Three-phase PWM Research Articles

Application of Model Predictive Control to Ultra Sparse Matrix Rectifier

Ultra Sparse Matrix Rectifier (USMR) is considered to be one of the simplest and compact three-phase PWM rectifiers. It is a buck three-phase AC-DC converter with one-quadrant operation capability. In this paper, Model Predictive Control (MPC) is applied to USMR supplying inductive load. The discrete time model of the system is derived. Then, the MPC algorithm for the proposed system is discussed. Finally, the system is simulated using Matlab. The performance of the proposed USMR controlled using MPC is compared to the one using Space Vector Modulation (SVM). Simulation results show that the MPC has more harmonic performance benefits than the SVM one. However, the efficiency of the system that uses MPC is slightly lower than the one that uses SVM, due to the built in switching loss minimization of the SVM.

Methodology for Analysis and Design of DiscreteTime Current Controllers for Three-Phase PWM Converters

In this work, a methodology for the analysis and design of robust, high bandwidth current controllers for three phase converters is presented. The overall goal is to demonstrate how the proposed model based control structure and the design methodology lead to an optimized digital current controller that exhibits fast and smooth dynamics as well as an excellent disturbance rejection ability. First, accurate discrete time models are derived and used to review classical current control from the perspective of the synchronous and stationary reference frame. Then, implementation options for the synchronous frame proportional integral (SFPI) regulator and the proportional resonant (PR) regulator are discussed and systematically compared in the stationary frame leading to the formulation of a general controller framework based on space vector resonators. It embodies multiple complex resonators and can represent the SFPI regulator, the PR regulator and beyond that any higher order regulator structure. For this framework, a step by step design procedure based on the complex root locus is proposed that allows an insightful optimization of its feedback gains. Finally, the performance of the presented control design techniques is evaluated experimentally.

ESR and capacitance monitoring of a dc-link capacitor used in a three-phase PWM inverter with a front-end diode rectifier

Condition monitoring plays an important role in estimating health condition of capacitors because the ageing of the capacitors is usually accompanied by an increase in equivalent series resistance (ESR) and a decrease in capacitance. Either capacitance or ESR cannot be a unique indicator of the lifetime of capacitors in some cases. This paper presents a condition monitoring method of a dc-link capacitor used in a three-phase PWM inverter with a front-end diode rectifier intended for motor drives. The monitoring method extracts both the ESR and capacitance of a capacitor under test from the actual ripple current and voltage without disconnecting the capacitor nor injecting an additional current. The monitoring method, therefore, can be implemented online. Experimental results verify that the monitoring method independently obtains the ESR and capacitance changes of the capacitor under test. This contributes to accurate lifetime estimation of dc-link capacitors.

Passive control of three-phase PWM rectifier and its damping characteristics of CSR

Due to the current mode pwm rectifier model has strong coupling and nonlinear characteristics, the traditional linear control theory can’t achieve satisfactory effect based on passive control theory to realize current-mode PWM rectifier state variable linear resolve coupling, decoupling model. Base d on the design of the direct current control strategy, the theory and simulation experiments prove the feasibility and the effectiveness of solutions and achieve the ideal control effect. Damping is studied through experiments of passive control of the effect on the stability of the current-mode PWM rectifier system. It provides a theoretical and technical support in the application of the high-power current type inverter.

Design and Experimental Results of Universal Electric Vehicle Charger Using DSP

Owing to the growing concerns over energy depletion and environmental issues around the world, more and more attention is given on replacing the fuel-based automobiles with electric vehicles (EVs) which have the characteristics of zero-emission and low noise. As a result, various countries have taken specific initiatives to de-carbonize their transport sectors by developing their own EV industry. Regardless of the environmental and economic benefits, substantial scales of grid-connected EVs impose incredible difficulties to the power grid. The main issues caused by EV charging to the power grid include harmonics, voltage drop, system instability, system losses and grid overloading. Therefore, this paper presents design and development of a novel method, which is by applying voltage-oriented control (VOC) algorithm in battery charging of electric bus.The power system of this work consists of three-phase PWM rectifier. The proposed method is based on mathematical analysis. Simulation and experimental works are performed to investigate behavior and performance of the proposed algorithm. This paperclearly described implementation of low and medium power laboratory prototype and operation of digital signal processor (DSP) via MATLAB / Simulink for the proposed method.

Constant temperature control of tundish induction heating power supply for metallurgical manufacturing

The tundish induction heating power supply (TIHPS) is one of the most important equipment in the continuous casting process for metallurgical manufacturing. Specially, the constant temperature control is greatly significant for metallurgical manufacturing. In terms of the relationship between TIH load temperature and output power of TIHPS, the constant temperature control can be realized by power control. In this paper, a TIHPS structure with three-phase PWM rectifiers and full-bridge cascaded inverter is proposed. Besides, an input harmonic current blocking strategy and a load voltage feedforward control are also proposed to realize constant temperature control. To meet the requirement of the system, controller parameters are designed properly. Experiments are conducted to validate the feasibility and effectiveness of the proposed TIHPS topology and the control methods.

Direct Power Control of Three-phase PWM Converter Based on Novel Switch Table

The traditional direct power control of three-phase voltage source PWM rectifier is designed based on the 12 sector division of voltage vector space, and the reactive power will mutate at the beginning of odd sectors. In this paper, the voltage vector space is uniformly divided into 18 sectors. A new switch list is designed by analyzing the influence of the switching vector on the AC side output reactive power and active power of the power control system in different sectors. Through the simulation and analysis can prove that, based on the new direct power switch table control method has good control effect and can improve the power factor and the grid side power quality, reduce the harmonic content of the grid current, and to overcome the traditional switching table defects on reactive power control, reactive power changes more smooth and stable. To get a better static and dynamic control effect.

Virtual Synchronous Motor Based-Control of a Three-Phase Electric Vehicle Off-Board Charger for Providing Fast-Charging Service

This study introduces a three-phase virtual synchronous motor (VSM) control and its possible application for providing fast-charging service from off-board chargers of electric vehicles (EVs). The main circuit of the off-board charger consists of a three-phase voltage source PWM rectifier (VSR) and a resonant LLC zero-voltage-switching converter. In the proposed control approach, VSM-controlled pre-stage VSR emulates the external characteristics of a synchronous motor (SM), simultaneously, droop control based on charging mode in the VSM can satisfy the demand of the EVs constant-current fast-charging; The post-stage DC–DC converter is responsible for stabilizing the DC bus voltage. The feature of this control strategy is that VSM and fast charging control are implemented by the pre-stage converter, which has better coordination. In the MATLAB, the equivalent synchronous grid of the distribution network supplies to the power battery through the off-board charger, and the effectiveness of the presented control is demonstrated by typical working conditions.

The Design of Connection Solid Oxide Fuel Cell (SOFC) Integrated Grid with Three-Phase Inverter

Fuel cell technology is a relatively new energy-saving technology that has the potential to replace conventional energy technologies. Among the different types of generation technologies, fuel cells is the generation technologies considered as a potential source of power generation because it is flexible and can be placed anywhere based distribution system. Modeling of SOFC is done by using Nernst equation. The output power of the fuel cell can be controlled by controlling the flow rate of the fuels used in the process. Three-phase PWM inverter is used to get the form of three-phase voltage which same with the grid. In this paper, the planning and design of the SOFC are connected to the grid.

The undamped control for PWM rectifier based on LCL filter

LCL filter is applied in PWM rectifier with the better filtering effect. Its inductor also plays a role in inhibiting the current impact, which not only has a good dynamic performance, but also reduces the system cost. However, LCL filter can cause resonance in certain frequency that affects system performance, as well as the parameters of LCL filter are hard to design. With analysis on the theory and characters of the fixed switching frequency control strategy, an undamped control strategy of three-phase voltage PWM rectifier based on LCL filtering is proposed for the resonance of LCL filter. The delay of system and the fixed switching frequency are used to control the damp. PI regulator’s sampling time is adjusted to achieve the system stability. The structure of system is optimized by the design of simplified capacitance sensor. The simulation results show that this method has better dynamic performance, the current harmonic of grid side has reduced sharply, and the resonance of LCL filter has been inhibited effectively.

Direct Power Neuro-Fuzzy Controller Scheme of Three-Phase PWM Rectifiers for Power Quality Improvement

This paper investigates the design of an improvement scheme of direct power control (DPC) based on adaptive neuro-fuzzy inference system (ANFIS) for mitigation of power quality problems. The proposed control technique is performed using two ANFIS blocks. The first ANFIS block uses the grid voltage vector position, the errors of the instantaneous active and reactive powers. The second ANFIS block utilizes the dc link voltage error and its change. The purpose of the proposed control algorithm is to regulate perfectly dc link voltage, to control directly the instantaneous powers, near-sinusoidal source current waveforms and unity power factor (UPF) operation. The regulation method has been developed and simulated using MATLAB/Simulink environment. The numerical simulation results confirm the validity of the proposed control technique for three-phase PWM rectifiers and have proved excellent robustness and performance.

New Repetitive Current Controller for PWM Rectifier

This paper analyzed and designed a new Repetitive Current Controller (New RCC), performing a comparison with a traditional RCC. Based on the tracking performance by the original PI controller, the New RCC uses another PI controller to replace the compensator to achieve better control performance. That is the novel approach of the proposed method. And it has been proved in this paper that the controller is not sensitive to the controlled object, therefore it is suitable for use in complex object model scenarios. Simulations and experimental results demonstrate that the new RCC is effective in improving the AC current quality of the three-phase PWM rectifier, which is the right method of control, with high practical application value.

Fractional - order modelling and control for two parallel PWM rectifiers

For the purpose of improving control quality, fast response, stability and other quality indexes for parallel coupled PWM rectifiers, as well as derived from being able to determine the actual transfer function which is closer to the actual control object, the fractional-order transfer function of the three-phase PWM rectifiers. This paper used a fractional proportional Integral controller instead of a traditional PI controller. The use of the fractional-order controller object will help to design a higher precision fractional-order controller of the system. This paper analyzes the characteristics of the system, constructs the function of the fractional-order controller object, designs the current and voltage of the fractional-order controllers, performs the simulations and related experiments. Simulation and experiment results have demonstrated that using the fractional proportional integral controller to control the system of two parallel PWM rectifiers has resulted in ideal control, clearly improved control quality.

Fuzzy PI Compound Control of PWM Rectifiers with Applications to Marine Vehicle Electric Propulsion System

Within a marine vehicle electric propulsion system, three-phase voltage source PWM rectifiers instantaneously produce larger impulse current and overshoot of DC voltage during the startup and load transients, and may lead to system instability; a fuzzy PI compound control scheme is proposed to replace the traditional PI controller in the voltage outer loop. In order to circumvent the defects of the traditional PI controller, the voltage outer loop is designed by combining a fuzzy controller and a PI controller. Moreover, fuzzy control rules are employed to online adapt parameters of the PI controller, and thereby enhancing the system robustness, and contributing to faster dynamic response and smaller overshoot. Simulation results demonstrate that the proposed control scheme can effectively suppress the impulse current and overshoot of DC voltage during the startup and load transients, and improve the anti-disturbance ability of the rectifier and the operation reliability of the marine vehicle electric propulsion system.

Influence of Neutral-Point Voltage Deviation of PWM Converter on Insulation Monitoring in Medium-Voltage Networks

Insulation monitoring is crucial to personal safety and equipment operation in the power distribution system. Recently, with the rapid development of distributed generators, the three-phase voltage-source PWM converter (VSC) is widely used as the bidirectional interface between the dc microgrids and the distribution networks. This paper presents the relationship between the response of insulation monitoring device (IMD) and the neutral-point voltage deviation (NPVD) of VSC, by analyzing the disturbances of the switching function and the dc-side insulation balancing. Then, a method of detecting the NPVD for grid-connected VSC is proposed, based on the dc signal injection and the Duffing oscillator. Furthermore, the proposed method takes the mean and spectrum of the neutral-point voltage as the primal characteristics. Thus, the dc signal injection is adopted to detect the mean of the neutral-point voltage, and the Duffing oscillator is adopted to determine the frequency disturbance of the neutral-point voltage, respectively. The test result confirms the existence of the neutral-point voltage deviation and verifies the availability of the proposed method. Hence, the proposed method could be used to improve the response of IMD.

Robust Nonlinear Controller Design for Three Phase Grid Connected PV Systems with Improved Power Quality

The development of photovoltaic systems has increased due to the high demand for clean and green energy. Used worldwide for distributed power generation, the photovoltaic power must not only be maximized, but also adapted to the global standards on harmonic emissions limits. Therefore, tracking the Maximum Power Point and filtering harmonics became necessary. A three-phase grid-connected Photovoltaic system consisting of a photovoltaic (PV) array, a boost converter and a three-phase PWM inverter coupled through a low-pass filter to the electrical grid is studied in this paper. Two new control designs are developed to maximize power in the side of PV panels and to impose a unity power factor in the side of the grid, the first for the three-phase grid-connected systems with an L-filter and the second for the same systems with an LCL-filter. Both controls are analyzed and compared in details and their stability is demonstrated using Lyapunov analysis. The theoretical analysis and simulation results clearly illustrate that the proposed controllers have achieved the objectives. In order to demonstrate the good performance of the LCL-filter in minimizing the harmonics produced by the inverter, a comparison between the frequency responses of the injected currents using the LCL-filter and the L-filter is carried out.

Modeling, Design and Control of a Solar Array Simulator Based on Two-Stage Converters

Power inverters for photovoltaic (PV) applications must be tested according to standards in order to be certified and commercialized. A common practice to test PV inverters is the utilization of solar array simulators (SAS). This paper presents a SAS topology based on a double-stage structure: The first stage is based on a three-phase PWM rectifier, and the second stage is based on a bidirectional buck converter. This structure is responsible to emulate the photovoltaic array behavior. A methodology to design the SAS components and control system parameters is presented. This methodology considers a range of operation points of the SAS. Additionally, it is verified that the dc-link capacitance of the inverter under test can affect the SAS dynamic behavior and its output current ripple. The results are divided into two parts: resistive loads and commercial inverters. Firstly, the SAS steady-state operation following the solar array I–V curve is demonstrated through simulation and experimental results, using resistive loads. In the second part, two commercial inverters with different nominal power and dc-link capacitance are considered. Using the proposed design methodology, the SAS topology operates correctly and the maximum power point tracker of the inverter under test is not affected if its input capacitance is within the design limits.

Dead-beat instantaneous power control for off-board charger of electric vehicle for V2G application

Dead-beat instantaneous power control strategy for electric vehicle off-board V2G charger is presented in this paper, to suppress harmonic pollution to power grid and realize bi-directional flow of electric energy. The charger consists of three-phase voltage source PWM grid-side converter and bi-directional dc/dc converter. A double closed-loop for three-phase voltage source PWM grid-side converter is designed firstly. And the outer voltage loop is used to keep dc bus voltage constant. The expected switching voltage components are achieved by substituting predicted instantaneous power with its instruction value, to form the inner dead-beat instantaneous power loop. Then a voltage–current double closed-loop for bi-directional dc/dc converter is proposed to implement two-stage charging, combining with constant-current charging and constant-voltage charging. Finally, the effectiveness and feasibility of the proposed control strategy are verified on the power-hardware-in-loop-simulation platform.

A DG Inverter Model Based on PQ Control

并网逆变器作为连接分布式电源与电网的纽带，对分布式电源的并网性能有关键性的影响。本文设计了一种基于PQ控制的DG逆变器模型，逆变部分选用三相桥式PWM逆变器，采用SPWM调制方法，利用KCL和KVL，对其进行数学建模，通过分析其数学模型进行逆变控制器的设计。PQ控制模块(Controller)主要由具有频率跟踪作用的SPLL与提供坐标变换的dq变换模块(SPLL/dq_transform)、能够得到参考电流dq分量(iLdref, iLqref)的功率及功率因数控制(P/Q Control)模块、以及最终能够得到6路PWM控制信号的电流控制(I Control)模块组成。仿真结果表明：本文设计的基于PQ控制的DG逆变器模型性能优良。 Grid-connected inverter as a link between the distributed power supply and power grid, plays a key role to the distributed power supply and the network performance. In this paper, a DG inverter model based on PQ control is designed. The inverter is selected by using the three-phase bridge PWM inverter, and the KCL and KVL are used to model the mathematical model. The mathematical model is analyzed by the mathematical model so as to carry out the design of the inverter controller. PQ control module (Controller) provides the dq conversion module mainly by the frequency tracking effect of the SPLL and coordinate transformation (SPLL/dq_transform); it can get the reference current dq component (iLdref, iLqref), power and power factor control (P/Q control) module, and the final can be 6-way PWM control signal current control (I Control) module. The simulation results show that the DG inverter model based on PQ control is excellent in performance.

Simulation Study of Three - phase PWM Rectifier with Square of the Voltage Double Closed Loop Control

Based on the rotating coordinate system model, the mathematic analysis of the three-phase voltage-sourced PWM rectifier is carried out, and its feed-forward decoupling control strategy is studied. In order to realize the fast response of DC voltage and improve the dynamic and static performance of the rectifier, the double-closed-loop control of outer square of voltage loop and inner current loop is established. The control system of three-phase voltage-sourced PWM rectifier based on space vector modulation algorithm is designed. The simulation results demonstrate the designed model is accurate, and can achieve unity power factor control, DC voltage fast responses, and has not steady-state error.