Combined Method of Flow-Reduced Dump Load for Frequency Control of an Autonomous Micro-Hydropower in AC Microgrids

Nowadays, microgrids (MGs) play a crucial role in modern power systems due to possibility of integrating renewable energies into grid-connected or islanded power systems. The Load Frequency Control (LFC) is an issue of paramount importance to ensure MGs reliable and safe operation. Specifically, in AC MGs, primary frequency control of each energy source can be guaranteed in order to integrate other energy sources. This paper proposes a micro-hydro frequency control scheme, combining the control of a reduced dump load and the nozzle flow control of Pelton turbines operating in autonomous regime. Some works have reported the integration of dump load and flow control methods, but they did not reduce the dump load value and adjust the nozzle flow linearly to the power value demanded by users, causing the inefficient use of water. Simulation results were obtained in Matlab®/Simulink® using models obtained from previous research and proven by means of experimental studies. The simulation of the proposed scheme shows that the frequency control in this plant is done in correspondence with the Cuban NC62-04 norm of power energy quality. In addition, it is possible to increase energy efficiency by reducing the value of the resistive dump load by up to 7.5% in a case study. The validation result shows a 60% reduction of overshoot and settling time of frequency temporal behavior of the autonomous micro-hydro.

Digital Identification Algorithms for Primary Frequency Control in Unified Power System

The article studies and develops the methods for assessing the degree of participation of power plants in the general primary frequency control in a unified energy system (UES) of Russia based on time series analysis of frequency and power. To identify the processes under study, methods of associative search are proposed. The methods are based on process knowledgebase development, data mining, associative research, and inductive learning. Real-time identification models generated using these algorithms can be used in automatic control and decision support systems. Evaluation of the behavior of individual UES members enables timely prevention of abnormal and emergency situations. Methods for predictive diagnostics of generating equipment in terms of their readiness to participate in the primary frequency control are also proposed. In view of the non-stationarity of the load in electrical networks, the algorithms have been developed using wavelet analysis. Case studies are given showing the operating of the proposed methods.

Efficiency of steam turbines with bypass steam distribution for primary frequency control in power systems

This paper evaluates efficiency of steam turbines with bypass steam distribution involved in a process of primary frequency control in power systems. We calculated power of a steam turbine and power unit in general, and absolute electrical efficiency for both bypass and throttle steam distribution. It was found that bypass steam distribution increases absolute electrical efficiency of steam-gas units while operation under lower capacity. Economic indicators calculated for combined cycle gas units confirm effectiveness of steam turbines with bypass steam distribution involved in primary frequency control.

Testing Photovoltaic Power Plants for Participation in General Primary Frequency Control under Various Topology and Operating Conditions

The energy transition is accompanied by developing a digital decentralized low-carbon energy infrastructure with renewable-based generating plants as its main elements. In 2020, 15 photovoltaic power plants (PVPs) with an installed capacity of 364 MW were commissioned in Russia, which is 21.08% of the total installed PVP capacity of Russia. The findings of an analysis of Russia's current regulatory and technical documents (RTD) concerning the frequency and active power flow control are presented. They indicate that all PVPs must participate in the general primary frequency control (GPFC). This requirement is due to large frequency deviations of transient processes resulting from an emergency active power shortage, which can shut down frequency-maintaining generating plants by relay or process protection devices and industrial consumers with significant damage to them. The requirements suggest full-scale tests of PVP to confirm their readiness for participation in GPFC. The program and results of checking the algorithm of change in the PVP active power, depending on frequency, are demonstrated with an example of one PVP. The full-scale tests confirmed the compliance of the certified PVP with this requirement. The plans for involving PVPs in the power flow control under various topology and operation conditions are considered.