Is capacitor compensation provided in addition to variable frequency control?

No need to add any more; the frequency converter already has capacitors built in. A frequency converter is a control device that uses the on-off operation of power semiconductor devices to convert power supply of the standard frequency into electrical energy at another frequency. The main circuit of inverters can be broadly divided into two categories: the voltage-type inverters are those that convert the direct current from a voltage source into alternating current, and the filtering in the DC circuit is done using capacitors ； The current-type is a frequency converter that converts the DC of a current source into AC, with an inductor serving as the filter in its DC circuit.

It is advisable to add an inductive filter to the inverter’s DC bus when costs permit. If a capacitor compensator is to be used, it must be installed on the AC power side; it must under no circumstances be placed on the load side.

The frequency converter can affect the lifespan of the capacitors in the capacitor compensation cabinet. The proper approach is to install reactors at the input side of the capacitor compensation cabinet, as well as at the input side of the frequency converter cabinet. This is the latest practice. The main advantages are: 1. Limiting current surges caused by sudden changes in grid voltage or operational overvoltages, smoothing out the spike pulses present in the power supply voltage, or eliminating voltage defects that occur during the commutation process in bridge rectifier circuits, thereby effectively protecting the frequency converter； 　　2. Improve the power factor, as it can prevent interference from the power grid and reduce the pollution of the power grid caused by the harmonic currents generated by the rectification units. 　　3. Reducing the impact of three-phase voltage imbalance on inverters