Sinusoidal current‐tracking control for utility interactive inverter with an LCL filter

A voltage source inverter with an LCL filter is often used for a utility interface to control its output current to a grid side because of its harmonic reduction advantages. The integral compensator is often used to reduce the steady‐state errors. However, there is always a control delay due to sinusoidal variations. This paper proposes a digital sinusoidal compensator which is based on the internal model principle to realize a fast sinusoidal response with no delay. It is based on the internal model principle to realize a response with no deviation for a periodic sinusoidal reference input. It has a simple numerator and a denominator z² ? 2z cosωT + 1 of a transfer function which is equal to the z function of a sinusoidal waveform of the angular frequency ω and the sample time T. Compensator and feedback gains of the inverter are determined by the deadbeat or the optimal control principle. The proposed method is investigated for performances and it is validated through simulation and experimental results by a DSP control system. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(2): 22–28, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22339     

Soft‐switching converter with low circulating current and wide range of ZVS turn‐on

In this paper, a new hybrid dc–dc converter with low circulating current within the freewheeling interval, wide range of zero‐voltage switching and reduced output current ripple is presented. The proposed hybrid circuit includes two three‐level pulse‐width modulation converters and a series resonant converter with the shard lagging‐leg switches. Series resonant converter is operated at fixed switching frequency (close to series resonant frequency) to extend the zero‐voltage switching range of lagging‐leg switches. The output of series resonant converter is connected to the secondary sides of three‐level converters to produce a positive rectified voltage instead of zero voltage. Hence, the output inductances can be reduced. The reflected positive voltage is used to decrease the circulating current to zero during the freewheeling interval. Therefore, the circulating current losses in three‐level converters are improved. Finally, experiments are presented for a 1.44 kW prototype circuit converting 800 V input to an output voltage 24 V/60A. Copyright © 2015 John Wiley & Sons, Ltd.     

A T‐LCLC type immittance converter

“Immittance converter” is short for “impedance–admittance converter.” The immittance converter has an input impedance that is proportional to the admittance of the load connected across output terminals. In this converter, the output current is proportional to the input voltage and the input current is proportional to the output voltage. Consequently, it converts a constant voltage source into a constant current source and a constant current source into a constant voltage source. It is well known that the quarter‐wavelength transmission line shows immittance conversion characteristics. However, it has very long line length for the switching frequency, and is not suitable for power electronics application. Thus, we proposed immittance converters that consist of lumped elements L, C and show improved immittance conversion characteristics at a resonant frequency. In this paper, we propose a T‐LCLC‐type immittance converter, which has the transitive configuration and both advantages of T‐LCL‐ and π‐CLC‐type immittance converters. We show voltage–current transformation characteristics and frequency characteristics and efficiency characteristics of the T‐LCLC immittance converter. These characteristics were determined analytically and experimentally. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(3): 57–63, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10095     

Series resonant ZCS‐PFM DC‐DC power converter with high‐frequency high‐voltage transformer link for high‐power magnetron drive

This paper presents a single lossless inductive snubber‐assisted ZCS‐PFM series resonant DC‐DC power converter with a high‐frequency high‐voltage transformer link for industrial‐use high‐power magnetron drive. The current flowing through the active power switches rises gradually at a turned‐on transient state with the aid of a single lossless snubber inductor, and ZCS turn‐on commutation based on overlapping current can be achieved via the wide range pulse frequency modulation control scheme. The high‐frequency high‐voltage transformer primary side resonant current always becomes continuous operation mode, by electromagnetic loose coupling design of the high‐frequency high‐voltage transformer and the magnetizing inductance of the high‐frequency high‐voltage transformer. As a result, this high‐voltage power converter circuit for the magnetron can achieve a complete zero current soft switching under the condition of broad width gate voltage signals. Furthermore, this high‐voltage DC‐DC power converter circuit can regulate the output power from zero to full over audible frequency range via the two resonant frequency circuit design. Its operating performances are evaluated and discussed on the basis of the power loss analysis simulation and the experimental results from a practical point of view. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(3): 79–87, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20126     

Analysis,simulation and verification of a bipolar current source power resonant inverter

A high‐frequency bipolar current source resonant inverter introduced in this paper has dramatic zero‐voltage‐switching (ZVS) characteristic. The analytic expressions of the resonant voltage and current are given. It indicates that the resonant waveform is composed of two parts, i.e. the oscillatory component and the stationary component. In special cases, the resonant waveform degenerates into the mono‐frequency component, as presents the graceful sinusoidal wave with very low total harmonic distortion (THD) value. Based on the closed‐form voltage and current, the component stresses on reactive elements are obtained. The impact of different component values and operating frequencies on ZVS feature is also discussed. It should be noted that the ZVS merit may be lost if the components are carelessly selected. The validity of the theoretical analysis has been proven with Pspice simulations and experimental results. Copyright © 2004 John Wiley Sons, Ltd.     

Active shunt current shaping scheme for multiple paralleled DC–DC converters

A new shunt current shaping scheme for multiple paralleled dc–dc converters is proposed in this paper. The current command for the shunt current shaper is indirectly obtained by forcing the source current to follow the demanded sinusoidal signal. The amplitude of the demanded sinusoidal source current that is in‐phase with the source voltage can be determined from the sensed load currents of the post‐stage dc–dc converters. Neither high‐order filters nor time‐consuming computations are required. The shunt current shaper supplies all the harmonics and the out‐of‐phase fundamental of the distorted input current and the power source only supplies the in‐phase fundamental component. Experimental results on a prototype system verify the feasibility of the presented scheme. The implemented shunt current shaper demonstrates an efficiency of 92% and a nearly unity power factor at the utility side. Copyright © 2011 John Wiley & Sons, Ltd.     

A three‐vector‐based direct power control strategy for three‐phase voltage source PWM converters

For traditional direct power control strategy, there exist high steady‐state power ripples and large current harmonics. To solve this problem, this work proposes a novel three‐vector‐based direct power control strategy for three‐phase voltage source pulse‐width‐modulated (PWM) converters. Different from traditional predictive direct power control strategy, an improved vector table is presented and three voltage vectors are selected, which considers the impact of voltage vectors on the active and reactive power simultaneously. The performance of the three‐phase voltage source PWM converters with the proposed control strategy is investigated and compared with the predictive deadbeat direct power control strategy. Furthermore, the three‐phase voltage source PWM converters have also been tested in the condition of different loads and when voltage unbalance occurs. Simulation and experimental work are conducted. The results conclude that the proposed strategy is of simple structure and fast dynamic response. Besides, it can effectively reduce steady‐state power ripples and current harmonics, improving the performance of the three‐phase PWM converters. Copyright © 2016 John Wiley & Sons, Ltd.     

Analysis and design of a half‐bridge LLC series resonant converter employing two transformers

This paper presents a two‐transformer LLC series resonant converter (SRC), which is derived from incorporating two identical converters. The proposed converter allows a low‐profile power supply design for liquid crystal display (LCD) TVs and servers. The presented converter can equally share the total load current between two transformers and the output rectifier modules. Therefore, the heat problem can be effectively relieved. The steady‐state analysis and design of this new two‐transformer LLC SRC are described. The experimental results are recorded for a prototype converter with an output voltage of 12thinspaceV, an output power of 300 W, and a resonant frequency of 74 kHz. Copyright © 2011 John Wiley & Sons, Ltd.     

A three‐phase constant‐current source using an immittance converter

The term immittance converter refers to an impedance–admittance converter. The immittance converter has an input impedance that is proportional to the admittance of the load connected across output terminals. In this converter, the output current is proportional to the input voltage and the input current is proportional to the output voltage. Consequently, it converts a constant‐voltage source into a constant‐current source and a constant‐current source into a constant‐voltage source. It is well known that the quarter wavelength transmission line shows immittance conversion characteristics. However, it has a very long line length for the switching frequency, and is not suitable for power electronics applications. We thus proposed immittance converters that consist of lumped elements L, C and show improved immittance conversion characteristics at a resonant frequency. A three‐phase constant‐current source is proposed in this paper. It is possible to realize this by a simple circuit using an immittance converter. In this paper, circuit operation, characteristic equations, and results of simulation are described. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 151(4): 47–54, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20078     

A new current control strategy based on the internal model principle for a current balancer in single‐phase three‐wire distribution systems

This paper proposes a new current control strategy that is based on the internal model principle for a current balancer in single‐phase three‐wire distribution systems. The proposed current control strategy includes a sinusoidal reference input model to achieve the zero steady‐state error tracking. The appropriate control gains of this control strategy can be systematically determined by using a state‐feedback controller design method via linear matrix inequalities. The basic principle of the proposed control strategy is discussed in detail, and then confirmed by digital computer simulation using the PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that zero steady‐state error tracking is achieved by the proposed control strategy. Also, balanced source currents are obtained on the secondary side of a pole‐mounted distribution transformer while the load conditions are unbalanced. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

利用基波分析法的串联谐振电容充电电源建模

为进一步研究因具有电流源特性而已广泛应用于电容器充电电路中的串联谐振变换器,利用基波分析法分析了串联谐振变换器,建立了串联谐振变换器基波分析法的稳态模型并在适当修改后用于串联谐振电容充电电源的研究。用搭建的30 kW、1 kV电容充电电源样机验证的结果表明,实验与理论结果在特定条件下非常符合。利用该模型可更快地确定电路工作在给定条件下的谐振参数,使电源的整体效率和器件的应力都取得最优,使用稳态模型仿真可大大地节省仿真时间,从而使系统的设计更快捷,工作更稳定。     

Hybrid DC–DC converter with high efficiency,wide ZVS range,and less output inductance

In this paper, a new soft switching direct current (DC)–DC converter with low circulating current, wide zero voltage switching range, and reduced output inductor is presented for electric vehicle or plug‐in hybrid electric vehicle battery charger application. The proposed high‐frequency link DC–DC converter includes two resonant circuits and one full‐bridge phase‐shift pulse‐width modulation circuit with shared power switches in leading and lagging legs. Series resonant converters are operated at fixed switching frequency to extend the zero voltage switching range of power switches. Passive snubber circuit using one clamp capacitor and two rectifier diodes at the secondary side is adopted to reduce the primary current of full‐bridge converter to zero during the freewheeling interval. Hence, the circulating current on the primary side is eliminated in the proposed converter. In the same time, the voltage across the output inductor is also decreased so that the output inductance can be reduced compared with the output inductance in conventional full‐bridge converter. Finally, experiments are presented for a 1.33‐kW prototype circuit converting 380 V input to an output voltage of 300–420 V/3.5 A for battery charger applications. Copyright © 2015 John Wiley & Sons, Ltd.     

ANALYSIS OF POWER CONVERTER CONTROL USING NEURAL NETWORK AND RULE-BASED METHODS

ABSTRACT

Current-controlled voltage source inverters offer substantial advantages in improving motor system dynamics for high-performance ac drive systems. The controller switches follow a set of reference current waveforms. Fixed-band hysteresis and sinusoidal-band hysteresis controllers have been studied. The first part of this paper develops neural network and fuzzy logic based current-controlled voltage source inverters. The models and learning techniques have been investigated by simulation. The implementation of neural networks is described and simulation results are presented. In the second part of this paper, the new UPS (uninterruptible power supply) with fuzzy logic compensator is proposed. Proposed fuzzy logic compensator is used to prevent voltage drop from nonlinear load. The total harmonic distortion (THD) of proposed scheme is better than that of conventional deadbeat control method for linear and nonlinear load. In the third part of this paper, the application of fuzzy control to DC-DC converters operating at finite switching frequency is studied. Several control methods currently used for buck, boost and buck/boost converters are compared to the fuzzy converter control. Simulation results for several control methods are presented. The simulations show that the fuzzy control method has better dynamic performance and less steady state error.     

基于改进锁相环的单相光伏并网逆变器研制

介绍了一种应用于单相光伏并网逆变器的改进型软件锁相环算法,可使逆变器输出电流与电网电压同步.将电网电压通过相位延迟,得到静止坐标系下2个正交电压,采用虚拟d,q坐标变换,经过一系列处理后,得到电网电压的相位及频率,提高了锁相速度,消除了谐波干扰,快速锁定任意频率和幅值电网电压的相位和频率.利用准比例谐振(PR)控制器对...     

A novel active auxiliary circuit for efficiency enhancement integrated with synchronous buck converter

In this paper, a novel auxiliary circuit is introduced for the synchronous buck converter. This auxiliary circuit provides zero‐current, zero‐voltage switching conditions for the main and synchronous switches while providing zero‐current condition for the auxiliary switch and diodes. The proposed active auxiliary circuit integrated with synchronous buck converter that emanates to zero‐voltage transition (ZVT)–zero‐current transition (ZCT) pulse width‐modulated (PWM) synchronous buck converter is analyzed, and its operating modes are presented. The additional voltage and current stresses on main, synchronous and auxiliary switches get decimated because of the resonance of the auxiliary circuit that acts for a small segment of time in the proposed converter. The important design feature of soft‐switching converters is the placement of resonant components that mollifies the switching and conduction losses. With the advent of ZVT–ZCT switching, there is an increase in the switching frequency that declines the resonant component values in the converters and also constricts the switching losses. The characteristics of the proposed converter are verified with the simulation in the Power Sim (PSIM) software co‐simulated with MATLAB/SIMULINK environment and implemented experimentally. Copyright © 2016 John Wiley & Sons, Ltd.     

Three‐phase immittance converter

The immittance converter has an input impedance that is proportional to the admittance of a load connected across its output terminals. In this converter, the output current is proportional to the input voltage and the input current is proportional to the output voltage. Consequently, a constant‐voltage source is converted into a constant‐current source and a constant‐current source into a constant‐voltage source. The immittance converters consisting of only passive elements (inductors L and capacitors C) are suitable for use in the high‐frequency links in power electronics applications. Previously, we proposed several types of immittance converters and some applications to power electronics equipment. In this paper, we propose a new three‐phase immittance converter consisting of three L and C elements each to obtain an alternating current source from a three‐phase voltage source without control. This paper presents a configuration of the new three‐phase immittance converter that operates in either anti‐phase or in‐phase modes between the input voltage and the output voltage, and its voltage–current conversion characteristics and efficiency characteristics. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(1): 52– 58, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10169     

Design method considering the frequency band of the disturbance in the DC link voltage control system of hybrid electric vehicle driving systems

DC link voltage variable systems with DC/DC converter are used in hybrid electric vehicles for improving the power of the system by boosting the DC link voltage. Voltage feedback control using only proportional compensator has been proposed as a control method for the DC/DC converter. The control system can be easily designed, but there is a possibility that a steady‐state error occurs in the DC link voltage. In this paper, a proportional integral compensator is proposed to eliminate the steady‐state error of the DC link voltage in DC link voltage feedback controllers. In addition, when designing the gain of the compensator, the frequency band of the disturbance is considered. The proposed method is verified through experiments on the downsizing model.     

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.     

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.     

Proposal of voltage transient sag compensator with controlled gradational voltage

This paper presents a new concept for a voltage transient sag compensator and the experimental result of its 400‐V‐class compensator. This compensator is composed of the series connection of some inverter units with gradational output voltages. Because each output voltage is different by 2ⁿ times, an approximate sinusoidal voltage is generated by controlling operation of each inverter and compensates voltage sag of the power line. The compensator can be directly installed in a power line without an insertion transformer and a large filter, and thus it is expected to be a compact and economical system. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 154(3): 65–72, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20289