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A comparative study between four-level NSVM and three-level NSVM technique for a DFIG-based WECSs controlled by indirect vector control

Abstract

In this work, we present a comparative study between four-level neural space vector modulation (4L-NSVM) and three-level neural space vector modulation (3L-NSVM) technique in indirect vector control (IVC) of reactive and active power control of a doubly fed induction generator (DFIG) for wind energy conversion systems (WECSs). Two controls techniques using IVC-4L-NSVM and IVC-3L-NSVM are proposed and compared. The validity of the proposed control schemes is verified by simulation tests of a DFIG-based wind turbine system (WTSs). The stator active power, stator reactive power and rotor current is determined and compared in the above strategies. The obtained results showed that the proposed IVC with 4L-NSVM technique have reactive and stator active power with low powers ripples and low rotor current harmonic distortion than 3L-NSVM technique.

Open access
A Cost-Effective Resonant Switched-Capacitor DC-DC Boost Converter – Experimental Results and Feasibility Model

Abstract

This paper presents the results of experimental research of a resonant switched capacitor voltage multiplier in a cost-effective topology (CESCVM) with a limited number of active switches. In the charging mode of the switched capacitors, the converter utilizes only one active switch and a required number of diodes. Therefore, the cost of the converter is decreased as compared with that of a classical SCVM converter, owing to a lower number of switches and gate driver circuits, as well as a smaller PCB area. Moreover, the CESCVM has simpler control circuits and higher reliability. This paper presents the original experimental results of the operation of the CESCVM converter. A concept of the bootstrap supply of gate drivers of the flying switches is also examined.

Open access
Design of Helix Antenna for 9.2GHz in FEKO for FSO/RF Hybrid System Focused on Height of Helix

Abstract

Nowadays we are living in the ages of expansion of communication. The young generation depends on the online communications with other. Each of the devices is purposed to communication. Cloud data storage systems are available only with stable connection. Requirements are growing up to date. The answer on these requirements: the high speed of transmission, high level of security and wide bandwidth are optical communication systems. This system offers comparable features as optical system with physical optical fibers. But it has one big drawback. It is sensitivity to weather changes. We have to make backup link for case of outages. One part of design FSO/RF system in our case contains selection of appropriate type of RF antenna. We are looking for appropriate candidate. This paper is focused on analysis of helix antenna operating in non-licensed frequency range on 9.2GHz. The point of this paper is the examination of the impact of the height of helix designed antenna.

Open access
Dynamic Performance of Estimator-based Speed Sensorless Control of Induction Machines Using Extended and Unscented Kalman Filters

Abstract

This paper presents an estimator-based speed sensorless field-oriented control (FOC) method for induction machines, where the state estimator is based on a self-contained, non-linear model. This model characterises both the electrical and the mechanical behaviours of the machine and describes them with seven state variables. The state variables are estimated from the measured stator currents and from the known stator voltages by using an estimator algorithm. An important aspect is that one of the state variables is the load torque and, hence, it is also estimated by the estimator. Using this feature, the applied estimator-based speed sensorless control algorithm may be operated adequately besides varying load torque. In this work, two different variants of the control algorithm are developed based on the extended and the unscented Kalman filters (EKF, UKF) as state estimators. The dynamic performance of these variants is tested and compared using experiments and simulations. Results show that the variants have comparable performance in general, but the UKF-based control provides better performance if a stochastically varying load disturbance is present.

Open access
Effects of Grid Disturbances on Current Source Rectifier Controlled by FCS-MPC Algorithm

Abstract

Nowadays, the increasing number of non-linear loads influences the grid, causing grid voltage disturbances. These disturbances may be very dangerous for the equipment and can create faults in converter behaviour. However, the right control algorithm can improve the reliability of the work. For a current source rectifier, the finite control set model predictive control has been proposed. This method is very flexible because of the variety of the possible cost function forms. It has been examined under grid voltage disturbed by the higher harmonics and the voltage drop. Simulation results prove the ability to damp the distortions and to ensure the unity power factor. Summing up, the algorithm is a very good solution for use in applications such as battery charging, active power filtering and low-voltage direct current load feeding.

Open access
Estimation of Power and Delay in CMOS Circuits using Leakage Control Transistor

Abstract

With a rapid growth in semiconductor Industry, complex applications are being implemented using small size chips, with the use of Complementary Metal Oxide Semi-Conductors (CMOS). With the introduction of new Integrated Circuit (IC) technology, the speed of the circuits has been increased by around 30%. But it was observed that for every two years, the power dissipation of a circuit doubles. The main reason for this power dissipation is leakage currents in the circuit. To reduce these leakage currents, we can reduce the width of the device. In addition to this, we can use lector techniques that use Leakage Control Transistors (LCT) and High Threshold Leakage Control Transistors (HTLCT).In this paper; we present a circuit technique that uses 130 nano-meter CMOS VLSI circuits that use two extra transistors to mitigate the leakage currents. The proposed technique overcomes the limitations posed by the existing methods for leakage reductions an average leakage reductions is 82.5%.The estimation of power and delay will be discussed using LCT’s and HTLCT’s.

Open access
Extended Kalman Filter Based Speed-Sensorless Load Torque and Inertia Estimations with Observability Analysis for Induction Motors

Abstract

This paper aims to introduce a novel extended Kalman filter (EKF) based estimator including observability analysis to the literature associated with the high performance speed-sensorless control of induction motors (IMs). The proposed estimator simultaneously performs the estimations of stator stationary axis components of stator currents and rotor fluxes, rotor mechanical speed, load torque including the viscous friction term, and reciprocal of total inertia by using measured stator phase currents and voltages. The inertia estimation is done since it varies with the load coupled to the shaft and affects the performance of speed estimation especially when the rotor speed changes. In this context, the estimations of all mechanical state and parameters besides flux estimation required for high performance control methods are performed together. The performance of the proposed estimator is tested by simulation and real-time experiments under challenging variations in load torque and velocity references; and in both transient and steady states, the quite satisfactory estimation performance is achieved.

Open access
Extended T-type Inverter

Abstract

This paper presents a new concept for a power electronic converter - the extended T-type (eT) inverter, which is a combination of a three-phase inverter and a three-level direct current (dc)/dc converter. The novel converter shows better performance than a comparable system composed of two converters: a T-type inverter and a boost converter. At first, the three-level dc/dc converter is able to boost the input voltage but also affects the neutral point potential. The operation principles of the eT inverter are explained and a simulation study of the SiC-based 6 kVA system is presented in this paper. Presented results show a serious reduction of the DC-link capacitors and the input inductor. Furthermore, suitable SiC power semiconductor devices are selected and power losses are estimated using Saber software in reference to a comparative T-type inverter. According to the simulations, the 50 kHz/6 kVA inverter feed from the low voltage (250 V) shows <2.5% of power losses in the suggested SiC metal oxide-semiconductor field-effect transistors (MOSFETs) and Schottky diodes. Finally, a 6 kVA laboratory model was designed, built and tested. Conducted measurements show that despite low capacitance (2 × 30 μF/450 V), the neutral point potential is balanced, and the observed efficiency of the inverter is around 96%.

Open access
Introduction to the Special Section on State and Parameter Estimation Methods for Sensorless Drives

Abstract

This short article constitutes an introductory part of the Special Section (SS) on State and Parameter Estimation Methods in Sensorless Drives. In the current issue of the journal, the first part of this section is published. Accepted articles are focussed mainly on estimation of the state variables and parameters for vector-controlled induction motor (IM) drives, using different concepts, such as different types of Kalman filters (KFs) and model reference adaptive systems (MRASs). The KF was also proposed for brushless DC motor (BLDC). Also, neural networks (NNs) have been proposed for mechanical state variables’ estimation of the drive system with elastic couplings.

Open access
Model Predictive Control of Four-Leg Three-Level Flying Capacitor Converter: Influence of Model Parameter Mismatch

Abstract

This paper presents a control method for a four-leg three-level flying capacitor converter (FCC) operating as a shunt active power filter (SAPF), based on model predictive control with finite number of control states (FS-MPC). Current control and capacitor voltage balancing are described. Influence of the mismatch of the inductive filter model parameters on the current control precision is analysed. Results are supported by the experimental waveforms obtained with a 10kVA set-up.

Open access