Impedance-Based Stability Modeling and Analysis of Networked Converter Systems

Impedance-based stability modeling and analysis of converter systems is usually performed by partitioning a system into a source and a load subsystem, and formulating a single-input, single-output (SISO) system model based on input and output impedance of each subsystem. The method can also be applied to more complex systems such as large wind and PV farms based on aggregation. This paper proposes a multiple-input, multiple-output (MIMO) system model to extend the method to networked converter systems. Development of system models in such form is explained in detail by using a generic multi-converter system involving renewable energy generation and high-voltage dc transmission. Characteristics of the resulting MIMO system models are discussed and methods to assess its stability using frequency-domain techniques are presented. A case study is also presented using an example system consisting of three large wind farms. The small-signal analysis is validated by detailed electromagnetic transient (EMT) simulation.