Pulse Width Modulation Converter Research Articles

Control and performance analysis of grid‐connected variable speed wind turbine with dual stator‐winding induction generator for the contribution of both stator windings in active power transmission

Recently, variable speed wind turbines (WTs) employing dual stator-winding induction generators (DSWIGs) have gained interest in related kinds of literature. A DSWIG has two sets of stator windings known as power-winding (PW) and control-winding (CW), where CW is connected to a pulse-width modulation converter called semiconductor excitation controller (SEC). This study, first, presents a topology for connection of DSWIG-based WT to the grid, in which unlike most of the related kinds of literature, both the PW and CW contribute in transmission of active power to the grid. In the study system, PW is connected to the diode rectifier-boost converter and CW to the SEC, and thus PW and CW active powers are controlled by the related boost converter and SEC, respectively. Hence, this study extends theoretical expression and presents a new relation for the generator torque as a function of the CW and boost converter currents, and then develops control structures for the study system. Next, mathematical expressions are presented for the selection of excitation capacitor at the PW terminals. Besides, the presented control strategy of the system is modified to enhance the WT-low voltage ride-through capability. In the end, simulation results are presented for examining the system performance and verifying the theoretical analyses.

Bifurcation analysis of cascaded H-bridge converter controlled by proportional resonant

This paper is concerned with the nonlinear dynamics of Cascaded H-Bridge Converter under PR (Proportional Resonant) control. First, a stroboscopic mapping model of PWM (Pulse Width Modulation) converter is established and the corresponding dynamics, including bifurcations and chaos is investigated analytically. Taking the switching frequency, controller parameters as the bifurcation parameter, some different dynamic behaviors are identified over a wide range of some specified parameter. Moreover, the bifurcation condition is further verified based on the root locus diagram and Lyapunov exponential spectrum. Second, aiming at deriving the stability regions of PWM converter, the variable substitution approach is utilized to transform the non-autonomous converter model into an autonomous one. Then, the PR (Proportional Resonant) controller is applied to control the grid-side current, which can suppress the chaos and bifurcation in the current loop by increasing the proportional gain. Finally, the experiment results are presented to illustrate the validity of the control scheme.

A New Control Strategy for Three-Phase Shunt Active Power Filters Based on FIR Prediction

In this article, a new discrete-time control strategy for three-phase three-wire shunt active power filters (APFs) is presented, based on a mathematical model in the stationary reference frame. It involves a feedback-linearization-type approach to control the filter currents, whereby the voltage control loop is decoupled from the current control. The voltage control loop is for controlling the dc-side voltage of the pulsewidth modulation (PWM) converter, and employs a proportional-integral (PI) controller to generate the reference amplitude for the compensated grid currents. An important feature of the proposed control strategy is the compensation of the one-sampling-period delay caused by microcontroller computation using a finite impulse response (FIR) predictor. This predictor is designed to accomplish one-step-ahead prediction of the control variable, which is the PWM converter's switching function space vector. Furthermore, the FIR predictor is optimized so that the low-order harmonics in the control variable are predicted with minimal error. The proposed control strategy is analyzed to obtain the steady-state filter current error and ranges for the PI controller gains for stability. Simulation and experimental results are presented to show the effectiveness of the proposed shunt APF.

A modified modeling and dynamical behavior analysis method for fractional-order positive Luo converter

Compared to the integer-order modeling, the fractional-order modeling can achieve higher accuracy for designing and analyzing the DC-DC power converters. However, its applications in pulse width modulation (PWM) converters are limited due to the computational complexities. In this paper, a modified fractional-order modeling methodology for DC-DC converters is proposed, and its effectiveness is verified on the fractional-order positive Luo converters. Instead of using fractional-order calculus, the proposed methodology analyzes the harmonic components of the PWM converters by utilizing the non-linear vector differential equations of the periodically time-variant system. The final solution of the state variables is composed of two parts: the steady-state solution and the transient solution. The approximate steady state solution can be obtained by using the equivalent small parameter (ESP) method and the harmonic balance theory, while the main part of the transient solution can be obtained according to the explicit Grünwald-Letnikov (GL) approximation. In addition, the influence of the fractional orders on the performance of the DC-DC converters, and on the dynamic behaviors of the fractional-orders systems are also discussed in this paper. Compared to the conventional fractional-order numerical models, the proposed model is able to present the time-domain information more precisely, which helps to better reveal and analyze the non-linear behaviors of the DC-DC converters. The effectiveness of the work is demonstrated by the simulation and experimental results of the equivalent circuits built with fractional-order components.

Modeling of DSTATCOM Devices to Improve Dynamic Voltage Stability in a Microgrid with High Penetration of Motor Loads

A través de este artículo se propone y valida modelos de dispositivos de tecnología FACTS de tipo Compensador Estático Sincrónico para Distribución (DSTATCOM). En primera instancia, se presenta el modelado de un DSTATCOM simplificado realizado a través de una fuente de corriente controlada. Posteriormente, se expone un DSTATCOM modelado a través de estrategias de control considerando un conversor PWM (Pulse-Width Modulation - Modulación por ancho de pulsos). Los modelos propuestos de dispositivos DSTATCOM se validan en un sistema de prueba de Microrred Eléctrica (MRE) de la CIGRÉ. La presencia de cargas de tipo motor de inducción en la MRE requiere una considerable demanda de potencia reactiva, esto ocasiona inconvenientes para mantener la Estabilidad Dinámica de Tensión (EDT). Ésta situación se agrava ante la ocurrencia de fallas que desencadenen una operación aislada de la MRE. Para solucionar estos inconvenientes se hará uso de un dispositivo DSTATCOM. La conexión y ubicación óptima del DSTATCOM en la MRE se realiza a través de un algoritmo de búsqueda exhaustiva, considerando la premisa del mejor rendimiento en términos de EDT realizado a través de simulaciones dinámicas en PowerFactory DIgSILENT. Comparativamente se presentan los resultados obtenidos para los dos modelos realizados, demostrándose la mejora de la EDT en la operación aislada de la MRE con ambos modelos. Dependiendo del detalle y alcance de los estudios en el sistema de MRE, se puede elegir entre los modelos DSTATCOM desarrollados. Todos los detalles de modelos, esquemas de control y datos de los dispositivos DSTATCOM son proporcionados en este documento.

Analysis and Design of a Double Fuzzy PI Controller of a Voltage Outer Loop in a Reversible Three-Phase PWM Converter

Aiming at the application of a reversible three-phase pulse width modulation (PWM) converter with a wide range of AC side voltage and DC side voltage, a double fuzzy proportional integral (PI) controller for voltage outer loop was proposed. The structures of the proposed controller were motivated by the problems that either the traditional PI controller or single fuzzy PI controller cannot achieve high performance in a wide range of AC and DC voltage conditions. The presented double fuzzy controller studied in this paper is a sub fuzzy controller in addition to the traditional fuzzy PI controller; in particular, the sub fuzzy controller can get the auxiliary correction of PI control parameters according to the AC side voltage and the DC side given voltage variation of PWM converter after the reasoning of the sub fuzzy controller, while the traditional fuzzy PI controller outputs the correction of PI control parameters according to the DC voltage error and its error change rate. In this paper, the traditional fuzzy PI controller can be called the main fuzzy controller, and the adaptive adjustment of PI control parameters of the voltage outer loop is the sum of the PI parameter correction output by the main fuzzy controller and the auxiliary PI parameter correction output by the sub fuzzy controller. Finally, the experimental results show that the reversible three-phase PWM converter can achieve excellent dynamic and static performance in a wide range of AC voltage and DC voltage applications by using the proposed double fuzzy PI controller.

DC Converter with Wide Soft Switching Operation, Wide Input Voltage and Low Current Ripple

A soft switching current-source resonant converter is presented and implemented for wide voltage applications such as fuel cells and solar power. An LLC (inductor–inductor–capacitor) converter is adopted to accomplish zero voltage (current) operation on active switches (diodes). Thus, the circuit efficiency is increased. The interleaved pulse-width modulation (PWM) converter is employed on the input side to accomplish low input ripple current. A hybrid LLC converter is adopted to achieve wide voltage operation from Vin, min to 4Vin, min and to improve the weakness of a conventional LLC converter. Half-bridge diode rectification is employed on the output side to decrease power loss on the rectifier diode. To confirm the theoretical analysis and feasibility, experimental verifications with a 500-W prototype are demonstrated in this paper.

A Universal Wideband Device-Level Parallel Simulation Method and Conducted EMI Analysis for More Electric Aircraft Microgrid

The validation of electromagnetic compatibility for the microgrid of a more electric aircraft (MEA) is an essential test item before delivery for a trial flight, and it has always been urgently expected to be involved during the design stage. This article presents a universal method for wideband modeling and simulation of the MEA microgrid system in the time domain, regardless of the fact that motors are driven by which kind of converter, e.g., modular multilevel converter (MMC), 3-L neutral-point clamped (NPC), or 2-L pulsewidth modulation (PWM) converters. The insulated gate bipolar transistor and diodes are modeled with the physics-based dynamic model to emulate not only precise system-level performance of the system, but also to get an insight into the high-frequency oscillation between junction capacitance of the semiconductor modules and the parasitic parameters and high-frequency branch of other components, such as the permanent magnet synchronous motor (PMSM), transformer, and generator. To alleviate the attendant computational challenge, which could be extremely time-consuming (if no nonconvergence problem is encountered) when solved on traditional simulation platform, circuit partition based on transmission line decoupling, Norton equivalent parameter extraction, and TLM-link decoupling of submodules from the MMC bridge arms are utilized. The simulation program is executed on GPU to achieve massively parallel and accelerated solution. The accuracy and efficiency of the GPU-based parallel algorithm are validated by the comparison with the experimentally verified model in ANSYS Simplorer.

Condition Monitoring of DC-Link Electrolytic Capacitors in PWM Power Converters Using OBL Method

Since the lifespan of an electrolytic capacitor is relatively short compared to other power semiconductor devices, the failure rate accounts for 60% and, thus, it is the most vulnerable component of the power conversion device. Therefore, the accurate measurement of the lifetime of an electrolytic capacitor is very important in ensuring the reliability of the entire system, including the capacitor. In this paper, an online failure detection method for a DC-link electrolytic capacitor in a back-to-back Pulse width Modulation (PWM) converter using the opposition-based learning particle swarm optimization-based Support Vector Regression (OPSO-SVR) technique is proposed. In this method, the capacitance and the DC-link capacitor power have been used in offline mode for SVR training and testing. During the offline mode, the SVR parameters have been optimized with the OPSO algorithm to use online to estimate the real value of the DC-link capacitor. The experimental results prove the superiority of the proposed technique over the SVR.

Optimal Overlap-Time Distribution of Space Vector Modulation for Current-Source Rectifier

This article proposes an improved space vector modulation (SVM) for the current-source rectifier (CSR). Due to the overlap time during commutations of power switches, the pulsewidth-modulation (PWM) currents of CSR may suffer from a number of low-order (mainly fifth and seventh) harmonics, which seriously degrade the harmonic performance of currents and voltages on the grid side. Especially, the overlap-time effect becomes an important issue when the increased switching frequency is applied to CSR. To mitigate these low-order harmonics of the PWM converter currents resulted from the overlap-time effect, the relationship between the overlap time and the low-order harmonics in PWM currents and grid currents are analyzed at first. Then, the design process of the LC filter and the proposed SVM with optimal overlap-time distribution is presented in details. Finally, experimental results are conducted on a low power laboratory prototype to verify the effectiveness of the proposed method.

Analysis and Verification of a Wide Input Voltage PWM Converter with Variable Windings

A three-leg pulse-width modulation converter with auxiliary windings is provided and investigated to realize wide voltage operation and zero voltage switching characteristics on power switches. The presented converter has three converter legs on the input-side and two sets of winding turns on the output-side. Owing to the on/off states of the three converter legs and the two sets of secondary winding turns, the proposed converter can be operated under three different equivalent circuits to have wide input voltage operation from 30V ~ 240V (Vin,max = 8Vin,min). Compared with the multi-stage converters to realize wide input voltage operation, the proposed circuit topology has fewer circuit components and a simple control algorithm. Conventional duty cycle control with phase-shift between each converter leg is adopted to regulate load voltage and also accomplish zero voltage switching on active switches. The presented three-leg converter is tested with a laboratory circuit. Finally, experiments testify to the performance and validity of the presented converter.

Comparative study of indirect space vector and venturini modulation for matrix converter fed induction motor

This paper discusses the comparison method between two type modulations of direct matrix converter system with three-phase induction motor load. Matrix converter has accepted considerable interest as an alternative to conventional ac-dc-ac PWM (Pulse Width Modulation) converters in ac-ac conversion, especially for no-load induction motor drive. However, it is not convenient to control the matrix converter. The important point of the matrix converter is the modulation technique that has two different techniques in Venturini and indirect space vector modulation (ISVM). These methods are compared and analysed in the total harmonic distortion of output and input to find better performance for induction motor drive. Simulated input and output parameters of the matrix converter are presented using MATLAB/Simulink software for both modulation techniques. The result reveals smaller total harmonic distortion in ISVM than Venturini modulation for matrix converter.

Fault-tolerant control strategy for open-circuit fault of two-parallel-connected three-phase AC–DC two-level PWM converter

This paper proposes a fault-tolerant control (FTC) strategy for an open-circuit fault (OCF) of a single IGBT in a two-parallel-connected three-phase AC–DC pulse-width-modulation (PWM) converter system. In the case of the parallel-connected PWM converter system, the OCF of the IGBT causes not only DC-link voltage fluctuation and grid current distortion, but also a zero-sequence circulating current (ZSCC). Although the effect of these problems can be reduced by existing FTC methods which is used in the single PWM converter, it is difficult to totally mitigate the problems due to the ZSCC. Therefore, this paper proposes a new FTC strategy to suppress the ZSCC using the healthy converter in the parallel-connected converter. First, it is analyzed how the difference in common-mode (CM) voltage between the two converters causes ZSCC flowing inside the parallel-connected converter under the fault condition. And then, the limitation of the existing control method for ZSCC is explained. To suppress the ZSCC using the healthy converter, the proposed control method uses a d-axis voltage injection of the healthy converter which does not affect an active power control. The effectiveness of the proposed FTC strategy is verified through experimental results.

± 180° Discontinuous PWM for Single-Phase PWM Converter of High-Speed Railway Propulsion System

As high-capacity alternating current/direct current (ac/dc) power conversion systems, single-phase pulse-width modulation (PWM) converters used in high-speed railway propulsion systems adopt high-voltage Insulated-Gate Bipolar Transistors (IGBTs) as switching elements. Due to their high breakdown voltage characteristics, the switching dynamics are inferior to those of low-voltage IGBTs and switching losses are more dominant than conduction losses despite operating at relatively low switching frequencies of hundreds to several kHz. To solve this problem, this paper proposes ± 180° discontinuous PWM (DPWM) suitable for a single-phase circuit. With the simple addition of offset voltages, the proposed DPWM method can be implemented easily and switching losses can be reduced by half by clamping the switching legs of the H-bridge converter to the positive or negative dc rail during every half cycle. In addition, temperature deviation between the power stacks can be minimized by using selective application of clamping modes. The validity and effectiveness of the proposed DPWM are verified through simulations and experiments of a prototype converter.

Novel space vector PWM technology with lower common‐mode voltage for dual three‐phase PMSM

Pulse width modulation (PWM) converters generate switching common-mode voltages (CMV) across the load terminals. These voltages cause common mode currents, leading to bearing failure in motor loads and electromagnetic interference problems. This study proposes a novel space vector PWM strategy to reduce the CMV in the dual three-phase permanent magnet synchronous motor (PMSM) driven by two-level six-phase inverter. The novel space vector PWM algorithm discards the use of zero vectors. Firstly, the two largest voltage vectors of each sector are selected as main vectors to synthesise reference vector. Then, three groups voltage vector, which are opposite to the main vectors, have been selected as auxiliary vectors. Appropriate auxiliary vector selected is based on the length of zero voltage vector working time. Next, zero vector working time is distributed to the main and selected auxiliary vectors based on voltage-second principle. In addition, CMV and the harmonic component in z1z2 subspace of the proposed space vector PWM are analysed in detail. Finally, the expected CMV reduction to one-sixth of DC voltage and change rate of CMV in each cycle promised by the proposed novel space vector PWM are demonstrated with simulation and experimental results.

A Control Strategy for Suppressing Zero-Sequence Circulating Current in Paralleled Three-Phase Voltage-Source PWM Converters

In microgrids, paralleled converters can increase the system capacity and conversion efficiency but also generate zero-sequence circulating current, which will distort the AC-side current and increase power losses. Studies have shown that, for two paralleled three-phase voltage-source pulse width modulation (PWM) converters with common DC bus controlled by space vector PWM, the zero-sequence circulating current is mainly related to the difference of the zero-sequence duty ratio between the converters. Therefore, based on the traditional control ideal of zero-vector action time adjustment, this paper proposes a zero-sequence circulating current suppression strategy using proportional–integral quasi-resonant control and feedforward compensation control. Firstly, the dual-loop decoupled control was utilized in a single converter. Then, in order to reduce the amplitude and main harmonic components of the circulating current, a zero-vector duty ratio adjusting factor was initially generated by a proportional–integral quasi-resonant controller. Finally, to eliminate the difference of zero-sequence duty ratio between the converters, the adjusting factor was corrected by a feedforward compensation link. The simulation mode of Matlab/Simulink was constructed for the paralleled converters based on the proposed control strategy. The results verify that this strategy can effectively suppress the zero-sequence circulating current and improve power quality.

Analysis and Implementation of a Phase-Shift Pulse-Width Modulation Converter with Auxiliary Winding Turns

A phase-shift pulse-width modulation converter is studied and investigated for railway vehicle or solar cell power converter applications with wide voltage operation. For railway vehicle applications, input voltage range of dc converters is requested to have 30–40% voltage variation of the nominal input voltage. The nominal input voltages of dc converters on railway vehicles applications may be 37.5 V, 48 V, 72 V, 96 V and 110 V. Therefore, a new dc converter with wide input voltage operation from 25 to 150 V is presented to withstand different nominal input voltage levels such as 37.5–110 V on railway power units. To realize wide input voltage operation, an auxiliary switch and auxiliary transformer windings are used on output side of conventional full-bridge converter to have different voltage gains under different input voltage values. Phase-shift pulse-width modulation is adopted in the developed dc converter to accomplish soft switching operation on power switches. To confirm and validate the practicability of the presented converter, experiments based on a 300 W prototype were provided in this paper.

Passive Fault-Tolerant Model Predictive Control of AC/DC PWM Converter in a Hybrid Microgrid

This paper aims at presenting a novel fault-tolerant control (FTC) scheme for an AC/DC pulse-width modulation (PWM) converter operating in a microgrid framework. A group of interconnected loads and distributed renewable energy resources such as wind farm, solar photovoltaic (PV) farm, and a battery energy storage are considered to form a microgrid. The control system for the AC/DC PWM converter aims at tolerating the fault effects due to power-loss malfunctions in the solar system. A passive fault-tolerant control scheme based on model predictive control (MPC) is proposed and the effectiveness of the designed scheme is demonstrated in an advanced microgrid benchmark model implemented in MATLAB/Simulink environment.

Phase-Shift PWM Converter with Wide Voltage Operation Capability

A soft switching three-level pulse-width modulation (PWM) converter is presented for industrial electronics with wide voltage range operation, such as solar power or fuel cell applications. Phase shift PWM scheme is used on the input-side to accomplish the zero voltage turn-on on power switches and improve the converter efficiency. Three-level diode-clamp circuit topology is adopted in the presented circuit to lessen the voltage ratings on active devices for high voltage applications. Three sub-circuits with the different turns-ratio of transformers can be selected in the presented converter in order to achieve 10:1 (Vin,max = 10Vin,min) wide input voltage operation when compared to the conventional multilevel converter. The proposed circuit is a single-stage converter instead of two-stage converter to realize wide voltage operation. Therefore, the presented converter has less component counts. Finally, the design procedure and experiments with a 300W laboratory circuit are presented and discussed to confirm the circuit analysis and converter performance.

The Characteristics and Suppression of Common-Mode Current for Brushless Doubly Fed Generator System

Due to the cancellation of the brush and slip ring, the brushless doubly fed generator (BDFG) is more reliable than the doubly fed induction generator and it has wide prospect in the field of variable speed constant frequency power generation. However, the internal structure of BDFG is complex, which brings difficulties to the analysis of common-mode circuit and the suppression of common-mode current. Based on the structure of BDFG system, the common-mode voltage circuit paths are analyzed. The common-mode equivalent circuit model and the extraction method of equivalent common-mode impedance parameters are presented in this article. The characteristics of each common-mode circuit path are analyzed. The common-mode Path 3 (line-side converter-motor power winding-motor control winding-machine-side converter-line-side converter) is an important factor that affects the common-mode current characteristics of the BDFG system. The relationship between carrier difference and common-mode current characteristics of two pulsewidth modulation converters, in this path, is analyzed emphatically. In order to reduce the common-mode voltage, it is necessary to ensure the carrier synchronization between them. And the control method of carrier synchronization is provided. The experiment is designed based on the experiment platform of the BDFG system. The experimental results verify the correctness of the proposed model and theoretical analysis, as well as the effectiveness of the common-mode current suppression method.