Uneven Power Distribution Research Articles

Electrothermal coupling analysis of three-dimensional integrated microsystem based on dual cell method

With the improvement of the integration and power density of three-dimensional integrated microsystem, it is imperative to simultaneously investigate the multi-field coupling analysis of electrical design and thermal management. This paper is to investigate a three-dimensional integrated microprocessor system and realize the rapid electrothermal analysis of the system through an improved dual cell method (DCM). This method decomposes the constitutive matrix into a constant matrix and a temperature-dependent matrix by introducing the coupling of leakage power and material coefficients with temperature. In the calculation, only the temperature-dependent matrix needs to be updated and assembled, which makes the calculation speed faster than the traditional finite element method. The simulation results show that the speed of the proposed algorithm is improved by about 30% compared with that of the traditional finite element method. After considering the thermal coupling factors of material coefficient and leakage power, the hot spot temperature of the system increases by 20.8 K compared with before coupling. Finally, the algorithm proposed in this paper is used to study the layout of three-dimensional integrated microprocessor system. The influence of TSV array conventional layout and centralized layout under the processor core(core-layout) on the hot spot temperature of upper and lower chips are compared, and the influences of uneven power distribution on the two layouts are studied. The results show that compared with the conventional layout of TSV array, the core-layout can reduce the hot spot temperature of processor, but it will aggravate the hot spot problem of DRAM at the same time. And when the power is not evenly distributed on the four cores, the hot spot of DRAM under the core-layout will be more seriously affected. In conclusion, the algorithm model proposed in this paper can quickly analyze the electrothermal coupling problem of 3D integrated microsystem, realize the hot spot prediction of the system, and provide theoretical guidance for designing the chip layout of 3D integrated microsystem.

Submodule power balancing control of modular multilevel converters under capacitor degradation

Impedance characteristics of the floating capacitor in the submodule (SM) of a modular multilevel converter (MMC) change due to its chemical and aging characteristics. This can result in a rise of voltage ripple across SM capacitors, uneven power distribution among the SMs and could also interrupt the operation with prolonged use of degraded capacitors. Existing balancing approaches are presented for the MMC with equal SM capacitance and ignored the effect of capacitor degradation as well as parameter mismatch. Hence, a closed-loop control scheme that incorporates the effect of capacitor degradation is much necessitated. This study aims to overcome this gap by proposing a new power balancing control algorithm for SM capacitors, which effectively controls and evenly distributes the power among SMs. The efficacy of the proposed strategy is substantiated through PLECS simulations and OPAL-RT/OP4510 controller-based experiments on a single-phase MMC laboratory prototype.

Energy modes of a three-section inductor for heating aluminum

The article proposes a method for single-phase power supply of a three-section induction heater for aluminum ingots before extrusion. The solution allows you to flexibly control the heating mode of each section. The peculiarity of the synthesized mode is to increase the uniformity of heating the methodical load at the joints of the sections when replacing the three-phase winding circuit with a single-phase one. Changing the circuitry reduces the phase shifts of currents in adjacent sections. Uneven power distribution between the coils is proposed to be realized by local resonances in the windings. The resulting power factor of the inductor, close to unity, is provided by a common capacitor bank. The set of established modes of an induction heater was investigated using a simulation system built on the basis of a hybrid analysis. The numerical experiment was carried out in a specialized software environment based on a macromodel created using controlled sources. The achieved positive result from the modification of the device is evaluated by comparing the vector diagrams of the operating parameters for the initial and corrected states.

Being a Better Neighbor: A Value-Based Perspective on Negotiating Acceptability of Locally-Owned Wind Projects

We pose that instead of problematizing negative attitudes of local stakeholders, such as citizens and NGOs, wind energy implementers should be more focused on scrutinizing the acceptability of their projects. The emphasis in this study is on the potential for representation of local stakeholders’ values in the project design, including amongst others business model and placement. Informed by value sensitive design literature, we analyzed two contrasting, locally-owned wind projects in the Dutch province of Groningen: the implementation of mini-turbines in a national landscape and a large-scale multi MW wind project in an industrialized area close to a World Heritage nature reserve. The study analyses how the respective farmer-developers and other local stakeholders attempted to resolve or ameliorate inter- and intra-value conflicts regarding livability, economy, landscape, and nature. The value conflicts turned out to be fruitful to identifying key issues and creating more widely shared value conceptualizations and design priorities. Hence, from this study it can be concluded that value conflict can be productive if carefully unpacked and managed. Uneven power distribution among stakeholders in the planning process, overcoming incommensurability of perspectives, and creating intersubjectivity remain challenges.

Quantitative Comparison and Analysis of Different Power Routing Methods for Single-Phase Cascaded H-Bridge Photovoltaic Grid-Connected Inverter

The output power of each photovoltaic (PV) module is different in the single-phase cascaded H-bridge (CHB) PV grid-connected inverter due to irradiance intensity, ambient temperature, and aging degree of PV modules. When the PV modules are operating at their respective maximum power points, the corresponding dc-side voltages of the H-bridge units drift due to uneven power distribution, which will cause the maximum power point tracking failure. As a result, the grid current will deteriorate and even the system will become unstable. The power routing control methods based on fundamental voltage reconstruction, third harmonic injection and hybrid pulse width modulation can realize unequal power distribution between H-bridges to ensure the system stable operation. This article summarizes the abovementioned typical power routing control methods, derives the expressions of power routing ranges of different methods, then comprehensively and deeply compares the power routing capabilities of various methods qualitatively and quantitatively. The simulation results of a single-phase seven-level CHB PV grid-connected inverter demonstrate the validity of the theoretical analyses.

Effects of Wall Reflection on the Per-Antenna Power Distribution of ZF-Precoded ULA for Indoor mmWave MU-MIMO Transmissions

Indoor access points (APs) with large-scale antenna arrays are commonly deployed in the vicinity of a wall, where wall reflection (WR) affects the indoor electromagnetic (EM) wave propagation. In this letter, we investigate the effects of WR on the per-antenna power distribution of a transmit uniform linear array (ULA) adopting a zero-forcing (ZF) precoder. A new channel model is constructed to characterise the impact of both the line-of-sight (LOS) path and the WR path on indoor millimetre wave (mmWave) multi-user (MU) multiple-input multiple-output (MIMO) downlink transmissions. Specifically for the dual user equipment (UE) scenario, the ZF precoding matrix is analytically obtained and verified through simulations. The effects of WR on the per-antenna power distribution of the ZF-precoded ULA, in terms of the normalised power distribution and maximum power ratio (MPR), are evaluated through the comparisons between our proposed channel model and the pure LOS channel model. Our analytical and numerical results reveal the impact of AP configurations (the number of antennas and the AP-wall distance), multi-user spatial distribution (the angle of departure (AoD) and length of the LOS path for each user), and wall parameters (permittivity and thickness) on the power distribution across the ZF-precoded ULA. It is found that the effects of WR will exacerbate the uneven power distribution across the ZF-precoded ULA.

Review of the microheterogeneous thoria‐urania fuel for micro‐sized high temperature reactors

This paper presents a systematic review of the micro-modular thorium-fueled high temperature reactors (HTR) loaded with duplex fuel pellet design. Specifically, each unique criterion of the design is discussed separately in an attempt to understand the combined advantages of the proposed reactor. Micro modular HTRs have great potential as a source of electricity or industrial heat in the future. The use of thorium not only improves its economic performance and safety, but also prolongs its operation. Nevertheless, the traditional seed-and-blanket configuration would not be able to maximize the thorium fuel burnup. As such, a new tristructural-isotopic (TRISO) fuel based on duplex pellet designs were proposed instead. It should be noted that these duplex pellets were not practical for pressurized water reactor (PWR) technology due to its uneven power distribution which possibly leads to a very high local pellet temperature. However, this unorthodox inherent characteristics of the duplex pellets may actually suit the HTR burnup profile better due to its substantially higher thermal margin - thus possibly enabling a relatively long operation of the HTR. The paper shall thereby provide a reasonably sound justification for the detailed technical investigations of the proposed reactor design.

Analysis and Control of PV Cascaded H-Bridge Multilevel Inverter With Failed Cells and Changing Meteorological Conditions

This article proposes an approach to control a photovoltaic cascaded H-bridge multilevel inverter with failed cells and changing meteorological conditions for large-scale grid-connected applications. The controller development is based on an analysis of the interaction between the inverter common-mode and differential-mode quantities, which is done in the time domain, supported by a space vector representation analysis. The proposed approach is able to produce balanced three-phase line-to-line voltages and currents even if there is a failed cell or if the fluctuating meteorological conditions cause uneven power distribution among the bridges. This is achieved through the modification of the pulsewidth modulation reference phase voltage angles combined to the injection of a dynamic homopolar component. Such an approach avoids tripping the system due to the protective functions #25 and #87 for per grid applicable codes and standards. Numerical simulations and laboratory experiments performed on a seven-level converter with different abnormal conditions to confirm the effectiveness of the suggested control strategy.

Applying an RRI Filter in Key Learning on Urban Living Labs’ Performance

Urban living labs is a practical methodology in improving sustainability in cities by facilitating collaborative learning and innovation in a real-life environment, thereby mainly responding to the needs of users (citizens). The paper aims to filter a list of key learnings on urban living labs through the lens of Responsible Research and Innovation (RRI). One of the motivations is that key learnings on urban living labs are mainly derived from means-goal effectiveness (MGE) thinking while the urban setting calls for a broader perspective due to complexity and tension from the multi-actor, multifunctional, and multi-scalar character of cities. The filtering reveals almost 40 learnings as ‘overlap’ and ‘exclusive for MGE’. Importantly, five learnings are identified as specific for RRI and potentially enriching living lab methodology: ethical and normative principles like health, safety, security, and equality between societal groups, and a wider distribution of benefits and risks of living lab outcomes, in particular, contradictory sustainability issues. The RRI filtering causes three practical implications: coping with uneven power distribution between stakeholders, limited feasibility of applying the comprehensive learning framework, and challenges of overarching platform structures enabling to better incorporate RRI concerns in living lab methodology. The findings as presented in an adapted list are new, as RRI values and concerns have seldom been applied to practical innovation and have never been explicitly applied to urban living labs’ performance beyond the borders of effectiveness thinking.

A distributed coordinated economic droop control scheme for islanded AC microgrid considering communication system

The conventional PQ droop control method is easily affected by load changes and line impedance in the islanded AC microgrid and always results in the problems in dynamic performance. Therefore, the parallel Distributed Generators (DGs) have uneven power distribution and poor economy. To solve the problem of inaccurate power distribution of DGs and low operating costs, we propose an improved economic droop control strategy based on distributed algorithm, in which the second-level optimization control is added to iteratively modify the reference voltage and frequency in the droop control. In this process, the system optimal economic operating point will also be achieved. Considering the advantages of centralized and decentralized control, the control architecture based on sparse multi-agent communication network improves the robustness and flexibility of the system because there is no central leader. Finally, simulation analysis of the islanded AC microgrid is carried out by using PSCAD/EMTDC simulation software to verify that this strategy can achieve the precise control of the tie-line power according to the load demand response, and the optimal economic operation for each DG.

The Effect of Compression Force Uniformity on Bipolar Tissue Welding

Bipolar forceps are a type of electrosurgical device (ESD) widely used for tissue welding in modern surgeries. ESDs have many advantages over traditional surgical tools including reduced blood loss, improved efficiency, and lower surgeon fatigue. However, these devices suffer from tissue sticking and damage due to overheating which leads to poor tissue joint quality. The problem is potentially caused by uneven power distribution due to nonuniform compression applied by the bipolar forceps. In this study, the effect of compression force uniformity was investigated with an experimental setup to achieve a uniform and consistent compression force at the jaws of bipolar forceps. Comparative tissue welding experiments were conducted under both uniform and nonuniform compression force conditions with tissue mimicking material. In situ welding process parameters including compression force, electrical voltage, and current were collected and analyzed to understand the effect of compression force uniformity. The results indicate that tissue impedance is lower due to increased tool–tissue contact area; the electrical power is initially higher during the first few milliseconds of welding. The experimental device developed in this study provides an important platform to understand the difference of tissue welding process under uniform and nonuniform compression force conditions.

Impact of Switching Harmonics on Capacitor Cells Balancing in Phase-Shifted PWM-Based Cascaded H-Bridge STATCOM

The purpose of this paper is to investigate the impact of switching harmonics on the instantaneous power distribution in the cells of a cascaded H-bridge-based STATCOM when using phase-shifted pulse width modulation. The case of high- and low-switching frequency for the converter cells is investigated and the interaction between voltage and current harmonics is analyzed. It is shown that in both cases, this interaction results in an uneven power distribution among the cells in the same phase leg, leading to drifting of the dc-capacitor voltages and thereby the need for proper stabilization control loops. It is also shown that the selected frequency modulation ratio affects the active power distribution among the cells. In particular, the selection of a noninteger frequency modulation ratio helps in providing a more uniform power distribution among cells of the same phase leg, thus contributing to the capacitors balancing. A methodology for optimal selection of the frequency modulation ratio is given. Theoretical conclusions are validated through simulation and experimental results.

Ultracapacitor-Battery Hybrid Energy Storage System Based on the Asymmetric Bidirectional <italic>Z </italic>-Source Topology for EV

This paper proposes an ultracapacitor (UC)-battery hybrid energy storage system (HESS) for electric vehicle based on asymmetric bidirectional Z -source topology. Compared with the conventional two-stage design, the HESS can be incorporated into the traction inverter system, leading to better performance and lower cost. The UC energy can be effectively utilized due to the buck/boost characteristic in the Z -source converter; meanwhile, the battery converter gets eliminated in this case. The assumption about the symmetry in the Z -source topology impendence network states for the conventional analysis no longer applies to the proposed HESS configuration. The asymmetric characteristic related with the uneven power distribution of UCs and battery is mathematically excavated in detail. The frequency dividing coordinated control is proposed to exploit the advantages of UCs and battery. The battery peak current estimation is then investigated. Finally, the steady performance and transient response in both traction and regenerative modes are verified by simulation and experimental results.

Leadership in Mexico: cultural factors affecting organisational leadership

The purpose of this article was to provide an overview of cultural factors affecting organisational leadership in Mexico. A comprehensive review, analysis, and synthesis of the literature on cultural aspects that affect or could affect organisational leadership in Mexico were conducted. The findings of the study suggest that there are certain cultural values such as low acceptance of ambiguity, feeling comfortable with rules, avoiding risk, and willingness to accept uneven power distribution, which could influence leadership practices in Mexico. Effective leadership styles in Mexico are those that take into consideration the particularities of the Mexican culture. This article has implications for expatriates assigned to leadership positions in Mexico. It is important that expatriates managing a Mexican workforce be aware of the cultural factors that could impact Mexicans' expectations about leadership. By being aware of the cultural factors influencing leadership in Mexico, human resource professionals of MNCs can facilitate management development programs to better prepare expatriates for leadership positions in Mexico.

Experimental study on the safety of Kyoto University Research Reactor at natural circulation cooling mode

In this study, the natural circulation cooling capacity of Kyoto University Research Reactor (KUR) is experimentally investigated by measuring the inlet and outlet temperatures of the core under natural circulation operation at various thermal powers ranging from 10kW to 100kW and the shutdown state. In view of the uneven power distribution and the resultant inconsistent coolant outlet temperature in the core, eight measuring points located separately in the outlet of the fuel elements were chosen to investigate the distribution of the outlet temperature of the core. The natural circulation cooling capacity represented by the average natural circulation flow velocity in the core is calculated from the temperature difference between the outlet and inlet temperature of the core. The measured outlet temperature of the fuel elements shows a cross-sectional distribution agreeing with the distribution of the thermal output of the fuel elements in the core. Since the measured outlet temperatures decrease quickly in the flow direction in a small local region above the outlet of the core, the mixing of the hot water out of the core with the cold water around the core outlet is found to happen in the small region not more than 5cm far from the core outlet. The natural circulation flow velocity in the core increases non-linearly with the thermal power. The safety of KUR has been analysed by conservatively estimating the highest coolant temperature, the highest fuel cladding temperature, the highest fuel meat temperature and the minimum DNBR under all of the normal operations with natural circulation cooling mode. The natural circulation operation at the thermal power of 100kW is the most serious operating condition. The average natural circulation flow velocity at the thermal power of 100kW is 3.13cm/s. All of these estimated parameters under normal natural circulation operation meet the safety criterion of research reactor.

A new pilot design for NC‐OFDM systems under power constraints

ABSTRACTThe pilot design is one of the key issues that has to be solved in order to improve the performance of non‐continuous orthogonal frequency division multiplexing (NC‐OFDM) systems in cognitive radio context. Equally‐spaced and equally‐powered pilot tones that are the optimal pilot design for conventional OFDM systems cannot be applicable to NC‐OFDM systems with the non‐continuous(NC) spectrum. In NC‐OFDM systems, the secondary users(SUs) communicate to each other by spectrum mapping the primary users(PUs)’ band to protect the PUs from interference. So the SUs’ available subcarriers’ positions and power allocation will be changed with PUs’ active state and interference constraints. The NC available spectrum and power distribution bring new challenges on system design, which make the pattern of pilots in the frequency domain vulnerable. Several recent researches have studied the optimal or suboptimal pilot designs under equally‐powered assumption. In this paper, we only focus on the comb‐type pilot design under uneven power distribution hypothesis for the NC‐OFDM transmission. Firstly, based on maximising each available subcarrier’ power under PUs’ interference temperature constraints, the pilot power constraints have been discussed, then the formula between pilot positions and pilot powers have been derived by minimising the channel estimation mean square error; moreover, a suboptimal pilot design under the pilot power constraints is also presented. The proposed pilot design cannot only obtain better channel estimation performance compared with previous pilot designs, but also consider the PUs’ communication reliability. Simulation results demonstrate the effectiveness of the proposed method. Copyright © 2013 John Wiley & Sons, Ltd.

Hybrid cascaded H-bridge inverter with even power distribution and improved total harmonic distortion: analysis and experimental validation

For high-power applications, cascaded H-bridge (CHB) inverters are conventionally controlled by selective harmonic mitigation (SHM) strategy. This technique is applied to reduce the switching loss and the optimised switching angles are calculated to mitigate low-order harmonics at the output voltage. However, this strategy causes an uneven power distribution among the CHB cells. Also mitigating more harmonics needs more number of pulses and consequently higher switching frequency and dissipated power. This study proposes a new hybrid CHB inverter with optimised dc sources. Considering the optimisation of the CHB dc sources' values along with the optimised switching angles, significant improvements such as mitigating more low-order harmonics, even power distribution among the CHB cells and reducing the switching loss are achieved. Analysis and simulations are carried out on a five-level CHB inverter. Experimental verifications also validate the simulation results. The results demonstrate that the new hybrid CHB inverter considerably improves the performance of the conventional SHM strategy.

Improving on Assembly of SCWR Using MOX Fuel

A calculation is made for certain Supercritical Water Cooled Reactor (SCWR) using UO2 fuel and MOX fuel respectively. The results indicate that MOX fuel has a simple power distribution with UO2 fuel, but there is a larger power uneven factor when using MOX fuel, and using MOX fuel including weapon grade Pu has larger power uneven factor than using MOX fuel including reactor grade Pu. However, in the case of same power distribution, the fuel rod using MOX fuel has a higher temperature than the one using UO2 fuel. Therefore with the more uneven power distribution, the fuel in SCWR using MOX fuel has a higher temperature. This will result in a big security issue when using MOX fuel in original design of SCWR. Through analyzing the result of power distribution, an improved assembly of SCWR is presented. It can reduce the power uneven factor and increase the security of fuel rod using the improved assembly of SCWR.

Innovation drivers and barriers in food processing

PurposeThe food processing industry, confronted with increased global competition and more stringent customer demands, is pressurized to improve the pace and quality of its innovation processes. This paper aims to find out what factors constitute the main drivers and barriers to innovation and to explore how far the food processing industry can rely on the principles of innovation management developed in high‐tech industries to improve its innovation performance.Design/methodology/approachThe study is based on the investigation of nine multinational food processing companies with their headquarters and/or major operations in The Netherlands. For this study a research questionnaire was developed, based on theoretical insights derived from the industrial organization theory and the resource‐based view. In each company the research director, CTO, or CEO completed the questionnaire and was interviewed about different aspects of innovation management.FindingsThe food processing industry can indeed rely on the principles of innovation management. However, there is clear room for improvement. Especially the potential of “open innovation” with suppliers and buyers to leverage innovation resources and capabilities is underutilized. Interestingly, the uneven power distribution in the chain, especially the high pressure of buyers, acts as a strong driver for innovation. Seen in this light it is noteworthy that in most companies the communication from R&D to marketing needs further improvement to enhance customer orientation, one of the main drivers of innovation success.Originality/valueThis study is the first to investigate innovation management concepts related to success in the food processing industry.

Wireless network cocast: location-aware cooperative communications with linear network coding

In wireless networks, reducing aggregate transmit power and in many cases, having even power distribution increase the network lifetime. Conventional direct transmission (DTX) scheme results in high aggregate transmit power and uneven power distribution. In this paper, we consider location-aware cooperation-based schemes namely immediate-neighbor cooperation (INC), maximal cooperation (MAX), and wireless network cocast (WNC) that achieve spatial diversity to reduce aggregate transmit power and even power distribution. INC utilizes twouser cooperative communication, resulting in good reduction of aggregate transmit power and low transmission delay; however, power distribution is still uneven. MAX utilizes multi-node cooperative communication, providing incremental diversity to achieve even power distribution and substantial reduction in aggregate transmit power. Transmission delay in MAX, however, grows quadratically with network sizes. As a result, the novel WNC is proposed to achieve incremental diversity as in MAX and low transmission delay as in INC. In WNC, mobile units acting as relays form unique linearly-coded signals from overheard signals and transmit them to the destination, where a multiuser detector jointly detects the symbols from all received signals. Performance evaluation in uniformly distributed networks shows that INC, MAX, and WNC substantially reduce aggregate transmit power while MAX and WNC also provide even power distribution.