Active damping control of a high-power PWM current-source rectifier for line-current THD reduction

The use of active damping to reduce the total harmonic distortion (THD) of the line current for medium-voltage (2.3-7.2 kV) high-power pulsewidth-modulation (PWM) current-source rectifiers is investigated. The rectifier requires an LC filter connected at its input terminals, which constitutes an LC resonant mode. The lightly damped LC filter is prone to series and parallel resonances when tuned to a system harmonic either from the utility or from the PWM rectifier. These issues are traditionally addressed at the design stage by properly choosing the filter resonant frequency. This approach may result in a limited performance since the LC resonant frequency is a function of the power system impedance, which usually varies with power system operating conditions. In this paper, an active damping control method is proposed for the reduction in line current THD of high-power current-source rectifiers operating at a switching frequency of only 540 Hz. Two types of LC resonances are investigated: the parallel resonance excited by harmonic currents drawn by the rectifier and the series resonance caused by harmonic pollution in the source voltage. It is demonstrated through simulation and experiments that the proposed active damping control can effectively reduce the line-current THD caused by both parallel and series resonances.     

A 6.6-kV transformerless shunt hybrid active filter for installation on a power distribution system

This paper presents a fully-digital-controlled shunt hybrid filter for damping of harmonic propagation in power distribution systems. The harmonic propagation is caused by resonance between line inductances and power capacitors installed for power factor correction. A possible solution to damping out harmonic propagation is based on installation of a shunt pure active filter at the end of a feeder. This paper proposes a shunt hybrid active filter characterized by series connection of a seventh-tuned LC filter per phase and a small-rated three-phase active filter. Like the pure filter, the hybrid filter is connected to the end bus of a feeder. The capacitor of the LC filter imposes a high impedance to the fundamental frequency, so that the fundamental voltage appears across the capacitor. This unique feature allows us to directly connect the hybrid filter to the 6.6-kV power line without step-down transformers. Furthermore, the capacitor used in this hybrid filter is lighter, cheaper and smaller than the transformer used in the pure filter. Theoretical analysis, along with experimental results obtained from a 200-V, 20-kW laboratory system, verifies the viability and effectiveness of the proposed hybrid filter.     

牵引供电区段车网耦合系统谐波电流分析及抑制策略

本文以哈大高铁西四牵引供电区段及CRH380BG型动车组车网耦合为研究对象,分析牵引网高低次谐波产生机理,建立了车网耦合系统的数学模型,对动车组不同位置不同工况谐波电流进行仿真分析。针对牵引供电区段谐波电流特性,提出基于阻波高通滤波器的抑制策略,对满功率动车组不同工况谐波电流抑制方案验证,为哈大高铁西四牵引供电区段谐波抑制问题提供了理论参考依据。     

Current waveform control of PWM converter system for harmonic suppression on distribution system

The voltage waveform on the electric power distribution system is distorted by harmonic-producing loads. Regardless of the terminal voltage waveform with or without harmonics, the conventional current waveform of the pulsewidth-modulated converter systems connected to the power distribution system is always controlled to be sinusoidal. For harmonic suppression of the voltage and current on the distribution system, the authors propose the distorted current waveform whose harmonic components are in phase with the terminal voltage harmonics. The effectiveness of the proposed current waveform has been verified by experiments.     

考虑孤岛现象的储能系统奇次谐波频谱分析

为了实现对电力储能系统的协调控制能力,提出基于孤岛现象的储能系统奇次谐波频谱分析方法,构建多类型储能系统的奇次谐波检测模型,在孤岛现象作用下进行储能系统的低频成分抑制,将总储能中的低频成分指派给蓄电池,根据储能系统奇次谐波分量,进行超级电容器之间的功率分配,获取能量型储能系统奇次谐波频谱分量,采用波动平抑策略,在考虑孤岛现象作用下,基于模型预测控制算法进行储能系统奇次谐波频谱分析和特征提取,实现功率型超级电容器储能之间的功率优化分配。仿真结果表明,采用该方法进行储能系统奇次谐波频谱特征提取的准确性较好,提高了储能系统的协调控制能力,储能功率得到提升。     

DSP- and GPS-based synchronized measurement system of harmonics in wide-area distribution system

With the recent progress in power electronics devices, harmonic pollution in the power system becomes a significant problem. Therefore, a great deal of attention has been paid to harmonic regulations and suppression technologies. As the utility power distribution system becomes broader and more complex, advanced harmonic measurement and analysis technologies are required. This paper presents the advanced measurement system of harmonics in a wide-area distribution system. The proposed measurement system has the following features. The measurement unit at each point in the distribution system consists of a digital signal processor as a high-speed processor and a global positioning system as a synchronization measurement. These units as terminals at multipoints in the distribution system are connected to the central monitoring station by the Internet. By using this system, the harmonic flows in the distribution system are measured and, hence, harmonic modeling can be realized in real time.     

A robust multilevel hybrid compensation system for 25-kV electrified railway applications

On many electrified railway systems with single-phase 25-kV industrial frequency supply, the power quality can be particularly poor when conventional thyristor based locomotives are operating, and this constrains the amount of power that can be delivered to the locomotives. This paper presents a hybrid shunt compensation system consisting of alternatively a cascaded or a reduced topology multilevel active power filter, and a low rating passive damping filter. The active power filter is controlled by a novel hysteresis current regulation strategy, and both mitigates low-order voltage harmonic distortion along the feeder and provides root mean squared voltage support. The passive filter damps harmonic resonances that are typical in such 25-kV traction systems. The results show that the filter system can significantly increase traction system power transfer capacity with only a relatively small capital investment, allowing older thyristor based locomotives and increased traffic levels to be supported without necessarily requiring a complete system upgrade. Simulation and experimental results are included showing the performance of the filter for both steady state and transient conditions.     

基于STM32的电网谐波检测仪的研究

电力系统在运行过程中,会产生很多谐波,严重影响到电能的质量,为了方便实时监测谐波以及加强谐波管理,谐波检测仪就显得尤为重要。以传统单片机设计的谐波检测仪的电参数测量方法精度不够高,越来越难以满足目前电网检测的需要,而以DSP设计的检测仪成本高、难推广。针对这种现状,设计了一种多功能、低成本、高精度的电网谐波检测仪,它是基于最新Cortex-M3内核的STM32,并结合了三相多功能高精度计量芯片ADE7878,具有很强的实时性、精确度,为电力系统谐波的检测和抑制提供了重要的依据。     

A novel shunt hybrid active power filter based on magnetic flux compensation

In this article, the principle of a novel shunt hybrid active power filter (APF) based on magnetic flux compensation is proposed. The parallel transformer can exhibit nearly zero impedance to harmonic current whereas the zero magnetic flux condition is satisfied for harmonics, which leads harmonic current to flow into the transformer branch. Meanwhile, the transformer can exhibit continuously adjustable impedance to the fundamental current based on fundamental magnetic flux compensation, which works together with the passive power filter to compensate for reactive power. A mathematical model is established for system stability analysis and steady state estimation. The experimental results verify that the performance of the proposed APF is satisfactory in harmonic suppression as well as reactive power compensation.     

行波管谐波注入技术新进展

根据Rowe理论计算行波管的1D圆盘模型生成的TWTRF2.0程序用来计算谐波注入对基波功率增长及管内谐波抑制的影响。LMSuite程序用来计算谐波注入对交调(IM3)的抑制。两程序的计算结果与实验符合得比较好。     

Proximity Coupled Microstrip Patch Antenna With Reduced Harmonic Radiation

The purpose of this work is to propose a new method to suppress the harmonic radiation from a microstrip patch antenna with proximity coupled feeding line implemented in a multilayer substrate. The goal of the design is the suppression of the resonances at the 2nd and 3rd harmonic frequencies to reduce spurious radiation due to the corresponding patch modes to avoid the radiation of harmonic signals generated by non-linear devices at the amplifying stage. The study shows the possibility of controlling the second harmonic resonance matching by varying the length of the feeding line. On the other hand, the suppression of the third harmonic is achieved by using a compact resonator. This resonator consists of a printed metallization with a via connected to the ground plane (mushroom type) in a multilayer configuration. Comparing with conventional electromagnetically coupled patch antenna, the radiated power of the proposed antenna at the 2nd and 3rd harmonic frequencies is reduced by 14 dB and 8 dB, respectively.      

Microwave harmonic generation in a plasma capacitor

Microwave harmonic generation in a plasma capacitor is investigated both theoretically and experimentally. Deficiencies of previous harmonic generation theories are pointed out and a nonlinear one-dimensional mathematical model, which includes the reactive nonlinearities due to the spatial variation of E, is developed. This nonlinear plasma capacitor model indicates that under certain electron-density and capacitor-plate spacing conditions strong harmonic resonances and an antiresonance are present. The antiresonance occurs when nω= ωpand the resonances occur when nω≳ ωp, where ωp=plasma frequency, ω= the fundamental frequency, and n is the harmonic number. Harmonic generation in a number of gases is investigated experimentally in a coaxial discharge structure. Third-harmonic (9-GHz) efficiencies of up to 13 percent, and third-harmonic output power in excess of 600 mW are reported. Double-probe and microwave-scattering measurements show that enhanced harmonic generation occurs at the above resonances and, hence, substantiate the non-linear plasma capacitor theory. In order to explain the harmonic output power variations that occur with pressure variation and gas type, a graphical method of analysis based on experimental fact and pressure-collision frequency-electron energy curves is presented. This method of analysis not only yields results that compare qualitatively with experimental observations, but it may also possibly be used to design and predict the performance of future plasma frequency multipliers.     

Harmonic and reactive power compensation based on the generalizedinstantaneous reactive power theory for three-phase four-wire systems

This paper presents harmonic and reactive power compensation based on a generalized theory of instantaneous reactive power for three-phase power systems. This new theory gives a generalized definition of instantaneous reactive power, which is valid for sinusoidal or nonsinusoidal and balanced or unbalanced three-phase power systems with or without zero-sequence currents and/or voltages. The properties and physical meanings of the newly defined instantaneous reactive power are discussed in detail. A harmonic and reactive power compensator based on the new theory for a three-phase harmonic-distorted power system with zero-sequence components in the load current and/or source voltage is then used as an example to show harmonic and reactive power measurement and compensation using the new theory. Simulation and experimental results are presented     

基于配电系统节电器的谐波抑制研究

模拟配电网用户侧典型负荷组成,搭建了节电器节电行为研究平台.通过电能质量分析仪、三相可编程电源等在线监测与分析仪器,研究了配电系统节电器在阻感负荷运行工况下对负荷侧电网谐波的抑制行为.结果表明,配电系统节电器抑制电力用户侧谐波效果明显,单相电流谐波可降低2％ ～5％,波型稳定,电能质量得到有效提高.     

The propagation of harmonic currents generated by inverter-fedlocomotives in the distributed overhead supply system

Pulse-width-modulated converter-fed locomotives generate current harmonics that give rise to traveling waves in the overhead supply system. The waves are partially reflected at the feeding substances, causing parallel and series resonances at various discrete frequencies. An investigation based on the wave propagation approach demonstrates the influence of the track topography and the varying position of locomotives within the track. The distribution of harmonic currents in the overhead supply system is evaluated and discussed. These currents are shown to be much higher in certain locations of the railway track than the harmonic current injected by a locomotive. They may also appear at distant tract locations. The natural resonances in the overhead supply system determine the intensity of electromagnetic interference with the track-side communication lines     

适用于4G无线LTE通信系统的紧凑型谐波抑制功率放大器

为了满足4G无线移动通信LTE系统对功率放大器的性能需求,提出了一种新型采用低通滤波器（Low-Pass Filter,LPF）集成的n次谐波抑制紧凑型功率放大器。该功率放大器使用低通滤波器作为输出阻抗变换网络,以便得到所需阻抗产生最大功率,从而省略了传统的输出匹配网络。所以,相较于传统的功率放大器,提出的功率放大器尺寸减少了25%。此外,由于在输出端使用了低通滤波器,大幅抑制了（2次-5次）谐波,衰减程度较大。提出的功率放大器的设计频率为2.6 GHz,适用于LTE系统。仿真结果与实测结果比较吻合,证明了提出的设计有效性。     

A novel open-loop control method for a current-source active power filter

This paper presents a new control system for a current-source active power filter. The harmonic current compensation is realized using only a feedforward control of the load currents. The LC filter resonance of the converter is damped in an open-loop manner using the dynamic equations of the supply filter. The benefits of the proposed control system are that it is simple and straightforward, the number of measurements and sensors can be minimized, and also that the LC filter size can be optimized according to proper harmonic distortion level of the supply currents without care about the stability issues of the closed-loop system. This usually leads to reduction of the filter size. Also, the changes in fundamental current components of the active filter can be effectively realized when the active power filter can also be used as a fast reactive power compensator. The control system also includes the calculation delay compensation of the digital control system. The control system is realized using a single-chip Motorola MPC555 microcontroller. The tests with the prototype show effective current harmonic compensating performance of the nonlinear loads.     

New hybrid active power filter for harmonic current suppression and reactive power compensation

In the case of undistorted and balanced grid voltages, low ratio shunt active power filters (APFs) can give unity power factors and achieve current harmonic cancellation. However, this is not possible when source voltages are distorted and unbalanced. In this study, the cost-effective hybrid active power filter (HAPF) topology for satisfying the requirements of harmonic current suppression and non-active power compensation for industry is presented. An effective strategy is developed to observe the effect of the placement of power capacitors and LC filters with the shunt APF. A new method for alleviating the negative effects of a nonideal grid voltage is proposed that uses a self-tuning filter algorithm with instantaneous reactive power theory. The real-time control of the studied system was achieved with a field-programmable gate array (FPGA) architecture, which was developed using the OPAL-RT system. The performance result of the proposed HAPF system is tested and presented under nonideal supply voltage conditions.     

可重构多波段功率放大器设计与研究

为满足现代无线通信系统对多模式多制式功放的要求,提出了一种基于谐波抑制且双开关控制的可重构多波段功率放大器设计方案。利用单刀单掷PIN开关调节输入匹配网络中的可变电容,实现了三个频段处输入匹配网络的自由切换;利用单刀三掷开关控制带有谐波抑制的三路输出匹配网络,功放可工作在三个频段并提高了整体效率。为验证上述方案的可行性,采用型号为CGH40010F的GaN晶体管设计了一款工作在1.75 GHz、2.1 GHz和2.6 GHz的可重构功率放大器。制作了实物并测试,测试结果表明,在三个频段处功放的增益均大于10.2 dB,效率大于41.5%,输出功率约为38 dBm。满足基站对功放多模式多制式的要求,为无线系统模块设计提供了一种新颖的功放结构。     

Fast Simulation of steady-state temperature distributions in electronic components using multidimensional model reduction

In this paper, a model reduction technique is applied to the thermal modeling of electronic components and devices with complex geometries. The reduced-order model is capable of predicting a complete detailed three-dimensional temperature distribution in the original model. The small size and the simplicity of the reduced model allows for the very quick simulation of the device under a wide range of input parameters, such as different boundary conditions and power distributions. Use of the reduced-order model in a thermal design cycle can have a significant effect on both prediction accuracy and simulation efficiency. In the paper, the usefulness of this technique is demonstrated through examples from different electronic devices and packages. Accuracy of the reduced-order model is validated by comparison with the solution to a detailed numerical model.