Archives of Electrical Engineering

Based on the respective characteristics of line-commutated converter high-voltage direct current (LCC-HVDC) and voltage-source converter high voltage direct cur- rent (VSC-HVDC), two additional emergency DC power support (EDCPS) controllers are designed, respectively. In addition a coordinated control strategy based on a hybrid multi-infeed HVDC system for EDCPS is proposed. Considering the difference in system recovery between LCC-HVDC and VSC-HVDC in EDCPS, according to the magnitude of the amount of potential power loss, the LCC-HVDC and VSC-HVDC priority issues of boosting power for EDCPS are discussed in detail. Finally, a hybrid three-infeed HVDC that consists of two parallel LCC-HVDCs and one VSC-HVDC that is built in PSCAD/EMTDC are simulated. The effectiveness of the proposed approach is verified based on this hybrid three-infeed HVDC system.

The smart grid concept is predicated upon the pervasive use of advanced digital communication, information techniques, and artificial intelligence for the current power system, to be more characteristics of the real-time monitoring and controlling of the supply/demand. Microgrids are modern types of power systems used for distributed energy resource (DER) integration. However, the microgrid energy management, the control, and protection of microgrid components (energy sources, loads, and local storage units) is an important challenge. In this paper, the distributed energy management algorithm and control strategy of a smart microgrid is proposed using an intelligent multi-agent system (MAS) approach to achieve multiple objectives in real-time. The MAS proposed is developed with co-simulation tools, which the microgrid model, simulated using MATLAB/Simulink, and the MAS algorithm implemented in JADE through a middleware MACSimJX. The main study is to develop a new approach, able to communicate a multi-task environment such as MAS inside the S-function block of Simulink, to achieve the optimal energy management objectives.

Room temperature vulcanized (RTV) silicone rubber is widely used to prevent pollution flashover with its excellent hydrophobicity and hydrophobicity transfer. However, RTV coatings are at the risk of deterioration and failure in heavily polluted operating environment. In this paper, RTV coated insulators with different suspension heights operating in coal ash polluted areaswere sampled. Pollution degree, pollution composition and aging degree of coatings were tested. The result shows that the insoluble pollution contains Al(OH)3 filler precipitated from RTV coating, which indicates the aging of the RTV coating. The top surface coating is more affected by ultraviolet and rainwater than the bottom surface resulting in more serious degradation. As the pollution degree of the lower phase insulator is heavier than that of the upper phase insulator, the erosion effect of pollution on the RTV coating is more intense. The fillers and rubber molecules of RTV continuously precipitate into the pollution layer, leading to further aging. Therefore, the overall aging degree of the lower insulator coating is more serious than that of the upper insulator coating.

A probable risk for different diseases has been reported due to exposure of peoples living in the vicinity of electrical substations and electrical workers. The aim of this paper is to examine and reduce the induced current density due to the power system field acting on human beings in the working environment, by using the spheroidal calculation model. The results obtained by means of computer programs developed by the author in the MATLAB environment are compared with the limit values given by the International Committee on Non-Ionizing Radiation Protection (ICNIRP) for demonstrating the degree of danger due to the induced current and have a certain guidance function for worker’s health to ensure their safety.

When the traditional multi-motor speed synchronous control strategy is applied to the vacuum pump system, it is prone to the drawbacks of large synchronization error. In this paper, a simplified mathematical model of the motor for a vacuum pump is established and the transfer function is introduced, which weakens the multivariable, strong coupling and nonlinear characteristics of the motor system. According to the basic principle of the relative coupling control strategy, the neural network Proportion Integration Differentiation (PID) is introduced as a speed compensator in this system. It effectively improves the synchronization and anti-interference ability of the multi motor.

The smart household connected to the energy dispatch arises to overcome the environmental crisis, encourages the penetration of renewable energies and promotes consumer respond to intraday market prices. Aquaponic production results from the combination of fish farming and hydroponics (cultivating plants using fish waste as nutrients). The prototype was built based on the rule of the 3 Rs: reduce, reuse and recycle. The crop reduces the consumption of water and energy, reuses water in a recirculation process, which is filtered by: 1) gravity, 2) biofilters and 3) porosity. Recycling is expanded to plastic containers and food containers of polystyrene. The aquaponic production system is decorative, completely organic (without chemicals), promotes the growth of green areas for comfortable homes and allows the consumption of healthy food, as well as energy planning to save energy. The system is done with a digital level control connected to a water pump and an oxygen pump. A novel method allows the aggregator to optimize the recirculation programming of the aquaponic system for periods of 24 hours. The method maximizes the economic benefits with the help of an energy balance between hours.

In this paper, we propose sensorless backstepping control of a double-star induction machine (DSIM). First, the backstepping approach is designed to steer the flux and speed variables to their references and to compensate uncertainties. Lyapunov”s theory is used and it demonstrates that the dynamic tracking of trajectories tracking is asymptotically stable. Second, unfortunately, this law control called sophisticated is a major problem which leads to the necessity of using a mechanical sensor (speed, load torque). This imposes an additional cost and increases the complexity of the montage. In practice, this variable is unknown and its measurement is expensive. To restrain this problem we estimate speed and load torque by using a Luenberger observer (LO). Simulation results are provided to illustrate the performance of the proposed approach in high and low variable speeds and load torque disturbance.

The smart grid concept is predicated upon the pervasive With the construction and development of distribution automation, distributed power supply needs to be comprehensively considered in reactive power optimization as a supplement to reactive power. The traditional reactive power optimization of a distribution network cannot meet the requirements of an active distribution network (ADN), so the Improved Grey Wolf Optimizer (IGWO) is proposed to solve the reactive power optimization problem of the ADN, which can improve the convergence speed of the conventional GWO by changing the level of exploration and development. In addition, a weighted distance strategy is employed in the proposed IGWO to overcome the shortcomings of the conventional GWO. Aiming at the problem that reactive power optimization of an ADN is non-linear and non-convex optimization, a convex model of reactive power optimization of the ADN is proposed, and tested on IEEE33 nodes and IEEE69 nodes, which verifies the effectiveness of the proposed model. Finally, the experimental results verify that the proposed IGWO runs faster and converges more accurately than the GWO.

An electric turnout heating (ETH) system is an essential technical and economic issue. Uninterrupted operation of the turnouts is crucial to maintaining railway transport safety. The classic heating system is characterized by high energy consumption. The usage of it is extremely expensive, so the need to optimize the current system becomes more and more critical. At the same time, the progress in the contactless heating method has become a promising alternative. The paper presents the results of tests performed for electric turnout heating systems for two types of heaters. In the first place, the analysis of heat distribution was performed using the ANSYS Fluent v.16. The temperature fields in the turnout models filled with a model of semi-melting snow were analyzed. Thanks to cooperation with the Railway Institute inWarsaw the second stage of the research was possible to be completed.

In this part, the models were implemented in the real world using the 49E1 railway turnout. The numerical solutions were validated by the experiments. The verification showed a high level of agreement among the results. The obtained results indicate the need for further tests of heating systems, to validate an optimal method of turnout heating. It was found that in the classic ETH, the working space area consumes a tremendous amount of energy. To ensure a higher efficiency of the heating process, the contactless heater is proposed as an alternative.

In order to meet the application requirements of high-power mobile inductively-coupled power transfer (ICPT) equipment, the structure of the dual transmitter and pickup can be used to improve the transmission power of the ICPT system. However, this structure cannot easily describe the change of the mutual inductance parameter in the moving state, making the mathematical model difficult to establish. The change of load parameters during the movement will affect the current and voltage at the transmitter and pickup coils. Aiming at these problems, this paper proposes a dual transmitter and pickup ICPT system based on inductor-capacitor-inductor (LCL) compensation network, and analyzes its power trans- mission efficiency. By setting the shape and size of the coil, the influence of the change of the mutual inductance parameters on the system efficiency during the movement is reduced. The changes of the mutual inductance parameters of the ICPT system under the moving state are simulated by changing the coupling coefficient in the PSpice software. The results show that the structure of the ICPT system used in this paper can improve the output power and reduce the influence of the system when the load changes.

In order to solve the problem of harmonic waves caused by battery energy storage (BES) and distributed generation (DG) inverters in an active distribution network, an intelligent optimal dispatching method based on a modified flower pollination algorithm (MFPA) is proposed. Firstly, the active distribution network dispatching model considering the power quality (PQ) problem caused by BES and DG is proposed. In this model, the objective function considers the additional network loss caused by a harmonic wave, as well as the constraints of the harmonic wave and voltage unbalance. Then, the MFPA is an improvement of a flower pollination algorithm (FPA). Because the MFPA has the characteristics of higher solution accuracy and better convergence than the FPA and it is not easy to fall into local optimal, the MFPA is used to solve the proposed model. Finally, simulation experiments are carried out on IEEE 37 bus and IEEE 123 bus systems, respectively. The experimental results show that this method can achieve satisfactory power quality while optimizing the total active power loss of the branch. The comparative experimental results show that the developed algorithm has better convergence than the FPA.

Analog circuits need more effective fault diagnosis methods. In this study, the fault diagnosis method of analog circuits was studied. The fault feature vectors were extracted by a wavelet transform and then classified by a generalized regression neural network (GRNN). In order to improve the classification performance, a wolf pack algorithm (WPA) was used to optimize the GRNN, and a WPA-GRNN diagnosis algorithm was obtained. Then a simulation experiment was carried out taking a Sallen–Key bandpass filter as an example. It was found from the experimental results that the WPA could achieve the preset accuracy in the eighth iteration and had a good optimization effect. In the comparison between the GRNN, genetic algorithm (GA)-GRNN and WPA-GRNN, the WPA-GRNN had the highest diagnostic accuracy, and moreover it had high accuracy in diagnosing a single fault than multiple faults, short training time, smaller error, and an average accuracy rate of 91%. The experimental results prove the effectiveness of the WPA-GRNN in fault diagnosis of analog circuits, which can make some contributions to the further development of the fault diagnosis of analog circuits.

Variable speed and low voltage electrical drives are commonly operated by frequency converters. According to recent developments, there is a trend in the area of semi-conductors, that switching frequency and voltage slew rate will increase significantly. The aim of these semiconductors is to reduce the switching losses and to increase the switching frequency, which enables to reduce the size of passive components in the power- electric circuit. This results in less material effort and lower cost, for the power electronic component. However, electric motors operated by high slew rate inverters show problems in the winding insulation, which have to be analyzed. Such problems are well known for high voltage machines. Due to the increasing slew rate, this problematic occurs in low voltage machines nowadays as well. Here, the influence of fast switching semiconductors on the winding insulation system is studied, using accelerated ageing tests with fast switching high-voltage generators.

Cells of a prototype powered wheelchair can be designed in various connections to provide different supply voltages which has impact on the efficiency of other wheelchair drive elements. The impact of cell configuration and resulting battery voltage on overall efficiency of power elements have been studied to determine the optimal configuration and voltage of the pack. A brief description of a battery energy storage system was given, and main requirements and variables were introduced to reveal the flexibility of the battery design. The efficiency versus supply voltage plots of a drive converter and battery charger were presented and discussed to find the optimal battery voltage. The motor design was analyzed from the fill factor perspective. The calculated efficiency parameters of all drive power elements were used to discuss and select an optimal battery cell configuration.

The existence of inrush current poses a significant problem during the start-up process within three-phase voltage-source rectifiers. To address this problem, this study proposes a strategy to suppress the inrush current effectively based on the virtual-resistor- control method, while preventing the increase in cost of the system and complexity of the algorithm. First, a mathematical model is established based on the dq coordinate frame, and the primary cause of the inrush current is analyzed. Then, the design process of the virtual-resistor-control method is detailed. Finally, the accuracy and effectiveness of the proposed method are verified by simulations and experiments. The results show that the inrush current can be more than two times the rated current before the addition of the virtual resistor. The start-up process can be realized without the inrush current after the addition of the virtual resistor, it does not need to increase hardware costs, there is no secondary inrush current, and the sensitivity of the parameters and the complexity of control are low.

Disk motors are characterized by the axial direction of main magnetic flux and the variable length of the magnetic flux path along varying stator/rotor radii. This is why it is generally accepted that reliable electromagnetic calculations for such machines should be carried out using the FEM for 3D models. The 3D approach makes it possible to take into account an entire spectrum of different effects. Such computational analysis is very time-consuming, this is in particular true for machines with one magnetic axis only. An alternate computational method based on a 2D FEM model of a cylindrical motor is proposed in the paper. The obtained calculation results have been verified by means of lab test results for a physical model. The proposed method leads to a significant decrease of computational time, i.e. the decrease of iterative search for the most advantageous design.