Switching Function Approach Research Articles

Design of Main Circuit Parameters for Modular Multilevel Matrix Converter in LFAC System

The low-frequency AC (LFAC) transmission is a competitive scheme for offshore wind power integration, in which the modular multilevel matrix converter (M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C) is the key equipment. In this brief, the selection methods of the M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C main circuit parameters are proposed. First, the maximum arm voltage is derived and the selection method of the sub-module (SM) number is established. Then, according to the switching function approach, the analytical expressions of the average SM capacitor current and the average SM capacitor voltage are derived. On this basis, the selection method of the SM capacitance is proposed. Additionally, the design principle of the arm inductance is proposed. Finally, a case is elaborated to illustrate the proposed M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C main circuit parameter selection methods and provide a reference for practical projects.

A novel switching function approach for data mining classification problems

Rule induction (RI) is one of the known classification approaches in data mining. RI extracts hidden patterns from instances in terms of rules. This paper proposes a logic-based rule induction (LBRI) classifier based on a switching function approach. LBRI generates binary rules by using a novel minimization function, which depends on simple and powerful bitwise operations. Initially, LBRI generates instance codes by encoding the dataset with standard binary code and then generates prime cubes (PC) for all classes from the instance codes by the proposed reduced offset method. Finally, LBRI selects the most effective PC of the current classes and adds them into the binary rule set that belongs to the current class. Each binary rule represents an If–Then rule for the rule induction classifiers. The proposed LBRI classifier is based on basic logic functions. It is a simple and effective method, and it can be used by intelligent systems to solve real-life classification/prediction problems in areas such as health care, online/financial banking, image/voice recognition, and bioinformatics. The performance of the proposed algorithm is compared to six rule induction algorithms; decision table, Ripper, C4.5, REPTree, OneR, and ICRM by using nineteen different datasets. The experimental results show that the proposed algorithm yields better classification accuracy than the other rule induction algorithms on ten out of nineteen datasets.

A linear switching function approach to sliding mode control and observation of descriptor systems

This paper investigates sliding mode control and observation problems for descriptor systems via a linear switching function approach. A generalized regular form and a generalized observer regular form, which are counterparts of the regular form and the observer regular form for normal systems respectively, are first introduced for descriptor systems. Then systematic ways to design the sliding mode controller and the descriptor sliding mode observer for descriptor systems are presented by virtue of linear switching functions. Necessary and sufficient conditions are established to determine the existence of the proposed sliding mode controller and descriptor sliding mode observer. In terms of the proposed sliding mode control and observation method, a descriptor sliding mode observer-based sliding mode controller is also developed for descriptor systems. It shows that under mild assumptions, the associated sliding motion for descriptor systems is of reduced order and the separation principle holds if the amplitude of high-order sliding mode controllers in the control input can be selected appropriately.

Modeling and Direct Power Control Method of Vienna Rectifiers Using the Sliding Mode Control Approach

This paper uses the switching function approach to present a simple state model of the Vienna-type rectifier. The approach introduces the relationship between the DC-link neutral point voltage and the AC side phase currents. A novel direct power control (DPC) strategy, which is based on the sliding mode control (SMC) for Vienna I rectifiers, is developed using the proposed power model in the stationary <TEX>${\alpha}-{\beta}$</TEX> reference frames. The SMC-based DPC methodology directly regulates instantaneous active and reactive powers without transforming to a synchronous rotating coordinate reference frame or a tracking phase angle of grid voltage. Moreover, the required rectifier control voltages are directly calculated by utilizing the non-linear SMC scheme. Theoretically, active and reactive power flows are controlled without ripple or cross coupling. Furthermore, the fixed-switching frequency is obtained by employing the simplified space vector modulation (SVM). SVM solves the complicated designing problem of the AC harmonic filter. The simplified SVM is based on the simplification of the space vector diagram of a three-level converter into that of a two-level converter. The dwelling time calculation and switching sequence selection are easily implemented like those in the conventional two-level rectifier. Replacing the current control loops with power control loops simplifies the system design and enhances the transient performance. The simulation models in MATLAB/Simulink and the digital signal processor-controlled 1.5 kW Vienna-type rectifier are used to verify the fast responses and robustness of the proposed control scheme.

Position Sliding Mode Control of Manipulator Joint Based on Genetic Algorithm

In order to improve the control performance of position trajectory tracking of manipulator joint, a sliding mode control (SMC) method based on genetic algorithm(GA) is proposed in this paper. In this method, the performance of SMC algorithm is improved through adjusting the parameters of switching function and exponential approach law by genetic algorithm. The method was applied to accomplish the precise position control of manipulator joint. Simulation experiments show that the response time in manipulator joint control system by the SMC method based on GA is reduced 0.62s than the ordinary SMC algorithm. And the system restore stability time with a load change is also reduced 0.7s. External disturbance has no significant effect on the control system. The chattering of controller output is significantly reduced.

Corrections to “Remedial Switching Function Approach to Improve Reliability for AC–AC Converters” [Jun 07 541-543

In the above-named work [ibid., vol. 22, no. 2, pp. 541-543, Jun. 2007], the two coefficients in the second and the third matrices in equations (4), (6), and (7) should have appeared as given in this correction. All the theory and verification results are correct, except the coefficients. Since the authors used the correct coefficients in the simulations and the experiments appeared in the article, the results are all reported to be correct.

A Frequency Domain Approach for Modeling DC Arc Furnaces under Fluctuating Conditions

This paper presents a direct method in the frequency domain for modeling DC arc furnaces (DCAF) under fluctuating conditions. The procedure takes advantage of the switching function approach for obtaining a detailed representation of the DCAF. The model provides very fast calculations of the flicker interharmonic voltages and currents as well as it offers a basis for estimating the fluctuations of the arc from measurements on the AC side. With this procedure, an exhaustive analysis is developed where a deep insight is provided for better understanding the process by which flicker interharmonic components are generated. With this, flicker power flow in terms of Pst values is possible not only for the DCAF installation but also for large systems where the DCAF is connected. The method has been validated with measurements and with time domain simulations.

Remedial Switching Function Approach to Improve Reliability for AC–AC Converters

A study of switching function approach is presented for remedial control techniques against open-switch and open-phase failures occurring in ac-ac converters. Switching function matrices, containing symmetric and antisymmetric mode matrices with appropriate sequences of input voltages, are developed to synthesize redefined output waveforms under the faults.

Modelling and control of three-phase∕switch∕level fixed-frequency PWM rectifier: state-space averaged model

A new and simple state model of a three-phase, three-switch, three-level, fixed-frequency pulse-width-modulated rectifier is presented. The modelling approach uses the state-space averaging technique in continuous current mode. The averaging process is applied on two time intervals: the switching period for average current evaluation, and the mains period for average voltage computation. A basic mathematical model of the converter is first established. A simplified time-invariant model is then deduced using the rotating Park transformation. The steady-state regime is analysed on the basis of the model obtained, and converter design criteria consequently discussed. The proposed modelling approach is then verified numerically through a digital implementation of the converter in the Matlab/Simulink framework, using the switching function approach. The numerical results show the reliability of the proposed model that would be then easily applied to the design of suitable duty-cycle-based control schemes.

Harmonic analysis of converter-fed DC systems under unbalanced and harmonic supply voltages

The analysis of converter-fed DC systems under balanced steady-state and transient conditions is well documented in the literature; normal practice is to consider the DC system supplied from a three-phase balanced source at the fundamental frequency. The concept of switching functions has been proposed before to evaluate the harmonic content of a phase-controlled six-pulse three-phase converter under both balanced and unbalanced supply conditions. However, the supply voltages were only at the fundamental frequency. This paper extends the switching function approach to analyze the harmonic content of a phase-controlled DC system when the supply voltages may be unbalanced and contain harmonic components. The input power, harmonic and distortion factors are obtained for different firing angles and compared with those of the ideal balanced case when the DC load consists of a DC motor operating at a constant torque.

Optimal power control strategies for neutral point clamped (NPC) inverter topology

A programmed pulsewidth modulation (PWM) technique for selectively eliminating several lower-order harmonics at the output of a neutral point clamped (NPC) inverter topology is investigated. The switching function approach is utilized to derive relevant analytical expressions for input/output variables. A thorough evaluation of the NPC inverter topology based on the switching function approach is described. Optimal power control strategies for an NPC inverter employing programmed PWM patterns are proposed. For a constant-frequency variable-voltage NPC inverter power supply, the proposed strategy is to maintain a minimum specified total harmonic distortion employing a low-output impedance filter. In the case of an NPC inverter powering an AC motor drive, the proposed strategy is to maintain a minimum specified harmonic current factor. The proposed power control strategies are achieved without substantial increase in inverter switching frequency and are therefore suitable for high-power applications employing gate-turn-off-thyristor (GTO) type devices. >