International University of Travnik , Travnik , Bosnia and Herzegovina
International University of Travnik , Travnik , Bosnia and Herzegovina
The paper analyzes one concrete implementation of a phase-coupled loop, which was fully implemented digitally. Control electronics of rectifiers and inverters are based on microcontrollers. The goal of the design of control electronics in both cases was to minimize additional electronics, since microcontrollers are already used. In the rectifier, the thyristors in the bridge are controlled practically directly from the microcontroller port, while in the inverter, the output signal of the counter is directly used to control the bridge transistors. For both devices, it is necessary to provide synchronous operation with the network in a certain way, because for this purpose a number is reserved in the memory of the microcontroller whose value changes synchronously with the phase of the network voltage. In the case of rectifier control, the value of the "sample" table is used for ignition. It is similar with the inverter, where based on the value in the memory of the microcontroller, the sine function is read in the table. If the program incorporates the possibility to influence the value of the number representing the frequency (phase increment), but in such a way that the final result is that the phases of the reference and output waves are identical, it can be considered that both the rectifier and the inverter will work in sync with network.
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