Sergey Kovalenko

Impact of smart electric thermal storage on transmission grid limitations

This paper examines the potential benefits smart and quickly controllable load can provide for transmission network congestion management if end-users give the transmission network operator or an independent aggregator service access to disconnect their devices in case of contingencies. The necessary amount of available quickly controllable load for the fulfilment of N-1 criteria is found for the case study of the Latvian power system. Of particular interest is the possibility to increase the maximum available transfer capacity between the Latvian and Estonian bidding areas by removing the N-1 provision from the calculation of the cross-border trading capacity if it can be supplied by the controllable load instead. For this purpose, a steady-state power flow model of the 330 kV transmission network and its interconnections with neighboring countries is used for simulations.

Impact of controlled load on the Latvian power system stability

In most countries, electricity is bought and sold at regulated and non-regulated prices. Non-regulated prices are mainly set on the wholesale electricity market and can significantly increase during peak periods due to input of more expensive generation. Another problem, which leads to an increase in prices on the market, is to achieve the carrying capacity of certain sections that does not allow transferring the necessary amount of electricity in the deficit area. At that, overloaded network elements are more prone to emergency shutdown that is not allowable in the peak periods, because it can cause serious system failures. One of the problem solutions may be a load regulation, which, in its turn, may provide both long-term and short-term perspectives. Long-term perspective is aimed to improve energy efficiency carrying out the modernization and reconstruction of the main equipment or the construction of generation sources, etc. Short-term perspective is focused directly on demand management. This article discusses the possible scenarios of the impact of regulated load on the stability of the Latvian power system, based on the power system model circuit created in the software ETAP POWER STATION.

New methods and approaches for monitoring and control of complex electrical power systems stability

Stability of complex electrical power systems (EPS) is an important technical property, indicator of reliable and efficient operation of the EPS. The concept of stability can be divided into three types: the static, dynamic and resulting one. Static stability is the ability of the system to restore normal operation after minor perturbations, in its turn, dynamic and resulting stability is the ability of the system to restore normal operation after large disturbances. The most dangerous system condition is asynchronous operation, when the system loses resulting stability. This paper is devoted to the evaluation issues of static stability of operation mode on the example of the Latvian power system 330 kV. It is separately described the principle of operation of the elimination automatic device of asynchronous operation (AGNA, out of step protection), as a modern reliable means of emergency automation to preserve resulting stability.

Modified givens method for the analysis power system static stability

The current stage of the world energy development is characterized by the creation of powerful territorial and integrated power systems. A gradual unification of the energy markets of different countries is currently going on within a free market: the configuration of networks has been changing, additional relations appear, new energy companies and unions are formed, a sector of renewable sources is rapidly developing with its characteristic distributed generation (decentralization), therefore, the most urgent matter of finding and creating new methods and algorithms for calculation and analysis of complex EPS. In particular, it concerns the issue of problem solving of large-scale power systems with a detailed accounting of basic elements of the system. All ongoing and planned changes both directly and indirectly affect the network configuration, which in its turn leads to the appearance of additional generation and load nodes and, consequently, it requires careful economic and technical computations, in particular, the static stability assessment of the power system.

Isolines of characteristic polynomial for power system static stability analysis

The market economy dictates the terms of unification of the energy systems of the countries that leads to a change in number of interconnections, the increase of the transmitted power, and therefore, it is necessary to reconfigure the networks and, consequently, the recalculation of their normal modes, as well as the project assessment of static stability is required. Stability is an important constraint in power system operation and control. Power system stability is understood as the ability to regain an equilibrium state after being subjected to a physical disturbance. Principal among methods of static stability analysis is the determination of system stability on the consideration of eigenvalues in steady state condition. This provides appropriate strategy to have a quick decision on the systems steady state behavior. The configuration of the electrical systems should be often changed in terms of market relations. The research is aimed to overcome the difficulties while dealing with the characteristic polynomial of a higher degree. Latvian power systems static stability is evaluated applying the methods of localization of the roots of the CP and isolines.

Localization of the roots of the characteristic polynomial (CP) and isolines to analyze static stability

The market economy dictates the terms of unification of the energy systems of the countries that leads to a change in number of interconnections, the increase of the transmitted power, and therefore, it is necessary to reconfigure the networks and, consequently, the recalculation of their normal modes, as well as the project assessment of static stability is required. Stability is an important constraint in power system operation and control. Power system stability is understood as the ability to regain an equilibrium state after being subjected to a physical disturbance. A key method among those of static stability analysis is the determination of system stability on the consideration of eigenvalues in steady state condition. This provides appropriate strategy to have a quick decision on the systems steady state behavior. The configuration of the electrical systems should be often changed in terms of market relations. The research is aimed to overcome the difficulties while dealing with the characteristic polynomial of a higher degree. Latvian power systems static stability is evaluated applying the methods of localization of the roots of the CP and isolines.

Algorithmization in the task of optimization of cascade hydro power plants

Our work focuses on the problem of optimizing a cascade of three small hydro power plants. The optimization is based on deciding how much electricity to produce dependent on the day-ahead hourly electricity prices. The problem is reduced to controlling the water volumes in the cascades reservoirs. We examine two approaches — linear programming based on Matlabs Simplex method (the Linprog function) and a Dynamic programming method. Linear programming is used for the limiting case when electricity prices exhibit daily cyclicality and Dynamic programming works for a finite time period. Two numerical examples are considered.

Factorization of a characteristic polynomial by random search one of its trinomial divisors

In the paper the application of Monte Carlo approach for random search algorithms to finding a pair of conjugated roots of a characteristic polynomial (ChP) is presented. The proposed technique is oriented only to ChPs with real coefficients. The search is produced on the basis of random numbers with uniform distribution in a rather narrow bounded region of the complex plane. Two search methods are considered here: 1) Indirect method to finding a pair of complex conjugate roots; 2) Direct method which results are coefficients of the trinomial divisor of the ChP. Then the conjugated roots can be easily found as roots of the trinomial divisor. If high precision is necessary then the best random hit is used as good initial estimate for further specification of better results by the iterative Newtons method for two equations with two unknowns (the Jacobian is a 2×2 matrix). The specified techniques can be very easily and simply realized in the environment of MS Excel or MATLAB functions at minimum computing resource. The both proposed here methods can be used in the educational process providing good visualization of the study area. Irrespective of the high degree of ChP it is possible to direct the search process so that to find at once only those roots that are of interest in connection with the problem of stability of the corresponding electrical system. The offered algorithms allow creating effective software products.

A study of the change in assessing the stability of the interconnected system when connecting a link (line) between its two subsystems

Under the current conditions of electricity market liberalization, it is often necessary to rapidly perform considerable changes in the power flows of cross-border lines or between isolated subsystems inside the country. For this purpose, in most cases, it is possible to use a simple connection / disconnection of a connection, which leads to a change in the topology of two subsystems. In such a situation it is quite reasonable to consider an issue regarding the change of the stability assessment for the generators on either side of the boundary interconnection before and after switching. In this paper, the authors have studied how the matrix eigenvalues of the coefficients of the two subsystems change after being combined into a single matrix; also, they have derived the conditions at which rapid assessment of the stability of the newly formed interconnected system can be performed according to preliminary estimates of the two subsystems before their interconnection. It has been indicated how and for what purposes this approach can be used when studying the stability of complex electrical systems.