Decentralized adaptive neural network control of cascaded DC–DC converters with high voltage conversion ratio

Decentralized output voltage tracking of cascaded DC–DC converters is an interesting topic to obtain a high voltage conversion ratio. The control purpose is challenging due to the load resistance changes, renewable energy supply voltage variations and interaction of the individual converters. In this paper, four novel decentralized adaptive neural network controllers are designed on the cascaded DC–DC buck and boost converters under load and DC supply voltage uncertainties. In the beginning, individual buck and boost converter average models that can operate in both continuous and discontinuous conduction modes are derived. Then, the interconnected and decentralized state-space models of cascaded buck and boost converters are extracted. These models are highly nonlinear with unknown uncertainties which can be estimated by neural networks. Further, two decentralized adaptive backstepping neural network voltage controllers are proposed on cascaded buck converters to deal with uncertainties and interactions. However, these control strategies are not applicable to a boost converter due to its non-minimum phase nature. Then, two novel decentralized adaptive neural network with a conventional proportional–integral reference current generator are developed on the cascaded boost converters. Practical stability of the overall system is guaranteed for the proposed controllers using Lyapunov stability theorem. Finally, four control strategies provide good quality of output voltage in the presence of uncertainties and interactions. Comparative simulations are carried out on cascaded buck and boost converters to validate the effectiveness and performance of the designed methods.     

Optimal control of voltage source converters under power system faults

For the integration of renewable energy in power systems, Voltage Source Converters (VSCs) must transfer power from a DC source to an AC grid with effective control of the DC voltage. An important demand is that the converters remain connected to the grid even under severe voltage perturbations. In these situations, the power transfer capability of the converter suffers a drastic reduction, which may cause over-voltages. In this paper, a multi-variable optimal control with anti-windup compensation is proposed with the aim of improving performance, especially under severe voltage faults. The proposed control scheme is evaluated by simulations using a detailed model of the VSC.     

Performance Enhancement of PV Based Boost Cascaded Fifteen Level Inverter for AC Loads

In this research work, single-stage fifteen levels cascaded DC-interface converter (CDDCLC) is proposed for sun arranged photovoltaic technology (PV) applications. The proposed geography is joined with help DC chopper and H-associate inverter to upgrade the power converter to accomplish the diminished harmonic profile. In assessment with the customary inverter structures, the proposed system is used with diminished voltage stress, decreased switch count and DC source tally. The proposed research work with cascaded DC link converter design requires three DC sources for combining fifteen-level AC output. This investigation structure switching technique is phase opposition and disposition pulse width modulation technique (POPD) which results in improved quality of obtained output AC power with 6.73% THD and also determinedly recommended for power converters used in UPS and drive applications since it is extremely affordable. A simulation and prototype model of fifteen-level CDDCLC system is deployed and its performance is analyzed for various operating conditions.     

含电动汽车充电站的多端直流微电网研究

为未来大规模能源互联网的形成以及多种新能源的接入提供技术支撑,设计直流微电网的拓扑结构,提出了一种四端口环网的直流电网拓扑结构,实现交流电网、储能单元、直流负荷、风力发电和光伏发电与直流电网的互联。首先研究了交流电网与直流电网的接口方式和相关技术参数,提出了光伏发电、风力发电和储能单元等接口的技术配置。其次,研究了整个直流微电网的启停时序,设计了直流电网的接线方式、电压等级和容量,最后基于MATLAB Simulink平台搭建了直流园区系统仿真模型,然后对典型工况进行了仿真分析：（1）储能单元由放电到能量为零;（2）储能单元由充电到能量充满;（3）VSC1变换器功率反转;（4）负荷跳变;（5）储能单元由放电到充电。这些工况基本包涵了直流微电网可能出现的运行状态,对直流微电网的运行管理有较高的参考价值。     

Stability of current-mode control for DC–DC power converters

DC–DC power converters are switched devices whose averaged dynamics are described by a bilinear second-order system with saturated input. In some cases (e.g., boost and buck–boost converters), the input output dynamics can be of nonminimum-phase nature. Current-mode control is the standard strategy for output voltage regulation in high dynamic performance industrial DC–DC power converters. It is basically composed by a saturated linear state feedback (inductor current and output voltage) plus an output voltage integral feedback to remove steady-state offset. Despite its widespread usage, there is a lack of rigorous results to back up its stabilization capability and to systematize its design. In this paper, we prove that current-mode control yields semiglobal stability with asymptotic regulation of the output voltage.     

基于能量流动双PWM协调控制

基于双PWM结构,根据系统能量流动分析系统在能量平衡状态和能量不平衡状态下系统各部分间的能量关系,并建立双PWM结构能量数学模型;针对系统输出能量与消耗能量不平衡时造成的直流母线电压波动以及输出功率不匹配的问题,建立关于直流母线电压以及网侧电流d轴分量的约束条件,保证系统能量能够平滑变化;采用约束条件对整流器电压外环以及功率内环进行修正,用以实现整流侧输出能量与逆变侧消耗能量的快速平衡,达到双PWM结构间协调控制的目的;根据仿真结果表明,系统在电机功率突变时,能够实现能量的快速平衡,并且能够减少直流母线电压波动,减少网侧谐波分量和直流侧电容。     

基于滑模控制的独立光伏发电系统控制策略

针对独立运行的光伏发电系统,提出了基于滑模控制的最大功率跟踪(MPPT)策略;针对光伏微源输出功率随机性引起的逆变器输入侧直流母线电压波动,通过储能控制实现电压稳定;针对负载变化引起的系统输出电压波动,设计了系统输出电压电流双闭环控制器。通过MatLab/Simulink对提出控制策略进行了仿真验证。分析结果表明,所提出滑模控制策略可实现光伏电池的MPPT;储能控制策略可有效抑制光伏微源输出功率波动引起的直流母线电压波动;输出电压控制策略能稳定系统电压,确保安全可靠运行。     

一种反激式双输出DC/DC变换器的设计与实现

针对市场上DC/DC开关电源高压输出时,输出电压纹波较大问题,介绍了一种±50 V双输出DC/DC开关电源的设计方法及测试结果。该电路采用电流控制型PWM控制芯片,工作于反激模式。输入输出通过光耦实现隔离。该DC/DC变换器具有带负载能力强、纹波低、输出电压高等特点,可为电子设备提供稳定的供电电压。     

基于动态电价引导的风光水储多源能量管理

楼宇智能微网采用一个多输入直流变换器,代替多个单输入直流变换器,实现风光水储能量汇集,简化电路,降低成本,提高能源综合利用率。它优先利用分布式能源,并能根据大电网动态引导电价移峰填谷,降低楼宇总电费,还利用储能装置和抽水储能赚取电网峰谷差价。多种分布式能源单独/同时连续供给负荷,增加新能源消纳能力,提高自动需求响应的快速性、可靠性和灵活性。小功率仿真实验验证了多源能量汇集的可行性和混合供电系统的稳定性。     

Power management for a DC MicroGrid integrating renewables and storages

A power management controller for a DC MicroGrid containing renewable energy sources, storage elements and loads is presented. The controller ensures power balance and grid stability even when some devices are not controllable in terms of their power output, and environmental conditions and load vary in time. Power balance and desired voltage level for the DC MicroGrid are considered as constraints for the controller. Simulations and an experimental setup are implemented to show the effectiveness of the proposed control action.     

FPGA based design and implementation of power conditioning unit for fuel cell powered vehicle using adaptive vector reference control method

The output of renewable energy is the power of low voltage and high current rated designs. Due to the output voltage being too low it does not meet the required maximum voltage load requirements. Therefore, in order to meet the high voltage load, the required limit of the power converter (DC-DC) is used to increase the voltage to the maximum. . The DC output voltage from a renewable energy source is given as input to a DC-DC converter, and the output generated from the converter is used to drive a load. KY boost converter is one of the recently developed DC-DC converters to reduce output voltage ripple. It is suitable for operation in equipment to below low ripple conditions. The disadvantage of this converter is that the boost voltage is a very low design parameter. To obtain the desired boosted voltage, and also to reduce the output voltage ripple, an optimized algorithm is used. Compared with the existing Drosophila optimization technology, the proposed Adaptive Vector Reference Control (AVRC) Method has higher convergence characteristics and lower output ripple. The simulation results are verified by MATLAB simulation with hardware results. The hardware is developed using the Xilinx FPGAs SPARTAN 6A controller, which simplifies the XC3S500E development board prototype in addition to providing additional flexibility for further improvements. The results clearly show improved performance and validate the model.     

Multifunctional Capabilities of Grid Connected Distributed Generation System with Non‐Linear Loads

This paper deals with the integration of distribution energy resource (DER) connected to a three‐phase grid connected system feeding a variety of loads. The DER is controlled to provide power quality improvement capabilities viz. power factor correction, harmonic reduction, voltage regulation, and load balancing, and it is realized as a voltage source converter (VSC). The developed controller is based on Synchronous Reference Frame (SRF) Theory and an energy based controller that also includes additional features viz. filtration of fundamental voltage extracted from the polluted utility grid voltages. This new controller, realized as an energy controller, is implemented over the square of the DC link voltage of the DER. The control algorithm has been tested for several power quality improvement features and works well for power factor correction, voltage regulation, harmonic reduction, and operation under unbalanced load conditions. Extensive simulation and hardware results are demonstrated on a prototype developed in the laboratory.     

Supervisory control design for systems of multiple sources of energy

This paper describes a supervisory control strategy for electrical energy transfers in multisource renewable energy systems. The sources are coupled onto a DC bus through DC/DC power converters. The aim is to control the energy transfers, according to the sources power and load variations. The controller determines the operating mode of the system. Then, it calculates the power ratio provided by each source and drives the DC/DC power converters with local current and voltage loops in order to regulate the voltage on the DC bus according to a reference value. The main contributions are to use the duty cycle values of the DC/DC power converters as decision criteria to switch the power sources and drive the power ratios, and to present the complete strategy in a single hierarchical control scheme with three stages. A non linear model of the closed loop system is also detailed in order to work out sufficient conditions for asymptotic stability. Finally, the proposed control scheme is validated with an experimental device developed by GREAH Research Group for the control of energy transfers in multi-source renewable energy systems.     

含恒功率负荷的直流微电网系统性稳定性研究

传统的直流微电网稳定性分析法主要集中于基于阻抗匹配准则的小信号稳定性研究,现以含有恒功率负荷的直流微电网为研究对象,对直流微电网稳定性进行系统性分析,即在直流微电网满足大信号稳定性的基础上再去讨论其小信号稳定性。根据直流微电网稳态数学模型,通过李雅普诺夫间接法分析直流微电网满足大信号稳定性时的区域条件;提出一种基于高通滤波的有源补偿方法来增大系统阻尼,减小恒功率负载的负阻尼效应对直流母线电压稳定性的影响;建立含有有源补偿器的直流微电网的小信号模型,采用阻抗匹配准则分析加入有源补偿方法后直流系统的小信号稳定性。仿真结果验证了有源补偿方法对直流母线电压的补偿效果。     

Optimization of harmonics with active power filter based on ADALINE neural network

Mostly the power quality issues in the distribution line system happen due to the presence of harmonics. Especially, the nonlinear loads such as power electronic converters, high-speed semi-conducting switches, and solid state drives were the major causes for harmonics in distorted power system signals. Moreover, the estimation of magnitude and the phase of this harmful harmonic interference are necessary. By taking in to consideration of all the above factors, this paper develops an efficient technique for harmonic estimation and detection of the renewable wind energy resources and elimination of these harmonics will also be done accordingly for getting desired output from wind energy. 8 bit inputs (4 + 4) are collected and used to generate the intended input set for ANN training. The proposed work develops an Adaptive Linear Neural Network (ADALINE) for the estimation of harmonics which is the novelty of this work. For making the harmonics content more negligible and to enhance the load power quality, an Active Power Filter (APF) is used. The novel control design is developed with a Pulse Width Modulation (PWM) control. In addition, feed forward networks (trained by back propagation algorithm) works like a hysteresis band comparator. An APF control design is developed with ADALINE network in which the load and current along with voltage will be analyzed and then the controller will be calculating the control signal by considering the reference compensation current. Afterwards, the power system is injected with compensating current. The simulation is carried out with Matlab-Simulink laboratory prototype is developed with Xilinux 3E Spartan FPGA board to verify the proposed control designs. The proposed work is compared with exiting method comprising Shunt Active Power Filters (SAPF) with ADALINE for the performance perspectives. This method was found to be effective in terms of many parameters such as load voltage, load current, voltage, reactive power, real power and especially THD value than those of the existing works which are considered.     

Robust output regulation of Zeta converter with load/input variations: LMI approach

The output regulation of DC–DC converters is a challenging problem due to the fast switching behavior in the presence of the uncertainty/variation in the model, input, and load. In this paper, the Zeta converter is first analyzed and then using the Linear Matrix Inequality (LMI) theory a robust controller is designed to cope with this issue. Inspired by the photovoltaic applications of the Zeta converter, and due to the nature of the solar cells, not only the load variations but also the input voltage variations are considered in the controller design. Finally, the proposed controller is implemented in a DSP-based controller and its performance is experimentally verified and compared with the widely used PI controller.     

基于模糊PID控制的双向DC/DC变换器研究

双向DC/DC变换器是指在保持变换器两端的直流电压极性不变的情况下,根据实际需要完成能量双向传输的直流变换器。它在直流不间断电源系统、分布式电站、电动汽车以及太阳能电池阵中有广泛的应用。通过对双向半桥变换器的分析,并将其与蓄电池相结合使用,完成能量的双向传输和电池能量对电网的回馈。由于DC/DC变换器在升降压的过程中产生的严重的非线性问题,在控制方案上,采用模糊PID控制的电压、电流双闭环控制。仿真表明,与传统的PID控制相比,该控制方案有效提高了变换器的鲁棒性,减小输出电压波动,能够实现能量的双向流动。     

基于双调谐滤波的动态电压恢复器设计

针对储能装置为不可控整流器的动态电压恢复器易造成直流侧电压不稳定以及电网谐波污染的问题,给出了采用低通滤波和电压闭环控制策略稳定直流侧电压的方法;提出了在不可控整流器前并联双调谐滤波器来滤除谐波,降低储能装置对电网的谐波污染的方法,并详细介绍了双调谐滤波器参数的设计原则。仿真和实验结果验证了设计的合理性。     

DSP的有源钳位反激式光伏并网逆变器设计

本文设计了一套以TI公司的TMS320F28335浮点型DSP为控制核心的单相光伏并网微型逆变器,光伏电池输出的直流电经交错并联反激式变换器转换为2倍于电网频率的正弦双半波电流,再用极性反转桥将正弦双半波电流转换为与电网同频同相的交流电并入电网.采用有源钳位电路能使MOSFET管实现零电压开关(ZVS).提出的一种改进型扰动观察法,可提高MPPT效率.样机实验波形表明,该光伏逆变器输出电流谐波含量较少,能够向电网输送高质量的电能.     

Power flow control based on bidirectional converter for hybrid power generation system using microcontroller

Energy flow management of photovoltaic (PV) based ON-Grid system using BDC converter is analysed and implemented in this paper. The intermittent nature of renewable energies makes the unstable operation of utility grid system. In order to ensure the stable operation of the utility grid system and to support smart grid functionalities, there is the requirement of power electronics participation is high. So that, Grid-connected PV with converters plays an essential role in power management. In this paper, a suitable bidirectional converter (BDC) with advanced optimization control strategies has proposed for power flow management. Further this converter provides a high efficiency, enhanced control flexibility and has the capability to operate in different operational modes from the input to output. The power from PV and grid satisfies the load demand and maintains the continuous power flow to load. The power balance improvement in BDC has power factor correction, harmonics elimination and voltage regulation at AC mains. This paper proposes the analysis of Genetic Algorithm tuning PID (GA-PID) control a process that effectively reduces the bidirectional converter harmonics; this aim is attained and shown in both MATLAB/Simulink and experimental results.