VVVF on-line control of matrix converters

A matrix converter does not have any energy storage components, so it is smaller than a converter-inverter system with same KVA. Although a matrix converter requires 18 switching devices instead of 12, each device capacity is 0.383 times with a total capacity of 0.575 times that of the converter-inverter system. For the matrix converter, we proposed a firing sequence which eliminated voltage and current spikes in switching operations and a control method I which generated the output voltage of 0.866 times the supply voltage. Moreover, we proposed control method II which improved the waveform distortion of the input current and realized unity input power factor. In this paper, we propose a new VVVF gate circuit based on control method II for matrix converter, which can on-line control input current waveform and output voltage waveform to sinusoidal even if there is fluctuation, asymmetry, and/or harmonics in the supply voltage. We also confirm by experiments that the waveform distortion of the input current and the input power factor were greatly improved. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 119(2): 81–90, 1997     

Suppression of harmonic spikes in switching converter output usingdithered sigma-delta modulation

In this paper, dithered sigma-delta modulation is proposed as an effective modulation scheme for a switching converter, to suppress harmonic spikes. The proposed scheme has a simple configuration, which comprises a first-order sigma-delta modulator and a random dither generator. The first-order sigma-delta, modulator produces a switching pulse waveform that has the same low-frequency component as the reference input. Also, the random dither disperses the switching frequency of output pulse waveform, which results in reduction of harmonic spikes. The relationship between the harmonic spectra and sampling numbers per switching cycle is studied through computer simulations, and performance is confirmed in an experimental setup     

基于直流侧有源谐波抑制方法的高功率密度多脉波整流器

为提高多脉波整流器的谐波抑制能力和功率密度,提出了一种使用直流侧有源谐波抑制方法和星形联结自耦变压器的多脉波整流器。该整流器的两个整流桥分别与两个Boost变换器相连,通过控制Boost电路的输入电感电流使整流器输入电流近似为正弦波;使用星形联结自耦变压器作为移相变压器,该变压器绕组结构交互联结,可显著降低变压器的容量,提高系统的功率密度。计算了使整流器输入电流为正弦波时的Boost变换器电感电流理论波形,并给出了可实现的电感电流波形,进一步分析了直流侧谐波抑制方法对星形联结自耦变压器容量的影响。仿真及实验结果表明,该整流器可有效抑制输入电流谐波,且具有较高的功率密度。     

Evaluation of third harmonic component effects in five-phasesynchronous reluctance motor drive using time-stepping finite-elementmethod

Interaction of the third harmonic magnetic field with the third harmonic current in a five-phase synchronous reluctance motor (SynRM) can produce additional torque. However, it is still not clear about the SynRM power factor and its impact on the associated power converter because of the third harmonic components. Using time-stepping finite-element method, a mathematical model of the SynRM, which allows any desired harmonic component in computation, is presented. Performance of the five-phase SynRM with two rotor structures has been computed. The study finds that contribution of the third harmonic current to the output torque depends on the rotor structures. It is also shown that the required terminal voltage to regulate the desired current waveform is substantially increased, a result not reported before     

ip-iq检测法的单周控制三电平有源电力滤波器

并联型有源电力滤波器APF可以有效补偿由非线性负载产生的谐波和无功功率电流。为了实现单独对谐波分量、无功功率分量进行补偿,或者对谐波和无功功率分量同时进行补偿这些不同的补偿目标,同时为了满足大功率、高电压和输出电流波形畸变小的需要,提出了将中点箝位变换器和ip-iq电流检测法应用于单周控制有源电力滤波器的方法。采用ip-iq电流检测算法可分离出负载电流中的谐波分量、无功功率分量,且电网电压波形畸变不影响检测结果,故可提供不同补偿目标的参考信号。理论推导和仿真结果表明,该法能分别单独补偿谐波分量、无功功率分量,或者同时补偿谐波和无功功率分量,而且电网电压波形畸变不影响补偿效果。通过将ip-iq电流检测法运用于单周控制三电平有源电力滤波器,既实现多种补偿目标,又具有电网电压波形畸变不影响补偿效果、单周控制策略简单、三电平变换器输出电流波形畸变小的优点。     

有源电力滤波器主电路死区延时的研究

作为有源电力滤波器（APF）主电路的PWM变流器,由于开关器件并非理想,控制信号得到响应需要一段时间,又由于为了防止上下两桥臂直通而造成短路,故在上下两臂通断切换时留一小段死区时间。从而给输出的PWM波形带来一定影响,降低了APF装置的谐波补偿效果。在使用改进规则采样法对PWM波形进行调制时,通过将调制得到的上下桥臂关断时间点提前一个死区延时的时间,即实现了在PWM调制过程中完成死区延时的有效补偿。该方法简单易行,适于有源电力滤波器的工程应用。     

一种新型电压源换流器的研究

为了改善轻型直流输电网络的波形质量，目前电压源换流器使用较多的高频有源开关器件，导致成本增高，损耗加大，限制了其实际应用。本文提出了一种Buck型电压源换流器(BVSC)，该BVSC由一组双Buck变换器和一个工频逆变桥组成，仅用两个高频开关，即可取得较好的输出波形。为了进一步解决大功率应用时的高频开关的局限性，文中还提出了一种新型的双频控制Buck型电压源换流器(DBVSC)，DBVSC在BVSC的基础上附加了一个双Buck变换器，使原BVSC工作在高频，仅处理谐波功率，而附加的BVSC工作在低频，处理基波功率。DBVSC既可以改善换流器输出电流波形质量，又可以减小系统损耗，提高功率等级，特别适合于大功率应用。文中推导了基于单周控制思想的控制方程，运用简单的控制电路实现要求，通过仿真研究，证实了理论分析的正确性。     

矩阵式变换器改善智能建筑电能质量的研究

矩阵式变换器是直接交-交变换装置,没有中间大容量直流储能环节、功率密度高、体积小、重量轻,可获得和输入交流电压同频且相位可控的输入电流和负载所需的电流波形,谐波分量小,使用寿命长,能忍受高温、粉尘等恶劣运行环境.本文分析了矩阵式变换器用于智能建筑的可能性,在基于RB-IGBT构成的三相/三相矩阵式变换器-异步电动机系统上,实验验证了系统在不同工况下的输入输出电流均可调制为正弦波,输入输出电流谐波分量减少,用于智能建筑可改善电能质量,达到节能效果.     

Soft‐Switching Interleaved PFC Converter with Lossless Snubber

This paper describes a soft‐switching interleaved power factor correction (PFC) converter with a lossless snubber. AC–DC converters require a unity input power factor characteristic with highly efficient operation to prevent the inflow of harmonic current to the power source. The proposed PFC converter improves the input current ripple with interleave control. The converter realizes a high efficiency by the soft‐switching operation of all switching devices without a large auxiliary resonant circuit. This paper introduces the soft‐switching operation of the converter. In order to confirm the validity of the proposed converter, experiments with a prototype of the PFC converter have been performed. The experimental results indicate that the proposed converter can realize the soft‐switching operation of all switching devices, a reduction in the input current ripple, a unity power factor of 98% or more, a sinusoidal input current, and constant output voltage control. The efficiency of the proposed PFC converter with a lossless snubber is higher than that without the lossless snubber. The results presented in this paper confirm the validity of the proposed converter.     

电源变换器在风力发电中的技术研究

随着风力发电技术的快速发展,高性能的电源变换技术受到人们的广泛关注.在此采用基于DSP的数字控制技术,设计了一个新型的AC/DC/AC电源变换器.该变换器前级为三相两开关Boost PFC电路,采用DSP产生两路相位差为180°频率可变的PWM信号进行控制,实现了部分解耦控制,能有效减少输入电流的谐波含量并提高功率因数...     

Performance improvement of sensorless vector control for matrix converter drives using PQR power theory

This paper presents a new method to improve sensorless performance of matrix converter drives using PQR power transformation. The non-linearity of matrix converter drives such as commutation delay, turn-on and turn-off time of switching device, and on-state switching device voltage drop is modelled using PQR transformation and compensated using a reference current control scheme. To eliminate the input current distortion due to the input voltage unbalance, a simple method using PQR transformation is also proposed. The proposed compensation method is applied for high performance induction motor drives using a 3 kW matrix converter system without a speed sensor. Experimental results are shown to illustrate the feasibility of the proposed strategy.     

Quasi‐active power factor correction on flyback‐based dc/dc converter

This paper presents a novel input current shaper based on a quasi‐active power factor correction (PFC) scheme. In this method, high power factor and low harmonic content are achieved by providing an auxiliary PFC circuit with a driving voltage which is derived from a third winding of the transformer of a cascaded dc/dc flyback converter. It eliminates the use of active switch and control circuit for PFC. The auxiliary winding provides a controlled voltage‐boost function for bulk capacitor without inducing a dead angle in the line current. Since the dc/dc converter operates at high switching frequency, the driving voltage is also of high switching frequency, which results in reducing the size of the magnetic components. Operating principles, analysis and experimental results of the proposed method are presented. Copyright © 2011 John Wiley & Sons, Ltd.     

Power quality improvement in 3-phase 3-wire distribution systems using modular active power filter

Active power filters have been introduced for the purpose of power quality improvement. The power converter used as an active filter is rated based on the magnitude of the injected current and is operated at the switching frequency required to perform the filtering job successfully. Excessive losses are expected if the converter's power rating and switching frequency are both high. In this paper, an efficient and reliable active filter system for the power quality enhancement is proposed. The proposed filter is based on 3-phase PWM-controlled current–source converter (CSC) modules, where each filter module is dedicated to eliminate a specific harmonic and/or balance the line currents. Based on the information extracted from the line by the ADALINE, each leg of every CSC module is independently controlled to perform the balancing or/and harmonic filtering in a 3-phase 3-wire distribution system. As the harmonic order increases, the magnitudes of the harmonics decrease and their frequencies increase. Therefore, the power rating of the active filter modules will decrease and their switching frequency (bandwidth) will increase with the harmonic order. As a result, the overall switching losses are minimized due to balanced ‘power rating-switching frequency’ product. An economic study shows that the modular approach is superior to the conventional one converter scheme. Furthermore, the modular approach offers higher reliability, as the failure of one converter does not jeopardize the whole filtering mission. Speed and accuracy of ADALINE, self-synchronizing harmonic tracking, optimized dc-side current values and minimal converter losses are additional features of the proposed filter. The theoretical expectations are verified by digital simulation using EMTDC simulation package.     

Dynamic model development and control for multiple‐output flyback converters in DCM and CCM

Multiple‐output flyback converters are widely used in switching power supplies due to their low component count and cost‐effective structure. The main problem of this structure is how to balance output voltages in different load conditions. This paper proposes a new approach for single‐input multiple‐output flyback converters operating in DCM and CCM by a small‐signal averaged model. The averaged model is derived by presenting the piecewise‐linear waveform for the inductor currents inside the converter. In DCM, the magnetizing current and currents through the output windings reach zero when the switch is turned off. In CCM, the magnetizing current of the converter is continuous over a switching interval and this possibility exists that only some of the output diodes completely conduct when the switch is off. The proposed model of the converter can be used in a wide range of operations within identical and non‐identical loading conditions. Using a laboratory prototype, several case studies and input‐to‐output transfer functions are considered to verify the proposed model. The controller design is performed for the both CCM and DCM, and then dynamic characteristics of the overall system are evaluated.     

Experimental evaluation of active power factor correction techniques in a single-phase AC-DC boost converter

The increasing need to improve power quality with the reduction of the harmonic content of current and voltage waveforms has been intensively analyzed in several studies, thus motivating the proposal of many high power factor rectifiers based on the classic converters such as boost and buck-boost. Moreover, distinct control techniques have also been proposed due to the commercial availability of integrated circuits (ICs) dedicated to impose sinusoidal input currents in switch-mode power supplies (SMPSs). The boost converter operating in continuous conduction mode (CCM) is by far the most traditional choice for this purpose due to circuit simplicity and low electromagnetic interference (EMI) levels. Within this context, this work analyzes some of the most important control techniques used in power factor correction (PFC). The performance of a single-phase boost converter using peak current mode control (PCMC), average current mode control (ACMC), and one cycle control (OCC) is evaluated experimentally in detail. A comprehensive analysis of key aspects such as the input current waveform and respective harmonic content, dc output voltage, and dynamic response of the converter is also presented.     

幅相控制PWM变流器电流谐波分析及参数选择

从幅相控制的观点出发。用Fourier级数分析方法对变流器的高频模型进行了电流谐波分析。基于分析结果，确定了变流器输入端电感和开关频率的选择方法，并用计算机仿真的方法对理论进行了分析验证，最后给出了实验结果。     

低输入电流纹波大升压比差动Boost型逆变器研究

为减少功率变换级数以及低频纹波对输入直流电源的影响,具有大升压能力和低输入纹波的单相逆变器具有重要的研究意义。深入研究了大升压比差动Boost逆变器电路拓扑、纹波抑制策略、电流纹波回路、输入电流反馈和输出电压复合控制策略。在传统波形控制基础上,通过输入电流反馈在输出滤波电容上叠加低频偶次电压,进一步减小输入电流中相应偶次谐波分量,使逆变器输出侧低频脉动功率在输出滤波电容与负载之间传递,阻断其向输入源传递;采用前馈与比例积分控制策略提高输出电压质量和输入电流质量。不同负载下的实验结果验证了此变换器的可行性。     

碱金属热电转换器功率调节系统研究

针对碱金属热电转换器(AMTEC)的伏安特性,设计了DC/DC和DC/AC两级变换的功率调节系统.功率调节系统采用高频变压器隔离,避免了工频变压器产生的一系列问题.DC/DC变换器采用移相ZVS(零电压开关)PWM全桥变换和电压闭环控制,把AMTEC在较宽范围变动的输出电压变成稳定的直流电压.逆变器控制采用优化的特定消谐PWM技术,以滤波后总谐波含量(THD)为目标函数,计算预定开关角度.整个系统具有电压输入范围宽、转换效率高、输出波形THD低等优点.     

基于基波分析方法的绕组电流谐波计算研究

三相双有源桥DC-DC变换器的固有软开关能力、滤波电容器电流低等特点而广泛应用于直流配电网。基于三相双向有源桥DC-DC变换器的拓扑结构,分析了不同联接方式下的高频三相变压器的电压电流波形。基于变压器在三种不同联接方式下的近似等效电路模型和电压与电流之间的相量图,采用基波分析方法推导了高频三相变压器绕组电流的各阶次谐波计算表达式,结合各阶次谐波频率下的交流电阻系数表达式,进而实现绕组高频损耗的计算。最后,将解析计算结果与仿真结果进行对比,结果表明各阶次谐波电流幅值、绕组总损耗值与解析计算方法的最大误差为8.4%,验证了解析计算方法的正确性。     

含滤波器的多换流站谐波阻抗模型与谐波交互影响研究

当多个换流站位于相邻交流电网时,换流站之间电气距离较小,一些特定的交流滤波器组合投切方式可能会引发换流站之间谐波电流的交互影响。基于谐波阻抗方法定义了换流站谐波电流影响系数,用于计算换流站之间谐波电流的交互影响程度。以银川东站与灵州站构成的多换流站系统为例,搭建含有交流滤波器的谐波阻抗模型,针对特征谐波,计算谐波电流影响系数,分析了交流滤波器组合投切对银川东站、灵州站谐波电流交互作用的影响。结果显示11、13次谐波电流的交互影响较小,23、25次谐波电流的交互影响较大,且特定滤波器的投切会造成各换流站交流母线谐波电流的明显变化。最后,建立PSCAD电磁暂态仿真模型,对上述分析结果进行了验证。