Continuous PWM Research Articles

SVPWM‐Based Algorithm for Reduced THD and Switching Losses Under Varying Fundamental Frequency and Load in a VSI

ABSTRACTThe present study explores the influence exerted by various pulse width modulation (PWM) techniques upon harmonic distortion and switching losses of a voltage source inverter. In the context of this inquiry, a generalized algorithm for variable frequency operations, inspired by continuous and discontinuous PWM is outlined in this article. The algorithm is explicitly formulated as a function of fundamental frequency and the load power factor angle with the objective of minimizing total harmonic distortion (THD) and switching losses within a specified frequency range. The algorithm is segmented into various regions of frequency, guided by the theory that each region corresponds to a distinct PWM technique that yields reduced harmonic distortion. In this article, a minimum switching loss algorithm is introduced and implemented using both BCPWM and ABCPWM techniques. The algorithm is specifically designed to minimize switching losses across the entire range of load power factor angles. The integration of switching loss algorithm with the selection of the optimal PWM technique across different frequency ranges results in reduced switching losses and harmonic distortion. This leads to a comprehensive PWM algorithm that efficiently reduces both THD and switching losses during dynamic frequency and load changes. Experimental and theoretical evidences demonstrate the efficacy of the proposed algorithm in attaining minimum harmonic distortion and reduced switching loss operation during variations in fundamental frequency and load.

Novel Space-Vector PWM Schemes for Enhancing Efficiency and Decoupled Control in Quasi-Z-Source Inverters

This paper investigates the development of pulse width modulation (PWM) schemes for three-phase quasi-Z-source inverters (qZSIs). These inverters are notable for their voltage boost capability, built-in short-circuit protection, and continuous input current, making them suitable for low-voltage-fed applications like photovoltaic or fuel cell-based systems. Despite their advantages, qZSIs confront challenges such as increased control complexity and a larger number of passive components compared to traditional voltage source inverters (VSIs). In addition, most existing PWM schemes for qZSIs lack the capability for independent control of the amplitude modulation index and duty cycle, which is essential in closed-loop applications. This study introduces innovative space-vector PWM (SVPWM) schemes, addressing issues of independent control, synchronization, and unintentional short-circuiting in qZSIs. It evaluates several established continuous and discontinuous PWM schemes, and proposes two novel decoupled SVPWM-based schemes that integrate dead time and in which the shoot-through occurrence is synchronized with the beginning of the zero switching state. These novel schemes are designed to reduce switching losses and improve qZSI controllability. Experimental validation is conducted using a custom-developed electronic circuit board that enables the implementation of a range of PWM schemes, including the newly proposed ones. The obtained results indicate that the proposed PWM schemes can offer up to 6.8% greater efficiency and up to 7.5% reduced voltage stress compared to the closest competing PWM scheme from the literature. In addition, they contribute to reducing the electromagnetic interference and thermal stress of the related semiconductor switches.

Development of Various Types of Independent Phase Based Pulsewidth Modulation Techniques for Three-Phase Voltage Source Inverters

Discontinuous pulse-width-modulation (DPWM) methods have been extensively used in the industrial area to reduce overall losses, which decreases the corresponding thermal stress on the power switches of converters. However, local thermal overload can arise due to different aging conditions of semiconductor devices or failure in the cooling system. This leads to reduced reliability of the converter system due to the low expected lifespan of the most aged switches or phase legs. In this paper, the modified DPWM strategies for independent control of per-phase switching loss are introduced to deal with this matter. The proposed per-phase DPWM techniques are generated by modifying the conventional three-phase DPWM methods for reducing the switching loss in a specific leg, whereas the output performance is not degraded. This paper reports on output performance, including output current total harmonic distortion (THD) and power loss of switching devices, analysis for the various modified DPWM strategies for independent control of per-phase switching loss, which is applicable in 2-level 3-phase voltage source inverters (2L3P VSIs). The results are compared to the corresponding continuous PWM technique to verify and analyze the effectiveness and accuracy of the modified DPWM strategies for independent control of per-phase switching loss.

Discontinuous PWM Technique With Reduced Low-Order Harmonic Distortion for High-Power Applications

The modulation techniques used in high power applications have to generate high quality waveforms with reduced switching losses. As an attractive alternative, Discontinuous PWM (DPWM) techniques present lower device switching frequencies than conventional continuous PWM methods lowering the converter switching loss. Considering the same cooling system, this allows to increase the carrier frequency of DPWM methods displacing the main switching harmonics to higher frequencies. As a main drawback, when low carrier to fundamental ratios are used, DPWM methods present some undesired low-order harmonics that are required to be filtered. This paper presents a low-order harmonic minimization method for synchronous DPWM methods by modifying the conventional modulating reference to limit low order harmonics amplitude, while keeping the same effective switching frequency and thus limited switching losses.

Dynamic Deformation Oriented Thermo-Mechanical Performance Assessment for Automotive Power Module With Various PWM Schemes

Motivated by advances in semiconductor technology and policies from the government, the electric vehicle (EV) has become a promising solution to climate change worldwide. As the core component of the EV, the power module is expected to have high reliability. Considering the different field demands, the power module is generally driven by various pulse width modulation (PWM) schemes. However, how to assess and select the appropriate PWM scheme based on the specific field application is a knotty challenge. In this paper, a new perspective from the dynamic deformation of the power module is proposed to evaluate various PWM schemes. Based on experimental results, the power loss of the power module is calibrated and applied to the finite element analysis (FEA) model to clarify the deformation mechanism. Besides, the deformation measurement platform with high resolution and accuracy based on the confocal sensor is customized. Comparative results demonstrate that the FEA simulation model presents high agreement with the experimental results in terms of the maximum temperature and overall deformation, which confirm the accuracy of the power loss model. Furthermore, the continuous PWMs (CPWMs) generate the highest temperature and deformation, while the discrete PWM2 (DPWM2) presents the lowest temperature and deformation. The hysteresis curve of the power module consisting of the temperature and deformation is observed. The DPWM2 shows a 53% reduction in the closed area of the hysteresis curve compared to CPWMs, which indicates that it causes the lowest damage degree to the power module. In addition, the experimental results of the partial deformation demonstrate that the DPWM2 also has the lowest partial deformation among various PWMs. Generally, the DPWM2 is recommended when the DPWMs are enabled in the high-speed region of the EV.

Dual randomized discontinuous pulse width modulation for three-phase inverter

ABSTRACT The discontinuous PWM technique, with its advantage over the continuous PWM technique in reducing switching losses in power converters, is gaining popularity. However, its deterministic nature results in discrete harmonics with significant amplitudes, which leads to electromagnetic interference (EMI) emissions. The randomised PWM technique is gaining more interest because of its effectiveness in spreading the harmonic spectrum and thus reducing EMI problems in power converters. This paper presents a carrier-based dual randomised discontinuous PWM (DRDPWM) method for a three-phase voltage inverter. The DRDPWM method combines the random carrier frequency (RCF-DPWM) and random pulse position (RPP-DPWM) schemes. In addition to reducing switching losses, DRDPWM can achieve a broad spread of the voltage spectrum with significantly smaller amplitudes. Furthermore, it produces less inverter output current distortion when compared to traditional DPWM and simple random (RCF-DPWM and RPP-DPWM) schemes. Simulations and experimental results confirm the effectiveness of the suggested method for spreading the voltage spectrum compared to simple random schemes. Additionally, an evaluation of the performance of all randomised discontinuous schemes is conducted based on a number of assessment metrics, including the switching loss factor (SLF), the power spectral density (PSD), the harmonic spread factor (HSF), and the quality factor (QF).

A Carrier-Based Discontinuous PWM for an 80 Kw PV Inverter With the Reduction of the DC-Link Voltage Ripple and Common Mode Current

Discontinuous pulse width modulation (DPWM) method is broadly used in three-phase inverter to achieve high efficiency through the reduction of the switching loss. The high-power rating photovoltaic (PV) inverter with DPWM has its intrinsic issues such as large DC-link voltage ripple and high-frequency resonant current due to the large stray capacitance proportional to the power rating. To extend the application of DPWM from 10 kW to 80 kW PV inverter, a new DPWM method (DPWMn) which divides the clamping period into <i>n</i> intervals is proposed to achieve the three objectives simultaneously: 1) reduction of the DC-link voltage ripple; 2) suppression of the high-frequency current oscillation; 3) improve the efficiency compared to the continuous space vector PWM (SVPWM). The proposed DPWMn is validated by an 80 kW three-phase T-type PV inverter. Compared to the SVPWM, the DPWMn has reduced 30&#x0025; switching loss while maintaining the similar power quality and the common mode current. Compared to the existing DPWM methods, DPWMn reduces the voltage ripple by 52&#x0025; and has the minimum energy ripples. Furthermore, the carrier-based DPWMn only utilizes the measured voltage and can be easily implemented.

Design of Synaptic Driving Circuit for TFT eFlash-Based Processing-In-Memory Hardware Using Hybrid Bonding

This paper presents a synaptic driving circuit design for processing in-memory (PIM) hardware with a thin-film transistor (TFT) embedded flash (eFlash) for a binary/ternary-weight neural network (NN). An eFlash-based synaptic cell capable of programming negative weight values to store binary/ternary weight values (i.e., ±1, 0) and synaptic driving circuits for erase, program, and read operations of synaptic arrays have been proposed. The proposed synaptic driving circuits improve the calculation accuracy of PIM operation by precisely programming the sensing current of the eFlash synaptic cell to the target current (50 nA ± 0.5 nA) using a pulse train. In addition, during PIM operation, the pulse-width modulation (PWM) conversion circuit converts 8-bit input data into one continuous PWM pulse to minimize non-linearity in the synaptic sensing current integration step of the neuron circuit. The prototype chip, including the proposed synaptic driving circuit, PWM conversion circuit, neuron circuit, and digital blocks, is designed and laid out as the accelerator for binary/ternary weighted NN with a size of 324 × 80 × 10 using a 0.35 μm CMOS process. Hybrid bonding technology using bump bonding and wire bonding is used to package the designed CMOS accelerator die and TFT eFlash-based synapse array dies into a single chip package.

Per-Phase Analysis, Efficient Implementation and Performance Evaluation of a 24-Sector Discontinuous PWM for Split-Phase Induction Motor Drives

Space vector-based 24-sector pulse width modulation (PWM) techniques for split-phase induction motor (SPIM) drive offer better performance than the 12-sector PWM methods; however, these methods are complex to implement. This paper analyses a space vector based 24-sector discontinuous PWM from a per-phase perspective. Analysis of three-phase average pole voltages, pertaining to this method, shows that each phase is clamped for a 60 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> interval in each half cycle, which is divided into three sub-intervals of 15 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> , 30 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> and 15 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> , respectively. The common-mode voltage is shown to be related to the fundamental voltage of one of the phases in each sector and to that of different phases in different sectors. This analysis leads to an understanding of the offset voltages to be added to the two sets of three-phase sinusoidal modulating signals for generating the equivalent modulating signals for the two inverters driving the SPIM. Further analysis of the switching sequences suggests appropriate carrier waves for the modulating signals to be compared against. The computationally efficient implementation of the 24-sector discontinuous PWM (DPWM-1), thus developed, is validated on a 6-kW laboratory prototype SPIM drive. Stator flux ripple-based analysis is used to evaluate stator current distortion and rms torque ripple of different PWM techniques. Simulated instantaneous torque ripple and torque harmonic spectra of the different techniques are compared. The proposed method offers lower THD at high speeds and lower switching loss at high power factors than the 24-sector continuous space vector PWM with significantly low computational effort.

Component-Level Modeling of More Electric Auxiliary Power Units for Cooperative Control

Today, the more electric aircraft (MEA) concept is gaining tremendous popularity. As a key component of the MEA, a more electric auxiliary power unit (MEAPU) integrated model with high accuracy and real-time performance is essential when conducting cooperative control and hardware-in-the-loop (HIL) test research. This paper proposes a novel MEAPU integrated model consisting of a MEAPU component-level-model (CLM) and a starter-generator (SG) model. Firstly, a MEAPU CLM was built and a continuous scaling method for the component characteristic map in the CLM is proposed to improve the model’s accuracy. Then, a double winding induction starter-generator (DWISG) model based on the electromagnetic theory, which is quite time consuming, was simplified using the pulse width modulation (PWM) rectifier linearization method. Finally, considering the coupling relationship between the MEAPU CLM and DWISG, an accurate real-time MEAPU integrated model was built and its simulation results were analyzed. Compared with the test results, the error of the proposed model was less than 0.5%; meanwhile its single-step simulation time was less than 20 ms, which can meet the demands of cooperative control and HIL test research. Furthermore, the continuous scaling method and PWM rectifier linearization method were found to be effective for modeling other MEAPUs and more electric engines (MEE).

Improved PWM Strategies to Mitigate Dead-Time Distortion in Three-Phase Voltage Source Converter

Pulsewidth modulation (PWM) strategies, including continuous PWM (CPWM) and discontinuous PWM (DPWM), have been efficiently applied in the three-phase voltage source converters (VSCs). In the three-phase VSCs, dead-time distortion is inevitable. The characteristics of the dead-time distortion of three-phase VSCs with CPWM strategies have been studied extensively, whereas those of DPWM strategies have not been studied in detail. In this article, a comparative analysis of the dead-time distortion of CPWM strategies and DPWM strategies is conducted. Furthermore, the improvement of the PWM strategies to mitigate dead-time distortion is presented. The improved PWM strategies inject the compensation signals to the modulation signals to reconstruct the dead-time voltage error, which can significantly reduce the dead-time distortion of various PWM strategies. Experimental tests are conducted and the experimental results are provided to verify the analysis results of the dead-time distortion of DPWM strategies and the improved PWM strategies.

3-레그형 2상 인버터에서의 전류 복원 영역 확장

For measuring phase currents of two-phase motors driven by the three-leg inverters, the leg shunt resistors inserted between the lower switch of each inverter leg and the negative DC rail can be used instead of the expensive Hall-effect sensors. The two-leg shunt method using shunt resistors located on the two-phase legs has a limited current measurement range. In addition to this method, the three-leg shunt method can reconstruct the immeasurable phase currents by using an additional shunt resistor on a neutral leg. Therefore, the current measurement range can be wider than that in the two-leg shunt method. However, this method cannot properly reconstruct the currents in the specific areas where the voltage modulation index of the inverter is high, thereby decreasing the DC voltage utilization rate, and increasing the torque ripple of the motors. To improve this problem, this paper analyzed the current reconstruction areas of a three-leg type two-phase inverter applied CPWM(Continuous Pulse Width Modulation) method, and proposed a simple technique to expand the areas. The proposed technique can expand the current reconstruction areas by securing the turn-on time of the inverter lower switches utilizing the DPWM(Discontinuous PWM) method, which results in the improvement of DC voltage utilization rate.

Research and Development of Adjustable Discontinuous Pulse Width Modulation Method for Three-Phase Voltage Source Inverter

Continuous pulse width modulation (CPWM) and discontinuous pulse width modulation (DPWM) strategies are used to control voltage source inverter operation. CPWM strategies allow for the reduction of total harmonic distortion values, while DPWM strategies provide a more effective reduction in inverter switching losses. The paper is devoted to the problem of improving the three-phase voltage source inverter efficiency by a controlled transition from CPWM to DPWM. The article proposes an adjustable discontinuous pulse width modulation (ADPWM) method, which means a transition from space vector PWM (refers to CPWM strategies) to DPWM in all inverter phases when the switches’ temperatures exceed the allowable value in at least one of the inverter phases. The method flowchart is presented and an algorithm for modifying the envelope curve within one sector is given. In order to test the ADPWM method a Simulink-model of a three-phase voltage source inverter and its control system were developed. A study of the proposed ADPWM method’s efficiency in comparison with CPWM, PCDPWM and NCDPWM methods was carried out using a Simulink-model. It was established that the proposed ADPWM method provides dynamic losses reduction in the inverter switches by 2.86 times compared to CPWM and by 1.89 times compared to PCDPWM and NCDPWM methods. Power supply systems for medium and high-power AC motors provide a promising area for application of the proposed ADPWM method.

A Carrier-Based Discontinuous PWM Method for a Five-Level Flying Capacitor Rectifier With Unbalanced DC-Link Voltages

Unbalanced dc-link voltages occur when five-level flying capacitor (5L-FC) rectifier has dual dc loads of different rated voltages. Compared with traditional continuous pulsewidth modulation (CPWM) strategies, discontinuous PWM (DPWM) methods have more advantages in high-frequency and high-power applications for less commutation and higher efficiency. Therefore, this article proposes a carrier-based DPWM method for 5L-FC rectifiers with unbalanced dc-link voltages. The proposed method is first analyzed in the revised space vector diagram considering unbalanced dc voltages to divide subsectors and find available clamping modes, then it is implemented by applying carrier-based PWM with injecting clamping compensation component, which greatly reduces the implementation complexity. There is a pair of redundant clamping modes with opposite effects on the neutral-point (NP) in each subsector. Thus, the NP voltage can be actively controlled by selecting suitable clamping mode in each subsector. In addition, the allowable ranges of unbalanced voltage degree and unbalanced power degree are investigated in detail. Simulations and experiments verified the effectiveness and performance of the proposed method.

A Hybrid DPWM for Vienna Rectifiers Based on the Three-Level to Two-Level Conversion

In view of the large neutral-point (NP) voltage fluctuation and the high low-frequency harmonics in the input current of conventional discontinuous pulse width modulation (DPWM) for the Vienna rectifier, a hybrid DPWM (HDPWM) is proposed on the basis of three-level to two-level conversion. The proposed HDPWM combines the modulation degree of freedom, namely the vector synthesis direction and the equivalent zero vector distribution coefficient. Under the two-level modulation unit, the shift angles that satisfy the predefined NP balance requirement for HDPWM are accurately calculated. Compared with the continuous PWM and conventional DPWM, the proposed HDPWM could effectively suppress the zero-crossing distortion, reduce the NP fluctuation and the switching losses. Simulation and experiment results demonstrate that the proposed HDPWM could reduce the NP voltage fluctuation to 1/2 of the conventional DPWM with reduced input current low-frequency harmonics and no zero-crossing distortion.

Optimal Periodic Variable Switching PWM for Harmonic Performance Enhancement in Grid-Connected Voltage Source Converters

Variable switching frequency PWM (VSFPWM) modulation can be advantageously implemented in industrial applications, such as renewable energy, motor drives, and uninterrupted power supply (UPS) systems, to reduce the injected current harmonic amplitudes, to suppress audible noise, and to improve semiconductor power efficiency. In this article, the usage of periodic VSFPWM methods in a voltage source converter (VSC) is proposed, analyzed, and benchmarked in terms of harmonic spectrum spreading, following the IEEE-519 current harmonic standard for the connection to the distribution grid. Particular attention is paid to the influence of VSFPWM on the ac filter design. First, the analytical model of the voltage harmonic spectrum generated by a three-phase three-wire two-level VSC implementing several periodic VSFPWM methods is derived. Subsequently, a design guideline for the commonly used <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> filter in the grid-tied VSC application is proposed, which minimizes the size requirement of the necessary components. The voltage spectrum models of the proposed VSFPWM method and the optimal switching profiles are verified by MATLAB/Simulink simulations and a 5-kW three-phase two-level VSC hardware demonstrator. The study shows that the ac filter power density for the studied VSFPWM methods can be greatly increased when compared with the conventional and widely employed constant switching frequency continuous PWM strategies.

A Unified Carrier-Based Pulsewidth Modulation for Three-Phase Vienna-Type Rectifiers

Compared with space-vector pulsewidth modulation (SV-PWM) schemes, carrier-based PWM (CB-PWM) schemes feature less digital calculation burden. Unfortunately, since different CB-PWM schemes were not represented by a unified expression and the relationship between the injected zero-sequence components (ZSCs) and the switching-state sequences is not revealed, the CB-PWM has poor flexibility in designing the switching-state sequences. In this article, a unified carrier-based PWM (UCB-PWM) is proposed to unify the expressions of different CB-PWM schemes. The ZSC of the proposed UCB-PWM is classified into a basic ZSC (B-ZSC) and a redundant ZSC (R-ZSC). The B-ZSC is a shared component of all CB-PWM schemes, and the dwelling time of redundant small vectors can be distributed by injecting different R-ZSCs. Also, the neutral-point voltage balance control based on either continuous PWM or discontinuous PWM (DPWM) can be achieved by injecting R-ZSCs. Besides, not only the existing carrier-based DPWM schemes but also new carrier-based DPWM schemes are derived by the proposed UCB-PWM. Finally, experimental results verify the correctness and advantages of the proposed UCB-PWM.

Evaluation and comparison of sideband harmonics and acoustic responses with continuous and discontinuous PWM strategies in permanent magnet synchronous motor for electric vehicles

Evaluation and comparison of sideband harmonics and acoustic responses with continuous and discontinuous PWM strategies in permanent magnet synchronous motor for electric vehicles

30° Discontinuous PWM-Based Closed Loop Volts/Hz Control of Induction Motor Drive with Slip Regulation

This paper proposes 30° discontinuous PWM-based closed loop volts/Hz control of induction motor drive with slip regulation. The voltage source inverter is carried out with various pulse width modulation (PWM) schemes such as continuous PWM (CPWM) and discontinuous PWM (DPWM) schemes. The inverter's performance is affected by these PWM schemes. Therefore, this paper investigates the PWM schemes for the inverter. It aims to identify a best PWM scheme based on the total harmonic distortion and torque ripple analysis for constant volts/Hz induction motor drive amongst the various PWM schemes in open loop and closed loop and also proposes a 30° DPWM-based closed-loop control. The performance investigations of various PWM schemes based on inverter-fed induction motor have been evaluated analytically and using MATLAB/Simulink environment. Experimental results have been validated. The combination of 30° DPWM with PI control and slip regulation for induction motor makes the speed control system robust and ideal for low-accuracy applications.

Space vector PWM ‐based current error boundary investigations for three‐level VSI fed induction motor drive

Field oriented control (FOC) of induction motor (IM) powered by a three-level voltage source inverter (3L -VSI) with space vector (SV) based continuous and dis -continuous pulse width modulation (PWM) is presented in this paper. The current error variations in each sector with above-mentioned PWM techniques are monitored and analyzed mathematically. These boundary investigations play a great role in the implementation of Current Error Space Phasor (CESP) based hysteresis current controller (HCC) which incorporates the advantages of a constant switching frequency PWM fed three-level inverter (3LI) into highly dynamic current controlled – voltage source inverter. As a preliminary step, FOC of IM with the conventional space vector PWM and bus clamping PWM (BC30 and BC60) fed 3LI have been simulated using SIMULINK toolbox of MATLAB. Transient analysis of the drive with acceleration, deceleration, and load change studies with different switching schemes are analyzed with d SPACE RTI1103 experimentation on a 2.2 kW three-phase IM drive in detail.