  A novel class of explicit high-order energy-preserving methods are proposed
for general Hamiltonian partial differential equations with non-canonical
structure matrix. When the energy is not quadratic, it is firstly done that the
original system is reformulated into an equivalent form with a modified
quadratic energy conservation law by the energy quadratization approach. Then
the resulting system that satisfies the quadratic energy conservation law is
discretized in time by combining explicit high-order Runge-Kutta methods with
orthogonal projection techniques. The proposed schemes are shown to share the
order of explicit Runge-Kutta method and thus can reach the desired high-order
accuracy. Moreover, the methods are energy-preserving and explicit because the
projection step can be solved explicitly. Numerical results are addressed to
demonstrate the remarkable superiority of the proposed schemes in comparison
with other structure-preserving methods.
