This component can be used to model a photovoltaic (PV) source. The PV source is assumed to consist of several strings of PV modules connected in parallel, where each string can consist of a number of PV modules connected in series. All PV modules in the array are assumed identical.
A PV module can be represented using the electrical equivalent circuit shown below:
Equivalent Circuit of PV Module
The photo current, Iph, generated when the module is exposed to light, varies linearly with solar irradiance. The current Id through the anti-parallel diode is largely responsible for producing the nonlinear I-V characteristics of the PV cell.
Application of the Kirchhoff’s current law to the circuit gives:
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(PV-1) |
Substitution of relevant expressions for the diode current Id and the shunt branch current Ish yields:
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(PV-2) |
Where Io is the diode saturation current, Ai is the diode ideality factor, and VT is the module thermal voltage given by:
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(PV-3) |
Where Ns is the number of PV cells connected in series in the module, k is the Boltzmann constant (1.3806503×10-23 J/K), q is the electron charge (1.60217646×10-19 C), and T is the PV cell temperature in Kelvin.
The photo current is related to the short-circuit current as given in PV-4, and therefore a function of the solar radiation on the plane of the PV module G and the cell temperature T.
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(PV-4) |
The diode saturation current is also a nonlinear function of both the irradiance G and cell temperature T. It is related to the open-circuit voltage and short-circuit current as given in PV-5:
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(PV-5) |
The short-circuit current Isc(G,T) and the open-circuit voltage Voc(G,T) at the given G and T are required for determining Iph(G,T) and Io(G,T).
The short-circuit current of the PV module is directly proportional to the irradiance G and linearly varies with the cell temperature T, and typically modeled as:
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(PV-6) |
Where Isc_STC is the short-circuit current at standard test conditions, defined by GSTC (= 1000 W/m2) and TSTC (= 25°C). The temperature coefficient of the short-circuit current δIscT is typically given as a percentage variation of Isc_STC per degree centigrade (%/°C), and it is a positive value.
The variation of the open-circuit voltage with the irradiance G and the cell temperature T can be modeled as:
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(PV-7) |
Where Voc_STC is the open-circuit voltage at the standard test conditions. The temperature coefficient of open circuit voltage δVocT is typically given as a percentage variation of Voc_STC per degree centigrade (%/°C). The value of δVocT is negative as Voc drops with the increase in cell temperature. The nonlinear dependence of open-circuit voltage with irradiance is modeled using δVocG. The impact of G and T on the other parameters, Ai, Rs, and Rsh, can be considered negligible.
In order to simulate the PV array, the parameters of the PV module equivalent circuit (Ai, Rs, Rsh, Iph, and Io) need to be determined. This component uses a search algorithm to determine the PV module equivalent circuit parameters from the information available in PV module datasheets, which typically provide the maximum power, voltage and current at the maximum power point, open-circuit voltage, and short-circuit current at the standard test conditions and at the nominal operating conditions. These data, together with the number of PV cells connected in series in the module, is sufficient to estimate the PV module parameters. The temperature coefficients of the open-circuit voltage (δVocT) and short-circuit current (δIscT), which are needed to model the variation of PV module output with the temperature, are also available in the module datasheets. The value of δVocG is not available in typical datasheets, but it can be evaluated using the open-circuit voltage at the nominal operating cell temperature (NOCT). The computed PV module parameters can be found in the runtime messages.
G: Instantaneous value of solar radiation on the panel (W/m2).
T: Instantaneous value of cell operating temperature (°C).
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More: |
PSCAD General Reference [23] PSCAD General Reference [50] |
PV Array ConfigurationPV Array Configuration
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PV Array Name |
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Name for the array (optional). |
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Number of Modules Connected in Series per Array |
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INTEGER |
Constant |
Number of PV modules connected in series in each of the module strings in the array. |
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Number of Module Strings in Parallel per Array |
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INTEGER |
Constant |
Number of PV module strings connected in parallel to form the array. |
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Graphics Display |
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Choice |
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Select Standard or Industry. |
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Irradiance at STC |
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REAL |
Constant |
Irradiation at the standard test conditions at which the module parameters are specified [W/m2]. |
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Cell Temperature at STC [°C] |
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REAL |
Constant |
Temperature at the standard test conditions at which the module parameters are specified [°C]. |
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Maximum Power at STC |
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REAL |
Constant |
Maximum power at the standard test conditions [W]. |
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Open Circuit Voltage at STC [V] |
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REAL |
Constant |
Open-circuit voltage at the standard test conditions [V]. |
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Short Circuit Current at STC [A] |
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REAL |
Constant |
Short-circuit current at the standard test conditions [A]. |
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Voltage at Maximum Power Point at STC [V] |
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REAL |
Constant |
Voltage at the maximum power point at the standard test conditions [V]. |
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Current at Maximum Power Point at STC [A] |
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REAL |
Constant |
Current at the maximum power point at the standard test conditions [A]. |
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Nominal Operating Cell Temperature (NOCT) |
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REAL |
Constant |
Cell temperature under nominal operating conditions defined by the irradiance, ambient temperature, and the wind speed [°C]. |
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NOCT Irradiance |
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REAL |
Constant |
Irradiance used to define NOCT. This is different to irradiance under nominal operating conditions [W/m2]. |
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Open Circuit Voltage at NOCT |
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REAL |
Constant |
Open circuit voltage under nominal operating conditions [V]. |
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Number of Series Connected Cells in Module |
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REAL |
Constant |
Number of PV cells connected in series in a PV module. |
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Temperature Coefficient of Power |
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REAL |
Constant |
Percentage change in maximum power per 1oC increase of cell temperature [%/°C]. |
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Temperature Coefficient of Short Circuit Current |
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REAL |
Constant |
Percentage change in short-circuit current per 1 °C increase of cell temperature [%/°C]. |
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Temperature Coefficient of Open Circuit Voltage |
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REAL |
Constant |
Percentage change in open circuit voltage per 1 °C increase of cell temperature [%/°C]. |
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Irradiance at STC |
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REAL |
Constant |
Irradiation at the standard test conditions at which the module parameters are specified [W/m2]. |
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Cell Temperature at STC [°C] |
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REAL |
Constant |
Temperature at the standard test conditions at which the module parameters are specified [°C]. |
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Maximum Power at STC |
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REAL |
Constant |
Maximum power at the standard test conditions [W]. |
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Open Circuit Voltage at STC [V] |
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REAL |
Constant |
Open-circuit voltage at the standard test conditions [V]. |
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Short Circuit Current at STC [A] |
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REAL |
Constant |
Short-circuit current at the standard test conditions [A]. |
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Voltage at Maximum Power Point at STC [V] |
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REAL |
Constant |
Voltage at the maximum power point at the standard test conditions [V]. |
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Current at Maximum Power Point at STC [A] |
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REAL |
Constant |
Current at the maximum power point at the standard test conditions [A]. |
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Nominal Operating Cell Temperature (NOCT) |
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REAL |
Constant |
Cell temperature under nominal operating conditions defined by the irradiance, ambient temperature, and the wind speed [°C]. |
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NOCT Irradiance |
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REAL |
Constant |
Irradiance used to define NOCT. This is different to irradiance under nominal operating conditions [W/m2]. |
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Open Circuit Voltage at NOCT |
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REAL |
Constant |
Open circuit voltage under nominal operating conditions [V]. |
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Number of Series Connected Cells in Module |
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REAL |
Constant |
Number of PV cells connected in series in a PV module. |
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Temperature Coefficient of Power |
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REAL |
Constant |
Percentage change in maximum power per 1oC increase of cell temperature [%/°C]. |
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Temperature Coefficient of Short Circuit Current |
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REAL |
Constant |
Percentage change in short-circuit current per 1 °C increase of cell temperature [%/°C]. |
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Temperature Coefficient of Open Circuit Voltage |
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REAL |
Constant |
Percentage change in open circuit voltage per 1 °C increase of cell temperature [%/°C]. |
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Photo Current per Module |
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Text |
Output |
Name for the photo current [kA] per module. |
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Internal Diode Current per Module |
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Text |
Output |
Name for the internal diode current [kA] per module. |
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Internal Diode Voltage per Module |
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Text |
Output |
Name for the internal diode voltage [kV] per module. |
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Internal Power Loss per Module |
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Text |
Output |
Name for the internal power loss [MW] per module. |
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Output Power per Module |
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Text |
Output |
Name for the output power [MW] per module. |
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PV Array Output Current |
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Text |
Output |
Name of the PV array output current [kA]. |
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PV Array Output Voltage |
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Text |
Output |
Name for the PV array output voltage [kV]. |
