Active Harmonic Filter Technology History, Evolution and Future


Doctor_Character-04-1Hello Readers, this article discusses the evolution of active filters as a harmonic mitigation solution and where it is getting to in the future. 


With the increasing number of power electronic equipment’s in the power system, the need to maintain sinusoidal line voltages and currents have become the need of the hour.

Harmonics in power system is caused by both domestic and industrial loads. Traditionally, harmonic distortion has been dealt with the use of passive LC filters. However, their application may result in parallel resonances with the network impedance, over compensation of reactive power at fundamental frequency, and poor flexibility for dynamic compensation of different frequency harmonic components.

Therefore, to overcome these problems and to provide adaptability to load variations in network and instantaneous adjustable solutions, Active Harmonic Filters were implemented. They regulate terminal voltage to improve voltage balance, compensate harmonics and reactive power and suppress flicker in electrical systems. The controller is the most indispensable part of the Active harmonic filter. The performance and reliability of the system greatly relies on it.


Starting from 1971, a number of configurations, such as the active series filter, active shunt filter, and combination of these filters have been developed and materialized for UPS applications. From 1976, a significant number of publications have reported on three phase three wire Active Harmonic Filter’s. Active shunt, active series, and combinations of both, named as active power quality conditioners, as well as passive filters combined with active shunt and active series Harmonic Filter’s are some typical configurations used. These configurations are used to resolve the problems of excessive neutral current, unbalanced load currents, heating issues and the previously mentioned problems which mainly occur due to nonlinear unbalanced loads and other power quality issues.


Passive Harmonic Filter


One of the major factors in advancing the Active Harmonic Filter technology was the invention of fast self-commutating solid-state devices. With the introduction of IGBT’s, the evolution of Active Harmonic Filter technology got a real boost and, at present, they are considered as ideal solid-state devices for Active Harmonic Filter’s. The improved sensor technology has also contributed to the enhanced performance of the Active Harmonic Filter. The next breakthrough in the evolution of Active Harmonic Filter development has resulted from the microelectronics revolution. Now, it is feasible to implement complex algorithms online for the control of the Active Harmonic Filter at a reasonable cost.

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Selection of the Active Harmonic Filter for a particular application is an important task for end users and application engineers. There are widely varying application requirements, such as single-phase or three-phase, three-wire and four wire systems, requiring current-or voltage-based compensation. Moreover, there is a number of Active Harmonic Filter configurations which may cater to the needs of individual users. The proper rating of a passive harmonic filter must be concluded from the rating of a non-linear load without a harmonic filter and that of an active harmonic filter based on rectifier parameters without a filter. Selecting an Active Harmonic Filter of the correct size is the key to achieve optimum cost/benefit ratio, i.e. desired current harmonic reduction with minimum filtering effort.

Some of the leading Active Harmonic Filter manufacturers of today’s market are COMSYS, MERUS POWER, INPHASE POWER, SCHAFFNER and ABB. The InPhase Power Active Harmonic Filter stands out in the crowd in a number of ways. InPhase Power which is an Indian company provides 100% indigenous technology with up to 1000A in a single equipment. It has emerged as the only one in the market to provide Direct High Voltage Compensation with advanced DSP control and INPHASE CLOUD Computational system for online monitoring of faults in electrical systems with SMS alert facility. Application of LCL filters and rigorous algorithm for better compensation makes it the right choice power quality issues. InPhase Power also offers direct 690v Active Harmonic Filters  typically used in Furnace kind of applications. To top it all InPhase Power won the Ministry of MSME Award for Innovation in Renewable Energy & Power Quality Solutions which shows the reliability and dependability of InPhase Power products.

       ahf                                                    Active Harmonic Filter                                              


Today, Active Harmonic Filter technology is well matured, and a number of manufacturers are producing Active Harmonic Filter’s with large and varied capacities. The utilities in the long run will induce the consumers with nonlinear loads to use the Active Harmonic Filter’s for maintaining the power quality at acceptable levels. Many Active Harmonic Filter configurations are available to compensate harmonic current, reactive power, neutral current, unbalance current and harmonics these days.

With the advent of new and improved technology implementing faster devices the filter size and its performance can greatly improve, increasing the reliability and adaptability to perturbations in our power system network. The future looks promising as the IGBT technology  which is the key system component in Active Filters are evolving very faster and with robust capability.  The futuristic Active Filters might be compact, modular with ability to compensate higher orders and respond much quicker. Not leaving the reliability of these Active Filters will also be high in comparison to the current generation filters with more rugged capability for Industrial environments. InPhase as a pioneer in power quality and as a manufacturer of Active Harmonic Filter is working towards bringing these latest generation products to your door steps.

Meet you again with a interesting article, until then  bye from Dr.InPhase

Thank you!


Thanks for reading…if you have questions don’t forget to ask me. You could write to me to or call +919632421402

IInphaseLogo(300dpi) (1)nPhase Power is a Power Electronic Product company manufacturing products for Power Quality and Power Conversion. InPhase is manufacturer of Active Filter, Active Harmonic Filter, Solar Inverter. InPhase majors in power system design for power quality and conversion. Driven by a management that has a combined experience of over 60 years in power system and power electronics InPhase nurtures innovation and passion in this field.

3 thoughts on “Active Harmonic Filter Technology History, Evolution and Future

  1. Utsav Sharma

    Hello Dr. InPhase,
    Another breakthrough technology for active harmonic filter is instantaneous power theory based harmonic filter. Many of us researchers implemented it on hardware and got impressive results with hysteresis control.

    1. admin

      Hi utsav,

      Instantaneous power theory is one such methods but industry has gone past these methodologies. In fact our implementation algorithm for AHF is way much advanced then that. However we appreciate your interest towards active filter and work being carried out on the same.

      Team InPhase


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