Assessment of synchronous-frame PI current control dynamics by means of multivariable analysis with time-delays consideration

Current control performance is key in some ac power conversion applications, such as renewable energies and motor drives. This paper presents a method for accurate assessment of dq-PI current controllers dynamics. The proposed methodology is based on linear control for multivariable systems. First, the plant and controller matrices are modeled including time-delays and cross-coupling effects. Subsequently, the closed-loop characteristic polynomial is obtained from the sensitivity matrices. Then, a computer-aided process to calculate the system closed-loop poles (eigenvalues of the characteristic polynomial as a function of the control gains) is applied. From some specific constraints (e.g., desired time responses), the optimum tuning is available by inspection of the closed-loop root-loci. Different tests have been performed in a 6 kVA lab-prototype. The experimental results prove the validity and accuracy of the analysis.