Thyristor Bridge Research Articles

Air‐cored axial flux permanent magnet generator for direct driven micro wind turbines

AbstractThis paper presents the development of an Air‐Cored Axial Flux Permanent Magnet Generator (ACAF PMG) integrated for direct battery charging scheme for urban and rural micro‐wind turbine applications rated at 1 kW. The proposed generator has a Single Stator Double Rotor configuration with a relatively short axial length. In this paper, the analytical model for generator sizing is presented and the main parameters are defined. Novel analytical model is presented to determine the required number of turns for each phase in order to produce a balanced voltage in the three phases. The generator is electromagnetically analyzed using Finite Element model and simulated using Matlab/Simulink to predict its performance under several operating conditions. The effect of retainment ring type on the generator performance is also demonstrated. The machine is harnessed to a battery bank via a three‐phase fully controlled converter using six bridge thyristors to regulate the output voltage delivered from the generator to the battery. Generator model and simulation results are validated via experimental tests. The preliminary experimental results showed a good match with the simulation results. Moreover, the proposed machine is compared favourably with other counter machines of similar configuration and power ratings in terms of machine size, power‐to‐weight ratio, and voltage regulation. This paper therefore demonstrates the concrete benefits of utilizing the axial flux PMG in scavenging energy to generate electrical power from micro wind turbines.

Sliding mode approach for control and observation of a three phase AC-DC pulse-width modulation rectifier

Introduction. For AC-DC conversion systems, the electrical systems typically use thyristor or diode bridge rectifiers, which have relatively poor performance. Nowadays, three-phase pulse-width modulation rectifiers are widely applied in various applications for their well-known intrinsic benefits, such as adjustable DC link voltage, unity power factor, bidirectional power flow and very low total harmonic distortion. Purpose. The objective of this work is to achieve better stability and dynamic performance using sliding mode strategy for control and observation. Methods. For that purpose, first a sliding mode controller is introduced on the DC-link side to ensure a fast and accurate response of the output load voltage. Then, the sliding mode approach is employed to control the quadrature and direct components of power to maintain the input power factor at unity. Finally, this approach is used to design two observers for grid voltage estimation and online variation of load resistance. To overcome the problem associated with the use of the classical low-pass filter, an adaptive compensation algorithm is used to compensate the attenuation of the amplitude and phase delay of the observed grid voltages. This algorithm is based on the use of the two low-pass filters in cascade and ensures the minimization of chattering. Results. Comparative studies have been carried out between sliding mode control method for controlling the three-phase AC-DC pulse-width modulation rectifier and other conventional techniques. The validation by simulation and the tests carried out gave very satisfactory results and proved the effectiveness and feasibility of the sliding mode for both control and observation of three phase pulse-width modulation rectifier.

Impact of power supply fluctuation and part load operation on the efficiency of alkaline water electrolysis

Contrary to traditional electrolysers which operate continuously at their nominal load, future alkaline electrolysers need to be able to operate over a wide load range due to the variability of renewable electricity supply. We have investigated how the residual ripples from thyristor-based power supplies are influenced by the operating load of the system, and how these ripples affect the efficiency of alkaline electrolysers. For this, a simulation tool was developed which combines a six-pulse bridge thyristor rectifier model with closed-loop current control and semi-empirical electrolysis models. The electrolysis models can simulate the potential response to both direct and high amplitude alternating currents for lab-scale and industrial electrolysers. The electrolysis model of the lab-scale electrolyser was validated with experiments with a square wave current input. The models show that without filters the ripples result in a total system efficiency loss of 1.2–2.5% at full load and of 5.6–10.6% at a part load of 20% depending on the type of electrolyser. The implementation of an optimized L-filter suppresses residual ripples and reduces the efficiency losses to 0.5%–0.8% at full load and to 0.8–1.2% at the minimum load.

ПРОЦЕССЫ КОММУТАЦИИ ВЕНТИЛЬНЫХ ТОКОВ ПОЛУПРОВОДНИКОВОГО ВОЛЬТОДОБАВОЧНОГО УСТРОЙСТВА

One of the main tasks of a railway power supply system is the provision of increased traffic volumes especially on direct current railway sections. For this reason the personnel of traction substations uses various means and methods of power supply strengthening including boosters representing two parallel thyristor bridges shunted by diodes. The paper considers three processes of commutation of rectifier currents arising in boosters: between two thyristors, between a shunt diode and thyristors and between thyristors and a shunt diode. The paper presents a detailed mathematical description of these processes. As a result, the authors gained a general formula for calculation of all three angles of commutation, with the use of which the authors have carried out all calculations. Reliability of gained expressions is confirmed on a physical model.

Simulation Studies of Energy Recovery in a BLDC Motor-Based Kinetic Energy Storage

This paper presents research conducted on the development of an innovative system to increase the amount of energy recovered from a high-speed kinetic energy storage based on a three-phase permanent magnet brushless (PM BLDC) motor/generator (mogen) with a flywheel-shaped rotor, compared to the efficiency obtained for standard solutions with power electronics systems. This kinetic energy storage is currently under development. In the system presented in the paper, the regulated DC output voltage of the 6T thyristor bridge is controlled with a tolerance within ±10% of the reference voltage for a variable power load. The input voltage of the rectifier is a three-phase trapezoidal-shaped voltage from the rotating mogen, whose amplitude can vary from 0 to 650 V and frequency from 0 to 250 Hz voltage. The article presents example results of simulation tests of the mogen-based kinetic energy storage model with the thyristors’ firing angle control system. As part of the research, a prototype of the rectifier was built on a laboratory scale, to confirm the validity of the assumptions regarding the synchronization and control method of the bridge using a new design of the thyristor gate drivers.

Режимы работы полупроводникового вольтодобавочного устройства для регулирования напряжения на тяговых подстанциях

One of the ways to strengthen the DC power supply system of the main railways of Russia is the use of semiconductor voltage-boosting devices for voltage regulation at traction substations. The work of diode and thyristor bridge rectifiers connected in series with it is considered in the article. The analysis is performed under the condition that active and reactive resistances of the supply network and the converter transformer are zero. It was found out that, depending on the magnitude of the control angle, such a converter can have two modes of operation. For these modes, time diagrams of the rectified voltages of both the thyristor bridge and the entire converter are constructed. Expressions are obtained for determining the average values of the rectified voltages of a 12-pulse diode rectifier of a serial type and a 12-pulse thyristor rectifier of a parallel type connected in series with it. The calculation of the adjustment characteristics of this adjustable converter is performed.

Comparison of thyristor and insulated-gate bipolar transistor -based power supply topologies in industrial water electrolysis applications

The demand for green hydrogen is growing as the increasing production of pure hydrogen can no longer be based on fossil hydrocarbons. As water electrolysis would move from niche to a significant consumer of emission-free electricity, the efficiency of electrolytic gas production, lifetime of water electrolysis systems, and balance in the electricity grid become essential. The operational and investment costs of an industrial-scale alkaline water electrolyzer with four practical rectifier topologies are investigated. The results show thyristor-based rectifiers provide poor quality for the AC and DC sides, which leads to nonoptimal specific energy consumption (SEC) of the water electrolyzer and a notable reactive power component. Transistor-based topologies may offer up to 4.5% lower SEC of the electrolyzer than the conventional 6-pulse thyristor bridge. The reactive power results in additional costs in either investments in compensation equipment or regular allowance costs. An additional DC/DC converter can be installed to improve the power quality for the electrolyzer, but the second conversion stage adds to the system complexity and cost without eliminating reactive power. A modular single-stage rectifier based on insulated-gate bipolar transistor (IGBT) bridges is suggested as an alternative to provide improved power quality for both the electrolyzer and the electricity grid.

Electromechanical installation based on high power current pulse generator

Electromechanical installation containing electromagnetic s noid with a piston operating in reciprocating motion mode has been developed. Technologies with similar operating modes are widely used in various industries (mechanical engineering, metallurgy, mining, mechanics, robotics, as presses for forging and stamping, as well as jack-hammers in crushing devices for coal, ore and rock). An economically effective generator of high power unipolar current pulses (with unique systems that allow adjustment of the main parameters in a wide range and with high speed: the frequency of pulse reproduction, amplitude) was used as a power source for electromechanical installation. The principle of operation of the generator is based on periodic discharge of pre-charged capacitors to a low-resistance active-inductive load. Generator contains power unit, consisting of a capacitor discharge unit for load; a generator control system (GCS), consisting of a capacitor charging unit (reversible thyristor converter with counter-parallel connected thyristor bridges); a recharge unit and an automatic control system of the ACS. According to the known equations, parameters of mechanical and electrical parts of the electromechanical installation were calculated: initial coordinate of the piston; magnetomotive force arising from change in inductance L(x) ; spring force; the force of resistance to the piston, proportional to the speed of its movement; force action on the piston; amplitude, duration and frequency of reproduction of current pulses. A simulation model of the installation has been developed in the MATLAB-SIMULINK environment. The graphs of transient processes during operation of the installation at idle and under load were built. Analysis of the operating modes of the installation was carried out. Developed electromechanical installation for influencing load with the aim of its destruction or deformation with a system of automatic control of parameters makes it possible to regulate process parameters with high speed: force and distance traveled by the piston.

Nonlinear Autoregressive with Exogenous Model to Diagnosis Aircraft Motor Faults Under Different Operating Conditions

Robust fault analysis (FA) including the diagnosis of faults and predicting their level of fault severity is necessary to optimize maintenance and improve reliability. This study aimed at presenting a technique to diagnosis faults of electronic switch in permanent magnet synchronous motor in Aircraft. The current output of both thyristor bridges and the diode of system excitation is monitored under healthy and faulty operations. Features extracted at different operations using Multi-scale wavelet decomposition (MSWD) to extract the useful features. MSWD features are used to train nonlinear autoregressive with exogenous model which sequentially operated to evaluate the fault level in case open circuit that developing across a switch under different operating condtions. The two models have been tested and designed due to the simulated data, where the results showed acceptable effectiveness in the diagnosis of various types of fault.

Effect of power quality on the design of proton exchange membrane water electrolysis systems

Water electrolyzer technologies may play a key role in the decarbonization of the fossil-fueled world economy. Electrolytic hydrogen production could bridge emission-free power generation and various energy end-use sectors to drive the energy system towards a net zero-emission level. In order to reduce the economic cost of the required energy transition, both the overall system efficiency in converting electrical energy into the chemical energy carried by hydrogen, and the material used to build electrolytic cell stacks, should be optimal. The effect of power quality on the specific energy consumption of proton exchange membrane (PEM) water electrolyzers is investigated with a semi-empirical cell model. An experimentally-defined polarization curve is applied to analyze cell-specific energy consumption as a function of time in the case of sinusoidal current ripples and ripples excited by an industrial 12-pulse thyristor bridge. The results show that the effective electrolyzer cell area should be up to five times as high as an ideal DC power supply when powered by the 12-pulse thyristor rectifier supply to match the specific energy consumption between the two power supply configurations. Therefore, the improvement of power quality is crucial for industrial PEM water electrolyzer systems. The presented approach is applicable to simulate the effect of power quality for different proton exchange membrane electolyzers.

A Flexible Didactic Platform for Thyristor-Based Circuit Topologies

The objective of this article is to present a flexible didactic platform for thyristor-based circuits. When compared to the existing academic and commercial teaching platforms the proposed one is modular and shows more flexibility. Using the same basic thyristor module, several topologies can be built, including solid-state relays, thyristor bridge rectifiers, and others. All development steps are detailed. Examples of teaching applications, such as the operation of a controlled rectifier, are presented to demonstrate the functionality and didactic usage. Experimental results are also included for the presented applications.

Power quality and reactive power of water electrolyzers supplied with thyristor converters

Industrial water electrolyzers apply direct current in kiloampere ranges. Therefore, rectifiers are typically based on thyristors despite the high amplitude current fluctuation excited by the rectifier. This paper studies the effect of thyristor rectifiers on the power quality of the electrolyzer stack and the supplying AC grid. The thyristor bridge excites high current and power fluctuation causing additional losses in the electrolytic cells. Further, the both AC supply side and DC output power factors are low especially under partial load conditions. The reactive power is divided into phase shift and distortion components. In the case of thyristor rectifier without any passive filter components the distortion reactive power component is dominating. The simulated results are supported by the power factor measurements of an industrial alkaline water electrolyzer. It is proposed that electrolyzer stack manufacturers should give requirements for the DC power quality to maximize the stack energy efficiency and lifetime.

Power quality estimation of water electrolyzers based on current and voltage measurements

The ripple of the supplied direct current has a significant effect on the energy efficiency of the water electrolyzer cell. Hydrogen production is defined by the current mean value, but current harmonics generate additional losses in the electrolyzer cell. However, the direct measurement of the DC current in the kiloampere range may be a challenging task compared with the voltage, which is practically in the range of a few hundreds volts in the electrolyzer stack. The effect of current harmonics on the energy efficiency and the voltage mean and root-mean-square (RMS) values is analyzed analytically based on the measured polarization curve of the PEM electrolyzer cell. The results show that both in the case of a theoretical sinusoidal current ripple and a practical thyristor bridge supply, the voltage mean or RMS values do not give a reliable estimate of the power quality. Instead, the voltage waveform as a function of time or the difference between the current mean and RMS values should be monitored.

Распределение мощности между обмотками тяговых трансформаторов на основе цифровой фильтрации

The purpose of the paper is to present an improved method of active power equalization on the secondary windings of the Scott traction transformer in the power supply systems of AC railways located in the proximity to the facilities of the agroindustrial complex, gas supply systems, etc. Active power distribution using automatically controlled thyristor bridges with pulse width modulation and capacitive storage devices allows to reduce the asymmetry and unsinusoidality of currents and voltages in the primary three-phase network almost to zero at suddenly appearing and disappearing mobile traction loads, such as high-speed electric trains. To control the currents and voltages in the windings, digital filtering algorithms have been applied, which form the required number of voltage levels at a given frequency of pulse width modulation. The efficiency of these algorithms is confirmed by computer simulation in the Matlab environment. It is proposed to improve the method of power equalization on the secondary windings of the Scott traction transformer with the use of digital filtering-based automatic control algorithms. The power equalization device together with the Scott transformer ensure high quality of electric energy in the primary three-phase network in terms of asymmetry and unsinusoidality of currents and voltages, due to which electromagnetic compatibility of the traction power supply system and the power supply system of various agricultural facilities, oil and gas complex, and others located in the proximity of railways is provided.

Assessing the Impact of Harmonics and Interharmonics of Top and Mudpump Variable Frequency Drives in Drilling Rigs

Declining extraction costs and process efficiencies have incented the revival of the oil and gas sector postrecession. The application of drilling rigs has been done more efficiently. These loads are very large, temporary in nature, and mobile. The drilling of each well can be done as quickly as a few hours and typically not more than a few days. These massive loads are complex to own, maintain, and operate, as a result few specialized drillers share the market. Because of the requirements for variable speed and control, drilling rigs are driven by variable frequency drives (VFDs), which are in their clear majority of older technologies such as six-pulse thyristor bridge or SCR-driven motors. These technologies are known to impose steep ramp rates (up and down) as well as rich harmonic content and variable, typically low, power factor. Furthermore, the locations of drilling rigs are typically remote, where distribution systems, if present, are weak, which lead to large background voltage distortions when such loads are present. This paper presents measurements, simulations, and analytical assessments of the characteristics and effects of harmonics and interharmonics (IHs) generated by top-drive and mud-pump VFDs in a large drilling rig operated in Alberta, Canada. Measurement results reveal very high harmonic and IH generation. To further refine the impact assessment of these harmonic emissions, the harmonic attenuation effect of the VFDs is quantified to avoid overestimating the harmonic generation of the loads. The thermal impact of the current harmonics on the coupling transformer is also quantified.

초전도 에너지 저장 장치용 3상 사이리스터 브리지의 비대칭 제어에 관한 연구

초전도 에너지 저장 장치용 3상 사이리스터 브리지의 비대칭 제어에 관한 연구

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.

Study the Effect of Serial Inductance on Reducing the Current Harmonic Distortion of Three-Phase Bridge Rectifier

The aim of this paper is to analyze the influence of adding serial inductance in AC side of the 3ph -6 pulse bridge rectifier on the reduction of harmonic distortion rate. A simulated model with serial inductance was analyzed. The 3-phase 6-pulse diode bridge rectifier was chosen because it corresponds to the operation of the 6-pulse thyristor bridge rectifier at maximum load (while keeping the angle α = 0). Both the total harmonic distortion (THDi) and the power factor (PF) for the circuit have been measured. The results obtained of the THDi has been recorded for four values of serial inductance and results was compared with the (IEEE 519-1992) standard. Comparison results indicates that for values of inductive reactance (Xi) up to 67% cause a reduction of THDi which is above the standard values, while for (Xi) more than 67% cause a reduction in THDi within the acceptable standard level. Analyzing of results prove that the adding of serial inductance at the AC side leads to good reduction in harmonic distortion rate, but with some reduction in power factor value, which results in some energy losses.

CONTROL SYSTEM OF STEEL BATTERY CHARGER

A practical realization of control of a diode–thyristor bridge is provided in this paper. The proposed control logic is applied to an NiCd accumulator charger. These accumulators are used for power supply of electrical devices and equipment in CFR locomotives. The control system provides a regular mode of NiCd accumulators charging and discharging, and, in this way, their long lifespan. A hardware configuration and a control algorithm for efficient NiCd accumulator charging and preventing overcharging and overheating are provided.

Diagnostics of the thyristor bridge fault based on the detection of the line-frequency second harmonic in the output current of an AC/DC converter

In this paper was presented the technical procedure implemented for the fault diagnostics of the thyristor bridge in an AS/DC converter. During the development of the new generation of digital controllers for AC/DC converters, it was required for these devices to have a possibility for a real-time detection of the thyristor converter fault. Thyristor bridge fault should be detected without the need for the state monitoring of the particular power semiconductor switches or rapid fuses. Thyristor bridge fault was identified using the measurement of the line-frequency second harmonic in the rectifier output current signal. Output voltage and current waveforms were presented, as well as the current spectra, in the cases of the thyristor bridge operation without one switch. The operation principle was described for a protection from an asymmetric operation of a thyristor bridge. A negative influence of high-order harmonics was analysed on the particular rectifier components, both in the cases of the output voltage control, as well as for operation in the current limit mode.