Dead Beat Research Articles

Design and experimental verification of a dead beat power control strategy for low cost three phase PWM converters

As a cost-effective and reliable alternative to standard three phase PWM converters, the low cost converters have attracted great attentions today. While the research trends mainly focused on using these converters for AC motor drives, some successful efforts in grid connected applications are also reported. These works use the voltage oriented technique to regulate the active and reactive power exchanges with the electric grid. This paper presents a dead beat direct power control strategy for grid integration of low cost three phase PWM converters. While keeping the advantages of fast and accurate power control associated to the VOC technique, the proposed strategy offers a considerably simpler algorithm. Extensive simulation and experimental results are provided which confirm the validity of the proposed technique.

Hybrid learning control strategy for three-phase uninterruptible power supply

This study is concerned with the control of three-phase uninterruptible power supply (UPS) systems based on a hybrid controller. A UPS must be able to maintain regulated output voltage in the face of all line/load disturbances. In order to achieve this, the control system of a UPS must have a fast transient response and a low steady-state error. Fast controllers cannot always maintain the required steady-state accuracy. Therefore in this study, a hybrid control solution is proposed. In the proposed method, a fast, yet simple, controller based on deadbeat (DB) control law is used to achieve the fast transient response required for UPS output voltage control. Noting that non-linear loads that tend to distort UPS output voltage in steady-state have periodic waveforms in nature, a type of learning controller known as a repetitive controller is added to the DB controller to improve steady-state performance of the UPS system. This results in distortion-free output voltage along with a fast error convergence. The system modelling and controller design for the proposed structure are presented in this study. A brief stability analysis is given. Both simulations and experimental results are shown for verification of the theoretical analysis.

CONSTANT FREQUENCY DIGITAL HYSTERESIS-BAND CURRENT CONTROLLER FOR A THREE-PHASE VOLTAGE INVERTER

In order to reduce the harmonic content normally generated at the input of AC motor drives as a result of using three-phase voltage-fed inverters (VFI) for supplying electric drives with AC motors, and thus, to improve the input power factor of such machines, hysteresis current control technique is usually used to control the amplitude of three-phase motor currents and to decrease the phase shift between these currents and their corresponding voltages. Hysteresis current technique is considered to have a very simple implementation and an instantaneous current control, resulting in a fast response. However, the switching frequency is not constant and varies over a wide range during each half-cycle of the AC input source, and consequently the load current harmonic ripple is not optimal [J. Salmon & H. Zhang, Power and Energy Systems, 2004; Buso et at., IEEE Transactions on Industrial Applications, 2000]. In this paper, an improved implementation of hysteresis current control of three-phase voltage-source inverter with constant frequency is presented. In order to do that, before developing any inverter prototype, it is very convenient to use one of the several dynamic system software simulators available such as the phase-locked-loop (PLL) with the dead beat current control, even at a high rate of output voltage change, such as required in fast drive systems, and other highly demanding applications. Stability analysis and performance are confirmed through simulation results using Matlab/Simulink and Simplorer 6.

Evaluation of Current Controllers for Distributed Power Generation Systems

This paper discusses the evaluation of different current controllers employed for grid-connected distributed power generation systems having variable input power, such as wind turbines and photovoltaic systems. The focus is mainly set on linear controllers such as proportional-integral, proportional-resonant, and deadbeat (DB) controllers. Additionally, an improved DB controller robust against grid impedance variation is also presented. Since the paper discusses the implementation of these controllers for grid-connected applications, their evaluation is made in three operating conditions. First, in steady-state conditions, the contribution of controllers to the total harmonic distortion of the grid current is pursued. Further on, the behavior of controllers in the case of transient conditions like input power variations and grid voltage faults is also examined. Experimental results in each case are presented in order to evaluate the performance of the controllers.

VEGF-PLCgamma1 pathway controls cardiac contractility in the embryonic heart.

The strength of the heart beat can accommodate in seconds to changes in blood pressure or flow. The mechanism for such homeostatic adaptation is unknown. We sought the cause of poor contractility in the heart of the embryonic zebrafish with the mutation dead beat. We find through cloning that this is due to a mutation in the phospholipase C gamma1 (plcgamma1) gene. In mutant embryos, contractile function can be restored by PLCgamma1 expression directed selectively to cardiac myocytes. In other situations, PLCgamma1 is known to transduce the signal from vascular endothelial growth factor (VEGF), and we show here that abrogation of VEGF also interferes with cardiac contractility. Somewhat unexpectedly, FLT-1 is the responsible VEGF receptor. We show that the same system functions in the rat. Blockage of VEGF-PLCgamma1 signaling decreases calcium transients in rat ventricular cardiomyocytes, whereas VEGF imposes a positive inotropic effect on cardiomyocytes by increasing calcium transients. Thus, the muscle of the heart uses the VEGF-PLCgamma1 cascade to control the strength of the heart beat. We speculate that this paracrine system may contribute to normal and pathological regulation of cardiac contractility.

RELATIVELY OPTIMAL CONTROL: THE STATIC SOLUTION

A relatively optimal control is a stabilizing controller that, without initialization nor feedforwarding and tracking the optimal trajectory, produces the optimal (constrained) behavior for the nominal initial condition of the plant. In a previous work, a linear dynamic relatively optimal control, for discrete–time linear systems, was presented. Here a static solution is shown, namely a dead–beat piecewise affine state–feedback controller based on a suitable partition of the state space into polyhedral sets. The vertices of the polyhedrons are the states of the optimal trajectory, hence a bound for the complexity of the controller is known in advance. It is also shown how to obtain a controller that is not dead–beat by removing the zero terminal constraint while guaranteeing stability. Finally, the proposed static compensator is compared with the dynamic one.

DESIGN OF AUGMENTED FAULT DETECTION FILTER FOR FAULT TOLERANT CONTROL

In this paper, a new Fault-Tolerant Control System strategy is presented for linear dynamic systems. The detection and isolation of each jump is achieved by the Kalman filter designed under a dead beat constraint allowing the maximum adaptability of the fault magnitude estimation in the case of abrupt change. By using the state estimation corrected by the estimation of jumps we will describe a integrated Fault Tolerant Control via a particular LQG approach.

Sensor Fault Diagnostics of Magnetically Suspended Sliders

While magnetically suspended sliders controlled under five degrees of freedom have been used as a linear guide system for wafer transportation in clean atmosphere, three degrees of freedom controlled sliders may be applied to suspensory equipments which can move on a ceiling board without an effect of friction. Hence, using this slider with a propeller, a transportation system without a track can be constructed. In this paper, sensor fault diagnostics using an observer for magnetically suspended sliders is discussed and the design method for the dead beat observer which can maintain stability in replacement of outputs caused by isolation of a faulty sensor is proposed. In experiments, disturbance signals are added to a displacement sensor and the responses are measured. Sensor faults are successfully detected and isolated by the designed diagnostic system for various disturbances.

DIGITAL PID DESIGN FOR MAXIMALLY DEADBEAT AND TIME-DELAY TOLERANCE

This paper presents a new approach to design a digital PID controller for a given LTI plant. By using the Tchebyshev representation of a discrete time transfer function and some new results on root counting with respect to the unit circle, we show how the digital PID stabilizing gains can be directly obtained by solving sets of linear equations. This solution is attractive because it determines the entire set of stabilizing PID gains constructively if exists, Using this characterization of the stabilizing set, we present solutions to two design problems: a) Maximally dead beat design where we determine the smallest circle within the unit circle wherein the closed loop characteristic roots may be placed by PID control, b) Maximal delay tolerance-where we determine the maximal loop delay that can be tolerated under PID control.

Dead beat controllability of polynomial systems: symbolic computation approaches

State and output dead beat controllability tests for a very large class of polynomial systems with rational coefficients may be based on the quantifier elimination by partial cylindrical algebraic decomposition (QEPCAD) symbolic computation program. The method is unified for a very large class of systems and can handle one- or two-sided control constraints. Families of minimum time state/output dead beat controllers are obtained. The computational complexity of the test is prohibitive for general polynomial systems, but by constraining the structure of the system we may beat the curse of complexity. A computationally less expensive algebraic test for output dead beat controllability for a class of odd polynomial systems is presented. Necessary and sufficient conditions are given. They are still very difficult to check. Therefore, a number of easier-to-check sufficient conditions are also provided. The latter are based on the Grobner basis method and QEPCAD. It is shown on a subclass of odd polynomial systems how it is possible to further reduce the computational complexity by exploiting the structure of the system.

Output Dead Beat Control for a Class of Planar Polynomial Systems

Output dead beat control for a class of nonlinear discrete time systems, which are described by a single input-output (I-O) polynomial difference equation, is considered. The class of systems considered is restricted to systems with a two-dimensional state space description. It is assumed that the highest degree with which the present input appears in the equation is odd. Necessary and sufficient conditions for the existence of output dead beat control and for the stability of the zero output constrained dynamics are presented. We also design a minimum time output dead beat control algorithm (feedback controller) which yields stable zero dynamics, whenever this is feasible. A number of interesting phenomena are discussed and illustrated with examples.

Stabilization of linear systems in the presence of output measurement saturation

This note considers siso nonlinear systems, which have a linear controllable and observable part followed by a measurement saturation nonlinearity. A controller is presented, which feeds back only the saturating output measurements and nevertheless globally asymptotically stabilizes the system. The equilibrium is actually reached in finite time, i.e. the controller is dead beat.

Invariant Sets and Output Dead Beat Controllability for Odd Polynomial Systems: The Gröbner Basis Method

An algebraic test for output dead beat controllability for a class of odd polynomial systems is presented. Necessary and sufficient conditions are given. They are in general very difficult to check. Therefore, a number of easier-to-check sufficient conditions are also provided. The tests can be automatized using symbolic manipulation software packages and are based on the Gröbner basis method, Some examples are presented.

On the evaluation of control systems

A theoretical comparison criterion is developed in order to evaluate a control method vs any other method with respect to a specific system. The complete modal synthesis of optimal state feedback is compared against the dead beat design using the proposed criterion. The comparison shows clear qualitative and quantitative differences. The comparison study is demonstrated via a process model of a water turbine plant. The evaluation of controllers is based on five structural measures of controllability, affectability, decoupleability, observability and robustness against parameter variations, mathematical model uncertainties and possible external disturbances.

One-Step-Ahead Control of Nonlinear Discrete Time Systems with One-Dimensional Zero Dynamics: Global Stability Conditions

The output dead beat control issue in one step is addressed for a class of discrete time systems described by a nonlinear input/ output recursive representation. Global stability conditions are established in the case of one-dimensional zero dynamics. The results are illustrated with applications to polynomial and neural dynamical systems.

A software design for microcomputer based digital instrumentation scheme using a spectral observer

This paper presents a new recursive discrete-time filter for real-time monitoring of voltage, current, active and reactive power of an electrical/electronic network using a spectral observer. From a signal model comprising a decaying d.c., fundamental and harmonic components, an interpolating spectral observer is constructed to give the desired Fourier coefficients recursively. Initially, a dead beat spectral observer is designed with different sampling rates for the digital instrumentation scheme. Further, the performance of the spectral observer has been studied by placing the poles of the observer at locations other than the origin of the ( Z-plane) complex plane. The fast computational processing capability of this algorithm makes it suitable for microprocessor applications. This digital instrumentation scheme is tested in real-time for a laboratory electrical network using an LSI-11/23, 16-bit microcomputer.

Disturbance observer based fully digital controlled PWM inverter for CVCF operation

A new approach for digital feedback control of a PWM inverter is proposed, in which an output DB (deadbeat) control is achieved combined with a disturbance observer. In the proposed scheme, the pole placements of the state observer and the disturbance observer are chosen separately. When the two observers employed the same pole placements, the experimental setup had a tendency to become unstable due to the detection error. By selection of the different pole placements, the disturbance observer quickly estimates the disturbance and feedforward disturbance cancellation is achieved. Then the state observer estimates the state variables at the next sampling instant, and the deadbeat controller is applied to the nominal system. This scheme has advantages in robustness in the practical application. From the view point of UPS applications, the advantages and disadvantages are discussed through simulations and experiments. Compared with other digital control laws, the superiority of the proposed control law is verified. >

Digital Control of Three Phase PWM Inverter for UPS Application based on Disturbance Observer and Deadbeat Control.

A new approach to digital feedback control of PWM inverter is proposed, in which an output DB (dead beat) control is achieved with a disturbance observer. In this scheme, the state observer and disturbance observer are used, and pole placement of these two observers are chosen separately. When these observers employ the same pole placement, the system has tendency to become unstable. By selecting the different pole placement, the disturbance observer only eliminates the disturbance, and state observer only estimates the state variable of the next sampling instant.From the view point of UPS applications, the advantages and disadvantages are discussed through simulations and experiments.

Digital Control Method Using Full-Order Observer on Three-Phase Inverter for UPS.

Uninterruptible power supplies (UPSs) as power sources in computer systems must be offer high quality and high reliable power to their system. To realize such UPSs, inverter controllers in the UPSs must be digitalized with micro processors. And, it is necessary to obtain high sampling frequency and satisfactory compensation for the processor operating time lag and disturbances in the control system. Besides, simple control algorithm is demanded due to application of the digital controllers to low cost UPSs. Then, a control method using full-order observer in the current minor loop is proposed. In this method, to shorten the algorithm, disturbances are assumed as a state valuable, vD(n) where vD(n+1)=vD(n), and the observer is established in the minor loop. To increase the compensation for the time lag and the disturbances, the observer estimates the time-lagahead current and disturbance, and the observer carries out dead beat operation. Experiments demonstrates that this control method provides excellent characteristics of the inverter for the UPSs.

Design of dead beat controller for electrohydraulic speed servo system

This paper deals with the control methods of electro-hydraulic speed servo control system with large power which is used in the aeroplane engine simulating rig. In order to obtain the fast response characteristics in the system, the dead beat control method combined with the fuzzy control is adopted by means of the simplified first-order and second-order mathematical models are established, and control experiments is carried out. The experimental results show that the satisfactory response characteristics are obtained by using the dead beat control method combined with the fuzzy control with the second-order model.