Inverter Temperature Derate of Max Power

[dguittet]

Describe the bug

• The inverter temperature derate curves apply derates to efficiency as a function of temperature. However, a derate applied to power is consistent with real world operation of many inverters.
• In the GUI, there's y-axis unit confusion between ratio and percent.
• Default in GUI should be more informative, showing a few Vdcs for the default inverter with piecewise functions.

Expected behavior
The y-axis should be the ratio of the max output power to the rated power. Once the maximum output is limited by a higher temperature, the existing inverter model will produce lower efficiencies across all input DC power. Example:

Additional context
Lower efficiency at high temperatures could be a real physical behavior, but likely isn't as important to capture as the power limiting (or current) built into many inverters.

Here are a few other power vs temp curves for reference:
https://www.ge.com/renewableenergy/sites/default/files/related_documents/lv5plus-solar-inverter-datasheet.pdf, page 2.
https://files.sma.de/downloads/Temp-Derating-TI-en-15.pdf, page 2 for temp-only, page 3 for temp and Vdc.
https://solar.huawei.com/en/download?p=%2F-%2Fmedia%2FSolar%2Fattachment%2Fpdf%2Fla%2Fservice%2Fcommercial%2Fproduct%2Fdatasheet%2FSUN2000-60KTL-M0_Deratingcurve.pdf, page 2