Synchronous-frame proportional-integral (PI) current control is the most popular solution in industrial permanent-magnet synchronous motor (PMSM) drive systems. However, due to the nonlinearities from large parameter uncertainties and complex operating conditions, it is challenging to select the parameters of the PI controller with satisfactory performance by trial-and-error. To this end, this paper presents an uncertainty-and-disturbance-estimator-based current control scheme for PMSM drives, which has a simple structure and is robust to machine parameter perturbations. Meanwhile, it is interesting that the controller parameters (proportional and integral gains) are simply expressed in the desired closed-loop bandwidth and the approximate lumped disturbance bandwidth. A simple dual-loop tuning algorithm is also proposed to select the appropriate controller parameters, and trial-and-error can be largely avoided. Finally, the efficacy of the proposed control method is fully supported by comparative experimental validation with the synchronous-frame PI control on a dSPACE DS1103-based PMSM drive prototype.

This paper proposes a proportional-integral (inertial) multiresonant (PIMR) type repetitive control (PIMR-type RC) scheme for a grid-tied inverter. The proposed control scheme is composed of a repetitive controller in parallel with a proportional gain for the purpose of replacing lots of parameters of the conventional proportional multiresonant controller, and therefore, only a few parameters need to be designed. The proportional gain not only improves the dynamic response, but also enables repetitive controller (RC) to accommodate a larger RC gain, and hence a faster convergence rate. Theoretical analysis and stability analysis of PIMR-type RC are given, and then a practical step-by-step design tutorial is also provided. The experimental results validate the feasibility and outstanding performance of the proposed control scheme.

Repetitive control (RC) can offer a promising accurate voltage control scheme for constant-voltage constant-frequency (CVCF) pulse width modulation (PWM) inverters to compensate the harmonic distortion caused by nonlinear loads. However, limited by digital sampling, conventional RC with integer phase lead compensation cannot exactly compensate the system phase lag, which may result in instability in the case of low sampling frequency. In this paper, a fractional phase lead compensation RC (FPLC-RC) scheme is proposed to enable the phase lead step to be fractional, which can enlarge the stability region and improve the tracking accuracy. A newly devised finite-impulse response fractional lead filter based on Lagrange interpolation is applied to approximate the fractional lead items. Meanwhile, the synthesis and analysis of fractional phase lead RC for a single PWM inverter are given. Furthermore, simulations and experiments are provided to demonstrate the validity of the proposed FPLC-RC scheme.

Phase lead compensation precision dramatically affects the performance of a repetitive controller (RC). Integer order phase lead compensation of proportional integral multiresonant type RC (PIMR-RC) with low sampling frequency cannot meet the need of fine phase compensation. In addition, the digital control delay affects the actual modeling of the system, and then influences the precision phase compensation. To finely compensate the phase lag of the PIMR-RC system, this article proposes a fine fractional order phase lead compensation PIMR-RC scheme based on a novel phase lead infinite impulse response (IIR) filter. Its comprehensive synthesis is systematically detailed, including actual modeling considering 1.5-period digital control delay, IIR fractional lead filter design, stability analysis, and parameter optimization. Finally, experiments on a 2 kW prototype grid-tied inverter are successfully carried out to verify the solution.

Repetitive controller (RC) and multiple quasi-resonant controllers (MQ-RSC), both based on internal model principle, are widely used in ac voltage/current control of single-phase inverters due to their high tracking accuracy for sinusoid reference and superior harmonics suppression capabilities. However, both controllers have their respective strengths and weaknesses regarding parameter design complexity, convergence rate, or stability margin. In this paper, the mathematical equivalence between various types of RCs and MQ-RSC are established comprehensively, which offers a new perspective for analyzing and designing these two types of controllers. The equivalent relations reveal the connection between the internal model coefficients of RCs and the equivalent resonant bandwidths of MQ-RSC. Based on this equivalent relations, a novel design way of RCs is proposed to enhance the frequency robustness. Furthermore, a new MQ-RSC design method is also put forward to simplify the design process. Experimental results on a 1.5-kW single-phase grid-tied inverter validate the accuracy of the equivalence relations and showcase their valuable roles in the design of RC and MQ-RSC.