一种新型回路电阻测试仪的研究与设计

针对传统低压回路电阻测试仪只能在被测设备停电时使用的一大限制,本文提出并设计了一种新型低压回路电阻测试仪。该仪器可在低压设备运行状态下对其回路电阻进行测量,在保证测量精度的前提下减少了设备停电率,大大提高了工作效率。     

分布式发电与智能微电网虚拟仿真实验设计与实现

针对难以开展分布式发电、微电网规划设计、运行控制等物理实验的难题,基于虚拟仿真3D技术构建了海岛和工业园区微电网场景,设计了实例认知、仿真实验、综合设计三层次五模块实验教学方案。通过该虚拟仿真实验,有助于学生掌握微电网规划设计、能量管理、参数设计等原理与方法,全面培养学生分析解决问题能力和研究创新能力。     

A multiagent‐based microgrid operation method considering charging and discharging strategies of electric vehicles

In this paper, we propose a multiagent‐based microgrid (MG) operation method considering charging and discharging electric vehicles (EVs). The proposed system consists of five types of agents: single microgrid controller agent, several load agents, several gas turbines/engine agents, several photovoltaic generation agents, and several electric vehicle agents. In the proposed method, the load balancing can be realized by suppressing sudden fluctuations in supply and demand balance due to the synchronization of charging and discharging of EVs. From the simulation results, it can be seen that the proposed multiagent system could realize the load equalization in MG.     

Advanced controller design based on gain and phase margin for microgrid containing PV/WTG/Fuel cell/Electrolyzer/BESS

Nowadays, with the increase in the amount of power generation related to renewable energy resources, the need for energy storage and management is raised. In this regard, the hydrogen energy plays a critical role in the development of renewable technologies. In view of the above, advanced controller design is presented in this paper to effectively perform load frequency control of islanded fuel cell microgrid based on the wind turbine, photovoltaic, fuel cell, electrolyzer, battery energy storage systems, and residential and commercial loads. The controller design is based on the determination of the controller parameters that the fuel cell microgrid system will provide the desired dynamic properties. In the proposed controller design, virtual gain and phase margin testers are added to provide the desired dynamic properties. The controller's stable parameter plane is determined with the help of the stability boundary locus method, taking into account time delay, gain, and phase margin. First, the accuracy of the stable parameter plane determined for the proposed controller design is demonstrated by means of time domain and eigenvalue analyzes. Finally, in order to show the performance of the advanced controller design and the success of the fuel cell as a backup generator, analysis studies have been carried out using actual data of solar and wind, and appropriate changes of load in studied microgrid.     

基于多代理系统的快速分布式微网经济调度方法

为满足微网对于快速经济调度的需求,利用多代理系统的分布式计算能力,先令设备代理进行本地寻优,信息搜集代理再从中选出拥有全局最低平均价格的出力变化量,在多轮计算后使用微调找到近优解。此方法可兼容各种形式的成本函数。在60个不同场景中进行对比仿真,此方法分别在51和27个场景中的运算结果优于遗传算法和内点法,且在所有场景中运算速度明显更快,这保证了该文方法在大规模微网中的适用性。     

Enhancing stability region of time‐delayed smart power grids by non‐integer controllers

In this study, the impacts of non‐integer order controller on the stable parameter space of the microgrid (MG) frequency control system with fixed communication time delay are investigated and discussed with the help of the stability boundary locus (SBL) method. This study proposes a non‐integer order controller for the load frequency control (LFC) of the MG systems. To that end, the load frequency model of the MG is formulated and then the characteristic equations of this model are obtained. Then, with the help of this characteristic equation, the stable parameter space of the non‐integer controller is determined with regard to different time delay (τ ) and fractional integral order values (α ) using the SBL method. In order to show the accuracy of the obtained stable parameter space, time domain and generalized modified Mikhailov (GMM) criterion studies are carried out for different values of (τ ) and (α ). According to the results obtained, the areas of stable parameter space according to different α values and τ = 1.6 are calculated as 444.8860 for α = 0.4 , 342.9728 for α = 0.7 , 259.3578 for α = 1 , 216.2541 for α = 1.3 and 159.6826 for α = 1.6 . In addition, the areas of stable parameter space according to different τ values and α = 1.4 are calculated as 784.5222 for τ = 1 , 106.3219 for τ = 2 , 29.6959 for τ = 3 and 11.5946 for τ = 4 . Despite the extreme variability arising from nature of resources that make up the MG, the designed non integer order controller with the values selected within the stable parameter space stably carries out LFC control of the MG.     

A voltage support control strategy based on three-port flexible multi-state switch in distribution networks

Voltage sags in power system may lead to serious problems such as the off-grid of distributed generation and electrical equipment failures. As a novel type of power electronic equipment, a flexible multi-state switch (FMSS) is capable to support the voltage during the grid faults. In this paper, a voltage control strategy to support the voltage in a distribution network is proposed by introducing three-port FMSS. The positive–negative-sequence compensation (PNSC) scheme is adopted to control the active and reactive current. This control scheme eliminates active power oscillations at the port of voltage sags and reduces coupling oscillations of other ports. Based on the characteristics of the voltage support under PNSC scheme, two voltage support strategies are proposed. A proportional-integral controller is introduced to provide the reactive power references, which eliminates the errors when estimating the grid voltage and impedance. A current limiting scheme is adopted to keep the port current in a safe range by adjusting the active and reactive power references. The voltage support strategies in two different voltage sags are simulated, and results show the feasibility and effectiveness of the proposed control strategies.     

基于ＰＩＤ控制算法的直流微网容错控制方法研究

构建直流微网容错控制对象模型，调节直流微电网的输出回路参数；以输出功率、直流微网的 参考电压、弱电网下系统惯性响应特征等为约束参量，构建直流微网容错控制目标函数，在不同电网强度下 进行直流微网容错控制的参数自整定性调节，采用无功环比例积分控制方法进行直流微网容错寻优分析， 建立模糊 ＰＩＤ控制模型，采用变结构的模糊 ＰＩＤ控制方法进行直流微网容错控制过程中的自适应加权学习 和误差反馈调节，实现直流微网容错控制改进设计。仿真结果表明，采用该方法进行直流微网控制的容错 性能较好，输出稳定性较强，具有较好的直流微网输出增益。     

Compensation of droop control using common load condition in DC microgrids to improve voltage regulation and load sharing

DC microgrid is one feasible and effective solution to integrate renewable energy resources, as well as to supply reliable electricity. The control objective of DC microgrids is to obtain system stability, low voltage regulation and equal load sharing in per unit. The droop control is an effectively method adopted to implement the control of microgrids with multiple distributed energy units. However in the application of low-voltage DC microgrids, the nominal reference mismatch and unequal cable resistances require a trade-off to be made between voltage regulation and load sharing. In this paper, a unified compensation framework is proposed using the common load condition in local controller, to compensate the voltage drop and load sharing errors. The voltage deviation is compensated with a P controller while the load sharing is compensated through a PI controller. An additional low bandwidth communication is introduced to share the output current information, and the average output current in per unit is generated to represent the common load condition. The performance of the proposed method is analyzed and compared with basic droop control and hierarchical structure method. The large signal stability is analyzed to define the margin of compensation coefficients. Simulations and experiments are carried out to verify the performance of the proposed method.     

Primary and secondary control of an autonomous solar microgrid based power-to-X: Renewable hydrogen conversion

The desire of achieving carbon neutrality and the decarbonization objective is the key driver for the interest in green hydrogen for power plant generation as a clean and flexible energy carrier. In fact, the use of hydrogen-based generating plants as hydrogen fuel cells in solar microgrids plays a major role in the energy transition and adds more reliability to this type of microgrid. This study presents a hierarchical control level 1 and 2 of an islanded microgrid with green hydrogen production, storage, and re-electrification. The purpose of this article is to control a stand-alone/off-grid microgrid with renewable hydrogen storage-based non-dispatchable sustainable energy solutions. An energy management strategy was implemented and a primary and secondary control was applied in order to maintain the voltage and frequency of the islanded microgrid at their steady state values.