Eiji Hiraki

Terminal voltage regulation characteristics by static var compensator for a three-phase self-excited induction generator

In this paper, the practical impedance approach steady-state analysis in the frequency domain for the three-phase self-excited induction generator (SEIG) with squirrel-cage rotor is presented along with its operating performance evaluations. The three-phase SEIG is driven by a variable-speed prime mover(VSPM) in addition to a constant-speed prime mover (CSPM) such as a wind turbine and a micro gas turbine for clean alternative renewable energy in rural areas. The basic steady-state characteristics of the VSPM are considered in the three-phase SEIG approximate equivalent circuit and the operating performance of the three-phase SEIG coupled with a VSPM and/or a CSPM are evaluated and discussed online under the conditions related to the speed changes of the prime mover and the electrical inductive load power variations with simple computation processing procedures. A three-phase SEIG prototype setup with a VSPM is implemented for small-scale clean renewable and alternative energy utilizations. The experimental performance results give good agreement with those obtained from the simulation results. Furthermore, a proportional-integral (PI) closed-loop feedback voltage regulation of the three-phase SEIG driven by the VSPM on the basis of the static var compensator (SVC) composed of the thyristor phase-controlled reactor in parallel with the thyristor switched capacitor and the fixed-excitation capacitor bank is designed and considered for the wind generation as a renewable power conditioner. The simulation analysis and experimental results obtained from the three-phase SEIG with SVC for its voltage regulation prove the practical effectiveness of the additional SVC with the PI-controller-based feedback loop in steady-state operation in terms of high performance with low cost.

Bidirectional DC-DC Converter with Full-bridge / Push-pull circuit for Automobile Electric Power Systems

In recent years, energy storage systems assisted by super capacitor have been widely researched and developed to progress power systems for the electronic vehicles. In this paper, a full-bridge/push-pull circuit-based bidirectional DC-DC converter and its control methods are proposed. From the results of detailed experimental demonstration, the proposed system is able to perform adequate charge and discharge operation between low-voltage high-current super capacitor side and high-voltage low-current side with drive train and main battery. Furthermore, conduction losses and voltage/current surge are drastically reduced by ZVS operation with loss-less snubber capacitor in high voltage side as well as the synchronous rectification in low-voltage high-current super capacitor side.

Time-sharing boost chopper cascaded dual mode single-phase sinewave inverter for solar photovoltaic power generation system

This paper presents a novel prototype circuit topology and control scheme of a high efficiency time-sharing dual mode single-phase sinewave PWM inverter for small scale solar PV power generation system, which is composed of partially controlled sinewave absolute PWM boost chopper in the first power processing stage as well as partially controlled sinewave PWM inverter in the second power processing stage. Its unique operating principle of two power processing stage with time-sharing dual mode sinewave modulation strategy is described in addition to a design example. Finally, this new conceptual single-phase sinewave PWM inverter related to solar PV power generation system suitable for residential application is evaluated and discussed on the basis of computer simulation and experimental results. The effectiveness of proposed inverter is proved from a practical point of view.

Smart Charger for Electric Vehicles With Power-Quality Compensator on Single-Phase Three-Wire Distribution Feeders

In this paper, we propose a smart charger for electric vehicles (EVs) with a power quality compensator. The proposed smart charger consists of four-leg IGBTs. Three legs are used for a single-phase full-bridge-based PWM rectifier, which converts power from ac to dc during the battery-charging operation, or from dc to ac during the battery-discharging operation. This PWM rectifier can compensate reactive and unbalanced active currents on single-phase three-wire distribution systems because the third leg is connected to the neutral line of single-phase three-wire distribution feeders. The fourth leg is used as a bidirectional dc-dc converter for battery-charging and discharging operations. The three-leg PWM rectifier uses only constant dc-capacitor voltage control, which is commonly used in active power line conditioners. Thus, the authors have developed the simplest possible control method for a single-phase power quality compensator. The basic principle of the proposed smart charger is discussed in detail, and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that balanced source currents are obtained on the secondary side of the pole-mounted distribution transformer for battery-charging and discharging operations.

A Novel Detection Method of Active and Reactive Currents in Single-Phase Circuits Using the Correlation and Cross-Correlation Coefficients and Its Applications

This paper proposes a novel method of detecting the active and reactive currents in single-phase circuits using the correlation and cross-correlation coefficients in the time domain. The active current is detected using the correlation coefficient between the source voltage and load current waveforms, and the reactive current is detected using the cross-correlation coefficient. The basic principle of the proposed detection method is discussed, and the proposed method is applied to a previously proposed single-phase shunt active filter for consumer electronic equipment. Simulation and experimental results demonstrate the excellent practicability of the proposed detection method.

Three-phase self-excited induction generator driven by variable-speed prime mover for clean renewable energy utilizations and its terminal voltage regulation characteristics by static VAr compensator

In this paper, the practical impedance approach steady-state analysis in the frequency domain of the three-phase self-excited induction generator (SEIG) with squirrel cage rotor is presented along with its operating performance evaluations. The three-phase SEIG is driven by a variable-speed prime mover (VSPM) such as a wind turbine for the clean alternative renewable energy in rural areas. The basic steady-state characteristics of the VSPM are considered in the three-phase SEIG approximate electro-mechanical equivalent circuit and the operating performances of the three-phase SEIG coupled by a VSPM in the steady-state analysis are evaluated and discussed on line under the conditions related to the speed changes of the prime mover and the electrical inductive load power variations with simple computation processing procedures. A three-phase SEIG prototype setup with a VSPM is implemented for the small-scale clean renewable and alternative energy utilizations. The experimental performance results give good agreements with those ones obtained from the simulation results. Furthermore, a PI controlled feedback closed-loop voltage regulation of the three-phase SEIG driven by the VSPM on the basis of the static VAr compensator (SVC) composed of the thyristor phase controlled reactor (TCR) in parallel with the thyristor switched capacitor (TSC) and the fixed excitation capacitor bank (FC) is designed and considered for the wind generation as a renewable power conditioner. The simulation analysis and experimental results obtained from the three-phase SEIG with SVC for its voltage regulation prove the practical effectiveness of the additional SVC with the PI controller-based feedback loop in the steady-state operations in terms of the fast response and the high performances.

Quasi-Resonant Dual Mode Soft Switching PWM and PDM High-Frequency Inverter with IH Load Resonant Tank

In this paper, a novel type auxiliary active resonant capacitor snubber assisted zero current soft switching pulse modulation single-ended push pull (SEPP) series load resonant inverter with two auxiliary resonant lossless inductor snubbers is proposed for consumer high-frequency induction heating (IH) appliances. Its operating principle in steady state is described by using each mode equivalent circuits. The new multi resonant high-frequency inverter can regulate its output power under a condition of a constant frequency zero current soft switching (ZCS) commutation principle on the basis of asymmetrical PWM control scheme. The consumer brand-new IH products using proposed ZCS-PWM series load resonant SEPP high-frequency inverter is evaluated and discussed as compared with conventional high-frequency inverter on the basis of experimental results. In order to extend ZCS operation ranges under a low power setting PWM, the pulse density modulation (PDM) strategy is demonstrated for high frequency multi resonant inverter. Its practical effectiveness is substantially proved from an application point of view

An Isolated Bidirectional DC-DC Soft Switching Converter for Super Capacitor Based Energy Storage Systems

In recent years, power electronic energy storage systems using super capacitor bank have been widely studied and developed for the electronic vehicles. In this paper, a full-bridge/centertapped push-pull circuit with active clamp-based soft switching bidirectional DC-DC converter and its control method are presented and discussed. From the results of basic experimental demonstration, the proposed system is able to perform adequate charging and discharging operation between low- voltage high-current super capacitor side and high-voltage low-current side with drive train and main battery. In addition, RCDi snubber losses appeared in the basic circuit topology are drastically reduced by ZCS/ZVS operation with the assistance of newly added active clump circuit, as well as ZVS operation with lossless snubber capacitor in high-voltage primary side.

Next generation high efficiency high power dc-dc converter incorporating active switch and snubbing capacitor assisted full-bridge soft-switching PWM inverter with high frequency transformer for large current output

This paper presents a new circuit topology of dc busline switch-assisted full-bridge soft-switching PWM inverter type dc-dc power converter which is composed of typical voltage source H full-bridge type high frequency PWM inverter in addition to a single dc busline side power semiconductor switching device for PWM scheme and a capacitive lossless snubber. Under the newly-proposed high frequency inverter link dc-dc high power conditioning and processing circuit, all active power switches in the full-bridge arms and dc busline can achieve ZVS/ZVT turn-off commutation operation. On the other hand, although the conduction power loss of dc busline switch increases a little, the total turn-off switching losses of full-bridge type PWM inverter and dc busline switch with the single lossless capacitive snubber parallel with dc busline can be significantly decreased. As a result, the switching frequency of high frequency inverter power stage using IGBTs can be actually selected more than about 10 kHz. The more the switching frequency of full-bridge inverter increases, the more newly-proposed soft-switching dc-dc power converter with a high frequency transformer link has remarkable advantage as for the power conversion efficiency and power density as compared with the conventional hard-switching inverter type dc-dc power converter. The effectiveness of this new converter topology is proved for low voltage and large current dc-dc power supplies from a practical point of views.

Small-scale wind turbine coupled single-phase self-excited induction generator with SVC for isolated renewable energy utilization

In this paper, the static VAR compensator (SVC) composed of the fixed excitation capacitor(FC) in parallel with the thyristor switched capacitor (TSC) and the thyristor controlled reactor (TCR) is applied to regulate and stabilize the generated terminal voltage of the single-phase self-excited induction generator (SEIG) for the passive load variations and the prime mover speed changes. The conventional fixed gain PI controller is employed to adjust the equivalent capacitance of the single-phase SVC in the output of the single-phase SEIG. The closed-loop terminal voltage responses due to different inductive passive load disturbances in the single-phase SEIG using the single-phase SVC with the PI controller are considered and discussed herein. A prototype setup for the single-phase SEIG with SVC voltage regulation feedback control scheme is implemented. The experimental results of this power conditioner are illustrated and give good agreements with the digital simulation results.