State-Space Modeling of Grid-Connected Power Converters Considering Power-Internal Voltage Characteristics

To analyze the stability of power electronics-dominated systems, this paper develops a state-space model of power converters including the DC-link voltage control, where the power-internal voltage (PIV) characteristics of the power converters are considered. The PIV concept comes from the inertia characteristic and swing equation of synchronous generators. It reflects the relationship between the output power and converter internal voltage, the converter response to grid disturbances, and finally, the impact of power converters on the grid stability. In the proposed model, the inputs are the outer controller references and the converter output power, i.e., the power at the point of common coupling (PCC). The output of the model is the internal voltage that determines the grid power distribution, including the power at the PCC. The power will be fed back to the converters as an input, and thinks the closed-loop model of the converter-based system is obtained. Importantly, the parameters of the proposed model are independent of the power grid, but related to the converter operation points and parameters. This makes the model more general and can be employed to analyze multiple converter-based systems. Furthermore, a case study is conducted in this paper to demonstrate the model and the stability analysis.