Single-phase Pulse Width Modulation Rectifier Research Articles

Disturbance Decoupling for a Single-Phase Pulse Width Modulation Rectifier Based on an Extended H-Infinity Filter

The growing utilization of single-phase pulse width modulation (PWM) rectifiers in various applications has spurred interest in detecting and monitoring faults in these devices. In particular, voltage and current sensors play a crucial role in the control loop of these rectifiers. However, sensor faults can significantly affect the converter’s performance and availability. This paper introduces a novel and efficient method for detecting and decoupling sensor faults in single-phase PWM rectifiers. The proposed method utilizes residual generation and incorporates an extended filter within the rectifier. Unlike conventional filters, the presented fault detection and isolation (FDI) method effectively eliminates the influence of disturbances on the residual signal. This feature helps prevent false alarms in the monitored system, ensuring reliable fault detection. To evaluate the effectiveness of the approach, hardware-in-the-loop and simulation tests were conducted. The results from these tests provide substantial evidence supporting the efficacy of the proposed method. The hardware-in-the-loop experiments involved real-world implementation, validating the practicality and reliability of the approach. Meanwhile, simulation tests allowed for a comprehensive analysis of system behavior and performance under various fault scenarios. The findings demonstrate the rapid and dependable nature of the proposed method for detecting and decoupling sensor faults in single-phase PWM rectifiers. By effectively mitigating the impact of disturbances on the residual signal, false alarms are minimized, ensuring accurate fault detection. The experimental validation highlights the practical applicability and effectiveness of the proposed approach, making it a valuable contribution to fault detection in single-phase PWM rectifiers.

Low-Frequency Oscillation Analysis in Train-Traction Power Supply System Using an SISO Voltage Loop Model

Low-frequency oscillation (LFO) in the train-grid coupling system severely endangers the stability and safety of railway operation. It is well known that this phenomenon is caused by impedance mismatch among the trains and the traction power supply system (TPSS). A novel voltage loop model of the single-phase pulsewidth modulation rectifier is proposed in this article. Unlike the commonly adopted multi-input multi-output (MIMO) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$q$ </tex-math></inline-formula> impedance model in the literature, this is a single-input single-output (SISO) model that enjoys some advantages, such as easier calculation of the system poles and quantitative analysis of the stability margin. The most attractive character of this model in comparison to the MIMO one is perhaps the decoupling of the controller and the voltage loop. This paves the way toward the analytical design of the dc-link voltage controller (DVC), whereas the impedance model is mainly useful for analysis. Furthermore, the maximum amount of trains allowed for keeping stability is derived from the steady-state equation. Robust stability margin (RSM) and sensitivity analysis are adopted to quantitatively investigate the influence of the control parameters and the circuit element parameters. LFO is guaranteed to be eliminated permanently by adjusting the controller parameters.

A New Technique for Online Open Switch Fault Detection and Location in Single-phase Pulse Width Modulation Rectifier

A New Technique for Online Open Switch Fault Detection and Location in Single-phase Pulse Width Modulation Rectifier

Robust current control scheme for single‐phase PWM rectifiers based on improved μ ‐synthesis in electric locomotive

The parameter perturbation of grid-side equivalent inductance is a significant feature of the uncertainty in the single-phase pulse-width modulation rectifiers system for the electric locomotive. This characteristic tends to reduce the robustness of the rectifier system. This study handles these problems in the framework of the structured singular value, which helps to reduce the influence of model parameter perturbation, caused by measurement error and operation condition change, on the robustness. However, the conventional μ-synthesis robust controls only reflect tracking and anti-disturbance performance by weighting functions and ignoring the dynamic response performance. Herein, a direct current control (DCC) scheme based on improved μ-synthesis is proposed. A desired closed-loop transfer function is introduced to the conventional μ-synthesis control structure to ameliorate the performance of the dynamic response. Furthermore, considering the external disturbances on the system control output, a suitable weighting function is used to restrict the external disturbance. The input–output relationship of the generalised open-loop plant can thus be constructed accordingly. The proposed control scheme is compared with the widely applied proportional–integral-based DCC scheme and the conventional μ-synthesis DCC scheme. Hardware-in-the-loop experiment results show promising dynamic performance as well as stronger robustness against parameter perturbation and external disturbances.

Optimized Switching Finite Control Set Model Predictive Control of NPC Single-Phase Three-Level Rectifiers

A new model predictive control scheme, optimized switching finite control set model predictive control, is studied in this article for neutral-point-clamped (NPC) single-phase three-level pulsewidth modulation (PWM) rectifiers. To ensure the actual stability of the power converter, the ac-side current error of single-phase PWM rectifier and the neutral point voltage of the converter are both converged to the bounded invariant set, and the adjustment of system performance is thus realized by setting the bounded invariant set. Based on the NPC single-phase three-level PWM rectifier model, the ac-side current, the neutral point voltage, and the current error in the future time can be predicted in advance. The above objectives are achieved by optimizing the selection of switch combinations. The advantage of the proposed method is that it can reduce the average switching frequency of the converter when the ac-side current error and the neutral point voltage of the converter are controlled within a certain range, which makes it suitable for the application of high-power single-phase PWM rectifier.

A new pulsating power elimination method based on ANFIS and PR control structures applicable for single-phase PWM rectifiers

In the input power of single-phase Pulse Width Modulation (PWM) rectifiers there is a pulsating portion with twice the grid frequency. To prevent the transferring of pulsating power to the DC side, it should be filtered properly. A convenient method is to install a high-capacitance capacitor at the DC side which cannot be an appropriate solution due to its undesirable characteristics. This paper proposes an active method for eliminating the pulsating power in which the control system is based on Adaptive Network-based Fuzzy Inference System (ANFIS) architecture. To improve the controller performance, an online supervisory learning algorithm based on the Error Back Propagation (EBP) learning method is employed. This approach leads to a control system with minimal structure, enhanced accuracy and improved dynamics. Also, a Proportional Resonant (PR) controller is proposed and the results of two controllers are compared with each other and with one of the most outstanding previous works. Moreover, a superseded control method based on ANFIS architecture for the conventional control system of single-phase PWM rectifiers is suggested. The proposed methods’ efficiency are confirmed by extensive simulations in MATLAB/Simulink.

Simple and effective open switch fault diagnosis of single-phase PWM rectifier

In order to obtain lower harmonics distortion and higher power factors, single-phase pulse-width modulation (PWM) rectifiers are adopted in AC railway drive systems. Therefore, its reliability is of most importance with regard to the safe operation of the train. In this paper, a fault diagnosis method for open switch fault in single-phase PWM rectifier is proposed based on the switching system theory. It requires no additional sensor, nor extra operation states need to be set. Four observers which correspond to four kinds of open switch faults are utilized to detect and locate the faults. Real-time simulations are carried out to validate the effectiveness of this method.

Low-Frequency Oscillation Analysis of the Train-Grid System Based on an Improved Forbidden-Region Criterion

With the increasing number of electric locomotives and electric multiple units (EMU) operating in one power section simultaneously, low-frequency oscillation (LFO) may occur. LFO may cause serious railway accidents, which will dramatically influence the stable operation of the power system. In this paper, LFO is solved by establishing a simplified mathematical model of the generalized EMU and a dq-decoupled small-signal model of the single-phase pulsewidth modulation rectifier. Then, an improved forbidden-region criterion (IFRC) is proposed to analyze the stability of the train-grid system and a comparison of the classical criteria is listed to show the advantages of the IFRC. The proposed criterion has less conservatism and higher accuracy than the forbidden-region-based criterion, which has better performance than the classical criteria. Moreover, the analysis result is successfully reproduced by establishing the time-domain simulation model in MATLAB/Simulink and RT-LAB, which verifies the effectiveness and accuracy of the proposed criterion. Finally, the development of IFRC shows the influence of gird parameters, traction parameters, and control parameters of the train-grid system. Ten ways to suppress the LFO are provided according to the simulation results.

Sensor Fault Diagnosis and System Reconfiguration Approach for an Electric Traction PWM Rectifier Based on Sliding Mode Observer

Single-phase pulse-width modulation (PWM) rectifier is commonly used in a high-speed railway electric traction system. Occurrence of unexpected failure in the sensors of the detection system may lead to feedback values deviation and system degradation, which can be extremely detrimental to the operation safety of the electric locomotive. This paper presents a fast and reliable fault diagnosis and fault resilient control strategy for catenary current and dc-link voltage sensor faults in the control system for an electric traction single-phase PWM rectifier. Sliding mode observers are designed to produce analytical redundancy. In order to avoid unobservable states and fluctuation introduced by discrete dynamics in observer design, a novel description for switching variables is presented in system modeling. Normalized residuals are generated using measured and observed values. The fault diagnosis unit proposed can detect and isolate three types of sensor faults online by comparing residuals with thresholds. System reconfiguration is realized by substituting the observed values for the information of faulty sensors. Simulation and experimental results are demonstrated to validate the effectiveness of the strategy.

EMI and ground leakage current reduction in single‐phase grid‐connected power converter

Ground leakage current in a power converter is a major concern, which has stringent limitations due to safety concerns. Presence of high-frequency pulses, with high d v /d t due to switching actions in common-mode (CM) voltage, result in injection of current waveforms with large d i /d t spikes into the ground and causes high electromagnetic interference (EMI) noise level. In this study, a new method is proposed to make the CM voltage, of a single-phase grid-connected inverter, sinusoidal and free of high-frequency pulses. The proposed method consists of two parallel connected H-bridge power converters, which uses unipolar pulse width modulation (PWM) with carrier interleaving angle of 180°. The proposed method reduces the ground leakage current by more than an order of magnitude. A novel modification to the LCL filter is proposed which further reduces the leakage current by 48%. It is shown that these modifications make the overall system insensitive to circuit non-idealities. Experimental results based on ground leakage current measurements on a 7.5 kW parallel single-phase PWM rectifier are presented. These results validate the effectiveness of the proposed method.

Vehicle-Grid System Modeling and Stability Analysis With Forbidden Region-Based Criterion

The voltage low frequency oscillation (LFO), between traction network and electric locomotives or electric multiple units in high speed railway, is a typical phenomenon happening in cascade systems with power electronic converters accessed, which is regarded as the stability problem of a vehicle-grid (V2G) system in general. To address the problem, the mathematical model of the V2G system is deduced in detail first, and a generalized dq -decoupled small-signal model of a single-phase pulse width modulation rectifier is established in this process. Then, a novel stability criterion based on forbidden region for dq-decoupled multi-input multi-output cascade systems is proposed to analyze the stability of the V2G system. The proposed criterion has less conservatism than singular-value criteria and norm criteria, and can be applied for systems with either high or low power factor. The comparison with other criteria and simulation results verifies that the proposed forbidden region-based criterion performs well in the analysis of the critical condition of LFO. Moreover, the impact factors of LFO, both grid parameters and vehicle parameters, are researched based on the proposed stability analysis criterion and the simulation verification, which provides design guidance for the V2G system to restrain LFO.

An Open-Switch Fault Diagnosis Method for Single-Phase PWM Rectifier Using a Model-Based Approach in High-Speed Railway Electrical Traction Drive System

The converter with a single-phase rectifier, a dc-link circuit and a three-phase inverter is widely applied in high-speed railway electrical traction drive system. The fault frequency of single-phase rectifier is higher than that of three-phase inverter. Thus, this paper presents a new and fast model-based approach for open-switch fault diagnosis of the single-phase pulse width modulation rectifier, based on the mixed logical dynamic model and residual generation. It requires no additional hardware but only some measurements and command signals which are available in control system. This diagnosis method is quite suitable for electrical traction application due to the fast diagnosis time, simple structure and high reliability. Experimental results confirm the effectiveness and accuracy of the proposed algorithm. It is shown that such diagnosis method can locate the faulty switch in a few milliseconds which is important to avoid catastrophic consequences.

Repetitive control‐based single‐phase bidirectional rectifier with enhanced performance

In this study, a single-phase pulse-width modulation rectifier with regenerative capability has been presented. Here, the main purpose is to achieve unity power factor with least harmonics on AC-side source current while having regulated DC voltage at output. It is very difficult to achieve aforementioned goals with commonly used proportional-integral (PI) regulators due to their limited control bandwidth, especially under rapidly varying input AC and dynamic load conditions. The disturbances on DC side are mainly due to double frequency ripple components, which are periodic in nature and are very much prominent in single-phase rectification. The problem may be further exaggerated due to the presence of periodic noise/disturbances in input AC supply. Hence, a repetitive controller (RC) is designed, which is well known for its capabilities in tracking periodic disturbances. The systematic design and modelling of stable RC controller based on internal model principle theory has been presented. The proposed control technique has been developed and simulated in MATLAB/SimPower System. The experimental results have been presented and analysed in detail to validate the performance of the proposed RC control technique in comparison with its PI counterpart.

A Straightforward Procedure to Select Passive Elements in Single-phase Pulse-width Modulation Rectifiers with Developed Resonant Current Controller

With increasing DC loads, single-phase pulse-width modulation rectifiers have been used widely. In this article, based on a mathematical model and equations of a system, a new straightforward procedure is developed to calculate input filter inductance and output filter capacitance values. To avoid filter overdesign, which results in higher cost and size, this procedure is useful and helps design engineers to select the filter passive elements values properly and simply. The proposed procedure is subjected to set inductor current and capacitor voltage ripple at their acceptable range. Moreover, an improved current controller based on a proportional-resonant controller is developed. This controller can remove specific input current harmonic components, which results in lower total harmonic distortion for input current. A 4-kW prototype is provided based on a digital signal processor (DSP)-based digital controller to support all of the theoretical analyses. Several simulations and experimental results verify the effectiveness of the developed current controller at both steady-state and dynamic conditions. Also, the results verify the validation of the developed procedure in maintaining the voltage and current ripple at their expected values.

Online open‐switch fault diagnosis method in single‐phase PWM rectifiers

On the basis of sampling theory, an online open-switch fault diagnosis and location method for single-phase pulse-width modulation rectifiers applied in electric railway traction is presented. First, on the basis of analysing the features of the post-fault line current under instantaneous current control strategy at low switching frequency, two specific pulse sequences for sampling line current are generated via the modulation. Then, the DC component of the sampled signal, which is easy to use for diagnostic decision, is obtained through filters. Experimental results are presented to illustrate the validity of the proposed scheme.

Active Power Decoupling for High-Power Single-Phase PWM Rectifiers

Single-phase pulsewidth modulation rectifiers suffer from ripple power pulsating at twice the line frequency. The ripple power is usually filtered by a bulky capacitor bank or an LC branch, resulting in lower power density. The alternative way is active power decoupling, which uses an active circuit to direct the pulsating power into another energy-storage component. The main dc-link filter capacitor can, therefore, be reduced substantially. This paper proposed a new scheme of active power decoupling. The circuit consists of a third leg, an energy-storage capacitor and a smoothing inductor. The topology combined the advantages of high energy-storage efficiency and low requirement on control bandwidth. Both the pulsating power from the ac source and the reactive power of the smoothing inductors are taken into consideration when deriving the power decoupling scheme. The active power filter's (APF) capacitor voltage control system consists of inner loop pole-placement control and outer loop proportional-resonant control. To enhance the steady-state performance, the capacitor voltage reference is modified in a closed-loop manner. Simulation and experimental results show that the proposed APF scheme has good power decoupling performance and is more suited for high-power applications where switching frequency is limited.

Repetitive Compensation of Fluctuating DC Link Voltage for Railway Traction Drives

AC-fed railway traction drives suffer from pulsating input power because of the single-phase pulse width modulation rectifier at the front end. An LC filter is often needed at the dc link to absorb the pulsating power. However, this greatly reduces the power density. An effective way to get rid of this clumsy filter is to compensate pulse width calculation of the traction inverter so that it does not produce harmful subharmonics (beat components) in the output voltage/current even with a fluctuating dc link. For limited switching frequency at high power level, it is difficult for conventional feed-forward compensation methods to achieve good results. A repetitive dc link voltage predictor is proposed in this paper to improve the compensation performance. It capitalizes on the repetitiveness of the dc link ripple and can predict the average value of the dc link voltage in the next switching period. An area-equalization-based algorithm is then used to calculate the required pulse width. Experiments show that compared with conventional methods, the proposed one can reduce the steady-state beat current by six to seven times. The dynamic beat current during load transients is also negligible when dynamic drop of the dc link voltage is kept below 10%.

A High Power Density Single-Phase PWM Rectifier With Active Ripple Energy Storage

It is well known that single-phase pulse width modulation rectifiers have second-order harmonic currents and corresponding ripple voltages on the dc bus. The low-frequency harmonic current is normally filtered using a bulk capacitor in the bus, which results in low power density. However, pursuing high power density in converter design is a very important goal in the aerospace applications. This paper studies methods for reducing the energy storage capacitor for single-phase rectifiers. The minimum ripple energy storage requirement is derived independently of a specific topology. Based on the minimum ripple energy requirement, the feasibility of the active capacitor's reduction schemes is verified. Then, we propose a bidirectional buck-boost converter as the ripple energy storage circuit, which can effectively reduce the energy storage capacitance. The analysis and design are validated by simulation and experimental results.

Input Current Harmonics in a Regenerative Multicell Inverter With Single-Phase PWM Rectifiers

Harmonics are a very important issue in the design and operation of medium-voltage inverter drives, due to restrictions imposed by regulations. This paper studies the harmonics generated by a three-phase multicell cascade inverter, with single-phase pulsewidth modulation rectifiers at the input side of each cell; thus, the entire topology is able to regenerate power to the net. This paper identifies accurately the harmonic generation process in the dc-link voltage, the input current of each cell, and, therefore, at the input side of the inverter. Moreover, this paper proposes a method to reduce and, in some cases, eliminate the input current harmonics, reaching a very high input power factor for any operation condition. Simulation and experimental results are provided to validate the theoretical analysis.

Input Current Harmonics in a Regenerative Multicell Inverter With Single-Phase PWM Rectifiers

Harmonics are a very important issue in the design and operation of medium-voltage inverter drives, due to restrictions imposed by regulations. This paper studies the harmonics generated by a three-phase multicell cascade inverter, with single-phase pulsewidth modulation rectifiers at the input side of each cell; thus, the entire topology is able to regenerate power to the net. This paper identifies accurately the harmonic generation process in the dc-link voltage, the input current of each cell, and, therefore, at the input side of the inverter. Moreover, this paper proposes a method to reduce and, in some cases, eliminate the input current harmonics, reaching a very high input power factor for any operation condition. Simulation and experimental results are provided to validate the theoretical analysis.