CN104679936A - PMFCL (permanent-magnet-biased fault current limiter) magnetic current thermal coupling modeling method - Google Patents
PMFCL (permanent-magnet-biased fault current limiter) magnetic current thermal coupling modeling method Download PDFInfo
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Abstract
The invention discloses a PMFCL (permanent-magnet-biased fault current limiter) magnetic current thermal coupling modeling method. The PMFCL magnetic current thermal coupling modeling method includes establishing a 2D model of a half-wave current-limiting topological structure of the PMFCL; employing finite element software Ansoft to simulate the model; establishing a 3D model of the half-wave current-limiting topological structure of the PMFCL by the aid of the Ansoft; establishing a transient thermal analysis model in the ANSYS, subjecting the transient thermal analysis model to finite element mesh generation and subjecting a temperature field to graph mapping to the 3D model of the half-wave current-limiting topological structure of the PMFCL, and accordingly obtaining a temperature field calculation result of a PMFCL device at any moments. According to the arrangement, electromagnetic fields and current vectors of a winding and components of a linear PMFCL are analyzed and calculated with thermal fields to obtain magnetic-current-thermal coupling analysis, accordingly imparting a significant reference for material types and parameter designs of the PMFCL.
Description
Technical field
The invention belongs to electric power system fault current limliting field, particularly a kind of permanent magnetism saturation type fault current limiter magnetic current thermal coupling modeling method.
Background technology
Along with the expanding day of China's electrical network scale, the increasing rapidly of power system load, constantly the putting into operation and each large regional grid interconnected of large sized unit, the short-circuit current level of electric system increases day by day, the short circuit current level of many areas particularly coastal economy developed regions electrical network, has pressed on towards the maximum allowable level even exceeding electric power code defined.Short-circuit current is excessive, not only can cause power system voltage and frequency instability, and can produce strong thermal effect and electric power impact, damages electrical equipment and insulation thereof.Moreover, the step voltage brought thus, also day by day serious to problems such as the electromagnetic interference (EMI) of communication apparatus.For ensureing the safe, reliable of electric system and stable operation, this just needs to upgrade various power transmission and transforming equipment in electrical network, such as primary cut-out, transformer, mutual inductor and substation bus bar, framework, wire, supporting insulator and grounded screen etc., brought harsher requirement is increased to meet short circuit current level, electric grid investment cost is increased greatly, electrical network even may be caused optional without primary cut-out.Therefore, limiting short-circuit current has become a unavoidable important technical and economic problems in contemporary power network development.
Traditional short-circuit current limiting measure mainly contains: 1. on electric network composition, considers improve electric pressure, segmentation bus or system and adopt the methods such as unit connection to large sized unit power plant; 2., in the method for operation, the earth-free or neutral grounding by small resistance mode of transformer neutral point is adopted, and at the minimum place of penetration by loop network solution inscription of loop etc.; 3., on electrical equipment, consider to adopt the measure such as reactor and high-impedance transformer.But the cost of transformation electric network composition is very high; Change the method for operation and will cause the reduction of Operation of Electric Systems reliability, adopt high-impedance transformer and current-limiting reactor significantly will increase via net loss and reduce operation of power networks stability.Although above-mentioned measure can solve the suppression problem of grid short circuit electric current to a certain extent, bar none the dirigibility to operation of power networks, reliability and economy are brought negative effect in various degree.
Fault current limiter is as a kind of novel failure current limit technology, effectively can limit the capacity of short circuit of electrical network, thus greatly alleviate dynamic, the thermally-stabilised burden of the various high voltage electric equipments such as isolating switch, improve its operational reliability and serviceable life, ensure that the safety and stablization of electrical network are run.Permanent magnetism saturation type fault current limiter (PMFCL) has hybrid magnetic line structure, and wherein permanent magnet provides the perseverance being similar to DC excitation steady bias magnetic field, and winding current then can produce alternating magnetic field.This mixed magnetic circuit structure causes stray component comparatively complicated, mainly comprise the stray field etc. of the stray field on permanent magnet and iron core surface, winding inter-turn stray field and iron core turning or junction, when system is short-circuited, stray field can distort, for more effectively analyzing the magnetic efficiency of restrictor, need to set up reliable leakage field analytical model according to experimental study.Eddy current loss in iron core is comparatively large on the impact of restrictor serviceability, is the key factor will considered in optimal design.
Finite element analysis is utilized to carry out simulation modeling to restrictor; the feature that restrictor changes of magnetic field and temperature rise change can be obtained by simulating its state under normal work and short trouble; thus take measures to protect to it for these features, the Calculation results obtained also has certain reference value for restrictor Material selec-tion and parameter designing.
Summary of the invention
Object of the present invention is exactly to solve the problem, propose a kind of permanent magnetism saturation type fault current limiter magnetic current thermal coupling modeling method, the method utilizes finite element analysis software Ansoft Maxwell and Ansys to carry out magnetic-stream-thermal field order coupling analysis to permanent magnetism saturation type fault current limiter, by carrying out exploratory experiment to rational structure and material, software analysis is utilized to obtain reaching the model of better current limitation effect.
To achieve these goals, the present invention adopts following technical scheme:
A kind of permanent magnetism saturation type fault current limiter magnetic current thermal coupling modeling method, comprises the following steps:
(1) the half-wave current limliting topological structure 2D model of permanent magnetism saturation type fault current limiter is set up, the parameter of each structured material in setting model;
(2) in modeling process, external drive is applied to current limliting copper winding, by the short-circuit condition of control load, realizes the switching of permanent magnetism saturation type fault current limiter duty;
(3) simulation parameter is set, utilizes finite element software Ansoft to emulate described model; Obtain permanent magnetism saturation type fault current limiter half-wave current limliting topology is transitioned into failure current limit state Distribution of Magnetic Field figure by normal operating conditions;
(4) based on the half-wave current limliting topological structure 2D model of permanent magnetism saturation type fault current limiter, Ansoft is utilized to set up the half-wave current limliting topological structure 3D model of permanent magnetism saturation type fault current limiter;
(5) consider the heat stability of equipment, in ANSYS, set up transient thermal analytical model, the external applied load of Electromagnetic Calculation data as thermal analysis model is used; Finite element mesh subdivision is carried out to described transient thermal analytical model, makes the result of calculation of described analytical model closer to legitimate reading;
(6), after completing finite element mesh subdivision, carry out the setting of boundary condition and map excitation interpolation; Loss is mapped in structured grid, solve solver is utilized to carry out solving calculating, obtain the Temperature Distribution of model, by temperature field simplifying plan in the half-wave current limliting topological structure 3D model of permanent magnetism saturation type fault current limiter, obtained the Calculated Results of Temperature Field of the whole permanent magnetism saturation type fault current limiter equipment of any time by the preprocessor of ANSYS, and demonstrate the dynamic changing process in whole temperature field.
The half-wave current limliting topological structure 2D model of the permanent magnetism saturation type fault current limiter set up in described step (1) is specially:
1) whole region is that calculating solves territory, solves overseasly to be assumed to be vacuum; Infinite boundary condition is introduced, i.e. balloon boundary condition when Outer Boundary Conditions is set; On the sideline arranging balloon boundary condition, magnetic field neither vertical sideline is also not parallel to sideline;
2) material of core portion is R2K3D type ferrite;
3) ferritic relative permeability is non-linear, the relative permeability data acquisition BH curve of input material;
4) permanent magnet material is NDFe35, and magnetizing direction is Y direction, and two ends permanent magnet magnetizing direction is contrary, in total, form closed magnetic circuit;
5) two iron cores are all wrapped current limliting copper winding outward.
In described step (2), the external drive circuit that current limliting copper winding applies is specially:
Power frequency electric potential source Vc1, pull-up resistor R1, current limliting copper winding W1 and W2, permanent magnetism saturation type fault current limiter and reometer A1 are sequentially connected in series; Described pull-up resistor R1 arranges votage control switch S_v, and it self cut-off, is subject to the control of pulse voltage source Vc2; Initial time switch disconnects, and circuit is in normal operating condition, and after a certain moment, switch closes, then normal operating load is shorted, and system is in short trouble state.
The half-wave current limliting topological structure 3D model of the permanent magnetism saturation type fault current limiter set up in described step (4) is specially:
1) surrounding clear area is outward that calculating solves territory, and vacuum is appointed as in perimeter; When arranging Outer Boundary Conditions, adopt default boundary condition, namely magnetic field intensity tangential component perseverance is null boundary condition, in addition, also need to consider radiation boundary condition, this boundary condition is used for simulating the situation needing the loose magnetic considered, namely at infinity magnetic field is zero;
2) in 3D model, permanent magnet and performance core of safety valve in gas-fired instrument structure are rectangular parallelepiped; Two ends permanent magnet magnetizing direction is contrary, and whole restrictor is unshakable in one's determination forms annular closed magnetic circuit with permanent magnet;
3) two outer coilings of performance core of safety valve in gas-fired instrument exchange copper winding; In Modling model process, exchanging copper winding is the path needing to set driving source; In the winding of three-dimensional model, two copper windings cut two planes, flow into face as electric current, then on cross section, apply current excitation.
The concrete grammar of described step (5) is:
Maxwell 3D module is called in ANSYS Workbench, the permanent magnetism saturation type fault current limiter half-wave current limliting topology 3D model set up before importing and Electromagnetic Calculation destination file, set up transient thermal analysis module, and Electromagnetic Calculation destination file is read in, the external applied load of Electromagnetic Calculation data as thermal analysis is used.
In described step (6) when carrying out mesh generation and arranging, select inside selection subdivision to arrange and carry out subdivision to the whole inside of model, arranging in interface at subdivision can setup unit maximal side and required largest unit number; When setup unit maximal side, if numerical value is excessive, the degree of accuracy calculated cannot be ensured; If numerical value is too small, then calculated amount is excessive causes computing time long; Through Multi simulation running and results contrast, the selected optimal unit maximal side value that can ensure more excellent degree of accuracy and take less system resource.
The invention has the beneficial effects as follows:
The present invention's application finite element analysis software Ansoft Maxwell carries out analytical calculation to the electromagnetic field in linear pattern permanent magnetism saturation type fault current limiter winding and parts and current phasor, and apply ANSYS software on this basis and add thermal field and carry out magnetic-Flow-heat coupling analysis, obtain the thermo parameters method in its winding, iron core and permanent magnet element, its result has important references to the material type selecting of PMFCL and parameter designing and is worth.
The present invention utilizes the simplification structure of linear pattern permanent magnetism saturation type fault current limiter, modeling in Ansoft Maxwell software, model is symmetrical rectangular configuration, and be reduced to symmetrical cavity body exchanging a winding, so just at utmost decrease taking resource for computer system when software carries out analytical calculation.Respectively Electromagnetic Calculation is carried out to 2D, 3D model of PMFCL, draw the distribution situation of main magnetic field distribution and outside stray field in all parts, and obtain the current magnitude of PMFCL under normal operating conditions and short trouble duty and magnetic flux value, the current limitation effect of fault current limiter to short trouble big current can be demonstrated intuitively by contrast.
Utilize finite element analysis software ANSYS to carry out magnetic-Flow-heat coupling analysis to PMFCL, the distribution situation analyzing the electromagnetic field obtained wherein is carried out Analysis On The Transient Temperature as load introducing, draw the thermo parameters method figure of PMFCL in Maxwell.Subdivision being carried out to its structure, is not obtaining the temperature variation in iron core in the same time, draw PMFCL heating the Temperature Rising Law, for the parameter optimization of restrictor provides reference value, also providing a kind of effective Research approach for realizing its high-voltage large-capacity simultaneously.
Accompanying drawing explanation
Fig. 1 is the φ of orthoscopic PMFCL
e-i curve synoptic diagram;
Fig. 2 is PMFCL half-wave current limliting topological structure 2D model schematic of the present invention;
Fig. 3 is current limliting copper winding external drive circuit diagram in 2D model of the present invention;
Fig. 4 is PMFCL half-wave current limliting of the present invention topology 2D model emulation current magnitude schematic diagram;
Fig. 5 (a)-Fig. 5 (d) is the Distribution of Magnetic Field figure of PMFCL half-wave current limliting topological structure 2D model of the present invention four typical time in the whole course of work;
Fig. 6 is PMFCL half-wave current limliting topological structure 3D model schematic of the present invention;
Fig. 7 is linear pattern PMFCL half-wave current limliting of the present invention topology 3D model facetization figure;
Fig. 8 is PMFCL half-wave current limliting of the present invention topology 3D model emulation electric current and magnetic linkage oscillogram;
Fig. 9 is that PMFCL model thermal field of the present invention analyzes mesh generation schematic diagram.
Embodiment:
Below in conjunction with accompanying drawing and embodiment, the present invention will be further described:
Permanent magnetism saturation type fault current limiter principle of work
Based on the current limliting Analysis on Mechanism of the permanent magnetism saturation type fault current limiter (hereinafter referred to as PMFCL) in magnetic field
Fig. 1 gives magnetic flux unshakable in one's determination in the half-wave current limliting topology of orthoscopic PMFCL
ewith the relation curve of winding current i.Wherein, broken line ABCDE is the track of half-wave current limliting topology working point unshakable in one's determination, AB, BD and DE represent respectively restrictor forward saturation region, move back saturation region and reverse saturation region.When the systems are operating normally, the strong bias magnetic field that permanent magnet produces makes iron core be in degree of depth saturation region AB always, and magnetic flux unshakable in one's determination meets φ
e>=φ
s, winding shows as low induction reactance.When system is short-circuited fault, the mmf that major break down electric current produces offsets the mmf of permanent magnet gradually, makes unshakable in one's determinationly depart from saturation region and enter and move back saturation region BD, and magnetic flux meets-φ
s≤ φ
e≤ φ
s, winding externally shows as high induction reactance and limiting short-circuit current.If short-circuit current continues to increase to i
maxabove, then φ
e<-φ
s, the mmf that strong exchange current produces is ordered about iron core and is entered reverse saturation region DE, and PMFCL loses current limiting capacity.
For analyzing the field flux distribution change of PMFCL in whole effective flow restriction zones BD, define two stages of working point unshakable in one's determination experience herein: in 1) the current limliting stage I, be transitioned into a C from a B, be called first kind equivalent magnetic circuit modeling; 2) the current limliting stage II, be transitioned into a D from a C, be called Equations of The Second Kind equivalent magnetic circuit modeling.
A kind of permanent magnetism saturation type fault current limiter magnetic current thermal coupling modeling method, comprises the following steps:
(1) the half-wave current limliting topological structure 2D model of permanent magnetism saturation type fault current limiter is set up, the parameter of each structured material in setting model;
In model, each material parameter is relevant to the material chosen.
1. choosing of winding material be exactly the material selection considering general winding in reality is copper.
2. the choosing to compare in engineering and apply aluminium cobalt nickel permanent magnet, permanent-magnet ferrite, rare earthcobalt permanent magnet and Nd-Fe-B permanent magnet more widely of permanent magnet.Contrast situation is as table 1:
The Performance comparision of the typical hard magnetic material of table 1
More than Integrated comparative four kinds of hard magnetic materials, select neodymium iron boron first-selected as the permanent magnet of low capacity and high-voltage large-capacity PMFCL, and simulation and experiment of the present invention all select N35 model neodymium iron boron as the permanent magnet of PMFCL.
3. choosing of performance core of safety valve in gas-fired instrument material compared for ferro-silicium, Rhometal, amorphous soft magnetic alloy and soft magnetic ferrite.Contrast situation is as shown in table 2:
The Performance comparision of the typical soft magnetic material of table 2
More than Integrated comparative four kinds of soft magnetic materials, first-selected ferro-silicium is as the core material of Large Copacity permanent magnet bias type fault current limiter, and Fe-Si-B system non-crystaline amorphous metal can be used as alternative; Low capacity experimental study can replace with soft magnetic ferrite.
(2) in modeling process, apply external drive to current limliting copper winding, the duty of permanent magnetism saturation type fault current limiter encourages the magnetic flux of electric current and the iron core being applied to copper winding jointly to determine by external circuit;
(3) simulation parameter is set, utilizes finite element software Ansoft to emulate described model; Obtain permanent magnetism saturation type fault current limiter half-wave current limliting topology is transitioned into failure current limit state Distribution of Magnetic Field figure by normal operating conditions;
(4) based on the half-wave current limliting topological structure 2D model of permanent magnetism saturation type fault current limiter, Ansoft is utilized to set up the half-wave current limliting topological structure 3D model of permanent magnetism saturation type fault current limiter;
(5) consider the heat stability of equipment, in ANSYS, set up transient thermal analytical model, the external applied load of Electromagnetic Calculation data as thermal analysis model is used; Finite element mesh subdivision is carried out to described transient thermal analytical model, makes the result of calculation of described analytical model closer to legitimate reading;
(6), after completing finite element mesh subdivision, carry out the setting of boundary condition and map excitation interpolation; Loss is mapped in structured grid, solve solver is utilized to carry out solving calculating, obtain the Temperature Distribution of model, by temperature field simplifying plan in the half-wave current limliting topological structure 3D model of permanent magnetism saturation type fault current limiter, obtained the Calculated Results of Temperature Field of the whole permanent magnetism saturation type fault current limiter equipment of any time by the preprocessor of ANSYS, and demonstrate the dynamic changing process in whole temperature field.
1.Maxwell 2D simulation modeling
The magnetic parameter of 1.1 PMFCL topologys and structural parameters
Set up the half-wave current limliting topological model of permanent magnetism saturation type fault current limiter, following table is the parameter of each structured material in model.
The magnetic material parameter of table 3 PMFCL topology
1.2 restrictor 2D modelings
Utilize finite element software Ansoft to carry out modeling and simulating to permanent magnetism saturation type fault current limiter, 2D model half-wave current limliting topological structure schematic diagram as shown in Figure 2:
(1) whole region is that calculating solves territory, solves overseasly to be assumed to be vacuum.Infinite boundary condition is introduced, i.e. balloon boundary condition when Outer Boundary Conditions is set.On the sideline arranging balloon boundary condition, magnetic field neither vertical sideline is also not parallel to sideline.
(2) material of core portion is R2K3D type ferrite, and material parameter is as shown in table 4:
Table 4 R2K3D type ferrite material parameter
(3) ferritic relative permeability is non-linear, owing to not having R2K3D ferrite model in Maxwell soft material storehouse, so need the relative permeability data acquisition BH curve of manual input material.
(4) permanent magnet material is NDFe35, and magnetizing direction is Y direction, and two ends permanent magnet magnetizing direction is contrary, in total, form closed magnetic circuit.
(5) two iron cores are all wrapped current limliting copper winding outward, and upper and lower umber of turn is respectively 150 circles.
1.3 magnetic circuit which couple are analyzed---external drive circuit
In modeling process, need to apply external drive to current limliting copper winding, the duty of PMFCL encourages the magnetic flux of electric current and the iron core being applied to copper winding jointly to determine by external circuit.By the short-circuit condition of control load, realize the switching of permanent magnetism saturation type fault current limiter duty.External circuit figure electric power as shown in Figure 3, comprises power frequency electric potential source in circuit, in power supply, sense is the resistance value of 6.5mH, PMFCL itself is 2.3 Ω, and two current limliting copper windings in series connect, normal operating load resistance 63.2 Ω.Also be provided with votage control switch and model thereof and ON-OFF control circuit, switch S _ v controls short-circuit process, it self cut-off, is subject to the control of left side excitation voltage source Vc2, initial time switch disconnects, what now simulate is circuit normal operating condition, after a certain moment, switch closes, then normal operating load is shorted, simulation be that system is in short trouble state.
S_V is votage control switch pipe, votage control switch pipe must use together with votage control switch model element, some fundamental characteristics of votage control switch pipe are arranged and are arranged by votage control switch tube model element smodell, votage control switch tube model element can arrange element as the identical votage control switch pipe of multiple fundamental characteristics, when including the votage control switch pipe of different qualities in same circuit, correspondingly will increase votage control switch tube model element and it will be arranged.Being associated of the votage control switch tube model element that votage control switch Guan Yuqi is corresponding is that title by the MOD model in votage control switch tube elements parameter being set to corresponding votage control switch tube model element realizes.
Arranging supply voltage Uss is 220V, and switch S _ v closure time (namely starting short circuit duration) is for closed during 0.04s.Electric system power-frequency voltage frequency is 50Hz, and it is 0.1s that setting solves T.T..For ensureing certain accuracy, arranging and solving step-length is 0.001s.
Fig. 4 gives PMFCL and proceeds to current magnitude in the whole process of short trouble duty in winding by normal operating conditions.In figure, each gauge point is respectively instantaneous peak current.As can be seen from gauge point current value, during normal work, system power is about 2A, and be short-circuited during 0.04s fault, and loaded impedance is shorted, and system power increases instantaneously.Because the model built is half-wave current limliting model, than the current value size of calibration half cycles with negative half period ripple, the current limitation effect of PMFCL intuitively can be arrived.
From gauge point m3, m5, m7 in figure, positive half cycle current peak value is limited in about 28A, and negative half period ripple electric current (gauge point m4, m6) does not work due to restrictor, and current peak reaches 53A.Visible, PMFCL serves significant metering function when system jam.
ANSOFT is utilized to draw field pattern, obtain the Distribution of Magnetic Field figure of orthoscopic PMFCL half-wave current limliting topology four typical time in the whole course of work (being transitioned into failure current limit state by normal operating conditions), as shown in Fig. 5 (a)-Fig. 5 (d).As can be seen from Fig. 5 (a), in normal working hour, the bias magnetic field in the same way that PMFCL two ends permanent magnet produces forms closed magnetic circuit by performance core of safety valve in gas-fired instrument.During 0.04s, system is short-circuited fault, and along with the increase exchanging winding short circuit currents, the Distribution of Magnetic Field in PMFCL distorts gradually, and as shown in Fig. 5 (b), now main magnetic circuit does not change completely.After this short-circuit current continues to increase, and region, reversed magnetic field appears in PMFCL stage casing core portion, as shown in Fig. 5 (c), namely there is the closed-loop path formed by performance core of safety valve in gas-fired instrument and clearance, and two ends closed magnetic circuit is still formed by permanent magnet bias magnetic field.The large minor swing change of circuit short circuit currents, the region, reversed magnetic field that short-circuit current produces expands thereupon, and (or reduction) influences each other with the permanent magnet closed magnetic circuit at two ends, now due to the change of magnetic flux in iron core, restrictor plays the effect of limiting short-circuit current.
In 2.Maxwell 3D, PMFCL transient magnetic field is analyzed
Relative to three-dimensional modeling, in aforesaid Maxwell 2D modeling and simulating, two-dimentional modeling to be only Z-direction thickness be zero special said three-dimensional body, after completing two-dimentional modeling and simulating, carry out three-dimensional modeling based on this.The model structure of orthoscopic PMFCL is comparatively simple, Ansoft can be utilized directly to set up solid model, as shown in Figure 6.
2.1 PMFCL half-wave current limliting topology 3D model Brief description
Linear pattern permanent magnet bias type fault current limiter half-wave current limliting topological model parameter is consistent with aforementioned 2D model, no longer lists herein.
(1) surrounding clear area is outward that calculating solves territory, and vacuum is appointed as in perimeter.When Outer Boundary Conditions is set, adopt default boundary condition, namely magnetic field intensity tangential component perseverance is null boundary condition, in addition, also need to consider radiation boundary condition, this boundary condition is used for simulating the situation of loose magnetic needing to consider, namely at infinity magnetic field is zero, and the balloon boundary condition in this and 2D model is similar.
(2) in 3D model, permanent magnet and performance core of safety valve in gas-fired instrument structure are rectangular parallelepiped.Two ends permanent magnet magnetizing direction is contrary, and whole restrictor is unshakable in one's determination forms annular closed magnetic circuit with permanent magnet.
(3) two outer coilings of performance core of safety valve in gas-fired instrument exchange copper winding.In Modling model process, it is significant to note that the interpolation of driving source in three-dimensional model, exchanging copper winding is the path needing to set driving source.In the winding of three-dimensional model, two copper windings cut two planes, flow into face as electric current, then on cross section, apply current excitation.
2.2 orthoscopic PMFCL half-wave current limliting topology 3D model meshes subdivisions
In the three-dimensional model, Ansoft supports triangular pyramid finite elements subdivision, and such cellular construction is succinct, can carry out stable mesh generation, make the result of calculation of institute's analytical model closer to legitimate reading to all kinds of entity.When carrying out subdivision and arranging, select inside selection subdivision to arrange and carry out subdivision to the whole inside of model, arranging at subdivision can setup unit maximal side and required largest unit number in interface.When setup unit maximal side, if numerical value is excessive, the degree of accuracy calculated cannot be ensured; If numerical value is too small, then calculated amount is excessive causes computing time long.Through Multi simulation running and results contrast, the selected optimal unit maximal side value that can ensure more excellent degree of accuracy and take less system resource.Orthoscopic PMFCL half-wave current limliting topology 3D model facetization situation as shown in Figure 7.
Arrange consistent when emulating with the aforementioned 2D carried out, supply voltage Uss is 220V, switch S _ v closure time (namely starting short circuit duration) for 0.04s close.Electric system power-frequency voltage frequency is 50Hz, and it is 0.1s that setting solves total duration, solves step-length and is set to 0.001s.With the analysis and solution of 2D model unlike, when computational analysis 3D model, introduce the eddy effect of permanent magnet and coiler part.
In Fig. 8, dotted line is the line electricity flow valuve of model in whole duty, and solid line is the magnetic flux in winding A.Positive half cycle current peak value (gauge point m2, m4) and negative half-cycle current peak value (gauge point m1, m3) in comparison diagram, can find out that PMFCL serves certain current limitation effect, but be subject to the restriction of material character, the short-circuit current through current limliting is still very large.
Solid line is magnetic linkage waveform, and before 0.04s (short trouble generation), iron core is in degree of depth state of saturation, and along with the vibration of sinusoidal current, in iron core, flux change rate is very little, and the external induction reactance of PMFCL is very little.After system is short-circuited fault, winding short circuit currents value is increased sharply, and in iron core, magnetic flux changes thereupon, and iron core enters linear work district.As can be seen from the peak value of magnetic linkage squiggle, in whole simulation process, iron core does not enter reverse saturation region and loses metering function.
Permanent magnetism saturation type fault current limiter magnetic-Flow-heat coupling field modeling analysis in 3.ANSYS
Permanent magnetism saturation type fault current limiter is the high-voltage electrical equipment be directly installed in electric system, and except normal operating conditions, it also works when electric system is short-circuited fault as important current limiter.In practical engineering application, because the effect such as ubiquity eddy effect, electromagnetic action (comprising electromagnetic crosstalk and electromagnetic consumable) and heat interchange in electrical equipment, and each material components all exists maximum normal working temperature in device, so the heat stability of equipment must be considered.
Operationally, a part of electromagnetic energy changes in order to heat energy PMFCL equipment, and namely equipment operationally, creates electromagnetic consumable in winding and miscellaneous part, and these losses are dispersed in surrounding medium with form of thermal energy, finally causes PMFCL device temperature to raise.In order to ensure the serviceable life of current-limiting apparatus, reduce system loss, computational analysis is carried out in the equipment temperature rise tackled under PMFCL normal operating conditions and fail operation state, and ensureing that all parts temperature is no more than on the basis of the highest normal working temperature restriction, takes more effective cooling provision.
3.1 thermal field analysis modeling processes and load load and arrange
The material properties relevant with thermodynamic analysis has coefficient of heat conductivity, specific heat, density of material, and these attributes are all the functions relevant with temperature.Following table gives PMFCL each several part material thermal behavior attribute.
Table 5 PMFCL each structured material thermal behavior attribute list
Maxwell 3D module is called in ANSYS Workbench, the linear pattern PMFCL half-wave rectification topological model set up before importing and Electromagnetic Calculation destination file, set up transient thermal analysis module, and Electromagnetic Calculation destination file is read in, thus data sharing is completed in whole process, namely the external applied load that Electromagnetic Calculation data are analyzed as warm blood is used.Complete the preset of material and after carrying out material properties distribution to all parts, starting to carry out stress and strain model.Provide the user the high mesh generation of degree of freedom in ANSYS to arrange, due to the relatively simple and easy and symmetrical shape of PMFCL model, so have employed the higher automatic mode for Electromagnetic Calculation of precision when grid division.As seen from Figure 9, each division unit is the rectangular parallelepiped of rule, and whole equipment altogether subdivision is 6302 hexahedral elements.
After completing mesh generation, the setting of boundary condition can be carried out and map excitation interpolation.Choose the core portion in model, arranging film coefficient is 5, film coefficient is the convective heat-transfer coefficient between fluid and wall, then loss is mapped in structured grid, after utilizing solve solver to carry out solving calculating, by temperature field simplifying plan in PMFCL model, the Calculated Results of Temperature Field of the whole PMFCL equipment of any time can be read by the preprocessor of ANSYS, and the dynamic changing process in whole temperature field can be demonstrated.
3.2 analysis of simulation result
From temperature field pattern, due to the existence of direct impedance, under the effect of fault big current, exchange in copper winding and produce larger thermal losses, in whole current limliting process, winding central region temperature rises the fastest.Under the effect of heat transfer and thermal convection, heat, unshakable in one's determinationly to be risen very soon with the portion temperature that winding directly contacts to performance core of safety valve in gas-fired instrument transmission by winding, and the portion temperature that winding both ends contact with ferrite is also increased significantly.
The thermal losses produced in the PMFCL course of work can be divided into iron loss and winding copper loss, and iron loss mainly comprises magnetic hysteresis loss, eddy current loss and abnormal wear under alternating magnetization; Winding copper loss is primarily of ohmic loss and eddy current loss composition.Ohmic loss is relevant with copper winding AC resistance, and eddy current loss has two main image factors, and one is due to kelvin effect, and two is the changes of magnetic field situations in winding.In the computational analysis of this device, do not relate to high frequency situations, so first can ignore kelvin effect, and the changes of magnetic field of winding inside is very little, therefore also the eddy current loss exchanged in copper winding can be ignored.In the course of work of whole device, the magnetic circuit change in permanent magnet and performance core of safety valve in gas-fired instrument greatly, so mainly consider the eddy current loss of these two parts when analysis thermal field.
Can find out when facilities for observation temperature field dynamic changing process, at the fault money that is short-circuited, PMFCL temperature is lower, and temperature ascendant trend is comparatively slow, and performance core of safety valve in gas-fired instrument internal temperature is substantially constant; After short trouble occurs, exchange electric current in copper winding and increase rapidly, can see that winding temperature rises rapidly, the heat that winding sends is by the surface of contact of itself and performance core of safety valve in gas-fired instrument to iron core transmission, and then inside unshakable in one's determination starts to occur temperature rise.It can thus be appreciated that eddy effect not only can reduce the normal operating magnetic field flux in iron core, cause the working point of soft magnetic ferrite to offset to linear zone, equipment also can be made to produce temperature rise and cause local overheating.It should be noted that, carrying out in the process of computational analysis to the whole duty of PMFCL, leakage field effect, eddy effect and temperature-rise effect three intercouple impact, first vortex field is because the stray field with exchanging in copper winding unshakable in one's determination produces, eddy effect makes to produce extra temperature rise in fault current limiter, and temperature rising and vortex field itself also can have influence on the distribution of stray field in device.
When system worked well, exchange electric current in winding and be in normal value, whole PMFCL device temperature is room temperature, exchanges on copper winding and occurs faint temperature rise; Along with the increase of working hour, affecting the local temperature rise occurring rule in the middle part of performance core of safety valve in gas-fired instrument by eddy effect, there is temperature rise point in inside unshakable in one's determination; At 0.04s moment generation systems short trouble, because the short-circuit current exchanged in winding increases rapidly, there is obvious temperature rise in copper winding, heat by winding and surface of contact unshakable in one's determination to internal divergence unshakable in one's determination, and the eddy effect aggravation of now performance core of safety valve in gas-fired instrument inside, performance core of safety valve in gas-fired instrument internal vortex temperature rise region and expand gradually with winding temperature rise region and squeeze out Liang Tiao topical hypothermia at iron core and be with.
The environment of PMFCL residing in practical engineering application is very complicated, inner, outside many factors all can have influence on the working temperature of equipment and then affect its stability, may be there is thermal extremes or microthermal climate situation in physical environment, the heating of electrical equipment under normal operation and failure condition also may make PMFCL be operated among very steady state.For permanent magnet, abnormal temperature may cause its permanent magnetic to be damaged, and heating and cooling also can make permanent magnet that demagnetization phenomenon occurs repeatedly, and for soft magnetic ferrite, temperature also can have influence on its magnetic permeability, loss and saturation induction density.As can be seen from the result of emulation, PMFCL is in whole process, and performance core of safety valve in gas-fired instrument is subject to the impact of AC coil heat trnasfer and internal vortex loss two aspect, and temperature rise is the most serious, so in actual moving process, because the affecting its current limiting performance and may be subject to certain impact of temperature rise.In order to ensure that restrictor can keep normal work, the measure such as external refrigeration, adjustment structure parameter can be adopted to reduce the temperature rise of equipment to a certain extent.
In a word, by utilizing finite element software to the analogue simulation of restrictor in the present invention, result in Ansoft Maxwell is known, permanent magnetism saturation type fault current limiter has obvious restriction for short-circuit current, because structural parameters and material etc. can have influence on its current limitation effect, exploratory experiment can be carried out to rational structure and material, utilize software analysis to obtain reaching the model of better current limitation effect.ANSYS software then can be analyzed magnetic-Flow-heat coupling field, obtains along with time variations, the Changing Pattern of PMFCL temperature, thus can be protected equipment according to the generate heat feature of temperature rise of each several part, avoids the too high infringement brought equipment of temperature rise.Realize high-voltage large-capacityization to restrictor is also a kind of well emulation verification method simultaneously.
By reference to the accompanying drawings the specific embodiment of the present invention is described although above-mentioned; but not limiting the scope of the invention; one of ordinary skill in the art should be understood that; on the basis of technical scheme of the present invention, those skilled in the art do not need to pay various amendment or distortion that creative work can make still within protection scope of the present invention.
Claims (6)
1. a permanent magnetism saturation type fault current limiter magnetic current thermal coupling modeling method, is characterized in that, comprise the following steps:
(1) the half-wave current limliting topological structure 2D model of permanent magnetism saturation type fault current limiter is set up, the parameter of each structured material in setting model;
(2) in modeling process, external drive is applied to current limliting copper winding, by the short-circuit condition of control load, realizes the switching of permanent magnetism saturation type fault current limiter duty;
(3) simulation parameter is set, utilizes finite element software Ansoft to emulate described model; Obtain permanent magnetism saturation type fault current limiter half-wave current limliting topology is transitioned into failure current limit state Distribution of Magnetic Field figure by normal operating conditions;
(4) based on the half-wave current limliting topological structure 2D model of permanent magnetism saturation type fault current limiter, Ansoft is utilized to set up the half-wave current limliting topological structure 3D model of permanent magnetism saturation type fault current limiter;
(5) consider the heat stability of equipment, in ANSYS, set up transient thermal analytical model, the external applied load of Electromagnetic Calculation data as thermal analysis model is used; Finite element mesh subdivision is carried out to described transient thermal analytical model, makes the result of calculation of described analytical model closer to legitimate reading;
(6), after completing finite element mesh subdivision, carry out the setting of boundary condition and map excitation interpolation; Loss is mapped in structured grid, solve solver is utilized to carry out solving calculating, obtain the Temperature Distribution of model, by temperature field simplifying plan in the half-wave current limliting topological structure 3D model of permanent magnetism saturation type fault current limiter, obtained the Calculated Results of Temperature Field of the whole permanent magnetism saturation type fault current limiter equipment of any time by the preprocessor of ANSYS, and demonstrate the dynamic changing process in whole temperature field.
2. a kind of permanent magnetism saturation type fault current limiter magnetic current thermal coupling modeling method as claimed in claim 1, is characterized in that, the half-wave current limliting topological structure 2D model of the permanent magnetism saturation type fault current limiter set up in described step (1) is specially:
1) whole region is that calculating solves territory, solves overseasly to be assumed to be vacuum; Infinite boundary condition is introduced, i.e. balloon boundary condition when Outer Boundary Conditions is set; On the sideline arranging balloon boundary condition, magnetic field neither vertical sideline is also not parallel to sideline;
2) material of core portion is R2K3D type ferrite;
3) ferritic relative permeability is non-linear, the relative permeability data acquisition BH curve of input material;
4) permanent magnet material is NDFe35, and magnetizing direction is Y direction, and two ends permanent magnet magnetizing direction is contrary, in total, form closed magnetic circuit;
5) two iron cores are all wrapped current limliting copper winding outward.
3. a kind of permanent magnetism saturation type fault current limiter magnetic current thermal coupling modeling method as claimed in claim 1, is characterized in that, is specially in described step (2) to the external drive circuit that current limliting copper winding applies:
Power frequency electric potential source Vc1, pull-up resistor R1, current limliting copper winding W1 and W2, permanent magnetism saturation type fault current limiter and reometer A1 are sequentially connected in series; Described pull-up resistor R1 arranges votage control switch S_v, and it self cut-off, is subject to the control of pulse voltage source Vc2; Initial time switch disconnects, and circuit is in normal operating condition, and after a certain moment, switch closes, then normal operating load is shorted, and system is in short trouble state.
4. a kind of permanent magnetism saturation type fault current limiter magnetic current thermal coupling modeling method as claimed in claim 1, is characterized in that, the half-wave current limliting topological structure 3D model of the permanent magnetism saturation type fault current limiter set up in described step (4) is specially:
1) surrounding clear area is outward that calculating solves territory, and vacuum is appointed as in perimeter; When arranging Outer Boundary Conditions, adopt default boundary condition, namely magnetic field intensity tangential component perseverance is null boundary condition, in addition, also need to consider radiation boundary condition, this boundary condition is used for simulating the situation needing the loose magnetic considered, namely at infinity magnetic field is zero;
2) in 3D model, permanent magnet and performance core of safety valve in gas-fired instrument structure are rectangular parallelepiped; Two ends permanent magnet magnetizing direction is contrary, and whole restrictor is unshakable in one's determination forms annular closed magnetic circuit with permanent magnet;
3) two outer coilings of performance core of safety valve in gas-fired instrument exchange copper winding; In Modling model process, exchanging copper winding is the path needing to set driving source; In the winding of three-dimensional model, two copper windings cut two planes, flow into face as electric current, then on cross section, apply current excitation.
5. a kind of permanent magnetism saturation type fault current limiter magnetic current thermal coupling modeling method as claimed in claim 1, it is characterized in that, the concrete grammar of described step (5) is:
Maxwell 3D module is called in ANSYS Workbench, the permanent magnetism saturation type fault current limiter half-wave current limliting topology 3D model set up before importing and Electromagnetic Calculation destination file, set up transient thermal analysis module, and Electromagnetic Calculation destination file is read in, the external applied load of Electromagnetic Calculation data as thermal analysis is used.
6. a kind of permanent magnetism saturation type fault current limiter magnetic current thermal coupling modeling method as claimed in claim 1, it is characterized in that, in described step (6) when carrying out mesh generation and arranging, select inside selection subdivision to arrange and carry out subdivision to the whole inside of model, arranging in interface at subdivision can setup unit maximal side and required largest unit number; When setup unit maximal side, if numerical value is excessive, the degree of accuracy calculated cannot be ensured; If numerical value is too small, then calculated amount is excessive causes computing time long; Through Multi simulation running and results contrast, the selected optimal unit maximal side value that can ensure more excellent degree of accuracy and take less system resource.
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| CN110021929A (en) * | 2018-12-29 | 2019-07-16 | 国网内蒙古东部电力有限公司经济技术研究院 | A kind of high-speed switch type fault current limiter electro-magnetic transient time-domain-simulation modeling method |
| CN110021929B (en) * | 2018-12-29 | 2023-01-13 | 国网内蒙古东部电力有限公司经济技术研究院 | Electromagnetic transient time domain simulation modeling method for fast switch type fault current limiter |
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