Firing Angle Research Articles

Enhanced Active Filter for Single-Phase Controlled Rectifier Applications

Active filter can be used to increase the performance of single-phase controlled rectifier by reducing the generated ripple and harmonic distortion. Active filter can also increase power factor and efficiency of thyristor. In this work, active filter was designed by using NPN Bipolar Junction Transistor (BJT) compared with active filter created by utilizing NPN Metal Oxide Semiconductor Field Effect Transistor (MOSFET). The obtained efficiency of BJT based active filter with firing angles of 0° to 90° were 87.01% - 96.67%. Whereas, MOSFET based active filter produced comparable efficiency between 90.62% - 96.07%. It can be seen that MOSFET based active filter produced higher efficiency at firing angle of 0° which was 90.62% compared to BJT based active filter that has produced efficiency of 87.01% at the same firing angle. Both active filters obtained similar power factors within the range of 0.57 lagging – 0.92 lagging. It is expected that this work can be useful for the design of active filters for various power electronics applications including the design of High Voltage Direct Current (HVDC) power transmission system.

Particle swarm optimization technique for multilevel inverters in solar harvesting micro grid system

In on grid solar generation system the irradiance causes voltage mismatch as a result of this the nonlinearities increase in the output voltage of the multilevel inverter. The sunlight is not uniform at all places, variation in irradiance is inevitable when it comes to solar power. The Solar power is not similarly circulated there is a change in sun orientation with respect to geometrical positions. The un symmetrical voltage results in unbalancing and introduces more harmonics. The article proposed here analyses a topology where a DC-DC converter is utilized ahead of the multilevel inverter so as to overcome the voltage varieties, thereby reducing the harmonics in the system. Particle swarm optimization is carried out in minimizing the Harmonics. Different observation and studies working stages their simulations and results for both are studied and recorded. Since solar energy is an essential, a complete analysis of this is done. A variety of initial calculations in designing the converter are also carried out. Similar calculations are also carried out informing the solar panel and harvesting the energy. By facilitating MATLAB simulation of particle swarm optimization for firing angles employed in multilevel inverter along with the converter. The measure of total harmonic distortion THD obtained is taken as a measure of evaluation for the performance of this combined system.

Angle of impact determination from bullet holes in a metal surface

Using the best-fit ellipse method, single bullet impacts in thin sheet metal were assessed to investigate the accuracy of impact angle estimation. When a bullet passes through a metal panel, the yielding nature of metal causes changes to the metal surface and the resultant hole. This deformation of the metal complicates the assessment of single impacts using the ellipse method. Determining the correct impact angle may not be obvious and results in considerable errors between the known and calculated angle. To determine if the calculated angle varies in any particular way to the known angle, impacts were created on metal panels using six different types of 9 mm ammunition and seven angles from 90° to 14°. Impact angles, determined using the ellipse method, were compared with known firing angles and the error pattern assessed. The results show an error pattern with a significant quadratic relationship for three ammunition types, with the error pattern for the remaining three ammunitions not explained by a quadratic formula and requiring further study. Results suggest that single bullet impacts for a given type of ammunition with a quadratic error pattern, can be assessed with accuracy due to a more consistent behavior. This characteristic pattern of error requires further study but is a promising step for determining an accurate impact angle and bullet path from a single impact point in a metal surface.

Converter based distributed drive system with enhanced dynamic response

In this paper optimized converter based motor drive system is presented with enhanced dynamic response. A detailed design including source, storage and motor drive is proposed for various operating modes. The controlled distribution system is experimented to meet a guideline of the industry specific applications. Furthermore, compensation is provided from the power regenerated inside the drive. The storage with cascaded converters can supply the additional energy requirements when the drive is subjected to transients. The optimized controller is designed to control the individual phase voltage, speed and the firing angle of cascaded and lead converter. A voltage balancing control with isolated power regenerative control system is established to achieve the smooth power flow in the designed drive system. The experimental output voltage, Power flow and speed control are presented to explain the systems dynamic performance.

A New High-Efficiency Power Management Circuit for a Novel Two-Phase Compensated Pulse Alternator

A new, high-efficiency power management circuit for a novel small-sized, two-phase compensated pulse alternator (compulsator) is designed to provide high pulsed powers, making itself a promising compact power supply system for a number of applications, like producing nanosized powders by explosion of wires. The design and manufacture of this novel small-sized compulsator was successful with favorable efficiency validated. Along with this, compulsator is a newly designed high-efficiency power converter circuitry designed by this study for converting the alternating power generated by the compulsator to unipolar pulse power. The designed converter consists of two parallel single-phase rectifiers on the two-phase power generated by the designed compulsator. The rectification is enabled by using thyristors as power switches for the converter. The switching of thyristors is made possible by all-analog controller circuits, which decide the firing angle based on sensed pulsed power in two phases in real time. Experiments are conducted, with the result showing that the designed compulsator and power management circuit can generate a peak current up to the level of 2.178 kA. and a current density of 96.133 kA/m2, which was never seen by prior works.

Voltage and frequency control of wind–diesel power system through adaptive sliding mode control of superconducting magnetic energy storage

The random nature of wind power along with active and reactive load changes results in both frequency and voltage fluctuations in a wind–diesel power system. In order to improve the dynamic performance by regulating the frequency as well as voltage of the system, an adaptive sliding mode control strategy is proposed on superconducting magnetic energy storage unit interfaced with a wind–diesel power system. Sliding mode control strategy developed with the superconducting magnetic energy storage unit achieves fast and effective exchange of real and reactive power via firing angle control of the converter. With the help of suitable switching surface design and use of adaptive control law, chattering elimination and controller robustness is achieved. This work is carried out in MATLAB/Simulink, and simulation results presented shows a positive impact of proposed scheme.

Feasibility Analysis of Magnetorheological Absorber in Recoil Systems: Fixed and Field Artillery

Magnetorheological (MR) absorbers in the artillery recoil systems are usually used to dissipate the impact energy as much as possible and reduce the recoil force transmitted to the artillery carriage, while the firing stability of artillery during buffer process is rarely considered. In this paper, we analyzed the firing stability characteristics of the fixed artillery and the field artillery systems and established corresponding mechanical models. Then, we proposed the ideal recoil F-v curves of these two kinds of artillery respectively. The “platform effect” of recoil curve was taken as the recoil force control target of the fixed artillery, while based on the firing stability, the linear segmented recoil curve was drawn up as the ideal recoil buffer control target of the field artillery. To verify the feasibility and controllability of the designed multi-stage MR absorber in two kinds of recoil buffer system, the impact tests were conducted under different current loadings. The test results show that the designed MR absorber can realize different buffer control effects by changing the input current, but the ideal “platform effect” recoil curve of the fixed artillery cannot be completely realized due to small controllable damping force output. In the field artillery recoil system, the MR absorber can realize ideal recoil buffer control in the range of 0 to 25 degree firing angles.

Extended SVC Modeling for Frequency Regulation

This letter proposes an extended SVC model with thyristor firing angle law to improve transient performances of frequency and voltage of multi-machine power systems. A firing angle control synthesis framework for imposing any desired SVC susceptance value without linearization around a fixed operation point is proposed. In light of this method, the designed firing angle controller only requires local bus measures and parameters. The performance of the extended firing angle-controlled SVC model is evaluated on a 150-bus 27-machine power system and compared with conventional SVC model.

Enhanced Commutation Failure Predictive Detection Method and Control Strategy in Multi-Infeed LCC-HVDC Systems Considering Voltage Harmonics

Voltage harmonics are very likely to cause commutation failure (CF) in multi-infeed LCC-HVDC systems. However, this has not been sufficiently considered in earlier CF detection methods and control strategies. In this paper, by incorporating the voltage harmonics into the inverter quasi-steady-state model, an extinction angle predictive algorithm is firstly presented to propose the enhanced CF predictive detection method. Compared to earlier methods, the enhanced method can detect both local and concurrent CFs more accurately. Moreover, the enhanced method is then used as the starting unit of the enhanced CF predictive control strategy to enable its effective activation. To develop the enhanced strategy, a firing angle order predictive algorithm is introduced using the inverter quasi-steady-state model with the voltage harmonics considered. Compared to earlier strategies, the enhanced strategy can mitigate both local and concurrent CFs more effectively. Furthermore, the response speed of the enhanced method and strategy is evaluated by comparing CF characteristics and signal process delay. It is shown that since the timescales of the voltage harmonics induced CFs are longer than signal process delay, the response speed is fast enough to ensure their practicality. Finally, simulation results based on a dual-infeed LCC-HVDC system validate the enhanced method and strategy.

Determining the features of loading the improved bearing structure of a platform wagon for the transportation of military equipment

The paper reports the improvement in the bearing structure of a platform wagon that transports military equipment and is involved in artillery fire. A special feature of the platform wagon is the presence of rotary sectors made from a composite material with viscous or elastic-viscous links, which makes it possible to absorb the kinetic energy that is transmitted to the frame when firing from the wagon, as well as enables the loading/unloading of military equipment from its side. We have investigated the dynamic loading of the bearing structure of a platform wagon for military equipment transportation and combat operations. A mathematical model has been constructed, which takes into consideration the movement of the bearing structure of a platform wagon when firing from it. It has been considered that the platform wagon is loaded with two anti-aircraft guns. The mathematical model was solved in the Mathcad programming environment. The study was conducted in a flat coordinate system. We have determined the accelerations that act on the bearing structure of a platform wagon. The maximum acceleration rate, in this case, is about 3.6 m/s 2 at bouncing oscillations and 4.0 m/s 2 at galloping oscillations. In other words, considering the proposed technical solutions, the dynamic loading of the bearing structure of a platform wagon in the vertical plane at firing decreases by almost 30 %. The magnitude of the acceleration is almost independent of the firing angle in this case. The derived acceleration values have been taken into consideration in determining the strength indicators for the bearing structure of a platform wagon. Calculation was carried out by the method of finite elements in the CosmosWorks programming environment. The maximum equivalent stresses in the bearing structure of a platform wagon amounted to about 285 MPa; they are concentrated in the region where the bearing structure rests on the trolley. Consequently, the durability of the bearing structure of a platform wagon is ensured. Modal analysis of the bearing structure of a platform wagon has been conducted. The values of the natural oscillation frequencies are within allowable limits. Our research would contribute to designing innovative structures for platform wagons

Analysis of energy flows in the power supply system with a thyristor voltage converte

A numerical analysis of energy flows in a three-phase power supply system with a sine wave EMF source, active load and a thyristor converter that distorts the sine waveform and generates higher harmonics is performed. The influence of the thyristor non-sinusoidal voltage on the energy flows and the power factor of the source is analyzed. Thyristor converter is considered as a nonlinear electric power unit consuming electricity from the primary power source at a fundamental frequency, part of which is converted and returned back to the network as a secondary energy stream of zero-sequence systems and higher harmonics, thereby reducing the overall power factor and the quality of electricity becomes worse. It is analyzed the influence of the considered harmonics quantitative composition on the accuracy of the currents and voltages calculations. The dependence of the higher harmonics amplitudes on the thyristor firing angle is established. The constant component and the 2nd order harmonic voltage are the most denoted in the thyristor harmonics spectrum. In general case it is shown that in the nonlinear circuit with a sinusoidal power source, even in the absence of inductive and capacitive electric load, the fundamental current harmonic of the power source does not coincide in phase with the sinusoidal EMF of the source. Thus, the thyristor can be considered as a reactive inductive element that consumes reactive power of the fundamental frequency of current, regardless of the its firing angle and the presence of other reactive elements in the system. Therefore, in order to increase the power factor, it is necessary to compensate the reactive power of displacement only at the current fundamental frequency, which should be recorded by electronic meters. It is proposed to use the relative current value of the first harmonic of the power source to characterize the effect of the secondary energy flow on the total power factor. In a four-wire network, the presence of a thyristor converter causes a significant current increasing in the neutral wire, even under symmetrical phase loading, due to the zero sequence currents flowing, which are multiple of three, and they must be taken into account during wire cross-section selection and power losses calculation. It is proposed the practical measures to limit the level of higher harmonics and improve the electricity quality.

Induced Magnetism of the MoS2 Monolayer during the Transition Metal (Fe/Ni) Bombardment Process: A Nonadiabatic Ab Initio Collision Dynamics Investigation.

The source of induced magnetism in the MoS2 monolayer induced by transition metal (Fe/Ni) collision is investigated using nonadiabatic ab inito molecular dynamics simulations that take into account high-spin and low-spin energy states during trajectory integration. By considering various metal firing angles, a strong interaction between the Fe/Ni atom and the MoS2 surface can be observed because of enormous increase in the kinetic energy of the metal atom. When firing along the Mo–S bond, the Fe bullet is pulled more strongly than when firing along the S–Mo–S bisector. Spin polarization of MoS2 is gradually induced when Fe approaches the surface and eliminated when Fe roams around a potential energy trap on the MoS2 layer. We observe that there is charge transfer between Fe and Mo atoms, which enhances the probability of electron pairing and leads to instantaneous vanishing of total magnetization. The Ni–MoS2 system is found to establish a total magnetization of 1.5–4 μB when Ni is 2.0 Å above the surface. Interestingly, the strong bonding attachment of Ni suppresses the band gap to at least 40%.

A Hybrid Compensator Configuration for VAR Control and Harmonic Suppression in All-Electric Shipboard Power Systems

This paper proposes a cost-effective compensator to suppress harmonics and compensate the power factor of all-electric shipboard power systems (SPSs). This compensator, which is based on a fixed capacitor-thyristor controlled reactor (FC-TCR), behaves as a low-pass filter and therefore can reject both low and high-order harmonics. Moreover, the FC-TCR compensator is featured by the low switching losses; hence, it can effectively be implemented for low and medium voltage applications. The design of the filter is detailed via equivalent lossy circuits, which exhibit the mechanism of the harmonic mitigation. Furthermore, theoretical analyses and mathematical developments are suggested to enhance the filtering performance. Besides, details of the Fixed-Point iteration technique which is applied to extract the firing angle of the TCR are conducted. A practical SPS is selected to ensure and demonstrate the performance of proposed methodology via thorough simulations under MATLAB/Simulink environment. The obtained results verify the theoretical analyses and confirm the effectiveness of proposed solution.

Reduced Harmonics Generated and Reactive Volt-Ampere absorption of HVDC Converter Using By-Pass Switch

Control of a conventional converter station which uses a three-phase controlled bridge for converting AC to DC and vice-versa is achieved by fast-acting control of the valve firing angles. Tap-changers which are fitted on the converter transformer provide a near constant AC voltage input to the bridge to correct relatively slow changes of AC voltage. This paper describe a modification of the conventional bridge circuit, using by-pass valves connected to tapping points on the secondary winding of the transformer. This scheme permits a wide range of voltage control with a reduction in both the harmonic generation and the reactive voltampere absorption, and possibly eliminates the need for an on-load tap-changer on the converter transformer. Experimental results on a laboratory model compare well with the predicted values.

Harmonic interaction of a static Var compensator with AC power system containing multiple non-linear loads

In this paper a study of the impact of the harmonics generated by a static Var compensator (SVC) is presented. The SVC is modeled, in the harmonic domain, as a coupled current source by using the complex Fourier transforms. Then, this model is converted to polar form to be integrated into the harmonic power flow program. This approach has been carried out on the IEEE 14 bus test power system, in order to show its effectiveness in evaluating the impact of harmonics, injected by the shunt compensating devices, and its interaction with the AC transmission system, in meshed power networks. Since the SVC consists of a thyristorcontrolled reactor (TCR) and a fixed capacitor, the harmonic currents are functions of the TCR thyristors firing angles. The variation of the total voltage harmonic distortion as function of firing angle changes and location of nonlinear loads is clearly presented and discussed.

Comparison of an Off-Line Optimized Firing Angle Modulation and Torque Sharing Functions for Switched Reluctance Motor Control

In this paper, a comparison of the simple firing angle modulation method (FAM) and the more advanced torque sharing function (TSF)-based control of switched reluctance motor (SRM) is presented. The off-line procedure to tailor and optimize the parameters of chosen methods for off-the-shelf SRM is explained. Objective functions for optimization are motor efficiency, torque ripple, and integral square error. The off-line optimization uses a finite element method (FEM) model of the SRM. The model was verified by measurement on the SRM. Simulation results showed that FAM has comparable efficiency to TSF, but has a much higher value of torque ripple. The presented off-line procedure can be used for single or multi-objective optimization.

Estimation of Dynamic Compensation for Renewable-Based Hybrid DG in Radial Distribution System Using Least Error Iterative Method

In this paper, wind diesel-based hybrid electrical system is proposed as distributed generator (DG) for radial distribution system (RDS). Since renewable-based DGs and especially wind operated electric generating system requires reactive power for its excitation along with the reactive power demand for maintaining the voltage profile at all buses in RDS, a fast and adequate dynamic compensation is required along with DG. The main contribution of this paper is to optimize the amount of reactive power supplied by dynamic compensator using new proposed approach of least error voltage constraint iterative approach. The paper is starting with the selection procedure of most sensitive bus satisfying three voltage stability indices fast voltage security index, line quality factor and voltage stability index followed by the selection of DG optimal size using optimization approach with multiconstraints all together, namely total real and reactive power loss, voltage limits voltage stability indices and voltage stability indices. The result shows how the dynamic compensator can maintain voltage level by releasing additional reactive power with the adjustment of firing angle for different levels for multidynamic load changes.

Investigation of sidewall height effect on the burning rate and flame tilt characteristics of pool fire in cross wind

In the current study the combining effect of sidewall height and cross air flow on the mass burning rate, flame height and flame tilt behavior of pool fire has been experimentally investigated. The mass burning rate increases as the cross wind velocity increases. The presence of sidewalls also influences the mass burning rate, as it is increased at lower cross wind velocities and decreased as this velocity further increases. A dimensionless parameter is introduced to illustrate the sidewall height effect on the mass burning rate. The effect of sidewall height on burning rate, flame height, and flame tilt angle of pool fire is further investigated. The flame height is an exponential function of a new dimensionless parameter Fr˜. Based on the experimental results, new empirical correlations are proposed to predict flame height and flame tilt angle α in relation to the combining effects of sidewall height and cross wind.

Method for testing output limit of AVR in AC exciter excitation system

The excitation system of synchronous generator plays an important role in the static and dynamic stability of power system. ‘Guide for modelling generator excitation system’ requires that the excitation system of new generators should be modelled and remodelled when the excitation system is upgraded. Testing the output limit of AVR is an important content of modelling. Considering inability of tetsing the output limit of AVR in AC exciter excitation system, this paper analyzes the reason using test data firstly, then proposes a new method to test the output limit of AVR, by modifying the maxim firing angle, the output limit can be got, the new method is verified during modelling test of a 145MW generator finally.

Replication of the Al/Ti Metal Intermetallic Laminates Using LS Dyna for Tungsten Alloy Penetrator Application

In this study, the simulation of the Al/Al3Ti metal intermetallic laminates was done using finite element analysis software LS Dyna, under high-speed impact loading using a tungsten projectile. These MILs were processed by diffusion bonding under the condition (575 °C, 4 MPa and 6 h), which was further annealed for 48 h. In LS Dyna, the projectile was fired at different velocities such as 900 m/s, 1200 m/s and 2000 m/s to varying angles of 0°, 30° and 60°. In each case, the penetration depth of the projectile and the number of layers damaged were found to understand the resistance offered by the MILs to the projectile. The time versus projectile penetration depth graph and the corresponding stress distribution in the MILs in each case were plotted to understand the extent of damage caused. Further, the velocity, energy and crack density distribution graphs were extracted from LS Dyna to understand in detail the journey of the projectile through the MIL. It was found that greater the angle of firing, the lesser the penetration depth of the projectile but at the cost of more damage to the layers up to which the projectile penetrated through the MIL.