A Novel DQ Impedance Measurement Method in Three-Phase Balanced Systems

The stability of electronic power systems is essential to the safety and reliability of the system designs. Optimum stability analysis and measurement techniques are being discussed more frequently in the literature. One approach of assessing system stability is the Generalized Nyquist Criterion (GNC), which is based on d-q frame impedances. An impedance measurement unit (IMU) can be used to acquire d-q frame impedances for a three-phase balanced system. A novel d-q frame impedance measurement method, namely the single-phase impedance measurement approach, is applied to a three-phase balanced passive circuit and a voltage source inverter (VSI) separately. In this approach only single-phase data are needed. A comparison of measured results proves the capability of the single-phase impedance measurement method to obtain three-phase d-q frame impedances. In the passive circuit, both measurement methods only demand single-phase perturbation. In the converter circuit, the three-phase impedance measurement method still only needs a single-phase perturbation while the single-phase impedance measurement method requires three separate balanced single-phase perturbations.