PWM Method Research Articles

A Tactical Chaos based PWM Technique for Distortion Restraint and Power Spectrum Shaping in Induction Motor Drives

The pulse width modulated voltage source inverters (PWM-VSI) dominate in the modern industrial environment. The conventional PWM methods are designed to have higher fundamental voltage, easy filtering and reduced total harmonic distortion (THD). There are number of clustered harmonics around the multiples of switching frequency in the output of conventional sinusoidal pulse width modulation (SPWM) and space vector pulse width modulation (SVPWM) inverters. This is due to their fixed switching frequency while the variable switching frequency makes the filtering very complex. Random carrier PWM (RCPWM) methods are the host of PWM methods, which use randomized carrier frequency and result in a harmonic profile with well distributed harmonic power (no harmonic possesses significant magnitude and hence no filtering is required). This paper proposes a chaos-based PWM (CPWM) strategy, which utilizes a chaotically changing switching frequency to spread the harmonics continuously to a wideband and to reduce the peak harmonics to a great extent. This can be an effective way to suppress the current harmonics and torque ripple in induction motor drives. The proposed CPWM scheme is simulated using MATLAB / SIMULINK software and implemented in three phase voltage source inverter (VSI) using field programmable gate array (FPGA).

PWM方式を用いたスイッチトリラクタンスモータの制御電圧源ベクトル制御

PWM方式を用いたスイッチトリラクタンスモータの制御電圧源ベクトル制御

Performance Comparison of Three-Step and Six-Step PWM in Average-Current-Controlled Three-Phase Six-Switch Boost PFC Rectifier

In this paper, a three-step PWM method for the average-current-controlled three-phase six-switch boost PFC rectifier is proposed. It is shown that the three-step PWM compared to the conventional six-step PWM exhibits a lower total harmonic distortion of the input currents and higher power factor. However, the three-step PWM, unlike the six-step PWM, is adversely affected by the duty-cycle limitations and has unbalanced conduction losses of the upper and lower switches of the three-phase rectifier bridge. The average-current control of the three-step and six-step PWM is illustrated with MATLAB/Simulink simulation waveforms and experimentally verified on a 3 kW prototype.

一种消除LED显示屏动态假轮廓的脉宽调制法

Aimed at the problem of dynamic false contour in LED display when playing the motion images,a novel of PWM method named concentrated gated pulse width modulation was proposed.Based on the GPWM,the approach fixes the decimal subfields on the center of one PWM period,and then figures out the number of subfields corresponding to the integer weight bits,and locate them near the decimal subfields.Theoretical analysis and experiments show that CGPWM has the similar lighting function with linear PWM,and consequently reduces the average DFC values between any two gray levels from 0.6under the control of GPWM to 0.2.CGPWM can eliminate DFC effectively while maintaining high refresh frequency and rich gray levels,and thus improve the image quality greatly.Furthermore,the processing to implement CGPWM is simple without extra hardware.

A Phase-Shifted-PWM D-STATCOM Using a Modular Multilevel Cascade Converter (SSBC)—Part I: Modeling, Analysis, and Design of Current Control

This paper presents and discusses a phase-shifted-PWM distribution static synchronous compensator (D-STATCOM) using the modular multilevel cascade converter based on single-star bridge cells (MMCC-SSBC). A three-phase 140-V 10-kVA SSBC-based STATCOM with a cascade count $N=6$ is designed, constructed, and tested for verifying the performance and functionality of the medium-voltage D-STATCOM in both steady and transient states. The 13-level line-to-neutral (25-level line-to-line) voltage at the ac side yields an almost sinusoidal line current with a total harmonic distortion value of 1.7%. An analytical model for the phase-shifted PWM is proposed to design the current control gains. Two phase-shifted PWM methods, which are named as one-cell and all-cells update methods, are theoretically and experimentally compared. The all-cells update method can reduce the inherent time delay, thus resulting in a faster and more stable system response than the one-cell update method.

English

A major advancement in the research area of space vector pulse width modulation (SVPWM) in recent years is the introduction of the nearest three vector algorithm computational intensity is still a drawback of SVPWM methods in real time applications, especially in the case of multilevel inverter operation. To solve the problem of computational complexity in multilevel inverters due to the large number of space vectors and redundant switching states, a simple space vector PWM method is proposed. Based on this method, the location of the reference voltage vector can be easily determined and the calculation of dwell times becomes very simple. More importantly, the proposed method is general and can be directly applied to the cascaded H-bridge inverter of any voltage levels. This proposed method is tested for seven level and nine level cascaded H-Bridge inverter drive system and the simulated results were presented.

Sliding Mode Control of H Bridge Inverter Based DSTATCOM for Reactive Power Compensation

Reactive power compensation plays a key role in reducing distribution losses by improving power factor. A three phase three wire DSTATCOM consisting of a five level H-bridge Voltage Source Converter (VSC) is proposed for improving power factor in the distribution system at the Point of Common Coupling (PCC) when the load is continuously changing. The sliding mode control algorithm is used for reactive power compensation and achieve unity power factor. To accomplish this DSTATCOM is controlled to supply or absorb reactive power at PCC. Sinusoidal PWM method is used for obtaining the switching pulses for the cascaded H-bridge converter. The performance of the DSTATCOM controlled distribution system is validated by simulations using MATLAB/Simulink software and Power System block set toolboxes.

Theoretical Considerations for Single-Phase Interleaved Converters Operated With SHE-PWM

This letter defines selective harmonic elimination pulse width modulation (SHE-PWM) formulations for single-phase, interleaved converters. Through precalculated solutions, interleaved converters work at the same operating point while eliminating multiple low-order harmonics. It is shown that multiple continuous solutions can be acquired for three-level interleaved waveforms. Extending the method to multiple levels further complicates the problem and reduces both the number and continuity of the solutions. Searching for solutions when the maximum possible number of harmonics, that can be minimized using this PWM method, is reduced confirms that such compromise can provide additional solutions with a minimal effect on the waveform's harmonic distortion. The SHE-PWM considerations are verified with simulations and experimental results.

The Research of a Piezoelectric Valve Positioner Control Algorithm

The dynamic characteristic of smart valve positioner is nonlinear in its operational range, while the traditional five-step method or a single switch PID control algorithm could not meet a nonlinear model uncertain control system for high-speed, high-precision control. This paper presents a new control algorithm which five-step switching method with backward PWM and PID control method combines, it realize that the opening degree of the valve is fast and accurate positioning under conditions in nonlinear. The experimental result show that the control algorithm is better than the five-step control method and PID control algorithm, and the algorithm is simple, high reliability, speed control, and have certain adaptive and robustness, valve positioning accuracy to meet the control requirerments.

A Simple and Direct Dead-Time Effect Compensation Scheme in PWM-VSI

This paper presents the direct compensation of the switching interval error of the effective voltage vectors by the dead time of a pulsewidth modulation voltage source inverter (PWM-VSI). The output voltages of a three-phase PWM-VSI are distorted and have voltage errors from the dead time to avoid the shoot-through of inverter arms and the time delay of the gate drive. Voltage distortion increases the harmonics of the output voltages and decreases control performance. This paper presents a simple and direct compensation technique to solve this problem in a three-phase VSI. The practical switching output voltages are determined by the dc-link voltage, the switching signals of each phase, the dead time, the time delay, and the current polarities of each phase. For these reasons, output voltage errors are not constant. In order to analyze the dead-time effect in the actual switching voltages of each phase, the practical switching voltages in a sampling period of a space vector PWM (SVPWM) method are calculated according to the current polarity. In the calculation, the dead time, the time delay of devices, and the voltage drops on power devices are included to consider nonlinear voltage distortion. From these practical switching voltages during the switching intervals in a sampling period, the average output voltages of each phase can be derived, and the output voltage errors between the voltage commands and the average output voltages of each phase are obtained. The SVPWM switching intervals of each phase can be derived by the average output voltages that are calculated according to the current polarity and nonlinear voltage distortion to compensate for the output voltage errors. With the simple detection of the current polarity, the practical errors of the switching intervals of each phase can be compensated by the addition of the compensated switching time. Simulation and experimental results validating the proposed compensation method are presented in this paper.

English

This project presents a design of a PID algorithm for driving agricultural robot motors. This approach has been proved with MATLAB simulation results. This kind of position control can be improved using adaptive algorithm. This project also described implementation of PID using PWM method. The robot prototype can move rapidly with the controller. Based on the study, the accuracy of the moving velocity of the robot can be further improved, such as the use of artificial neural networks and genetic algorithms for precise speed control. The results obtained from the PID simulation in MATLAB-Simulink shows that PID algorithm gives considerable

Analysis of T-Source Inverter with PWM Technique for High Voltage Gain Application

This paper deals with Analysis of T-Source inverter with PWM Technique for high voltage gain application. The T-source impedance network is newly introduced to overcome the problems of Z-source inverter. This T-source inverter is similar to Z-source inverter except the use of high frequency low leakage inductance transformer. It has low reactive components in compare with conventional ZSI. This T-source inverter has an ability to perform dc to ac power conversion and it provides buck -boost operation in a single stage. The traditional inverters cannot provide such feature. Operating principle of T-source inverter is almost same as that of ZSI. All traditional PWM methods can be used to control T-source inverter. The utilization of shoot-through switching state is enhanced in T-source inverter which helps in the unique usage of buck-boost feature to the inverter. It is recommended that to maintain the constant voltage in the input side to get the appropriate output voltage.

Novel Three-Phase PWM Voltage-Fed Rectifier with an Auxiliary Resonant Commutated Pole Link

A novel auxiliary resonant commutated pole (ARCP) link for three-phase PWM voltage-fed converter is presented. The ARCP link consists of two auxiliary switches, one resonant inductance, and six diodes, which is simpler than the conventional ARCP designs. Based on the phase and amplitude control, the proposed converter can take a minimum switching times PWM method, which results in reduced losses and a simplified control. In addition, the zero-voltage resonance modes are analyzed. Finally, simulation and experimental results show that the system can realize zero-voltage switching with a unity power factor.

Voltage Balancing Scheme in MMC – A New Approach

Abstract This article proposes an online voltage balancing scheme using a new comparative reference wave modulation technique applied to modified modular multilevel converter (MMMC). Recent applications of modular multilevel converter (MMC) in high-voltage DC systems experience many problems with unbalancing of upper and lower arms, due to which circulating currents are rotating in the legs of MMC. These circulating currents pass through the arm inductors and create power loss across the inductor which consequently affects the efficiency of system. In order to overcome the unbalancing and to reduce the power losses, it proposes a new topology for existing MMC called as MMMC. Its main idea is to the balance the system voltage according to the difference between upper and lower arm currents. The upper and lower arm capacitors voltages can be well balanced by proposed technique. Compared to conventional PWM methods, this method can be realized easily. Particularly, this method has not used any kind of sorting technique, which makes it suitable for MMC with a large number of sub-modules. With experiments, the proposed method has been verified successfully.

Research on the SVPWM Technology Used in PMSM Speed Regulation System

Principle of space vector PWM was established, modulation function of load phase voltages were computed, correlation between space vector PWM and sinusoidal PWM methods was reexamined in this paper. Theory and simulation results shows SVPWM has an advantage of higher utilization of DC voltage, lower torque ripple and so on in PMSM speed regulation system.

New space vector PWM method based on virtual flux vector for T-NPC Inverter

This paper proposes a new SVPWM algorithm for operating the three-level TNPC topology. The idea of this algorithm is approximating as close as possible the locus of actual virtual flux vector and ideal one and minimizing the numbers of switching in one switching interval to improve the efficiency of the whole system. The virtual flux vector is monitored to determine the sector and the proper non-zero voltage vectors. The performance of the converter and the comparison of different modulation methods are analyzed. Simulation and experimental results show that the proposed method provides high efficiency.

1인승 전기차량의 임베디드 전동제어장치 설계

본 논문은 1인승 전기차량의 임베디드 전동 제어장치 설계를 제안하였다. 제안된 임베디드 장치는 PIC18F8720 프로세서, 16Mb flash ROM, 32Mb SDRAM과 신호처리회로로 설계되었다. 제안된 1인승 전기차량은 4KW 인휠 BLDCM, <TEX>$180^{\circ}$</TEX> 도통 공간 벡터제어 3상 전압형 인버터, PID 속도제어기와 전동제어 장치와 임베디드 제어장치로 구성된다. 이 1인승 전기차량은 역 3륜 형태의 기계적인 구조를 가지고 있으며, 인휠 BLDCM과 틸팅 기능을 가지는 조향 메카니즘이 적용되었다. 또한 제안된 임베디드 전동제어장치의 성능은 PEV에 대한 Lab 실험과 도로 주행시험을 통하여 검증하였다. This paper presents the design of embedded electrical power control unit for Personal Electrical Vehicle(PEV). The embedded unit is designed using PIC18F8720 processor, 16Mb flash ROM, 32Mb SDRAM and signal condition circuits. The proposed PEV consists of 4KW in-wheel Brushless DC Motor(BLDCM), 3 phase voltage source inverter with the <TEX>$180^{\circ}$</TEX> conduction space vector PWM method, PID speed controller and the embedded control unit. The PEV has mechanical manufacture of inverse 3 wheel system, which is applied by the in-wheel BLDCM and steering mechanism with tilting function. Also, the performances of the proposed embedded electrical power control unit are verified through the lab experiment and road driving test of PEV.

Intelligent Controller for Shunt Active Power Filter to Improve Power Quality

This paper presents a comparative study on performance of conventional PI controller and fuzzy controller on three phase, three wire voltage source inverter based shunt active filter that is used to compensate the harmonics currents drawn by non-linear loads in distribution systems. Hysteresis PWM method is used to generate the pulses to the switches used in active filter. The compensation is based on PLL method of fundamental current extraction. The nonlinear load taken into account is a three phase diode bridge rectifier.

A NOVEL SINGLE-PHASE CASCADED H-BRIDGE INVERTER WITH NEW CELL CONFIGURATION AND REDUCED POWER ELECTRONICS COMPONENTS WITH LOW THD

This project presents Single-phase Cascaded H-Bridge Inverter with minimum number of power electronics devices. The proposed Inverter consists of 4 unidirectional switches and single bidirectional switch in each cell. Single carrier and Multicarrier PWM method is used to generate the multilevel output. The proposed multilevel Inverter is compared with conventional symmetrical CHB, Asymmetrical CHB with binary and trinary configurations. The comparison will be made on the basis of number of components, number of DC sources, number of Balancing capacitors, Switching and conduction losses. The proposed Cascaded H-Bridge Inverter will be simulated using MATLAB/SIMULINK and will be implemented in hardware also using SPARTAN3A DSP.

Bi-Directional Multi-Level Converter for an Energy Storage System

This paper proposes a 3 kW single-phase bi-directional multi-level converter for energy storage applications. The proposed topology is based on the H-bridge structure with four switches connected to the DC-link. A simple phase opposition disposition PWM method that requires only one carrier signal is also suggested. The switching sequence to balance the capacitor voltage is considered. The topology can be extended to a nine-level converter or a three-phase system. The operating principle of the proposed converter is verified through a simulation and an experiment.