Two-phase Load Research Articles

A Power Factors Full-Dimensionally Hunted Power Distribution Strategy for Railway Power Flow Controller Considering Regenerative Braking

Railway power flow controller (RPFC), as a promising technical route for railway power regulation, its rating determinization and the related flexible power regulation perplex designers and hinder large-scale applications, especially when the regenerative braking energy (RBE) is non-negligible. In this paper, a general power factors full-dimensionally hunted power distribution strategy (PFFDH-PDS), applicable for both off-line design & real-time control, is proposed. Two key methods are developed: 1) Full-dimensionally hunting the power factors (PFs) under the developed mathematic framework, from which the global optimal compensating power and RPFC's rating can be worked out; 2) Precisely partitioning two-phase loads on their PF-P and PF-PF distributing panels; in both methods, RBE is considered. By adopting PFFDH-PDS, RPFC's rating can be reduced by almost 60% compared to the conventional method, while the system has satisfactory grid-connection compatibility. Finally, the effectiveness and performance of the proposal are verified & conducted by real-measured data.

Flexible load control of new energy based on improved genetic algorithm

In the medium and low voltage distribution network, the load form of users is complex and changeable. There are a large number of single-phase and two-phase loads connected to the distribution network, resulting in a three-phase unbalanced operation of the distribution network. With the development of the new energy, the high proportion of distributed new energy will further aggravate the three-phase imbalance of the distribution network. Therefore, this paper proposes a coordinated optimization framework of droop parameters based on the multi-converter droop control, which takes the minimum loss of the distribution network as the optimization objective, and optimizes the reference point and the slope of the VSC droop hierarchically. A small-signal stability optimization dispatching method for the VSC droop slope in the DC distribution network is proposed. By adding small-signal stability constraints to the slope optimization model, the optimal slope command and slope stability region which can ensure the small-signal stable operation of the system are obtained. Experiments show that the optimization model of the VSC small-signal stability slope can make the droop control instruction significantly improve the small-signal stability of the system to adapt to the intra-day source load power fluctuations with a small economic cost. The slope stability region pre-optimization model can provide a reliable stability slope upper limit for the slope optimization problem based on ensuring the system operation economy. The research in this paper can make full use of the flexible control ability of power electronic equipment, and then suppress the three-phase imbalance, which is of great significance to improve the security and economy of the distribution system operation.

Study of the Current Harmonics Generated by Two-Phase Loads on HV Transmission Power Grid: a Case Study of a Substation Supplying the High-Speed Rail

Study of the Current Harmonics Generated by Two-Phase Loads on HV Transmission Power Grid: a Case Study of a Substation Supplying the High-Speed Rail

A novel two-phase load compensation method under unbalanced voltages for renewable energy integration

This paper explores new design methods for correcting unbalanced power distribution networks in order to improve the power quality and reliability for sensitive industrial loads. While traditional compensators typically need to be connected to all the three phases of the AC network, this paper proposes a novel three-phase voltage balancing compensator that can operate with a connection to only two of the three phases. The new concept is based on the phasor symmetrical component theory, which can be implemented using either mechanically switched reactors (MSRs), TCRs (thyristor-controlled reactors) or VSCs (Voltage source converters). Three methods are presented to calculate the value of the proposed two-phase compensator, i.e., discrete solution, analytical solution and novel simplified solution. The discrete solution is solved via the exhaustive search method, which was successfully used by StruthersTech to correct the power quality of an unbalanced industrial power system. The analytical solution is based on the nodal voltage of analysis method. The simplified solution derives a practical albeit approximated relationship between the negative sequence source voltage and zero sequence load voltage, thus avoiding the need to solve nonlinear equations. Dynamic simulations are implemented using MATLAB/Simulink Simscape Blockset to validate the effectiveness of the proposed two-phase voltage balancing method.

The Use Of A Synthetic Putty Graft In Extraction Sockets Combined With Immediate Implant Installation: 3 Cases

In these three different cases, synthetic putty graft material has proven to be a reliable alternative to autologous bone for implant placement, directly into the anterior extraction socket of the maxilla. This study presents three different patients who require implants in the anterior maxilla. Immediate implant placement was the treatment solution of choice. Because the aesthetic expectations and the initial screw-in torque are different however, a differentiation between direct loading, a phase 1 or a phase 2 approaches was made. Clinical results show that synthetic putty is an effective alternative to transplantations with xenograft or allogeneic graft materials in single-phase, two-phase, and direct loading.

Cyclic tests of steel tee energy absorbers for precast exterior wall panels in steel building frames

This paper focuses on a new type of exterior wall system for steel building frames. The wall system consists of precast reinforced concrete wall panels that are bolted to the beams of a steel building frame and are equipped with the inter-panel steel tee energy absorbers. The precast wall panels and the steel tees are expected to remain elastic and absorb hysteretic energy under the frame inter-story drifts caused by earthquakes, respectively. To demonstrate the perceived benefits of the exterior wall system and investigate the behavior of the steel tee energy absorbers, a group of five specimens with each consisting of a steel frame, a pair of precast wall panels and a set of six steel tee energy absorbers were designed, constructed and tested. The test parameters varied among the specimens were the geometries of the steel tee energy absorbers and the technology adopted to develop them. The steel frame and the precast wall panels were re-used in all specimens. Each specimen was tested through a two-phase loading program which imposed the inter-story drift demands with progressively increasing and constant peak amplitudes, respectively. All the specimens sustained the maximum inter-story drift angle of 0.05 rad or larger and exhibited a stable energy dissipation response. The tests demonstrated the damage free response of the precast exterior wall panels as well as the replaceability of the steel tee energy absorbers. Based on an idealized curvature distribution in the webs of the steel tee energy absorbers, the classic beam theory, and the virtual work theory, this research established a simplified model for computing the strengths of the steel tee energy absorbers as well as their contribution to the lateral strength of the frame. The model was found to be able to provide acceptable predictions for the tested specimens and it is recommended for future design.

Simulation of the static synchronous compensator for the system voltage unbalance and high current harmonics compensation from single phase non-linear load

This paper presents the STATCOM model in PSIM, which compensate grid voltage unbalance and current harmonics from the non-linear, two-phase load. Grid voltage unbalance level and harmonics current of non-linear load given from measurement. The model of STATCOM is a 6-level voltage inverter. System voltage, and harmonics currents are controlled. All modes are realized and plots are plotted.

An Assessment on the Plastic Capacity of Pipe-in-Pipe Systems Under Damage Progression Effect

Abstract In recent years, pipe-in-pipe (PiP) systems have been employed in an increasing number of subsea projects. According to the previous studies, the external pressure required to develop the initial local buckle on the PiP system is significantly higher than the pressure required to propagate the buckle along the system. In this respect, it is reasonable to investigate a novel topic where the propagation of buckle is induced by a lateral interference load instead of external pressure (e.g., diagonal fishing gear impact). On this subject, the recent studies showed the progression of plastic damage along a single-walled pipe, which is induced by a lateral load, could significantly lower the load-carrying capacity of the pipe. The present study investigates this finding for a PiP solution under a two-phase loading condition: in phase 1, the PiP solution is subject to 75 mm perpendicular indentation, and in phase 2, the resulting plastic damage in phase 1 is translated and induced longitudinally along the PiP system. Furthermore, using finite element analyses, the effect of combined loading (axial and lateral load) on the load-carrying capacity of the PiP specimen is investigated. The test results show that upon the initiation of damage progression, the load-carrying capacity of the PiP specimen (against the lateral indentation) declines by 10%. Also, the numerical results show that the structural resistance of a PiP specimen against a lateral indentation drops significantly when the inner pipe is subject to axial compression.

Hybrid Discontinuous Space Vector PWM Strategy for Three-Level Inverters under Two-phase Loads Condition

The output performance of three-level inverters will be deteriorated under two-phase loads condition if conventional discontinuous PWM (DPWM) strategies are adopted. To solve the above issue, the amplitude and the phase angle of basic voltage vectors are modified in this article. Accordingly, sectors and triangles of the space vector diagram are reconsidered, duty cycles of basic vectors synthesized the reference vector are recalculated. And then four types of DPWM applicable for two-phase load are put forward. Although the harmonic distortion of the output waveform is reduced, discontinuous intervals are not optimum distributed. To further improve the output waveform quality, the amplitude of average current ripple vector is introduced as the evaluation index to redistribute discontinuous intervals of phase voltage in each fundamental period. Then, a hybrid DPWM strategy is presented and the harmonic distortion of the output waveform is minimized. Meanwhile, the neutral-point voltage ripple and the switching loss are also suppressed. The effectiveness of the hybrid DPWM strategy is verified by both simulation and experimental results.

A Two-Phase Load Balancing Algorithm for Cloud Environment

Load balancing is the phenomenon of distributing workload over various computing resources efficiently. It offers enterprises to efficiently manage different application or workload demands by allocating available resources among different servers, computers, and networks. These services can be accessed and utilized either for home use or for business purposes. Due to the excessive load on the cloud, sometimes it is not feasible to offer all these services to different users efficiently. To solve this excessive load issue, an efficient load balancing technique is used to offer satisfactory services to users as per their expectations also leading to efficient utilization of resources and applications on the cloud platform. This paper presents an enhanced load balancing algorithm named as a two-phase load balancing algorithm. It uses a two-phase checking load balancing approach where the first phase is to divide all virtual machines into two different tables based on their state, that is, available or busy while in the second phase, it equally distributes the loads. The various parameters used to measure the performance of the proposed algorithm are cost, data center processing time, and response time. Cloud analyst simulation tool is used to simulate the algorithm. Simulation results demonstrate superiority of the algorithm with existing ones.

Efficient load balancing techniques for multi-datacenter cloud milieu

Load balancing is a challenge in the cloud network for proper resource utilization and improvement of makespan. To overcome the problem of load balancing various static and dynamic scheduling methods come into existence. In this paper, we have proposed two multi-datacenter two-phase load adjustment techniques for load balancing and apposite task scheduling. Our proposed methods allocate user jobs to different virtual machines present in different datacenters based on better makespan. Here we have considered communication delay and bandwidth requirement for inter-datacenter task migration. The simulation result specifies that proposed techniques give a significant improvement in makespan and resource utilization when compared with existing algorithms.

Source-side low-frequency harmonic suppression method for matrix converter

ABSTRACT Matrix converters (MCs) with a two-phase load can be used to drive a symmetrically or independently controlled load. Because MCs do not have a large-capacity energy storage unit when a two-phase output voltage is independently controlled, the ripple in the output power is coupled with the source side. However, the conventional modulation strategy significantly increases the number of low-frequency harmonics in the source side. The harmonic content also increases with the increase in output voltage asymmetry. In this paper, a dual current decoupling control strategy is proposed based on a source-side negative-sequence regulator. This method can suppress the input low-frequency harmonic by tracking and reasonably configuring the pulsating power, thereby improving the source-side performance. Moreover, simulations and experimental results verify the effectiveness of the proposed control strategy.

Discontinuous Space Vector PWM Strategy for Three-Phase Three-Level Electric Vehicle Traction Inverter Fed Two-Phase Load

Discontinuous pulse width modulation (DPWM) strategies are usually adopted to reduce the switching loss and output current ripple of three-phase three-level traction inverters under three-phase load conditions. However, if there is a short circuit in any arbitrary phase or the inverter is used to feed a two-phase load, the output performance of conventional DPWM strategies will be deteriorated. Here, four improved DPWM (IDPWM) strategies for three-phase three-level neutral-point-clamped (NPC) traction inverter fed two-phase load are proposed. Unlike three-phase load conditions, the phase angle and the amplitude of each basic voltage vector in the space vector diagram are modified under two-phase load conditions. Consequently, sectors are re-divided and duty cycles of basic vectors during synthesis are recalculated. Clamping intervals of each phase for the four type discontinuous PWM (DPWM) strategies are rearranged according to the modified space vector diagram; then, the proposed DPWM strategies can be obtained. Compared with the conventional DPWM strategies, the output current waveform quality of the proposed strategy is significantly improved. Meanwhile, the amplitude of the neutral-point voltage ripple is also reduced.

Two-phase induction load in a three-phase electrical grid

Two-phase induction load in a three-phase electrical grid

Two-Level Optimisation and Control Strategy for Unbalanced Active Distribution Systems Management

This article proposes a new approach to the operation of unbalanced Active Distribution Systems (ADS) using an economic dispatch optimisation model for Active Distribution Systems Management (ADSM). The model proposes a two-level control strategy. The first one poses an optimisation problem with the objective of minimising total active power losses in the ADS and the second one proposes an algorithm that controls the position of the taps of three-phase on-load tap-changer (OLTC) transformers to ensure compliance with the technical constraints imposed by the Distribution System Operator (DSO). The optimisation problem is solved by MATLAB <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sup> and DIgSILENT PowerFactory <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sup> for power systems static simulations. This paper includes a novel peer to peer communication framework between MATLAB <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sup> /DIgSILENT <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sup> . The control and optimisation strategy is validated on the IEEE 34-Node Distribution Test Feeder. This network incorporates balanced and unbalanced three-phase loads, single-phase loads in the different phases, and two-phase loads. In this scientific paper, photovoltaic (PV) and wind power generation (WT) have been integrated to test feeder operation, with the support of battery energy storage systems (BESS). The correct operation of the proposed ADSM is demonstrated using numerical simulation on five scenarios considering several configurations of the renewable generation units and the batteries. The strategy has also been validated in a more extensive distribution network, proving its good performance.

A generalized switching function-based discontinuous space vector modulation technique for unbalanced two-phase three-leg inverters

This paper presents a discontinuous space vector modulation technique for unbalanced two-phase three-leg inverters. This technique is based on the shift-angle and generalized modulation algorithm obtained for generating the unbalanced two-phase output voltage. Furthermore, the discontinuous switching sequence intends to improve the commutations of power switching devices in each inverter leg that achieves a minimum number of switching state changes in one sampling cycle. Therefore, the switch commutations can be reduced by one-third in one main period. The step- by-step procedure of the modulation algorithm for easy implementation in a digital control platform is discussed. The performance of the developed modulation technique is verified through both simulation and experimental results in a nonunity power factor balanced two-phase load and asymmetrical two-phase induction motor drive.

Application and performance analysis of the novel flow-guided vertical packing tray

In order to achieve higher throughput and better tray efficiency, this paper proposed a new type of flow-guided vertical packing tray, referred to as Novel FVPT, according to the design idea of composition. The novel tray was subjected to a cold mode experiment using an air-water (oxygen-enriched water) system in a 500 mm diameter Plexiglas column. The experiment included the clear liquid height, the dry pressure drop, the total pressure drop, entrainment, weeping and mass transfer efficiency. The correlation of the performance of the novel tray with the two-phase loading was invested in this work. Based on the mechanism of the pressure drop, the fundamental model of dry pressure drop of the novel tray was proposed. In addition, the industrial application of the novel tray was illustrated. The results showed that the novel tray with high throughout and better tray efficiency brought great economic and environmental benefits.

Two-phase load balancing for data center networks using OpenFlow

Two-phase load balancing for data center networks using OpenFlow

Collaborative Load Management with Safety Assurance in Smart Grids

Load shedding can combat the overload of a power grid that may jeopardize the grid’s safety. However, disconnected customers may be excessively inconvenienced or even endangered. With the emergence of demand-response based on cyber-enabled smart meters and appliances, customers may participate in solving the overload by curtailing their demands collaboratively such that no single customers will have to bear a disproportionate burden of reduced usage. However, compliance or commitment to curtailment requests by untrusted users is uncertain, which causes an important safety concern. This article proposes a two-phase load management scheme that (i) gives customers a chance to curtail their demands and correct a grid’s overload when there are no immediate safety concerns but (ii) falls back to load shedding to ensure safety once the grid enters a vulnerable state. Extensive simulations based on a 37-bus electrical grid and traces of real electrical load demonstrate the effectiveness of this scheme. In particular, if customers are, as expected, sufficiently committed to the load curtailment, overloads can be resolved in real time by collaborative and graceful usage degradation among them, thereby avoiding unpleasant load shedding.

A Power Factor-Oriented Railway Power Flow Controller for Power Quality Improvement in Electrical Railway Power System

Focusing on the freight-train dominant electrical railway power system (ERPS) mixed with ac–dc and ac–dc–ac locomotives (its power factore[0.70,0.84]), this paper proposes a power factor-oriented railway power flow controller (RPFC) for the power quality improvement of ERPS. The comprehensive relationship of the primary power factor, converter capacity, and the two-phase load currents is built in this paper. Besides, as the main contribution of this paper, the optimal compensating strategy that suited the random fluctuated two-phase loads is analyzed and designed based on a real traction substation, for the purposes of satisfying the power quality standard, enhancing RPFC's control flexibility, and decreasing converter's capacity. Finally, both the simulation and the experiment are used to validate the proposed conceive.