Difference Between Dynamic Compensation and Static Compensation

The main function of reactive power compensation is to improve the power factor in power supply systems, thereby reducing equipment capacity and power losses, stabilizing voltage, and enhancing power supply quality. It also increases transmission stability and capacity in long-distance transmission, and balances the active and reactive power of three-phase loads. Therefore, selecting appropriate reactive power compensation devices can effectively reduce power supply system losses and improve grid quality. Conversely, improper selection may lead to voltage fluctuations, increased harmonics, and other issues.

Static Compensation and Its Advantages

Static compensation refers to compensation where capacitors are not switched in real-time based on fluctuations in reactive power. Instead, switching is deliberately delayed, typically by more than 40 seconds. As electrical equipment is connected or disconnected, the reactive power required by the grid changes accordingly. To avoid frequent switching, which could damage switching components and subject capacitors to excessive impact, a deliberate delay is implemented. Capacitors are only switched on when the power factor of the supply circuit stabilizes below a predetermined value. Conversely, if the power factor remains above a certain value or if reactive power is fed back into the grid, capacitors are switched off after a delay, provided the condition persists.

Static compensation does not adversely affect the average power factor of a consumer over a period, nor does it impact the billing practices of power supply companies. On the contrary, by avoiding frequent switching, it extends the service life of the switching components and compensation capacitors. Additionally, since switching is not performed in real-time based on reactive power fluctuations, contactors suffice as switching components, reducing the cost of the compensation device and simplifying maintenance.

Due to these advantages, static compensation devices are almost universally employed today.

Dynamic Compensation and Its Advantages

Dynamic compensation involves switching capacitors in real-time, closely following changes in the load's reactive power. To achieve this real-time tracking, the entire process-from signal detection to capacitor switching-must be completed within 10 to 20 milliseconds. Electromagnetic components cannot meet this rapid switching requirement, as even the fastest would take at least 0.2 seconds. Therefore, electronic detection and thyristor-based switching are used to meet the demands for fast detection and switching.

Dynamic capacitor compensation is not a new technology; it has long been applied in electric arc steelmaking furnaces. During the melting process of an arc furnace, short networks occur intermittently, and the resulting surge currents cause severe voltage fluctuations on the supply busbar, adversely affecting other users. This specific type of instantaneous voltage fluctuation is called "voltage flicker" or "power flicker." To mitigate these adverse effects and improve the voltage quality of the power system, instantaneous tracking compensation with capacitors is introduced. The reactive power required by the arc furnace is instantly supplied locally by the capacitors, eliminating the need for long-distance transmission from the grid. This reduces voltage flicker on the common busbar supplying the arc furnace, thereby improving power supply quality.