Smart Grids and Micro-Grids. Umashankar Subramaniam
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Название: Smart Grids and Micro-Grids

Автор: Umashankar Subramaniam

Издательство: John Wiley & Sons Limited

Жанр: Физика

Серия:

isbn: 9781119760603

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СКАЧАТЬ addition with ideality factor, light generated current and diode saturation current to estimate the five parameters of SPV. But in some cases, the value of shunt or series resistance is maintained constant to estimate the MPP which decreases the maximum power accuracy of SPV. The work in [5], presents the parameter estimation using NR and Levenberg-Marquardt method. In which, the author estimates the maximum power by modifying the characteristic equations for change in irradiance and temperature separately. The study fails to consider the variation in parameters under dynamic conditions and also the combined effect of change in temperature and irradiance is not considered simultaneously. The work reported in [13], uses the particle swarm optimization (PSO) to deduce the parameters and the results obtained are compared with NR. The result reveals that the NR method gives best results for monocrystalline type of SPV panel compared to PSO. However, this study neglects the shunt resistance for estimating the maximum power at MPP. Similarly, the study in [14] considers the series resistance and diode thermal voltage for estimation of maximum power. Nonetheless, in the literature the variation in shunt resistance, series resistance and thermal voltage are considered for estimation of maximum power using NR technique. However, the authors in [15] accounted the variation in parameters of Rse, Rsh, and Vt to estimate the maximum voltage and current using GS technique. Therefore, attempt has been made in this chapter to estimate the five parameters of the PV panel for deducing the maximum voltage and current under variations in solar irradiance and operating temperature by considering change in Rse, Rsh, and Vt. Then, the results obtained are compared with literature work using GS technique to determine the equivalent parameters of the PV module of a single diode model (SDM) and to estimate the maximum power from the PV system. The main contributions of this chapter are as follows:

       The parameters of series resistance (Rse), shunt resistance (Rsh) and diode thermal voltage (Vt) are estimated by solving three non-linear equations using NR method under STC for SDM of solar PV. Then, the derived solution from NR were used to extract the light generated current (ILG), and diode reverse saturation current (Isat).

       The variation in shunt, series, and thermal voltage are calculated under dynamic conditions using the data given in the manufacturer data sheet by using appropriate equations. Then, these values are used to evaluate the maximum voltage and current at MPP by solving the two non-linear equations using NR technique.

       The unknown parameters and MPP are evaluated for different PV modules of KD245GX, U5-80 and Shell SP70 using Matlab simulation. The I-V and P-V characteristics of HST60FXXXP solar PV panel obtained during simulation are validated with experimental results.

      Where, I-Output current of PV panel terminals in Amps, V-output voltage of PV panel terminals in Volts, ILG -Light generated current of PV panel in Amps, Ns-Number of series connected solar cells, Isat- Reverse saturation current of diode in Amps, Rse, and Rsh –Series and shunt resistance of solar PV module in Ohms. The thermal voltage (Vt) of a diode for one individual cell is represented as,

      (1.2)

      Where, A depicts the ideality factor of diode, k represent the Boltzmann constant (1.3806 × 10-23 J/K), Tc is the SPV module temperature (STC) in K, and q is the Electronic charge (1.602 ×1019C). The unknown parameters of PV panel namely ILG, Isat, A, Rse and Rsh can be calculated by numerical and analytical approaches using the information of datasheet given by the manufacturer for the PV module at STCs [15]. From (1.1), it is observed that the I-V characteristics curve greatly depends on five unknown parameters of the SPV cell. Therefore, the accurate estimation of electrical parameters is very important to achieve the characteristics closer to real time. The equations used to determine these five parameters such as ILG, Isat, A, Rse and Rsh using numerical techniques are as follows:

      Step-1: Short Circuit Condition (SCC) - During this condition, the output voltage across the panel becomes zero (V=0) resulting in maximum short circuit current (Isc). This can be obtained by substituting V=0 in (1.1) resulting,

      (1.3)

      By substituting the short circuit conditions in (1.1) and after few simplifications, the light generated current (ILG) can be expressed as [17, 18]:

      Step-2: Open Circuit Condition (OCC) – During OCC, the panel output current is zero (I=0) and substituting this condition in (1.1) becomes [17, 18]:

      Step-3: Maximum Power Point condition (MPP)- The maximum point voltage Vmpp and current Impp of PV panel is available in manufacturer datasheet. By substituting these parameters in (1.1) we get,

      The derivative at the maximum power point (MPP) is zero as the tangent at MPP is parallel to voltage axis [19]. Therefore,

      The derivative of current with respect to voltage at SCC is mainly determined using the shunt resistance as [15],

      (1.8)