Bipolar Converter Research Articles

High gain bipolar converter with reduced input current ripple for fuel cell integrated DC microgrid

High gain bipolar converter with reduced input current ripple for fuel cell integrated DC microgrid

Multi‐port bidirectional isolated DC–DC resonance converter with constant phase current for application in bipolar DC microgrids

AbstractThis paper proposes a new DC–DC bipolar resonance converter that combines a dual‐active‐bridge and a multi‐port resonance Buck‐Boost converter. This structure uses a resonance network between the input and output ports, which has the following advantages: it creates a constant current supply in the open‐loop mode; it keeps the current phase of the output ports constant under different loads; and it allows reversing the power from any output port by adjusting the phase shift of its switches, if the converter is connected to a DC microgrid. In this way, power can be exchanged among each of the output ports and input ports. The advantages of this converter are bidirectional power exchange, power exchange between output ports, soft switching, high efficiency, integration of transformer parasitic elements, and the modular capability to connect multiple resources at the input. Furthermore, the proposed structure of the bipolar converter has been implemented for verification purposes, and its results are presented in three modes: open loop, voltage control, and current control. Additionally, the results of different modes of power sharing and their bidirectionally are shown.

A Symmetric Bipolar Quadratic Buck–Boost Converter With Synchronous Triple Switches

A novel non-isolated bipolar DC-DC converter is described in this study. The proposed converter provides negative and positive outputs with the same voltage level and common ground. It exploits three power switches with the synchronous operation, resulting in a simple controller and driver implementation. Compared with the conventional counterpart DC-DC converters, the proposed converter offers buck-boost ability with a wide control range of the switching duty cycle. Additionally, the proposed converter draws a continuous and smooth current from the DC input source, making it an excellent choice for renewable energy sources (RES) and energy storage systems (ESS). Likewise, the proposed quadratic converter can provide a higher voltage boost ability with the same switching duty cycle compared to the existing transformerless bipolar converters. Hence, it offers lower conduction losses and higher efficiency for the same demanded output voltages. Theoretical analysis and experimental results based on a sample prototype are presented to prove the proposed converter's performance in CCM mode.

Contribution to the Development of a Smart Ultrasound Scanner: Design and Analysis of the High-Voltage Power Supply of the Transmitter

A smart ultrasound scanner plays an important role in the transition to point-of-care imaging. DC–DC bipolar converters are essential in the generation of the ultrasound burst signal as they power the piezoelectric transducer. The conventional bipolar converter has minimal output gain and high-voltage stress, and the longer duty cycle on the semiconductors produces high conduction losses and reduces the efficiency of the system. The transmitter supply voltage is minimal, necessitating the use of high-gain bipolar converters. This proposed study is concerned with the development of an improved high-output voltage gain symmetric bipolar DC–DC converter topology which may be suitable for applications such as powering a smart ultrasound scanner transmitter. The proposed converter combines the conventional single-ended primary inductor converter (SEPIC) with a voltage multiplier cell (VMC) to improve voltage gain, transistor duty cycle, efficiency, and reliability. The present study describes the working principle of the proposed converter. The analysis of the voltage gain is carried out in continuous current mode (CCM) and discontinuous current mode (DCM), taking into account the nonidealities of the device. The simulation of the proposed system is carried out in the numerical environment Matlab/Simulink in order to verify its characteristics. A prototype model is realized and the experimental study presented validates the theoretical arguments and simulations. Due to the advantages of continuous input current, self-balancing bipolar outputs, and small component size, the proposed converter is a suitable choice for smart ultrasound transmitters.

Reconstruction of QPSK Modulation Digital Communication Learning with Rewiring Modicom 5/1 and Modicom 5/2

Communication systems are very decisive in modern warfare, the use of long-range weapons without crew requires a long-distance communication system using digital modulation communication. One of the basics of digital modulation communication that is important is QPSK modulation, so the Department of Electronics develops learning by conducting research on QPSK modulation and demodulation by conducting research on series block systems built on Modicom 5/1 and Modicom 5/2. Modicom 5/1 consists of blocks, namely the separation of serial data into MSB and LSB data, Unipolar to bipolar converters, Modulator I and Modulator Q and the summation of the Op-Amp. The Modicom 5/2 consists of a QPSK detector, a two-order filter, a comparator and a decoder differential. The results of the study prove that serial data from modicom 3/1 is in the form of serial data (D0,D1,D2,D3,D4,D5) separated by MSB data separator blocks (D0,D2,D4) and LSB (D1,D3,D5), serial data MSB and LSB (unipolar data standard (0V/+5V)) are converted to bipolar standard digital data (-4V/+4V) by a unipolar to bipolar converter block system. Balance Modulator (IC 1496) with MSB signal input ( I ) on modulator 1 carrier frequency of 960kHz (∟0º) and 960 kHz (∟-180º) on modulator 2 is LSB (Q) will output data in the form of an analog sine signal with a frequency of 960 KHz with different phase according to carrier signal '0'=∟-90º or '1'=∟-270 . the sum of the Module I and Q signal modules into phase angles of 00(45º),10(135º),11(225º), 01 (315º). The QPSK detector by means of the information signal is generated 4 times, the phase is detected (IC PLL) then divided by 4 , phase difference angle as control switch signal I and Q to get signal I and signal Q . The I and Q signals are filtered by fourth order butterworth then the I and Q signal data as comparator inputs to get a logic 0 or 1. Data I and O as logic data (0/1) as MSB and LSB data are combined again into discrete serial data with blocks differential decoder by using the PISO register (parallel input serial output) using IC 17HC175.

A Bipolar Output Active-Switched-Inductor Converter for Bipolar DC Microgrid

A bipolar DC microgrid shows good performance since it improves the efficiency and system’s reliability. To transmit power to the load, several DC-DC converters are required by the conventional bipolar DC microgrid, which results into large weight, volume, and high cost. To integrate bipolar DC microgrid with the photovoltaic (PV) module, a novel bipolar output converter is proposed in this paper. This converter possesses very simple circuit configuration and can achieve a high step-up voltage gain by adopting active-switched-inductor (ASL) network; meanwhile, bipolar output voltage is between positive line (P), negative line (N), and common ground (O), which can offer three voltage classes (Vdc, +0.5 Vdc and -0.5 Vdc). To verify the precision of the analysis of the proposed converter, a prototype has been designed and experiments are performed in the lab.

A new scheme of zero-sequence overcurrent protection of converter transformer based on zero-mode inrush current characteristics in station area

Under the development trend of AC/DC hybrid power grids, converter transformers are indispensable as AC/DC conversion equipment, whose safety and stability are particularly important. There have been many serious accidents where the zero-mode inrush current(abbreviated as ZMIC) of high-impedance transformers caused the zero-sequence backup protection of the transformer and even the upper-level line to malfunction. As a type of high-impedance transformer, the converter transformer may cause the existing zero-sequence protection(abbreviated as ZSP) to malfunction due to the ZMIC generated during no-load operation. However, its winding connection form and no-load operation method are different from ordinary high-impedance transformers. There may be sympathetic interaction between multiple transformers. So, it is necessary to analyze the ZMIC separately.Through the existing ZMIC equivalent circuit of converter transformer, the amplitude relationship and attenuation characteristics of four bipolar converter transformer ZMIC are clear, which lay the foundation of the following protection scheme.The fact that ZMIC may cause the zero-sequence overcurrent protection to malfunction is found through PSCAD (Power Systems Computer-Aided Design) simulation. An inrush current identification scheme based on the station area information of the relationship between zero-mode inrush fundamental wave and harmonic amplitude is proposed. Considering the system resistance, closing angle, CT saturation, and fault conditions, the effectiveness of the proposed scheme and its superiority compared with the existing inrush current identification methods are verified.

Bipolar Bidirectional DC-DC Converter for Bi-Polar DC Micro-grids with Energy Storage Systems

ABSTRACT This paper proposes a non-isolated bipolar bidirectional DC–DC converter with an interleaved switched capacitor for bipolar DC micro-grids suitable for both low-power and high-power applications to achieve high-voltage gain. Interleaved structure on the low-voltage side is proposed to realise current sharing to reduce current ripple and switched capacitor topology on high-voltage side to achieve high-voltage gain. Soft switching, high efficiency and simple control make this converter employable in several applications such as electric vehicles, energy storage systems, etc. Simulation and hardware results are presented to highlight the merits of the proposed converter topology.

Design of an efficient bipolar converter with fast MPPT algorithm for DC nanogrid application

SummaryA single‐input bipolar converter has been proposed along with a fast MPPT tracking algorithm. The proposed converter is used as an interface for PV panel to perform twofold task of effectively extracting the maximum power from the PV side and efficiently delivering the extracted power to the load. For effectively tracking the MPP (maximum power point) of PV panel, a modified perturb and observe (MP&O) algorithm has been proposed in the paper. Proposed algorithm works effectively even under fast variations of irradiation and ambient temperature. The proposed converter has been developed with a target application in DC nanogrid by providing two loading points with amplitude balanced bipolar outputs. Moreover, least input current ripple (compared with other conventional DC‐DC converters) aids the MPP algorithm in improving the tracking efficacy. As the proposed converter has synchronous switching operation at both output terminals referred to input side, the power conversion efficiency of the converter is very high. Two out of three switches used are ground referenced; thus, design complexity of the converter is greatly reduced. Proposed converter with the MP&O algorithm has been analyzed, and the simulation results are obtained using MATLAB/Simulink. A laboratory developed prototype is used to experimentally validate the proposed converter.

Performance of MPPT-Based Minimum Phase Bipolar Converter for Photovoltaic Systems

The change in environmental conditions and dynamic loading distort the smooth and stable MPPT operation. Conventionally, boost and boost-derived converters are used for MPPT operations, which inherently display right half plane zero (RHPZ). The presence of RHPZ causes a transient undershoot and overshoot in the output voltages. A tradeoff between bandwidth and stability is another issue with such converters. In order to address these issues, a minimum-phase bipolar converter (MPBC) is proposed to facilitate the MPPT operation. The MPBC is derived by combining the Ćuk and SEPIC converters with some circuit modifications in both of them. These circuit modifications eliminate RHPZ from the proposed MPBC. Due to the minimum-phase behavior, the proposed MPBC can achieve high bandwidth with improved phase margin, which is required for the fast and stable MPPT operation. MPBC can operate at the high load current and provides wide operating ranges for the MPPT operation due to its buck and boost capabilities. The transient analysis of the proposed MPBC is carried out to compare its performance with the conventional bipolar converter. A 600-W scaled-down laboratory prototype is developed and implemented using Texas Instrument TMS320F28335 processor to validate the performance of the MPBC for photovoltaic systems.

Hybrid control strategy for effective frequency regulation and power sharing in multi‐terminal HVDC grids

This study proposes a hybrid control (HC) strategy for improved frequency regulation and power sharing in multi-terminal HVDC (MTDC) integrated AC grids. The proposed method uses the topology of bi-polar converters in the MTDC system to improve power sharing and frequency regulation. In this methodology, the two voltage source converters (VSCs) in a bi-polar topology are operated with individual specified control methods. In the proposed HC method, one of the converters operate in voltage square frequency droop ( ) and another in power frequency droop (Pf) control methods. This HC strategy is implemented for grid side voltage source converters in MTDC grids. Further, the performance of frequency regulation and autonomous power sharing of the proposed HC technique is compared with the conventional voltage and frequency droop (PVf) and improved control methodologies. In order to validate the proposed method, two AC-MTDC systems are considered. In both the systems, mesh typed MTDC CIGRE B4 DC test system is in common, it is integrated with two-area power system and New England IEEE 39-bus system to form two different AC-MTDC systems.

Predictive factors of diagnostic conversion from major depressive disorder to bipolar disorder in young adults ages 19–34: A nationwide population study in South Korea

BackgroundPredicting patients who convert to bipolar disorder is important for deciding appropriate treatment for young adults with major depressive disorder (MDD). We focused on the predictive factors of bipolar conversion in a large population of young adults. MethodsA nationwide, population-based electronic medical records database from the Health Insurance Review & Assessment service of South was used to investigate adjusted hazard ratio (HR) of each potential predictor of the bipolar converter group compared to the non-converter group using Cox regression analysis including age of onset, medication use, clinical features, comorbid disorders, admission, self-harm, and negative life events in childhood. ResultsAmong 291,721 subjects who were initially diagnosed with MDD in young adults, 12,376 subjects experienced diagnostic conversion to bipolar disorder. The cumulative incidence was 6.46% during the average 3.26 years of follow-up. Among the predictive factors during diagnosis of MDD, antipsychotic use (HR 3.12, 95%CI, 2.99–3.26, p < 0.0001) and mood stabilizers (HR 2.45, 95%CI, 2.35–2.55, p < 0.0001) showed the strongest association with diagnostic conversion to bipolar disorder. In addition, female sex, younger age of onset, mood stabilizer use, recurrent depression, psychotic symptoms, and admission to a psychiatric ward during diagnosis of MDD were also associated with diagnostic conversion to bipolar disorder. ConclusionIn young adults with MDD, antipsychotic and mood stabilizer use during diagnosis of MDD were the strongest predictive factors with diagnostic conversion to bipolar disorder during follow-up. If young adults with MDD need antipsychotics or mood stabilizer, patients should be carefully evaluated for possibility of bipolar disorder.

Minimum phase bipolar converter for DC microgrid applications

This study proposes a minimum phase bipolar converter for dc microgrid applications, which is derived from the combination of C'uk and Sepic converters with some modifications in both of them in order to get a minimum phase system. In the proposed bipolar converter (PBC), the equivalent series resistance of transfer capacitors of both C'uk and Sepic converters is increased by adding resistances and introducing magnetic coupling between the filter inductors of the Sepic converter with a series RC network. These circuit modifications eliminate right half plane zero from the PBC and thereby make it a minimum phase, unlike the conventional C'uk-Sepic bipolar converter. Due to the minimum phase behaviour, the proposed converter can deliver high load current, achieves high bandwidth and facilitates simpler controller design in contrast to the conventional C'uk-Sepic bipolar converter. Detailed steady state and dynamic modelling of the PBC has been carried out in order to show its advantages. A 500 W laboratory prototype has been developed and implemented using field programmable gate array-based system to verify the operation of the proposed converter.

Analysis of Faults in Multiterminal HVDC Grid for Definition of Test Requirements of HVDC Circuit Breakers

This paper provides a detailed analysis of the temporal development of fault currents in a multiterminal high-voltage direct-current (MT-HVDC) grid composed of a bipolar converter configuration. The sequence of events following the occurrence of a pole-to-ground fault is identified, divided into three distinct periods; namely, submodule capacitor discharge, arm current decay, and ac in-feed periods. The critical parameters that have a significant impact on the fault current in each period are discussed. The impacts of various parameters of the HVDC grid such as the size of the current limiting reactor, ac grid strength, as well as the location of the fault within the grid are studied through PSCAD/EMTDC simulation. Then, a fault current interruption process using models of various HVDC circuit breaker technologies and the resulting stresses are studied. Both serve as important inputs to define test procedures. It is found that the HVDC circuit breakers are subjected to not only dc current and voltage stresses but also energy stress. These stresses are translated into test requirements.

The Minimization of Torque Ripples of Segmental Type Switched Reluctance Motor by Particle Swarm Optimization

In this study, we realized a controller design which can reduce torque ripple of 10/8 Switched Reluctance Motor (SRM). To perform the study, a Switched Reluctance Motor with 5 phase, U type segmental rotor was used. The control of the SRM was actualized by bipolar converter used H-bridge topology. The control signals of converter are obtained by control circuit designed by using dsPIC33EP512MU810. One of the reasons of the current ripples in the SRM is ON-OFF times in a period of the control signals. When the ripples of the current reduced, the ripples of torque of the SRM also reduced. Therefore, in this study, the ON-OFF times in a period of phase control signals were determined by an algorithm used particle swarm optimization. When SRM was controlled by this algorithm developed, the decreasing of its torque ripples was determined.

Adaptive Droop Control for Effective Power Sharing in Multi-Terminal DC (MTDC) Grids

Following a converter outage in a Multi-Terminal DC (MTDC) grid, it is critical that the healthy converter stations share the power mismatch/burden in a desirable way. A fixed value of power-voltage droop in the DC link voltage control loops can ensure proper distribution according to the converter ratings. Here a scheme for adapting the droop coefficients to share the burden according to the available headroom of each converter station is proposed. Advantage of this adaptive (variable) droop scheme for autonomous power sharing is established through transient simulations on an MTDC grid with four bipolar converters and DC cable network with metallic return. Results for both rectifier and inverter outages under two different scenarios are presented. Post-contingency steady-state operating points obtained from transient simulation are shown to be consistent with those derived analytically. Impact of varying droop coefficients on the stability of the MTDC grid is established. An averaged model in Matlab/SIMULINK which has been validated against detailed switched model in EMTDC/PSCAD is used for the stability and modal analysis.

A Study of Solar Energy Produce Hydrogen Combine Fuel Cell Generator System

This paper aims to study the solar energy produce hydrogen combine fuel cell generation system. Utilization digital signal processor of power conversion for solar charging system for the overall system control center to achieve all stability of power system The system consists of a solar module to DC 14V 37W, PEMFC power generation 30W, digital signal processor( TMS320LF2407), assembly of bipolar electrolyzer and power converter The self –made hydroxide ion film of this experiment is excellent performance in separating hydrogen from Oxygen, so the hydrogen purity can be as high as 99.2%,and the generating efficiency of the fuel cell can be maintained at 29%.

Single Inductor DC-DC Converter with Independent Bipolar Outputs Using Charge Pump

This paper describes a bipolar output DC-DC converter that uses a single inductor for size andcost reduction. We propose a timing diagram for a charge pump circuit which generates the negative outputvoltage, and present its con guration, operation principle and simulation results. We also show that employingpseudo-continuous conduction mode improves cross-regulation between the two outputs.

Efficient HVDC converter model for real time transients simulation

An efficient model has been developed to simulate high voltage direct current (HVDC) power converters in real-time transient simulators. Real time performance of 45 /spl mu/s per solution step has been achieved for a 12-pulse monopolar converter and 81 /spl mu/s for the bipolar converter using a single processor Pentium Pro 200 MHz desktop computer. The HVDC power converter model is solved simultaneously with the power network. Simultaneous solution makes the model capable of sustained long-time simulation for real time testing of system performance and control functions.

Stressing of turbine-generator-exciter shafts by variable-frequency currents superimposed on DC currents in asynchronous HVDC links and following disturbances at converter stations

Ripple currents on the DC side of both HVDC synchronous and asynchronous links together with cleared HVDC and AC system disturbances can excite in some circumstances onerous torsional vibrations in large steam generator shafts. The problem has assumed importance in recent months on account of the HVDC link between Scotland and Northern Ireland going ahead, on account of the proposed Eire/Wales link, and because AC/DC/AC couplers are to be installed extensively to interconnect the East and West European grid systems. This paper discusses and analyses excitation of shaft torsional vibrations in steam turbine-generator-exciter shafts in close proximity to HVDC power converter substations by: (i) variable-frequency ripple currents superimposed on the DC currents in asynchronous links; and (ii) disturbances at bi-polar converter stations. Detailed simulation of the HVDC converter and generator is necessary for precise assessments of shaft torsional response following HVDC converter station faults. 500 MW, 660 MW, 1000 MW and 1300 MW machines are considered in the analyses that are made. >