An Active Harmonic Filter, also known as an Active Power Filter, can help improve power quality and protect your electrical system. Enhance efficiency and reduce energy costs.

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Uses and benefits

Active Harmonic Filters are essential for maintaining optimal power quality in electrical systems. They effectively eliminate harmonic pollution, balance loads, and correct power factor, ensuring smooth and efficient operation. By reducing waveform distortion and preventing overheating, these filters protect equipment from damage and lower maintenance costs. Additionally, they mitigate voltage drops and temperature rise in transformers and cables, further enhancing the reliability and efficiency of your power system. Investing in Active Harmonic Filters is a proactive step towards safeguarding your electrical infrastructure and improving overall energy efficiency. Here are the top 6 uses and benefits:

• Eliminate harmonic pollution
  Harmonic voltages and current in an electric power system are the result of non-linear electric loads. Harmonic frequencies within the power grid are a frequent cause of power quality problems.
• Power Factor and Load Balancing capabilities
  As the active harmonic filters are measuring each phase, they can redirect existing load currents to balance the phases. Additionally, remaining compensation capacity can be utilised to correct power factor by injecting reactive power into the power system.
• Protect your electrical system
  The presence of harmonics in electrical systems can lead to potential damage of equipment, disrupting regular functioning of devices and leading to increased running costs. The use of filtering in cases of harmonic distortion can reduce overheating of equipment and nuisance tripping of circuit breakers and fuses. It can also improve power quality contributing to reduced energy costs.
• No risk of harmonic resonance
  Infinite impedance to grid avoids potential harmonic resonance problems.
• Significantly reduce voltage waveform distortion
  As voltage harmonics are instigated by current harmonics flowing through system impedance, the implementation of active harmonic filters in electric power system will also mitigate voltage distortion (voltage distortion, or THDv.
• Reduced voltage drop and temperature rise on transformer & cables
  Current harmonics increase the RMS current flowing in an electric power system and thereby, increase the power losses. These increased currents and losses in transformers and electric motors result in over-heating and overloading in neutral conductors.

How an Active Harmonic Filter works

Before we can describe how an Active Harmonic Filter works, lets dive in deep and describe what harmonics are?

Harmonics are that part of a signal whose frequencies are integral multiples of the system’s fundamental frequency. For example, with a 50Hz fundamental frequency (which we operate on in Australia), we can expect harmonics at 100Hz (2nd order harmonics), 150Hz (3rd order), 200Hz (4th order), and so on. Alternating current (AC) and voltage waveforms, when representing the fundamental frequency, are sinusoidal. 50Hz simply means the sinusoidal waveform occurs 50 times each second. Harmonics of the third order, for example, occur 150 times per second; fifth order harmonics 250 times per second and so on.

All AC waveforms deviate from the ideal sinusoidal shape due to the different harmonics present in the electrical system. We call such waveforms distorted or complex waveforms.

Basically, everything we do in an attempt to increase reliability and/or save money with regard to efficient electrical equipment creates an issue with regard to harmonic propagation. The introduction of LED lighting, adoption to variable speed drives, uninterruptible power supplies (UPS), HVAC systems, lift and escalator systems and other non-linear loads result in the propagation of harmonics. A load is said to be non-linear when the waveform associated with the current is not the same as waveform associated with the voltage.

Supply Authorities (e.g. TasNetworks, Essential Energy, Western Power, Energex, Ergon Energy, SA Power Networks, Citipower and Powercor, etc.), monitor the degree of distortion at the point of common coupling (PCC) – basically where a consumer connects to the electricity grid – and the customer has a responsibility to ensure the harmonic levels are within the limitation set forth in the relevant Australian Standards. If a customers installation is found to be outside of the level outlined in AS the supply authority will request harmonic filtering be installed.

How does an Active Harmonic Filter reduce harmonics?

The Active Harmonic Filter works in much the same way as the Static Var Generator (to learn more about what a Static Var Generator is click here) in that The AHF monitors the load current in real time through external current transformers (CT’s) and through the internal firmware of the device determines the harmonic component of the load current. The device then generates a current with an amplitude in the inverse direction to that individual harmonic – essentially cancelling it out.

Why should you purchase an Active Harmonic Filter from Enginuity Power Solutions?

When you choose our Active Harmonic Filter product, you are choosing the most simple, turnkey solution to improve your power quality and meet Australian Standards.

To set you up with the solution for your specific application, all we need is some very basic information that you or any maintenance electrician can easily gather. Our team then takes this data and, using a series of automated calculators, we can quickly match you with the right solution. This cuts out the need for on-site studies by engineering teams or specialist contractors which saves you time and money.

We will then ship out the product with all mounting configuration, current transformers, cabinet, and all other infrastructure required to fit on site. Commissioning and technical support is provided throughout the installation process.

Our Active Harmonic Filter equipment is certified for the Australian market and tested to the following standards:

IEC -6-2:
IEC -6-4:
IEC -1:

**Certificate of Conformity EMC issued by TUV Rheinland

How do you know if you need an Active Harmonic Filter?

To help determine whether you need an Active Harmonic Filter, Enginuity Power Solutions can help quickly assess your situation and provide guidance. Our products are turnkey solutions and can usually be installed with minimal disruption by a qualified electrician. We also have engineers available to assist. The simplest way forward is to get in touch.

Active Harmonic Filter

Introduction

There are a number of electrical devices that have nonlinear operating characteristics i.e even when applied voltage is sinusoidal in nature, the current drawn by the device is non-sinusoidal in nature. These nonlinear devices used in power distribution circuits create nonlinear currents and which subsequently causes voltage distortions. These nonlinear currents and voltages have been generally referred to as harmonic currents and voltages. The proliferation of electronic switching devices in modern equipment has resulted in a significant increase in the amount of harmonic pollution in the electrical distribution systems. These harmonics if disregarded or undetected may cause harmonic resonant conditions, which could present system operating problems resulting in complaints from customers and reduced life of power equipment as well as degraded efficiency and performance. Harmonic currents and voltages can cause many unfavourable effects on the power system itself and the connected loads. Malfunctioning of electronic equipment, capacitor failure, transformer and neutral conductor overheating, excessive heating in rotating machinery are some of these effects.

Harmonic currents are generated by non-linear loads like

• LED and CFL lighting,
• Switch Mode Power Supply (SMPS) units (computers, PLCs),
• Variable frequency drives used with motors
• UPS
• Arc furnaces & SCR temperature controllers Battery chargers & Rectifiers

Impact of harmonic

a. Grid side

• Reduction in efficiency of power generation, transmission, and utilization
• Aging of the installed electrical plant components and shortening of their useful life
• Reduced ability to transfer power (kW) through existing T&D infrastructure and transformers
• Overloading, overheating and failure of power factor correction capacitors, distribution transformers and neutral conductors.
• T&D capability in many parts of India has to be de-rated by upto 10% due to increasing level of harmonics generated from consumer side of meter
• Harmonics result in capacity reduction and higher fuel consumption for DG Sets or Captive Power Plants

b. Customer side

• Overheating of transformers, motors and cables
• Reduction in available capacity of transformers and switchgear
• Excess neutral currents
• Power factor capacitor failures
• Spurious operations of fuses, circuit-breakers and other protective equipment
• Increased failure of electronic devices
• Capacity limits on stand-by generators and UPS systems
• Higher losses in transformers, motors, cables leading to higher power bills

C. Power factor

The true power factor is the product of displacement & distortion power factor.If the harmonic distortion in more in the system, then the true power factor cannot be improved with just power factor correction capacitors. This can result in power factor penalties, loss of power factor incentives and higher electricity billing in locations with KVAh billing.

Harmonic study

The harmonic content varies from one installation to the other. This is based on the type of loads as well as the location of the loads in the power distribution system. A proper power quality audit of the site has to be conducted to understand the harmonic distortion levels in terms of current and voltage. The typical audit will document the following parameters to help propose the right solution to reduce the harmonics.

Reference standard for harmonic study

The limitation for injection of harmonic current into the mains is regulated by standards like

• IEEE Std. 519-: IEEE Recommended Practices and Requirements for Harmonic Control in Electric Power Systems
• Ministry of Power (Central Electricity Authority) Notification No: 12/X/STD(CONN)/GM/CEA (21-Feb-07)
• The Central Electricity Authority (Technical Standards for Connectivity to the Grid) Regulations,
• Part IV: Grid Connectivity Standards applicable to the Distribution Systems and Bulk Consumers

Figure 2 Harmonics Limits as per IEEE 519

The above figure 2 shows the harmonic current limits as specified by IEEE 519.

The intent of IEEE to specify this limits is to:

Link to SINAVA

• Limit the harmonic current injection from customers so that they will not cause voltage distortion on the mains power supply
• Limit the overall harmonic voltage distortion of the mains voltage provided by the power supplier

These limits were intended to be applied at the point of common coupling between the customer and the utility mains

The harmonic limits are specified based on

• The ratio of Isc/IL
• Total Demand Distortion(TDD)

a. PCC – Point of common coupling

Point of Common Coupling (PCC) with the consumer/utility interface is the closest point on the utility side of the customer’s service where another utility customer is or could be supplied.

b. Ratio of Isc/IL

Isc is the maximum short-circuit current at the PCC which is basically a three-phased bolted short circuit current and ILis the maximum demand load current at the PCC. This maximum demand current value is established at the point of common coupling and should be taken as the sum of the currents corresponding to the maximum demand measured in the electricity meter during each of the twelve previous months divided by 12.

c. TDD–Total demand distortion

Total Demand Distortion (TDD) is almost similar to Total Harmonic Distortion (THD). The THD is calculated based on the momentary content of harmonic current compared to the momentary fundamental current whereas Total Demand Distortion (TDD) is calculated based on the momentary content of harmonic current compared to maximum demand load current at the PCC.

Connection principles

The Active Harmonic Filter is the proven solution to supply the harmonic currents required by the nonlinear loads and has been proven to be effective for applications across industries to help customers meet the IEEE and CEA guidelines. The Active Harmonic Filter is connected in parallel (shunt) with each of three phase conductors of a 3-phase, 3-phase, 4-wire electrical power system.

The active filter shall be suitable for connection at an electrical distribution panel, transformer secondary or at an individual load. The AHF will be installed in parallel to the harmonic generating loads. CT connected to the distribution system has to measure the current being drawn by the load and should feed a compensation current into system based on the actual current for amplitude & harmonic order, whose amplitude and individual harmonic order is exactly equal to the current drawn by the load, but which is 180 degree out of phase with it. So the harmonic currents are cancelled.

Application of Active Harmonic Filters

An Active Harmonic Filter (AHF) provides an effective means to mitigate harmonics, reduce process-related voltage fluctuations and improve equipment operating life and system capacity. It can be part of a power factor correction and harmonic filtering system.

a. Power factor improvement

The apparent power (Kilovolt Amperes or KVA) used in an electrical system by an industrial or commercial facility has two components:

• Real Power (Kilowatts or kW) which produces work
• Reactive Power (Kilo Volt Amperes Reactive or KVAr) which generates the magnetic fields required
• In inductive electrical equipment (AC motors, transformers, inductive furnaces, ovens, etc.)

The relationship between kVA, kW and KVAr maybe is represented by triangle as follows

kVA2 = kW2 + kVAR2

The ratio of Real Power (kW) to Total Power (kVA) is called the Power Factor (PF = kW / kVA)

The best way to improve the power factor is to reduce the KVAr consumption by injecting the required KVAr locally at the PCC. In case of harmonic rich installations, the power factor is based on the displacement and distortion factor as explained in section 2.c.

In most of the installations, the customer uses power factor correction capacitors for power factor improvement and the Active Harmonic Filters are mostly used for reducing the total harmonic distortion The Active Harmonic Filters have the ability to improve displacement power factor by injecting the required reactive currents if the feature is enabled. Further the Active Harmonic Filter can also improve the distortion power factor by countering and cancelling the harmonic currents.

Improvement of true power factor by harmonic current (THDi) reduction is demonstrated in several sites. Higher the original THDi, more is the true power factor improvement when THDi is reduced by using an Active Harmonic Filter as measured in several customer sites in the table below.

Case study – food processing industry

The customer is a major food processing unit based out of Coimbatore (a city in southern part of Tamil Nadu) who produces tasty and healthy dairy products and other food range of ‘Ready to cook’ Instant Mixes’.

a.Challenges faced

Customer were facing challenges due to harmonics like

• Regulations of DISCOMs to restrict the current harmonic (THDi) to
• Frequent failures of electronic components
• Increased losses and higher temperature on cables and transformer

b. Solution proposed

We performed a load study to understand the harmonic content and the summary of our findings are as below

Thee customer wanted to reduce the THDi to less than 8% and we proposed the customer to install anactive
harmonic filter of 200A at the PCC.

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