrial Electronics Laboratory at the Swiss Federal Institute of Technology, Lausanne, Switzerland, has built a prototype of a revolutionary two-wheeled vehicle. Due to its configuration with two coaxial wheels, each of which is coupled to a DC motor, the vehicle is able to do stationary U-turns. A control system, made up of two decoupled state-space controllers, pilots the motors so as to keep the system in equilibrium.

780 citations


Journal ArticleDOI
TL;DR: In this paper, the authors proposed an adaptive MPPT algorithm for photovoltaic (PV) power generation systems based on a short-current pulse of the PV to determine an optimum operating current where the maximum output power can be obtained and completely differs from conventional hill-climbing-based methods.
Abstract: This paper proposes a novel maximum-power-point tracking (MPPT) method with a simple algorithm for photovoltaic (PV) power generation systems. The method is based on use of a short-current pulse of the PV to determine an optimum operating current where the maximum output power can be obtained and completely differs from conventional hill-climbing-based methods. In the proposed system, the optimum operating current is instantaneously determined simply by taking a product of the short-current pulse amplitude and a parameter k because the optimum operating current is exactly proportional to the short current under various conditions of illuminance and temperature. Also, the system offers an identification capability of k by means of fast power-versus-current curve scanning, which makes the short-current pulse-based MPPT method adaptive to disturbances such as shades partially covering the PV panels and surface contamination. The above adaptive MPPT algorithm has been introduced into a current-controlled boost chopper and a multiple power converter system composed of PV-and-chopper modules. Various operating characteristics have experimentally been examined on this multiple PV-and-chopper module system from a practical viewpoint and excellent MPPT performance has been confirmed through the tests.

642 citations


Journal ArticleDOI
TL;DR: Using this approach, it can be verified that the space-vector modulation technique, owing to the intrinsic two degrees of freedom, represents the general solution of the modulation problem of matrix converters.
Abstract: In this paper, a novel representation of the switch state of a three-phase to three-phase matrix converter is presented. This approach, based on space-vector notation, simplifies the study of the modulation strategies, leading to a complete general solution of the problem and providing a very useful unitary point of view. The already established strategies can be considered as particular cases of the proposed general solution. Using this approach, it can be verified that the space-vector modulation technique, owing to the intrinsic two degrees of freedom, represents the general solution of the modulation problem of matrix converters. This technique can be considered the best solution for the possibility to achieve the highest voltage transfer ratio and to optimize the switching pattern through a suitable use of the zero configurations.

579 citations


Journal ArticleDOI
TL;DR: The main results obtained through the research done on these converters over this period are topology and derivation of multicell choppers and voltage-source inverters; harmonics cancellation; open-loop modulation techniques; self-balancing understanding; and optimization.
Abstract: Multicell power converters were introduced ten years ago. This paper summarizes the main results obtained through the research done on these converters over this period: topology and derivation of multicell choppers and voltage-source inverters; harmonics cancellation; open-loop modulation techniques; self-balancing understanding; and optimization. During this same period, industrial products using this technique have been developed and the corresponding know-how has contributed to the field in various ways, such as modular design, low inductance busbars, specific drivers, etc.

540 citations


Journal ArticleDOI
Iqbal Husain1
TL;DR: A hybrid torque-ripple-minimizing controller that incorporates the attractive features of some of the techniques developed in the past decade is presented along with simulation and experimental results.
Abstract: The torque pulsations in switched reluctance motors (SRMs) are relatively higher compared to sinusoidal machines due to the doubly salient structure of the motor. The magnetization pattern of the individual phases together with the T-i-/spl theta/ characteristics of the motor dictate the amount of torque ripple during operation. Both machine design and electronic control approaches have been used to minimize the torque ripple in SRMs. This paper presents an extensive review of the origin of torque ripple and the approaches adopted over the past decade to minimize the torque ripple. A hybrid torque-ripple-minimizing controller that incorporates the attractive features of some of the techniques developed in the past decade is presented along with simulation and experimental results.

397 citations


Journal ArticleDOI
TL;DR: Simulation and experimental results show how to operate this converter in order to maintain equal charge/discharge rates from the DC sources (batteries, capacitors, or fuel cells) in an HEV.
Abstract: This paper presents transformerless multilevel converters as an application for high-power hybrid electric vehicle (HEV) motor drives. Multilevel converters: (1) can generate near-sinusoidal voltages with only fundamental frequency switching; (2) have almost no electromagnetic interference or common-mode voltage; and (3) make an HEV more accessible/safer and open wiring possible for most of an HEV's power system. The cascade inverter is a natural fit for large automotive hybrid electric drives because it uses several levels of DC voltage sources, which would be available from batteries, ultracapacitors, or fuel cells. Simulation and experimental results show how to operate this converter in order to maintain equal charge/discharge rates from the DC sources (batteries, capacitors, or fuel cells) in an HEV.

384 citations


Journal ArticleDOI
TL;DR: The authors present results of bit error measurements taken with an IEEE 802.11-compliant radio modem in an industrial environment and show that the popular Gilbert/Elliot model and a modified version of it are a useful tool for simulating bit errors on a wireless link, despite their simplicity and failure to match certain measured statistics.
Abstract: The design and simulation of coding schemes, medium access control (MAC), and link-layer protocols for future industrial wireless local area networks can be supported by some understanding of the statistical properties of the bit error patterns delivered by a wireless link (which is an ensemble of transmitter, channel, receiver, modems). The authors present results of bit error measurements taken with an IEEE 802.11-compliant radio modem in an industrial environment. In addition to reporting the most important results, they draw some conclusions for the design of MAC and link-layer protocols. Furthermore, they show that the popular Gilbert/Elliot model and a modified version of it are a useful tool for simulating bit errors on a wireless link, despite their simplicity and failure to match certain measured statistics.

Journal ArticleDOI
TL;DR: How the switched reluctance generator (SRG) converts energy as directed by a controller is discussed, and the implications of the energy conversion process on how the SRG is controlled are identified.
Abstract: This paper discusses how the switched reluctance generator (SRG) converts energy as directed by a controller. Beginning with a review of the electromechanics of generation, the paper identifies the implications of the energy conversion process on how the SRG is controlled. The structure of the SRG controller for speed-control and power-control applications is discussed. Practical implementation details for commutation of the SRG are reviewed. Concepts are illustrated with a 6-kW SRG designed to serve as a starter/alternator in automotive applications.

Journal ArticleDOI
TL;DR: An effective balancing strategy suitable for MPC conversion systems with any number of DC-link capacitors is presented here and has been carefully studied to optimize the converter efficiency.
Abstract: The converter topologies identified as diode-clamped multilevel (DCM) or, equivalently, as multipoint clamped (MPC), are rarely used in industrial applications, owing to some serious drawbacks involving mainly the stacked bank of capacitors that constitutes their multilevel DC link. The balance of the capacitor voltages is not possible in all operating conditions when the MPC converter possesses a passive front end. On the other hand, in AC/DC/AC power conversion, the back-to-back connection of a multilevel rectifier with a multilevel inverter allows the balance of the DC-link capacitor voltages and, at the same time, it offers the power-factor-correction capability at the mains AC input. An effective balancing strategy suitable for MPC conversion systems with any number of DC-link capacitors is presented here. The strategy has been carefully studied to optimize the converter efficiency. The simulation results related to a high-power conversion system (up to 10 MW) characterized by four intermediate DC-link capacitors are shown.

Journal ArticleDOI
TL;DR: Simulation and practical results will confirm the performance of the proposed strategy when using the multilevel inverter to control an induction motor by the DTC principle.
Abstract: In this paper, the requirements imposed by a direct torque control (DTC) strategy on multilevel inverters are analyzed. A control strategy is proposed in order to fulfill those requirements when a flying-capacitor multilevel inverter is used. Simulation and practical results will confirm the performance of the proposed strategy when using the multilevel inverter to control an induction motor by the DTC principle. Also, the advantages of using a multilevel inverter with a DTC strategy are shown by simulation results.

Journal ArticleDOI
TL;DR: A new protocol, flexible time-triggered communication on controller area network, is presented, which fulfills both requirements: it supports time- Triggered Communication in a flexible way as well as being an efficient combination of both time- and event- triggered traffic with temporal isolation.
Abstract: The requirement for flexible operation is becoming increasingly important in modern industrial systems. This requirement has to be supported at all system levels, including the field level in process industry, as well as the cell and machine control levels in manufacturing industry, where fieldbus-based communication systems are commonly found. Furthermore, typical applications at these levels require both time- and event-triggered communication services, in most cases under stringent timing constraints, to convey state data in the former case and alarms and management data in the latter. However, neither the requirement for flexible operation under guaranteed timeliness nor for joint support of time and event-triggered traffic are efficiently fulfilled by most of existing fieldbus systems. This paper presents a new protocol, flexible time-triggered communication on controller area network, which fulfills both requirements: it supports time-triggered communication in a flexible way as well as being an efficient combination of both time- and event-triggered traffic with temporal isolation. These types of traffic are handled by two complementary subsystems, the synchronous and the asynchronous messaging systems, respectively. The paper includes a justification for the new protocol as well as its description and worst case temporal analysis for both subsystems. This analysis shows the capability of the protocol to convey real-time traffic of either type.

Journal ArticleDOI
TL;DR: The fundamental theory of the switched reluctance motor is presented with a number of new equations to show how the practical development of a design calculation should proceed, and this leads to a discussion of physical characteristics required to achieve satisfactory performance and to reduce acoustic noise.
Abstract: The fundamental theory of the switched reluctance motor is presented with a number of new equations. It is used to show how the practical development of a design calculation should proceed, and this leads to a discussion of physical characteristics required to achieve satisfactory performance and to reduce acoustic noise. The paper makes a few generic observations on the characteristics of successful products that use switched reluctance motors. It is written at a basic engineering level and makes no attempt to apply sophisticated optimization theory.

Journal ArticleDOI
TL;DR: This paper compares four power converter topologies for the implementation of flexible AC transmission system (FACTS) controllers: three multilevel topologies (multipoint clamped, chain, and nested cell) and the well-established multipulse topology.
Abstract: This paper compares four power converter topologies for the implementation of flexible AC transmission system (FACTS) controllers: three multilevel topologies (multipoint clamped (MPC), chain, and nested cell) and the well-established multipulse topology. In keeping with the need to implement very-high-power inverters, switching frequency is restricted to line frequency. The study addresses device count, DC filter ratings, restrictions on voltage control, active power transfer through the DC link, and balancing of DC-link voltages. Emphasis is placed on capacitor sizing because of its impact on the cost and size of the FACTS controller. A method for the dimensioning the DC capacitor filter is presented. It is found that the chain converter is attractive for the implementation of a static compensator or a static synchronous series compensator. The MPC converter is attractive for the implementation of a unified power flow controller or an interline power flow controller, but a special arrangement is required to overcome the limitations on voltage control.

Journal ArticleDOI
TL;DR: A real-coded genetic algorithm (GA) is used to optimize the noise covariance and weight matrices of the EKF, thereby ensuring filter stability and accuracy in speed estimation.
Abstract: This paper presents a novel method to achieve good performance of an extended Kalman filter (EKF) for speed estimation of an induction motor drive. A real-coded genetic algorithm (GA) is used to optimize the noise covariance and weight matrices of the EKF, thereby ensuring filter stability and accuracy in speed estimation. Simulation studies on a constant V/Hz controller and a field-oriented controller (FOC) under various operating conditions demonstrate the efficacy of the proposed method. The experimental system consists of a prototype digital-signal-processor-based FOC induction motor drive with hardware facilities for acquiring the speed, voltage, and current signals to a PC. Experiments comprising offline GA training and verification phases are presented to validate the performance of the optimized EKF.

Journal ArticleDOI
TL;DR: Experimental results indicate that the proposed modulation technique is effective for the reduction of harmonics in multilevel converters, and both the theoretical and simulation results are well validated.
Abstract: This paper proposes a novel modulation technique to be applied to multilevel voltage-source converters suitable for high-voltage power supplies and flexible AC transmission system devices. The proposed technique can generate output stepped waveforms with a wide range of modulation indexes and minimized total voltage harmonic distortion. The main power devices switch only once per cycle, as is suitable for high-power applications. In addition to meeting the minimum turn-on and turn-off time requirements for high-power semiconductor switches, the proposed technique excludes from the synthesized waveform any pulses that are either too narrow or too wide. By using a systematic method, only the polarities and the number of levels need to be determined for different modulation levels. To verify the theory and the simulation results, a cascaded converter-based hardware prototype, including an 8-b microcontroller as well as modularized power stage and gate driver circuits, is implemented. Experimental results indicate that the proposed technique is effective for the reduction of harmonics in multilevel converters, and both the theoretical and simulation results are well validated.

Journal ArticleDOI
TL;DR: Different ways to introduce soft switching in multicell converters are investigated and the concept of distributing power over several switches, giving more degrees of freedom and using less passive components, is extended further with the stacked multICEll topology.
Abstract: Multicell converters were introduced ten years ago and, over this period, their properties have been thoroughly analyzed. Since then, this concept has lead to some other innovative topologies which are briefly presented in this paper. Different ways to introduce soft switching in multicell converters are investigated. The concept of distributing power over several switches, giving more degrees of freedom and using less passive components, is extended further with the stacked multicell topology. Finally, direct AC-AC converters using the multicell approach are described.

Journal ArticleDOI
TL;DR: A novel DC-AC converter for applications in the area of distributed energy generation systems, e.g., solar power systems, fuel-cell power systems in combination with supercapacitor or battery energy storage, using an isolated multicell topology is presented.
Abstract: This paper presents a novel DC-AC converter for applications in the area of distributed energy generation systems, e.g., solar power systems, fuel-cell power systems in combination with supercapacitor or battery energy storage. The proposed converter is realized using an isolated multicell topology where the total AC output of the system is formed by series connection of several full-bridge converter stages. The DC links of the full bridges are supplied by individual DC-DC isolation stages which are arranged in parallel concerning the dc input of the. total system. Therefore, all switching cells of the proposed converter can be equipped with modern low-voltage high-current power MOSFETs, which results in an improved efficiency as compared to conventional isolated DC-AC converters. Furthermore, the cells are operated in an interleaved pulsewidth-modulation mode which, in connection with the low voltage level of each cell, significantly reduces the filtering effort on the AC output of the overall system. The paper describes the operating principle, analyzes the fundamental relationships which are relevant for component selection, and presents a specific circuit design. Finally, measurements taken from a 2-kW laboratory model are presented.

Journal ArticleDOI
TL;DR: This paper presents some solutions for the active control of the voltages across the flying capacitors in the presence of rapid variation of the input voltage.
Abstract: The multicell converters introduced more than ten years ago make it possible to distribute the voltage constraints among series-connected switches and to improve the output waveforms (increased number of levels and apparent frequency). The balance of the constraints requires an appropriate distribution of the flying voltages. This paper presents some solutions for the active control of the voltages across the flying capacitors in the presence of rapid variation of the input voltage. The latter part of this paper is dedicated to the observation of these voltages using an original modeling of the converter.

Journal ArticleDOI
TL;DR: This new control method is an attractive alternative to the classic multilevel pulsewidth modulation techniques considering the following aspects: voltage and current total harmonic distortion; range of linear operation; and number of commutations.
Abstract: This paper presents a switching strategy for multilevel cascade inverters, based on the space-vector theory. The proposed switching strategy generates a voltage vector with very low harmonic distortion and reduced switching frequency. This new control method is an attractive alternative to the classic multilevel pulsewidth modulation techniques considering the following aspects: (1) voltage and current total harmonic distortion; (2) range of linear operation; and (3) number of commutations.

Journal ArticleDOI
TL;DR: This paper shows how the matrix converter disadvantages-the lack of bidirectional power devices, the lower voltage transfer ratio, and the overvoltages caused by the input filter during power-up-that have delayed the industrial implementation have been overcome.
Abstract: The trend in electrical drives is to integrate the frequency converter, the electrical motor, and even the gear or the pump into a single unit, in order to reduce the costs, to increase the overall efficiency and the equipment reliability. This paper presents the first integrated regenerative frequency converter motor for industry applications, based on a matrix converter topology. The low volume, the sinusoidal input current, the bidirectional power flow, and the lack of the bulky and limited-lifetime electrolytic capacitors recommend this topology for this application. This paper shows how the matrix converter disadvantages-the lack of bidirectional power devices, the lower voltage transfer ratio, and the overvoltages caused by the input filter during power-up-that have delayed the industrial implementation have been overcome. In order to demonstrate the validity of the solution, a 4-kW matrix converter motor prototype is built using a standard frequency converter motor enclosure for testing the requirements for an industrial drive. The tests demonstrate the good performance of the drive.

Journal ArticleDOI
TL;DR: An equivalent circuit of the three-level NPC inverter is derived that facilitates an understanding of the balancing mechanisms and it is illustrated how the natural balancing can be enhanced by using a passive balancing circuit which provides a low impedance at the sampling frequency.
Abstract: This paper explores the natural balancing mechanisms of the three-level neutral-point-clamped (NPC) multilevel inverter. An equivalent circuit of the three-level NPC inverter is derived that facilitates an understanding of the balancing mechanisms. This is followed by a detailed analysis of the balancing mechanisms. The theory is applied to a three-level NPC inverter under vector control. It is shown that this inverter possesses natural balancing mechanisms in which the load impedance and spectra of the switching functions play an important role. Finally, it is illustrated how the natural balancing can be enhanced by using a passive balancing circuit which provides a low impedance at the sampling frequency.

Journal ArticleDOI
TL;DR: The modularity concept applied to medium-voltage adjustable speed drives is addressed and a new modular motor-modular inverter system where the motor winding connections are reconnected into several three-phase groups according to the voltage level is extended.
Abstract: In this paper, the modularity concept applied to medium-voltage adjustable speed drives is addressed First, the single-phase cascaded voltage-source inverter that uses series connection of insulated gate bipolar transistor (IGBT) H-bridge modules with isolated DC buses is presented Next, a novel three-phase cascaded voltage-source inverter that uses three IGBT triphase inverter modules along with an output transformer to obtain a 3-pu multilevel output voltage is introduced The system yields in high-quality multistep voltage with up to four levels and low dv/dt, balanced operation of the inverter modules, each supplying a third of the motor rated kVA The concept of using cascaded inverters is further extended to a new modular motor-modular inverter system where the motor winding connections are reconnected into several three-phase groups, either six-lead or 12-lead connection according to the voltage level, each powered by a standard triphase IGBT inverter module Thus, a high fault tolerance is being achieved and the output transformer requirement is eliminated A staggered space-vector modulation technique applicable to three-phase cascaded voltage-source inverter topologies is also demonstrated Both computer simulations and experimental tests demonstrate the feasibility of the systems

Journal ArticleDOI
TL;DR: This paper covers the range of topics related to sensorless control of switched reluctance motor (SRM) drives from their fundamentals to their limitations and state of the art and future trends to help the reader develop a systematic understanding of the sensorless techniques that have been developed over the past two decades.
Abstract: This paper covers the range of topics related to sensorless control of switched reluctance motor (SRM) drives from their fundamentals to their limitations and state of the art and future trends. This should help the reader to develop a systematic understanding of the sensorless techniques that have been developed over the past two decades. The inherent vulnerability to mechanical failures, extra cost, and size associated with external position sensors such as optical encoders, resolvers, and custom-designed Hall-effect sensors has motivated many researchers to develop sensorless control techniques for SRM drives. Ideally, it is desirable to have a sensorless scheme, which uses only terminal measurements and does not require additional hardware or memory while maintaining a reliable operation over the entire speed and torque range with high resolution and accuracy. Advances in the development of low-cost digital-signal-processor-based microcontrollers have paved the way for the fulfillment of this objective. It is, furthermore, our view that the existing trends in the development of more powerful processors will ultimately replace the concept of sensorless controls with the concept of eliminating the need for position sensing, a concept that will further revolutionize the motor drive technology.

Journal ArticleDOI
TL;DR: A new space-vector pulsewidth-modulation strategy is presented to avoid that low-frequency output voltage distortion in three-level neutral-point-clamped voltage-source inverters.
Abstract: In three-level neutral-point-clamped voltage-source inverters, proper modulation allows the average voltages of the DC-link capacitors to be kept at one-half the level of the DC-link voltage. However, in some operating conditions, a low-frequency ripple appears in the neutral-point potential and its frequency is three times that of the output voltages. As a result, the output voltages also have low-frequency distortion, which includes even and odd multiples of the fundamental. In this paper, a new space-vector pulsewidth-modulation strategy is presented to avoid that low-frequency output voltage distortion. This modulation method tries to balance the voltages of the capacitors by using only three vectors per modulation cycle. The duty ratios are directly calculated from the space-vector diagram, even when balance is not achieved. For all cases, the result is a balanced set of three AC output voltages. Some simulated and experimental results are given to validate the method.

Journal ArticleDOI
TL;DR: In this paper, the input current performance of matrix converters is analyzed, especially with reference to the operating conditions determined by unbalanced supply voltages, and it is concluded that when the input voltages are unbalanced to a significant extent, a dynamic input current modulation strategy has to be preferred, since a lower harmonic line current distortion will appear.
Abstract: In this paper, the input current performance of matrix converters is analyzed, especially with reference to the operating conditions determined by unbalanced supply voltages. The space-vector modulation (SVM) technique is utilized to calculate the duty cycles of the active voltage vectors that must be applied, in each switching cycle period, in order to satisfy the input and output requirements. A detailed theoretical analysis of the input current harmonic content under unbalanced input voltage conditions is presented for two different current modulation strategies. On the basis of numerical simulations as well as measurements on a laboratory prototype setup, the strategies' performance are compared and the validity of the theoretical investigation confirmed. It is concluded that, when the input voltages are unbalanced to a significant extent, a dynamic input current modulation strategy has to be preferred, since a lower harmonic line current distortion will appear.

Journal ArticleDOI
TL;DR: The proposed scheme has shown its robustness on low output voltage distortion, excellent voltage regulation, and it is insensitive to load variation, even under nonlinear loads.
Abstract: This paper presents a novel discrete-time sliding-mode control algorithm for an uninterruptible power supply (UPS) inverter design. The approach offers a dual-loop design, in which a current predictor utilizes the tracking error of output voltage to estimate the desired inductor current, while a current controller is adopted to regulate the inductor current and, thus, produces a control command to the pulsewidth modulation inverter. An explicit condition for stable controller design is derived. The efficacy of this scheme is validated via a successful implementation on a digital-signal-processor-based UPS inverter. The proposed scheme has shown its robustness on low output voltage distortion, excellent voltage regulation, and it is insensitive to load variation, even under nonlinear loads. Experimental studies were performed to further validate the effectiveness of this scheme.