Case Study: XPQ Active Filters are used for Harmonic Reduction in Haier IOT Center

XiChi XPQ-Active Power Harmonic Filter. Filtering effect >97%, used to reduce harmonics in power system and improve power quality. Below is an application case.

• Power Harmonic Control Case

• 3 Application Schemes of Active Harmonic Filter

• Causes of Power Harmonics

• The Harm of Harmonics to Power System

• Solutions for Harmonic Control

• Active Power Harmonic Filter Working Principle

Power Harmonic Control Case

Project: Harmonic Reduction in Haier IOT Center

Solution Provider: Xichi Electric

Harmonic filters used: XPQ-APF

Treatment  method: Centralized Management

Haier Internet of Things Global Innovation Center, as the world's first innovation center centered on the experiential value of Internet of Things scenarios, leads the leapfrog upgrade of industrial parks and realizes the digitization and intelligence of Haier's industry.

In this project, 6 power distribution rooms are equipped with our 1750A Active Power Harmonic Filters. At the same time, Xichi frequency converters were installed in the central air-conditioning pump room, with a total power of 2700KW.

Our technicians conducted a scientific analysis of the main loads such as frequency conversion motors and lighting appliances on site, and combined the analysis data with the actual situation, decided to adopt a centralized management method to control the harmonics of the power distribution system.

XPQ- APF(Active Power Filter) Application System Solution Diagram

① Voltage Transformer

② Incoming feeder cubicle  

③ Capacitance compensation cubicle

④ Active Harmonic filter Cubicle

⑤ Outgoing feeder Cubicle

⑥ Outgoing feeder Cubicle

Project Photos

Result of APF Harmonic Control

The above data show that the Active Power Harmonic Filter (APF/AHF) suppresses the harmonic current on the load side to a great extent, and the overall harmonic filtering effect is obvious.

After the harmonic pollution is controlled, the power quality is improved, the system operation is safer and more stable, and the efficiency is higher.

3 Application Schemes of Active Harmonic Filter

In the process of electrical system design, to effectively reduce the generation of harmonics, harmonic control schemes need to be formulated for different applications.

Three application schemes of Active Harmonic Filters:

(1) Centralized processing:

It is generally applicable to occasions where the harmonic content of a single device is small, the layout is relatively scattered, the number is large, and the overall harmonic current is large, such as general wards and general consulting rooms in medical buildings.

(2) Partial treatment:

It is suitable for occasions where harmonics are relatively concentrated in certain feed-in circuits, or where local requirements for power quality are high, and it can prevent harmonics from interfering with local power systems.

For example, operating rooms, ICU and other departments in medical buildings store a large number of precision instruments and areas where UPS is used.

(3)On-site control: 

It is suitable for occasions where the harmonic source is relatively clear and the harmonic content of a single device is large, and it can prevent harmonic current from affecting the equipment in the area of MRI, CT and other inspection places in medical buildings.

In the actual application of active filters, different control measures need to be adopted for different applications. During the system design process, the appropriate capacity should be selected according to the calculation results of different compensation currents to achieve effective harmonic suppression and governance effects and ensure the safe operation of the power supply system.

Causes of Power Harmonics

The sources of power harmonics in the power system can be roughly divided into the following three categories:

Source 1: quality of power generation;

The production of generators in power companies is mostly based on three-phase windings, and absolute symmetry is almost impossible to achieve. The uniformity and consistency of the generator iron core cannot be reliably guaranteed, so the quality of the generator is affected to a certain extent, which in turn affects the quality of power supply, and harmonics will be generated during operation.

Source 2: Transmission and distribution system;

In the power transmission and distribution system, the main source of harmonics is the power transformer. Due to the existence of various influencing factors, in the process of designing transformers, the working magnetic density is usually selected in the saturation stage, so as to avoid the waste caused by excessive capacity. Although this design method can ensure the economy of the transformer, the transformer will generate harmonic current during operation.

Source 3: Electrical equipment

Non-linear equipment containing ferromagnetic or electric arcs, such as AC arc furnaces, etc.

Nonlinear components containing semiconductors.

The Harm of Harmonics to Power System

1. Harm to transmission and distribution lines.

It will affect the stable operation of the line to a certain extent.

Since the transmission and distribution lines are equipped with relay protection devices that can provide security for line equipment, but due to the existence of harmonics, the protection devices may malfunction or refuse to operate, which affects the safety and stability of the line.

2. Reduce the quality of power supply.

Due to the influence of power harmonics, the voltage and current in the power grid will be distorted, the grid voltage will drop, the grid capacity will be wasted and the power quality will be affected.

3. Damage to electrical equipment.

Under the influence of power harmonics, the voltage and current will change, which will affect the safety of the equipment, and the insulation of the equipment will age and the service life will be shortened.

Solutions for Harmonic Control

The basic idea of controlling the harmonic pollution problem:

1. Install harmonic compensation devices to compensate harmonics, which is suitable for various harmonic sources;

2. Transform the harmonic source itself.

So that it does not generate harmonics, and the power factor can be controlled to 1.

For the projects that have been put into use, more harmonic compensation devices are currently used.

Harmonic compensation devices are further divided into passive filtering and active filtering. Among them, the active filter has a good treatment effect and can filter out multiple and high-order harmonics at the same time without causing resonance, so it is widely used.

Active Power Harmonic Filter Working Principle

APF is a new type of power electronic device for dynamically suppressing harmonics and compensating reactive power. It can compensate harmonics that vary in size and frequency and reactive power that vary. Its application can overcome the shortcomings of traditional harmonic suppression and reactive power compensation methods such as LC filters.

There are two types of APF: parallel type and series type. The former is widely used. The parallel active filter is mainly used to control current harmonics, and the series active filter is mainly used to control problems caused by voltage harmonics.

APF active harmonic filter is essentially a controlled constant voltage source, which has little effect on system impedance. Targeted treatment of each harmonic, and can be configured as a hybrid active filter compensation device, the filter and compensation can be performed simultaneously, the full response time is short, the output is continuously adjustable, and the consistency is good. It is currently the best choice in the field of power quality control, especially in harmonic control.

Xichi Electric produces and sells Power Quality Control Devices, and provides Power Quality Solutions.

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