Optimal Coordination Scheme Research Articles

Hybrid Tripping Characteristic-Based Protection Coordination Scheme for Photovoltaic Power Systems

Due to the high penetration of renewable energy sources into the electrical power network, overcurrent relays coordination with highly sensitive and selective protection systems are now two of the most important power protection concerns. In this research, an optimal coordination strategy utilising a new hybrid tripping scheme based on current–voltage characteristics has been devised for overcurrent relays in a power network coupled to a photovoltaic system. This research develops and proves a new optimal coordination scheme based on two optimisation methods, the vibrating particles system and particle swarm optimisation algorithms, in consideration of the impact of renewable sources on fault characteristics. The new optimal coordination approach aims to improve the sensitivity and dependability of the protection system by reducing the tripping time of the overcurrent relays by employing a new hybrid tripping scheme. A specific case study, Conseil International des Grands Réseaux Electriques (CIGRE) distribution network connected to two photovoltaic systems is constructed and presented utilising Industrial software (namely ETAP), and the outcomes of the proposed optimal coordination scheme are compared with standard and recent characteristics from the literature. The hybrid tripping scheme and optimisation techniques are evaluated using different fault and power network model scenarios. The results show that the optimal hybrid tripping scheme provided successfully decreases the overall operating time of the overcurrent relays and increases the sensitivity of the relay during all fault scenarios. The reduction in overall time for the proposed hybrid tripping scheme was 35% compared to the literature for the scenario of a power grid with and without photovoltaic systems.

Optimal coordination of unbalanced power distribution systems with integrated photovoltaic systems and semi‐fast electric vehicles charging stations

Increased integration of photovoltaics (PVs) systems and charging stations for electric vehicles (EVs) has led to a substantial increase in the level of voltage unbalance beyond the acceptable limit. Ordinary voltage regulation devices such as on-load tap changers (OLTCs) and distribution static synchronous compensator (DSTATCOM) are sometimes incapable of adequately addressing this issue without proper coordination with PVs and EVs. This paper presents a novel real-time optimal coordination scheme to determine the tap position of OLTC, the amount of reactive power to be exchanged by DSTATCOM and a PV inverter, and the phase connection of EVs. The proposed scheme aims to maintain the voltage magnitude and voltage unbalance within the statutory limit while minimising the power losses in an active unbalanced power distribution system. Advanced and hybrid particle swarm optimisation (AHPSO) algorithm is also developed to solve the optimisation problem, and its robustness in comparison with other techniques is verified. The impact of uncoordinated voltage control and proposed control on voltage unbalance and power losses are investigated. Time-series simulations confirm the significance and scalability of the developed coordination control scheme on IEEE 37-node and IEEE 123-node test feeders with real data and different PV penetration levels.

Highly Fast Innovative Overcurrent Protection Scheme for Microgrid Using Metaheuristic Optimization Algorithms and Nonstandard Tripping Characteristics

The incorporation of renewable energy microgrids brings along several new protection coordination challenges due to the new and stochastic behaviour of power flow and fault currents distribution. An optimal coordination scheme is a potential solution to develop an efficient protection system to handle the microgrid protection challenges. In this paper, new optimal Over Current (OC) relays coordination schemes have been developed using nonstandard tripping characteristics for a power network connected to renewable energy resources. The International Electrotechnical Commission (IEC) microgrid and IEEE-9 bus systems have been used as benchmark networks to test and evaluate the coordination schemes. The proposed OC relays coordination approach delivers a fast and more reliable performance under different OC faults scenarios compared to traditional approaches. In addition, to improve and evaluate the performance of the proposed coordination approach, four modern and novel metaheuristic optimization algorithms are developed and employed to solve the OC relay coordination problem, namely: Modified Particle Swarm Optimization (MPSO), Teaching Learning (TL), Grey Wolf Optimizer (GWO) and Moth-Flame Optimization Algorithm (MFO). In this paper, the modern metaheuristic algorithms have been employed to handle the impact of renewable energy on the grid, and enhance the sensitivity and selectivity of the protection system. The test cases, consider the impact of integrating the different levels of renewable energy resources (with a capacity increment of 25% and 50%) in the microgrid on the OC relays protection performance by using nonstandard and standard tripping characteristics. In addition, a comparison analysis for the modern metaheuristic algorithms with Particle Swarm Optimization (PSO) algorithm as a common and standard technique in solving coordination problems under different fault scenarios considering also the higher impedance faults are introduced. The results in all cases showed that the proposed optimal nonstandard approach successfully reduced the overall tripping time and improve the performance of the protection system in terms of sensitivity and selectivity.

Advanced Coordination Method for Overcurrent Protection Relays Using New Hybrid and Dynamic Tripping Characteristics for Microgrid

Nowadays, the Overcurrent (OC) and Earth Fault (EF) relays coordination problem is one of the most complex and challenging concerns of power protection and network operators due to the high and volatile generation capacity of renewable energy sources in the grid. In this article, a new and dynamic optimal coordination scheme based on a novel hybrid tripping characteristic has been designed and developed for Over Current Relays (OCRs). Considering the impact of renewable energy sources such as the photovoltaic (PV) system on fault characteristic, this work presents and verifies a novel dynamic and hybrid tripping to achieve minimum tripping time and improve the OCR and EF relays coordination performance in terms of security, sensitivity, and selectivity. The proposed dynamic and hybrid scheme will help the OCRs to cover the EF events, and it has been tested under different fault scenarios compared to the literature. The IEEE-9 and IEEE-33 bus systems are implemented in the ETAP package to validate the effectiveness of the proposed hybrid characteristics against traditionally well-established IEC characteristics. Furthermore, the performance of the proposed advance and dynamic protection approach which doesn’t require a communication infrastructure is investigated for a power network with PV plants under different grid operation modes and topology to provide more robustness protection system. The results, as presented using Industrial software (ETAP), showed that the novel dynamic and hybrid tripping scheme improved the speed of the total time tripping different fault scenarios and location by more than 50% and covers all EF events compared to traditional OCR schemes from the literature. The proposed novel dynamic approach has superior performance in detecting high-impedance faults and significantly reducing the tripping time on the IEEE 33 bus network by 47%.

Highly sensitive and fast microgrid protection using optimal coordination scheme and nonstandard tripping characteristics

Tripping time and optimal overcurrent coordination are nowadays one of the main power system protection concern, due to the high penetration of renewable energy sources in the electrical power network. In this article, optimal coordination scheme has been developed using nonstandard tripping characteristics for the Over Current Relays (OCRs) in a power network connected to a Photovoltaic System (PV). Considering the impact of Distribution Generation (DG) on fault currents and locations on the network, this paper presents and verifies an optimal coordination scheme based on two optimization methods, Particle Swarm Optimization (PSO) algorithm and Genetic Algorithm (GA). The optimal coordination scheme aims to improve the sensitivity and reliability of the protection system by using a nonstandard tripping characteristic to reduce the operating time of OCRs. A specific case study, IEEE-9 bus connected to PV system is developed and presented using Industrial software (ETAP) and the results of the proposed optimal coordination scheme is compared to conventional characteristics in the literature. The proposed nonstandard OCR coordination scheme and optimization algorithms are evaluated using different fault and power network model scenarios. The results indicate that the proposed optimal nonstandard scheme successfully reduce the total operating time of OCRs and improve the relay sensitivity during minimum and maximum fault scenarios.

A real-time optimal coordination scheme for the voltage regulation of a distribution network including an OLTC, capacitor banks, and multiple distributed energy resources

The progression towards smarter grids, incorporating clean energy resources, has increased the integration of distributed generators (DGs) into power distribution networks. The DGs often cause a rise in voltage at their points of common coupling. Ordinary voltage regulation devices such as on-load tap changers (OLTCs) are not capable of addressing these issues adequately without careful coordination with DGs. In this paper, a new supervisory control and data acquisition-based two-stage voltage control scheme for the coordination of an OLTC transformer, capacitor banks (CBs) and the DGs is presented. The proposed scheme sets forth a new criterion for the selection of tap positions of an OLTC. In the first stage, tap positions of the OLTC are changed optimally using the micro genetic algorithm, whereas in the second stage, a recursive genetic algorithm is run to minimise the power losses in order to find the optimal reactive powers for the distribution network. Stochastic modelling of wind speed and solar irradiance data is also performed. The scheme is verified by studying it under four different test cases. An OLTC, CBs, photovoltaic panels, wind power DGs and dispatchable DGs are installed in the distribution network, and an IEEE 37-node test feeder is used for the verification of the proposed scheme. The simulation results show that the scheme achieves the objective of voltage regulation.

Autonomous optimal coordination scheme in protection system of power distribution network by using multi-agent concept

A protection system using a multi-agent concept for power distribution networks is proposed. Every digital over current relay(OCR) is developed as an agent by adding its own intelligence, self-tuning and communication ability. The main advantage of the multi-agent concept is that a group of agents work together to achieve a global goal which is beyond the ability of each individual agent. In order to cope with frequent changes in the network operation condition and faults, an OCR agent, proposed in this paper, is able to detect a fault or a change in the network and find its optimal parameters for protection in an autonomous manner considering information of the whole network obtained by communication between other agents. Through this kind of coordination and information exchanges, not only a local but also a global protective scheme is completed. Simulations in a simple distribution network show the effectiveness of the proposed protection system.