Hi Yusuph,
Thank you for sharing your system details and the P&O code. Looks like the root of the issue lies in the interaction between the boost-converter design, the load demand, and the MPPT algorithm. While the PV is delivering ~555 W at 42 V, the boost stage is only reaching ~52 V output under load and drawing ~409 W; this indicates that under that load the boost converter cannot maintain the full duty-cycle/gain required to reach 100 V.
The reason could be:
- The maximum duty ratio (here, limited it at 0.92) may not allow sufficient gain for 42 V to 100 V under heavy load, especially if losses and non-idealities are present.
- The inductor, switching MOSFET/diode losses, and the load current (which is higher when boost voltage is lower) may saturate or increase losses, reducing efficiency and limiting achievable voltage.
- The MPPT algorithm may be optimising for PV power at 42 V but not checking whether the boost converter is capable of raising to 100 V under that power and load current; therefore, the link voltage is collapsing to ~52 V to allow the current required for ~409 W rather than supporting full 100 V.
- If the motor inverter and motor draw a certain current at 100 V, the boost converter must supply a corresponding input current from the PV; maybe the PV current or the converter is hitting a limit (e.g., inductor saturation, switch current, thermal limit) so the converter auto-limits itself to ~52 V.
You may try the following to resolve your issue:
- Do check the boost converter design: verify the sizing of the inductor, switching devices, diode, layout, and whether they are capable of delivering the higher duty cycle/gain at your target current. The following documentation may help: https://www.mathworks.com/help/sps/ug/solar-pv-system-maximum-power-point-tracking-using-boost-converter.html and https://imperix.com/wp-content/uploads/2018/08/Boost-for-PV-panel-EN.pdf
- https://www.ti.com/lit/ug/tidu404/tidu404.pdf
- Consider adding a control loop for the boost output voltage (i.e., ensure the boost converter transitions from MPPT mode to “voltage‐regulation” mode when PV power allows). Many MPPT systems operate in MPPT mode until the DC link voltage target is reached, then switch to constant voltage regulation. (https://www.mathworks.com/help/sps/ug/solar-pv-system-maximum-power-point-tracking-using-boost-converter.html)
- Verify the achievable duty cycle: The ideal boost-gain formula is 𝑉𝑜𝑢𝑡 = 𝑉𝑖𝑛 / (1−𝐷) (disregarding losses) so for 42 V to 100 V you may need D ≈ 0.58 in ideal case (assuming continuous mode). But real-world losses (switch losses, diode drop, inductor resistance, switching transitions, current ripple) reduce gain, meaning you may need D much higher, but since it is capped at 0.92. At D = 0.92 the theoretical ideal gain is ~12.5× (42 V × 12.5 ≈ 525 V) but in practice at high current the losses will limit actual achievable gain dramatically. So, the system may be forced to settle at ~52 V output under the demanded current.
- Suggest measuring the boost converter’s input current, output current, switch and inductor conditions (e.g., current waveforms, heating, saturation signs) under load and light load. Check if the converter is reaching a current limit or thermal limitation.
- If the motor inverter demands full 100 V to get full power, you might consider: (a) reducing required voltage or motor ratings, (b) using a converter stage with higher switching frequency/optimised components, or (c) re-configuring the PV array (higher input voltage) to reduce the required duty ratio/gain for the boost stage.
Kindly reach out to MathWorks Technical Support for more help. (https://www.mathworks.com/support/contact_us.html)
