| Abstract |
An array of solar panels is connected to the mains
through a three-phase active voltage-source inverter and a
step-up transformer. The inverter synchronizes to the grid by
means of a robust phase-locked loop (PLL), using input's
quadrate method, and a multi-variable filter removes voltage
harmonics caused by unbalance and distortion.
The PWM active inverter utilizes a voltage oriented control
(VOC) control structure, using a Park Transform, to convert
the measured ac currents to synchronous reference properties
(d-q reference). Since both the PLL and the VOC are sharing
some common properties (Park Transform, reference angle),
they are combined in one circuit. A field programmable gate
array (FPGA) is used for the purpose. Cumbersome algorithms
like sine and cosine calculations are replaced by look-up tables.
This provides a fast and reliable tool, and no other control
circuits are needed for inverter operation.
Equipment for maximum power point tracking and monitoring
and protecting schemes are beyond the scope of this article.
Simulations and experimental results are presented. |
