Converter cooling system and control method thereof and converter

Abstract

Provided are a converter cooling system and a control method thereof and a converter, wherein the converter cooling system comprises: a two-speed circulation pump, whose outlet is connected to the water inlet of the converter via a pipeline; and an external cooling radiator, whose water inlet is connected to the water outlet of the converter via a pipeline, and whose water outlet is connected to the inlet of the two-speed circulation pump via a pipeline, wherein the two-speed circulation pump is a circulation pump capable of operating at a predetermined speed and a speed less than the predetermined speed, and the two-speed circulation pump operates at a speed less than the predetermined speed in response to the operating power of the converter being less than or equal to a predetermined threshold. The converter cooling system can adjust the flow rate of the cooling medium in the cooling system in real time according to the operating power of the converter, thereby reducing the power consumption of the circulation pump, reducing the self-consumption of electricity during the operation of the wind turbine generator set, and increasing the operating power generation of the wind turbine generator set.

Description

Technical Field

[0001] The present disclosure belongs to the technical field of wind power converter cooling, and more specifically, relates to a converter cooling system and a control method thereof, and a converter. Background Art

[0002] At present, the converter used as the core component in the megawatt-class wind turbine is a full-power water-cooled converter, which mainly uses water cooling to dissipate heat from the converter. This water-cooling method relies on a circulating pump to drive a cooling medium with a constant pressure and flow rate to flow continuously through the converter power device cold plate and the water-air heat exchanger in the converter cabinet, so that after taking out the heat, it exchanges heat with the atmosphere through an external cooling radiator and dissipates the heat into the air. At present, the circulating pumps used in the converter cooling system in the wind power industry mostly use single-speed centrifugal pumps. This single-speed circulating pump can provide the cooling medium with a constant pressure and flow rate required for converter cooling to ensure that the converter can operate at full power. However, the wind turbine is in a low-power operating state most of the time. At this time, the converter has a low operating power and generates a small loss. A lower cooling capacity can meet its heat dissipation needs. Therefore, the converter cooling system using a single-speed circulating pump has a large power loss, which leads to an increase in self-consumption of electricity during the operation of the wind turbine. Summary of the invention

[0003] The purpose of the exemplary embodiment of the present disclosure is to provide a converter cooling system and a control method thereof and a converter. The converter cooling system uses a dual-speed circulation pump, which can adjust the flow rate of the cooling medium in the cooling system in real time according to the operating power of the converter, thereby reducing the power loss of the circulation pump, and reducing the self-consumption of electricity during the operation of the wind turbine generator set, thereby increasing the operating power generation of the wind turbine generator set.

[0004] An exemplary embodiment of the present disclosure provides, on the one hand, a converter cooling system, characterized in that the converter cooling system comprises: a two-speed circulation pump, whose outlet is connected to the water inlet of the converter via a pipeline; and an external cooling radiator, whose water inlet is connected to the water outlet of the converter via a pipeline, and whose water outlet is connected to the inlet of the two-speed circulation pump via a pipeline, wherein the two-speed circulation pump is a circulation pump capable of operating at a predetermined speed and a speed less than the predetermined speed, and the two-speed circulation pump operates at a speed less than the predetermined speed in response to the operating power of the converter being less than or equal to a predetermined threshold.

[0005] Optionally, the dual-speed circulation pump operates at the predetermined speed in response to the operating power of the inverter being greater than the predetermined threshold.

[0006] Optionally, the predetermined threshold is determined based on an operating power of the converter when the dual-speed circulation pump operates at a rotation speed less than the predetermined rotation speed.

[0007] Optionally, the predetermined threshold is determined by the following operations: determining the flow rate at which the converter cooling system operates stably when the dual-speed circulation pump operates at a speed less than the predetermined speed; and determining the predetermined threshold based on the operating power of the converter at the flow rate.

[0008] Optionally, the operations of determining the predetermined threshold value based on the operating power of the inverter at the flow rate include: determining the first operating power of the inverter at the flow rate based on the heat exchange power of the external cooling radiator when the difference between the outlet water temperature of the external cooling radiator and the ambient temperature is less than a first threshold at the flow rate; determining the second operating power of the inverter at the flow rate based on the loss of the inverter when the difference between the inlet water temperature of the inverter and the outlet water temperature of the inverter is less than a second threshold at the flow rate; determining the first maximum operating power of the water cooling device inside the inverter at the flow rate; determining the second maximum operating power of the air cooling device inside the inverter at the flow rate; and determining the minimum value of the first operating power, the second operating power, the first maximum operating power and the second maximum operating power as the predetermined threshold.

[0009] Optionally, the flow rate is a flow rate obtained based on the performance curve of the two-speed circulation pump at a speed less than the predetermined speed and the flow pressure loss curves of each component in the series circuit of the converter cooling system except the two-speed circulation pump, so that the sum of the pressure losses of the components is equal to the head of the two-speed circulation pump at a speed less than the predetermined speed.

[0010] Optionally, the heat exchange power of the external cooling radiator is determined when the difference between the outlet water temperature of the external cooling radiator and the ambient temperature is less than a first threshold value at the flow rate, and then according to the operating efficiency curve of the inverter, the power corresponding to the loss of the inverter as the heat exchange power is determined as the first operating power of the inverter at the flow rate.

[0011] Optionally, according to an operating efficiency curve of the converter, the power corresponding to the loss is determined as a second operating power of the converter at the flow rate.

[0012] Optionally, the loss is determined based on a specific heat capacity, a density, the second threshold value, and the flow rate of a cooling medium of the converter cooling system.

[0013] On the other hand, an exemplary embodiment of the present disclosure provides a control method for an inverter cooling system, characterized in that the inverter cooling system comprises: a two-speed circulation pump, whose outlet is connected to the water inlet of the inverter via a pipeline; and an external cooling radiator, whose water inlet is connected to the water outlet of the inverter via a pipeline, and whose water outlet is connected to the inlet of the two-speed circulation pump via a pipeline, wherein the two-speed circulation pump is a circulation pump capable of operating at a predetermined speed and a speed less than the predetermined speed, and the control method comprises: determining the operating power of the inverter; in response to the operating power of the inverter being less than or equal to a predetermined threshold, operating the two-speed circulation pump at a speed less than the predetermined speed.

[0014] Optionally, the control method further comprises: in response to the operating power of the converter being greater than the predetermined threshold, operating the dual-speed circulation pump at the predetermined speed.

[0015] Optionally, the predetermined threshold is determined based on an operating power of the converter when the dual-speed circulation pump operates at a rotation speed less than the predetermined rotation speed.

[0016] Optionally, the predetermined threshold is determined by the following steps: determining the flow rate at which the converter cooling system operates stably when the dual-speed circulation pump operates at a speed less than the predetermined speed; and determining the predetermined threshold based on the operating power of the converter at the flow rate.

[0017] Optionally, the step of determining the predetermined threshold value based on the operating power of the converter at the flow rate includes: determining the first operating power of the converter at the flow rate based on the heat exchange power of the external radiator when the difference between the outlet water temperature of the external radiator and the ambient temperature is less than a first threshold at the flow rate; determining the second operating power of the converter at the flow rate based on the loss of the converter when the difference between the inlet water temperature of the converter and the outlet water temperature of the converter is less than a second threshold at the flow rate; determining the first maximum operating power of the water cooling device inside the converter at the flow rate; determining the second maximum operating power of the air cooling device inside the converter at the flow rate; and taking the minimum value of the first operating power, the second operating power, the first maximum operating power and the second maximum operating power as the predetermined threshold.

[0018] Optionally, the flow rate is a flow rate obtained based on the performance curve of the two-speed circulation pump at a speed less than the predetermined speed and the flow pressure loss curves of each component in the series circuit of the converter cooling system except the two-speed circulation pump, so that the sum of the pressure losses of the components is equal to the head of the two-speed circulation pump at a speed less than the predetermined speed.

[0019] Optionally, the heat exchange power of the external cooling radiator is determined when the difference between the outlet water temperature of the external cooling radiator and the ambient temperature is less than a first threshold value at the flow rate, and then according to the operating efficiency curve of the inverter, the power corresponding to the loss of the inverter as the heat exchange power is determined as the first operating power of the inverter at the flow rate.

[0020] Optionally, according to an operating efficiency curve of the converter, the power corresponding to the loss is determined as a second operating power of the converter at the flow rate.

[0021] Optionally, the loss is determined based on a specific heat capacity, a density, the second threshold value, and the flow rate of a cooling medium of the converter cooling system.

[0022] Another aspect of an exemplary embodiment of the present disclosure provides a converter, characterized by comprising the converter cooling system described above.

[0023] According to an exemplary embodiment of the present disclosure, a converter cooling system and a control method thereof, as well as a converter are provided. The converter cooling system uses a dual-speed circulation pump, which can adjust the flow rate of the cooling medium in the cooling system in real time according to the operating power of the converter, thereby reducing the power loss of the circulation pump, and reducing the self-consumption of electricity during the operation of the wind turbine generator set, thereby increasing the operating power generation of the wind turbine generator set.

[0024] In addition, according to the present disclosure, the threshold value can be determined more accurately, so that the flow rate of the cooling medium in the cooling system can be adjusted at an appropriate time, and the power loss of the circulation pump can be reduced while the converter can be operated safely and stably.

[0025] Additional aspects and / or advantages of the present disclosure will be set forth in part in the following description and in part will be apparent from the description or may be learned through practice of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and / or other objects and advantages of the present disclosure will become more apparent through the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0027] Figure 1 is a schematic block diagram showing a converter cooling system according to an exemplary embodiment of the present disclosure;

[0028] Figure 2 is a flowchart illustrating a control method of a converter cooling system according to an exemplary embodiment of the present disclosure. DETAILED DESCRIPTION

[0029] Exemplary embodiments of the present disclosure will now be described in detail, examples of which are shown in the accompanying drawings, wherein like reference numerals refer to like parts. The embodiments will be described below by referring to the drawings in order to explain the present disclosure.

[0030] Figure 1 is a schematic block diagram illustrating a converter cooling system according to an exemplary embodiment of the present disclosure.

[0031] like Figure 1 As shown, the converter cooling system 100 of the exemplary embodiment of the present disclosure includes a dual-speed circulation pump 30 and an external cooling radiator 20 , and cools the converter 10 by circulating a cooling medium in the converter cooling system 100 .

[0032] Specifically, as an example, the outlet of the dual-speed circulation pump 30 is connected to the water inlet of the inverter 10 via a pipeline, the water outlet of the inverter 10 is connected to the water inlet of the external cooling radiator 20 via a pipeline, and the water outlet of the external cooling radiator 20 is connected to the inlet of the dual-speed circulation pump 30 via a pipeline.

[0033] When the two-speed circulation pump 30 is in operation, it drives the cooling medium to flow in the pipeline, and makes the cooling medium flow into the converter 10 first to absorb the heat generated inside the converter 10, and then makes the cooling medium that absorbs the heat and becomes a high-temperature cooling medium flow into the external cooling radiator 20, and the heat absorbed by the high-temperature cooling medium is released through heat exchange between the external cooling radiator 20 and the atmosphere, so that the cooling medium becomes a low-temperature cooling medium and returns to the two-speed circulation pump 30.

[0034] Here, the converter 10 is a device in a wind turbine generator set for converting three-phase AC power into DC power and converting DC power into three-phase AC power, and can be various existing high-power or full-power converters. The external cooling radiator 20 can be various existing radiators that can actively or passively exchange heat with the atmosphere.

[0035] In an exemplary embodiment of the present disclosure, the dual-speed circulation pump 30 is a circulation pump that can operate at a predetermined speed and a speed less than the predetermined speed. Here, the predetermined speed can be set to any value as needed. As an example, the predetermined speed can be set to a cooling medium that can provide a constant pressure and flow rate required for converter cooling and ensure that the converter can operate at full power. That is, at this predetermined speed, the converter can operate at full power. For example, in order to reduce the power consumption of the circulation pump, when the single-speed circulation pump in the existing converter cooling system using a single-speed circulation pump is replaced with a dual-speed circulation pump, the predetermined speed of the dual-speed circulation pump can be made the same as the speed of the replaced single-speed circulation pump. That is, when selecting a dual-speed circulation pump, a dual-speed circulation pump whose performance curve when operating at a predetermined speed is consistent with the performance curve of the replaced single-speed circulation pump can be selected.

[0036] In addition, in an exemplary embodiment of the present disclosure, the two-speed circulation pump 30 in the converter cooling system 100 operates at a speed less than a predetermined speed in response to the operating power of the converter 10 being less than or equal to a predetermined threshold. That is, when the operating power of the converter 10 is less than or equal to the predetermined threshold, the two-speed circulation pump 30 operates at a speed less than the predetermined speed. In short, when the operating power of the converter 10 is relatively small, the two-speed circulation pump 30 is not operated at a high speed (predetermined speed), but is operated at a low speed (a speed less than the predetermined speed), thereby reducing the power loss of the circulation pump, reducing the self-consumption of electricity during the operation of the wind turbine generator set, and increasing the operating power generation of the wind turbine generator set. In other words, the cooling capacity of the two-speed circulation pump 30 when operating at a low speed is sufficient to cope with the heat generated by the converter 10 at a relatively small operating power.

[0037] Here, the predetermined threshold value can be determined by experiments, software simulation, or theoretical calculation, but is not limited thereto, and can also be determined by other existing methods capable of determining the predetermined threshold value. As an example, the predetermined threshold value can be determined based on the operating power of the converter 10 when the dual-speed circulation pump 30 is running at a speed less than the predetermined speed. Further, the predetermined threshold value can be set to a value below the operating power of the converter 10 when the dual-speed circulation pump 30 is running at a speed less than the predetermined speed. Thus, while reducing the power consumption of the circulation pump, the converter 10 can also be operated safely and stably.

[0038] Specifically, as an example, the predetermined threshold value can be determined by the following operations: first, the flow rate at which the converter cooling system 100 operates stably when the dual-speed circulation pump 30 operates at a speed less than a predetermined speed is determined. Here, the flow rate can be determined by various existing methods, such as by experiments, software simulation, or theoretical calculation.

[0039] As an example, the flow rate may be a flow rate obtained by making the sum of the pressure losses of each component equal to the head of the two-speed circulating pump 30 at a speed less than the predetermined speed, based on the performance curve of the two-speed circulating pump 30 at a speed less than the predetermined speed and the flow pressure loss curve of each component other than the two-speed circulating pump 30 in the series circuit of the converter cooling system 100. Specifically, the relationship between the head and the flow rate when the two-speed circulating pump 30 is stably running at a speed less than the predetermined speed can be known from the performance curve of the two-speed circulating pump 30 at a speed less than the predetermined speed, and the pressure loss of each component at different flow rates can be known from the flow pressure loss curve of each component. In addition, in order to make the converter cooling system 100 meet the system stable operation conditions, it is necessary to make the sum of the pressure losses of each component other than the two-speed circulating pump 30 in the series circuit of the converter cooling system 100 equal to the head of the two-speed circulating pump 30 at a speed less than the predetermined speed. Therefore, by substituting each flow value into the performance curve and the flow pressure loss curve in turn, the flow rate that makes the sum of the pressure losses of each component in the series circuit of the converter cooling system 100 except the two-speed circulation pump 30 equal to the head of the two-speed circulation pump 30 at a speed less than the predetermined speed can be determined.

[0040] It should be noted that the components of the series circuit of the converter cooling system 100 except the dual-speed circulation pump 30 include, for example, an external cooling radiator, a pipeline and a converter. Specifically, the cooling circuit inside the converter includes, for example, a branch for cooling the power device, a branch for cooling the main circuit cabinet and a branch for cooling the reactor, and the three branches are connected in parallel. It can be understood that the branches of the cooling circuit inside the converter are not limited to this, and can change according to the specific situation of the converter, and the number of branches can also be changed as needed. At this time, it is assumed that the pressure loss of the external cooling radiator under the flow rate Q is a, and the pressure loss of the pipeline under the flow rate Q is b. Since the cooling circuit inside the converter is connected in parallel, the pressure loss of each branch under the flow rate Q is consistent with c. It should be noted that the flow rate Q mentioned here is the total flow of the series circuit of the entire cooling system. The flow rate allocated to each branch of the parallel cooling circuit inside the converter can be different, without restriction, but the pressure loss is consistent with c. In this way, in order to make the converter cooling system 100 meet the system stable operation conditions, the performance curve of the two-speed circulation pump 30 at a speed less than the predetermined speed should have a head H=a+b+c at the flow rate Q. Therefore, it can be judged whether the flow rate Q can make H=a+b+c. If H=a+b+c can be made, the flow rate Q is the flow rate that makes the converter cooling system 100 operate stably when the two-speed circulation pump 30 runs at a speed less than the predetermined speed.

[0041] After the flow rate Q is determined, the predetermined threshold value may be determined according to the operating power of the converter 10 at the flow rate Q. Here, as an example, the operating power of the converter 10 at the flow rate Q may include: the first operating power of the converter 10 at the flow rate Q determined according to the heat exchange power when the difference between the outlet water temperature of the external cooling radiator 20 and the ambient temperature is less than the first threshold value at the flow rate Q, the second operating power of the converter 10 at the flow rate Q determined according to the loss when the difference between the inlet water temperature of the converter 10 and the outlet water temperature of the converter 10 is less than the second threshold value at the flow rate Q, the first maximum operating power of the water cooling device inside the converter 10 at the flow rate Q, and the second maximum operating power of the air cooling device inside the converter 10 at the flow rate Q, etc. Here, the first threshold value is the design temperature difference between the outlet water temperature of the external cooling radiator and the ambient temperature, which is used to measure the heat exchange capacity of the external cooling radiator to ensure that the temperature of the cooling medium entering the converter 10 does not exceed the upper limit value required by the converter 10. In addition, the second threshold is the design temperature difference between the inlet and outlet of the cooling medium of the converter 10. Therefore, the predetermined threshold can be determined according to each operating power of the converter 10 under the flow rate Q mentioned above.

[0042] As an example, the operation of determining the predetermined threshold value according to the operating power of the converter 10 at the flow rate Q includes: determining the first operating power of the converter 10 at the flow rate Q according to the heat exchange power of the external cooling radiator 20 when the difference between the outlet water temperature of the external cooling radiator 20 and the ambient temperature is less than the first threshold at the flow rate Q; determining the second operating power of the converter 10 at the flow rate Q according to the loss of the converter 10 when the difference between the inlet water temperature of the converter 10 and the outlet water temperature of the converter 10 is less than the second threshold at the flow rate Q; determining the first maximum operating power of the water cooling device inside the converter 10 at the flow rate Q; determining the second maximum operating power of the air cooling device inside the converter 10 at the flow rate Q. That is, determining each operating power of the converter 10 at the flow rate Q. Here, the determination of each operating power is not in order, and can be determined at the same time or in any order.

[0043] The various operating powers of the converter 10 under the flow rate Q can be determined by various existing methods, for example, by experiments, by software simulation, or by theoretical calculation.

[0044] Specifically, as an example, the heat exchange power of the external cooling radiator 20 when the difference between the outlet water temperature of the external cooling radiator 20 and the ambient temperature is less than the first threshold value under the flow rate Q can be determined, and then the power corresponding to the loss of the converter 10 as the heat exchange power is determined as the first operating power of the converter 10 under the flow rate Q according to the operating efficiency curve of the converter 10. Here, the operating efficiency curve of the converter 10 is an inherent characteristic curve of the converter 10, which shows the relationship between the power and the loss of the converter 10. That is, the heat exchange power of the external cooling radiator 20 when the difference between the outlet water temperature and the ambient temperature is less than the first threshold value under the flow rate Q is first determined, and then the heat exchange power is used as the loss (heat loss) of the converter 10, and the corresponding power of the converter 10 is determined as the first operating power of the converter 10 under the flow rate Q according to the operating efficiency curve of the converter 10. Here, the heat exchange power of the external cooling radiator 20 can be determined by various existing methods, for example, by experiments, by software simulation, or by theoretical calculation.

[0045] In addition, as an example, based on the operating efficiency curve of the converter 10, the power corresponding to the loss of the converter 10 when the difference between the inlet water temperature of the converter 10 and the outlet water temperature of the converter 10 is less than the second threshold value at the flow rate Q can be determined as the second operating power of the converter 10 at the flow rate Q. Here, the cooling medium absorbs the loss (heat loss) of the converter 10 at the flow rate Q, so that the difference between the inlet water temperature of the converter 10 and the outlet water temperature of the converter 10 is less than the second threshold value. At this time, the loss absorbed by the cooling medium can be determined by various existing methods. As an example, the loss can be determined based on the specific heat capacity, density, second threshold value and flow rate of the cooling medium. Specifically, it can be determined by the following formula.

[0046] P=C p ×ΔT2×Q×ρ

[0047] Where P is the loss, C p is the specific heat capacity of the cooling medium, ρ is the density of the cooling medium, ΔT2 is the second threshold, and Q is the flow rate.

[0048] Then, according to the operating efficiency curve of the converter 10 , the power corresponding to the loss is used as the second operating power of the converter 10 under the flow rate Q.

[0049] Next, the first maximum operating power of the water-cooled device inside the converter 10 at the flow rate Q and the second maximum operating power of the air-cooled device inside the converter 10 at the flow rate Q can be determined by various existing methods as described above. It should be noted that the water-cooled device inside the converter 10 refers to the device in the converter 10 that is cooled by water cooling, such as the power device in the converter 10. The air-cooled device inside the converter 10 refers to the device in the converter 10 that is cooled by water-air heat exchange, such as the reactor and the main circuit cabinet in the converter 10. It can be understood that the cooling method of the device inside the converter can be specifically selected according to its heating situation, and is not limited to this embodiment.

[0050] After various operating powers of the converter 10 under the flow rate Q are determined, a minimum value among the first operating power, the second operating power, the first maximum operating power and the second maximum operating power may be determined as a predetermined threshold.

[0051] Thus, the threshold value can be determined more accurately, so that the flow rate of the cooling medium in the cooling system can be adjusted at an appropriate time, thereby reducing the power loss of the circulation pump and enabling the converter to operate safely and stably.

[0052] In addition, in an exemplary embodiment of the present disclosure, the dual-speed circulation pump 30 in the converter cooling system 100 can be operated at a predetermined speed in response to the operating power of the converter 10 being greater than a predetermined threshold. As a result, the flow rate of the cooling medium in the cooling system can be adjusted in real time according to the operating power of the converter 10, and the dual-speed circulation pump 30 is operated at a predetermined speed when the converter 10 is operating at full power, and the dual-speed circulation pump 30 is operated at a speed lower than the predetermined speed when the converter 10 is operating at low power, thereby reducing the power consumption of the circulation pump that operates at a predetermined speed regardless of the operating power of the converter 10 in the prior art, reducing the self-consumption of the wind turbine generator set during operation, and increasing the operating power generation of the wind turbine generator set.

[0053] Figure 2 is a flowchart illustrating a control method of a converter cooling system according to an exemplary embodiment of the present disclosure.

[0054] The control method of the converter cooling system of the exemplary embodiment of the present disclosure can be used for Figure 1The converter cooling system 100 shown, specifically, includes a dual-speed circulation pump 30 and an external cooling radiator 20, and cools the converter 10 by circulating a cooling medium in the converter cooling system 100. As an example, the outlet of the dual-speed circulation pump 30 is connected to the water inlet of the converter 10 via a pipeline, the water outlet of the converter 10 is connected to the water inlet of the external cooling radiator 20 via a pipeline, and the water outlet of the external cooling radiator 20 is connected to the inlet of the dual-speed circulation pump 30 via a pipeline.

[0055] In an exemplary embodiment of the present disclosure, the dual-speed circulation pump 30 is a circulation pump that can operate at a predetermined speed and a speed less than the predetermined speed. Here, the predetermined speed can be set to any value as needed. As an example, the predetermined speed can be set to a cooling medium that can provide a constant pressure and flow rate required for converter cooling, and ensure that the converter can operate at full power. That is, at this predetermined speed, the converter can operate at full power. For example, in order to reduce the power consumption of the circulation pump, when the single-speed circulation pump in the existing converter cooling system using a single-speed circulation pump is replaced with a dual-speed circulation pump, the predetermined speed of the dual-speed circulation pump can be made the same as the speed of the replaced single-speed circulation pump. That is, the dual-speed circulation pump can be a dual-speed circulation pump whose performance curve when operating at a predetermined speed is consistent with the performance curve of the replaced single-speed circulation pump.

[0056] like Figure 2 As shown, firstly, step S10 is performed to determine the operating power of the converter 10. The operating power of the converter 10 is the power when the converter is operating normally after the wind turbine generator set is started. The operating power of the converter 10 can be measured in real time to confirm the operating state of the converter 10. The operating power of the converter 10 can also be measured at a predetermined time according to the previous operating state of the converter 10. The present disclosure is not limited to this, and the operating power of the converter 10 can also be determined by other methods.

[0057] Next, after determining the operating power of the converter 10, step S20 is performed, and in response to the operating power of the converter 10 being less than or equal to the predetermined threshold, the two-speed circulation pump 30 is operated at a speed less than the predetermined speed. That is, when the operating power of the converter 10 is less than or equal to the predetermined threshold, the two-speed circulation pump 30 is operated at a speed less than the predetermined speed. In short, when the operating power of the converter 10 is relatively small, the two-speed circulation pump 30 is not operated at a high speed (predetermined speed), but at a low speed (a speed less than the predetermined speed), thereby reducing the power loss of the circulation pump, reducing the self-consumption of electricity during the operation of the wind turbine generator set, and increasing the operating power generation of the wind turbine generator set. In other words, the cooling capacity of the two-speed circulation pump 30 when operating at a low speed is sufficient to cope with the heat generated by the converter 10 at a relatively small operating power.

[0058] Here, the predetermined threshold value can be determined by experiments, software simulation, or theoretical calculation, but is not limited thereto, and can also be determined by other existing methods capable of determining the predetermined threshold value. As an example, the predetermined threshold value can be determined based on the operating power of the converter 10 when the dual-speed circulation pump 30 is running at a speed less than the predetermined speed. Further, the predetermined threshold value can be set to a value below the operating power of the converter 10 when the dual-speed circulation pump 30 is running at a speed less than the predetermined speed. Thus, while reducing the power consumption of the circulation pump, the converter 10 can also be operated safely and stably.

[0059] Specifically, as an example, the predetermined threshold value can be determined by the following steps: First, the flow rate at which the converter cooling system 100 can operate stably when the dual-speed circulation pump 30 operates at a speed less than a predetermined speed is determined. Here, the flow rate can be determined by various existing methods, such as by experiments, software simulation, or theoretical calculation.

[0060] As an example, the flow rate may be a flow rate obtained by making the sum of the pressure losses of each component equal to the head of the two-speed circulating pump 30 at a speed less than the predetermined speed, based on the performance curve of the two-speed circulating pump 30 at a speed less than the predetermined speed and the flow pressure loss curve of each component other than the two-speed circulating pump 30 in the series circuit of the converter cooling system 100. Specifically, the relationship between the head and the flow rate when the two-speed circulating pump 30 is stably running at a speed less than the predetermined speed can be known from the performance curve of the two-speed circulating pump 30 at a speed less than the predetermined speed, and the pressure loss of each component at different flow rates can be known from the flow pressure loss curve of each component. In addition, in order to make the converter cooling system 100 meet the system stable operation conditions, it is necessary to make the sum of the pressure losses of each component other than the two-speed circulating pump 30 in the series circuit of the converter cooling system 100 equal to the head of the two-speed circulating pump 30 at a speed less than the predetermined speed. Therefore, by substituting each flow value into the performance curve and the flow pressure loss curve in turn, the flow rate that makes the sum of the pressure losses of each component in the series circuit of the converter cooling system 100 except the two-speed circulation pump 30 equal to the head of the two-speed circulation pump 30 at a speed less than the predetermined speed can be determined.

[0061] It should be noted that the components of the series circuit of the converter cooling system 100 except the dual-speed circulation pump 30 include, for example, an external cooling radiator, a pipeline and a converter. Specifically, the cooling circuit inside the converter includes, for example, a branch for cooling the power device, a branch for cooling the main circuit cabinet and a branch for cooling the reactor, and the three branches are connected in parallel. It can be understood that the branches of the cooling circuit inside the converter are not limited to this, and can change according to the specific situation of the converter, and the number of branches can also be changed as needed. At this time, it is assumed that the pressure loss of the external cooling radiator under the flow rate Q is a, and the pressure loss of the pipeline under the flow rate Q is b. Since the cooling circuit inside the converter is connected in parallel, the pressure loss of each branch under the flow rate Q is consistent with c. It should be noted that the flow rate Q mentioned here is the total flow of the series circuit of the entire cooling system. The flow rate allocated to each branch of the parallel cooling circuit inside the converter can be different, without restriction, but the pressure loss is consistent with c. In this way, in order to make the converter cooling system 100 meet the system stable operation conditions, the performance curve of the two-speed circulation pump 30 at a speed less than the predetermined speed should have a head H=a+b+c at the flow rate Q. Therefore, it can be judged whether the flow rate Q can make H=a+b+c. If H=a+b+c can be made, the flow rate Q is the flow rate that makes the converter cooling system 100 operate stably when the two-speed circulation pump 30 runs at a speed less than the predetermined speed.

[0062] After the flow rate Q is determined, the predetermined threshold value may be determined according to the operating power of the converter 10 at the flow rate Q. Here, as an example, the operating power of the converter 10 at the flow rate Q may include: the first operating power of the converter 10 at the flow rate Q determined according to the heat exchange power when the difference between the outlet water temperature of the external cooling radiator 20 and the ambient temperature is less than the first threshold value at the flow rate Q, the second operating power of the converter 10 at the flow rate Q determined according to the loss when the difference between the inlet water temperature of the converter 10 and the outlet water temperature of the converter 10 is less than the second threshold value at the flow rate Q, the first maximum operating power of the water cooling device inside the converter 10 at the flow rate Q, and the second maximum operating power of the air cooling device inside the converter 10 at the flow rate Q, etc. Here, the first threshold value is the design temperature difference between the outlet water temperature of the external cooling radiator and the ambient temperature, which is used to measure the heat exchange capacity of the external cooling radiator to ensure that the temperature of the cooling medium entering the converter 10 does not exceed the upper limit value required by the converter 10. In addition, the second threshold is the design temperature difference between the inlet and outlet of the cooling medium of the converter 10. Therefore, the predetermined threshold can be determined according to each operating power of the converter 10 under the flow rate Q mentioned above.

[0063] As an example, the step of determining the predetermined threshold value according to the operating power of the converter 10 at the flow rate Q includes: determining the first operating power of the converter 10 at the flow rate Q according to the heat exchange power of the external cooling radiator 20 when the difference between the outlet water temperature of the external cooling radiator 20 and the ambient temperature is less than the first threshold at the flow rate Q; determining the second operating power of the converter 10 at the flow rate Q according to the loss of the converter 10 when the difference between the inlet water temperature of the converter 10 and the outlet water temperature of the converter 10 is less than the second threshold at the flow rate Q; determining the first maximum operating power of the water cooling device inside the converter 10 at the flow rate Q; determining the second maximum operating power of the air cooling device inside the converter 10 at the flow rate Q. That is, determining each operating power of the converter 10 at the flow rate Q. Here, the determination of each operating power is not in order, and can be determined at the same time or in any order.

[0064] The operating powers of the converter 10 under the flow rate Q can be determined by various existing methods, for example, by experiments, by software simulation, or by theoretical calculation.

[0065] Specifically, as an example, the heat exchange power of the external cooling radiator 20 when the difference between the outlet water temperature of the external cooling radiator 20 and the ambient temperature is less than the first threshold value under the flow rate Q can be determined, and then the power corresponding to the loss of the converter 10 as the heat exchange power is determined as the first operating power of the converter 10 under the flow rate Q according to the operating efficiency curve of the converter 10. Here, the operating efficiency curve of the converter 10 is an inherent characteristic curve of the converter 10, which shows the relationship between the power and the loss of the converter 10. That is, the heat exchange power of the external cooling radiator 20 when the difference between the outlet water temperature and the ambient temperature is less than the first threshold value under the flow rate Q is first determined, and then the heat exchange power is used as the loss (heat loss) of the converter 10, and the corresponding power of the converter 10 is determined as the first operating power of the converter 10 under the flow rate Q according to the operating efficiency curve of the converter 10. Here, the heat exchange power of the external cooling radiator 20 can be determined by various existing methods, for example, by experiments, by software simulation, or by theoretical calculation.

[0066] In addition, as an example, based on the operating efficiency curve of the converter 10, the power corresponding to the loss of the converter 10 when the difference between the inlet water temperature of the converter 10 and the outlet water temperature of the converter 10 is less than the second threshold value at the flow rate Q can be determined as the second operating power of the converter 10 at the flow rate Q. Here, the cooling medium absorbs the loss (heat loss) of the converter 10 at the flow rate Q, so that the difference between the inlet water temperature of the converter 10 and the outlet water temperature of the converter 10 is less than the second threshold value. At this time, the loss absorbed by the cooling medium can be determined by various existing methods. As an example, the loss can be determined based on the specific heat capacity, density, second threshold value and flow rate of the cooling medium. Specifically, it can be determined by the following formula.

[0067] P=C p ×ΔT2×Q×ρ

[0068] Where P is the loss, C p is the specific heat capacity of the cooling medium, ρ is the density of the cooling medium, ΔT2 is the second threshold, and Q is the flow rate.

[0069] Then, according to the operating efficiency curve of the converter 10 , the power corresponding to the loss is used as the second operating power of the converter 10 under the flow rate Q.

[0070] Next, the first maximum operating power of the water-cooled device inside the converter 10 at the flow rate Q and the second maximum operating power of the air-cooled device inside the converter 10 at the flow rate Q can be determined by various existing methods as described above. It should be noted that the water-cooled device inside the converter 10 refers to the device in the converter 10 that is cooled by water cooling, such as the power device in the converter 10. The air-cooled device inside the converter 10 refers to the device in the converter 10 that is cooled by water-air heat exchange, such as the reactor and the main circuit cabinet in the converter 10. It can be understood that the cooling method of the device inside the converter can be specifically selected according to its heating situation, and is not limited to this embodiment.

[0071] After various operating powers of the converter 10 under the flow rate Q are determined, a minimum value among the first operating power, the second operating power, the first maximum operating power and the second maximum operating power may be determined as a predetermined threshold.

[0072] Thus, the threshold value can be determined more accurately, so that the flow rate of the cooling medium in the cooling system can be adjusted at an appropriate time, thereby reducing the power loss of the circulation pump and enabling the converter to operate safely and stably.

[0073] In addition, in an exemplary embodiment of the present disclosure, the control method of the converter cooling system 100 may further include the following steps: in response to the operating power of the converter 10 being greater than a predetermined threshold, the dual-speed circulation pump 30 is operated at a predetermined speed. Thus, the flow rate of the cooling medium in the cooling system can be adjusted in real time according to the operating power of the converter 10, the dual-speed circulation pump 30 is operated at a predetermined speed when the converter 10 is operating at full power, and the dual-speed circulation pump 30 is operated at a speed less than the predetermined speed when the converter 10 is operating at low power, thereby reducing the power loss of the circulation pump that operates at a predetermined speed regardless of the operating power of the converter 10 in the prior art, reducing the self-consumption of the wind turbine generator set during operation, and increasing the operating power generation of the wind turbine generator set.

[0074] A converter according to an exemplary embodiment of the present disclosure includes Figure 1 The converter cooling system 100 shown can adjust the flow rate of the cooling medium in the cooling system in real time according to the operating power of the converter, thereby reducing the power loss of the circulation pump and reducing the self-consumption of power during the operation of the wind turbine generator set, thereby increasing the operating power generation of the wind turbine generator set.

[0075] The above embodiments of the present disclosure are merely exemplary, and the present disclosure is not limited thereto. It should be understood by those skilled in the art that these embodiments may be modified without departing from the principles and spirit of the present disclosure, wherein the scope of the present disclosure is defined in the claims and their equivalents.

Claims

1. A converter cooling system for a wind turbine generator set, It is characterized in that The converter cooling system comprises: A two-speed circulation pump, the outlet of which is connected to the water inlet of the converter via a pipeline; and The water inlet of the external cooling radiator is connected to the water outlet of the converter via a pipeline, and the water outlet is connected to the inlet of the dual-speed circulation pump via a pipeline. The dual-speed circulation pump is a circulation pump capable of operating at a predetermined speed and a speed less than the predetermined speed, and the dual-speed circulation pump operates at a speed less than the predetermined speed in response to the operating power of the converter being less than or equal to a predetermined threshold, The predetermined threshold is determined based on the operating power of the converter when the dual-speed circulation pump operates at a rotation speed less than the predetermined rotation speed.

2. The converter cooling system according to claim 1, It is characterized in that The dual-speed circulation pump operates at the predetermined speed in response to the operating power of the inverter being greater than the predetermined threshold.

3. The converter cooling system according to claim 1, It is characterized in that The predetermined threshold is determined by: Determine a flow rate for enabling the converter cooling system to operate stably when the two-speed circulation pump operates at a speed less than the predetermined speed, wherein enabling the converter cooling system to operate stably means that the sum of the pressure losses of the components other than the two-speed circulation pump in the series circuit of the converter cooling system is equal to the head of the two-speed circulation pump at a speed less than the predetermined speed; The predetermined threshold is determined according to the operating power of the converter at the flow rate.

4. The converter cooling system according to claim 3, It is characterized in that The operation of determining the predetermined threshold value according to the operating power of the converter at the flow rate includes: determining a first operating power of the converter at the flow rate according to a heat exchange power of the external cooling radiator when the difference between the outlet water temperature of the external cooling radiator and the ambient temperature is less than a first threshold at the flow rate; determining a second operating power of the converter at the flow rate according to a loss of the converter when the difference between the inlet water temperature of the converter and the outlet water temperature of the converter is less than a second threshold at the flow rate; Determine a first maximum operating power of a water cooling device inside the converter at the flow rate; determining a second maximum operating power of an air-cooling device inside the converter at the flow rate; A minimum value among the first operating power, the second operating power, the first maximum operating power, and the second maximum operating power is determined as the predetermined threshold.

5. The converter cooling system according to claim 3, It is characterized in that The flow rate is obtained based on the performance curve of the two-speed circulation pump at a speed less than the predetermined speed and the flow pressure loss curves of each component in the series circuit of the converter cooling system except the two-speed circulation pump, so as to make the sum of the pressure losses of the components equal to the head of the two-speed circulation pump at a speed less than the predetermined speed.

6. The converter cooling system according to claim 4, It is characterized in that Determine the heat exchange power of the external cooling radiator when the difference between the outlet water temperature of the external cooling radiator and the ambient temperature is less than a first threshold value at the flow rate, and then determine the power corresponding to the loss of the converter as the heat exchange power as the first operating power of the converter at the flow rate according to the operating efficiency curve of the converter.

7. The converter cooling system according to claim 4, It is characterized in that According to the operating efficiency curve of the converter, the power corresponding to the loss is determined as the second operating power of the converter at the flow rate.

8. The converter cooling system according to claim 4, It is characterized in that The loss is determined based on a specific heat capacity, a density, the second threshold, and the flow rate of a cooling medium of the converter cooling system.

9. A control method for a converter cooling system of a wind turbine generator set, It is characterized in that The converter cooling system comprises: A two-speed circulation pump, the outlet of which is connected to the water inlet of the converter via a pipeline; and The water inlet of the external cooling radiator is connected to the water outlet of the converter via a pipeline, and the water outlet is connected to the inlet of the dual-speed circulation pump via a pipeline. Wherein, the dual-speed circulation pump is a circulation pump capable of operating at a predetermined speed and a speed less than the predetermined speed, The control method comprises: determining an operating power of the converter; In response to the operating power of the converter being less than or equal to a predetermined threshold, the dual-speed circulation pump is operated at a speed less than the predetermined speed, The predetermined threshold is determined based on the operating power of the converter when the dual-speed circulation pump operates at a rotation speed less than the predetermined rotation speed.

10. The control method of the converter cooling system according to claim 9, It is characterized in that The control method further comprises: In response to the operating power of the converter being greater than the predetermined threshold, the dual-speed circulation pump is operated at the predetermined rotation speed.

11. The control method of the converter cooling system according to claim 9, It is characterized in that The predetermined threshold is determined by the following steps: Determine a flow rate for enabling the converter cooling system to operate stably when the two-speed circulation pump operates at a speed less than the predetermined speed, wherein enabling the converter cooling system to operate stably means that the sum of the pressure losses of the components other than the two-speed circulation pump in the series circuit of the converter cooling system is equal to the head of the two-speed circulation pump at a speed less than the predetermined speed; The predetermined threshold is determined according to the operating power of the converter at the flow rate.

12. The control method of the converter cooling system according to claim 11, It is characterized in that The step of determining the predetermined threshold value according to the operating power of the converter at the flow rate comprises: determining a first operating power of the converter at the flow rate according to a heat exchange power of the external cooling radiator when the difference between the outlet water temperature of the external cooling radiator and the ambient temperature is less than a first threshold at the flow rate; determining a second operating power of the converter at the flow rate according to a loss of the converter when the difference between the inlet water temperature of the converter and the outlet water temperature of the converter is less than a second threshold at the flow rate; Determine a first maximum operating power of a water cooling device inside the converter at the flow rate; determining a second maximum operating power of an air-cooling device inside the converter at the flow rate; The minimum value among the first operating power, the second operating power, the first maximum operating power and the second maximum operating power is used as the predetermined threshold.

13. The control method of the converter cooling system according to claim 11, It is characterized in that The flow rate is obtained based on the performance curve of the two-speed circulation pump at a speed less than the predetermined speed and the flow pressure loss curves of each component in the series circuit of the converter cooling system except the two-speed circulation pump, so as to make the sum of the pressure losses of the components equal to the head of the two-speed circulation pump at a speed less than the predetermined speed.

14. The control method of the converter cooling system according to claim 12, It is characterized in that Determine the heat exchange power of the external cooling radiator when the difference between the outlet water temperature of the external cooling radiator and the ambient temperature is less than a first threshold value at the flow rate, and then determine the power corresponding to the loss of the converter as the heat exchange power as the first operating power of the converter at the flow rate according to the operating efficiency curve of the converter.

15. The control method of the converter cooling system according to claim 12, It is characterized in that According to the operating efficiency curve of the converter, the power corresponding to the loss is determined as the second operating power of the converter at the flow rate.

16. The control method of the converter cooling system according to claim 12, It is characterized in that The loss is determined based on a specific heat capacity, a density, the second threshold, and the flow rate of a cooling medium of the converter cooling system.

17. A converter for a wind turbine generator set, It is characterized in that The invention comprises a converter cooling system for a wind turbine generator set according to any one of claims 1 to 8.

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