The passive filter compensation device consists of filter capacitors, filter reactors, thyristor cutting devices, controllers and protection circuits. Design the filter compensation branch according to the harmonic characteristics, harmonic content and reactive power of the circuit. Working principle: Provides a very impedance channel for harmonic currents of a certain frequency, forming a shunt relationship with the grid impedance, allowing harmonics to flow into the harmonic branch, greatly reducing the harmonic voltage distortion rate injected into the PCC. Passive filter compensation devices are widely used, have strong stability, high power factor, can control harmonics and compensate for reactive power. Suitable for metallurgical smelting, shipbuilding, cement products, plastic packaging, steel rolling, copper rolling, coal mining, tire industrial processing, etc.
Active filter is a new type of power electronic device that dynamically suppresses harmonics and compensates reactive power. Working principle: The sampling circuit detects the circuit and extracts the harmonic components in the circuit through internal DSP calculation. By driving the IGBT, the inverter is controlled to generate harmonics in the opposite direction to the harmonics and injected into the power grid to achieve filtering purposes. Based on the same principle, the active filter can also compensate the negative sequence current weight of the asymmetric three-phase circuit to achieve three-phase unbalance compensation and reactive power compensation functions. Active filters are designed to filter harmonics and do not require reactive power compensation. They are especially suitable for frequency conversion rectification systems with high power factors and large harmonic voltages. In addition, it is also highly targeted for high-power consumption systems with indicators such as reaction speed, filtration range, and filtration efficiency. It is suitable for industrial fields such as shipbuilding, steel rolling, automobile manufacturing, papermaking, and textiles, as well as exhibitions with strict power quality requirements. Center and commercial buildings.
Both passive filter compensation devices and active filters have corresponding advantages and disadvantages: the former is applicable to a wide range of conditions and operates safely and reliably. The system harmonic voltage can be greatly controlled according to the GB/T14549-93 limit standard, and can be applied to impact, etc. The disadvantage is that harmonics cannot be fully absorbed and processed, and the design can avoid the safety risks caused by reaching the resonance center. At the same time, when the power factor of the power supply itself is too high, the passive filter compensation device cannot be put into use. The filter capacitor should be maintained and replaced regularly to prevent the frequency drift of the filter capacitor itself from causing resonance threats. The latter has strong filtering capabilities and a filtering compensation efficiency of more than 90%. Harmonic currents can be controlled when the background power factor is too high. Since it is modular, it is easy to replace and maintain. The disadvantages are high operating heat, harsh usage conditions, surrounding cooling, heat dissipation, ventilation, and high maintenance costs, but it cannot greatly increase the background harmonic voltage.