It is known from the fact that Harmonic Distortion is one of the main power quality problems frequently encountered by the utilities. The harmonic problems in the power supply are caused by the non-linear characteristic based loads. The presence of harmonics leads to transformer heating, electromagnetic interference and solid state device mal-functioning. Hence keeping in view of the above concern, research has been carried out to mitigate harmonics. This paper presents an analysis and control methods for hybrid active power filter using Discrete Pulse Width Modulation and Space Vector Pulse Width Modulation (SVPWM) for Power Conditioning in distribution systems. The Discrete PWM has the function of voltage stability, and harmonic suppression. The reference current can be calculated by‘d-q’ transformation. In SVPWM technique, the Active Power Filter (APF) reference voltage vector is generated instead of the reference current, and the desired APF output voltage is generated by SVPWM. The THD will be decreased significantly by SVPWM technique than the Discrete PWM technique based Hybrid filters. Simulations are carried out for the two approaches by using MATLAB, it is observed that the %THD has been improved from 1.79 to 1.61 by the SVPWM technique.
- Discrete PWM Technique
- Hybrid Active Power Filter
- Reference Voltage Vector
- Space Vector Pulse Width Modulation (SVPWM)
- Total Harmonic Distortion (THD)
- Voltage Source Inverter (VSI)
Figure 1. Configuration of an APF using SVPWM
EXPECTED SIMULATION RESULTS:
Figure 2. Source current waveform with hybrid filter
Figure 3. FFT analysis of source current with hybrid filter
Figure 4. Simulation results of balanced linear load
(a) The phase-A supply voltage and load current waveforms
(b) The phase-A supply voltage and supply current waveforms
Figure 5. Simulation results of unbalanced linear load
(a) Three-phase load current waveforms
(b) Three-phase supply current waveforms
Figure 6. Simulation results of non-linear load
(a) The three-phase source voltage waveforms
(b) The three-phase load current waveforms
(c) The three-phase source current waveforms
Figure 7. Harmonic spectrum of non-linear load
(a) The phase-A load current harmonic spectrum
(b) The phase-A source current harmonic spectrum
In this paper, a control methodology for the APF using Discrete PWM and SVPWM is proposed.These methods require a few sensors, simple in algorithm and are able to compensate harmonics and unbalanced loads. The performance of APF with these methods is done in MATLAB/Simulink. The algorithm will be able to reduce the complexity of the control circuitry. The harmonic spectrum under non-linear load conditions shows that reduction of harmonics is better. Under unbalanced linear load, the magnitude of three-phase source currents are made equal and also with balanced linear load the voltage and current are made in phase with each other. The simulation study of two level inverter is carried out using SVPWM because of its better utilization of DC bus voltage more efficiently and generates less harmonic distortion in three-phase voltage source inverter. This SVPWM control methodology can be used with series APF to compensate power quality distortions. From the simulated results of the filtering techniques, it is observed that Total Harmonic Distortion is reduced to an extent by the SVPWM Hybrid filter when compared to the Discrete PWM filtering technique i.e. from 1.78% to 1.61%.
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