PLECS simulation model for single-phase photovoltaic grid connected inverter

PLECS simulation model for single-phase photovoltaic grid connected inverter

The peak output power is 3kW

The power generation system consists of a solar array providing approximately 380VDC steady-state output, an IGBT based full bridge inverter, and an LCL output filter connected to a 230Vrms, 50Hz single-phase power supply.
In this example, the sunshine and temperature related data of BP365 65w solar modules have been mapped. The array includes 22 modules, each connected in series, with 2 series connected in parallel. The surface current data is saved in one. The mat file contains information on characteristic IV curves at three temperatures: 0 to 1kWh/m2 of sunlight, 0 to 25V of voltage, 0, 25, and 50.

The control system consists of three control loops: Maximum Power Point (MPP) controller, voltage controller, and current controller. These can be seen in the circuit diagram of Figure 1. The external control loop is an MPP controller that ensures maximum power extraction from the PV column at a given level of sunlight. To achieve this, it uses the MPP algorithm (known as dP/dV (incremental conductance) control) to calculate the optimal PV terminal voltage, which is implemented using C-Script blocks. The voltage control circuit is based on a Type 2 controller, which adjusts the PV voltage to the optimal level by controlling the amount of current injected into the grid. The innermost control loop, namely the current controller, sets the modulation index of the inverter to inject the required current into the grid. The current controller is based on a PR controller with a resonance frequency of 50Hz to ensure that there is no tracking error. Finally, a unipolar modulation scheme with a switching frequency of 25 kHz was deployed. In addition, the LCL output filter also includes a damping resistor to ensure the stable operation of the current controller.

The simulation shows the output of the array and inverter under startup conditions and when the system stabilizes to steady-state conditions. The first range displays the sine power supply voltage, injected sine grid current, and the resulting grid power. The second range displays the voltage, current, and power generated by the PV array. The XY diagram provides power and voltage characteristics as well as the impact of MPP controller on array output power.

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At the beginning of the simulation, the DC bus capacitor is pre charged to 388V, resulting in minimal startup transient behavior. The specified nominal value of sunshine is 1kWh/m2. At t=2s, the sunshine level decreased to 0.7 kWh/m2, and the XY plot showed reaching a new MPP.
Users can manipulate the level of sunlight, temperature, and array scaling characteristics, and can also build blocks for photovoltaic modules containing their own IV current surface data.