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A major challenge in a photovoltaic (PV) system is to identify the line-to-line faults that occurred under low irradiance conditions, during day-to-night/night-to-day transitions in the presence of blocking diodes. Due to active maximum power point tracker, these faults may not be identified and continue to be hidden even if the system returns to a high irradiance condition, since the magnitude of fault current may be less than the rating of the protection device (fuse). Those uncleared faults may subsequently lead to reduced peak output power, reliability issues, and may even cause fire risks. To address these issues, a method is proposed to identify the pre-existing/undetected faults using the transitory conditions that occur during the preturn on/off condition of the PV inverter (checking mode). From these transitory conditions, the I–V curve of the PV array is exploited without the need for additional components or sensors. Additionally, there is no need to disconnect the PV array from the setup. Moreover, the local minima is tracked, to discriminate the faults and partial shading conditions. The proposed algorithm is tested on a small-scale grid-connected PV system and implemented in LabVIEW. The results demonstrate the efficacy of proposed algorithm in detecting the pre-existing/undetected faults.

The primary objective of Maximum Power Point Tracking (MPPT) for PV systems connected to a low-voltage DC grid is to extract the maximum possible power output from the PV array. Normally high-frequ...

The nonlinear characteristics of a photovoltaic (PV) array, maximum power point tracking of the PV inverter, presence of blocking diodes, and lower irradiation prevent the conventional protection devices to trip under certain faults and lead to reduced system efficiency and fire hazards. Moreover, the PV characteristics under certain partial shading conditions are similar to that under fault conditions. Hence, it is imperative to detect faults and differentiate faults from the partial shading condition to avoid false tripping of the system. This paper proposes a simple fault detection method using the available data of array voltage and current by means of wavelet packets. The proposed scheme is simulated using MATLAB/Simulink and is experimentally tested on a 1.6-kW $\text{4}\,\times \,\text{4}$ PV array to validate its performance.

Global maximum power point tracking (GMPPT) strategies for photovoltaic systems are effective under nonuniform irradiation conditions but cause unnecessary power loss due to wide search under uniform irradiance. This paper proposes a scheme for detecting the type of irradiation, viz., uniform or nonuniform, using the trend observed in the string maximum power point (MPP) voltage and current. This partial shading detection scheme is implemented in a GMPPT control strategy combining the conventional perturb and observe (P&O) algorithm and the Fireworks Algorithm (FWA). Under uniform irradiation conditions, the P&O algorithm is used owing to the lower magnitude of power oscillations during tracking as compared to the FWA. On the other hand, under partial shading conditions, the FWA is employed due to its global search and fast tracking capability. The proposed GMPPT method is tested experimentally to verify its effectiveness under different shading patterns.

Maximum power point tracking (MPPT) is essential for a photovoltaic (PV) system in order to maximise the utilisation of solar energy. Under partially shaded conditions (PSC), PV strings with bypass diodes exhibit multiple peaks in the power-voltage ( P - V ) characteristics. Although various Global MPPT (GMPPT) algorithms have been proposed to address this issue, most of them cannot distinguish between PSC and uniform insolation, leading to the scan of the entire P - V curve under uniform insolation levels. This study introduces a general method to detect the occurrence of PSC in a PV string thereby dispensing the need to scan the entire PV curve under uniform insolation. Further, a simple technique is proposed to determine the GMPP with the minimum possible search space under PSC. The proposed algorithms for the detection of partial shading and GMPPT are validated experimentally.

This paper presents a scheme for extending low speed operation of a wind driven Doubly Fed Induction Generator (DFIG) with limited rating converters (30%). In this scheme, a low voltage is applied to the stator at rotor speeds below the normal range (0.7 p.u.) while the nominal voltage is applied when the rotor speed is above this range. The switch-over to a lower stator voltage below a threshold speed facilitates to maintain the operational efficiency with the same fractional rated converters. Simulations results of a typical 250 kW DFIG in Matlab/Simulink environment reveal that, a lower stator voltage increases the generator efficiency at lower speeds without exceeding (limited) rating of the rotor side power converter. Typically the speed range is extended by 20% when reduction in voltage is 42%. With a 250 kW generator the energy harvested over one year is increased by 61.1 MWh with the proposed scheme. The scheme is simple, economical and can be implemented through speed sensor and contactors. Experiments on a laboratory test set up demonstrate the efficacy of the proposition.

Partial shading decreases the power output of PV arrays due to mismatch losses. These losses are dependent on the shading pattern and the relative positions of shaded modules in the array. Various static and dynamic reconfiguration techniques have earlier been proposed to mitigate these losses. In an earlier proposed static reconfiguration technique, the power generation is enhanced by altering the physical location of the PV panels using a random Sudoku configuration without modifying the TCT (Total-Cross-Tied) based electrical connections. However, this arrangement faces drawbacks due to ineffective dispersion of shade and significant increase in wiring required. In this work, an optimal Sudoku arrangement to overcome these drawbacks is formulated. Further analysis indicate that the global peak of the optimal Sudoku based PV array occurs as the right most peak in the curve for most shading conditions, thus evidently obviating the need for complex MPPT (Maximum-Power-Point-Tracking) algorithms. The proposed configuration is compared with various other existing reconfiguration schemes in terms of power output and the comparison is presented. In addition, a general formulation is proposed to expand this pattern to any generic array. A strategy is also proposed to make such an interconnection practicable for very large size PV arrays.

In the context of recent advancements in 3-phase phase-locked loop (PLL) structures to tackle grid imperfections, this paper attempts to shift focus towards dynamic response optimization for fast tracking of disturbed grids, as opposed to Wiener optimization, a trade-off between filtering characteristic and dynamic response. In this respect, an ingenious self-consistent model (SCM)-based approach is proposed which explores filter design in the presence of frequency shifts and phase jumps, and facilitates the analytical computation of unique loop filter parameters. Trial and error in filter parameter selection is inconvenient, but more importantly, even rigorous trials would be insufficient in qualifying the non-existence of a better design. Having eliminated trial and error, this novel technique limits transients to user specifications while fixing on an optimum damping ratio, to yield the best fit. The design methodology is applied to three existing 3-phase PLL structures modelled in MATLAB/Simulink, and the proposed method is further evaluated through extensive simulations and performance comparisons with the traditional Wiener approach. To enhance the understanding of model behaviour and the feasibility of practical implementation, comprehensive three-dimensional (3-D) lookup tables are presented. They enable the study of optimized filter parameter variations for a range of grid disturbances, and broaden the application to filter optimization in real-time. In the interest of the reader, this paper is structurally split into two parts. Part 1 covers the premise and theory that explicates the proposed SCM methodology. The detailed analysis and verification of the SCM are covered in Part 2.

A major challenge in the photovoltaics (PV) systems is to make it energy efficient. Partial shading reduces the energy yield of PV systems and introduces multiple peaks in the P - V characteristics. The maximum power point trackers (MPPTs) work in conjunction with the boost converter and track the global peak in the P - V characteristics. The boost converter used for MPPT is generally designed to operate with high efficiency at the maximum power point (MPP) voltage of the array by assuming a single peak power point on the P - V characteristics. However, the efficiency of the boost converter varies with the input voltage, and the MPP of the load when the converter efficiency is considered is different from the MPP of the PV array. Since the maximisation of power in the load is ultimately desirable, this study focuses on the maximisation of power to the load. The power transferred to load under different shading patterns is analysed and the results of the study are demonstrated through simulation and experimental results.