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Partial shading is a common and difficult problem to be solved in a photovoltaic (PV) system. Numerous efforts have been introduced to mitigate this problem. Some commonly used approaches are deploying some metaheuristic (MH) algorithm to track the multiple-peak P-V curve of partially shaded PV system. Cuckoo search (CS) is a new optimization algorithm based on the MH approach. It has been used to solve an optimization problem in many applications, including the maximum power point tracking (MPPT) problem. The CS algorithm performs well in tracking the global maximum power point (GMPP). However, just like any other MH algorithm, there is still a dilemmatic trading between their accuracy and the tracking time needed to find GMPP. This paper proposes a new MPPT algorithm by combining the CS algorithm with golden section search (GSS) to take beneficial features from both the algorithms. To validate the proposed algorithm, it is evaluated with various cases of partial shading. The simulation and experimental results show a noticeable performance improvement compared with the original CS algorithm and other MH algorithms.

Photovoltaic modules subjected to partial shading conditions (PSC) can drastically decrease their power output. Hence, there have been various maximum power point tracking (MPPT) control algorithms developed to reduce or counteract the shading effects. Recently, a new metaheuristic algorithm known as firefly algorithm (FA) was developed, which, under PSC, has been shown to successfully track the global maximum point (GMP). Nevertheless, the FA still has some inherent problems that may hinder the performance of the MPPT. This paper modifies the existing FA to counteract these problems. As will be demonstrated in this paper, the proposed modified FA method can reduce the number of computation operations and the time for converging to the GMP that the existing FA requires. Experimental results show that the proposed method can track the global point under various PSC, has a faster convergence time compared with the FA, and can effectively suppress power and voltage fluctuations.

Conventional maximum power point tracking (MPPT) methods such as perturb-and-observe (P&O) method can only track the first local maximum point and stop progressing to the next maximum point. MPPT methods based on particle swarm optimization (PSO) have been proposed to track the global maximum point (GMP). However, the problem with the PSO method is that the time required for convergence may be long if the range of the search space is large. This paper proposes a hybrid method, which combines P&O and PSO methods. Initially, the P&O method is employed to allocate the nearest local maximum. Then, starting from that point on, the PSO method is employed to search for the GMP. The advantage of using the proposed hybrid method is that the search space for the PSO is reduced, and hence, the time that is required for convergence can be greatly improved. The excellent performance of the proposed hybrid method is verified by comparing it against the PSO method using an experimental setup.

An admittance or impedance matrix of a power converter is highly desirable for harmonic analysis of a power system. However, power converters are inherently nonlinear and time-varying systems. Therefore, a small-signal harmonic model needs to be derived. While there have been many methods to obtain the small-signal models of DC-DC converters, most of these methods cannot be directly applied to AC-DC converters. Moreover, while accurate methods exist for obtaining accurate models of open-loop AC-DC converters, there are few existing methods for obtaining accurate models for closed-loop AC-DC converters. This paper proposes an analytical method for obtaining an accurate small-signal harmonic model for a power converter. The proposed method is based on state-variable sensitivity methods, which have been previously used to derive a transfer function of a DC-DC converter. This paper will show what modifications are required to extend it to derive the small-signal harmonic model of a closed-loop AC-DC converter. A small-signal harmonic model of a closed-loop pulse-width modulated (PWM) voltage source converter (VSC) with synchronous frame current controllers and a dc voltage controller is derived based on the proposed method. The results are in good agreement with large-signal simulations by means of PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]