DSP based inverter control for alternate energy systems

This paper presents a DSP based algorithm to control inverters used in interfacing alternate energy systems with the electric utility. Since a constant and ripple free dc bus voltage is not ensured at the output of alternate energy sources, the main aim of the proposed algorithm is to make the output of the inverter immune to the fluctuations in the dc input voltage. In this paper a modified space vector pulse width modulation (SVPWM) technique is proposed which will maintain the quality of the ac output of the inverter, regardless of the ripple present at the inverter input. The principle is explained qualitatively and extensive experiments have been carried out to verify and validate the proposed algorithm. A 16-bit fixed-point C2000 family DSP from Texas Instruments was used as the controller to implement the proposed control algorithm.     

Output power control for large wind power penetration in small power system

Nowadays, wind turbine generator (WTG) is increasingly required to provide control capabilities regarding output power. Under this scenario, this paper proposes an output power control of WTG using pitch angle control connected to small power systems. By means of the proposed method, output power control of WTG considering states of power system becomes possible, and in general both conflicting objectives of output power leveling and acquisition power increase are achieved. In this control approach, WTG is given output power command by fuzzy reasoning which has three inputs for average wind speed, variance of wind speed, and absolute average of frequency deviation. Since fuzzy reasoning is used, it is possible to define output power command corresponding to wind speed condition and changing capacity of power system momentarily. Moreover, high performance pitch angle control based on output power command is achieved by generalized predictive control (GPC). The simulation results by using actual detailed model for wind power system show the effectiveness of the proposed method.     

Energy storage-based power buffering control for photovoltaic power generation system

光伏发电系统输出的最大功率随外界环境变化而波动,无法满足负荷的供电需求,针对该问题,建立了基于储能系统的光伏发电系统结构,介绍了光伏发电系统运行原理,分析了系统功率与直流母线电压的关系,设计了无源式储能系统和有源式储能系统对功率进行缓冲以满足控制目标.仿真结果表明,有源式储能系统较无源式储能系统有更好的功率调节作用,通过双向DC-DC变换器的储放能量自动切换控制,使得光伏发电系统输出的功率与负荷需求功率良好匹配,直流电压稳定.     

Reactive power control of wind farms for voltage control applications

In the last few years, there is a strong trend towards decentralised production and supply, leading to a situation where a growing number of small and medium size producers will be connected to energy networks. But at the same time, the power quality of the generation must be ensured and this means that the electrical parameters of the distribution network have to be maintained within their upper and lower limits. Therefore, new problems related to the management and operation of energy transfer and distribution and to the efficient distribution of renewable energy in the grids are actually arising. Hence, it is reasonable to think that dispersed generation (wind energy generation in this paper) should start to take part in the control of electric variables, and in particular, in reactive power control which is directly related to the voltage level control of distribution networks. This paper presents a control strategy developed for the reactive power regulation of wind farms made up with double fed induction generators, in order to contribute to the voltage regulation of the electrical grid to which farms are connected.     

Model predictive control for wind power gradients

We consider the operation of a wind turbine and a connected local battery or other electrical storage device, taking into account varying wind speed, with the goal of maximizing the total energy generated while respecting limits on the time derivative (gradient) of power delivered to the grid. We use the turbine inertia as an additional energy storage device, by varying its speed over time, and coordinate the flows of energy to achieve the goal. The control variables are turbine pitch, generator torque and charge/discharge rates for the storage device, each of which can be varied over given ranges. The system dynamics are quite non‐linear, and the constraints and objectives are not convex functions of the control inputs, so the resulting optimal control problem is difficult to solve globally. In this paper, we show that by a novel change of variables, which focuses on power flows, we can transform the problem to one with linear dynamics and convex constraints. Thus, the problem can be globally solved, using robust, fast solvers tailored for embedded control applications. We implement the optimal control problem in a receding horizon manner and provide extensive closed‐loop tests with real wind data and modern wind forecasting methods. The simulation results using real wind data demonstrate the ability to reject the disturbances from fast changes in wind speed, ensuring certain power gradients, with an insignificant loss in energy production. Copyright © 2014 John Wiley & Sons, Ltd.     

电力系统鲁棒励磁控制器的设计

较系统地介绍了电力系统鲁棒励磁控制器的设计方法。给出单机无穷大系统中水轮发电机组的线性化模型,在此基础上推导出了所研究系统的状态空间描述,并按鲁棒控制理论设计了鲁棒励磁控制器。最后,用计算机仿真的方法对该控制器进行了研究,结果表明线性鲁棒励磁控制器在稳定系统方面优于线性最优励磁控制器。     

Digital power factor control and reactive power regulation for grid-connected photovoltaic inverter

The overall efficiency of photovoltaic (PV) systems connected to the grid depends on the efficiency of direct current (DC) of the solar modules to alternate current (AC) inverter conversion. The requirements for inverter connection include: maximum power point, high efficiency, control power injected into the grid, high power factor and low total harmonic distortion of the currents injected into the grid. An approach to power factor control and reactive power regulation for PV systems connected to the grid using field programmable gate array (FPGA) is proposed. According to the grid demands; both the injected active and reactive powers are controlled.In this paper, a new digital control strategy for a single-phase inverter is carried out. This control strategy is based on the phase shift between the inverter output voltage and the grid voltage, and the digital sinusoidal pulse width modulation (DSPWM) patterns, in order to control the power factor for a wide range of the inverter output current and consequently the control and the regulation of the reactive power will be achieved. The advantage of the proposed control strategy is its implementation around simple digital circuits.In this work, a simulation study of this strategy has been realized using Matlab/Simulink and PSIM. In order to validate its performance, this control has been implemented in a FPGA. Experimental tests have been carried out demonstrating the viability of this control in order to control the power factor and the injected power into the grid.     

Adaptive fuzzy control for wind-diesel weak power systems

This work is concerned with the development of an adaptive fuzzy logic controller for a wind-diesel system composed of a stall regulated wind turbine with an induction generator connected to an AC busbar in parallel with a diesel generator set having a synchronous generator. In this work we propose to use an adaptive network based inference system (ANFIS) in order to generate fuzzy membership functions and control rules for the controller. A feedback linearized proportional integral controller is used to provide the required expert knowledge. A controller design process is identified; it consists of generating input-output data pairs to identify the control variables range and initial fuzzy memberships, and then to tune or adapt them using an ANFIS network structure. The controller inputs are the frequency error and its integral for the governor part of the controller, and the voltage and frequency errors for the automatic voltage regulator. These are readily measurable quantities leading to a simple controller which can be easily implemented     

Output power dispatch control for a wind farm in a small power system

Nowadays, a wind turbine generator (WTG) is required to provide control capabilities as the output power of WTG fluctuates. Under this scenario, this paper proposes an output power control method of a wind farm (WF) connected to a small power system using pitch angle control. In this control approach, the WF output power control is achieved by two control levels: central and local. In the central control, the WF output power command is determined by considering the frequency deviations and wind speeds using a fuzzy function. Then, the local output power commands for each of the WTGs are based on the proposed dispatch control. In the proposed dispatch control, the output commands of each WTG are determined by considering wind conditions for each of the WTGs. The simulation results by using an actual detailed model for the wind power system show the effectiveness of the proposed method. Copyright © 2010 John Wiley & Sons, Ltd.     

基于交叉权重因子的高比例风电接入电网有功校正控制方法

在重载线路输送功率约束下,充分挖掘轻载线路的输送能力,成为在现有网架结构下提高风电外送的重要途径。文章引用交叉权重思想,从潮流基本方程出发,利用线路潮流与注入有功功率灵敏度的关系,提出基于交叉权重因子的有功校正控制方法,根据交叉权重确定风电场调节顺序,使潮流分布均匀合理。该方法可充分发挥轻载线路功率输送能力,缓解在风电大发时部分线路重负荷问题,进而在电网结构不变的条件下有效提高风电送出功率。     

分散式风力发电机组的电压控制

风电的分散式开发不同于大规模开发和分布式开发,由于分散风电靠近负荷中心,直接接入配电网,且不加装无功补偿调节装置SVC,配网中较大的电压波动给分散风电的并网运行带来影响。文章讨论了配网对分散风电的电压控制特点和要求,结合风电机组无功控制能力,并推导出满足配网电压调节要求的风电机组无功控制范围和对机组设备的要求。     

Supercapacitors for power control in a grid-connected photovoltaic system

并网光伏发电系统输出功率的波动性和随机性给并网后系统稳定性,光伏发电消纳以及光伏电站电能质量等方面带来了负面影响,制约了光伏发电的发展.针对这一问题,将超级电容器作为功率调节装置,控制光伏并网系统按指定值平滑,准确地输出功率,使光伏发电具有可调度性.在分析了超级电容特性,系统构成和双向DC/DC变换器状态空间平均小信号模型的基础上,提出功率,电流双闭环反馈滞环电流控制策略,控制超级电容器吸收或补充输出功率的波动成分.在PSCAD/EMTDC 电力系统仿真软件中构建仿真模型,对提出的系统和控制策略进行了仿真分析,良好的仿真结果验证了方法的可行性.     

Distributed generation output control for network power flow management

The development stages in the output control of distributed generation (DG) for network power flow management are illustrated. The first stage requires an assessment of the location of thermally vulnerable components within the distribution network. This is achieved through the offline calculation of thermal vulnerability factors that relate component power flow sensitivity factors to component thermal limits. This directly informs Stage 2 - the installation of meteorological stations and component temperature monitoring equipment for network thermal characterisation. In Stage 3, steady-state component rating models are populated with real-time environmental information from the meteorological stations to generate component real-time thermal ratings. In Stage 4, the power flow sensitivity factors calculated in Stage 1 are embedded within a network power flow management system which, together with the component real-time thermal ratings calculated in Stage 3, is used to control the power output of DG schemes.     

基于TCN的大功率交流传动机车网络控制系统

详细地阐述了基于TCN的大功率交流传动电力机车网络控制系统的组成和功能,重点分析了系统的核心技术,提出了系统的应用价值及推广前景。     

DF8B型机车的恒功率控制及高原功率修正

比较了几种内燃机车在高原地区使用时可以采用的恒功率控制及修正方案,并介绍了青藏铁路用DF8B型机车的高原功率自动修正方法。     

Terminal sliding mode control for maximum power point tracking of photovoltaic power generation systems

This paper presents a novel terminal sliding mode control (TSMC) method for maximum power tracking of photovoltaic (PV) power systems. First, an incremental conductance method is used for maximum power point (MPP) searching. It provides good efficiency under rapidly changing atmospheric conditions, but the accuracy for finding the MPP is highly related to the MPP tracking control. Therefore, a TSMC-based controller is developed to regulate the system to the searched reference MPP. Different from traditional sliding mode control, the developed TSMC assures finite convergence time for the MPP tracking. Furthermore, a common singularity problem that exists in traditional TSMC is removed in this paper. Even if considering uncertainty in the PV power system, the TSMC guarantees high robustness. Finally, several simulations and experiments show the expected control performance.     

Solar energy in providing for alternate lifestyles

Exploitation of cheap and abundant reservoirs of fossil fuels, we know, has permitted some cultures to develop a lifestyle and standard of living which depletes natural resources. To reduce the severity of this draw-down, a concept has been developed which combines the best of modern technology and the experience of more primitive societies in producing a residential option which is low in environmental impact as well as aesthetically attractive.

An educational demonstration of this residential concept is to be developed on a six-acre plot 25 miles southwest of Chicago. This paper will identify the design and usage features which enable the occupants to collect all their residential energy from the sun, to receive all their water from natural rainfall, and to recycle their wastes for return to a horticultural plot which will provide most of their food.

This paper will also discuss the adaptability of this concept to a variety of situations through modifications or abbreviations.     

基于卡尔曼滤波的波浪发电系统反步法最优功率跟踪控制

常规变速控制系统的精度不高,变换器晶闸管开关动作产生的高频纹波较大,为此提出一种基于卡尔曼滤波的反步控制方法。文章通过分析波浪能提取装置的受力及幅频特性,获取了波浪能转化效率最大化的控制条件,并搭建了一套基于卡尔曼滤波的波浪发电反步最优功率控制系统。通过仿真研究了3种控制方法的控制精度和有效性,仿真结果表明:低通滤波反步法存在相位延迟,不能满足最大功率捕获策略的相位条件,影响系统的最终有功功率输出;反步法的跟踪误差较大,导致系统输出的有功功率较低;卡尔曼滤波反步法的动态性能较好,跟踪电流的波形振幅较小,能保证系统全局收敛,在电机速度方向、幅值和频率突变的情况下,仍能快速准确跟踪给定信号,鲁棒性和抗干扰能力更好。     

基于光伏电站有功出力DE求解的无功优化控制策略

文章在分析光伏电站的有功出力对其无功电压和有功损耗影响的基础上,综合考虑光伏逆变器和SVG的无功调节能力,提出一种基于光伏电站有功出力的无功优化控制策略。以光伏电站内部电压偏差最小和有功损耗最小为优化目标建立多目标优化模型,运用模糊理论将其处理为单目标优化模型,最后采用差分进化算法进行求解。经算例仿真,验证了所提策略的可行性和优越性。     

基于有限时间控制的风电机组恒功率控制

针对风力机组的恒功率控制问题,提出了一种基于有限时间控制的方法,分别设计浆距角和转速控制器。通过调节桨距角,使风电场有功功率输出在有限时间内收敛到给定值;转速控制器对发电机的d,q轴电压Ud和Uq的控制,实现转矩响应和转速在有限时间内收敛到期望值。有限时间控制器可实现机组有功功率输出在有限时间内收敛到给定值。仿真结果表明,设计的控制方法是有效的。