Harmonic filters

You can buy them already designed and built for any application. Google harmonic filter

Sounds like a good homework project. Let us know what you find.

"designing of filters for the particular application will be really a interesting job"

It will be interesting, let us know how you get on with it.

well for a high power distribution network we may use the following procedure [ Generally power factor correction requirement at fundamental frequency is also considered for filter design]

- In the first step for existing and functional networks harmonic current measurements is performed at selected points to identify the harmonic currents injected into the network by the harmonic sources. These measurements reflect harmonic currents for one operating configuration and the loads prevailing at the time of measurements only. These may not represent conservative estimates of harmonic currents available.

- In the second step, the measurement information of the first step will be used along with design data of harmonics where available from non-linear loads, generating harmonic currents. A computer network model will be prepared as per IEEE standards and the effect of various harmonic sources at various harmonic orders will be examined. Various harmonic distortion factors will be computed as outlined in relevant IEEE standards. The advantage of computer model and simulation is that it can take care of large number of operating configurations and conservative estimates of harmonic currents, which cannot be covered by field measurements. Field measurements of the first step, can however be used to validate the computer model developed.

- In the third step, harmonic driving point impedances of all buses of interest will be generated at various harmonic orders and plots of the driving point impedances will be generated with respect to a range of harmonic orders [orders 1 through 50]. These plots indicate series and parallel resonance conditions in network.

- In the fourth step, analysis of results of the first 3 steps will be carried out and solutions needed to solve any harmonic related problems will be obtained. These solutions are verified by using the computer model developed. The problems that might arise could be excessive harmonic distortion factors beyond relevant IEEE specified standards, existence of resonance conditions close to an exciting harmonic frequency. Where these problems are encountered, solutions will be provided by introduction of harmonic filters and its design will be verified again by using the computer model developed. Recommendations include specifications on sizing of individual components of the harmonic filters.

Dear Raghunath sir,

Excellent reply. I am taking a PQ survey various places and explain me for the following Suppose the THD (I) - 20% and the THD(V) - 4% the individual spectrum of harmonics will be individual Current Har spectrum3rd 7%, 5th 12% and 7th 5%.

Please explain me how to start the design of filters. I just given the example of the above details and if you require I will send the actual study report also.

regards

Ravi - coimbatore

well , the fundamental of tuning a filter to a particular frequency is well known.

The size of Capacitor is first determined by power factor correction needed at fundamental frequency.

The inductor is then selected to filter a specific harmonic current and is placed in series with the capacitor chosen. [May be along with a resistive element as the assembly will have some resistance also, Further resistance may be deliberately used to limit unwanted harmonic currents also]

Harmonic analysis is performed with the entire network model and at different fault levels of the grid to which the network is connected.

Harmonic current flows through the filters are computed and those which flows in the network are also computed.

The improvement in network harmonic indices are verified by computer simulation.

The filter sizing based on possible flow of other harmonic sources in the network are determined.

The specifications for filters are then determined.

can u pls share me your contact details