Profit maximization for large-scale energy storage systems to enable fast EV charging infrastructure in distribution networks

Large-scale integration of battery energy storage systems (BESS) in distribution networks has the potential to enhance the utilization of photovoltaic (PV) power generation and mitigate the negative effects caused by electric vehicles (EV) fast charging behavior. This paper presents a novel deep reinforcement learning-based power scheduling strategy for BESS which is installed in an active distribution network. The network includes fast EV charging demand, PV power generation, and electricity arbitrage from main grid. The aim is to maximize the profit of BESS operator whilst maintaining voltage limits. The novel strategy adopts a Twin Delayed Deep Deterministic Policy Gradient (TD3) algorithm and requires forecasted PV power generation and EV smart charging demand. The proposed strategy is compared with Deep Deterministic Policy Gradient (DDPG), Particle Swarm Optimization and Simulated Annealing algorithms to verify its effectiveness. Case studies are conducted with smart EV charging dataset from Project Shift (UK Power Networks Innovation) and the UK photovoltaic dataset. The Internal Rate of Return results with TD3 and DDPG algorithms are 9.46% and 8.69%, respectively, which show that the proposed strategy can enhance power scheduling and outperforms the mainstream methods in terms of reduced levelized cost of storage and increased net present value

Energy management considering multiple power markets and microgrid storage

The operational cost of a microgrid is significantly influenced by the response of storage systems and the complexities of the power market’s tariff structures. This paper addresses the challenges arising from the coexistence of new market entries and traditional tariffs, which contribute to a complex market environment. To tackle this issue, the paper establishes a microgrid market environment encompassing four types of tariffs. By modeling the response of electric storage and cold storage in a microgrid, the study formulates a non-linear mixed-integer optimization problem. Numerical studies are then conducted to verify the model and analyze market performance. The results reveal a trade-off in behavior among different market entries when optimizing the total cost of microgrid operation. These findings shed light on the complexities and trade-offs involved in microgrid operational cost optimization within a diverse market environment, offering valuable insights for market participants

DG islanding operation detection methods in combination of harmonics protection schemes

Usages of Renewable Energy resources is increasing in different sections of energy consumption in the world. An unfortunate forecast for use of fossil-fuel sources has provide huge amount of uncertainty and concerns about the future of energy consumption and future resources for feeding the systems and hence it has been resulted in increase in use of replacement sources of energy most importantly the renewable sector including wind and solar systems. These sources are important due to not only non-dependence of them on fossil sources, but also due to significant reduction they can achieve in generation of CO2 and other greenhouse gases. These sources can be used in two different techniques. They can only provide necessary energy for a group of known loads, or they can distribute their energy generation toward network for use of all loads possible. This second wayout generate some advantages and disadvantages. It can enhance the voltage profiles and reduce power losses on systems, but it can also mislead the protection equipments and provide dangers of electrifying since they are generation sources connected directly to the distribution power systems. Also, if the main networks eject from the grid (based on the operation of circuit breakers or black out, etc.) these sources can keep generating electricity in an "Islanding" mode which is not suitable if it happens unintentionally. In this paper, several methods are explained to provide techniques to recognize and detect these incidents and to prevent them by using circuit breakers and other protective equipments. Since both reliability and security of DGs implementations is important for sources, it is needed to cut the electricity generation when it is needed and not to cut it when it is not necessary to keep feeding the loads as maximum period as possible and this fact leads us to provide secure methods to make sure that unacceptable conditions are certainly reached. Due to this statement, combination of- ordinary methods is a more secure method for recognizing the islanding operation mode and make sure that these criteria is reached. Based on IEEE1547 Standard, islanding operation must be detected and disconnected in a maximum of 2 seconds period and this should be observed on all detection and protection methods of Anti-Islanding state for DGs

DC-DC converters application in fuel-cell stack grid integration

In this paper different Fuel-Cell Implementation possibilities to power network are provided and accordingly will discuss considerations for grid connection of renewable energy resources using power electronic resources particularly Fuel-Cell Stacks and will study methods to connect output power of these sources to the system. The basis of network connection of stacks is mostly complex due to the fact that output voltage of these types of sources is usually in minimum of 40 to a maximum of 80 Volts and hence connection of these sources to power networks and heavy high current loads without interference of different types of DC-DC Converters in DC part and PWM Inverters in the AC part of connection is impossible. The sequence of DC-DC-AC should be considered in advance for these systems to prevent faults and separation of these low-voltage sources from the higher voltage networks. So a study on various types of DC-DC converters and different techniques used to connect fuel-cell stacks to grid is done and considerations of separation for network connection of these low voltage DC sources of fuel-cell stack energy to provide adequate energy for both single and three phase loads is studied. Analyses are done to verify the results of connection methods in power electronic equipments

Affects of TCSC usages on Distance protection and Voltage profile of a system ; a novel

TCSCs are used in power systems to improve the profile of Voltage, flexibility and overall power flow capacity of power systems. The basic concept of TCSC usages is that by changing transmission line's impedance, increasing the power transfer capability is reachable and also changing the voltage profile of the system and affecting the stability is possible as well. In this paper, a full study has been done on affects of using Thyristor Controlled Series Capacitors on Voltage profile, Stability and Distance protection of the Power System. Simulations have been done on IEEE Standard model to verify the results. Results show that TCSC will improve Voltage profile and stability on system, But will decrease the accuracy on Distance protection operation since it changes the level of impedance and hence effect on the distance protection relay operation. References suggest using FCL technique to reduce effects of TCSC on Distance Protection. So, first a study on TCSC effects is done. Then, Voltage collapse possibility on stability discussions of power system will be studied. TCSC Simulation Results over stability and Voltage profile show that voltage collapse could be delayed in case of using a TCSC on transmission line. Simulation results on 14 Bus Standard IEEE system verify proposed theory

Renewable hybrids grid-connection using converter interferences

Use of Renewable Energy power sources is the best possible solution today to reduce increasingly risk of global warming and the most important type of renewable is Wind and Solar energies which are the most efficient. The green power generation resources are used power generators in Distributed Generation (DGs) sources that are in direct relation with the use of micro capacity power generating units of power system that are installed in distribution level of power systems or all segments that loads and energy consumers are located. Hybrid systems vary in models. The best hybrid model available today is combination of grid connected wind turbines and solar PV cells that can compensate each other in the grid connected state. In addition, solar cells provide electricity required in day-time while wind turbines compensate the power needed in the night period. Solar cells are consisted of a series of assembly of different cells together to form a flat photovoltaic system to absorb the photons and generate electricity by electrons energized in the circuit. On the other hand, Systems for conversion of energy of wind use PM Synchronous Generators. Recently, wind turbines are even enhanced to use VSD drives to provide the machine the ability of generation in cases that rotational speed varies with changes in speed of wind. The simplified version of the solar-wind hybrid system is provided and Simulations are done to confirm expectation outcomes of this connection