Category Archives: R&D

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.

InPhase Insight: Why minimalistic design is essential in Power Electronics

This article is about how mimimalistic design is made a philosophy at InPhase Power to achieve simple but effective solutions

Dr InPhaseHello Readers, Good day. After quite some effort i have pulled out one of our Research Fellows to come out and write to the world about our design Philosophy which puts simplicity at the forefront before all. This article will give you a very good idea on how the Research team at InPhase is working tireless to create beautiful Products that looks simple but  functions extra-ordinary. Happy Reading.

Why actually we need a minimalistic approach in design ?

The concept of minimalistic approach in design varies with different field of applications. Design for Minimal Execution time is critical in many cases like in high speed networking devices. Design for Minimal Power consumption is critical for low-power battery-operated devices e.g. mobile phones or digital watches. Design for Maximal Fault tolerance is critical for cases where manual inspection (or repair) is difficult or impossible e.g. submarine systems and electronic devices on Mars Missions. Design for Minimal Radiation leakage is critical for removing interference between medical electronics Devices (and aircraft systems etc). Design for Testability is another critical aspect. Even though minimal hardware helps in certain aspects it might not always be the right objective to achieve it mandatorily. A good design happens not by the only objective to minimize the hardware, but it comes along with the optimized use of all the available resources in a cost saving package without compromising the output.

Minimalism is Also an Iceberg!

What we see from minimalism at first is only the success part. We imagine a clear home with no mess, we see a nice wardrobe that is never outdated and a bank account full of savings. But minimalism is about sacrifices, resilience and change. Minimalists do a lot of things differently from the majority. They face judgement and criticism. To work well, minimalism has to be in your head and in your heart. It has to be thought about and felt. It’s more than owning less. It’s focusing on what truly counts. This is the same case as we do a design in Power Electronics at InPhase . To keep the design minimal and powerful, a lot of work is done in the background.


Fast Changing digital domain!

When we think about ‘low power electronics circuits’ the first image that come across our mind is a Printed circuit board with a number of integrated circuits mounted on it . Gone are those days where analog circuits dominated the electronics manufacturing process. This is the age of high end Digital Signal Processors, FPGAs, FPAAs and other high speed processing devices that can do the mathematical and logical calculations within a minimal footprint of 5 x 5 mm. A single FPGA chip can do the job of more or less 50 Analog ICs thus saving time, cost with increased precision. Analog system just aides the digital controller in the processing. But still, the scope of analog ICs and associated devices exists only because rapid change in technology is reaching the industries in a much slower pace and many industries inhibit to get adapted to the change. InPhase stands out in this and uses the advanced DSP technology for the design of its master controller, which is used as the main control board for its prime products like Active Harmonic Filters and Solar central Inverters.

What InPhase Provides

pecInPhase currently uses Dual Core Delfino Microcontroller with a processing speed of 200MHz. The Delfino™  Microcontroller is a powerful 32-bit floating-point microcontroller unit (MCU) designed for advanced closed-loop control applications such as industrial drives and servo motor control; solar inverters and converters; digital power; transportation; and power line communications. The integrated analog and control peripherals also let designers consolidate control architectures and eliminate multiprocessor use in high-end systems. Digital signal processing (DSP) devices currently have higher central processing unit (CPU) performance (clock rates over 100 MHz) and integration of advanced high-speed peripherals. Great strides have been made in DSP power reduction through CMOS process technology. These advances have increased the complexity of the DSP board design, which provide more analog challenges than a simple digital design. Thus great care is required while designing the board and InPhase  Controller does that without much complications. The main attractions of InPhase  Controller are

  1. A single versatile controller capable of controlling Active harmonic filter, 2 level and 3 level solar central inverters and various custom converters. This uniqueness actually reduces the discrepancy of selecting controller for different applications.
  2. The InPhase  Controller is a single board which is capable of producing up to 24 PWMS. It also have capabilities to process several analog I/Os and digital I/Os. The integrated communication system works based on advanced communication protocols like CAN, RS485 and RS232.
  3. The InPhase  Controller is designed in such a way that low voltage and high voltage components are separated with necessary isolation. This reduces the EMI interference and gives protection for low power ICs.
  4. Use of minimal components reduces the size of the Printed circuit board and thereby reduces the number of board traces.
  5. The reduction in number of board traces will eventually leads to reduction in power loss and thus increases the overall efficiency.

All these features of InPhase Controller provides utmost satisfaction for its customers who uses any of its products like InPhase Active harmonic filters , Solar central Inverters or other custom converters.

Doctor Hi

Well Overall simple design means also there are less number of interconnections, lesser components and eventually Lesser maintenance. Will see you back with another wonderful article soon.

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.