阅读说明：本技术 一种风电变流器冷却风扇的控制方法 (Control method of cooling fan of wind power converter ) 是由 黄建鹏 刘明辉 于 2021-08-06 设计创作，主要内容包括：本发明涉及一种风电变流器冷却风扇的控制方法,由多个冷却风扇对风电变流器进行冷却,具体包括如下步骤：(1)预设冷却风扇启动阀值和死区设定值；(2)根据测得的风电变流器冷却系统出口的温度在不同区间控制启动冷却风扇的数量,再根据每个冷却风扇的累计运行时间控制预定的启动冷却风扇,累计运行时间少的冷却风扇优先启动,风电变流器冷却系统出口的温度的不同区间的分隔点为步骤(1)中的冷却风扇的各启动阀值。本发明可以保证每个风扇运行时间大体相同,防止某个风扇使用频率过高而损坏,提高冷却风扇的整体可靠性,进而提高变流器和风力发电机组可靠性。尤其是对于海上风力发电机组来说,由于其维护不方便,这种策略的优势更为明显。(The invention relates to a control method of a cooling fan of a wind power converter, which is used for cooling the wind power converter by a plurality of cooling fans and specifically comprises the following steps: (1) presetting a starting threshold value and a dead zone set value of a cooling fan; (2) and (3) controlling the number of the started cooling fans in different intervals according to the measured temperature of the outlet of the wind power converter cooling system, and then controlling the preset started cooling fans according to the accumulated running time of each cooling fan, wherein the cooling fans with less accumulated running time are started preferentially, and the separation points of the different intervals of the temperature of the outlet of the wind power converter cooling system are the starting threshold values of the cooling fans in the step (1). The invention can ensure that the running time of each fan is approximately the same, prevent a certain fan from being damaged due to overhigh use frequency, improve the overall reliability of the cooling fan and further improve the reliability of the converter and the wind generating set. Especially for offshore wind generating sets, the advantage of the strategy is more obvious because of the inconvenient maintenance.)

1. A control method for a cooling fan of a wind power converter is characterized in that the wind power converter is cooled by a plurality of cooling fans, and specifically comprises the following steps:

(1) presetting a starting threshold value and a dead zone set value of a cooling fan;

(2) and (3) controlling the number of the started cooling fans in different intervals according to the measured temperature of the outlet of the wind power converter cooling system, and then controlling the preset started cooling fans according to the accumulated running time of each cooling fan, wherein the cooling fans with less accumulated running time are started preferentially, and the separation points of the different intervals of the temperature of the outlet of the wind power converter cooling system are the starting threshold values of the cooling fans in the step (1).

2. The method for controlling the cooling fans of the wind power converter according to claim 1, wherein n cooling fans are used to cool the wind power converter, the start threshold in step (1) is provided with n start thresholds, which are K1 and K2 … … Kn, n start thresholds constitute n +1 temperature intervals, which are less than K1, K1-K2, and K2-K3 … …, respectively, when the temperature at the outlet of the cooling system of the converter is in the first temperature interval, the cooling fans are all stopped, when the temperature at the outlet of the cooling system of the converter is in the 2 nd temperature interval, the 1 cooling fan with the shortest accumulated running time is controlled to run, and simultaneously, the accumulated timer of the running cooling fans is controlled to start timing, when the temperature at the outlet of the cooling system of the converter is in the 3 rd temperature interval, the 2 cooling fans with the shortest accumulated running time are controlled to run, and meanwhile, controlling an accumulative timer of the running cooling fan to start timing, and controlling all the n cooling fans to run and the accumulative timer of the cooling fan to start timing when the temperature of the outlet of the converter cooling system is in the (n + 1) th temperature interval by analogy.

3. The method for controlling the cooling fans of the wind power converter according to claim 2, wherein at least n cooling fans cool the wind power converter, and the specific control steps in the step (2) are as follows:

(2.1) firstly entering a first control mode, stopping running of all cooling fans at the moment, stopping timing of all running time accumulation timers of all the cooling fans, and entering a step (2.2) if the temperature of an outlet of the converter cooling system is greater than K1 and less than K2; if the temperature of the outlet of the cooling system of the converter is more than K (n-1) and less than Kn, entering the step (2. n), and if the temperature of the outlet of the cooling system of the converter is more than Kn, entering the step (2. n + 1), wherein K1 is more than K2 is more than … … Kn;

(2.2) entering a second control mode, comparing the accumulated running time of the n cooling fans, controlling the starting of 1 cooling fan with the shortest accumulated running time, if the accumulated running time of 2-n fans is the same and the time is the shortest, controlling the starting of the cooling fan with the previous control serial number, and controlling the starting of the accumulated timer of the running cooling fan; then, if the temperature of the outlet of the cooling system of the converter is greater than K2 and less than K3, entering step (2.3), and so on, if the temperature of the outlet of the cooling system of the converter is greater than K (n-1) and less than Kn, entering step (2. n), if the temperature of the outlet of the cooling system of the converter is greater than Kn, entering step (2. n + 1), and if the temperature of the outlet of the cooling system of the converter is less than K1 minus a dead zone value, entering step (2.1);

(2, n) entering an nth control mode, comparing the accumulated running time of n fans, controlling the start of n-1 cooling fans with the shortest accumulated running time, if the accumulated running times of 2-n cooling fans are the same, controlling the start of 2 cooling fans with the front serial numbers, if the accumulated running times of n-1 fans are the same and the running time is the longest, controlling the start of the cooling fan with the shortest running time and the cooling fan with the front serial number in the n-1 cooling fans with long running time, and simultaneously controlling the start of the timing of an accumulated timer of the running cooling fans; then, if the outlet temperature of the converter cooling system is greater than Kn, the step (2. n + 1) is carried out, if the outlet temperature of the converter cooling system is less than K1, the step (2.1) is carried out, and the like, and if the outlet temperature of the converter cooling system is greater than K (n-3) and less than K (n-2), the step (2. n-2) is carried out; finally, if the outlet temperature of the converter cooling system is larger than K (n-2) and smaller than K (n-1) minus the dead zone value, entering the step (2. n-1);

(2, n + 1) entering an n +1 control mode, wherein n cooling fans run simultaneously and the cumulative timers of the n cooling fans count simultaneously; then, if the temperature of the outlet of the converter cooling system is less than K1, entering the step (2.1); and (3) if the outlet temperature of the cooling system of the converter is greater than K1 and less than K2, entering the step (2.2), and so on, if the outlet temperature of the cooling system of the converter is greater than K (n-2) and less than K (n-1), entering the step (2. n-1), and if the outlet temperature of the cooling system of the converter is less than Kn minus a dead zone value, counting the step (2. n).

4. The method for controlling the cooling fans of the wind power converter according to claim 3, wherein at least 3 cooling fans cool the wind power converter, and the specific control steps in the step (2) are as follows:

(2.1) firstly entering a first control mode, stopping running of the cooling fans at the moment, stopping timing of running time accumulation timers of the cooling fans, and entering a step (2.2) if the temperature of an outlet of the converter cooling system is greater than a first set threshold and less than a second set threshold; if the outlet temperature of the cooling system of the converter is greater than the second set threshold value and less than a third set threshold value, entering a step (2.3); if the outlet temperature of the cooling system of the converter is greater than a third set threshold value, entering a step (2.4), wherein the first set threshold value is smaller than the second set threshold value and smaller than the third set threshold value;

(2.2) entering a second control mode, comparing the accumulated running time of the 3 cooling fans, controlling the starting of the 1 cooling fan with the shortest accumulated running time, if the accumulated running time of the 3 cooling fans is the same, or if the accumulated running time of the 2 cooling fans is the same and the time is the shortest, controlling the starting of the cooling fan with the previous serial number, and simultaneously controlling the accumulated timer of the running cooling fan to start timing; then, if the temperature of the outlet of the cooling system of the converter is greater than a second set threshold and less than a third set threshold, entering a step (2.3), if the temperature of the outlet of the cooling system of the converter is greater than the third set threshold, entering a step (2.4), and if the temperature of the outlet of the cooling system of the converter is less than the first set threshold minus a dead zone value, entering a step (2.1);

(2.3) entering a third control mode, comparing the accumulated running time of the three fans, controlling the starting of the 2 cooling fans with the shortest accumulated running time, if the accumulated running time of the 3 cooling fans is the same, controlling the starting of the 2 cooling fans with the front serial numbers, if the accumulated running time of the 2 fans is the same and the running time is the longest, controlling the starting of the cooling fan with the shortest running time and the cooling fan with the front serial number in the 2 cooling fans with the long running time, and simultaneously controlling the starting of the accumulated timer of the running cooling fans; then, if the temperature of the outlet of the converter cooling system is greater than a third set threshold value, entering a step (2.4), if the temperature of the outlet of the converter cooling system is less than a first set threshold value, entering a step (2.1), and if the temperature of the outlet of the converter cooling system is greater than the first set threshold value and less than a second set threshold value minus a dead zone value, entering a step (2.2);

(2.4) entering a fourth control mode, wherein 3 cooling fans run simultaneously and the accumulative timers of the 3 cooling fans count simultaneously; then, if the temperature of the outlet of the converter cooling system is smaller than a first set threshold value, entering a step (2.1); if the outlet temperature of the cooling system of the converter is greater than a first set threshold value and less than a second set threshold value, entering the step (2.2); and (4) if the outlet temperature of the cooling system of the converter is smaller than the third set threshold value minus the dead zone value, counting the step (2.3).

Technical Field

The invention belongs to the technical field of heat dissipation control, and particularly relates to a control method of a cooling fan of a wind power converter.

Background

The core devices of the converter are power electronic devices such as IGBT (insulated gate bipolar transistor) and the like, a large amount of heat can be generated in the operation process, and if the heat cannot be dissipated in time, the devices such as IGBT and the like can be damaged; at present, the converter is cooled by air-water cooling or air-air cooling, but no matter the converter is cooled by air-water cooling or air-air cooling, heat and air need to be exchanged by a cooling fan, so that the internal temperature of the converter is reduced, and the normal operation of the converter is ensured.

For the converter of large-scale wind generating set, based on the consideration of installation position restriction and cost, generally, a plurality of cooling fans are arranged to dissipate heat, each cooling fan has the restriction of service life, if the operation of each fan cannot be reasonably controlled, the use frequency of some fans is too high, the use frequency of some cooling fans is lower, the damage probability of the cooling fan with higher use frequency is higher, thereby the integral availability of the cooling fan is influenced, the availability of the converter is further influenced, and whether the use frequency of each cooling fan is balanced or not is not considered in the control logic of the cooling fan of the converter using the heat dissipation of a plurality of cooling fans at present.

In view of the foregoing, it is desirable to provide a method for controlling a cooling fan of a wind power converter, which prevents a certain cooling fan from being damaged due to an excessively high operating frequency, improves the overall reliability of the cooling fan, and further improves the reliability of the converter and the wind turbine generator set.

Disclosure of Invention

The invention aims to provide a control method of a cooling fan of a wind power converter, which can prevent a certain cooling fan from being damaged due to overhigh use frequency, improve the overall reliability of the cooling fan and further improve the reliability of the converter and a wind generating set.

The above purpose is realized by the following technical scheme: a control method for a cooling fan of a wind power converter is characterized in that the wind power converter is cooled by a plurality of cooling fans, and the control method specifically comprises the following steps:

(1) presetting a starting threshold value and a dead zone set value of a cooling fan;

(2) and (3) controlling the number of the started cooling fans in different intervals according to the measured temperature of the outlet of the wind power converter cooling system, and then controlling the preset started cooling fans according to the accumulated running time of each cooling fan, wherein the cooling fans with less accumulated running time are started preferentially, and the separation points of the different intervals of the temperature of the outlet of the wind power converter cooling system are the starting threshold values of the cooling fans in the step (1).

The further technical scheme is that the wind power converter is cooled by n cooling fans, n starting thresholds in the step (1) are provided, the n starting thresholds are K1 and K2 … … Kn respectively, n +1 temperature intervals are formed by the n starting thresholds, the n starting thresholds are respectively smaller than K1, K1-K2 and K2-K3 … … and larger than Kn, when the temperature of the outlet of the cooling system of the converter is located in a first temperature interval, the cooling fans stop running, when the temperature of the outlet of the cooling system of the converter is located in a second temperature interval, the 1 cooling fan with the shortest accumulated running time is controlled to run, an accumulated timer of the running cooling fans is controlled to start timing, when the temperature of the outlet of the cooling system of the converter is located in a third temperature interval, the 2 cooling fans with the shortest accumulated running time are controlled to run, and the accumulated timer of the running cooling fans is controlled to start timing at the same time, and by analogy, when the temperature of the outlet of the converter cooling system is in the (n + 1) th temperature interval, controlling all the n cooling fans to operate and starting the timing of the accumulative timer of the cooling fans.

The further technical scheme is that the wind power converter is cooled by at least n cooling fans, and the specific control steps in the step (2) are as follows:

(2.1) firstly entering a first control mode, stopping running of all cooling fans at the moment, stopping timing of all running time accumulation timers of all the cooling fans, and entering a step (2.2) if the temperature of an outlet of the converter cooling system is greater than K1 and less than K2; if the temperature of the outlet of the cooling system of the converter is more than K (n-1) and less than Kn, entering the step (2. n), and if the temperature of the outlet of the cooling system of the converter is more than Kn, entering the step (2. n + 1), wherein K1 is more than K2 is more than … … Kn;

(2.2) entering a second control mode, comparing the accumulated running time of the n cooling fans, controlling the starting of 1 cooling fan with the shortest accumulated running time, if the accumulated running time of 2-n fans is the same and the time is the shortest, controlling the starting of the cooling fan with the previous control serial number, and controlling the starting of the accumulated timer of the running cooling fan; then, if the temperature of the outlet of the cooling system of the converter is greater than K2 and less than K3, entering step (2.3), and so on, if the temperature of the outlet of the cooling system of the converter is greater than K (n-1) and less than Kn, entering step (2. n), if the temperature of the outlet of the cooling system of the converter is greater than Kn, entering step (2. n + 1), and if the temperature of the outlet of the cooling system of the converter is less than K1 minus a dead zone value, entering step (2.1);

(2, n) entering an nth control mode, comparing the accumulated running time of n fans, controlling the start of n-1 cooling fans with the shortest accumulated running time, if the accumulated running times of 2-n cooling fans are the same, controlling the start of 2 cooling fans with the front serial numbers, if the accumulated running times of n-1 fans are the same and the running time is the longest, controlling the start of the cooling fan with the shortest running time and the cooling fan with the front serial number in the n-1 cooling fans with long running time, and simultaneously controlling the start of the timing of an accumulated timer of the running cooling fans; then, if the outlet temperature of the converter cooling system is greater than Kn, the step (2. n + 1) is carried out, if the outlet temperature of the converter cooling system is less than K1, the step (2.1) is carried out, and the like, and if the outlet temperature of the converter cooling system is greater than K (n-3) and less than K (n-2), the step (2. n-2) is carried out; and finally, if the outlet temperature of the converter cooling system is larger than K (n-2) and smaller than K (n-1) minus the dead zone value, entering the step (2. n-1).

(2, n + 1) entering an n +1 control mode, wherein n cooling fans run simultaneously and the cumulative timers of the n cooling fans count simultaneously; then, if the temperature of the outlet of the converter cooling system is less than K1, entering the step (2.1); and (3) if the outlet temperature of the cooling system of the converter is greater than K1 and less than K2, entering the step (2.2), and so on, if the outlet temperature of the cooling system of the converter is greater than K (n-2) and less than K (n-1), entering the step (2. n-1), and if the outlet temperature of the cooling system of the converter is less than Kn minus a dead zone value, counting the step (2. n).

The further technical scheme is that the wind power converter is cooled by at least 3 cooling fans, and the specific control steps in the step (2) are as follows:

(2.1) firstly entering a first control mode, stopping running of the cooling fans at the moment, stopping timing of running time accumulation timers of the cooling fans, and entering a step (2.2) if the temperature of an outlet of the converter cooling system is greater than a first set threshold and less than a second set threshold; if the outlet temperature of the cooling system of the converter is greater than the second set threshold value and less than a third set threshold value, entering a step (2.3); if the outlet temperature of the cooling system of the converter is greater than a third set threshold value, entering a step (2.4), wherein the first set threshold value is smaller than the second set threshold value and smaller than the third set threshold value;

(2.2) entering a second control mode, comparing the accumulated running time of the 3 cooling fans, controlling the starting of the 1 cooling fan with the shortest accumulated running time, if the accumulated running time of the 3 cooling fans is the same, or if the accumulated running time of the 2 cooling fans is the same and the time is the shortest, controlling the starting of the cooling fan with the previous serial number, and simultaneously controlling the accumulated timer of the running cooling fan to start timing; then, if the temperature of the outlet of the cooling system of the converter is greater than a second set threshold and less than a third set threshold, entering a step (2.3), if the temperature of the outlet of the cooling system of the converter is greater than the third set threshold, entering a step (2.4), and if the temperature of the outlet of the cooling system of the converter is less than the first set threshold minus a dead zone value, entering a step (2.1);

(2.3) entering a third control mode, comparing the accumulated running time of the three fans, controlling the starting of the 2 cooling fans with the shortest accumulated running time, if the accumulated running time of the 3 cooling fans is the same, controlling the starting of the 2 cooling fans with the front serial numbers, if the accumulated running time of the 2 fans is the same and the running time is the longest, controlling the starting of the cooling fan with the shortest running time and the cooling fan with the front serial number in the 2 cooling fans with the long running time, and simultaneously controlling the starting of the accumulated timer of the running cooling fans; then, if the temperature of the outlet of the converter cooling system is greater than a third set threshold value, entering a step (2.4), if the temperature of the outlet of the converter cooling system is less than a first set threshold value, entering a step (2.1), and if the temperature of the outlet of the converter cooling system is greater than the first set threshold value and less than a second set threshold value minus a dead zone value, entering a step (2.2);

(2.4) entering a fourth control mode, wherein 3 cooling fans run simultaneously and the accumulative timers of the 3 cooling fans count simultaneously; then, if the temperature of the outlet of the converter cooling system is smaller than a first set threshold value, entering a step (2.1); if the outlet temperature of the cooling system of the converter is greater than a first set threshold value and less than a second set threshold value, entering the step (2.2); and (4) if the outlet temperature of the cooling system of the converter is smaller than the third set threshold value minus the dead zone value, counting the step (2.3).

According to the characteristic that the heat emitted by the wind power converter is different along with the difference of output power, for the converter which uses a plurality of cooling fans for heat dissipation, the number of the started fans is determined according to the temperature value of the output port of the converter, and the started fans are determined according to the accumulated running time of each fan. Especially for offshore wind generating sets, the advantage of the strategy is more obvious because of the inconvenient maintenance.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention.

Fig. 1 is a control logic diagram of a control method of a cooling fan of a wind power converter according to an embodiment of the present invention;

FIG. 2 is a cooling fan control logic diagram in control mode 2 according to an embodiment of the present invention;

fig. 3 is a cooling fan control logic diagram in control mode 3 according to an embodiment of the present invention.

Detailed Description

The present invention will now be described in detail with reference to the drawings, which are given by way of illustration and explanation only and should not be construed to limit the scope of the present invention in any way. Furthermore, features from embodiments in this document and from different embodiments may be combined accordingly by a person skilled in the art from the description in this document.

The embodiment of the invention provides a control method of a cooling fan of a wind power converter, which comprises the following steps of, with reference to fig. 1, cooling the wind power converter by a plurality of cooling fans:

(1) presetting a starting threshold value and a dead zone set value of a cooling fan;

(2) and (3) controlling the number of the started cooling fans in different intervals according to the measured temperature of the outlet of the wind power converter cooling system, and then controlling the preset started cooling fans according to the accumulated running time of each cooling fan, wherein the cooling fans with less accumulated running time are started preferentially, and the separation points of the different intervals of the temperature of the outlet of the wind power converter cooling system are the starting threshold values of the cooling fans in the step (1).

On the basis of the above embodiment, in another embodiment of the present invention, the wind power converter is cooled by n cooling fans, n starting thresholds in step (1) are provided, which are K1 and K2 … … Kn, n starting thresholds constitute n +1 temperature intervals, which are less than K1, K1 to K2, and K2 to K3 … … and greater than Kn, when the temperature at the outlet of the cooling system of the converter is in the first temperature interval, the cooling fans stop operating, when the temperature at the outlet of the cooling system of the converter is in the 2 nd temperature interval, 1 cooling fan with the shortest accumulated operating time is controlled to operate, and the accumulated timer of the operated cooling fans is controlled to start timing, when the temperature at the outlet of the cooling system of the converter is in the 3 rd temperature interval, 2 cooling fans with the shortest accumulated operating time are controlled to operate, and the accumulated timer of the operated cooling fans is controlled to start timing, and by analogy, when the temperature of the outlet of the converter cooling system is in the (n + 1) th temperature interval, controlling all the n cooling fans to operate and starting the timing of the accumulative timer of the cooling fans.

On the basis of the above embodiment, in another embodiment of the present invention, at least n cooling fans cool the wind power converter, as shown in fig. 2 and fig. 3, the specific control steps in step (2) are as follows:

(2.1) firstly entering a first control mode, stopping running of all cooling fans at the moment, stopping timing of all running time accumulation timers of all the cooling fans, and entering a step (2.2) if the temperature of an outlet of the converter cooling system is greater than K1 and less than K2; if the temperature of the outlet of the cooling system of the converter is more than K (n-1) and less than Kn, entering the step (2. n), and if the temperature of the outlet of the cooling system of the converter is more than Kn, entering the step (2. n + 1), wherein K1 is more than K2 is more than … … Kn;

(2.2) entering a second control mode, comparing the accumulated running time of the n cooling fans, controlling the starting of 1 cooling fan with the shortest accumulated running time, if the accumulated running time of 2-n fans is the same and the time is the shortest, controlling the starting of the cooling fan with the previous control serial number, and controlling the starting of the accumulated timer of the running cooling fan; then, if the temperature of the outlet of the cooling system of the converter is greater than K2 and less than K3, entering step (2.3), and so on, if the temperature of the outlet of the cooling system of the converter is greater than K (n-1) and less than Kn, entering step (2. n), if the temperature of the outlet of the cooling system of the converter is greater than Kn, entering step (2. n + 1), and if the temperature of the outlet of the cooling system of the converter is less than K1 minus a dead zone value, entering step (2.1);

(2, n) entering an nth control mode, comparing the accumulated running time of n fans, controlling the start of n-1 cooling fans with the shortest accumulated running time, if the accumulated running times of 2-n cooling fans are the same, controlling the start of 2 cooling fans with the front serial numbers, if the accumulated running times of n-1 fans are the same and the running time is the longest, controlling the start of the cooling fan with the shortest running time and the cooling fan with the front serial number in the n-1 cooling fans with long running time, and simultaneously controlling the start of the timing of an accumulated timer of the running cooling fans; then, if the outlet temperature of the converter cooling system is greater than Kn, the step (2. n + 1) is carried out, if the outlet temperature of the converter cooling system is less than K1, the step (2.1) is carried out, and the like, and if the outlet temperature of the converter cooling system is greater than K (n-3) and less than K (n-2), the step (2. n-2) is carried out; and finally, if the outlet temperature of the converter cooling system is larger than K (n-2) and smaller than K (n-1) minus the dead zone value, entering the step (2. n-1).

(2, n + 1) entering an n +1 control mode, wherein n cooling fans run simultaneously and the cumulative timers of the n cooling fans count simultaneously; then, if the temperature of the outlet of the converter cooling system is less than K1, entering the step (2.1); and (3) if the outlet temperature of the cooling system of the converter is greater than K1 and less than K2, entering the step (2.2), and so on, if the outlet temperature of the cooling system of the converter is greater than K (n-2) and less than K (n-1), entering the step (2. n-1), and if the outlet temperature of the cooling system of the converter is less than Kn minus a dead zone value, counting the step (2. n).

The invention provides a specific embodiment, as shown in fig. 1-3, a wind power converter is cooled by 3 cooling fans, wherein the cooling fans are a No. 1 fan, a No. 2 fan and a No. 3 fan respectively. Presetting a starting threshold value and a dead zone set value of a cooling fan in the step (1); setting a first set threshold, a second set threshold and a third set threshold which are respectively K1, K2 and K3, and recording the dead zone set value as H;

as shown in fig. 2 and fig. 3, the specific control steps in step (2) are as follows: (2.1) firstly entering a control mode 1, stopping running of the cooling fans at the moment, stopping timing of running time accumulation timers of the cooling fans, and entering a step (2.2) if the temperature of an outlet of the converter cooling system is greater than a first set threshold and less than a second set threshold; if the outlet temperature of the cooling system of the converter is greater than the second set threshold value and less than a third set threshold value, entering a step (2.3); if the outlet temperature of the cooling system of the converter is greater than a third set threshold value, entering a step (2.4), wherein the first set threshold value is smaller than the second set threshold value and smaller than the third set threshold value;

(2.2) entering a control mode 2, comparing the accumulated running time of 3 cooling fans, namely t1, t2 and t3, controlling the starting of 1 cooling fan with the shortest accumulated running time, if the accumulated running time of 3 cooling fans is the same, or if the accumulated running time of 2 fans is the same and the time is the shortest, controlling the starting of the cooling fan with the front serial number, and simultaneously controlling the start of the timing of an accumulated timer of the running cooling fan; then, if the temperature of the outlet of the cooling system of the converter is greater than a second set threshold value K2 and less than a third set threshold value K3, entering step (2.3), if the temperature of the outlet of the cooling system of the converter is greater than a third set threshold value K3, entering step (2.4), and if the temperature of the outlet of the cooling system of the converter is less than the first set threshold value minus a dead zone value (K1-H), entering step (2.1);

(2.3) entering a control mode 3, comparing the accumulated running time of the three fans, namely t1, t2 and t3, controlling the starting of the 2 cooling fans with the shortest accumulated running time, if the accumulated running time of the 3 cooling fans is the same, controlling the starting of the 2 cooling fans with the first serial numbers, if the accumulated running time of the 2 fans is the same and the running time is the longest, controlling the starting of the cooling fan with the shortest running time and the cooling fan with the first serial number in the 2 cooling fans with the longer running time, and simultaneously controlling the start of the timing of the accumulated timer of the running cooling fans; then, if the temperature of the outlet of the converter cooling system is greater than a third set threshold value K3, entering a step (2.4), if the temperature of the outlet of the converter cooling system is less than a first set threshold value K1, entering a step (2.1), and if the temperature of the outlet of the converter cooling system is greater than the first set valve and a value K1 is less than a second set threshold value minus a dead zone value (K2-H), entering a step (2.2);

(2.4) entering a control mode 4, wherein 3 cooling fans run simultaneously and the accumulative timers of the 3 cooling fans count simultaneously; then, if the temperature at the outlet of the converter cooling system is smaller than a first set threshold value K1, entering a step (2.1); if the outlet temperature of the cooling system of the converter is greater than a first set threshold value K1 and less than a second set threshold value K2, entering the step (2.2); if the converter cooling system outlet temperature is less than the third set threshold minus the deadband value (K3-H), step (2.3) is taken.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.