Auxiliary Power Supply Research Articles

Digital-Power-Communication Concept for Energy Coordination in PV-Battery-Charging DC Microgrid

A new digital-power-communication (DPC) concept is proposed to better realize information interaction and energy coordination in the PV-battery-charging DC microgrid, which uses the DPC auxiliary power supply as carrier. The DPC auxiliary power supply can be used to replace other communication modules as a common carrier for auxiliary power supply and information interaction of microgrid interface converter. Then, the implementation conditions of DPC are indicated that this communication concept requires active power consumption and an adjustable resonant network. Meanwhile, an appropriate circuit topology of the DPC auxiliary power supply is evolved. Furthermore, an integrated control method of optimal-admittance information regulation & power supply is further proposed for the DPC auxiliary power supply, and the implementation mechanism of this method is analyzed in detail by establishing the admittance model. More importantly, based on this method, the contradiction between power supply quality and signal intensity can be solved in the transmit mode, and the received signal intensity of the communicating node can be significantly enhanced in the receive mode. Finally, the PVbattery-charging DC microgrid platform is developed, and the experiment result verify the feasibility of the DPC concept and the effectiveness of the proposed control method.

An improved Buck converter with high frequency and high step‐down ratio for auxiliary power supply applications

AbstractBuck converter is a good candidate for the non‐isolated auxiliary power supply (APS) due to its simple structure and high efficiency. However, it can hardly be adopted in applications that required a very high step‐down ratio due to the difficulty to realize an ultra‐low duty cycle, especially when the switching frequency becomes higher and higher. Here, an improved Buck converter is proposed for high‐frequency and high‐step‐down‐ratio APS application. With the control method based on energy extraction, the proposed topology can achieve an ultra‐low equivalent duty cycle. Thus, a high step‐down ratio can be achieved under a high switching frequency. Moreover, the proposed structure can be applied on several types of the main power stage through the power switch sharing technique. Finally, the prototype with the switching frequency of 1 MHz and the step‐down ratio of 18:1 is verified by the experimental results.

Prospects for the application of battery energy storage systems in NPP auxiliary power supply systems

One of the characteristics of energy strategy, which currently implementing is atomic energy elaboration and NPP development with rising part of atomic generation in national energy system. Of course one of the most important property of atomic generation is safety (Chernobyl, Three Mile Island, Fukushima Daiichi accidents). To maintain the operation of security systems in conditions of loss of external power supply, autonomous power sources - diesel-generator sets are used, but their use is associated with a number of difficulties of operation and maintenance, and currently developing technologies allow to realize new processes of energy transformation. And on the other hand modern technologies are providing access to new energy saving technologies. In this article we will try to compare energy storage systems, which use different physical principles and try to review their advantages and particularities. Also we especially explore operational advantages of battery energy storage systems and their influence on atomic safety and maintenance cycles and also integrating to digital control system and more effective generation and flexibility during NPP operation with conclusion about new business for «Rosatom» company.

Use of Physics-Based Models for Different Applications of Electrochemical Energy Storage and Conversion Devices

This talk will present the application of physics-based models applied to two different electrochemical storage and conversion systems, viz. Li-ion batteries and Proton Exchange Membrane Fuel Cells (PEMFCs). Battery energy storage system (BESS) is becoming a crucial part of standalone renewable hybrid power systems due to the intermittent nature of power generation and for aiding in various operations like frequency regulation, voltage support, and peak shaving. The lithium-ion battery is a promising choice for BESS due to its high energy density, power density, operating voltage, negligible self-discharge, suitable operating temperature range, modularity, and reliability. A standalone renewable hybrid power system framework with lithium-ion battery energy storage is developed to investigate its performance using physics-based battery models. Power management and control strategies are developed for standalone renewable hybrid power systems. These control strategies can track the MPP of the solar cells and wind turbines while avoiding overcharging the battery and guaranteeing 0% dumping power under different ambient and working conditions. The battery is exposed to harsh ambient conditions in the real world, resulting in the dynamic and continuous capacity fade. A thermal management and control strategy is developed to analyze the effect of temperature on lithium-ion batteries' performance and degradation without using external cooling systems. Dynamic battery degradation analysis and life prediction are essential for better techno-economic estimation of renewable hybrid power systems. The impact of BESS size variation on degradation and the cost of energy generation is analyzed. The developed renewable hybrid power system framework is independent of location and system size and can be extended to incorporate other renewable energy generation sources and energy storage systems.The second part of this talk will focus on using physics-based models to understand the water dynamics and degradation mechanisms inside PEMFC, which is necessary for water management, long-life operation, and cost reduction. PEMFCs have emerged as an alternative green energy technology in various applications such as automobiles, portable and stationary applications, and auxiliary power supplies for space exploration missions. The cost and durability targets remain unmet largely, which restrains the commercialization of the PEMFCs. The major difficulty in modeling lies in the wide scale of dimensions from the millimeter level (flow channel) to the micron level (catalyst layer (CL) thickness). The multi-scale physics-based model enables the life cycle analysis of PEMFC under various operating conditions. The mass transport limitation is the major hurdle in performance enhancement for higher current density operations. It arises from the liquid water generated during the electrochemical reactions, which hinders the reaction sites of CL and oxygen transport reaction sites in the gas diffusion layer, resulting in performance deterioration. Many experimental studies reported the two-phase flow visualization techniques in PEMFCs, viz. neutron imaging, optical visualization, and X-ray radiography. However, the difficulties in conducting experiments for flow visualization and related parameters such as liquid volume fraction have encouraged researchers to adopt numerical simulations that are less expensive and computationally efficient. Understanding liquid water movement inside the cell at the micro-scale help to improve the PEMFC performance at the stack level. Here, we develop a comprehensive 3-D, multiphase, non-isothermal, steady-state physics-based model of the PEMFC that can closely approximate the liquid water flooding and membrane drying. The findings from this work can be used to design an efficient flow configuration and to study membrane deformation due to the shrinking-swelling under humidification and thermal cycling. The ultimate goal of the multi-scale model is to enhance the PEMFC stack output with less degradation.

Auxiliary Power Supply System with Parallel-Connected DC–AC Inverters for Low-Floor Light Rail Vehicle

This research proposes a roof-mounted auxiliary power supply (APS) system for 600 VDC low-floor light rail vehicles (LRVs). The proposed APS system consists of five parallel-connected dc–ac inverter modules (modules 1–5). Inverter modules 1 and 2 are three-phase dc–ac inverters for the compressor motors of the air conditioning system, and inverter modules 3 and 4 are three-phase dc–ac inverters for the air pump motors of the air supply system. Inverter module 5 is a single-phase dc–ac inverter for the 220 VAC power supply of onboard electric loads. Simulations and experiments were carried out under variable load torques and output frequencies for modules 1–4 and under full and no resistive loads for module 5. The measured total input current and total input power of the proposed APS system under the full-load condition are 114.36 A and 68.84 kW. The total efficiency of the proposed APS system (modules 1–5) is 97.05%. The proposed APS system is suitable for 600 VDC low-floor LRVs. The novelty of this research lies in the use of five parallel-connected inverter modules, as opposed to the three-phase output transformer or isolated dc–dc converter in the early and conventional APS systems. Specifically, the proposed APS system requires neither a three-phase output transformer nor an isolated dc–dc converter.

A Class-E-Based Multichannel Auxiliary Power Supply With Individual Hysteresis Control

A high performance auxiliary power supply (APS) with multiple isolated outputs plays a crucial role in ensuring the effective operation of power converter systems. An isolated resonant current source converter is usually adopted as the APS in medium-voltage (MV) applications with the advantages of low coupling capacitance and high insulation strength. In this paper, a Class E-based multichannel APS, featuring a low component count, modular circuit structure and ease of scalability to multiple output channels, is proposed. The operation principle of the proposed circuit is presented in detail. To overcome the cross-regulation problem in multiple outputs, an individual hysteresis control approach is introduced to regulate each output separately and decouple the multiple outputs. The converter performance under open/short-circuit fault conditions is also explored with the proposed control scheme. Design considerations, including the zero-voltage-switching (ZVS) realization and the output power capabilities, are presented, together with a step-by-step parameter design approach. Finally, an 8 output APS experimental prototype (with different output voltage levels) is presented. The experimental results demonstrate the output voltage decoupled regulation and load independent ZVS performance of the prototype.

Auxiliary Power Supply for Input-Series Output-Parallel Medium-Voltage Solid State Transformers

Auxiliary power supply (APS) is an essential component of medium voltage (MV) solid state transformers (SSTs) feeding the auxiliary units, such as gate drivers, controllers and sensors. Usually APSs are obtained from the distributed bus, which may cause the input voltage imbalance before the main power transmission. This paper proposed a new design for isolated APS of an input-series output-parallel (ISOP) SST. The designed distributed MV APSs are galvanically isolated by flybacks, and the centralized APS on the low voltage (LV) side is supplied from the MV APSs via a decoupling four-port medium frequency transformer (MFT) with high isolation voltage. To solve the issue of input voltage imbalance posed by the ISOP system, a dual-loop control scheme based on APS-fluctuating is proposed, which can realize output voltage regulation (OVR) and input voltage sharing (IVS) simultaneously. The small-signal model, start-up strategy and parameter design of the proposed system are investigated. Finally, a 500 V/2.2 kW lab prototype of SST with APS has been built and the overall system efficiency reaches 95.1%.

Incorporation of fuel cell in oil refinery a step to achieve net zero-carbon emission goal

The usage of fuel cells is growing rapidly in various industries, and employing it as an alternative power source in oil refineries which will assist many large oil firms in achieving the global energy transition. The present paper focusses on significant utilization of fuel cell in downstream refinery to reach sustainable energy pathway towards net zero emission. The combination of gas turbine technology with high temperature fuel cells provides a power generating platform with ultra-high efficiency, ultra-low emissions, and fuel flexibility. Advances in R & D helps in reducing the cost of fuel cell and are now being used to power fuel cell producing energy ranging from 1 Watt to 10 Megawatt. The auxiliary power supplies and heat energy needed in refineries can be replaced by the use of these fuel cell. Fuel cell can be used in conjunction with the gas turbine for power supply with greater efficiency and lesser use of hydrocarbon-based fuel especially in equipments such as hydrotreater, desalting unit, pump and compressor unit etc. The heat generation in the fuel cell is associated with voltage losses and this generated heat can be used in reformer for hydrogen production, for space heating and preheating the steam required for heating of crude in crude oil distillation unit, vacuum jet, power turbines etc. With virtually zero harmful emission, minimal amount of space and higher efficiency reaching up to 60 %, the fuel cell can be utilized for optimum energy distribution in auxiliary units used in refinery.

Medium-Voltage Isolated Auxiliary Power Supply Design for High Insulation Capability, Ultra-Low Coupling Capacitance, and Small Size

To fully utilize the benefits of MV SiC-based converter and achieve high power density, the isolated auxiliary power supply (IAPS) needs to be as small as possible. However, the high insulation and low coupling capacitance requirements, considering the high voltage and high dv/dt, are constraints of size reduction. This paper proposes a MV IAPS design for high insulation capability, ultra-low coupling capacitance, and small size. The topology selection, efficiency, load regulation, coupling capacitance, and size reduction considerations are discussed. A 2.5 W MV IAPS is designed and built for a 10 kV SiC MOSFET-based 13.8 kV/100 kW three-phase converter, achieving a partial discharge inception voltage of higher than 15 kV RMS, ultra-low coupling capacitance of 1.03 pF, and smaller size than that of the commercial products as well as the state-of-art research prototypes. Experimental results of partial discharge (PD) test, 10 kV SiC MOSFET-based half-bridge test, and 13.8 kV/100 kVA three-phase converter full rating test are conducted for design validation.

A nine-switch inverter with reduced leakage current for PV grid-tied systems using model-free predictive current control

To address the leakage current problem of transformerless three-phase inverters for photovoltaic (PV) grid-tied systems, H8 and improved H8 inverters were proposed to alleviate the leakage current of the PV grid-tied systems to a certain extent. However, these inverters cannot avoid the high-frequency switching of the generated common mode voltages (CMVs) among multiple levels, resulting in the unsatisfactory effect of the leakage current suppression of these inverter topologies. In order to solve these problems, an auxiliary power supply based nine-switch (AP-H9) inverter with reduced leakage current is proposed in this paper. A DC auxiliary circuit containing a switch is added to the inverter based on the H8 inverter, and one or more diodes are connected in reverse parallel with other corresponding switches to form the H9 inverter topology. By properly controlling the nine switches and using the reverse diodes to divide the DC voltage , the CMV of the system is limited to 2/3 times of the DC voltage, which can effectively suppress the leakage current of the PV grid-tied system. In addition, a model-free predictive current control (MFPCC) method based on ultra-local model is presented to eliminate the dependence of inverter control performance on system parameters. This method uses the voltage and current information of the previous two moments to realize the online update of the gain and dynamic part of the ultra-local model, and then obtain the predicted voltage vector for the next moment. Moreover, the switching loss optimization constraint is considered in the cost function to further improve the efficiency of the inverter. Finally, an experimental prototype is developed. The simulation and experimental results show that the proposed inverter and its control method can effectively suppress the leakage current of PV grid-tied system, and are insensitive to parameter changes.

Research on the Control Strategy of Urban Integrated Energy Systems Containing the Fuel Cell

As a new type of energy with the advantages of high efficiency, clean and pollution-free, fuel cells have attracted the attention of many experts and scholars. The efficient utilization of fuel cells will certainly become the mainstay of energy transformation and environmental protection. However, fuel cells have low power density, soft electrical output characteristics, and significantly delayed response to sudden load changes. When fuel cells are used as power supply energy alone, the output voltage fluctuates greatly, and the power supply reliability could be higher. To increase the fuel cell’s service life in real world applications, a DC converter and an appropriate auxiliary energy storage power supply are combined to form a fuel cell hybrid power supply system that makes efficient use of the auxiliary energy storage system’s availability, enhances the power supply system’s adaptability through dynamic reconfiguration, and provides better flexibility overall. This work proposes a method for managing the energy produced by an urban integrated power supply system that includes fuel cells, supercapacitors, and solar cells. Applying the IF-THEN rule of load power and the state of charge of the supercapacitors, the power balance is adjusted between the su-percapacitors, photovoltaic cells, and fuel cells according to the defined fuzzy logic control. The intermittent nature of solar power production and the erratic nature of fuel cell output may both be mitigated using this technique, allowing the load power to operate more reliably. The simulation results show that the control strategy adopted in this paper is able to not only meet the load requirements but also reasonably allocate the functional requirements and improve the working efficiency of the system, resulting in a clear optimization effect on the system’s control. In this paper, we focus on the fuel cell hybrid power supply system design, and then we use the idea of fuzzy logic control energy management to build the structure of the fuzzy logic control system, design the fuzzy controller, determine the functions, and verify the solutions through simulation and experimentation.

Integrated Nanogrid for the Impressed Current Cathodic Protection System in Desalination Plant

The impressed current cathodic protection (ICCP) scheme is a more reliable and efficient method of corrosion prevention mechanism than the sacrificial method. Currently, the grid connected transformer rectifier units supported with a battery banks are used for the ICCP-based corrosion protection system in the desalination plant. This conventional method is entirely grid-dependent, more expensive, and suffers during prolonged grid failure. The present trend of industrialization is the application of multi-renewable energy sources based on a nanogrid to power the station’s auxiliary power supply. This paper introduces a concept of distributed energy resources (DERs) operated integrated nanogrid (ING) system to provide a stable power supply solution to the ICCP scheme. A 100-million-litter per day capacity-based seawater desalination plant (SWDP) in India has been chosen as the test station. The conceptual hardware design and operational logic details for smooth integration of the integrated nanogrid module into the ICCP scheme of the Desalination plant is proposed. This research aims to investigate the behaviour of DERs during on-grid, off-grid and switching over from one mode of operation to another and vice-versa by using the accelerated Gauss–Seidel method in ETAP software (version 16.0.0). The simulation results confirm that the ING suffers from a high-frequency change rate during islanded operation, and in some cases, a complete blackout occurs. A PLC-based Smart Versatile ING Controller has been suggested to overcome the blackout issue. Finally, it has been proven that the stability of an industrial power system can be improved further by introducing the ING module into it.

Exponential Curve-Based Control Strategy for Auxiliary Equipment Power Supply Systems in Railways

An exponential curve-based (ECB) control strategy has been proposed in this paper. The proposed ECB control strategy is based on the growth and decay of charge in the series RC circuit and the harmonic elimination by detecting the Fourier expansion series of the auxiliary equipment power supply system’s (AEPSS) three-phase output voltage level. It can quickly adjust each duty cycle to the best value for driving the isolated three-phase inverter (ITPI) and produce a three-phase 380 VAC/60 Hz output. A comparison of the AEPSS output performance using the traditional voltage cancellation method (VCM) and the proposed ECB control strategy was performed. The hardware implementation of the system was performed on the prototype developed in the laboratory. These control strategies are tested under three conditions, i.e., (i) Vi = 550 VDC. (ii) Vi = 750 VDC. (iii) Vi = 800 VDC. The total harmonic distortion (THD) is 13.7%, 14.5%, and 14.9%, and the output voltage Vo is 372.3 VAC, 377.3 VAC, and 385.3 VAC using the traditional control strategy at three test conditions, respectively. However, the THD is 7.2%, 7.8%, and 8.0%, and the output voltage Vo is 382.2 VAC, 381.2 VAC, and 381.9 VAC using the proposed ECB control strategy under the test conditions. It is obvious from the hardware results that the output voltage harmonics and output voltage level for the proposed ECB control strategy are superior to the traditional VCM. The voltage produced from the AEPSS using the proposed ECB control strategy is more stable and has better quality. In addition, the filter size is also reduced.

A Compact Auxiliary Power Supply Design for a Medium Frequency Solid State Transformer

The design of auxiliary power supply (APS) in solid-state transformers (SSTs) is quite challenging. To minimize the isolation requirement, this APS is usually powered by dc-link capacitors. However, it poses voltage unbalance issues when the main converter is not in operation. To address this problem, a compact and cost-effective APS design is proposed, which utilizes the isolation structure of main medium-frequency transformers (MFTs). The proposed APS system also provides half-duplex communication, which replaces the costly optical fiber system. The interference between main and auxiliary power transfer links has been significantly reduced by the decoupled transformer design and the dual-band scheme for inductor-inductor-capacitor (LLC) and inductor-capacitor-inductor-capacitor (LCLC) converters. In addition, a new startup strategy with a low standby power is applied to this APS system. A 3.2-kW SST prototype with a peak efficiency of 97.9% has been built, whose APS is 6 W. The experimental results verify the feasibility and performance of the proposed techniques.

Magnetic Decoupling of Winding Design in Dual Wound Generators

A general shipboard power system contains multiple electrical machine sets to provide electrical power with different ratings for both the propulsion system and the ship service. In order to achieve the most compact design and maximize the weight reduction, a study of using a single dual wound generator to replace the electrical machine sets is presented in this paper. It consists of dual two-layer windings of different pole numbers which use the same slots and share one prime mover, producing two independent power supplies. This paper verifies a dual wound machine designed for no electromagnetic coupling by algebraically analyzing the spatial harmonic magnetic field distribution. Further verification of the absence of electromagnetic coupling due to both the airgap and slot leakage fluxes is provided by 2D finite element modeling. The dual wound generator prototype using the principle is designed, built and experimentally tested. The experimental results match well with the simulation results, validating the independence of the two power outputs and showing that the winding end-turns also do not couple. The results are significant for applications where multiple independent power supplies are needed, or where an auxiliary power supply is needed which could be drawn from an existing traction motor.

Blackstart Capability of Modular Multilevel Converters From Partially-Rated Integrated Energy Storage

This paper discusses blackstart provision enabled by Modular Multilevel Converters (MMC) with integrated partially-rated Energy Storage (ES) systems. It is demonstrated that ES units integrated in an MMC for ancillary service provision can be utilised to energise the auxiliary power supply electronics of the submodules (SMs), fully charge the converter capacitors, and establish voltage at the ac and dc terminals. This feature can prove especially useful during the converter start-up phase in passive grids or following a post-fault disconnection event. For an MMC with integrated ES, the added functionality of charging the converter capacitors and starting-up the adjacent networks requires no additional infrastructure – only an updated control scheme. The charging algorithm goes through successive steps: ES-SM charging, <styled-content style="color:black" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">activation of the Auxiliary Power Supplies in the SMs</styled-content> , active charging of all SMs, <styled-content style="color:black" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">and finally,</styled-content> connection to the grid. The effectiveness of the method is confirmed by simulation results where a fully disconnected MMC charges nominally within 2 seconds, and connects to <styled-content style="color:black" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a passive</styled-content> ac network. <styled-content style="color:black" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">By using a grid forming control scheme, the converter ramps up the voltage at the ac terminals and supplies 5% of active and reactive power with only 4% of ES-SMs per stack.</styled-content>

Buck-Boost Type High Step-Down Low Power Modular Converter for Medium Voltage DC Systems

The medium-voltage dc (MVDC) system are intensely investigated by both industry and academy. However, how to realize a lower power circuit directly fed by MVDC is an important but easily neglected problem, which seriously affects the reliability of the dc system. The current high step-down circuits are mostly suitable for high-power applications, while the circuits for low-power applications are designed case by case. To address the obstacle, a generalized buck-boost type high step-down converter (BHSC) structure is proposed in this article. The submodules of BHSC are derived from basic dc–dc converter. As a result, the features of high modularity, simple structure, and low cost can be obtained, and each submodule operates independently without communication and synchronization to achieve voltage balance. Furthermore, a submodule strategy with Bang-Bang control, instead of hardware modification, is proposed to overcome the limitation of BHSC generality in medium-voltage (MV) and high-voltage (HV) applications, due to the operating current difference in different submodules of the cascaded structure. Therefore, BHSC can be easily extended to MV or HV by increasing the number of submodules. Finally, an experimental evaluation of a 1 kV/80 W prototype converter is presented, which can be applied as auxiliary power supply for high-power converter.

Design and Performance analysis of Cuk SIDO Converter using PI-Lead compensator for EV Auxiliary Power Supply

Design and Performance analysis of Cuk SIDO Converter using PI-Lead compensator for EV Auxiliary Power Supply

Railway Auxiliary Power Supply System: A Modular Multilevel Converter Approach

When it comes to power railway systems, two main aspects must be considered: (i) the power of the propulsion of the train, which is responsible for the movement of the train; (ii) the power of the auxiliary services, which is responsible for the power inside the train for commodity and service of the passengers. As such, two different converters are used, namely the propulsion converter and the static converter, respectively. This paper proposes a new topology of a static converter, using a modular multilevel converter with high frequency output, with a high frequency transformer to reduce the size of the converter. The output of the converter is responsible for creating a stable single-phase voltage, with nominal values of 230 V - 50 Hz, from a highly variant input voltage available on the DC-link.

A strategy to identify breakdown location in MITICA test facility: results of high voltage test campaign

The Acceleration Grid Power Supply of the MITICA test facility in Padova (Italy) is currently under commissioning. The power conversion system, the DC generator, and the High Voltage equipment have been individually commissioned, whereas the integration tests are ongoing. It is a challenging process due to the unconventional application, to the variety of different electrical technologies involved and to the complexity of the interfaces.During the integrated tests of the power supplies the achievement of 700 kV stable operation has been demonstrated for the first time in a Neutral Beam Injector, but an unexpected event occurred, most likely a breakdown in the HV part, which resulted in a fault of the DC generator. A subsequent test using an auxiliary power supply was performed to check the voltage withstanding capability of the HV plant, but another breakdown occurred at around 1MV.This paper describes the activity performed to identify the location of the breakdowns affecting the integrated tests. A test campaign has been devised with increased diagnostic capabilities and specific strategy conceived to trigger intentional breakdowns in specific locations and collect measurement patterns for different cases. The results of the campaign will be presented and the current understanding of the issue will be described, with a view on future tests and further improvements of diagnostics.