Calculation Method for the Forced Excitation Capacity of the Stator Winding of a Superconducting Synchronous Condenser

Abstract

The present invention relates to a calculation method for the field-weakening capacity of the stator winding of a superconducting synchronous condenser. By inputting the parameters of the stator winding, the parameters of the stator cooling water, and the material property parameters of the stator and the stator cooling water, the stator winding loss under rated conditions, the heating power of the stator winding during field weakening, the stable outlet temperature of the water-cooled stator winding before field weakening, the final steady-state outlet temperature of the stator winding if the field-weakening current persists, the time constant of the temperature rise of the water-cooled stator winding during field weakening, and the allowable duration for reaching the allowable limit temperature rise of the winding under overcurrent during field weakening are calculated in sequence. This duration represents the field-weakening capacity of the stator winding of the superconducting synchronous condenser. By only inputting 10 parameters, the field-weakening capacity of the water-cooled stator winding of the superconducting synchronous condenser can be automatically calculated, which well meets the needs of the design of superconducting synchronous motor schemes and the calculation of stator field-weakening capacity. The method is convenient, rapid, and accurate, and has the characteristics of less input data, simple operation, fast calculation and plotting, and concise and intuitive calculation formulas.

Description

Technical Field

[0001] The present invention relates to a cooling technology, and particularly to a calculation method for the field-weakening capacity of the stator winding of a superconducting synchronous condenser. Background Art

[0002] The field-weakening requirement for the new generation of distributed superconducting synchronous condensers is relatively high. Calculating the field-weakening capacity of its water-cooled stator winding is an important link in the product design and development. The accuracy of the stator field-weakening capacity calculation not only affects the determination of the product design scheme, but also is closely related to the safety of the water-cooled synchronous condenser operating under extreme field-weakening conditions and at high altitudes.

[0003] In the past, when considering the field-weakening capacity of the water-cooled stator winding, a simple adiabatic process was generally considered, and the influence of the stator cooling water on the temperature of the stator winding during the field-weakening process was not fully considered. In order to scientifically, reasonably and accurately obtain the stator field-weakening capacity of the superconducting synchronous condenser, new ideas are needed. Summary of the Invention

[0004] Aiming at the problems existing in the calculation of the field-weakening capacity of the water-cooled stator winding in the design, a calculation method for the field-weakening capacity of the stator winding of a superconducting synchronous condenser is proposed, which comprehensively considers the influence of the stator cooling water and is a calculation method for the allowable duration under any k-fold field-weakening overcurrent of a superconducting synchronous condenser with convenient calculation.

[0005] The technical solution of the present invention is as follows: a calculation method for the field-weakening capacity of the stator winding of a superconducting synchronous condenser, inputting the parameters of the stator winding, the parameters of the stator cooling water, and the material property parameters of the stator and the stator cooling water. First, calculate the rated operating condition stator winding loss and the stator winding heating power during field-weakening according to the parameters of the stator winding; then, calculate the stable outlet temperature of the water-cooled stator winding before field-weakening and the final steady-state outlet temperature of the stator winding if the field-weakening current persists according to the calculation results, the parameters of the stator cooling water, and the material property parameters of the stator cooling water; then, calculate the time constant of the temperature rise of the water-cooled stator winding during the field-weakening process; finally, use the calculated time constant to calculate the allowable duration to reach the allowable limit temperature rise of the winding under the field-weakening overcurrent, and this duration represents the field-weakening capacity of the stator winding of the superconducting synchronous condenser.

[0006] Further, the parameters of the stator winding include the rated line current I of the stator winding N , the resistance R of each phase of the stator winding cuS , the number of phases m of the stator winding phS , the additional loss Q of the stator winding LcuS , the field-weakening multiple k of the stator winding, and the weight M of the stator copper wire cuS ; the parameters of the stator cooling water include the flow rate QL of the stator cooling water wS , and the temperature rise limit value θ of the water-cooled stator winding cuLim; The stator material property parameter is the specific heat capacity C of the stator copper wire cuS ; The stator cooling water material property parameter is the specific heat capacity C of the stator cooling water wS .

[0007] Furthermore, the basic copper loss Q of the stator winding under the rated condition cuS = m phs ·I N 2 ·R cuS ×10 -3 , I N Unit: A, R cuS Unit: Ω, Q cuS Unit: kW;

[0008] The rated condition stator winding loss Q cuSt = Q cuS + Q LcuS , including the basic copper loss and additional loss, unit: kW; The heating power Q of the stator winding under the k-fold forced excitation over-current condition of the stator cuSfo = k 2 ·Q cuSt , unit: kW.

[0009] Furthermore, the stable outlet temperature of the water-cooled stator winding before forced excitation is:

[0010] C wS Unit: J / kg / K, the stator cooling water flow rate QL ws Unit t / h, θ0, unit: K;

[0011] The final steady-state outlet temperature of the stator winding when the k-fold forced excitation current of the stator persists is:

[0012] Unit: K.

[0013] Furthermore, the time constant τ of the temperature rise of the water-cooled stator winding during forced excitation, unit: s; M cuS Unit: kg.

[0014] Furthermore, the allowable duration Δt for reaching the allowable limit temperature rise of the winding under forced excitation over-current fo = t lim - t0, the starting moment of stator forced excitation The moment when the stator reaches the allowable limit temperature rise under k-fold forced excitation over-current

[0015] Furthermore, the calculation method is implemented in the Windows operating system by using EXCEL language to compile an input parameter file and associate it with the editing formula.

[0016] The beneficial effects of the present invention are as follows: The method for calculating the excitation capability of the stator windings of a superconducting synchronous condenser, by inputting a calculation model and excitation parameters, achieves a quick calculation of the permissible duration of a superconducting synchronous condenser under any k-fold excitation overcurrent, taking into account the influence of stator cooling water, through a simple six-step process. Only 10 parameters are required to automatically calculate the stator excitation capability, effectively meeting the requirements for calculating the excitation capability of the water-cooled stator of a superconducting synchronous condenser, achieving the goal of convenient, rapid, and accurate determination of the water-cooled stator excitation capability. This method overcomes the shortcomings of the prior art and features minimal input data, simple operation, rapid calculation and plotting, and a concise and intuitive process. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flow chart of the method for calculating the strong excitation capability of the stator winding of the superconducting phase shifter of the present invention. DETAILED DESCRIPTION

[0018] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0019] like Figure 1 The flow chart of the calculation method of the stator winding excitation capability of the superconducting phase regulator is shown. The calculation method includes the following steps:

[0020] Step 1: Input the parameters of the calculation model and the physical properties required to complete the calculation:

[0021] The parameters for constructing the calculation model include: stator winding rated line current I N (Unit: A), stator winding resistance per phase R cuS (Unit: Ω), number of stator winding phases m phS , additional loss of stator winding Q LcuS (Unit: kW), stator winding excitation multiple k, stator cooling water flow QL wS (Unit: t / h), stator copper wire weight M cuS (Unit: kg), water-cooled stator winding temperature rise limit θ cuLim (Unit: K);

[0022] The material property parameters required to complete the calculation include: stator cooling water specific heat C wS (Unit: J / kg / K), stator copper wire specific heat C cuS(Unit: J / kg / K);

[0023] Step 2: Calculate the winding heating power under k times the field-forced overcurrent of the stator: Use the calculation formula to calculate the rated copper loss Q of the stator winding in sequence cuS of the stator winding, the rated total loss Q cuSt of the stator winding, and the winding heating power Q cuSfo under k times the field-forced overcurrent of the stator. The calculation formula is:

[0024] Q cuS = m phs ·I N 2 ·R cuS ×10 -3

[0025] Q cuSt = Q cuS + Q LcuS

[0026] Q cuSfo = k 2 ·Q cuSt

[0027] In the formula:

[0028] Q cuS is the basic copper loss of the stator winding under rated conditions, unit: kW; the function of "×10 -3 " in its calculation formula is to convert the loss value in "W" to the loss value in "kW";

[0029] Q cuSt is the total loss of the stator winding including the basic copper loss and additional loss under rated conditions, unit: kW; when the stator winding is energized with alternating current, there is a copper wire loss, which is the total loss Q cuSt . The joule heat loss of copper generated by passing direct current with the same effective value is called the basic copper loss, that is, Q cuS . Passing alternating current will cause the skin effect of the current, resulting in less current-carrying area compared to direct current. Therefore, the alternating current has a greater loss than the direct current, and the extra part is the additional loss brought by the skin effect, called the copper wire additional loss Q LcuS ;

[0030] Q cuSfo is the winding heating power of the stator winding under the condition of k times the field-forced overcurrent of the stator, unit: kW.

[0031] Step 3: Calculate the steady-state temperature rise of the outlet water of the stator winding before field forcing. The calculation formula is:

[0032]

[0033] Where: θ0 is the steady-state temperature rise of the outlet water of the winding under the rated condition before the stator's forced excitation, unit: K; the reason for the existence of "×3600" in its calculation formula is the water flow rate QL ws Taking "t / h" as the unit, when converting the time unit "h" to the unit "s", it is necessary to multiply by the coefficient 3600.

[0034] Step 4: Calculate the steady-state temperature rise of the outlet water of the winding when reaching a new thermal equilibrium under the stator's k-fold forced excitation overcurrent, and the calculation formula is

[0035]

[0036] Where: θ ∞ is the steady-state temperature rise of the outlet water of the winding when reaching a new thermal equilibrium under the stator's k-fold forced excitation overcurrent, unit: K; the reason for the existence of "×3600" in its calculation formula is the water flow rate QL ws Taking "t / h" as the unit, when converting the time unit "h" to the unit "s", it is necessary to multiply by the coefficient 3600.

[0037] Step 5: Calculate the time constant of the stator winding temperature rise, and the calculation formula is

[0038]

[0039] Where: τ is the time constant of the stator winding temperature rise under the stator's k-fold forced excitation overcurrent, unit: s; the role of "×10 -3 " is to convert the loss value in the denominator with the unit of "kW" to the loss value with the unit of "W".

[0040] Step 6: Calculate the allowable duration for reaching the allowable limit temperature rise of the winding under the stator's k-fold forced excitation overcurrent, and the calculation formula is:

[0041]

[0042]

[0043] Δt fo = t lim - t0

[0044] Where: t0 is the moment when the stator's forced excitation starts, unit: s; t lim is the moment when reaching the allowable limit temperature rise of the winding under the stator's k-fold forced excitation overcurrent, unit: s; △t fo is the allowable duration for reaching the allowable limit temperature rise of the winding under the stator's k-fold forced excitation overcurrent, unit: s.

[0045] If multiple different k values are set and loop operation statements from Step 2 to Step 6 are added, the calculation of the forced excitation ability of the stator winding under multiple forced excitation overcurrent values can be performed.

[0046] The new algorithm provided by the present invention can be completed by manual calculation (the patent calculation results can be obtained according to the formula in the patent method using a scientific calculator). In order to more intuitively reflect the calculation idea proposed by the present invention, EXCEL in the OFFICE office software is selected as the input and output interface for the case, and the calculation of the present invention can be realized by using the function of EXCEL.

[0047] As shown in Table 1, in this embodiment, under the windows operating system, an EXCEL file named SCSFO (Super-Conductive condensor Stator winding Force Over-current calculation method) for automatically calculating the stator forced excitation capacity of a superconducting synchronous condenser is compiled using the EXCEL language. This program is a common document of the table tool EXCEL under the windows operating system.

[0048] Table 1

[0049]

[0050]

[0051] Taking the forced excitation calculation of the water-cooled stator winding of a 10 Mvar superconducting synchronous condenser as an example, its stator forced excitation capacity is calculated, and the specific operation process is as follows:

[0052] Step 1: Open EXCEL. As shown in Table 1, below the cell of "1a. Parameters for constructing the calculation model", input the model data in sequence, including the rated line current I of the stator winding N = 525 A, the resistance R per phase of the stator winding cuS = 0.0883 Ω, the number of phases m of the stator winding phS = 3, the additional loss Q of the stator winding LcuS = 26.8 kW, the forced excitation multiple k of the stator winding, the cooling water flow rate QL of the stator wS = 3.5 t / h, the weight M of the stator copper wire cuS = 490 kg, the temperature rise limit θ of the water-cooled stator winding cuLim = 50 K; as shown in Table 1, below the cell of "1b. Material property parameters required for the calculation", input the physical property data in sequence, including the specific heat C of the stator cooling water wS = 4200 J / kg / K, the specific heat C of the stator copper wire cuS = 390 J / kg / K.

[0053] Step 2: According to the calculation formula content in Steps 2 to 6 of the aforementioned calculation method in EXCEL, a calculation formula is compiled based on the application of simple EXCEL functions to automatically generate Q cuS , Q cuSt , Q cuSfo , θ0, θ ∞ , τ, t0, t lim , △t fo The calculation results are shown in Table 2 below:

[0054] Table 2

[0055]

[0056] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A calculation method for the forced excitation ability of the stator winding of a superconducting synchronous condenser, characterized in that, Input the parameters of the stator winding, the parameters of the stator cooling water, and the material property parameters of the stator and the stator cooling water. First, calculate the rated condition stator winding loss and the stator winding heating power during forced excitation according to the parameters of the stator winding. Then, calculate the stable outlet temperature of the water-cooled stator winding before forced excitation and the final steady-state outlet temperature of the stator winding if the forced excitation current persists, based on the calculation results, the parameters of the stator cooling water, and the material property parameters of the stator cooling water. After that, calculate the time constant of the temperature rise of the water-cooled stator winding during forced excitation. Finally, use the calculated time constant to calculate the allowable duration to reach the allowable limit temperature rise of the winding under forced overcurrent. This duration represents the forced excitation capacity of the stator winding of the superconducting synchronous condenser. The parameters of the stator winding include the rated line current I of the stator winding N , the resistance R per phase of the stator winding cuS , the number of phases m of the stator winding phS , the additional loss Q of the stator winding LcuS , the excitation boost multiple k of the stator winding, and the weight M of the stator copper wire cuS ; the parameters of the stator cooling water include the flow rate QL of the stator cooling water wS , the temperature rise limit θ of the water-cooled stator winding cuLim ; the parameter of the stator material property is the specific heat C of the stator copper wire cuS ; the parameter of the stator cooling water material property is the specific heat C of the stator cooling water wS ; The basic copper loss Q of the stator winding under the rated condition cuS = m phs ·I N 2 ·R cuS × 10 -3 , I N Unit: A, R cuS Unit: Ω, Q cuS Unit: kW; Rated operating condition stator winding loss Q cuSt = Q cuS + Q LcuS , including basic copper loss and additional loss, unit: kW; The heating power Q of the stator winding under the k-fold forced excitation overcurrent condition of the stator cuSfo = k 2 ·Q cuSt , unit: kW; The stable outlet water temperature of the water-cooled stator winding before forced excitation is: C wS Unit: J / kg / K, stator cooling water flow rate QL ws Unit: t / h, θ0, unit: K; If the k-fold field-weakening current of the stator persists, the final steady-state water outlet temperature of the stator winding is: Unit: K; The time constant of the temperature rise of the water-cooled stator winding during the strong excitation process τ Unit: s; M cuS Unit: kg; The duration Δt allowed for reaching the allowable limit temperature rise of the winding under the strong excitation overcurrent fo = t lim - t0, the moment when the stator strong excitation starts The moment when the stator reaches the allowable limit temperature rise of the winding under k times the strong excitation overcurrent 2. The calculation method for the forced excitation ability of the stator winding of a superconducting synchronous condenser according to claim 1, wherein The calculation method is implemented by using EXCEL language to compile the input parameter file and associate it with the editing formula under the windows operating system.

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