三相逆变并网系统的分数阶建模与控制器设计研究

首先基于分数阶微积分理论分析讨论分抗元件的基本特性,并在Matlab/Simscape平台搭建分抗元件的器件级仿真模块,以实现分数阶逆变系统的器件级仿真;其次建立三相并网逆变器的分数阶高低频数学模型,推导分数阶电流内环的解耦控制结构,并引入分数阶PI^λ控制器建立分数阶光伏并网双闭环控制系统。仿真结果表明：所建分抗元件仿真模块能在所选频率段准确模拟分抗元件外特性,分数阶光伏三相逆变器拥有更好的动静态特性,分数阶双闭环控制效果明显优于整数阶双闭环控制。     

基于分数阶电路模型的电动汽车微电网分数阶控制调频策略

文章引入分数阶建模理论,对电动汽车充放电电路的电感电容进行了分数阶等效建模。为了在负荷扰动时提高充放电系统抗扰动性能,提升频率振荡的快速收敛特性和稳定性,在换流器的电流前馈解耦控制中引入分数阶PI控制策略,进行分数阶控制参数的优化,基于MATLAB/Simulink仿真平台搭建了电动汽车充放电分数阶模型。通过算例验证表明,文章所提出的电动汽车分数阶控制模型,在实现微电网与电动汽车双向功率交互的同时,实现了对微电网频率的调节,提高了系统的鲁棒性;控制参数λ的调节,有助于提高系统频率振荡的收敛速度。     

可编程交流电源的分数阶多重复控制技术研究

为了解决多重复控制器精确跟踪多周期信号的难题,针对可编程交流电源提出了一种简单高性能的分数阶多重复控制（MRC）策略,使之能快、准、稳地产生所需的含多个基波频率的多周期性电压信号,用于工业产品测试等用途。首先提出一种由多重复控制器与状态反馈控制器优势互补组合而成的MRC方案及其分析与设计方法,其中包括重复控制器的增益稳定判据以及整定规则。然后,为克服常规数字多重复控制器无法精准调节多周期信号的不足,提出了将多重复控制器分数阶化的解决方案。最后,在1台可用于可编程交流电源的单相逆变器上进行了实验,实验结果验证了所提控制方案的有效性。     

分布式电源对配电网电压骤降影响的仿真研究

随着国家大力推进分布式电源的发展,配电网电压骤降现象将变得更为复杂。基于分布式电源接入配电网的特点,运用电磁暂态仿真PSCAD/EMTDC软件建立分布式电源模型,应用所建立的模型对某企业电网络进行仿真计算,研究分布式电源在不同故障类型、并网方式、容量、接入位置等因素下对电压骤降的影响,得到分布式电源缓解电压骤降问题的策略。     

分布式电源并网对电网运行和管理制度的影响及思考

结合苏州当前分布式电源接入电网项目的情况,总结了分布式电源发展的一些态势和规律,从继电保护、短路电流、谐波污染、无功平衡、经济运行等方面分析了光伏发电并网对电网的影响,分析了分布式电源并网运行后对原有电网管理制度带来的冲击,提出了在分布式电源并网利用中,电网公司作为重要的参与者和“补贴”方,应思考参与各方合作共赢的机制,确保分布式电源并网利用的高效安全以及可持续性.     

基于线损最优的分布式电源接入技术分析

为确保含分布式电源（DG）接入配电网的线损率最低,使配网运行期间的节能降耗目标实现。本文阐述分布式电源接入配电网线损计算方法,以效益最大化为目标,建立遗传算法模型,结合配电网基本情况及模拟结果,输出最终优化指标,实现负荷节点配电容量的最优补偿。本案例通过模型分析和算法研究,输出配网线损率最低优化结果,以望借鉴。     

考虑控制策略的逆变型分布式电源故障分析方法

考虑控制策略的逆变型分布式电源（IBDG）和传统的同步发电机有很大的差异,为了分析逆变型分布式电源和传统发电机的区别以及在控制策略下IBDG的故障输出特性,首先建立了满足控制目标的方程组,然后结合满足外部系统的约束条件,提出了一种计及控制策略的IBDG的故障分析方法.最后结合实例对分析方法进行仿真验证,证明所提方法的正确性,这为考虑控制策略的IBDG故障分析提供一种较为精确的计算方法.     

大量分布式光伏电源并网后的区域保护实现方法

研究了光伏电源并网的故障问题,分析了单个光伏电源并网与大量光伏电源并网的故障特性和保护动作特性。基于大量分布式光伏并网的运行特点及故障发生后的动作行为分析,提出了基于装置采集电量的主保护和基于网络通讯的区域后备保护方案。为尽量减少对现有系统的改动以及减少分布式光伏电源并网的投资,方案依托于新一代的分布式光伏并网接口装置来实现。该装置不仅能解决电网区域后备保护问题,还节约了投资,方便了现场设备安装和维护,为分布式光伏电源并网的大面积推广奠定基础。     

分布式电源与电网同步的研究

在分布式电源并网系统中,通过获取电网侧的瞬时相位信息,使逆变器输出与电网保持同频、同相。文章分析了单同步坐标系软件锁相环算法和双二阶广义积分器锁相环算法的性能特点,根据优势互补的方法,通过检测电路检测三相电路的状态,正确地对锁相环进行切换,以快速精确的检测出正序电压和相位,保证系统中的逆变器正常工作。同时通过利用单纯形法对其锁相环的控制器参数进行优化。研究结果表明,根据电网侧的工作状态,合理地切换锁相环的工作模式,可以快速精确地追踪电网相位和频率信息。     

基于分数阶LCL滤波器的风力发电网侧控制研究

为提高并网电能质量,提出采用分数阶PI（PI^λ）控制器来实现网侧控制、采用分数阶LCL（FOLCL）滤波器进行滤波的方案。首先通过理论推导得出FOLCL滤波器能从根本上避免谐振的特性,然后建立网侧逆变系统分数阶数学模型,并推导分数阶双闭环控制结构,最后在网侧引入PI^λ控制器并对其参数进行设计。仿真实验结果表明：FOLCL滤波器可从根本上避免谐振;所设计的FOLCL滤波器效果明显优于传统的整数阶LCL（IOLCL）滤波器;所建全分数阶逆变并网系统各项指标均明显优于传统方案。     

Wavelet transform-based fault detection method for hydrogen energy-based distributed generators

Integration of hydrogen energy-based distributed generators (HEBDGs) to the main grid causes some power quality (PQ) problems. The conventional fault detection methods fail to detect some PQ disturbances, thus intelligent methods are proposed in the literature recently. This paper focuses on developing a wavelet transform (WT)-based fault detection method for HEBDG systems to detect PQ disturbances in the low-voltage grid connection. The proposed method uses the discrete WT and Daubechies wavelets of order 4 to detect the voltage swell, voltage sag, voltage interruption and transient disturbances in a HEBDG system. The performance of the WT-based method is also compared with the conventional fault detection methods, and using the time-frequency domain analysis by WT increases the stability of the proposed method. The results verify that the conventional methods are not capable of detecting some PQ disturbances properly, but the proposed WT-based method is more reliable according to the conventional methods.     

Fault location method for petal-shaped distribution network with inverter-interfaced distributed generators

In this paper, a fault location method for the petal-shaped distribution network (PSDN) with inverter-interfaced distributed generators (IIDGs) is proposed to shorten the time of manual inspection. In order to calculate the fault position, the closed-loop structure of the PSDN is skillfully exploited, and the common control strategies of IIDGs are considered. For asymmetrical faults, a fault line identification formula based on the negative-sequence current phase differences is presented, and a fault location formula only utilizing the negative-sequence current amplitudes is derived to calculated the fault position. For symmetrical faults, the positive-sequence current at both ends of lines and the current output from IIDGs are used to identify the fault line, and the positive-sequence current on multiple lines are used to pinpoint the fault position. In this method, corresponding current phasors are separated into amplitudes and phases to satisfy the limitation of communication level. The simulation results show that the error is generally less than 1%, and the accuracy of the proposed method is not affected by the fault type, fault position, fault resistance, load current, and the IIDG penetration.     

分布式发电机组经济效益评估模型

根据风电、太阳能、燃气轮机等分布式发电机组的特点,建立了分布式发电机组经济效益评估模型,用于优化配置微电网的发电设备。以某实际微网系统典型日负荷为算例进行仿真,结果验证了该评估模型的有效性。     

Review of anti-islanding techniques in distributed generators

In this paper a revision about different techniques for islanding detection in distributed generators is presented. On one hand, remote techniques, not integrated in the distributed generators, are discussed. On the other hand, local techniques, integrated in the distributed generator, are described. Furthermore, it is discussed how the local techniques are divided into passive techniques, based on exclusively monitoring some electrical parameters, and active techniques, which intentionally introduce disturbances at the output of the inverter, in order to determine if some parameters are affected.     

A new fuzzy adaptive particle swarm optimization for daily Volt/Var control in distribution networks considering distributed generators

This paper presents a novel approach for daily Volt/Var control in distribution systems using Distributed Generation (DG) units. The impact of DG units on Volt/Var control is significant in a distribution network with radial configuration and small X/R ratio. In this paper, a price-based approach is adopted to determine the optimum active and reactive power dispatch for the DG units, the reactive power contribution of the capacitor banks, and the tap settings of the transformers in a day in advance. A fuzzy adaptive particle swarm optimization (FAPSO) method is used to solve the daily Volt/Var control which is a non-linear mixed-integer problem. A mathematical expression of the proposed method and its effectiveness using simulation results are provided.     

A robust control method for a PV-supplied DC motor using universal learning networks

In this paper, a new robust control method and its application to a photovoltaic (PV) supplied, separately excited DC motor loaded with a constant torque is discussed. The robust controller is designed against the load torque changes by using the first and second ordered derivatives of the universal learning networks (ULNs). These derivatives are calculated using the forward propagation algorithm, which is considered as an extended version of real time recurrent learning (RTRL). In this application, two ULNs are used: The first is the ULN identifier trained offline to emulate the dynamic performance of the DC motor system. The second is the ULN controller, which is trained online not only to make the motor speed follow a selected reference signal, but also to make the overall system operate at the maximum power point of the PV source. To investigate the effectiveness of the proposed robust control method, the simulation is carried out at four different values of the robustness coefficient γ in two different stages: The training stage, in which the simulation is done for a constant load torque. And the control stage, in which the controller performance is obtained when the load torque is changed. The simulation results showed that the robustness of the control system is improved although the motor load torque at the control stage is different from that at the training stage.     

燃气轮机余热锅炉噪声综合治理

介绍了燃气轮机余热锅炉HRSG (Heat Recovery Steam Generator)噪声源的产生机理和噪声特性,提出了HRSG噪声的计算原理.结合实际工程项目,针对不同的噪声设计要求,按锅炉本体,烟囱,给水泵,排气管,炉顶平台和其他设备等不同区域,对燃机余热锅炉噪声进行综合治理,并提出了具体设计结构.大量工程...     

A new signal processing-based islanding detection method using pyramidal algorithm with undecimated wavelet transform for distributed generators of hydrogen energy

Machine learning-based fault detection methods are frequently combined with wavelet transform (WT) to detect an unintentional islanding condition. In contrast to this condition, these methods have long detection and computation time. Thus, selecting a useful signal processing-based approach is required for reliable islanding detection, especially in real-time applications. This paper presents a new modified signal processing-based islanding detection method (IDM) for real-time applications of hydrogen energy-based distributed generators. In the study, a new IDM using a modified pyramidal algorithm approach with an undecimated wavelet transform (UWT) is presented. The proposed method is performed with different grid conditions with the presence of electric noise in real-time. Experimental results show that oscillations in the acquired signal can be reduced by the UWT, and noise sensitivity is lower than other WT-based methods. The non-detection zone is zero and the maximum detection and computational time is also 75 ms at a close power match.     

A robust control strategy for combining DCV control with economizer control

Combining demand controlled ventilation (DCV) control and economizer control achieves acceptable and even better indoor air quality with minimum coil energy consumption. The control instability during the transition processes between different control modes are among the major difficulties faced when utilizing economizer control and when combining DCV control with economizer control in applications. A robust control strategy, using “freezing”, gain scheduling, integral term reset and feedback transition control for different transition processes, is developed for addressing these problems. They are evaluated on an air handling unit (AHU) using various simulation tests. The test results demonstrate that the robust control strategy allows stable and robust AHU control.     

Optimization with constraints for excitation control in synchronous generators

Electric power networks are being modified fast, mainly due to the changes introduced in generation systems and load features. Research studies indicate that this process is going to continue in the near future. In this context, several control strategies and devices are used to increase the stability and performance of the new power systems. An optimization with constraints for the excitation control in synchronous generators is presented in this work, in order to damp oscillations in the grid. Generator states move away from their operating points in presence of disturbances in the electric network such as sudden load variations, transmission line losses and short circuits. Then, the generator states must be brought back to its equilibrium point by the excitation control. As the generator model is nonlinear, the controller tuning in order to perform this function is not easy, being necessary to apply nonlinear techniques to obtain a high performance. Moreover, optimal control schemes are currently required owing to a demanding market which rewards power units that deal with energy in an optimal way and keep the generator stable even under network faults.