High-voltage Bus Research Articles

Enabling High-Power Conditioning and High-Voltage Bus Integration Using Series-Connected DC Transformers in Spacecrafts

This article proposes a photovoltaic power processor for high-voltage and high-power distribution bus, between 300 V and 900 V, to be used in future space platforms like large space stations or lunar bases. Solar arrays with voltages higher than 100 V are not available for space application, being necessary to apply power conversion techniques. The idea behind this is to use series-connected zero-voltage and zero-current unregulated and isolated DC converters to achieve high bus voltage from the existing solar arrays. Bus regulation is then achieved through low-frequency hysteretic control. Topology description, semiconductor selection, design procedure, simulation and experimental validation, including tests in vacuum and partial pressures, are presented.

A Novel Single-Stage AC/DC Converter Integrated Interleaved DCM Boost PFC and LLC DC–DC With Reduced Bus Voltage

Due to the applied pulse frequency modulation (PFM) control and switch integration, single-stage Boost-LLC AC/DC converters suffer from high bus voltage which makes them difficult to operate for high voltage input. To solve this issue, a novel single-stage AC/DC Converter by incorporating the interleaved DCM boost cell and an LLC cell is proposed. Different from the existing topology, in the proposed converter, two capacitors employed for splitting the ac input voltage into two parts are placed before the rectifier bridge. Thus, the voltage across each PFC cell is halved and the bus voltage can be significantly reduced. Furthermore, two high-frequency diodes and one filter capacitor are omitted, which helps improve the zero-crossing distortion of the input current. More importantly, the circuit efficiency is thus increased. Hence, low bus voltage, low component count, and high efficiency are the main advantages of the proposed converter. Simulations and experimental results are presented to prove the above features of the proposed converter.

State of Charge Balancing Control for Multiple Output Dynamically Adjustable Capacity System

<div>A multiple output dynamically adjustable capacity system (MODACS) is developed to provide multiple voltage output levels while supporting varying power loads by switching multiple battery strings between serial and parallel connections. Each module of the system can service either a low voltage bus by placing its strings in parallel or a high voltage bus with its strings in series. Since MODACS contains several such modules, it can produce multiple voltages simultaneously. By switching which strings and modules service the different output rails and by varying the connection strategy over time, the system can balance the states of charge (SOC) of the strings and modules. A model predictive control (MPC) algorithm is formulated to accomplish this balancing. MODACS operates in various power modes, each of which imposes unique constraints on switching between configurations. Those constraints are mathematically formalized so that MPC can be applied to minimize predicted SOC differences over a finite time horizon. In this article, several variations that vary in how freely strings can connect and disconnect from the bus bars are presented. Methods allowing more flexibility in configuration changes can balance SOCs more quickly but take more computation to resolve. In contrast, simpler schemes reduce computation and simplify implementation, but take longer to balance the SOCs. Simulation results illustrate the expected behavior.</div>

Comparison and Optimization of Non-isolated DC-DC Converters for Electric Vehicle Applications

This paper discusses the importance of electric vehicles in solving the problem of environmental pollution. In electric vehicles, DC/DC converter is a vital part to connect many electrical units with high voltage bus, so it plays a vital and indispensable role in electric vehicles. The paper analyzes the disadvantages of isolated DC/DC converter, and concludes that non-isolated DC/DC converter is a more suitable technical solution for electric vehicles. The research paper introduces a number of fundamental non-isolated DC/DC converter topologies before analyzing the technical optimization strategies of a number of DC/DC converters in general. which are Half-bridge converters, Cascaded Half-bridge converter (CHB), multi-phase interleaved parallel converter, tri-level converter, soft-switching converter, and switched-capacitor converter (SC converter). The benefits and drawbacks of these DC/DC converter optimization measures are compared, the findings can serve as a technical framework for guiding the application of DC/DC converter technology in the context of electric vehicles. Finally, this paper analyzes and looks forward to the development prospect of flying switched-capacitor DC/DC converters (FCDCs) technology, puts forward the existing technical problems, and gives suggestions for the solution of these problems, which is conducive to the wider application of this technical solution in electric vehicles.

New Modular Multilevel DC–DC Converter Derived from Modified Buck–Boost DC–DC Converter

Raising the electrification ratio to 100% is still a formidable challenge in Indonesia, especially in the remote areas of the eastern part of the archipelago. A DC microgrid system is one of the most viable solutions to increase the electricity supply in remote areas, taking advantage of various renewable energy sources that are located near the rural load centers. A DC–DC power converter for a rural DC microgrid system needs to have a high voltage gain to facilitate the power conversion from low-voltage PV output to a high-voltage DC microgrid bus, a very low input ripple current to help maintain the PV or battery lifetime, and be highly modular for ease of transport and assembly. Many topologies have been proposed to obtain high voltage gain, very low ripple current, and modularity. However, they usually use either bulky and lossy magnetic components, are sensitive to component parameter variance and need special voltage-balancing techniques, or have different component ratings for their multilevel configuration which weakens the modularity aspect. This paper proposes a new modular multilevel DC–DC converter that is very suitable for rural DC microgrid applications based on a modified buck–boost topology. The proposed converter is easily stackable to achieve high voltage gain and does not require any voltage balancing techniques, thus enhancing the modularity characteristics and simplifying its control method. Moreover, the ripple current can be reduced by employing a multiphase configuration. This converter can also facilitate bidirectional power flow to serve as a battery charger/discharger. A comprehensive analysis of voltage gain and ripple current are presented to explain the inner workings of this converter. Finally, the performance of this converter is verified through simulation and experiment, showing the converter’s modularity, bidirectional power capability, and potential to achieve voltage gain and ripple-current requirements of the DC microgrid system.

Analysis of short-circuit behavior and failure modes in SiC power devices

This essay presents the advantages of SiC power devices, while the short-circuit characteristics limit their development. The device short-circuit will seriously affect the efficiency of the use of the period. When a load short circuit occurs, both ends of the power MOSFET device will be directly connected to the high bus voltage; therefore, the short circuit process poses a great challenge to the device's ability to withstand high voltage, high current, and high junction temperature simultaneously. In this thesis, the short-circuit process of SiC power devices is investigated by designing a detection circuit, and two failure mechanisms of SiC MOSFET power devices are explained through the understanding of the failure mechanism.

A SOGI-based adaptive controller design for second-harmonic currents suppression of variable frequency loads in DC buildings

DC buildings with integrated DC transformers (DCTs), as a typical representative of photovoltaics, energy storage, direct current, and flexibility (PEDF) building systems, are a crucial approach to reducing carbon emissions. Heating, ventilation, and air conditioning (HVAC) systems are typical loads in DC buildings that primarily aim to enhance the air quality and thermal comfort. However, the variable frequency drives (VFDs) used in HVAC systems can generate second-harmonic currents (SHC), which decrease equipment reliability and system power efficiency. To prevent SHC on the low-voltage side from flowing to the high-voltage bus, even in the grid, a second order generalized integrator (SOGI)-based adaptive controller for suppressing the SHC of variable frequency loads in DC buildings is proposed. The controller employs a phase-locked loop (PLL) to provide feedback on the VFD output frequency to the DCT control loop's notch filter, enabling adaptive suppression of the variable frequency SHC. Firstly, an accurate small-signal model of DCT based on Fourier series is established, which considers the inductor current. Then, the formula for DCT equivalent impedance is derived based on the model, and the feasibility of suppressing the SHC by increasing the equivalent impedance at variable frequency is analyzed. To enhance the stability of DC buildings, the parameters of the controller are designed to improve dynamic performance. Finally, the simulation results and experimental results verify the effectiveness and feasibility of the proposed adaptive controller compared to other suppression strategies.© 2017 Elsevier Inc. All rights reserved.

Pre-sizing of a modular high power density DC/DC converter with GaN components

Finding the most appropriate architecture to achieve a function is a major engineering challenge. In the power conversion context, the question that arises is: what is the best trade-off between an architecture based on a single high-power converter and another based on the combination of multiple low-power converters? This article aims to answer this question in the specific case of the isolated interface between the low voltage (28VDC) and high voltage (±270VDC) buses of an aircraft. Towards this goal, the targeted power electronics converter is carefully modeled in order to obtain an accurate and fast computing model. A technological database of the different usable components is then used to feed an optimization algorithm. The execution of the latter achieves an attractive and robust result showing an excellent performance in terms of power-to-weight ratio, which is the key index of this study. The precision and speed of this computer-aided design is based on analytical models that are quick to run and therefore enable exploring almost exhaustively the search space. More specifically, the high-frequency transformer has a large relative mass and generates significant losses that are difficult to assess. A major modeling effort has been undertaken and has been enabled to define a simplified but convincing and accurate model (successfully assessed on a wide bandwidth using an experimental setup). It was used for the first time in this optimization process. According to the targeted aeronautical specifications, the two best solutions would make it possible to achieve a mass power density of 4.5kW/kg, i.e. twice as high as traditional solutions. This result very clearly shows that the appropriate use of the new GaN transistors makes it possible to make a technological breakthrough. Considering the voltage and current ratings of these components, this shows that the combination of multiple partial converters is very promising and will make it possible in the future to achieve a significant increase in the compactness of electrical power conversion functions. This sizing study therefore clearly shows the potential of the standardized design of power electronics converters and the search for the best combinations (series, parallel) to meet any specific specifications. Additionally, the developed approach, based on a modeling effort, especially as far as the high-frequency transformer is concerned, and collection of manufacturer data, also makes it possible to limit the implementations and associated tests.Hence, the main contributions of this article are (i) the assembly of the analytical models of the various components constituting an isolated DC–DC power supply, (ii) the simplification of an analytical model of the planar HF transformer, its experimental validation and its first use in a loop of optimization, (iii) the fact of showing supporting figures that GaN technology enables technological breakthroughs to achieve high power density, which opens the way to modular architectures based on partial converters of electrical power, (iv) the comprehensive description of a powerful pre-study design tool enabling to greatly reduce power converters’ time to market.

Mitigation of Power Losses and Enhancement in Voltage Profile by Optimal Placement of Capacitor Banks With Particle Swarm Optimization in Radial Distribution Networks

The prime purpose of placing a capacitor bank in a power system is to provide reactive power, reduce power losses, and enhances voltage profile. The main challenge is to determine the optimum capacitor position and size that reduces both system power losses and the overall cost of the system with rigid constraints. For this purpose, different optimization techniques are used, for example Particle Swarm Optimization (PSO) which converges the complex non-linear problem in a systematic and methodological way to find the best optimal solution. In this paper, the standard IEEE 33-bus and 69-bus systems are used to find the optimum location and size of the capacitors bank. These power networks are simulated in Siemens PSS®E software. For the optimum solution of capacitor banks, the PSO algorithm is used. The PSO fitness function is modelled in such a way which contains the high average bus voltage, the small size of capacitor banks, and low power losses. The fitness function used is a weighted type to reduce the computation time and multi-objective function complexity.

Modeling and control of islanded DC microgrid fed by intermittent generating resources

In this paper an islanded microgrid fed through the wind and solar energy resources is presented. The power flow within the microgrid is controlled using a Neutral Point Clamped Dual Active Bridge (NPC-DAB) converter. In the proposed dc microgrid, the solar energy source is associated at the low voltage (LV) bus and the wind energy source is connected at the high voltage (HV) bus. A permanent magnet synchronous generator (PMSG) machine is used in wind energy conversion system. The real time solar radiation and wind speed data of Rupangarh, Rajasthan, India is used as an input for renewable energy resource. The NPC-DAB will work as a power electronics juncture for expediting the energy exchange in the islanded DC Microgrid. The proposed closed loop controller based on the capacitor voltage and load voltage will expedite a complete automatic operation of the islanded DC-microgrid considering various load changes. The system is studied without storage element as the automatic control of energy generation and load feeding is carried out by the NPC-DAB, also this makes the scheme cost effective. The optimum duty ratios for NPC-DAB operation are obtained and thus the increased load demand is met. The modeling of PMSG, NPC-DAB and wind energy system is discussed in details in this work. The proposed system is studied in MATLAB/Simulink environment and results are obtained for different load variations. All the wind control parameters, NPC-DAB waveforms, load waveforms are also plotted using MATLAB.

Two-Switch Forward Converter With an Integrated Buck Converter for High Bus Voltage in Satellites

As satellite missions become increasingly diverse, the power capacity of satellites continues to increase. Accordingly, the weight and loss of the electrical power system of the satellite must be reduced. Thus, a high bus voltage is required for the electrical power system of the satellite. However, most high-power dc/dc converter topologies, such as half-bridge and full-bridge dc/dc converters have leg-structures, which violate the heritage design characteristics of the dc/dc converters for satellites. To solve these problems, a two-switch forward converter with an integrated buck converter is proposed in this article. By integrating the buck converter into the two-switch forward converter, one switch and one diode are eliminated in the proposed converter, and consequently, its cost, weight, and volume can be greatly reduced. Moreover, the zero-voltage switching of the low-side switch can be achieved. Therefore, the proposed converter achieves a high efficiency under the entire load condition compared with conventional converters. The effectiveness and feasibility of the proposed converter were verified with a prototype of 300–330 V input and 600 W (150 V/100 V) output.

Non-Backflow-Power and Reduced-Switching-Loss Modulation for Bidirectional Series Resonant Converter With Wide Gain Range

In the achievement of high power efficiency over a wide gain range for a bidirectional series resonant converter (BSRC), conduction losses caused by backflow power and switching losses are two challenges. In this article, a novel modulation of the BSRC is proposed for a wide voltage gain range and high efficiency as well. With the proposed modulation, the BSRC can operate in both buck- and boost-like modes for a wide gain range. The resonant current is in phase with the terminal voltage on both primary and secondary sides, to eliminate the backflow power for the reduction of conduction losses. Hard turn-off problem is alleviated with a resonant current fully released before the completion of the switching cycle. Thus, the number of hard switching actions is significantly reduced compared with existing modulation schemes in the literature. A control scheme based on state-flowchart is also proposed to realize seamless transition among different working modes. To validate the proposed modulation, a 1 kVA prototype of BSRC is developed and interfaces a high-voltage bus ranging from 240 to 480 V and a low-voltage bus ranging from 24 to 56 V. Compared with conventional modulation schemes, efficiency enhancement can be observed over the whole operating range.

Systematic Review on Phase-Shift Optimization Strategies of Dual Active Bridge based DC-DC Converter

Bidirectional DC-DC converters (BDC) between high and low voltage buses are the most promising in latest research for their use cases in micro-grids. Specifically, the dual active bridge (DAB) topology of BDC has vast number of applications and its ability to transmit power in both directions makes it effective for utilities in consumer-prosumer setup. In recent years, a substantial amount of research has been conducted to eliminate one of the crucial drawbacks of DABs which is the mitigation of DC-Bias current resulting from practical limitations of switches. DC-Bias current is the leading cause of switch stress resulting in reduced converter reliability and efficiency. Numerous strategies have been devised to overcome this issue which includes methods like flux suppression, dynamic optimization, transient control, and piecewise linear transient phase shift optimization. In each of these categories several studies devised various techniques to increase operation efficiency, the dynamic response optimization (including model predictive controls and ANNs) can also be seen in recent research trends. This state-of-the-art systematic review is conducted on the recent developments in phase shift optimization techniques developed to increase the overall efficiency of isolated DABs. Considering it as a wide research discipline, the intervention criteria of searching the relevant primary studies is chosen to be strict. Some systematic reviews accommodate all the recent studies of this area, this review particularly is conducted to enhance the view only towards the phase shift-based optimization strategies and provide boarder insights of DAB optimization to researchers and engineers. It was seen that other than 3 basic phase shift techniques (SPS, DPS, TPS), studies with modified versions enhance the efficiency of DAB by mitigating the DB current.

“Design and development of magnetic field harvester to power wireless sensors in smart Grid”

Abstract Real time monitoring of high voltage devices in smart grid is implemented using wireless sensors. They ensure reliable power transfer and avoid cascading power failures. Powering these sensors remotely is a challenge. This paper presents a novel method of powering sensors remotely using magnetic field harvester. A dumbbell shaped magnetic core is designed and optimized to harvest magnetic field near high voltage bus bars/transformers in electrical substation. The harvested power is rectified and boosted. Impedance matching circuit is designed to obtain maximum power transfer to the wireless sensor. The energy thus harvested is used to power wireless sensors and make them self sustainable. The experimental results show that the proposed core with 40,000 turns can harvest 17.6 mW of output power when placed in magnetic flux density of 9 µTrms.

Interval Type2 Fuzzy Logic Based STATCOM Controller for Stabilizing a Mixed Electrical Network System

Adding renewable energy plants to the electrical grid reduces the performance of energy systems. This results in problems including power fluctuations and poor voltage quality. This paper presents an interval type2 fuzzy logic-based controller, consisting of current and voltage regulators, that is applied to a STATCOM to regulate the DC voltage under various operating conditions. a membership functions not used before in this filed have been used to generate IT2FL sets output. The STATCOM has been connect with the high voltage bus bar in order to use one STATCOM for all the loads According to comparative studies, the proposed method outperforms traditional PI and type1 fuzzy logic-based controllers.The simulation has been implemented using MATLAB/SIMULINK software and the results confirm the feasibility of the proposed system.

Design and verification of the energy system of the China space station core module

<p indent="0mm">After its successful launch on April 29, 2021, the China space station core module has been operating stably in orbit. The energy system is an important part of the core module, converting solar energy into electricity and then controlling and regulating the electric energy to provide a continuous, stable, and reliable power supply to all electrical equipment. This paper introduces the structure of the energy system used in the module, analyzes the design of independent energy health management, high voltage bus regulation, and large flexible solar cell wing, and introduces on-orbit flight verification.

A proposed wide-area stabilization system through a large-scale fleet of electric vehicles for grid

A wide-area grid is a large-scale high voltage power system with regional grids integrated by transmission lines. This work proposes a Wide-Area Stabilization System (WASS) with Phasor Measurement Unit (PMU) sensors and battery converters to mitigate transients in inter-area transmission lines caused by an (N-1) event of line trip. PMU is a measuring device capable of monitoring high voltage buses' magnitude and phase angle in a power grid on a time scale synchronized with a global reference clock. The outreaching time synchronization allows wide-area monitoring of the state of the power system and electrical protection. Three PMU-WASS are modeled on an IEEE 68-buses system and simulated using the YVI Photon++ platform for power system dynamic studies. The results show that the proposed WASS with energy storage avoids the system collapse after line tripping. This research reveals that strict requirements for electrical power converters bring systemic benefits and may be needed ahead of the future large-scale worldwide expansion of electric vehicles fleet.

Interference to the Secondary Cable Caused by a Very Fast Transient Overvoltage in a Gas-Insulated Switchgear Substation

When a very fast transient overvoltage (VFTO) propagates in a high-voltage bus, the capacitive voltage transformer (CVT) causes considerable interference on its secondary side, which will affect the normal operation of the secondary equipment. In this article, a CVT equivalent calculation circuit model was established, and the disturbance voltage of the secondary cable was deduced and calculated. Using electromagnetic transient simulation software, a simulation model of the secondary cable disturbance caused by the VFTO in a 500 kV gas-insulated switchgear (GIS) substation was established, the disturbance voltage at the end of the secondary cable was simulated and analyzed, and the effects of the length of the secondary cable and the grounding mode of the shield on the disturbance were studied. Combined anti-interference measures are also suggested, which use a spiral tube damping busbar, grounding at both ends of the shield using multistrand conductors and installing filter capacitors, all of which greatly reduce the amplitude and harmonic components of the disturbance voltage of the secondary cable.

Bidirectional Power Sharing of Modular DABs to Improve Voltage Stability in DC Microgrids

The dual active bridge (DAB) converters have the capability of handling high power in compact form and it is one of the key elements for interconnecting different dc microgrid clusters. A DAB also offers bidirectional power transfer with galvanic isolation between two power buses of similar or different voltage levels, i.e., low voltage and high voltage buses. In microgrid applications, bus voltage regulation is necessary for an uninterrupted power flow and reliable operation of dc microgrids. Due to the galvanic isolation and modularity nature of a DAB, the output can be easily interconnected for efficient and reliable power sharing. In this article, taking the advantage of modularity property of the DAB, an efficient and improved power sharing scheme is developed to stabilize the bus voltage in microgrid applications. A robust bidirectional power sharing control strategy is developed between DABs from different high voltage buses to low voltage buses that improves the voltage stability. An advanced supervisory controller is designed by considering the nonlinearity and uncertainty that ensures stable dc bus voltage and reliable power sharing among DABs under different operating conditions. The controller is validated theoretically and a small-scale laboratory prototype is developed. The concept is verified experimentally at different possible scenarios. From theoretical and experimental results, it is found that the proposed DAB control provides excellent performance in terms of power sharing, dc-bus voltage regulation and power quality.

On-Grid solar microgrid temperature monitoring and assessment in real time

Remote solar panel temperature monitoring in micro-grid has been proposed. A three-phase voltage source converter (VSC) type inverter has been employed for conditioning the input power from solar photovoltaic arrays. The three-phase inverter's output was linked to a transformer and a high-voltage grid bus before being distributed to different load ends. The inverter's output currents were recorded and evaluated. At typical operating circumstances, subharmonics, DC components, and Total Harmonic Distortion (THD) of inverter secondary currents were measured. Then, at various temperature levels, wavelet decomposition, i.e., skewness and kurtosis on line currents, was estimated. At various decomposition levels, detailed and approximate coefficients were produced, and their skewness and kurtosis values were used to examine the nature of these coefficients. Different modelling approaches have been used to extract distinct aspects for evaluating temperature impacts on solar panels and remote monitoring of microgrids.