MHD instability at the cathode spot as the origin of the vortex formation in high-intensity plasma arcs

Magnetohydrodynamic instability in a high-intensity arc, similar to typical arcs in DC electric arc furnaces, is simulated using an induction based model under 2D axisymmetric conditions. Time-averaged results show a good agreement with steady-state calculated results expected for a stable arc. The transient results declare that z-pinch close to the cathode, occurring due to the high electrical current density, is responsible for arc instability in this region. The unstable behavior of the arc can be evaluated in a periodic procedure. Moreover, correlations between the fluctuations in total voltage drop curve and the arc shape are investigated: when the arc is in form of column (or bell) the total voltage drop is on a minimum peak; if there is an irregular expansion of the arc in form of arms, the total voltage drop shows a maximum peak.

Analysis of ocean wave power plant buoy system at Kelong

The potential of sea waves, located precisely in the Berakit area, can be used as electrical energy on a small scale. Kelong is a floating house situated on the coast, which anglers (fishermen) use to catch fish. In the Bintan area, there are two types of kelong, namely floating kelong and cacak (permanent) kelong. Floating kelong, as the name implies, is a kelong that can be moved anywhere. During the fish season, the kelong are offered to the middle of the sea, but if the west wind season or not during the fish season, the kelong will be brought ashore. On the other hand, kelong cacak are usually not far from the beach or coast and cannot be moved and operated at night by using a lamp to catch cuttlefish or anchovies. This research was conducted on Kelong Cacak and Floating Kelong (pontoon) located in Berakit, Disability Telok Sebong, Kabubapen Bintan. The power generation system was built using the buoy method. Based on the research results, the wave power plant can be driven by sea waves with an average height of 6 cm and produces a voltage and continuously the voltage is not always stable. The maximum peak output voltage is up to 15 Volt DC; after knowing the test results, the power plant can supply as a charger for the battery in the kelong cacak of 0.8839 Volt DC with an average battery voltage of 10.052 Volt DC and total voltage charging is 0.37 Volt DC, with average battery voltage 11.4902 Volt DC on Floating Kelong (Pontoon).

Implementation of a Hybrid ANN-Based Filter for the Reduction of Harmonic Currents

Harmonic distortions caused by non-linear loads (NLLs) affect the behavior of electrical systems, creating harmonics in the fundamental signal. As a result, this deteriorates the power quality. Therefore, this work proposes the implementation of a hybrid filter based on an artificial neural network (ANN) control system, focused on subharmonic, interharmonic and odd harmonic distortions generated by a three-pulse cycloconverter. In addition, a passive double tuned filter was implemented to damp even and odd harmonics. As a result, the simulation performed in MATLAB/SIMULINK showed that the responses produced by the ANN are approximate to the distortions present in the electrical system. Consequently, the levels of total voltage distortions (THDV) and total current distortions (THDI) are reduced. Therefore, the ANN control system improves the quality in the electrical network because the current and voltage harmonics comply with the electrical standards.

New Sub-Module with Reverse Blocking IGBT for DC Fault Ride-Through in MMC-HVDC System

When integrating multi-grid renewable energy systems, modular multi-level converters (MMCs) are promising for high-voltage DC (HVDC) transmission. Because of the characteristics of the system, however, it is more difficult to prevent a fault at the DC terminal than at the AC terminal of the MMC. Accordingly, a fault ride-through (FRT) strategy for the operation of the MMC in the DC terminal is required for stable system operation. In this paper, a solution for closed-circuit overcurrent caused by a permanent line-to-line DC fault is proposed. This method is able to reduce the fault current through the adjustment of the slope of the total voltage in the system by operating a sub-module having lower switching losses and fewer passive devices compared with existing topologies. Additionally, through the equivalent circuit of the proposed scheme in a sub-module in case of a fault, the FRT mechanism for the fault current is explained. The feasibility of this proposed technique was verified through time-domain simulations implemented by Powersim, Inc.

A Theorem on Power Superposition in DC Networks

The superposition theorem, a particular case of the superposition principle, states that in a linear circuit with several voltage and current sources, the current and voltage for any element of the circuit is the algebraic sum of the currents and voltages produced by each source acting independently. The superposition theorem is not applicable to power, because it is a non-linear quantity. Therefore, the total power dissipated in a resistor must be calculated using the total current through (or the total voltage across) it. The theorem proposed and proved in this paper states that in a linear DC network consisting of resistors and independent voltage and current sources, the total power dissipated in the resistors of the network is the sum of the power supplied simultaneously by the voltage sources with the current sources replaced by open circuit, and the power supplied simultaneously by the current sources when the voltage sources are replaced by short-circuit. This means that the power is superimposed. The theorem can be used to simplify the power analysis of DC networks. The analysis results are validated via numerical examples.

A Theorem on Power Superposition in DC Networks

The superposition theorem, a particular case of the superposition principle, states that in a linear circuit with several voltage and current sources, the current and voltage for any element of the circuit is the algebraic sum of the currents and voltages produced by each source acting independently. The superposition theorem is not applicable to power, because it is a non-linear quantity. Therefore, the total power dissipated in a resistor must be calculated using the total current through (or the total voltage across) it. The theorem proposed and proved in this paper states that in a linear DC network consisting of resistors and independent voltage and current sources, the total power dissipated in the resistors of the network is the sum of the power supplied simultaneously by the voltage sources with the current sources replaced by open circuit, and the power supplied simultaneously by the current sources when the voltage sources are replaced by short-circuit. This means that the power is superimposed. The theorem can be used to simplify the power analysis of DC networks. The analysis results are validated via numerical examples.

High-Speed and Large-Amplitude Resonant Varifocal Mirror

We design, fabricate, and measure high-speed resonant varifocal mirrors for a reflective type focus scanning optical element. A circumference supported type mirror and a node supported type mirror with a 1 mm diameter driven by an electrostatic actuator are investigated. In the node supported type, a larger amplitude compared to that of the circumference supported type was obtained. The fabricated mirror could operate at approximately 450 kHz with axisymmetric deformation. The focal length was calculated to be ±28 mm at an applied total voltage amplitude of 150 V.

Optimal volt/var control of distribution system using MOPSO

This paper presents a novel method for solving multi-objective Volt/Var control of radial distribution system. The Volt/Var control is formulated as a multi-objective optimization problem which consists of the following objectives: minimization of real power loss, minimization of total voltage deviation and minimization of number of OLTC’s and capacitor operation and voltage fluctuations for a day-a-head in Distribution system.The Proposed MOPSO Algorithm is used to find the optimal settings of control variables such as On-Load tap changer (OLTC) and Shunt Capacitor. The proposed MOPSO algorithm is tested on a standard IEEE33-bus and 69-bus distribution system.

Harmonics Mitigation Based on the Minimization of Non-Linearity Current in a Power System

Harmonic issues in power systems are becoming an important topic for industrial customers and power suppliers alike due to their adverse effects in both consumer appliances as well as for utility suppliers. Consumers should seek to reduce harmonic pollution, regardless of voltage or current distortion already present in the network. This article suggests a new method for suppressing distortions by using the non-linearity current index (NLCI) to determine the shunt single-tuned passive filter (STPF) compensator value in non-sinusoidal power systems, with the objective of maintaining the power factor within desired limits. The objective of the proposed method is to minimize the nonlinear current of customer’s loads in the power system at the point of common coupling (PCC). Moreover, the proposed design takes into consideration other practical constraints for the total voltage and individual harmonic distortion limits, ensuring compliance with (Institute of Electrical and Electronics Engineers) IEEE 519-2014 guidelines, maintaining distortions at an acceptable level while also abiding by the capacitor loading constraints established in IEEE 18-2012. The performance of the optimally designed compensator is assessed using well documented IEEE standards based on numerical examples of nonlinear loads taken from previous publications.

Numerical Simulation Research of Fracmemristor Circuit Based on HP Memristor

Since we cannot solve the equation, we know nothing about the properties of the fracmemristor circuit. In this paper, HP memristor is used in fracmemristor circuit for the first time. After a series of mathematical processing, the HP fracmemristor can be equivalent to two parts which are represented as F and VM, respectively. The F part is the fractance. The VM part is related to the current, and it can best reflect the fracmemristor property of the circuit. Therefore, we hope that we can understand the fracmemristor circuit by the simulation research of the HP fracmemristor circuit. Firstly, the amplitude frequency characteristic and phase frequency characteristic of HP fracmemristor are obtained by using Matlab. And compared with the fractance, they have different characteristics. After that, the 1/2 order fracmemristor property is studied. By approximating processing the 1/2 Laplasse operator and then using Laplasse transform and inverse Laplasse transform, we can get the total resistance change with time, the changes of total resistance with the current figure, the voltage of part F changes with the current, the voltage of part VM with the current changes, as well as the total voltage with current changes. From these diagrams, the U-I diagram of the VM section intersects at two points. The currents at these two points are symmetrical about the origin, and the voltages at the two points are slightly different. Moreover, the magnitude of the current and voltage is stable at the point of intersection, and does not change with the magnitude of the input current. For HP fracmemristor circuits, its properties depend on the size of the current. When the current is very small, the HP fracmemristor exhibits the characteristics of fractance, and the influence of the VM part can be ignored. With the increase of current, the effect of fractance F is reduced, and the effect of VM is increased. When the current increases to a certain size, the output of the circuit is the same as that of the VM part, and the effect of the fractance F part can be ignored.