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Description

The internal diagram of the photovoltaic generation system (PVGS) is shown in the figure below. The PVGS features a PV array that is connected to an inverter via a boost DC-DC converter. The PV array model contains many types of modules predefined from the database of the California Energy Commission (CEC)

More than 21,000 modules from leading manufacturers are listed in this database which includes the manufacturer's specifications measured for standard test conditions (STC), meaning Irradiance of 1000 W/m2 and 25 °C.

The boost converter controls the PV array in two modes of operation: maximum power point tracking (MPPT); and curtailment. In mode 1 the boost converter duty cycle is calculated by a perturb-and-observe (P&O) MPPT algorithm to ensure maximum power extraction from the array for a given solar irradiation. In curtailment mode the duty cycle of the boost converter is controlled to follow the active power reference.

Both the DC-DC converter and the three phase AC interface converter use switching functions. The inverter’s function is to maintain and regulate the DC link voltage and the reactive power at their respective commanded values at the point of common coupling (PCC). A RL choke filter is used to connect the inverter to the grid. The choke filter must be designed to limit the total harmonic distortion of the PVGS current injected into the grid at the point of common coupling (PCC).

The PVGS must be connected to the grid using an external step-up transformer. It is recommended to use a star-delta transformer with a base power of 1.2 times the nominal power of the PVGS. The model is not compatible with load flow. 

PVGS components schematic

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Important Notice

Refer to Photovoltaic Generation System (PVGS) - Average for a detailed description of the PVGS configuration and mask parameters.  For a detailed description of the interface converters with the switching functions please refer to 2-Level Converter (Switching Function) and Boost Converter (Switching Function).

References