[Show abstract][Hide abstract]ABSTRACT: A digital current and voltage predictive controller (CVP) is proposed for high switching frequency, low power SMPS. The predictions of the inductor current and capacitor output voltage are performed simultaneously by adopting a flexible PWM pattern that enables dynamic adjustment of the time of the voltage events. The CVP controller preserves the merits of predictive current-mode control and allows to further improve the dynamic performances. With the knowledge of the inductor current, the performances of the CVP controller are analyzed compared to a deadbeat controller. Experimental results of a current sensorless implementation verify better closed-loop performances than those of PID, RST and sliding-mode controllers. The lab-scale prototype implemented in an FPGA supports a switching frequency up to 4 MHz only limited by the discrete buck converter.
[Show abstract][Hide abstract]ABSTRACT: This paper presents a comparative study of three predictive current control schemes for permanent-magnet synchronous machine (PMSM) drives. The first control scheme predicts the future evolution of the currents for each possible configuration of the inverter legs. Then, the switching state which minimizes a given cost function is selected and applied during the next sampling time. The second control scheme uses a modulator to apply two configurations of the inverter legs during a computation period. Among these configurations, one leads to null voltages. The duration of the other configuration is calculated in order to minimize the distance between the obtained state vector and the desired one. The third control scheme uses a model of the PMSM in order to predict the stator voltages which allows us to reach the desired currents after one modulation period. An algebraic method is presented to compute the duty cycle of each leg of the inverter in a direct manner. These control schemes are detailed and tested using the same switching frequency on the same test bench (1.6-kW PMSM drive). A simulation study is performed in order to compare sensitivity to parameters of each control scheme. Experiments confirm the simulation results.
Full-text · Article · Aug 2009 · IEEE Transactions on Industrial Electronics
[Show abstract][Hide abstract]ABSTRACT: Distribution analysis of network traffic is the basis issue in numerous networked applications. A synthetic method for the analysis of network traffic distribution is proposed in this paper. At first, the sampled network traffic data are processed with time scale. Secondly, semi-Markov model is introduced to describe the characteristic of the network traffic. Busy threshold and idle threshold are set to differentiate the network traffic as three states: busy, middle and idle. The characteristic of the network traffic and the conversion relationship between different states are studied. Thirdly, the model library of parameter and non-parameter estimations is established. At last, distribution fittings are done. The method is suitable for the analysis of the network traffic using all protocols and is more rational than using a specific distribution. Experiment results show the correctness and validity of the method.
[Show abstract][Hide abstract]ABSTRACT: This paper presents a predictive current control (PCC) strategy applied to an induction motor (IM) drive. In contrast to conventional vector control, where the inverter is not taken into account by the controller, the PCC considers the state of the inverter as a discrete control variable. Based on a simplified state space model of the IM and the inverter, the proposed control scheme calculates the state vector evolution direction in the d- and q-reference frame for all possible switching states of the inverter. The switching state which minimizes a given cost function is selected and is applied during an adapted duration which is calculated for each computation cycle. As the control requires the knowledge of the instantaneous rotor fluxes and in order to improve the control robustness, a reduced-order extended high gain observer is proposed for estimation of rotor fluxes and inverse rotor time constant. The simulation results validate the observer. The controller is implemented on a 5.5 kW IM drive with a digital-signal-processor (DSP) on a DSpace1103 board. Experimental results show the effectiveness and the performances of the proposed control.
[Show abstract][Hide abstract]ABSTRACT: This paper presents a control scheme for a multilevel multi-cell converter. For this type of converters, load current and capacitor voltages must be jointly controlled. Moreover the real-time constraint is important. This constraint leads us to propose a control based on a simplified state-space model. The model allows predicting the state vector evolution for every converter configuration. The control algorithm directly determines the converter switching state which minimizes a simple cost function. A normalization of the state variables is proposed for the cost function calculation in order to ensure a trade-off between the tracking of the load current and the tracking of the capacitor voltages. The proposed control scheme is detailed and compared with a classical control scheme with simulations. Finally, experimental results are presented to show the effectiveness of the proposed method.
[Show abstract][Hide abstract]ABSTRACT: This paper presents the experimental results-based comparison of two predictive current controls (PCC) for permanent magnet synchronous machines (PMSM) drives. The first tested control scheme is based on a model including the inverter and the PMSM and taking into account the discrete nature of the inverter leg states. It predicts the future evolution of the currents for each possible configuration of the inverter. The switching state which minimizes a given cost function is selected. The selected inverter state is applied during the next sampling time. The second tested control scheme uses a model of the PMSM to predict the output voltages which allow to reach desired currents after one modulation period. A new algebraic method is presented to directly compute the duty cycle of each leg. Then a modulator generates the corresponding gate drive pulses of the inverter. These two control schemes are tested with a 1.6 kW PMSM drive at several operating points during steady state and transient operation. A detailed comparison of results is given. Advantages and drawbacks of each method are discussed.
[Show abstract][Hide abstract]ABSTRACT: Many research efforts have been dedicated to matrix converters for several years. As major technological issues are now solved, this structure will widespread in industrial applications, in particular with AC motors. Current control is a key issue for AC motor drives, so many control schemes have been proposed. Some of them proposed at first for inverters, were applied to matrix converters. Among algorithms used with inverters, predictive control shows very good performances. In this paper a new control scheme is proposed for a matrix converter- fed permanent magnet synchronous machine. Literature about matrix converter technology and control and about predictive control for inverter-fed AC machines is reviewed. The proposed predictive control principle, the model of the whole machine - converter and the cost-function are detailed. The method offers a trade-off between the quality of motor currents and input power factor. Finally experimental results are reported. The feasibility and the effectiveness of the proposed method is assessed.
[Show abstract][Hide abstract]ABSTRACT: This paper presents a control scheme suitable for systems composed of a continuous process modulated in energy by a power converter with a finite number of topologies. To track the continuous reference values, a topology of the power converter is determined from a criterion based on a process state variable model and taking into account the possible topologies of the power converter. The proposed hybrid control scheme is applied to an electrical motor drive composed of an inverter coupled to a permanent magnet synchronous machine. An evolution which insures a fixed modulation frequency is also proposed. Experimental results validate the feasibility and effectiveness of the proposed schemes.
Preview · Article · Mar 2008 · IEEE Transactions on Industrial Electronics
[Show abstract][Hide abstract]ABSTRACT: In this paper, fixed-frequency direct torque control (DTC) of a permanent magnet synchronous motor (PMSM) is presented. In this method, the stator voltage vector is generated according to the increase stator flux components in the stationary frame ( alpha,beta ). A control algorithm based on predictive control to reduce the effect of the computing time on the stator flux vector position is also presented. The implementation of this method in the case of a PMSM, which is done without hysteresis regulators, is simple and does not require any filter. Simulation and experimental results show that the proposed method reduces the torque ripple while achieving a good dynamic response.
No preview · Article · Feb 2008 · Canadian Journal of Electrical and Computer Engineering
[Show abstract][Hide abstract]ABSTRACT: 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.
[Show abstract][Hide abstract]ABSTRACT: Analogue control of monolithic DC/DC converters is technologically coming to a limit due to high switching frequency and a request for large regulation bandwidth. Digital control is now experimented for low-power low-voltage switch-mode power supply. Digital implementation of analogue solutions does not prove real performances. This paper compares a classical digital controller to a candidate alternative strategy. Sensitivity functions are used to compare controller performances. An off-line approach using fuzzy logic to quantify controller performances and a genetic algorithm to obtain an optimal controller is presented. A so-called RST algorithm optimized with this approach shows better performances.
[Show abstract][Hide abstract]ABSTRACT: Analogue control of monolithic DC/DC converters is coming to a limit due to high switching frequency and a request for large regulation bandwidth. Digital control is now experimented for low-power low-voltage switch-mode power supply. Digital implementation of analogue solutions does not prove real performances. Other digital controllers have been experimented but applied to discrete converters. This paper compares a classical digital controller to a possible alternative strategy. Sensitivity functions are used to compare controller performances. RST algorithm determined by robust pole assignment shows better performances
[Show abstract][Hide abstract]ABSTRACT: In this paper, we present a novel control strategy for motor drivers, which we have called fixed switching frequency hybrid control (FSPHC). Based on models of both motor and inverter, the hybrid control uses a formal representation of the inverter-machine group behaviour. For one constant period modulation, switching states and different vector application times are determined. This control scheme is applied to a permanent magnet synchronous motor and satisfactory experimental results are showed.
[Show abstract][Hide abstract]ABSTRACT: This paper presents a new method of control applied in electropneumatic field. This strategy is issued from hybrid control theory recently applied in control of asynchronous or synchronous electrical motor (1, 2). The interest of these procedure concerns the possibility of controls the position of an electropneumatic piston all along the cylinder stroke with standard on/off valve. Nowadays the industrial electropneumatic process used on/off valve for point to point aim with displacement from one extremity of cylinder to the other one. When different desired positions are required the constructors used specific components issued from proportional technology: servovalve or servodistributor for example. The evolution in the automation process is moving towards a need of obtaining greater versatility and increased precision in compressed air driven equipment. This means obtaining proportional operation of the power element as a function of an electric control signal. Nevertheless, when the desired precision is near the millimetre and not very good performances are need during dynamic stage, the useful of proportional technology can be debatable. Indeed the system cost and its complexity to tune can be two drawbacks that on/off technology with the proposed algorithm, can be concurrence. Based on both the models of cylinder and valves, the hybrid control presented here determines the best state of valves by tracking reference values of the cylinder states in the state space. Then a simplified model of electropneumatic system is presented and used to synthesised hybrid control algorithm. Experimental results are presented and discussed.
[Show abstract][Hide abstract]ABSTRACT: This paper presents a new and simple approach for sensorless speed control of asynchronous machine. It shows a self-contained electronic module which determines the speed of the machine with only two phase current measurements. Thus, the speed calculation is independent on the machine parameters and on control laws; this allows to design the control by considering the speed as an input. The principle of the method is based on rotor slot harmonics without high frequency injection. In fact, the rotor slot harmonics depend on rotor speed. These signals appear in the stator's spectrum with very low amplitude, in particular for a motor with skewed rotor slots. Moreover, the harmonics move with stator frequency. An analog adaptive band pass filter follows and amplifies this harmonics. As the response time is high at low speed, a digital algorithm is included in the microcontroller in order to decrease the response time. The proposed indirect speed sensor requires only some classical analog components and a low cost microcontroller. A short time calibration is necessary for the first start time of the inverter and the motor. Experimental results on a testing bench with different speed benchmarks are presented.
[Show abstract][Hide abstract]ABSTRACT: In this paper, we present a novel control strategy for motor drivers, which we have called 'hybrid direct-torque control'. Based on models of both motor and inverters, the hybrid control uses a formal representation of inverter-machine behavior to determine the optimal switching state and vector application time. In contrast to conventional direct-torque control, which is based on the presence of hysteresis controllers and a switching table, the hybrid control involves tracking reference values of the electrical state in the state space. Observers and estimators of torque and flux are unnecessary. This control scheme is applied to a winding rotor synchronous motor.
[Show abstract][Hide abstract]ABSTRACT: Direct-torque-control (DTC) is nowadays a classical technique for variable speed control of induction machines. Many implementations have been presented in literature DTC algorithm requires velocity for some parts and flexibility for other parts. Digital-signal-processors (DSP) have been used for flexibility, but field-programmable-gate-arrays (FPGA) have been preferred for velocity. Using one device (DSP or FPGA) for DTC implementation has been reported as not optimal. Codesign appears as a promising methodology for partitioning the DTC algorithm between flexible and fast parts. Codesign requires user-specifications to help the partitioning with regard to the awaited control performances. Authors discuss two experimental implementations at extremities of the codesign space, i.e. full-software or full-hardware implementation. For each implementation, the DTC algorithm requires adaptations. Authors detail each development, and full-codes are available on a dedicated web-site. Validation results are presented for both implementations. Performances, advantages, and limitations of both implementations are compared. The necessary specifications for codesign development may then be identified.
[Show abstract][Hide abstract]ABSTRACT: Hard switching DC/DC converters have been studied for decades. Many control techniques have been reported, and textbooks detail so-called classical control design methods. The buck converter is known as a simple topology of satisfying stability. However the monolithic integration of a buck converter including the control system leads to a possible non-stable converter in case of large load transient. More generally it is difficult to certify the accuracy of the control system. Integrated switch-mode power supplies needs to be investigated focusing control design issues. Global efficiency dictates to limit the budgets in biasing current of control loops, hence limits their bandwidth. Among others, this latter limitation renders the classical control design methods non satisfying. The paper investigates the control design challenge related to integration of switch-mode power supplies (SMPSs). Applications are discussed from simulation point-of-view. Particularly a trade-off must be set between control accuracy and performances on load transients. As it is not possible to specify the worst-case load transient, classical control design methods do not offer satisfying results. Alternative control design methods are investigated. Sensitivity transfer functions are introduced and an application method is detailed. Hybrid system methods are also investigated and their application is discussed. The design of integrated SMPSs requires adequate modifications of CAE-tools and design flows.
[Show abstract][Hide abstract]ABSTRACT: A direct stator flux linkage control for permanent magnet synchronous motor is presented. Contrary to conventional direct torque control (DTC), the proposed control, which works with fixed switching frequency, can reduce torque ripple and current distortion. The implementation in a test bench shows the effectiveness of this control.