actually for grid synch. process i want to implement these two methods. among these, for PLL i would like to go with [Vgrid TO V(alpha-beta) TO V(d-q). so can anyone explain the whole process thoroughly ?
Dear Joshi Darshan,
d-q is preferred as v and i are available as dc quantities and control is easier.
Best wishes !
Standard practice is to use PLL which can be implemented in many ways.
But using ZCD will be the easiest one.
Alternately, you can also use ATAN2 function.
Hello.
Application of ZCD is easier, but in actual practice PLL's are implemented for precise synchronization of systems. PLL's are quick as compared to ZCD. Also by application of SDFT we can improve response time of conventional PLL.
PLL is comparatively better choice as tracking is better and fast but zero crossing detection is easy to implement.
First convert Vabc to Vd and Vq and therefore there is two option of PLL but easier one to use Vq for theta calculation. After Vq, PI controller is used as a filter then add reference frequency in radian i.e. 2*pi*50 or 60 Hz and then used integrator.
ZCD is very easy to implement and works very well, but when the system is distorted multiple crossing by zero can occur in a period and so multiple detection may occur causing syncronization errors. In this situation a PLL is desired to obtain a secure syncronization. Nowadays PLL can be easily implemented in digital devices.
Dependent of the inverter power, if your inverter is of very low power (ej: 100w-500w), surely, you must use easy algorithms and low software resources, where the ZCD is a aceptable option for the operation.
In other hand, the greater the power of your inverter, you will must require more resources software, measurement and more sophisticated algorithms, where the PLL is required.
I would not recommend dq control on single-phase converters. You will loose "information" during transients. You may find relevant information and references on this paper:
Article Cascade-Free Model Predictive Control for Single-Phase Grid-...