Low Power Rating Research Articles

A novel dual-leg DC-DC converter for wide range DC-AC conversion

This paper proposes DC–AC Dual-leg dual-stage Conversion (DDC) and DC–AC Direct single-stage conversions (DSC). Conventional energy conversion system has only two-stage conversion, so it has some drawbacks such as huge power loss, less conversion range and lower power rating. So direct conversion, dual-leg step-up and step-up conversions are the solutions to get wide voltage conversion efficiently. The proposed converter can perform the power conversion from battery DC supply into AC with 1:1 ratio, step-up AC, and step-down AC in both directions. Also, it can perform rectifier operation from grid AC supply into DC with 1:1 ratio, step-down DC, and step-up DC. Step-up, step-down and ideal operations are possible within a single circuit; its operation is similar to solid-state DC–AC/AC–DC transformer. The ideal operation, Step-down to Step-up conversion and Step-up to Step-down conversion are possible on both sides, so this converter can handle a wide range of voltage. Power distribution is achieved with voltage regulation between battery/DC-load and AC-load/grid using the proposed control strategy with proper modulation. A prototype model of a 2-kW power rating validates the advantages and feasibility of the proposed methodology.

A non‐isolated high voltage gain DC–DC converter based hybrid switched LC network for renewable energy applications

AbstractThis paper presents a new high voltage gain DC–DC converter for renewable energy applications without the need for a galvanic isolation. The converter combines the active switched‐inductor network and the switched‐capacitor network to boost the voltage gain ratio without a high duty ratio. The presented converter uses clamping capacitors to minimize the maximum voltage stress of the power‐switching devices; hence, low power rating devices can be employed. Furthermore, the converter operates at a high switching frequency. Therefore, the use of small inductors and capacitors is the main advantage. The paper describes in detail the operating mode and design procedures of the converter. Additionally, the associated power losses and the efficiency are calculated. A 200‐W laboratory prototype was fabricated, and experimental results verified the theoretical analysis.

Waveform and Spectral Characteristics of Supraharmonic Unsymmetrical Conducted EMI of Switched-Mode Power Supplies

Switched-mode power supplies (SMPSs) are a relevant and widespread source of unsymmetrical conducted emissions, as they feed various electrical appliances and information technology equipment in office and residential contexts and, despite their low power rating, the limits are the same as those of larger equipment. Given the peculiar emission waveform (mixing impulsive components and switching components), assessment should be carried out with care to select parameters that guarantee both the detection of the maximum level of emissions and a high level of repeatability and reproducibility. A range of cases based on six different SMPS products was considered, exploring both time- and frequency-domain characteristics, and identifying the most relevant phenomena and advisable parameters choices. Typical behavior and suitable settings were exemplified with a range of measured emission records: the Fourier time window length and EMI receiver dwell time were considered, as well as the relevance of loading conditions to include in a comprehensive test program. Such records were made available in a linked dataset to allow for replication of the experiments and foster further findings and discussion.

A Coordinated Control Method for Integrated System of Wind Farm and Hydrogen Production: Kinetic Energy and Virtual Discharge Controls

This paper proposes a novel coordinated control method of wind farms (WFs) and hydrogen production systems (HPSs). In a grid-connected system where the WF and the HPS are connected to the grid, the WF can supply the power to the grid, producing hydrogen in the HPS. Moreover, the output fluctuation of the WF can be mitigated when the HPS produces hydrogen from the output surplus. The purpose of the grid-connected system is to smooth the WF output fluctuation sufficiently, produce hydrogen constantly, and maintain a high capacity factor in the HPS. The proposed coordinated control achieves the mitigation of the WF output and the high capacity factor in the HPS. The key ideas are 1) utilizing the kinetic energy of wind generators and 2) virtual discharge of the HPS. The fluctuation components of the WF output are compensated by both the WF and the HPS. The proposed coordinated controller enables us to produce hydrogen constantly in the HPS with a low-rated power. The advantage of the proposed coordinated control is verified by a comparative analysis with conventional methods through simulations using real wind data.

Design Simulation of Improved Power Quality Conditioner System for Enhancement of Power Quality

The increased usage of power-sensitive electronic devices has prompted interest in power conditioning solutions, which is no surprise. As a result, some type of compensation must be supplied if power output remains below the standards' prescribed limitations. The UPQC (Unified Power Quality Controller) is one of numerous AC Transmission System families that can control voltage, impedance, and phase angle among other factors (FACTS). This study focuses on modern UPFC systems that have increased power quality efficiency to help utilities reduce voltage concerns. One of the FACTS controls for lowering stress sales effects is a unified power quality conditioner (UPQC). The quadrature voltage is specified using the UPQC series compensator. As a result, the compensator series never utilizes active power in a continuous scenario. As mentioned in the approach, a low power rating compensator injects voltage to remedy the system's power quality problem. The voltage is decreased and the power factor is raised when the fluid logic controller is used in conjunction with traditional UPQC. Furthermore, the load factor has been improved. The circuit is then imitated in MATLAB / SIMULINK using a fluctuating logo controller.

Investigation of Distribution Transformers Vibrations in Terms of Core and Winding Condition Assessment

This work refers to the criterion values used to assess the state of the active part of the transformer based on the analysis of the effective value of the total vibration acceleration and the frequency spectrum. It was proved in the work that the criteria values should be differentiated for transformers of different rated power. Transformers with lower rated power are characterized by lower RMS values of vibration acceleration than units with higher rated power, which cannot remain without impact on the criteria values. Trend analysis of the total aRMS values may reveal increasing defects before the currently applicable criteria values are exceeded. In addition, the influence of the position of the sensor on the frequency spectrum of the obtained signals was analyzed. It was proved that the sensors should be mounted in the middle of the transformer tank, between its lower part and the cover. The dependence of RMS value of vibration acceleration on no-load losses was also determined for transformers of different types but the same rated power. This relationship will not have a large share in the total vibrations of the transformer, due to slight changes in the value of aRMS occurring for all analyzed units.

Comparative Study of Energy Consumption and CO2 Emissions of Variable-Speed Electric Drives with Induction and Synchronous Reluctance Motors in Pump Units

This study carried out a comparative analysis of indicators of electricity consumption and CO2 emissions for four-pole induction motors (IMs) of efficiency classes IE3 and IE4 with a rated power of 2.2–200 kW in a variable speed pump unit. In addition, innovative IE4 converter-fed synchronous reluctance motors (SynRMs) were evaluated. The comparison was derived from the manufacturer’s specifications for the power drive systems (PDSs) at various rotational speeds and loads. The results showed that the emission indicators for IE3 class motors were significantly worse compared with IE4 class motors for low power ratings, which make up the vast majority of electric motors in service. This justifies expanding the mandatory power range for IE4 motors to at least 7.5–200 kW or even 0.75–200 kW, as it will dramatically contribute to the achievement of the new ambitious goals for reducing greenhouse gas emissions. In addition, the operational advantages of IE4 SynRMs over IE4 IMs were demonstrated, such as their simpler design and manufacturing technology at a price comparable to that of IE3 IMs.

Impact of core power density on economics of a small integral PWR

Increasing the core power density of nuclear reactors allows higher power generation from the same volume, reducing the cost of the plant. The lower power rating and higher degree of inherent safety for small modular reactors motivate exploring the highest achievable power density to improve their economics and overcome lack of economy of scale. Given the urgency to deploy carbon free energy sources in the near term, the current nuclear fuel supply must be adopted. Assuming standard 17x17 pressurized water reactor (PWR) fuel assemblies with enrichment below 5%, a parametric study on core power density of an integral PWR (iPWR) is performed. The reference core design is rated at 60 kW/L and composed of 77 reduced-height fuel assemblies. The reactivity control during normal operation is assumed to utilize soluble boron and fuel burnable poisons. The commercial STUDSVIK code package is used to design cores ranging from 20 kW/L to 170 kW/L. This range results in respective output powers between 50 and 420 MWe for an assumed 32% plant thermal efficiency. Core safety parameters, such as peaking factors, Minimum Departure from Nucleate Boiling Ratio and maximum fuel temperatures are evaluated for all designs. Simplified economic evaluation of lifetime-levelized unit costs for the fuel cycle, operation and maintenance and capital expenditures was performed as a function of power density. The relatively low core discharge burnup (32 MWD/kgU) leads to high lifetime-levelized fuel cycle unit cost for the reference core. However, increase in power density allows significant reduction in operation, maintenance and capital unit costs. Doubling power density resulted in 80% reduction in total levelized cost of electricity. The unique features of a forced circulation iPWR technology combined with compact steam generator technology could allow achieving high power densities (greater than 125 kW/L). Specific examples on relationship of cost and safety margins are also discussed.

Performance enhancement of single-phase induction motor using GA based multi-objective Optimisation

ABSTRACT Single-phase induction motors (SPIMs) are commonly used in domestic and industrial applications because of their robustness, low power rating, and simple input power requirement. Due to their widespread application, the dynamic performance and efficiency at the operating point have become vital to ensure energy conservation. This paper is aimed to optimise both the dynamic performance and efficiency of SPIM for water pump application at rated speed. Multi-objective optimisation is performed by employing the genetic algorithm using a Maxwell-2D transient solver. The analysis presents the comparison between the optimised and basic motor designs while considering various manufacturing constraints. The study proposes a framework for performance enhancement of SPIM while verifying the optimal solution through sensitivity analysis. The obtained results show the high performance of optimised SPIM design with a 17% increase in efficiency compared to the basic motor.

Maybe less is more: Considering capacity factor, saturation, variability, and filtering effects of wave energy devices

While a great deal of research has been performed to quantify and characterize the wave energy resource, there are still open questions about how a wave energy developer should use this wave resource information to design a wave energy converter device to suit a specific environment or, alternatively, to assess potential deployment locations. It is natural to focus first on the impressive magnitudes of power available from ocean waves, and to be drawn to locations where mean power levels are highest. However, a number of additional factors such as intermittency and capacity factor may be influential in determining economic viability of a wave energy converter, and should therefore be considered at the resource level, so that these factors can influence device design decisions. This study examines a set of wave resource metrics aimed towards this end of bettering accounting for variability in wave energy converter design. The results show distinct regional trends that may factor into project siting and wave energy converter design. Although a definitive solution for the optimal size of a wave energy converter is beyond the reaches of this study, the evidence presented does support the idea that smaller devices with lower power ratings may merit closer consideration.

Design and modelling of self‐excited SRG and FM‐SRG for wind energy generation

The paper discusses the design and analysis of synchronous reluctance generator with a rating of 2.1 kW. These generators with low power ratings may be a suitable candidate for the rural electrification. In synchronous reluctance generator, the design of the rotor is the most challenging part of the design. Here, the thickness of the axial and tangential ribs plays a significant role in its performance. The design procedure presented in the paper includes the effect of stator resistance, as it cannot be neglected in the design of synchronous reluctance generator with low power ratings. The paper discusses the design procedure of synchronous reluctance generator and analyses the self-excited ferrite-magnet synchronous reluctance generator. Various parameters of the designed machine are analysed through an analytical model and Ansys Electronics Desktop software. Further, the paper also includes the experimental validation of the synchronous reluctance generator results obtained through finite element analysis. The paper also proposes formulae to approximate the minimum values of the excitation capacitor requirement, for a self-excitation of synchronous reluctance generator with inductive load.

Design of 6S8P axial flux permanent magnet brushless DC motor with double-sided rotor

Electric motors developed rapidly in this decade. That is because electric motors have many advantages over conventional engines. The types of electric motors also vary, from low rated power to high rated power. Electric motors become an essential part of many sectors, such as industry and transportation. Brushless Direct Current Motor (BLDC) is one of the electric motors that has been developed because it has advantages compared to BDC motors. Low-power BLDC motors are widely used in several fields, such as computer construction, robots, and aviation. Research on the form of BLDC motor construction needs to be done to find out the maximum performance of a BLDC motor. Testing of a small motor axial flux permanent magnet brushless direct current with the double-sided rotor (AFPM BLDC DR) was carried out to determine the values of rotational speed, torque, mechanical power, and efficiency. Based on the test, a maximum rotational speed of 2365 rpm, the torque of 0.055 Nm, and the effectiveness of 70.34% are obtained.

Pulse Tripling Circuit and Twelve Pulse Rectifier Combination for Sinusoidal Input Current

In this paper, a novel pulse tripling circuit (PTC) is suggested, to upgrade a polygon autotransformer 12-pulse rectifier (12-PR) to a 36-pulse rectifier (36-PR) with a low power rating. The kVA rating of the proposed PTC is lower compared to the conventional one (about 1.57% of load power). Simulation and experimental test results show that the total harmonic distortion (THD) of the input current of the suggested 36-PR is less than 3%, which meets the IEEE 519 requirements. Also, it is shown that in comparison with other multi-pulse rectifiers (MPR), it is cost-effective, its power factor is near unity and its rating is about 24% of the load rating. Therefore, the proposed 36-PR can be considered as a practical solution for industrial applications.

A Comparative Assessment of the Energy Consumption of Induction and Synchronous Reluctance Drives of a Pump Unit Taking into Account Losses in a Frequency Converter

This paper presents a comparative analysis of the energy consumption of induction and synchronous reluctance electric drives of low rated power used in the water-supply system of a large building. An induction motor (IM) and synchronous reluctance motor (SynRM) were manufactured using the same motor housing. Test results of the variable speed drive employing an IM and SynRM are presented in a wide range of operating modes. The calculation of motor efficiency at points where there is no experimental data is carried out using polynomial interpolation. The influence of the motor type on the losses in a two-stage frequency converter is investigated using analytical and numerical methods. It is shown that despite a number of theoretical assumptions the analytical method used has a relatively small error. In addition, an alternative approach is proposed for determining values of the current and the power factor of the motor that is needed for calculating the losses in the frequency converter. By considering an example of a 1.1-kW drive, it is shown that using an SynRM can significantly reduce the energy consumption of the pump unit as compared to an IM.

Analysis and Validations of Modularized Distributed TL-UPQC Systems With Supervisory Remote Management System

Parallel operation of distributed power converters is used to realize high rated power and low current ripples with low rated power devices. It is also being preferred since central compensators fail to identify power quality problems reflected on low voltage levels, especially with the new structure of microgrids. This article proposes a novel parallel operation between modularized distributed transformerless unified power quality conditioner (TL-UPQC) for low voltage distribution networks. The operation is intended to improve the grid voltage profile while considering the connected modules rated capacity. The proposed methodology is suitable for smart grid applications where multiple renewable energy sources are integrated with the network. An advanced control technique that allows monitoring, wireless communication and coordination between the connected modules is presented. The proposed control methodology allows modularity and operation flexibility. System characterization has been studied to evaluate the influences of communication delays on overall system stability. The system has been evaluated by controller hardware-in-the-loop testing methodology. The power stage is simulated in a real time digital simulator, while the control algorithm is developed in a digital signal processor. Experimental results including random behavior of a photovoltaic system are presented.

Tri-window compensator for loads with non-periodic current

This paper presents a new technique for the compensation of non-periodic load current. The method provides control references for three co-located devices, each corresponding to one moving calculation window and one decomposed part of the compensated current. They are slow compensator with high power rating, large calculation window, and low switching frequency; fast compensator with lower power rating, shorter calculation window, and higher switching frequency; and the reactive compensator which is an ordinary static VAR compensator (SVC). A fuzzy based adaptive window is proposed for the slow compensator to find the optimum window for different load characteristics. The technique is evaluated using real-world data and controller hardware-in-the-loop (HIL) implementation.

Gravo‐aeroelastic scaling of a 13‐MW downwind rotor for 20% scale blades

AbstractA 105‐m, 13‐MW two‐bladed downwind Segmented Ultralight Morphing Rotor (SUMR‐13) blade was gravo‐aeroelastically scaled by 20% to a 20.87‐m‐long demonstrator blade and confirmed through structural ground testing. The subscale model was achieved through geometric scaling and by aeroelastic scaling principles based on operational flapwise deflections combined with rotational and structural frequencies while retaining the turbine tip‐speed ratio. In particular, the subscale demonstrator was designed to replicate, as closely as possible, the nondimensional geometry, the ratio of centrifugal to gravitational moments, the tip‐speed ratio, and the nondimensional rotation rate. The intent for this demonstrator was to achieve the same nondimensional flapwise blade deflections and dynamics of the full‐scale 13‐MW rotor. The manufactured SUMR‐D blade resulted in less than half of the mass of the conventional two‐bladed Controls Advanced Research Turbine (CART2) rotor blade based on scaling and a lower power rating, though with some differences in mass and stiffness from the ideal scaled‐down design to meet safety requirements at the test site. To achieve proper scaling, operational pitch control set points were altered to account for the differences by evaluating simulated operation of both the SUMR‐13 and SUMR‐D rotors. Structural testing of the SUMR‐D blade investigated the response to well‐defined flapwise loads and indicated that the subscale blade had the appropriate elastic properties needed for both scaling and for safe operational field testing.

Experimental Analysis of Salt Hydrate Latent Heat Thermal Energy Storage System With Porous Aluminum Fabric and Salt Hydrate as Phase Change Material With Enhanced Stability and Supercooling

Abstract Phase change materials (PCMs), especially salt hydrates possess high volumetric energy storage capacity in their transition temperature range. These materials are used in applications where it is necessary to store thermal energy due to temporary load shift between demand and availability. Thus, possible applications are HVAC, recovery of waste heat, and defense thermal management. Despite salt hydrates potential, the practical feasibility of latent heat storage with salt hydrates is limited due to low power rating, supercooling, phase segregation, and long-term stability. Its low power rating and long-term stability limits its application in most applications. This work experimentally validates the stability and thermal performance of a compact heat exchanger charged with salt hydrate during melting and freezing. The compact heat exchanger was designed with fins on both the heat transfer fluid (HTF) and salt hydrate PCM side. The thermal performance of the latent heat thermal energy storage system (LHTESS) was evaluated for various operating conditions. The results show that LHTESS could achieve an average heat transfer coefficient of 124 and 87 W/(m2 K) during melting and solidification, respectively. The stability of the system in suppressing supercooling was validated over 800 cycles with nucleating agent and active homogenous nucleation techniques. The supercooling was reduced to 3 °C with zinc hydroxyl nitrate as nucleating agent and less than 1 °C with the active homogenous nucleation technique. The LHTESS showed less than 6% degradation in energy storage capacity over 800 cycles.

A Unidirectional Hybrid HVDC Transmission System Based on Diode Rectifier and Full-Bridge MMC

To reduce the cost of bulk power transmission using voltage source converter high-voltage DC (HVDC) technology, a unidirectional hybrid converter is proposed, where a diode rectifier (DR) and a modular multilevel converter (MMC) based on full-bridge (FB) submodules are connected in series on DC side. The FB-MMC controls its DC voltage to regulate the transmitted power. The majority of the power transmission is via the DR considering its cost and efficiency superiority and only low power rating FB-MMC is required. A thyristor valve is equipped at the DC side of the FB-MMC to prevent potential overcharge of the FB submodules during DC faults. Compared to conventional MMCs, losses can potentially be reduced by around 20%. An active power controller is proposed to regulate the DC voltage of the FB-MMC so as to control the transmitted power. With the inverter station controlling its DC terminal voltage constant, the FB-MMC increases the output DC voltage to increase the transmitted power and vice versa. To alleviate overvoltage of the HVDC link during AC grid faults of the inverter station, a dynamic DC voltage limiter is designed to actively reduce the DC output voltage of the FB-MMC. Simulation results confirm the proposed converter operation and control.

A new semi-empirical wind turbine capacity factor for maximizing annual electricity and hydrogen production

The capacity factor is an important wind turbine parameter which is ratio of average output electrical power to rated electrical power of the wind turbine. Another main factor, the AEP, the annual energy production, can be determined using wind characteristics and wind turbine performance. Lower rated power may lead to higher capacity factor but will reduce the AEP. Therefore, it is important to consider simultaneously both the capacity factor and the AEP in design or selecting a wind turbine. In this work, a new semi-empirical secondary capacity factor is introduced for determining a rated wind speed at which yearly energy and hydrogen production obtain a maximum value. This capacity factor is expressed as ratio of the AEP for wind turbine to yearly wind energy delivered by mean wind speed at the rotor swept area. The methodology is demonstrated using the empirical efficiency curve of Vestas-80 2 MW turbine and the Weibull probability density function. Simultaneous use of the primary and the secondary capacity factors are discussed for maximizing electrical energy and hence hydrogen production for different wind classes and economic feasibility are scrutinized in several wind stations in Kuwait.