Curve magnetic valve structure, curve magnetic valve type controllable reactor and application
Technical Field
The invention belongs to the technical field of reactive power compensation of power systems, and particularly relates to a curve magnetic valve structure, a curve magnetic valve type controllable reactor and application.
Background
At present, a magnetic valve controlled reactor (MCR) is an important reactive compensation device, the reactive power of which is continuously adjustable, and is more convenient to use in an extra-high voltage environment than a Thyristor Controlled Reactor (TCR), and is currently widely used in an electric power system.
However, because the operating principle of the MCR is based on the magnetic saturation of the magnetic valve, each harmonic is inevitably generated in the saturation process, and as the operating voltage and the capacity of the MCR increase, the injected harmonic also increases, and if no limiting measures are taken, the harmonic injection into the power grid will affect the system safety. And the operation cannot be stabilized.
The harmonic suppression method is generally classified into an external circuit suppression method or an internal magnetic circuit suppression method. The circuit suppression method achieves the purpose of suppressing harmonic waves by externally changing the connection mode of the magnetically controlled reactor or adding an additional filtering device or other equipment, but the application of the additional equipment can cause cost increase, and the cost is higher because the additional equipment is not suitable to be added under certain environments. The internal magnetic circuit inhibition method can fundamentally reduce the harmonic output of the magnetic valve type controllable reactor by improving the internal magnetic valve structure of the magnetic valve type controllable reactor, and the key point is the optimization of the magnetic valve structure.
The traditional multi-stage magnetic valve structure only considers harmonic optimization under the condition of extreme saturation, namely the maximum-minimum sectional area ratio is 3:1, which is not comprehensive enough, and if the sectional area ratio is reduced, the harmonic optimization is more severe, so that the harmonic can be reduced as much as possible by adopting the curved magnetic valve (similar to infinite stage) structure.
Through the above analysis, the problems and defects of the prior art are as follows:
(1) the maximum-minimum sectional area ratio of the magnetic valve is not considered in the prior art, and if the maximum-minimum sectional area ratio is reduced, the material utilization rate can be improved, but a more severe harmonic optimization problem is brought.
(2) Therefore, the invention further provides the structure of the curved magnetic valve on the basis of the defects, a brand-new structure similar to infinite series is adopted to achieve the effect of extremely reducing harmonic waves, and the harmonic optimization is better than that of the original structure.
The difficulty in solving the above problems and defects is:
the traditional research is limited to the condition that the magnetic valve is in ultimate saturation, namely the maximum-to-minimum sectional area ratio is 3:1, the constraint is released, an idea can be provided for improving the material utilization rate, the difficulty of harmonic optimization is increased, and the curved magnetic valve structure is provided for greatly reducing the harmonic output.
The significance of solving the problems and the defects is as follows: the situation of the magnetic valve is considered more fully, i.e. the maximum and minimum cross-sectional ratio of the magnetic valve is included, and in this case a curved magnetic valve structure is provided which reduces the harmonic output very much.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a curved magnetic valve structure, a curved magnetic valve type controllable reactor and application. The purpose is to improve the material utilization rate of the magnetically controlled reactor and reduce output harmonic waves to the maximum extent.
The invention is realized in such a way that the curve magnetic valve structure fits the magnetic valve curve according to Gaussian integration and particle swarm optimization algorithm after determining the maximum and minimum sectional area ratio to obtain the magnetic valve shape with the lowest harmonic.
Further, different maximum to minimum cross-sectional area ratios KlGreater than 1 and less than 3.
Further, the ratio of the maximum cross-sectional area to the minimum cross-sectional area KlThe calculation method which is more than 1 comprises the following steps:
optimization of the (2m +1) subharmonic (3, 5, 7 … subharmonic) satisfies the requirement that the cross-sectional area ratio is at least greater than
And the larger the sectional area ratio is, the larger the optimization margin is, and different curve shapes are designed under the condition of different sizes of the sectional area ratios.
Further, the curved magnetic valve structure is a multi-stage magnetic valve structure with infinite stages.
Further, a rectangular coordinate system is established along the axial direction and the radial direction by taking the outer edge of the minimum cross section as an origin, A0Is the smallest magnetic valve cross-sectional area, AlIs the sectional area of the iron core, and l is the length of the magnetic valve; the cross-sectional area of a certain part in the magnetic valve is AxThe right subscript x represents the distance of the section from the smallest section, the largest core section outer edge according to KlThe other end point of the determining curve magnetic valve designs the shape of the magnetic valve to be a continuous single-gradual-changeFunction f (x) curve structure of increasing features.
Another object of the present invention is to provide a curved magnetic valve type controllable reactor, comprising: the magnetic valve comprises I, II two symmetrical working column iron cores, wherein a small section with the length of l is arranged in the middle of each working column iron core, and the small section is a curved magnetic valve structure;
the two ends of the curve magnetic valve structure magnetic valve are respectively symmetrically distributed with windings, the upper and lower windings are connected with taps through silicon controlled rectifier K1,K2And the upper and lower windings of the two working column cores are connected in parallel to a power grid after being connected in a cross way, and a freewheeling diode D spans across the cross end point.
Another object of the present invention is to provide a method for adjusting a reactance value and a reactance capacity of a curve magnetic valve type controllable reactor, the method comprising:
the DC excitation is adjusted by controlling the conduction angle of the controllable silicon, the principle is similar to full-wave rectification, and then the magnetic saturation of the magnetic valve is changed, the equivalent magnetic conductivity is changed, and the reactance value and the reactance capacity are smoothly changed.
The invention also aims to provide an application of the curve magnetic valve type controllable reactor in power system harmonic adjustment.
By combining all the technical schemes, the invention has the advantages and positive effects that:
on the basis of the structure of the traditional magnetically controlled reactor, the shape of a single machine or multiple stages of the traditional magnetic valve is changed, and a curve structure is adopted.
The maximum and minimum sectional area ratio of the magnetically controlled reactor is reasonably designed according to actual conditions, namely the sectional area ratio is at least larger than that of the magnetically controlled reactor when (2m +1) subharmonic (3, 5 and 7 … subharmonic) is considered to be optimized
And the larger the sectional area ratio is, the larger the optimization margin is, and different curve shapes are designed under the condition of different sizes of the sectional area ratios.
After the maximum-minimum sectional area ratio is determined, a magnetic valve curve is fitted according to Gaussian integration and a particle swarm optimization algorithm, and the shape of the magnetic valve with the lowest harmonic is obtained.
The curve magnetic valve structure provided by the invention can further fully reduce harmonic waves, and only the condition that the ratio of the cross-sectional area of the maximum magnetic valve to the cross-sectional area of the minimum magnetic valve is 1:3 is analyzed in the existing research, if the ratio can be reduced, the material utilization rate is improved, and the cost is reduced.
The design of the invention can reduce the harmonic output as much as possible and reduce the influence of the output harmonic of the magnetically controlled reactor on the power system.
The design of the invention considers the cross-sectional area ratio of the maximum and minimum magnetic valves, and the material utilization rate can be improved although the harmonic optimization is more severe when a smaller proportion is selected in the design.
The invention provides a curve magnetic valve type controllable reactor structure, and a complete curve magnetic valve optimization design method is constructed by carrying out optimization design on the ratio of the maximum sectional area to the minimum sectional area of a magnetic valve and the curve shape of the magnetic valve, so that the harmonic wave is reduced as far as possible while the material utilization rate is improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained from the drawings without creative efforts.
Fig. 1 is a schematic diagram of a magnetic valve type controllable reactor structure provided by an embodiment of the invention.
FIG. 2 is a schematic diagram of a curved magnetic valve structure provided by an embodiment of the present invention.
Fig. 3 is a diagram of Simulink simulation results provided by an embodiment of the present invention.
FIG. 4 is a graph showing the effect of a 22kVA/380V experimental prototype provided by the embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Aiming at the problems in the prior art, the invention provides a curved magnetic valve structure, a curved magnetic valve type controllable reactor and application thereof, and the invention is described in detail with reference to the accompanying drawings.
Fig. 1 is a structure diagram of a magnetic valve type controllable reactor. The magnetic valve type controllable reactor comprises I, II two symmetrical working columns, each of which has a small section with length l in the middle, called magnetic valve.
Windings are symmetrically distributed at two ends of the magnetic valve, the upper and lower windings are connected with taps through a silicon controlled rectifier K1,K2And the upper and lower windings of the two working columns are connected in parallel to a power grid after being connected in a cross way, and a freewheeling diode D spans across the cross end point.
The magnetic valve type controllable reactor adjusts the direct current excitation size by controlling the conduction angle of the silicon controlled rectifier, the principle is similar to full wave rectification, the magnetic saturation of the magnetic valve is further changed, the equivalent magnetic conductivity is changed, and therefore the reactance value and the reactance capacity are smoothly changed.
The invention provides a novel curve magnetic valve structure based on a traditional magnetically controlled reactor, and the magnetic valve part is shown in figure 2 (a schematic diagram of the curve magnetic valve structure).
Similar to a multistage magnetic valve type controllable reactor, the curve magnetic valve type controllable reactor is equivalent to an infinite-stage multistage magnetic valve type controllable reactor, and the fundamental principle can be referred to in the document 'harmonic analysis mathematical model of a multistage saturation magnetic valve type controllable reactor'. The following description is made of different points with reference to fig. 2:
(1) taking into account different maximum to minimum cross-sectional area ratios KlThe default of the traditional literature is 3:1, the magnetically controlled reactor can reach the limit saturation, different area ratios can be considered in the process of optimization design, the minimum section area is 1 part, and the temporary range of the maximum section area is larger than 1 and smallerAt 3.
(2) Establishing a rectangular coordinate system along the axial direction and the radial direction by taking the outer edge of the minimum cross section as an origin as a graph A0Is the smallest magnetic valve cross-sectional area, AlIs the core cross-sectional area and l is the magnetic valve length. The cross-sectional area (infinitesimal) of a certain position in the magnetic valve is AxThe right subscript x represents the distance of the section from the smallest section, the largest core section outer edge according to KlThe change is changed, which determines that the other end point of the curve magnetic valve designs the magnetic valve shape as a shape function f (x) which has the characteristic of continuous monotone increasing.
The harmonic mathematical model of the curve magnetic valve can be obtained after the different points:
wherein, betaxIs the magnetic saturation, beta, of the infinitesimal magnetic valve at a distance x from the smallest cross-section0The minimum section magnetic saturation is 0 in the initial state without DC excitation, and the maximum value is beta0max=(kl-1)π,i1First name value for fundamental current, Bt0Is the magnetic induction at the critical saturation of the minimum cross section, i(2m+1)Is the famous value of the 2m +1 th harmonic current, N is the number of turns of the working coil, mu0Is a vacuum magnetic permeability.
The invention changes the structure of the magnetic valve, and the different points of the magnetic valve part are shown by the formula (1), namely, a curve magnetic valve harmonic mathematical model.
The following table shows the optimal harmonics under different maximum-to-minimum cross-sectional area ratios obtained after designing an optimal curve according to a flow chart, including three-phase (without considering the third harmonic, the third harmonic is offset by a triangular connection method) and single-phase conditions:
TABLE 1 harmonic distortion ratio after harmonic optimization of curved solenoid valves under different area ratios
The table exemplifies that the area ratio is within the range of 1.5-3 and every 0.1 is a partition according to the flow chart, more area ratio situations or specific harmonics of a certain order can be refined in practical application, and the optimization of 5 harmonics when the area ratio is too small does not meet the formula (3) and far exceeds the national standard, so that the optimization is not listed.
The method herein is applicable to any number in the range of the maximum to minimum cross-sectional area ratio from 1 to 3, depending on which harmonics are optimized and other practical situations, such as a particular higher harmonic, as a range is an inexhaustible example, but the optimization method is applicable.
Hereinafter, the magnetic valve is exemplified as being capable of reaching a half-limit saturation at maximum when the area ratio is 2.
The optimized shape of the curved magnetic valve is the optimized shape chart of the curved magnetic valve when the area ratio of the curved magnetic valve is 2 in figure 4.
The invention is further described below in connection with simulation experiments.
After the method is optimized, the maximum value of the total harmonic distortion rate is about 0.84%, and the lower harmonic content can be kept in the whole range. Theoretical analysis can be further verified through Simulink simulation, and the simulation enables the magnetic valve to gradually reach half-limit saturation through gradually increasing direct current excitation so as to demonstrate the harmonic content condition in the whole working range: as shown in the simulation results of Simulink of fig. 3.
By utilizing the optimization method, a 22kVA/380V test prototype is designed, and the physical diagram is shown in figure 4 (the physical diagram of a test curve magnetic valve). The harmonic output conditions under different working current conditions are tested, the result is matched with the simulation result, the national harmonic standard is met, and the effectiveness of the invention is verified.
In the description of the present invention, "a plurality" means two or more unless otherwise specified; the terms "upper", "lower", "left", "right", "inner", "outer", "front", "rear", "head", "tail", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, should not be construed as limiting the invention. Furthermore, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
It should be noted that the embodiments of the present invention can be realized by hardware, software, or a combination of software and hardware. The hardware portion may be implemented using dedicated logic; the software portions may be stored in a memory and executed by a suitable instruction execution system, such as a microprocessor or specially designed hardware. Those skilled in the art will appreciate that the apparatus and methods described above may be implemented using computer executable instructions and/or embodied in processor control code, such code being provided on a carrier medium such as a disk, CD-or DVD-ROM, programmable memory such as read only memory (firmware), or a data carrier such as an optical or electronic signal carrier, for example. The apparatus and its modules of the present invention may be implemented by hardware circuits such as very large scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., or by software executed by various types of processors, or by a combination of hardware circuits and software, e.g., firmware.
The above description is only for the purpose of illustrating the present invention and the appended claims are not to be construed as limiting the scope of the invention, which is intended to cover all modifications, equivalents and improvements that are within the spirit and scope of the invention as defined by the appended claims.