Developing a harmonics education facility in a power system simulator for power engineering education

In this paper, a harmonics education facility is designed and merged into an existing power system simulator in the National Taiwan Institute of Technology (NTIT), as shown in Figure 1. This facility consists of a nonlinear load and a filter bank. The nonlinear load is a widely used three-phase, 6-pulse controlled rectifier that produces harmonic currents with the orders of 6k±1. The filter bank that includes two single-tuned filters and a damped (high-pass) filter is used to eliminate the harmonic currents. A simple commercial recorder and an energy analyzer are used to measure distorted waveforms, harmonic currents and voltages, and power data. The parallel resonant condition caused by shunt capacitors is also analyzed in this paper. Several suggested experiments are given. Students that have the background of basic power system engineering courses can easily accept and understand the harmonics concepts introduced in this paper. The proposed facility is expected to be used in the NTIT courses, Power Systems Laboratory, Reactive Power Compensation Technology, and Electric Power Quality, for several advanced experiments. The power system simulator in the National Taiwan Institute of Technology was originally designed for purely sinusoidal operations. For the purpose of harmonics education, a high precision harmonic (Figure Presented) Figure 1. Power system simulator and the incorporated harmonics education facility Table 1. Harmonic source: module and filter bank module PCC Load Bus With With With With With Without 5/7/11th Without 5th 7th 11th 5/7/11th Filter Filter Filter Filter Filter Filter Filter V(Volt) 456 458 179.6 180.1 179.7 180.2 181.2 VTHD,% 5.2 2.7 5.7 4.4 4.9 3.1 3.2 I1,(A) 1.7 1.7 4.4 4.1 4.3 4.1 4.0 I5,% 20.5 8.8 22.5 8.2 24.7 16.2 8.6 I7,% 9.8 2.4 10.1 8.4 2.1 13.2 1.9 I11,% 6.9 3.8 7.2 7.1 6.8 4.0 3.5 ITHD,% 25 11.4 27 16 27 28 12 p.f. 0.93 0.99 0.93 5 0.97 0.95 0.95 0.99 (Figure Presented) Figure 2. Harmonic source module and filter bank module currents source which consists of a 6-pulse controlled rectifier and a digitized triggering control circuit is designed and implemented to simulate a nonlinear load, as shown in Figure 2. The 6-pulse controlled rectifier is a very basic and typical converter structure in many industrial facilities utilizing DC sources, such as traction vehicles, arc furnaces, and servo systems. It can be seen as a typical nonlinear load in the power distribution system. So it is very suitable to be the source of harmonic currents. The characteristic harmonic currents produced by the rectifier will pollute the power distribution system. Harmonic mitigation can be obtained with the addition of a filter bank. Students have to switch in each section of the filter in sequence and investigate the effects on harmonics filtering as shown in Table 1.