Application of 690V active power filter in practice 2020 Dec.11

Enterprise background

A well-known listed company, mainly producing and selling white cardboard, cultural paper, cardboard paper, gypsum face paper, and paper pulp. The company has offices in 30 provinces, cities and autonomous regions in China, and its products are exported to Southeast Asia and other countries and regions.

The listed company has an annual production capacity of million tons of machine-made paper. Information media paper and writing paper are national inspection free products, and enterprise information construction is listed in the top 500 in the country. The company attaches great importance to scientific and technological research and development. In recent years, it has continuously increased R&D investment, introduction and training of scientific and technological talents, and has established cooperative relations with many scientific research institutes. Now it has lots of inventions and patents, and has undertaken the torch project construction of the Chinese Ministry of Science and Technology. The company has obtained the international quality system certification and "adopting international standard product mark certificate", and the product quality standard is in line with international standards.

Project main equipment and test data

01 Site conditions

The company's production is inseparable from the paper machine, because the matching ABB frequency converter is connected in series between the paper machine and the power supply, the motor speed can be adjusted. However, because the frequency converter is a non-linear equipment, it will inevitably produce high-order harmonics in operation, which will cause adverse effects on the motor. The frequency of the input current is a variable for the motor running under the variable frequency speed control conditions. The speed of the motor can be adjusted by changing the frequency of the input current. However, the change of input current frequency will affect the output shaft power of the motor.

But the motor running under the condition of frequency conversion and speed regulation has a lot of high-order harmonics in the input current, because of the additional loss caused by the harmonic current. At the same time, due to the influence of harmonic current, the output shaft power is decreased, the operation efficiency is reduced, and the temperature rise is increased. In addition, the additional magnetic field generated by the harmonic current rotates at a high speed relative to the rotating shaft, and the shaft potential generated by the harmonic current is higher, which will break through the oil film of the bearing and cause damage to the shaft current through the bearing.

There is distributed capacitance between the coils of the motor. When the high harmonic voltage is input, the voltage sharing among the coils is uneven, which leads to the insulation aging of the high-voltage coil accelerating and the insulation damage of the first turn coil. In the drive system of frequency conversion and speed regulation, the amplitude of the output voltage of the frequency converter is three times of the rated voltage.

In addition, the voltage change rate (DU / DT) of the frequency converter is very high. The vibration caused by it makes the stress of the motor coil become larger and lead to the aging of the coil insulation. Under the condition of high switching frequency, if the length of connecting cable between inverter and motor is too long, standing wave will be generated, which will lead to the increase of motor terminal voltage. This high voltage will also accelerate the aging of coil insulation and affect the service life of motor.

Front view Back view Interior view

02 Test equipment and test data

Main test equipment

Advanced power quality function, unprecedented power analysis performance

Take the Fluke 435 II three-phase power quality analyzer as your insurance policy. No matter what happens to the equipment, you can rest assured with F435 II three-phase power quality analyzer. Equipped with advanced power quality measurement function and power loss cost calculation function, this model can solve any power consumption problems.

Electrical parameter waveform data capture – capture fast RMS values to view each waveform to determine how voltage, current, and frequency values interact
Power inverter efficiency – power inverter efficiency
Electric energy evaluation - Quantitative judgment of the improvement of energy consumption of energy saving equipment before and after installation
First-line troubleshooting – quickly diagnose screen display problems to restore online operation
Preventive maintenance - monitor and forecast before power quality problems cause downtime
Long term analysis - identify problems that are difficult to detect or intermittent
Load study - verify the capacity of the electrical system before increasing the load

Before the transformation, GE passive filter was used to control the field harmonics as shown in the figure below, and the effect of harmonic treatment was not ideal; after the transformation, the effect of harmonic treatment was obvious after using our company's active filter as shown in the figure.

Transformer name main transformer 6AA0202

Transformer specifications: 2500kVA 10/0.7kV

Not invested After investing

Transformation effect: after the power quality and harmonic control of 6AA0202 transformer in low-voltage power distribution room, the power factor is increased to above 0.95, and the maximum fifth harmonic is reduced from 22.6% before transformation to 4.8%.

Transformer name main transformer 5AA0204

Transformer specifications: 2500kVA 10/0.7kV

Not invested After investing

Transformation effect: after the power quality and harmonic control of 5AA0204 transformer in low-voltage power distribution room, the power factor is increased to above 0.95, and the maximum fifth harmonic is reduced from 42.2% to 2.5%.

Transformer name main transformer 6AA0608

Transformer specifications: 2500kVA 10/0.7kV

Not invested After investing

Transformation effect: after the power quality and harmonic control of 6AA0608 transformer in low-voltage power distribution room, the power factor is increased to above 0.95, and the maximum fifth harmonic is reduced from 29.3% before transformation to 19%.

Harmonic standard and user allowable value

01 National standard harmonic voltage limits

The harmonic voltage limits of public power grid specified in the national standard GB / T 14549-93 "Power Quality Public Grid Harmonics" are shown in the table below; 10kV substation 0.4kV busbar load injection system of each harmonic current at 0.4kV busbar harmonic voltage distortion rate shall be less than the harmonic voltage limit of 0.4kV voltage level listed in the following table.

Harmonic voltage limits of public power grid (phase voltage)

02 Allowable value of harmonic current in national standard

According to the national standard, the allowable values of each harmonic current injected into the common contact of the system under the verified reference short-circuit capacity are shown in the table below. The national standard 0.4kV reference short-circuit capacity stipulates 10MVA, 10kV reference short-circuit capacity stipulates 100MVA.

Total allowable value of harmonic current injected into common connection point Ihp(A)

Product features and main functions

Function of active power filter

01 Enhance the operation safety and reliability of power system

Have you ever encountered such problems：

When the transformer is running, it will overheat violently without any reason, even lead to the serious accident of transformer burning out;
The power system protection device acts without reason, the PLC system is often burned out, the system power is cut off, or the protection device does not act when it should, resulting in the loss of protection of the power system and causing huge losses;
The system grounding fault caused by insulation aging frequently occurs in the cable line which is still in service life;
Normal use of air conditioning and other electrical equipment often have switch burnout failures;
The computer, television and other display equipment used display distortion, screen shaking;
The lighting equipment is often on and off without any reason, etc.

Most of these problems are caused by harmonics in power grid.

The more serious problem is that after the accident, due to the user's lack of measurement means, many hidden dangers caused by design defects often make the accident responsibility cannot be confirmed.

Using active power filter can solve the above problems for you.

02 Function of energy saving and efficiency increasing

The harmonics existing in power system will reduce the operation efficiency of all kinds of power equipment, and the use of active filter equipment can save part of the energy loss.

Harmonic will produce a part of the harmonic reactive power demand, because the ordinary reactive power compensation equipment can not compensate for the harmonic. Therefore, in fact, the reactive power demand generated by harmonics has not been dealt with, which has a certain impact on the operation of various power equipment. The use of active filter equipment can improve this aspect, and play a certain auxiliary function for the compensation effect of ordinary reactive power compensation equipment, so that the energy saving can reach 5% with active filter equipment.

03 Function of reducing consumption and emission reduction

The harmonics existing in the power system will bring a lot of heat loss to users. For example:

The harmonics in the power grid will increase the line loss by two times;
It will lead to serious overheating of the transformer and increase copper and iron losses by 2.5 times;
Harmonic makes transformers, capacitors, cables and other equipment overheat, insulation aging and reduce service life;
Harmonic makes most of the power equipment fault increase sharply, increasing the maintenance cost of users.

The use of active power filter equipment can help you recover this loss.

Project summary

Through monitoring, the listed company has a large content of harmonic frequencies such as the 5th and 7th on-site; through the use of Jiangsu Sfere Electric’s 690V active filter device, it can automatically track the harmonic current generated by the load and make the N line current is significantly reduced and the harmonic currents of each order are effectively suppressed, which improves the stability of the power supply system, eliminates the harm of harmonics on the communication system, and has received good operating results to ensure the safe and reliable operation of the entire system.

Through the application in the listed company, the 690V active filter device has been put into use, which ensures that the harmonic current of the listed company decreases significantly, and the power factor at the incoming cabinet of each transformer is increased to 0.98. Under the condition of sufficient capacity, the on-site current distortion rate has dropped from 26% to about 5%, which is highly praised by users.