Harmonic Filter

Prevent equipment failure and breakdowns
When many small harmonic-producing devices are collectively causing large amounts of harmonic pollution, filtering the main power supply is a very useful solution.harmonic filters effectively prevent failures and breakdowns of devices since they help correct non-linear loads. The filters also provide energy efficiency, which helps extend the durability of the device.

Help in maximum use of installed capacity
An ideal example of harmonic filters maximizing installation capacity is their use in the AC lines parallel to the loads that produce offending harmonics. The harmonic filters inject inverted current into the AC lines and cancel harmonics, improving electrical stability.

Improve energy efficiency
One of the best aspects of harmonic filters is that they are scalable and sized to the harmonic current for multiple loads. You can also install additional units if the total harmonic current exceeds the rating of the single harmonic filter. They also decrease the emission of carbon dioxide.

Reliable and provide continuity
Harmonic Filters are handy for areas with significant non-linear loads and many DC drives because they reduce production disruptions. Therefore, these filters also extend the device's life, enabling them to perform consistently well.

Curb service and maintenance costs
Any electrical device that operates at maximum efficiency is bound to work without issues. This theory is applicable for devices with harmonic filters. Unless the capacitors and resistors are required, the harmonic filter does not require custom fabrication because it is largely impedance-independent. According to the manufacturers, harmonic filters can handle wideband harmonic frequencies to minimize service costs.

Prevent and reduce energy loss
Harmonic pollution is synonymous with energy loss because it affects electrical installations' reliability, safety, and efficiency. An harmonic filter installed on the main power supply can counteract all harmonic currents before reaching the transformer. They also reduce the absorption of reactive power and reduce wear and tear, thereby preventing energy loss.

Active Harmonic Filter
Active Harmonic Filter an active harmonic filter is something like a boost regulator. The concept used in an active filter is the introduction of current components using power electronics to remove the harmonic distortions produced by the non-linear load. Active harmonic filters are mostly used for low-voltage networks.There are three types of active harmonic filters based on the way they are connected to the AC distribution network.

Passive Harmonic Filter
Passive Harmonic Filter a passive harmonic filter is built using an array of capacitors, inductors, and resistors. It can take the form of a simple line reactor or may use a series of parallel resonant filters to eliminate harmonics. Passive harmonic filters are also divided based on the way they are connected with the load.

Inverter topology
Most modern AHFs are built on a 3-level NPC inverter topology which brings several benefits compared to AHF's built on the conventional 2-level topology. In a 3-level topology, the switching frequency and voltage stress are distributed among the IGBTs. Reduced stress extends the lifetime of the power electronics. 3-level NPC inverter produces an output waveform that is closer to sinusoidal, which enables a reduced physical size of the whole AHF system, due to the smaller LC-filter. Higher efficiency, lower losses, and lower noise levels are also achieved. These make the overall cost of ownership much lower.

Losses
Depending on design and topology, AHFs can have higher or lower losses. Checking the losses is important as they will reduce the life cycle cost of the investment. Usually, AHF's have about 2-3% losses (depending on rated power). AHF's built on 3-level NPC inverter topology have lower losses than 2-level ones. Depending on the user profile, reduced losses create a potential for considerable financial savings if the LCC is calculated over a period of a few years.

Response time
Some power quality phenomena occur extremely fast, requiring the mitigation to be even faster. If the process is affected by fast voltage fluctuations or transients, it is very important to evaluate the AHF's overall response time. Typical applications that require fast mitigation are for example welding machines, lifts, and cranes.

Interharmonics
Interharmonics are usually caused by synchronization issues. If the installation includes inter harmonic sources, the manufacturer should be consulted as not all AHFs can deal with this. It is a common issue with cyclo converters or some types of older wind turbine generators.

Harmonic compensation capacity
Harmonics can be seen in the odd and even orders. Common capacity for AHFs is 25th or 50th harmonic order. Sometimes there is a claim of being able to mitigate the 51st harmonic, which has little value as harmonic orders of 51st and above do not appear in electric power systems. An important issue is that the AHF can offer the possibility of selecting which harmonic order to compensate. For some devices, it is possible to select the whole harmonic spectrum (1st to 50th, odd and even), but for some others, only a few harmonic orders can be selected. Depending on the application, the capacity to compensate for a certain harmonic order is a critical issue affecting the whole system's performance.

Electromagnetic compatibility (EMC)
In some countries, there are strict guidelines regarding the EMC. To be sure that the AHF is not causing interference it must be fitted with a properly designed EMC filter.

Voltage
AHFs are offered in a range of voltages, the most common is 200V up to 690V. Some manufacturers can produce AHFs for even higher voltages, up to 1000V, without a step-up transformer, reducing costs and footprint. It is possible to connect AHFs to medium voltage systems using a suitable step-up transformer. Step-up (or step-down) transformers can reduce compensation performance due to increased impedance between the AHF and network.

Identify the problem
If you're troubleshooting or maintaining your harmonic filters, the first step is to identify the problem or symptom that could indicate a malfunction or failure. Common signs of harmonic filter problems include excessive heat or noise from the filter or its components, blown fuses, tripped breakers, damaged capacitors, abnormal voltage or current readings or fluctuations, poor power factor, low efficiency, equipment malfunction or failure due to harmonic interference, and error codes or alarms from the filter controller or monitoring system.

Check the filter settings
The next step in troubleshooting and maintaining your harmonic filters is to check the filter settings and parameters. Depending on the type and model of your filter, you may have different options and modes to adjust the filter operation and performance. For example, some active filters have a tuning mode that allows you to set the filter response to specific harmonic orders or frequencies. Some hybrid filters have a switching mode that enables you to switch between passive and active filtering or between different passive filter configurations. You should consult the filter manual or manufacturer for the recommended settings and parameters for your application and load conditions.

Perform routine maintenance
The third step in troubleshooting and maintaining your harmonic filters is to perform routine maintenance tasks to prevent or reduce the risk of problems and failures. This includes cleaning the filter enclosure and components, checking the wiring and connections, testing the components for signs of wear or malfunction, replacing faulty or worn-out components, updating the filter firmware or software if necessary, and reviewing the performance and operation data. You should follow the manufacturer's guidelines for frequency and procedures of maintenance tasks, and keep a record of activities and results for future reference.

Troubleshoot specific issues
The fourth step in troubleshooting and maintaining your harmonic filters is to troubleshoot specific issues that may arise during the filter operation or maintenance. These issues may include filter overload or underload, filter resonance, or filter instability. Filter overload or underload occurs when the current exceeds or falls below the rated value, causing the filter to overheat, trip, or lose effectiveness. This could be caused by changes in the load profile, system configuration, or filter settings. Filter resonance happens when the filter impedance matches the system impedance at a certain harmonic frequency, leading to an increase in voltage and current harmonics. Filter instability occurs due to feedback or interaction with other filters or devices in the system.

Verify the results
The fifth step in troubleshooting and maintaining your harmonic filters is to verify the results of your actions and ensure that the filter is working properly and effectively. You should measure the voltage and current harmonics at the filter input and output again using a power quality analyzer or a harmonic meter. You should compare the results with the previous measurements and the expected values. You should also check the filter temperature, noise, and status indicators to confirm that they are within normal ranges.

Zhejiang Nengrong Electric Power Equipment Co.,Ltd. was established in 2007 (formerly known as Yueqing Zhongrong Power Compensation Equipment Co., Ltd.). It is a high-tech enterprise that provides power system power quality monitoring and control, reactive power compensation, harmonic control, and power safety protection equipment as its core business. Since its establishment, we have always adhered to the concept of "energy conservation creates value, protection builds harmony" and are committed to providing high-quality products and comprehensive solutions for users in various fields to improve power quality, optimize control, save energy and reduce consumption, and protect power grid safety.