Predictive control of an axial flux permanent magnet synchronous machine

This paper examines the (dis)advantages of predictive control for the torque regulation of an axial flux permanent magnet synchronous machine fed by a two-level voltage source inverter. Three different types of predictive controllers are studied: finite-set model based predictive control, deadbeat control and finite-set model based predictive control with duty cycle calculation. A standard PI controller is added to provide a benchmark. The real-life performance of the control algorithms is tested on a 4 kW laboratory drive setup. It is concluded that the PI controller shows superior steady-state behavior, whereas the predictive controllers excel when it comes to dynamic performance

Double Deadbeat Plus Repetitive Control Scheme for Microgrid System

Parallel connection of converters is a convenient choice when system capacity is to be increased. Parallel-connected voltage source converters, especially neutral point clamped converters, are one of the best choices for its range. However, with the parallel connectivity, the converter possesses a circulating current in its legs, which consequently threatens the safe operation of the system. To alleviate this circulating current problem, in this paper, a double deadbeat (DD) plus repetitive control (RC) scheme is proposed. The RC scheme is employed to mitigate the circulating currents and the DD loop control scheme is employed to achieve a high operating bandwidth for voltage and current characteristics. Furthermore, the DD loop is associated with an adaptive controlling technique, which adjusts internally by itself and provides better performance for nonlinear loads. The proposed DD method forces the equivalent system elements to be placed outside the closed loop, which does not affect the system stability. Initially, the system has been executed with a conventional proportional + integral scheme and then with the proposed DD + RC scheme. The proposed method is verified by implementing a Simulink model in the OPAL-RT platform. Furthermore, the proposed method is built with a prototype, and its results are explored

Sensorless finite-control set model predictive control for IPMSM drives

This paper investigates the feasibility of a sensorless field oriented control (FOC) combined with a finite control set model predictive current control (FCS-MPC) for an interior permanent magnet synchronous motor (IPMSM). The use of a FCS-MPC makes the implementation of most of the existing sensorless techniques difficult due to the lack of a modulator. The proposed sensorless algorithm exploits the saliency of the motor and the intrinsic higher current ripple of the FCS-MPC to extract position and speed information using a model-based approach. This method does not require the injection of additional voltage vectors or the periodic interruption of the control algorithm and consequently it has no impact on the performance of the current control. The proposed algorithm has been tested in simulation and validated on an experimental set-up, showing promising results

Performance degradation of surface PMSMs with demagnetization defect under predictive current control

To control the current of a surface mounted permanent magnet synchronous machine fed by a two-level voltage source inverter, a large variety of control algorithms exists. Each of these controllers performs differently concerning dynamic performance and control- and voltage quality, but also concerning sensitivity to demagnetization faults. Therefore, this paper investigates the performance degradation of three advanced predictive controllers under a partial demagnetization fault. The three predictive controllers are: finite-set model based predictive control, deadbeat control, and a combination of both previous algorithms. To achieve this goal, the three predictive controllers are first compared under healthy conditions, and afterwards under a partial demagnetization fault. A PI controller is added to the comparison in order to provide a model-independent benchmark. Key performance indicators, obtained from both simulations and experimental results on a 4 kW axial flux permanent magnet synchronous machine with yokeless and segmented armature topology, are introduced to enable a quantification of the performance degradation of the controllers under a demagnetization fault. A general conclusion is that the deadbeat controller shows superior control quality, even under partial demagnetization

Anti-disturbance sliding mode based deadbeat direct torque control for PMSM speed regulation system

Deadbeat direct torque control (DBDTC) calculates the voltage vector based on the motor mathematical model and tracks the torque and flux reference within only one sampling cycle. However, in the traditional DBDTC, the reference torque is generated by a speed PI controller, which presents a low dynamic and poor precision, particularly under external disturbances. To sort out this issue, this paper proposes an improved DBDTC control method basing on the sliding mode strategy. First, an anti-disturbance sliding mode controller (ASMC) is presented which is superior in offering a fast and accurate reference torque for DBDTC. Along the way, an extended sliding mode disturbance observer is introduced which estimates total disturbances and compensates the sliding mode controller. To reduce the chattering of sliding mode control, a novel reaching law is proposed. This novel reaching law introduces system state variable in the exponential terms of power reaching law, and meanwhile including an adaptive exponential reaching action. By this means, it increases system convergence rate to the sliding mode surface while suppressing sliding mode chattering. Finally, both simulation and experimental results show that the proposed control method has better performance in terms of torque ripple reduction, speed dynamic response

Decoupled Discrete Current Control for AC Drives at Low Sampling-to-Fundamental Frequency Ratios

Implementation of proportional-integral (PI) controllers in synchronous reference frame (SRF) is a well-established current control solution for electric drives. It is a general and effective method in digital control as long as the ratio of Sampling to Fundamental (S2F) frequency ratio, rS2F, remains sufficiently large. When the aforesaid condition is violated, such as operations in high-speed or high-power drives, the performance of the closed-loop system becomes incrementally poor or even unstable. This is due to the cross-coupling of the signal flow between d and q axes, which is introduced by the SRF. In this article, an accurate model of current dynamics which captures the computational delay and PWM characteristics in discrete time domain is developed. This motivates the investigation of eliminating cross-coupling effects in PMSM drive systems. A new current control structure in the discrete time domain is proposed targeting full compensation of cross-coupling effects of SRF whilst improving dynamic stiffness at low S2F ratios. The matching simulation and experimental results carried out on a 5-kW high speed drive corroborate the theoretical analysis