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Development of a model of an electric network for managing the quality of electric energy

Content

Introduction

At present, the problem of the quality of electricity is reaching a new level. This is due to the changes that are taking place in the electricity industry as a whole. The emergence of new consumers, the use of energy-saving installations, the transition to digital devices, the development of alternative energy and the introduction of distributed generation leads to increased distortion of the quality of electricity (CE). The development of electric networks takes place along the path of increasing their connectivity, as a result of which their structure changes, and the networks become multi-circuit. This is especially evident in networks of 6–10 kV and 0.4 kV. All these changes lead to an exacerbation of the problem of FE, while the approaches to the assessment and management of FE remain unchanged. The previous management principles do not give the desired effect, and the model of the electric network for managing the quality of electricity, corresponding to modern challenges, is currently lacking.

Proceeding from this, the aim of the work is to develop a model of the electric network based on a systematic approach that allows for effective management of the quality of electric energy with a dynamically changing structure of the network and the composition of sources of distortion of the quality of electricity.

This goal should be achieved by the following tasks:

  • analysis of the requirements of the regulatory framework for the regulation and control of CE to build a model of the electric network
  • identification of new properties in modern electrical networks that affect CE;
  • development of principles for constructing a model of an electrical network;
  • building a model of an electric network for controlling FE.

Analysis of the requirements of the regulatory framework for the regulation and control of CE for the construction of a model of an electric network

Currently, Russia has documents on the regulation and quality control of electricity in electric networks, adapted to the market of electric energy and power [1, 2]. CE indicators and standards are established at the points of transmission of electric energy (TPE) to users of electric networks of low, medium and high voltage power supply systems for general use of alternating three-phase and single-phase currents with a frequency of 50 Hz [1]. At the points of transmission of electric energy, electricity is converted into goods in accordance with the contract for the supply or services for the transmission of electric energy of established quality, the responsibility of which is borne by the grid organization. On its side, GOST 32144–2013 proposes to the consumer to provide conditions under which the deviations of the supply voltage at the terminals of the electrical receivers do not exceed the permissible values ​​established for them, if the requirements of this standard for CE at the point of transmission of electric energy are met. This is consistent with the fact that suppliers of electric energy are responsible for ensuring the quality of electric energy supplied to consumers, and manufacturers of electrical installations and electrical equipment and consumers purchasing it are responsible for ensuring that the specified equipment and installations do not create unacceptable conductive electromagnetic interference. The introduction of the concept of TPE in [1] has led to a change in the principles of controlling the quality of electric energy, which must be taken into account when developing a model of an electric network for managing FE. To consider the conceptual approaches to the CE management model, it is necessary to analyze the current state of electric networks.

Identification of new properties in modern electrical networks that affect CE

At the moment, the electric power system is divided into subsystems that are market participants – generation, electric grid complexes and consumers. From the standpoint of managing the quality of electric energy, it does not make sense to consider the FE problem separately for electric grid complexes. This is due not only to the functioning of the electricity markets, but also to the introduction of new innovative technologies and devices that lead to the emergence of new functional properties of networks:

  • the saturation of the network with active elements that allow you to change the topological parameters of the network;
  • the ability to reduce the load on the distribution network during peak periods due to the management of consumers' electrical equipment, the use of distributed generation and alternative sources of electricity from the consumer (batteries, solar panels and other renewable sources);
  • optimization of electricity generation and consumption by regulating the load with maximum regard for consumer requirements (including economic), as well as increasing the capacity of power lines;
  • involvement of consumer regulators in the process of regime management;
  • self-diagnosis, prevention of systemic accidents (failures) and self-healing, and, as a result, reduction of lack of electricity supply to consumers;
  • increasing the observability of the network (information collection) about its current state, including external environmental influences, as well as the processing of this information in real time, including through the use of digital performance devices.

Based on the new properties, the mathematical model of the electric network should include not only networks of different owners, but also generation, consumers, as well as elements that correspond to these network properties. To date, electric network models have been developed for analysis and control of modes (steady and transient), models for calculating electricity losses, network models for controlling reactive power flows, each of which has its own construction principles and performs its own functions. Existing models cannot be applied to the CE management task, since they solve other problems and do not take into account indicators of the quality of electricity. It should be noted that there is currently no network model that would clearly fulfill the tasks of applying a systematic approach to managing the quality of electric energy. The principles for constructing such a model cannot be similar to the principles for constructing the above models. In view of the foregoing, the electric network for controlling FE should be considered from the perspective of a systematic approach.

Development of principles for constructing a model of an electric network for energy quality management

To build a network model, the following modeling principles were chosen: systemic; validity and consistency: completeness of funds used; correctness; the truth of the result; maximum effect: adequacy; compliance of the model with the task being solved; abstracting from secondary details; the correspondence between the required accuracy of the simulation results and the complexity of the model; multivariance of implementations of model elements; modular construction.

Based on the principle of consistency, to solve the tasks of managing FE, the network is considered as a complex of interconnected elements. This is due to the fact that relations with other objects of the electric power system are taken into account: with power sources, including distributed generation, with consumers, energy and capacity markets. The principle of consistency assumes the division of the system into subsystems according to a number of signs, for example, according to the classes of rated voltage, hierarchical, functional sign, etc., which must be taken into account in the model.

The principle of correctness implies compliance of the implemented network model with the set goals and the reliability of the expected results. It is this principle that makes it possible to implement in the model the possibility of using information of different quality, including incomplete, for controlling FE.

The principle of validity and consistency is implemented in the selection of models of parameters of the regime, indicators of electric power quality (PCE), ensuring consistency in the accuracy of the intermediate and final result under given conditions, taking into account the work of energy and power markets.

The principle of completeness of the means used means obtaining the desired result by the selected combination of technologies and technical solutions. Its application will allow you to choose the optimal mathematical apparatus and software for implementing the model.

The principle of truthfulness of the result is implemented taking into account the metrological security of the problem being solved and is based on energy balances and error balances of various kinds. Given the fact that information for managing CE should be collected from different sources and from different owners, and their measuring tools have different errors and their saturation is also different, the implementation of this principle in the model will allow to avoid incorrect results during management.

The principle of maximum effect means the need to achieve the desired result at minimum cost. Using this principle will ensure the minimum cost of the electric network model for controlling the FE during its implementation.

The adequacy principle provides for the model to meet the objectives of the study in terms of complexity and organization, and the model to be considered for the electric network in question in terms of the set of selected properties. Based on this principle, it is envisaged to use such models of mode parameters, SCE and the equivalent of the electric network, which will ensure the achievement of the goal with the minimum complexity of the model structure.

Using the principle of model compliance with the problem being solved means that the model should be built to solve the whole complex of problems that are part of the problem of controlling the quality of electricity in electric networks, taking into account their new properties and features, as well as market relations in the electric power industry. The principle of abstracting from minor details implies a simplification of the model while maintaining the essential properties of the network presented as a system. The classical presentation of this principle is as follows: the model should be simpler than the prototype. Its use will dramatically reduce the requirements for the volume and quality of the source information used to control the quality of electricity.

According to the correspondence principle, between the required accuracy of modeling results and the complexity of the model, when developing a model, its complexity is reduced in the following ways: aggregation, that is, a decrease in the number of variables; replacing the non-linear dependence of the linear in the simulation of the SCE; by changing constraints – by varying constraints one can find possible boundary values ​​of the network model efficiency with different quality of the initial information; limitations of model accuracy – the accuracy of model results cannot be higher than the accuracy of the source data.

A variety of implementations of the models of the information field, the elements used to control the FE, depending on the degree of uncertainty, will ensure the optimal ratio of accuracy/complexity. This is the essence of the principle of multivariance of implementations of network model elements for controlling FE.

Subject to the principle of modular model construction, it becomes possible to use separate modules with minimal connections between them, which greatly simplifies the network model for controlling FE. In this case, the allocation of modules should be made taking into account the separation of the model according to the stages of the solution and the modes of operation of the network. The effectiveness of control actions for managing the quality of electricity directly depends on the network node in which they are implemented. For this purpose, the network model should contain a criterion for the sensitivity of nodes to the introduced control actions.

References

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