High-efficient three-phase on-line UPS by using T-source inverter with third harmonic injected maximum constant boost PWM control

This paper presents the analysis of three-phase on-line uninterruptible power supply (UPS) by employing T-source inverter (TSI) with third harmonic injected maximum constant boost PWM control and the results are compared with traditional UPS. Traditional UPS consists of step-up transformer or DC–DC booster along with voltage source inverter which decreases the efficiency and increases energy conversion cost. The proposed three-phase UPS using TSI has high-voltage boost capability through shoot-through zero state which is not present in traditional voltage source inverter (VSI) and current source inverter. This proposed UPS with TSI increases the efficiency with fewer components, reduces the harmonics, increases the voltage gain, and reduces the voltage stress. The performance of three-phase on-line UPS based on TSI is analyzed and evaluated in MATLAB/SIMULINK software and the results are compared with Z-source inverter-fed UPS and VSI-fed UPS. Experimental results are presented for the validation of the simulation and theoretical analysis.     

Design and implementation of PV-based three-phase four-wire series hybrid active power filter for power quality improvement

This paper proposes a Photovoltaic (PV)-based three-phase four-wire Series Hybrid Active Power Filter (SHAPF), it comprises of a Series Active Power Filter (SAPF) and an LC shunt passive filter. The proposed system eliminates both the current and voltage harmonics and compensates reactive power, neutral current and voltage interruption. A SAPF demands a source of energy for compensating the voltage sag/swell. This system found a new topology for SHAPF which utilizes the PV with DC–DC boost converter as a source of DC power for the series active filter. The compensation current reference evaluation is based on the twin formulation of the vectorial theory of electrical power theorem with Fuzzy Logic Controller (FLC). The PV array/battery managed DC–DC boost converter is employed to step up the voltage to meet the DC bus voltage requirement of the three-leg Voltage Source Inverter (VSI). The foremost benefit of the proposed system is that, it will provide uninterrupted compensation for the whole day. This system utilizes the renewable energy; accordingly saves the energy and provides the uninterruptable power supply to critical/sensitive load, through the PV array/battery bank during both day time and night time. An experimental model was established and results were obtained, which indicated the capability of the proposed control scheme.     

Analytical closed-form investigation of pwm inverter induction motor drive performance under dc bus voltage pulsation

The voltage unbalance conditions at the input rectifier stage of the AC?DC?AC rectifier-inverter fed induction motor drive is analysed. This unbalance can cause significant voltage harmonic of twice the line frequency 2f1 in the DC bus. This voltage ripple can have a degrading effect on the induction-machine performance characteristics. The authors present an analytical closed-form mathematical model and analysis of the impact of DC bus ripple voltage of the three-phase voltage source inverter with the space-vector PWM on the induction machine phase voltages, currents and torque pulsations. The analytical expressions for the voltage and current space vectors as a function of the DC bus voltage pulsation are derived. Using superposition, the separate parts of the motor currents can be determined. From the current space vectors, the torque behaviour is estimated, again as a function of DC link voltage pulsation. Next, it is shown that the DC link voltage ripple components may cause large torque pulsation. The proposed analytical method is based on the mixed p?z approach, enabling presentation of the results in lucid and closed form. To verify the effectiveness of the proposed analytical model, experimental results based on laboratory setup were obtained.     

Modeling of Eddy-Current Loss of Electrical Machines and Transformers Operated by Pulsewidth-Modulated Inverters

Pulsewidth-modulated (PWM) inverters are used more and more to operate electrical machines and to interface renewable energy systems with the utility grid. However, there are abundant high-frequency harmonics in the output voltage of a PWM inverter, which increase the iron losses and result in derating of the machine or transformer connected to them. Predicting the iron losses caused by the PWM supply is critical for the design of electrical machines and transformers operated by PWM inverters. These losses are primarily attributed to eddy-current loss caused by the PWM supply. In this paper, after analyzing the harmonic components of PWM voltage, we derive the effects of different parameters of PWM switching on the eddy-current loss. We compare the iron losses modeled with the proposed analytical methods on a three-phase transformer, a dc motor, and an induction motor with the results of time-stepping finite-element analysis and experiments. We provide detailed equations for the prediction of iron losses. These equations can be directly applied in the design and control of PWM converters and electric motors to improve energy efficiency in electrical machines and transformers operated from PWM converters.      

Single-phase induction motor drive system using z-source inverter

Employing conventional three-phase inverter in variable speed single-phase drive suffers from limited maximum output voltage applied to motor or voltage utility factor (VUF). In this study, a z-source inverter (ZSI) has been used to drive a single-phase induction motor (SPIM). By the proposed topology, VUF and consequently torque speed characteristic of the single-phase motor is improved. The equations for employing ZSI in SPIM drive and modulation method are described. Results of two simulations using conventional inverter and ZSI are presented. The results show that using ZSI leads to an increase in motor electromagnetic torque compared to conventional three-phase inverter due to improved VUF. The experimental results confirm the theory and simulation.     

Analytical evaluation of DC capacitor RMS current and voltage ripple in neutral-point clamped inverters

The sizing of the DC-link capacitor in a three-level inverter is based on the RMS current flowing through it. This paper analyses the DC-link capacitor RMS current in a neutral-point clamped (NPC) inverter and expresses the same as a function of modulation index, line-side current amplitude and power factor. Analytical closed-form expressions are derived for the capacitor RMS current for single-phase half-bridge, single-phase full-bridge and three-phase three-leg topologies of a three-level inverter. The worst-case capacitor current stress is determined for each topology based on the analytical expressions. Further, analytical expressions are derived for the RMS values of low-frequency and high-frequency capacitor currents. These expressions are then used to estimate voltage ripple across the DC capacitor for sinusoidally modulated three-phase NPC inverter. The analytical expressions for the RMS current and voltage ripple are validated experimentally over a wide range of operating points.     

Eighteen-sided polygonal voltage space-vector-based PWM control for an induction motor drive

An inverter scheme with 18-sided polygonal voltage space-vector structure is proposed for induction motor drive applications. An open-end winding configuration is used for the drive scheme. The motor is fed from one end with a conventional two-level inverter and from the other end with a three-level inverter, realised by cascading two conventional two-level inverters. The inverters are fed with asymmetrical DC-link voltages. A simple linear PWM control scheme up to 18-step mode is proposed, based only on the motor reference phase amplitudes. The proposed scheme gives an increased modulation range with the elimination of the 5th, 7th, 11th and 13th-order harmonics, for the entire modulation range, when compared with any conventional schemes. The absence of low-order harmonics gives nearly sinusoidal currents throughout the modulation range, and makes PWM control of voltage very simple, with low inverter switching frequencies, especially in the extreme modulation range.     

一种线性保护输入的恒压LED驱动电源设计

采用对母线电压进行反馈调节的恒压控制方式,设计研究了一种新型高压(260AC)线性保护输入LED驱动电路.利用LD7591GS芯片控制的脉冲宽度调制(PWM)电路和外围光耦电压反馈电路以及LNK564芯片控制的线性隔离变换电路,通过对驱动电路拓扑结构进行研究设计,并对变压器参数进行优化,实现了电压反馈的线性保护输入LED驱动电源设计.实验结果表明,采用外围电压反馈方式电路和线性隔离保护电路调整的LED驱动电源电路具有较好的安全稳定特性和低纹波PWM输出波形,并具有高转化效率,良好的抗电磁干扰性能和稳定的恒压功能.     

Zero-voltage-switching DC/AC inverter

A novel zero-voltage-switching (ZVS) DC/AC inverter is proposed. The proposed inverter can not only provide output voltage that is higher or lower than DC input voltage but can also use the pulse-width modulation (PWM) control technique. Furthermore, in the proposed inverter, besides operating at constant frequency, all semiconductor devices operate at soft-switching without additional voltage stress and current stress. A design example of 1000 W ZVS-PWM buck-boost inverter is examined to assess the inverter performance     

低调制度下二极管箝位型多电平 逆变器新型PWM控制方法

二极管箝位型多电平逆变器作为一种应用于高压大功率变换场合的变换器,其PWM控制技术是研究的核心内容之一。本文针对已有载波PWM方法中低调制度下电平退化的问题,提出了一种新颖的载波PWM方法,既便是在低调制度下,所有的电平都能够得到应用。仿真结果表明,这种方法可以提高二极管箝位型逆变器在低调制度下的器件利用率,使得逆变器在低调制度下工作于较高频率。     

Multi-criteria-based design approach of multi-phase permanent magnet low-speed synchronous machines

A design methodology dedicated to multi-phase permanent magnet synchronous machines (PMSMs) supplied by pulse width modulation voltage source inverters (PWM VSIs) is presented. First, opportunities for increasing torque density using the harmonics are considered. The specific constraints caused by the PWM supply of multi-phase machines are also taken into account during the design phase. All the defined constraints are expressed in a simple manner by using a multi-machine modelling of the multi-phase machines. This multi-machine design is then applied to meet the specifications of a marine propeller: verifying simultaneously four design constraints, an initial 60-pole three-phase machine is converted into a 58-pole five-phase machine without changing the geometry and the active volume (iron, copper and magnet). First, a specific fractional-slot winding, which yields to good characteristics for PWM supply and winding factors, is chosen. Then, using this winding, the magnet layer is designed to improve the flux focussing. According to analytical and numerical calculations, the five-phase machine provides a higher torque (about 15%) and less pulsating torque (71% lower) than the initial three-phase machine with the same copper losses.     

Recurrent wavelet neural network controller with improved particle swarm optimisation for induction generator system

A recurrent wavelet neural network (RWNN) controller with improved particle swarm optimisation (IPSO) is proposed to control a three-phase induction generator (IG) system for stand-alone power application. First, the indirect field-oriented mechanism is implemented for the control of the IG. Then, an AC/DC power converter and a DC/AC power inverter are developed to convert the electric power generated by a three-phase IG from variable frequency and variable voltage to constant frequency and constant voltage. Moreover, two online trained RWNNs using backpropagation learning algorithm are introduced as the regulating controllers for both the DC-link voltage of the AC/DC power converter and the AC line voltage of the DC/AC power inverter. Furthermore, an IPSO is adopted to adjust the learning rates to further improve the online learning capability of the RWNN. Finally, some experimental results are provided to demonstrate the effectiveness of the proposed IG system.     

Feedforward simple control technique for on-chip all-digital three-phase AC/DC power-MOSFET converter with least components

A novel simple control technique for on-chip all-digital three-phase alternating current to direct current (AC/DC) power-metal oxide semiconductor field-effect transistors (MOSFET) converter with least components, which is employed to obtain small current and DC output voltage ripples as well as excellent performance, and using a feedforward simple control method for DC output voltage regulation is proposed. The proposed all-digital feedforward controller has the features of low cost, simple control, fast response, independence of load parameters and the switching frequency, it has no need for compensation, and high stability characteristics; moreover, the proposed controller consists of three operation amplifiers and few digital logic gates that are directly applied to the three-phase converter. The power-MOSFETs are also known as power switches, whose control signals are derived from the proposed all-digital feedforward controller. Instead of thyristors or diodes, the application of power-MOSFETs can reduce the loss of AC/DC converter that is proper to the power supply system. The input stage of an AC/DC converter functions as a rectifier and the output stage is a low pass inductor capacitor (LC) filter. The input AC sources may originate from miniature three-phase AC generator or low-power three-phase DC/AC inverter. The maximum output loading current is 0.8 A and the maximum DC output ripple is less than 200 mV. The prototype of the proposed AC/DC converter has been fabricated with Taiwan Semiconductor Manufacturing Company (TSMC) 0.35 mum 2P4M complementary MOS (CMOS) processes. The total chip area is 2.333 1.960 mm². The proposed AC/DC converter is suitable for the following three power systems with the low power, DC/DC converter, low-dropout linear regulator and switch capacitor. Finally, the theoretical analysis is verified to be correct by simulations and experiments.     

敏感用户高品质交-直流级联供电方案研究

工业过程中大量使用的变频器(variable frequency drive,VFD)在采用传统交流供电时易受到电压暂降影响,传统治理方式存在检测延时、控制复杂等问题。为此,该文从敏感负荷变频器在电网扰动工况下的供电需求量化出发,围绕供电拓扑设计、DC/DC变换器的控制策略及储能单元容量配置等方面,构建一种实用化工业用交-直流级联供电方案。该文利用电压暂降过程中直流供电回路与敏感负荷间的压差自感应控制,实现交-直流供电回路无扰动切换,提高电压暂降治理响应的快速性;采用两相交错并联DC/DC变换器接入集中式储能,减少储能系统纹波系数,并给出两相均流控制方法。最后,通过Matlab/Simulink中的建模仿真与样机的实验测试,验证所提方案能够在交流系统发生不同严重程度电压暂降过程中为各类敏感负荷提供稳定的连续供电,为解决工业敏感用户高品质供电问题提供可实用的新思路。     

压电式提花经编机自升压节能控制电路设计

针对提花经编机压电贾卡针（piezo jacquard needle,PJN）的驱动电路存在功耗高、需要额外的高压电源等问题,设计了一种将自升压电路和工作电路集成为具有能量回收功能的新型PJN驱动电路。基于压电陶瓷晶片的压电方程和PJN结构,介绍了PJN的工作原理,详细分析了所提出的PJN驱动电路的工作模态,给出了电路模态转换的脉冲宽度调制（pulse width modulation,PWM）控制策略。新型PJN驱动电路采用储能电感器代替传统驱动电路的限流电阻器,不仅能够限制PJN的正向充电电流,减少能量损耗,而且可以利用从低压电源吸收的能量将PJN的低压供电电源自适应升压至工作状态所需的高压。为了验证电路的自升压过程,进行了仿真分析。仿真结果表明,该新型PJN驱动电路具有自升压功能,无须外接高压工作电源,仅需低压供电电源即可以高压驱动PJN,能有效降低功耗,实现节能环保,具有广阔的工程应用前景。     

Multiple-load series resonant inverter for induction cooking application with pulse density modulation

Multiple-load induction cooking applications are suitable used when multi-output inverters or multi-inverters are needed for multiple-load operation. Some common approaches and modifications are needed in inverter configuration for multiple-load application. This paper presents an inverter configuration with two loads by using pulse density modulation control technique. It allows the output power control of each load independently with constant switching frequency and constant duty ratio. The pulse density modulation control technique is obtained using phase on–off control between two legs of the inverter to reduce acoustic noise. The two-load three-leg inverter configuration provides reduction of the component count for extension of multiple loads. The control technique provides a wide range of output power control. In addition, it can achieve efficient and stable zero voltage switching operation in the whole load range. The proposed control scheme is simulated and experimentally verified with two-load inverter configuration.     

Minimization and identification of conducted emission bearing current in variable speed induction motor drives using PWM inverter

The recent increase in the use of speed control of ac induction motor for variable speed drive using pulse width modulation (PWM) inverter is due to the advent of modern power electronic devices and introduction of microprocessors. There are many advantages of using ac induction motor for speed control applications in process and aerospace industries, but due to fast switching of the modern power electronic devices, the parasitic coupling produces undesirable effects. The undesirable effects include radiated and conducted electromagnetic interference (EMI) which adversely affect nearby computers, electronic/electrical instruments and give rise to the flow of bearing current in the induction motor. Due to the flow of bearing current in the induction motor, electrical discharge machining takes place in the inner race of the bearing which reduces the life of the bearing. In high power converters and inverters, the conducted and radiated emissions become a major concern. In this paper, identification of bearing current due to conducted emission, the measurement of bearing current in a modified induction motor and to minimize the bearing current are discussed. The standard current probe, the standard line impedance stabilization network (LISN)), the electronics interface circuits are used to measure high frequency common mode current, bearing current and to minimize the conducted noise from the system. The LISN will prevent the EMI noise entering the system from the supply source by conductive methods, at the same time prevents the EMI generated if any due to PWM, fast switching in the system, will not be allowed to enter the supply line. For comparing the results with Federal Communications Commission (FCC) and Special Committee on Radio Interference (CISPR) standards, the graphs are plotted with frequency Vs, line voltage in dBμ V, common mode voltage in dBμ V and the bearing current in dBμ A with out and with minimizing circuits.     

Advanced control for PWM converter and variable-speed induction generator

The paper describes a simple control structure for a vector-controlled stand-alone induction generator (IG) used to operate under variable speeds. Deadbeat current control is developed for a voltage source PWM converter and the three-phase variable speed squirrel-cage IG to regulate DC-link and generator voltages with newly designed phase-locked-loop circuit. The required reactive power for the variable-speed IG is supplied by means of the PWM converter and a capacitor bank to build up the voltage of the IG without the need for a battery and to reduce the rating of the PWM converter with the need for only three sensors. This proposed scheme can be used efficiently for variable speed wind or hydro energy conversion systems. The measurements of the IG system at various speeds and loads are given and show that this proposed system is capable of good AC and DC voltages regulation     

Control of a converter system for an asymmetrical parameter type two-phase induction motor drive operating in motoring and generating modes

The control of a converter system is presented and discussed for an asymmetrical parameter type two-phase induction machine drive that is operating in motoring and generating modes. The proposed system consists of back-to-back voltage source converters. For a machine side, a three-leg voltage source converter provides both unbalanced and balanced two-phase output voltages with a scalar V/F control based on a carrier space vector pulse width modulation (SVPWM) technique. For a front end, a single-phase AC/DC doubled voltage converter with hysteresis current control is used to keep DC-link voltage constant, thus resulting in a bi-directional power flow operation for the motoring and generating modes. A closed-loop design for the DC-link voltage is fully given and also included is a review of carrier-based SVPWM for two-phase three-leg VSI. The proposed drive system was both simulated using MATLAB/SIMULINK and implemented on digital microcontrollers. The comparative performance evaluation of the whole system between balanced and unbalanced two-phase voltages for the machine is given. The simulation and experimental results show that the unbalanced phase voltage offers better performance for the whole system.     

Modelling and analysis of an open-loop induction motor drive incorporating the effect of inverter dead-time

The objective of this paper is to study the influence of inverter dead-time on steady as well as dynamic operation of an open-loop induction motor drive fed from a voltage source inverter (VSI). Towards this goal, this paper presents a systematic derivation of a dynamic model for an inverter-fed induction motor, incorporating the effect of inverter dead-time, in the synchronously revolving dq reference frame. Simulation results based on this dynamic model bring out the impact of inverter dead-time on both the transient response and steady-state operation of the motor drive. For the purpose of steady-state analysis, the dynamic model of the motor drive is used to derive a steady-state model, which is found to be non-linear. The steady-state model shows that the impact of dead-time can be seen as an additional resistance in the stator circuit, whose value depends on the stator current. Towards precise evaluation of this dead-time equivalent resistance, an analytical expression is proposed for the same in terms of inverter dead-time, switching frequency, modulation index and load impedance. The notion of dead-time equivalent resistance is shown to simplify the solution of the non-linear steady-state model. The analytically evaluated steady-state solutions are validated through numerical simulations and experiments.