Flux Observer-Based MTPF/MTPV-Operation With Low Parameter Sensitivity Applying Deadbeat-Direct Torque and Flux Control

Abstract

Through a combination of flux and current observers, deadbeat-direct torque and flux control for interior permanent magnet synchronous machines has preferred features comparing to the existing current vector control (CVC). These include simpler flux weakening control, less parameter sensitivity with increasing speed due to the Gopinath-style flux observer and evading of anti-windup strategies at the inverter voltage limit. The operation throughout the entire torque-speed range can be accomplished with a single control law. For the second flux weakening region, the algorithm inherently achieves the maximum torque per flux (MTPF) operation by applying the square-root-condition (SRC). In contrast to CVC, no look-up-table nor solving the parameter-dependent MTPF equation is required. In this article, the equivalence of the SRC method to the conventional MTPF strategy is demonstrated analytically, graphically, in simulation, and through experimental results without any stability problems. A sensitivity analysis regarding the machine parameters and iron losses compares and evaluates both methods. Superior performance of the SRC algorithm compared to the conventional method is proven.