Research on Distributed Cooperative Control Strategy of Microgrid Hybrid Energy Storage Based on Adaptive Event Triggering

Distributed collaborative control strategies for microgrids often use periodic time to trigger communication,which is likely to enhance the burden of communication and increase the frequency of controller updates,leading to greater waste of communication resources.In response to this problem,a distributed cooperative control strategy triggered by an adaptive event is proposed.By introducing an adaptive event triggering mechanism in the distributed controller,the triggering parameters are dynamically adjusted so that the distributed controller can communicate only at a certain time,the communication pressure is reduced,and the DC bus voltage deviation is effectively reduced,at the same time,the accuracy of power distribution is improved.The MATLAB/Simulink modeling and simulation results prove the correctness and effectiveness of the proposed control strategy.

A novel coordinated control strategy considering power smoothing for a hybrid photovoltaic/battery energy storage system

This work presents a novel coordinated control strategy of a hybrid photovoltaic/battery energy storage(PV/BES) system. Different controller operation modes are simulated considering normal, high fluctuation and emergency conditions. When the system is grid-connected, BES regulates the fluctuated power output which ensures smooth net injected power from the PV/BES system. In islanded operation, BES system is transferred to single master operation during which the frequency and voltage of the islanded microgrid are regulated at the desired level. PSCAD/EMTDC simulation validates the proposed method and obtained favorable results on power set-point tracking strategies with very small deviations of net output power compared to the power set-point. The state-of-charge regulation scheme also very effective with SOC has been regulated between 32% and 79% range.

Wind Power Flow Optimization and Control System Based on Rapid Energy Storage

风电功率的间歇与波动致使电场容量可信度低、可调度性差；同时易引起局部电网的电压不稳、频率波动，影响了系统的电能质量及稳定性。针对此现象，将超级电容器与蓄电池组成快速储能装置，用于风电的潮流优化控制。采用三重双向直流变换电路控制储能元件间的功率流动；采用四象限交直流变换电路控制储能与电网间的能量交换。提出基于超级电容器电压低频波动抑制的功率分配方法，可显著减少蓄电池的充放次数；提出基于储能元件荷电状态的储能能量调整规则，可避免储能元件的过充和频繁深度放电，以优化其功率调节能力。实验结果表明，系统可实现2种储能元件的优势互补，能有效平滑调节风电注入电网的有功功率，并实时补偿控制风电接入点的无功功率。

Hybrid Power Systems Energy Controller Based on Neural Network and Fuzzy Logic

This paper presents a novel adaptive scheme for energy management in stand-alone hybrid power systems. The proposed management system is designed to manage the power flow between the hybrid power system and energy storage elements in order to satisfy the load requirements based on artificial neural network (ANN) and fuzzy logic controllers. The neural network controller is employed to achieve the maximum power point (MPP) for different types of photovoltaic (PV) panels. The advance fuzzy logic controller is developed to distribute the power among the hybrid system and to manage the charge and discharge current flow for performance optimization. The developed management system performance was assessed using a hybrid system comprised PV panels, wind turbine (WT), battery storage, and proton exchange membrane fuel cell (PEMFC). To improve the generating performance of the PEMFC and prolong its life, stack temperature is controlled by a fuzzy logic controller. The dynamic behavior of the proposed model is examined under different operating conditions. Real-time measured parameters are used as inputs for the developed system. The proposed model and its control strategy offer a proper tool for optimizing hybrid power system performance, such as that used in smart-house applications.

Analysis of Hybrid Rechargeable Energy Storage Systems in Series Plug-In Hybrid Electric Vehicles Based on Simulations

In this paper, an extended analysis of the performance of different hybrid Rechargeable Energy Storage Systems (RESS) for use in Plug-in Hybrid Electric Vehicle (PHEV) with a series drivetrain topology is analyzed, based on simulations with three different driving cycles. The investigated hybrid energy storage topologies are an energy optimized lithium-ion battery (HE) in combination with an Electrical Double-Layer Capacitor (EDLC) system, in combination with a power optimized lithium-ion battery (HP) system or in combination with a Lithium-ion Capacitor (LiCap) system, that act as a Peak Power System. From the simulation results it was observed that hybridization of the HE lithium-ion based energy storage system resulted from the three topologies in an increased overall energy efficiency of the RESS, in an extended all electric range of the PHEV and in a reduced average current through the HE battery. The lowest consumption during the three driving cycles was obtained for the HE-LiCap topology, where fuel savings of respectively 6.0%, 10.3% and 6.8% compared with the battery stand-alone system were achieved. The largest extension of the range was achieved for the HE-HP configuration (17% based on FTP-75 driving cycle). HP batteries however have a large internal resistance in comparison to EDLC and LiCap systems, which resulted in a reduced overall energy efficiency of the hybrid RESS. Additionally, it was observed that the HP and LiCap systems both offer significant benefits for the integration of a peak power system in the drivetrain of a Plug-in Hybrid Electric Vehicle due to their low volume and weight in comparison to that of the EDLC system.

Towards Implementation of Smart Grid: An Updated Review on Electrical Energy Storage Systems

A smart grid will require, to greater or lesser degrees, advanced tools for planning and operation, broadly accepted communications platforms, smart sensors and controls, and real-time pricing. The smart grid has been described as something of an ecosystem with constantly communication, proactive, and virtually self-aware. The use of smart grid has a lot of economical and environmental advantages;however it has a downside of instability and unpredictability introduced by distributed generation (DG) from renewable energy into the public electric systems. Variable energies such as solar and wind power have a lack of stability and to avoid short-term fluctuations in power supplied to the grid, a local storage subsystem could be used to provide higher quality and stability in the fed energy. Energy storage systems (ESSs) would be a facilitator of smart grid deployment and a “small amount” of storage would have a “great impact” on the future power grid. The smart grid, with its various superior communications and control features, would make it possible to integrate the potential application of widely dispersed battery storage systems as well other ESSs. This work deals with a detailed updated review on available ESSs applications in future smart power grids. It also highlights latest projects carried out on different ESSs throughout all around the world.

An Advanced FMRL Controller for FACTS Devices to Enhance Dynamic Performance of Power Systems

The parameters of power system slowly change with time due to environmental effects or may change rapidly due to faults. It is preferable that the control technique in this system possesses robustness for various fault conditions and disturbances. The used flexible alternating current transmission system (FACTS) in this paper is an advanced super-conducting magnetic energy storage (ASMES). Many control techniques that use ASMES to improve power system stability have been proposed. While fuzzy controller has proven its value in some applications, the researches applying fuzzy controller with ASMES have been actively reported. However, it is sometimes very difficult to specify the rule base for some plants, when the parameters change. To solve this problem, a fuzzy model reference learning controller (FMRLC) is proposed in this paper, which investigates multi-input multi-output FMRLC for time-variant nonlinear system. This control method provides the motivation for adaptive fuzzy control, where the focus is on the automatic online synthesis and tuning of fuzzy controller parameters (i.e., using online data to continually learn the fuzzy controller that will ensure that the performance objectives are met). Simulation results show that the proposed robust controller is able to work with nonlinear and nonstationary power system (i.e., single machine-infinite bus (SMIB) system), under various fault conditions and disturbances.

Hybrid Power System Options for Off-Grid Rural Electrification in Northern Kenya

For domestic consumers in the rural areas of northern Kenya, as in other developing countries, the typical source of electrical supply is diesel generators. However, diesel generators are associated with both CO2 emissions, which adversely affect the environment and increase diesel fuel prices, which inflate the prices of consumer goods. The Kenya government has taken steps towards addressing this issue by proposing The Hybrid Mini-Grid Project, which involves the installation of 3 MW of wind and solar energy systems in facilities with existing diesel generators. However, this project has not yet been implemented. As a contribution to this effort, this study proposes, simulates and analyzes five different configurations of hybrid energy systems incorporating wind energy, solar energy and battery storage to replace the stand-alone diesel power systems servicing six remote villages in northern Kenya. If implemented, the systems proposed here would reduce Kenya’s dependency on diesel fuel, leading to reductions in its carbon footprint. This analysis confirms the feasibility of these hybrid systems with many configurations being profitable. A Multi-Attribute Trade-Off Analysis is employed to determine the best hybrid system configuration option that would reduce diesel fuel consumption and jointly minimize CO2 emissions and net present cost. This analysis determined that a wind-diesel-battery configuration consisting of two 500 kW turbines, 1200 kW diesel capacity and 95,040 Ah battery capacity is the best option to replace a 3200 kW stand-alone diesel system providing electricity to a village with a peak demand of 839 kW. It has the potential to reduce diesel fuel consumption and CO2 emissions by up to 98.8%.

Control strategy for energy recovery system in hybrid forklift

After analyzing the working condition of the conventional diesel forklift,an energy recovery system in hybrid forklift is considered and its simulation model is built.Then,the control strategy for the proposed energy recovery system is discussed,which is validated and evaluated by simulation.The simulation results show that the proposed control strategy can achieve balance of the power and keep the state of charge(SOC) of ultra capacitor in a reasonable range,and the fuel consumption can be reduced by about 20.8% compared with the conventional diesel forklift.Finally,the feasibility of the simulation results is experimentally verified based on the lifting energy recovery system.

Coordinated control strategy for a PV-storage grid-connected system based on a virtual synchronous generator

Due to the characteristics of intermittent photovoltaic power generation and power fluctuations in distributed photovoltaic power generation,photovoltaic grid-connected systems are usually equipped with energy storage units.Most of the structures combined with energy storage are used as the DC side.At the same time,virtual synchronous generators have been widely used in distributed power generation due to their inertial damping and frequency and voltage regulation.For the PV-storage grid-connected system based on virtual synchronous generators,the existing control strategy has unclear function allocation,fluctuations in photovoltaic inverter output power,and high requirements for coordinated control of PV arrays,energy storage units,and photovoltaic inverters,which make the control strategy more complicated.In order to solve the above problems,a control strategy for PV-storage grid-connected system based on a virtual synchronous generator is proposed.In this strategy,the energy storage unit implements maximum power point tracking,and the photovoltaic inverter implements a virtual synchronous generator algorithm,so that the functions implemented by each part of the system are clear,which reduces the requirements for coordinated control.At the same time,the smooth power command is used to suppress the fluctuation of the output power of the photovoltaic inverter.The simulation validates the effectiveness of the proposed method from three aspects:grid-connected operating conditions,frequency-modulated operating conditions,and illumination sudden-drop operating condition.Compared with the existing control strategies,the proposed method simplifies the control strategies and stabilizes the photovoltaic inverter fluctuation in the output power of the inverter.

Optimal Energy-Efficient Transmission for Hybrid Spectrum Sharing in Cooperative Cognitive Radio Networks

In order to improve the energy efficiency(EE)in cognitive radio(CR),this paper investigates the joint design of cooperative spectrum sensing time and the power control optimization problem for the secondary user systems to achieve the maximum energy efficiency in a cognitive network based on hybrid spectrum sharing,meanwhile considering the maximum transmit power,user quality of service(QoS)requirements,interference limitations,and primary user protection.The optimization of energy efficient sensing time and power allocation is formulated as a non-convex optimization problem.The Dinkelbach’s method is adopted to solve this problem and to transform the non-convex optimization problem in fractional form into an equivalent optimization problem in the form of subtraction.Then,an iterative power allocation algorithm is proposed to solve the optimization problem.The simulation results show the effectiveness of the proposed algorithms for energy-efficient resource allocation in the cognitive network.

Research on power control strategy of household-level electric power router based on hybrid energy storage droop control

In the light of user-side energy power control requirements, a power control strategy for a household-level EPR based on HES droop control is proposed, focusing on the on-grid, off-grid and seamless switching process. The system operating states are divided based on the DC bus voltage information with one converter used as a slack terminal to stabilize the DC bus voltage and the other converters as power terminals. In the on-grid mode, the GCC and the HES are used as the main control unit to achieve on-grid stable operation, whereas in the off-grid mode, the PV, HES and LC are used as the main control unit at different voltages to achieve stable operation of the island network. Finally, a DC MG system based on a household-level EPR is developed using the PSCAD / EMTDC simulation platform and the results show that the control strategy can effectively adjust the output of each subunit and maintain the stability of the DC bus voltage.

Average Current Control with Internal Model Control and Real-time Frequency Decoupling for Hybrid Energy Storage Systems in Microgrids

Among hybrid energy storage systems(HESSs),battery-ultracapacitor systems in active topology use DC/DC power converters for their operations.HESSs are part of the solutions designed to improve the operation of power systems in different applications.In the residential microgrid applications,a multilevel control system is required to manage the available energy and interactions among the microgrid components.For this purpose,a rule-based power management system is designed,whose operation is validated in the simulation,and the performances of different controllers are compared to select the best strategy for the DC/DC converters.The average current control with internal model control and real-time frequency decoupling is proposed as the most suitable controller according to the contemplated performance parameters,allowing voltage regulation values close to 1%.The results are validated using real-time hardware-in-the-loop(HIL).These systems can be easily adjusted for other applications such as electric vehicles.

A Novel Polymorphic Topology with Hybrid Control Strategy Based LLC Resonant Converter for Ultra-Wide Input Voltage Range Applications

To realize effective utilization of renewable energy sources,a novel polymorphic topology with hybrid control strategy based LLC resonant converter was analyzed and designed in this paper.By combining the merits of a full bridge LLC resonant converter,three-level half bridge LLC resonant converter,and variable frequency control mode,the converter realizes an intelligent estimation of input voltage by automatically changing its internal cir-cuit topology.Under this control strategy,different input voltages determine different operation modes.This is achieved in full bridge LLC mode when the input voltage is low.If the input voltage rises to a certain level,it operates in three-level half bridge LLC mode.These switches are digital and entirely carried out by the DSP(Digi-tal Signal Processor),which means that an auxiliary circuit is unnecessary,where a simple strategy of software modification can be utilized.Experimental results of a 500W prototype with 100V~600V input voltage and full load efficiency of up to 92%are developed to verify feasibility and practicability.This type of converter is suitable for applications with an ultra-wide input voltage range,such as wind turbines,photovoltaic generators,bioenergy,and other renewable energy sources.

计及SOC自恢复的混合储能平抑风电功率波动控制

混合储能系统能够较好地应对复杂的风电波动,有效地提高电网的稳定性和安全性。在混合储能平抑风电功率波动的典型应用场景下,该文首先提出一种计及荷电状态(SOC)自恢复的混合储能平抑风电功率波动控制方法,在满足风电平抑需求的情况下,通过模型预测控制快速调节储能在平抑功率过程中的荷电状态,提高储能持续稳定运行能力;然后,为提高混合储能系统协调运行能力,设计了加权滑动平均(WMA)-模糊控制策略对超级电容和蓄电池功率进行动态分配;最后,结合实际风电功率数据,通过仿真验证了所提策略能有效平衡储能寿命和平抑风电波动的矛盾,能充分考虑两种储能设备的特性差异并提高功率分配的合理性。

平抑风电波动的电-氢混合储能容量优化配置

针对电-氢混合系统协同平抑接入新型电力系统的新能源波动问题,提出考虑碱性电解槽运行特性的电-氢混合储能容量优化配置方案。首先,基于经验模态分解,将原始风电功率信号分解为符合波动量限值的直接并网分量和混合储能功率任务;在综合考虑电化学储能和氢储能介质充放电功率约束和存储状态约束的基础上,制定计及碱性电解槽运行特性的混合储能能量管理策略。基于此策略,以综合成本最小为目标,建立用于平抑风电波动的电-氢混合储能容量配置模型,并通过实际数据进行计算分析。算例结果表明,所提策略下的容量配置方案,在满足平抑需求的前提下,可以有效提高系统经济性。

基于混合储能的交直流混联微电网功率分级协调控制策略

针对交直流混联微电网孤岛运行时,仅靠互联变流器协调网间功率无法有效缓解系统频率与电压波动,且单一蓄电池储能难以适用多场景功率需求的问题,提出利用超级电容和蓄电池混合储能的交直流混联微电网功率协调控制策略。将混合储能作为储能子网连接在直流母线上,优先采用超级电容平抑交直流子网内功率波动,提出以储能荷电状态来划分五种工作模式的改进混合储能控制策略。兼顾超级电容快速响应特性和减少互联变流器的频繁起动,根据直流子网电压和交流子网频率波动程度,提出功率自治和功率互济工况的两级分层协调控制策略。通过设计混合储能处于不同工作模式的网间功率互济场景,仿真证明了所提混合储能和互联变流器协调控制策略能够平抑各子网负荷功率波动。