A wind speed measurement system and method using a constant temperature hot wire anemometer

Abstract

The present invention discloses a wind speed measurement system and method using a constant temperature hot wire anemometer, belonging to the technical field of wind power generation. A number of hot wire probes are sequentially arranged on the leading edge center line from the root section to the tip section of any blade of a wind turbine; the hot wire metal wire and the ambient temperature sensor are exposed on the blade surface, the probe temperature sensor is connected to the hot wire metal wire, the probe temperature sensor and the ambient temperature sensor are respectively connected to the data processing unit, the hot wire metal wire and the data processing unit are respectively connected to the current shunt regulation processor, the current shunt regulation processor is respectively connected to the current signal total receiver and the current source, and the current signal total receiver is connected to the data receiving and storage device through a communication module. The present invention has a reasonable structure, gives full play to the advantages of the hot wire speed measurement technology, can accurately, real-time and continuously measure wind speed data, and has good application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of wind power generation, and in particular relates to a wind speed measurement system and method using a constant temperature hot wire anemometer. Background Art

[0002] In the past 10 years, China's wind power industry has shown a rapid development trend. With the development of wind turbine technology, the design capacity of a single unit will be greatly improved compared to the current stage, and the corresponding blade length will also increase significantly. The performance evaluation of large-capacity and long-blade wind turbine units is based on accurate wind speed measurement. At present, cup anemometers are usually installed on the upper part of the wind turbine nacelle. The measured wind direction data is used for wind turbine yaw adjustment. However, the cup anemometer has many sources of measurement error, the wind speed measurement error is large, and the measured wind speed is the hub height wind speed value, which has limited effect on accurately measuring or calculating the wind speed distribution within the swept surface of the wind rotor.

[0003] Due to the large length of wind turbine blades, for example, in 2018, the average rotor diameters of global onshore wind turbines and offshore wind turbines reached 110m and 148m respectively. In such a large range of wind rotor swept area, the height and horizontal distribution of wind speed are not uniform, especially in the height direction. Therefore, if the wind speed data and wind shear law at the hub height cannot reflect the distribution characteristics of wind speed, it will inevitably indirectly affect the utilization rate of wind energy and the accurate evaluation of wind turbine performance. If the spatial and temporal distribution of wind speed in a close range upstream of the wind rotor swept area can be accurately measured and recorded, the wind energy capture efficiency Cp of the wind turbine blades can be analyzed more effectively and accurately, so as to carry out subsequent optimization design and transformation, and further improve the efficiency of wind turbines. In fact, at this stage, there is no effective way to measure the distribution of wind speed in the time and space dimensions over the entire wind rotor swept area. Summary of the invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide a wind speed measurement system and method using a constant temperature hot wire anemometer, which has a reasonable structural design and can accurately, real-time and continuously measure wind speed data.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention discloses a wind speed measurement system using a constant temperature hot wire anemometer, comprising a current signal total receiver, a communication module, a current shunt adjustment processor, a current source, a data processing unit, a data receiver and memory, and a plurality of hot wire probes;

[0007] A plurality of hot wire probes are sequentially arranged on the leading edge center line from the root section to the tip section of any blade of the wind turbine generator set; the hot wire probe comprises a hot wire, a probe temperature sensor and an ambient temperature sensor; the hot wire and the ambient temperature sensor are exposed from the blade surface, the probe temperature sensor is connected to the hot wire, the probe temperature sensor and the ambient temperature sensor are respectively connected to a data processing unit, the hot wire and the data processing unit are respectively connected to a current shunt regulation processor, the current shunt regulation processor is respectively connected to a current signal total receiver and a current source, and the current signal total receiver is connected to a data receiving and storage device through a communication module.

[0008] Preferably, the hot wire probe also includes a connecting rod and two fork rods fixed on the leading edge center line; the fork rod is vertically arranged on the outside of the blade surface where the leading edge center line is located, and the two fork rods are parallel to each other, and the hot wire metal wire is fixedly connected to the two fork rods; one fork rod is connected to the current shunt regulation processor through the connecting rod, and the other is grounded through the connecting rod.

[0009] Further preferably, the two fork rods are wrapped with a protective cover on the outside, and the protective cover is filled with insulating material.

[0010] Further preferably, the fork rod and the connecting rod are made of copper or silver.

[0011] Preferably, the annular sweep areas of adjacent hot wire probes are equal.

[0012] Preferably, the grounding end of the current source is grounded after passing through the wind turbine blades, the hub, the nacelle and the tower in sequence.

[0013] Preferably, the communication module is a wireless communication module.

[0014] The present invention discloses a method for measuring wind speed using the wind speed measurement system using the constant temperature hot wire anemometer, comprising:

[0015] The current shunt regulation processor shunts the current from the current source and outputs it to each hot-wire probe. The hot-wire metal wire generates heat after current passes through it. The data processing unit processes the probe temperature data measured by the probe temperature sensor and the ambient temperature data measured by the ambient temperature sensor and sends them to the current shunt regulation processor. The current shunt regulation processor is preset with the difference between the probe temperature and the ambient temperature. The current shunt regulation processor adjusts the current value of the hot-wire probe according to the preset value and the measured value of the difference between the probe temperature and the ambient temperature until the difference between the probe temperature and the ambient temperature reaches the preset value. The current signal total receiver sends the current value of the hot-wire probe to the data receiving and storage device via the communication module. The data receiving and storage device measures the wind speed value according to the current value of the hot-wire probe combined with the corresponding relationship between the calibrated current value and the wind speed.

[0016] Preferably, based on the measured wind speed value, the wind kinetic energy of the annular area swept by the blade with the hot wire probe within a data recording period T is calculated as:

[0017]

[0018] Among them, r i is the radius of the swept area of ​​the i-th hot wire probe; n is the speed of the wind wheel; u i,w is the wind speed at the location of the i-th hot wire probe; ρ is the air density;

[0019] The number of data recording cycles N when the blade with the hot wire probe sweeps one circle T =60 / (nT), the wind kinetic energy in the entire rotor swept area is:

[0020]

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] The present invention discloses a wind speed measurement system using a constant temperature hot wire anemometer. The constant temperature hot wire probe keeps the working temperature of the hot wire constant by adjusting the heating current. When the heat generated by the hot wire (proportional to the square of the current) and the convective heat transfer between the wire and the ambient airflow (proportional to the temperature difference and the convective heat transfer coefficient) reach a balance, the current and the convective heat transfer coefficient (a function of the wind speed) are directly corresponding to each other due to the constant temperature difference. By optimally arranging the calibrated constant temperature hot wire probe at a suitable position in the span direction of the fan blade, such as the center line of the leading edge, the wind speed data can be obtained by recording the current data of each measuring point during the operation of the fan. The present invention makes full use of the outstanding advantages of the hot wire sensitive element, such as small geometric size, small thermal inertia, high response frequency, continuous measurement, high spatial resolution, and small interference to the measured flow field. Compared with traditional speed measurement methods such as pitot tubes or cup anemometers, it has the advantages of accuracy, precision, real-time and continuity.

[0023] Furthermore, the hot wire is fixed by a fork rod on the outside of the blade surface and is used as a connecting wire through a connecting rod, so the connection is reliable.

[0024] Furthermore, the fork rod is wrapped with a protective cover on the outside, which can improve the stability of the structure and play an insulating role.

[0025] Furthermore, the fork rod and the connecting rod are made of copper or silver with low resistivity, which can reduce the influence of the heating of the non-hot wire part on the temperature measurement of the hot wire metal wire and further reduce the measurement error.

[0026] Furthermore, the annular sweep areas of adjacent hot wire probes are equal, which facilitates the calculation and comparison of wind energy within each annular sweep area and reduces errors caused by the hot wire probe distribution design.

[0027] Furthermore, the grounding end of the current source is grounded in sequence through the wind turbine blades, the hub, the nacelle and the tower, thereby improving the safety and stability of the system.

[0028] Furthermore, the communication module adopts a wireless communication module, which reduces wiring, effectively reduces space, and ensures efficient data transmission.

[0029] The method for measuring wind speed using the wind speed measurement system using the constant temperature hot wire anemometer disclosed in the present invention is simple to operate, gives full play to the advantages of the hot wire anemometer technology, can accurately, real-time and continuously measure wind speed data, and has good application prospects.

[0030] Furthermore, based on the measured wind speed value, the speed part of the blade's own rotation is excluded under the premise of effective yaw of the wind turbine, so as to obtain the input wind energy data during the operation of the wind turbine. This can be used as a reference for selecting the optimal operating state of the wind turbine, and can also be used as more accurate data for wind turbine performance analysis and feasibility study of quality improvement and efficiency enhancement. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the structure of the device arranged at the center line of the leading edge of the fan blade of the present invention;

[0032] Figure 2 A circuit diagram of a single hot wire probe of the present invention;

[0033] Figure 3 is a schematic structural diagram of the hot wire probe of the present invention;

[0034] Figure 4 FIG. 4 is a circuit system diagram of N hot-wire probes of the present invention.

[0035] In the figure: 1-blade root section; 2-blade tip section; 3-blade surface; 4-blade leading edge; 5-leading edge centerline; 6-current signal total receiver; 7-communication module; 8-current shunt regulation processor; 9-current source; 10-hot wire probe; 11-hot wire wire; 12-fork rod; 13-data processing unit; 14-data receiving and storage; 15-protective cover; 16-connecting rod; 17-the first hot wire probe; 18-the i-th hot wire probe; 19-the N-th hot wire probe; 20-probe temperature sensor; 21-ambient temperature sensor. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments, the contents of which are intended to explain the present invention rather than to limit it:

[0037] like Figure 1 The wind speed measurement system using a constant temperature hot wire anemometer of the present invention selects a blade in a common three-blade wind turbine and its connecting hub to arrange and install N constant temperature hot wire probes and their accessories, namely, a constant temperature hot wire anemometer, hereinafter referred to as hot wire probe 10.

[0038] The structure of the hot wire probe 10 is shown in Figure 3 , a hot wire 11 is welded on two parallel fork rods 12, and the fork rods 12 are installed vertically on the curved surface where the center line 5 of the leading edge of the blade is located. The length of the fork rod 12 exposed outside the blade surface 3 should be determined with reference to parameters such as the size of the blade, and should avoid being in the speed change area after the wind flows around the leading edge 4 of the blade, that is, to ensure that the wind speed in the space where the hot wire 11 is located is equal to the incoming wind speed when the blade is not rotating. The main body of the fork rod 12 is wrapped with a protective cover 15, which is filled with insulating material. The fork rod 12 is tightly installed on the blade surface 3 through a connecting rod 16. The materials of the fork rod 12 and the connecting rod 16 are selected to be metal copper or silver with low resistivity. While being connected and fixed, they can also be used as connecting wires for the hot wire 11.

[0039] The hot wire probe 10 is a constant temperature hot wire probe, which has two temperature sensors inside, one of which is a probe temperature sensor 20 for measuring the temperature of the hot wire 11, and the other is an ambient temperature sensor 21 for measuring the temperature of the wind. Since the fan blades rotate slowly, the temperature change when the air flows through the blades can be ignored, that is, the wind temperature is considered to be constant.

[0040] The working current of the hot wire 11 is provided by the current source 9, which is installed in the hub and has a variable output current. The current source 9 is divided into N currents by the current shunt adjustment processor 8 to heat the N corresponding hot wires 11. The grounding end of the current source 9 passes through the inside of the blade, the hub, the nacelle and the tower for grounding.

[0041] Since the probe temperature sensor 20 and the ambient temperature sensor 21 are arranged on the hot wire probe 10, these two sensors are directly connected to the corresponding data processing unit 13 to digitally process the measured temperature value and calculate the difference between the probe temperature and the ambient temperature. The temperature difference is returned to the corresponding channel in the current shunt adjustment processor 8, and the current shunt adjustment processor 8 determines whether the temperature difference is equal to the fixed temperature difference set by the calibration, and adjusts the heating current accordingly. If the returned temperature difference is lower than the set temperature difference, the heating current is increased, otherwise the heating current is reduced until the temperature difference between the hot wire 11 and the environment is equal to the set temperature difference. Since the response time of the hot wire probe 10 is short, the feedback adjustment can be completed in a very short time, and the adjustment time will not affect the measurement and recording of the wind speed.

[0042] like Figure 2 In the current shunt regulating processor 8, each current channel has a heating current value output interface in addition to outputting current and receiving the returned temperature difference signal, which is connected to the current signal total receiver 6 installed in the hub. After the current signal total receiver 6 collects the current value signals corresponding to the N hot wire probes 10, it transmits these signals to the data receiving and storage device 14 arranged at the wind turbine cabin or the bottom of the tower through the communication module 7. The communication module 7 is preferably a wireless communication module. The data can be incorporated into the SCADA data system of the wind turbine or calculated and analyzed separately. Each data can be directly calculated from the wind speed in combination with the calibrated corresponding relationship between the current and the wind speed.

[0043] As for the specific number N of the hot wire probes 10, it can be determined in combination with the specific length of the blade and the wind layout conditions of the wind field. The first hot wire probe 17 of the whole set of devices is arranged on the leading edge centerline 5 close to the root section 1, the Nth probe 19 is arranged on the leading edge centerline 5 close to the tip section 2, and the remaining (N-2) probes are arranged in sequence on the leading edge centerline 5 between the first hot wire probe 17 and the Nth hot wire probe 19. In principle, the annular sweeping area of ​​every two adjacent hot wire probes 10 is the same (see the following formula).

[0044]

[0045] Wherein, ri is the radius of the sweep circle where the i-th hot-wire probe is located, 1≤i≤N. Each hot-wire probe 10 can be arranged and installed in the above-mentioned manner. Figure 1 and Figure 4 .

[0046] Since the hot wire probe 10 is much smaller than the size of the fan blade, the arrangement of N hot wire probes 10 can have a negligible effect on the flow field when the fan is running, that is, the wind speed measured by the hot wire probe 10 can be considered as the speed in front of the leading edge 4 of the fan blade. This speed contains two parts. The first part is the incoming flow speed. Due to the effect of the yaw system, it can be considered that the wind is always perpendicular to the swept area of ​​the wind wheel; the second part is the rotation speed of the hot wire probe 10 with the blade in the swept area. These two speeds are perpendicular to each other, and their combined speed is the wind speed measured by the hot wire probe, as shown below.

[0047]

[0048] Among them, u i,m is the measured wind speed at the location of the i-th hot wire probe; u i,w is the wind speed at the location of the i-th hot wire probe; w is the circumferential speed of the wind wheel, rad / s; r i is the radius of the i-th hot wire probe 18 within the sweeping area.

[0049] The wind speed values ​​of each measuring point are obtained, and it can be approximately considered that the wind speed of the annular area passed by each hot wire probe 10 remains consistent within each cycle T (time interval) of temperature signal recording. That is, within a signal recording cycle T, the wind kinetic energy of the annular area swept by the blades where the hot wire probe 10 is arranged is:

[0050]

[0051] Among them, r i is the radius of the i-th hot wire probe 18 in the sweeping area, m; n is the speed of the wind wheel, rpm; u i,w is the wind speed at the location of the i-th hot wire probe, m / s; ρ is the air density, kg / m 3 .

[0052] When the blade with the hot wire probe 10 sweeps a circle, the number of data recording cycles N during this time is T =60 / (nT). If the hardware and other capabilities allow, the recording frequency should be set to a smaller value to improve the accuracy of the data. The wind kinetic energy in the entire wind rotor swept area is calculated using the following formula, which assumes that the wind speed distribution in the swept area remains unchanged during one rotation of the impeller. This processing method has been reliably verified in the long-term actual operation of the wind turbine.

[0053]

[0054] Under the premise that the yaw system of the wind turbine is operating normally, the wind speed direction is perpendicular to the swept surface of the wind rotor. Through the data recording and processing of N hot wire probes 10, the total amount of wind kinetic energy flowing through the swept surface of the wind rotor during the operation of the wind turbine can be quantitatively obtained. Combined with the power generation of the wind turbine during this time, the overall wind energy capture efficiency Cp of the wind turbine can be more accurately calculated; wind speed data in different wind speed time periods can also be extracted, combined with the power generation of the unit, to evaluate the change law of the wind energy capture efficiency Cp of the wind turbine blades in different wind speed ranges. This method can provide data support for the selection of the optimal operating state of the wind turbine, and has great guiding value for the optimization design of wind turbine blades and the preliminary analysis and research on quality and efficiency improvement.

[0055] It should be noted that the above is only a part of the implementation of the present invention, and equivalent changes made to the system described in the present invention are all included in the protection scope of the present invention. Those skilled in the art of the present invention can replace the specific examples described in a similar manner, as long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they all belong to the protection scope of the present invention.

Claims

1. A method for measuring wind speed using a constant temperature hot wire anemometer, characterized in that: The system comprises a current signal total receiver (6), a communication module (7), a current shunt adjustment processor (8), a current source (9), a data processing unit (13), a data receiving and storage device (14), and a plurality of hot wire probes (10); A plurality of hot wire probes (10) are sequentially arranged on a leading edge center line (5) from a blade root section (1) to a blade tip section (2) of any blade of a wind turbine; the hot wire probe (10) comprises a hot wire (11), a probe temperature sensor (20) and an ambient temperature sensor (21); the hot wire (11) and the ambient temperature sensor (21) are exposed from a blade surface, the probe temperature sensor (20) is connected to the hot wire (11), the probe temperature sensor (20) and the ambient temperature sensor (21) are respectively connected to a data processing unit (13), the hot wire (11) and the data processing unit (13) are respectively connected to a current shunt regulation processor (8), the current shunt regulation processor (8) is respectively connected to a current signal master receiver (6) and a current source (9), and the current signal master receiver (6) is connected to a data receiving and storage device (14) via a communication module (7); the annular sweeping areas of adjacent hot wire probes (10) are equal; The current shunt adjustment processor (8) shunts the current from the current source (9) and outputs it to each hot wire probe (10). The hot wire metal wire (11) generates heat after the current is passed through it. The data processing unit (13) processes the probe temperature data measured by the probe temperature sensor (20) and the ambient temperature data measured by the ambient temperature sensor (21) and sends them to the current shunt adjustment processor (8). The current shunt adjustment processor (8) is preset with the difference between the probe temperature and the ambient temperature. The current shunt adjustment processor (8) adjusts the current value of the hot wire probe (10) according to the preset value and the measured value of the difference between the probe temperature and the ambient temperature until the difference between the probe temperature and the ambient temperature reaches the preset value. The current signal total receiver (6) sends the current value of the hot wire probe (10) to the data receiving and storage (14) via the communication module (7). The data receiving and storage (14) measures the wind speed value according to the current value of the hot wire probe (10) combined with the corresponding relationship between the calibrated current value and the wind speed. Based on the measured wind speed value, the wind kinetic energy of the circular area swept by the blade provided with the hot wire probe (10) within a data recording period T is calculated as: Among them, r i is the radius of the swept area of ​​the i-th hot wire probe; n is the speed of the wind wheel; u i,w is the wind speed at the location of the i-th hot wire probe; ρ is the air density; When the blade equipped with the hot wire probe (10) sweeps one circle, the number of data recording cycles N T =60 / (nT), the wind kinetic energy in the entire wind rotor swept area is: 。 2. The method for measuring wind speed using a constant temperature hot wire anemometer according to claim 1, characterized in that: The hot wire probe (10) further comprises a connecting rod (16) and two fork rods (12) fixed on the leading edge center line (5); the fork rod (12) is vertically arranged outside the blade surface where the leading edge center line (5) is located, and the two fork rods (12) are parallel to each other, and the hot wire metal wire (11) is fixedly connected to the two fork rods (12); one fork rod (12) is connected to the current shunt adjustment processor (8) through the connecting rod (16), and the other fork rod (12) is grounded through the connecting rod (16).

3. The method for measuring wind speed using a constant temperature hot wire anemometer according to claim 2, characterized in that: The two fork rods (12) are wrapped with a protective cover (15) on the outside, and the protective cover (15) is filled with insulating material.

4. The method for measuring wind speed using a constant temperature hot wire anemometer according to claim 2, characterized in that: The fork rod (12) and the connecting rod (16) are made of copper or silver.

5. The method for measuring wind speed using a constant temperature hot wire anemometer according to claim 1, characterized in that: The grounding end of the current source (9) is grounded after passing through the wind turbine blades, the hub, the nacelle and the tower in sequence.

6. The method for measuring wind speed using a constant temperature hot wire anemometer according to claim 1, characterized in that: The communication module (7) is a wireless communication module.

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