Showing papers presented at "International Power Electronics and Motion Control Conference in 2004"

DC microgrid based distribution power generation system

Abstract: This paper describes an autonomous-control method for a DC microgrid system having distribution power generators. This system consists of following five generation and control units; a solar-cell generation unit, a wind-turbine generation unit, a battery energy-storage unit, a flywheel power-leveling unit, and an AC grid-connected power control unit. The proposed control method intended for suppression of circulating current detects only the DC grid voltage. Each unit could be controlled autonomously without communicating each other. This method brings high reliability, high-flexibility and maintenance-free operation to the system. Experimental results from a 10 kW-prototype system verify the validity and effectiveness of the proposed control method.

Analysis of multiphase space vector pulse width modulation based on multiple d-q spaces concept

Abstract: Multiphase motors are usually designed to have the concentrated winding and nonsinusoidal air gap flux density distribution in order to maximize the torque per ampere. This means that the phase voltage of a multiphase motor has the nonsinusoidal waveform. Accordingly, the conventional analysis on a multiphase space vector pulse width modulation (SVPWM), which is confined to a sinusoidal phase voltage, should be extended to a nonsinusoidal phase voltage. In this paper, based on a multiple d-q spaces concept a novel analysis on a multiphase SVPWM to synthesize an arbitrary nonsinusoidal phase voltage is proposed. Through out this paper, a five-phase inverter is used as a practical example. The basic concepts can be easily extended to an n-phase inverter.

Control characteristics of a fibonacci-search-based maximum power point tracker when a photovoltaic array is partially shaded

Abstract: This paper deals with maximum power point tracking control of photovoltaic generators Photovoltaic generation systems need maximum power point tracker (MPPT) because the output power depends on the operating voltage and current The authors have proposed the MPPT employing line search algorithm with fibonacci sequence Finding maximum power point is difficult when a photovoltaic array is partially shaded, because two or more maximum power points may appear In this paper, the authors improve the proposed method in order to find the global maximum under the partially shaded condition The improved algorithm has good performance in many experiments In addition, the authors also mention that the compensation of the large output fluctuation caused by the proposed MPPT by using a wind turbine generator as a kind of flywheel energy storage

The state of the art of electric vehicles technology

Abstract: In a world where environment protection and energy conservation are growing concerns, the development of electric and hybrid vehicles (EV/HEV) has taken on an accelerated pace. The dream of having commercially viable electric/hybrid vehicles is becoming a reality. Electric and hybrid vehicles are gradually available in the market. This paper reviews the present status of electric and hybrid vehicles worldwide and their state of the art, with emphasis on the engineering philosophy and key technologies. The importance of the integration of technologies of automobile, electric motor drive, electronics, energy storage and controls, and the importance of the integration of society strength from government, industry, research institutions, electric power utilities and transportation authorities are addressed. The challenge of EV commercialization is discussed

Vector control and synchronization of doubly fed induction wind generator system

Abstract: A variable speed constant frequency (VSCF) doubly fed induction generator (DFIG) system using back-to-back converter for wind turbine is described. Based on analysis of stator flux oriented vector control theory of doubly fed induction generator, a maximal power point track (MPPT) and control strategy for the unity power factor of stator output is explored. The paper also discusses the feasibility and advantage of soft synchronizing of doubly fed induction generator to the grid by using stator voltage control method and soft disconnecting of the generator from the grid. The system implementation and the experimental results are given.

A novel type of utility-interactive inverter for photovoltaic system

Abstract: A novel utility-interactive inverter for photovoltaic system is proposed. This inverter has no transformer to reduce the size but has a unique power processing system consisting of a DC-DC converter and a single-phase semibridge inverter. The DC-DC converter is a two-quadrant type and performs boost/buck-mode operations to feed-forward/feed-back the instantaneous power to/from the utility. The feed-backing function is rarely utilized for such as controlling the power-factor in utility side to regulate the utility voltage. Although both the DC-DC converter and the inverter operate with high-frequency switching at all the time in the conventional scheme, only the DC-DC converter or the inverter operate with high-frequency switching in the proposed one. Thus, the switching losses are reduced significantly in the new system. Additionally, the DC-DC converter controls the input current so that the DC-inductor traps the ripple-power fed back from the utility. As a result, a large capacitor is not necessary to connect in the input of inverter in this new system. In the products, the efficiency marked very high value (i.e., 95.5 [%] and 95.1 [%] in the half-load and the rated full-load condition of 4.5 kW, respectively) where the utility voltage is 240 [V/sub RMS/] and the solar-cells voltage is 200 [V]. On the other hand, the total-harmonic-distortion of the utility current of the product marked very low value (i.e., 1.6 [%]) in the rated condition. The size of the power unit including the heat sink is reduced to 2/3 of the conventional one.

Design of PID controller for boost converter with RHS zero

Abstract: This paper gives a new solution for controlling boost converter that exhibits inverse response (IR) due to the presence of right hand side (RHS) zero. The RHS Zero /spl eta/ imposes a limit on the attainable closed-loop bandwidth of the controlled converter thereby reducing the controller gain K/sub c/. A comparative study is made by introducing different controller tuning methods such as internal model control (IMC), synthesis, equating coefficient and Ziegler-Nichol's (Z-N) techniques applicable to voltage control of dc-dc boost converter. The paper also presents closed loop simulation results of the converter for load regulation and line fluctuation. The results reveal that, synthesis method gives superior performance in terms of lowest ISE value.

Medium voltage drives: what does the future hold?

Abstract: Medium voltage industrial AC drives have been in use for a number of decades. The technology has evolved and is well accepted today, however, one medium voltage drive can look quite different from the next. This paper will review the present topologies implemented by manufacturers. It will discuss new and enabling technologies which could impact medium voltage drives in the future. An example of such a technology is the power semiconductor device. Its present state and possible evolution will be presented along with the potential impact on medium voltage drive topologies. The paper will conclude with a hypothesis of a future medium voltage industrial AC drive accounting for the needs of the end user

A bidirectional DC/DC power electronic converter for an energy storage device in an autonomous power system

Abstract: The paper discusses a bidirectional DC/DC converter for interfacing an energy storage device in an autonomous power system, which consists of wind turbines and diesel generation units. The operation condition variations, such as switching load, could cause significant dynamics in an autonomous system. An energy storage device can effectively increase the utilization of the renewable energy and improve the capability of dealing with dynamics. This paper studies a two-bridge type of power electronic system for interfacing an energy storage system that can provide the short-term power balance and smoothes the power variation. A control strategy is presented. The simulation results have demonstrated that the system can provide fast response to secure the system reliability and power quality

An integrated power electronics modular approach: concept and implementation

Abstract: Assemblies of power semiconductor switches achieved to some extent, the number of interconnects and their associated drive circuit are at present available in modules. Upward into the multikilowatt range, mixed mode module construction is used. This incorporates monolithic, hybrid, surface mount and wirebond technology. However, a close examination of the applications in motor drives and power supplies indicates that there has been no dramatic volume reduction of the subsystem. The power semiconductor modules have shrunk the power switching part of the converter, but the bulk of the subsystem volume still comprises the associated control, sensing, electromagnetic power passives (inductors, transformers, capacitors) and interconnects. This paper addresses the improvement of power processing technology through advanced integration of power electronics. The goal of a subsystem in a module necessitates this advanced integration, incorporating active switching stages, EMI-filters and electromagnetic power passives into modules. The central philosophy of the technology development research in the National Science Foundation Engineering Research Center for power electronic systems is to advance the state of the art by providing the concept of integrated power electronics modules (IPEMs) for all these functions. The technology underpinning such an IPEM approach is discussed. The fundamental functions in electronic power processing, the materials, processes and integration approaches and future concepts are explained

Study on regenerative braking of electric vehicle

Abstract: This paper discusses the regenerative braking system for electric vehicle (EV) that performs regenerative energy recovery based on analytical deduction of several regenerative braking systems with the microscopic view of pulse width modulation (PWM) driving, a constant regenerative current control scheme is proposed, thereby providing improved performance and the energy recovery efficiency at minimum cost. Experimental results of EV show that the proposed regenerative braking control strategy has not only excellent control performance, but also make the very significant energy saving possible.

Control and topologies for three-phase three-level active power filters

Abstract: Active power filters have been reported effective in eliminating the reactive and harmonic current in the power lines. Most previously proposed methods are based on two level inverters and thus are suitable for low voltage use. In this paper, topologies and control are proposed for three-level three-phase active power filters that expend the voltage and power to the levels desirable for industrial applications. The proposed three-phase active power filter with one-cycle control features high voltage operation with reduced voltage stress on the semiconductor components and simple control circuitry that needs no reference calculation, dq conversion, nor multipliers. Laboratory experimental results based on a 1 kW prototype have demonstrated excellent harmonic suppression capability and rigid robustness.

Suppression techniques of common-mode voltage generated by voltage source PWM inverter

Abstract: Voltage source PWM inverters generate high frequency common-mode voltage, which induces high shaft voltage, leads to bearing current, and results in premature bearing failure. The generating mechanism of common-mode voltage of voltage source PWM inverters is discussed, which illustrates that common-mode voltage is ladder-type high dv/dt and high frequency step voltage, its amplitude varies with the states of switching devices. According to theoretical analysis and based on conventional sinusoidal output filter, common-mode connection is introduced, i.e., the neutral point of filter Y-connected RC network is connected to the midpoint of DC bus of the inverter. Thus, an improved common-mode sinusoidal output filter is achieved, which can eliminate over-voltage and suppress common-mode voltage, the differential-mode and common-mode problems can be solved synchronously. Simulations and experiments indicate the effectiveness of the proposed common-mode filter.

Continuing education in power electronics

Abstract: Continuing education has become an increasingly important part of the mission of higher education in the United States and around the world. The objective of engineering continuing education is to help practicing engineers stay current with technology advances relevant to their current or future job assignments. This paper presents the strategies and guidelines for the continuing education in power electronics. Critical issues pertaining to engineering education, such as on how to identify learning needs, define learning outcomes, design course contents, select instructional methods, assess student performance, and conduct course evaluation, are discussed in details.

A fuel cell system with Z-source inverters and ultracapacitors

Abstract: In this paper a fuel cell system with Z-source inverter and ultracapacitors for voltage sag compensation is proposed The structure of Z-source inverter is simple It has unique features that can boost without a DC/DC converter using only a modified switching pattern Fuel cells have unique output characteristics The fuel cell system can experience start-up transient and voltage sag Simulation results show that the proposed fuel cell system with Z-source inverter and ultracapacitors is capable of operating with stable response to the system transient and voltage sags

DC link and dynamic performance features of PWM IGBT current source converter induction machine drives with respect to industrial requirements

Abstract: When rating the IGBT PWM current source induction machine drive in relation to industrial requirements, there are some important performance features to be studied. These are especially the dynamic control performance and the size and influence of the inductance in the DC link. These subjects and their interference are evaluated here, giving a basis for rating. With a high pulse frequency of the converters, with respect to the current ripple, only a low inductivity in the DC link is necessary, leading to low weight and volume and improving the ideal basic dynamic performance, too. A high dynamic performance, comparable to PWM voltage source induction machine drives, is reached when, beneath a DC link inductance with suitable low inductivity, selected control methods as field oriented control and, as chosen here, optimal state control, are applied. The basic performance is analysed and the the results are partially verified by measurements at a 7.5 kW test drive.

Novel hybrid 12-pulse line interphase transformer boost-type rectifier with controlled output voltage

Abstract: This paper describes two novel hybrid 12-pulse line interphase transformer rectifier systems with integrated single-switch or two-switch boost-type output stage. The boost stage allows controlling the output voltage to a constant value independent of line voltage or output power variations. In combination with low complexity and/or high reliability the hybrid rectifier concept therefore is of potential interest for supplying electrically powered actuators of future more-electric-aircrafts. The principle of operation and the dimensioning of the systems are discussed. Furthermore, a control concept guaranteeing a symmetric distribution of the load current to the individual systems of the two-switch topology is proposed. The theoretical considerations are experimentally confirmed for a 10 kW laboratory prototype. Finally, the single- and the two-switch system are comparatively evaluated concerning input current ripple, power factor, and overall efficiency.

An improved space vector PWM control algorithm for multilevel inverters

Abstract: The research on the multilevel inverter has been receiving wide attention mainly due to its capability of high voltage operation without switching devices connected in series. In this paper, a simple, detailed and general space vector algorithm is given. To facilitate the design and digital implementation of the space vector algorithm, all the space vectors are transformed from the commonly used Cartesian coordinate system to a 60/spl deg/ coordinate system. At the same time, two switching states selection algorithms are studied for multilevel inverters: large small alternation (LSA) method and all mean (AM) switching states method, in which the latter one can give better performance in terms of the harmonics content on the transformer primary side though it has a higher device switching frequency than that of LSA. AM switching states selection method makes the concept of space vector modulation (SVM) consistent in two-level voltage source inverters and multilevel inverter; both output equivalent mean switching sates in every sampling period. Both of these two methods also features easy implementation and generality and can be used in any high-level cascaded H-bridge inverters. They are verified through computer simulations and experiments.

Evaluation of additional loss in induction motors, consequent upon repair and rewinding

Abstract: This paper is concerned with the effect upon the efficiency, and particularly the effect on the stray load loss of induction motors due to the process of repair and rewinding. To assess these changes, a range of induction motors covering powers between 5.5 kW and 225 kW have been very carefully tested both before and after rewinding. The sources of loss in induction motors are several, and all apart from stray load loss can be determined experimentally with reasonable accuracy. Stray load loss however is more challenging. The standard experimental approach of input-output power measurement, using the IEEE 112-B or C390 technique, is frequently used to evaluate stray load loss but has limitations. A limited set of results obtained by calorimetric methods has been used to validate the standard test methods. The most significant changes to the loss in induction motors caused by the repair process would be expected to be to stator copper loss, to core loss and to stray load loss. This is shown to be the case but the overall effect is normally less than 0.5% efficiency loss. Occasionally efficiency loss up to 0.8%, occurs for motors with core faults from new. With random-wire-wound machines, it is possible to compensate somewhat for this increase in core and stray load loss by using a 'tight' winding to reduce the copper loss. The trade associations of machine repairers EASA (USA) and AEMT (UK) sponsor the work as part of research into the influence of electric motor repair upon machine losses.

Zero-voltage-switching PWM full-bridge three-level converter

Abstract: This paper proposes a novel control scheme allowing the full-bridge (FB) three-level (TL) converter to achieve zero-voltage-switching (ZVS) for the main switches while operating under three-level mode and two-level mode without penalizing the efficiency, which makes the converter adaptive to wide input voltage range. Furthermore, the voltage stress of the main switches is only half of the input voltage, which makes it very suitable in high input voltage applications. Compared with traditional FB converter, the output filter inductance of FB TL converter is significantly reduced due to lower high-frequency content of the secondary rectified voltage. Additionally the input current of the converter has quite little ripple, the input filter can be reduced. The operation principle of the FB TL converter is analyzed and verified on a 3 kW, 100 kHz prototype.

PM brushless drives with low-cost and low-resolution position sensors

Abstract: PM brushless AC (BLAC) motor drive usually requires a high-resolution sensor, e.g. encoder, for rotor position detection. However, the encoder encounters problems such as high cost, low reliability, complicated installation and limited operation speed. To eliminate the encoder, a position estimation method using one or three low-cost and low-resolution Hall sensors is proposed for BLAC drive. A BLDC drive with a single Hall sensor is also presented. Both are experimentally investigated, with some particular problems being highlighted and solved.

Impact of voltage phase jump on loads and its mitigation

Abstract: Mitigation of the impacts of source-side voltage disturbances through series voltage compensation technique is considered The power quality enhancement technique is shown to result in phase shift on load terminal voltages The effect of the phase-shift on the loads is then examined by taking the dynamics of the loads under the phase disturbance condition into consideration The analysis permits an insight into the inherent characteristics of the load dynamics to be gained A new method of introducing the phase shift is then proposed The method balances the need for achieving acceptable load swings while maximizing the saving in the stored energy of the series custom power device

Fuzzy logic speed control of a DC motor

Abstract: This work presents a simulation of the speed control of a DC motor using fuzzy logic control (FLC) at MATLAB environment. The fuzzy logic controller designed in this study applies the required control voltage based on motor speed error (e) and its change (ce). The performance of the driver system was evaluated through digital simulations using Simulink toolbox of Matlab/spl reg/. The simulation results show that the control with FLC outperforms PI control in terms of overshoot and steady state error.

A novel three-level SVPWM algorithm considering neutral-point control, narrow-pulse elimination and dead-time compensation

Abstract: This paper introduced a simple but effective three-level SVPWM algorithm. On the basis of this algorithm, a simple neutral-point balancing and narrow-pulse elimination algorithm without current sensor is proposed, and dead time is compensated in the algorithm also. The result of test verified that this algorithm is simple to be carried out, harmonics in output waveform are small, neutral-point potential can be controlled very well and narrow-pulse problem is solved as well. Because dead time is compensated at the same time, the output waveform is improved and output torque is strengthened at low frequency. Finally, good result was achieved on a three-level model inverter developed with TMS320LF2407 DSP.

Adjustable speed drives - future challenges and applications

Abstract: The main trends within adjustable drives in industrial and appliance applications for the next decade are discussed based on the newest developments seen on the market and a few historical trends. Different drive configurations are presented and the general demands to adjustable speed drives are specified. Further on power architectures and motor types are discussed in a short term and long-term view. Possible drivers of the future development are identified, and the concept of an 'electronic motor' is discussed. A number of applications are presented where variable speed is attractive

Analysis and mitigation of interactions between PFC converters and the AC source

Abstract: Converter-source interaction is a common phenomenon in power electronic systems and can lead to deteriorated performance or even system instability. Experimental results are first presented in this paper to demonstrate that such interactions also exist in AC systems involving single-phase PFC converters and can lead to significantly increased harmonic distortion. Mathematical models and experimental measurement techniques are then presented for the prediction and analysis of such interactions. A mitigation method based on damping of the PFC converter input filter is also presented. Emphasis of the work is applications in future airborne power systems where undesirable converter-source interactions are likely to occur due to limited system capacities and the use of large number of PFC converters

Differential mode EMC input filter design for a three-phase buck-type unity power factor PWM rectifier

Abstract: For a three-phase buck-type PWM rectifier input stage of a high-power telecommunications power supply module a differential mode EMC filter is designed which ensures compliance to EN 55022 class B. The design is based on a harmonic analysis of the converter input current and a mathematical model of the measurement procedure including the LISN and the test receiver. Guidelines for a successful filter design are given and components for a 5 kW prototype of the rectifier system are selected. There, the damping of filter resonance is optimized for given attenuation in order to facilitate a higher stability margin for the system control. Furthermore, the dependency of the filter input and output impedances and attenuation characteristic on the inner mains impedance is discussed. Finally, the theoretical considerations are verified by conducted emission measurements and the high quality sinusoidal shape of the resulting mains current is demonstrated.

Active control of a hybrid fuel cell-battery system

Abstract: A hybrid system of a fuel cell and battery connected to a non-linear load is presented in this paper. As the load is subject to change drastically, a control system is designed to protect the fuel cell against sudden change of load power. In order to design control system, numerous experiments have been performed on fuel cell and battery to determine the time constants. Modeling and analysis of the system as welt as simulation and experimental results are presented.

A new type of induction machine with inner and outer double rotors

Abstract: A new type of double-rotor induction machine (DRIM) with inner and outer rotors has the advantage of low leakage inductance and high operation performance. This paper introduces the structure and operation principle of the DRIM. A prototype machine has been designed and built. The magnetic field analysis by means of the MAGNETO software shows that the magnetic field distribution of the DRIM is reasonable and similar to the conventional machine, in spite of its structure and stator windings being greatly different from the conventional induction machine

Power electronics as efficient interface of renewable energy sources

Abstract: The global electrical energy consumption is steadily rising and consequently there is a demand to increase the power generation capacity. A significant percentage of the required capacity increase can be based on renewable energy sources. Wind turbine technology, as the most cost effective renewable energy conversion system, will play an important part in our future energy supply. But other sources like microturbines, photovoltaics and fuel cell systems may also be serious contributors to the power supply. Characteristically, power electronics will be an efficient and important interface to the grid and this paper will first briefly discuss three different alternative/renewable energy sources. Next, various configurations of the wind turbine technology are presented, as this technology seems to be most developed and cost-effective. Finally, the developments and requirements from the grid are discussed.