Optimal configuration strategy of energy storage system in high photovoltaic penetration micro-grid based on voltage sensitivity analysis

Energy storage is an effective measure to deal with internal power fluctuation of micro-grid and ensure stable operation, especially in the micro-grid with high photovoltaic(PV) penetration. Its capacity configuration is related to the steady, safety and economy of micro-grid.In order to improve the absorptive capacity of micro-grid on maximizing the use of distributed PV power in micro-grid, and improve the power quality, an optimal energy storage configuration strategy is proposed, which takes many factors into account, such as the topology of micro-grid, the change of irradiance, the load fluctuation and the cable. The strategy can optimize the energy storage allocation model to minimize the storage power capacity and optimize the node configuration.The key electrical nodes are identified by using the sensitivity coefficient of the voltage, and then the model is optimized to simplify calculation. Finally, an example of the European low-voltage micro-grid and a micro-grid system in the laboratory is used to verify the effectiveness of the proposed method.The results show that the proposed method can optimize the allocation of capacity and the node of the energy storage system.

Study and Implementation on Batteries Charging Method of Micro-Grid Photovoltaic Systems

In the micro-grid photovoltaic systems, the random changes of solar radiation enable lead-acid batteries to experience low SOC (State of Charge) or overcharged for periods of time if directly charged with such traditional methods as decreased charging current, which will reduce lifetime of batteries. What’s more, it’s difficult to find a proper reduction coefficient in decreasing charging current. To adapt to the random changes of circumstance and avoid selecting the reduction coefficient, a new fast charging method named decreased charging current based on SOC is proposed to apply into micro-grid photovoltaic systems. It combines batteries’ SOC with the maximum charging voltage to determine the charging rate without strictly selecting reduction coefficient. By close-loop current control strategy and related scheme, the experiment proves the new method is feasible and verifies that, comparing with decreased charging current, the improved method make batteries’ SOC reach 100% in shorter time as well as the temperature of batteries raise more slowly.

光储微网系统并网/孤岛运行控制策略

首先介绍了储能变流器在光储微网系统不同运行模式下的控制策略。在并网运行模式下,针对光储微网系统中公共连接点(point of common coupling,PCC)处的电压会受到负载变化和光伏出力波动的影响,提出一种基于储能的电压管理控制策略。该控制策略可通过储能变流器的PQ控制,来维持PCC点母线电压在额定电压?10%的范围内波动,从而满足负载对电压质量的需求。当配电网发生故障或储能出力已达功率限值仍不能维持PCC点母线电压在允许范围内时,光储微网切换为孤岛运行模式,此时储能系统采用V/f控制来保证微网系统电压和频率的稳定,并联合光伏系统共同为负载供电。建立光储微网系统的仿真模型,给出变流器的控制策略以及PCC点母线电压的控制流程,仿真结果验证了提出控制策略的有效性。

Influence of Taxation on Supply and Demand in Tomorrow's Crowd Energy Paradigm

The emergence of the energy self-sufficient home presents a new role for government taxation. Policymakers now face the challenge of reflecting this technological change in their decision-making and must assume a greater level of engagement. This paper proposes a number of original fiscal concepts for policymakers to implement in the support of micro-grid development. These are designed to optimise a sustainable transition away from the centralised energy system whilst creating shared value among stakeholders throughout the value chain. Concepts are based on residential micro-grid schemata in Switzerland and are applicable in other countries.

Economic benefit evaluation method for the micro-grid renewable energy system operation

The development of micro-grid renewable energy system in China has achieved rapid growth in recent years,and the micro-grid renewable energy system has been drawing more and more attention by its flexible operation.Due to the randomness,fluctuation,uncertainty of the wind and photovoltaic renewable generation,abundant flexibility is required to meet the needs of safe,reliable and independent operation of the micro-grid energy system.We need to connect large energy systems to accept outside assistance when the micro-grid renewable energy system is short of adjustment capability.Independent operation and network operation will affect the economic benefit of the micro-grid energy system,so it is practically meaningful to study on the economic benefit evaluation of the micro-grid renewable energy system.This paper proposes a micro-grid energy system operation simulation model about wind and photovoltaic generation,the uncertainty of which is tackled based on the scenario generation and extraction techniques.Based on the proposed indices,the economic benefit could be evaluated by simulating the micro-grid energy system operation.The proposed method is validated by a real micro-grid energy system.