Showing papers on "PWM rectifier published in 2021"

Wideband dq -Frame Impedance Modeling of Load-Side Virtual Synchronous Machine and Its Stability Analysis in Comparison With Conventional PWM Rectifier in Weak Grid

Abstract: The load-side virtual synchronous machine (LVSM) enables the load to actively participate in the grid regulation, but it might still induce oscillations in a weak grid. Considering the dc-link voltage controller, power loops, ac voltage and current loops, the control delay, and sampling filters, the wideband dq -frame impedance model of the LVSM is first established, and it is found that $Z_{dd}$ exhibits negative resistor impedance within 10 Hz. In addition, the dq -frame impedance of the LVSM is approximately inductive above 10 Hz. Then, using the dq -frame impedance-based approach, the comparative study shows that the smaller the proportional gain and integral gain of the dc-link voltage controller are, the more stable the conventional voltage source rectifier (VSR) is in a weak grid. However, the larger the proportional gain is, the smaller the integral gain is, the more stable the LVSM is in a weak grid. Furthermore, the voltage feedforward decreases the stability margin of the VSR in a weak grid, while the virtual moment of inertia $J$ and the damping gain $D_{p}$ affect the stability of the LVSM, and the smaller $J$ and $D_{p}$ are, the more stable the LVSM is in weak grid. Finally, simulations and experimental results verify the impedance model and the stability analysis.

Direct power control of three-phase PWM-rectifier with backstepping control

Abstract: Pulse Width Modulation (PWM) rectifiers belong to the best solutions to improve the quality of electrical energy transfer from a source to a receiver. In fact, this chapter proposes a method for regulating the three-phase PWM rectifier and ensuring the elimination of total harmonic distortion to obtain a non-contaminated system operating within a unity power factor. This regulation method is contracted via analogy to the direct torque control (DTC) of an electrical machine. In place of the torque and stator flux, active and reactive power are the corrected variables. That work suggests the study of a direct power control (DPC) of a three-phase PWM rectifier by deploying a backstepping for the correction of the DC bus voltage. The assessment of the validity and dynamic performance of the control methods was checked by simulation using MATLAB / SIMULINK environment under various conditions, such as the variation of the reference voltage and the load. The results of the simulation showed the robustness of direct power control based on the backstepping control technique.

ANN-based dynamic control and energy management of inverter and battery in a grid-tied hybrid renewable power system fed through switched Z-source converter

Abstract: The multidimensional purposes of grid-tied hybrid renewable system such as tracking of maximum power, increasing the power conversion efficiency, reducing the harmonic distortions in the injected current and control over power injected into the grid are presented in this paper by developing a laboratory-scale setup. To ensure continuous current operation at the shoot through mode of grid connected inverter, a switched Z-source converter is utilized at the PV side. The PWM rectifier connected with the wind turbine transforms AC power into dc. Individual power converters with conventional PI controllers have been dedicated for each power source, and control strategy uses only one reference voltage so as to increase the maximum power tracking speed from both PV and wind sources. The battery energy management is performed by artificial neural network (ANN) to enhance the stable power flow and increase the lifespan of the storage system. Finally, the voltage at the point of common coupling is fed to ANN-based space vector-modulated three-phase inverter and the converted AC power is injected to the grid. The overall system performance is measured by estimating the quality of injected power. A stable operation of the proposed microgrid system is verified by varying input and load at the grid. A continuous-time simulation model is realized in MATLAB and is validated using experimental prototype. This benchmark system provides various research scopes for the future smart grids.

Model Predictive Current Control with Fixed Switching Frequency and Dead-Time Compensation for Single-Phase PWM Rectifier

Abstract: The research object of this paper is single-phase PWM rectifier, the purpose is to reduce the total harmonic distortion (THD) of the grid-side current. A model predictive current control (MPCC) with fixed switching frequency and dead-time compensation is proposed. First, a combination of an effective vector and two zero vectors is used to fix the switching frequency, and a current prediction equation based on the effective vector’s optimal action time is derived. The optimal action time is resolved from the cost function. Furthermore, in order to perfect the established prediction model and suppress the current waveform distortion as a consequence of the dead-time effect, the dead-time’s influence on the switching vector’s action time is analyzed, and the current prediction equation is revised. According to the experimental results, the conclusion is that, firstly, compared with finite-control-set model predictive control, proportional-integral-based instantaneous current control (PI-ICC) scheme and model predictive direct power control (MP-DPC), the proposed MPCC has the lowest current THD. In addition, the proposed MPCC has a shorter execution time than MP-DPC and has fewer adjusted parameters than PI-ICC. In addition, the dead-time compensation scheme successfully suppresses the zero-current clamping effects, and reduce the current THD.

Generalized Predictive DC-Link Voltage Control for Grid-Connected Converter

Abstract: The main function of the grid-connected converter in many applications is to control the DC-link voltage with high performance, i.e. strong disturbance rejection capability and good dynamic response. Take the grid connected PWM rectifier of a motor drive system as an example, good disturbance rejection capability is essential for the DC-link voltage control to address the varying loads on the motor side, and the dynamic process of the DC-link voltage control is preferred to be fast and overshoot-free, so as to adaptively adjust the DC-link voltage according to the motor speed and reduce the switching losses. However, the performance of the conventional PI-based DC-link voltage control is not always satisfying and can be further improved. In this paper, the generalized predictive control (GPC) method is applied to the DC-link voltage control of a grid-connected converter for the first time, which can provide both good disturbance rejection capability and satisfying dynamic performance. Moreover, stability analysis of the proposed GPC-based DC-link voltage control strategy is theoretically studied, and a parameter tuning guideline is provided. The effectiveness and advantages of the proposed method are validated with experimental results.

Simulation model of 3-phase PWM rectifier by using MATLAB/Simulink

Abstract: Many industrial applications require the use of power electronic devices, which in turn help in overcoming the problems of variable load and fluctuations that occur at the end of feeding. The current study emphasizes that the use of different electric power generation systems with industrial applications needs control devices to work on improving the power quality and performance of systems in which there is an imbalance in the voltage or current due to the change of loads or feeding from the source. The present study also presents a model of a transformer widely used in industrial applications and this work includes simulating a three-phase rectifier by MATLAB. There are four cases in this work HWR (uncontrolled and controlled) and FWR (uncontrolled and uncontrolled) with different loads (R, RL & RC) including full wave type AC/DC using six electronic transformer silicon control rectifier (SCRs) once as well as unified half wave using three electronic transformer silicon control rectifier (SCRs). Simulation results include input, output voltage, and current with the waveform.

Design and Control of Grid-Connected PWM Rectifiers by Optimizing Fractional Order PI Controller Using Water Cycle Algorithm

Abstract: In this paper water cycle algorithm-based fractional order PI controller (FOPI) is proposed for virtual flux-oriented control of a three-phase grid-connected PWM rectifier. FOPI controller makes the PWM rectifier control more robust due to the fractional behavior. Fractional-order controllers have an additional degree of freedom, so a wider range of parameters is available to provide better control and robustness in the plant. The optimization and design of the FOPI controller are done using the water cycle algorithm (WCA). WCA is an optimization method inspired by monitoring the water cycle operation and flow of water bodies like streams and rivers toward the sea. The performance of the FOPI controller is compared with the classical integer order PI controller. The parameters of PI and FOPI controllers are optimized and designed using the WCA technique, leading to WCA-PI and WCA-FOPI controllers. The system is tested using MATLAB/Simulink. The simulation results verify the better performance of WCA-FOPI in terms of settling time, rise time, peak overshoot, and Total Harmonic Distortion (THD) of grid current. A robustness measurement with line filter parametric variations and non-ideal supply voltage (unbalance and distorted supply voltage) is carried out. The WCA-FOPI demonstrates more robustness as compared to WCA-PI. Simulation findings validate the WCA-FOPI controller outcomes as compared to WCA-PI in terms of control effect and robustness.

Sensor Fault Diagnosis and Unknown Disturbances Estimation of High Switching Frequency Single-phase PWM Rectifier

Abstract: The fault and disturbances estimation has an important role in the modern traction railway system. This paper proposes a unique method for the real-time robust sensor fault detection and unknown bounded disturbances estimation of high switching frequency single-phase pulse width modulation (PWM) rectifier. The new state observer is designed for open-circuit sensors fault for single-phase PWM rectifier. The digital realization method is used to minimize the observer fluctuation in presence of fault with and without external disturbance. The fault diagnosis approach constitutes on threshold establishment with respect to residual generation based on observer and estimator. The impact of uncertainties is reduced and the convergence speed of fault estimation and accuracy is improved by H∞ performance level. The extensive simulations are implemented to validate the effectiveness of the proposed algorithm. From the presented results, the performance of the proposed method is illustrated along with the fault isolation and disturbance estimator.

Finite Control Set Model Predictive Direct Power Control of Single-Phase Three-Level PWM Rectifier Based on Satisfactory Optimization

Abstract: In this paper, a finite control set model predictive direct power control (FCS-MPDPC) method based on satisfactory optimization, for single-phase three-level PWM rectifier, is proposed to achieve global optimization that takes into account all its objectives and constraints. Satisfaction optimization aims to obtain the satisfactory solution after coordination of multiple goals, instead of the optimal solution of a single goal. By replacing “optimal” with “satisfaction”, more control degrees of freedom are acquired, so that low-priority auxiliary control objectives can participate in the optimization process. Meanwhile, in order to enhance the description accuracy of FCS-MPDPC method for the future trend of PWM rectifier, the prediction time domain is extended from the traditional single-step to multi-step, and the average switching frequency model is established to realize the low switching frequency control. The satisfactory optimized FCS-MPDPC method proposed in this paper is compared, through simulation and experimental results, with the standard FCS-MPDPC method, which verifies the effectiveness and superiority of the proposed algorithm.

Monitoring and control of a permanent magnet synchronous generator-based wind turbine applied to battery charging

Abstract: The battery charging control within wind turbine applications is the most important challenge in standalone exploitation mode because of the random nature of wind energy and irregular use of electr...

Conceptual Study of Vernier Generator and Rectifier Association for Low Power Wind Energy Systems

Abstract: In this paper, we study a wind energy conversion system designed for domestic use in urban or agricultural areas. We first present the turbine, which was specifically designed to be installed on the buildings that it supplies. Based on turbine characteristics, we perform analytical sizing of a Permanent Magnet Vernier Machine (PMVM), which will be used as a generator in our energy conversion system. We show the influence of this generator on system operation by studying its association with a PWM rectifier and with a diode bridge rectifier. We then seek to improve generator design so that the turbine operates closely to maximum power points, while using a simple and robust energy conversion system. We use simulation to show the improvements achieved by taking into account the entire energy conversion system during machine design.

Super twisting sliding mode approach applied to voltage orientated control of a stand-alone induction generator

Abstract: To enhance the robustness and dynamic performance of a self-excited induction generator (SEIG) used in a stand-alone wind energy system (WES), a virtual flux oriented control (VFOC) based on nonlinear super-twisting sliding mode control (STSMC) is adopted. STSMC is used to replace the conventional proportional-integral-Fuzzy Logic Controller (PI-FLC) of the inner current control loops. The combination of the proposed control strategy with space vector modulation (SVM) applied to a PWM rectifier brings many advantages such as reduction in harmonics, and precise and rapid tracking of the references. The performance of the proposed control technique (STSMC-VFOC-SVM) is verified through simulations and compared with the traditional technique (PI-FLC-VFOC-SVM). It shows that the proposed method improves the dynamics of the system with reduced current harmonics. In addition, the use of a virtual flux estimator instead of a phase-locked loop (PLL) eliminates the line voltage sensors and thus increases the reliability of the system.

Discrete Dynamical Predictive Control on Current Vector for Three-Phase PWM Rectifier

Abstract: In order to improve the current performance of AC side for a three-phase PWM rectifier, this paper puts forward a current vector predictive control strategy. The discrete dynamic response of the current vector during the control period has been deduced through the discrete solving of Taylor series expansion and finite order truncation, so that the prediction of the current vector is achieved and testified by the relative distance. Then the discrete dynamical prediction control strategy of the current vector is proposed with the timings analysis to improve the rapidity and accuracy of the current vector tracking. Simulations and experiments are given to testify and verify the dynamic/steady-state performance and the efficiency of the control strategy, which can effectively improve the current vector tracking performance and reduce the harmonics and ripples.

Energy conversion device and vehicle

Abstract: The invention provides an energy conversion device and a vehicle, and the energy conversion device comprises a reversible PWM rectifier, wherein a first end and a second end of each bridge arm of thereversible PWM rectifier are respectively connected together to form a first confluence end and a second confluence end; a motor coil which comprises a first winding unit and a second winding unit which are connected with the reversible PWM rectifier; a bidirectional leg which is connected in parallel with the reversible PWM rectifier; and a charging and discharging connecting end group which comprises a first charging and discharging connecting end connected with the midpoint of the bidirectional bridge arm, a second charging and discharging connecting end connected with the first winding unit and a third charging and discharging connecting end connected with the second winding unit, wherein an external alternating current port is connected with the charging and discharging connecting endgroup. When the device is applied to the vehicle, the alternating-current charging and discharging circuit and the driving circuit can reuse the reversible PWM rectifier and the motor coil, and the problems that an existing overall control circuit comprising a battery charging circuit and a motor driving circuit is complex in structure, low in integration level, large in size and high in cost aresolved.

A Single-Stage Isolated AC–DC Converter to Interlink Utility Grid and Renewable Energy Sources in a Residential DC Distribution System

Abstract: This article proposes a single-stage isolated PWM rectifier topology to interlink utility grid and renewable energy sources in a 380-V dc distribution system for residential applications. The proposed topology provides both the power factor correction and output dc voltage regulation within a single power conversion stage. Furthermore, it includes an integrated flyback-based active lossless clamp (ALC) circuit to mitigate the device overvoltage issues generally noticed in the isolated single-stage PWM rectifiers. Thus, low-voltage-rating devices can be selected. The regenerative feature of the flyback ALC circuit along with soft-switching of the main converter structure helps in realizing higher efficiency. A dual-duty hybrid control algorithm is also reported to improve the converter performance. An SiC mosfet -based 1.5-kW hardware prototype is developed. The converter performance is evaluated from the experimental results obtained during both the steady state and dynamic operation. Comprehensive performance analysis and comparison study have also been presented in this article.

A Novel Three-Vector-Based Model Predictive Direct Power Control for Three-Phase PWM Rectifier

Abstract: A novel strategy of three-vector-based model predictive direct power control (MPDPC) is proposed for three-phase Pulse-width Modulation (PWM) rectifier. Under ideal grid conditions, three-vector MPDPC is studied, and a good control effect has been achieved. However, under the unbalanced power grid condition, the traditional control strategy has some problems, such as a high harmonic content of current and large instantaneous power pulsation. A new three-vector model predictive control is proposed based on the new instantaneous power theory, and the objective function is established by instantaneous power error. The duty cycle of the selected vector is calculated by solving the optimal objective function. Under an unbalanced power grid, this paper takes a three-phase PWM rectifier as a research object, and carries out simulation and experimental tests on the traditional and new control strategies. The experimental results show that the new control strategy has lower current harmonics, and eliminates the twice grid-frequency oscillation of the grid in instantaneous power.

Single-Phase Three-Level PWM Rectifier Predictive Control With Fixed Switching Frequency Based on Current Convex Optimization

Abstract: This article proposes a fixed switching frequency predictive control method for neutral point clamped (NPC) single-phase PWM rectifier to achieve global optimization of the current during the entire switching cycle. Through the optimization of the switching sequence, a three-stage switching sequence that can control the midpoint potential balance is obtained. The extreme point, the initial point, and the end point of the current error within the switching period are employed to establish an error matrix, and the error matrix l 2-norm minimality is considered as the optimization objective. This optimization problem is a convex optimization problem, and the optimal duty cycle of the switching sequence can be obtained by solving the convex problem. The optimal duty cycle of each feasible switching sequence is obtained, and then the switching sequence that minimizes the error matrix l 2-norm is selected as the system output among all feasible switching sequences. Finally, the experimental results show that the proposed control scheme has good performance.

The PWM rectifier with LCL filter direct power control based on power damping feedback

Abstract: Based on the topology and mathematical model of the three-phase voltage source PWM rectifier with LCL filter, the resonance produced by the LCL filter and the design method of filter parameters is analyzed. For the resonance problem of the LCL filter, a direct power control strategy of the LCL PWM rectifier based on power damping feedback is proposed. The double-loop control structure is constructed for the inner loop power and outer loop current. The virtual voltage source is constructed as equivalent to power damping in the power loop. The power loop of the output is adopted as a command value in the input current loop, and the current loop is designed to use deadbeat control to ensure the accuracy of current tracking. SVPWM is introduced in this novel direct power control method to generate PWM signals to drive the rectifier power switch and achieve a fixed switching frequency. The experimental results show that this proposed control method can achieve the unit power factor operation of the rectifier while it’s suppressing the resonance, and the system has a better dynamic and static performance.

Variable Pulse Density Modulation for Induction Heating

Abstract: Induction heating enables the conversion of electrical energy to thermal energy with a fast, high conversion efficiency and the ability to partially heat be used in a wide variety of welding industries. Conventional diode/SCR rectifiers and mid-frequency/high-frequency resonant inverters used to power conventional induction heaters will have low efficiency, low input power factor, high THD input current. Recently, a research has been done on a current fed three phase-three switch PWM rectifier, producing high power factor but also high current THD. The paper proposes a voltage fed three phase-three switch PWM rectifier with simple structure and control to achieve high power factor and lower current THD. A new variable pulse density modulation without online calculation has been proposed. The preliminary simulation and experimental results verify the feasibility and efficiency of the proposed configuration.

The Online Stator Winding Insulation Monitoring for PMSG-PWM rectifier System under Various Working Conditions

Abstract: The permanent magnet synchronous generator (PMSG) connected to pulse width modulation (PWM) rectifier is widely used in the renewable energy applications, such as direct–drive wind turbines and marine current turbines. The reliability of the PMSG is crucial due to the high maintenance cost of the turbines. The stator winding insulation is one of the main reasons for the PMSG failures. However, the current technologies can only detect the insulation failure when the short-circuit failure has already happened, which cannot avoid the corresponding downtime losses. Therefore, the online monitoring method for stator winding insulation is performed on the PMSG-PWM rectifier system in this paper for the first time. The factors affecting the voltage harmonics on the stator winding insulation are studied and their effects on the monitoring results are analyzed. Based on the flow path of the insulation leakage current and the phase-to-ground voltage, the insulation impedance can be measured online. The effects of the rotor position and the working condition are also analyzed. The effectiveness of the online condition monitoring method for PMSG-PWM rectifier system under various working conditions is verified using offline and online tests.

Lyapunov Function Based Flux and Speed Observer Using Advanced Non-linear Backstepping DVC for PWM-Rectifier Connected Wind-turbine-driven PM Generator

Abstract: In this paper, modeling, and speed/position sensor-less designed Direct Voltage Control (DVC) approach based on the Lyapunov function are studied for three-phase voltage source Space Vector Pulse Width Modulation (SVPWM) Rectifier Connected to a Permanent Magnet Synchronous Generator (PMSG) Variable Speed Wind Power Generation System (VS-WPGS). This control strategy is based on voltage orientation technique without mechanical speed sensor. Advanced Non-linear Integral Backstepping Control (IBSC) of the Generator Side Converter (GSC) has the ability to have a good regulation of the DC link voltage to meet the requirements necessary to achieve optimal system operation, regardless of the disturbances caused by the characteristics of the drive train or some changes into the DC load. The estimation of the speed is based on Model Reference Adaptive System (MRAS) method. This method consists in developing two models one of reference and the other adjustable for the estimation of the two d-q axis components of the stator flux from the measurement of currents, the speed estimated is obtained by canceling the difference between the reference stator flux and the adjustable one using Lyapunov criterion of hyper-stability. Some results of simulation using Matlab/Simulink® are presented, discussed to prove the efficiency and robustness of the system control policy for WPGS against external and internal perturbations.

An Improved Model-Free Finite Control Set Predictive Power Control for PWM Rectifiers

Abstract: The performance of conventional finite control set predictive control (FCSPC) is deteriorated when model parameters are not accurately known. To improve the robustness against model mismatches, model-free FCSPC (MF-FCSPC), which relies on only sensored information, has been proposed in the existing literature. However, the prior MF-FCSPC suffers from random power spikes and higher current distortions. In this paper, a MF-FCSPC based on an enhanced mechanism for storing and updating current difference is proposed, which shows strong robustness as that of the prior MF-FCSPC but still maintaining good performance as like a well-tuned FCSPC. To verify the effectiveness of the developed method, several simulation and experimental tests were carried out on a two-level PWM rectifier platform. The obtained results confirm the feasibility and superiority of the proposed MF-FCSPC when compared with the conventional FCSPC and prior MF-FCSPC.

Application of Model Compensated Active Disturbance Rejection Control in Electric Vehicle Charging

Abstract: The DC bus voltage is often affected by grid voltage fluctuations and load changes when Electric Vehicles(EV) are connected to the grid to charge. Taking the PWM rectifier of EV charging system as the research object, apply the Linear Active Disturbance Rejection Controller(LADRC) to the DC link. In order to optimize the performance of LADRC and improve the disturbance estimation accuracy of the linear extended state observer, this paper proposes a Model-Compensated Linear Active Disturbance Rejection Control(MC-LADRC) strategy. This strategy uses some known disturbances for feedforward compensation, which reduces the observation pressure of Linear Extended State Observer(LESO). Firstly this paper derives the mathematical model of MC-LADRC, and then analyzes the control performance of the strategy in the frequency domain. Finally, the control strategy is applied to the charging system, and the dynamic and steady-state performance of the DC side is simulated and verified.

Research and Design of Three-Stage Power Electronic Transformer

Abstract: With the development of smart grid and the advancement of renewable resource utilization technology, power electronic transformers have become an important energy conversion devices. Only AC ports are existed in traditional transformers. But power electronic transformers take into account both DC and AC ports, and have the advantage of facilitating the access of renewable energy compared with traditional AC systems. A three-stage power electronic transformer is proposed, which is composed of a three-phase PWM rectifier, a DAB DC-DC converter, and a three-phase inverter. And using the simulation platform based on MATLAB-SIMULINK to simulate and verify the proposed three-stage power electronic transformer. The verification results show that the power electronic transformer realizes the operation of unity-power factor on the grid side, the output voltage is controllable and it can be connected to the DC port.

Voltage Control of Multiphase Cage Induction Generators at a Speed Varying over a Wide Range

Abstract: The subject of this publication is a method of controlling the DC voltage of a PWM rectifier supplied by a multiphase cage induction generator with the number of stator phases greater than three operating in a wide range of driving speeds. Voltage regulation is performed by changing the frequency and amplitude of the stator voltages with simultaneous switching of the phase sequence of these voltages. The step change of the voltage sequence is made in the designated ranges of the generator speed, which enables the stabilization of the output voltage in a wide range from the minimum speed of about 25% of the rated speed. Such sequence switching changes the number of pole pairs produced by the winding for each supply sequence. The difference compared to multi-speed induction machines is that, in the presented solution, there is only one winding, not a few, which enables good use of the machine’s magnetic core in the same dimensions as for the three-phase machine of a similar power. Steady-state characteristics and dynamic operation were obtained using laboratory measurements of a standalone nine-phase induction generator. The automatic control system maintained the output voltage at the set level, regardless of the generator load and driving power.

PWM rectifier impedance modelling and analysis

Abstract: PWM rectifiers are widely used in the field of new energy power generation. The study of small signal impedance modeling of PWM rectifier is helpful to analyze the stability of new energy grid connected impedance. In this paper, the small-signal impedance model of the PWM rectifier is first established, and then the impedance model of the PWM rectifier is scanned through MATLAB using the impedance sweep method, and compared with the analytical expressions in this paper, the accuracy of the impedance model of PWM rectifier established in this paper is verified.

Islanding detection in microgrid using ai techniques and supervised classifiers

Abstract: A well-organized micro grid based hybrid renewable energy resources (HRES) with islanding detection is presented in this paper. HRES includes solar panel, wind energy conversion system (WECS) with DFIG and battery system which are controlled individually. As the outcome of PV is not constant, Adaptive neuro fuzzy inference system (ANFIS) based MPPT is executed to control the SEPIC converter. For WECS with DFIG, AC-DC conversion takes place with the aid of PWM rectifier and the control of rectifier is carried out with a PI controller. The Artificial-Neural-Network (ANN) is utilized to estimate the State of Charge (SOC) of the battery. Islanding is a major issue in distributed generation (DG) and this is detected by Convolutional Neural Network (CNN) classifier which is more accurate and faster. The proposed methodology is verified through simulation in MATLAB and it is observed that the source current THD of 4.72% is attained, while the islanding is detected in 0.8ms.