What are the adjustment methods of diesel generator excitation regulators?

The excitation system is an important part of the diesel generator set, which has a great influence on the safe and stable operation of the power system and the generator itself. The excitation regulator is one of the main components of the excitation system of the diesel generator set. The excitation regulator controls the output of the excitation power unit according to the input signal and the given regulation criterion. The automatic excitation regulator of the excitation system has a considerable effect on improving the stability of parallel units in the power system.

Diesel generators

 

       The excitation system is an important part of the diesel generator set, which has a great influence on the safe and stable operation of the power system and the generator itself. The excitation regulator is one of the main components of the excitation system of the diesel generator set. The excitation regulator controls the output of the excitation power unit according to the input signal and the given regulation criterion. The automatic excitation regulator of the excitation system has a considerable effect on improving the stability of parallel units in the power system. Then in this article, Dingbo Electric Power will introduce to you what kinds of adjustment methods are available for the excitation regulator of diesel generator sets.

 

       1. Constant terminal voltage (automatic) operation mode

       The closed-loop automatic adjustment mode of the generator excitation system. In this operating mode, the main task of the digital excitation regulator is to maintain the generator terminal voltage constant, generally using the generator terminal voltage as a feedback quantity to achieve PID regulation; in order to improve the stable conditions of the power system operation , the digital excitation regulator can also achieve more complex control laws, such as power system stabilizer (PSS) additional control, linear optimal excitation control (LOED), nonlinear excitation control (NEC) and so on. The operation mode of constant machine terminal voltage (self-power) is the main operation mode of the digital excitation regulator.

 

       2. Constant excitation current (manual) operation mode

       Generally speaking, excitation regulators have two operating modes, "automatic" and "manual", and digital excitation regulators are no exception. In the constant excitation current (manual) operation mode, the digital excitation regulator takes in the signal, compares it with the given value, and sends the control signal to the phase-shift trigger unit after the calculation of the proportional (integral) control law. Due to the limited range of voltage setting in the automatic operation mode, when the generator boost test is performed after the unit is installed, repaired or tripped in an accident, the excitation of the generator is usually adjusted manually to adjust the terminal voltage or the reactive power of the generator. Flirting is relatively smooth, and the adjustment range can be wide.

 

       1. The operation mode of the three-machine system

       Compared with the operation mode in which the two sets of regulators are mutually standby, the main purpose of using the three-machine system is to further improve the reliability and safety of the operation of the digital excitation regulator device by increasing the hardware investment. The three-machine operation mode can be further divided into three-machine standby operation mode and three-out-two voting operation mode;

 

       2. Three-machine standby operation mode

       The working principle of this method is that in addition to the automatic switching between the A machine and the B machine, a backup C machine is also designed. When machine A and machine B both fail, machine C can automatically switch to online operation. Machine C can be designed to have the same functions as machines A and B, but in general, the probability of machine A and machine B failing at the same time is small. To simplify the scheme, machine B can be designed to have a simpler excitation control function, such as only ensuring power generation. The machine continues to run according to the constant excitation current (manual) operation mode.

 

       3. Three out of two voting operation mode

       In this starting mode, the three sets of regulators all work online, the three sets of regulators receive the same external input signal, and the software and hardware structure areas of the three sets are exactly the same. When the three sets of regulators have two sets of output results—the same , that is, the output result is sent to the controlled object part in the excitation system as the output of the digital excitation regulator.

 

       When two sets of regulators in the three machines fail, the digital excitation regulator cannot work. Therefore, the three-to-two voting operation mode has no improvement in reliability compared with the operation mode of the two-machine mutual backup operation. The advantage of the three-to-two voting method is reflected in the improvement of the operation safety of the device, that is, the output of the wrong excitation control signal can be better avoided, thereby avoiding the occurrence of mis-excitation and out-of-control of the generator.