definition
Automatic gain control (AutomaTIc Gain Control)
An automatic control method that automatically adjusts the gain of the amplifier circuit in accordance with the signal strength.
The circuit that realizes this function is called AGC ring for short. The AGC loop is a closed-loop electronic circuit, which can be divided into a gain-controlled amplifier circuit and a control voltage forming circuit. The gain controlled amplification circuit is located in the forward amplification path, and its gain changes with the control voltage.
Control Method
The basic components of the control voltage forming circuit are the AGC detector and low-pass smoothing filter, and sometimes also include components such as gate circuits and DC amplifiers. The output signal u0 of the amplifying circuit is detected and filtered by a filter to remove low-frequency modulation components and noise, and a voltage uc for controlling the gain-controlled amplifier is generated. When the input signal ui increases, u0 and uc also increase accordingly.
The increase of uc decreases the gain of the amplifier circuit, so that the change of the output signal is significantly smaller than the change of the input signal, and the purpose of automatic gain control is achieved. The control methods for the gain of the amplifier circuit are: ①Change the DC working state of the transistor to change the current amplification factor β of the transistor. ② Insert an electronically controlled attenuator between the amplifier stages. ③ Use electronically controlled variable resistor as amplifier load. The AGC circuit is widely used in various receivers, recorders and measuring instruments. It is often used to keep the output level of the system within a certain range, so it is also called automatic level control; when used in a voice amplifier or radio, it is said For automatic volume control.
application
In the power industry, AGC refers to: AutomaTIc GeneraTIon Control (AGC, AutomaTIc Generation Control) is one of the paid auxiliary services provided by grid-connected power plants. The generator set is within the specified output adjustment range. Follow the instructions issued by the power dispatching and trading agency, and adjust the power generation output in real time according to a certain adjustment rate to meet the service requirements of the power system frequency and tie line power control. In other words, automatic power generation control (AGC) makes secondary adjustments to the output of some power units in the grid to meet the control target requirements; its basic functions are: load frequency control (LFC), economic dispatch control (EDC), and reserve capacity monitoring (RM) , AGC performance monitoring (AGC PM), tie line deviation control (TBC), etc .; to achieve its basic goals: to ensure the balance of power generation output and load, to ensure that the system frequency is rated, so that the net regional tie line power flow is equal to the plan, the minimum Regional operating costs.
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