Schaffner use Active Harmonic Filters to Clean up Conference Center

In this case study of the Luzern Conference Center in Switzerland, Schaffner demonstrate the full utility of the active harmonic filter application. The active filters are distributed throughout the building to compensate not only harmonics but also power factor correction as well as load balancing.

Leave it to the Swiss to adapt to multifunctional tools.


Vacon Launches NXC Low Harmonic Drive Based on Active Harmonic Filter Technology

Vacon Low Harmonic NXCVacon joins Danfoss as the second tier 1 drives manufacturer to integrate an active harmonic filter with a drive to lower harmonics. Vacons stand-alone NXC range previously offered 12 pulse as well as active front end drive solutions.

The Low Harmonic NXC was recently shown at a large exhibition in Sweden and is reportedly offered on a project by project basis but will become a standard offering in the near future. The system shown, verifies the smaller foot print and weight of the Active Filter drive system compared to the more common Active Front End drives. The active filter NXC also has a lower power loss, which is becoming more important as the EN 50598-2 standard is introduced.

Low Voltage Active Filter as a Medium Voltage STATCOM for Windpower

Fortum Kville Power station

Kville power station compenstated by Comsys STATCOM design.

When the 32 MW Kville wind power station was being built in Sweden, the local grid owner Fortum was looking for alternatives for inductive compensation.  The long underground cable length cause a dynamic capacitive reactive power problem that normally is compensated using a large MV inductor. The inductor is very large and costly device at these sizes and Fortum wished to investigate other alternatives.

Comsys used its extensive knowledge from MV applications in applying its liquid cooled low voltage Active Filter with a step up transformer to create a 2,5 MVA STATCOM solution to solve the problem. If applied correctly, an active technology is very compact and flexible enabling high availability. Comsys liquid cooled modular design offers a high degree of redundancy and availability as the modules can be operated individually.

A further complication was the requirement to measure at the PCC on the 130 kV level so the Low Voltage ADF STATCOM worked through two step-up transformers. After extensive simulations by Comsys, the system was designed and supplied through the turn key integrator Siemens.

Comsys modular design AHF

Comsys P700 modular STATCOM solution

The active filters where installed in an existing building and the step-up transformer was installed outside, saving valuable indoor space and requiring no additional transformer cooling.

The solution dynamically compensates the capacitive reactive power and keeps it in line with the utility’s requirement. Due to the STATCOM following the load dynamically and observing both voltage and current, optimal grid conditions are ensured during all operating conditions.

The investment cost was reported to be lower than using the customized inductor solution proving the competitiveness of small active STATCOM versus passive options.

The ADF P700 STATCOM is a perfect solution in a dynamic environment such as wind farms. It is as cost effective and compact as a passive solution but with superior performance.

AHF Compensates Thruster and Refrigeration Compressor

Danfoss used an Active Harmonic Filter to compensate the THD of their installed 960 kW of VFDs for thruster and refrigeration compressor on the fishing vessel Gitte Henning #8. The AHF ensured to keep the installation within class requirements. Read more at:

Danfoss VFDs on Gitte Henning #8

Active Harmonic Filter as a Tool to Save Money

Power quality mitigation products are not only used to fulfil regulations such as IEEE-519 and G5/4. They have actual effects saving both power and increasing productivity. This presentation by ABB exemplifies some of their early case studies indicating savings of up to 10%. Note that these savings compare to having no harmonic mitigation.

The cases below clearly show the great business value of implementing a high power quality standard within your facility.  The secondary effects of complying with IEEE 519 or similar standards enables the local grid to be dimensioned for less reactive power and harmonic current thus saving money through thinner cabling, smaller transformers etc. Power quality mitigation is not only a cost in the general investment calculation but a tool to save money.

ABB presentation: PQF-Energy_Savings

IEEE 519 and Active Harmonic Filters

Electric Grid

Electric Grid (Photo credit: Wikipedia)

Standards governing distiortion parameters in the electric grid such as IEEE 519, G5/4, EN 61000, EN 50160 and D-A-CH-CZ among others most often require voltage harmonic distortion to be below 5-8%. These are all recommended, not obligatory practices.

Although adherence to standards such as IEEE 519 is not obligatory, more and more utilities and other parties of interest are using these standards as a benchmark to place demands on their customers. This is a way for them to be able to guarantee disturbance free delivery on their end. It is also used as a part of an active environmental agenda to show a decreased energy usage and reduced energy costs for many energy intensive processes.

One way to meet the new requirements is to simply reduce the harmonics to an acceptable level. Many modern active harmonic filters can pinpoint the harmonic orders that are contributing, and the compensation power can be optimized to meet the requirements in the most cost efficient way.

The modern Active Harmonic Filter is one of the most efficient harmonic solutions the market today. Filters are commonly available in a 208 – 480V version and a 480 – 690V. The Active Harmonic Filter can be combined with 6 pulse drives and will be placed in parallel with the load, minimizing the need of compensation power to 20 – 30 % of the load. The parallel placement will also ensure the redundancy in the design, which is a major advantage in a critical applications. Modular solutions, which are now more commonly available gives a dynamic and agile solution to work for future improvements to existing machinery. This is all in keeping with the spirit of standards such as the IEEE 519 toward a sustainable energy future.

Low Harmonic Drive Optimization

Earlier on the blog, we have defined the Active Harmonic Filter (AHF) as the best low harmonic choice for variable speed drives. A common question often put is whether the drive has to be fitted with a line filter as well.

In theory a well designed Active Filter can compensate a drive without a choke but this may not be the optimal solution. This would create the need for a bigger Active Filter, and the drives rectifier would be stressed by the compensation power from the filter. This in turn would reduce the drive’s life span.

A very common solution is to install a 2% or 5% choke on the drive. Many high quality drives have such chokes fitted as standard. Fitting a choke reduces the harmonics from 85-100% to about 35-40% which is a very cost effective solution. The remaining, and significantly lower THD, means the size of the final and more expensive filtering is much smaller.

The choke will also dampen the compensation power affecting the drive. Leaving out the choke, the drive’s rectifier will degrade over time.

So the answer is yes, a Low Harmonic Drive system using Active Harmonic Filters will benefit from using a choke to complement. It gives the overall system a lower cost and higher availability.