capcorrect() voltage validation uses incorrect chained comparison

[marcostfermin]

Describe the bug

capcorrect() attempts to detect missing voltage inputs using if VLL == VLN == V is None:, which does not correctly test whether all three voltages are None. This can lead to incorrect acceptance or rejection of input combinations.

Reproduction Code

# Setup
import electricpy as ep

# Code which causes failure
# All voltages omitted
ep.capcorrect(Qc=100e3, f=60)

Expected behavior

The function should reliably detect that no voltage was provided and raise a clear ValueError indicating that one of V, VLN, or VLL must be specified.

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: [e.g. Linux]
• Python Version [e.g. 3.7]
• Version [e.g. 0.2.1]

Additional context

This should be implemented as:
if (VLL is None) and (VLN is None) and (V is None):.