Single-phase Grid-connected PV System with Golden Section Search-based MPPT Algorithm*

 ABSTRACT:

 Maximum power point tracking (MPPT) is a technique employed for with variable-power sources, such as solar, wind, and ocean, to maximize energy extraction under all conditions. The commonly used perturb and observe (P&O) and incrementalconductance (INC) methods have advantages such as ease of implementation, but they also have the challenge of selecting the most optimized perturbation step or increment size while considering the trade-off between convergence time and oscillation. To address these issues, an MPPT solution for grid-connected photovoltaic (PV) systems is proposed that combines the golden section search (GSS), P&O, and INC methods to simultaneously achieve faster convergence and smaller oscillation, converging to the MPP by repeatedly narrowing the width of the interval at the rate of the golden ratio. The proposed MPPT technique was applied to a PV system consisting of a PV array, boost chopper, and inverter. Simulation and experimental results verify the feasibility and effectiveness of the proposed MPPT technique, by which the system is able to locate the MPP in 36 ms and regain a drifting MPP in approximately 30 ms under transient performance. The overall MPPT efficiency is 98.99%.

 KEYWORDS:

1.      Grid-connected system

2.      Maximum power point tracking (MPPT)

3.      Photovoltaic (PV) system

4.      Single-phase inverter

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 

Fig. 1 Control block diagram of the single-phase grid-connected PV system

 EXPECTED SIMULATION RESULTS:

Fig. 2 Simulation results under the conditions of S=237 W/m2, T=13.9 ℃

Fig. 3 Simulation results under the conditions of S=930 W/m2, T=37.5 ℃

CONCLUSION: 

In this paper, a GSS-based multi-stage MPPT technique that combines GSS with P&O and INC was proposed to achieve fast convergence to the MPP with small oscillation. The proposed multi-stage MPPT technique starts by searching the vicinity of the MPP by P&O in the first stage. Then, it quickly narrows the width of the interval with the golden ratio in the second stage, and the located MPP by is verified by the INC method in the third stage. The advantages of P&O, GSS, and INC are exploited, while their disadvantages are avoided. Therefore, this MPPT algorithm provides fast response and high tracking efficiency, as shown through the simulation and experimental results. The simulation and experimental results verified the feasibility and effectiveness of the proposed MPPT technique. The proposed MPPT technique mainly targets the MPP of a unimodal function, i.e., the curve has only one extremum, but it is not suited to multimodal functions, i.e., the curve has multiple extrema when partial shading happens. Thus, to apply the proposed MPPT technique to partial shading conditions, more points must be inserted into the GSS scheme to locate the MPP. The application of the proposed MPPT technique under the partial shading condition remains as future work.

REFERENCES:

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