PWM Rectifier Research Articles

Fault diagnosis for three-phase PWM rectifier based on deep feedforward network with transient synthetic features

Three-phase PWM rectifiers are adopted extensively in industry because of their excellent properties and potential advantages. However, while the IGBT has an open-circuit fault, the system does not crash suddenly, the performance will be reduced for instance voltages fluctuation and current harmonics. A fault diagnosis method based on deep feedforward network with transient synthetic features is proposed to reduce the dependence on the fault mathematical models in this paper, which mainly uses the transient phase current to train the deep feedforward network classifier. Firstly, the features of fault phase current are analyzed in this paper. Secondly, the historical fault data after feature synthesis is employed to train the deep feedforward network classifier, and the average fault diagnosis accuracy can reach 97.85% for transient synthetic fault data, the classifier trained by the transient synthetic features obtained more than 1% gain in performance compared with original transient features. Finally, the online fault diagnosis experiments show that the method can accurately locate the fault IGBTs, and the final diagnosis result is determined by multiple groups results, which has the ability to increase the accuracy and reliability of the diagnosis results.

Basic Comparison And Evaluation Of Functionality AC-AC Matrix Converter Concepts For HEV Vehicle - Part I

The paper deals with the direct AC-AC propulsion system and compares two matrix converter concepts with fivephase traction induction motors (IM) for the hybrid electric vehicle (HEV) including electronic differential. The first one consists of [3x5] matrix converter and [3x1] active PWM rectifier (4Q-converter) for full power performance. The second one comprises one [3x5] matrix converter for full power and auxiliary [0x5] matrix converter for partial output
 power. Configurations of [3x5] + [0x5] MxC converters with five-phase motor(s) are not analyzed in available literature so far. The advantage of the proposed connection is in supposed higher efficiency of matrix converter then clasiccal VSI one. Part I deals with a theoretical study of converter concepts for hybrid electric vehicle. Based on simulation results the comparison and evaluation of the property and quality of the quantities of different type of the matrix powertrain are discussed in Part II.

Holistic Control Approach for the Grid-Connected Converter of a Battery Energy Storage System

This paper introduces a holistic control approach applied to a grid-connected converter of a Battery Energy Storage System (BESS). The BESS is mainly used for power peak shaving, frequency supporting, and islanded operation mode which implies multiple control transitions depending on the operation mode. One existing challenge is related to the multiple tuning controllers for the grid-connected converter required for each operation mode, including the rectifier operation. Moreover, when the rectifier operation is running the system is naturally nonlinear which motivates the use of nonlinear controllers. From this standpoint, a strong motivation for this research is the seeking of a holistic control to face all the operation-mode changes seamlessly. Hence, the merit of the proposed holistic control approach consists of using a unique tuning process based on the linear technique of state feedback with integral action for all operation modes, which are: 1) grid-connected mode as an inverter, 2) grid-connected mode as a rectifier, and 3) islanded mode. Of special attention is the grid-connected mode as rectifier since the proposal avoids the introduction of the PWM rectifier model which increases the model order and is inherently nonlinear. A thorough analysis of eigenvalues in open loop and closed loop with the same tuning gains is presented to demonstrate the stability and feasibility of the proposal. An affordable tuning methodology is proposed considering the physical restrictions of the grid-connected converter related to the LCL-filter bandwidth and the switching frequency. To demonstrate the merits of the holistic control approach, several simulations are presented using PSCAD/EMTDC on a 100 kW, 480 V rated BESS using a delta-connected LCL filter for interconnecting with the grid. Simulation results show that the seamless capability with steady-state and transient state operation runs smoothly.

Single-Phase Five-Level Flying-Capacitor Rectifier Using Three Switches

In this paper, a unidirectional single-phase five-level PWM rectifier based on flying-capacitor topology operating as PFC is proposed. The main feature is the fact that the proposed converter has three active switches, therefore offering a cost reduction compared to traditional five-level topologies. The multilevel voltage operation reduces the weight and bulk of the magnetic devices. Moreover, 82% of the semiconductors are subject to one fourth to DC output voltage which allows the use of low voltage semiconductor devices. An extensive mathematical analysis, control-oriented modeling in addition to experimental results are presented in order to demonstrate the feasibility of the structure.

An Intelligent Fault Diagnosis Method for Open-Circuit Faults in Power-Electronics Energy Conversion System

Applying the fault diagnosis techniques to power electronic equipments is beneficial to improve the stability and reliability of renewable energy system, because power electronic equipments are a key component of renewable energy system that largely defines their performance. This paper presents a novel intelligent fault diagnosis method for a three-phase power-electronics energy conversion system based on knowledge-based and data-driven methods. Firstly, the three-phase AC currents of the power-electronics energy conversion system are collected and used to analyze. Secondly, the feature transformation, a knowledge-based method, is utilized to preprocess the fault data. After feature transformation, the slopes of current trajectories (transformed features) are not affected by different loads. And then random forests algorithms (RFs), a data-driven method, are adopted to train the fault diagnosis classifier with the processed fault data. Finally, the proposed method is implemented online on an actual three-phase PWM rectifier platform. The results show that the proposed fault diagnosis method can successfully detect and locate the open-circuit faults in IGBTs of the three-phase PWM rectifier. In addition, the proposed method is suitable for most of three-phase power-electronics energy conversion systems.

A novel IGBT open-circuit protection method for three-phase PWM rectifier

A novel IGBT open-circuit protection method for three-phase PWM rectifier

A Novel Double Closed-loop Control Method for Single-phase PWM Rectifier

Abstract The research object is the single-phase PWM rectifier in this paper. The goal of DC voltage dynamic response speed improvement and unit power factor realization is the rectifier oriented. Based on current inner loop DQ decoupling control and voltage outer loop adaptive fuzzy PI control, a double closed-loop control method for single-phase PWM rectifier is proposed. Firstly, based on the second-order generalized integrator algorithm, the DQ current decoupling control mathematical model is established by analyzing the rectifier decoupling control. Secondly, fuzzy PI control algorithm is designed for voltage outer loop control. Finally, simulation verification is carried out. Simulation results prove that the proposed control strategy has good dynamic performance.

A novel IGBT open-circuit protection method for three-phase PWM rectifier

In order to avoid the damage or the secondary fault caused by serious over-current, a new solution for protection of IGBT open-circuit faults in three-phase PWM rectifier is presented in this paper. Firstly, the open-circuit faults features of three-phase PWM rectifier have been analysed, and it was found that the most obvious features of open-circuit faults in three-phase PWM rectifier are the rise of some phase currents and the drop of DC voltage. Secondly, compared with the maximum and minimum absolute values of phase currents under normal state, one of them always can be 1.3 times larger than that of normal state when open-circuit faults occur in IGBTs except all IGBTs. Finally, by observing the DC voltage and the currents' behaviour, the maximum-minimum values-based method can detect the open-circuit faults of the system. The experiment results have verified that the method can effectively detect the open-circuit faults in IGBTs and protect the system.

Simplified Input Voltage Sensorless Vector Control for PWM Rectifiers

A conventional input-voltage sensor-based vector-controlled PWM rectifier is used in wide range of applications due to its well-known control structure, simple design, and good dynamic performance. Many existing input voltage sensorless methods have a control structure significantly different from that of conventional vector control, involving additional computational and design efforts. This article proposes a simplified input voltage sensorless control which has the same control structure as that of vector control and can utilize similar controller design procedure. The input voltage required for a phase-locked loop (PLL) is estimated from the current controller output using a simple algebraic equation. The sensorless PLL, so obtained, is mathematically modeled, and its frequency response is shown to be similar to that of a sensor-based PLL. The performance of the proposed method is compared with those of existing methods in terms of input power factor, response to distorted input voltage, sensitivity to system parameter, and computation time requirement through simulations and experiments. Apart from having the lowest computation requirement, the proposed method is shown to achieve the sensorless operation without any performance degradation, compared to the sensor-based operation, and with robustness to parameter variation. The proposed method includes a start-up procedure, which ensures low starting transient current.

Fractional-Order Modeling and Analysis of a Three-Phase Voltage Source PWM Rectifier

In this paper, the fractional-order modeling and analysis of a three-phase voltage source PWM rectifier (VSR) are researched considering the fractional-order characteristics of actual inductors and capacitors. While the Caputo fractional calculus operator is used to describe the fractional-order characteristics of an inductor and a capacitor, the fractional-order model of a three-phase VSR is established in the three-phase static coordinate system. With the coordinate transformation, the fractional-order model is expressed in the two-phase static coordinate system and in the synchronous rotation coordinate system, respectively. Simulation results verify the effectiveness of the established models, and indicate that the fractional-order models can describe the operating characteristics of a three-phase VSR more accurately. Besides, compared with the traditional integer-order three-phase VSRs, the three-phase VSRs which contain the fractional-order inductors and the fractional-order capacitor can present better static and dynamic performance indexes (such as smaller overshoot and shorter regulation time) by appropriately selecting the orders of the inductors and the capacitor.

Online Inductance Identification of a PWM Rectifier under Unbalanced and Distorted Grid Voltages

Direct power control (DPC) works well under ideal grid voltage conditions with accurate parameters. However, under unbalanced and distorted network conditions, significant power ripples and current harmonics arise in conventional DPC if no special measures are taken. Furthermore, the system performance further deteriorates if the inductance value differs from the actual value. To cope with the problems above, this article proposes an online inductance identification method for the DPC of a PWM rectifier under unbalanced and distorted network conditions. It is shown that the proposed method can guarantee sinusoidal characteristics of the grid current and reduce power ripples under unbalanced and distorted network conditions when the identification algorithm is enabled. The presented simulated and experimental results confirm the effectiveness of the proposed method.

Model predictive direct power control based on error correction for three‐phase voltage source PWM rectifier

Model predictive direct power control based on error correction for three‐phase voltage source PWM rectifier

Embedded Electrical Network Advance Controlling Based on SVC Device and Automatic Voltage Regulator

This paper studies the control of embedded electrical network (EEN), which can be described as multi-turbo-alternators connected in parallel with various linear or nonlinear loads, and poorly known characteristics. Moreover, the transfer function of global model will be obtained using the perturbation singular method, by linearization model and separation of fast and slow variables. Then, the control of small disturbances will be performed by an automatic voltage regulator using three-phase PWM rectifier. Moreover, the static VAR compensator (SVC) device is implemented in embedded network to control the voltage stability for a large disturbance when the network is affected by voltage dip or open circuit. The SVC will be controlled by adjusting exactly the firing angle of thyristors that will improve the voltage stability at the bus bar, by injecting or absorbing the reactive power. The SVC control algorithm is firstly simulated in real time using a microcontroller device, for a variable load, after will be implemented in MATLAB/Simulink S-Function, to verify its efficiency with the EEN.

Direct Power Control of PWM Rectifiers With Online Inductance Identification Under Unbalanced and Distorted Network Conditions

In the conventional direct power control (DPC) methods, the grid currents are highly distorted, and substantial ripple is present in the dc-bus voltage under unbalanced and distorted grid conditions. Various improved DPC methods have been proposed to address these problems, but these methods are generally complicated and not easy to use because of the complex controlling structures, need for considerable tuning, and so on. This paper proposes an improved DPC method obtained by simply adding a compensation term to the original power references. The compensation power is obtained by analyzing the power ripple in the input line inductance based on extended power theory. The reference voltage vector is subsequently calculated from the new power reference and synthesized by space vector modulation. To improve the robustness of the proposed DPC against inductance variations, an online inductance identification technique based on the gradient correction method is proposed and combined with the proposed DPC. The presented simulation and experimental results demonstrate that the proposed method can achieve sinusoidal grid currents and significantly reduce the dc-voltage ripple even with mismatched inductance under unbalanced and distorted grid conditions.

Design and Analysis of 4 Kw Srm Drive for Air-Conditioned Pwm Rectifier and Buck-Boost Pfc Converter

In domestic applications like air conditioners Buck or Cuk converter fed by Permanent Magnet Brushless DC Motors (PMBLDCM) are applicable in literature. Due to drawbacks of economical factor and non availability of permanent magnets these motors are not preferable in these days and are compensated by using Switched Reluctance Motor (SRM) as it has benefits of simple design and low cost. For domestic applications accessible input is AC, a diode bridge rectifier is a simple way of converting AC to DC but it produces lower order harmonics, a low power factor on supply side and variable DC on DC side. In order to overcome this problem PWM rectifier and Buck-Boost Converters are proposed for harmonic mitigation and power factor modification. This paper describes the design analysis (calculations) of 200V, 4KW, 2500 RPM 6/4 pole SRM. Analysis is carried out for SRM drive in air-conditioner (ac) application with PWM rectifier and Buck-Boost converter (BBC) for Power Factor Correction and harmonic mitigation. In proposed work the analysis was carried out for 6/4 SRM with various conditions like initial condition, step variation in dc link voltage, at fixed DC link voltage and variation in source voltage. MATLAB/SIMULINK model of SRM drive for different conditions said above were developed and results were also discussed in this paper. Voltage and current waveforms representing power factor is shown for the SRM drive system with PFC- PWM rectifier and Buck Boost converter. Comparison between proposed converters fed SRM and existing converters like Buck, Cuk converter fed PMBLDCM and Zeta converter fed SRM were given along with their THD. THD was reduced and limited within IEEE standards when operating SRM drive with PFC converter.

Control for Three-Phase LCL-Filter PWM Rectifier with BESS-Oriented Application

This paper deals with a battery energy storage system (BESS) in only one of its multiple operating modes, that is when the BESS is charging the battery bank and with the focus on the control scheme design for the BESS input stage, which is a three-phase LCL-filter PWM rectifier. The rectifier's main requirements comprise output voltage regulation, power factor control, and low input current harmonic distortion, even in the presence of input voltage variations. Typically, these objectives are modeled by using a dq model with its corresponding two-loop controller architecture, including an outer voltage loop and a current internal loop. This paper outlines an alternative approach to tackle the problem by using not only an input–output map linearization controller, with the aim of a single-loop current control, but also by avoiding the dq modeling. In this case, the voltage is indirectly controlled by computing the current references based on the converter power balance. The mathematical model of the three-phase LCL-filter PWM rectifier is defined based on the delta connection of the filter, which accomplishes the requirements of a 100 kW BESS module. Extensive simulation results are included to confirm the performance of the proposed closed-loop control in practical applications.

Analysis and suppression of high-frequency oscillation between converter-based source and loads in an island power system

In island power system with strong mutual interaction of power electronic devices, stability problems such as high-frequency oscillation are prone to occur. Firstly, a small-signal sequence impedance model of an island power system is built by harmonic linearization method. It is found that the output sequence impedance of the source PWM inverter in the system is not affected by the stable operating point, but the input sequence impedance of the load PWM rectifier will decrease with the increase of power. Then, based on the sequence impedance model and Nyquist stability criterion, the influence of load type and load power on stability of the island power system is analyzed, which can reveal that high-frequency oscillation occurs when the source PWM inverter interacts with the load PWM rectifier. The essential reason of the high-frequency oscillation is that the capacitive output impedance of the source PWM inverter does not match the inductive output impedance of the load PWM rectifier at high-frequency areas. Aiming at this issue, an impedance reconstruction control for the source PWM inverter is proposed, which improves the phase of the output sequence impedance of the source PWM inverter at high-frequency areas to effectively suppress the high-frequency oscillation of the system. Finally, experiment results verify the correctness of analysis and effectiveness of the proposed control strategy.

Model predictive direct power control using optimal section selection for PWM rectifier with reduced calculation burden

The conventional model predictive direct power control (CMPDPC) selects two adjacent vectors and one zero vector during one control period. The cost function with minimum power ripple is to calculate the duration. However, it could occur the negative duration problems, mainly at section switching. This unexpected negative duration may result in power notch and current harmonic increase. Although, it could be improved by reselecting vector when negative duration occurs. But, the power variation rate and duration for reselected vector must be calculated again. In order to reduce the computational burden, an optimal section selection model predictive direct power control (OMPDPC) is proposed in this paper. The relationship of power variation rate between adjacent voltage vectors is developed. Then, the new vectors and duration based the table is introduced to replace with the original calculated results. Meanwhile, low switching losses vector sequence and one step delay compensation are investigated. The computational burden of this new method is reduced and it is quite easy to implement. The power notch could be greatly alleviated. The effectiveness of the proposed method is demonstrated by comparing with other two methods under various conditions. Simulation and experiment results are given to validate the proposed OMPDPC method.

Research on Harmonic Suppression of High Temperature Boiler Based on Three-phase PWM Rectifier

Traditional boiler temperature control is based on thyristor voltage regulation, and the output AC voltage is controlled by controlling the trigger angle α of thyristor, so that the boiler temperature can be controlled in the pre-set range. However, this way of voltage regulation and temperature control will cause serious harmonic pollution to the power grid, and the output current has high harmonic content and low power factor. At the same time, the traditional three-phase load connection mode generally adopts star connection, and the load is pure resistive silicon carbide. Because of long-term use, the aging of silicon carbide heating rod is different, in fact, it is asymmetric load, three-phase load. The unbalance will cause three-phase unbalance, which will make the voltage of a certain phase exceed the rated working voltage of the heating rod, and greatly reduce the service life of the heating rod. Therefore, in order to improve the efficiency of power supply, reduce harmonic pollution and solve the problem of three-phase unbalance, this paper proposes a three-phase PWM rectifier circuit, which converts AC to DC, and realizes DC voltage regulation and temperature control through PI regulator. In this paper, the feasibility of the scheme is verified by simulation and comparative analysis.

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 electricity. Within this problematic, this paper deals with monitoring and control of a permanent magnet synchronous generator voltage for battery charging. In the proposed topology, the output direct drive PMSG is linked to the battery through a vector-controlled pulse modulated (PWM) rectifier. Most wind energy conversion systems are based on precise knowledge of the wind speed, which makes the adjustment of the charge voltage relatively complicated, and degrades the powers captured with erroneous measurements of this wind speed. In this context, all the efforts of this work are meant to simplify and improve the dynamic performance of the system. The technique used in this work is devoid of wind measurement. By neglecting different losses, the approach adopted leads us to the reference electromagnetic torque, assuming that the wind speed and consequently the rotational speed of the turbine vary slowly in steady state. Using the load current and voltage measures, the proposed controllers calculate permanently the power reference that corresponds to the fixed battery voltage. A vector control approach is adopted to achieve decoupled power control on the supply side power converter by generating the direct and quadrature control voltages. These voltages are necessary to generate the corresponding duty cycles of the PWM active switching devices. Hence, the PWM rectifier maintains the battery voltage at a fixed value by balancing both the rectifier output current and the load input current. To activate the vector control, two dynamic controllers are designed, simulated, and compared. The first controller is based on simple PI regulators. Meanwhile, the second one, which is a sliding mode technique, is applied to control the battery voltage. In order to assess the effectiveness of the used techniques, simulation models have been subjected to critical conditions of changing in speed and load. Simulation results revealed a poor accuracy of the first technique during transients and its close correlation under load disturbance. Whereas the sliding mode controller has high precision and strong robustness in steady state and during transient phases. The system simulation is performed using MATLAB/SIMULINK.