- Dettagli della rivista
- Formato
- Rivista
- eISSN
- 2543-4292
- ISSN
- 2451-0262
- Pubblicato per la prima volta
- 16 Apr 2016
- Periodo di pubblicazione
- 1 volta all'anno
- Lingue
- Inglese

#### Cerca

- Accesso libero

An Overview of Design, Control, Power Management, System Stability and Reliability in Electric Ships

Pagine: 5 - 29

#### Astratto

With the fast development of power electronics techniques, electrification of shipboard power systems (SPS) is an unstoppable trend, and the concepts of electric ships (ESs) and all-electric ships (AESs) emerge. In order to meet the constantly increasing electricity demand in SPS, the medium voltage direct current (MVDC) SPS becomes a promising shipboard electrical network architecture. This paper aims to present a comprehensive review of the design, control, power management, system stability and reliability in ESs. The most recent technologies and academic achievements in these fields are discussed. In the near future, it is possible that the electric propulsion technology will be widely applied to various types of ships.

#### Parole chiave

- electric ship
- control algorithms
- power electronics techniques
- power drive system
- stability

- Accesso libero

Control of a Doubly Fed Induction Generator at Grid Voltage Imbalance

Pagine: 31 - 48

#### Astratto

Properties and control of a doubly fed induction machine operating under unbalanced grid voltage conditions have been presented. The proposed method does not include symmetrical sequences decomposition and is realized in a rotating frame not synchronized either with the grid voltage vector or with the stator flux vector. The method uses a reference torque and the reference

#### Parole chiave

- doubly fed induction generator
- power and torque control
- unbalanced grid

- Accesso libero

Hybrid MPPT Algorithm for PV Systems Under Partially Shaded Conditions Using a Stochastic Evolutionary Search and a Deterministic Hill Climbing

Pagine: 49 - 59

#### Astratto

A hybrid maximum power point tracking method has been proposed for the photovoltaic system using a stochastic evolutionary search and a deterministic hill climbing algorithm. The proposed approach employs the particle swarm optimizer (PSO) to solve a dynamic optimization problem related to the control task in a

#### Parole chiave

- maximum power point tracking
- photovoltaic system
- hybrid part–stochastic part–deterministic search rule
- particle swarm optimization
- partial shading
- hill climbing

- Accesso libero

State Observer for Doubly-Fed Induction Generator

Pagine: 61 - 75

#### Astratto

The purpose of this paper is to show a new state observer for doubly-fed generator. A proposed

#### Parole chiave

- doubly-fed induction generator
- non-linear control
- state observer
- power control

- Accesso libero

Problems of Designing State Feedback Controllers for Objects with Transfer Function Zeros

Pagine: 77 - 92

#### Astratto

The analysis of the influence of transfer function zeros on the parameters of state feedback controllers has been conducted. If a transfer function of a control object has zeros which are located closely to poles, the control object tends to singularity, and the influence of the input control signal to the states of the control object becomes weaker. The problem of the state feedback controller synthesis becomes ill-conditioned, which leads to the appearance of extremely large state feedback coefficients. In this case, the state feedback coefficients are sensitive to the parameters of the control object. As a result, the parametric robustness of the control system is reduced. Known methods of structural analysis of control object models are included amongst different methods of the numerical evaluation of the controllability and the observability, as well as methods of the model order reduction. These methods have some disadvantages, such as dependence on the state space representation form of the control object, ignoring a part of the control object model. In this paper, some ways of the preliminary structural analysis of the state space models of control objects have been proposed. The singular (Hankel) matrix is proposed for analyzing the properties of control object models. The singular matrix is the invariant characteristic of the control object in various state space forms and it characterizes the property of the control object completeness. As a result of the research, it was found that the coefficients of the state feedback controller are inversely proportional to the determinant of the singular matrix, and the determinant of the singular matrix is equal to the resultant of the transfer function polynomials. Thus the value of the determinant of the singular matrix depends on the location of the zeros of the transfer function. The method of the structural transformation (decomposition) of the control object for the defining the need of the reducing the order of the control object model is proposed.

#### Parole chiave

- zeros of a transfer function
- observability
- controllability
- Hankel matrix
- state feedback controller
- resultant
- residues

- Accesso libero

Modified Scheme of Predictive Torque Control for Three-Phase Four-Switch Inverter-Fed Motor Drive with Adaptive DC-Link Voltage Imbalance Suppression

Pagine: 93 - 101

#### Astratto

Classical voltage space vector modulation techniques cannot be efficiently applied in four-switch three-phase voltage inverter-fed electrical drives due to a voltage offset in DC-link capacitors. The capacitor voltages imbalance is a result of a bidirectional current which flows in a phase of an electric motor that is connected to a DC-link capacitor midpoint. To overcome this problem which leads to an incorrect inverter voltage modulation or even can affect the DC-link capacitors, predictive control algorithms considering the voltage offset in DC-link capacitors have been developed. Despite the predictive methods are highly effective, they require to adjust the cost function weighting factors which is normally an inexplicit task. In this paper, an on-line tuning method of the weighting factor related to the capacitor voltages imbalance incorporated in the cost function of the predictive algorithm has been proposed. According to the proposed approach, the weighting factor is self-adjusted so that the DC-link capacitor voltages are stabilized as well as a high quality of the drive control is remained simultaneously, regardless of its operating point. The proposed strategy has been validated by using simulation model of the induction motor drive system.

#### Parole chiave

- fault tolerant systems
- semiconductor faults
- four-switch inverter
- predictive control
- cost function
- variable speed drives

- Accesso libero

Application of Industrial Frequency Converters for Project-Oriented Education of Controlled Electrical Drives

Pagine: 103 - 116

#### Astratto

In the perspective of current trends in engineering education, aiming at meeting industry requirements, especially in the field of power electronics and motion control, the article presents a way of teaching electric drive control in undergraduate engineering programmes using experimental setups with AC motors equipped with industrial frequency converters. The setups consist of two motors: induction and PMSM (each one can act as a motor or a load machine) and a number of other elements necessary in contemporary drive systems: speed sensors, temperature sensors and braking resistors. While using such setups students can learn about various issues related to AC motor control, both in terms of scalar and field-oriented control methods in all three drive operating modes: torque, velocity and position control. The laboratory setups allow students to familiarize themselves with such detailed issues as: vector control without a speed sensor, various ways of voltage control in a DC input circuit of the voltage inverter during motor braking or the influence of the type and value of load torque on drive system operation. Classes can have a classical form or they can be taught in the open-laboratory system.

#### Parole chiave

- education
- controlled electrical drives
- ac motors
- control algorithms
- designing

- Accesso libero

A Method of Reducing Switch Count in Three-Level NPC Inverter – Analysis in Steady States

Pagine: 117 - 126

#### Astratto

The proof of a concept for a new method of modulation has been presented which reduce switch count in a three-level neutral point clamped (3L-NPC) inverter. The method is an implementation of space vector modulation (SVM) by means of a prediction algorithm and sequences of transistors, which are not common in use. Those sequences make active use of clamping diodes of the inverter. The prediction algorithm analyzes possible sequences of transistors’ states and choose those which offers smaller switch count. Measurements of steady states were taken on prototype 3L-NPC.

#### Parole chiave

- reduction of switch count
- three-level NPC inverter
- space vector modulation

- Accesso libero

EMC Requirements for Power Drive Systems

Pagine: 127 - 135

#### Astratto

Electromagnetic compatibility requirements for immunity tests have been presented and the emission levels of electromagnetic disturbances in adjustable speed power drive systems have been determined. The disturbances are divided into two groups: low-frequency (up to 50 harmonics of the power supply system) and high-frequency (above 150 kHz). The lack of legal regulations on permissible disturbance level in the frequency range from 2.5 kHz to 150 kHz has also been mentioned. This range is considered high frequency by the authors. Standarized compatibility levels and sample measured parameters of the electromagnetic environment have also been shown. An exemplary reaction of the drive to the most common disturbances in the power supply system has been presented.

#### Parole chiave

- power drive system
- electromagnetic compatibility
- immunity on disturbances
- emission level

- Accesso libero

Diagnostic System for Induction Motor Stator Winding Faults Based on Axial Flux

Pagine: 137 - 150

#### Astratto

The article presents the results of research on the use of an axial flux in the diagnostics of induction motor stator winding fed by a frequency converter. Voltage signal waveforms proportional to the axial flux were recorded during motor operation under various conditions and were analyzed with regard to the detection of stator winding short circuits. The taps of the selected coil turns of stator phases were introduced into the tested motor, which allowed to physical modelling inter-turn short circuits. The structure and operation of the computer system used to monitor the state of induction motor windings were discussed. The developed diagnostic system was made in the National Instruments LabVIEW environment. The analysis of faults of the axial flux was made in the detection of induction motor stator winding. The results of experimental research conducted using the developed diagnostic system have also been presented.

#### Parole chiave

- stator winding faults
- inter-turn short circuits
- axial flux
- diagnostic system

- Accesso libero

Application of Neural Networks to Detect Eccentricity of Induction Motors

Pagine: 151 - 165

#### Astratto

The possibility of using neural networks to detect eccentricity of induction motors has been presented. A field-circuit model, which was used to generate a diagnostic pattern has been discussed. The formulas describing characteristic fault frequencies for static, dynamic and mixed eccentricity, occurring in the stator current spectrum, have been presented. Teaching and testing data for neural networks based on a preliminary analysis of diagnostic signals (phase currents) have been prepared. Two types of neural networks were discussed: general regression neural network (GRNN) and multilayer perceptron (MLP) neural network. This paper presents the results obtained for each type of the neural network. Developed neural detectors are characterized by high detection effectiveness of induction motor eccentricity.

#### Parole chiave

- neural network
- general regression neural network
- multilayer perceptron
- eccentricity
- induction motor

- Accesso libero

Inductive Current Transducers in the Frequency Range Up to 150 kHz

Pagine: 167 - 176

#### Astratto

The article presents the results of the research on inductive current transducers in the form of a uniform winding non-magnetic ring with a rigid and flexible construction encompassing the flow of processed current in the frequency range of up to 150 kHz. The results for the developed transducer were related to the results obtained in simulations conducted on the transducer simplified model. The frequency tests of this type of transducers are of key significance in the assessment of the applicability of a given transducer in the measurements of network signals with high-order harmonics, and particularly in the assessment of the construction capacity of inductive current transducers in the form of the Rogowski coil.

#### Parole chiave

- current
- Rogowski coil
- inductive current transducer