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MPPT controller with constant voltage source

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Feb 4, 2023
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On my boat I have two three phase generators with stator and rotor build-in into engine (directly on propeller shaft) followed by inverter to 230 V 50 Hz as a separate unit. Unfortunately later has burnt. Spare part is no more available and I need to find another solution. I can only use outputs of two three phase isolated and floating delta connected windings with voltage between 100 V 33 Hz (1000 RPM) and 260 V 100 Hz (3000 RPM) with maximum power up to 3 kW each.

My first idea was using two three phase bridge rectifiers with DC sides tighten together and connected to switching power supply with wide input voltage range (130 VDC – 370 VDC) and 48 VDC output followed by standard inverter 48 VDC to 230 VAC 50 Hz. This solution should work, but is rather complicated and expensive.

Next option is applying MPPT solar inverter where rectified output from generator is connected to solar input. This should not work as MPPT controller want to “trim” input parameters to satisfy MPP as it was listed many times on different forums. But, my case is not following MPP. My demand is not to work at MPP. My source is of constant voltage type, whatever the demand will be. Some figures: 6 kW from generator, 3.6 kW maximum power of inverted 230 VAC, 0.5 – 2.5 kW typical power of all appliances combined (never reach 3.6 kW). No connection to batteries. So, there will be no need for the controller to reach MPP. With constant input voltage only input current is going to change according requested power. It looks to me as if I have 1000 W solar panel and only 10 W demand. In this case voltage on solar input is almost the same with demand of 9 W, 10 W or 11 W. Current change is not affected input voltage. This is my case, I think. In such case MPPT solar inverter should not try to reach MPP. Of course, I will need to have adequate RPM not to burn my windings, but this is another story (1500 RPM is enough for all purposes).

Since I did not find any discussion of MPPT controller operation far away of MPP, my question is: do I think right and second solution is feasible? Or not?


It's not clear why you want to use an MPPT controller circuit when you don't want MPPT control.
Makes little sense to me.
Actually I don’t need an MPPT controller, but I didn’t find any better approximation to DC/AC converter with wide DC input (130 VDC – 370 VDC) on market. I simply try to find a replacement to broken 3.5 kW DC/AC converter.

Any better idea than solar MPPT controller is highly appreciated.


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