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White paper and application notes

Application Note - Improving multi-pulse Drives with Active Filters

This application note describes the possibilities to improve multi-pulse drives by applying relatively small Active Filter to the installation. Multi-pulse drives have several problems that causes them to behave like a non-ideal multi-pulse drive, e.g., the 5th harmonic is not fully eliminated. By using a well-tuned Active Filter inside the Multi-pulse drive, the drive can be adjusted to have a perfect multi-pulse behavior. It furthermore gives the opportunity to compensate the residual harmonics of the drive with the available capacity of the Active Filter. These improvements can be achieved even by retrofitting an Active Filter into existing multi-pulse drive applications.



Application note: Global vs Local Compensation

This application note describes the benefits of global compensation over local compensation of harmonics in plants with numerous large variable speed drive, such as water treatment plants. By carefully applying global compensation instead of local compensation, a solution with a certain degree of redundancy is usually significantly more cost efficient. The results are general and does not only apply only to water treatment. It is also demonstrated that by carefully sizing a system, oversizing can be avoided.



Comparing Harmonics Mitigation Techniques

The document at hand compares harmonic mitigation techniques in a range of applications and settings. Theoretical and practical comparisons are made between active and passive series and shunt filters. The overall context is to reduce harmonic loading in a drive system. Advantages and disadvantages of parallel and series approaches is discussed, as well as advantages and disadvantages of active and passive solutions. Practical results are discussed in a number of case studies.



ADF Wireless Access Point

Using the ADF Dashboard in SCC2 software 2.1 or later, available for ADF P25/P100/P300, you can now switch to a smart-device friendly interface. This interface features a card-based Web User Interface (WUI) which enables simplified access from smart devices such as smart phones and tables (it still works great from your laptop or desktop). In addition to this, the card based WUI comes with an optimized web server capable of handling multiple transient connection, which ensures responsiveness.

Wireless access for ADF units

Wireless phone webpage rev2By ordering the ADF with an integrated Wireless Access Point (WAP), you can now access the ADF without connecting to the Ethernet cable, which is especially usable when the ADF is placed in inconvenient locations, or when setting up an ADF without an HMI.


The wireless access point simplifies commissioning and supervision of ADF systems, and in addition works as a portable, wireless HMI. The user interface is identical in smart phones, tablets or laptops, however the card-based UI automatically scales for an optimal presentation depending on screen size.

Hardware configuration

The wireless access point will use the ethernet connection on the SCC2. It is also possible to use a single wireless access point for several systems using a switch.

Parallel operation with Multi-Master

Sometimes more than a single active filter is needed to compensate the distortion created by a load. The modular approach used by Comsys offers the possibility to combine up to 6 modules (PPM) in one control-computer (SCC2). But what to do if even more power is needed?

For this, Comsys offers a Multi-Master setup to combine up to 15 control-computer together.

Multi-Master brings therefore the possibility to combine up to 90 power modules into one big ADF.

Multi-Master brings the possibility to combine up to 90 power modules into one big ADF


The backbone of the Multi-Master is the CAN communication used to transfer setpoints between the control-computer. A communication bus is constructed here where one of the ADFs will take over the roll of the master and all other ADFs will take the roll of a follower. The follower only does whatever the master tells them to do over the CAN interface.


The setup is very easy, by only giving each system an identification number, the communication can be established within seconds.

Multi Master networking

Compensation settings will then also be transferred from the master node to all the follower nodes.

Multi Master compensation


The operation of each ADF is, even during Multi-Master, completely independent. Starting, stopping and errors are not connected to the Multi-Master operation. The transferred information is how many systems are running at each moment and what the compensation setpoint is. Based on that each running ADF is generating the needed compensation current. If one ADF stops, then the information is distributed to all other systems and they will take over the workload of the stopped system immediately.

If for some reason the master stops, a new master will be identified directly, and it will take over the master role. This happens on the fly.


With Multi-Master it is possible to design a redundancy scheme on every level. N+1, N+2, 2N …

With the basic operations of the multi-master you directly get a basic redundancy already with 2 systems in the loop.

Real-time access, monitoring, and configuration

laptop and tablet 

Accessing the ADF Dashboard

The ADF Dashboard, or Web User Interface (WUI), allows control of the entire system via a web browser. By connecting your computer to the ADF system via Ethernet or a wireless adapter, you can access the ADF Dashboard using any standards-compliant modern web browser (like Internet Explorer, Edge, Chrome, Firefox, Safari). The ADF Dashboard is provided by a built-in web server and is available with all ADF Products.

Using the ADF Dashboard to configure your ADF systems

Each ADF system can be configured either via the module’s HMI directly or via the ADF Dashboard. When using the ADF Dashboard, no extra software or tools are needed to commission and configure the ADF. The easy-to-use interface enables quick and efficient commissioning of the ADF system, and provides a more advanced overview with customizable options than when using the HMI.

Monitoring power quality performance through the ADF Dashboard

In the ADF Dashboard, you can instantly view:

  • The power quality levels of your system
  • Your system status
  • The overall performance of the system
  • Power quality data
  • Phase order
  • Power levels
  • FFT bar charts
  • Waveforms
  • System configuration
  • Compensation configuration
  • Trigger events and warnings


Spectrum view

Waveform view

Click to enlarge the images

Remote support for your system

The ADF Dashboard leverages the remote support capabilities in several ways.

Remote support options:

  • Option 1: Comsys Support can connect to the system via VPN or remote desktop
  • Option 2: Log/trend files may be downloaded and sent to service/support

It is very easy with the ADFs ethernet and build in webserver to build a time saving remote access solution. For example via a VPN tunnel or a 3G/4G router you can access the ADFs web user interface. With such a setup it is possible to control the system remotely, monitor the status and even debug/troubleshoot an ADF.

The trend log and TFR download enables you to dive deep into a problem without being on site. This reduces the support cost and traveling time. It also allows you to get a quick overview of many systems from a central location.

Automated Diagnostics

The ADF performs a self-test during startup, providing human-readable error and information messages

The ADF performs a self-test during startup, providing human-readable error and information messages. Problems in the installation can be quickly and directly detected by the ADF. This makes the commissioning process fast, simple, safe and gives immediate results.

Resonance Detection 

The ADF Dashboard offers the possibilities to activate resonance detection. The ADF will automatically shut down individual harmonics when a resonance occurs, for example, if the resonance limit is set to 8%, the ADF will disable any harmonic with more than 8% voltage distortion - other harmonics keep running. This means, if a resonance occurs in the grid during operation, the ADF will not make it worse. When the ADF detects that the resonance is gone, compensation will automatically resume. Thus, this functionality helps protect the facility.

Compensation 2

Log Functionality 

ADF P100 and ADF P300 series of products include a transient fault recorder (TFR) and a trend log. With these, systems can be troubleshooted remotely, and problems can be detected not only in the ADF but also in the installation. The data is stored on a SD-card and can be obtained over the network. In the TFR, we can see waveforms, system state, control state, and ambient data. In the trend, we can se how the system has been performing over very long periods of time. These proprietary features help us give our customers the best possible support.

Log functionality 1
View of the trend file

Log functionality 2
View of the TRF file


Eliminate the need for current transformers

ADF is the only solution with Sensorless Control, meaning we entirely remove the need for current transformers. In cases where reduced voltage distortion is the goal, we have the opportunity to directly reduce voltage harmonics instead of compensating the load current and then reduce voltage harmonics as a side effect.

no cts necessary

Compensation without current transformers

When you need a retrofit solution or you have a complicated set-up, it can be very difficult to add current transformers. But with Sensorless Control, ADF technology can compensate without them—so you eliminate the need for current transformers altogether.

Sensorless control completely eliminates the need of current transformers, summation transformers and complex configuration of operation modes in the ADF.

Sensorless Control

Benefits of Sensorless Control

  • More flexibility when it comes to where and how to install the ADF unit(s).
  • In highly complex setups with multiple feeders (transformers and/or generators).
  • Complexity is highly reduced.
  • Reduced overall hassle of installation and compensation.

Sensorless Control can isolate sub-grids and compensate background distortion, which further improves the flexibility and adaptability of the ADF platform. For example, on a diesel-electric vessel with a main 690V grid that is polluted with harmonics, we can select to compensate only the 480V sub-grid which is feeding sensitive and/or expensive equipment such as a ROV.

Check out this video that guides you through Sensorless Control

Sensorless Control is now available on all ADF products. Explore the range of solutions now.

ADF: How we tune power

An ADF unit is basically a very advanced computer-controlled current generator with the ability to instantly produce any shape or form of compensation current.

A simplified diagram of the ADF operating principle is shown in the figure below.


Each ADF unit is connected in parallel, in shunt, with the load that requires compensation. The power flows of electrical currents between the load and the network are measured and analyzed [ 1 ] to determine if disturbances such as reactive displacement and/or harmonics are present.

If found, the ADF unit injects phase currents [ 2 ] that are the exact opposite of, for example, the harmonics and/or reactive displacement. This is done in order to cancel out the load behavior [ 3 ].

The result is an ideal load with a minimum of power losses and disturbances. The energy profile then appears ideal to the transformer.

Watch this short film for an introduction to ADF Technology

ADF helps you save:


Since one module supports multiple drives, you can save space and ensure fl exibility for the future.


Increase energy efficiency while reducing the expense of replacing worn equipment.


Avoid unnecessary downtime for maintenance or replacement of equipment affected by power quality issues.


ADF-type technology is already being included in regulatory demands and equipment warranties — a trend that will only continue to grow.



When it comes to regulatory compliance, you need a solution you can depend on. But more than that, why not consider a solution that leaves room for growth? With ADF, you can remain care-free in the knowledge that this low harmonic solution will ensure you meet necessary standards.
See some examples here on the left.


With increasingly sensitive equipment, come stricter technical infrastructure demands and increasing electrical disturbances. Avoid this concern over loss of warranties with a stable and reliable power quality solution.


A reliable power quality solution ensures that unstable power is compensated. With ADF, you lower the risk for wear, expensive shutdowns, and replacement.


To see how ADF technology compares to conventional power quality compensation products, explore our technology comparison.

Power Quality Technology Comparison

Traditionally, fixed electro-mechanical and semiconductor-controlled filters and/or compensators have been used to limit behaviors that waste energy. These solutions operate mainly on a fixed or stepped basis using passive elements. But these solutions have multiple disadvantages:

  • they add losses
  • are installation-specific
  • have no ability to adapt to dynamic load changes

Active Dynamic Filters

Compared to other power quality technologies, ADF provides a solution that is hard to beat. It is an efficient system that leads to low losses, but more than that, it provides a reliable toolbox that can seamlessly address a variety of disturbances, from THD to flicker.

And ADF does that as a lighter, more compact package that has been certified according to most standards, such as DNV GL, ABS, and BV.

ADF vs. Multipulse vs. AFE vs. Passive Filters

Explore the table below to see how ADF technology compares to existing compensation solutions.

  ADF Multipulse AFE Passive Filter
Losses green green red green
Total harmonic distortion green yellow green red
Physical size green red yellow red
green LOW yellow MEDIUM red HIGH
  ADF Multipulse AFE Passive Filter
Meets Regulation* blue half blue blue white
Specified harmonic selection blue white green white
Resonance elimination blue white white white
Flicker compensation blue white white white
Configurable blue white half blue white
Although other solutions will meet some of your needs, you can rely on ADF to meet all of them.

The ADF product range

Our products solve a variety of problems and are suitable for a range of industries. Contact a local expert for advice on what solutions might be right for you.

Key Feature ADF P100 ADF P200 ADF P300 ADF P700 Statcom
Compact, wall mounted blue blue    
Harmonics compensation blue blue blue blue
Reactive power compensation blue blue blue blue
Eliminates resonances   blue    
Interharmonics compensation   blue    
Flicker compensation blue   blue blue
Load balancing blue   blue blue
Medium voltage applications     blue blue
Available with liquid cooling     blue blue
Four-wire version blue      
Voltage range 208 – 690 V 208 – 480 V 208 – 690 V Up to 36 kV
Industrial blue blue blue blue
Commercial blue blue blue  
Utility   blue blue blue
Marine, offshore blue   blue  
Sensor-less control blue blue blue blue


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Feel free to download the pdf about Comsys ADF Technology
Feel free to download the pdf about Comsys' ADF Technology.


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