CN109240195B - Control method and control system for cooling system of oil-immersed converter transformer - Google Patents
Control method and control system for cooling system of oil-immersed converter transformer Download PDFInfo
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- CN109240195B CN109240195B CN201811221038.6A CN201811221038A CN109240195B CN 109240195 B CN109240195 B CN 109240195B CN 201811221038 A CN201811221038 A CN 201811221038A CN 109240195 B CN109240195 B CN 109240195B
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B19/00—Programme-control systems
- G05B19/02—Programme-control systems electric
- G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
- G05B19/05—Programmable logic controllers, e.g. simulating logic interconnections of signals according to ladder diagrams or function charts
- G05B19/054—Input/output
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/08—Cooling; Ventilating
- H01F27/085—Cooling by ambient air
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/08—Cooling; Ventilating
- H01F27/10—Liquid cooling
- H01F27/12—Oil cooling
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/10—Plc systems
- G05B2219/11—Plc I-O input output
- G05B2219/1105—I-O
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Abstract
The invention discloses a control method and a control system for a cooling system of an oil-immersed converter transformer. The method determines whether the cooler needs to be started according to the top oil temperature or the current load, and further determines the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started cooler according to the harmonic content when the cooler needs to be started. Therefore, the starting number of the coolers is determined according to the harmonic content of the converter transformer during operation, the operation speed of the circulating oil pump and the cooling fan is controlled in real time based on the harmonic content, the condition that the temperature distribution difference of hot spots of the converter transformer is large when the harmonic component is serious is fully considered, the temperature rise of the converter transformer is reliably and effectively controlled, the safe and stable operation of the converter transformer can be ensured, and the on-site detection effect and the engineering practical value are good.
Description
Technical Field
The invention relates to the field of cooling systems, in particular to a control method and a control system for a cooling system of an oil-immersed converter transformer.
Background
With the development of direct-current transmission systems in China, the transmission grade is higher and higher, the demand of ultrahigh-voltage and extra-high-voltage direct-current converter transformers is increased continuously, and the guarantee of safe and stable operation is particularly important. The converter transformer is used as core power equipment in a direct current transmission project and has important functions of rectifying alternating current and inverting direct current. The converter transformer is accompanied by more high-frequency harmonic waves during operation, which has great test on the performances of the converter transformer such as electric heating and the like. When the harmonic wave is serious, the dielectric loss of the converter transformer is increased, the stray loss of the converter transformer is increased due to the magnetic leakage of the harmonic wave, and meanwhile, the problems of serious additional loss and local overheating generated in an iron core, a winding and a metal structural part of the converter transformer are caused due to the heating problem caused by the skin effect of a conductor under the harmonic wave, the insulation aging problem caused by thermal failure is caused, even the large-area power failure caused by the converter station accident can be directly caused, and the disastrous loss is caused.
At present, a conventional large oil-immersed converter transformer generally adopts a forced oil circulation air cooling mode, and when the temperature of the converter transformer rises, the switching of a fan and an oil pump of the converter transformer is controlled by acquiring data such as top oil temperature, actual load and the like of the converter transformer, so that the effect of cooling the converter transformer is achieved. However, the harmonic waves existing in the converter transformer cause large temperature distribution differences of hot spots of the converter transformer, so that the conventional forced oil circulation air cooling mode cannot ensure safe and stable operation of the converter transformer.
Disclosure of Invention
The invention aims to provide a control method and a control system for a cooling system of an oil-immersed converter transformer, which fully consider the situation that the temperature distribution difference of hot spots of the converter transformer is large when harmonic components are serious, realize reliable and effective control on the temperature rise of the converter transformer, ensure the safe and stable operation of the converter transformer and have good field detection effect and engineering practical value.
In order to achieve the purpose, the invention provides the following scheme:
a control method of a cooling system of an oil-immersed converter transformer comprises a plurality of groups of coolers, wherein each group of coolers comprises a circulating oil pump, a circulating oil pump motor connected with the circulating oil pump, a cooling fan and a cooling fan motor connected with the cooling fan, and the control method comprises the following steps:
acquiring the top oil temperature of the converter transformer and the current load of the converter transformer;
determining whether a cooler needs to be started according to the top oil temperature or the current load to obtain a first judgment result;
when the first judgment result shows that the cooler needs to be started, acquiring the harmonic content of the converter transformer;
and determining the rotating speed of a circulating oil pump motor of the started cooler and the rotating speed of a cooling fan motor according to the harmonic content.
Optionally, the determining whether the cooler needs to be started according to the top oil temperature or the current load to obtain a first determination result specifically includes:
acquiring a rated load of the converter transformer and a top oil temperature threshold value of the converter transformer;
judging whether a cooler starting condition is met or not, and obtaining a first judgment result, wherein the cooler starting condition is as follows: the current load is greater than or equal to 0.7 times of the rated load, or the top oil temperature is greater than or equal to the top oil temperature threshold.
Optionally, the determining the rotation speed of the circulating oil pump motor and the rotation speed of the cooling fan motor of the started cooler according to the harmonic content specifically includes:
obtaining a harmonic content interval, wherein the harmonic content interval comprises: a first harmonic interval, a second harmonic interval, a third harmonic interval and a fourth harmonic interval;
determining a harmonic content interval in which the harmonic content is located;
when the harmonic content interval in which the harmonic content is located is a first harmonic interval, starting a group of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content;
when the harmonic content interval in which the harmonic content is located is a second harmonic interval, starting two groups of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content;
when the harmonic content interval in which the harmonic content is located is a third harmonic interval, starting three groups of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content;
and when the harmonic content interval in which the harmonic content is located is a fourth harmonic interval, starting four groups of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content.
Optionally, the first harmonic interval is (0, 10%), the second harmonic interval is [ 10%, 15%), the third harmonic interval is [ 15%, 20%), and the fourth harmonic interval is [ 20%, 50%).
Optionally, the determining, according to the harmonic content, the rotation speed of the circulating oil pump motor of the cooler and the rotation speed of the cooling fan motor that are started includes:
judging whether the harmonic content is smaller than a harmonic threshold value or not, and obtaining a second judgment result;
when the second judgment result shows that the harmonic content is greater than or equal to the harmonic threshold, determining that the rotating speed of the circulating oil pump motor is the maximum rotating speed of the circulating oil pump motor, and the rotating speed of the cooling fan motor is the maximum rotating speed of the cooling fan motor;
when the second determination result indicates that the harmonic content is less than a harmonic threshold,
according to the formula:
determining the frequency of the circulating oil pump motor, wherein f1Representing the frequency of the circulating oil pump motor, HRU representing the harmonic content, HRUmaxRepresenting the harmonic threshold, fmax1Representing the frequency corresponding to the maximum rotating speed of the circulating oil pump motor;
according to the formula:
determining the frequency of the cooling fan motor, wherein f2Indicating the frequency of the cooling fan motor, fmax2A frequency indicating a maximum rotation speed of the cooling fan motor;
according to the formula:
determining the rotational speed of the circulating oil pump motor, wherein n1Indicating the rotational speed, p, of the circulating oil pump motor1The number of pole pairs of a circulating oil pump motor is represented; s1The slip ratio of the circulating oil pump motor is represented;
according to the formula:
determining the rotational speed of the cooling fan motor, where n2Indicating the speed of rotation, p, of the cooling fan motor2Representing the number of pole pairs of the cooling fan motor; s2Indicating the slip of the cooling fan motor.
The utility model provides a control system of oil-immersed converter transformer's cooling system, cooling system includes the multiunit cooler, every group the cooler include the circulating oil pump, with circulating oil pump motor, the cooling fan that the circulating oil pump is connected and with the cooling fan motor that the cooling fan is connected, control system includes:
the oil temperature and load acquisition module is used for acquiring the top oil temperature of the converter transformer and the current load of the converter transformer;
the first judgment module is used for determining whether the cooler needs to be started according to the top oil temperature or the current load to obtain a first judgment result;
the harmonic content obtaining module is used for obtaining the harmonic content of the converter transformer when the first judgment result shows that the cooler needs to be started;
and the motor rotating speed determining module is used for determining the rotating speed of a circulating oil pump motor of the started cooler and the rotating speed of a cooling fan motor according to the harmonic content.
Optionally, the first determining module includes:
the device comprises a rated load and oil temperature threshold value obtaining unit, a control unit and a control unit, wherein the rated load and oil temperature threshold value obtaining unit is used for obtaining the rated load of the converter transformer and the top layer oil temperature threshold value of the converter transformer;
the first judgment unit is used for judging whether a cooler starting condition is met or not and obtaining a first judgment result, wherein the cooler starting condition is as follows: the current load is greater than or equal to 0.7 times of the rated load, or the top oil temperature is greater than or equal to the top oil temperature threshold.
Optionally, the motor speed determination module includes:
a harmonic interval acquisition unit configured to acquire a harmonic content interval, where the harmonic content interval includes: a first harmonic interval, a second harmonic interval, a third harmonic interval and a fourth harmonic interval;
the harmonic content interval determining unit is used for determining a harmonic content interval in which the harmonic content is located;
a cooler starting unit for
When the harmonic content interval in which the harmonic content is located is a first harmonic interval, starting a group of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content;
when the harmonic content interval in which the harmonic content is located is a second harmonic interval, starting two groups of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content;
when the harmonic content interval in which the harmonic content is located is a third harmonic interval, starting three groups of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content;
and when the harmonic content interval in which the harmonic content is located is a fourth harmonic interval, starting four groups of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content.
A cooling system for an oil immersed converter transformer, the cooling system comprising: a temperature sensor, a variable frequency power sensor, an A/D conversion module, a controller, a variable frequency speed regulator, a cooling fan motor, a cooling fan, a circulating oil pump motor and a circulating oil pump, wherein,
the temperature sensor and the variable-frequency power sensor are both connected with a converter transformer, the A/D conversion module is respectively connected with the variable-frequency power sensor and the temperature sensor, the controller is respectively connected with the A/D conversion module and the variable-frequency speed regulator, the variable-frequency speed regulator is respectively connected with the cooling fan motor and the circulating oil pump motor, the cooling fan is connected with the cooling fan motor, the circulating oil pump is connected with the circulating oil pump motor, and the controller is used for controlling the cooling fan motor to move to drive the cooling fan to rotate according to the control method and controlling the circulating oil pump motor to move to drive the circulating oil pump to move.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the control method and the control system for the cooling system of the oil-immersed converter transformer provided by the invention determine whether the cooler needs to be started according to the top oil temperature and the current load, and further determine the rotating speed of a circulating oil pump motor of the started cooler and the rotating speed of a cooling fan motor according to the harmonic content when the cooler needs to be started. Therefore, the starting number of the coolers is determined according to the harmonic content of the converter transformer during operation, the operation speed of the circulating oil pump and the cooling fan is controlled in real time based on the harmonic content, the condition that the temperature distribution difference of hot spots of the converter transformer is large when the harmonic component is serious is fully considered, the temperature rise of the converter transformer is reliably and effectively controlled, the safe and stable operation of the converter transformer can be ensured, and the on-site detection effect and the engineering practical value are good.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
Fig. 1 is a flowchart of a control method for a cooling system of an oil-immersed converter transformer according to an embodiment of the present invention;
fig. 2 is a block diagram of a control system of a cooling system of an oil-immersed converter transformer according to an embodiment of the present invention;
fig. 3 is a block diagram of a cooling system of an oil-immersed converter transformer according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a control method and a control system for a cooling system of an oil-immersed converter transformer, which fully consider the situation that the temperature distribution difference of hot spots of the converter transformer is large when harmonic components are serious, realize reliable and effective control on the temperature rise of the converter transformer, ensure the safe and stable operation of the converter transformer and have good field detection effect and engineering practical value.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Fig. 1 is a flowchart of a control method for a cooling system of an oil-immersed converter transformer according to an embodiment of the present invention. As shown in fig. 1, a method for controlling a cooling system of an oil-immersed converter transformer, where the cooling system includes multiple groups of coolers, and each group of coolers includes a circulating oil pump, a circulating oil pump motor connected to the circulating oil pump, a cooling fan, and a cooling fan motor connected to the cooling fan, the method includes:
step 101: and acquiring the top oil temperature of the converter transformer and the current load of the converter transformer.
Step 102: and determining whether a cooler needs to be started according to the top oil temperature or the current load to obtain a first judgment result.
Step 103: and when the first judgment result shows that the cooler needs to be started, acquiring the harmonic content of the converter transformer.
Step 104: and determining the rotating speed of a circulating oil pump motor of the started cooler and the rotating speed of a cooling fan motor according to the harmonic content.
Specifically, step 102: determining whether a cooler needs to be started according to the top oil temperature or the current load to obtain a first judgment result, which specifically comprises:
acquiring a rated load of the converter transformer and a top oil temperature threshold value of the converter transformer;
judging whether a cooler starting condition is met or not, and obtaining a first judgment result, wherein the cooler starting condition is as follows: the current load is greater than or equal to 0.7 times of the rated load, or the top oil temperature is greater than or equal to the top oil temperature threshold. The range of the top oil temperature threshold is [50 ℃, 60 ℃), and preferably, the top oil temperature threshold is 55 ℃.
Specifically, step 104: determining the rotating speed of a circulating oil pump motor of the started cooler and the rotating speed of a cooling fan motor according to the harmonic content, and specifically comprising the following steps of:
obtaining a harmonic content interval, wherein the harmonic content interval comprises: a first harmonic interval, a second harmonic interval, a third harmonic interval, and a fourth harmonic interval. In this embodiment, the first harmonic interval is (0, 10%), the second harmonic interval is [ 10%, 15%), the third harmonic interval is [ 15%, 20%), and the fourth harmonic interval is [ 20%, 50%);
determining a harmonic content interval in which the harmonic content is located;
when the harmonic content interval in which the harmonic content is located is a first harmonic interval, starting a group of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content;
when the harmonic content interval in which the harmonic content is located is a second harmonic interval, starting two groups of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content;
when the harmonic content interval in which the harmonic content is located is a third harmonic interval, starting three groups of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content;
and when the harmonic content interval in which the harmonic content is located is a fourth harmonic interval, starting four groups of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content.
Further, the determining the rotation speed of the started circulating oil pump motor of the cooler and the rotation speed of the cooling fan motor according to the harmonic content specifically includes:
and judging whether the harmonic content is smaller than a harmonic threshold value or not, and obtaining a second judgment result. Optionally, the range of the harmonic threshold is 20% to 30%, and the harmonic threshold in this embodiment is 20%;
when the second judgment result shows that the harmonic content is greater than or equal to the harmonic threshold, determining that the rotating speed of the circulating oil pump motor is the maximum rotating speed of the circulating oil pump motor, and the rotating speed of the cooling fan motor is the maximum rotating speed of the cooling fan motor;
when the second determination result indicates that the harmonic content is less than a harmonic threshold,
according to the formula:
determining the frequency of the circulating oil pump motor, wherein f1Representing the frequency of the circulating oil pump motor, HRU representing the harmonic content, HRUmaxRepresenting the harmonic threshold, fmax1Representing the frequency corresponding to the maximum rotating speed of the circulating oil pump motor;
according to the formula:
determining the frequency of the cooling fan motor, wherein f2Indicating the frequency of the cooling fan motor, fmax2A frequency indicating a maximum rotation speed of the cooling fan motor;
according to the formula:
determining the rotational speed of the circulating oil pump motor, wherein n1Indicating the rotational speed, p, of the circulating oil pump motor1The number of pole pairs of a circulating oil pump motor is represented; s1The slip ratio of the circulating oil pump motor is represented;
according to the formula:
determining the rotational speed of the cooling fan motor, where n2Indicating the speed of rotation, p, of the cooling fan motor2Representing the number of pole pairs of the cooling fan motor; s2Indicating the slip of the cooling fan motor.
Fig. 2 is a block diagram of a control system of a cooling system of an oil-immersed converter transformer according to an embodiment of the present invention. As shown in fig. 2, a control system of a cooling system of an oil-immersed converter transformer, where the cooling system includes multiple groups of coolers, each group of coolers includes a circulating oil pump, a circulating oil pump motor connected to the circulating oil pump, a cooling fan, and a cooling fan motor connected to the cooling fan, and the control system includes:
the oil temperature and load obtaining module 201 is used for obtaining the top oil temperature of the converter transformer and the current load of the converter transformer;
a first determining module 202, configured to determine whether a cooler needs to be started according to the top oil temperature or the current load, and obtain a first determination result;
a harmonic content obtaining module 203, configured to obtain a harmonic content of the converter transformer when the first determination result indicates that the cooler needs to be started;
and a motor rotating speed determining module 204, configured to determine a rotating speed of a circulating oil pump motor of the started cooler and a rotating speed of a cooling fan motor according to the harmonic content.
Specifically, the first determining module 202 includes:
the device comprises a rated load and oil temperature threshold value obtaining unit, a control unit and a control unit, wherein the rated load and oil temperature threshold value obtaining unit is used for obtaining the rated load of the converter transformer and the top layer oil temperature threshold value of the converter transformer;
the first judgment unit is used for judging whether a cooler starting condition is met or not and obtaining a first judgment result, wherein the cooler starting condition is as follows: the current load is greater than or equal to 0.7 times of the rated load, or the top oil temperature is greater than or equal to the top oil temperature threshold.
Specifically, the motor speed determination module 204 includes:
a harmonic interval acquisition unit configured to acquire a harmonic content interval, where the harmonic content interval includes: a first harmonic interval, a second harmonic interval, a third harmonic interval and a fourth harmonic interval;
the harmonic content interval determining unit is used for determining a harmonic content interval in which the harmonic content is located;
a cooler starting unit for
When the harmonic content interval in which the harmonic content is located is a first harmonic interval, starting a group of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content;
when the harmonic content interval in which the harmonic content is located is a second harmonic interval, starting two groups of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content;
when the harmonic content interval in which the harmonic content is located is a third harmonic interval, starting three groups of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content;
and when the harmonic content interval in which the harmonic content is located is a fourth harmonic interval, starting four groups of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content.
Fig. 3 is a block diagram of a cooling system of an oil-immersed converter transformer according to an embodiment of the present invention. As shown in fig. 3, a cooling system of an oil-immersed converter transformer includes: a temperature sensor 300, a variable frequency power sensor 301, an A/D conversion module 302, a controller 303, a variable frequency governor 304, a cooling fan motor 305, a cooling fan 306, a circulating oil pump motor 307 and a circulating oil pump 308. In this embodiment, the controller 303 is a PLC controller.
The temperature sensor 300 and the variable frequency power sensor 301 are both connected to a converter transformer, the a/D conversion module 302 is connected to the variable frequency power sensor 301 and the temperature sensor 300, the controller 303 is connected to the a/D conversion module 302 and the variable frequency speed regulator 304, the variable frequency speed regulator 304 is connected to the cooling fan motor 305 and the circulating oil pump motor 307, the cooling fan 306 is connected to the cooling fan motor 305, the circulating oil pump 308 is connected to the circulating oil pump motor 307, and the controller 303 is configured to control the cooling fan motor 305 to drive the cooling fan 306 to rotate according to the control method, and control the circulating oil pump motor 307 to drive the circulating oil pump 308 to move.
It can be seen that the cooling system comprises three major parts: the first part is an oil circuit system composed of a cooler body, an oil flow pipeline, a valve and the like, the second part is an air flow system composed of a fan blade, a motor, an air duct and the like, and the third part is a circuit system formed by connecting an alternating current contactor, a relay, a temperature sensor, a wiring terminal, an electric wire and the like. The circuit system controls the oil circuit system and the air flow system to reasonably and effectively control the operating temperature of the converter transformer so as to ensure the uniform temperature of the converter transformer. Specifically, the temperature sensor 300 is configured to acquire a top layer oil temperature of the converter transformer and a working environment temperature of the converter transformer, the variable frequency power sensor 301 is configured to acquire each subharmonic content in the converter transformer, the a/D conversion module 302 converts an analog signal of the sensor into a digital signal and transmits the digital signal to the controller 303, and the controller 303 controls the variable frequency speed regulator 304 to control the cooling fan motor 305 of the converter transformer cooling system to move to drive the cooling fan 306 to rotate, and controls the circulating oil pump motor 307 to move to drive the circulating oil pump 308 to move.
In this embodiment, the variable frequency power sensor 301 is used to obtain the harmonic content of each time of the converter transformer, the variable frequency power sensor 301 performs ac sampling on the current signal in the converter transformer, and then connects the sampled value with the digital input secondary instrument through a transmission system such as a cable or an optical fiber, the a/D conversion module 302 performs calculation on the sampled value of the current to obtain parameters such as fundamental current and harmonic current, and the variable frequency power sensor 301 can be used to measure any electrical parameter within a bandwidth range. And when the capacity of the oil-immersed converter transformer exceeds 180000kVA or the voltage is more than 220kV, cooling the transformer by adopting a strong oil circulating air cooling mode. The variable frequency power sensor 301 uses the broadband characteristics of the SP series variable frequency power sensor, particularly the broadband characteristics at high voltage, and can be used for harmonic analysis or power quality analysis in the case where higher harmonics are contained, such as the output of a frequency converter. The a/D conversion module 302 converts the analog signal collected by the variable frequency power sensor into a digital signal through a certain circuit and transmits the digital signal to the controller 303, so as to control the variable frequency governor after program operation.
The controller 303 is a control center of the cooling system, and reasonably controls the output of a cooling fan and a circulating oil pump of the converter transformer through signals acquired by the sensor. The variable frequency governor 304 controls the rotation speed of the asynchronous motor by changing the frequency of the alternating current. The circulating oil pump of the converter transformer adopts a medium-speed pump and a 4-pole motor, and the rotating speed is close to 1500 r/min. The cooling fan of the converter transformer is additionally provided with an air duct, a mesh enclosure and a related supporting device, and is matched with a fan with high wind speed and high total pressure head.
In this embodiment, the converter transformer cooling system includes 5 sets of coolers, and each set has 1 circulating oil pump and 3 cooling fans. When the harmonic content detected in real time is within the (0, 10%) interval, 1 group of coolers is started, and the coolers comprise 1 oil pump and 3 fans. When the harmonic content detected in real time is in the range of [ 10%, 15%), 2 groups of coolers are started, including 2 oil pumps and 6 fans. When the harmonic content detected in real time is in the interval of [ 15%, 20%), starting 3 groups of coolers comprising 3 oil pumps and 9 fans. When the harmonic content detected in real time is in the interval of [ 20%, 50%), 4 groups of coolers are started, including 4 oil pumps and 12 fans. In order to meet various operation conditions of the converter transformer, 1 standby cooler is additionally arranged, and the converter transformer can be automatically put into operation when the operation cooler fails. Each converter transformer has 15 fans, and the group hierarchical control is adopted, so that the automatic switching of the cooler follows the principle of 'first-throw first-retreat and circular standby'.
For example, each unequal harmonic component exists in a 500kV converter transformer, and the measured ratio of the fundamental component to each harmonic component (subharmonic) is approximately 1:0.172:0.105:0.039:0.021:0.012:0.0098, wherein when the harmonic component is greater than 23 or more, the ratio of the harmonic component to the fundamental is less than 0.01, so that the harmonics of 23 or more can be ignored, and the ratio of the total harmonic component is approximately 27.5%.
The interval of the harmonic content of the converter transformer is the fourth harmonic interval, the harmonic content is serious, so that the converter transformer is high in loss and serious in heating, and 4 groups of coolers are used in the cooling system and comprise 4 circulating oil pumps and 12 cooling fans, so that the converter transformer is ensured to be uniform in temperature, and the problem of local overheating is avoided.
Meanwhile, the PLC controller sends an instruction to the variable frequency speed regulator 304 according to the harmonic content of the converter transformer obtained by the variable frequency power sensor 301, and performs variable frequency speed regulation control on the output of the cooling fan and the circulating oil pump of the converter transformer. In the embodiment, the asynchronous motor of the cooling fan is a 4-pole motor with the rotating speed of 1450r/min, and is used for a fan with the diameter of an impeller not larger than 400 mm; the circulating oil pump of the converter transformer adopts a medium-speed pump and a 4-pole motor, and the rotating speed is close to 1500 r/min.
The invention determines the number of the starting groups of the cooling fan and the circulating oil pump of the converter transformer and the output power according to the harmonic content of the converter transformer during operation, fully considers the condition of larger temperature distribution difference of hot spots of the converter transformer when the harmonic component is serious, realizes reliable and effective control on the temperature rise of the converter transformer, can ensure the safe and stable operation of the converter transformer, and has good field detection effect and engineering practical value.
Claims (9)
1. A control method for a cooling system of an oil-immersed converter transformer is characterized in that the cooling system comprises a plurality of groups of coolers, each group of coolers comprises a circulating oil pump, a circulating oil pump motor connected with the circulating oil pump, a cooling fan and a cooling fan motor connected with the cooling fan, and the control method comprises the following steps:
acquiring the top oil temperature of the converter transformer and the current load of the converter transformer;
determining whether a cooler needs to be started according to the top oil temperature or the current load to obtain a first judgment result;
when the first judgment result shows that the cooler needs to be started, acquiring the harmonic content of the converter transformer;
and determining the rotating speed of a circulating oil pump motor of the started cooler and the rotating speed of a cooling fan motor according to the harmonic content.
2. The control method according to claim 1, wherein the determining whether the cooler needs to be started according to the top oil temperature or the current load to obtain a first determination result specifically includes:
acquiring a rated load of the converter transformer and a top oil temperature threshold value of the converter transformer;
judging whether a cooler starting condition is met or not, and obtaining a first judgment result, wherein the cooler starting condition is as follows: the current load is greater than or equal to 0.7 times of the rated load, or the top oil temperature is greater than or equal to the top oil temperature threshold.
3. The control method according to claim 1, wherein the determining of the rotation speed of the circulating oil pump motor and the rotation speed of the cooling fan motor of the started cooler according to the harmonic content specifically comprises:
obtaining a harmonic content interval, wherein the harmonic content interval comprises: a first harmonic interval, a second harmonic interval, a third harmonic interval and a fourth harmonic interval;
determining a harmonic content interval in which the harmonic content is located;
when the harmonic content interval in which the harmonic content is located is a first harmonic interval, starting a group of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content;
when the harmonic content interval in which the harmonic content is located is a second harmonic interval, starting two groups of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content;
when the harmonic content interval in which the harmonic content is located is a third harmonic interval, starting three groups of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content;
and when the harmonic content interval in which the harmonic content is located is a fourth harmonic interval, starting four groups of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content.
4. The control method according to claim 3, characterized in that the first harmonic interval is (0, 10%), the second harmonic interval is [ 10%, 15%), the third harmonic interval is [ 15%, 20%), and the fourth harmonic interval is [ 20%, 50%).
5. The control method according to claim 3, wherein the determining of the rotation speed of the circulating oil pump motor and the rotation speed of the cooling fan motor of the started cooler according to the harmonic content specifically comprises:
judging whether the harmonic content is smaller than a harmonic threshold value or not, and obtaining a second judgment result;
when the second judgment result shows that the harmonic content is greater than or equal to the harmonic threshold, determining that the rotating speed of the circulating oil pump motor is the maximum rotating speed of the circulating oil pump motor, and the rotating speed of the cooling fan motor is the maximum rotating speed of the cooling fan motor;
when the second determination result indicates that the harmonic content is less than a harmonic threshold,
according to the formula:
determining the frequency of the circulating oil pump motor, wherein f1Representing the frequency of the circulating oil pump motor, HRU representing the harmonic content, HRUmaxRepresenting the harmonic threshold, fmax1Representing the frequency corresponding to the maximum rotating speed of the circulating oil pump motor;
according to the formula:
determining the frequency of the cooling fan motor, wherein f2Indicating the frequency of the cooling fan motor, fmax2A frequency indicating a maximum rotation speed of the cooling fan motor;
according to the formula:
determining the rotational speed of the circulating oil pump motor, wherein n1Indicating the rotational speed, p, of the circulating oil pump motor1The number of pole pairs of a circulating oil pump motor is represented; s1The slip ratio of the circulating oil pump motor is represented;
according to the formula:
determining the rotational speed of the cooling fan motor, where n2Indicating the speed of rotation, p, of the cooling fan motor2Representing the number of pole pairs of the cooling fan motor; s2Showing cooling fan motorsSlip ratio.
6. The utility model provides a control system of oil-immersed converter transformer's cooling system, its characterized in that, cooling system includes the multiunit cooler, every group the cooler include circulating oil pump, with circulating oil pump motor, cooling fan that circulating oil pump is connected and with the cooling fan motor that cooling fan is connected, control system includes:
the oil temperature and load acquisition module is used for acquiring the top oil temperature of the converter transformer and the current load of the converter transformer;
the first judgment module is used for determining whether the cooler needs to be started according to the top oil temperature or the current load to obtain a first judgment result;
the harmonic content obtaining module is used for obtaining the harmonic content of the converter transformer when the first judgment result shows that the cooler needs to be started;
and the motor rotating speed determining module is used for determining the rotating speed of a circulating oil pump motor of the started cooler and the rotating speed of a cooling fan motor according to the harmonic content.
7. The control system of claim 6, wherein the first determining module comprises:
the device comprises a rated load and oil temperature threshold value obtaining unit, a control unit and a control unit, wherein the rated load and oil temperature threshold value obtaining unit is used for obtaining the rated load of the converter transformer and the top layer oil temperature threshold value of the converter transformer;
the first judgment unit is used for judging whether a cooler starting condition is met or not and obtaining a first judgment result, wherein the cooler starting condition is as follows: the current load is greater than or equal to 0.7 times of the rated load, or the top oil temperature is greater than or equal to the top oil temperature threshold.
8. The control system of claim 6, wherein the motor speed determination module comprises:
a harmonic interval acquisition unit configured to acquire a harmonic content interval, where the harmonic content interval includes: a first harmonic interval, a second harmonic interval, a third harmonic interval and a fourth harmonic interval;
the harmonic content interval determining unit is used for determining a harmonic content interval in which the harmonic content is located;
a cooler starting unit for
When the harmonic content interval in which the harmonic content is located is a first harmonic interval, starting a group of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content;
when the harmonic content interval in which the harmonic content is located is a second harmonic interval, starting two groups of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content;
when the harmonic content interval in which the harmonic content is located is a third harmonic interval, starting three groups of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content;
and when the harmonic content interval in which the harmonic content is located is a fourth harmonic interval, starting four groups of coolers, and determining the rotating speed of a circulating oil pump motor and the rotating speed of a cooling fan motor of the started coolers according to the harmonic content.
9. A cooling system for an oil immersed converter transformer, the cooling system comprising: a temperature sensor, a variable frequency power sensor, an A/D conversion module, a controller, a variable frequency speed regulator, a cooling fan motor, a cooling fan, a circulating oil pump motor and a circulating oil pump, wherein,
the temperature sensor and the variable-frequency power sensor are both connected with a converter transformer, the A/D conversion module is respectively connected with the variable-frequency power sensor and the temperature sensor, the controller is respectively connected with the A/D conversion module and the variable-frequency speed regulator, the variable-frequency speed regulator is respectively connected with the cooling fan motor and the circulating oil pump motor, the cooling fan is connected with the cooling fan motor, the circulating oil pump is connected with the circulating oil pump motor, and the controller is used for controlling the cooling fan motor to move to drive the cooling fan to rotate according to the control method of any one of claims 1 to 5 and controlling the circulating oil pump motor to move to drive the circulating oil pump to move.
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| CN113123990B (en) * | 2021-04-30 | 2022-04-08 | 中国矿业大学 | Oil-immersed transformer fan air quantity abnormity monitoring method based on oil index identification |
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