The PV emulator control is experimentally implemented using the DSP-2 board developed at the Institute of Robotica of Faculty of Electrical Engineering and Computer Science in Maribor, Slovenia.
The DSP-2 board is a high performance, floating-point digital signal processor – based inverter controller. This board, in combination with DSP-2 library, can be successfully used for several industrial applications.
In general, the DSP-2 board allows control algorithms, set up in Matlab/Simulink® environment, to be implemented and verified in suitable development systems, at a significantly low cost.
The board is based on the Texas Instruments TMS320C32 DSP and the FPGA XCS40-4PQ240C, member of Xilinx Spartan family. It is equipped with 4 x 12 bit simultaneous A/D converters with serial output and a two channels 12 bit D/A converter with serial input and unipolar output from 0 to 4 V.
DSP-2 library for Simulink® enables rapid transition from the simulation in Simulink® to the real time operation on the DSP-2 board.
DSP-2 library in combination with DSP-2 Terminal interface enables online changing of the Simulink® block parameters, by the parameter inspector window, while the code is executed.
In Fig. 8.33 a picture of the DSP-2 board is shown.
In general, for the implementation of the PV emulator control, it is necessary to use four inputs, i. e., current, voltage, solar irradiance, and temperature. In particular, current and voltage are those sampled at the emulator output, while solar irradiance and temperature are set by the operator or given by external sensors. In the specific case, since a PV model using a regression law to relate temperature and solar irradiance is adopted, only the solar irradiance values are given as input via software to the control board, according to the test to be performed.
The output of the board is the duty cycle generated by PWM block, taken from the DSP-2 library. When the output of the PWM is set to “1”, the power device is active.
In Fig. 8.34 the block diagram of the emulator control, including the PV model, the pole placement-based controller and the PWM modulator, is sketched.
The current and voltage are acquired by two analog inputs indicated as DSP-2 AI.
The solar irradiance G is set by software either if constant or if following a given profile.
The block indicated as DSP-2 PWM is a three-phase pulse width modulator suitably handled to give the switching command for the IGBT (only one input is used). Finally, the blocks indicated as DSP-2 TT allow the corresponding variables to be displayed in the DSP-2 Terminal interface.
Fig. 8.35 DSP-2 Terminal interface
In Fig. 8.35 Terminal interface, with superimposed the parameter inspector window is shown, as an example.