Three-phase Pulse Width Modulation Rectifier Research Articles

Design and Implementation of Robust H∞ Control for Improving Disturbance Rejection of Grid-Connected Three-Phase PWM Rectifiers

In response to the high performance requirements of pulse width modulation (PWM) converters in grid-connected power systems, H-Infinity (H∞) control has attracted significant research interest due to its robustness against parameter variations and external disturbances. In this work, an advanced robust H∞ control is proposed for a grid-connected three-phase PWM rectifier. A two-level control strategy is adopted, where cascaded H∞ controllers are designed to simultaneously regulate the DC bus voltage and input currents even under load disturbances and non-ideal grid conditions. As a result, unit power factor, stable DC bus voltage, and sinusoidal input currents with lower harmonics can be accurately achieved. The design methodology and stability of the proposed controller are verified through a comprehensive analysis. Simulation tests and experimental implementation on a dSPACE 1103 board demonstrate that the proposed control scheme can effectively enhance disturbance rejection performance under various operating conditions.

Finite-Time Adaptive Fuzzy Control for Three-Phase PWM Rectifiers With Improved Output Performance

For three-phase pulse width modulation (PWM) rectifiers, system uncertainties, such as load disturbances, parametric uncertainties, and grid disturbances, may result in significant DC-link voltage fluctuations, degrade the quality of grid currents, and even lead to system instability. To address this issue, a modified dynamic model of the PWM rectifier with system uncertainties is established, and a finite-time adaptive fuzzy control (FTAFC) method with the dual-loop structure is proposed. In the outer voltage loop, a finite-time adaptive law is used to maintain stable DC-link voltages despite load disturbances. In the inner power loop, an adaptive fuzzy technique is used to estimate and compensate system uncertainties, thus ensuring finite-time power tracking. It is confirmed that all signals of the closed-loop system are finite-time bounded. The experimental and simulation results demonstrate the effectiveness of the proposed method.

Sliding mode approach for control and observation of a three phase AC-DC pulse-width modulation rectifier

Introduction. For AC-DC conversion systems, the electrical systems typically use thyristor or diode bridge rectifiers, which have relatively poor performance. Nowadays, three-phase pulse-width modulation rectifiers are widely applied in various applications for their well-known intrinsic benefits, such as adjustable DC link voltage, unity power factor, bidirectional power flow and very low total harmonic distortion. Purpose. The objective of this work is to achieve better stability and dynamic performance using sliding mode strategy for control and observation. Methods. For that purpose, first a sliding mode controller is introduced on the DC-link side to ensure a fast and accurate response of the output load voltage. Then, the sliding mode approach is employed to control the quadrature and direct components of power to maintain the input power factor at unity. Finally, this approach is used to design two observers for grid voltage estimation and online variation of load resistance. To overcome the problem associated with the use of the classical low-pass filter, an adaptive compensation algorithm is used to compensate the attenuation of the amplitude and phase delay of the observed grid voltages. This algorithm is based on the use of the two low-pass filters in cascade and ensures the minimization of chattering. Results. Comparative studies have been carried out between sliding mode control method for controlling the three-phase AC-DC pulse-width modulation rectifier and other conventional techniques. The validation by simulation and the tests carried out gave very satisfactory results and proved the effectiveness and feasibility of the sliding mode for both control and observation of three phase pulse-width modulation rectifier.

Advanced Control of Three-Phase PWM Rectifier Using Interval Type-2 Fuzzy Neural Network Optimized by Modified Golden Sine Algorithm

Three-phase Pulse-Width Modulated (PWM) rectifiers used between the power grid and the load in applications requiring DC voltage have features such as high efficiency, high power factor, and low harmonics. This paper proposes a hybrid control approach to improve the dynamic performance of three-phase PWM rectifiers under different operating conditions. Operating conditions are considered as step response, internal disturbance, and regenerative operation. First, Interval Type-2 Fuzzy Neural Network (IT2FNN) is designed and then antecedent and consequent parameters of IT2FNN are optimized with Modified Golden Sine Algorithm (GoldSA-II). The dynamic performance of the hybrid controller, named GoldSA-II-IT2FNN, is analyzed for all operating conditions in Matlab/Simulink environment. The simulation studies are realized to evaluate the performance of the proposed controller. In the simulations, settling times of proposed controller are observed as 27.2 ms, and 10.8 ms for step response, respectively. Moreover, recovery times are calculated as being 12 ms to 5.5 ms for internal disturbance, and 7.2 ms to 19 ms for regenerative operation, respectively. The obtained results demonstrate that the proposed controller not only provides better dynamic performance but also improves the stability of PWM rectifier.

Generalized Clarke Transformation and Enhanced Dual-Loop Control Scheme for Three-Phase PWM Converters Under the Unbalanced Utility Grid

Three-phase grids imbalance causes serious alternating input current distortion in three-phase pulsewidth modulation (PWM) rectifiers where the conventional control scheme is employed. In this article, a generalized Clarke transformation is proposed to convert three-phase unbalanced sinusoidal quantities to two orthogonal sinusoidal quantities with equal amplitudes. Then, these two orthogonal sinusoidal quantities could be converted to two direct quantities by the Park transformation. Furthermore, based on the generalized Clarke transformation, an enhanced dual-loop control (EDLC) scheme is proposed to control the three-phase PWM rectifier in the synchronous rotating frame. Finally, a 5-kW Vienna-type rectifier prototype was built to verify the proposed generalized Clarke transformation and the proposed EDLC control scheme. Experimental results show that, by using the proposed EDLC scheme, the low current total harmonic distortion is achieved even both the amplitude and phase of the utility grid voltages are unbalanced.

Performance of Neutral Point Clamped Five Level Inverter Using Space Vector Modulation Control Fed by DPC-VF-SVM Rectifier

The purpose of this paper is to develop a control and regulation method for the input DC voltage of a five level neutral point clamping (NPC) inverter feeding a induction motor. In this context, the authors propose in the first part, the control strategy of three-phase pulse width modulation rectifier, they propose the virtual flux-based direct control (DPC_VF) with vector modulation (SVM), this method is applied for the enhancement of network power quality by compensation of harmonic currents produced by an non linear load, and good regulation of DC-bus voltage. The second part of the paper is dedicated to the presentation of the model of the three phase, five-level NPC voltage source inverter with its space vector modulation (SVM) control method. The performance of the proposed strategy in terms of out-put voltage and THD has studied successfully and shown using MATLAB/Simulink.

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

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.

Implementation on the dSPACE 1104 of VOC-SVM based anti-windup PI Controller of a three-phase PWM rectifier

<p><span>The study made in this paper concerns the use of the voltage-oriented control (VOC) of three-phase pulse width modulation (PWM) rectifier with constant switching frequency. This control method, called voltage-oriented controlwith space vector modulation (VOC-SVM). The proposed control scheme has been founded on the transformation between stationary (α-β) and and synchronously rotating (d-q) coordinate system, it is based on two cascaded control loops so that a fast inner loop controls the grid current and an external loop DC-link voltage, while the DC-bus voltage is maintained at the desired level and ansured the unity power factor operation. So, the stable state performance and robustness against the load’s disturbance of PWM rectifiers are boths improved. The proposed scheme has been implemented and simulated in MATLAB/Simulink environment. The control system of the VOC-SVM strategy has been built based on dSPACE system with DS1104 controller board. The results obtained show the validity of the model and its control method. Compared with the conventional SPWM method, the VOC-SVM ensures high performance and fast transient response.</span></p>

Data‐driven design of fault diagnosis for three‐phase PWM rectifier using random forests technique with transient synthetic features

A three-phase pulse-width modulation (PWM) rectifier can usually maintain operation when open-circuit faults occur in insulated-gate bipolar transistors (IGBTs), which will lead the system to be unstable and unsafe. Aiming at this problem, based on random forests with transient synthetic features, a data-driven online fault diagnosis method is proposed to locate the open-circuit faults of IGBTs timely and effectively in this study. Firstly, by analysing the open-circuit fault features of IGBTs in the three-phase PWM rectifier, it is found that the occurrence of the fault features is related to the fault location and time, and the fault features do not always appear immediately with the occurrence of the fault. Secondly, different data-driven fault diagnosis methods are compared and evaluated, the performance of random forests algorithm is better than that of support vector machine or artificial neural networks. Meanwhile, the accuracy of fault diagnosis classifier trained by transient synthetic features is higher than that trained by original features. Also, the random forests fault diagnosis classifier trained by multiplicative features is the best with fault diagnosis accuracy can reach 98.32%. Finally, the online fault diagnosis experiments are carried out and the results demonstrate the effectiveness of the proposed method, which can accurately locate the open-circuit faults in IGBTs while ensuring system safety.

DC-link voltage control of three-phase PWM rectifier by using artificial bee colony based type-2 fuzzy neural network

The pulse width modulation (PWM) rectifiers are nonlinear systems due to semiconductor switches in their structure. Therefore, these rectifiers draw a distorted current from AC supply. Many different improvements have been proposed to overcome problems caused by PWM rectifiers. In this paper, DC-link voltage of three-phase PWM rectifier is regulated by using a Type-2 Fuzzy Neural Network (T2FNN) controller that parameters are optimized by using Artificial Bee Colony (ABC) optimization method. The parameters in antecedent and consequent parts of T2FNN are optimized by ABC optimization method. The performance of ABC-T2FNN controller is analyzed under different operating conditions through simulation model based on MATLAB. The operating conditions are considered as constant input, set point, a step DC load change, unbalanced AC supply and regenerative mode. The simulation results obtained from the proposed controller are verified by comparing with the results of the classical T2FNN. When the results of PWM rectifiers are investigated, it is seen that PWM rectifier based on the proposed controller has better dynamic response for all operating conditions than conventional T2FNN controller.

Fix-frequency robust power model predictive control method for three-phase PWM rectifiers under unbalanced grid conditions

Under unbalanced grid conditions, the controller design of a three-phase pulse width modulation (PWM) rectifier is based on an instantaneous power model. By calculating the current references of the converter according to the instantaneous power model, traditional voltage-oriented control (VOC) methods realize the positive-sequence and negative-sequence active and reactive current control of the converter separately using the proportional-integral (PI) controller. However, due to the inner current loop control structure of the traditional VOC method, it is impossible to realize the regulation of all six power components in a common instantaneous power model under an unbalanced grid. Meanwhile, the control performance of the traditional VOC method with a PI controller is degraded under the circuit parameters uncertainty condition. In this paper, a fixed switching frequency robust power model predictive control method (FRP-MPC) is proposed for three-phase PWM rectifiers under the unbalanced grid condition. The proposed control strategy has a number of advantages. An improved instantaneous power model is used for the fixed switching frequency model predictive controller design under the unbalanced grid condition, which has less power variables than the common instantaneous power model. The robustness of the MPC controller is improved by adding a robust item into the predictive model under circuit parameters uncertainty. Simulation and experiment results verify the effectiveness of the proposed control method.

Linear Active Disturbance Rejection Control for Three-Phase Voltage-Source PWM Rectifier

Three-phase voltage-source pulse width modulation (PWM) rectifier has been widely employed in various industrial applications. For the traditional dual-loop PI control of three-phase voltage-source PWM rectifier, the voltage loop and current loop have poor disturbance rejection performance and long response time. A linear active disturbance rejection control (LADRC) strategy is proposed for three-phase voltage-source PWM rectifier in this paper. The coupling variable and external disturbance in the model of PWM rectifier are observed and compensated by linear extended state observer (LESO) in two-phase synchronous reference frame. The LADRC outer-voltage loop controller and LADRC inner-current loop controller of PWM rectifier are designed. The proposed control strategy is compared and verified with PI control and ADRC by MATLAB/Simulink. Simulation and experimental results confirm the superiority of proposed control strategy in dynamic performance and disturbance rejection.

Asymmetrical Cascaded Three-Phase AC–DC Converters With Injection Transformers

In this paper, three generalized configurations of three-phase pulsewidth modulated (PWM) rectifiers are presented. They are composed of cascaded cells, each formed by a three-phase bridge of switching devices and a three-phase transformer to cascade the cells and isolate the load from the power source. One configuration is bidirectional, whereas the other two are unidirectional alternatives that replace power switches for diodes in some legs. The turns ratios of transformers from each cell are designed in order to provide the required gain and number of levels in the inverted multilevel voltage, enhancing power quality while attending requirements for proper operation in each case. Configurations with two and three cells are compared by means of simulations between themselves and with three conventional three-phase PWM rectifiers: the two-level insulated gate bipolar transistor bridge and the multilevel neutral point clamped (NPC) bridge and NPC H-bridge. Many degrees of asymmetry between the transformers in each cell, determined by the turns ratios, are considered to evaluate their impact on the topologies with relation to performance and cost. It is shown that proposed multilevel rectifiers present lower harmonic distortion, semiconductor losses, and switching stress, and some options with intermediate asymmetry are considered as good alternatives to the most asymmetrical cases. Experimental results are also provided for configurations with two cells, to demonstrate their lower harmonic distortion and power losses compared to the conventional isolated two-level PWM rectifier.

Three-Vector-Based Low-Complexity Model Predictive Direct Power Control Strategy for PWM Rectifier Without Voltage Sensors

A voltage sensorless control of low-complexity model predictive direct power control (LC-MPDPC) for pulsewidth modulation (PWM) rectifier is proposed. The conventional LC-MPDPC adopts one or two voltage vectors during one control period, which achieve good steady-state performance and quick dynamic response. In addition, based on the mathematical model of the real system, the conventional method only requires one prediction to find the optimal voltage vector, which reduces the control complexity and computational burden. However, the use of one or two vectors during one sampling interval presents abundant current harmonics and high power ripples, and the switching frequency is variable. In order to solve these problems while preserving all the advantages of the conventional LC-MPDPC, this paper presents a novel control scheme, with the aim of operating at a constant switching frequency and obtaining an excellent steady-state performance at a low switching frequency. The proposed method is based on an optimal application of three voltage vectors in a symmetrical way, which takes advantage of advanced PWM techniques. Furthermore, the virtual flux-based control scheme is introduced to achieve voltage sensorless control. The proposed strategy is compared with the conventional MPDPC methods and its effectiveness is confirmed by both simulation and experimental results from a three-phase PWM rectifier under 1000-W operation condition.

Adaptive neural networks for AC voltage sensorless control of three-phase PWM rectifiers

In this paper, a new adaptive grid voltages estimator for AC voltage sensorless control of three-phase pulse-width modulation (PWM) rectifier is proposed. This method is based on a simple adaptive neural network (ANN) to estimate online the grid voltages. Its main advantages are the simplicity and low computational cost requirements. The proposed ANN estimator is inserted in voltage-oriented control (VOC) to perform an AC voltage sensorless control scheme. As the start-up is a common problem in case of sensorless control, a new start-up process is also proposed for estimating initial values of the grid voltages. Experimental tests are carried out to verify the feasibility and robustness of the proposed ANN estimator. Obtained results show good performances of the proposed AC voltage sensorless control scheme in normal and severe grid voltage conditions.

A Novel Robust Model Predictive Controller for Aerospace Three-Phase PWM Rectifiers

This paper presents a novel Model Predictive Direct Power Control (MPDPC) approach for the pulse width modulation (PWM) rectifiers in the Aircraft Alternating Current Variable Frequency (ACVF) power system. The control performance of rectifiers may be largely affected by variations in the AC side impedance, especially for systems with limited power volume system. A novel idea for estimating the impedance variation based on the Bayesian estimation, using an algorithm embedded in MPDPC is presented in this paper. The input filter inductance and its equivalent series resistance (ESR) of PWM rectifiers are estimated in this algorithm by measuring the input current and input voltage in each cycle with the probability Bayesian estimation theory. This novel estimation method can overcome the shortcomings of traditional data based estimation methods such as least square estimation (LSE), which achieves poor estimation results with the small samples data set. In ACVF systems, the effect on the parameters estimation accuracy caused by the number of sampling points in one cycle is also analyzed in detail by simulation. The validity of this method is verified by the digital and Hard-in-loop simulation compared with other estimation methods such as the least square estimation method. The experimental testing results show that the proposed estimation algorithm can improve the robustness and the control performance of the MPDPC under the condition of the uncertainty of the AC side parameters of the three-phase PWM rectifiers in aircraft electrical power system.

Virtual Flux Direct Power Control for PWM Rectifiers Based on an Adaptive Sliding Mode Observer

In the traditional virtual flux estimation for a three-phase pulsewidth modulation rectifier, the integration element causes problems for the initial value and dc bias, and the unstable grid voltage induces a nonconstant flux amplitude. To address these issues, an improved direct power control scheme based on an adaptive sliding mode observer is proposed in this work. The observer employs a sigmoid function as switch function to estimate the grid-side source voltage. Meanwhile, an adaptive compensator instead of pure integral element is also designed to dynamically adjust compensation. The stability of this observer is proved by the Lyapunov function; moreover, simulations and experimental results indicate that this new virtual flux observer substantially improves the observation accuracy based on voltage sensorless control. The application of this strategy successfully suppresses the fluctuation of the dynamic voltage response in the dc bus, eliminating high-frequency noise from the grid side, while simultaneously boosting the power quality.

A Maximum Current Control Method for Three-Phase PWM Rectifier for the ITER In-Vessel Vertical Stability Coil Power Supply

The required peak current and peak voltage of ITER in-vessel vertical stability (VS) coil power supply are up to 80 kA and 2.4 kV, so VS coil power supply needs a pulse width modulation (PWM) rectifier to achieve high power factor operation under the highly transient power demand of the value of 144 MW. A new maximum current control method for three-phase voltage source PWM rectifier based on its mathematical model in $d$ – $q$ frame and improved by dual-closed-loop control method has been presented. This control method meets the fast power charging demand and the dc-side voltage stabilization demand of power supply, and achieves a unity or high power factor operation; its controller is easier to be designed and implemented than dual-closed-loop control at charging mode. The advantages and feasibility of this control method have been verified by simulation and experiment.

Grid Voltages Estimation for Three-Phase PWM Rectifiers Control Without AC Voltage Sensors

This paper proposes a new ac voltage sensorless control scheme for the three-phase pulse-width modulation rectifier. A new startup process to ensure a smooth starting of the system is also proposed. The sensorless control scheme uses an adaptive neural (AN) estimator inserted in voltage-oriented control to eliminate the grid voltage sensors. The developed AN estimator combines an AN network in series with an AN filter. The AN estimator structure leads to simple, accurate, and fast grid voltages estimation, and makes it ideal for low-cost digital signal processor implementation. Lyapunov-based stability and parameters tuning of the AN estimator are performed. Simulation and experimental tests are carried out to verify the feasibility and effectiveness of the AN estimator. Obtained results show that the proposed AN estimator presented faster convergence and better accuracy than the second-order generalized integrator-based estimator; the new startup procedure avoided the overcurrent and reduced the settling time; and the AN estimator presented high performances even under distorted and unbalanced grid voltages.

An Improved Control Strategy of Three-Phase PWM Rectifiers Under Input Voltage Distortions and DC-Offset Measurement Errors

This paper proposes an enhanced current control strategy to reject the impact of dc-offset measurement error and the distortion in the supply voltage on the dc output voltage and the input current performance of three-phase pulse-width modulation rectifiers. The proposed current controller designed in the synchronous reference frame is developed with a proportional integral (PI) and two vector PI (VPI) controllers. The PI controller regulates the fundamental current to follow its reference generated from outer dc-link voltage control, meanwhile two VPI controllers tuned at the fundamental grid frequency ( $\omega _{s}$ ) and $6\omega _{s}$ are employed to eliminate the dc and harmonic components in the input current. Compared with the standard resonant controllers, the proposed VPI controller offers some advantages such as simpler and straightforward tuning process for controller gains and more robust control system against control delay time and frequency variations. Thanks to the effectiveness of the VPI controllers, the dc output voltage is controlled at a stable manner without any ac ripple, and the three-phase input currents are controlled to be balanced, sinusoidal, and extremely low dc component despite the presence of the dc-offset measurement error and distorted supply voltage conditions. Various experimental tests are provided to verify the effectiveness of the proposed control algorithm.