Steady-state analysis of power system harmonics using equivalent split-circuit models

In this paper we introduce a novel algorithm for harmonic steady-state analysis of power systems that is based on the equivalent split-circuit models recently introduced for power flow analysis. By using an equivalent circuit with current and voltage as the state variables, we extend the harmonic balance method that is used for nonlinear circuit simulation in the frequency domain to capture the frequency harmonics and inter-harmonics induced into a power grid due to nonlinear components. This enables the direct incorporation of physics-based steady-state models of power electronics and smart grid devices directly within the power-system simulation framework. For demonstration, steady-state models of a diode and a nonlinear core saturation inductor are derived and incorporated into the steady-state models of a three-phase full bridge rectifier and a magnetic core saturation transformer. These components are simulated within the proposed power flow analysis framework for a multi-bus power system.