一种电源-电容串联型直流变换器

提出了一种电源-电容串联型直流变换器,这种拓扑结构可以同时为两路直流电源升压,并且有效降低了半导体器件的电压与电流应力。与双路Boost型直流变换器相比,该电源-电容串联型直流变换器在不增加功率器件数量的前提下,显著降低了半导体器件的电压与电流应力,适用于分布式光伏并网逆变器的直流变换级。主要涉及该直流变换器的运行方式、电压与电流应力分析、效率对比,并通过实验验证了该直流变换器的可行性。     

基于交错控制的三电平升压型DC/DC光伏控制器研究

提出了一种应用于非隔离光伏并网系统的前级DC/DC三电平升压型变换器及其控制方法。该变换器采用Boost三电平(Boost Three-level,Boost-TL)拓扑结构,分析了其工作原理,推导并建立了系统的数学模型。为了减小输出电压和电感电流纹波,提出了采用两开关管移相180°的交错控制策略。同时,针对直流母线中点电位不平衡问题,通过采取一种调整开关管导通时间的方法,实现了两输出电容电压的平衡。该变换器具有体积小、器件电压应力低和转换效率高的优点。最后,搭建了23 kW的实验平台,通过仿真和实验验证了所提控制方法的正确性和有效性。     

DC/DC升压变换器串级控制

为改善DC／DC升压变换器的控制性能，设计了一种串级结构的控制器。控制器的外环采用PI控制算法，以电容电压为被控量，内环则采用积分增益可调的PI控制算法，以电感电流为被控量。该种结构的控制器不但有效解决了系统非最小相位特性给控制器设计带来的难题，而且可使被控系统获得良好的动态特性，并对系统参数变化有着很强的鲁棒性。对DC／DC升压变换器的仿真结果表明，该控制方案是可行的。     

一种混合开关电感和开关电容的高增益DC/DC变换器

针对传统Z源DC/DC变换器存在的输入电流不连续、输出电压增益不够高和功率器件电压应力较高等不足,利用开关电感和开关电容技术,提出了一种混合开关高增益DC/DC变换器。该变换器主电路中只用到1个储能电容,结构简单,与现有典型的高增益阻抗源DC/DC变换器相比,所提出的混合开关电感和开关电容的DC/DC变换器可以实现更高的输出电压增益,同时电容和开关器件的电压应力较低。详细分析了所提变换器的工作原理,通过在实验室中所建立的输入电压16～40 V、输出电压26～107 V和输出功率7～114 W的原型验证了其性能。     

无直流电容单PWM型功率变换器整流桥换流控制

无直流电容单PWM型功率变换器是减少大容量无功元件的新型拓扑之一,该功率变换器具有结构简单、电压利用率高、损耗较低等优点,其难点问题是如何实现整流桥安全换流.本文首先对其工作原理进行分析,然后围绕整流桥换流策略、电压利用率、补偿直流电压波动的SVPWM算法等问题进行理论研究,得出了有效的整流桥换流策略和逆变桥修正SVPWM算法,仿真和实验结果表明所设计的算法正确,为该功率变换器实用化奠定了基础.     

Advanced power conditioner using sinewave modulated buck–boost converter cascaded polarity changing inverter

This paper presents an advanced power converter employs a sinusoidal voltage absolute value tracking buck–boost DC–DC converter in the first power processing stage and a polarity changing full-bridge inverter in the second stage. The proposed power conversion system has the capability of delivering good quantitative and qualitative sinusoidal output current and voltage waveforms with good output voltage regulation. Consequently, the complete voltage regulator system, which is mainly suitable for new energy generation systems as well as energy storage systems, can be constructed compactly and inexpensively without DC link electrolytic capacitor. Also, the paper presents an auxiliary passive resonant circuit for soft switching operation. Simulation results using PSIM software are presented to verify the operation principles and feasibility of the proposed power conversion system. Finally, these results are verified by means of an experimental prototype.     

High‐efficiency transformerless buck–boost DC–DC converter

A novel high‐efficiency transformerless buck–boost DC–DC converter is proposed in this paper. The presented converter voltage gain is higher than that of the conventional boost, buck–boost, CUK, SEPIC and ZETA converters, and high voltage gain can be obtained with a suitable duty cycle. The voltage stress across the power switch is low. Hence, the low on‐state resistance of the power switch can be selected to decrease conduction loss of the switch and improve efficiency. The input current ripple in the presented converter is low. The principle of operation and the mathematical analyses of the proposed converter are explained. The validity of the presented converter is verified by the simulation results in PSCAD/EMTDC software and experimental results based on the prototype circuit with 250 W and 40 kHz. Copyright © 2017 John Wiley & Sons, Ltd.     

DC-bus voltage control of three-phase AC/DC PWM converters usingfeedback linearization

In this paper, a fast voltage control strategy of three-phase AC/DC pulsewidth modulation (PWM) converters applying a feedback linearization technique is proposed. First, incorporating the power balance of the input and output sides in system modeling, a nonlinear model of the PWM converter is derived with state variables such as AC input currents and DC output voltage. Then, by input-output feedback linearization, the system is linearized and a state feedback control law is obtained by pole placement. With this control scheme, output voltage responses become faster than those in a conventional cascade control structure. For robust control to parameter variations, integrators are added to the exact feedback control law. Since the fast voltage control is feasible for load changes, it is shown that the DC electrolytic capacitor size can be reduced. In addition, the capacitor current is analyzed for size reduction of the capacitor. As is usual with PWM converters, the input current is regulated to be sinusoidal and the source power factor can be controlled at unity. The experimental results are provided to verify the validity of the proposed control algorithm for a 1.5 kVA insulated gate bipolar transistor PWM converter system     

考虑直流调制的交直流系统中长期电压稳定协调控制

综合考虑直流系统整流侧和逆变侧控制量的调制,协调交流系统和直流系统各控制量,提出了一种考虑直流调制的交直流系统中长期电压稳定协调控制方法。首先,推导出换流母线电压对整流侧和逆变侧换流器传输功率的灵敏度解析表达式,并基于轨迹灵敏度建立以节点电压轨迹偏差和控制代价最小为综合目标的模型预测控制优化模型。然后,根据对系统控制轨迹的预测,进行交直流系统控制数量自适应调整和控制地点优选,以提高模型预测控制的效率,协调交直流系统各控制量进行电压滚动优化控制。最后,对交直流混联系统进行仿真,结果表明针对不同的故障场景,所提控制方法均能有效调制直流系统传输功率和熄弧角,全面协调交直流系统的各种控制手段,提高系统中长期电压稳定性。     

The resonant DC link converter-a new concept in static powerconversion

A novel approach to realizing efficient high-performance power converters is presented. The concept of a resonant DC link inverter has been proposed and realized with the addition of only one small inductor and capacitor to a conventional voltage source inverter circuit. The proposed technology is capable of switching almost an order of magnitude faster than state-of-the-art voltage source inverters at significantly improved efficiencies using the same family of devices. The topology is especially suitable for high-power applications using gate turn-off devices. A 4.5 kW inverter has been fabricated and tested extensively in the laboratory, and the superior characteristics of the resonant DC link topology have been verified     

二极管箝位型四电平逆变器的中点电压平衡控制方法

二极管箝位型四电平逆变器具有开关器件少、输出电压高、结构紧凑、功率密度高的优点,在中压变频调速领域有很好的应用潜力.针对其母线中点电压平衡问题,提出一种新型载波交叠PWM调制策略,满足伏秒平衡原则.在此基础上进一步提出了一种可平衡母线中点电压的解耦控制方法,将3个母线电容的电压平衡控制分为2个解耦的控制目标:1)上、下...     

A four level rectifier inverter system for drive applications

In a motor drive, the converters must be able to handle bidirectional real power flow. So far, DC voltage balancing has not been satisfactorily discussed for the case when real power is drawn from the inverter. This article addresses the control issues involved in a four-level inverter based AC drive application. The DC capacitor voltages are balanced for both motoring and regenerating modes of the inverter-motor system. In addition, DC voltages can be balanced even during motor startup with the associated large overcurrents     

应用于风电场内部组网的多端直流系统研究

提出了利用多端直流系统作为风电场组网方式时,网侧逆变器的控制策略。风电场多端直流系统由多个电压源换流器(VSC)并联组成,发电侧VSC控制风机向直流系统输送能量,再经网侧逆变器并网。根据状态空间平均法,得到VSC的动态数学模型及等效电路。以此为基础设计了网侧逆变器的解耦控制器,既能保持直流系统电压恒定,从而向交流系统传送有功,又能独立调节输出的无功,为交流侧提供电压支撑。数字仿真结果表明该控制器具有良好的性能。     

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     

交流不对称故障下的LCC-MMC混合直流系统输送功率提升策略研究

将常规两端直流输电系统逆变站的电网换相换流器(LCC) 替换为模块化多电平换流器(MMC)所构成的混合直流输电系统,可结合两种换流器的优点而具有广阔的应用前景。在研究其基本稳态控制特性的基础上,重点分析了交流电网不对称故障引起的直流输送功率下降及中断问题。通过分析混合直流系统的交流故障特征,发现交流不对称故障发生在整流侧时易引起直流电压下降甚至输送功率的中断,发生在逆变侧时易引起直流系统电压异常。鉴于此,提出了基于MMC典型控制的附加直流电压控制策略,在其调制范围内通过降低故障时逆变侧的参考直流电压以提高直流系统的输送能力。若检测到本站直流电压的交流分量大小超过限定值,则附加控制策略自动投入,无需依靠换流站间的通信。最后,通过PSCAD/EMTDC电磁暂态仿真验证了所提控制策略的可行性。     

DC/DC开关电容变换器的控制技术

根据DC/DC开关电容变换器目前的最新发展状况,对各种控制技术做了较为深入的探讨和分析,指出采用DC/DC开关电容变换器的软开关技术,不仅可以解决长期困扰变换器的功率和效率问题,而且给DC/DC开关电容变换器带来了崭新的发展。     

无通信互联线储能系统的直流母线协调控制策略

针对无通信互联线的储能系统如何在不增加系统成本和复杂度的前提下维持直流母线功率平衡及电压稳定,提出了一种直流母线协调控制策略,DC/AC变流器采用定直流电压或定交流电压控制,两台DC/DC变换器采用包含电池充放电控制的改进型二阶直流电压偏差控制。通过对系统典型工况的分析,说明了系统中各个装置是如何协调工作的。搭建了微网实验平台对所提出的控制策略进行了实验验证,实验结果证明了该控制策略的有效性和实用性。     

基于SPWM调制的双Boost单级DC/AC电路研究

介绍了双Boost DC/AC单级正弦波逆变电路结构,并分析了其工作原理.描述了在采用SPWM调制技术时该逆变电路各个功率开关触发信号的逻辑配合关系,应用PSPICE软件对其进行仿真,列出了仿真参数,给出了电容电压和负载电压、以及调制给定电压和逆变器输出电压的仿真结果.同时,构建了相应的实验电路,给出了主要的技术参数,测取了多种电流和电压的相关波形.实践研究表明,基于SPWM调制的双Boost变换电路可以实现50 kHz高频功率变换下的单级升压工频逆变输出.     

一种并联输入并联输出的宽范围双向隔离DC/DC变换器

目前,DC/DC变换器广泛应用于新能源发电、电动汽车以及锂电池化成分容等领域。针对低压大电流双向功率传输应用场合,提出了一种输入并联输出并联的宽范围双向隔离DC/DC变换器。该变换器由2个相同的两级式DC/DC变换器组成,前级采用高效率LLC谐振变换器作为直流变压器,以实现电气隔离;后级采用交错式Buck/Boost变换器,保证宽范围电压输出和高动态性能。所提变换器能够实现功率的双向传输,且采用了一种功率方向改变时,无需进行功率流向判断与开关逻辑切换的调制策略,简化了系统的控制策略并提高可靠性。设计了1台3 kW的实验装置,实验结果验证了所提变换器及其控制方法的可行性和有效性。     

Investigation of performance of UPFC without DC link capacitor

This paper presents an analysis of the dynamic operation of unified power flow controller without DC link capacitor. In this scheme of UPFC the shunt converter present in the static synchronous compensator is operated as a current source rectifier, which maintains a fixed DC voltage and DC current on the DC link without capacitor. The capacitor in the DC link is replaced by an AC filter on the line side with a very small value to reduce higher order harmonics. The voltage source inverter present in the series compensator is operated with space vector modulation technique. The proposed scheme is fully validated through digital simulation. The simulated results show that the DC link voltage is maintained constant without DC link capacitor; STATCOM provides good voltage regulation and static synchronous series compensator influences power flow over the transmission line. Transient responses of single machine infinite bus power system have also been presented.