The AGC (Automatic Generation Control) and AVC (Automatic Voltage Control) of photovoltaic power plants are two important control systems, whose main function is to ensure the safe, stable, and economical operation of the power system.
AGC (Automatic Generation Control)
Function: The AGC system is mainly used to automatically control the output of generators in the power system, maintain the frequency of the power system within an appropriate range, and ensure the stability of the power grid.
Parameters:
Total active power: Refers to the total power generation of the power station.
Reactive power: Refers to the reactive power of a power station.
Maximum Adjustable Range: Refers to the maximum power range that the power station can adjust.
Number of inverters: Refers to the number of inverters in the power station.
AVC (Automatic Voltage Control)
Function: The AVC system is used to control reactive power and voltage regulating equipment in the power grid, achieving the goal of ensuring safe, high-quality, and economical operation of the power grid. AVC automatically controls reactive power and voltage regulating equipment in the power grid through computer and communication technology, maintaining the voltage of the grid within an appropriate range.
Parameters:
Target voltage: represents the target voltage value that the power grid wishes to maintain.
Reactive power optimization algorithm: used to calculate the target reactive power of the current online adjustable equipment (inverter, SVC, SVG) in the target state.
The AGC (Automatic Generation Control) and AVC (Automatic Voltage Control) systems of photovoltaic power plants are the two core applications of power system dispatch automation systems.
Collaboration of control objectives:
AGC is mainly responsible for active power control, which adjusts the active output of the generator set to track the planned values of system frequency and interconnection line power, and maintains the flow level of important sections or lines of the power grid within a safe range.
AVC is responsible for reactive power control, maintaining grid voltage compliance and reducing network losses by adjusting the reactive compensation level of reactive equipment.
Coordination of control strategies:
In the power system, there is a coupling relationship between active power and reactive power, and the separate operation of AGC and AVC will affect each other's control effect. Therefore, a coordinated control scheme of AGC and AVC connected at the minute and second time scales is proposed.
At the minute level, an optimal power flow model was established that links active power and reactive power together, and a joint optimization control method of AGC and AVC was proposed.
At the second level, the control strategies of AGC and AVC have been improved, and a coordinated correction control method for AGC and AVC has been proposed.
Real time monitoring and rapid response:
The AVC system will continuously monitor the voltage of each node in the power grid and quickly issue instructions to adjust the excitation system of the generator set when voltage deviation from the set value is detected, so as to restore the voltage to normal level.
The AGC system automatically adjusts the generator output based on the power system frequency measured by sensors, maintaining the frequency of the power system within an appropriate range.
Data collection and instruction execution:
The photovoltaic AGC/AVC group control and adjustment terminal supports remote adjustment function, which receives the main station adjustment instructions and decomposes them for execution to each inverter. Realize the upload of data such as total active and reactive power, maximum adjustable range, and number of inverters; Support the parsing of instructions issued by DMS; Based on the operational performance of the on-site inverters, decompose the target values into the adjustment quantities of each inverter according to the rules; And adjust each inverter according to the decomposed instructions.
Through this collaborative mechanism, AGC and AVC systems jointly maintain the stability of the power system. AGC controls the "rhythm" of frequency, while AVC ensures the "tone" of voltage. The two complement each other and are indispensable.
Photovoltaic inverters play a crucial role in AGC (Automatic Generation Control) and AVC (Automatic Voltage Control) systems, as follows:
Power regulation:
In the AGC system, the photovoltaic inverter is responsible for regulating the output power of the photovoltaic array to maintain balance with the grid demand. Due to changes in solar radiation and weather conditions, the output power of photovoltaic power generation will fluctuate. The AGC system regulates photovoltaic power generation by controlling the output power of the inverter to maintain stable operation of the power grid.
Reactive power control:
In the AVC system, photovoltaic inverters are used to control the voltage level of the power grid, ensuring the quality of power supply and the normal operation of equipment. The integration of photovoltaic power generation systems will have an impact on the voltage of the power grid, especially in situations where there are significant changes in lighting conditions. The AVC system adjusts the grid voltage by controlling the reactive power output of the inverter.
Maximum Power Point Tracking (MPPT):
Photovoltaic inverters have maximum power point tracking function, which can achieve maximum power output of solar panels by changing the load impedance, thereby improving the power generation efficiency of photovoltaic systems.
Grid protection function:
Photovoltaic inverters also have a series of protection functions, such as islanding protection, overload protection, grounding protection, etc., to ensure the safe and stable operation of photovoltaic power plants.
Response to AGC instruction:
When the AGC host receives a mismatch between the current active power plan value and the current output of the photovoltaic power station, it will issue instructions to the inverter, and the inverter will adjust the output power according to these instructions to achieve the adjustment of active power.
Reactive power regulation capability:
Under steady-state conditions of the power grid, the AVC host will fully utilize the reactive power regulation capability of the inverter to regulate the voltage. When the reactive power regulation capability of the inverter is insufficient, the reactive power regulation of the SVC/SVG device will be considered.
Coordination and control:
In the event of a power grid failure, the AVC host quickly adjusts the reactive power of the SVC/SVG device to restore the voltage to normal levels. After the power grid recovers from the fault, the AVC host can replace the reactive power already put into operation by adjusting the reactive power output of the inverter, allowing it to reserve reasonable dynamic reactive power storage.
