Digital Ballast Load Controller for a Small Hydropower Plant

Abstract: For small HPPs operating as off-grid low capacity generation facilities, it is advisable to adjust the ballast load capacity for the AC frequency deviation from the nominal value. At present, there are two practical circuit designs of this type of a controller: 1. Step ballast load connection to the generator output using a contactor-relay switching; and 2. The use of analog power semiconductor automation (analog ballast load). The advantage of this solution is more accurate automatic control. One of the most promising circuit designs for small HPP ballast load controllers is a digital frequency controller. Digital measurement is widely used in modern circuitry, characterized by high accuracy and is well combined with a stepwise automatic ballast switched by thyristor contactors. The practice of using digital frequency controllers to stabilize the rotational speed of an off-grid small HPP has shown that they provide adequate power plant dynamic indicators and stable plant operation with almost all types of hydraulic turbines. This work, based on the analysis of the current use of digital frequency controllers as automatic ballast load controllers for small HPPs, proposes the use of automatic digital microprocessor control systems. © 2020, Allerton Press, Inc.