how would I synchronized the frequency and voltage of the grid to my solar inverter?

[D.A.(Tony)Stewart]

You must consider the PLL is only one of many feedback references need to control a good inverter.

The maximum dissipation in your inverter as well as the demand for micro-grid architecture feedback to indicate what power factor you need to supply or when you may not supply to the grid ( e.g at noon when load is light)

So I suspect in modern grid-tied inverters (GTI's) they sense current supplied, voltage detected in range, surge detection, suppression, phase of power supplied and can respond to SCADA micro-grid controls when off-peak demands prohibit generation on the grid.

There are also digital PLL's which use pulse counter/dividers from stable XTAL clocks that respond to fractional N or pulse-swallow and pulse insertion methods to adjust phase or frequency continuously, ( according to required slew rate)

Solutions to stability of the network with micro-grid architecture with GTI's is a topic familiar with someone I know who teaches at U of T.

 

[D.A.(Tony)Stewart]

THere are two basic GTI's Voltage driver and Current driver.
Using V and I sense, a simple regulator dumps all the power that is available from battery or PV as long as ;
1) the current is sinusoidal ,
2) input voltage range does not cause undervoltage ( impedance ratio)
3) does not cause over current or overtemp or affect PMMT on PV)

Then Phase of driver is simple I follows a filtered V with zero phase error. Or in other words, separating I & Q components of generated power making Q=0 ( reactive) or PF=1 by adjusting phase of driver or average time delay to switch stored energy to grid. As such this is a phase comparator can be called PLL but not using a VCO, rather some sort of timing control to adjust phase.

Protection for OVP, OCP, OTP for output and UVP for both input and output may be wise to include, but then you dont really need a PLL in a traditional sense.

Current mode control is better for stability with current sense feedback as it is more linear. PWM control is best method using Sine waveform to follow to minimize THD and make life easier for controlling sine current out.

The realization of a simple transformerless design can be very few parts, as long as the requirements are clearly defined with consideration to above. THe cost of the active components may be higher than expected for higher power transfer with inductive storage of energy for 1 cycle minimum and Ride-Through (RT) management as previously mentioned by FVM.

Solid grounding is required but isolation from peripheral communication.

 

[dann11]

I have tested one microinverter, and it has a software monitoring and during the run it suddenly shows a message that there is a fault that occur and it is overcurrent.. what is the possible cause of overcurrent? and how should I deal with it?

 

[KlausST]

Hi,

A new problem...

Maybe you should consider starting a new thread. If you do so, please leave a link here.

Please add what type of converter you use and give more additional informations.

Klaus

 

[HanyHamed]

PLL is used to feed the grid angle to the vector controller which is the main controller to drive the converter in unity power factor. So use vector control method. The idea is to set the q component of the grid current to zero hence align the d component with voltage vector. The park trnsformation is fed with the grid estimated angle by the PLL circuit.

 

[DanyR]

Hi, perhaps this project may be of some use: https://www.edaboard.com/threads/346709/