Excessive use of nonlinear and time varying devices results in harmonic currents in the secondary distribution system. The suppression of harmonics is a dominant issue and one of the practical ways to compensate harmonics is shunt active power filter (SAPF). The core part of the SAPF is control techniques used for reference current generation. This paper presents a comprehensive study of three control strategies namely instantaneous reactive power (p – q) theory, synchronous reference frame (SRF) theory and instantaneous active and reactive current (id – iq) component method for SAPF in a three phase three wire distribution system. These three control methods aims to compensate harmonics, reactive power and load unbalance under sinusoidal balanced supply voltage conditions. Simulation results present a relative investigation of three control techniques based on current THD and load unbalance.
- Hysteresis band current control (HBCC)
- Id – iq method
- Nonlinear loads
- P – q theory
- Shunt active power filter
- SRF theory
Fig. 1. SAPF connected to distribution grid
EXPECTED SIMULATION RESULTS:
Fig. 2. Simulation results of SAPF with p-q theory under nonlinear balanced
load (a) Source voltage (b) Load current (c) Source current after filtering
(d) Compensation current.
Fig. 3. Simulation results of SAPF with id-iq method under nonlinear
balanced load (a) Source current after filtering (b) Compensation current
Fig. 4. Simulation results of SAPF with id-iq method under nonlinear
unbalanced load (a) Source voltage (b) Load current (c) Source current
after filtering (d) Compensation current.
Fig. 5. Dynamic performance of SAPF during load change with id-iq method
- Load current (b) Source current (c) Compensation current.
Fig. 6. (a) Source voltage (V) and load current (A) (b) Source voltage (V)
and source current (A) (c) Compensation current (d) Reactive power
demand of the load (e) Reactive power supplied by the SAPF (f)
Reactive power supplied by the source.
The harmonic distortions exist in the distribution system due to the massive use of power electronic based nonlinear loads. Harmonic distortions can result in serious problems such as increase in current, reactive VAs, VAs, power factor reduction and increase in losses. The SAPF with three control strategies viz. p-q theory, SRF theory and id-iq method has been studied in this paper. The simulation has been carried out for different load scenarios and the THD, percentage of individual dominant harmonics has also observed. From the simulation analysis, it is observed that the SAPF giving quite reasonably good performance in compensating harmonics, reactive power and load unbalance. Among the three control techniques, it is noticed that the id-iq method gives reasonably better performance in terms of current THD.
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