An overview of the application and advantages of low-voltage side parallel active filter devices in distribution networks of factories and mines

Introduction: In recent years, many factories and mines have used a large number of harmonic interference source load devices such as thyristor rectification and commutation equipment, electric arc furnaces, and intermediate frequency furnaces. These devices absorb a large amount of reactive power and reduce the power factor of users. The harmonic problem is getting worse. According to the power industry quality standards and management regulations, the local power supply departments have issued corresponding harmonic limit criteria and measures, and the assessment and governance of enterprises and institutions with serious harmonic pollution. Therefore, filtering harmonics, improving power factor, and extending equipment life are the top priorities for such enterprises to save energy, reduce production efficiency and improve product quality.
The traditional method of harmonic suppression and reactive power compensation is to use a passive filter device composed of an inductor and a capacitor. The device is connected in parallel with the non-linear load to be compensated, and provides a low-resistance path for the harmonics, and also provides a load for the load. The required reactive power. Although the passive filtering device has the advantages of simplicity and convenience, it also has many disadvantages.
The active power filter (APF) device not only reduces the floor space, but also effectively solves the problems of the passive filter device. There is an essential difference between active filtering and passive filtering. It is based on the principle of dynamically compensating harmonics. It uses modern power electronic devices and computer technology to quickly track the harmonic magnitude and characteristics of harmonics generated by the device. The current is directed to the purpose of simultaneously filtering out harmonics of various components. It is generally composed of an electronic power converter with high controllability and fast response of the semiconductor power converter.
1 Application example of ANAPF low-voltage active filter in the factory 1.1 Project introduction Qinhuangdao An Electronics Co., Ltd. has 5 sets of rectifier transformers in the distribution system, mainly supplying power to 10 melting intermediate frequency electric furnaces. This type of equipment adopts 12-pulse thyristor rectification method, which produces severe non-sinusoidal distortion and a large number of high-order harmonics in the production process, causing serious interference to its own power distribution system and public power grid. At the same time, because the nonlinear load is inductive, the power factor of the self-distribution system is deteriorated, and the 11th and 13th harmonic currents of the 10kV incoming line exceed the national standard requirements, thereby greatly affecting the electrical energy of the power distribution system and the public power grid. quality. If harmonic control is not carried out, it will not only cause damage to the company's own power distribution system, but also endanger the safety of the public power grid.
1.2 ANAPF filter device principle ANAPF series active power filter device, connected to the grid in parallel, through real-time detection of harmonic and reactive components of the load, using PWM converter technology to generate a current harmonic component from the converter The inverse component corresponding to the reactive component is injected into the power system in real time to achieve harmonic control and reactive power compensation.
The principle is as follows:
1.3 Scheme design The 10kV high voltage system is divided into 4 segments and 5 segments of busbars. The active power filter capacity of each busbar is 450A. Three filters of model ANAPF100-400/B are used in parallel to pass the harmonics of 0.4kV/10kV. The transformer sends the harmonics to the 10kV side and superimposes the load harmonics to achieve the function of harmonic cancellation with the power grid.
1.4 Comparison of harmonic current spectrum before and after treatment:

1.5 governance effect

After using two sets of active power filter devices for treatment in the 4th and 5th segments of the 10kV bus , the system harmonics are well suppressed, and the 11th and 13th harmonics are completely limited to the national standard. The reliability of the system's power supply eliminates the hidden dangers of system harmonics on the power grid system, and has received good results to improve the power quality of the grid.

Wiring

Three-phase three-wire or three-phase four-wire

Access voltage

3 × 380V ± 10%

Access frequency

50Hz ± 2%

Dynamic compensation response time

Dynamic response < 4ms , full response time < 20ms ;

On-off level

10kHz

Function setting

Only compensate harmonics, only compensate for reactive power, compensate for harmonics and compensate for reactive power; manual and automatic switching.

Harmonic compensation times

2-21 times

Type of protection

DC overvoltage IGBT overcurrent device temperature protection

Overload protection

Automatic current limit at set value, no overload occurs

cooling method

Intelligent air cooling

noise

< 65db ( in the cabinet and operating in rated state )

Working temperature

-10 °C ~ +45 °C

Working environment humidity

< 85% RH does not condense

Installation occasion

Indoor installation

Altitude

≤ 1000m (higher altitude needs derating)

In and out line

Down and down

Protection level

IP21

Intelligent communication interface

RS485/MODBUS-RTU

Remote monitoring

Optional

Dimensions (mm)

(W × D × H)

30A

50A

75A

100A

600 × 500 × 1500

600 × 500 × 1500

600 × 500 × 1800

800 × 600 × 2200

Weight (kg)

Three-phase four-wire

Three-phase three-wire

30A , 50A

75A , 100A

30A , 50A

75A , 100A

280

360

240

290

Description:

1. The compensation current can be determined by the measured data, or the compensation current can be calculated through detailed information of the power system (single line diagram, transformer, load condition, etc.);

2 , three-wire system needs to configure 2 or 3 CT (for phase A and phase C ), four-wire system needs to configure 3 CT (for phase A, phase B and phase C ).

2.2 ANAPF active filter quotation and component list

3 Parallel ANAPF application advantages 1) Filtering harmonics ANAPF has wide filtering range, high filtering efficiency and filtering rate of over 92%: passive filtering equipment uses compensation capacity to set LC filtering branch for fixed subharmonics. The subharmonic filtering effect is poor; the harmonic components of the system are very complicated, and the system power factor is already high. The fundamental compensation capacity is too small, and it is impossible to set a specific LC filter branch to ensure that each filter rate meets the requirements. In particular, the second harmonic content of the system is large, and according to the principle of the LC filter branch, the second harmonic impedance is almost the same as the fundamental wave, and the filtering rate is extremely low.
2) Prevent harmonic amplification, suppress resonance function ANAPF has no energy storage original, is not affected by system parameters and design parameters, and will not resonate with the system; passive filtering equipment, setting high-order filter branch will be Low-order harmonic amplification, and the 2~13th harmonic content of the system is large. The set filter branch is easy to amplify other sub-harmonics; the system parameters and design parameters are inconsistent or changeable, and the system exists. The risk of resonance.
3) Other ANAPF response time is less than 10ms, delay time is less than 100us; reactive power compensation is programmable, it can be compensatory reactive power, and can also compensate for inductive reactive power; strong load capacity, automatic current limiting, no overload, use High life; small size, easy to install; passive filter device with slow dynamic response; only compensable reactive; limited to LC device characteristics, LC parameters may change after long-term operation; large volume, debugging is more complicated.
4 Conclusions 1) The modular parallel active filter device designed in this paper is a new type of filter compensation device that can be used in low-voltage power distribution systems. The device itself can compensate the high-order harmonics and the fundamental reactive power of the system at the same time, has high adaptability, high filtering precision and good compensation effect.
2) The device has various protection functions, which can suppress parallel or series resonance caused by system parameter changes, and can also prevent reactive over-compensation.
3) Based on the original capacitor reactive power compensation device of the enterprise, the filter and reactive power hybrid compensation system composed of capacitor and active filter device is designed to save the user's investment cost and shorten the construction period. The harmonic control project of the distribution network provides an efficient compensation device with good application value and application prospects.
4) The expansion of the unit capacity of the active filter device module and the further improvement of the voltage level can be used as the direction of future research.

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