This paper deals with the power quality improvement in a conventional electronic load controller (ELC) used for isolated pico-hydropower generation based on an asynchronous generator (AG). The conventional ELC is based on a six-pulse uncontrolled diode bridge rectifier with a chopper and an auxiliary load. It causes harmonic currents injection resulting distortion in the current and terminal voltage of the generator. The proposed ELC employs a 24-pulse rectifier with 14 diodes and a chopper. A polygon wound autotransformer with reduced kilovolts ampere rating for 24-pulse ac–dc converter is designed and developed for harmonic current reduction to meet the power quality requirements as prescribed by IEEE standard-519. The comparative study of two topologies, conventional ELC (six-pulse bridge-rectifier-based ELC) and proposed ELC (24-pulse bridge-rectifier-based ELC) is carried out in MATLAB using SIMULINK and Power System Block set toolboxes. Experimental validation is carried out for both ELCs for regulating the voltage and frequency of an isolated AG driven by uncontrolled pico-hydro turbine.
- Electronic load controller (ELC)
- Isolated asynchronous generator (IAG)
- Pico-hydro turbine
- 24-pulse bridge rectifier.
Fig. 1. IAG system configuration and control strategy of a chopper switch in a six-pulse diode bridge ELC.
EXPECTED SIMULATION RESULTS:
Fig. 2. Simulated transient waveforms of IAG on application and removal of consumer load using six-pulse diode-bridge-rectifier-based ELC.
Fig. 3. Simulated transient waveforms on application and removal of consumer load using 24-pulse rectifier-based ELC.
Fig. 4. Waveforms and harmonic spectra of (a) conventional six-pulse ELC current (ida ), (b) generator voltage (va), and (c) generator current (ia ) under the zero consumer load conditions.
Fig. 5. Waveforms and harmonic spectra of (a) proposed 24-pulse ELC current (ida ), (b) generator voltage (va ), and (c) generator current (ia ) under the zero consumer load conditions.
The proposed ELC has been realized using 24-pulse converter and a chopper. A comparative study of both types of ELCs (6-pulse and 24-pulse configured ELC) has been demonstrated on the basis of simulation using standard software MATLAB and developing a hardware prototype in the laboratory environment. The proposed 24-pulse ELC has given improved performance of voltage and frequency regulation of IAG with negligible harmonic distortion in the generated voltage and current at varying consumer loads.
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