Power quality integrated 

 

With the development of national economy in China, the non-linear, asymmetric and impulsive loads in the power grid are increasing, which will cause the following adverse effects:

1) The reactive power and harmonic current generated by the nonlinear load infiltrates into the power system in large quantity without control for a long time, increasing the loss of the system.

2) The rapid impact load (such as rolling mill, welding machine, large punch, etc.) absorbs reactive power from the power grid while generating voltage fluctuation and flicker to reduce the effective output of the motor, which reduces the product's finished product rate and shortens the service life of the equipment.

3) Unsymmetrical load intensifies the imbalance of the power grid.

 

In view of the above situation, IN-Power Electric takes the lead in introducing LSVG dynamic filtering compensation device, which combines advanced power electronic technology with traditional filtering compensation method, with the following functions:

 

1) Harmonic control function

a) 2nd -51st wide range filtering, filtering rate ≥95%

b) Harmonic elimination for neutral line

 

2) Reactive compensation

a) Bidirectional reactive power output

b) Accurate reactive compensation

c) Target power factor setting

d) Capacitor status monitoring

 

3) Balance three-phase current

a) Accurately adjust the system three-phase current

b) Reduce the operating current of the neutral line

 

4) Other functions

a) Energy-saving working mode

b) Time setting

c) Fault self-recovery

d) Function of over-temperature capacity reducing

 

 

Technical advantages

1) Unified control

The active filtering unit directly controls the switching of the traditional filtering compensation unit to avoid capacity impact between the two.

2) Diverse combinations

For different working conditions, the active filter can be combined with the common compensation capacitor, the separate compensation capacitor (L-N，L-L) and the intelligent capacitor.

3) High cost performance

The product makes full use of the economical efficiency of traditional filter compensation products and the advanced nature of power electronic products. The traditional filter compensation unit performs coarse adjustment for basic reactive power and absorbs some harmonics; the active filter unit makes fine compensation for the rapidly changing reactive power demand and harmonic current. At the same time, the reactive power bidirectional regulation of the active filter unit can be used to effectively control the reactive power releasing and make up the inherent deficiency of the traditional filter compensation device.

4) Low self-loss

Compared with the pure power electronic solution, LSVG products have replaced most of the capacity with traditional filtering compensation products. As the loss of traditional product itself is much lower than IGBT switch loss, the active filtering capacity accounts for a small proportion and the loss of the complete device is low.

5) High reliability

LSVG products have advanced fault-tolerant operation function, that is, when an active filtering unit or a traditional filtering compensation unit exits due to failure, the LSVG control system will automatically screen the fault unit to ensure the normal operation of other normal units. Meanwhile, when the active filter unit is stopped due to transient state fault, the traditional filter compensation unit can still operate independently.

 

Product combination mode:

 

1) Active filter + common compensation capacitor

The solution is applicable to industrial loads with low power factor, serious harmonic pollution and basic balanced three-phase current. The traditional filter compensation unit compensates the basic reactive power of the system and absorbs a small amount of harmonic current; The active filter unit is used to control the harmonic current of the system. The surplus capacity of the active filter can compensate the rapidly changing reactive power linearly and provide the power factor of the system.

 

 

	Before control	After control
Current waveform diagram
Power grid parameters
Effect:  Before control, the system current waveform distortion was very serious, showing an "M" shape, the total harmonic distortion rate (THD) of the current was as high as 29.8%, and the power factor of the system was only 0.70.After control, the total harmonic distortion rate (THD) of the current is only 1.4%, the current waveform is basically sine wave, and the power factor of the system is as high as 0.96.

 

2) Active filter + separate compensation capacitor

The solution is aimed at the residential electric load with unbalanced three-phase current, small reactive power demand or even reactive power releasing. The separate compensation capacitor can be used to compensate the basic active and reactive power imbalance, so as to achieve the general balance of the three-phase current and improve the power factor of the system. The active filter unit is used to filter out the harmonic current of the single-phase nonlinear load. At the same time, the reactive power in-situ balance is realized by the fine compensation of reactive power and the reactive power releasing is controlled. Finally, the three-phase current is fully balanced through the accurate adjustment of the three-phase current, and the quality problem of power distribution and transformation can be comprehensively solved to ensure the electricity safety of residents.

 

 

	Before control	After control
Current parameter of the system
Power parameter of the system
Effect: Before control, the three-phase current of the system was seriously unbalanced, the maximum current distortion rate (THDi) was 52.38%, the current waveform was seriously distorted, the minimum power factor of the system was 0.8681, and there was reactive power releasing (reactive power was negative).After control, the three-phase current of the system is basically the same, the maximum current distortion rate (THDi) is 4.23%, the current waveform is basically sine wave, and the power factor of the system is over 0.99.