Diode Rectifier Research Articles

System topologies, key operation and control technologies for offshore wind power transmission based on HVDC

Offshore wind power (OWF) is considered a perfect energy source for the future low-carbon power system. However, the growing offshore distance and water depth would require more cost-efficiency and reliable techniques than the HVAC solution, which indicates the OWF HVDC transmission technique will be a promising solution. In this paper, the current situation of OWF-HVDC projects is introduced at first. Then, despite the most popular topology-modular multilevel converter, other alternative converters and system topologies with higher power density and cost-efficiency are presented, including the hybrid modular multilevel converter, alternative arm converter, and diode rectifier. Next, several multi-terminal topologies are introduced, which synthesize the advantages of different converters. Finally, the key technologies for OWF HVDC operation and control are summarized, including grid-forming control strategy for offshore wind turbine, harmonic instability suppression, and frequency regulation participation strategy design.

Coordinate control strategy for hybrid HVDC system based on DR-MMC with offshore wind farm integration

Offshore wind farm integrated by hybrid rectifier, which is composed by series-connected diode rectifier (DR) and MMC, to onshore grid is investigated in this paper. As the instinct conduction characteristics of DR, whole HVDC system shows different characteristics. In this paper, steady operation principle is analysed, and multi-target coordinate control strategy based on current droop for the hybrid HVDC system is proposed. Simulation results in PSCAD/EMTDC verify the effectiveness of proposed control strategy during steady operation and start up.

A phase‐shift modulated series resonant converter achieving zero‐voltage and zero‐current switching for wide output voltage range battery charging applications

AbstractIn this article, a phase‐shift modulated zero‐voltage and zero‐current switching (ZVZCS) series resonant converter (SRC) was proposed for constant current (CC) and constant voltage (CV) charging operating at the series resonant frequency. Wide output voltage range is achieved by adjusting the duty cycle of the primary inverter for CC charging and unity gain is for CV charging at full duty cycle. By tuning resonant tank parameters, discontinuous conduction mode (DCM) and boundary conduction mode (BCM) are obtained in CC charging and CV charging, respectively, which ensures zero‐current switching (ZCS) of rectifier diodes and nearly ZCS of leading leg in whole charging profile. Meanwhile, a constant triangular current provided by a novel auxiliary circuit is used to implement zero‐voltage switching (ZVS) for all primary MOSFETs with a reduced conduction loss. The auxiliary current is independent of duty cycle and load variation. Compared with the conventional ZVZCS phase‐shift full‐bridge converter with capacitive output filter, smaller conduction loss and turn‐off loss can be obtained in battery charging profile. Detailed circuit operation principles and model analysis are presented. A 100 kHz/1 kW prototype is built to verify the performance.

High-power electric propulsion wide-voltage power processing unit technology

In response to the needs of high-power electric propulsion systems for power processing units that can adapt to a wide range of voltages and can achieve high-efficiency conversion throughout the range, this thesis plans to research on the technology of high-power electric propulsion wide-voltage power processing unit. This thesis proposes an isolated widevoltage flexible mainstream combined converter and its control method. By optimizing the number of series series on the secondary side of the dual-bridge topology, the stress of the device is reduced. By embedding a lossless spike absorption diode on the secondary side, the resonant voltage spike of the rectifier diode is effectively reduced. Through the optimized design of the smooth switching control strategy, the adjustment range of the converter is broadened. Through the control strategy of the in-phase shift switch of the leading bridge, the current sharing of the converter is realized and the power density of the converter is improved. The prototype developed in this thesis has an input voltage of 80-120V, an output voltage of 500-1500V, a rated power of 5kW, and a conversion efficiency of up to 95%, which verifies the correctness and effectiveness of the related technology.

Investigation and Reduction of EMI Noise Due to the Reverse Recovery Currents of 50/60 Hz Diode Rectifiers

Alternating current (ac)/ Direct current (dc) power converters with dc-bus filters can achieve high power density, however, it was found in this article that the reverse recovery currents of the 50/60 Hz diode bridge can lead to significant electromagnetic interference (EMI) noise violating EMI standards above 150 kHz. This article analyzed and quantified the mechanism of the EMI generation due to the reverse recovery currents of the 50/60 Hz diodes. It was found that although the reverse recovery of the 50/60 Hz diode bridge repeats at a frequency of 50/60 Hz, the EMI can be very high above 150 kHz due to the operating principle of electromagnetic compatibility spectrum analyzers. Two techniques were proposed to reduce the EMI due to the reverse recovery of the diode bridge. The analyses were validated by either simulations or experiments.

Self-Synchronizing Control and Frequency Response of Offshore Wind Farms Connected to Diode Rectifier Based HVDC System

Light-duty offshore wind power system has been a research hotspot in recent years. The diode rectifier based HVDC scheme is a promising solution and has attracted more and more attention. In this paper, a self-synchronizing control for offshore wind farms connected to diode rectifier based HVDC system is proposed. The active power of each wind turbine is controlled by regulating the amplitude of the AC voltage, while the reactive power is used to adjust the offshore frequency. The proposed control is a decentralized scheme. Thus, no communication network or GPS is required and only the local information is used in the control system. The synchronization of wind turbines is achieved by the proposed self-synchronizing frequency control instead of using phase-lock loop. Besides, in order to make offshore wind farms provide necessary frequency support to the onshore power system, a communication-less frequency regulation scheme with artificial coupling method is proposed. The feasibility and effectiveness of the proposed self-synchronizing control and frequency regulation scheme are verified through simulation studies in PSCAD/EMTDC platform.

Power Factor Correction Using a Series Active Filter

Abstract: Power factor correction (PFC) for single-phase diode rectifiers utilising a series active filter is demonstrated in this project at a minimal cost. When compared to the typical PFC, the suggested PFC has reduced power device ratings requirements, which results in cheaper costs and improved efficiency. It can also eliminate the requirement for a large inductor in the typical PFC, making it more compact. This study examines the proposed PFC's topology, operating principle, and application concerns. The control approach and simulation results are presented in detail. Prototypes of 1-kW are made and the experimental findings are shown to verify the theoretical analysis. Index Terms: Harmonic resonance, hybrid active filter, industrial power system.

Control Strategy for Offshore Wind Farms with DC Collection System Based on Series-Connected Diode Rectifier

The DR-HVDC (Diode rectifier-based HVDC) transmission topology was recently proposed for integration on large offshore wind farms due to its low investment cost and high reliability. To further reduce the investment, a DC collection topology based on the series-connected diode rectifiers (DR) is proposed, where no offshore platform is needed. However, units of series-connected topology (SCU) show coupling issues, such as overvoltage, energy curtailment, and fault isolation. First, the coupling mechanism is analyzed, and a suitable operation mode for SCUs is selected to ensure the safe operation of the DC system. Then, the linear relationship of active power and output DC current and DC voltage of SCUs is analyzed, and a novel coordinate control strategy for DC wind farms is proposed, where an onshore converter adapts a DC current controller and wind turbines adapt a mediate output voltage control strategy. The mediate output voltage control strategy includes a triple loop with power loop, mediate output voltage loop, and current loop. Also, the DC open line fault, DC grounding fault, and AC grounding fault of the onshore grid are investigated, and a protection strategy is proposed. A 160 MW wind farm with a DR-SCU DC collection system is built in PSCAD/EMTDC to verify the validity of the proposed control strategy under unequal wind speeds, DC fault, and onshore AC fault, and the results validate the performance of the proposed strategy.

High-power cold diodes for the protection of a 1.5 T superconducting MRI magnet system

Cold diodes play a crucial role in various operational aspects of the superconducting magnet of magnetic resonance imaging (MRI) scanners. The forward and reverse characteristics and failure modes are studied for two types of high-power rectifier diode to find their suitability for application at 4.2 K in a whole-body 1.5 T superconducting MRI magnet system. The diodes are characterized at various temperatures (300 K, 77 K and 4.2 K) in the current range up to 600 A. The turn-on voltage of the diodes at 4.2 K is found to be increased by 7–12 times that of room temperature. The diodes show negative differential resistance (NDR) beyond 1 A of forward current at 4.2 K. The forward voltage stabilizes in the range of 1.22–1.24 V after attaining the turn-on voltage in the range of 5–8 V. The significance of NDR is analysed for the MRI magnet. The long-term stability of the forward voltage is studied at 77 K with 550 A of forward current. Two modes of diode failure are also studied to foresee any failure during the operation of the magnet.

Разработка источника питания для позиции виброакустической диагностики подшипников локомотивного депо

Purpose: Two possible variants of power sources are considered: controlled three-phase bridge rectifier circuit with a step-down transformer and a pulse converter, getting power from the mains via uncontrolled three-phase bridge rectifier (Larionov circuit) for bringing into rotation with the required frequency of wheel-motor units of electric locomotives and electric trains at the position of indiscriminate diagnosis of bearings. In both cases, it is assumed that power sources receive electro-energy from a depot circuit — 380/220 V, 50 Hz. The comparison of proposed power supply options based on the assessment of energy consumption efficiency is carried out. A capacity coefficient and capacity loss in power supplies are used as measures for energy-consumption efficiency. Methods: Analytical methods are used to determine capacity losses in a transformer, controlled three–phase thyristor rectifier, uncontrolled three-phase diode rectifier, input filter of a pulse converter, IGBT transistor and reverse diode of a pulse converter. Results: Energetical indicators were determined: power losses in a transformer, a controlled three–phase thyristor rectifier, an uncontrolled three-phase diode rectifier, an input filter of a pulse converter, an IGBT transistor and a reverse diode of a pulse converter. Based on the pursued assessment of the energetical indicators of power supply two options, it is concluded on feasibility of transformer-free circuit application in bearings’ position of vibration-acoustic diagnosis. Practical importance: A variant of an energy–efficient power supply for the position of indiscriminate vibroacoustic diagnosis is proposed, which includes an uncontrolled semiconductor rectifier and a pulse converter, accomplished using an IGBT transistor.

Study of a novel soft‐switched Vienna rectifier using simple active technique

SummaryIn recent years, efficient power transfer is getting increasing attention in high‐power conversion systems such as fast battery charger systems primarily necessitate an energy efficient, compact, and reliable power electronic converter scheme. This has stirred vigorous research in high‐power converter‐based power electronic systems which are feasible in actual practice and perform efficiently. In view of this fact, a novel soft‐switched T‐type boost rectifier Vienna topology is proposed, which can be considered as a potential candidate in high‐power conversion systems. The proposed converter scheme operates at high‐switching frequency with soft‐switching conditions by employing a simple active snubber circuit, which results in high‐efficiency and high‐power density with low cost. The low components count, simple power and control circuitry, comparable stresses, and performance are the distinctive features of the proposed converter scheme. Furthermore, the proposed topology achieves high‐switching operation while reducing reverse recovery rectifier diode losses and semiconductor losses. The proposed converter scheme's construction, operating principle, and practical implementation are carried out using a low‐scale laboratory prototype. In order to evaluate, a comparison with existing soft‐switched rectifier topologies is performed in terms of components count. In addition, a MATLAB/Simulink designed subsystem is used to assess the semiconductor devices switching power losses in comparison to its hard‐switched counterpart.

A SERIES RECONFIGURABLE STRUCTURE RESONANT CHOPPER FULLY SOFT-SWITCHED DUAL-ACTIVE-BRIDGE WITH DUAL TANK

Compared to the dual-active-bridge converter, the Double-bridge arrangement thunderous converter (DBSRC) can extend delicate exchanging run. To encourage broaden the soft-switching extend and progress the circuit execution, a modern DBSRC with double tank based on DBSRC is proposed in this paper. This modern converter highlights two thunderous tanks and a tapped transformer, and it can perform superior than the DBSRC by optimized tap coefficient x of the tapped transformer. Its operation guideline, voltage pick up, the soft-switching characteristics, and yield control are analyzed in detail, and compared with the DBSRC. Comes about appear that the pro-posed dual-tank topology has displayed higher voltage pick up, more extensive soft-switching locale, and bigger yield control than the conventional DBSRC when the tap-coefficient x is chosen sensibly. DC-to-DC bidirectional resounding converter to be utilized for bidirectional control exchange applications particularly battery charging discharging applications in electrical vehicles. Its similar to an LLC resonant converter, but on the secondary side of the circuit, an additional inductor and capacitor have been added to make the resonant network symmetric for operation in both forward and backward directions. The switches in the inverting step have zero voltage switching (ZVS). Under ZCS, the rectifier diodes on the secondary side also turn off. ZVS and ZCS reduce losses and enable high-frequency operation, resulting in smaller magnetic elements and filter capacitors, lowering size, weight, and volume while enhancing power density. INDEX TERMS—dual active bridge (DAB), dual-bridge series resonant converter (DBSRC), soft-switching, dual-tank, tapped- transformer, tap-coefficient

Desain Closed-Loop Boost Converter Berbasis Voltage Lift Cell Untuk Implementasi Penguat Tegangan

In this new era the use of Photovoltaic (PV) is increasingly being used as an energy source. However, this technology has a drawback, namely, the intensity of the sun's light is always changing every time. This can cause the output voltage of the Photovoltaic (PV) Cell to be variable or indeterminate. In the Photovoltaic (PV) Cell, a dc-dc converter circuit is needed which functions to regulate and change the output of the Photovoltaic (PV) Cell. Conventional DC-DC boost converters are unable to provide a high step-up voltage boost due to the effects of switching power, rectifier diodes, and equivalent series resistance of inductors and capacitors. In this study, a closed loop design using a PID controller and analysis of a non-isolated boost dc-dc converter based voltage lift technique were carried out to achieve a high step-up voltage gain. In the presented converter two inductors, three capacitors and three power diodes are used. From this structure, this converter is referred to as a voltage lift cell-based boost converter. The structure of the presented converter is considered very simple, since it has only two stages of power. The voltage and current equations of each element with the converter voltage gain under continuous conduction mode (CCM) were extracted. In addition, the steady state analysis of the amplified stress and boundary conditions is discussed in this study. This boost converter circuit is simulated through the PSIM application. From the simulation results in the PSIM application, it is found that the boost converter circuit is able to increase the voltage from 100 V to 400 V and has an error value of 0. The specifications of the simulation results are a duty cycle of 0.6, and a frequency of 10,000 Hz

Application of Single-Phase Supply AC-DC-AC VFD for Power Factor Improvement in LED Lighting Devices Loaded Power Distribution Lines

More and more light-emitting diode lighting devices (LED) are being connected to modern power distribution lines. In addition to its many positive features, this poses problems in terms of reactive power compensation. The large number of LEDs interacting with traditional reactive power compensators leads to a harmful phenomenon—overcompensation. This was experimentally determined in the investigated power distribution lines. Along with LEDs, a large number of devices with variable frequency drives (VFD) are connected to the same power distribution lines. This study presents an innovative approach to conventional diode rectifier supply side AC-DC-AC VFDs. It is proposed to use these VFDs as a reactive power compensation device while maintaining their main functions—motor powering and motor speed control. Minor improvements have been proposed to enable these VFDs to provide and draw out reactive power, thereby keeping power factors close to the unit in LED-loaded power distribution lines. The proposed improvements are based on the interaction between the power distribution lines inductivity and the DC circuit capacitance of the VFD. It has been shown that the power factor can be controlled by varying the capacity of the DC circuit. The ability of the AC-DC-AC VFD to compensate for the reactive power provided by the light-emitting diode lighting devices was confirmed by mathematical calculations and experimentally with a laboratory prototype.

Parallel Operation of Permanent Magnet Generators and Diode Rectifiers in Maritime DC Power System Considering Fuel Economy

The dc grid system is attracting attention as a new electric power distribution method for several vessel kinds due to its high fuel efficiency compared with the ac grid. The combination of a wound rotor generator (WRG) and a diode rectifier [diode front end (DFE)] has been typically applied as a generation part of the dc grid. Still, the combination of a permanent magnet generator (PMG) and a DFE has been recently studied to take advantage of their simplicity, cost-effectiveness, robustness, high reliability, and high efficiency. However, although a single-operation mode of the “PMG + DFE” system was analyzed in the literature, research for the parallel operation of the “PMG + DFE” system has not yet been conducted. The “PMG + DFE” system should be operated along the optimal operating line (OOL) in the power–voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V$ </tex-math></inline-formula> ) domain to minimize fuel consumption. This OOL in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V$ </tex-math></inline-formula> domain includes negative, zero, and positive slopes under light, medium, and heavy loads, respectively. Therefore, if the conventional droop control is applied to this system, it cannot be operated along the OOL. This article introduces modified droop control for operating paralleled “PMG + DFE” system along the OOL in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V$ </tex-math></inline-formula> domain. Furthermore, a mode change strategy from the single-operation mode to the parallel-operation mode is proposed. The validity of the proposed modified droop control is verified by computer simulation and a small-scaled experimental test.

Comparative Study of Switched Reluctance Generators With Separate Field Current and Circulating Current Excitations

In this paper, a circulating-current-excited switched reluctance generator system with the diode rectifier is comparatively studied with a field-current-separated switched reluctance generator. By using a DC power source connected in series with the winding to provide the circulating current, a controllable excitation field is established in the proposed generator. To highlight the influence of this DC voltage source, the injected field current of the field-current-separated generator is kept the same as the circulating current of the circulating-current-excited generator. Then, both advantages and disadvantages of the generators are summarized. The circulating-current-excited switched reluctance generator system inherits both the advantages of good reliability of the separated-winding generator by using the diode rectifier and low copper loss of the integrated-winding machine by combining the AC and DC current in one set of windings. Furthermore, two more practically conventional field-current-separated generators are also compared with the proposed generator in terms of the external characteristics. These two conventional generators have different winding configurations. At last, the analysis is verified by experiments.

Design of Savonius model wind turbine for power catchment

In this study, the fossil fuel usage by-product is carbon dioxide, which is known as the primary cause in global warming. Alternatively, wind energy is a clean alternative energy source compared the fuel consumption can cause smoke pollution. The goal of the work is to develop a pollution controller device model Savonius wind turbine to represent the characterized actual speed wind turbine concepts into convert kinetic energy into electric energy from campus and monitoring all output data display on the cloud. The wind speed operation is enabled through the use of ESP8266 as internet of things (IoT) platform and the alternating current (AC) direct current (DC) harvesting circuit into improve stability of the wind energy performance. Secondly, a magnet coil synchronous generator is used, which is a grid coupled through a diode rectifier and voltage source converter. The parameters that have been measured using wireless fidelity (Wi-Fi) module ESP8266 are considering wind speed, current, voltage and power. The wind speed with 7.8 MPH can produce a maximum output voltage and output current of 1.104 V and 4.321 μA, respectively. Blynk applications functional as role present performance monitoring kit wind turbine analysis with more precise and efficient in anywhere and anytime.

An Effective Charger for Plug-In Hybrid Electric Vehicles (PHEV) with an Enhanced PFC Rectifier and ZVS-ZCS DC/DC High-Frequency Converter

A plug-in hybrid electric vehicles (PHEV) charger adapter consists of an AC/DC power factor correction (PFC) circuit accompanied by a full-bridge isolated DC/DC converter. This paper introduces an efficient two-stage charger topology with an improved PFC rectifier as front-end and a high-frequency zero voltage switching (ZVS). Current switching (ZCS) DC/DC converter is the second part. The front-end converter is chosen as bridgeless interleaved (BLIL) boost converter, as it provides the advantages like lessened input current ripple, capacitor voltage ripple, and electromagnetic interference. Resettable integrator (RI) control technique is employed for PFC and DC voltage regulation. The controller achieves nonlinear switching converter control and makes it more resilient with the faster transient response and input noise rejection. The second stage incorporates a resonant circuit, which helps in achieving ZVS/ZCS for inverter switches and rectifier diodes. PI controller with phase shift modulator is used for second-stage converter. It improves the overall efficacy of the charger by lowering the switching losses, lowering the voltage stress on the power semiconductor devices, and reversing recovery losses of the diodes. The simulations and experimental results infer that the overall charging efficiency increases to 96.5%, which is 3% higher than the conventional two-stage approach using the interleaved converter.

Control of the Parallel Operation of DR-HVDC and VSC-HVDC for Offshore Wind Power Transmission

This paper presents a control of the parallel operation of diode rectifier based high-voltage direct current (DR-HVDC) and voltage source converter based HVDC (VSC-HVDC) links. The two links are connected to offshore wind farms (OWFs). The VSC-HVDC controls the voltage and frequency of the offshore AC-grid needed for the OWFs start-up. The proposed grid forming control is based on controlling the OWFs voltage by controlling the active power balance at the VSC-HVDC AC-bus. When the OWFs inject more power than a certain active power reference established for the VSC-HVDC, the OWFs voltage increases and the DR-HVDC starts conducting. Then, the offshore voltage automatically accommodates the required value for transmitting the OWFs power through the DR-HVDC link while the system frequency is controlled by the VSC-HVDC through satisfying the reactive power balance. The power transmitted through the VSC-HVDC can be set by adjusting the corresponding power command while the DR-HVDC will automatically close the power balance. The main advantage of the proposed control system is that the VSC-HVDC can be sized just to support the system energization; while once the OWFs are in operation, the DR-HVDC will be loaded automatically. Simulation results verify the proposed control system.

A High-Efficiency Wireless Power Transfer System Using Quasi-Z-Source Inverter and Current-Double Synchronous Rectifier for Low-Voltage and High-Current Applications

In low-voltage and high-current wireless power transfer systems (LVHC WPTSs), the loss of power loop is usually large due to the high current. More critically, the equivalent load resistance (ELR) is usually much lower than the optimal load resistance, which leads to serious heating and low system efficiency. This article proposes a new technology, which employs the current-double synchronous rectifier (CDSR) to replace the traditional diode rectifier and dc/dc converter on the secondary side, and thus, the ELR can be adjusted in a large range by regulating the duty cycle of CDSR and the system can always work at the maximum efficiency point. In addition, the traditional dc/dc converter and inverter are replaced by the quasi-Z source inverter (q-ZSI) on the primary side, which can boost the dc-link voltage of inverter and reduce the current of power loop, so as to reduce the heating and improve the system efficiency further. Furthermore, the cooperative working mechanism of q-ZSI and CDSR for high-efficiency and constant power (CP) charging is analyzed thoroughly. Finally, the viability of the proposed topology is verified in a 1-kW prototype with 48-V input and 24–33.6-V output voltage, and the maximum efficiency of the prototype achieves 87.4%.