Choosing a Power Source of Autonomous Energy-Power Supply of Technological Processes with System Testing for Stability

Author Name(s): Vladimir A. Glukharev, Dmitry A. Solovyev, Ivan N. Popov, Andrei A. Verzilin, Dmitry V. Sivitsky
Author Email: rector@sgau.ru

Abstract

This paper presents a method for selecting a source of comparable electrical power with a test of stability of an autonomous power supply system, using the example of a process of a grain’s preliminary cleaning. The factors of violation of stability due to the feature of starting modes of the node of the electric motor load are considered. An assessment of factors that are taken into account in various approaches to determine source of the power supply is given. The calculated dependencies that consider the power ratio of the powered electric motors and electric generator are proposed, regarding the overload capacity of the generator and function of changing voltage value of the generator when a load is applied. The voltage drop in system due to the large starting currents of short-circuited asynchronous electric motors is
determined for the given parameters of the drive internal combustion engine, and automatic control of the generator excitation. By checking fulfillment of conditions for stability of the power supply system, the obtained analytical dependencies in relation to determining parameters of an autonomous power supply source for a multi-motor load are solved. The methodical apparatus given here allows the calculation of minimum required power of the power supply source, and determination of the system’s performance by checking for stability.

Introduction

The power supply system is considered as part of the regional energy system as a rule. It includes: power supply centers of the power system, switchgears, substation, power lines of various voltage classes, and consumer receivers. The centralized generating stations produce electricity, transmit it over long distances, while the grid companies supply electricity to various consumers through medium and low voltage distribution networks. Consumers play a subordinate role in such a system.
Modern infrastructural conditions for the development of rural areas lead to an increase in the energy intensity of consumers. This is particularly related to the quantitative distribution of various electrical units and complexes, and changes in the modes and schedules of electric power consumption, which in turn requires an increase in the length and configuration of electrical networks. But the seasonality of many technological processes in agricultural production causes seasonal demand for heat and electricity, which reduces the feasibility of upgrading and expanding the rural power grid industry. In this case, it is advisable to switch from the power supply of agricultural enterprises to the power supply of technological processes, and the departure from the centralized power supply to the distributed energy sector,
while maintaining the quality of the power supply.

Conclusion

The proposed method of selecting a generator of comparable power for powering an electromotive load node allows justifying the minimum required rated power of the power supply source, and making a conclusion about performance of system by checking the stability conditions. It was determined that for the considered motor load node, the minimum required rated power of the power supply source is 41% higher than the total installed power of the power consumers. Checking the stability of the power supply system includes monitoring the voltage recovery at the start of the
electric motors, and allows you to determine the performance of the system at the start of each subsequent electric motor. The calculated voltage drop for the considered motor load unit, with the total power of all installed electric motors
is equal to 15 kW, and when choosing a generator Sg nom.= 31 kWA, makes no more than 15%. The function of voltage variation is monotonously increasing, including in the most difficult conditions, with the direct start of the
latter in the technological chain of the electric motor. It indicates the stability and efficiency of the system. When choosing a generator Sg nom.= 22 kWA, while the last electric motor is started, the function of voltage variation is monotonously decreasing. It indicates that the system is not stable, and the voltage drops further in a prolonged start condition, which leads to the inability to perform a successful start.

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