Maximum Torque per Ampere (MTPA) Control for IPMSM Drives Using Signal Injection and an MTPA Control Law

This paper presents a maximum torque per ampere (MTPA) control scheme for interior permanent magnet synchronous motor drives. In this scheme, an enhanced signal injection technique is responsible for correcting the MTPA reference deviation due to motor parameter variations, and a derived MTPA control law is responsible for generating constant-parameter model-based MTPA current references to enhance the dynamic performance of the MTPA operation. Unlike previous signal injection techniques, the enhanced injection technique directly injects signals into the d- and q-axis currents and extracts the MTPA indicator from the reconstructed dc-link current. Hence, this enhanced injection technique avoids any transformations associated with polar coordinates, and it does not depend on a dc-link voltage sensor or a high-resolution speed sensor. The derived MTPA control law, unlike conventional MTPA control laws, can be realized in real time without mathematical approximations or lookup tables. With the combination of the enhanced signal injection technique and the derived MTPA control law, the proposed MTPA scheme can achieve an accurate and fast MTPA operation. Simulation and experimental results confirm the validity of the proposed MTPA scheme.