An Adaptive Feed-Forward Phase Locked Loop for Grid Synchronization of Renewable Energy Systems under Wide Frequency Deviations

Abstract

Synchronization is a crucial problem in the grid-connected inverter’s control and operation. A phase-locked loop (PLL) is a typical grid synchronization strategy, which ought to have a high resistance to power system uncertainties since its sensitivity influences the generated reference signal. The traditional PLL catches the phase and frequency of the input signal via the feedback loop filter (LF). In general, to enhance the steady-state capability during distorted grid conditions generally, a filter tuned for nominal frequency is used. This PLL corrects large frequency deviations around the nominal frequency, which increases the PLL’s locking time. Therefore, this paper presents an adaptive feed-forward PLL, where the input signal frequency and phase under large frequency deviations are tracked precisely, which overcomes the above-mentioned limitations. The proposed adaptive PLL consists of a feedback loop that reduces the phase error. The feed-forward loop predicts the frequency and phase error, and the frequency adaptive FIR filter reduces the ripples in output, which is due to input distortions. The adaptive mechanism adjusts the gain of the filter in accordance with the supply frequency. This reduces the phase and frequency error and also decreases the locking time under wide frequency deviations. To verify the effectiveness of the proposed adaptive feed-forward PLL, the system was tested under different grid abnormal conditions. Further, the stability analysis has been carried out via a developed prototype test platform in the laboratory. To bring the proposed simulations into real-time implementations and for control strategies, an Altera Cyclone II field-programmable gate array (FPGA) board has been used. The obtained results of the proposed PLL via simulations and hardware are compared with conventional techniques, and it indicates the superiority of the proposed method. The proposed PLL effectively able to tackle the different grid uncertainties, which can be observed from the results presented in the result section.

Load Shifting and Peak Clipping for Reducing Energy Consumption in an Indian University Campus

“…Table 7 shows that the average load demand is 44, and the peak demand is 90.92 kW for the daily load profile. Consequently, the load factor is increased by about 1.5%, taking into account the daily load profile and by 3.8% for the monthly load profile [57][58][59][60][61]. It is confirmed that increasing the load factor enhances the energy efficiency measures on campus.…”

Power Management in Solar PV - Microhydro Hybrid System Using Power Angle Control Strategy with Syncronverter

“…Phase-Locked Loop (PLL) is used among various synchronization techniques to synchronize the SV to MHP in this study. PLL is a well-known, and widely used control technique for three-phase power systems is synchronous reference frame Phase Locked Loop (PLL) [26]. The modelling of SV is based on the mathematical equations where equations for voltage signal and power are shown below:…”

Grid-Connected Renewable Energy Sources: A New Approach for Phase-Locked Loop with DC-Offset Removal

“…The power generated from RESs must be shaped in order to be interfaced with the grid by employing Power Electronics Converters (PEC) [3]. In grid-connected RES systems, the most popular synchronization technique is based on Phase-Locked Loops, (PLL) which synchronize the output power from the PEC with the electrical grid [4][5][6][7][8].…”

“…The second and third parts of SRF-PLLs are the Loop Filter (LF) and the Voltage-Controlled Oscillator (VCO) [8]. The LF is a Proportional Integrator (PI) controller that is mainly responsible for suppressing disturbances inside the PLL control loop.…”