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Three Phase AC Impedance Tester

Fig. 1. The CPES Three-Phase AC Impedance Tester Used to Characterize High Performance AC Systems: Control System (left), Injection and Sensing Hardware (right).
Advances in power systems and the integration of three phase power electronics based processing and control elements into large scale industrial and vehicle platforms has greatly advanced our capability to manipulate three phase power for numerous applications ranging from personal travel to global security. Such an improvement does not come, however, without a cost. As we have improved the performance and quality of our systems via better load management, we have in turn placed a larger burden on the supply side, leading to new small signal dynamic behavior introduced by our load and source subsystems.

CPES has developed a three-phase impedance tester for the purposes of characterizing these three-phase load and source dynamics by measuring the load and source subsystem impedances. This tester is capable of measuring impedance in the d-q frame identified by its reaction to a set of injected three-phase currents perturbing the system. The system utilizes a PC running Matlab for supervisory control and data acquisition, providing commands to the CPES Universal Controller which controls power injection hardware. The system is comprised of technology ranging from an embedded FPGA based control platforms, digital signal processors with communication support for USB and GPIB, and windows applications implementing data storage and computation. The system presents the results to the user via a customized graphical user interface to abstract from its user the mathematical process used to obtain the impedance from a series of acquired system responses, allowing the user to focus on the end results and their application instead of the mechanics of the procedure.

The CPES Three Phase AC Impedance Tester is a useful utility for three-phase power electronics equipment developers and system integrators to characterize their equipment in order to further understand issues associated with their system's integration capabilities and dynamic performance. Target integration platforms include aircraft electrical systems, shipboard power systems, hospitals, data centers, and other small to medium three-phase power electronics systems at the sub-Megawatt level.
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