Junction temperature monitoring method and system for thyristor of static frequency converter

Abstract

The invention discloses a static frequency converter thyristor junction temperature monitoring method and system, and the method comprises the steps: comparing a thyristor loss measured value with a thyristor loss estimated value, and outputting a calculated junction temperature value as an effective junction temperature value when a difference value between the thyristor loss measured value and the thyristor loss estimated value is lower than a threshold value. According to the method, the temperature rise of the thyristor shell is calculated through the thyristor shell temperature rise coefficient model and the radiator thermal resistance model which are established offline, and the junction temperature of the thyristor is calculated by combining the actually measured environment temperature and the thyristor thermal resistance model; and meanwhile, an off-line established thyristor shell temperature rise-loss model is introduced, the corresponding actually measured thyristor loss is obtained through the calculated shell temperature rise, and when the real-time calculated loss and the actually measured loss value are smaller than a certain threshold value, the junction temperature is calculated as effective output, so that the calculation accuracy is improved.

Description

Technical Field

[0001] The invention belongs to the field of online monitoring of electric power equipment, and in particular relates to a method and system for monitoring junction temperature of a thyristor of a static frequency converter. Background Art

[0002] Static Frequency Converter is mainly used for starting large synchronous motors, especially in the field of pumped storage, for starting pumps in pumped storage units.

[0003] Static frequency converters are used to start pumped storage power station units, dragging the units from a stationary state to a synchronous speed, and exiting operation after being connected to the grid. A single start-up runs for about 5 minutes, and multiple units can be started continuously. It is a short-time working system, and the temperature rise of the thyristor is approximately linear, and usually does not reach thermal stability. With the continuous increase in the capacity of pumped storage units, the capacity of the single unit in operation has reached 400MW, and the capacity of the static frequency converter has also reached nearly 30MW, which is accompanied by larger thyristor losses and temperature rises.

[0004] Static frequency converters are medium voltage products, with an operating voltage of 10kV or even higher, and require a high insulation level for the measuring components. In addition, for air-cooled SFCs, the wind speed in the closed air duct is high, the number of components to be measured is large, and the installation and fixation of the measuring components is difficult. In summary, based on the current temperature measurement methods, it is not suitable to install external measuring components on engineering products, and the temperature measurement of thyristors in static frequency converters has always been a difficult problem in the industry. Summary of the invention

[0005] The purpose of the present invention is to provide a method and system for monitoring junction temperature of thyristors of a static frequency converter, which can obtain effective junction temperature data and improve calculation accuracy.

[0006] In order to achieve the above object, the solution of the present invention is:

[0007] A method for monitoring the junction temperature of a thyristor in a static frequency converter compares a measured thyristor loss value with an estimated thyristor loss value. When the difference between the measured thyristor loss value and the estimated thyristor loss value is lower than a threshold, the calculated junction temperature value is output as an effective junction temperature value.

[0008] The above measured values ​​of thyristor losses are obtained based on the following thyristor case temperature rise-loss model;

[0009] The steps for constructing the thyristor housing temperature rise-loss model are:

[0010] Step a1, setting the thyristor loss to P31, making the static inverter start running from the stopped state, the thyristor shell temperature starts to rise from the ambient temperature when the thyristor is in the stopped state, until the thyristor temperature rise is stable, and recording the steady-state value F1;

[0011] Step a2, for i=2, 3, ..., n, respectively perform the following operations: set the thyristor loss to P3i=P31+(i-1)*ΔP3, make the static inverter start running from the stopped state, and the thyristor case temperature starts to rise from the ambient temperature when the thyristor is in the stopped state until the thyristor temperature rise is stable, and record the steady-state value Fi;

[0012] Step a3, drawing a curve based on all measuring points (Fj, P3j), j = 1, 2, ..., n, and obtaining a thyristor case temperature rise-thyristor loss model;

[0013] The thyristor loss measured value is obtained according to the following thyristor case temperature rise-loss model, including, according to the current temperature rise measured value, determining the loss measured value corresponding to the temperature rise measured value by the thyristor case temperature rise-thyristor loss model.

[0014] The above thyristor loss estimates are calculated as follows:

[0015] Step b1, calculate the thyristor conduction loss P AV :

[0016]

[0017] Where V T0 is the thyristor threshold voltage, which can be obtained by consulting the thyristor manual according to the thyristor model; I TAV is the average on-state current flowing through the thyristor, f is the operating frequency of the thyristor, r T is the on-state resistance of the thyristor;

[0018] Step b2, calculate the thyristor turn-off loss P OFF :

[0019] Among them, the thyristor withstands the turn-off voltage V Thy :

[0020] Thyristor commutation circuit current change rate:

[0021] Among them, V Line is the line voltage, α is the conduction angle of the thyristor, and L is the inductance of each phase;

[0022] According to V Thy and Check the turn-off loss curve in the device manual to get P OFF ;

[0023] Step b3, calculate the estimated thyristor loss value P according to the following formula: CAL :

[0024] P CAL =P AV +P OFF .

[0025] The above outputs the calculated junction temperature value as the effective junction temperature value, including obtaining the calculated junction temperature according to the following formula:

[0026] T C =T0+K R-C +K C-J

[0027] Among them, T C To calculate the junction temperature, T0 is the ambient temperature, K R-C is the temperature rise of the thyristor housing, K C-J The temperature rise of crust.

[0028] The above crust temperature rise K C-J Estimated value P by thyristor loss CAL Obtained by multiplying the heat sink-case-junction thermal resistance.

[0029] The above thyristor shell temperature rise K R-C The calculation method is:

[0030] First, compare the real-time change of the estimated value of the static inverter thyristor loss ΔP = P CAL(N) -P CAL(N-1) The relationship between P and 0, CAL(N) is the estimated value of thyristor loss at the current moment N, P CAL(N-1) is the estimated value of thyristor loss at the previous moment N-1;

[0031] When the change ΔP>0, the shell temperature rise calculation formula is as follows:

[0032] K R-C =K C0 +R·t

[0033] Where R is the temperature rise coefficient, K C0 is the initial junction temperature, t is the update time of the junction temperature;

[0034] When the change ΔP<0, the shell temperature rise calculation formula is as follows:

[0035] K R-C =K C0 -D·t

[0036] Where D is the temperature reduction coefficient.

[0037] The above temperature rise coefficient R is determined according to the following steps:

[0038] Step c1, setting the thyristor loss to P11, controlling the static frequency converter to start running from a stopped state for a specific time T1, during which the temperature of the thyristor shell of the static frequency converter starts to rise from the ambient temperature when the static frequency converter is in the stopped state, and recording the temperature rise curve at the specific time T1, wherein the slope R1 of the temperature rise curve is the temperature rise coefficient;

[0039] Step c2, for h=2, 3, ..., m, respectively perform the following operations: set the thyristor loss to P1h=P11+(h-1)*ΔP1, control the static inverter to start running from a stopped state for a specific time T1, during which the thyristor housing temperature of the static inverter starts to rise from the ambient temperature when the inverter is in the stopped state, and record the temperature rise curve at the specific time T1, where the slope Rh of the temperature rise curve is the temperature rise coefficient;

[0040] Step c3, respectively recording the curves with corresponding slopes from R1 to Rm, wherein the slopes from R1 to Rm are the temperature rise coefficients.

[0041] The above temperature reduction coefficient D is determined according to the following steps:

[0042] Step d1, setting the thyristor loss to P21, controlling the static frequency converter to start from the rated operation state, and operate at a specific time T2 below the rated power, and recording the cooling curve of the specific time T2, wherein the slope D1 of the cooling curve is the cooling coefficient;

[0043] Step d2, for k=2, 3, ..., u, respectively perform the following operations: set the thyristor loss to P1k=P11+(k-1)*ΔP2, control the static inverter to start running for a specific time T2 from a stopped state, record the cooling curve of the specific time T2, and the slope Dk of the cooling curve is the cooling coefficient;

[0044] Step d3, respectively record the curves with corresponding slopes D1 to Du, wherein the slopes D1 to Du are the temperature reduction coefficients.

[0045] A thyristor junction temperature monitoring system for a static frequency converter, comprising:

[0046] A difference calculation module is used to calculate the difference between the measured value of thyristor loss and the estimated value of thyristor loss;

[0047] A comparison module, used for comparing the difference between the actual measured value of the thyristor loss and the estimated value of the thyristor loss with a threshold value to obtain a comparison result;

[0048] The junction temperature calculation module is used to calculate the junction temperature, and

[0049] The junction temperature output module is used to output the calculated junction temperature value obtained by the junction temperature calculation module as an effective junction temperature value when the difference between the actual thyristor loss value and the estimated thyristor loss value is lower than a threshold value.

[0050] After adopting the above scheme, the present invention calculates the thyristor shell temperature rise through the offline thyristor shell temperature rise coefficient model and the heat sink thermal resistance model, and calculates the thyristor junction temperature in combination with the measured ambient temperature and the thyristor thermal resistance model; at the same time, the offline thyristor shell temperature rise-loss model is introduced, and the corresponding measured thyristor loss is obtained through the calculated shell temperature rise. When the real-time calculated loss and the measured loss value are less than a certain threshold value, the calculated junction temperature is used as an effective output to improve the calculation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is the monitoring principle diagram of the present invention;

[0052] Figure 2 It is an off-line test shell temperature rise-loss model;

[0053] Figure 3 It is an offline test temperature rise coefficient model;

[0054] Figure 4 This is a schematic diagram of the loss and temperature coefficient curve of a typical static inverter during operation. DETAILED DESCRIPTION

[0055] The technical solutions and beneficial effects of the present invention will be described in detail below with reference to the accompanying drawings.

[0056] In view of the difficulty of measuring the temperature of thyristors in static frequency converters, the present invention provides a temperature monitoring method combining offline measurement with online estimation. The temperature rise coefficient model of the thyristor shell of the static frequency converter is established offline, including the temperature rise coefficient model and the temperature drop coefficient model under the proportional thyristor loss power; then the temperature coefficient and the shell temperature rise calculation formula are selected according to the change in the loss to calculate the shell temperature rise. In order to ensure the accuracy of the calculated value, the shell temperature rise-loss model of the thyristor shell of the static frequency converter is established offline. Under the same shell temperature rise, when the measured loss of the thyristor and the calculated loss are less than a certain value, the calculated junction temperature is considered to be valid. Since the shell temperature rise in the shell temperature rise-loss model is a value under thermal equilibrium, and the power loss of the static frequency converter changes in real time during the actual operation process and is a short-time working system, the shell temperature of the thyristor will not reach thermal equilibrium. It can be accurately monitored by the shell temperature rise calculation model introduced in the present invention, and its value is usually near the offline measured value. The thyristor junction temperature can be calculated by the shell temperature rise. When the difference between the online estimated loss value and the offline measured loss value is within a certain range, the calculated junction temperature can be output as the effective junction temperature.

[0057] like Figure 1 As shown, the present invention provides a method for monitoring junction temperature of a thyristor of a static frequency converter, comprising the following steps:

[0058] Step A, obtaining the measured value of thyristor loss; comprising the following steps:

[0059] Step 1: Establish the temperature rise-loss model of the thyristor housing of the static inverter offline. The specific steps are:

[0060] Step 11, the initial test condition is that the static inverter is in a stopped state and the thyristor housing temperature is the ambient temperature;

[0061] Step 12, start the static frequency converter to start running, set the thyristor loss to P31, until the thyristor temperature rise is stable, record the steady-state value F1, and use the value (F1, P31) as a measurement point;

[0062] Step 13, start the static inverter from the initial stop state, then change the thyristor loss, set the thyristor loss to increase proportionally from P31 to P3n, record the corresponding steady-state values ​​F1 to Fn, and draw curves from P31 to P3n corresponding to F1 to Fn respectively, that is, draw curves based on all measuring points (Fi, P3i) (i = 1, 2, ..., n), and you can get Figure 2 The thyristor case temperature rise-thyristor loss model shown;

[0063] According to the thyristor shell temperature rise-thyristor loss model, the corresponding measuring point of the temperature rise can be found in the curve based on the current measured temperature rise, so as to determine the current measured loss value;

[0064] Step B, obtaining an estimated value of thyristor loss; comprising the following steps:

[0065] Step 2, when the static frequency converter is running, collect the voltage and current analog quantities flowing through the thyristor in real time, and obtain the estimated value of the thyristor loss through the thyristor loss model; specifically, the steps include:

[0066] Step 21, calculate the thyristor conduction loss P AV :

[0067]

[0068] Where V T0 is the thyristor threshold voltage, which can be obtained by consulting the thyristor manual according to the thyristor model; I TAV is the average on-state current flowing through the thyristor, which can be calculated based on the current analog quantity collected in real time; f is the operating frequency of the thyristor, r T is the on-state resistance of the thyristor;

[0069] Step 22, calculate the thyristor turn-off loss P OFF :

[0070] Among them, the thyristor withstands the turn-off voltage VThy :

[0071] Thyristor commutation circuit current change rate:

[0072] Among them, V Line is the voltage analog quantity (line voltage) collected in real time, α is the conduction angle of the thyristor, and L is the inductance of each phase;

[0073] According to V Thy and Check the turn-off loss curve in the device manual to obtain P OFF ;

[0074] Step 23, based on the above, the estimated thyristor loss value P can be calculated CAL :

[0075] P CAL =P AV +P OFF

[0076] Step C, to ensure the validity of the calculated junction temperature, the estimated value of the thyristor loss is compared with the measured value. When the difference between the estimated value of the thyristor loss and the measured value is within the threshold, the calculated junction temperature of the thyristor is obtained and output as the effective junction temperature value; comprising the following steps:

[0077] Step 3, offline establishing a temperature rise coefficient model of the thyristor shell of the static frequency converter, the shell temperature rise coefficient model includes a temperature rise coefficient model and a temperature drop coefficient model under different thyristor loss powers; since the static frequency converter is a strong air cooling system, when the thyristor loss changes, the temperature rise coefficient model and the temperature drop coefficient model curves are fixed slope linear curves in a short time;

[0078] Wherein, the method for establishing the temperature rise coefficient model is:

[0079] Step 311, the initial test condition is that the static inverter is in a stopped state and the thyristor housing temperature is equal to the ambient temperature;

[0080] Step 312, start the static frequency converter to start running, set the thyristor loss to P11, stop running the static frequency converter after running for a specific time, record the temperature rise curve of the specific time period, the slope R1 of the temperature rise curve is the temperature rise coefficient; the specific time can be set to 5 minutes;

[0081] Step 313, repeat the above steps, the thyristor loss increases step by step from P11 to P1n in proportion to ΔP1, and the corresponding curves with slopes R1 to Rn are recorded respectively, where the slopes R1 to Rn are the temperature rise coefficients, and the following can be obtained: Figure 3 (a) shows the temperature rise coefficient model of the thyristor.

[0082] The method for establishing the temperature drop coefficient model is:

[0083] Step 321, setting the initial condition that the static inverter is running in the rated operating state, at which time the thyristor loss is the rated value and the thyristor shell temperature rise is the design value;

[0084] Step 322, changing the output power of the static inverter to make it work below the rated power, setting the thyristor loss to P21, running for a specific time, and recording the cooling curve, the slope D1 of the cooling curve is the cooling coefficient; the specific time can be set to 5 minutes;

[0085] Step 323, restore the static inverter to the initial rated operating state, then change its output power to below the rated power, set the thyristor loss to increase step by step from P21 to P2n in proportion to ΔP2, and record the corresponding curves with slopes D1 to Dn according to the above method, where the slopes D1 to Dn are the temperature reduction coefficients, and the following can be obtained: Figure 3 (b) Thyristor temperature reduction coefficient model shown.

[0086] Step 4: According to the estimated value of the thyristor loss of the static inverter, the real-time change ΔP=P CAL(N) -P CAL(N-1) Select the shell temperature rise coefficient and shell temperature rise calculation model, where P CAL(N) is the estimated value of thyristor loss at the current moment N, P CAL(N-1) is the estimated value of thyristor loss at the previous moment N-1;

[0087] When the thyristor loss ΔP>0, according to P cAL(N) Determine the temperature rise coefficient R of the corresponding curve, and the shell temperature rise calculation formula is as follows:

[0088] K R-C =K C0 +R·t

[0089] Among them, t is the update time of the junction temperature, that is, within the junction temperature calculation step T, the latest junction temperature result is updated every time t.

[0090] When the thyristor loss ΔP<0, according to P CAL(N) Determine the temperature drop coefficient D of the corresponding curve, and the shell temperature rise calculation formula is as follows:

[0091] K R-C =K C0 -D·t

[0092] In the formula, K C0 is the initial junction temperature, K R-C To calculate the shell temperature rise in real time;

[0093] Step 5: The temperature rise of the thyristor shell K R-C 、Crust temperature rise K C-J And the ambient temperature T0 can be used to obtain the calculated junction temperature;

[0094] Thyristor calculated junction temperature: T C =T0+K R-C +K C-J

[0095] In the formula, K C-J Through the thyristor loss P CAL Obtained by multiplying the heat sink-case-junction thermal resistance.

[0096] The typical static inverter working process loss and temperature coefficient curve diagram can be referred to Figure 4 .

[0097] The embodiment of the present invention further provides a static inverter thyristor junction temperature monitoring system, comprising:

[0098] A difference calculation module is used to calculate the difference between the measured value of thyristor loss and the estimated value of thyristor loss;

[0099] A comparison module, used for comparing the difference between the actual measured value of the thyristor loss and the estimated value of the thyristor loss with a threshold value to obtain a comparison result;

[0100] The junction temperature calculation module is used to calculate the junction temperature, and

[0101] The junction temperature output module is used to output the calculated junction temperature value obtained by the junction temperature calculation module as an effective junction temperature value when the difference between the actual thyristor loss value and the estimated thyristor loss value is lower than a threshold value.

[0102] Each module in the monitoring system can implement the contents of each step in the aforementioned monitoring method.

[0103] The above embodiments are only for illustrating the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for monitoring junction temperature of a thyristor of a static frequency converter, characterized in that: The measured thyristor loss value is compared with the estimated thyristor loss value, and when the difference between the measured thyristor loss value and the estimated thyristor loss value is lower than a threshold value, the calculated junction temperature value is output as an effective junction temperature value.

2. The method for monitoring junction temperature of thyristor of static frequency converter according to claim 1, characterized in that: The measured value of thyristor loss is obtained according to the following thyristor shell temperature rise-loss model; The steps for constructing the thyristor housing temperature rise-loss model are: Step a1, setting the thyristor loss to P31, making the static inverter start running from the stopped state, the thyristor shell temperature starts to rise from the ambient temperature when the thyristor is in the stopped state, until the thyristor temperature rise is stable, and recording the steady-state value F1; Step a2, for i=2, 3, ..., n, respectively perform the following operations: set the thyristor loss to P3i=P31+(i-1)*ΔP3, make the static inverter start running from the stopped state, and the thyristor case temperature starts to rise from the ambient temperature when the thyristor is in the stopped state until the thyristor temperature rise is stable, and record the steady-state value Fi; Step a3, drawing a curve based on all measuring points (Fj, P3j), j = 1, 2, ..., n, and obtaining a thyristor case temperature rise-thyristor loss model; The thyristor loss measured value is obtained according to the following thyristor case temperature rise-loss model, including, according to the current temperature rise measured value, determining the loss measured value corresponding to the temperature rise measured value by the thyristor case temperature rise-thyristor loss model.

3. The method for monitoring junction temperature of thyristor of static frequency converter according to claim 1, characterized in that: The thyristor loss estimate is calculated by the following steps: Step b1, calculate the thyristor conduction loss P AV : Where V T0 is the thyristor threshold voltage, which can be obtained by consulting the thyristor manual according to the thyristor model; I TAV is the average on-state current flowing through the thyristor, f is the operating frequency of the thyristor, r T is the on-state resistance of the thyristor; Step b2, calculate the thyristor turn-off loss P OFF : Among them, the thyristor withstands the turn-off voltage V Thy : Thyristor commutation circuit current change rate: Among them, V Line is the line voltage, α is the conduction angle of the thyristor, and L is the inductance of each phase; According to V Thy and Check the turn-off loss curve in the device manual to get P OFF ; Step b3, calculate the estimated thyristor loss value P according to the following formula: CAL : P CAL =P AV +P OFF 。 4. The method for monitoring junction temperature of thyristor of static frequency converter according to claim 1, characterized in that: Outputting the calculated junction temperature value as the effective junction temperature value includes obtaining the calculated junction temperature according to the following formula: T C =T0+K R-C +K C-J Among them, T C To calculate the junction temperature, T0 is the ambient temperature, K R-C is the temperature rise of the thyristor housing, K C-J The temperature rise of crust.

5. The method for monitoring junction temperature of thyristor of static frequency converter according to claim 4, characterized in that: The crust temperature rise K C-J Estimated value P by thyristor loss CAL Obtained by multiplying the heat sink-case-junction thermal resistance.

6. The method for monitoring junction temperature of thyristor of static frequency converter according to claim 4, characterized in that: The thyristor housing temperature rise K R-C The calculation method is: First, compare the real-time change of the estimated value of the static inverter thyristor loss ΔP = P CAL(N) -P CAL(N-1) The relationship between P and 0, CAL(N) is the estimated value of thyristor loss at the current moment N, P CAL(N-1) is the estimated value of thyristor loss at the previous moment N-1; When the change ΔP>0, the shell temperature rise calculation formula is as follows: K R-C =K C0 +R·t Where R is the temperature rise coefficient, K C0 is the initial junction temperature, t is the update time of the junction temperature; When the change ΔP<0, the shell temperature rise calculation formula is as follows: K R-C =K C0 -D·t Where D is the temperature reduction coefficient.

7. The method for monitoring junction temperature of thyristor of static frequency converter according to claim 6, characterized in that: The temperature rise coefficient R is determined according to the following steps: Step c1, setting the thyristor loss to P11, controlling the static frequency converter to start running from a stopped state for a specific time T1, during which the temperature of the thyristor shell of the static frequency converter starts to rise from the ambient temperature when the static frequency converter is in the stopped state, and recording the temperature rise curve at the specific time T1, wherein the slope R1 of the temperature rise curve is the temperature rise coefficient; Step c2, for h=2, 3, ..., m, respectively perform the following operations: set the thyristor loss to P1h=P11+(h-1)*ΔP1, control the static inverter to start running from a stopped state for a specific time T1, during which the thyristor housing temperature of the static inverter starts to rise from the ambient temperature when the inverter is in the stopped state, and record the temperature rise curve at the specific time T1, where the slope Rh of the temperature rise curve is the temperature rise coefficient; Step c3, respectively recording the curves with corresponding slopes from R1 to Rm, wherein the slopes from R1 to Rm are the temperature rise coefficients.

8. The method for monitoring junction temperature of thyristor of static frequency converter according to claim 6, characterized in that: The temperature drop coefficient D is determined according to the following steps: Step d1, setting the thyristor loss to P21, controlling the static frequency converter to start from the rated operation state, and operate at a specific time T2 below the rated power, and recording the cooling curve of the specific time T2, wherein the slope D1 of the cooling curve is the cooling coefficient; Step d2, for k=2, 3, ..., u, respectively perform the following operations: set the thyristor loss to P1k=P11+(k-1)*ΔP2, control the static inverter to start running for a specific time T2 from a stopped state, record the cooling curve of the specific time T2, and the slope Dk of the cooling curve is the cooling coefficient; Step d3, respectively record the curves with corresponding slopes D1 to Du, wherein the slopes D1 to Du are the temperature reduction coefficients.

9. A static inverter thyristor junction temperature monitoring system, characterized in that: include, A difference calculation module is used to calculate the difference between the measured value of thyristor loss and the estimated value of thyristor loss; A comparison module, used for comparing the difference between the actual measured value of the thyristor loss and the estimated value of the thyristor loss with a threshold value to obtain a comparison result; The junction temperature calculation module is used to calculate the junction temperature, and The junction temperature output module is used to output the calculated junction temperature value obtained by the junction temperature calculation module as an effective junction temperature value when the difference between the actual thyristor loss value and the estimated thyristor loss value is lower than a threshold value.

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