Abstract
Phase locked loop (PLL) is an important part of the control unit of the grid connected power converter. The method of zero crossing detection (ZCD) does not produce accurate phase information when grid is non-ideal. In this work, a synchronous reference frame (SRF) PLL method to obtain accurate phase information when the grid voltages are unbalanced is proposed. The performances of the PLL have been verified for ideal and abnormal grid conditions such as unbalance, voltage sag, faults condition etc. Based on the results obtained, the developed PLL gives better fault ride when unbalances in the three phase input signals are overall handled well by the PLL system as it locks the two signal back within the first cycle. It also overcomes a phase jump after 5 milli-seconds from the time the fault was introduced and performs better tracking of the grid voltage and that of the renewable energy source. Keywords: Phase locked loop (PLL), grid synchronisation, simulations, PI regulator, hybrid system
Highlights
The integration of large scale wind and solar power systems to the grid is a growing trend in modern power system (Wei Zhao, 2012)
The voltage controlled oscillator (VCO), generates at its output an AC signal whose frequency is shifted with respect to a given central frequency ωc, as a function of the input voltage provided by the low pass filter (LPF) (Arruda et al, 2001)
Ghoshal et al (2012) and Cherif (2007) reported techniques through which Phase locked loop (PLL) performance can be improved in the event of grid pertubation
Summary
The integration of large scale wind and solar power systems to the grid is a growing trend in modern power system (Wei Zhao, 2012). Phase lock Loop is vital for control and tracking of phase and frequency of the incoming signal of grid connected systems such as distributed generation (Ghoshal, 2011). Ghoshal et al (2012) and Cherif (2007) reported techniques through which PLL performance can be improved in the event of grid pertubation In their works, a proper PI regulator was designed and implemented to study the phase tracking and error rejection ability for control systems. AKOH et al: DEVELOPMENT OF PHASE LOCK LOOP SYSTEM FOR SYNCHRONIZATION OF A HYBRID SYSTEM this work adopted the synchronously rotating reference frame (SRF) based method of PLL design to develop a prototype capable of synchronizing a distributed generation with the grid under different perturbation, so as to improve the power quality.
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