Why do we need ankeri's active power filter in frequency converter occasions?

The harmonic control scheme of ankerui active power filter in frequency converter

Encore Cui Yuanhang

background

Frequency converter because of its small size 、 Light weight 、 Low cost and high efficiency , It is very popular in various production fields , Especially in fans 、 Water pump 、 Transmission system has been widely used in the field . Although the application of frequency converter has produced remarkable energy-saving effect , But the following harmonic problems can not be ignored , Harmonic current is injected into the power grid , Not only increase the line loss 、 Shorten the service life of power transmission and distribution components , And it increases the loss of rotating motor 、 Increased low-level noise 、 Pulsating torque, etc , Will cause relay protection 、 The automatic control device works disorderly . At the same time, the inverter itself is composed of power electronic devices with different topologies , It is in weak capacitive state during operation （ Commonness of voltage source equipment ） state , It can amplify the harmonics of a specific frequency of the system .

The load characteristics of distribution system can be divided into two categories

1 ►  Linear load （ Pure resistance 、 Pure capacitance 、 Pure inductance ）; Linear loads generally do not produce harmonics , Therefore, there is no harmonic amplification or oscillation caused by harmonics .

2 ►  Nonlinear load （ Power electronics , During operation, the resistance - Rong - Switch between sensibility ）. The nonlinear load will be in capacitive state due to its operating state - Switch between sensibility , And the operation itself will also produce harmonic current , Therefore, the capacitive and inductive equipment oscillations caused by harmonics generally occur , Harmonic amplification 、 Damage to electrical equipment, etc .

The amplification is mainly reflected in the following three aspects

The harmonic generated by the frequency converter triggers the oscillation between pure inductive and pure capacitive equipment in the distribution system , The manifestation is that the cable is hot 、 Distribution switch tripped 、 System overvoltage protection, etc

Parallel resonance occurs between the frequency converter and the frequency converter , The manifestation is system overvoltage 、 If the frequency converter is light, it will protect the tripping , In serious cases, the power devices of the frequency converter may be partially burnt

A large number of frequency converters operate in capacitive state , Frequency converter and transformer （ perceptual ） Series resonance is generated between , The manifestation is that a large current is generated between the transformer and the feeder cabinet 、 The system busbar is seriously heated 、 The main switch of transformer incoming line trips frequently 、 Large area damage of electric equipment, etc

Based on the above factors , There are many on-site harmonic control measures for frequency converter, which is urgent , However, it is also necessary to comprehensively and systematically plan the governance plan , At present, the main control measures of frequency converter are as follows

One

Standard inverter input reactor （ Increase the internal resistance of inverter power supply , Ensure that the inverter branch is in inductive state ）

Two

Standard passive harmonic filter （ It has the function of series reactor , At the same time, it can filter part of harmonic current ）

3、 ... and

Adopt multiphase pulse rectification （ Special transformers are required , High requirements for inverter operation linkage ）

Four

Add active power filter （ It is widely used , But we have to deal with them 1、2 In combination with ）

In view of the above treatment measures and our extensive on-site operation experience , If active power filter is selected, it is impossible to avoid harmonic amplification ②/③ Caused on-site fault phenomenon , Once a fault occurs, there is a great risk of damage to other electrical equipment, including the active power filter . So it is suggested to choose 1+4 or 2+4 At present, the most common management measures are , The effect of stable operation is obvious , Also suggest 1、2 It is better to select the standard incoming reactor or harmonic filter of the original inverter , Because the power device topology of the frequency converter is not uniform among manufacturers , It has a great influence on the design parameters of reactor .

summary

Summary analysis , We can clearly understand the cause of harmonic generation of frequency converter , And the root causes of most power failures , Passive filter can be adopted in the treatment measures 、 Active power filter 、 Increase feeder loop impedance 、 Cut off the harmonic transmission path and call on the non-linear equipment development manufacturers such as frequency converters to produce green harmonic free products , Only in this way can the harmonic generated by the frequency converter be controlled within the minimum range , Finally, scientific power consumption will be achieved 、 Green electricity 、 Reduce harmonic pollution 、 The purpose of improving power distribution quality .