The negative effects from power quality problem in power grid to customers mainly lies in the two aspects: harm on harmonic and voltage decrease. XD Hi-tech provides the customers with complete treatment solutions for harmonic and voltage decrease and supplies the world’s leading treatment products,which are Harmonic Filters.

1. Active Filter

The active filter has the characteristic of high controll ability and quick response, which can compensate each harmonic and automatically produces the reactive power that needs to change. The characteristics will not influenced by the system, and harmonic will not be amplified, and with the merits of small size and weight, it has become the main method for power harmonic suppression and reactive compensation. Active filter is in parallel with the load that generates harmonic, and produces harmonic current as per measured results, which is equal to the harmonic current in size and opposite in direction, therefore, the system acquired a pure fundamental current. Active filter has the ability of compensating multi harmonic current (2-50 times) simultaneously, it can automatically follow and control in real time, which will effectively eliminate harmonic and dynamically compensate the reactive power and improve the three-phase imbalance. Besides, it is different from common passive filter, it will not affected by system operation mode and will not produce harmonic and resonance and has a strong adaptability to power system.

2. Passive Harmonic Filter

Passive harmonic filter is composed of capacitor and series reactor. Typical passive harmonic filter includes harmonic loop of three frequency bands, which is usually 5th, 7th, 11th harmonic filters.

The design of capacitor capacity in harmonic filter is made as per the reactive power that needs to compensate to the system at fundamental frequency. For choosing of electric reactor inductance, when at certain harmonic frequency, electric reactor and capacitor can constitute serial resonance loop and make the harmonic filter form low impedance at the harmonic frequency, to make majority harmonic current flow into filter. Passive harmonic filter has the characteristics of simple structure, stable performance and notably power-saving effect, etc.

Passive harmonic filter is designed as per customers’ requirements and detailed system parameters, to achieve the best effects in reactive power compensation and harmonic filtering.

3. Third Harmonic Filter

Third harmonic filter is mainly composed of capacitor series connecting reactor. It provides low impedance loop at third harmonic frequency, to filter majority third harmonic current, and can simultaneously improve third harmonic current and harmonic voltage of three phases and neutral line.

The design of capacitor capacity in third harmonic filter is made as per the reactive power that needs to compensate to the system at fundamental frequency. For choosing of electric reactor inductance, when at third harmonic frequency, electric reactor and capacitor can constitute serial resonance loop and make the harmonic filter form low impedance at third harmonic frequency, to make majority harmonic current flow into filter.

4. Zero Sequence Filter

Zero harmonic will be produced between connecting phase of non-linear single phase load, and superposition will be on neutral line, and the harmonic current will flow to power grid, which will result in serious distortion in voltage waveform and current waveform in system. One of the most serious problems of power quality in urban power gird is zero harmonic interference.

Zero sequence filter can eliminate superposition on neutral line and improve equipment safety and power supply quality, effectively reduce power loss. After installing filter, regular and reverse fundamental wave current will not be affected. Zero sequence filter has the following excellent natures: In AC power grid, it can sharply reduce the zero sequence current in null line, and protect the load against the interference of zero sequence current; it can recover balance partially on the three-phase unbalance load; it can improve voltage waveform that been interfered, and increase power factor, and reduce power loss. Zero sequence filter has extremely high reliability, which is often installed in series with the load side.