Introduction
The electric power industry since its inception has become a basic sector for all other branches of production and operation in all spheres of society. Over the years, this feature of electricity is becoming increasingly important. At the current stage of development of the electricity, reliable and stable electricity supply relates to issues of national security and is a prerequisite for economic development in any country [1-3].
The improvement of Electric Power Systems (EPS) is an objective process, which is conditioned by various factors , and which collectively define the operating conditions of EPS .
The Reformation of the global and domestic power, which has being taking place since the last 15-20 years is accompanied by a number of contradictions between economic relations and the methods and means of securing durability of EPS [4-8]. The improved operational efficiency, reliability and further development of the power system is closely connected with the necessity of solving complex problems, management of the system in pre- breakdown and breakdown conditions [8-10].
Relevance of the work
The management of EPS under the new conditions of their operation requires effective implementation of the electricity market entity contractual relationship. You must make maximum use of the potential competitive generation and capacity of electrical networks, which comes into conflict with certain conditions to ensure system reliability and the EES mode survivability. When managing a set of scheme-mode states of EES, the mode state is not only accompanied by the probability of an accident, but could lead to serious consequences in case of breakdown [11-13].
One of the most dangerous emergency situations of the EES is stability disruption of the parallel operation and the asynchronous mode. The feature of the present stage of development of EPS is that on the one hand the likelihood of multi-asynchronous mode is increased, and on the other hand the use of innovative technologies enables the creation of systems that provide management and transitional regimes of the EPS on a qualitatively new level which would eliminate the disparity between the economic requirements of management regimes and capabilities to ensure survivability. During operation of power systems and power systems around the world, in 2002-2005 years there were violations of their stable operation with the emergence of dual-frequency and multifrequency induction stroke [14-15].
The asynchronous mode in the EPS is one of the most difficult breakdown modes, in which may damage the equipment, lead to the disruption of electricity consumers and the unwanted development of an breakdown with serious consequences for electric power facilities [11-13].
In this regard, the role of automatic elimination of asynchronous operation (ALARA) substantially increases.
Therefore, the creation of the management of electromechanical processes, which provides resynchronization, after a short induction course that meets the requirements of the development of intellectual EPS (Smart Grid) is an important scientific and technical challenge.
Thus, the theme of work is aimed at developing methods for identifying and management of the asynchronous mode in the EPS is important.
Recearch objectives
To achieve these goals in the following tasks:
– identifying the trends for EPS and capability of new technologies for their use for achieving the work goals;
– analysis methods for detection and regimes controls, primarily related to the registration of the current settings and methods of pattern recognition, which for various reasons could not be fully realized before;
– development of a method to improve the accuracy of separation of synchronous oscillations and asynchronous regimes;
– Development of control method asynchronously.
- development and research of the effectiveness of the control algorithms of the AR at different scheme-operation conditions of the energy system
Content of work
In introduction, the relevance of the topic was stated, the purpose are stated set to tackle major issues, provisions have being formulated reflecting the originality and work value.
In the first section, of the trends analysis of control systems development of power systems was carried done, the capabilities of flexible technologies of power lines (FACTS) and the monitoring of transients (WAMS - SMPR) was examined. The redundancy reduction of control effects can be achieved through the use of this new technology that allows a synchronized measurements distributed system of voltage and current vectors. It is noted that one of the priorities of technological development is the creation and introduction of monitoring system transients into service, providing the needed information about the electromechanical transient mode. The features of SMPR that distinguishes it from the existing telemetering systems are the synchronized measurements modes using space satellites and the registration parameters discreteness, component 0,02 ÷ 0,2 sec.
These technologies are used to build effective management systems of emergency operation, including the AR.
In this section, the classification of the AR detection methods was cited.
Particular attention is drawn to the so-called rapid tests that use the parameters of the current regime and their derivatives, which helps to predetermine the stability breakdown situation. A number of factors, including relatively low accuracy is not possible to implement such methods. The use of digital recording with synchronized measurements allows us to consider the use of rapid methods for detection of AR.
In the second section, the analysis of existing devices ALARA, which in a number works is conventionally represented in three groups:
– Types of panels that use electromechanical devices:
– Microprocessor devices;
– Multifunctional devices that ALARA is one of the functions of the device.
To identify and eliminate AR on the conventional panels using starting element that reacts (locks) to the following parameters:
– The rate of drag reduction (ALARA FSSS);
– Increasing the phase angle of electricity transmission (ALARA FPFU);
– asynchronous rate cycles (ALARA PC);
– Fluctuations in the phase current (ALARA FTC).
One of the main methods based on distance approach is to build a response region (lateral parts of the complex resistance) at high loads and reactive loads, the need to calculate the changes in the rate of change in impedance disturbance. Averaging the speed change ΔR / ΔT leads to significant errors. Another disadvantage is the need to harmonize the various activities with the switch to the angle between the voltage vectors.
Digital devices of ALARA are built on the assessment of the angle between the EMF asynchronously moving parts of EES. By way of assessing the angle of ALARA all devices can be divided into two groups:
– Devices with indirect angle estimation;
– A device with a direct angle estimate.
The main disadvantage of the 1st group devices is the low reliability of AR detection time. There is a great chance as their are nonselective action at deep synchronous swing (I-error of the first kind) and their response is considerably later than the time of AR (error II-the second kind). Attempts to resolve this 1st kind issue, will inevitably lead to the loss of the principal properties of the device ALARA - the identification of AR at its early stage, and in some cases - even to response failure.
The main disadvantage of the 2nd group devices is the need to change the setting device, depending on the mode change of EPS.
It is shown that the description specification of the physical processes in the rotor of a synchronous generator provides the oscillations detection mode and the transition to the AP. The digital technology capabilities make it possible to realize an expression for the induction time which is obtained using the frequency characteristics of generators, which not only increases the level of recognition of characteristic modes, as well as reduce the demands on the preliminary investigation of the transient states features in a certain scheme-mode situation (Fig. 1).
Figure 1 – Areas of regimes depending on the slip angle
The following sections tends to use the following approaches to developing a method of asynchronous mode operation:
– Identification of models based on measurements and the use of measurements;
– using the measured values ??of the parameters of the current regime in the criteria for recognition of standards characteristic modes;
– the establishment and use of the relationship of the conditions and control actions of selective automation of prevention and elimination of asynchronous operation (SAPLAR) proposed in [14,15].
– the control of asynchronous operation of transmission line impact on its switches [16];
– the use of expressions for the induction time of the synchronous generator [17].
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