Optimal robust controller design of a high performance vector controlled synchronous permanent magnet motor drive

Summary form only given. A critical evaluation of the cascade decentralized controller now commonly used in high-performance drives has been undertaken. It has been shown that this structure is only useful for drives where (a) the disturbances are significant and nonexciting, i.e. constant, and (b) part of the model has non-minimum-phase characteristics and the portion of the model that has minimum-phase characteristics has much uncertainty associated with it. A controller design methodology that is based on linear quadratic formulation and that accommodates constraints on inverter voltage and currents has been proposed for vector-controlled AC drive. A multivariable-frequency-domain approach using singular value techniques applied to the loop transfer function of the closed-loop system and the bounded norm of possible parameter variations has been used to ensure stability robustness, disturbance rejection, low- and high-frequency modeling errors, and sensitivity reduction over the entire operability region. This has been combined with certain stabilizability conditions of the closed-loop system to obtain the optimal achievable controller performance. A controller design of a vector-controlled permanent-magnet synchronous motor drive driven by a sine-triangle-current-regulated PWM inverter using the proposed methodology has been undertaken and compared with a design based on the cascade and decentralized controller for both unexciting and time-limited-exciting reference and disturbance signals