Effective Torque Ripple Reduction of Permanent Magnet Brushless DC Motor

To reduce commutation torque ripple, a model predictive control (MPC) for permanent brushless DC motors (BLDCM) is presented (CTR). Torque ripples cause vibration noise and decrease efficiency. The suggested MPC system is constructed by forecasting the phase current with the aim of minimizing the BLDCM\u27s CTR and taking into consideration the CTR sources. The method presented in this paper is a unique methodology for suppressing CTR over the whole speed range, avoids more complex current controllers or modulation models, and overcomes the challenges of commutated-phase-current control. The ideal switching state is instantly selected and implemented during the next sample period according to the preset cost function in order to match the slope rates of outgoing and incoming phase currents during commutation, ensuring the minimum of commutation torque ripple. The modelling and experiment findings show that the suggested method can effectively reduce CTR over a wide speed range and achieve the better CTR minimization performance. The results are then compared to the outcomes of various torque ripple reduction(TRR) techniques

Symmetrical six-phase induction machines: a solution for multiphase direct control strategies

Six-phase induction machines are considered an interesting multiphase option because they can benefit from the well-known three-phase converter technology. These multiphase machines can be classified according to the spatial distribution of their windings into two main groups: asymmetrical and symmetrical six-phase machines. In the case of symmetrical sixphase machines, some sets of voltage vectors show an important advantage from the point of view of the - current mitigation. They provide an active production in the - plane with a completely null injection of - components. This fact is a desired feature for direct control strategies, such as standard model predictive control (MPC), where a single switching state is applied during the entire sampling period. Based on these statements, this work proposes an MPC strategy for symmetrical six-phase induction machines using voltage vectors with null - voltage production in order to obtain the flux/torque generation with minimum - currents. Simulated results have been included to validate the goodness of the developed control scheme.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Open-Phase Fault Operation of 5-Phase Induction Motor Drives using DTC Techniques

Direct torque control (DTC) is extensively used in conventional three-phase drives as an alternative to field-oriented control methods. The standard DTC technique was originally designed to regulate two independent variables using hysteresis controllers. Recent works have extended the procedure for five-phase drives in healthy operation accounting for the additional degrees of freedom. Although one of the main advantages of multiphase machines is the ability to continue the operation in faulty conditions, the utility of DTC after the appearance of a fault has not been covered in the literature yet. This paper analyses the operation of a five-phase induction motor drive in faulty situation using a DTC controller. An open-phase fault condition is considered, and simulation results are provided to study the performance of the drive, comparing with the behavior during healthy state

Open-Phase Fault Operation of 5-Phase Induction Motor Drives using DTC Techniques

Direct torque control (DTC) is extensively used in conventional three-phase drives as an alternative to field-oriented control methods. The standard DTC technique was originally designed to regulate two independent variables using hysteresis controllers. Recent works have extended the procedure for five-phase drives in healthy operation accounting for the additional degrees of freedom. Although one of the main advantages of multiphase machines is the ability to continue the operation in faulty conditions, the utility of DTC after the appearance of a fault has not been covered in the literature yet. This paper analyses the operation of a five-phase induction motor drive in faulty situation using a DTC controller. An open-phase fault condition is considered, and simulation results are provided to study the performance of the drive, comparing with the behavior during healthy state

Model predictive control of six-phase induction motor drives using virtual voltage vectors

The most serious and recent competitor to the standard field oriented control for induction motors (IM) is the finite control set model predictive control (FCS-MPC). Nevertheless, the extension to multiphase drives faces the impossibility to simultaneously regulate the flux/torque and the secondary current components (typically termed x − y in the literature). The application of a single switching state during the whole sampling period inevitably implies the appearance of x − y voltage/currents that increase the system losses and deteriorate the power quality. These circulating currents become intolerably high as per the unit x − y impedance and the switching frequency diminish. Aiming to overcome this limitation, this work suggests the integration of virtual voltage vectors (VVs) into the FCS-MPC structure. The VVs ensure null x − y voltages on average during the sampling period and the MPC approach selects the most suitable VV to fulfill the flux/torque requirements. The experimental results for a six-phase case study compare the standard FCS-MPC with the suggested method, confirming that the VV-based MPC maintains the flux/torque regulation and successfully improves the power quality and efficiency

Model Predictive Control based on Dynamic Voltage Vectors for Six-phase Induction Machines

Model predictive control (MPC) has been recently suggested as an interesting alternative for the regulation of multiphase electric drives because it easily exploits the inherent advantages of multiphase machines. However, the standard MPC applies a single switching state during the whole sampling period, inevitably leading to an undesired x y voltage production. Consequently, its performance can be highly degraded when the stator leakage inductance is low. This shortcoming has been, however, mitigated in recent work with the implementation of virtual/synthetic voltage vectors (VVs) in MPC strategies. Their implementation reduces the phase current harmonic distortion since the average x y voltage production becomes null. Nevertheless, VVs have a static nature because they are generally estimated offline, and this implies that the flux/torque regulation is suboptimal. Moreover, these static VVs also present some limitations from the point of view of the dc-link voltage exploitation. Based on these previous limitations, this article proposes the implementation of dynamic virtual voltage vectors (DVVs), where VVs are created online within the MPC strategy. This new concept provides an online optimization of the output voltage production depending on the operating point, resulting in an enhanced flux/torque regulation and a better use of the dc-link voltage. Experimental results have been employed to assess the goodness of the proposed MPC based on DVVs.Ministerio de Ciencia, Innovación y Universidades RTI2018-096151-B-100

Constrained Model Predictive Control in Nine-phase Induction Motor Drives

The advent of powerful digital signal processors (DSPs) has recently permitted the real-time implementation of model predictive control (MPC) in high-performance electric drives. Nevertheless, the use of MPC together with multiphase systems is increasingly challenging as the number of phases gets higher. On the positive side, the redundancy provided by the extra phases also opens the possibility to further optimize the control action. This work describes the implementation of MPC for nine-phase drives using a three-step approach with an initial discarding of the switching states, a dynamic selection of the voltage vectors using hard constraints (HCs), and an improved performance including soft constraints (SCs). Experimental results confirm the ability of the proposed MPC to highly reduce the computational burden and switching frequency, while maintaining satisfactory steady-state and dynamic performance

FCS-MPC-Based Current Control of a Five-Phase Induction Motor and its Comparison with PI-PWM Control

This paper presents an investigation of the finite-control-set model predictive control (FCS-MPC) of a five-phase induction motor drive. Specifically, performance with regard to different selections of inverter switching states is investigated. The motor is operated under rotor flux orientation, and both flux/torque producing (d-q) and nonflux/torque producing (x-y) currents are included into the quadratic cost function. The performance is evaluated on the basis of the primary plane, secondary plane, and phase (average) current ripples, across the full inverter's linear operating region under constant flux-torque operation. A secondary plane current ripple weighting factor is added in the cost function, and its impact on all the studied schemes is evaluated. Guidelines for the best switching state set and weighting factor selections are thus established. All the considerations are accompanied with both simulation and experimental results, which are further compared with the steady-state and transient performance of a proportional-integral pulsewidth modulation (PI-PWM)-based current control scheme. While a better transient performance is obtained with FCS-MPC, steady-state performance is always superior with PI-PWM control. It is argued that this is inevitable in multiphase drives in general, due to the existence of nonflux/torque producing current components. © 1982-2012 IEEE

Continuous-control-set Model Predictive Current Control of Asymmetrical Six-phase Drives Considering System Non-idealities

Finite-control-set model predictive control (FCS-MPC) of multiphase (n-phase, n is assumed to be an odd number for simplicity) drives is challenging because of the large number of actual/virtual voltage vectors and the need for current control in (n-1)/2 sub-spaces (or planes; multi-plane current control). Any sub-optimal design (poor or no current control in some of the (n-1)/2 planes) may result in high individual plane current ripples, due to the low reactance. This work therefore investigates continuouscontrol-set (CCS) MPC for constant switching frequency multiphase motor drives as another alternative. The highbandwidth CCS-MPC is designed to accurately account for system non-idealities, namely digital control and pulse width modulation delays, inverter dead time, and measurement noise. It will be shown that the CCS-MPC has the advantages of full voltage vector space access, regular switching characteristic, and improved cycle-by-cycle tracking control, while maintaining some of the known advantages of the FCS-MPC, e.g., intuitive cost function design, model-based control, and fast dynamics. The proposed control scheme is benchmarked experimentally against the classical, proportional-integral-based, fieldoriented control in conjunction with an asymmetrical sixphase induction motor drive