Double Converter Research Articles

Single‐pole tripped emergency control and multistep power recovery strategy for a symmetric bipolar VSC‐HVDC system

In a symmetric bipolar voltage sourced converter-high voltage direct current system (VSC-HVDC) with a conventionally independent power controller, a single-pole converter unit malfunction or conversion capacity limitation results in a power imbalance for this converter station. To address this, a centralized power control strategy with single-pole tripped emergency control and a multistep power regulation strategy for parallel double converter units is proposed. Firstly, considering the power conversion limitation or power asymmetrical operation caused by single-unit malfunction, the tripped emergency coordination between two converter units can be accomplished to realize a constant transmission power capacity of this converter station. Secondly, for the recovery process of the faulty converter unit, the multistep power switching strategy is adopted. When the fault has been removed and the faulty converter unit is deblocked to reconnect to the DC grid, the proposed strategy is used to achieve self-adaptive power regulation. By adopting this strategy, the large power fluctuations in the process of reconnection can be effectively alleviated. Finally, a simulator based on PSCAD/EMTDC is indicated. The results show that the developed control strategy can realize self-adaptive imbalanced power adjustment between two parallel converter units and single-pole tripped unit smoothing reconnection.

Electromagnetic Compatibility Analysis and Optimization Design of Switching Power Supply Printed Circuit Board

Printed Circuit Board (PCB) is not only an important electrical module of information equipment, but also an important source of electromagnetic radiation. Only when PCB works normally and is compatible with other electrical equipment, the whole information equipment can work normally. Because of the complexity of PCB structure and the difficulty of modeling, the EMC (Electromagnetic Compatibility) analysis of PCB is very difficult. For this reason, Taking the widely used full bridge current double rectifier converter as an example, aiming at the electromagnetic compatibility problems caused by the PCB design of the switching power supply, this paper proposes a simulation method based on the electromagnetic field by establishing the near-field radiation model of the PCB, analyzes the areas with high radiation intensity in the PCB layout, by optimizing the layout and wiring of the PCB, the electromagnetic compatibility performance of the switching power supply is improved. The simulation results show that the near-field radiation characteristics of PCB can be predicted by introducing the electromagnetic field simulation method in the design stage, according to the characteristics of the magnetic field, the optimal design is realized, so that the EMC of the switching power supply reaches the standard, and finally the working performance of the switching power supply is improved.

Research and Analysis of a Novel Voice Coil Motor With Wireless Power Supply

The moving-coil type voice coil motor (VCM) has very light moving mass, which can achieve higher reciprocating frequency and work efficiency. However, the power supply lead connected to the moving coil can be easily broken under long-term reciprocating motion, so it is rarely used in compressor drive systems. The core technology of the compressor development trend is a driving motor with high-efficiency, high reciprocating frequency, certain piston stroke, and light moving mass. Due to its structural characteristics, the moving-coil type VCM has broad application prospects. This article proposes a new structure for power supply of a moving coil VCM based on the principle of electromagnetic induction. The proposed VCM can overcome the problems of aging and disconnection of power supply lines caused by reciprocating motion, and meet the requirements of high-frequency and long-term repetitive action of the moving coil. The content of this article is as follows. First, the construction of the proposed VCM is introduced. Second, the power-driven circuit based on interleaving double switch forward converter is provided. Finally, two working modes of drive circuit for reciprocating motion are proposed. Simulation and experimental results verify the effectiveness of the method.

The inverter with reverse connected double converter driving unbalanced loads

ABSTRACT Inverter circuits play an important role in providing energy to multiple loads or energy lines. In cases where power lines or loads are unbalanced, it is important to balance and regulate the power it carries. Therefore, in this study, an inverter structure with an inverted connecting double dc-dc converter is used to drive unbalanced loads. While load balancing is performed by changing the widths of the pulse width modulation that make up the voltage in load balancing methods in other inverter studies, the maximum point of the generated voltage is changed by affecting the operating times of the converters in this study. First, the circuit structure and the working order of the circuit are given. Then three-phase balanced and unbalanced loads are driven. The unbalanced loads driven are finally balanced with the proposed circuit structure. Distortions of load currents are decreased as %3, 51. This distortion value is lower than 4% reported by the international IEEE, while the obtained load currents maintain a smooth sinusoidal structure.

Key technologies of ultra-high voltage hybrid LCC-VSC MTDC systems

The key technologies of ultra-high voltage hybrid LCC-VSC MTDC systems are investigated, focusing on the design of system configurations, converter topologies and the control and protection system. A double converter per pole of VSC connection is proposed along with the design of a 5000 MW VSC valve to develop a ± 800 kV/5000 MW large-capacity power transmission. The hybrid MMC topology capable of clearing the DC faults and the control strategy are developed to effectively improve the reliability in case of overhead line faults. The control and protection system of the LCC-VSC MTDC system is introduced to offer flexible operations under both normal and abnormal conditions, which includes voltage/current margin-based coordination, converter switch-in and switch-out, re-connection and drop-off of a third station. Simulations of an LCC-VSC MTDC system based on the LCC-VSC MTDC project are performed.

A Single Transformer for Active Cell Equalization Method of Lithium-Ion Batteries with Two Times Fewer Secondaries than Cells

In this paper, the concept of active cell-balancing technique, by using a multiple-outputs double-forward converter for lithium-ion (Li-ion) batteries, is investigated. It controls two times more cells than secondaries, and it equalizes eight cells in a series. In this method, four secondaries can reasonably be wound with the same back electromotive force (EMF). This means a low pin count on the transformer and a low bill of materials (BOM). The bridge uses four N-channel MOSFETs as switches, which means two times fewer transistors than cells, resulting in fewer switching losses. This scheme is applied for controlling the minimum voltage among the cells of the lithium-ion battery. It uses a multi-winding transformer based on a forward double converter structure. Conventional schemes using a multi-winding transformer for electric vehicles (EVs) require an equal number of secondaries per cell. This scheme requires one secondary for two adjacent cells, thus the number of secondaries is reduced by a factor of two. Also, the redistribution of charge from a high cell to a low cell does not require many switching components and little intelligence to determine low cell voltage detection. The basic principle of this method is to use the overall battery pack voltage as a reference to supply individual cells, using a forward converter containing a transformer with a well-chosen winding ratio. The experimental and simulation results are performed to verify the feasibility of the proposed system.

Dynamic and Static Characteristics of Double Push Rods Electromechanical Converter

Due to the influence of material characteristics and winding power, single output electromagnet has limited ability to improve the dynamic characteristic of electro-hydraulic valve. Therefore, an electromechanical converter with double push rods is proposed in this paper, which can simultaneously output two electromagnetic forces, can push or pull the valve core and sleeve according to the current direction and realize rapid operation of load. According to the electromagnetic principle and the magnetic circuit analysis method, the mathematical model and equivalent circuit of the electromechanical converter with double push rods are established. Through the finite element simulation model of the electromechanical converter with double push rods with the same magnetization directions, the changing rules of its magnetic field distribution and force–displacement behaviors are studied and analyzed. According to the analysis results, the electromagnetic mechanical parameters and mechanical structure of the electromechanical converter with double push rods are determined, and the prototype is made. The test platform for the push-pull characteristics of the electromechanical converter with double push rods is built, and its static and dynamic characteristics are tested and analyzed. The results show that the thrust and pull output characteristics of the internal and external push rods are basically consistent with the simulation output, and proportional to the current density of the coil; the push-pull hysteresis of internal and external push rods output force is less than 5%; and the dynamic time response characteristics of the displacement and force are obtained. The hysteresis effect of output force is improved effectively through the H bridge drive control circuit modulated by PWM. Compared with the displacement response of a single-winding electromagnet with a similar volume, it can effectively improve the dynamic displacement response. Follow-up work will further optimize the structure of the electromechanical converter and test the corresponding pilot valve. The research results provide a new theory for improving the output characteristics of electro-hydraulic pilot valve and have an extremely high engineering application value and broad application prospect.

Double Integrated-Buck Boost Converter versus Double Integrated-Buck Topology for LED Lamps

In this paper a comparative study between two different approaches for LED driving based on the double integrated buck boost and a double integrated Buck converter. It presents a single-stage, single-switch, transformer less ac/dc converter suitable for Led lighting applications. High Brightness Light Emitting Diodes (HB LEDs) can be seriously considered for replacing conventional halogen, incandescent and fluorescent lamps in general illumination including streetlights due to the rapid development in LED technology in recent years. In many offline applications, maintaining a high-power factor and low harmonics are of primary importance. Single stage power factor pre-regulation technology is mainly preferred in cost sensitive applications where power factor regulation is necessary, as adding additional power factor correction controller will surely increase the cost. Here a high-power-factor, long life integrated converter able to supply LED lamps from ac mains is presented. This topology integrates a buck-boost type power-factor correction (PFC) cell with a buck–boost dc/dc converter there by providing the necessary high input power factor and low Total Harmonic Distortion (THD). An isolation transformer increases complexities in the implementation of feedback and control. The proposed topology is non-isolated and hence much simpler in implementation. The main advantage of this converter is that this circuit uses only one controllable switch. The converter is used to provide power factor correction in streetlight application. A Double integrated buck converter finds application in fields of solid-state lighting. Buck Converter is widely used for step down dc-dc conversion when there is no isolation requirement. The narrow duty cycle of the buck converter limits its application for high step-down applications. The double integrated buck converter overcomes its limitation. This converter also provides high power factor and output current regulation. A Double integrated buck converter uses for the offline power supply for LED lighting based on the integration of a buck power factor corrector (PFC) and the tapped buck dc/dc converter having high step-down capability and good output current regulation. Due to the high reliability, the simple structure, and the low component count, the proposed topology effectively results to be very suitable for medium power solid-state lighting applications. From Comparative analysis of two circuits integrated double buck boost converter is found to be more efficient with high power factor and low THD.

A Proposal of Project of PI controller gains used on the Control of Doubly-Fed Induction Generators

This paper groups basic information about the control of doubly-fed induction generators (DFIG) for wind power generation. The DFIG stator is connected directly to the power grid and its rotor is connected by a double converter called back-to-back. To carry out the control of the generated power, are needed some calculations with complexity equivalent to the machine model, making it difficult to obtain controllers' initial parameters of a part of the system. In this sense, this paper has presented a proposal for the design of the gains of the proportional-integral controller (PI) used in the power vector control for the DFIG rotor drive side using the pole compensation technique. It has also presented the current mesh control of the converter connected to the main grid, the design of the DC link capacitance and the inductance of the harmonic filter. With the above proposals, satisfactory results were obtained both in simulation and in experiment, through an analysis of a simplified model of the machine model. The control derived from the simplified analysis of the model showed similar results compared to the complete and complex model of the machine proposed by other authors.

Low Input Current Ripple Quasi-Single-Stage Power Supply Based on Double Resonant Tank LLC Converter for Maglev Control System Applications

High input voltage, multiple low voltage outputs and high working temperature are the main design challenges for magnetic levitation (maglev) control power supply. The traditional solutions have several problems, such as the uncontrolled duty ratio, the poor cross-regulation capability and low reliability. In order to solve these problems, a quasi-single-stage solution employing the double resonant tank LLC topology is proposed and developed in this paper. The proposed solution can increase significantly the overall conversion efficiency because of the achieved soft-switching over the entire operation range. Moreover, the low input current ripple, high magnetic utilization and high reliability can be achieved. Experimental results of a 210-W laboratory prototype with 220–380[Formula: see text]V input and four outputs are presented to demonstrate the declared features.

도시철도 직류급전용 더블컨버터의 출력특성 향상을 위한 모드 변환 시 점호각 제어 연구

도시철도 직류급전용 더블컨버터의 출력특성 향상을 위한 모드 변환 시 점호각 제어 연구

The Double Forward Converter with Synchronous Rectification

In many switching power supply converters, diode rectifiers are used to obtain the DC output voltage. The conduction loss of these diodes rectifier contributes significantly to the overall power loss, especially for low-voltage, high-current converter applications. The conduction loss of rectifying diode is given by the product of its forward-voltage drop and forward conduction current. By replacing the diode rectifiers with a MOSFET operating as a synchronous rectifier (SR), the equivalent forward-voltage drop can be lowered and, consequently, the conduction loss can be reduced because the switching power supply converter need high efficiency. The double forward converter with synchronous rectification is proposed in this paper. The circuit’s guidelines of the double forward controller in the double forward converter and the synchronous rectifier controller in the synchronous rectification are also presented. Validity of the proposed double forward converter with synchronous is confirmed by simulations.

Analysis of optical fiber-based LP(01) ↔ LP(02) mode converters for the O-, S-, and C-Band.

This paper proposes a double fiber taper-based mode converter that converts LP(01) to LP(02) and vice versa. The first taper is used to convert LP(01) to some higher order LP(0m) (m>1) modes while the second taper suppresses the undesired higher order modes (m>2) and results in LP(02) overwhelmingly dominated. A simulation shows that conversion efficiency of almost 100% at the central wavelength of O-, S-, and C-Band, and above 98% over the S- and C-Band was achieved. Moreover, suppression of undesired higher order modes is more than 10 dB over the whole O-, S-, and C-Band. In particular, the suppression is more than 19 dB for the whole C-Band. The analysis also shows that the performance of the mode converter is not sensitive to slight variations of the converter's parameters. The same converter also can be used to convert LP(02) back to LP(01). It is shown that conversion efficiency higher than 99% and suppression of undesired higher order modes higher than 30 dB can be obtained. Further, a (de)multiplexer for an LP(02) and an LP(01) mode was designed using the mode converter combined with a symmetric directional coupler. The multiplexer is broadband and has an insertion loss less than 0.5 dB in the C-Band.

Research on the Performance of Point Absorber

Rational exploitation of wave energy makes great contribution to relief the current global energy crisis. Power generation has been taken into the agenda as the main form to utilize wave energy. The point absorber in this paper is simplified to three modules: floater, pontoon and chain. Based on the theory of linear regular wave, the research task of the point absorber is to improve the conversion efficiency and device reliability. This paper researched on the double floater wave energy converter by hydrodynamic numerical calculation, studied the factors that contain the PTO system damping coefficient, wave frequency and the device mass and other factor which can influence the energy conversion efficiency. At last, we found an optimized method for the energy conversion efficiency.

The Series and Parallel Energy Storage System Based on Super Capacitors

The series and parallel energy storage system based on super capacitors can quickly adjust a wide range of active and reactive power in two directions, which is a new way to improve the stability and power quality of new energy power generation system. In this paper, double converters structure is used to achieve the series and parallel compensation effect and their control strategies according to Instantaneous Power Theory. It is simulated in PSCAD that series and parallel energy storage system of super capacitor contribute to the impact on wind turbines power as environment conditions change. Simulation results show that the energy storage system can greatly improve the stability and power quality of grid-connected wind turbines.

A Novel Dead-Time Control Method for Double End Converter

In order to achieve symmetry of the drive signal and suppress the magnetic bias, a novel dead-time control method for the double end converter is put forward in this paper, which can generate two independent and complementary PWM waveforms by configuring EPWM (Enhanced Pulse Width Modulator) module. The magnetic bias problems of the double end converter, principle of EPWM module and adjustment process of the dead-time control method are analyzed. Two different dead-times can de realized by setting the rising edge delay and falling edge delay of the corresponding registers in Dead-band (DB) module in one cycle to meet the requirement of drive signals. Experimental research on the novel dead-time control method is done on the push-pull forward circuit and the experiment results verify the feasibility of the proposed method.

Interleaved Double Dual Boost Converter for Renewable Energy System

This paper presents an interleaved double dual boost converter (IDDB) used in renewable energy application where high voltage gain is required such as fuel cell or photovoltaic applications, etc. Two types of controllers are applied to this converter, 1) a controller based on Flatness properties for regulating the output voltage (outer loop); 2) a sliding mode controller for inductor current (inner loop). The variation of the input voltage is compensated by trajectory planning process. The validation of the proposed system is done through experimental results.

Study of Interleaved Double Dual Boost Converter for Renewable Energy Source System

This paper presents an interleaved double dual boost converter used in renewable energy application, for example, photovoltaic cell. The converter is interesting because its high voltage gain property. Its operating functions in the possible cases are detailed. Moreover, the presence of negative current in a certain operating point is investigated. The validation of the proposed system is done through experimental results.

LED Lamp Power Supply without Electrolytic Capacitors based on Integrated Double Buck-Boost Converter Operating in Full DCM

In this paper the integrated double buck-boost converter (IDBBC) operating with both stages in discontinuous conduction mode (DCM) is analyzed. The converter is intended to supply high-voltage LED lamps from the mains, typically in street lighting applications. A high input power factor is assured by operating the first stage in DCM, thus complying with current harmonic injection standards. In this work, the second stage is also operated in DCM as an option to the continuous conduction mode (CCM) that has been studied in a previous paper. The behavior of the converter with both stages in DCM is compared with that of the converter operation with the second stage in CCM. It is demonstrated that with both converters operating in DCM the filter capacitances are reduced even further, allowing for the use of long-life non-electrolytic capacitors. A laboratory prototype to supply a 70 W LED lamp with nominal voltage of 200 V from a 230 V/50 Hz mains maintaining the same design conditions as in the previous work is presented. A comparison of both prototypes is also carried out.

Power Quality Simulation of Grid-Connected Doubly Fed Wind Turbine

With the increasing proportion of distributed generation, higher requirement on power quality of distributed generation system is put forward by utilities. This paper first introduced the main indices and international standards related to power quality, and then built the DFIG dynamic model in which the double PWM converter and variable pitch control strategy were applied. Simulation of power quality of unbalanced system is conducted using PSCAD/EMTDC.