Harmonic Distortion Evaluations and Controlling Harmonics
Control only when harmonics create a problem. Types of problems:
- • load harmonic currents are too large;
- • path for harmonic currents is too long electrically (too much impedance) producing voltage distortion or communication-line interference;
- • response of system magnifies one or more harmonics.
Reducing Load Harmonic Current
Sometimes transformer connections can be changed. For example:
- • phase shift on some transformers supplying 6-pulse converters;
- • delta windings block triplen currents;
- • zig-zag transformers can supply triplens.
Perform harmonic studies when:
- • a problem occurs, to find a solution
- • planning large capacitor bank installation on either utility or industrial systems
- • planning installation of large nonlinear loads such as adjustable speed motor drives
- • designing a harmonic filter or converting a capacitor to a harmonic filter
Since harmonic loading, DC injection, voltage ripple, and voltage range of operation are key areas that influence the operation of the transformer in renewable energy and microgrid systems, the HBFEM will be an effective method to analyze the harmonic problem in the transformer connected with voltage or current sources. The detailed HBFEM numerical model will be discussed in Chapter 6.