Vadims Strelkovs

Development and integration of adaptive underfrequency load shedding into the smart grid

The objective of underfrequency load shedding (UFLS) is to balance generation and load in case of a significant drop in frequency. Conventional UFLS schemes rely on parameters that are obtained by analyzing predefined scenarios that might not coincide with the actual emergency process. Improved UFLS scheme is presented in the paper that estimates accurate values of active power deficiency thus presenting an opportunity to enhance the efficiency and reliability of power system operation. The theory of the presented scheme is verified by computer modelling. Integration of the new UFLS scheme into the smart grid where it can be most effective by taking advantage of digital communication systems and smart meters is also discussed.

Interconnection of power systems with different under-frequency load shedding schemes

Development of power systems leads to new interconnections that can join power systems with different approaches regarding under-frequency load shedding (UFLS). Parallel operation of different UFLS schemes is analyzed in this paper considering possible UCTE / NORDEL and IPS / UPS interconnection. It is shown that due to differences between UFLS schemes the interconnections stability can be endangered.

Frequency and active power control in islanded power systems based on the magnitude of the disturbance estimation

Paper presents the difficulties of existing anti-emergency automation when operating in islanded power system. The operation of existing anti-emergency automation is apprized from the point of view of elimination of active power deficiency or surplus. Shortages of existing anti-emergency automation as well as necessary areas for improvements are shown. New method for estimation of active power deficiency or surplus is proposed. It is based on the use of the mathematical description of the considered system to provide more accurate operation of anti-emergency automation, for instance, when shedding load or starting generation reserves. The analysis as well as possible application of the proposed method for estimation of active power deficiency or surplus is presented.

The Latvian experience and problems of the grid integration of renewable energy sources in the power system

This paper considers development trends and perspectives for widespread implementation of distributed generation, based on renewable energy sources (RES) in the Baltic States. The main issue of the research is integration of RES into the power grid and electricity markets. Paper provides an overview of legislative statements and main rules, which regulates formal relationships between power producers using RES and network operators. Major problems and barriers that limit intensive development of RES are identified and possible solutions to overcome them are proposed.

Dynamic's problems of frequency and active power control in electric power system

One of the main problems in the area of frequency control is providing proper dynamics of frequency and active power deviation. The paper deals with analysis of the frequency and active power deviation dynamics during turbine governor action. For providing effective frequency control dynamic characteristics of governors should be very similar. The authors suggest a new method for control of the output power of generators using a necessary dynamic law. It allows ensuring frequency and active power control in a mode, adaptive to the operational conditions. Developed dynamic model was used for analysis of frequency and active power behavior during disturbances in the power system. Results of mathematical modeling were compared with the field tests carried out at the hydro power plant. Field tests proved effectiveness of suggested new control method.

Under-Frequency Load Shedding System

During emergency situations in the power system caused by generating power deficiency frequency decline can happen. Dynamics of underfrequency during deficiency of generation in the power system can have very different character. It depends on the value of disturbance, response of emergency automation and the governor system.

Problems of putting into operation generating reserves of the power system during frequency deviation

Paper considers problems of frequency control during power system islanding using as an example the joint electric power system of the Baltic States. Existing frequency actuated emergency automation system is non-adaptive to the variety of emergency situations. New mode for determination of deficiency value in the islanded power system is suggested to control generating reserves actuation. Results of mathematical simulation of frequency control are presented.