Ana Llor

Implementation of Hybrid Control for Motor Drives

This paper presents the implementation of a hybrid-control strategy applied to a permanent-magnet synchronous-motor (PMSM) drive. Hybrid control is a general approach for control of a switching-based hybrid system (HS). This class of HS includes a continuous process controlled by a discrete controller with a finite number of states. In the case of ac motor drives, in contrast to conventional vector control like proportional-integral control or predictive control, where the inverter is not taken into account by the controller, hybrid control integrates the inverter model and considers the state of the inverter as a control variable. It allows to obtain faster torque dynamics than vector-control algorithms. The hybrid control algorithm requires both computing velocity for real-time implementation and code flexibility for management of low-performance functions and analog-digital interfaces. Codesign appears as a promising methodology for partitioning hybrid-control algorithm between software (flexible) and hardware (velocity) while taking care of overall time constrains. In this paper, the implementation of hybrid-control algorithm for a PMSM drive is performed through a codesign approach on an Excalibur board, embedding a CPU-core (Nios-2 by Altera) inside an APEX20KE200EFC484-2X field-programmable gate array. The partitioning of software and hardware parts is explained. Experimental results show the effectiveness of the implementation. Performances, advantages, and limitations are discussed.

A new approach to Predictive Torque Control with Dual Parallel PMSM system

An original approach to Predictive Torque Control “Split and Seek” (PTC SS) for Mono-Inverter Dual-Parallel Permanent Magnet Synchronous Machines (PMSM) system is presented. Only one cost function for both PMSM is defined to be minimized through the PTC approach. Unlike the Master-Slave classical control, solution of the cost function will depend on both PMSM references. The principle of this approach is to extend the possibilities of control by offering additional virtual vectors and to find the vector which minimizes the cost function. This process includes two steps: first one is searching for the angle and second one is searching for the magnitude. A model of the system is used to predict the behavior in the next sampling interval under these different virtual voltage vectors. After that, space vector modulation (SVM) technique will be applied to synthesize this vector. Simulations were built under Matlab/Simulink software to verify the applicability of this new approach. The obtained results verify the synchronism of two machines and the correct current tracking under different load and speed conditions. The performance improvement is highlighted from specific tests.

Hybrid direct power control using p-q-r power theory applied on 3-phase 4-wire active power filter

An hybrid control approach of the p-q-r power theory applied to a 3 phase 4 wire active power filter is proposed. The mathematical model developed is based on the direct power control theory. This technique inherits not only the simplicity of the conventional direct power control but also offers a good dynamic response in active filtering. The analysis is verified using the PSIM simulation software.

Predictive Torque Control - A solution for mono inverter-dual parallel PMSM system

The objective of this paper is to present a Predictive Torque Control (PTC) algorithm for controlling system composed by two Permanent Magnet Synchronous Motors (PMSM) operating in parallel, fed by a single power inverter. In this system, it is expected that both motors will get the same speed even if they have different conditions of load torque. The principle of PTC algorithm is considered as follows: a model of the system is used to predict the system behavior under a set of configurations of a power inverter, a cost function is built from the predicted values and their references and an optimal algorithm will be solved to find the best configuration to apply to the system in the next time step. Simulation results in Matlab/Simulink indicated that the algorithm (PTC) is well adapted for the synchronism of this system over a wide range of operations.

An Active Power Filter Using a Sensorless Muticell Inverter

Unlike traditional inverters, multicell inverters have the following advantages: lower switching frequency, high number of output levels and less voltage constraints on the IGBTs. Significant performances are provided with this structure which is constituted with flying capacitors. This paper deals with a predictive and direct control applied to the multicell inverter. To perform the capabilities of multicell active filter, a voltage control method of flying capacitor, based on the use of a switching table, is added. Flying capacitor voltages are kept on a fixed interval and precise voltage sensors are not necessary. The association of predictive control and voltage balancing increases considerably the bandwidth of active filter.

Geometrical approach of current predictive control for four-leg converters

Four-leg converters are used in several applications that require neutral wire (distributed generation systems, APF). To act on converter switches, three-dimensional space vector pulse width modulation (3-DSVPWM) is usually used. This modulation generates pulses according to the reference voltages issued from a controller. In this paper, a current predictive controller is proposed for 4-leg voltage-source converter. The proposed controller generates control signals without voltage reference calculation. To do this task, geometrical properties of the predicted-current projections are used.

Comparison of direct power control with hybrid approach on 3-Phase 4-wire active power filter between p-q-0 and p-q-r power theory

New hybrid control approach of the pq control theory applied to the 3 phase 4 wire active power filter is proposed. This technique inherits not only the simplicity of the conventional direct power control but also offers a good dynamic response in active filtering. In this paper, the proposed control method is implemented for two different instantaneous power theories, i.e. p-q-0 and p-q-r power theory. The comparison between them is oriented around the harmonic contain of the source current for each method and the unbalanced current index. The analysis is verified using the PSIM simulation software.

Different solutions of predictive control for two synchronous machines in parallel

The parallel operation of two synchronous machines connected to the same inverter requires taking into account information from both electrical machines to, on the one hand, ensure the stability of the whole system, and secondly to control energy efficiency. The classical approach is based on a master-slave procedure, where the master machine will be piloted while the second is simply connected in parallel. For the master machine it is then possible to determine the best control configuration of the inverter in order to minimize a criterion related to the current error. In this paper we propose three alternatives of predictive control, based on an evaluation of a global criterion taking into account sequentially or simultaneously the operating point of each machine. The control laws are then compared in terms of performances and losses. A fourth control law is proposed considering a single criterion applied to both machines at the same time. This last control law considers a large number of virtual control vectors whose enforcement is carried out through a modulation technique, such as SV-PWM. Digital simulation results obtained via Matlab-Simulink are showed for a low power application (800 W).

Control strategy with variable commutation instants for MPC based on two flying capacitors connected in parallel

In this work we propose a control strategy based on Model Predictive Control (MPC) with variable commutation instants at constant frequency. Two stages are used by association of a reduced cost function and a state machine which selects the optimum state. The strategy is applied to flying capacitor converters connected in parallel, which requires the development of strategies capable to control the external and internal variables of the converter.

Direct Model-Predictive Control With Variable Commutation Instant: Application to a Parallel Multicell Converter

This paper presents a new formulation of a finite control set model-predictive control (FCS-MPC) algorithm, allowing to determine the best commutation instant in order to optimize the converter current tracking. This algorithm, mixing properties of FCS-MPC method and time resolution related to pulse width modulation schemes, is illustrated in a parallel flying capacitor converter. The parallel association of classical commutation cells is a good solution for increasing the output current driven by the converters, while the standard semiconductor technology is used. The control strategy used with this type of connection must be able to ensure not only a good distribution of the output current among the different legs, but also the balancing of the floating capacitor voltages.