dann11
Full Member level 3
I wanted to make a solar inverter, but the problem i have is, i dont know how to synchronized my inverters frequency and voltage to the grid. Is there any circuit configuration that will help me to do that? thanks..
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thanks for the reply.. I just have a few questions for you, if you dont mind..
with the PLL circuit, will it have help me control any changes in the grid frequency? what are the possible causes of frequency variation across the inverters output? and how about the output voltage of my inverter? will a voltage sense circuit enough for me to control any changes on it?
thanks again..
I presume there's pretty much literature about grid-tied inverters.
A PLL to track the grid frequency is a good idea. A grid-tied inverter is usually controlled to feed the available input power to the grid. A straightforward way is to operate it as sinusoidal current source phase locked to the grid voltage.
For you
One would treat the grid as a short circuit load to a sine function, compared to your source and use that as the voltage and phase reference into two regulators. One for power limit and one for phase control of your controlled oscillator with a phase detector (PLL) and some frequency reference that can be tuned by analog or digital methods. Other regulators you need compare power available to output and charge control to state-of-charge, by CC,CV,float methods. Feedback to control includes overtemp protection (OTP), OCP,OVP , line fault detection.
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https://googleresearch.blogspot.ca/2014/12/little-box-challenge-academic-awards.html
Doesn't make much sense.i need a feedback from the grid where current must be sensed and then the current sensed will serve as the input to the PLL? where exactly should i put the PLL's output? should i connect the PLL's output to the PWM circuit?
Synchronization to the current means the inverter's power factor is undetermined and can't be controlled to near unity, as it would be required.2) as soon as it is connected you should adjust PLL with current/phase shift (your voltage to your current)
Maybe a misunderstanding. In my eyes the PLL frequency has to be controlled to get the desired phase angle (current to voltage).Synchronization to the current means the inverter's power factor is undetermined and can't be controlled to near unity, as it would be required.
Perhaps a stupid question: Why would a simple generator (here invertor) provide reactive power to the grid? I can understand it could be interesting to make the overall power factor better, but is this the task of an (again simple) invertor?This thesis "proposes a low complexity grid synchronization method which extracts both the parallel component and the orthogonal component from the grid voltage while sufficiently filtering out grid distortions. The grid synchronizer is easy to implement and provides the inverter the capability of controlling the reactive power generation without the need for dq frame transformation."