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This article proposes the combination of filament-heating and cavity-driven circuit with gain-frequency regulation control for magnetrons. This article is motivated because some existent magnetron-driven systems often adopted two resonant circuits individually for filament heating and cavity driving, resulting in limited flexibility of power delivery and modulation. Therefore, this article develops an integrated resonant power circuit that excels at the capability improvement of filament heating and cavity driving in the same time such that the design process and power conversion can be simplified while the output power is effectively induced. Meanwhile, by considering that the microwave source emission in the magnetron is often affected by the variation of internal impedance, this article includes a gain-frequency tracking control. Through this way of controller design, both heating power and cavity power are found to be well regulated and the constant-power operation can be better achieved. To confirm the effectiveness of this magnetron-driven design, both circuit simulation and hardware realization are accomplished. Analysis results and experimental outcome support the practicality of the approach, benefiting the realization of microwave energy applications.

This article proposes a misalignment-insensitive inductive power transfer (IPT) via interoperable tricoil module and dynamic power control. Since the misaligned coils is known to affect the power transmission efficiency and coupling performance, the article is devoted to the design of an interoperable tricoil module along with power modulation technique in the anticipation of reaching the misalignment-insensitive IPT. In this circuit design, three half-bridge inverters are deployed to drive three transmitting coils. Both geometric structure and magnetic field of coil modules are assessed. A dynamic power control strategy is implemented to adjust the amount of transferable power following the determination of the direction of movement of receiving coils, ensuring a higher efficiency of power transfer and coupling balance at the time of misalignment. To validate the practicality of this approach, the hardware prototype of tricoil module with IPT capability of 3.2-kW is realized with a 7% improvement of efficiency at a misalignment of 100 mm. These results support the feasibility of the proposed approach, serving as beneficial references for automatic guided vehicle applications.

This paper presents a design enhancement of a power supply system for brushless dc (BLDC) motor-driven circuits with state-of-charge (SOC) equalization and capacity expansion. The proposed design incorporates different types of battery as the input power, in which SOC equalization and battery modularization are both concerned. Through the proposed control strategy, it achieves the SOC balance among batteries, avoiding damages caused by overdischarging. Meanwhile, considering that BLDC motors require multiple input sources, this study develops an integrated dual-output converter that exhibits the features of both forward converter and flyback converter. To validate the feasibility of this proposed method, different test scenarios have been evaluated via the prototype completed in the laboratory. Experimental results reveal that this approach is capable of providing consistent outputs under different load conditions along with the achievement of SOC equalization among batteries, thereby serving as beneficial references for BLDC circuit applications.

The study proposes a modular design of plasma-driven system with an integrated resonant circuit and regulation mechanism. This design is developed to increase the expansion capability of plasma-driven systems. In the study, step-up transformers are combined with resonant circuits as a hybrid resonant tank, which is then augmented with plasma loads as a module to provide expandable capacities for a system. Analysis of resonant circuit and connected modules is performed to find design parameters. Feedback voltage control and asymmetric pulse width modulation are meanwhile applied to stabilize the system and regulate the plasma generation. To validate this proposed method, the circuit hardware realization has been completed under different scenarios. Test results indicate that this proposed system produces a higher concentration of plasma with an expanded capacity, supporting the feasibility and practicality for plasma industry applications.

This paper proposes the auxiliary magnetic repeater-aided dual-output wireless charging with coupling analysis and power transfer capability considerations, in which the coupling resonance under different gap distances are concerned as well. This study analyzes the circuit architecture based on the simplification of equivalent models, by which parameters of resonant circuit are determined. Through the proposed design of a dual-output system, the balanced output power is seen to be achieved with higher flexibility. Experimental outcomes indicate that this proposed approach exhibits a satisfactory efficiency under various test scenarios. Test results concluded from comparisons between the proposed system and conventional system further supports the effectiveness of the auxiliary magnetic repeater for the increment of power transfer efficiency and system stability. The outcomes gained from practical tests are anticipated to serve as useful references for automated guided vehicles applications.

This paper proposes a plasma-driven system with piezoelectric transformer-based feedback control approaches along with a contactless power source. The research is motivated because many plasma-driven circuits employed the bulky components as resonant circuit and current feedback sensors. Hence, this study proposes to utilize one piezoelectric ceramic transformer to serve for both resonance tank and feedback devices in order to achieve low cost and design simplification. Moreover, since the plasma discharge often suffers the problem of high humidity and particle-polluted environment, a contactless power transfer circuit integrated with a high-frequency coil is developed as the power source, by which the electrode damage can be better prevented. To reach a better discharge quality and own a higher flexibility of regulating power, the study also completes a constant-power control mechanism and a phase-locked loop control. Both software simulations and hardware realization have been accomplished. Analysis results and experimental outcome help validate the practicality of the proposed approach.

This paper proposes an improved half-bridge inverter with wide-input-voltage capability for ozone-driven circuits. The study is motivated because the limited regulation of input voltage often affects the operation flexibility of ozone-driven circuits. Therefore, a modification of a half-bridge inverter along with a multiwinding coil design is proposed in this study, anticipating an increase in the range of input voltage and benefiting the industry applications. To confirm the practicality of this method, a hardware circuit was made with extensive validation. Experimental outcomes support the feasibility of this proposed method for ozone generators, exhibiting a potential of the method extending to other voltage-source applications.

In this paper, a magnetron-driven system with simple preheat method and power modulation is presented. Since the resonance microwave transmission of the magnetron requires a stable DC high-voltage and an AC preheating voltage, this paper is devoted to simplifying the system architecture while a sufficient resonant gain to drive the magnetron is ensured. In this design, a simple preheating method using the filament coil of the magnetron is also adopted to achieve the preheating requirement of magnetron, which is followed by the utilization of a frequency modulation approach to stabilize the output voltage. To confirm the feasibility of this proposed system, the hardware realization of a 1.3 kW prototype is completed. Experimental results have demonstrated the effectiveness of this magnetron-driven system for microwave industry applications.

In this paper, a wireless power transmission with foreign-object detection (FOD) consideration is proposed. In the foreign-object detecting technique, a closed-loop feedback control is proposed by tracking the voltage and current of transmitting coil in order to signal the occurrence of a significant phase difference, anticipating preventing the system from potential risks. To validate the effectiveness of this method, three scenarios of foreign intrusions are taken into considerations. Experimental results obtained from these test cases consolidate the feasibility of maintaining a better secured power-transmitting system.

This paper presents inductive power transfer (IPT) systems for a piezoelectric transformer (PT) based ozone-driven circuit with flexible capacity operation and frequency-tracking mechanism. The proposed system consists of an IPT circuit as the front stage along with an ozone-driven circuit as the back stage. Considering that the ozone generator system was often used under high-humidity and particle-polluted environment, the study hence proposes a contactless power source such that the oxidization and rustiness can be better avoided. Next, by taking the system expansion into consideration, this paper proposes multiple modular parallel PTs in order to increase the output capacity of the designated circuit. This is further followed by a frequency-tracking control developed to promote power delivery efficiency. To confirm this proposed method, the developed system has been realized with hardware circuit validation. Experimental results demonstrate that the proposed system not only delivers the power effectively, but also ensures balanced output current of each PT, thereby facilitating the approach for the ozone-driven applications.

This paper proposes an application of piezoelectric transformer (PT) based inverters for alternating current (ac) light-emitting diode (LED) lighting-driven systems with a new resonant topology and frequency-tracking technique. This proposed architecture comprises a full-bridge phase-shift inverter with a PT-based C-L-C series resonant circuit, piezoelectric ceramic transformers, and a microwinding resonant transformer to extend the range of operation frequency, hence achieving a two-terminal alternating voltage to drive ac LED arrays while stabilizing the resonant characteristics. In this system design, a frequency-tracking mechanism is also integrated into the field-programmable gate array controller to improve operation efficiency. Since only the secondary current of the resonant transformer is required for the controller, the circuit implementation is simple and additional sensor devices can be largely saved. Moreover, by considering that the frequency-gain characteristics of PTs may be affected due to temperature changes; the controller is designed to adjust the operation frequency swiftly in order to restrict the temperature effect. This proposed method has been verified on modular ac LED lighting systems. Test results confirm the feasibility of the method for lighting system applications.

Leakage current and temperature are common features of zinc oxide (ZnO) arrester degradation in power systems; however, for substation engineers, these key features often bring difficulties in grasping the operating conditions of ZnO arresters because of insufficient maintenance references. Therefore, in this study, the aim is to propose a systematic method to facilitate the realization of predictive maintenance of ZnO arresters in energy systems. The method begins with the feature extraction of ZnO arresters by using on-line resistive current monitoring and infrared radiation (IR) image inspection. A regression model based on the temperature difference, the total leakage current, and the resistive leakage current is then formulated to assist in the insulation diagnosis. This approach is useful to observe the insulation condition, thereby benefiting the predictive maintenance of ZnO arresters. In order to validate the effectiveness of the method, it has been applied to inspect several ZnO arresters installed in a 345 kV substation in Taiwan. Results show that this proposed method performs more effectively than published techniques.

This paper proposes the luminance enhancement with low-frequency driving techniques for cold cathode fluorescent lamp (FL) (CCFL)-based lighting systems. The driver architecture features a full-bridge phase-shift inverter with a resonant tank and a three-winding step-up transformer to reduce leakage current, remove parasitic capacitance, enhance optical efficiency, balance and increase lamp uniformity, and achieve two-terminal high-voltage low-frequency driving of CCFLs. The low-frequency control of the driving technique is implemented in a field-programmable gate array controller to achieve luminance enhancement. The control strategy starts igniting the lamp with a high frequency and then reduces to low frequency in order to facilitate the linear increment of lamp brightness. Through the employment of this proposed approach, since the primary current of the transformers is only required, the circuit implementation can be completed with ease. Experimental results show that the proposed technique and control strategy help enhance luminance efficiency and reduce leakage current, demonstrating the practicality for the application considered.

This paper presents a methodology to reduce the ferroresonance between a bus potential transformer and circuit breaker grading capacitance. It starts with the investigation of the relations between ferroresonance of a bus potential transformer and circuit breaker grading capacitance, where different resistors are simulated to add in the secondary side of bus potential transformers, anticipating that the ferroresonance occurrence can be better comprehended. In the study, both the driving force factor and the ratio of system-to-ground capacitance and inductance are assessed. In order to confirm the feasibility of the proposed strategy, a ferroresonance-suppression device has been developed and several scenarios have been examined through digital simulations, laboratory analyses, and field validations. Test results support this proposed approach for its ferroresonance-suppression application that is considered.

This paper proposes a hybrid firefly algorithm (HFA) to assist in decision-making for reactor arrangement in underground cable transmission systems. The HFA method is proposed based on the analysis of phototaxis behavior of fireflies, and enables solving the optimization problem effectively. In this study, by formulating high relationships among connected reactors, sheath loss, and induced voltage, the HFA method is employed to determine the appropriate reactor placement in an underground transmission systems. Through the tests made on different transmission lines along with the results compared to other methods, the proposed approach provides satisfactory decision support for reactor placement and serves as a beneficial reference for underground transmission planning and design.

A rapid charge strategy based on the residual energy evaluation is proposed for LiFePO $_{4}$ (LFP) batteries to reduce charging time and improve charging performance. In the approach, the residual energy model was formulated based on the measured terminal voltage with respect to a certain state of charge value. Subsequently, the stored energy of an LFP battery was evaluated by using the obtained voltage characterizations. This is followed by the difference calculated between the fully stored energy and the residual energy such that the suitable time to enact the high-rate charge is determined, thereby ensuring a battery of full capacity in stable, safe, and nonovercharged conditions. Moreover, for the hysteresis effects that may affect the battery voltage evaluation, they are also included in the charge process in this study. In order to validate the method, this proposed strategy has been examined from perspectives of charge time, charge efficiency, and the number of charge cycles. Compared with other charge strategies, both the charge time and the charge efficiency are highly improved, hence confirming the feasibility of the method for energy storage applications.

With the time–frequency localization characteristics embedded in Wigner distribution, the time and frequency information of a waveform can be both integrally presented. Yet, due to the cross-term problem, the inspection performance is often affected. Therefore, in this study, with the assistance of a window function design, we have proposed a modified Wigner distribution method and applied to voltage flicker-generated signal analysis. This approach not only effectively reserves the merits of Wigner distribution and short-time Fourier transform, but also highly decreases the probability of cross-term occurrence. In order to confirm the feasibility of the method, it has been tested to inspect several voltage flicker-generated signals collected from both simulated waveforms and field measurements. Test results support the feasibility of the method for the application investigated.

This paper endeavors to apply a hybrid bird-mating optimization approach to connection decisions of distribution transformers. It is expected that with the aid of hybrid bird-mating approach, the voltage imbalance and deviation can be mitigated, hence ensuring a satisfactory supplying power more effectively. To evaluate the effectiveness of this method, it has been tested through practical distribution systems with comparisons to other methods. Test results help confirm the feasibility of the approach, serving as beneficial references for the improvement of electric power grid operations.

This paper proposes to install an additional distribution transformer to convert the open-wye/open-delta connection to wye/delta connection, anticipating mitigating the impact of a larger amount of PV systems connected to the distribution network. To validate the proposed scheme, various amounts and connections of PV systems are analyzed along with the examination of different scenarios. Simulation results confirm the benefits of this scheme to endure a higher impact of PV penetration. The outcomes gained from these tests are practically useful for utility engineers to make planning decisions.

Comprehension of open-circuitvoltage (OCV) function and battery impedance can be used to evaluate the residual energy and dynamic voltage response of lithium batteries. However, noise contamination during data sampling may affect the accuracy of the derived OCV function and battery impedance extraction, resulting in a poor evaluation performance. By aiming at formulating a more representative circuit-based model, this study proposes a hybrid averaging method along with an impedance network observation approach that is embedded within a time-frequency localisation method, anticipating eliminating the influences of sampling noise such that the characterisation of the OCV function and battery impedances can be better ensured. In such an integrated approach, the trimmed relevance vector regression is also added, which is followed by two cascaded R-C networks in order to fit the characteristics of battery impedances. Through the method proposed in this paper, it is found that the average error can be decreased to be less than 20 mV. Both battery residual energy and I-V performance are more effectively comprehended.

In this paper, the circuit design of a resonant inverter for plasma-driven system is studied. Based on the half-bridge inverter structure, the proposed circuit has included the soft-switching techniques so that the investment on heat dissipation can be greatly saved. Moreover, this paper has investigated plasma power control under different conditions. Via the developed control circuit to formulate the relationships between the output power and voltage as a quadratic function, the output power of the system can then be controlled and becomes insensitive to plasma voltage variations. In order to solidify the practicality of this circuit design, mathematical analyses and experimental validations have been thoroughly performed. Test results help confirm the effectiveness of the method, demonstrating its feasibility and practicality for high-frequency-drive industry applications.

In this paper, an inverter array structure for the distributed generation is proposed. In the method, the inverter array is organized by basic and extended units, in which basic units are grouped to evenly share the capacity of primary energy source while extended units are designated for online redundant services. Through this design, it is not only beneficial to improve the reliability of energy production but also owns high flexibility of capability extension. To validate the effectiveness of this method, both simulations and hardware realizations have been made and evaluated. Test results help support the proposed approach for grid-connected operations.

In this paper, a feature extraction approach embedded with wavelet computation is applied to enhance the auxiliary overcurrent protection, by which the transformer inrush current discriminating from internal fault can be achieved. This proposed method starts with a feature extraction of acquired differential current waveform following the execution of wavelet computation. Then, the extracted features are expressed as a group of quantitative turning points to serve as indicators for overcurrent recognition. It is found that by this way of design, the inrush current can be effectively discriminated from the fault current. To validate the effectiveness of the method, it was applied to various simulated scenarios as well as employed to inspect a 60 MVA, 161/23.9 kV transformer connected to a 161 kV power system in Taiwan. Test results help support the feasibility of the method for the application considered. Copyright © 2009 John Wiley & Sons, Ltd.

In this paper, a slantlet transform is proposed with the field-programmable gate array (FPGA) hardware realization for electrical power system disturbance detection. By embedding the slantlet functions into wavelet basis, the method is anticipated to increase the capability of signal discrimination, hence improving the grasping the disturbance intrusion. Furthermore, with the hardware realization of FPGA chip, the practicality of the method can be better ensured. In order to validate the effectiveness of the proposed approach, several scenarios have been considered and verified with good agreement.

In this paper, a wavelet transform-based approach is proposed to detect the occurrence of islanding events in distributed generation systems. Thanks to time–frequency localization capabilities exhibited by wavelet transform, the approach embedded with this transform technique has grasped the appearance of the islanding event in a highly effective manner. Moreover, for those regions which are in need of a better visualization, the proposed approach would serve as an efficient aid such that the mains power disconnection can be better distinguished. To validate the feasibility of this approach, the method has been validated through several scenarios. Test results supported the effectiveness of the method for the application considered.

This paper proposes a circuit that combines the class E inverter with DC-DC converter so as to provide dual controllable outputs. This study is motivated because the industrial equipment often needs different voltage sources to operate, yet with an inadvertent choice of parameters in the isolated converters, the voltage quality is often highly affected. Therefore, by connecting an auxiliary power switch and a diode in series between class E inverter and DC-DC converter, a circuit with dual controllable outputs is suggested. Moreover, the input inductor and a power switch in the class E inverter are shared with DC-DC converter for the energy storage, hence reducing the number of elements when compared to published techniques. This proposed circuit is completed with hardware experiments performed under different load conditions. Test results support the practical values of this proposed circuit for supplying source applications.

The open-wye/open-delta transformers are being adopted in Taiwan to supply either three-phase or single-phase loads, yet it has caused a phase unbalance problem. In this study, a bird-mating optimization (BMO) is hence motivated to assist in the coordinated switching of phase connection in open-wye/open-delta transformers such that the voltage unbalance and power loss can be better ameliorated. By mimicking the bird-mating behaviors, this algorithm excels at the optimal search with a reduced computation effort and a higher efficiency, hence suitable for a better arrangement of phase connection in open-wye/open-delta transformers. To confirm the effectiveness of such an intelligent method, two practical distribution systems of Taiwan Power Company were tested, by which the proposed one was further compared with other published techniques. From the test results, they have demonstrated the feasibility of the method as the decision support to enhance the coordination of phase connection of open-wye/open-delta transformers in a power grid.

This paper presents a wireless power transfer design with pick-up device position detection for dynamic power transmission. Since the fixed-point inductive charging is short of providing the power to the moving equipment, the paper is hence motivated to sense the pick-up device, by which the power and flux can be better regulated, meanwhile benefiting the efficiency and maintaining the voltage profile. As for the control strategy made in this study, the voltage of transmission coil is served as the feedback signal, with which the dynamic protection is reached while the modular platform organized by inductive coils are well accomplished. To validate the effectiveness of this method, the prototype is tested to dynamically deliver the power at 5 cm gap. Test results indicate that the power of each transmission coil can be effectively adjusted, where an 82.55% efficiency of the system can be expected. This method owns a high potential of extending to industrial applications when the dynamic power delivery is considered.

A hybrid-loop control approach applied to inverter circuit design with piezoelectric transducers is proposed in this paper. This approach was motivated because the transducer is easily affected by the temperature effect and damping pressure, causing the mechanical frequency drift and unstable current variation. In view of these demerits, a hybrid-loop control mechanism is suggested to achieve both phase-tracking and constant-current control such that both operation frequency and vibration strength can be well controlled while maintaining a stable mechanical frequency. Moreover, by embedding this hybrid control concept into microprocessor controller units without adding any further sensors devices, the design cost is found to be meanwhile reduced. To validate the feasibility of this approach, the method has been validated through mathematical analysis and hardware realization. Test results confirm the performance improvement of the approach for piezoelectric transducer applications.

In this paper, a continuous wavelet transform-based approach is applied to enhance the damage-detection capability of wind turbine blades. With the time--frequency localization features embedded in wavelets, the time and scale information of the acquired signals can be presented as a visualization scheme, where the condition monitoring of turbine blades can be better realized. Based on these sensor signals, this proposed approach was applied to discriminate the damaged structure from the healthy one under several scenarios. Test results have demonstrated the practicality and advantages of the proposed method for the application considered

In this paper, a new approach for the design of line interactive uninterruptible power supplies (UPS) without load current sensors is proposed. Based on the interactive structure, this system is constructed that includes the power factor improvement capability in anticipation of increasing the quality of supplying power. With the employment of such an approach, the power converter can be adaptively operated at the active power filter mode or backup mode, by which the power can be supplied to the connected load very reliably. Moreover, as the proposed circuit needs only one current feedback signal where the load current sensors can be saved, the circuit design can be thus simplified significantly. In order to confirm the effectiveness of this proposed design, the approach has been tested through the theoretical analysis and experimental validation under different test scenarios. Test results help support the feasibility and practicality of the method for the application considered.

In this paper, an application of wavelet packet-enhanced arithmetic coding to compress the electric power disturbance data is proposed. In the proposed method, the wavelet packet is first applied in anticipation that the disturbance signal can be optimally decomposed into higher frequency components and lower frequency ones on a best wavelet basis. Then, the arithmetic coding approach is utilized to reduce the redundancy of data encoding, thereby lowering down the cost related with data storage and transmission. This integrated method has been tested on different scenarios and the results are compared with other published techniques.

In this paper, a continuous wavelet transform-based approach is proposed to assist the measurement of voltage flicker. With the time-frequency localization characteristics embedded in wavelets, the time and frequency information of a waveform is seen integrally presented, thereby enhancing the monitoring capability of voltage flicker signals at different time intervals. By embodying the Gaussian wavelet function, this proposed wavelet-direct demodulation method was also compared with the frequency-domain direct demodulation and indirect demodulation approaches based on the evaluation of flicker-frequency response and the amount of system frequency deviation. Comparison results indicated that the proposed method owns the higher reliability and better visualization. Signal components at any frequency-of-interest can be also more easily supervised. The approach has been applied to investigate various simulated voltage flicker-generated signals, and inspect the data recorded from the actual arc furnace operation. Test results support the proposed method in good agreement.

In this paper, a new approach for the design of dynamic voltage restorer is proposed. By installing the filtering scheme at utility side and load side, the designated dynamic voltage restorer not only effectively compensates the voltage disturbances, but also helps ensure the supplying power quality. To validate the effectiveness of the method, several disturbance scenarios including voltage sag, oscillatory transients and power surges were examined in the simulation study. This is further supported through the hardware realization of the proposed design, where experimental results obtained under load change and voltage distortion scenarios were both investigated. Test results revealed that the proposed method is able to withstand possible disturbances at a faster dynamic response, thereby consolidating the feasibility and practicality of the approach for the applications considered.

Realization of wavelet transform on field-programmable gate array (FPGA) device for the detection of power system disturbances is proposed in this paper. This approach provides an integral signal-processing paradigm, where its embedded wavelet basis serves as a window function to monitor the signal variations very efficiently. By using this technique, the time information and frequency information can be unified as a visualization scheme, facilitating the supervision of electric power signals. To improve its computation performance, the proposed method starts with the software simulation of wavelet transform in order to formulate the mathematical model. This is followed by the circuit synthesis and timing analysis for the validation of the designated circuit. Then, the designated portfolio can be programmed into the FPGA chip through the download cable. And the completed prototype will be tested through software-generated signals and utility-sampled signals, in which test scenarios covering several kinds of electric power quality disturbances are examined thoroughly. From the test results, they support the practicality and advantages of the proposed method for the applications.

An application of Coiflet wavelet transform for the study of power system disturbance-generated signals is proposed. Because the wavelet transform possesses the time-frequency localization characteristics, the time and frequency information of a waveform can be integrally presented. Therefore, this approach can be more efficient in monitoring time-varying disturbances when compared with those Fourier transform-based methods. Moreover, when compared with the Morlet wavelet transform, the merits of easier implementation presented by Coiflet transform method as a discrete form further solidify the practicality for electric power quality applications. This approach has been validated through various test scenarios, including oscillatory transients, voltage sag, voltage swell, momentary interruption, and flat-top. Test results demonstrated the feasibility of the method for the applications considered.

In this paper, a Morlet wavelet transform approach for the study of time-varying power system harmonics is proposed. By this method, because the time–frequency localization characteristics are embedded in wavelets, the time and frequency information of a waveform can be simultaneously presented as a visualized scheme. Different from the fast Fourier transform, the wavelet transform approach is more efficient in monitoring the signals of interest when time varies. The proposed method has been applied to visualize inrush current harmonics of transformers and to investigate arc-furnace-generated signals. From the test results, the merits of the proposed method have been demonstrated for applications.

An application of continuous wavelet transform (CWT) for the analysis of voltage flicker-generated signals is proposed. With the time-frequency localization characteristics embedded in wavelets, the time and frequency information of a waveform can be integrally presented, thereby enhancing the monitoring of voltage flicker-generated signals at different time intervals. The Morlet wavelet has been selected as the basis function for the CWT in the proposed method. The merit of the method lies in that the signal component at any frequency of interest can be more easily monitored than by discrete wavelet transform (DWT). The high frequency required in the voltage flicker study can be also comfortably accomplished. This approach has been applied to investigate various simulated voltage flicker-generated signals, and inspect the data recorded from the actual are furnace operation. Test results help solidify the practicality and advantages of the proposed method for the applications.

In this paper, an islanding detection approach for dispersed generators with a self-commutated static power converter is proposed. This method is suggested based on the monitoring of the magnitude and sign change in /spl part/f/sub B//|/spl part/P/sub L/. To facilitate the detection process, a designated circuit for generating the output power deviation is also developed. The proposed method has been tested under various scenarios in order to examine the detection performance and operation reliability. It is found that the proposed method effectively detects the islanding event when different amount of power mismatch is considered. Moreover, by employing the simulated disturbances to the test system, the outcome reveals that the probability of false alarm is low. Test results solidify the feasibility of the method for the application considered.

In this paper, a control algorithm for the performance improvement of three-phase three-wired active power filters under nonideal mains voltages is proposed and analyzed. It begins with an analysis of an instantaneous reactive power algorithm that was previously applied to the three-phase active power filter design. In that design, the circuit performance was found unsatisfactory under nonideal test scenarios. Our proposed design was, therefore, motivated in order to solve such problems. In the proposed scheme, not only was the control circuit simplified, but it also served as a potential candidate for the performance improvement of active filter design. The proposed algorithm has been implemented as a prototype. Results of experimental verification under various scenarios are presented.

In this paper, a voltage-source voltage-control active power filter is developed. This active power filter has the performance of current harmonic suppression and power factor correction. The proposed active power filter has the performance of improving power quality of the load side. This performance is superior to the current-control active power filter in which the power quality of the load side depends on the utility directly. Additionally, a new phase shift control circuit is proposed and applied in the developed active power filter prototype.

An application of Morlet wavelets to the analysis of high-impedance fault generated signals is proposed in this paper. With the time-frequency localization characteristics embedded in wavelets, the time and frequency information of a waveform can be presented as a visualized scheme. Different from the fast Fourier transform, the wavelet transform approach is more efficient in monitoring fault signals as time varies. The proposed method has been applied to discriminate the high-impedance faults from the normal switching events, and to examine the faults under various grounds including Portland cement, wet soil and grass. Testing results have demonstrated the practicality and advantages of the proposed method for the applications.

A wavelet transform approach using a Morlet basis function is proposed to supervise power system disturbances in this paper. With the time-frequency localization characteristics embedded in wavelets, the time and frequency information of a waveform can be presented as a visualized scheme. Different from the fast Fourier transform, the wavelet transform approach is more efficient in monitoring various disturbances as time varies. The method has been tested on the detection of various simulated disturbances including voltage sag, voltage swell, momentary interruption and oscillatory transients and on the harmonic analysis of the arc furnace from the field test data. Testing results demonstrated the practicality and advantages of the proposed method for the applications.

In this paper, application of a wavelet transform approach for the data reduction of power quality disturbances is proposed. In this approach, we extracted the difference signals between the original signal and the reference waveform by a subtractor. These extracted signals were then compressed through wavelet transform methods. In this way, the amount of data was shown significantly reduced. The data transmission and storage capability can be also enhanced. We have investigated towards the reduction of various power quality disturbance data by the proposed method. Test results demonstrated the effectiveness of the method for the applications.

This paper proposes a feedback signal detection method and frequency-tracking control approach for inductive power transfer (IPT) systems. The power delivery efficiency is increased by utilizing a resonance compensation circuit and frequency-tracking control. Yet, it was observed that the resonance characteristics of IPT systems are easily influenced by load impedance and coil gap, hence frequency-tracking control is integrated into the microprocessor control unit (MCU) controller such that the operation frequency can be closely locked with the primary current phase. In the circuit design, a voltage across RDS(on) of the power MOSFET is utilized to compensate the resonance features of IPT system, by which the system delivery efficiency and zero-voltage switching can be both achieved. This proposed system has been tested under several scenarios. Test results help confirm the feasibility of IPT module for the application that is investigated.

This paper proposes a contactless energy-transfer system (CETS) for lithium iron phosphate battery-charging circuits. In the study, the design flow of contactless transformers and compensated circuit are investigated through the analysis of their impedance-matching and resonant features, by which the appropriate inductive coils can be optimally determined such that power transmission efficiency can be increased. Moreover, an algorithm of charging strategy is integrated into the microcontroller chip to facilitate the charging process. From theoretical analysis and hardware realization, they help support the proposed approach applied for the performance improvement of lithium iron phosphate battery-charging applications.

This paper proposes a piezoelectric transformer based on a resonant inverter that allows varying-capacity for ozone generation. The drawback of a piezoelectric transformer (PT) lies in its limited ability to transfer power, rendering it unable to provide sufficient current. Therefore, this study proposes a resonance topology with multiple modular parallel PTs using a PT-equivalent circuit derivation, and analyzes the resulting resonance curve characteristics. The proposed resonance topology can flexibly expand the output capacity, and stabilize the resonance characteristics and mechanical frequency. These results show that the proposed device is better suited to controller design. In addition, the study embeds an asymmetrical pulse width modulation (APWM) control concept into the microprocessor control unit such that the operating power of the ozone generator can be well regulated. This method has been realized with hardware circuit verification. Results demonstrate that the proposed inverter effectively drives the ozone generator system, regulates the operation power, and achieves the zero-voltage switching. The proposed design also ensures that the output current of each PT is evenly balanced, thereby facilitating the flexible capacity operations of the approach for industrial applications.

This paper proposes a new resonant circuit enhanced with a new tracking control approach for a piezoelectric transformer-based LED lighting system. In this method, the LED driver architecture features full bridge phase shift converter with C-L-C series-resonant circuit along with the piezoelectric transformer. Then, the concept of tracking control is well designated into the FPGA controller such that a higher efficiency of operation can be better reached. Besides, since only the secondary current of resonant transformer is needed for the controller, it helps facilitate the circuit implementation. From experimental results, they solidify the feasibility of this method for modular LED lighting applications.