Harmonic Filter System Research Articles

Analysis of Electromagnetic Processes in a Traction Network in Connecting a Reactive Power Compensation and Harmonic Filtering System at a Sectioning Station

To increase the railway capacity, a controlled static reactive power generator is connected at a sectioning station. To reduce the cost indicators of the controlled installation and decrease the power losses, a combined reactive power compensation and harmonic filtering system is proposed, in which the following components are connected in parallel: an uncontrolled bank of shunt capacitive compensation with reduced cost indicators and a static reactive power generator. The total reactive power of the combined system is equal to the specified one. At low traction loads, the static generator operates in the mode of inductive power generation, due to which reactive power is smoothly regulated over the entire load range. Since the existing generator power is reduced by 2-3 times (at the same set power), the total increased power losses are also reduced. For analyzing the electromagnetic processes in the traction network, an electric rolling stock nonlinear model is developed. The article shows how the traction current higher harmonic components are filtered and demonstrates the combined system operability in terms of reactive power compensation under various traction loads by analyzing the waveforms of electromagnetic processes.

The reactive power demand in DEMO: Estimations and study of mitigation via a novel design approach for base converters

In the present pre-conceptual design, the base converters to supply the main DEMO poloidal magnets are rated for 45 kA and about 10 kV. If the traditional design approach, based on thyristor bridges, was adopted, this would result in very large reactive power exchanged when low voltage values are required by the load. To satisfy the limitations imposed by National Grid Operators, the reactive power should be compensated inside the DEMO Plant Electrical System by means of a Reactive Power Compensation and Harmonic Filtering system. This could represent an additional cost and takes up a large area of the plant. This paper shows that the reactive power demand, estimated with an analytical model starting from the current/voltage waveforms foreseen in DEMO magnets, is huge. Therefore, an innovative approach, based on Active Front End converters, is proposed and compared with the traditional solution for coil power supplies.

The Power Characteristic Results According to the Superconducting Magnet Coil Load Tests of the Motor Generator System

When the poloidal field (PF) magnet power supplies (MPSs) of 11 units are operated, maximum power of 200 MVA is required to achieve long pulse operation of Korea superconducting tokamak advanced research (KSTAR). Motor generator (MG) system was installed to resolve the power shortage because the available grid power is only 100 MVA at the National Fusion Research Institute site. MG system is composed of mechanical devices (stator, rotor, bearings, etc.), power control devices (variable voltage variable frequency and exciter), power facilities (transformers, switchboard, uninterruptible power system, filter, dynamic brake, etc.), utilities (cooling water pump, heat exchangers, cooling fans, oil circulation pump, mechanical brake, etc.), and control systems. MG system supplies power to the PF MPS of 11 units. And we configure the reactive power compensator (RPC) and harmonic filter (HF) system to stabilize the MG power system. After installing the MG system, individual tests and dummy coil tests were conducted to determine the safety and performance of MG system. And we completed the commissioning of the MG system by carrying out the superconducting magnet coil load tests for the 2014 KSTAR experiment. MG system was operated up to 150 MVA of PF MPS with the RPC and HF system. And the maximum operating duration was about 100 s. In this paper, we discuss about the power characteristic results of the MG system according to the superconducting magnet coil load tests.

Analysing of Harmonics Affecting the Energy Quality in Opium Alkaloids Plant's Power System

The quality of energy has been defined to control harmonics caused by non-linear loads and international standards were brought to overcome the harmonic related problems. In determining the power quality, parameters like current-voltage harmonic, transient, flicker, current and voltage imbalance between phases, K factor are examined according to these international standards. The biggest disadvantage of harmonics is that they do not affect the power quality over an individual network but also affect the entire energy system primarily neighbouring facilities. Therefore, the energy system of Opium Alkaloids Plant was examined by using measurements information of current and voltage harmonics affecting the energy quality. And, it has been determined that the harmonics have a negative impact on energy quality. According to these findings, it has been proposed to install a well-designed filter for elimination of harmonics. Besides, it has been emphasised that new hardwares and devices should be chosen to support this harmonic filtering system in the future.

Simulation and test results of low-order band harmonic filters to decrease resonance phenomenon in the KSTAR power system

The superconducting magnet power supply which supplies superconducting magnet coil (SC) with the power to generate plasma during a KSTAR experiment for nuclear fusion research is a nonlinear load. Characteristic harmonics are generally produced since it converts AC to DC using 6 or 12 pulsed operation. However, non-characteristic harmonics or inter-harmonics are generated according to output control characteristics. Also, 95% out of the power generated from superconducting magnet coil is reactive power. Therefore, harmonic and reactive power occurring during operation have some bad influences such as voltage drop, voltage distortion and decrease in power factor on the KSTAR power system, and reactive power compensator (RPC) & harmonic filter (HF) system which is able to compensate harmonic and reactive power at the same time was established and has been operated [1]. However, out of non-characteristic harmonics and inter-harmonics caused by output control characteristics of superconducting magnet power supply, the more compensation volume of the RPC & HF system increases, the more voltage distortion with harmonic expansion is caused by harmonics in a low-order band due to the parallel resonance in a low-order band between the KSTAR power system and the RPC & HF system. As a result, it has serious effect on the injection capacity restriction of the RPC & HF system, the unstable operation control of superconducting magnet coil, and the operation of main cooling facilities. This paper presents reasons of the resonance phenomenon of the KSTAR power system and suggests a design plan of additional facilities for stable operation of the KSTAR power system, and proves their effects through the simulation and test results.

The simulation and test results of the TSC type RPC & HF system for enhancement of the KSTAR power system stabilization

The Korea Superconducting Tokamak Advanced Research (KSTAR) device requires a large pulse power to generate and confine plasma in order to function as a nuclear fusion device. Such a large pulse power causes voltage-drop and voltage-distortion in the electric power system, because it generates large reactive power and harmonic currents. These effects are detrimental to other experimental devices and deteriorate the power quality delivered by the power system. Therefore, it is important to stabilize the KSTAR power system by compensating for the reactive power and rejecting the harmonic currents using a Reactive Power Compensator (RPC) & Harmonic Filter (HF) system. The TSC type RPC & HF system has been fabricated to have a total capacity of 35MVar and included two features. The first is a fast response speed of within 10 cycles to compensate for the reactive power. The second is a stable KSTAR power system in which no resonance is detected due to the installation of the TSC type RPC & HF system. This paper presents simulation results of the TSC type RPC & HF system and test results of the plasma experiment of KSTAR carried out in 2009.

Stabilization of the KSTAR Power System for the First Plasma Operation

After more than ten years of construction, the Korea Superconducting Tokamak Advanced Research (KSTAR) device finally completed its assembly in June 2007. We conducted the first plasma operation from April 2008 to July 2008 and succeeded in the plasma generation in July 2008. The electric power system for the first plasma operation is made up of various electric devices, including 154-kV circuit-breaker systems, a 154/22.9-kV 50-MVA transformer, 22.9-kV circuit-breaker systems, and reactive power compensator (RPC) and harmonic filter (HF) systems. When the poloidal-field magnet power supplies were operated, the reactive power and harmonic currents (12n ± 1) were generated instantaneously in the KSTAR electric power system for the first plasma generation due to the characteristics of the KSTAR superconducting coils. The measured voltage drop and harmonics seriously affected the other experimental equipment as well. Therefore, it is important to compensate the reactive power and remove the harmonics with the RPC and HF system for the superconducting tokamak device. In this paper, we discuss the stability of the electric power system and the operational results of the RPC and HF systems during the KSTAR first plasma operation. Furthermore, the upgrade plan of the electric power system based on the KSTAR operation plan will be discussed.

Optimized combined harmonic filtering system

This paper presents a thorough analysis of the operation for the combined filtering system consisting of a passive filter with diodes connected in parallel with the capacitors and a low-power inverter. The diodes limit the voltage across the capacitors and the inverter starts to work when disturbances occur in the three-phase network, sending back to the network the excess energy taken by all the capacitors from the network during these disturbances. The proposed combined filtering system has reduced size and cost as well as high efficiency. Laboratory experiments and simulation results proving the effectiveness of the solution are also presented.