Asynchronous Generator Automated Control System for Supplying Electricity to Sprinkling Machine

Abstract

Sprinkling is often employed to water crops as it creates required soil water regime without any disruptions. The frequent use of squirrel-cage motor with geared trolley and boost pump within the sprinkling machine makes it necessary to employ additional ways to reduce stall current. This raises several scientific issues: defining nature and type of power load of a sprinkling machine, electric generator operational analysis, defining working algorithm of asynchronous generator voltage stabilizing system. The use of asynchronous generators for autonomous power supply is constrained by an insufficient degree of voltage and frequency stabilization. To analyse asynchronous generator operating cycle a laboratory stand has been developed to study the operating modes of an asynchronous generator for a sprinkling machine. An asynchronous motor is connected to an asynchronous generator through an elastic coupling. Its rotation speed is controlled by a frequency converter by means of feedback with an encoder mounted on the motor shaft. Generator energy parameters are measured via network analyzer. Controller algorithm is generated in CoDeSys programme. Stabilization or regulation of voltage is carried out by switching on the capacitor battery through electric contactors using the PLС100 discrete output module, controlled by voltage feedback. Rheostats and a motor load are connected to the generator network to change the current drain. The parameters are monitored and the stand is controlled via computer. Communication between the devices is carried out via the RS-485 interface using the Modbus RTU protocol. To implement the capacitor control algorithm, the lower and upper permissible voltage values for a three-phase load are used in accordance with GOST. At startup, the main capacitors are turned on, then when the capacity increases, the voltage is compared with the reference, if it is less than allowed, additional capacitors must be turned on, if the voltage is more than allowed, additional capacitors are disconnected. Control of the emergency operation is monitored by the current in the phases.