Understanding the AGC (Automatic Generation Control) and are both core means for grid operators to remotely and automatically control the output (active or reactive) of power plants.
1. AGC-automatic generation control
1.
Control object: active power output by the power station.
Working principle: The energy management system of the power grid dispatching center calculates the total active power regulation demand required to maintain the frequency stability according to the load forecast of the whole network, the operation status of the unit, the tie line plan and the system frequency measured in real time. This total demand will be allocated to each power plant (including photovoltaic power plants) participating in AGC according to a certain strategy (such as the proportion of regulation capacity). The dispatching center sends the active power set value command to the AGC system of the photovoltaic power station in real time through a dedicated communication channel (such as the power dispatching data network). After receiving the set value command, the AGC system of the photovoltaic power plant will quickly adjust the actual active power output of the power plant to make it as close as possible to and track the set value.
2. When the set value is lower than current maximum power, the AGC system controls the inverter group to reduce the actual output power ( "load reduction").
Energy storage system coordination: If the power plant is equipped with batteries Light Abandonment: When the set value is required to be lower than maximum power under the current lighting conditions, it is essentially an active light abandonment. 3. Why do PV power plants need to participate in AGC? Fluctuations in the load (increase or decrease) can cause the frequency to deviate from the rated value (e.g. 50 Hz). Traditional power plants respond through governors, but in a high proportion of new energy grids, photovoltaic power plants must also contribute their regulation capacity to maintain frequency stability. Meet the requirements of grid connection: modern grid specifications mandate that large photovoltaic power plants have AGC function and can adjust active power output according to dispatching instructions. Participation in the electricity market: In the ancillary services market, there are benefits to be gained from providing AGC regulation capability. 2. AVC-automatic voltage control 1. Control object: reactive power output by the power station (or target grid-connected point voltage). Working principle: The EMS system of the power grid dispatching center calculates the total reactive power regulation demand (or the voltage target value of key nodes) required to maintain voltage stability and reactive power balance according to the node voltage, reactive power flow, equipment status and other information monitored in real time by the whole network. This demand or target value is assigned to each power plant and substation (including PV plants) participating in the AVC. The dispatching center sends the reactive power set value or voltage set value command to the AVC system of the photovoltaic power station through the communication channel. After receiving the instruction, the AVC system of the PV plant will quickly adjust the reactive power output of the plant (or control the voltage of the grid-connected point to the set value by adjusting the reactive power output).
(2) AVC is the" reactive power/voltage remote control "of the PV plant. The core purpose of adjusting reactive power output (or directly controlling the voltage of the grid-connected point) according to the dispatching command is to help the power grid stabilize the voltage. 
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