Digital Excitation Control System Research Articles

A Cost-Effective Redundant Digital Excitation Control System and Test Bed Experiment for Safe Power Supply for Process Industry 4.0

Recently, the energy demand and supply situation in the Republic of Korea (ROK) has been largely affected by the fluctuations in the energy markets around the world. Such a situation has provided a basis for requiring improvements to power plant facilities. The automatic generator voltage control systems in large-scale power plants are adopting a rapid-response static excitation method to improve the transient stability. A domestic commercially developed large-scale triple-redundant excitation system is currently operated by the 1000 MW-class nuclear power plant and its efficiency has been verified at the same site. However, such a system is too costly for smaller power plants so that a reliable and low-cost redundant digital excitation control system was developed and introduced in this study to resolve the cost problem. The system has improved its stability and reliability at the same time through double (redundant) configuration. Additionally, the system’s performance was put to the test by conducting a series of control function tests after applying it to the gas turbine used in a thermal power station. This study includes the development of system hardware, simulations as well as on-site experiments and each element was validated as a result. Also, the study discusses and validates the method used for replacing the protective relays at the Kanudi power plant operating in Papua New Guinea. The replacement of 27 and 81 protective relays at the existing power plant was carried out as they did not function properly. New relays were installed after removing the power supply in the existing panel. The individual power output sections of new relays were connected in parallel with the existing properly functioning relays, as previous protective relays had only allowed monitoring without outputting the contents. Thus, the new protective system was designed to enable both existing and new relays to carry out the detection function. It was validated that the replacement was successful. The new system with the new relays is performing properly by protecting its power generator and preventing further accidents.

Self-Tuning of the PID Controller for a Digital Excitation Control System

This paper proposes an indirect method for self-tuning of the proportional, integral, and derivative (PID) controller gains. Some of the modern voltage regulator systems are utilizing PID control for stabilization. Based on given excitation system parameters, several PID tuning approaches are reported. Since in general, these parameters are not available during commissioning, specifically the machine time constants, this lack of information causes a considerable time delay and cost of fuel usage for commissioning the automatic voltage regulator (AVR). To reduce the commissioning time and cost, the excitation system parameters are automatically identified and the PID gains are calculated using well-developed algorithms. Recursive least-square (RLS) with linearization via feedback is proposed to identify the system parameters. The performance of the proposed method is evaluated with several generator sets. With self-tuned PID gains, commissioning is accomplished very quickly with excellent performance results.

The Development of Digital Excitation Control System for Diesel Generator of Nuclear Power Plant and Its Application

The excitation control system of an emergency diesel generator is classified as a kind of safety-related system. Compared with other control systems in a power plant, this system is required to be more reliable and have better performance. In this paper, the digital multi-redundant excitation system for a diesel generator was proposed. The signal processing system of the proposed system makes high speed signal processing and arithmetic in excitation control possible. The improved soft start algorithm and multiple PI parameters adaptation considering the diesel generator characteristics were implemented in the proposed system. The developed system was applied to a nuclear power plant successfully.

A digital excitation control system for use on brushless excited synchronous generators

Automatic voltage regulators for small to medium size brushless excited synchronous generators have traditionally utilized analog electronics. Modern voltage regulator systems are beginning to utilize the power, flexibility, and cost advantage of the microprocessor for control. Furthermore, digital voltage regulators have the added advantage of ease of compensator custom-design. This paper presents a new method for determining the stability parameters for small/medium size generators that have limited effect on overall system stability. A digital excitation control system (DECS) is used as a platform for this discussion. DECS utilizes a discrete proportional, integral and derivative (PID) control algorithm. A direct design (pole placement) method for selecting PID parameters is presented along with the test results.