Conducted electromagnetic emissions in induction motor drivesystems. II. Frequency domain models

For pt.I see ibid., vol.13, no.4, p.757-67 (1998). Predicting conducted emissions in pulsewidth modulation (PWM) inverter induction motor drive systems requires various frequency-dependent effects to be considered. A frequency domain method has advantages in such cases compared to a time domain approach. Based on the modal analysis presented in Part I, this paper develops frequency domain models to evaluate the spectra of the conducted emissions directly. The common and differential mode excitation sources are modeled in the frequency domain and related to the switching functions of the PWM inverter. Network models are established where the induction motor is represented using its frequency-dependent impedance characteristics, which can be obtained from measurements. The influences of system unbalances and of transmission-line effects due to long cables are investigated. Predicted emission spectra are compared with laboratory measurements and those derived from the time domain simulation. It is found that the agreement is good. The proposed method allows emission spectra to be predicted without recourse to specialist circuit simulators     

PFC full bridge rectifiers EMI modeling and analysis-common mode disturbance reduction

Switched mode power supplies must comply with electro-magnetic interference (EMI) regulations. Due to technological improvements, switching frequencies have been increased leading to reduced passive component values but also greater EMI levels, especially conducted common mode disturbances. This paper presents a simple and effective EMI forecast method to study and to analyze the conducted EMI effects before prototype testing. The methodology is validated and applied to the single phase full bridge power factor correction (PFC) rectifier. Several techniques to reduce common mode current (CMC) levels created by the converter are presented. The study is based on high frequency models and understanding of phenomenon. Looking at the control strategies and/or the propagation paths, it is demonstrated that EMI levels may be reduced. It is shown that with symmetrical EMI propagation paths, synchronized control strategies such as bipolar pulse width modulation (PWM) are preferred and lead to reduced CMC levels. On the other hand, with asymmetrical propagation paths, unipolar and half bridge control strategies may be preferred to reduce both differential mode current (DMC) and CMC levels. Results are validated using practical experiments performed under EMI regulation testing conditions.     

Software waiting loop length control: Technique for reduction ofradiated EMI from microprocessor-based PWM drive system

A novel technique, referred to as software waiting loop length control (SWLLC), for reducing the radiated EMI from microprocessor-based PWM drive systems is presented. By randomly changing the length of the software waiting loops, the energy concentrated into discrete bands by the action of periodic signals on the external and internal buses of the microprocessor system can be spread across a larger frequency range. Using this technique, significant reduction of radiated interference levels has been observed in a typical PWM drive system     

Stabilizing control method for suppressing oscillations ofinduction motors driven by PWM inverters

A novel control method that suppresses oscillations generated when an induction motor is driven by PWM (pulse width modulated) inverters is described. The suppression is done by keeping the power direction constant throughout the period of oscillation of the negative current component of the inverter input current. This period is determined only by the frequency of the PWM signals. Because it is not affected by motor parameters, such as the number of poles or motor capacity, the gains of the regulator in the control system do not have to be adjusted, even if this method is applied to various kinds of induction motor drive systems. Experiments have proven that oscillations can be suppressed regardless of the motor type or speed. This stabilizing control is suitable for general-purpose inverters that drive various types of motors     

Electromagnetic interference (EMI) of system-on-package (SOP)

Electromagnetic interference (EMI) issues are expected to be crucial for next-generation system-on-package (SOP) integrated high-performance digital LSIs and for radio frequency (RF) and analog circuits. Ordinarily in SOPs, high-performance digital LSIs are sources of EMI, while RF and analog circuits are affected by EMI (victims). This paper describes the following aspects of EMI in SOPs: 1) die/package-level EMI; 2) substrate-level EMI; 3) electromagnetic modeling and simulation; and 4) near electromagnetic field measurement. First, LSI designs are discussed with regard to radiated emission. The signal-return path loop and switching current in the power/ground line are inherent sources of EMI. The EMI of substrate, which work as coupling paths or unwanted antennas, is described. Maintaining the return current path is an important aspect of substrate design for suppressing EMI and for maintaining signal integrity (SI). In addition, isolating and suppressing the resonance of the DC power bus in a substrate is another important design aspect for EMI and for power integrity (PI). Various electromagnetic simulation methodologies are introduced as indispensable design tools for achieving high-performance SOPs without EMI problems. Measurement techniques for near electric and magnetic fields are explained, as they are necessary to confirm the appropriateness of designs and to investigate the causes of EMI problems. This paper is expected to be useful in the design and development of SOPs that take EMI into consideration.     

Properties of High-Frequency Conducted Noise from Automotive Electrical Accessories

This paper describes generation mechanisms and electrical characteristics of high-frequency conducted noise from electrical contacts and accessory drive/control motors, which may cause logic errors in automotive electronic devices. High-frequency conducted noise due to contacts in both horn sounding and lighting circuits results from spark discharge initiated by breakdown across the contacts; and a showering arc which sustains spark discharge for hundreds of microseconds was observed at contacts in lighting circuits. High-frequency conducted noise due to accessory drive/control motors was caused by reactance voltage fluctuations and commutator sparks. To analyze electrical characteristics of high-frequency conducted noise, a measuring system for amplitude distributions in both the time domain and the frequency domain was developed, and an attempt was made to fit a distribution pattern to observed data in each domain. In the time domain, the noise voltages due to contact breaking were distributed between 360 and 530 V. The distribution pattern in the time domain fitted closely to the normal distribution curve, while the pattern in the frequency domain fitted to the lognormal distribution curve.     

Measurement of conducted electromagnetic emissions in PWM motordrive systems without the need for an LISN

This paper presents a technique for measuring the conducted electromagnetic emissions produced by pulse-width modulated (PWM) inverter induction motor drive systems. The method does not require an artificial line-impedance stabilizing network (LISN) but does, however, allow the emission levels to be calculated as if an LISN were present. Testing can be performed when an LISN is either unavailable, prohibitively expensive, or impractical to include in the supply. This is often the case for large drive systems or for systems already installed in the field. A normal RF voltage probe and a spectrum analyzer are used to measure the spectra of the common-mode and differential-mode excitation sources due to the inverter switching. Line inductors for high-frequency (HF) isolation are required for some of the tests, but the cost and complexity of these compared to an LISN is low. Common-mode and differential-mode Thevenin equivalent circuits are then derived from measured impedances. The emissions for any defined supply impedance (including an LISN) can then be determined. A laboratory test on a 15 kW PWM drive system is carried out to verify the accuracy and effectiveness of the proposed method     

A transconductance driven-right-leg circuit

Biopotential measurements are very sensitive to electromagnetic interference (EMI). EMI gets into the acquisition system by many ways, both as differential and common mode signals, driven-right-leg circuits (DRL) are widely used to reduce common mode interference. This paper reports an improvement on the classic DRL. The proposed circuit uses a transconductance amplifier to drive the patient's body. This configuration has some interesting properties, which provide an extended bandwidth for high-frequency EMI rejection (such as fluorescent lights interference). The improvement is around 20 dB for frequencies of few kilohertz and the circuit is easy to compensate for stability. A comparative analysis against a typical DRL is presented, the results obtained have been experimentally tested.     

Design and performance of a passive EMI filter for use with a voltage-source PWM inverter having sinusoidal output voltage and zero common-mode voltage

This paper deals with integrating a small-sized passive electromagnetic interference (EMI) filter with a voltage-source pulse-width modulated (PWM) inverter. The purpose of the filter is to eliminate both high-frequency common-mode and normal-mode voltages from the three-phase output voltages of the inverter. A laboratory system consisting of a 5-kVA inverter, a 3.7-kW induction motor, and a specially-designed passive EMI filter was constructed to verify the viability and effectiveness of the filter. As a result, both line-to-line and line-to-neutral output voltages look purely sinusoidal as if the inverter were an ideal three-phase variable-voltage, variable-frequency power supply when viewed from the motor terminals. This results in a complete solution to serious EMI issues related to high-frequency common-mode and normal-mode voltages produced by the PWM inverter.     

A Current-to-Frequency Converter for Switched-Current Circuits

A current-to-frequency converter using switched-current (SI) circuits is proposed. The SI integrator with a hold-and-reset switch can control integration by the output signals. In the proposed circuit the oscillation frequency can be controlled by the input current, and the circuit is operated in the current domain. This is verified by HSPICE simulations.     

基于不变分布的开关变换器混沌PWM特性分析及频谱优化设计

本文利用统计分析工具,采用不变分布作为新的参数指来研究混沌PWM调制开关变换器的动态行为,基于不变分布分析了混沌开关变换器PWM驱动脉冲的频率特性,量化分析得到其特征参数和频谱特征.研究表明初值敏感不影响混沌开关变换器的电流、电压、驱动脉冲的分布,不影响频谱的形状,所以研究不变分布从而提取混沌开关变换器的整体特征是研究混沌开关变换器的有效手段,并且可以由此优化设计频谱有效抑制EMI.     

基于FPGA及DDS技术的USM测试电源的设计

超声波电机的运转需要一个两相相差90°（或可调）的高频交流信号源。本方案采用DDS技术的设计思路,用VHDL硬件描述语言对FPGA器件编程产生了两相四路高频信号。该信号经过驱动隔离电路施加于H桥逆变器中,在电感的平滑作用下,生成了满足USM测试要求的可调频、调相、调幅的两相高频交流信号源,成功地对USM45电机进行了驱动测试。该电路可用于研究超声波电机的运行状态的研究及获取其最佳工作点参数。     

A robust hysteresis current-controlled PWM inverter for linear PMSMdriven magnetic suspended positioning system

Hysteresis current-controlled pulsewidth modulation (PWM) is very robust but it possesses nonconstant switching frequency, and it is difficult to use for high-performance position servo applications. This paper presents a robust hysteresis current-controlled PWM scheme for a magnetic suspended positioning system driven by an inverter-fed linear permanent-magnet synchronous motor having improved performance in these two areas. In the proposed control scheme, the conventional hysteresis PWM mechanism is augmented by a robust harmonic spectrum-shaping controller. The error signal, which represents the switching frequency deviated from the set one, is detected using a notching filter inverse model. Then, the current command is adjusted by a robust compensation signal. The hysteresis band can be equivalently varied to let the dominant harmonic frequency of inverter output be constant, wherein the frequency can easily be changed by tuning the center frequency of the notch filter. The gating signal of switches is not needed to be sensed for making the proposed control. The constant-frequency control performance yielded by the proposed controller is rather insensitive to the system disturbances and the neutral voltage variation due to isolated Y connection. Through applying the proposed PWM inverter, satisfactory position control requirements can be achieved by properly setting the dominant harmonic frequency according to the electromechanical model of the positioning system     

Single-Phase Multilevel PWM Inverter Topologies Using Coupled Inductors

The number of voltage levels available in pulsewidth modulation (PWM) voltage source inverters can be increased by using a split-wound coupled inductor within each inverter leg and interleaved PWM switching of the upper and lower switches. The magnetizing inductance of the symmetrical split-wound inductor filters the high-frequency PWM voltage differences between the upper and lower switches. The same inductor presents a three-level PWM voltage at the inverter output terminals, with the winding leakage inductance being located in series with the low-frequency output current. Deadtime PWM signal delays can be reduced as dc-rail short circuits are not possible: as a result, the quality and voltage range of the PWM output is improved. Since the inductor windings are technically exposed to high-frequency PWM ac voltages with no dc components, device voltage drops help to reduce the buildup of winding dc currents. Theoretical analysis and a sample design case are presented to illustrate how to design suitable inductors for the various topologies. Simulation and experimental results are used to illustrate the operation of the proposed inverter structures.      

A highly effective load adaptive servo drive system for speed control of travelling-wave ultrasonic motor

This paper presents a highly effective load adaptive drive system to control the speed of a travelling-wave ultrasonic motor. The motor driver was built based on the two-phase high-frequency inverter using the mechanical resonant frequency of the ultrasonic motor. To digitally control the drive system, a TMS320F243 digital signal processor was adapted to the driver. The developed system includes two feedback loops; speed control loop and feedback voltage-resonant frequency tracking loop. The driving frequency was used as a control input to control the motor. Direct pulse-width modulation (PWM) control was used to obtain the required driving frequency. The developed drive system was experimentally tested under several operating conditions. The obtained results demonstrated the effectiveness of the drive system for high performance drive applications.     

基于加速度回路的天线随动系统控制器设计

为了解决天线随动系统所存在的振颤现象和全数字化实现等问题,介绍了一种基于加速度回路的全数字化天线随动系统控制器,该系统以DSP芯片TMS320F2812为核心控制芯片,采用速率陀螺平台稳定系统、数字PID控制算法和脉宽调制驱动方式,通过引入加速度回路抑制系统的高频振荡,极大地改善了系统的稳定性和动态品质,具有极高的应用价值。     

Current mode high-frequency KHN filter employing differential class AB log domain integrator

In this study, a current mode log domain differential Class AB biquad filter based on Kerwin–Huelsman–Newcomb (KHN) structure has been synthesized by using the state-space method and by adopting translinear circuits. The proposed circuit can produce second-order low pass, band pass, high pass, all pass, and notch filter characteristics. The circuit is synthesized for high-frequency applications, i.e. around 100 MHz. The natural frequency and Q quality factor of the filter can be tuned electronically by varying the currents of current sources. Moreover, by varying currents of selected current sources, one can change the characteristics of the notch filter to generate general, low pass, and high pass notch filters. The designed circuit is simulated in both time domain and frequency domain in PSpice by using both idealized and NE 600 series type real transistors that are suitable for high-frequency operations. The frequency as well as time domain responses are found to be as expected. In addition to these simulations, THD and noise analysis are carried out. The details of obtained results are given.     

Electromagnetic Design Techniques for Liquid Crystal Display Driver ICs

A simple method of verifying electromagnetic interference (EMI) reduction effects for liquid crystal display (LCD) driver integrated circuits (ICs) is proposed. In this paper, we discuss correlations between radiated emissions and high-frequency currents of power system at three different levels: print circuit board (PCB) level, chip level, and functional circuit level. The EMI design points for LCD driver ICs are presented too. Simulated and measured results prove that our EMI design effectively reduces LCD EMI noise.     

Distributed integrated circuits: an alternative approach tohigh-frequency design

Distributed integrated circuits are presented as a methodology to design high-frequency communication building blocks. Distributed circuits operate based on multiple parallel signal paths working in synchronization that can be used to enhance the frequency of operation, combine power, and enhance the robustness of the design. These multiple signal paths usually result in strong couplings inside the circuit that necessitate a treatment spanning architecture, circuits, devices, and electromagnetic levels of abstraction