On-line monitoring device and method for thermal state of flexible DC converter valve based on heat transfer model

Abstract

The invention discloses an online monitoring device and method for the thermal state of a flexible direct current converter valve based on a heat transfer model, and relates to the field of power equipment monitoring. At present, the monitoring cost of the flexible direct current converter valve is high, and it is not possible to monitor it online in real time. The invention comprises a water-cooled radiator, a temperature sensor, a flow sensor, a signal transmission device and a host computer, wherein the temperature sensor comprises a first temperature sensor Tin arranged at the water inlet of the water-cooled radiator, a second temperature sensor Tout arranged at the water outlet of the water-cooled radiator, a third temperature sensor Tair for detecting the external ambient temperature, a fourth temperature sensor Ts1, a fifth temperature sensor Ts2, a sixth temperature sensor Ts3, a seventh temperature sensor Ts4 arranged around the bottom substrate of the IGBT device, and an eighth temperature sensor Tsink arranged on the side of the water-cooled radiator. The technical solution does not require an insulation box, and directly monitors the thermal state of the converter valve online in real time by collecting temperature and flow information, discovers problems in time, and improves the working reliability of the flexible direct current converter valve.

Description

Technical Field

[0001] The present invention relates to the field of power equipment monitoring, and in particular to a device and method for online monitoring the thermal state of a flexible direct current converter valve based on a heat transfer model. Background Art

[0002] With the improvement of power electronic devices, my country's high-voltage direct current transmission technology has developed rapidly. The flexible direct current transmission technology based on voltage source converter (VSC) and modular multilevel converter (MMC) has the advantages of not prone to commutation failure, independent control of active and reactive power, easy power flow reversal, reactive power support for AC power grid, and power supply for passive systems. It stands out in direct current transmission technology. A series of direct current demonstration projects have been built and put into operation. The operation and maintenance problems brought about by them will gradually become the focus of attention of operation and maintenance units.

[0003] The flexible DC transmission system uses fully controlled insulated gate bipolar transistor (IGBT) voltage source converter as the converter equipment of the converter station. As the core equipment of the converter station, the converter valve is expensive and important. Once a failure occurs, it will not only cause the DC to stop operating, but in severe cases, it will cause the converter valve and valve hall to catch fire, causing huge economic losses.

[0004] The loss and junction temperature of the converter valve IGBT module are important evaluation indicators of its reliability. There are three main methods for measuring the loss of the converter valve IGBT module: double pulse method, electrical measurement method and calorimetry method. The first two methods can measure the loss of the converter valve IGBT module in the laboratory, but cannot be actually applied to field measurement, and their measurement accuracy is lower than that of the calorimetry method. Existing research [CN110412369A-A flexible DC converter valve power module loss measurement system] uses calorimetry for a small-scale test platform for power modules. However, this calorimetry method often places the test piece in an insulated box, and uses directional air flow to take away the heat on the test piece. The loss can be obtained by measuring the temperature difference between the air inlet and the air outlet. However, when the radiator is not equipped with an insulated box and relies on the radiator surface to directly dissipate heat to the outside, it is difficult to accurately measure the heat radiation to the outside in all directions. It is only suitable for experimental environments. During testing, it needs to be placed in a laboratory and an insulated box needs to be set up outside. It cannot be applied to online measurements at the flexible DC converter valve hall. At present, the current technology has high monitoring costs for flexible DC converter valves, and online real-time monitoring is not possible, so the working reliability of the flexible DC converter valve cannot be effectively guaranteed. Summary of the invention

[0005] The technical problem to be solved and the technical task proposed by the present invention are to improve and perfect the existing technical solutions, and provide an online monitoring device and method for the thermal state of a flexible direct current converter valve based on a heat transfer model, so as to achieve the purpose of accurately measuring the thermal state of the flexible direct current converter valve. To this end, the present invention adopts the following technical solutions.

[0006] A device for online monitoring the thermal state of a flexible direct current converter valve based on a heat transfer model comprises a water-cooled radiator, a temperature sensor, a flow sensor, a signal transmission device and a host computer. The flexible direct current converter valve to be measured is arranged in the water-cooled radiator. The water-cooled radiator is provided with a plurality of temperature sensors. The flow sensor comprises a flow sensor Vin arranged at the water inlet of the water-cooled radiator. The temperature sensor and the flow sensor are connected to the host computer through the signal transmission device. The temperature sensor comprises a first temperature sensor Tin arranged at the water inlet of the water-cooled radiator, a second temperature sensor Tout arranged at the water outlet of the water-cooled radiator, a third temperature sensor Tair for detecting the external ambient temperature, a fourth temperature sensor Ts1, a fifth temperature sensor Ts2, a sixth temperature sensor Ts3, and a seventh temperature sensor Ts4 arranged around the bottom substrate of the IGBT device, and an eighth temperature sensor Tsink arranged on the side of the water-cooled radiator.

[0007] Preferably, the distance between the fourth temperature sensor Ts1, the fifth temperature sensor Ts2, the sixth temperature sensor Ts3, and the seventh temperature sensor Ts4 and the bottom substrate of the converter valve IGBT module is 1.5 mm. The distance is set to make the temperature measurement point as close as possible to the bottom substrate of the IGBT module under the premise of considering the diameter of the optical fiber temperature measurement probe (2 mm), and the measured temperature is as close as possible to the bottom substrate temperature of the IGBT module.

[0008] Preferably, the first temperature sensor Tin is an optical fiber temperature sensor, the measuring end of which is tightly attached to the outer tube wall of the water inlet of the water-cooled radiator by means of a fixing tape, and the outer side of the fixing tape is fixed for a second time by means of an electrical insulating tape. The optical fiber temperature sensor is double-coated, and can be insulated while being reliably fixed, so that the optical fiber temperature sensor can work reliably and stably.

[0009] Preferably, the fourth temperature sensor Ts1, the fifth temperature sensor Ts2, the sixth temperature sensor Ts3, the seventh temperature sensor Ts4 and the eighth temperature sensor Tsink are fixed to the surface of the corresponding flexible direct current converter valve module radiator through adhesive heat dissipation silicone. The temperature sensor is fixed to the flexible direct current converter valve radiator through adhesive heat dissipation silicone to reduce the measurement inaccuracy caused by the thermal insulation layer.

[0010] Preferably, the third temperature sensor Tair, the fourth temperature sensor Ts1, the fifth temperature sensor Ts2, the sixth temperature sensor Ts3, the seventh temperature sensor Ts4 and the eighth temperature sensor Tsink are all optical fiber sensors, and the length of a single fiber is 3 meters; the signal transmission device is fixed to the equipotential point on the upper surface of the DC energy storage capacitor housing nearby, and after the signal transmission device is fixed, it is fixed with a diameter of not less than 25mm. 2 The BVR soft copper busbar is reliably connected to the equipotential point. The signal transmission device is fixed to the equipotential point on the upper surface of the DC energy storage capacitor shell, which can reduce the impact of voltage difference on the signal transmission device and is conducive to improving its working stability.

[0011] Preferably, the flow sensor is an ultrasonic flow sensor, which is installed in a non-breaking tube manner and attached to the outer wall of the branch pipe of the converter valve, and fixed to the output port or input port of the converter valve with an insulating soft clamp; the inner shielding layer of the flow sensor transmission wire is reliably connected to the outer casing of the signal transmission device.

[0012] Another object of the present invention is to provide a method for online monitoring of thermal status of a flexible direct current converter valve module; the method for online monitoring of thermal status of a flexible direct current converter valve comprises the following steps:

[0013] 1) The first temperature sensor Tin, the second temperature sensor Tout, the third temperature sensor Tair, the fourth temperature sensor Ts1, the fifth temperature sensor Ts2, the sixth temperature sensor Ts3, the seventh temperature sensor Ts4 and the eighth temperature sensor Tsink collect temperature information in real time; the flow sensor Vin collects flow information in real time; and sends the collected temperature information and flow information to the host computer through the signal transmission device;

[0014] 2) The host computer obtains the size data of the water pipe and the collected temperature and flow information; based on the pipeline heat transfer model, the average inlet and outlet temperature of the cooling water is calculated, and the heat dissipation of the cooling water carried away by the cooling medium is calculated according to the average inlet and outlet temperature of the cooling water and the pipeline flow rate;

[0015] 3) The host computer obtains the size information of the radiator and the collected temperature information, and calculates the natural convection heat transfer coefficient of the air based on the convection heat transfer coefficient correlation formula; and calculates the amount of air heat dissipated by the water-cooled radiator to the air based on the natural convection heat transfer coefficient of the air and the heat dissipation area of ​​the water-cooled radiator;

[0016] 4) The host computer calculates the loss of the converter valve IGBT module according to the heat dissipation of cooling water and air, displays the relationship curve between time and heat dissipation, and performs online monitoring of the thermal state of the converter valve; the loss of the converter valve IGBT module is the sum of the heat dissipation of cooling water carried away by cooling water and the heat dissipation of air carried away by the surrounding air;

[0017] 5) The host computer determines whether the current operating status is normal based on the water-cooled radiator temperature data, cooling water temperature and flow rate data, and converter valve module loss; if not, an alarm will be issued.

[0018] Preferably, the loss Q of the converter valve IGBT module is calculated as follows:

[0019] A) According to the principle of heat transfer, the loss Q of the converter valve module is equal to the heat Q taken away by the cooling water 1 And the heat dissipation Q of the water cooling radiator to the surrounding air 2 The sum of

[0020] Q=Q 1 +Q 2 (1)

[0021] B) The heat dissipation of cooling water is calculated as follows:

[0022] Q 1 =ρ w ·v in ·A in ·c pw ·(T out -T in ) (2)

[0023] In the formula, Q 1 Indicates the heat taken away by water, in W; ρ w Indicates the density of cooling water, kg / m 3 ;v in Indicates the water inlet flow rate in m / s, measured by an ultrasonic flow sensor; A in Indicates the cross-sectional area of ​​the water pipe inlet, in m 2 ;c pw Represents the specific heat capacity of water, in J / (kg·K);

[0024] T in Indicates the inlet water temperature, in K; T out represents the outlet water temperature, in K. The density and specific heat capacity of cooling water are affected by temperature. To improve the calculation accuracy, ρ in formula (2) is replaced by w is replaced by the calculated ρ w (T); replace c in formula (2) pw is replaced by the calculated c pw (T);

[0025] ρ w (T)=838.466135+1.40050603T-0.003011237T 2 +3.71822313×10 -7 T3

[0026] c pw (T)=12010.1471-80.4072879T+0.309866854T 2 -5.38186884×10 -4 T 3 +3.62536437×10 -7 T 4

[0027] Where T is the average value of cooling water inlet and outlet temperatures;

[0028] When the fiber optic temperature sensor probe measures the wall temperature of the inlet and outlet pipes, since the average temperature of the water flow in the pipe cannot be directly obtained, in order to increase the inlet and outlet temperature T of the water cooling radiator in and T out The measurement accuracy is improved by solving the established pipeline heat transfer model to monitor the average temperature of the water flow in the pipe.

[0029] In the pipeline heat transfer model, r i 、r o Respectively represent the inner wall radius and outer wall radius of the tube; r m Surface wall midpoint radius; T f represents the average temperature of the water in the pipe, T a represents the air temperature outside the tube, T i , T m and T o They represent the temperature of the inner wall node, the center node and the outer wall node of the tube respectively; the density of the tube wall ρ t Specific heat capacity c t , thermal conductivity k t are constants, h i 、h o are the convection heat transfer coefficients inside and outside the tube, respectively;

[0030] Define Δr=(r o -r i ) / 4, then r m =r i +2Δr,r o =r i +4Δr, using Fourier's law of heat conduction and the principle of energy conservation, the inner wall node T i Establishing the heat balance equation

[0031]

[0032] Correspondingly, the middle node T of the pipe wall m

[0033]

[0034] External wall node T o

[0035]

[0036] Since only the outer wall temperature T is obtained by real-time monitoring o , and its rate of change with time dT / dt, so by inverting the above heat balance equation, the relationship between the temperature of the fluid in the tube and the temperature of the outer wall of the tube is established;

[0037] First, establish the node temperature T in the middle of the pipe wall m With T o and T a Direct relationship:

[0038]

[0039] Then establish the inner wall temperature T i With T m , T o Relationship:

[0040]

[0041] Finally, the temperature of the fluid in the tube and the adjacent nodes T i , T m Relationship:

[0042]

[0043] At this point, based on the real-time monitored tube outer wall temperature data, equations (6), (7), and (8) are recursively used to obtain the average temperature of the cooling medium fluid in the tube, that is, the cooling medium inlet and outlet temperatures in equation (1);

[0044] C) Calculation formula for the heat dissipation of the water cooling radiator to the surrounding air

[0045] Q 2 =h air ·A·(T s -T a ) (9)

[0046] In the formula, Q 2 Indicates the heat taken away by the air, in W; h air Indicates the air convection heat transfer coefficient, the unit is W / (m 2 ·K); A represents the effective surface area of ​​the water cooling radiator of the converter valve, in m 2 ; T s Indicates the average surface temperature of the water-cooled radiator, in K; T a Indicates the ambient temperature in K;

[0047] In formula (9), the effective heat dissipation area of ​​the water-cooled radiator is calculated according to the geometric dimensions of the water-cooled radiator, and the average surface temperature T of the water-cooled radiator is s =((T s1 +T s2 +T s3 +T s4 ) / 4+T sink ) / 2;

[0048] Convective heat transfer coefficient h air The Rayleigh number is obtained by the natural convection correlation of the vertical plate.

[0049]

[0050] Where g is the acceleration of gravity, 9.8m / s; β is the thermal expansion coefficient of air, which is the qualitative temperature of air T f = the inverse of (Ts+Ta) / 2; ρ a is the density of air, in kg / m 3 , whose value is: a =358.517T f -1.00212 ;c pa is the specific heat capacity of air, in J / (kg·K), and its value is:

[0051]

[0052] μ is the dynamic viscosity of air, in kg / m·s, and its value is:

[0053] μ=(-8.3123×10 -12 T f 2 +4.4156×10 -8 T f +6.2299×10 -6 ) / (358.517T f -1.00212 );

[0054] L is the height of the water cooling radiator;

[0055] Then calculate the Nusselt number

[0056]

[0057] In the formula, k a is the thermal conductivity of air, which is:

[0058]

[0059] Combining (10) and (11), we can get h a =Nu*k a / L, and then use formula (9) to get the heat dissipation of the water-cooled radiator to the air.

[0060] This method is comprehensive, taking into full account the impact of component size on temperature measurement, and making corresponding corrections to make temperature data more accurate, and the energy consumption calculated based on this more accurate.

[0061] Beneficial effects:

[0062] 1. This technical solution is based on the fact that the temperature around the IGBT is the temperature most relevant to the IGBT junction temperature among the measurable temperatures on site. It uses it together with the IGBT module loss as a thermal state quantity to monitor and evaluate the health status of the flexible DC converter valve with good accuracy. This technical solution does not require an insulation box, but directly collects temperature and flow information to conduct real-time online monitoring of the thermal state of the converter valve, detects problems in a timely manner, and improves the working reliability of the flexible DC converter valve.

[0063] 2. This technical solution uses multiple temperature sensors located at different positions to measure the temperature in real time, further improving the accuracy. It can monitor the IGBT module loss while monitoring the thermal state of the flexible DC converter valve in real time online.

[0064] 3. This technical solution comprehensively considers the factors affecting the loss of the IGBT module of the flexible direct current converter valve, and establishes a quantitative relationship between the measured temperature of the pipe wall and the average temperature of the water flow in the pipe through a heat transfer model, thereby improving the monitoring accuracy of the converter valve module loss using the calorimetric method.

[0065] 4. The multi-point temperature and cooling flow data of the water-cooled radiator monitored in this technical solution, as well as the calculated loss of the converter valve module, can be used to comprehensively monitor the health status of the flexible direct current converter valve, making it easier for staff to perform timely maintenance of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 It is a schematic diagram of the structure of the present invention.

[0067] Figure 2 It is a sensor position diagram of the present invention.

[0068] Figure 3 It is a heat transfer model diagram of the radiator water pipe of the present invention.

[0069] Figure 4 It is a flow chart of the present invention.

[0070] Figure 5 It is a schematic diagram of the thermal state monitoring of the converter valve of the present invention.

[0071] In the figure: 1. Water-cooled radiator; 2. Temperature sensor; 3. Flow sensor; 4. Signal transmission device; 5. Host computer; 6. IGBT module; 7. DC energy storage capacitor. DETAILED DESCRIPTION

[0072] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings.

[0073] like Figure 1 , 2 As shown, the present invention includes a water-cooled radiator 1, a temperature sensor, a flow sensor 3, a signal transmission device 4 and a host computer 5. The measured flexible direct current converter valve IGBT module 6 is arranged in the water-cooled radiator 1. The water-cooled radiator 1Vin is provided with multiple temperature sensors Vout. The flow sensor 3 includes a flow sensor arranged at the water inlet of the water-cooled radiator 1. The temperature sensor and the flow sensor 3 are connected to the host computer 5 through the signal transmission device 4; the temperature sensor includes a first temperature sensor Tin arranged at the water inlet of the water-cooled radiator 1, a second temperature sensor Tout arranged at the water outlet of the water-cooled radiator 1, a third temperature sensor Tair for detecting the external ambient temperature, and a fourth temperature sensor Ts1, a fifth temperature sensor Ts2, a sixth temperature sensor Ts3, and a seventh temperature sensor Ts4 arranged around the bottom substrate of the IGBT module; and an eighth temperature sensor Tsink arranged on the side of the water-cooled radiator.

[0074] Among them, the distance between the fourth temperature sensor Ts1, the fifth temperature sensor Ts2, the sixth temperature sensor Ts3, and the seventh temperature sensor Ts4 and the bottom substrate of the IGBT device is 1.5 mm.

[0075] The measuring end of the first temperature sensor Tin is attached to the outer tube wall of the water inlet of the water-cooled radiator 1 by means of a fixing tape, and the outer side of the fixing tape is fixed for a second time by means of an electrical insulating tape. The optical fiber temperature sensor is double-coated, which can be insulated while being reliably fixed, so that the optical fiber temperature sensor can work reliably and stably.

[0076] The signal transmission device 4 is fixed to the equipotential point on the upper surface of the DC energy storage capacitor 7. After the signal transmission device 4 is fixed, it is not less than 25mm. 2 The BVR soft copper busbar is reliably connected to the equipotential point. The signal transmission device 4 is fixed to the equipotential point on the upper surface of the DC energy storage capacitor 7 shell, which can reduce the impact of voltage difference on the signal transmission device 4 and is conducive to improving its working stability.

[0077] In order not to damage the cooling system, avoid leakage, and improve the working stability of the cooling system, in this embodiment, the flow sensor 3 is an ultrasonic flow sensor 3, which is installed in a non-broken pipe manner and attached to the outer wall of the branch pipe of the converter valve IGBT module 6, and fixed to the output port or input port of the converter valve by an insulating soft clamp; the inner shielding layer of the transmission wire of the flow sensor 3 is reliably connected to the shell of the signal transmission device 4. The external ultrasonic flow sensor 3 can be easily monitored and maintained.

[0078] like Figure 4 As shown, the corresponding method for online monitoring of thermal status of flexible direct current converter valve module includes the following steps:

[0079] S1: The first temperature sensor Tin, the second temperature sensor Tout, the third temperature sensor Tair, the fourth temperature sensor Ts1, the fifth temperature sensor Ts2, the sixth temperature sensor Ts3, the seventh temperature sensor Ts4, and the eighth temperature sensor Tsink collect temperature information in real time; the flow sensor Vin collects flow information in real time; and sends the collected temperature information and flow information to the host computer through the signal transmission device;

[0080] S2: The host computer obtains the size data of the water pipe and the collected temperature and flow information; based on the pipeline heat transfer model, the average inlet and outlet temperature of the cooling water is calculated, and the heat dissipation of the cooling water carried away by the cooling medium is calculated according to the average inlet and outlet temperature of the cooling water and the pipeline flow rate;

[0081] S3: The host computer obtains the size information of the radiator and the collected temperature information, and calculates the natural convection heat transfer coefficient of the air based on the convection heat transfer coefficient correlation formula; and calculates the amount of air heat dissipated by the water-cooled radiator to the air according to the natural convection heat transfer coefficient of the air and the heat dissipation area of ​​the water-cooled radiator;

[0082] S4: The host computer calculates the loss of the converter valve IGBT module according to the heat dissipation of cooling water and the heat dissipation of air; wherein the loss of the converter valve IGBT module is the sum of the heat dissipation of cooling water carried away by cooling water and the heat dissipation of air carried away by surrounding air; at the same time, Figure 5 As shown, a curve showing the relationship between time and heat dissipation is used to monitor the thermal status of the converter valve.

[0083] S5: The host computer determines whether the current operating status is normal based on the water-cooled radiator temperature data, the cooling water temperature and flow rate data, and the converter valve module loss; if not, a warning will be issued.

[0084] Specifically, the loss Q of the converter valve IGBT module is calculated as follows:

[0085] 1) According to the principle of heat transfer, the loss Q of the converter valve module is equal to the heat Q taken away by the cooling water1 And the heat dissipation Q of the water cooling radiator to the surrounding air 2 The sum of

[0086] Q=Q 1 +Q 2 (1)

[0087] 2) The heat dissipation calculation formula of cooling water is as follows:

[0088] Q 1 =ρ w ·v in ·A in ·c pw ·(T out -T in ) (2)

[0089] In the formula, Q 1 Indicates the heat taken away by water, in W; ρ w Indicates the density of cooling water, kg / m 3 ;v in Indicates the water inlet flow rate in m / s, measured by an ultrasonic flow sensor; A in Indicates the cross-sectional area of ​​the water pipe inlet, in m 2 ;c pw Represents the specific heat capacity of water, in J / (kg·K);

[0090] T in Indicates the inlet water temperature, in K; T out represents the outlet water temperature, in K. The density and specific heat capacity of cooling water are affected by temperature. To improve the calculation accuracy, ρ in formula (2) is replaced by w is replaced by the calculated ρ w (T); replace c in formula (2) pw is replaced by the calculated c pw (T);

[0091] ρ w (T)=838.466135+1.40050603T-0.003011237T 2 +3.71822313×10 -7 T 3

[0092] c pw (T)=12010.1471-80.4072879T+0.309866854T 2 -5.38186884×10 -4 T 3 +3.62536437×10 -7 T4

[0093] Where T is the average value of cooling water inlet and outlet temperatures;

[0094] When the fiber optic temperature sensor probe measures the wall temperature of the inlet and outlet pipes, since the average temperature of the water flow in the pipe cannot be directly obtained, in order to increase the inlet and outlet temperature T of the water cooling radiator in and T out The measurement accuracy is improved by solving the established pipeline heat transfer model to monitor the average temperature of the water flow in the pipe.

[0095] like Figure 3 As shown in the pipeline heat transfer model, r i 、r o Respectively represent the inner wall radius and outer wall radius of the tube; r m Surface wall midpoint radius; T f represents the average temperature of the water in the pipe, T a represents the air temperature outside the tube, T i , T m and T o They represent the temperature of the inner wall node, the center node and the outer wall node of the tube respectively; the density of the tube wall ρ t Specific heat capacity c t , thermal conductivity k t are constants, h i 、h o are the convection heat transfer coefficients inside and outside the tube, respectively;

[0096] Define Δr=(r o -r i ) / 4, then r m =r i +2Δr,r o =r i +4Δr, using Fourier's law of heat conduction and the principle of energy conservation, the inner wall node T i Establishing the heat balance equation

[0097]

[0098] Correspondingly, the middle node T of the pipe wall m

[0099]

[0100] External wall node T o

[0101]

[0102] Since only the outer wall temperature T is obtained by real-time monitoring o, and its rate of change with time dT / dt, so by inverting the above heat balance equation, the relationship between the temperature of the fluid in the tube and the temperature of the outer wall of the tube is established;

[0103] First, establish the node temperature T in the middle of the pipe wall m With T o and T a Direct relationship:

[0104]

[0105] Then establish the inner wall temperature T i With T m , T o Relationship:

[0106]

[0107] Finally, the temperature of the fluid in the tube and the adjacent nodes T i , T m Relationship:

[0108]

[0109] At this point, based on the real-time monitored tube outer wall temperature data, equations (6), (7), and (8) are recursively used to obtain the average temperature of the cooling medium fluid in the tube, that is, the cooling medium inlet and outlet temperatures in equation (1);

[0110] 3) Calculation formula for the heat dissipation of the water cooling radiator to the surrounding air

[0111] Q 2 =h air ·A·(T s -T a ) (9)

[0112] In the formula, Q 2 Indicates the heat taken away by the air, in W; h air Indicates the air convection heat transfer coefficient, the unit is W / (m 2 ·K); A represents the effective surface area of ​​the water cooling radiator of the converter valve, in m 2 ; T s Indicates the average surface temperature of the water-cooled radiator, in K; T a Indicates the ambient temperature in K;

[0113] In formula (9), the effective heat dissipation area of ​​the water-cooled radiator is calculated according to the geometric dimensions of the water-cooled radiator, T s The water cooling radiator temperature T s1 , T s2 The average value of is obtained;

[0114] Convective heat transfer coefficient h air The Rayleigh number is obtained by the natural convection correlation of the vertical plate.

[0115]

[0116] Where g is the acceleration of gravity, 9.8m / s; β is the thermal expansion coefficient of air, which is the qualitative temperature of air T f = the inverse of (Ts+Ta) / 2; ρ a is the density of air, in kg / m 3 , whose value is: a =358.517T f -1.00212 ;c pa is the specific heat capacity of air, in J / (kg·K), and its value is:

[0117] μ is the dynamic viscosity of air, in kg / m·s, and its value is:

[0118] μ=(-8.3123×10 -12 T f 2 +4.4156×10 -8 T f +6.2299×10 -6 ) / (358.517T f -1.00212 );

[0119] L is the height of the water cooling radiator;

[0120] Then calculate the Nusselt number

[0121]

[0122] In the formula, k a is the thermal conductivity of air, which is:

[0123]

[0124] Combining (10) and (11), we can get h a =Nu*k a / L, and then use formula (9) to get the heat dissipation of the water-cooled radiator to the air.

[0125] This technical solution is comprehensive, taking into full account the impact of component size on temperature measurement, and making corresponding corrections to make temperature data more accurate, and the energy consumption calculated based on this more accurate.

[0126] above Figure 1-4The device and method for online monitoring of the thermal state of a flexible direct-current converter valve based on a heat transfer model shown is a specific embodiment of the present invention, which has embodied the essential characteristics and progress of the present invention. According to actual use needs and under the guidance of the present invention, equivalent modifications in shape, structure, etc. can be made to the device and method, which are all within the protection scope of this scheme.

Claims

1. An online monitoring device for thermal status of a flexible direct current converter valve based on a heat transfer model, characterized in that: The invention comprises a water-cooled radiator (1), a temperature sensor (2), a flow sensor (3), a signal transmission device (4) and a host computer (5); the measured flexible direct current converter valve IGBT module (6) is arranged in the water-cooled radiator (1); the water-cooled radiator (1) is provided with a plurality of temperature sensors; the flow sensor (3) comprises a flow sensor Vin arranged at the water inlet of the water-cooled radiator (1); the temperature sensor and the flow sensor (3) are connected to the host computer (5) via the signal transmission device (4); the temperature sensor comprises a first temperature sensor Tin arranged at the water inlet of the water-cooled radiator (1); a second temperature sensor Tout arranged at the water outlet of the water-cooled radiator (1); a third temperature sensor Tair for detecting the external environment temperature; a fourth temperature sensor Ts1, a fifth temperature sensor Ts2, a sixth temperature sensor Ts3 and a seventh temperature sensor Ts4 arranged around the bottom substrate of the IGBT device; and an eighth temperature sensor Tsink arranged on the side of the water-cooled radiator; The loss of the flexible DC converter IGBT module is the sum of the cooling water heat dissipation carried away by the cooling water and the air heat dissipation carried away by the surrounding air; The calculation method of the loss Q of the converter valve IGBT module is: A) According to the principle of heat transfer, the loss Q of the converter valve IGBT module is equal to the sum of the heat Q1 taken away by the cooling water and the heat Q2 dissipated by the water-cooled radiator to the surrounding air, that is, Q=Q1+Q2 (1) B) The heat dissipation of cooling water is calculated as follows: Q1=ρ w ·v in ·A in ·c pw ·(T out -T in ) (2) Where Q1 represents the heat taken away by water, in W; ρ w Indicates the density of cooling water, kg / m 3 ;v in Indicates the water inlet flow rate in m / s, measured by an ultrasonic flow sensor; A in Indicates the cross-sectional area of ​​the water pipe inlet, in m 2 ;c pw Indicates the specific heat capacity of water, in J / (kg·K); T in Indicates the inlet water temperature, in K; T out represents the outlet water temperature, in K. The density and specific heat capacity of cooling water are affected by temperature. To improve the calculation accuracy, ρ in formula (2) is replaced by w is replaced by the calculated ρ w (T); replace c in formula (2) pw is replaced by the calculated c pw (T); ρ w (T)=838.466135+1.40050603T-0.003011237T 2 +3.71822313×10 -7 T 3 c pw (T)=12010.1471-80.4072879T+0.309866854T 2 -5.38186884×10 -4 T 3 +3.62536437×10 -7 T 4 Where T is the average value of cooling water inlet and outlet temperatures; When the fiber optic temperature sensor probe measures the wall temperature of the inlet and outlet pipes, since the average temperature of the water flow in the pipe cannot be directly obtained, in order to increase the inlet and outlet temperature T of the water cooling radiator in and T out The measurement accuracy is improved by solving the established pipeline heat transfer model to monitor the average temperature of the water flow in the pipe. In the pipeline heat transfer model, r i 、r o Respectively represent the inner wall radius and outer wall radius of the tube; r m Surface wall midpoint radius; T f represents the average temperature of the water flow in the pipe, T a represents the air temperature outside the tube, T i 、T m and T o They represent the temperatures of the inner wall nodes, the center nodes, and the outer wall nodes of the tube respectively; Density of the tube wall ρ t Specific heat capacity c t , thermal conductivity k t are constants, h i 、h o are the convection heat transfer coefficients inside and outside the tube, respectively; Define Δr=(r o -r i ) / 4, then r m =r i +2Δr,r o =r i +4Δr, using Fourier's law of heat conduction and the principle of energy conservation, the inner wall node T i Establishing the heat balance equation Correspondingly, the middle node T of the pipe wall m External wall node T o Since only the outer wall temperature T is obtained by real-time monitoring o , and its rate of change with time dT / dt, so by inverting the above heat balance equation, the relationship between the temperature of the fluid in the tube and the temperature of the outer wall of the tube is established; First, establish the node temperature T in the middle of the pipe wall m With T o and T a Direct relationship: Then establish the inner wall temperature T i With T m , T o Relationship: Finally, the temperature of the fluid in the tube and the adjacent nodes T i , T m Relationship: At this point, based on the real-time monitored tube outer wall temperature data, equations (6), (7), and (8) are recursively used to obtain the average temperature of the cooling medium fluid in the tube, that is, the cooling medium inlet and outlet temperatures in equation (1); C) Calculation formula for the heat dissipation of the water cooling radiator to the surrounding air Q2=h air ·A·(T s -T a ) (9) In the formula, Q2 represents the heat taken away by the air, in W; h air Indicates the air convection heat transfer coefficient, the unit is W / (m 2 ·K); A represents the effective surface area of ​​the water cooling radiator of the converter valve, in m 2 ; T s Indicates the average surface temperature of the water-cooled radiator, in K; T a Indicates the ambient temperature in K; In formula (9), the effective heat dissipation area of ​​the water-cooled radiator is calculated according to the geometric dimensions of the water-cooled radiator, and the average surface temperature T of the water-cooled radiator is s =((T s1 +T s2 +T s3 +T s4 ) / 4+T sink ) / 2; Convective heat transfer coefficient h air The Rayleigh number is obtained by the natural convection correlation of the vertical plate. Where g is the acceleration of gravity, 9.8m / s; β is the thermal expansion coefficient of air, which is the qualitative temperature of air T f = the inverse of (Ts+Ta) / 2; ρ a is the density of air, in kg / m 3 , whose value is: a =358.517T f -1.00212 ;c pa is the specific heat capacity of air, in J / (kg·K), and its value is: μ is the dynamic viscosity of air, in kg / m·s, and its value is: μ=(-8.3123×10 -12 T f 2 +4.4156×10 -8 T f +6.2299×10 -6 ) / (358.517T f -1.00212 ); L is the height of the water cooling radiator; Then calculate the Nusselt number In the formula, k a is the thermal conductivity of air, which is: Combining (10) and (11), we can get h a =Nu*k a / L, and then use formula (9) to get the heat dissipation of the water-cooled radiator to the air.

2. According to claim 1, a device for online monitoring of thermal status of a flexible direct current converter valve based on a heat transfer model is characterized in that: The distance between the fourth temperature sensor Ts1 , the fifth temperature sensor Ts2 , the sixth temperature sensor Ts3 , and the seventh temperature sensor Ts4 and the bottom substrate of the IGBT device is 1.5 mm.

3. The device for online monitoring thermal status of a flexible direct current converter valve based on a heat transfer model according to claim 1, characterized in that: The first temperature sensor Tin is an optical fiber temperature sensor, the measuring end of which is tightly attached to the outer tube wall of the water inlet of the water-cooled radiator (1) by means of a fixing tape, and the outer side of the fixing tape is fixed for a second time by means of an electrical insulating tape.

4. The device for online monitoring thermal status of a flexible direct current converter valve based on a heat transfer model according to claim 3 is characterized in that: The fourth temperature sensor Ts1, the fifth temperature sensor Ts2, the sixth temperature sensor Ts3, and the seventh temperature sensor Ts4 are respectively fixed to the surface of the corresponding flexible direct current converter valve radiator through adhesive heat dissipation silicon.

5. The device for online monitoring thermal status of a flexible DC converter valve based on a heat transfer model according to claim 4, characterized in that: The third temperature sensor Tair, the fourth temperature sensor Ts1, the fifth temperature sensor Ts2, the sixth temperature sensor Ts3, the seventh temperature sensor Ts4, and the eighth temperature sensor Tsink are all optical fiber sensors, each of which is 3 meters long. The signal transmission device (4) is fixed to the equipotential point on the upper surface of the DC energy storage capacitor (7) shell. After the signal transmission device (4) is fixed, it is fixed with a diameter of not less than 25 mm. 2 The BVR soft copper busbar is reliably connected to the equipotential point.

6. The device for online monitoring thermal status of a flexible direct current converter valve based on a heat transfer model according to claim 1, characterized in that: The flow sensor (3) is an ultrasonic flow sensor (3), which is installed in a non-breaking pipe manner and attached to the outer wall of the branch pipe of the converter valve, and fixed to the output port or input port of the converter valve by an insulating soft clamp; the inner shielding layer of the transmission wire of the flow sensor (3) is reliably connected to the outer shell of the signal transmission device (4).

7. A method for online monitoring the thermal state of a flexible DC converter valve using an online monitoring device for thermal state of a flexible DC converter valve based on a heat transfer model as described in any one of claims 1 to 6, characterized in that The following steps are involved: 1) The first temperature sensor Tin, the second temperature sensor Tout, the third temperature sensor Tair, the fourth temperature sensor Ts1, the fifth temperature sensor Ts2, the sixth temperature sensor Ts3, the seventh temperature sensor Ts4, and the eighth temperature sensor Tsink collect temperature information in real time; the flow sensor Vin collects flow information in real time; and sends the collected temperature information and flow information to the host computer through a signal transmission device; 2) The host computer obtains the size data of the water pipe and the collected temperature and flow information; Based on the pipeline heat transfer model, the average inlet and outlet temperatures of the cooling water are calculated, and the heat dissipation of the cooling water carried away by the cooling medium is calculated based on the average inlet and outlet temperatures of the cooling water and the pipeline flow rate; 3) The host computer obtains the size information of the radiator and the collected temperature information, and calculates the natural convection heat transfer coefficient of the air based on the convection heat transfer coefficient correlation formula; And calculate the amount of heat dissipated from the water-cooling radiator to the air based on the natural convection heat transfer coefficient of the air and the heat dissipation area of ​​the water-cooling radiator; 4) The host computer calculates the IGBT module loss of the flexible DC converter valve according to the heat dissipation of cooling water and air, displays the relationship curve between time and heat dissipation, and performs online monitoring of the thermal state of the converter valve; the IGBT module loss of the flexible DC converter valve is the sum of the heat dissipation of cooling water carried away by cooling water and the heat dissipation of air carried away by the surrounding air; 5) The host computer determines whether the current operating status is normal based on the water-cooled radiator temperature data, cooling water temperature and flow rate data, and converter valve module loss; if not, an alarm will be issued.

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