  We study four young Pulsar Wind Nebulae (PWNe) detected in TeV gamma-rays,
G21.5-0.9, G54.1+0.3, Kes 75, and G0.9+0.1, using the spectral evolution model
developed and applied to the Crab Nebula in our previous work. We model the
evolution of magnetic field and particle distribution function inside a
uniformly expanding PWN considering a time-dependent injection from the pulsar
and radiative and adiabatic losses. Considering uncertainties in the
interstellar radiation field (ISRF) and their distance, we study two cases for
each PWN. Because TeV PWNe have a large TeV gamma-rays to X-rays flux ratio,
the magnetic energy of the PWNe accounts for only a small fraction of the total
energy injected (typically a few x 10^{-3}). The gamma-ray emission is
dominated by inverse Compton scattering off the infrared photons of the ISRF. A
broken power-law distribution function for the injected particles reproduces
the observed spectrum well, except for G0.9+0.1. For G0.9+0.1, we do not need a
low energy counterpart because adiabatic losses alone are enough to reproduce
the radio observations. High energy power-law indices at injection are similar
(2.5 -- 2.6), while low energy power-law indices range from 1.0 to 1.6. The
lower limit of the particle injection rate indicates that the pair multiplicity
is larger than 10^4. The corresponding upper limit of the bulk Lorentz factor
of the pulsar winds is close to the break energy of the broken power-law
injection, except for Kes 75.
