SVG module flexible temperature control method and device

Abstract

The invention discloses an SVG module flexible temperature control method and device. The method comprises the following steps: pre-constructing an SVG module heat transfer model; the heat transfer model comprises a heat transfer relationship among a first temperature measured at a bottom plate in the IGBT module, a second temperature measured at an air inlet of the cooling fan and an environment temperature of the case; the SVG module is powered on, and the fan runs at a full speed; sampling time is determined according to a time constant, the first temperature and the second temperature are monitored according to the sampling time, and the time constant is a time value when the temperature is stable after the output power of the IGBT module changes; and if the first temperature is greater than a first threshold value or the environment temperature is greater than a second threshold value, setting a target first temperature, substituting the target first temperature into a thermal model to calculate target generation power, and controlling power output by the inverter according to the target generation power. According to the flexible temperature control method provided by the invention, when the SVG module is at high temperature in summer, the number of times of automatic shutdown due to over-temperature protection is greatly reduced, so that the normal working time of reactive compensation of the SVG module is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of power control, and in particular to a method and device for flexible temperature control of an SVG module. Background Art

[0002] SVG modules are currently widely used in reactive power compensation devices. Most SVG module products manufactured by various manufacturers are designed based on the ambient temperature requirements of "DLT1216-2013 Static VAR Compensation Device": the ambient air temperature range of the installation and operation area is -40℃~+45℃. The module should be able to run at full load for a long time under the condition of ambient temperature of -40℃~+45℃, and will not automatically shut down due to the over-temperature protection function of the module.

[0003] The problem is that in actual application, when the ambient air temperature around the module is higher than the design index due to insufficient heat dissipation conditions in the application site, the module will automatically shut down due to the over-temperature protection function, resulting in the inability to achieve reactive power compensation. For example, in the summer, when multiple SVG modules are used in a power distribution room without air conditioning or cooling fans, the module itself is a heating element, and the heat generated is 3-5% of the rated power of the module. When multiple modules are used at full load at the same time, the temperature in the entire cabinet will reach above 45 degrees, and the highest cabinet temperature will reach 60 degrees or even higher. The full-load operation will automatically shut down after a short time. When the module temperature cools down, it will automatically restart at a fixed time, and the shutdown and restart cycle will be repeated until the set number of times is reached and it is completely shut down. This is exactly the time period when full-load reactive power compensation is required. For users, it will cause an increase in rate adjustment electricity charges. Summary of the invention

[0004] The present invention aims to solve the problem that, without changing the original radiator structure design, when the module is fully loaded and operates at a temperature exceeding the upper limit of the operating environment air temperature, the module will automatically shut down quickly and restart repeatedly until the start-stop limit number is reached for complete shutdown protection.

[0005] In order to solve the above technical problems, the present invention is solved by the following technical solutions:

[0006] A flexible temperature control method for an SVG module comprises the following steps:

[0007] Step 1: Pre-build the SVG module heat transfer model, as shown in Formula 1 and Formula 2

[0008] T1(t)=P(t)*Z1(t)+T2(t); Formula 1

[0009] T2(t)=P(t)*Z2(t)+Ta(t); Formula 2

[0010] Among them, T1 is the temperature measured at the bottom plate inside the IGBT module, recorded as the first temperature, and the IGBT module is the core device of the inverter in the SVG module; T2 is the temperature measured at the air inlet of the cooling fan of the SVG module, recorded as the second temperature; Ta is the ambient temperature of the SVG module chassis; t is the time variable; P is the generated power of the SVG module; Z1 is the thermal impedance formed by all objects in the SVG module chassis, and Z2 is the thermal impedance formed by the ambient air where the SVG module chassis is located;

[0011] Step 2: Power on the SVG module and run the fan at full speed.

[0012] Step 3, determining the sampling time with a time constant, monitoring the first temperature and the second temperature according to the sampling time, wherein the time constant is the time value for the temperature to stabilize after the output power of the IGBT module changes;

[0013] Step 4: if the first temperature is greater than the first threshold, or the ambient temperature is greater than the second threshold, then executing step 5, i.e. starting the flexible temperature control program;

[0014] Step 5, setting a target first temperature, substituting the target first temperature into Formula 1 and Formula 2 to calculate the target generated power, and the inverter controls the power output according to the target generated power;

[0015] The target first temperature is less than or equal to a first threshold value; and the second threshold value is determined according to an ambient temperature required by an SVG module execution specification.

[0016] Preferably, the method for controlling power output of the inverter according to the target generated power includes:

[0017] The reactive power demand value is calculated according to the AC sampling value of the power grid. If the reactive power demand value is less than or equal to the target generated power, the inverter is controlled to control the power output according to the reactive power demand value. If not, the inverter controls the power output according to the target generated power value.

[0018] Preferably, after the inverter controls the power output according to the target power generation, it further includes step six, as follows:

[0019] If the current first temperature is greater than or equal to the first threshold, return to step five;

[0020] If the current first temperature is less than the first threshold, the current ambient temperature is calculated according to Formula 2. If the current ambient temperature is less than the second threshold, the inverter executes the normal temperature reactive power compensation demand output control program and continues to monitor the first temperature and the second temperature at the sampling time.

[0021] If the current ambient temperature calculated according to Formula 2 is greater than or equal to the second threshold, it is determined whether there is a shutdown command. If so, the shutdown process is executed. If not, it returns to step three.

[0022] Preferably, the method further includes a process in which if the first temperature is greater than a third threshold, the system is shut down and an alarm is given, wherein the third threshold is determined according to a maximum junction temperature limit value of the IGBT module.

[0023] Preferably, the method further includes the following steps: if there are multiple IGBT modules in the SVG module, multiple first temperatures are detected, and a maximum value thereof is compared with a first threshold.

[0024] Preferably, the method for obtaining the ambient temperature includes:

[0025] The second temperature is collected, and the current power generated by the IGBT module is obtained and substituted into Formula 2 for calculation, or collected through a temperature sensor in the environment where the SVG module chassis is located.

[0026] Preferably, the construction method of Formula 1 and Formula 2 includes:

[0027] Determine the first temperature measurement point, the second temperature measurement point and the third temperature measurement point of the SVG module chassis, wherein:

[0028] The first temperature measuring point is located at the bottom plate inside the IGBT module, and the temperature measured at the first temperature measuring point is recorded as the first temperature T1;

[0029] The second temperature measuring point is located at the air inlet of the cooling fan of the SVG module, and the temperature measured at the second temperature measuring point is recorded as the second temperature T2;

[0030] The third temperature measurement point is located at the ambient temperature of the SVG module chassis, and the ambient temperature is recorded as Ta;

[0031] According to the heat transfer relationship between the first temperature measuring point, the second temperature measuring point and the third temperature measuring point, Formula 1 and Formula 2 are constructed:

[0032] Construct a temperature-controllable experimental environment and output at least one ambient temperature;

[0033] At each ambient temperature, the SVG module is started to output several fixed power points. According to the first temperature and the second temperature at different output powers, the Z1 and Z2 parameter values ​​at different ambient temperatures are calculated by substituting them into Formula 1 and Formula 2.

[0034] Preferably, the method for calculating the time constant τ includes: at each ambient temperature, starting the SVG module to output a number of fixed power points, recording the first temperature, the second temperature and the time value for temperature stabilization after outputting the corresponding fixed power points at different output powers, and calculating the average value of the time value for temperature stabilization as the time constant τ.

[0035] Preferably, the sampling time tc has a value range of τ≤tc≤5τ, where τ is a time constant, that is, the time value for temperature stabilization after the output power changes.

[0036] The present invention also provides an SVG module device, which uses the above method and preferred method to control temperature.

[0037] Beneficial effects: The present invention greatly reduces the number of automatic shutdowns of the SVG module due to over-temperature protection during high temperatures in summer, thereby extending the normal working time of reactive power compensation of the SVG module and reducing or even making the user's rate-adjusting electricity fee zero. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0039] Figure 1 It is the thermal model diagram of the SVG module;

[0040] Figure 2 It is a flow chart for testing the thermal model parameters of the SVG module;

[0041] Figure 3 This is the relationship between the IGBT temperature and power of the SVG module;

[0042] Figure 4 This is the main flow chart of temperature control of SVG module;

[0043] Figure 5 It is the flow chart of flexible control protection of over-limit reactive power compensation of SVG module. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be understood that the specific implementation methods described herein are only used to explain the present invention and do not limit the scope of protection of the present invention.

[0045] The temperature value of the SVG module during operation is given by the temperature measuring element inside the base plate of the IGBT module, a key component in the module converter. Its temperature value is determined by the following factors:

[0046] (1) Design of IGBT heat sink, fan, air duct, and chassis structure in SVG module: Once the structural design is finalized, the IGBT temperature rise and the thermal model of all objects in the SVG module are determined. Therefore, when the specifications of SVG modules from the same manufacturer are the same, the specific parameters of their thermal models are the same; when the specifications of SVG modules are different, the specific parameters of their thermal models are also different, and they need to be measured separately in the test. When the specifications of SVG modules from different manufacturers are the same, if the IGBT heat sink, fan, air duct, and chassis structure design in the module are different, the specific parameters of their thermal models will also be different. They need to be measured in the test.

[0047] (2) Ambient temperature;

[0048] (3) Output power of the converter with IGBT module as the core: The output power is positively correlated with the temperature rise, so a relationship model can be established.

[0049] Of course, if there are other influencing factors, the impact on the results is slight and can be treated as errors.

[0050] According to the above influencing factors, a mathematical model of temperature rise change of SVG module including these influencing factors is constructed, refer to Figure 2 , including the following steps:

[0051] According to the structural characteristics of the SVG module chassis, a heat transfer model is constructed:

[0052] Determine a first temperature measurement point, a second temperature measurement point and a third temperature measurement point, wherein,

[0053] The first temperature measuring point is located at the bottom plate inside the IGBT module, and the temperature measured at the first temperature measuring point is recorded as the first temperature T1;

[0054] The second temperature measuring point is located at the air inlet of the cooling fan of the SVG module, and the temperature measured at the second temperature measuring point is recorded as the second temperature T2;

[0055] The third temperature measurement point is located at the ambient temperature of the SVG module chassis, and the ambient temperature is recorded as Ta;

[0056] According to the heat transfer relationship between the first temperature measurement point, the second temperature measurement point and the third temperature measurement point, the following formula is constructed:

[0057] T1(t)=P(t)*Z1(t)+T2(t); Formula 1

[0058] T2(t)=P(t)*Z2(t)+Ta(t); Formula 2

[0059] Where t is the time variable, P is the power generated by the SVG module, Z1 is the thermal impedance formed by all objects in the SVG module chassis, and Z2 is the thermal impedance formed by the ambient air where the SVG module chassis is located.

[0060] Construct a temperature-controlled experimental environment and output at least one ambient temperature. The more ambient temperature schemes there are, the more accurate the parameters of the model will be.

[0061] At each ambient temperature, the SVG module is started to output several fixed power points. According to the first temperature and the second temperature at different output powers and the time value for temperature stabilization after outputting the corresponding fixed power points, the Z1 and Z2 parameter values ​​at different ambient temperatures are calculated.

[0062] The SVG module outputs several fixed power points that can be selected according to different product performance. For the same power point, the smaller the step size, the more accurate the data.

[0063] The time value for temperature stabilization is the average value of the time values ​​at different power points. This parameter is used as the temperature sampling time in application.

[0064] Principle analysis: Construct a mathematical model of heat transfer, refer to the concept of Foster thermal model, perform a technical transformation, and obtain the thermal model of the SVG module required by this application, such as Figure 1 shown.

[0065] T1(t)=P(t)*Z1(t)+T2(t); Formula 1

[0066] T2(t)=P(t)*Z2(t)+Ta(t); Formula 2

[0067] Z(t)=Rth*(1- ) Formula 3

[0068] τ=Rth*Cth Formula 4

[0069] in,

[0070] P is the generated power of the SVG module;

[0071] Rth1 is the thermal resistance formed by all objects in the SVG module chassis;

[0072] Cth1 is the heat capacity formed by all objects in the SVG module chassis;

[0073] T1 is the temperature measured by the internal bottom plate thermistor of the IGBT module in the SVG module (the temperature deviation from the IGBT junction temperature is given by each manufacturer), which is uniformly referred to as the "first temperature" in this article;

[0074] T2 is the temperature measured by the thermistor attached to the air inlet of the SVG module cooling fan; it is collectively referred to as the "second temperature" in this article;

[0075] Rth2 is the thermal resistance formed by the ambient air within a certain distance from the SVG module chassis;

[0076] Cth2 is the heat capacity formed by the ambient air at a certain distance from the SVG module chassis;

[0077] Ta is the ambient air temperature at a certain distance from the module; this document uniformly refers to it as "ambient temperature"; the "certain distance" referred to in this document is disclosed as 1 meter for example, and a reasonable error is allowed. Generally speaking, the temperature emitted by the SVG module chassis has a greater impact within a range of 1 meter, and other reasonable ranges such as 0.8 meters, 1.2 meters, etc. are also selectable parameters. Therefore, it can be known that the ambient temperature referred to in this application is the ambient temperature of the chassis affected by the operation of the SVG module chassis.

[0078] For example, the following parameters are provided as reference, the data is as follows Figure 3 :

[0079] (1) Set the ambient temperature test values ​​Ta to 45°C, 60°C, and 65°C respectively;

[0080] (2) The power output of the SVG module is measured in units of 5 kvar, and is recorded at Ta = 45°C, 60°C, and 65°C, respectively, from 0 kvar to 100 kvar, the internal stable temperature of the IGBT module bottom plate T1(t0)~T1(t20), and the actual stable temperature value of the SVG module T2(t0)~T2(t20) and the required time t0~t20.

[0081] Therefore, what actually needs to be measured is the first group T1(t0)~T1(t20) measured when the ambient temperature Ta is equal to 45℃, the second group T1(t0)~T1(t20) measured when the ambient temperature Ta is equal to 60℃, the third group T1(t0)~T1(t20) measured when the ambient temperature Ta is equal to 65℃, and the time t0~t20 required for the three groups of temperatures to stabilize.

[0082] According to the test data Ta, T1 and T2 data, substitute them into formula 1 and formula 2 to determine the values ​​of Z1 (t0) ~ Z1 (t20) and Z2 (t0) ~ Z2 (t20). Take the average value to get Z1v and Z2v.

[0083] The calculation method of the time constant τ includes: at each ambient temperature, starting the SVG module to output a number of fixed power points, recording the first temperature, the second temperature and the time value of temperature stabilization after the corresponding fixed power point is output at different output powers, and calculating the average value of the temperature stabilization time value as the time constant τ. According to the test data, the values ​​of three groups of stabilization time t0~t20 at three ambient temperatures Ta are determined, and the average value is taken as the time constant τ.

[0084] According to (Formula 3), when the sampling time is greater than or equal to 5τ, Z1v(t)=Rth is a constant. Therefore, it can be considered that Z1 is the thermal resistance Rth1 formed by all objects in the SVG module chassis, and Z2 is the thermal resistance Rth2 formed by the ambient air where the SVG module chassis is located. That is, Z1v=Rth1, Z2v=Rth2. According to the above derivation, when the sampling time is greater than or equal to 5τ, Z1 is equivalent to the thermal resistance formed by all objects in the SVG module chassis, and Z2 is equivalent to the thermal resistance formed by the ambient air where the SVG module chassis is located. Since the thermal capacitance Cth1 is an unstable parameter, in order to avoid the influence of this parameter on Z1 and Z2 as much as possible, it is best to take a sampling time greater than or equal to 5τ.

[0085] From (Formula 4), we can see that Rth is a constant, Cth is also a constant, so τ is also a constant.

[0086] (3) According to the test disclosed in Example 1, under the conditions of 45°C, 60°C, and 65°C ambient temperature, at full load power, T1(45°C), T1(60°C), T1(65°C) and T2(45°C), T2(60°C), T2(65°C) which stabilize after 5τ time can be obtained respectively. The experimenter obtains a method of using T1(45°C), T1(60°C), T1(65°C) and T2(45°C), T2(60°C), T2(65°C) as the detectable upper limit temperature instead of directly measuring the ambient temperature.

[0087] Taking the measured SVG module model of 100kvar as an example, according to the requirements of (3), the power-temperature relationship of the first temperature TI and the second temperature T2 at the extreme environments of 45℃, 60℃, and 65℃ is as follows: Figure 3 shown.

[0088] The calculated Rth1, Rth2, and τ parameters are substituted into Formula 1 and Formula 2 for the SVG module flexible control program operation (or SVG module flexible control method).

[0089] It should be noted that the set parameters are disclosed for example and are not absolute values. The minimum temperature of the ambient air temperature test value Ta is set with reference to the ambient temperature requirement of "DLT1216-2013 Static VAR Compensation Device" that "the ambient air temperature range of the installation and operation area is -40℃~+45℃". Therefore, in theory, qualified products will not automatically shut down due to the over-temperature protection function of the module when the ambient air temperature ranges from -40℃ to +45℃. Therefore, the minimum temperature of the test is set to 45℃. Of course, considering that the specifications of the products implementing the present invention are different or there are innovations, the product specifications when implementing the present invention are used as a reference. 45℃, 60℃, and 65℃ are only used to describe the solution ideas, and can also be 45℃, 50℃, 55℃ or 45℃, 55℃, 65℃, etc. The power output of the SVG module is in 5kvar units, and can also be 2kvar, 8kvar, or 10kvar, etc. If the relevant specifications change, or the implementer intends to perform flexible temperature control on the SVG module at other ambient temperatures, the adjusted ambient temperature is also within the protection scope of the present invention.

[0090] Embodiment 2: A flexible temperature control method for an SVG module, comprising the following steps:

[0091] Step 1: pre-build the SVG module heat transfer model according to the content disclosed in Example 1, such as Formula 1 and Formula 2:

[0092] T1(t)=P(t)*Z1(t)+T2(t); Formula 1

[0093] T2(t)=P(t)*Z2(t)+Ta(t); Formula 2

[0094] Wherein, T1 is the temperature measured at the bottom plate inside the IGBT module, recorded as the first temperature; T2 is the temperature measured at the air inlet of the SVG module cooling fan, recorded as the second temperature; Ta is the ambient temperature of the SVG module chassis; t is the time variable; P is the power generated by the SVG module; Z1 is the thermal impedance formed by all objects in the SVG module chassis, and Z2 is the thermal impedance formed by the ambient air where the SVG module chassis is located;

[0095] Step 2: Power on the SVG module and run the fan at full speed.

[0096] Step 3, determining the sampling time with a time constant, monitoring the first temperature and the second temperature according to the sampling time, wherein the time constant is the time value for the temperature to stabilize after the output power of the IGBT module changes;

[0097] Step 4: If the first temperature T1 is greater than the first threshold, or the ambient temperature Ta is greater than the second threshold, then execute step 5;

[0098] Step 5, setting a target first temperature T1', substituting the target first temperature T1' into Formula 1 and Formula 2 to calculate the target generated power P(t)', and the inverter controls the power output according to the target generated power P(t)';

[0099] The target first temperature T1' is less than or equal to a first threshold value; and the second threshold value is determined according to the ambient temperature required by the SVG module execution specification.

[0100] The method of controlling power output of the inverter according to the target generated power in step 5 preferably includes:

[0101] The reactive power demand value Q is calculated based on the AC sampling value of the power grid. If the reactive power demand value Q is less than or equal to the target power generation value P(t)', the inverter is controlled to output power according to the Q value. If not, the inverter outputs power according to the target power generation value. This situation takes into account that if the current reactive power demand value Q itself is already less than P(t)', it means that the output of the reactive power demand value Q actually required by the current load must be able to drop to the corresponding temperature. The reason why the current temperature is greater than the first threshold or the second threshold may be due to the transmission time problem.

[0102] After the inverter controls the power output according to the target power generation, step six is ​​also included, as follows:

[0103] If the current first temperature is greater than or equal to the first threshold, return to step five;

[0104] If the current first temperature is less than the first threshold, the current ambient temperature is calculated according to Formula 2. If the current ambient temperature is less than the second threshold, the inverter executes the normal temperature reactive power compensation demand output control program and continues to monitor the first temperature and the second temperature at the sampling time.

[0105] If the current ambient temperature calculated according to Formula 2 is greater than or equal to the second threshold, it is determined whether there is a shutdown command. If so, the shutdown process is executed. If not, it returns to step three.

[0106] Preferably, the method also includes a SVG module hardware self-check process, step 2, after the SVG module is powered on and the fan is running at full speed, it also includes step 2.1, executing the SVG module hardware self-check, if the hardware has a fault, the machine is shut down and an alarm is issued; if there is no fault, step 3 is executed.

[0107] For this preferred process, the following steps in step six are replaced or adjusted, and the other steps remain the same: if the current ambient temperature calculated according to formula 2 is greater than or equal to the second threshold, determine whether there is a shutdown command, if so, execute the shutdown process, if not, return to step 2.1.

[0108] It should be noted that this solution is implemented based on the fan running at full speed. At this time, the thermal resistance and thermal capacity of the objects inside the SVG module are constant values. When the air volume of the SVG module fan is a variable value, the thermal resistance and thermal capacity of the objects inside the SVG module are also variable values ​​and cannot be estimated.

[0109] According to the above SVG module thermal model, a control protection strategy and method for the output power of the IGBT converter in the SVG module is determined when the upper limit ambient temperature is exceeded.

[0110] The specific configuration ideas for the first threshold and the second threshold are as follows:

[0111] When Ta exceeds 45°C, when T1(t), T2(t), P(t), and Z2(t)=Rth2 are known, the specific temperature value of Ta can be calculated according to Formula 2. The experimenter takes Ta greater than 45°C as one of the necessary conditions for starting the SVG module flexible control program.

[0112] The method for acquiring the ambient temperature includes: acquiring the second temperature, and acquiring the current power generated by the IGBT module, substituting it into Formula 2 to obtain the value, or acquiring the value through a temperature sensor in the environment where the SVG module chassis is located.

[0113] The present application mainly adopts the method of obtaining the temperature by collecting the real-time second temperature T2 and calculating it, but it does not exclude the method of obtaining the temperature by directly installing a temperature sensor within a certain distance range (such as within 1 meter) of the SVG module chassis.

[0114] Furthermore, it also includes a process: if the first temperature is greater than the third threshold, the machine will shut down and give an alarm, and the third threshold is determined according to the maximum junction temperature limit of the IGBT module. The method for determining the third threshold according to the maximum junction temperature limit of the IGBT module is as follows: Exemplarily, the third threshold value of this application is 110°C. At present, the maximum junction temperature limit of the IGBT module given by most manufacturers is 150°C, and the maximum temperature limit of the bottom plate thermistor in the IGBT module is (150-X)°C. This is used as the SVG shutdown temperature limit value W1. The value of X combines the values ​​of the IGBT modules that have been listed by Chinese and foreign manufacturers, and considering the replaceability of the module, it is selected as 40°C. In this way, W1=110°C, and the SVG module is given a pre-overtemperature threshold buffer zone of 90°C<W2<110°C during design.

[0115] In addition, there are generally multiple IGBT modules in an SVG module, so there are multiple measured values ​​of the first temperature T1, and the maximum value is taken. T1=W2 or T1>90°C is used as the second necessary condition for starting the reactive compensation flexible control protection program.

[0116] When the overall thermal design of the SVG module is performed, if T1 is less than or equal to 90°C as the temperature standard when the module is working at full load under the condition of an ambient temperature of 45 degrees. After the actual design is completed, the T1 (45°C) value is obtained by experiment. Therefore, when the T1 (45°C) full load test value is less than or equal to 90°C, the thermal design of the SVG module is considered to meet the requirements.

[0117] For example, the first threshold value disclosed in this application is 90°C and the second threshold value is 45°C. In other SVG module products, the first threshold value and the second threshold value need to be determined according to the design standards of related products. For example, if there are some products that perform overall thermal design on the SVG module, if T1 is less than or equal to 85°C as the temperature standard when the module is working at full load under the condition of an ambient temperature of 45°C. Then the first threshold value is 85°C and the second threshold value is 45°C. Other specific parameters of the first threshold value and the second threshold value selected by those skilled in the art according to the above purpose are also within the protection scope.

[0118] The existing SVG module temperature protection logic is: when it is detected that the SVG module exceeds the preset protection threshold of 90°C, the SVG module automatically shuts down. The experimenters call this protection logic hard control protection logic.

[0119] The improved SVG module temperature protection logic is: the SVG module pre-overtemperature threshold buffer is preset to 90℃<W2<110℃. When the SVG module temperature reaches this threshold buffer, the module internal DSP software starts the flexible protection control program, which will flexibly adjust the SVG module IGBT converter output power according to the mathematical model established above, so that the module temperature is lower than the lower limit of the buffer temperature. The experimenters call this protection logic flexible control protection logic.

[0120] At the same time, when the ambient temperature Ta reaches the upper limit of the ambient temperature (that is, when Ta is greater than 45°C), the SVG module fan air volume output runs to the maximum value, and the temperature value T2 of the SVG module housing air inlet and the IGBT base plate temperature T1 are obtained through experiments under the change of the SVG module IGBT converter output power, as shown in the figure. Figure 3 shown.

[0121] According to the time constant τ, in the time range where the sampling time tc is greater than 5τ, the temperature value of the IGBT in the SVG module under any input power condition and a certain ambient temperature condition can be calculated using Formula 1.

[0122] It should be noted that 5τ is a theoretical value calculated based on the formula. In practical applications, the data calculated in the time range of τ≤tc≤5τ is not much different from 5τ or can be corrected with correction parameters. Therefore, the process in the figure is based on τ as an application reference.

[0123] It can be seen that the shorter the sampling time, the higher the data acquisition accuracy and the more accurate the control process. However, there will be certain errors in the calculation of the values ​​of Z1(t) and Z2(t). If the time constant τ is used as the sampling time, a correction parameter can be provided to ensure that Z1(t) and Z2(t) can be used as a constant value in this solution.

[0124] Substituting the time constant τ as the sampling time tc into Formula 3, we can see that Z(t)=Rth*0.63, and 0.63 is the correction parameter.

[0125] Similarly, when the SVG module measures that the T1 temperature enters the 90℃<W2<110℃ area, Rth1 and Rth2 are known conditions, and Formula 1 and Formula 2 can be used to calculate the power value of the SVG module that needs to be reduced to reduce T1 to less than 90℃ after 5τ time (or τ time).

[0126] The maximum junction temperature limit value given by the manufacturer's IGBT module is 150℃, and the maximum temperature limit value of the bottom plate thermistor in the IGBT module is 150-40=110℃. This is used as the SVG shutdown temperature limit value W1. Prevent abnormal over-temperature failure from causing damage to the SVG module. It should be noted that the maximum junction temperature limit values ​​given by IGBT modules from different manufacturers may be different, and they should be determined according to the actual product. The maximum temperature limit value of the bottom plate thermistor in the IGBT module set for the maximum junction temperature limit value can be obtained through multiple tests.

[0127] Figure 4 The main process of SVG module temperature control is disclosed. If the first threshold is 90°C, the second threshold is 45°C, and the third threshold is 110°C, combined with the hardware fault detection program and other processes, the SVG module flexible temperature control method is as follows:

[0128] S1, SVG module is powered on and the fan runs at full speed;

[0129] S2, SVG module hardware self-check, if the hardware is faulty, it will stop and display the fault information, if not, it will execute S3;

[0130] S3, monitoring the first temperature and the second temperature according to the sampling time;

[0131] S4, if the first temperature enters the window interval of 90°C<W2<110°C, the target generated power is calculated according to Formula 1 and Formula 2, and the inverter controls the power output according to the target generated power;

[0132] S5, if the first temperature is less than 90° C., the ambient temperature is calculated according to Formula 2; if the ambient temperature is greater than 45° C., the target generated power is calculated according to Formulas 1 and 2, and the inverter controls the power output according to the target generated power;

[0133] S6, if the first temperature is less than 90°C and the ambient temperature is less than 45°C, the inverter outputs a control program according to the normal temperature reactive power compensation demand, specifically referring to the reactive power compensation demand output control program with normal output within the standard range of "DLT1216-2013 Static VAR Compensation Device".

[0134] Exemplarily, the target first temperature is set to 88°C. When the SVG module exceeds the upper limit of the ambient temperature, the reactive compensation flexible control protection flow chart is as follows: Figure 5 When the SVG module exceeds the temperature limit, the power must be reduced to cool it down. The target power value needs to be set at a power value lower than 90°C. In addition, considering the time constant of temperature drop, the hysteresis value can be set within the range of 5°C. In this case, 88°C is selected.

[0135] Of course, in some embodiments, directly using 90°C as the target first temperature is also a feasible solution, and setting it to less than 90°C is safer. Figure 3 The 90℃ blue temperature line in the figure.

[0136] In addition, it should be noted that the shapes and names of the parts and components of the specific embodiments described in this specification may be different. Any equivalent or simple changes made based on the structure, features and principles described in the patent concept of the present invention are included in the protection scope of the patent of the present invention. The technicians in the technical field of the present invention can make various modifications or supplements to the specific embodiments described or replace them in a similar manner, as long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A flexible temperature control method for an SVG module, characterized in that: The following steps are involved: Step 1: Pre-build the SVG module heat transfer model, as shown in Formula 1 and Formula 2 T1(t)=P(t)*Z1(t)+T2(t); Formula 1 T2(t)=P(t)*Z2(t)+Ta(t); Formula 2 Among them, T1 is the temperature measured at the bottom plate inside the IGBT module, recorded as the first temperature, and the IGBT module is the core device of the inverter in the SVG module; T2 is the temperature measured at the air inlet of the cooling fan of the SVG module, recorded as the second temperature; Ta is the ambient temperature of the SVG module chassis; t is the time variable; P is the generated power of the SVG module; Z1 is the thermal impedance formed by all objects in the SVG module chassis, and Z2 is the thermal impedance formed by the ambient air where the SVG module chassis is located; Step 2: Power on the SVG module and run the fan at full speed. Step 3, determining the sampling time with a time constant, monitoring the first temperature and the second temperature according to the sampling time, wherein the time constant is the time value for the temperature to stabilize after the output power of the IGBT module changes; Step 4: If the first temperature is greater than the first threshold, or the ambient temperature is greater than the second threshold, execute step 5; Step 5, setting a target first temperature, substituting the target first temperature into Formula 1 and Formula 2 to calculate the target generated power, and the inverter controls the power output according to the target generated power; The target first temperature is less than or equal to a first threshold value; and the second threshold value is determined according to an ambient temperature required by an SVG module execution specification.

2. The SVG module flexible temperature control method according to claim 1, characterized in that: The method for controlling power output of an inverter according to target generated power includes: The reactive power demand value is calculated according to the AC sampling value of the power grid. If the reactive power demand value is less than or equal to the target generated power, the inverter is controlled to control the power output according to the reactive power demand value. If not, the inverter controls the power output according to the target generated power value.

3. The SVG module flexible temperature control method according to claim 1 or 2, characterized in that: After the inverter controls the power output according to the target power generation, step six is ​​further included, as follows: If the current first temperature is greater than or equal to the first threshold, return to step five; If the current first temperature is less than the first threshold, the current ambient temperature is calculated according to Formula 2. If the current ambient temperature is less than the second threshold, the inverter executes the normal temperature reactive power compensation demand output control program and continues to monitor the first temperature and the second temperature at the sampling time. If the current ambient temperature calculated according to Formula 2 is greater than or equal to the second threshold, it is determined whether there is a shutdown command. If so, the shutdown process is executed. If not, it returns to step three.

4. The SVG module flexible temperature control method according to claim 1 or 2, characterized in that: The method also includes a process in which if the first temperature is greater than a third threshold, the system is shut down and an alarm is given, wherein the third threshold is determined according to a maximum junction temperature limit value of the IGBT module.

5. The SVG module flexible temperature control method according to claim 1, characterized in that: The process is also included: if there are multiple IGBT modules in the SVG module, multiple first temperatures are detected, and the maximum value is compared with the first threshold.

6. The SVG module flexible temperature control method according to claim 1, characterized in that: The method for obtaining the ambient temperature includes: The second temperature is collected, and the current power generated by the IGBT module is obtained and substituted into Formula 2 for calculation, or collected through a temperature sensor in the environment where the SVG module chassis is located.

7. The SVG module flexible temperature control method according to claim 1, characterized in that: The construction methods of Formula 1 and Formula 2 include: Determine the first temperature measurement point, the second temperature measurement point and the third temperature measurement point of the SVG module chassis, wherein: The first temperature measuring point is located at the bottom plate inside the IGBT module, and the temperature measured at the first temperature measuring point is recorded as the first temperature T1; The second temperature measuring point is located at the air inlet of the cooling fan of the SVG module, and the temperature measured at the second temperature measuring point is recorded as the second temperature T2; The third temperature measurement point is located at the ambient temperature of the SVG module chassis, and the ambient temperature is recorded as Ta; According to the heat transfer relationship between the first temperature measuring point, the second temperature measuring point and the third temperature measuring point, Formula 1 and Formula 2 are constructed: Construct a temperature-controllable experimental environment and output at least one ambient temperature; At each ambient temperature, the SVG module is started to output several fixed power points. According to the first temperature and the second temperature at different output powers, the Z1 and Z2 parameter values ​​at different ambient temperatures are calculated by substituting them into Formula 1 and Formula 2.

8. The SVG module flexible temperature control method according to claim 1, characterized in that: The method for calculating the time constant τ includes: at each ambient temperature, starting the SVG module to output a plurality of fixed power points, recording the first temperature, the second temperature and the time value of temperature stabilization after outputting the corresponding fixed power points at different output powers, and calculating the average value of the time value of temperature stabilization as the time constant τ.

9. The SVG module flexible temperature control method according to claim 1 or 8, characterized in that: The sampling time tc ranges from τ≤tc≤5τ, where τ is the time constant, i.e., the time value for temperature stabilization after the output power changes.

10. An SVG module device, characterized in that: The temperature is controlled by using the SVG module flexible temperature control method described in any one of claims 1 to 9.

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