I am currently working on a project to harvest energy from solar PV panels. There are some difficulties that i am facing. I was able to achieve mppt using a constant resistive load with a converter. Implemented system is shown in the figure (Scenario 1). Now i want to extend this system by adding another converter (for current regulation) with a battery (as the only load in my whole system). The intended system is shown as Scenario 2. But i am unable to achieve mppt as well as current regulation. Is there any flaw in my system or approach? kindly guide me. System Diagram

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    \$\begingroup\$ As this is your project, what do you know about the components you are using and those you plan to use? How about the spec sheets - have you got them? \$\endgroup\$ – Solar Mike Mar 10 '19 at 21:09
  • \$\begingroup\$ MPP is a matter of how the converter loads the solar array. To feed this into AC power line requires constantly adjusting the output phasing; this is a task for the pulse-width-modulation of the switching converter. Thus non-battery loads are fine. \$\endgroup\$ – analogsystemsrf Mar 10 '19 at 21:16
  • \$\begingroup\$ If you cannot regulate the DCDC input impedance, then you cannot achieve MPPT It must be matched to the PV impedance Vmp/Imp so input dV/dI must equal PV impedance which rises as the sun sets \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Mar 10 '19 at 21:20
  • \$\begingroup\$ Solar Mike: yes i do know about the components. At least in simulation, i am 100% certain about the components and their values. \$\endgroup\$ – Muhammad Arsalan Mar 11 '19 at 4:39
  • \$\begingroup\$ Analogsystemsrf: I am currently not feeding my energy into AC lines. I am just making an efficient battery charger that harvest max energy and store it in the battery. \$\endgroup\$ – Muhammad Arsalan Mar 11 '19 at 4:40

But i am unable to achieve mppt as well as current regulation. Is there any flaw in my system or approach?

The flaw is in your approach. Putting a constant current into a battery implies establishing a constant power draw -- but "MPPT" stands for maximum power point tracking.

If a charging battery is the only load on your solar cell, the best you can hope for is to draw the maximum possible power from the cell (using MPPT) it is the cell that limits the power, and to regulate the current to the battery only when the cell can supply more power than the battery can absorb.

This is probably not possible without a combined battery charger/MPPT tracking algorithm that "understands" when it is limited by the cell, and when it is limited by the requirements of the battery.

On the bright side, with such a combined algorithm you'll only have one DC-DC converter.

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  • \$\begingroup\$ TimWescott: Thankyou for answering my question. However, I donot intend to charge my battery with constant current. MY reference for current regulation will be changing according to the available power generated by the PV array. To keep things easier, i am using a resistor instead of a battery, however, still, i am unable to achieve MPPT and output regulation (either current or voltage) together. \$\endgroup\$ – Muhammad Arsalan Mar 11 '19 at 4:46
  • \$\begingroup\$ Conservation of energy is a really basic part of physics, and regulating both input energy (i.e. MPPT) and output energy (current or voltage) together violates conservation of energy. The first question you should ask about a proposed energy conversion scheme is "does it violate conservation of energy?". If it does, scratch it off of your list of candidates and move on. \$\endgroup\$ – TimWescott Mar 11 '19 at 16:42
  • \$\begingroup\$ yes i believe this is what is happening \$\endgroup\$ – Muhammad Arsalan Mar 12 '19 at 5:03

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