What is the role of reactive power compensation in the power system?

In the power system, the role of reactive power compensation is mainly reflected in the following aspects:

1. Improve power factor and reduce loss

Problem: Inductive loads (such as motors, transformers, etc.) absorb reactive power, resulting in a decrease in power factor.

Function: Provide capacitive reactive power through compensation devices (such as capacitors, SVG, etc.) to offset the inductive reactive demand, thereby improving the power factor.

Effect: Reduce the active power loss of lines and transformers Avoid power supply companies charging additional electricity fees due to low power factor (many areas impose fines on users whose power factor does not meet the standards).

2. Stabilize system voltage

Problem: Insufficient reactive power will cause line voltage to drop, especially when overloaded or transmitted over long distances.

Function: The compensation device dynamically adjusts the reactive power to maintain the voltage within a reasonable range.

Effect: Prevent voltage collapse (such as voltage drop when a large load is started). Improve power supply reliability and avoid equipment damage due to unstable voltage.

3. Improve the transmission capacity of the power grid

Principle: The transmission capacity of the transmission line is limited by the thermal stability limit (current upper limit) and voltage stability.

Function: After reducing the reactive current, the line can carry more active power.

Effect: Release the capacity of the power grid and delay the demand for expansion investment.

4. Improve the quality of power

Problem: Non-linear loads (such as inverters and arc furnaces) will generate harmonics and voltage fluctuations.

Function: Modern dynamic reactive power compensation devices (such as SVG and STATCOM) can respond quickly, suppress harmonics, and balance three-phase imbalance.

Effect: Reduce voltage flicker and harmonic distortion rate, and meet the power supply requirements of sensitive equipment (such as precision instruments).

5. Reduce equipment capacity requirements

For example: When not compensated, the transformer needs to bear both active and reactive currents, resulting in "virtual occupation" of capacity.

Function: After compensation, the capacity of the transformer and the line can be used more efficiently to transmit active power.

Effect: Save equipment investment costs (such as choosing a smaller capacity transformer).

Common compensation methods

Fixed/group switching capacitors: low cost, suitable for steady-state loads.

Dynamic compensation (SVG, STATCOM): fast response speed (millisecond level), suitable for loads with large fluctuations. Synchronous phase condenser: traditional method, providing inertial support, but complex operation and maintenance.

Actual application scenarios

Industrial users: compensate inductive loads such as motors and welding machines to reduce electricity bills.

New energy sites: wind farms/photovoltaic power stations use SVG to compensate for reactive power to meet grid connection requirements.

Long-distance transmission: install compensation in the middle or end of the transmission line to maintain voltage stability.

Summary Reactive power compensation is a key means for the economic and safe operation of the power system. It optimizes the flow of reactive power to achieve energy saving and loss reduction, voltage stability and capacity release, which is crucial to modern power grids (especially scenarios with a high proportion of new energy access).