Analysis and implementation of a high‐efficiency zero‐voltage‐zero‐current‐switching DC–DC converter

A high‐efficiency zero‐voltage‐zero‐current‐switching DC–DC converter with ripple‐free input current is presented. In the presented converter, the ripple‐free boost cell provides ripple‐free input current and zero‐voltage switching of power switches. The resonant flyback cell provides zero‐voltage switching of power switches and zero‐current switching of the output diode. Also, it has a simple output stage. The proposed converter achieves high efficiency because of the reduction of the switching losses of the power switches and the output diode. Detailed analysis and design of the proposed converter are carried out. A prototype of the proposed converter is developed and its experimental results are presented for validation. Copyright © 2011 John Wiley & Sons, Ltd.     

A novel prototype of auxiliary edge resonant bridge leg link snubber‐assisted soft‐switching sine‐wave PWM inverter

This paper proposes a new circuit topology of the three‐phase soft‐switching PWM inverter and PFC converter using IGBT power modules, which has the improved active auxiliary switch and edge resonant bridge leg‐commutation‐link soft‐switching snubber circuit with pulse current regenerative feedback loop as compared with the typical auxiliary resonant pole snubber discussed previously. This three‐phase soft‐switching PWM double converter is more suitable and acceptable for a large‐capacity uninterruptible power supply, PFC converter, utility‐interactive bidirectional converter, and so forth. In this paper, the soft‐switching operation and optimum circuit design of the novel type active auxiliary edge resonant bridge leg commutation link snubber treated here are described for high‐power applications. Both the main active power switches and the auxiliary active power switches achieve soft switching under the principles of ZVS or ZCS in this three‐phase inverter switching. This three‐phase soft‐switching commutation scheme can effectively minimize the switching surge‐related electromagnetic noise and the switching power losses of the power semiconductor devices; IGBTs and modules used here. This three‐phase inverter and rectifier coupled double converter system does not need any sensing circuit and its peripheral logic control circuits to detect the voltage or the current and does not require any unwanted chemical electrolytic capacitor to make the neutral point of the DC power supply voltage source. The performances of this power conditioner are proved on the basis of the experimental and simulation results. Because the power semiconductor switches (IGBT module packages) have a trade‐off relation in the switching fall time and tail current interval characteristics as well as the conductive saturation voltage characteristics, this three‐phase soft‐switching PWM double converter can improve actual efficiency in the output power ranges with a trench gate controlled MOS power semiconductor device which is much improved regarding low saturation voltage. The effectiveness of this is verified from a practical point of view. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(4): 64–76, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20207     

Recurrent modified Elman neural network control of PM synchronous generator system using wind turbine emulator of PM synchronous servo motor drive

The recurrent modified Elman neural network (NN) controlled a permanent magnet (PM) synchronous generator system, which is driven by wind turbine emulator of a PM synchronous motor servo drive, is developed to regulate output voltage of rectifier (or AC to DC power converter) and inverter (or DC to AC power converter) in this study. First, the wind turbine emulator of a closed loop PM synchronous motor servo drive is designed to produce the maximum power for the PM synchronous generator system. Then, the rotor speed of the PM synchronous generator, the output DC bus voltage and current of the rectifier are detected simultaneously to yield maximum power output of the rectifier through DC bus power control. Because the PM synchronous generator system is a nonlinear and time varying dynamic system, the online training recurrent modified Elman NN control system is developed to regulate DC bus voltage of the rectifier and AC line voltage of the inverter in order to improve the control performance. Furthermore, the online training recurrent modified Elman NN control system with the variable learning rate is derived based on Lyapunov stability theorem, so that the stability of the system can be guaranteed. Finally, some experimental results are verified to show the effectiveness of the proposed recurrent modified Elman NN controlled PM synchronous generator system.     

A novel PWM technique with switching‐loss reduction for independent drive of two 3‐phase AC motors fed by a five‐leg inverter

This paper presents a novel pulse width modulation (PWM) technique with switching‐loss reduction for a five‐leg inverter (FLI). The PWM technique, in which the available maximum voltage for two motors adds up to DC bus voltage, has been proposed as the strategy for the FLI. Therefore, the DC bus voltage is fully available as the PWM strategy. However, the conventional PWM technique requires the frequency, phase, and amplitude of the phase voltage commands of a motor to produce zero‐sequence voltages (ZSVs). The novel PWM strategy has some efficient features. These features are discussed in this paper. The validity of the novel PWM technique will be shown by experimental results. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

ZVS DC/DC converter with series half‐bridge legs for high voltage application

This paper presents a new DC/DC converter with series half‐bridge legs for high voltage application. Two half‐bridge legs connected in series and two split capacitors are used in the proposed circuit to limit the voltage stress of each active switch at one‐half of input voltage. Thus, active switches with low voltage stress can be used at high DC bus application. In the proposed converter, two circuit modules are operated with an interleaved pulse‐width modulation scheme to reduce the input and output ripple currents and to achieve load current sharing. In each circuit module, two resonant tanks are operated with phase‐shift one‐half of switching cycle such that the frequency of the input current is twice the frequency of the resonant inductor current. Based on the resonant behavior, all MOSFETs are turned on at zero voltage switching with the wide ranges of input voltage and load conditions. The rectifier diodes can be turned off at zero current switching if the switching frequency is less than the series resonant frequency. Thus, the switching losses on power semiconductors are reduced. The proposed converter can be applied for high input voltage applications such as three‐phase 380‐V utility system. Finally, experiments based on a laboratory prototype with 960‐W rated power are provided to demonstrate the performance of proposed converter. Copyright © 2011 John Wiley & Sons, Ltd.     

A new method of damping harmonic resonance at the DC link in a large‐capacity rectifier‐inverter system

This paper proposes a new method of damping harmonic resonance in the DC link of a large‐capacity rectifier‐inverter system, such as in rapid‐transit railways. A voltage‐source PWM converter is connected in series to the DC capacitor of the rectifier through a matching transformer, acting as a damping resistor to the DC capacitor current. No filters are needed to extract harmonic components from the DC capacitor current. This results in a quick response and highly stable damping. The relationship between the control gain of the PWM converter and the required rating is theoretically discussed. We show that the required rating is less than one‐thousandth of that previously proposed. In particular, regenerating the power consumed by the PWM converter is very important because of the large power in practical systems. Normally, an additional PWM inverter is connected to the DC bus of the PWM converter to regenerate the consumed power. The additional inverter regenerates the DC power to the AC source through a transformer. This method, however, makes the damping circuit complex, thus the proposed method for the DC‐link harmonic resonance is less practicable. In this paper, a simple and novel scheme that utilizes the DC‐link voltage of the rectifier as a DC source for the PWM converter is proposed. The excellent practicability of the proposed damping method with the novel regenerating scheme is confirmed using digital computer simulation. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(2): 53–62, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10172     

A single‐stage LED streetlight driver with PFC and digital PWM dimming capability

This paper proposes a single‐stage light‐emitting diode (LED) driver that offers power‐factor correction and digital pulse–width modulation (PWM) dimming capability for streetlight applications. The presented LED streetlight driver integrates an alternating current–direct current (AC–DC) converter with coupled inductors and a half‐bridge‐type LLC DC–DC resonant converter into a single‐stage circuit topology. The sub‐circuit of the AC–DC converter with coupled inductors is designed to be operated in discontinuous‐conduction mode for achieving input‐current shaping. Zero‐voltage switching of two active power switches and zero‐current switching of two output‐rectifier diodes in the presented LED driver decrease the switching losses; thus, the circuit efficiency is increased. A prototype driver for powering a 144‐W‐rated LED streetlight module with input utility‐line voltages ranging from 100 to 120 V is implemented and tested. The proposed streetlight driver features cost‐effectiveness, high circuit efficiency, high power factor, low levels of input‐current harmonics, and a digital PWM dimming capability ranging from 20% to 100% output rated LED power, which is fulfilled by a micro‐controller. Satisfying experimental results, including dimming tests, verify the feasibility of the proposed LED streetlight driver. Copyright © 2016 John Wiley & Sons, Ltd.     

A High‐Efficiency Single‐Phase Utility Interactive Inverter with an Active Power Decoupling Function and its Control Method

The present paper introduces a single‐phase utility interactive inverter with a power decoupling function. In a conventional single‐phase inverter, power pulsation at twice the grid frequency appears in the input power. Hence, electrolytic capacitors having large capacitances have been connected to the DC input terminal to stabilize the input DC‐bus voltage. Because the lifetime of the electrolytic capacitor is relatively shorter than that of another component, the lifetime of the inverter is affected by the capacitor. In order to prevent such a problem, a novel single‐phase inverter circuit with an active power decoupling function is introduced. The pulsating power on the input DC‐bus line and the pulsated energy on the input DC capacitor is transferred to the energy in a small film capacitor. Hence, the extension of the inverter lifetime can be expected by substituting a small film capacitor for the large electrolytic capacitors. In addition, the loss in the power decoupling circuit is very small; hence, the reduction in the overall conversion efficiency of the inverter can be minimized. The effectiveness of the proposed method is verified using a 300 W experimental setup.     

A High‐Frequency Cycloconverter Based on a Phase‐Shift Control Method

This paper proposes a new control method for a high‐frequency cycloconverter consisting of two half‐bridge inverters and a series–resonant circuit. This cycloconverter acts as an ac‐to‐ac direct power conversion circuit without any dc stage. This circuit does not require a diode bridge rectifier, and thus, can be used to reduce forward voltage drops and power losses in the diodes. A new phase‐shift control method is proposed to regulate the capacitor voltage in each half‐bridge inverter and to achieve zero‐voltage switching. The proposed phase‐shift control is theoretically discussed and is also verified by an experimental circuit consisting of superjunction power MOSFETs. As a result, the proposed high‐frequency cycloconverter exhibits a good power conversion efficiency as high as 97.7% at the rated power of 1.3 kW.     

基于高功率因数控制的永磁同步电机无电解电容驱动系统控制策略

永磁同步电机无电解电容驱动系统因其成本与寿命的优势,在白色家电领域逐步得到广泛的应用。然而,由于使用小容量的薄膜电容取代大容量的电解电容,母线电压会以两倍工频波动,在母线电压处于波谷时,逆变器输出电压容易饱和,导致控制性能恶化,网侧电流畸变。因此,提出了一种基于高功率因数控制的转矩控制环和电压矢量修正策略,能够有效提升网侧功率因数,抑制网侧电流谐波并符合IEC 61000-3-2标准。该算法的有效性通过仿真得以验证。     

Study of a DC voltage equalizing circuit and a zero‐sequence voltage control method for a diode‐clamped linear amplifier

2,3 This paper proposes a DC voltage equalizing circuit for a diode‐clamped linear amplifier (DCLA). The DCLA consists of series‐connected complementary MOSFETs and diode clamping circuits, with an experimental efficiency as high as 90% without switching operation. The DCLA requires a DC voltage equalizing circuit to divide the DC voltage into several levels. The proposed DC voltage equalizing circuit allows the use of a diode rectifier with a smoothing capacitor as a power supply for the DCLA. Zero‐sequence voltage control is proposed to improve the efficiency of the DCLA. As a result, a prototype 12‐series DCLA demonstrates an experimental efficiency as high as 94.7%. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(2): 55–63, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21131     

Feasible enhancement of a three‐phase soft‐switching inverter with an auxiliary resonant DC link snubber

The purpose of this paper is to improve power conversion efficiency of a three‐phase voltage source type soft‐switching inverter with a single auxiliary resonant DC link (ARDCL) snubber. First, the operating principle of an ARDCL snubber discussed here is described. Second, this paper proposes an effective pulse pattern generation method of the zero voltage space vector of the three‐phase soft‐switching inverter using IGBTs or power modules that can reduce power losses in the ARDCL snubber treated here. In particular, a zero voltage holding interval in the DC rail busline of this three‐phase soft‐switching inverter is to be regulated according to the generation method of the zero voltage space vector. Third, the maximum modulation depth M_max under the condition of correction of the instantaneous voltage space vector can be improved by using a new zero voltage space vector generation method. Finally, the feasible experimental results of this inverter are obtained confirming the operating characteristics such as power conversion actual efficiency, as well as conventional efficiency THD and RMS value of the balanced three‐phase output voltage for an experimentally built three‐phase voltage source type soft‐switching pulse modulated inverter using the latest IGBT modules and evaluated from the standpoint of practical applications in industry UPS and new energy systems. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(1): 89–99, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10234     

Efficiency model of boost dc–dc PWM converters

A thorough efficiency analysis of a boost PWM converter taking into account the conduction losses, the diode power loss, the switching losses, the gate‐drive loss and the capacitive switching loss, for both continuous conduction mode and discontinuous conduction mode is presented. The analysis is extended in the synchronous rectification case where a self driven transistor instead of the diode rectifier is adopted. The expressions of the converter efficiency can be used to predict the circuit behaviour for both a constant input and constant output voltage operation. The model has been validated using SPECTRE simulator and a 0.35 µm CMOS process, and error always lower than 2% were found. Copyright © 2005 John Wiley & Sons, Ltd.     

A high‐input‐voltage backlight module driver for multi‐lamp LCD panels

A half‐bridge (HB) resonant inverter for driving a backlight module with multiple cold cathode fluorescent lamps (CCFLs) is proposed. Conventionally, a backlight module driving inverter is designed to operate with a low‐input DC voltage. Therefore, a buck converter is required to step down the high‐output DC voltage of a power factor correction (PFC) pre‐regulator. The circuit cost is high and the conversion efficiency is low. In this letter, a high‐input‐voltage HB resonant inverter with only one transformer is used to drive multiple lamps. Analysis and design considerations are discussed in detail. Simulations and experimental results are close to the theoretical prediction. Copyright © 2010 John Wiley & Sons, Ltd.     

An interleaved high step‐up DC‐DC converter with double boost paths

This paper proposed a novel high step‐up converter with double boost paths. The circuit uses two switches and one double‐path voltage multiplier cell to own the double boost and interleaved effects simultaneously. The voltage gain ratio of the proposed DC‐DC converter can be three times the ratio of the conventional boost converter such that the voltage stress of the switch can be lower. The high step‐up performance is in accordance with only one double‐path voltage multiplier cell. Therefore, the number of diodes and capacitors in the proposed converter can be reduced. Furthermore, the interleaved property of the proposed circuit can reduce the losses in the rectifier diode and capacitor. The prototype circuit with 24‐V input voltage, 250‐V output voltage, and 150‐W output power is experimentally realized to verify the validity and effectiveness of the proposed converter. Copyright © 2014 John Wiley & Sons, Ltd.     

Newly proposed hybrid resonant commutation bridge‐leg link snubber‐assisted three‐phase ZVZCS‐PWM soft‐switching inverter

This paper presents the newly proposed hybrid resonant commutation bridge‐leg link (HRCB) snubber circuit which can achieve zero voltage and zero current soft‐switching commutation for single‐phase and three‐phase voltage source‐type inverter, along with its unique features and operation principle. The circuit parameter design approach for the HRCB snubber circuit and the determination estimating scheme of the gate pulse timing processing which is more suitable and acceptable for single‐phase and space voltage vector modulated three‐phase voltage source inverter using the HRCB snubber circuit are described in this paper. In particular, the three‐phase voltage source soft‐switching inverter associated with the proposed HRCB circuits are evaluated and discussed from simulation and experimental viewpoints. The practical effectiveness of the HRCB snubber‐assisted three‐phase voltage source soft‐switching inverter using IGBT power modules which is based on the instantaneous space voltage vector modulation is clarified on the output voltage waveform, actual efficiency of electromagnetic noise in comparison with three‐phase voltage source‐type conventional hard‐switching inverter. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(4): 75–84, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20111     

Series resonant high‐voltage DC–DC converter with reduced component count

This paper proposes a novel zero‐current‐switching series resonant high‐voltage DC–DC converter with reduced component count. The series resonant inverter in the proposed topology has two power switches (insulated‐gate bipolar transistors, IGBTs), two resonant capacitors, and only one high‐voltage transformer (HVT) with center‐tapped primary windings. The power switches are connected in the form of a half‐bridge network. The leakage inductances of the transformer's primary windings together with the resonant capacitors form two series resonant circuits. The series resonant circuits are fed alternately by operating the power switches with interleaved half switching cycle. The secondary winding of the HVT is connected to a bridge rectifier circuit to rectify the secondary voltage. The converter operates in the discontinuous conduction mode (DCM) and its output voltage is regulated by pulse frequency modulation. Therefore, all the power switches turn on and off at the zero‐current switching condition. The main features of the proposed converter are its lower core loss, lower cost, and smaller size compared to previously proposed double series resonant high voltage DC–DC converters. The experimental results of a 130‐W prototype of the proposed converter are presented. The results confirm the excellent operation and performance of the converter. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Comparisons between a hybrid shunt active filter and a pure shunt active filter

This paper deals with the hybrid shunt active filter for harmonic compensation of a three‐phase diode rectifier in a 480‐V adjustable‐speed motor drive system. The hybrid filter is formed by a three‐phase LC filter tuned around the seventh harmonic frequency and a small‐rated three‐phase voltage‐source PWM inverter. The LC filter and PWM inverter are directly connected in series. As a result, the DC capacitor voltage of the PWM inverter in the hybrid filter is much lower than that of a conventional pure shunt active filter. This results in higher efficiency, less switching ripple, and less EMI emission. Computer simulation is carried out to compare the hybrid filter with the pure filter in terms of circuit configuration and filtering performance. Simulation results indicate that the hybrid filter is superior in effectiveness and viability to the pure filter. In addition, theoretical analysis based on vector loci confirms the validity of the simulation results. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(2): 61–70, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20145     

LLC resonant DC–DC converter with series‐connected primary windings of transformer

This paper proposes a zero‐voltage switching (ZVS) LLC resonant step up DC–DC converter with series‐connected primary windings of the transformer. The series resonant inverter in the proposed topology has two power switches (MOSFETs), two resonant capacitors, two resonant inductors, and only one transformer with center‐tapped primary windings. The power switches are connected in the form of a half‐bridge network. Resonant capacitors and inductors along with the primary windings of the transformer form two series resonant circuits. The series resonant circuits are fed alternately by operating the power switches with an interleaved half switching cycle. The secondary winding of transformer is connected to a bridge rectifier circuit to rectify the output voltage. The converter operates within a narrow frequency range below the resonance frequency to achieve ZVS, and its output power is regulated by pulse frequency modulation. The converter has lower conduction and switching losses and therefore higher efficiency. The experimental results of a 500‐W prototype of proposed converter are presented. The results confirm the good operation and performance of the converter. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.