In this paper a predictive control technique for an indirect matrix converter is proposed. The control strategy allows the output current control and the instantaneous reactive input power minimization of the converter without any weighting factor in the controller and, at the same time, the operation at fixed switching frequency. Simulation results validate the proposal under both steady and transient states.
The measurement of grounding system impedance may be affected by power system frequency interference and its harmonics. The Shifted Frequency Method (SFM) is potentially insensitive to the electromagnetic interference. In this paper, we evaluate this method in the hydroelectric power plant for two different load conditions of the connected overhead power lines. Presented field tests results further validate and justify the SFM method.
In two-pole Induction Machines the shaft leads to a fictitious increase of the inner yoke in the rotor. This effect is influenced by axial cooling vents in the rotor. Pre-existing analytical calculation methods estimate the magnetic voltage drop in the rotor for only one path of the magnetic flux. This is done by simplified boundary conditions and leads to inaccurate results. In this paper a semi-analytical method is introduced. Therefore the branch current method is used and the solution of the nonlinear equation system is disclosed. The results of the analytical calculations are validated by Finite Element Analysis. The involvement of the semi-analytical calculation in the magnetic circuit is illustrated. Further refinement steps are described. Applications for the semi-analytical calculation method are introduced for machine design considerations.
This paper deals with the concept of the stochastic optimization methodology for power line designing, which allows optimizing transmission network planning. The paper presents a comparison of both methods applied for selecting the best line design alternative - the deterministic economic intervals method and the stochastic approach based method, taking into account market conditions. Both methods are utilized for designing overhead power lines, including the choice of main line parameters such as tower height, type and coordinates, conductor type and cross-section, line fittings, etc. Moreover, the use of High Temperature Low Sag conductors - a part of the advanced technology - was evaluated alongside the use of conductors of the traditional type. The optimization problem is formulated as minimization of the total annual costs. The proposed methodology is tested in the developed tool, which is realized in MATLAB software by using the Monte Carlo method, and in an overhead power line designing program - PLS-CADD. Two basic case studies for verifying the proposed power line planning solution are presented in the paper.
In the paper some results of investigation of the single-phase transformer based AC pulse modulation mode regulated system of network voltage stabilization are presented. Switching processes in the device are regarded to application of transistor switches with proper snubbering circuits. Computer simulation as well experimental investigation of a model are done and its outcomes are presented.
The increase of storeyedness of dwelling houses and administrative buildings, far of the large point loads and separate regions with high load densities results in the necessity to enter higher level of voltage in the urban power supply system. These tendencies are typical for Riga city - the capital of Latvia and main administrative, industrial, financial, business and cultural centers. Existent 10 kV base voltage in Riga cannot provide increasing requirements to the feed of the large loads in infrastructure of modern cities. The introduction of higher voltage level should be justified by the economical and technical possibilities and advantages in comparison with the existing system of power supply. The paper focuses on the conception of 20 kV voltage introducing in Riga, evaluate the technical and economic possibilities for the progressive or sharp changing of voltage, develop the methodology of management of voltage level changing process in the distribution network of the large city. In the paper the technical economical model of the urban power supply system for the its qualitative and quantitative evaluation is presented. The optimal parameters of the power supply system and its technical economical indices at different load densities in the city and its suburbs are determined.
In an isolated and rural locations where the energy is derived from renewable sources, the load will suffer from large fluctuations due to the unpredictable nature of the underlying phenomena (wind or solar). This paper presents the implementation of practical control for standalone renewable energy source able to feed an isolated load with regulated voltage and satisfactory energy quality in remote areas. The proposed control scheme is verified both by simulation and through experiments. The simulation and experimental results are presented.
The simulation approach for assessment of adaptive algorithms based on stochastic search is described in this paper. In this research, the adaptive algorithms are used for railway safety system to improve existing braking by automatic smooth and precise braking of a train, avoiding passing the restrictive signal and prevent crashes. Simulation results are grouped for different types of trains to test the ability and efficiency of adaptive algorithms to find the solution in a wide range of conditions and situations.
This paper is considering application of smart meter data to predict electricity consumption of household consumers. The availability and amount of data is suitable for in-depth statistical analysis of electricity consumption profiles and the study of consumer's behavior. Prediction of electricity consumption is very important for electricity traders to balance their electricity purchase and sales portfolio, as well as to prepare optimal price products (offers) for their clients. Electricity consumption data of 500 consumers divided into 6 consumers groups was analyzed. The consumption data was derived from smart meters. As the next step, modern methods of electricity consumption forecasts would be applied to predict household electricity consumption.
In this study, a home energy management system structure is developed in order to determine the optimal commitment of a smart-household. Two types of loads are explicitly modeled: non-thermostatically controllable (electric vehicle, shiftable appliances) and thermostatically controllable loads (air conditioner, electric water heater). Furthermore, small-scale self-production is considered by means of a photovoltaic system. A test case using realistic data is presented in order to investigate the combined effect of the aforementioned assets under real-time pricing demand response.
This paper presents a multifunction control strategy for the stable operation of Distributed Generation (DG) units during grid integration. The proposed control model is based on Direct Lyapunov Control (DLC) theory and provides a stable region for the appropriate operation of DG units during grid integration. Using DLC technique in DG technology can provide the continuous injection of maximum active power in fundamental frequency from the DG source to the grid, compensating all reactive power and harmonic current components of grid-connected loads through the integration of DG link into the grid. Application of this concept can guarantee to reduce the stress on the grid during the energy demand peak. Simulation results are presented to demonstrate the proficiency and performance of the proposed DLC technique in DG technology.
The increase in nonlinear appliances in households is largely driven by their affordability. In the case of lighting appliances, it is necessary to use energy-saving light sources. A case study of the possibility of simultaneous connection of large amounts of lighting appliances and other nonlinear appliances used in households is conducted in this paper.A variant of distribution systems in housing estate is selected as an example. Simultaneous operation of a large number of these appliances in certain time periods and thus possible voltage distortion caused by higher order harmonics can be expected.This paper deals with two variants of possible load. In the first case the scenario with probable load is chosen. In the second case it is verified for extreme harmonics influence. Calculations are performed for the radial and the meshed network. In the particular case, calculations are verified by measurement.
This paper investigates into enriching a (step-down) classic Fibonacci switched capacitor converter voltage target ratios set by applying a multiphase switching. Simple theoretical closed-form expressions for equivalent output resistances are obtained using charge flow balance analysis that also provides a useful insight into switched capacitor and output voltage ripples. It is shown that employing a balanced multiphase switching allows for essential switched capacitor and peak-to-peak output voltage ripple (or, alternatively, output filter capacitance) reduction.
The concept of Carrier-Based Demand Response (CBDR) programs in Smart Multi-Energy Systems (MES) is proposed in this paper. It is discussed that by establishing the bi-directional relation between multi-energy demand and MES through the penetration of multi-carrier device technologies, the opportunity of demand-side participation in system operation can be activated. In this paper, the external dependency caused by multi-carrier devices is employed as a demand response. The CBDR is introduced as the flexibility of end-use to change the conversion pattern of input carriers into required demand. As the CBDR program is influenced by energy carrier prices, upstream network obligations and also the customer's behavior, its uncertainty is effectively modeled in this paper. The results compare the difference between the stochastic and deterministic approaches to the problem and show the improved accuracy through the stochastic modeling. The role of those customers that are not taking part in CBDR program is also investigated.
Stepper motors are widely used in open-loop positioning applications. They are the choice of actuation for the collimators in the Large Hadron Collider, the largest particle accelerator at CERN. In this case the combination of precise positioning requirements and the highly radioactive operating environment is unique. The latter forces both the use of long cables to connect the motors to the drives and also prevents the use of standard position sensors. However, reliable and precise operation of the collimators is critical for the machine. A problem arises however from the use of stepper motors in open-loop. The mechanics of the collimators can wear due to the abrupt motion and torque profiles that are applied by the motors. Closed-loop position control allows smoother movements to be applied but it requires position feedback. The use of sensors in radioactive environments is very limited for reliability reasons. In order to allow the use of position sensors without reducing the long term reliability of the whole system, the possibility to switch online from closed to open loop is proposed and validated in this paper. It allows the use of closed-loop control when the position sensors function correctly and to switch online to open-loop when there is a sensor failure, without the need to stop the machine.
This paper presents a new idea to benefit of eliminated harmonics current by using a new topology of hybrid active power filter (HAPF) to compensate harmonics current to be sinusoidal in order to feed some loads. The design and simulation of a new three phase HAPF circuit using a shunt active power filter (APF) connected in parallel with a capacitor (C) line of a (LC) low pass filter (LPF) has been submitted. The first aim of the new circuit is to use the LPF as a path to pass the fundamental frequency (50 Hz) current and eliminate other high order frequencies, while APF compensates high order frequencies and compensate reactive power of the circuit. The second aim is to benefit from the modified wave in the high frequency branch of LPF to use it as a useful power in order to feed different loads. In addition, With this topology, the resonance problem (which usually happens between LPF and the system) will disappear because of using of APF in the high frequency branch. The control circuit has been designed based on the instantaneous reactive power theory. A Clarke transformation equations and hysteresis current controller have been used in the HAPF's design. The proposed circuit has provided a good harmonic elimination, total harmonic distortion (THD) reduced, reactive power compensation and a reasonable sinusoidal waveform.
In this paper authors present a method for optimal sizing of supercapacitor (SC) energy storage system (ESS) for braking energy recovery in tram network. The method is applicable for segmented tram networks with radial feeding topology and a stationary storage system installed in traction substation. The method is demonstrated for one traction substation of Riga public transport network.
A hardware-in-the-loop (HIL) model of a centrifugal pump is proposed. The HIL simulator consists of the pump and pipeline imitators built on the basis of the variable speed drives (VSD) connected via the programmable logical controller (PLC, and profibus communication components. The mathematical description of the pressure maintenance represents a core of the simulation methodology. To study the system, a series of tests have been conducted that proved the designed system flexibility and accuracy in pressure imitation at both the static and the dynamic modes.
