A method for monitoring the state and evaluating the performance of a laser wireless energy transmission system

Abstract

The application relates to a kind of laser wireless energy transmission system state monitoring and performance evaluation method, comprising: according to the real-time parameter of each energy transmission link, the prediction of laser output power and photovoltaic array irradiation laser power is carried out, to build laser wireless energy transmission link performance evaluation parameter, extract transmission medium part in evaluation parameter;The transmission medium part of the laser wireless energy transmission link performance evaluation parameter of each energy transmission link is eliminated, to carry out laser, photovoltaic array group comprehensive performance evaluation;According to the comprehensive performance evaluation result, judge specific fault link, and judge the specific fault laser or photovoltaic array by switching access laser and photovoltaic array in fault link.Compared with prior art, the application can realize distributed system laser, photovoltaic array state monitoring and fault positioning in online condition, without additional laser power sensor or other auxiliary devices, with the advantages of system structure simplification, can be online identified.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser wireless energy transmission system evaluation, and particularly relates to a laser wireless energy transmission system state monitoring and performance evaluation method. BACKGROUND

[0002] With the development of photoelectric elements and wireless energy transmission technology, laser wireless energy transmission technology, as a long-distance and high-power energy transmission method, has attracted extensive attention and research. In actual application, real-time monitoring and fault positioning of the state of the laser wireless energy transmission system can effectively ensure the reliability and safety of the laser wireless energy transmission system by timely processing possible faults and problems.

[0003] In the energy transmission process, the laser wireless energy transmission system involves complex laser, optical elements, photovoltaic array and other components. The working state of these components can be affected by external environmental factors such as temperature, humidity, dust and vibration, or caused by internal factors such as equipment aging and component damage. In addition, the energy transmission channel of laser wireless energy transmission is free space (atmospheric environment, underwater environment, etc.), and the nonlinear time-varying characteristics of the transmission medium also affect the accuracy of state monitoring. Therefore, it is of great significance to perform real-time monitoring and timely fault diagnosis on the laser wireless energy transmission system.

[0004] The additional installation of laser power sensors at the transmitting end and the receiving end can conveniently evaluate the performance of the laser, laser transmission in the medium and photovoltaic array conversion, and help determine the specific performance of each link. However, the introduction of additional power sensors greatly increases the complexity and cost of the system.

[0005] In summary, as the application scenarios of laser wireless energy transmission technology gradually expand, the stability and reliability requirements of the system are also increasing. Therefore, it is necessary to study how to monitor the state of the system in real time with as few additional devices as possible, discover potential faults in a timely manner, and ensure stable operation of the system.

[0006] The existing related solutions have the following disadvantages:

[0007] 1. Related fault diagnosis researches are mostly for laser or photovoltaic array single devices, and require state information of the laser or photovoltaic array, or place them in a specific test environment. During the operation of the laser wireless energy transmission system, it is difficult to obtain all of these state information.

[0008] 2、In the laser wireless energy transmission, often with atmospheric environment, underwater environment, etc. as the energy transmission medium, the medium exists absorption, scattering, turbulence and other physical phenomena, laser energy transmission is affected by the medium visibility, humidity and other factors, the influence of the medium on the state monitoring and fault location in the transmission process needs to be considered.

[0009] 3、The laser wireless energy transmission system with a distributed structure has the characteristics of multiple transmission and multiple reception, complex structure, compared with the single link structure, the distributed structure system has the inter-link redundancy capability, the fault laser or photovoltaic array needs to be quickly located, so that the fault device is bypassed to prevent the further development of the fault.

[0010] 4、The existing offline fault diagnosis and state evaluation of the laser wireless energy transmission system has the characteristics of high accuracy and reliable diagnosis results; but the online state monitoring of the laser wireless energy transmission system still has irreplaceable advantages, which can effectively warn and facilitate the analysis of the running process and history. SUMMARY

[0011] The purpose of the present application is to overcome the above-mentioned defects of the prior art, such as the need for state information of the laser and photovoltaic array, the failure to consider the influence of the medium on the state monitoring and fault location in the transmission process, and the inability to quickly locate the fault device, and to provide a laser wireless energy transmission system state monitoring and performance evaluation method.

[0012] The purpose of the present application can be achieved by the following technical solutions:

[0013] A laser wireless energy transmission system state monitoring and performance evaluation method, comprising the following steps:

[0014] According to the real-time parameters of each energy transmission link in the laser wireless energy transmission system, the laser output power of each energy transmission link and the irradiation laser power of the photovoltaic array are predicted, so as to construct the laser wireless energy transmission link performance evaluation parameter;

[0015] According to the laser wireless energy transmission link performance evaluation parameters of different energy transmission links, the transmission medium part is extracted; the laser wireless energy transmission link performance evaluation parameters of each energy transmission link are eliminated from the transmission medium part, so as to perform comprehensive performance evaluation of the laser and photovoltaic array group;

[0016] According to the comprehensive performance evaluation results of each energy transmission link, the specific fault link is judged, and the laser and photovoltaic array in the fault link are switched to judge the specific fault laser or photovoltaic array, and the fault location result is obtained.

[0017] Further, the calculation expression of the laser wireless energy transmission link performance evaluation parameter is:

[0018] Further, the calculation expression of the laser wireless energy transmission link performance evaluation parameter is:

[0019] wherein pr is a laser wireless energy transmission link performance evaluation parameter, 1 ~ M is the energy transmission link number of the laser wireless energy transmission system, i LD LD is the laser current, temperature measurement information, u PV PV PV is the photovoltaic array voltage, current, temperature measurement information, f LD and f PV are the predicted results of the laser output power and the photovoltaic array irradiation laser power, respectively.

[0020] Further, the predicted expression of the laser output power is:

[0021] f LD (i LD , T LD ) = K (T LD ) * (i LD - i th )

[0022] wherein K (T LD ) represents the slope efficiency of the laser, i th represents the threshold current of the laser, i LD represents the working current of the laser.

[0023] The predicted expression of the photovoltaic array irradiation laser power is:

[0024]

[0025] wherein i PV represents the photovoltaic array output current; u PV represents the photovoltaic array output voltage; I0 is the diode reverse saturation leakage current; n is the diode ideality factor; q is the electronic charge quantity; N s is the number of series photovoltaic cells; k is the Boltzmann constant; T PV is the photovoltaic cell temperature; I sc is the short circuit current; k i is the temperature coefficient of the photo-generated current; T n is the photovoltaic array temperature corresponding to the standard test condition; G n is the photovoltaic array irradiance corresponding to the standard test condition; I rs is the reverse saturation current under the standard test condition, E g is the band gap of the semiconductor material; I sc is the short circuit current under the standard test condition; S PV is the photovoltaic array area; and R s ​​​is the equivalent series resistance, T is the operating temperature, and R is the resistance of the laser diode sh is the equivalent parallel resistance.

[0026] Further, in the process of predicting the laser output power, a neural network fitting method is adopted, taking the laser current and the laser temperature as inputs and the laser output optical power as output, and training based on a test data set, so that the neural network form of f LD (i LD , T LD ) is obtained.

[0027] In the process of predicting the irradiance laser power of the photovoltaic array, a neural network fitting method is adopted, taking the photovoltaic array voltage, current and operating temperature as inputs and the photovoltaic array irradiance laser power as output, and training based on a test data set, so that the neural network form of f PV (u PV , i PV , T PV ) is obtained.

[0028] Further, the method further comprises evaluating the performance state of the corresponding energy transmission link based on the calculation results of the laser wireless energy transmission link performance evaluation parameters of each energy transmission link and based on the pre-divided numerical interval.

[0029] Further, the extraction expression of the transmission medium part is:

[0030] η = min(pr1, pr2, …, pr M )

[0031] In the formula, η is the performance evaluation parameter of the laser transmission process in the medium, pr is the laser wireless energy transmission link performance evaluation parameter, and 1~M is the energy transmission link number of the laser wireless energy transmission system.

[0032] Further, the calculation expression of the performance evaluation parameter of the laser-photovoltaic array matching group obtained by eliminating the transmission medium part from the laser wireless energy transmission link performance evaluation parameter of each energy transmission link is:

[0033] pr chain_k = pr k - η (k = 1, 2…M)

[0034] In the formula, pr chain_k is the performance evaluation parameter of the kth energy transmission link.

[0035] Further, the process of judging the specific fault link according to the comprehensive performance evaluation results of each energy transmission link is specifically:

[0036] The performance evaluation parameters prchain_k If the preset threshold is exceeded, it is considered that the laser or photovoltaic array in the corresponding energy transmission link has obvious performance degradation; otherwise, fault positioning is not required.

[0037] Further, the threshold setting formula is:

[0038] pr th = [(1-a*b)*(1+a)-(1+a*b)*(1-a)] / [(1+a*b)*(1+a)];

[0039] a = (1-η) / (1+η);

[0040] In the formula, pr th is the threshold, b is the performance degradation coefficient of the laser or photovoltaic array, and η is the performance evaluation parameter of the extracted laser in the medium transmission process.

[0041] Further, the process of determining the specific faulty laser or photovoltaic array by switching the laser and photovoltaic array in the access fault link is:

[0042] Connect the laser or photovoltaic array before or after the energy transmission link in the fault link to one laser or photovoltaic array in the fault link to form multiple new links, evaluate the comprehensive performance of each new link, and determine the specific faulty laser or photovoltaic array.

[0043] Compared with the prior art, the present application has the following advantages:

[0044] (1) The energy transmission link performance evaluation parameter pr constructed by the present application can reflect the comprehensive performance of the electro-optical conversion, laser transmission, and optical-electrical conversion process in the laser wireless energy transmission. Compared with using the end-to-end efficiency of the link to evaluate the system performance, this evaluation parameter can be directly applied to different operating points of the same link or different links, normalized to the same scale, consistent, and not affected by the operating point of the laser or photovoltaic array at this time.

[0045] (2) The present application can separate and eliminate the medium loss part of the laser transmission process in the evaluation parameter pr based on the characteristics of the dispersed structure laser wireless energy transmission system. chain_k The separated evaluation parameter pr

[0046] (3) The present application can analyze the performance of the laser or photovoltaic array based on the comprehensive performance evaluation results pr of each energy transmission link. chain_kDetermine the specific fault link, and then for the specific fault link, by adjusting the laser-PV array matching group, the fault location can be realized; the distributed system laser, PV array state monitoring and fault location can be realized in online condition, without additional laser power sensor or other auxiliary devices, with the advantages of system structure simplification, online identification, etc., which has important significance for improving the reliability of laser wireless energy transmission system.

[0047] (4) The application evaluates the parameter pr chain_k , which can estimate the performance degradation of the transmission link, and realize the state monitoring of the laser transmission process, providing a basis for subsequent fault prediction and health management.

[0048] (5) The simulation and experimental research of the performance evaluation and fault location of the distributed structure laser wireless energy transmission system using the method of the application can provide theoretical support for improving the reliability of the laser energy transmission system, complete performance evaluation, guide the design of the fault diagnosis subsystem, and improve the system availability. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 A flowchart of a laser wireless energy transmission system state monitoring and performance evaluation method provided in an embodiment of the application is shown;

[0050] Figure 2 A schematic diagram of a distributed structure laser wireless energy transmission system provided in an embodiment of the application is shown;

[0051] Figure 3 A schematic diagram of a laser f LD and a PV array f PV provided in an embodiment of the application is shown;

[0052] Figure 4 A schematic diagram of a laser power setting provided in an embodiment of the application is shown;

[0053] Figure 5 A schematic diagram of a link performance evaluation parameter pr chain and a threshold pr th (normal condition) provided in an embodiment of the application is shown;

[0054] Figure 6 A schematic diagram of a link performance evaluation parameter pr chain and a threshold pr th (laser 1 performance degradation of 25%) provided in an embodiment of the application is shown;

[0055] Figure 7 A schematic diagram of a link performance evaluation parameter pr chain and a threshold pr thFig. 1 shows a schematic diagram of a laser wireless energy transmission system;

[0056] Figure 8 Fig. 2 shows a schematic diagram of an estimation result of transmission link performance attenuation provided in an embodiment of the present application. DETAILED DESCRIPTION

[0057] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0058] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0059] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0060] Embodiment 1

[0061] As shown in Fig. 1, the present embodiment provides a laser wireless energy transmission system state monitoring and performance evaluation method, including the following steps: Figure 1 S1: According to the real-time parameters of each energy transmission link in the laser wireless energy transmission system, the laser output power of each energy transmission link and the irradiation laser power of the photovoltaic array are predicted, so as to construct the laser wireless energy transmission link performance evaluation parameters;

[0062] S2: According to the laser wireless energy transmission link performance evaluation parameters of different energy transmission links, the transmission medium part is extracted; the laser wireless energy transmission link performance evaluation parameters of each energy transmission link are eliminated from the transmission medium part, so as to perform comprehensive performance evaluation of the laser and photovoltaic array group;

[0063] S3: According to the comprehensive performance evaluation results of each energy transmission link, the specific fault link is judged, and the laser and photovoltaic array in the fault link are switched to judge the specific fault laser or photovoltaic array, so as to obtain the fault positioning result.

[0064]

[0065] ​According to the method, three parts are mainly included: firstly, the energy transmission link performance evaluation parameter pr is constructed according to the laser wireless energy transmission system model, then the energy transmission medium related term is separated from the link performance evaluation parameters to obtain the comprehensive performance evaluation result of the laser and the photovoltaic array, and the comprehensive performance of the laser-photovoltaic array matching group can be judged according to the evaluation result, and the performance attenuation of each laser and photovoltaic array can be finally obtained by adjusting the laser-photovoltaic array matching relationship, so as to realize fault positioning.

[0066] The specific process of step S1 is as follows:

[0067] According to the mathematical model of the laser and the photovoltaic array, the laser wireless energy transmission link performance evaluation parameter pr is constructed, which can be expressed as:

[0068]

[0069] In the formula, pr is the laser wireless energy transmission link performance evaluation parameter, 1~M is the energy transmission link number of the laser wireless energy transmission system, i LD ,T LD is the laser current and temperature measurement information, u PV ,i PV ,T PV is the photovoltaic array voltage, current and temperature measurement information, f LD and f PV are the prediction results of the laser output power and the photovoltaic array irradiation laser power respectively.

[0070] As an optional implementation, f LD and f PV are functions derived according to the model parameters of the laser and the photovoltaic array, that is, the prediction expression of the laser output power is:

[0071] f LD (i LD , T LD ) = K(T LD ) * (i LD -i th ) (2)

[0072] In the formula, K(T LD ) represents the slope efficiency of the laser, i th represents the threshold current of the laser, and i LD represents the working current of the laser; in essence, the formula is to calculate the laser output optical power at this time according to the laser model and the laser current and temperature. In the case of normal operation of the laser, f LD (i LD , T LD ) ≈ P LDout, f(u, i, T) = P, where P is the actual output laser power at the time. The above method is to predict the laser output power according to the slope efficiency and threshold current of the laser. LD (i LD , T LD ) = P LDout , where P LDout is the actual output laser power at the time. The above method is to predict the laser output power according to the slope efficiency and threshold current of the laser.

[0073] The expression for predicting the irradiation laser power of the photovoltaic array is:

[0074]

[0075] In the formula, i PV represents the output current of the photovoltaic array; u PV represents the output voltage of the photovoltaic array; I0 is the reverse saturation leakage current of the diode; n is the diode ideality factor (1 ≤ n ≤ 2); q is the electronic charge quantity, q = 1.602 × 10 -19 C; N s is the number of series photovoltaic cells; k is the Boltzmann constant, k = 1.381 × 10 -23 J / K; T PV is the temperature of the photovoltaic cell (Kelvin K). I sc is the short-circuit current; k i is the temperature coefficient of the photo-generated current, which is an engineering / experience parameter; T n is the temperature of the photovoltaic array corresponding to the standard test condition; G n (W / m 2 ) is the irradiance of the photovoltaic array corresponding to the standard test condition. I rs is the reverse saturation current under the standard test condition, E g is the band gap of the semiconductor material (the band gap of gallium arsenide material is about 1.42 eV); I sc is the short-circuit current under the standard test condition; S PV is the area of the photovoltaic array; R s is the equivalent series resistance, T is the working temperature, and R sh is the equivalent parallel resistance.

[0076] In the normal working condition of the photovoltaic array, f PV (u PV , i PV , T PV ) ≈ P PVin , in the non-normal working condition of the photovoltaic array (local short circuit of the photovoltaic array or performance degradation caused by other reasons), f PV (u PV , i PV , T PV)>P PVin where P PVin represents the laser power irradiated by the photovoltaic array at this time. The above method is to predict the irradiation power of the photovoltaic array according to the classical five-parameter model of the photovoltaic array.

[0077] As an optional implementation, the laser output power prediction of the data-driven method can be carried out according to the laser test data, for example, a BP neural network fitting method is used, the laser current and the laser temperature are taken as inputs, and the laser output optical power is taken as output, training is carried out based on the test data set, and finally a neural network form of f LD (i LD , T LD ) can be obtained. The internal structure and the weight of the neural network contain the key information of the laser, and the established f LD (i LD , T LD ) can also be used in the method.

[0078] The irradiation laser power prediction of the photovoltaic array of the data-driven method can be carried out according to the photovoltaic array test data, for example, a BP neural network fitting method is used, the photovoltaic array voltage, current and working temperature are taken as inputs, and the photovoltaic array irradiation laser power is taken as output, training is carried out based on the test data set, and finally a neural network form of f PV (u PV , i PV , T PV ) can be obtained. The internal structure and the weight of the neural network contain the key parameters of the photovoltaic array, and the established f PV (u PV , i PV , T PV ) can also be used in the method.

[0079] As an optional implementation, a photovoltaic array irradiation laser power observer can be designed based on the state observer design principle according to the photovoltaic array model possessed, a closed-loop feedback is carried out between the observer current and the actual photovoltaic array current, and finally an observation value of the photovoltaic array irradiation laser power can be obtained. The f PV (u PV , i PV , T PV ) obtained by the method can also be used in the method.

[0080] In summary, the link performance evaluation parameter pr of each link can be obtained, which can mainly reflect the comprehensive performance in the processes of electro-optical conversion, laser transmission and optical-electric conversion of the laser wireless energy transmission.

[0081] Specifically, when the laser, photovoltaic array performance without degradation, laser transmission process loss can be ignored (short distance transmission) case, pr tends to 0, indicating that the energy transmission performance is better at this time.

[0082] When the laser, photovoltaic array performance degradation, or there is a certain loss in the process of laser transmission (medium and long distance transmission) case, pr will gradually rise, indicating that there is additional loss in the energy transmission link at this time, and the performance gradually decays.

[0083] When the laser, photovoltaic array performance decay is obvious, or the laser transmission environment is poor, pr will further rise.

[0084] When pr-->1, the energy transmission link is in a completely failed state at this time, no energy is transmitted from the transmitting end to the receiving end, corresponding to the complete damage of the laser or photovoltaic array, or the complete shielding of the laser light path.

[0085] The range of pr is [0, 1], and the numerical value of pr can reflect the additional loss of the laser wireless energy transmission link, which mainly includes three parts, including laser performance degradation, photovoltaic array performance degradation and loss caused by transmission medium.

[0086] Preferably, the state of the laser wireless energy transmission link at this time can be evaluated according to the numerical value of pr, when pr is close to 0 (for example, p<0.1), it can be judged that the laser wireless energy transmission system is in a normal operating state at this time; when pr is high, it can be preliminarily inferred that the medium efficiency is low (visibility decreases) or there are problems such as aging of optoelectronic devices at this time.

[0087] The proposed evaluation of the state of the laser wireless energy transmission link according to pr is compared with the evaluation of the state of the laser wireless energy transmission link according to the end-to-end (or electro-optical-electric) laser energy transmission efficiency η E-E , which is not affected by the operating point of the laser, photovoltaic array at this time, and is a consistent evaluation standard under different i LD , u PV , i PV and operating temperature.

[0088] Among them, the end-to-end laser energy transmission efficiency η E-E is the product of the laser efficiency, medium transmission efficiency and photovoltaic array efficiency, which can be represented as the output power of the photovoltaic array divided by the input power of the laser (P PVout / P LDin ), which can also reflect the state of the energy transmission link, and the higher the efficiency generally indicates the better the link performance, but due to the photoelectric nonlinear characteristics of the laser and the photovoltaic array, the system power demand (or laser power given) will also affect the end-to-end laser energy transmission efficiency η E-E . For example, under light load conditions, due to the efficiency characteristics of the laser and the photovoltaic array, η E-Ewill be significantly reduced, however the laser, photovoltaic array can still be in normal state, thus the end-to-end laser transmission efficiency η E-E cannot be directly used to evaluate the laser wireless energy transmission link state.

[0089] In addition, the end-to-end laser transmission efficiency η E-E also fails to take into account the influence of laser, photovoltaic array temperature, in some cases, with the change of temperature, the end-to-end laser transmission efficiency η E-E may also follow the change, but at this time the working state of the laser, photovoltaic array can not change (health index).

[0090] Step S2 specifically comprises the following steps:

[0091] S201: separate the transmission medium related term, construct η = min (pr1, pr2, …, pr M );

[0092] In step S1, the parameter pr that can reflect the state of the transmission link is finally obtained, which mainly includes the influence of the laser, photovoltaic array, and laser transmission medium. For a dispersed structure transmission system, it has the characteristics of multi-beam transmission, and the corresponding transmission medium part can be extracted according to the performance evaluation parameters of different links:

[0093] η = min (pr1, pr2, …, pr M ) (4)

[0094] Where M represents the number of transmission links in the dispersed structure, and η represents the performance evaluation parameter of the laser transmission process in the medium.

[0095] η ranges from [0, 1], and η is closer to 1, indicating that the medium loss is greater at this time, and η is closer to 0, indicating that the medium loss is smaller at this time.

[0096] When η = 0.11, it means that the medium transmission efficiency is about 80% at this time; when η = 0.33, it means that the medium transmission efficiency is about 50% at this time; according to the specific value of η, the laser energy transmission medium transmission efficiency can be evaluated.

[0097] In fact, this formula extracts the common additional loss in each link. For a dispersed structure laser wireless energy transmission system, multiple beams are transmitted in the medium, and there will be similar medium loss, so this method can be used for extraction.

[0098] The formula extracts the common additional loss in each link, which may extract the common additional loss of the laser and the photovoltaic array part. If all the lasers have a slight degree of aging (the actual output power is 95% of the theoretical output power), this part will also be extracted into the medium loss at this time. The probability of simultaneous failure of two optoelectronic devices in the actual operation of the laser wireless energy transmission system is significantly less than the probability of failure of a single optoelectronic device, and the probability of simultaneous failure of all optoelectronic devices is negligible. Therefore, the error of this method of extracting the common additional loss as the medium loss is acceptable, which will not affect the performance evaluation and specific positioning of the energy transmission system.

[0099] Further, in extremely rare cases, the medium loss in multi-beam energy transmission may be different, for example, it is possible that one of the beams is blocked, and this type of problem can be diagnosed by image processing method. In the laser wireless energy transmission system, the transmitting end is arranged with a capture, tracking, and aiming system, a CCD or CMOS image sensor is used to collect the image of the receiving end, and a target recognition method is used to recognize the laser spot and the photovoltaic array to complete the alignment of the laser. This type of problem of one beam being blocked can be identified and diagnosed by image processing algorithm. In actual operation, the blocked beam will be cut off or the energy transmission process of the link will be terminated for safety considerations. Therefore, it can be considered that each laser beam transmitted simultaneously under the same medium has similar medium loss, which can be extracted by this method.

[0100] S202: Perform laser-photovoltaic array group comprehensive performance evaluation pr chain_k = pr k -η(k=1,2...M)=f(pr LD_k ,pr PV_k );

[0101] After eliminating and separating the medium loss related items of the energy transmission link, the performance evaluation parameter pr chain_k of the laser-photovoltaic array matching group can be obtained, where k represents the link number and takes a value from 1 to M.

[0102]

[0103] The performance evaluation parameter pr chain_k of the laser-photovoltaic array matching group, which mainly reflects the comprehensive performance of the electro-optical conversion and optical-electrical conversion process in the laser wireless energy transmission. pr chain_k is different from pr k in that the former separates and eliminates the medium related items to a certain extent.

[0104] Further, when the laser and photovoltaic array performance are not degraded, pr chain_kApproaching 0, indicating that the energy transmission performance is better at this time.

[0105] When the laser, photovoltaic array performance exists deterioration, pr chain_k will gradually rise, indicating that the energy transmission performance at this time exists decay, the laser or photovoltaic array exists performance deterioration.

[0106] When the laser, photovoltaic array performance decay is obvious, pr chain_k will further rise.

[0107] When pr chain_k -->1, the energy transmission link at this time is in a complete failure state, no energy is transmitted from the transmitting end to the receiving end, corresponding to the complete damage of the laser or photovoltaic array.

[0108] The range of pr chain_k is [0, 1], and the numerical value of pr chain_k can reflect the additional loss of the laser wireless energy transmission link, which mainly includes two parts, including laser performance deterioration, photovoltaic array performance deterioration.

[0109] Preferably, the state of the laser wireless energy transmission link at this time can be evaluated according to the numerical value of pr chain_k , when pr chain_k approaches 0 (for example, pr chain_k <0.1), it can be judged that the laser and photovoltaic array in the laser wireless energy transmission system at this time are in a normal operating state; when pr chain_k is higher, it is preliminarily inferred that there may be problems such as aging of optoelectronic devices at this time.

[0110] The specific process of step S1 is as follows:

[0111] In step S2, the parameter pr chain_k reflecting the state of the laser-photovoltaic array in the energy transmission link can be finally obtained, which mainly includes the influence of the laser and the photovoltaic array. For a dispersed structure energy transmission system, by adjusting the group of laser-photovoltaic array, the fault can be finally located to a specific laser or photovoltaic array.

[0112] Only when pr chain_k exceeds the preset threshold pr th , that is, when the laser or photovoltaic array in the link has obvious performance deterioration, step S3 is executed.

[0113] Only when pr chain_k does not exceed the preset threshold pr th , it is considered that the laser or photovoltaic array in the link is basically in a normal working condition, and fault location is not needed at this time.

[0114] The threshold prth The smaller (closer to 0) the setting is, the higher the system sensitivity is, and the system reacts when the laser or photovoltaic array performance has a certain performance attenuation.

[0115] Threshold pr th The larger (closer to 1) the setting is, the lower the system sensitivity is, and the system reacts when the laser or photovoltaic array performance has more performance attenuation.

[0116] Further, assuming that the laser or photovoltaic array performance degradation coefficient b (k ∈ [0, 1]), b represents the actual output power divided by the ideal output power, when b = 0.8, it is considered that the laser or photovoltaic array performance is reduced by about 20%, and the threshold pr th can be set according to the following formula:

[0117]

[0118] In the formula, pr th is the threshold, b is the laser or photovoltaic array performance degradation coefficient, and η is the performance evaluation parameter of the extracted laser in the medium transmission process.

[0119] For example, when η = 0.11, it means that the medium transmission efficiency is about 80% at this time, b = 0.8 is taken, and it is considered that the laser or photovoltaic array performance is reduced by about 20% as the threshold, at this time, pr th can be taken as 0.108. When pr chain_k is less than 0.108, the overall performance attenuation of the laser-photovoltaic array matching group is less than 20%; when pr chain_k is greater than 0.108, the overall performance attenuation of the laser-photovoltaic array matching group exceeds 20%, and the faulty device needs to be further located as the laser or the photovoltaic array;

[0120] For example, when η = 0.11, it means that the medium transmission efficiency is about 80% at this time, b = 0.7 is taken, and it is considered that the laser or photovoltaic array performance is reduced by about 30% as the threshold, at this time, pr th can be taken as 0.171. When pr chain_k is less than 0.171, the overall performance attenuation of the laser-photovoltaic array matching group is less than 30%; when pr chain_k is greater than 0.171, the overall performance attenuation of the laser-photovoltaic array matching group exceeds 30%, and the faulty device needs to be further located as the laser or the photovoltaic array;

[0121] When pr chain_k exceeds the preset threshold pr th , it is considered that the laser-photovoltaic array matching group has a larger performance attenuation, and the specific fault position can be determined by changing the matching laser-photovoltaic array.

[0122] The process of determining the specific faulty laser or photovoltaic array by switching the laser and photovoltaic array in the faulty link is as follows:

[0123] Connect the laser or photovoltaic array in front or behind the faulty link to one laser or photovoltaic array in the faulty link to form multiple new links, evaluate the comprehensive performance of each new link, and determine the specific faulty laser or photovoltaic array.

[0124] For example, assume there are 3 laser wireless energy transmission links, denoted as links [1-1, 2-2, 3-3]. When pr chain_2 When the preset threshold is exceeded, it is considered that the link energy transmission performance has decreased significantly, and it is determined that laser 2 or photovoltaic array 2 is faulty. At this time, the laser-photovoltaic array matching group can be adjusted, laser 1 irradiates photovoltaic array 2 to form a new link (1-2), and laser 2 irradiates photovoltaic array 1 to form a new link (2-1). At this time, pr chain_(*1-2) and pr chain_(*2-1) That is, the performance of the new link can be determined, and ultimately the specific faulty device can be determined. If pr chain_(*1-2) is significantly higher, it can be determined that photovoltaic array 2 is faulty at this time, resulting in a more significant performance decrease in the link containing photovoltaic array 2, resulting in an increase in the corresponding link performance evaluation parameter pr chain_(2-2) and pr chain_(*1-2) .

[0125] Preferably, for the case of multiple lasers irradiating the same photovoltaic array, the fault location method can be used to determine whether the laser-photovoltaic array in the link is working normally according to the link performance evaluation parameter. Multiple lasers can be judged one by one, or can be judged in batches using a binary method or the like.

[0126] A specific example of the above method is provided as follows:

[0127] 1. For a certain dispersion structure laser wireless energy transmission system as shown in Figure 2 , the energy transmission link is 3, i.e. M = 3, there are 3 lasers and 3 photovoltaic arrays, the laser is an 808 nm semiconductor laser, and the photovoltaic array is a four-junction gallium arsenide photovoltaic array.

[0128] 2. In the actual experimental platform, the transmission distance is about 6 m, and after laser alignment, the medium energy transmission efficiency is about 100%, and the corresponding medium evaluation parameter η = 0. Under normal working conditions, pr1, pr2, pr3 all tend to 0, and the error mainly comes from modeling error, and laser output power instability (3%) and measurement error, etc.

[0129] 3. According to the laser manual data, f LD (iLD T LD )=K(T LD )*(i LD -i th The laser output power of the laser is measured using a laser power meter, and the relationship is as follows: Figure 3 As shown in the left figure, it can characterize the laser output power under a specific operating condition.

[0130] 4. To facilitate the analysis of system fault states, a simulation model of this distributed laser wireless energy transmission system was established and verified through simulation using MATLAB / Simulink. Photovoltaic array f PV (u PV i PV T PV The photovoltaic array irradiance power is observed using a state observer, and the observed time-domain waveform is as follows: Figure 3 As shown, the dashed line represents the actual irradiance, and the solid line represents the observer output, which can characterize the irradiance of the photovoltaic array under a specific operating condition.

[0131] Let lasers 1-3 and photovoltaic arrays 1-3 form three wireless laser power transmission links (1-1, 2-2, 3-3). Assume that the laser performance degrades to 98%, 96%, and 97% of its expected performance, respectively (simulating power loss due to laser power instability). The medium transmission efficiency is 82%, 83%, and 86%, respectively (medium efficiency includes medium scattering and absorption and additional losses from alignment). The photovoltaic array performance also degrades to 97%, 95%, and 97% of its expected performance, respectively. The laser power is given (the theoretically expected output power of the laser) as follows: Figure 4 As shown. Taking b = 0.8, that is, when the performance of the laser or photovoltaic array degrades by approximately 20%, the threshold pr is reached. th .

[0132] The simulation results are as follows: Figure 5 As shown, pr chain_k (k=1,2,3) are all relatively small and less than the threshold pr th At this point, the performance degradation of both the laser and photovoltaic array did not exceed 20%. When the power output of laser 1 decreases to 75% in a step at 0.12s, the simulation results are as follows. Figure 6 As shown, it can be seen that pr chain1 Exceeding the threshold pr th, it is possible that the laser or photovoltaic array in link 1 has a more obvious performance decline, and then by exchanging the matching relationship of the laser and photovoltaic array of link 1-2, the laser 1 irradiates the photovoltaic array 2, and the laser 2 irradiates the photovoltaic array 1, to form chain (1-2) and (2-1), in order to ensure that the transmission power of each link is unchanged, the power of laser 1 and 2 is exchanged.

[0133] The simulation results after the change are shown in Figure 7 , pr chain1-2 exceeds the threshold value pr th , combined with the discrimination information before and after the link recombination, pr chain_1-1 and pr chain_1-2 have a significant performance decline, which can determine that the laser-1 has a performance decline problem.

[0134] And, by transforming pr chain_1-2 , the estimation of the performance attenuation of the transmission link at this time can be obtained, as shown in Figure 8 . The estimation results are as follows: the link 3-3 has no attenuation, the medium attenuation is about 19.2%, the link 2-1 has an attenuation of about 4.2%, and before the failure, the link 1-2 has an attenuation of about 5.6%, and after the failure, the attenuation is about 26%.

[0135] In summary, the method constructs the energy transmission link performance evaluation parameter pr, which can evaluate the overall transmission performance of the link. For a dispersed structure laser wireless energy transmission system, the medium part is separated, and by pr chaink , the performance of the laser-photovoltaic array combination in the laser wireless energy transmission link can be evaluated, the energy transmission performance can be evaluated and related fault positioning can be carried out, and the improvement effect mainly lies in the insensitivity to the working point and the realization of the fault positioning of the laser-photovoltaic array. The reason for the above advantages is that the construction of the performance evaluation parameter can fully consider the nonlinear characteristics of the laser wireless energy transmission system and the characteristics of the simultaneous transmission of multiple beams in the dispersed structure.

[0136] The above describes the preferred embodiments of the present application in detail. It should be understood that those skilled in the art can make many modifications and changes without creative labor according to the concept of the present application. Therefore, any technical solution obtained by logical analysis, reasoning or limited experiment on the basis of the prior art according to the concept of the present application shall be within the protection scope determined by the claims.

Claims

1. A method for monitoring the state and evaluating the performance of a laser wireless energy transmission system, characterized in that, The method comprises the following steps: According to the real-time parameters of each transmission link in the laser wireless energy transmission system, the laser output power of each transmission link and the irradiation laser power of the photovoltaic array are predicted, and a laser wireless energy transmission link performance evaluation parameter is constructed; According to the laser wireless energy transmission link performance evaluation parameter of different transmission links, the transmission medium part is extracted, and the transmission medium part of the laser wireless energy transmission link performance evaluation parameter of each transmission link is eliminated, so as to perform comprehensive performance evaluation on the laser and photovoltaic array group; According to the comprehensive performance evaluation results of each transmission link, the specific fault link is judged, the laser and photovoltaic array in the fault link are accessed through switching, the specific fault laser or photovoltaic array is judged, and the fault positioning result is obtained; The calculation expression of the laser wireless energy transmission link performance evaluation parameter is: In the formula, pr is the performance evaluation parameter of the laser wireless energy transmission link, 1~M is the energy transmission link number of the laser wireless energy transmission system, i LD , T LD is the laser current, temperature measurement information, u PV , i PV , T PV is the photovoltaic array voltage, current, temperature measurement information, f LD and f PV are the laser output power prediction result and the photovoltaic array irradiation laser power prediction result respectively; The prediction expression of the laser output power is: wherein K ( T LD ) represents the slope efficiency of the laser, i th represents the threshold current of the laser, i LD represents the operating current of the laser; The prediction expression of the irradiation laser power of the photovoltaic array is: wherein i PV represents the photovoltaic array output current; u PV represents the photovoltaic array output voltage; I 0 is the diode reverse saturation current; n is the diode ideality factor; q is the electronic charge; N s is the number of series photovoltaic cells; k is the Boltzmann constant; T PV is the photovoltaic cell temperature; I sc is the short-circuit current; k i is the temperature coefficient of the photo-generated current; T n is the photovoltaic array temperature corresponding to standard test conditions; G n is the photovoltaic array irradiance corresponding to standard test conditions; I rs is the reverse saturation current under standard test conditions, E g is the bandgap of the semiconductor material; I sc is the short-circuit current under standard test conditions; S PV is the photovoltaic array area; is the equivalent series resistance, T is the operating temperature, is the equivalent parallel resistance; In the prediction process of the laser output power, a neural network fitting method is adopted, laser current and laser temperature are taken as inputs, and laser output optical power is taken as output, training is carried out based on a test data set, and finally a neural network form of ; In the process of predicting the irradiation laser power of the photovoltaic array, a neural network fitting method is adopted, the voltage, current and working temperature of the photovoltaic array are taken as inputs, the irradiation laser power of the photovoltaic array is taken as output, and based on a test data set, training is finally carried out to obtain a neural network form of ; The extraction expression of the transmission medium part is: η min( pr 1, pr 2,…, pr M ) In the formula, The calculation expression of the performance evaluation parameter of the laser-photovoltaic array matching group obtained after the transmission medium part of the laser wireless energy transmission link performance evaluation parameter of each transmission link is eliminated is: is a performance evaluation parameter of the laser transmission process in the medium, pr is a performance evaluation parameter of the laser wireless energy transmission link, and 1-M is the energy transmission link number of the laser wireless energy transmission system. The method further comprises evaluating the performance state of the corresponding transmission link based on the calculation results of the laser wireless energy transmission link performance evaluation parameter of each transmission link and the pre-divided numerical interval. In the formula, is a performance evaluation parameter of the kth energy transfer link.

2. The method of claim 1, wherein The process of judging the specific fault link according to the comprehensive performance evaluation results of each transmission link is specifically:

3. The method of claim 1, wherein, The setting formula of the threshold value is: corresponding to each power transmission link pr chain_k If the performance evaluation parameter corresponding to each power transmission link exceeds the preset threshold, it is considered that the laser or photovoltaic array in the corresponding power transmission link has obvious performance degradation; otherwise, fault positioning is not needed.

4. The method of claim 3, wherein, The process of judging the specific fault laser or photovoltaic array by switching and accessing the laser and photovoltaic array in the fault link is specifically: wherein pr th is a threshold value, b is a coefficient of the laser or photovoltaic array performance degradation, The laser or photovoltaic array of the transmission link before or after the fault link is connected to one laser or photovoltaic array in the fault link to form multiple new links, the comprehensive performance of each new link is evaluated, and the specific fault laser or photovoltaic array is determined. is a performance evaluation parameter of the extracted laser during the transmission process in the medium.

5. The method of claim 1, wherein, ​ ​

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