Reactive power measurement using the wavelet transform

This paper provides the theoretical basis for the measurement of reactive and distortion powers from the wavelet transforms. The measurement of reactive power relies on the use of broad-band phase-shift networks to create concurrent in-phase currents and quadrature voltages. The wavelet real power computation resulting from these 90° phase-shift networks yields the reactive power associated with each wavelet frequency level or subband. The distortion power at each wavelet subband is then derived from the real, reactive and apparent powers of the subband, where the apparent power is the product of the v, i element pair's subband rms voltage and current. The advantage of viewing the real and reactive powers. In the wavelet domain is that the domain preserves both the frequency and time relationship of these powers. In addition, the reactive power associated with each wavelet subband is a signed quantity and thus has a direction associated with it. This permits tracking the reactive power flow in each subband through the power system     

一种新型软开关BUCK变换器

本文提出一种新型软开关BUCK变换器。所提出的变换器具有如下的优点,零电压、零电流导通,零电压关断;不增加开关管的电压电流应力;输出电感电流工作在连续电流模式,其纹波很小;变换器可以工作在固定的频率,采用PWM控制。由于软开关的使用,变换器可以工作在很高的频率,同时其效率也很高。Pspice软件仿真验证了该电路的理论设计和分析。     

基于STM32的频率和功率可调非接触供电超声电源设计

为解决接触式供电中漏电、磨损、电能传输不良以及超声电源在加工中谐振频率漂移、跟踪速度慢、输出功率不稳定等问题,文章以STM32单片机作为主控系统,设计了一种频率和功率可调的非接触供电超声电源。根据采样反馈电路采集的电压电流相位差和有效值信号,采用锁相环和模糊比例积分(Proportional Integral, PI)控制相结合的方法对频率进行跟踪,并用传统 PI 控制法控制输出功率。在 Matlab 软件中搭建电源仿真模型,利用附加电阻、附加电感和附加电容模拟加工过程中负载参数的突变,对有频率调节和功率控制子系统以及没有子系统的电源模型分别进行仿真。仿真结果表明,电源输出功率稳定在 248 W。当负载参数发生改变时,电源的谐振频率发生漂移,经过频率自动跟踪子系统的调节后,电源在 0.01 s 后重新回到谐振状态。此控制算法实现了频率快速跟踪和功率控制。     

High power factor operation of resonant converters on the utility line

Operation and characteristics of resonant converters on the utility line are presented. Series-parallel (LCC-type) resonant converter operating with discontinuous current mode and continuous current mode (variable frequency control as well as fixed-frequency) are considered. Design examples are presented. SPICE simulation and experimental results obtained for the designed converters (rated at 150 W) are presented to verify the theory. It is shown that high line power factor (>0.95) and line current total harmonic distortion (THD) of <25% are obtained for the LCC-type converter for a wide load range (from full load to 10% rated load) without any active control, and the switch peak current decreases with the load current. With active line current control, low distortion and zero voltage switching for the entire cycle are realized.     

Single-stage unity power factor based electronic ballast

This paper deals with the design, modeling, analysis and implementation of unity power factor (UPF) based electronic ballast for a fluorescent lamp (FL). The proposed electronic ballast uses a boost AC–DC converter as a power factor corrector (PFC) to improve the power quality at the input ac mains. In this single-stage UPF based electronic ballast, boost PFC converter and a half bridge series resonant inverter (HBSRI) share a common power switch. Thus one power switch is reduced as compared to the conventional two-stage approach. The design, modeling, analysis and implementation of this topology were carried out in MATLAB-Simulink environment for a T8 36 W, 220 V, 50 Hz fluorescent lamp. The switching frequency was kept more than the resonant frequency of the inverter, to ensure the zero voltage switching (ZVS) operation of both power switches. This resulted in reduction of high frequency switching losses. The power quality parameters such as displacement power factor (DPF), distortion factor (DF), power factor (PF), crest factor (CF) and total harmonic distortion of ac mains current (THD_i) were evaluated to analyze the performance of proposed electronic ballast. Test results on a developed prototype of PFC electronic ballast were included to validate the design and simulated results.     

Virtual welding equipment for simulation of GMAW processes with integration of power source regulation

A two dimensional transient numerical analysis and computational module for simulation of electrical and thermal characteristics during electrode melting and metal transfer involved in Gas-Metal-Arc-Welding (GMAW) processes is presented. Solution of non-linear transient heat transfer equation is carried out using a control volume finite difference technique. The computational module also includes controlling and regulation algorithms of industrial welding power sources. The simulation results are the current and voltage waveforms, mean voltage drops at different parts of circuit, total electric power, cathode, anode and arc powers and arc length. We describe application of the model for normal process (constant voltage) and for pulsed processes with U/I and I/I-modulation modes. The comparisons with experimental waveforms of current and voltage show that the model predicts current, voltage and electric power with a high accuracy. The model is used in simulation package SimWeld for calculation of heat flux into the work-piece and the weld seam formation. From the calculated heat flux and weld pool sizes, an equivalent volumetric heat source according to Goldak model, can be generated. The method was implemented and investigated with the simulation software SimWeld developed by the ISF at RWTH Aachen University.     

有源电力滤波器半矢量预测控制策略研究

针对经典模型预测电流控制算法电压矢量选择范围有限、电流跟踪精度不高的问题,提出改进型模型预测电压控制算法。利用滚动寻优得到较优电压矢量,再利用较优电压矢量和零矢量各作用T_s/2得到半幅值矢量,根据较优电压矢量和半幅值矢量的评价函数选择最优电压矢量。每个周期仅增加一个电压矢量,能有效减小预测电压矢量和实际电压矢量之间的误差,实现对谐波电流的准确跟踪,提高有源电力滤波器的补偿性能。仿真结果表明,所提出的改进型模型预测电压控制算法与经典模型预测电流控制算法相比,补偿电流对参考电流的跟踪更加准确,经补偿后并网电流中的谐波含量由4.86%下降到3.32%,且在稳态和动态情况下都能实现单位功率因数并网。     

A single phase photovoltaic inverter control for grid connected system

This paper presents a control scheme for single phase grid connected photovoltaic (PV) system operating under both grid connected and isolated grid mode. The control techniques include voltage and current control of grid-tie PV inverter. During grid connected mode, grid controls the amplitude and frequency of the PV inverter output voltage, and the inverter operates in a current controlled mode. The current controller for grid connected mode fulfills two requirements – namely, (i) during light load condition the excess energy generated from the PV inverter is fed to the grid and (ii) during an overload condition or in case of unfavorable atmospheric conditions the load demand is met by both PV inverter and the grid. In order to synchronize the PV inverter with the grid a dual transport delay based phase locked loop (PLL) is used. On the other hand, during isolated grid operation the PV inverter operates in voltage-controlled mode to maintain a constant amplitude and frequency of the voltage across the load. For the optimum use of the PV module, a modified P&O based maximum power point tracking (MPPT) controller is used which enables the maximum power extraction under varying irradiation and temperature conditions. The validity of the proposed system is verified through simulation as well as hardware implementation.     

Design and implementation of FPGA-based phase modulation control for series resonant inverters

Owing to the tremendous advances in the digital technology, and improved reliability and performance of the digital control mechanisms, this paper focuses on design and implementation of digital controller using FPGA-based circuit design approach. The digital controller proposed is designed for series resonant inverter used in DC-DC converter applications. Phase modulation technique is proposed for the realization of digital controller on FPGA. The Series Resonant Converter (SRC) is considered in this paper as a preferred converter topology for high power, high voltage power supplies. This paper studies the implementation of phase shift modulation technique using FPGA. The inverter designed, is IGBT based, and Zero Voltage Switching (ZVS) technique is implemented due to reduced stresses on devices and increased efficiency. The phase modulated series resonant inverters (PM-SRC) promotes ZVS operation when its switching frequency is greater than resonant frequency. The designed PM controller is realized using FPGA on which control algorithm and other features of a controller are developed. The series resonant inverter is built and tested for full load under open loop and closed loop conditions at a switching frequency of 20 kHz. The results are presented under varying load conditions. The simulation and the experimental results were found to match closely.     

Analysis and implementation of an active snubber dc/dc converter with series?parallel connection in primary and secondary sides

An active snubber dc/dc converter to achieve zero voltage switching (ZVS) on power switch is presented. In the proposed converter, the primary windings of two transformers are connected in series so that the primary currents of the two transformers are equal. The secondary sides of the isolated zeta converters are connected in the parallel to share the load current and reduce the current stresses on the secondary windings of the two transformers. A boost type of active snubber is connected in parallel with the main switch to recycle the energy stored in transformer leakage and magnetizing inductors and to limit voltage stress of the main switch. During the transition interval between the active switch and the auxiliary switch, the resonance based on the resonant inductor and the output capacitor of the power switch will allow the switch to turn on at ZVS. The principle of operation, steady-state analysis and design consideration of the proposed converter are provided. Finally, experimental results for a 360 W (12 V/30 A) prototype circuit with 150 kHz switching frequency were given to demonstrate the circuit performance and verify the feasibility of the proposed converter.     

SCR软启动技术在变频空调中的应用

通过分析SCR软启动技术的工作原理,提出一种新的控制电路及控制方法,给出由专用的双核MCU组成的低功耗系统的硬件设计原理和软件设计方法。测试结果表明,采用差分电路、基准零点电路和移相PWM技术后,变频空调的启动电流大大减小,启动性能提高,保证变频空调的可靠性。     

基于可编程片上系统的宽频带超声波电源系统设计

针对当前超声波处理装置的频率单一、专机专用等问题,提出了一种基于可编程片上系统(System-On-aProgrammable-Chip,SOPC)的新型宽频带超声波电源系统。该系统基于现场可编程门阵列(Field-Programmable Gate Array,FPGA)可编程逻辑及数学运算等方面的优势,移植了NIOS II软核作为主控制器,移相脉宽调制(Phase-Shifted Pulse-Width-Modulation,PS-PWM)用于调频调功,正交相关电路检测输出电压与电流间的相位差。实验结果表明,该方案能在指定带宽范围内(20~40 k Hz)使超声波振子工作状态趋近于谐振状态。     

基于高低压电源切换的双环恒流控制电磁流量计励磁控制系统

为了提高电磁流量计高频方波励磁性能,基于励磁恒流控制仿真分析,采用外环高低压电源切换和内环电流微调的双环励磁恒流控制方式,以保证电磁流量计高频方波励磁时一次仪表输出信号零点稳定、电源利用效率高。设计方波励磁控制系统,以实现高频方波精确励磁。仿真结果表明,高压源电压越高越有利于拓宽励磁频率范围。实验结果表明,系统在高频方波励磁时,励磁电流响应速度快且电磁流量计传感器输出信号零点稳定。     

Design and analysis of a full bridge LLC DC-DC converter for auxiliary power supplies in traction

This paper focuses on an 8 kW LLC resonant full bridge DC-DC converter topology using a high frequency transformer for auxiliary power supply systems in traction. The full bridge DC-DC converter with the LLC resonant network has been tested under hard switching and zero current switching conditions with 100 kHz switching frequency. In addition to this, an observation made for the effect of dead time variation of the power switches to improve the overall system efficiency. This paper describes the efficiency of the ZCS full bridge converter by considering different input power levels and also compared with hard switched topology. This paper presents the operating principles, simulation analysis, and experimental verification for 3 kW to 8 kW LLC resonant full bridge converter with 1200 V/40 A IGBTs, and its efficiency comparison.     

A Technique for Calibrating Power Frequency Wattmeters at Very Low Power Factors

The application of a current comparator capacitance bridge to the measurement of the error of power frequency wattmeters at zero and very low power factors is described. The desired voltage, current, and power factor, leading or lagging, are established with a capacitive-type artificial load. The power factor is adjusted with reference to a loss-free gas-dielectric capacitor to within 1 × 10-5 or to an accuracy of 1 percent, whichever is greater, and voltage and current to an accuracy of better than 1 percent. Results of the measurements on representative commercially available electrodynamic and electronic wattmeters are given.     

Resonant Magnetoelectric Effect with Strongly Nonlinear Magneto-Elastic Coupling in Magnetoelectric Laminate Composites

Considering the complex strongly nonlinear coupling characteristic of the magnetostrictive strain and magnetization under the excitation of the bias magnetic field and the pre-stress in the giant magnetostrictive material, this paper adopts the nonlinear magnetostrictive constitutive model and the equivalent circuit method to establish a strongly nonlinear resonant magnetoelectric (ME) effect theoretical model for the ME laminate composites compounding by the giant magnetostrictive material and the piezoelectric material. For the L-T mode magnetostrictive/piezoelectric/magnetostrictive (MPM) ME laminate, the predicted results coincide well with the experiment results of the resonant frequency and the resonant ME field coefficient varying with the external magnetic field when the pre-stress degenerates to zero in our model. The agreement indicates the proposed theoretical model validity. On the basis, we use the theoretical model to forecast the varying characteristic of the resonant ME field coefficient and the resonant frequency effect under the influence of the different bias magnetic field and the pre-stress in ME laminate composites. And we also predict that the resonant ME coefficient and the resonant frequency appear "reversal" with the pre-stress increasing. After that, the influence of the different volume ratio on the ME effect and resonant frequency is analyzed. Particularly, a resonant frequency value not influenced by the volume ratio with increasing bias magnetic or pre-stress occurs. This research can provide theory basis for improving the resonant ME conversion performance and for controlling the resonant frequency under the excitation of the bias conditions (i.e. the bias magnetic field and the pre-stress) for the ME devices (i.e. sensor, transducer, microwave device and so on).     

Recurrent neural network control for LCC-resonant ultrasonic motor drive

A newly designed driving circuit for the traveling wave-type ultrasonic motor (USM), which consists of a push-pull DC-DC power converter and a two-phase voltage source inverter using one inductance and two capacitances (LCC) resonant technique, is presented in this study. Moreover, because the dynamic characteristics of the USM are difficult to obtain and the motor parameters are time varying, a recurrent neural network (RNN) controller is proposed to control the USM drive system. In the proposed controller, the dynamic backpropagation algorithm is adopted to train the RNN on-line using the proposed delta adaptation law. Furthermore, to guarantee the convergence of tracking error, analytical methods based on a discrete-type Lyapunov function are proposed to determine the varied learning rates for the training of the RNN. Finally, the effectiveness of the RNN-controlled USM drive system is demonstrated by some experimental results.     

25kV/2A谐振式恒流充电电源

为 1MJ 电容器储能系统研制了一台输出电压 25kV,输出电流2A的恒流充电电源。该电源采用零电流切换非连续全波谐振原理。串联 LC 谐振电路由接成全桥形式的4只大功率 IGBT 驱动,谐振频率固定为 80kHz,开关工作频率 30-65kHz 可调。谐振产生的非连续正弦形电流经匝比为 1:50 的高压变压器升压至 25kV,经快恢复高压二极管串组成的全桥电路整形为一系列非连续的半正弦状电流脉冲,给 10000μF 高压电容器组充电。最终充电电压和充电电流的大小由微处理器控制,前者正比于充电电流脉冲的总个数,后者则正比于开关工作频率。     

Direct airborne acoustic wave modulation of Fabry-Perot fiber laser (FPFL) over 100 kHz of operating bandwidth

The idea of applying a simple Fabry-Perot fiber laser (FPFL) set-up in a free-running condition as an acoustic sensing medium is proposed. Conventional optical microphone requires a stringently aligned diaphragm to mediate the acoustic impedance mismatch between air and silica fiber. Motivated by the difficulty of optical sensing of airborne acoustic waves, a new sensing method is proposed to sense acoustic waves without the assistance of a diaphragm as transducer. By studying the output power fluctuation of the FPFL, the operating bandwidth and sensitivity of the proposed sensing method are determined. The tunability of the resonant frequency from 5 kHz to 85 kHz allows sensing of acoustic waves in the range of 100 Hz to 100 kHz. Tuning of the resonant frequency can be performed by changing the optical pumping power from as low as 10 mW to 68.5 mW or higher.     

A novel driver with adjustable frequency and phase for traveling‐wave type ultrasonic motor

Abstract

This paper describes the design of a traveling‐wave ultrasonic motor (TWUSM) drive circuit, intended to simultaneously employ both driving frequency and phase modulation control. The operating principles and a detailed analysis of the proposed driving circuit, consisting of voltage‐controlled oscillator (VCO), voltage‐controlled phase‐shifter circuit and non‐resonant power amplifier converter, are introduced. To drive the USM effectively, a two‐phase power amplifier converter using non‐resonant output was designed to provide a balanced two‐phase voltage source. Two‐phase output driving voltages could be maintained at the same peak voltage value as the driving frequency under varying phase‐modulation processes. Detailed experimental results are provided to demonstrate the effectiveness of the proposed driving circuit.