Hello all,
I'm working to TRY to make my own mppt style controller using an atmel MCU and an existing boost buck controller. Everything is falling into plan logically except how to monitor the availiable power from the panels. Heres an example.
Assuming the PV is putting out 10Amps at 15V there should be 150W avail of incomming power. My calculations put the buck controller at ~90% efficient on the conservative side so I should be able to kick that down to say 13.8 or so (depending on the stage of charge of couse) with 9.7Amps.
Thats all fine and dandy but how do I measure the total current avail from the panels. As these are essentially a current source across a PN junction they SHOULD give a constant current and change in voltage but the IV curve (realistic - not the ideal) due to mismatches from shading or whatever shows that at some points this is not the case - the current changes.
So other than shorting the panels across a huge load resistor for a ms or so ever few seconds and measuring the voltage, how do I actually find (in real time mind you) the total power comming from the PV? Mind you that since the boost controller is being controlled by the MCU it is essentially (spelling?) a DC/DC converter for current so if the MCU can't determine total power in, it can't do relaible calculations to setup optimal load on the PV. Its for this reason that I don't think just a simple low side sense resistor will work. If the MCU is only thinking that half the available power is there, its only going to command convertion of half the avail power.
Thanks,
Shawn
I'm working to TRY to make my own mppt style controller using an atmel MCU and an existing boost buck controller. Everything is falling into plan logically except how to monitor the availiable power from the panels. Heres an example.
Assuming the PV is putting out 10Amps at 15V there should be 150W avail of incomming power. My calculations put the buck controller at ~90% efficient on the conservative side so I should be able to kick that down to say 13.8 or so (depending on the stage of charge of couse) with 9.7Amps.
Thats all fine and dandy but how do I measure the total current avail from the panels. As these are essentially a current source across a PN junction they SHOULD give a constant current and change in voltage but the IV curve (realistic - not the ideal) due to mismatches from shading or whatever shows that at some points this is not the case - the current changes.
So other than shorting the panels across a huge load resistor for a ms or so ever few seconds and measuring the voltage, how do I actually find (in real time mind you) the total power comming from the PV? Mind you that since the boost controller is being controlled by the MCU it is essentially (spelling?) a DC/DC converter for current so if the MCU can't determine total power in, it can't do relaible calculations to setup optimal load on the PV. Its for this reason that I don't think just a simple low side sense resistor will work. If the MCU is only thinking that half the available power is there, its only going to command convertion of half the avail power.
Thanks,
Shawn