Use of Optimization, Clustering, and Classification techniques in Active Distribution Network Protection: A Qualitative Analysis

Protection schemes are essential in active distribution networks and microgrids’ reliable, efficient, and flexible operation. However, the protection of these networks presents significant challenges due to operational changes, such as variations in topology, distributed energy resources connection/disconnection, and microgrid operating modes, among others. This paper proposes an adaptive protection scheme based on overcurrent devices with several setting groups based on artificial intelligence algorithms. The developed strategy is composed of two stages. In the off-line stage, a clustering technique is employed to group the active distribution network operating scenarios exhibiting similarities. The optimal settings for the protection devices are determined for each set of scenarios. On the other hand, in the on-line stage, the protection strategy’s implementation and operation, considering the active distribution network’s existing communication system, are defined. Furthermore, the approach formulates the overcurrent relay coordination as a mixed-integer non-linear optimization problem, and as a result, the optimal setting of the overcurrent protection devices is obtained. It aims to minimize the operating time, considering the transformers’ thermal limits, fuse operating curves, and overcurrent relay settings. The solution is determined by using an Augmented Lagrangian genetic algorithm. The presented protection scheme is validated on the modified IEEE 34 node test feeder, considering the main operating scenarios of the active distribution networks, such as topology changes, distributed energy resource connection/disconnection, and microgrid operating modes (on-grid and off-grid). The results obtained and its easy implementation indicates the high potential for real-life applications.

The performance of conventional protections has deteriorated in active distribution networks (ADN) because of high penetration of distributed generator (DG) and solid state transformer (SST). In this paper, based on the features of short-circuit current fed by DG and SST, the current distribution characteristics of ADN are analyzed. Moreover, a networked protection scheme is proposed for ADN. This scheme compares the amplitudes of negative-sequence, zero-sequence and phase currents between different ports of grid component to realize fault identification. It can act rapidly and has the ability to cope with large transition resistance. Communication system only needs to transmit current amplitude, and synchronous sampling is not required. In addition, there is no requirement for voltage measurement, which will help to reduce cost. The effectiveness of the protection scheme is verified via simulation tests.

The electrical protection of active distribution networks is crucial for ensuring reliable, safe, and flexible operations. However, protecting these networks presents several challenges due to the emergence of bi-directional power flows, network reconfiguration capabilities, and changes in fault current levels resulting from the integration of inverter-based resources. This paper introduces an innovative protection strategy for active distribution networks, leveraging the principles of distributed coordination and multi-agent systems. The proposed strategy consists of two stages. The first stage involves a fault detection algorithm that relies solely on local measurements, while the second stage uses agent classification to compute the optimal operating time based on a dynamic matrix representation of the fault path, combined with a simplified distributed optimization problem. The coordination process is formulated as a set of linear optimization problems, simplifying the solution. The proposed protection strategy is validated in a real-time simulation environment using a modified CIGRE MV European grid as a case study, considering low-impedance symmetric fault scenarios and topological changes. The results demonstrate that the protection scheme exhibits robust performance, enhancing the adaptability of the protection equipment while ensuring suitable sensitivity and operational speed.

This paper highlights the importance of chronology on voltage protection and control apparatuses in studies of voltage security in active distribution networks with high generation capacity. This paper presents simulation results of a real-life example of a long rural distribution feeder having three voltage regulators in cascade, and a customer whose demand accounts for a large percentage of the total feeder load. The customer is also an independent power producer and its location at the far end of the feeder yields an intricate voltage protection coordination when the customer ramps up and down its own generation at the peak-demand period.

In order to meet the high permeability and the access of large scale distributed generation, at present and in the future, active distribution network becomes the trend of smart grid research. This paper introduces the influence of distribution network voltage distribution and stability of distributed energy access based on active distribution network; The reactive power and voltage optimization control method of active power distribution network is summarized from the aspects of optimal voltage regulation measure, voltage regulation measure of power network equipment, reactive power optimal dispatch of power system, and so on. Analysis of the current status of the research, and summarized the existing active distribution network with a distributed power pickup distribution network reactive power and voltage control of the existence of some problems and the insufficiency still some problems that must be solved in the study of reactive power and voltage optimization control of active distribution network are pointed out.

For the distribution network with high permeability distributed energy access, distribution network fault current distribution network operation mode, the influence of the distributed power control strategy, and the existing in ring network cabinet configuration does not meet the high sensitivity and high reliability requirements of the active power of fuse protection, in this paper, an adaptive protection system for active distribution network is proposed by using the passive protection terminal installed in the ring network cabinet and the protection host configured at the dispatching end. The protection host receives SCADA data of distribution network scheduling to obtain the topology of active distribution network, uses distributed power supply voltage and grid voltage to adaptively calculate the passive protection setting value, and sends the setting value to the passive protection terminal through communication to realize the adaptive protection function of active distribution network. Finally, the simulation model is established, and the fuse protection of active distribution network and the adaptive protection system with passive protection terminals are compared, and the sensitivity and reliability of the adaptive protection scheme are verified.

Based on the analysis of the fault characteristics of the inverter interfaced distributed generation under PQ control and the influence of the distributed generation access on the traditional protection technology, an active distribution network protection scheme considering the capability of regional measurement is proposed. The protection scheme based on the direction of zone current is proposed for the region with enough capability of measurement. The distribution network is divided into zones, and the fault zone is judged by collecting the fault component of current at breakers. As for the region with poor capability of measurement, an reclosing scheme coordinated with DG re-grid timing is proposed. The proposed scheme effectively solves the influence of distributed generation access on traditional protection and reclosing of distribution network. The simulation results of the examples in PSCAD/EMTDC prove the effectiveness of the proposed scheme.

Master-slave strategy based in artificial intelligence for the fault section estimation in active distribution networks and microgrids

The large scale integration of new energy leads to great changes in the characteristics of power flow and fault characteristics of traditional radial distribution network, which has a great impact on the correct action of relay protection devices. The influence of different types of short circuit faults on the protection device is analyzed when the distributed power is connected to the starting bus and the intermediate bus. A current protection scheme using the innovation graph to calculate the correct estimate ratio of lines is proposed. In this scheme, the innovation graph parameters are calculated by the current innovation before the fault and after the fault, and the fault is judged only by comparing the correct estimate ratio of each line in the region. Compared with the conventional method of current protection, the scheme has lower requirements for communication system and improves the complex coordination between contiguous lines. A simplified distribution network model is established in PSASP software to verify the effectiveness of the proposed protection scheme.

Background: Introducing pilot protection in active distribution networks containing PV can improve the reliability and selectivity of protection. However, the basic communication facilities of the existing distribution network make it difficult to meet the requirements of data synchronization, and the PV T-connection to the network leads to sudden changes in the impedance angle. Methods: Therefore, pilot protection of a negative sequence and additional network considering PV is proposed. The scheme is based on the feature that the PV model only outputs positive sequence components after a fault. For asymmetrical faults, the negative sequence impedance detected at both ends of the protection is utilized to construct a comparative negative sequence impedance protection criterion. For symmetrical faults, the voltage characteristics of the faulty additional network are utilized to construct a protection criterion. Results: Finally, an actual distribution network model with PV is constructed in PSCAD to verify the effectiveness and reliability of the protection method. Conclusion: The protection method is selective and reliable and is not affected by high penetration rate and PV fault characteristics.

Distributed energy resource (DER) including wind power, solar energy and energy storage system (ESS) are connected to the active distribution network (ADN) in various combination ways, which makes the distribution network have interaction. As a bridge connecting the transmission grid (TG) and micro grid (MG), ADN breaks the traditional operation pattern of TG+ADN+MG. Considering the physical connections and shared information among TG, ADN and MG, this paper proposes a decentralized and parallel analytical target cascading (ATC) algorithm for TG+ADN+MG multi-level co-optimization dispatch considering primary and secondary frequency regulation. To explore the synergistic ability of the TG+ADN+MG coping with uncertainties of DER, i.e., wind power, the primary and secondary frequency regulation of TG are implemented to cope with uncertainties. Furthermore, the distributional uncertainties of wind power and load are well modeled by data driven, which is proposed in our previous work [1]. An improved 6-bus system is used to test the proposed model, the numerical results illustrate the effectiveness and efficiency of the proposed method.

This paper proposes a decentralized adjustable robust operation model achieving the coordinated operation between an active distribution network (ADN) and microgrids (MGs). Thanks to the autonomous characteristic and heterogeneity of the individual agents in ADNs with multi-MGs, we develop a tailored alternating direction method of multipliers (ADMM)based fully decentralized framework. The linear decision rules are utilized to reformulate the microgrid two-stage adjustable robust operation problem as a computationally tractable solution such that the proposed adjustable robust extension of decentralized ADMM is capable of handling renewable energy uncertainties. The numerical results illustrate the effectiveness of the proposed model.

With recent development of technology and management in power market and equipment, more and more distributed generation (DG) is embedded in the distribution network. However the approach of connecting DG in most cases is based on a so-called ‘fit and forget’ policy and the capacity of DG is limited rigidly by distribution system operator to avoid the negative effects of high level penetration. New management technologies have been proposed to handle the integration of DGs in the distribution networks. In this review, the micro grid (MG) was treated as the local control method to coordinate DGs within a small area of distribution network. And the active distribution network (AND) was treated as the global control mechanism to actively manage DGs, MGs and other equipment. The operation framework of ADN was firstly introduced. Then based on the static and dynamic models of DGs and MGs, impacts of DGs and MGs on the ADN are surveyed from power quality, stability to the operation. Finally, the conclusion and suggestion is given in this paper.

In the new era, consumers put forward higher requirements for the active distribution network. For safety reasons, it is also necessary to study the management technology of microgrid connected to the active distribution network. Based on this, this paper proposes a multi-agent based hierarchical coordinated voltage control technology for active distribution network Agent microgrid. Considering the characteristics of various distributed power sources, a multi-agent model of distributed power sources is established. Using multi-agent system to realize the coordinated control of distributed generation and traditional transformer regulation simplifies the calculation complexity on the basis of ensuring the accuracy of traditional power flow calculation, and has strong application value. Voltage and reactive power control based on multi-agent technology has better flexibility, intelligence and openness, and has achieved a leap forward compared with conventional power electronics technology.

With increasing connection of distributed generations (DGs), the power flow in electric distribution network is no longer unidirectional and the network has become active distribution network. Thus, the connection of DGs in electric distribution networks has created a challenge for distribution network operators due to bidirectional power flow. One of the main technical challenges of an active distribution network is to maintain an acceptable voltage level in the system. This has initiated efforts in using various voltage control strategies to regulate the network voltage profile so that the voltage is maintained at its allowable voltage limits. A number of voltage control methods have been applied to solve voltage control problems associated with the connection of DGs in a distribution system. These voltage control strategies may be classified as decentralized or distributed and centralized or coordinated voltage control. From the literature, a number of coordinated voltage control strategies have been implemented to provide better and faster control to the system. This chapter presents an improved coordinated voltage control method in active electric distribution network by coordinating the three voltage control methods, namely, power factor control, on load tap changer control and generation curtailment control. These voltage control methods are coordinated using fuzzy logic by considering the load bus voltages and DG power as inputs and the voltage control actions as the outputs. The fuzzy logic if-then control rules which are generated to build the fuzzy logic control system are based on the simulations results as well as from the previous works. Results obtained using the fuzzy logic based coordinated voltage control has shown that the voltages are able to be kept within its permissible limits.