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Harmonic pollution is considered to be one of the major power-quality problems in electric power systems. Correct identification of the dominant source of harmonic pollution is an essential step towards solving this problem. The total harmonic power (THP) method is one of the methods proposed in the literature for this purpose. However, the method is still debatable as its complete success has been questioned by some researchers. This paper tries to answer some concerns regarding the success of the THP method in radial systems by using several comprehensive case studies. Then, a modification to the method is proposed to generalize its application to nonradial systems. Moreover, to increase the reliability and applicability of the method, a new time-domain algorithm is proposed for measuring the harmonic, subharmonic and interharmonic powers for single-phase and three-phase four-wire systems. Index Terms--Harmonics, harmonic pollution, harmonic powers, point of common coupling (PCC).

A topology and switching algorithm are presented for producing split-phase output voltages using a current-sourced inverter (CSI). Split-phase generation has previously been accomplished using voltage-sourced inverters (VSIs). There are some advantages to instead using CSIs, such as improved output voltage waveform quality and built-in overcurrent protection; however, two issues have prevented their adoption to date. First, while a CSI does not require the input boost converter used by a VSI when fed from a low-voltage source, it may require a preconditioning circuit to provide the required dc current. Second, no algorithm for producing split-phase outputs with a CSI presently exists. This paper's two major contributions aim to solve these problems. A simple preconditioning circuit is presented to provide the necessary dc current and store energy in a capacitor bank for use during load transients. A switching algorithm is written to produce balanced split-phase output voltages under a variety of unbalanced loading conditions. It is demonstrated using simulation and experimental results on a 400-W prototype that the proposed system is able to successfully generate balanced output voltages under unbalanced, inductive, nonlinear, and transient loading conditions, while equalizing switch utilization and minimizing output voltage ripple. Index Terms--Current supplies, inverters, pulsewidth modulated inverters, pulsewidth modulation.

Although many researchers have investigated the use of different powertrain topologies, component sizes, and control strategies in fuel-cell vehicles, a detailed parametric study of the vehicle types must be conducted before a fair comparison of fuel-cell vehicle types can be performed. This paper compares the near-optimal configurations for three topologies of vehicles: fuel-cell-battery, fuel-cell-ultracapacitor, and fuel-cell-batteryultracapacitor. The objective function includes performance, fuel economy, and powertrain cost. The vehicle models, including detailed dc/dc converter models, are programmed in MATLAB/Simulink for the customized parametric study. A controller variable for each vehicle type is varied in the optimization. Index Terms--Batteries, dc-dc power conversion, fuel cells, optimization methods, vehicles.

In this paper, a MOSFET-based pulsed power supply capable of supplying square pulses of up to 3000 V and widths from nanoseconds to milliseconds is presented and used for an investigation into electroporation-mediated delivery of a plasmid DNA molecule into the pathogenic bacterium Escherichia coli O157:H7. It was concluded that increasing the electric field strength and pulse amplitude resulted in an increase in the number of transformants. However, increasing the number of pulses had the effect of reducing the number of transformants. In all the experiments, the number of calls that were inactivated by the exposure to the pulsed electric field were also measured. Index Terms--Bacterial transformation, DNA transfusion, electroporation, Escherichia coli.

The use of fuzzy logic controllers to improve the performance of HVDC systems under various faults and operating point changes has been well-documented. Recent research has shown that the optimal membership function width in a fuzzy controller is different for different system events (such as current order change or fault). This paper proposes an adaptive approach to designing a fuzzy logic controller for HVDC systems. Simulation data are used to create a look-up table for the fuzzy control system. Based on the operating point and the type and location of fault, the output of the table indicates the membership function width to be used in the fuzzy controller to obtain the best results (i.e., the lowest number of commutation failures). This paper presents the best controllers for nine faults at 27 operating points for the CIGRE benchmark HVDC system, but more importantly, uses trends to develop a method for finding these optimal controllers for other systems without the need for exhaustive simulation of each possibility. Index Terms--Adaptive control, fuzzy logic, HVDC transmission control.

In this paper, the control of an ac-dc-ac converter with a front-end diode rectifier and reduced dc-link capacitor based on the space vector modulation strategy is investigated. The modulation index is time-varying and determined by the instantaneous value of the dc voltage measured by a voltage sensor. Using a small bipolar capacitor, instead of a large electrolytic capacitor on the dc-link, increases the lifetime of the converter and reduces its size. The input current quality of this converter has been shown to be superior to that of the conventional ac-dc-ac converter with front-end diode rectifier. The perfectly sinusoidal local average output voltage can still be achieved under unbalanced input voltage condition by implementing a time-varying modulation index. The rule for determining the dc capacitance has also been studied in this paper. The simulation results obtained from PSIM simulation software and experimental results obtained from the lab prototype are used to verify the theoretical expectations. Index Terms--AC-DC-AC converter, front-end diode rectifier, reduced dc capacitor, space vector modulation, unbalanced input voltage.

STATCOM is a FACTS controller that is used in power systems to regulate the line voltage, enhance the power transmission capacity and extend the transient stability margin. STATCOM is conventionally realized by a voltage-source converter; however, being a current injection device, its performance can be improved when realized by a current-source converter (CSC) that can generate a controllable current directly at its output terminals. In this paper, a STATCOM based on the current-source converter topology is proposed. The nonlinear model of the current-source converter, which is the source of the difficulties in the controller design, has been modified to a linear model through a novel modeling technique. The proposed modeling technique is not based on the linearization of a set of nonlinear equations around an operating point. Instead, the power balance equation and a nonlinear input transformation are used to derive a linear model independent of the operating point. This model acts as the basis for the design of a decoupled state-feedback controller. The proposed STATCOM has been simulated using the PSCAD/EMTDC package. The simulation results show that a CSC-based STATCOM can result in excellent current and voltage waveforms as well as very short response time while operating at a low switching frequency. This makes the proposed scheme suitable for high power applications. Index Terms--CSC, decoupled state-feedback control, FACTS, linear model, STATCOM, VSC.

The control methodology of the active power-line filter is the key element for its successful performance in mitigating the line current harmonics. The control system processes the distorted line current signal and forces the converter to inject the proper compensating current. At the same time, it regulates the dc term, i.e., the dc current in the current source converter topology and the dc voltage in the voltage source converter topology. in this paper, a new intelligent control scheme for a modular single-phase active power filter based on the current source converter (CSC) topology is proposed. The intelligent controller utilizes two adaptive linear neurons (ADALINEs) to process the signals obtained from the power-line. The first ADALINE (the Current ADALINE) extracts the harmonic components of the distorted line current signal and the second ADALINE (the Voltage ADALINE) estimates the fundamental component of the line voltage signal. The outputs of the two ADALINEs are used to construct the modulating signals of a number of CSC modules, each dedicated to eliminate a specific harmonic. The proposed controller is also responsible for activating selected CSC filter module(s) to the electric grid. The automated activation of the corresponding filter module(s) is based on the decision-making rules in accordance with the current total harmonic distortion (TH[D.sub.i]) and the harmonic factor (HF) levels set by the IEEE 519-1992 standard. A special 3-level PWM switching strategy is proposed for the filter modules which results in a 50% reduction in the overall switching losses compared with the 2-level method. The proposed controller adjusts the [I.sub.dc] in each CSC module based on the present magnitude of the corresponding harmonic current which results in optimum dc-side current value and minimal converter losses. The high speed, accuracy, efficiency and flexibility offered by the proposed controller, combined with the fast response and low dc energy storage requirement of CSC topology, are the main advantages of the proposed active filter system. The analytical expectations are verified by digital simulation using EMTDC simulation package. Index Terms--Harmonic mitigation, ADALINE, active power filter, 3-level PWM technique, CSC, EMTDC.

The research on direct ac/ac conversion in the past twenty years has been following two major directions: 1) improving the performance of the original nine-bidirectional-switch matrix converter topology; 2) using converter topologies composed of unidirectional switches only. In this paper, a direct ac/ac converter topology based on current-source converter modules is proposed. It is shown, through analysis and simulation, that the proposed topology is free of any switching difficulties and gives high-quality sinusoidal waveforms on both sides. Furthermore, with the same number of semiconductor devices as in the original nine-bidirectional-switch matrix converter topology, it is able to perform all aspects of frequency changing, real power flow control, and independent reactive power flow control on both sides. The proposed topology finds applications in electric drive industry, as an ac motor drive, and power system industry, as an asynchronous link. Index Terms--AC/AC converter, CSC, frequency changer, high-quality sinusoidal waveforms, independent reactive power flow control, L-C filter, nine-bidirectional-switch, NPT IGBT, real power flow control, semiconductor devices, SVC, THDs, topology.

Three-phase voltage- and current-source converters are the building blocks of a great number of power electronic systems. The origin of difficulties in the control of the above converters is in their nonlinear nature. In this paper, a novel modeling technique is introduced to derive the linear models of the converters from the nonlinear transformations of the conventional nonlinear models. Then, based on the derived linear models, a high-performance linear controller with satisfactory performances is designed. The bold feature of the new model is the independence of the controller design from the operating point. A DSP-based control system has been built in the lab to verify the performance of the new models and the control algorithm. The simulation and experimental results are in close agreement. The results show that the dc term and the ac-side reactive power can be controlled independently in less than one cycle. Index Terms--Control algorithm, converter, DSP, nonlinear, PWM, reactive power.

This paper shows that the voltage-source matrix converter has all the features of an asynchronous intertie, namely: (1) frequency changing capability, (2) 360 [degrees] phase shift range, and (3) bi-directional real power transfer. In addition, it has the capabilities for: (4) series line reactance compensation using a complex conjugate property, and (5) static VAR compensation. Series reactance compensation gives rise to high synchronization power which improves transient stability. The matrix converter also has the flexibility to control both the transmitted real power and, independently, the reactive power flows at the sending-end and receiving-end of the transmission line. Keywords: AC transmission, FACTS, power flow controller, line compensation, phase shifter, asynchronous link, GTO, matrix converter.

This paper shows that by transforming both sides of the matrix converter to the d-q-o frames of their respective frequencies, there is significant simplification in the transformation matrix which enables the network of one side to be integrated to the other. Thus, it is possible to design for operation with field vector control on the motor side and unity displacement factor on the supply side. Laboratory experimental and digital simulation results are presented to substantiate the theory. The matrix converter used in the test is based on three modules of voltage-source SPWM converters to implement the nine switches and it has the innovative feature that the SVC voltages (for displacement factor improvement) can be derived from the zero-sequence voltages.

The peak line-to-line inverter ac voltage, in general, cannot exceed the supply dc voltage and transformers have to be used when voltage step-up is required. This paper describes how the necessity of using a Tri-Level PWM strategy in the Current Source Inverter can be turned into an advantage by producing a voltage boost so that transformers are no longer required. During the frequent occurrence of the 'shoot-through' states, which is the characteristic of the Tri-Level PWM-controlled inverter, magnetic energy builds up in the dc link inductor. At the end of these periods, the [L.sub.dc]d[I.sub.dc]/dt voltage across the inductor augments the inverter output voltage in the same way as in the basic boost type dc/dc converter. The paper describes the circuitry required to ensure linear control. Analytical, simulation, and experimental results are given. Applications are found in all instances where the ac voltage is higher than the available supply dc voltage.

Active power filtering is performed by detecting the line current and voltage signals, generating a current equal-but-opposite to the distortion current using a power converter and injecting the compensating current into the power line. In such applications, it is desirable to combine high power and high switching frequency while minimizing the losses. This asks for special converter topologies and control techniques. In this paper, a multi-converter active power-line filter, based on current-source converter (CSC) modules, is proposed. The power rating and switching frequency of each CSC module is equal to those required for the filtering job divided by the number of modules. The control system utilizes two linear adaptive neurons (ADALINE's) to process the signals obtained from the line. The first ADALINE (the Current ADALINE) extracts the harmonic components of the distorted line current signal and the second ADALINE (the Voltage ADALINE) estimates the fundamental component of the line voltage signal. The outputs of both ADALINE's are used to construct the modulating signals of the filter modules. The proposed modular active filter offers the following advantage: 1) high efficiency due to low conduction and switching losses; 2) high reliability and 3) high serviceability. The proposed active power-line filter treats the ac system on a per-phase basis, has fast response and adapts to the load variations. Theoretical expectations are verified by digital simulation using EMTDC simulation package. Index Terms--Active filter, ADALINE, modular, PWM converter.

Active power-line filtering is conventionally performed by injecting equal-but-opposite of the distortion into the line. The power converter used for this purpose is rated based on the magnitude of the distortion current and operated at the switching frequency dictated by the desired filter bandwidth. Fast switching at high power, even if technically possible, causes high switching losses. In this paper, a new modular approach to active harmonic filtering is proposed. The method utilizes two linear adaptive neurons (ADALINEs) to process the signals obtained from the line. The first ADALINE (the Current ADALINE) extracts the harmonic components of the distorted line current signal and the second ADALINE (the Voltage ADALINE) estimates the fundamental component of the line voltage signal. The outputs of both ADALINEs are used to construct the modulating signals of a number of current-source inverter (CSI) modules, each dedicated to eliminate a specific harmonic. The power rating of the modules will decrease and their switching frequency will increase as the order of the harmonic to be filtered is increased. The overall switching losses are minimized due to the selected harmonic elimination and balanced 'power rating'-'switching frequency' product. Power losses are also reduced by adjusting the [I.sub.dc] in each CSI module according to the present magnitudes of the individual harmonics to be filtered. Speed and accuracy of ADALINE, self-synchronizing harmonic tracking, optimum [I.sub.dc] value and minimal converter losses, high reliability and flexibility and speed and low dc energy requirement of the CSI, result in superb performance of the proposed active conditioner. The theoretical expectations are verified by digital simulation using EMTDC simulation package. Index Terms--Active power filter, ADALINE, CSI, EMTDC.