Power converter control based on neural and fuzzy methods

The new power converter control approaches based on neural network techniques and fuzzy logic theorems are briefly reviewed and discussed in this paper. Current-controlled voltage source inverters offer substantial advantages in improving motor system dynamics for high-performance AC drive systems. The controller switches follow a set of reference current waveforms. Fixed-band and sinusoidal-band hysteresis current controllers have been studied. The first part of this paper develops neural network and fuzzy logic based current-controlled voltage source inverters. The models and learning techniques have been investigated by simulation. The implementation of neural networks is described and simulation results are presented. In the second part of this paper, the new UPS (uninterruptible power supply) with fuzzy logic compensator is proposed. The proposed fuzzy logic compensator is used to prevent voltage drop from nonlinear loads. The total harmonic distortion (THD) of the proposed scheme is better than that of conventional deadbeat control methods for linear and nonlinear loads. The applications of fuzzy and neural network control to DC-DC converters operating at finite switching frequency are studied in the third part of this paper. The fuzzy logic and neural network controller for unity power factor rectifiers, half-bridge DC-DC ZVZCS converters, DC motor drives, induction motor drives and permanent-magnet motor drives are also discussed. Some simulations are presented in this paper.     

Unified subharmonic oscillation conditions for peak or average current mode control

This paper is an extension of the author's recent research in which only buck converters were analyzed. Similar analysis can be equally applied to other types of converters. In this paper, a unified model is proposed for buck, boost, and buck–boost converters under peak or average current mode control to predict the occurrence of subharmonic oscillation. Based on the unified model, the associated stability conditions are derived in closed forms. The same stability condition can be applied to buck, boost, and buck–boost converters. Based on the closed‐form conditions, the effects of various converter parameters including the compensator poles and zeros on the stability can be clearly seen, and these parameters can be consolidated into a few ones. High‐order compensators such as type‐II and PI compensators are considered. Some new plots are also proposed for design purpose to avoid the instability. The instability is found to be associated with large crossover frequency. A conservative stability condition, agreed with the past research, is derived. The effect of the voltage loop ripple on the instability is also analyzed. Copyright © 2014 John Wiley & Sons, Ltd.     

Analysis of a novel four-level DC/DC boost converter

In this paper, novel two-quadrant buck/boost and one-quadrant boost four-level DC/DC power converters are introduced. The primary application for these converters is that of interfacing a low-voltage DC source, such as a fuel cell or battery, to a high-voltage four-level inverter. One important feature of the four-level DC/DC power converters proposed is the ability to perform the power conversion and balance the inverter capacitor voltages simultaneously. With the capacitor voltage balancing, it is possible to obtain the full voltage from the inverter. For the boost converter, the steady-state and nonlinear average-value (NLAM) models are developed. The NLAM is verified against a detailed simulation of a four-level converter/inverter drive system. The proposed converter is experimentally verified using an 18 kW converter/inverter system     

一种基于模糊控制的降压变换器

基于模糊控制理论,结合非线性控制,提出了一种降压变换器的新型拓扑结构。该结构具有模糊控制策略的优点,且不用建立复杂的数学模型,控制方法简单,可使PWM开关变换器的输出电压,在有负载和电源电压干扰时,具有优良的动态响应。仿真和实验结果证明了该方法和结构的可行性和优越性。     

DC/DC变换器自适应模糊逻辑控制器设计

为DC/DC变换器设计了一种自适应模糊逻辑控制器（AFLC）。所提出的AFLC不需要专家系统提供决策参数和控制规则,而是使用模型数据文件来产生参数和规则,该模型数据文件包含输入输出对的整体概况。所提出的控制器使用8位微控制器来实现降压、升压和降压-升压变换器。     

Novel reactive power controllers for the STATCOM and SSSC

The paper investigates the dynamic operation of both static synchronous compensator (STATCOM) and static synchronous series compensator (SSSC) based on a new model comprising full 48-pulse GTO voltage source converter for combined reactive power compensation and voltage stabilization of the electric grid network. These key FACTS devices are power electronic GTO converters connected in parallel or series with the power system grid and are controlled by novel decoupled controllers. The complete digital simulation of the STATCOM and SSSC within the power system is performed in the MATLAB/Simulink environment using the power system blockset (PSB). The STATCOM scheme and the electric grid network are modeled by specific electric blocks from the power system blockset while the control system is modeled using Simulink. Two novel controllers for the STATCOM and SSSC are presented in this paper based on a decoupled current control strategy to ensure stable operation of the STATCOM under various load excursions. A novel control scheme for the static synchronous series compensator (SSSC) is also implemented to provide a full controllable series compensating (buck/boost) injected voltage over a specified capacitive and inductive range, independently of the magnitude of the transmission line current. The series reactive compensation scheme with an external dc power supply can also compensate for any voltage drops across resistive component of the transmission line impedance. The novel decoupled controller uses a phase locked loop (PLL) with a novel reduced inherent time delay to improve the transient performance of the SSSC. The performance of both STATCOM and SSSC schemes connected to the 230 kV grid are evaluated. The proposed novel control schemes for the STATCOM and SSSC are fully validated by digital simulation.     

Application of duality principle to synthesis of single‐stage power‐factor‐correction voltage regulators

The duality principle is applied to derive new single‐stage power‐factor‐correction (PFC) voltage regulators. This paper begins with an application of duality transformation to conventional discontinuous‐conduction‐mode buck, buck‐boost and boost converters. The resulting dual converters operate in the discontinuous capacitor voltage mode. These new converters provide the same PFC property, but in the dual manner. It is proved that in the practical case of the input being a voltage source, the mandatory insertion of inductance between the voltage input and the ‘dual PFC converter’ does not affect the power‐factor‐correcting property. A new single‐stage PFC regulator is derived by taking the dual of a well‐known circuit based on a cascade of conventional boost and buck converters. Analytical design expressions are derived, illustrating the relation between current stress and component values. Experiments are performed to confirm the operation of the circuit and its power‐factor‐correcting capability. Copyright © 2003 John Wiley & Sons, Ltd.     

具有快速负载动态响应的DC／DC开关变换器开环控制新策略

采用何种控制策略和如何实现控制方法是决定开关变换器的效率和性能的主要因素。单周控制方法是近年来提出的一种新型非线性控制策略。这对输入电源电压的变化具有快速的动态跟踪能力,但对负载变化的抑制能力差,基于等效受控源平均法,提出了一种新的非线性控制方法,使得PWM开关变换器的输出电压,在负载干扰和电源电压干扰下,具有优良的动态响应特性。以降压型变换器为例,首先建立开关变换器大信号低频平均电路模型。通过分析平均电路模型,可以推导出一种新型开环非线性控制策略。这种控制方法具有固有的稳定性,快速动态响应和无过冲等优点。为了实现新的控制方法,建立了电感电压低频分量的数学模型。计算机仿真和实验测试结果证明理论预期分析。     

New hysteresis control band of an unified power quality conditioner

Power quality problems have received a great attention nowadays because of their economical impacts on both utilities and customers. The current harmonics is the most common problem of power quality, while voltage sags is the most severe. This paper deals with an Unified Power Quality Conditioner for current and voltage perturbations compensation in a power distribution network. The topology is based on two 3-phase voltage source inverters acting respectively as a parallel active power filter and a series active power filter which share two DC link capacitors. The power flow, in the Unified Power Quality Conditioner system is analysed. A novel hysteresis current and voltage control methods of Unified Power Quality Conditioner are studied with the aim to have robust control of the output voltage of series part and the output current of the parallel part. The DC voltage controller optimizes the energy storage of the DC capacitor where a fuzzy logic controller is developed. Simulation results are presented and discussed to verify the dynamical behaviour of the Unified Power Quality Conditioner and to show the effectiveness of the used perturbation identification methods and hysteresis band adaptive controllers.     

基于MATLAB的模糊神经网络高压直流输电换流控制器的研究

在研究模糊逻辑控制技术、神经网络技术和高压直流输电（HVDC）系统的基础上，从原理上说明，对换流器两侧都采用模糊神经网络控制能有效地提高交流一直流（AC/DC）系统的动态特性和恒定性。整流侧和逆变侧分别提取直流线路电流、电压误差及其变化率作为模糊控制器的输入，输出作为神经网络的输入，分别控制电流和电压。用MATLAB对一典型12脉冲桥高压直流输电系统在传统控制和模糊神经控制下分别进行仿真。结果表明。与传统控制方法相比，当直流线路或者单相交流线路发生接地故障时。模糊神经控制能改善换流站直流电流和直流电压的恒定性，而且提高了交直流系统的暂态稳定性，并且双侧模糊逻辑控制要比单侧模糊逻辑控制效果好。     

一种用于配电系统三相不对称的新型补偿器

提出了一种用于补偿不对称负荷产生的负序、零序分量并调整负荷母线电压,且适用于三根三线制和三相四线制系统的新型无功补偿器。该补偿器由用于补偿负序分量并调整负荷母线电压的三相电压型逆变器和用于补偿零序分五的单相逆变器组成。采用基于d－q变换的瞬时值逆变器输出电压合成方法和SPWM调制方式来实现装置的快速响应。     

隔离型开关电感准Z源逆变器

为了克服传统Z源/准Z源拓扑升压能力不足、无法实现输入输出侧电气隔离等缺陷,提出了两种隔离型开关电感准Z源逆变器,利用隔离变压器代替传统准Z源拓扑中的一个电感,使电路具有升降压的功能。探讨了电路的工作原理及控制方法,仿真及实验结果证明了拓扑的有效性。     

A novel approach of reference current generation for power quality improvement in three-phase, three-wire distribution system using DSTATCOM

This paper presents a novel approach based on an improved instantaneous active and reactive current component theory for generating reference currents for distribution static compensator (DSTATCOM). Three-phase reference current waveforms generated by proposed scheme are tracked by the three-phase voltage source converter in a hysteresis band control scheme. The performance of the DSTATCOM using the proposed control strategy has been evaluated under various source and load conditions. The performance of the proposed control strategy has been evaluated in terms of load balancing, reactive power compensation, compensator rating and harmonic mitigation. A three-phase, three-wire distribution system supplying star connected linear as well as non-linear unbalanced load is considered for simulation study. The detailed simulation results using MATLAB/SIMULINK software are presented to support the feasibility of proposed control strategy.     

Teaching nonlinear modeling, simulation, and control of electronic power converters using MATLAB/SIMULINK

This paper describes an efficient method to teach analysis and simulation of power electronic converters to undergraduate students, using system level nonlinear state-space models. System-level modeling of power electronic converters reproduces only the ideal switching behavior of the semiconductors and is a useful concept for the numerical simulation of power converters, since simulations present no convergence problems and require little computational time. Switched state-space models, programmed in the MATLAB/SIMULINK software package, can be advantageously used to simulate power converters at the system level and also to design and study their controllers. Switched state-space nonlinear models should be obtained using a theoretical framework suitable for the enhanced control of variable structure power systems. Since the method is inherently nonlinear, no approximated linear models are needed; and since state-space models are used, modern control techniques (sliding mode, neural networks, fuzzy logic) for power converters can easily be used. This paper summarizes the proposed methodology and gives some examples.     

Design and Implementation of Adaptive Neuro–Fuzzy Inference System Based Control Algorithm for Distribution Static Compensator

This article focuses on the design and implementation of a distribution static compensator using an adaptive neuro–fuzzy inference system based controller. The distribution static compensator is controlled to provide power quality improvement, such as power factor correction, harmonics compensation, load balancing, and voltage regulation. Active and reactive power fundamental components of load currents are extracted using d-q theory. A distribution static compensator is realized using a voltage source converter. Both simulation and experimental results prove the effectiveness of the control algorithm under non-linear loads. The adaptive neuro–fuzzy inference system based controller works satisfactorily for power factor correction and harmonics reduction under balanced as well as unbalanced load conditions. Test results clearly depict the dynamics of the performance of the system under steady state as well as dynamics under load change and load unbalancing.     

High‐efficiency transformerless buck–boost DC–DC converter

A novel high‐efficiency transformerless buck–boost DC–DC converter is proposed in this paper. The presented converter voltage gain is higher than that of the conventional boost, buck–boost, CUK, SEPIC and ZETA converters, and high voltage gain can be obtained with a suitable duty cycle. The voltage stress across the power switch is low. Hence, the low on‐state resistance of the power switch can be selected to decrease conduction loss of the switch and improve efficiency. The input current ripple in the presented converter is low. The principle of operation and the mathematical analyses of the proposed converter are explained. The validity of the presented converter is verified by the simulation results in PSCAD/EMTDC software and experimental results based on the prototype circuit with 250 W and 40 kHz. Copyright © 2017 John Wiley & Sons, Ltd.     

Nonlinear intelligent DC grid stabilization for fuel cell vehicle applications with a supercapacitor storage device

This paper presents an intelligent DC link control using a fuzzy logic controller based on the differential flatness control theory for hybrid vehicle applications supplied by a fuel cell (FC) (main source) and a supercapacitor (auxiliary source). The energy in the system is balanced by dc bus energy stabilization (or indirect voltage regulation). A supercapacitor module functions by supplying energy to regulate the dc bus energy. The FC, as a slow dynamic source in this system, supplies energy to the supercapacitor module to maintain its charge. The FC converter combines four-phase parallel boost converters with interleaving, and the supercapacitor converter employs four-phase parallel bidirectional converters with interleaving. These two converters are called a multi-segment converter for high power applications. Because the model of the power switching converters is nonlinear, it is preferable to apply model-based nonlinear control strategies that directly compensate for the nonlinearity of the system without requiring a linear approximation. Using the intelligent fuzzy control law based on the flatness property, we propose straightforward solutions to hybrid energy management and to the dynamic and regulation problems. To validate the proposed method, a hardware system is developed with analogue circuits, and a numerical calculation is generated with a dSPACE controller DS1104. Experimental results for a small-scale power plant (a polymer electrolyte membrane FC (PEMFC) of 1200 W and 46 A with a supercapacitor module of 100 F, 500 A, and 32 V) in the laboratory corroborate the excellent performance of this control scheme during vehicle motor drive cycles.     

Three-phase buck/boost-type high-power-factor switching converter

The harmonic pollution caused by ac-to-dc converters has been of great concern. To overcome this problem, several power-factor-correction (PFC) converters have been developed and applied in recent years. However, several power converter systems, such as the motor drive system, with a wide V/F control range, uninterruptible power supply system and dc power supply system with universal input voltage range, require an ac-to-dc converter or an off-line converter (preregulator) with a wide output-voltage control range in order to be highly efficient. However, the most conventional PFC converters employ a voltage-fed or current-fed type topology and they have a lower or upper limitation of the output-voltage control range. Thus, they do not realize sufficiently high-system efficiency. On the other hand, a buck/boost converter has a wide control range of the output voltage and acts in PFC operation under an appropriate control technique. Thus, study of the possibility of using the buck/boost ac-to-dc converter with PFC and a wide output-voltage control range is important to the realization of harmonic-free and efficient power conversion systems. In this paper, the author proposes a three-phase bridge-type ac-to-dc converter system with a high input power factor and a wide output-voltage control range. The controller of the proposed system includes the following two new techniques. One is the pulse integral value modulation that compensates modulation errors in conventional pulse-width-modulation caused by dc current ripples or fluctuations of the current pulse amplitude. The other is a switching pulse pattern generator, using the idea of equivalent pulse current source for the bridge as a way to simplify the pulse pattern generation process. This paper describes the proposed converter system, the control and modulation principles, and experimental results that show the reliability and usefulness of the proposed buck/boost converter system. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (2): 41–55, 1997     

A Multi-Functional Single-Stage Power Electronic Interface for Plug-In Electric Vehicles Application

This paper proposes a Zeta-derived non-isolated single-stage power electronic interface for on-board application of plug-in electric vehicles, which provides all modes (plug-in charging, propulsion, and regenerative braking) of vehicle operation. In addition, the proposed converter can charge the battery through universal input voltage range, i.e., 90–260 V due to buck/boost operations in plug-in charging mode. In propulsion and regenerative braking modes, the proposed converter operates as conventional boost and buck DC/DC converter, respectively. Compared to existing single-stage converters, the proposed converter has least components to those converters which have buck/boost operation in plug-in charging mode. A voltage/current stresses and loss analysis of the converter have been investigated for each mode of converter operation. Detailed simulation and experimental results are given to show the effectiveness of the proposed converter.     

新型模糊逻辑二级电压控制器

摘要： 设计了一种新型的基于极坐标二值模糊逻辑规则的模糊逻辑二级电压控制器。该控制器有效地将模糊逻辑规则和二次电压控制相结合：将引导节点的电压偏差及其微分作为模糊逻辑控制规则的前项输入，与规则作用后，推理出相应的电压控制信号，然后引入比例积分器，得到区域无功控制信号，通过发电机的励磁控制，实现对引导节点电压的控制。该控制器通过引入控制发电机的参与因子，实现了区域内各控制发电机之间的相互协调和补充。以New England 39节点系统为例进行仿真计算，结果表明：所设计的二级电压控制器在系统发生电压扰动的期间，能够从区域电压稳定的角度出发，调整各级电压控制器的电压参考值从而调整其无功出力，为系统提供所需的电压支持，使得系统的负荷电压水平维持在较好的状态，提高了系统的电压稳定性。它比常规PID二级电压控制器具有更好的控制性能。