Pulse Width Modulation Switching Research Articles

Prediction of 2-level PWM inverter efficiency using MATLAB/Simulink

This article proposes a direct approach for the prediction of inverter efficiency using MATLAB/Simulink, instead of an indirect loss calculation approach based on analytical models. In analytical approach, efficiency is obtained by calculating individual losses separately, such as switching losses, conduction losses and harmonic losses using analytical models. However, this approach requires accurate analytical models and complicated calculations, due to the variation in the switching frequency, switching transient and modulation techniques. In the proposed approach, the actual waveform of the inverter system is directly generated using MATLAB/Simulink. The instantaneous voltage and current waveform including switching transients are generated. Thus, the proposed approach is very simple and convenient for efficiency prediction. The proposed approach also works for any system parameters or control methods, such as various pulse-width modulation (PWM) techniques, different switching frequencies, switching devices and load types. The proposed approach can be adopted for the efficiency prediction of any switching strategies and any types of inverters such as neutral-point-clamped (NPC) inverters, H bridge inverters and H5 topology, since the topologies are modelled as circuits in the MATLAB/Simulink program and no analytical model is required for the proposed approach. Furthermore, the proposed approach can provide operation techniques and conditions such as PWM techniques and switching frequency that offer high efficiency. In this article, inverter performance is evaluated for various PWM techniques and switching frequencies. The PWM technique and switching frequency that offer high efficiency is obtained. Finally, the proposed approach is verified by experimental results.

3레벨 4레그 PWM 컨버터의 커먼 모드 전압 저감

This paper presents a carrier-based pulse-width modulation(PWM) method for reducing the common-mode voltage of a three-level four-leg converter. The idea of the proposed PWM method is intuitive and easy to be implemented in digital signal processor-based converter control systems. On the basis of the analysis of space-vector PWM(SVPWM) and sinusoidal PWM(SPWM) switching patterns, the fourth leg pole voltage of the three-phase converter called "f leg pole voltage" is manipulated to reduce the common-mode voltage. To synthesize f leg pole voltage for the suppression of the common-mode voltage, positive and negative pole voltage references of f leg are calculated. An offset voltage is also deduced to prevent the distortion of a, b, and c phase voltages. The feasibility of the proposed PWM method is verified by simulation and experimental results. The common-mode voltage of the proposed PWM method in peak-to-peak value is 33% in comparison with that of the conventional SVPWM method. The transition number of the common-mode voltage is also reduced to 25%.

SRF based current controller using PI and HC regulators for DSTATCOM with SPWM switching

This paper presents Distribution Static Compensator (DSTATCOM) for compensation of unbalanced nonlinear load with dq0 current controller (using proportional integrator and harmonic compensation regulators) and Sinusoidal Pulse Width Modulation (SPWM) switching. The dq0 current controller is implemented in Synchronous Reference Frame (SRF) rotating at fundamental frequency and consists of Harmonic Compensation (HC) regulator (realized by sum of Sinusoidal Signal Integrators (SSI)) in parallel to Proportional Integrator (PI) regulator. The SSI provides high gain to specified tuned harmonic frequency and helps in improving filter current tracking performance for harmonic load current compensation. Each SSI in fundamental rotating dq0 reference frame can simultaneously compensate for two load current harmonics and thereby reducing the computational effort compared to SSI in stationary reference frame. Neutral current compensation, which is required for compensating unbalance in load, is carried out through 0-axis controller. SPWM switching strategy results in switching of inverter switches at constant frequency. This will simplify the design of inverter output filter (L/LC), reduces stress on switches and switching noise. Simulation studies of DSTATCOM load compensation using dq0 current controller with interface L and LC filters is carried out in Matlab/Simulink and the corresponding results are presented. Experimental studies are carried out on three phase DSTATCOM prototype using dSPACE 1104 with Matlab Real Time Interface (RTI).

Design of high voltage power converter for traveling wave tube amplifier

Traveling Wave Tubes (TWTs) are widely used in the radar and communications system as RF power amplifiers. A highly sophisticated power supply is required by TWT. In order to meet the severe requirements of Traveling Wave Tube Amplifier (TWTA), a novel two-stage topology high voltage converter for TWTA is proposed. The converter is based on Zero-Voltage Switching and Zero-Current Switching (ZVS/ZCS) resonant techniques. The high voltage converter operation principles are investigated and major features of the converter are discussed. The power switching mode of ZVS/ZCS is obtained. The experimental results show that the converter has good soft switching characteristics. Compared to the conventional hard switched Pulse Width Modulation (PWM) techniques, the high efficiency and low ripple of the converter for TWTA are realized. The efficiency of High Voltage Electronic Power Conditioners (HV-EPC) over 93.5% under the condition of 38∼46 V input voltage and 260∼300 W input power. The switching frequency of first-stage (preregulator) of HV-EPC is 89 kHz and the switching frequency of second-stage (postregulator) is 44.5 kHz. The highest output voltage of the HV-EPC is helix voltage which is about −6.8 kV. It is especially suitable for TWTA utilized in space satellite applications due to its high switching frequency and high power density.

Improved Load Compensation using Harmonic Compensator in dq0 Current Controller for DSTATCOM

Abstract This paper presents distribution static compensator (DSTATCOM) with dq0 current controller and sine pulse width modulation (SPWM) switching for compensation of unbalanced nonlinear load in distribution system. DSTATCOM, connected in parallel to load at the point of common coupling (PCC), is used for supplying reactive and harmonic components of load current demand. This dq0 current controller is implemented in synchronous reference frame (SRF) rotating at fundamental frequency and consists of harmonic compensation (HC) regulator along with proportional integrator (PI) regulator. HC regulator is realized by number of sinusoidal signal integrators (SSIs) in parallel. The SSI provides high gain for tuned harmonic frequency and helps in minimizing filter current tracking error while compensating for load harmonic currents. Zero-axis controller, which compensates load neutral current and helps in obtaining balanced utility currents, is provided along with d, q controllers. SPWM switching generates inverter gating pulses at constant frequency, which reduces stress levels on VSI switches and simplifies the design of interface filter. Simulation studies of DSTATCOM load compensation with dq0 current controller are carried out in Matlab/Simulink and experimental verification is done using dSpace 1104 with Matlab real-time interface (RTI).

DSP-Based Modified SPWM Switching Technique with Two-Degrees-of-Freedom Voltage Control for Three-Phase AC–DC Buck Converter

This paper presents a modified sinusoidal pulse-width modulation (SPWM) switching technique in three-phase ac–dc buck converter with new modulation strategy. The modulation strategy used two reference signals (0°–60° and 120°–180° sine wave) and one type of carrier signal, instead of two types of carrier signal to generate pulse-width modulation signals. A conventional 6-switch three-phase ac–dc buck converter is extended by comprising four diodes in each switch to achieve bidirectional power flow capability. A digital feedback voltage control using two-degrees-of-freedom-control approach is implemented to achieve the output voltage to equal the reference voltage with high dynamic performance and to obtain sinusoidal ac current with unity power factor. The modified SPWM switching strategy of ac–dc power flow and vice versa is discussed and verified via mathematical model. The validity of the proposed three-phase ac-dc buck converter with bidirectional capability its PWM and the feedback control strategy is verified through simulation and is implemented in a prototype using TMS320F28335 Digital Signal Processor.

Short-Circuit Fault Diagnosis for Three-Phase Inverters Based on Voltage-Space Patterns

This paper introduces a fault detection and isolation (FDI) method for faulty metal-oxide-semiconductor field-effect transistors in a three-phase pulsewidth-modulated (PWM) voltage source inverter. Short-circuit switch faults are the leading cause of failure in power converters. It is extremely vital to detect them in the early stages to prevent unwanted shutdown and catastrophic failures in motor drives and power generation systems. Against the common FDI methods for power electronic inverters that use phase currents and PWM gate control signals, the proposed method only uses the inverter output voltages. This method analyzes the PWM switching signals in a time-free domain that is called the voltage space. For a healthy inverter, the projection of the state transitions in the voltage space results in a cubic pattern. Each short-circuit switch fault uniquely changes the voltage-space pattern that allows isolating the faulty switch. The fault detection time is only within one PWM carrier period, which is significantly faster than current-based conventional methods. The FDI result does not depend on the load, the PWM switching frequency, and the feedback loop. This method can address the reliability problem of multilevel inverters in renewable electrical generation systems and can dramatically reduce the number of required sensors.

Improving Power Converter Reliability: Online Monitoring of High-Power IGBT Modules

The real-time junction temperature monitoring of a high-power insulated-gate bipolar transistor (IGBT) module is important to increase the overall reliability of power converters for industrial applications. This article proposes a new method to measure the on-state collector-emitter voltage of a high-power IGBT module during converter operation, which may play a vital role in improving the reliability of the power converters. The measured voltage is used to estimate the module average junction temperature of the high and low-voltage side of a half-bridge IGBT separately in every fundamental cycle of the current by calibrating them at load current. The measurement is very accurate and also measures the voltage at the middle of a pulse-width modulation (PWM) switching. A major objective is that this method is designed to be implemented in real applications. The performance of this technique is measured in a wind power converter at a low fundamental frequency. To illustrate more, the test method as well as the performance of the measurement circuit are also presented. This measurement is also useful to indicate failure mechanisms such as bond wire lift-off and solder layer degradation. The measurements of and rise in the junction temperature after five million cycles of normal operation of the converter are also presented.

A voltage balancing strategy with extended operating region for cascaded H-bridge converters

In this paper, a generalized switching technique for cascaded H -bridge (CHB) converters is proposed. To take advantage of both low- and high-frequency modulation techniques, a hybrid modulation method is utilized. The proposed technique employs the low-frequency switching for voltage balancing of the dc-link capacitors, and the high-frequency sinusoidal pulse-width modulation switching for shaping the input ac current. Using the proposed technique, the stable operating region of CHB converters is extended. The proposed technique is capable of maintaining the dc voltages balanced even under critical operating conditions in which the load of one H-bridge cell is removed. The validity and effectiveness of the proposed method is confirmed by several simulation and experimental tests on a seven-level CHB rectifier.

Design and Implementation of a Simple and Efficient Soft Switched PWM Inverter for Induction Motor Drives

The aim of study of this paper is design and implementation of a simple and efficient soft switched Pulse Width Modulation (PWM) for three-phase induction motor drives. Soft-switching techniques have gained popularity in recent times because they offer many advantages over hard-switched Pulse Width Modulated inverters such as higher efficiency, higher power density and better performances. The quasi-resonant DC-link is being designed, the simulation and experimental results prove that it achieves soft switching of all the main switches and resonant circuit switches at the same time it posses all the capabilities of conventional sinusoidal modulated PWM inverter. Finally, the efficiency of the Soft Switched Sinusoidal PWM (SSSPWM) inverter calculated from experimental results is compared with the conventional Hard Switched Sinusoidal PWM (HSSPWM) inverter, under identical load conditions. It is of great significance to improve the efficiency by reducing switching losses, high power density, high reliability and low electro management interference.

Three‐phase three‐level one‐cycle controlled bidirectional ac–dc neutral‐point‐clamped converter without having voltage sensors

A three-phase three-level bidirectional ac–dc neutral-point-clamped converter (3 L-NPC) based on one-cycle control (OCC) is proposed in this study. It ensures that the 3 L-NPC converter operates stably during inverting mode of operation. A neutral point potential regulator is also presented which adds a dc offset to the three-phase modulating signals to nullify the deviation in the neutral point potential. First, a one-cycle controlled (OCC) 3 L-NPC converter which requires the sensing of instantaneous phase voltages of the utility is presented. Subsequently, a modified version of the OCC-based 3 L-NPC converter which does not requires sensing of the instantaneous phase voltages is proposed. The modified OCC-based 3 L-NPC estimates instantaneous phase voltages of the source from the pulse width modulation (PWM) switching sequence of the converter. The viability of the schemes is confirmed through a detailed simulation and experimental studies.

Harmonics Reduction in Cascade H-Bridge Multilevel Inverters Using GA and PSO

This paper presents the mitigation of total harmonic distortions (THD) in cascade H-bridge multilevel inverter. Selective harmonic elimination pulse width modulation (SHE- PWM) switching method is used to calculate the values of switching angles from the solution of non-linear transcendental equations. These non-linear complex equations is minimized by the using of particle swarm optimization (PSO) and genetic algorithm (GA) techniques, and also have been compared the simulating and analyzing results related to harmonics.

PI CONTROLLER BASED OF MULTI-LEVEL UPQC USING DQ0 TRANSFORMATION TO IMPROVE POWER QUALITY IN DISTRBUTION SYSTEM

The aim of this paper is to improve power quality in the source side of distribution system using unified power quality conditioner (UPQC) by realization of cascaded multilevel inverter (MLI). The UPQC is an integration of series and shunt active power filters via common dc link which can mitigates various power quality issues like voltage sag, swell, harmonics, interruptions etc. The cascaded MLI offers low THD in the output waveform and flexible circuit layout. The sinusoidal pulse width modulation (SPWM) switching scheme is employed for better operation of MLI. The control mechanism of UPQC is derived from dq0 transformation which is simple in its design and gives better control characteristics. The PI controller can efficiently reduce the steady state error and this can be used in UPQC controller for better response. The regulation of source voltage in the distribution system using multilevel UPQC under nonlinear load condition is analyzed in MATLAB/SIMULINK environment.

A General Current Ripple Prediction Method for the Multiphase Voltage Source Converter

Current ripple is generated by pulse width modulation (PWM) switching in multiphase voltage source converters (VSCs). This letter introduces a general and fast current ripple prediction method for multiphase VSCs with arbitrary phase numbers. An equivalent converter-load model is derived for the n -phase converter system. By combining the common-mode voltage of both converter terminal and load, the equivalent circuit for each phase can be modeled. The voltage dropping on the ac inductor can be calculated for the 2 n + 2 zones in each switching cycle based on the equivalent circuit for each phase. Then the current ripple can be reconstructed based on the linear di/dt model in each zone. Simulation examples of five- and six-phase converters prove that the current prediction method is accurate. With this real-time prediction method, the current ripple can be controlled in application. An application example of five-phase variable switching frequency PWM is introduced to control the peak current ripple and reduce the switching losses.

An Effective Dithering Method for Electromagnetic Interference (EMI) Reduction in Single-Phase DC/AC Inverters

A comprehensive method of electromagnetic emission interference (EMI) reduction in dc/ac inverters through periodic dithering of the pulse-width modulated (PWM) switching frequency is presented in this paper. The periodic dithering is the process of changing the switching frequency of the PWM signal that drives the switches of the power electronics inverter. The effects of the various parameters involved in the PWM dithering process have been analyzed in this paper. The important parameters involved in the dithering process are the frequency range used for dithering, the periodic time of the dithering signal, and the phase of the dithering signal. The effect of each of these parameters has been studied to determine their values that minimize the EMI. Additionally, analytical expressions for theoretical prediction of the EMI levels at different frequencies have been derived for performance analysis during the design stage. The theoretical predictions for the dithering signals have been found to accurately correlate with both the simulation and experimental results.

Power Electronics and Energy Conversion Systems, Vol. 1: Fundamentals and Hard-Switching Converters [Book News

This book helps the reader master the switch-mode concept in pulse-width modulation (PWM) and resonant power supplies and then emphasizes statespace modeling in a deep way, seldom seen in power electronics literature. It explains how to obtain the converter open-loop transfer functions for dc voltage gain, ac line-to-load voltage, and duty cycle-to-output voltage, comparing two approaches: average state-space modeling and average switch modeling. Besides presenting the transfer functions for the buck, boost, buck-boost, Sepic, and Zeta converters in CCM, this book also obtains their transfer functions in DCM, showing the dissimilar dynamics regarding CCM while also presenting the transfer functions for the PWM switch, the zero-current resonant switch (ZCS), the zero-voltage resonant switch (ZVS),and the ZCS and ZVS buck, boost, andbuck-boost quasiresonant converters (QRCs), making this book truly unique.

Pulse width modulation schemes enabling single DC power source driven dual two‐level voltage source inverter with single voltage source inverter switching

Three-level voltage space phasor can be obtained using a dual two-level voltage source inverter (VSI). Two zero sequence voltage elimination pulse width modulation (PWM) switching variants are proposed in this paper for complete elimination of zero sequence voltage (ZSV) in the dual-VSI scheme. Both the PWM variants are designed in such a way that only one inverter is switched at any instant of time; to ensure that switching power losses in the dual-VSI is limited to one inverter only at any instant of time. Analytical expressions for the dwell times of the dual-VSI are developed and presented that successfully forces the ZSV in the dual-VSI to zero; at all instants of time. As a result, both the PWMs facilitate the dual-VSI to be driven from a single DC power source only. The implementation of the proposed PWM algorithms is greatly simplified and involves just the use of instantaneous magnitudes of the reference space vector. The implementation of PWMs totally avoids the time consuming task of sector identification and do not use look up tables. The PWMs proposed in this paper are first analysed, simulated using MATLAB/SIMULINK and then verified experimentally to validate the proposed PWMs.

Analysis, design and implementation of an improved two‐switch zero‐current zero‐voltage pulse‐width modulation forward converter

In this study, an improved two-switch zero-current zero-voltage switching pulse-width modulation (ZCZVS-PWM) forward converter, which employs a simple resonant lossless snubber circuit, is introduced. A simple resonant snubber circuit consists of a capacitor, an inductor and two diodes. In proposed converter, switch Q 1 operates under exactly zero-current switching at turn-on, and exactly zero-voltage switching (ZVS) at turn-off, and switch Q 2 operates under exactly ZCZVS at turn-on, and ZVS at turn-off, and the all-passive semiconductor devices operate under soft-switching at turn-on and turn-off. The proposed converter has no current and voltage spikes in the switches in comparison with the hard-switching forward converter counterpart and is suitable for high switching frequency and high-power operation. The proposed converter is analysed and various operating modes of the improved two-switch ZCZVS-PWM forward converter are discussed. Analysis and design considerations are presented and the prototype experimental results of a 160 W (32 V/5 A) proposed converter operating at 300 kHz switching frequency, confirm the validity of theoretical analysis.

Optimal Switching Pattern for PWM AC-AC Converters Using Bee Colony Optimization

This paper proposes a harmonic reduction approach for a pulse width modulation (PWM) AC-AC converters using Bee Colony Optimization (BCO). The optimal switching angles are provided by BCO to minimize harmonic distortions. The sequences of the PWM switching angles are considered as a technical constraint. In this paper, simulation results from various optimization techniques including BCO, Genetic Algorithm (GA), and Particle Swarm Optimization (PSO) are compared. The test results indicate that BCO can provide a better solution than the others in terms of power quality and power factor improvement. Lastly, experiments on a 200W AC-AC converter confirm the performance of the proposed switching pattern in reducing harmonic distortions of the output waveform.

A Soft Switching Full Bridge Converter With Reduced Parasitic Oscillation in a Wide Load Range

A phase-shift zero voltage switching (ZVS) pulse width modulation full-bridge converter with reduced parasitic oscillation across the rectifier is proposed. The introduced auxiliary transformer used as a voltage source forces the primary current commutating in advance. Parasitic voltage oscillation at secondary is well reduced and there is no duty cycle loss. ZVS of primary switches can be achieved in much wide load range with the help of an auxiliary coupled inductor, and the main transformer continuously transfers energy to load in a whole switching cycle, resulting in no circulating time, and ripple current flowing through the output filter inductor decreases significantly. In this paper, operation principle of the circuit is analyzed in detail. Besides, discussion of key characteristics and design considerations are also included. Finally, experimental results from a 480-W/48-V, 100-kHz prototype are presented to confirm the superior features of the proposed converter.