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Real-time simulation of large-scale active distribution networks exhibiting a wide range of time-scales puts forward higher requirements for simulation accuracy and efficiency. This paper presents an extendable method and design for the real-time simulation of active distribution networks utilising high-performance hardware field programmable gate arrays. In the aspect of numerical algorithm, a high-accuracy and stable multirate simulation algorithm is proposed. The entire active distribution network is decoupled into different subsystems by their inherent time-scales and distinct time steps are used to solve the subsystems. Then root-matching method is adopted to form the exponential difference equations that represent the behaviours of the electric distribution network being modelled, which eliminates the truncation errors and thus provides a highly accurate time-domain solution. To handle the interface between the subsystems, a multirate interfacing method is proposed. The hardware design of the multirate interfaces is presented as well. With the multirate algorithm, a fully functional extendable real-time simulator based on field programmable gate arrays is designed and implemented. Two modified IEEE 33-node systems with photovoltaics and energy storage are simulated on the 4-field-programmable-gate-arrays-based real-time simulator. Simulation results are compared with the commercial simulation tool PSCAD/EMTDC to validate the correctness and effectiveness of the proposed method and design.

This letter presents the latest improvements of a previously proposed parallel and multistep approach based on the functional mock-up interface standard for the simulation of electromagnetic transients. The improved approach extends the capacity of the original parallel asynchronous mode into accommodating the use of different time-steps in different decoupled subsystems. It also introduces a signal correction procedure using linear extrapolation in multistep simulations, greatly enhancing simulation flexibility, efficiency, and accuracy. Numerical examples are provided to demonstrate the computational advantages of the improved approach.

Using data from the China Household Income Project Survey (CHIPS 2013), this paper investigates the relationship between household registration control and the educational investment for the left-behind children from both theoretical and empirical perspectives by citing a theoretical model that includes factors such as household registration control, work schedules of agricultural migrants, and the educational investment for the left-behind children, as well as an empirical analysis using a mediation test model. The findings show that (1) deregulation of urban household registration helps migrant workers increase their investment in education-based human capital of their left-behind children, and the findings remain robust when the key independent and dependent variables are replaced. (2) By further using the mediation effect analysis, we find that the change in the duration of working outside the city plays a complementary mediating role between the two, and the mediation effect of the duration of working outside the city remains robust under the conditions of changing the key independent variables and changing the mediation effect test method. (3) Blockchain technology can strengthen the positive relationship between education investment and left behind children's learning outcomes.

This paper is related to research on parallelization techniques for the simulation of electromagnetic transients (EMTs). It presents a new approach based on a parallel-in-time equation grouping and reordering (PEGR) technique whose original theoretical formulation is modified, extended and generalized from state-space to the modified-augmented-nodal analysis (MANA) formulation method. The highly efficient sparse linear solver KLU is incorporated in the approach for power system network matrix solution. The proposed approach is implemented with OpenMP Multithreading for CPU-based parallelization. Test results show that EMT simulations can be accelerated by exploiting the intrinsic independency of certain solution procedures using the PEGR technique.

Real-time simulation of a microgrid involving massive high-frequency power electronic converters, various distributed generators and energy storage systems is computationally demanding. Due to the prominent computing resources and high speed communication, field programmable gate arrays (FPGAs) can be used together to realise the real-time simulation of a microgrid. For a complete multi-FPGA-based real-time simulator, interfaces are essential to communicate with each other and with different types of apparatus. The internal interfaces between FPGAs make it possible to operate in parallel, sharing the computational burden. External interfaces between an FPGA and physical devices contribute to the implementation of hardware-in-the-loop simulation. In this study, interfacing techniques including multi-FPGA system topology determination, time-step synchronisation mechanism and precise communication are proposed in detail. An analogue-to-digital and digital-to-analogue interface is designed to facilitate physical connections to external devices. A modified microgrid benchmark with photovoltaics and a battery is simulated with a time-step of 3 μs on a 4-FPGA-based real-time simulator. Simulation results are compared with PSCAD/EMTDC to validate the interface design.

Power system electro-magnetic transient programs (EMTP) have been popular among researchers and practitioners due to their detailed component modeling and high simulation accuracy for complex system operations. Despite broad applications in simulations with wide range of timescales, the small discretization step of these programs makes their use very time-consuming for system studies with long time span. Facing the increasingly complex power system transient characteristics and simulation demands, a multiscale algorithm that integrates the simulations of the electromagnetic and slower electromechanical transients is desirable. The multiscale simulation algorithm preserves the high fidelity of the EMTP and attains higher efficiency for the overall transient simulation. In this paper, we achieve this goal by exploiting the unique properties of the matrix exponential function. The proposed algorithm is capable of utilizing large step sizes to speed up the simulation of slow dynamics, whereas the fast transients are accurately reconstructed through efficient dense output mechanism, which is built upon the matrix exponential function computation. Numerical studies including a large-scale wind farm simulation are conducted to demonstrate the effectiveness of the proposed multiscale algorithm.

Flowers with more petals are of more ornamental value. It is well known that AGAMOUS (AG) is the core member of the C-class gene which plays an essential role in double flower formation and identification of stamens and carpels in Arabidopsis thaliana. We searched C-class genes in the genome of the carnation, and found two AG orthologs (DcaAGa, DcaAGb). Phylogenetic analysis showed that the two genes were closely related to the euAG subclade. Then we searched the genomes of other Caryophyllales plants (Beta vulgaris, Spinacia oleracea, Chenopodium quinoa) for C-class genes, and found that their C-class genes all belonged to the euAG subclade. Semi-quantitative PCR (sq-PCR) analysis indicated that the expression of DcaAG genes in the single flower phenotype was higher than that in the double flower phenotype. Quantitative real-time RT-PCR (qRT-PCR) analysis showed that the expressions of DcaAG genes in the flower bud were significantly different from those in the root, stem, and leaf between the single and double flower phenotype carnations, and that DcaAG genes were specifically expressed in the stamen and carpel of carnation. Moreover, the expression of other floral organ identity genes (AP1 and AP2, PI and AP3, SEP1 and SEP3 corresponding to the A-, B-, and E-class of genes, respectively) showed no significant difference in all floral organs between the single and double flower phenotype carnations, suggesting that C-class (DcaAG) genes might play an important role in the double flower phenotype in carnation. Petal loss or decrease, precocious flowering, silique shortening, and seed sterility were observed in 35S::DcaAGa and 35S::DcaAGb transgenic Arabidopsis plants. All these results show that DcaAG genes might affect the petal number negatively and have a specific function in stamen and carpel development in carnation.

This paper presents two variable time-step algorithms for time-domain simulation of electromagnetic transients. The first one has been created to simulate basic switching transients and the second one is intended to simulate power-electronic systems. Each algorithm is tested in a dedicated circuit. Simulation results yield excellent accuracy and significant improvements in computation time when compared to fixed time-step algorithm.

Reconfigurable computing is that the logical resources in the system can be reconfigured according to the real-time changing data flow to achieve different calculation functions. The reconfigurable computing system has both high efficiency on hardware and universality of software. The field programmable gate array (FPGA)-based real-time simulator for active distribution networks (ADNs) requires a long compilation time for case modification, with low efficiency and low versatility, making it inconvenient and difficult for users. To solve the problem of long compile time with a new case, a universal design of the FPGA-based real-time simulator for ADNs based on reconfigurable computing is proposed in this paper. It includes the universal design of the simulation parameter configuration, the simulation initial value setting, the linear equations solving module and the simulation result output module. The proposed universal design of the simulator makes the modification and change of the cases and parameters without recompiling and further improves the simulation efficiency. Simulation results are conducted and compared with PSCAD/EMTDC to validate the correctness and effectiveness of the universal design.

Modern power electronic circuits contain numerous switches driven by high frequency controllers and can cause discontinuities in time-domain simulation methods. This paper presents numerical problems resulting from discontinuities when simulating power electronic circuits. Limitations in existing methods are analyzed. Three new methods are proposed to improve accuracy and computational performance.

A series of Ba4Gd3Na3(PO4)6F2:Eu(2+) phosphors with a broad emitting band have been synthesized by a traditional solid state reaction. The crystal structural and photoluminescence properties of Ba4Gd3Na3(PO4)6F2:Eu(2+) are investigated. The different crystallographic sites of Eu(2+) in Ba4Gd3Na3(PO4)6F2:Eu(2+) phosphors have been verified by means of their photoluminescence (PL) properties and decay times. Energy transfer between Eu(2+) ions, analyzed by excitation, emission, and PL decay behavior, has been indicated to be a dipole-dipole mechanism. Moreover, the luminescence quantum yield as well as the thermal stability of the Ba4Gd3Na3(PO4)6F2:Eu(2+) phosphor have been investigated systematically. The as-prepared Ba4Gd3Na3(PO4)6F2:Eu(2+) phosphor can act as a promising candidate for n-UV convertible white LEDs.

With a high penetration of power electronic equipment, transient simulation for power electronic circuit has been a main challenge for performance improvement of the electromagnetic transient simulation tools. In this paper, two new solvers for the matrix exponential-based simulation method are proposed based on the dense output formula and Pade approximation of different orders. The proposed solvers are implemented with the optimal combination of numerical integration method and interpolation method. Both solvers are L-stable. One has 3rd-order accuracy which is more accurate than existing simulation tools in power electronic simulation. The other solver achieves 1st-order accuracy with a lower precision numerical integration method than the same-order algorithms and is appealing from computation speed perspective. Numerical studies including TCR circuit and two types of VSC-HVDC systems are conducted to demonstrate the effectiveness of the proposed solvers.

With the extensive application of power electronic equipment in power systems, electromagnetic transient (EMT) simulation involving power converters becomes more challenging. Due to its multithreads and high throughput architecture, the graphics processing unit (GPU) can be used to accelerate those EMT simulations. A GPU-based matrix exponential method and its memory management for power converter transient simulation are proposed in this paper. A parallel exponential integration algorithm is established from two aspects to fully utilize the GPU multithreads capability. The matrix exponentials which are recomputed with the on/off state changes of power electronic switches are cached in GPU memory. The simulation efficiency is improved by reusing the cached data and reducing heterogeneous data transmission between CPU and GPU. Several strategies are experimented to manage the cache memory considering the EMT simulation workflow. The proposed memory management expands the simulation capability by substantially reducing the memory requirement and maintains the speed advantage of the GPU-based simulator. The proposed method is tested on wind power plants of different scales with power electronic interfaced wind generators. Simulation results indicate that the proposed method and its memory management expand the simulation capability and achieve speedups.

A variety of numerical integration methods are currently being used for simulating electromagnetic transients in commercial software and experimental codes. This paper intends to provide a review and comparison of these methods for time-domain integration, including 2S-DIRK, ARTEMiS art5 solver, and a semi-analytical matrix exponential-based method. The possibility of utilizing these methods is explored for reliable and efficient treatment of discontinuity, which is known to give rise to numerical oscillations for the widely used trapezoidal method. Case studies are conducted to show the strengths and limitations of these methods and their combinations.

The field-programmable gate array (FPGA)-based real-time simulator takes advantage of many merits of FPGA, such as small time-step, high simulation precision, rich I/O interface resources, and low cost. The sparse linear equations formed by the node conductance matrix need to be solved repeatedly within each time-step, which introduces great challenges to the performance of the real-time simulator. In this paper, a fine-grained solver of the FPGA-based real-time simulator for active distribution networks is designed to meet the computational demand. The framework of the solver, offline process design on PC and online process design on FPGA are proposed in detail. The modified IEEE 33-node system with photovoltaics is simulated on a 4-FPGA-based real-time simulator. Simulation results are compared with PSCAD/EMTDC under the same conditions to validate the solver design.

Epub ahead of print; International audience; Roses have high cultural and economic importance as ornamental plants and in the perfume industry. We report the rose whole-genome sequencing and assembly and resequencing of major genotypes that contributed to rose domestication. We generated a homozygous genotype from a heterozygous diploid modern rose progenitor, Rosa chinensis ‘Old Blush’. Using single-molecule real-time sequencing and a meta-assembly approach, we obtained one of the most comprehensive plant genomes to date. Diversity analyses highlighted the mosaic origin of ‘La France’, one of the first hybrids combining the growth vigor of European species and the recurrent blooming of Chinese species. Genomic segments of Chinese ancestry identified new candidate genes for recurrent blooming. Reconstructing regulatory and secondary metabolism pathways allowed us to propose a model of interconnected regulation of scent and flower color. This genome provides a foundation for understanding the mechanisms governing rose traits and should accelerate improvement in roses, Rosaceae and ornamentals.

International audience; Dianthus is a large genus containing many species with high ornamental economic value. Extensive breeding strategies permitted an exploration of an improvement in the quality of cultivated carnation, particularly in flowers. However, little is known on the molecular mechanisms of flower development in carnation. Here, we report the identification and description of MADS-box genes in carnation (DcaMADS) with a focus on those involved in flower development and organ identity determination. In this study, 39 MADS-box genes were identified from the carnation genome and transcriptome by the phylogenetic analysis. These genes were categorized into four subgroups (30 MIKCc, two MIKC*, two M alpha, and five M gamma). The MADS-box domain, gene structure, and conserved motif compositions of the carnation MADS genes were analysed. Meanwhile, the expression of DcaMADS genes were significantly different in stems, leaves, and flower buds. Further studies were carried out for exploring the expression of DcaMADS genes in individual flower organs, and some crucial DcaMADS genes correlated with their putative function were validated. Finally, a new expression pattern of DcaMADS genes in flower organs of carnation was provided: sepal (three class E genes and two class A genes), petal (two class B genes, two class E genes, and one SHORT VEGETATIVE PHASE (SVP)), stamen (two class B genes, two class E genes, and two class C), styles (two class E genes and two class C), and ovary (two class E genes, two class C, one AGAMOUS-LIKE 6 (AGL6), one SEEDSTICK (STK), one B sister, one SVP, and one Ma). This result proposes a model in floral organ identity of carnation and it may be helpful to further explore the molecular mechanism of flower organ identity in carnation.

A series of tunable blue–green–yellow emitting Ba4Gd3Na3(PO4)6F2:Ce3+/Tb3+/Mn2+ phosphors have been synthesized by a traditional solid state reaction. The PL and PLE properties of Ba4Gd3Na3(PO4)6F2:Ce3+/Tb3+/Mn2+ have been investigated. Ba4Gd3Na3(PO4)6F2:Ce3+,Tb3+ exhibits two dominating bands situated at 356 nm and 547 nm, which originate from the allowed 5d–4f transition of the Ce3+ ions and the 5D4 → 7FJ (J = 6, 5, 4, 3, 2) transition of Tb3+ ions, respectively. The Mn2+ ions substitute Ba2+ and emit orange light centered at 571 nm. The dominating energy transfer processes from Ce3+ to Tb3+ and Mn2+ in the Ba4Gd3Na3(PO4)6F2 host were investigated and have been demonstrated to be the resonant type via a dipole–quadrupole interaction mechanism. The critical distances of Ce3+ and Tb3+, and Ce3+ and Mn2+ are 9.97–13.29 A and 7.67 A, respectively. The blue, green, and yellow colors can be tuned by the ratio of Ce3+/Tb3+/Mn2+, indicating that the phosphor may potentially be used as a tunable blue–green–yellow emitting phosphor for UV light-emitting diodes.

This paper proposes an accurate dense output formula for exponential integrators. The computation of matrix exponential function is a vital step in implementing exponential integrators. By scrutinizing the computational process of matrix exponentials using the scaling and squaring method, valuable intermediate results in this process are identified and then used to establish a dense output formula. Efficient computation of dense outputs by the proposed formula enables time integration methods to set their simulation step sizes more flexibly. The efficacy of the proposed formula is verified through numerical examples from the power engineering field.

Cymbidium goeringii Rchb.f. is an important ornamental plant with a striking well-differentiated lip. Its complex floral architecture presents an exciting opportunity to examine perianth development. In flowering plants, class A, B and E floral homeotic genes play key roles in the specification of perianth identity. In this study, we used a cDNA library of wild-type C. goeringii flower buds for transcriptome sequencing. Eighteen candidate class A, B and E genes (including AP1/FUL-, AP2-, DEF-, GLO-, SEP- and AGL6-like genes) were identified. Quantitative real time polymerase chain reaction (qRT-PCR) results showed that CgDEF1, CgSEP2 and CgAGL6-1 were strongly detected only in the sepals and petals and were significantly downregulated in the lips. CgDEF3, CgDEF4 and CgAGL6-3 were highly expressed in the lips and lip-like petals but were only minimally detected in the sepals. Yeast two-hybrid analysis indicated that CgDEF1 and CgGLO formed a heterodimer. CgAGL6-1/CgSEP2 and CgDEF1 formed higher-order protein complexes with the assistance of the CgGLO protein, and both CgAGL6-1 and CgSEP2 formed a heterodimer. CgDEF3/CgDEF4 could interact independently with CgGLO and CgAGL6-3, respectively, while CgDEF3 and CgDEF4 also formed heterodimers with the assistance of the CgGLO. Based on a comprehensive analysis relating these gene expression patterns to protein interaction profiles, the mechanism of sepal/petal/lip determination was studied in C. goeringii. Furthermore, a hypothesis explaining the sepal/petal/lip determination of C. goeringii is proposed. The lip-quartet (CgDEF3/CgDEF4/CgAGL6-3/CgGLO) promoted lip formation, whereas the sepal/petal-quartet (CgDEF1/CgAGL6-1/CgSEP2/CgGLO) promoted sepal/petal formation. These results enrich the current knowledge regarding the mechanism and pathways of perianth formation in orchids.

Facing the increasingly complex power system transient characteristics, the electromagnetic transient simulation tools are gaining popularity, thanks to their detailed modeling of power system equipment and high fidelity simulation results. Consequently, the Electro-Magnetic Transient Programs are increasingly used in simulation studies of higher dimensions and wider range of scales, which challenges the circuit-based algorithmic design of these programs. This paper proposes to use explicit integration formulas based on the matrix exponential function in the transient simulations of large-scale wind farms, which possess both high efficiency of explicit methods and numerical stability of implicit methods. A Krylov subspace-based order reduction technique embedded into the integration formulas was developed to specifically address the simulation needs of high dimensional EMT model of detailed wind farms. Numerical studies are conducted based on a realistic large-scale wind farm, where the proposed state space modeling framework is established, and the matrix exponential-based algorithm is implemented and compared against a set of classical stiff ODE solvers. Simulation tests with different fault types and fault locations are presented, showing a superior computation speed for studies with both equivalent and detailed wind farm modeling. On the other hand, numerical errors of the new algorithm are shown to be at least one order of magnitude smaller than other solvers in the range of typical step sizes, under the same simulation setting. These properties ensure an efficient, reliable and highly scalable simulation capability for the computation challenges in the studies of large-scale wind farms.

Aquaporins (AQPs) are essential channel proteins that execute multi-functions throughout plant growth and development, including water transport, uncharged solutes uptake, stress response, and so on. Here, we report the first genome-wide identification and characterization AQP (BvAQP) genes in sugar beet (Beta vulgaris), an important crop widely cultivated for feed, for sugar production and for bioethanol production. Twenty-eight sugar beet AQPs (BvAQPs) were identified and assigned into five subfamilies based on phylogenetic analyses: seven of plasma membrane (PIPs), eight of tonoplast (TIPs), nine of NOD26-like (NIPs), three of small basic (SIPs), and one of x-intrinsic proteins (XIPs). BvAQP genes unevenly mapped on all chromosomes, except on chromosome 4. Gene structure and motifs analyses revealed that BvAQP have conserved exon-intron organization and that they exhibit conserved motifs within each subfamily. Prediction of BvAQPs functions, based on key protein domains conservation, showed a remarkable difference in substrate specificity among the five subfamilies. Analyses of BvAQPs expression, by mean of RNA-seq, in different plant organs and in response to various abiotic stresses revealed that they were ubiquitously expressed and that their expression was induced by heat and salt stresses. These results provide a reference base to address further the function of sugar beet aquaporins and to explore future applications for plants growth and development improvements as well as in response to environmental stresses.

In order to meet the demand of fast electromagnetic transient simulation for large-scale interconnected power systems, a new method of GPU based parallel matrix exponential algorithm for power system electromagnetic transient simulation is presented in this paper. Firstly, the hardware structure and programming model of GPU are introduced. Then the high data parallelism based on matrix exponential integration algorithm is proposed. Then, a simulation test is carried out for a wind farm system including 17 WTGs. The accuracy and efficiency of the proposed method are verified. The results show that the speed of parallel computing based on GPU is about 2 times faster than that of CPU and Matlab/SimPowerSystems.

A series of Ba4-xGd3Na3 (PO4)6F2:xEu2+ phosphors are prepared by sintering a stoichiometric mixture of raw materials with an excess of BaF2 under a H2(10%)/N2 reducing atmosphere (1075 °C, 6 h).

Magnesium and aluminum were bonded successfully by using Mg–Al eutectic alloy as the solder under different pressures at 450 °C in atmosphere. The microstructures of the Mg/Al joints were characterized by SEM, the composition analyzed by EDS, and their bond strengths measured by the bend test. The results show that the bond strength of these Mg/Al joints is improved with increasing of holding pressure, while the holding time has no much effect on it. To demonstrate the potential application of the Mg–Al eutectic alloy solder, magnesium plate was coated with aluminum foil by this process and its corrosion resistance was evaluated by electrochemical test. It shows that the corrosion resistance of the magnesium plate with aluminum coating was remarkably improved, which exhibits a similar corrosion behavior to that of aluminum.

Dianthus chinensis , Dianthus barbatus and Dianthus superbus are members of the Caryophyllaceae and are grown widely as ornamental plants. Information about relative genetic relationships can facilitate breeding programs. Here, we have compared two polymerase chain reaction (PCR)-based systems (sequence-related amplified polymorphisms (SRAPs) and inter-simple sequence repeats (ISSRs)) and morpological trait measurements for their relative effectiveness in estimating the genetic diversity found between 22 Chinese pink ( D. chinensis ) inbred-lines, one accession of D. barbatus and one accession of D. superbus . Interspecific differences were readily detected but the markers were less reliable in distinguishing the accessions according to their region of origin or in separating the wild species from the cultivars. Morphological traits were found to be the least effective genetic markers. The relative effectiveness of the three systems as markers for genetic diversity was concluded to be SRAP > ISSR > morphological traits, but the combined data from ISSR + SRAP analyses was superior to all three. The information generated by the SRAP marker system correlated more closely with morphological variability than did the ISSR marker system. The morphological markers of plant height/crown size ratio, lower leaf length, ovary shape index and calyx length showed strong correlations with the genetic diversity index (GD ij , PPB(II) and PSB) as generated by the percentage of polymorphic bands and percentage of special bands of the PCR-based markers.

In this study, we aimed to maximize the rates of somatic embryogenesis achievable in anther cultures of Chinese pink (Dianthus chinensis L.) (2n = 2x = 30). The genotype of the donor plant was found to be a major factor in determining the success rate. Conditions imposed during anther culture (notably medium composition and light conditions) and pretreatments (namely, cold, heat, and mannitol incubations) were also found to influence somatic embryo induction. For example, the highest levels of embryogenic callus induction were achieved when the donor buds had been cold pretreated and the subsequent anther culture was maintained in darkness. Furthermore, there appeared to be an interaction of genotype with culture conditions. Thus, in cultures of the cultivar (cv.) ‘Carpet’, the highest rates of embryogenesis were obtained when the anthers had received a 5-d heat-shock, but such a thermal treatment did not generally produce a significant effect. Likewise, a 3-d mannitol pretreatment was optimal only for the cross-hybrid line ‘HC’. Assessment of the ploidy of the plants regenerated from the anther cultures revealed both diploid and tetraploid plants. Histological and cytological observations showed that all of these (both from n-pollen and 2n-pollen lines) derived from anther wall cells. Spontaneous chromosome doubling was inferred to have occurred during the embryogenic callus culture period.

Large-scale wind farm integration poses challenges to the modeling and simulation of power system electromagnetic transients. In this paper, state space modeling of typical induction generator wind farms is demonstrated using a subsystem assembly process, and a novel matrix exponential based simulation algorithm is applied, which is efficient, stable, and especially suitable for high dimensional nonlinear problems like wind farms. Numerical performance of the proposed algorithm is demonstrated through case studies.

The ever-increasing scale of system interconnection and diverse dynamic time constants of power equipment pose challenges to power system transient simulation algorithms. In this paper, an adaptive numerical integration method for DAE systems based on matrix exponential operator is presented. Krylov subspace technique is utilized to effectively reduce the problem dimension. A novel step adaption scheme is established to enable the method adjusting the computation step size according to error budget while maintaining the output step size unchanged. Acceleration is accomplished without perceived degradation in the simulation results. Numerical performance and computation efficiency is demonstrated through numerical case studies.

Model reduction is a popular trend in large-scale system simulations. It is also an effective way to improve the efficiency of distribution system simulations. In this paper, the realization of state-space-based model reduction methods in EMTP-type programs is presented. The state-space model of linear time-invariant distribution network is reduced and simulated with the detailed nodal model in EMTP-type programs. The combined state-space nodal analysis algorithm is adopted as the interface between the state-space models and the nodal models. Simulations are performed to show the feasibility and validity of the proposed method, and the improvement in efficiency with the application of model reduction.

The ever-increasing scale of system interconnection and diverse dynamic time constants of power equipment pose challenges to power system electromagnetic transients simulation algorithm. In this paper, an advanced numerical integration method based on matrix exponential operator is proposed. Krylov subspace approximation is utilized to effectively reduce the problem dimension, and an accurate dense output formula is established to enable the method adopting larger simulation step size and revealing higher frequency dynamic details simultaneously. Accuracy, numerical stability and computation efficiency is demonstrated through numerical case studies.

This paper proposes a coordinated control method of the diesel generators (DGs) and battery storage system (BSS) in AC island microgrid. When the DGs run as the main power source, an auxiliary power control signal is added to the conventional droop control for BSS to prevent system collapses caused by long-time over-current of the DGs, which can improve the stability of the microgrid. To avoid short-term outage when the main power source in the micro-grid changes from the DGs to BSS or from the BSS to the DGs, a seamless transition control strategy for the DGs and BSS is presented. Finally, the control methods previously mentioned had been validated with the PSCAD simulation software.

The integration of distributed energy resources into low and medium voltage networks will have profound impact on distribution network reconfiguration. In this paper, the impact of DG on distribution network reconfiguration is analyzed in both normal operation and post-fault scenarios with different load levels. Distribution system simulation is performed with the Open Distribution Simulator Software (OpenDSS). Due to the intrinsic nonlinear and non-differentiable mixed-integer nature of the problem, simulated annealing is used as the optimization algorithm. Using the proposed method, a case study of IEEE 33-bus system gives positive conclusions: in normal operation, the integration of DG increases the number of distribution network reconfiguration feasible solutions and reduces the total network loss of the optimal solution; while in post-fault condition, feasible solution can emerge with the integration of DG where there isn't any feasible solution originally. The integration of DG helps to ensure network power supply.