阅读说明：本技术 风力发电机组齿轮箱疲劳状态在线监测方法 (Wind generating set gear box fatigue state on-line monitoring method ) 是由 李海波 邓雨 文茂诗 代思维 邹亮 段文静 杨微 于 2021-09-15 设计创作，主要内容包括：本发明公开了一种风力发电机组齿轮箱疲劳状态在线监测方法,包括：首先根据风力发电机组的运行环境参数,确定风力发电机组齿轮箱的设计疲劳曲线；然后监测风力发电机组的输出电功率、发电机扭矩和发电机转速；之后通过输出电功率、发电机扭矩和发电机转速,结合齿轮箱速比和机械电气损耗参数,计算出齿轮箱输入端的扭矩和转速；再然后基于所述齿轮箱输入端的扭矩和转速,采用LDD疲劳计算方法计算得到所述齿轮箱的等效疲劳载荷；最后将计算得到的等效疲劳载荷与设计疲劳曲线进行比较,确定所述风力发电机组齿轮箱的疲劳状态,若齿轮箱处于疲劳状态,则风力发电机组可以采用预设的降容或将转速的方案,形成齿轮箱疲劳监测及控制干预的闭环监测。(The invention discloses an online monitoring method for fatigue state of a gearbox of a wind generating set, which comprises the following steps: firstly, determining a design fatigue curve of a gear box of the wind generating set according to the operating environment parameters of the wind generating set; then monitoring the output electric power, the torque of the generator and the rotating speed of the generator of the wind generating set; then, calculating the torque and the rotating speed of the input end of the gearbox by outputting electric power, the torque of the generator and the rotating speed of the generator and combining the speed ratio of the gearbox and mechanical and electrical loss parameters; then based on the torque and the rotating speed of the input end of the gearbox, calculating by adopting an LDD fatigue calculation method to obtain the equivalent fatigue load of the gearbox; and finally, comparing the calculated equivalent fatigue load with a designed fatigue curve to determine the fatigue state of the gearbox of the wind generating set, wherein if the gearbox is in the fatigue state, the wind generating set can adopt a preset reduction or rotation speed scheme to form closed-loop monitoring of gearbox fatigue monitoring and control intervention.)

1. A wind generating set gear box equivalent fatigue load monitoring method is characterized by comprising the following steps:

monitoring the output electric power, the torque of the generator and the rotating speed of the generator of the wind generating set;

calculating the torque and the rotating speed of the input end of the gearbox by outputting electric power, the torque of the generator and the rotating speed of the generator and combining the speed ratio of the gearbox and mechanical and electrical loss parameters;

and calculating the equivalent fatigue load of the gearbox by adopting an LDD fatigue calculation method based on the torque and the rotating speed of the input end of the gearbox.

2. The wind turbine generator system gearbox equivalent fatigue load monitoring method of claim 1, wherein calculating the torque at the gearbox input comprises:

calculating the electrical loss and the mechanical loss of the wind generating set according to the output electric power, the generator torque and the mechanical electrical loss parameters;

and calculating the torque of the input end of the gearbox through the torque of the generator, the speed ratio of the gearbox, the electrical loss and the mechanical loss.

3. The wind turbine generator system gearbox equivalent fatigue load monitoring method of claim 2, wherein the electrical and mechanical losses are calculated using linear interpolation based on the output electrical power, generator torque and mechanical electrical loss parameters.

4. A method for monitoring equivalent fatigue load of a gearbox of a wind turbine generator set according to any of claims 1-3, characterised in that the rotational speed of the input of said gearbox is calculated from said generator rotational speed and gearbox speed ratio.

5. A fatigue state online monitoring method for a gearbox of a wind generating set is characterized by comprising the following steps:

determining a design fatigue curve of a gear box of the wind generating set according to the operating environment parameters of the wind generating set;

monitoring the output electric power, the torque of the generator and the rotating speed of the generator of the wind generating set;

calculating the torque and the rotating speed of the input end of the gearbox by outputting electric power, the torque of the generator and the rotating speed of the generator and combining the speed ratio of the gearbox and mechanical and electrical loss parameters;

calculating to obtain the equivalent fatigue load of the gearbox by adopting an LDD fatigue calculation method based on the torque and the rotating speed of the input end of the gearbox;

and comparing the calculated equivalent fatigue load with a design fatigue curve to determine the fatigue state of the gearbox of the wind generating set.

6. The method for on-line monitoring of the fatigue state of the gearbox of the wind generating set according to claim 5, wherein the design fatigue curve is determined by adopting a simulation method according to the operating environment parameters of the wind generating set.

7. The method of claim 5, wherein calculating the torque at the input of the gearbox comprises:

calculating the electrical loss and the mechanical loss of the wind generating set according to the output electric power, the generator torque and the mechanical electrical loss parameters;

and calculating the torque of the input end of the gearbox through the torque of the generator, the speed ratio of the gearbox, the electrical loss and the mechanical loss.

8. The method for on-line monitoring the fatigue state of the gearbox of the wind generating set according to claim 5, wherein the electrical loss and the mechanical loss are calculated by adopting a linear interpolation method according to the output electric power, the generator torque and the mechanical electrical loss parameters.

9. The method of claim 5, wherein the rotational speed of the input end of the gearbox is calculated based on the generator rotational speed and the gearbox speed ratio.

10. A control method of a wind generating set is characterized by comprising the following steps:

determining a design fatigue curve of a gear box of the wind generating set according to the operating environment parameters of the wind generating set;

monitoring the output electric power, the torque of the generator and the rotating speed of the generator of the wind generating set;

calculating the torque and the rotating speed of the input end of the gearbox by outputting electric power, the torque of the generator and the rotating speed of the generator and combining the speed ratio of the gearbox and mechanical and electrical loss parameters;

calculating to obtain the equivalent fatigue load of the gearbox by adopting an LDD fatigue calculation method based on the torque and the rotating speed of the input end of the gearbox;

comparing the calculated equivalent fatigue load with a design fatigue curve to determine the fatigue state of the gearbox of the wind generating set;

and controlling the wind generating set by adopting a corresponding control strategy according to the fatigue state of the gear box of the wind generating set.

11. The wind turbine generator system control method according to claim 10, wherein the design fatigue curve is determined by simulation according to the operating environment parameters of the wind turbine generator system.

12. The wind park control method according to claim 10, wherein calculating the torque at the gearbox input comprises:

calculating the electrical loss and the mechanical loss of the wind generating set according to the output electric power, the generator torque and the mechanical electrical loss parameters;

and calculating the torque of the input end of the gearbox through the torque of the generator, the speed ratio of the gearbox, the electrical loss and the mechanical loss.

13. The wind park control method according to claim 10, wherein said electrical and mechanical losses are calculated using linear interpolation based on said output electrical power, generator torque and mechanical electrical loss parameters.

14. A method according to any of claims 10-13, characterised by calculating the rotational speed of the gearbox input from the generator rotational speed and gearbox speed ratio.

Technical Field

The invention relates to the technical field of monitoring or controlling of wind driven generators, in particular to an online monitoring method for a fatigue state of a gearbox of a wind driven generator set.

Background

The wind generating set is a system which obtains wind energy from wind through blades and converts the wind energy into mechanical energy, and the mechanical energy is converted into electric energy by a generator through transmission of a gear box. The blades, the gear box and the generator are three major components of the wind turbine generator set, and the design states of the three major components determine the overall performance of the wind turbine generator set. The unit power generation depends on the gearbox, so that the design research of the gearbox is very important.

At present, certain achievements are obtained for monitoring the gearbox at home and abroad, for example, a Marlin state monitoring system developed in Sweden and Puruff in Germany can better realize the functions of monitoring and analyzing the fault of the gearbox. Various domestic windmills have already carried out some experimental work, for example, dasp (data Acquisition and Signal processing) vibration systems developed by beijing oriental companies can better realize fault analysis and monitoring of gear boxes. However, at present, no technology for monitoring the fatigue state of the gearbox when the wind generating set operates exists.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides an online monitoring method for the fatigue state of a gearbox of a wind generating set, which can monitor the fatigue state of the gearbox when the wind generating set operates.

In a first aspect, a wind generating set gearbox equivalent fatigue load monitoring method is provided, and comprises the following steps:

monitoring the output electric power, the torque of the generator and the rotating speed of the generator of the wind generating set;

calculating the torque and the rotating speed of the input end of the gearbox by outputting electric power, the torque of the generator and the rotating speed of the generator and combining the speed ratio of the gearbox and mechanical and electrical loss parameters;

and calculating the equivalent fatigue load of the gearbox by adopting an LDD fatigue calculation method based on the torque and the rotating speed of the input end of the gearbox.

With reference to the first aspect, in a first implementable manner of the first aspect, calculating the torque at the gearbox input comprises:

calculating the electrical loss and the mechanical loss of the wind generating set according to the output electric power, the generator torque and the mechanical electrical loss parameters;

and calculating the torque of the input end of the gearbox through the torque of the generator, the speed ratio of the gearbox, the electrical loss and the mechanical loss.

With reference to the first implementable manner of the first aspect, in a second implementable manner of the first aspect, the electrical loss and the mechanical loss are calculated by using a linear interpolation method according to the output electric power, the generator torque and the mechanical electrical loss parameter.

With reference to the first aspect, the first or second implementable manner of the first aspect, in a third implementable manner of the first aspect, the rotational speed of the input of the gearbox is calculated from the generator rotational speed and the gearbox speed ratio.

In a second aspect, a method for online monitoring of fatigue state of a gearbox of a wind generating set is provided, which comprises the following steps:

determining a design fatigue curve of a gear box of the wind generating set according to the operating environment parameters of the wind generating set;

monitoring the output electric power, the torque of the generator and the rotating speed of the generator of the wind generating set;

calculating the torque and the rotating speed of the input end of the gearbox by outputting electric power, the torque of the generator and the rotating speed of the generator and combining the speed ratio of the gearbox and mechanical and electrical loss parameters;

calculating to obtain the equivalent fatigue load of the gearbox by adopting an LDD fatigue calculation method based on the torque and the rotating speed of the input end of the gearbox;

and comparing the calculated equivalent fatigue load with a design fatigue curve to determine the fatigue state of the gearbox of the wind generating set.

With reference to the second aspect, in a first implementation manner of the second aspect, the design fatigue curve is determined by using a simulation method according to an operating environment parameter of the wind turbine generator system.

With reference to the second aspect, in a second implementable manner of the second aspect, calculating the torque at the gearbox input comprises:

calculating the electrical loss and the mechanical loss of the wind generating set according to the output electric power, the generator torque and the mechanical electrical loss parameters;

and calculating the torque of the input end of the gearbox through the torque of the generator, the speed ratio of the gearbox, the electrical loss and the mechanical loss.

With reference to the second aspect, in a third implementable manner of the second aspect, the electrical loss and the mechanical loss are calculated by using a linear interpolation method according to the output electric power, the generator torque and the mechanical electrical loss parameters.

With reference to the second aspect, in a fourth implementable manner of the second aspect, the rotational speed of the gearbox input is calculated from the generator rotational speed and a gearbox speed ratio.

In a third aspect, a wind turbine generator system control method is provided, including:

determining a design fatigue curve of a gear box of the wind generating set according to the operating environment parameters of the wind generating set;

monitoring the output electric power, the torque of the generator and the rotating speed of the generator of the wind generating set;

calculating the torque and the rotating speed of the input end of the gearbox by outputting electric power, the torque of the generator and the rotating speed of the generator and combining the speed ratio of the gearbox and mechanical and electrical loss parameters;

calculating to obtain the equivalent fatigue load of the gearbox by adopting an LDD fatigue calculation method based on the torque and the rotating speed of the input end of the gearbox;

comparing the calculated equivalent fatigue load with a design fatigue curve to determine the fatigue state of the gearbox of the wind generating set;

and controlling the wind generating set by adopting a corresponding control strategy according to the fatigue state of the gear box of the wind generating set.

With reference to the third aspect, in a first implementable manner of the third aspect, the design fatigue curve is determined by using a simulation method according to an operating environment parameter of the wind turbine generator system.

With reference to the first implementable manner of the third aspect, in a second implementable manner of the third aspect, calculating the torque at the gearbox input comprises:

calculating the electrical loss and the mechanical loss of the wind generating set according to the output electric power, the generator torque and the mechanical electrical loss parameters;

and calculating the torque of the input end of the gearbox through the torque of the generator, the speed ratio of the gearbox, the electrical loss and the mechanical loss.

With reference to the third aspect, in a third implementable manner of the third aspect, the electrical loss and the mechanical loss are calculated by using a linear interpolation method according to the output electric power, the generator torque and the mechanical electrical loss parameter.

With reference to the third aspect and any one of the first to third implementable manners of the third aspect, in four implementable manners of the third aspect, the rotation speed of the input end of the gearbox is calculated according to the generator rotation speed and the gearbox speed ratio.

Has the advantages that: according to the method for monitoring the fatigue state of the gearbox of the wind generating set on line, monitoring data of torque and rotating speed of a high-speed shaft of the set are utilized, the speed ratio of the gearbox and mechanical and electrical losses are combined, the data are converted into the torque and the rotating speed of the input end of the gearbox, then the equivalent fatigue load of the gearbox is equivalent by adopting an LDD (light detection diode) calculation method, the fatigue state of the gearbox is monitored on line, and therefore when the fatigue of the running gearbox exceeds the design condition, control strategy intervention is started, and closed-loop monitoring of the fatigue monitoring and control intervention of the gearbox is formed.

Drawings

In order to more clearly illustrate the embodiments of the present invention, the drawings, which are required to be used in the embodiments, will be briefly described below. In all the drawings, the elements or parts are not necessarily drawn to actual scale.

FIG. 1 is a flowchart of a method for monitoring an equivalent fatigue load of a gearbox of a wind turbine generator system according to an embodiment of the present invention;

FIG. 2 is a flowchart of a method for online monitoring a fatigue state of a gearbox of a wind turbine generator system according to an embodiment of the present invention;

fig. 3 is a flowchart of a control method for a wind turbine generator system according to an embodiment of the present invention;

FIG. 4 is a diagram comparing the calculated torque at the input end of the gearbox with the simulation result, wherein Stationary Mx is the simulation result and Gear input torque is the calculated torque;

FIG. 5 is a comparison graph of the calculated result and the simulation result of the rotation speed at the input end of the gearbox, wherein Rotor speed is the simulation result, and Gear input torque is the calculated result.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and therefore are only examples, and the protection scope of the present invention is not limited thereby.

In a first embodiment, a flow chart of a wind turbine generator system gearbox equivalent fatigue load monitoring method shown in fig. 1 is provided, and the monitoring method includes:

step 1-1, monitoring output electric power, generator torque and generator rotating speed of a wind generating set;

step 1-2, calculating the torque and the rotating speed of the input end of the gearbox by outputting electric power, the torque of the generator and the rotating speed of the generator and combining the speed ratio of the gearbox and mechanical and electrical loss parameters;

and 1-3, calculating the equivalent fatigue load of the gearbox by adopting an LDD fatigue calculation method based on the torque and the rotating speed of the input end of the gearbox. Specifically, the method comprises the following steps:

firstly, the output electric power, the torque and the rotating speed of a generator in the wind generating set can be monitored through a monitoring system of the wind generating set; the torque and speed at the input of the gearbox can then be calculated by outputting electrical power, generator torque and generator speed, in combination with gearbox speed ratio and mechanical electrical loss parameters. The mechanical electrical loss parameters include a gearbox loss list and a generator loss list, both of which are directly available from the manufacturer.

The electric loss of the wind generating set under the output electric power can be determined by utilizing the generator loss list, the mechanical loss of the wind generating set under the generator torque can be determined by utilizing the mechanical loss list, the torque at the input end of the gear box can be reversely deduced by combining the speed ratio of the gear box, the electric loss, the mechanical loss and the generator torque, and the rotating speed at the input end of the gear box can be reversely deduced by the rotating speed of the generator and the speed ratio of the gear box.

The torque at the input of the gearbox can be calculated using the following calculation:

wherein the content of the first and second substances,is the ith data point for the generator torque,is the ith data point of the electrical loss,is the ith data point for mechanical wear.

The results obtained by the experimental simulation are shown in fig. 4, and it can be seen from fig. 4 that the torque at the input end of the gearbox calculated by the method substantially conforms to the actual conditions.

Finally, according to the rotating speed and the torque of the input end of the gearbox, the equivalent fatigue load of the gearbox can be calculated by an LDD fatigue calculation method, and the calculation formula is as follows:

wherein the content of the first and second substances,is the ith data point for the torque at the input to the gearbox,is the ith data point of the rotational speed at the input of the gearbox, dt is the time interval for data acquisition, and m is the test index for different positions of the gearbox, typically 10/3.

The calculated equivalent fatigue load can be used for evaluating the fatigue state of the gearbox, and a foundation is provided for realizing online monitoring of the fatigue state of the gearbox.

In this embodiment, it is preferable to calculate the electrical loss and the mechanical loss by using a linear interpolation method according to the output electric power, the generator torque, and the mechanical electrical loss parameter. The linear interpolation method is adopted for calculation, so that the electrical loss and the mechanical loss can be more accurately calculated, and the error of equivalent fatigue load calculation is reduced.

In this embodiment, it is preferable to calculate the rotational speed of the input of the gearbox based on the generator rotational speed and the gearbox speed ratio.

The rotational speed at the input of the gearbox can be calculated using the following calculation:

wherein the content of the first and second substances,is the ith data point for the generator speed, and n is the gearbox ratio.

The result obtained by the experimental simulation is shown in fig. 5, and it can be seen from fig. 5 that the rotating speed of the input end of the gearbox calculated by the method basically accords with the actual condition.

In a second embodiment, as shown in fig. 2, a flow chart of a method for online monitoring of fatigue state of a gearbox of a wind turbine generator system includes:

2-1, determining a design fatigue curve of a gear box of the wind generating set according to the operating environment parameters of the wind generating set;

step 2-2, monitoring the output electric power, the generator torque and the generator rotating speed of the wind generating set;

step 2-3, calculating the torque and the rotating speed of the input end of the gearbox by outputting electric power, the torque of the generator and the rotating speed of the generator and combining the speed ratio of the gearbox and mechanical and electrical loss parameters;

2-4, calculating to obtain the equivalent fatigue load of the gearbox by adopting an LDD fatigue calculation method based on the torque and the rotating speed of the input end of the gearbox;

and 2-5, comparing the calculated equivalent fatigue load with a designed fatigue curve, and determining the fatigue state of the gearbox of the wind generating set. Specifically, the method comprises the following steps:

firstly, the operating environment parameters of the environment where the wind generating set is located can be collected through an environment monitoring system according to the installation place of the wind generating set, and the design fatigue curve of the gear box of the wind generating set can be determined through the operating environment parameters.

Then, the equivalent fatigue load of the gearbox of the wind generating set is monitored. In this embodiment, the method for monitoring the equivalent fatigue load is the same as the method for monitoring the equivalent fatigue load of the gearbox of the wind turbine generator system, and specific technical principles and steps are not described herein again.

And finally, comparing the calculated equivalent fatigue load with the design fatigue curve, and if the equivalent fatigue load exceeds the design fatigue curve, the gearbox is in a fatigue state. Therefore, the fatigue state of the gearbox is monitored on line, and a foundation is provided for the fatigue control intervention of the gearbox.

In this embodiment, preferably, the design fatigue curve is determined by using a simulation method according to the operating environment parameters of the wind turbine generator system. Specifically, the existing simulation software can be used for simulation, for example, the bladed software is used for inputting the operating environment parameters of the installation place of the wind generating set, such as site wind speed, turbulence, air density and other data, into the simulation software for simulation calculation, so as to obtain the design fatigue curve of the wind generating set.

In this embodiment, preferably, calculating the torque at the input end of the gearbox comprises:

calculating the electrical loss and the mechanical loss of the wind generating set according to the output electric power, the generator torque and the mechanical electrical loss parameters;

and calculating the torque of the input end of the gearbox through the torque of the generator, the speed ratio of the gearbox, the electrical loss and the mechanical loss.

The mechanical electrical loss parameters include a gearbox loss list and a generator loss list, both of which are directly available from the manufacturer. The electric loss of the wind generating set under the output electric power can be determined by utilizing the generator loss list, the mechanical loss of the wind generating set under the generator torque can be determined by utilizing the mechanical loss list, the torque at the input end of the gear box can be reversely deduced by combining the speed ratio of the gear box, the electric loss, the mechanical loss and the generator torque, and the rotating speed at the input end of the gear box can be reversely deduced by the rotating speed of the generator and the speed ratio of the gear box.

In this embodiment, it is preferable that the electrical loss and the mechanical loss are calculated by a linear interpolation method according to the output electric power, the generator torque, and the mechanical electrical loss parameter.

In a third embodiment, as shown in fig. 3, a flow chart of a control method of a wind turbine generator system includes:

step 3-1, determining a design fatigue curve of a gear box of the wind generating set according to the operating environment parameters of the wind generating set;

step 3-2, monitoring the output electric power, the generator torque and the generator rotating speed of the wind generating set;

3-3, calculating the torque and the rotating speed of the input end of the gearbox by outputting electric power, the torque of the generator and the rotating speed of the generator and combining the speed ratio of the gearbox and mechanical and electrical loss parameters;

3-4, calculating to obtain the equivalent fatigue load of the gearbox by adopting an LDD fatigue calculation method based on the torque and the rotating speed of the input end of the gearbox;

step 3-5, comparing the calculated equivalent fatigue load with a designed fatigue curve, and determining the fatigue state of the gearbox of the wind generating set;

and 3-6, controlling the wind generating set by adopting a corresponding control strategy according to the fatigue state of the gear box of the wind generating set. Specifically, the method comprises the following steps:

firstly, a design fatigue curve of the wind generating set gear box can be determined according to the operating environment parameters of the wind generating set, in this embodiment, the determination method of the design fatigue curve is the same as the determination method of the design fatigue curve in the wind generating set gear box fatigue state online monitoring method, and the specific technical principle is not repeated here.

Then, the equivalent fatigue load of the gearbox of the wind generating set is monitored. In this embodiment, the method for monitoring the equivalent fatigue load is the same as the method for monitoring the equivalent fatigue load of the gearbox of the wind turbine generator system, and specific technical principles and steps are not described herein again.

And then, comparing the equivalent fatigue load with a design fatigue curve, and determining the fatigue state of the gearbox of the wind generating set.

And finally, controlling the wind generating set by adopting a corresponding control strategy according to the fatigue state of the gear box of the wind generating set.

If the gearbox is not in a fatigue state, the wind generating set can keep a normal operation state;

if the gearbox is in a fatigue state, the wind generating set can adopt a preset reduction or rotation speed reduction scheme, so that the fatigue of the gearbox is reduced. And when the fatigue of the gearbox operation exceeds the design condition, the control strategy intervention is started to form closed-loop monitoring of the gearbox fatigue monitoring and the control intervention.

In this embodiment, preferably, the design fatigue curve is determined by using a simulation method according to the operating environment parameters of the wind turbine generator system. The existing simulation software can be adopted for simulation, for example, the bladed software is adopted, and the data of the operating environment parameters of the installation place of the wind generating set, such as site wind speed, turbulence, air density and the like, are input into the simulation software for simulation calculation, so that the design fatigue curve of the wind generating set is obtained.

In this embodiment, preferably, calculating the torque at the input end of the gearbox comprises:

calculating the electrical loss and the mechanical loss of the wind generating set according to the output electric power, the generator torque and the mechanical electrical loss parameters;

and calculating the torque of the input end of the gearbox through the torque of the generator, the speed ratio of the gearbox, the electrical loss and the mechanical loss.

The mechanical electrical loss parameters include a gearbox loss list and a generator loss list, both of which are directly available from the manufacturer. The electric loss of the wind generating set under the output electric power can be determined by utilizing the generator loss list, the mechanical loss of the wind generating set under the generator torque can be determined by utilizing the mechanical loss list, the torque at the input end of the gear box can be reversely deduced by combining the speed ratio of the gear box, the electric loss, the mechanical loss and the generator torque, and the rotating speed at the input end of the gear box can be reversely deduced by the rotating speed of the generator and the speed ratio of the gear box.

In this embodiment, it is preferable that the electrical loss and the mechanical loss are calculated by a linear interpolation method according to the output electric power, the generator torque, and the mechanical electrical loss parameter.

In this embodiment, it is preferable to calculate the rotational speed of the input of the gearbox based on the generator rotational speed and the gearbox speed ratio. In this embodiment, the same calculation method as described above may be used to calculate the rotational speed at the input of the gearbox.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention, and they should be construed as being included in the following claims and description.