State monitoring and performance evaluation method for laser wireless energy transmission system

Abstract

The invention relates to a state monitoring and performance evaluation method for a laser wireless energy transmission system, and the method comprises the steps: carrying out the prediction of the output power of a laser device and the irradiation laser power of a photovoltaic array according to the real-time parameters of each energy transmission link, thereby constructing the performance evaluation parameters of a laser wireless energy transmission link, and carrying out the evaluation of the performance of the laser wireless energy transmission link. Extracting a transmission medium part in the evaluation parameters; a transmission medium part is eliminated for laser wireless energy transmission link performance evaluation parameters of each energy transmission link, so that comprehensive performance evaluation of a laser and a photovoltaic array group is carried out; and judging a specific fault link according to a comprehensive performance evaluation result, and judging a laser or a photovoltaic array with a specific fault by switching the laser and the photovoltaic array accessed into the fault link. Compared with the prior art, state monitoring and fault positioning of the laser and the photovoltaic array of the distributed system can be realized on line, additional laser power sensors or other auxiliary devices are not needed, and the system has the advantages of simple structure, on-line identification and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of laser wireless energy transmission system evaluation, and in particular to a laser wireless energy transmission system state monitoring and performance evaluation method. Background Art

[0002] With the development of optoelectronic components and wireless energy transmission technology, laser wireless energy transmission technology, as a long-distance, high-power energy transmission method, has received extensive attention and research. In practical applications, real-time monitoring and fault location of the status of the laser wireless energy transmission system, and timely handling of possible faults and problems can effectively ensure the reliability and safety of the laser wireless energy transmission system.

[0003] During the energy transmission process, since the laser wireless energy transmission system involves complex lasers, optical elements, photovoltaic arrays and other components, the working conditions of these components may be affected by external environmental factors such as temperature, humidity, dust, vibration, or 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 will also affect the accuracy of state monitoring. Therefore, it is of great significance to conduct real-time monitoring and timely fault diagnosis of the laser wireless energy transmission system.

[0004] Installing additional laser power sensors at the transmitting and receiving ends can more conveniently evaluate the laser, the transmission of the laser in the medium, and the conversion performance of the photovoltaic array, and help determine the specific performance of each link. However, the introduction of additional power sensors will greatly increase the optical path complexity and cost of the system.

[0005] In summary, as the application scenarios of laser wireless energy transmission technology gradually expand, the requirements for system stability and reliability are becoming higher and higher. Therefore, it is necessary to study how to monitor the status of the system in real time with as few additional devices as possible, detect potential faults in time, and ensure the stable operation of the system.

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

[0007] 1. Related fault diagnosis research is mostly aimed at single devices of lasers or photovoltaic arrays, which requires status information of lasers and photovoltaic arrays, or places them in a specific test environment. During the operation of the laser wireless energy transmission system, it is difficult to obtain all of this status information.

[0008] 2. In laser wireless energy transmission, the atmospheric environment, underwater environment, etc. are often used as energy transmission media. The medium has physical phenomena such as absorption, scattering, and turbulence. Laser energy transmission is affected by factors such as medium visibility and humidity. It is necessary to consider the impact of the medium on status monitoring and fault location during the transmission process.

[0009] 3. The dispersed structure laser wireless energy transmission system has the characteristics of multi-transmission-multi-reception and complex structure. Compared with the single-link structure, the dispersed structure system has redundancy between links. It is necessary to quickly locate the faulty laser or photovoltaic array so that the faulty device can be bypassed to prevent further development of the fault.

[0010] 4. The existing offline fault diagnosis and status assessment of the laser wireless energy transmission system are characterized by high accuracy and reliable diagnostic results; however, the online status monitoring of the laser wireless energy transmission system still has irreplaceable advantages, can provide effective early warning, and facilitate the analysis of the operation process and operation history. Summary of the invention

[0011] The purpose of the present invention is to provide a method for state monitoring and performance evaluation of a laser wireless energy transmission system in order to overcome the defects of the above-mentioned prior art, which require state information of lasers and photovoltaic arrays, do not consider the influence of the medium on state monitoring and fault location during transmission, and cannot quickly locate faulty components.

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

[0013] A method for state monitoring and performance evaluation of a laser wireless energy transmission system comprises 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 performance evaluation parameters of the laser wireless energy transmission link;

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

[0016] The specific faulty link is determined based on the comprehensive performance evaluation results of each energy transmission link, and the specific faulty laser or photovoltaic array is determined by switching the laser and photovoltaic array connected to the faulty link to obtain the fault location result.

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

[0018]

[0019] Where 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, and i LD ,T LD is the laser current and temperature measurement information, u PV ,i PV ,T PV is the voltage, current and temperature measurement information of the photovoltaic array, f LD With f PV They are the prediction results of laser output power and photovoltaic array irradiation laser power.

[0020] Furthermore, the prediction expression of the laser output power is:

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

[0022] In the formula, K(T LD ) represents the slope efficiency of the laser, i th represents the threshold current of the laser, i LD Indicates the operating current of the laser;

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

[0024]

[0025] In the formula, i PV Indicates 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 ideal factor of the diode; q is the amount of electron charge; N s is the number of photovoltaic units connected in series; 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 photocurrent; T n is the photovoltaic array temperature corresponding to the standard test conditions; G n is the irradiance of the photovoltaic array corresponding to the standard test conditions; I rs is the reverse saturation current under standard test conditions, E g I is the bandgap width of the semiconductor material; sc is the short-circuit current under standard test conditions; S PV is the photovoltaic array area; R sis the equivalent series resistance, T is the operating temperature, R sh is the equivalent parallel resistance.

[0026] Furthermore, in the process of predicting the laser output power, a neural network fitting method is used, with the laser current and laser temperature as input and the laser output optical power as output, and training is performed based on the test data set, and finally the f in the form of a neural network can be obtained. LD (i LD , T LD );

[0027] In the prediction process of the photovoltaic array irradiation laser power, a neural network fitting method is used, the photovoltaic array voltage, current, and operating temperature are taken as input, and the photovoltaic array irradiation laser power is taken as output. Training is performed based on the test data set, and finally the f in the form of a neural network can be obtained. PV (u PV ,i PV , T PV ).

[0028] Furthermore, the method also includes evaluating the performance status of the corresponding energy transmission link based on the pre-divided numerical intervals according to the calculation results of the laser wireless energy transmission link performance evaluation parameters of each energy transmission link.

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

[0030] η=min(pr1,pr2,…,pr M )

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

[0032] Furthermore, 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] Furthermore, the process of determining the specific faulty link according to the comprehensive performance evaluation results of each energy transmission link is specifically as follows:

[0036] The performance evaluation parameters pr corresponding to each energy transmission linkchain_k The values ​​are compared with the preset thresholds respectively. If the preset thresholds are exceeded, it is considered that the laser or photovoltaic array in the corresponding energy transmission link has obvious performance degradation; otherwise, there is no need to locate the fault.

[0037] Furthermore, 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 transmission process in the medium.

[0041] Furthermore, the process of determining the specific faulty laser or photovoltaic array by switching the laser and photovoltaic array in the faulty link is specifically as follows:

[0042] The laser or photovoltaic array of the energy transmission link before or after the faulty link is connected to a laser or photovoltaic array in the faulty link to form multiple groups of new links. The comprehensive performance of each group of new links is evaluated to determine the specific faulty laser or photovoltaic array.

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

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

[0045] (2) The present invention is based on the characteristics of the dispersed structure laser wireless energy transmission system, and can separate and eliminate the corresponding part of the dielectric loss in the laser transmission process in the evaluation parameter pr. The separated evaluation parameter pr chain_k It can be applied to different media conditions (such as high visibility-clear sky or other low visibility conditions), and can facilitate the performance analysis of lasers and photovoltaic arrays.

[0046] (3) The present invention aims at the characteristics of the dispersed structure laser wireless energy transmission system and based on the comprehensive performance evaluation results of each energy transmission link pr chain_kThe specific faulty link is determined, and then the fault location can be achieved by adjusting the laser-photovoltaic array matching group for the specific faulty link; the distributed system laser and photovoltaic array status monitoring and fault location can be achieved online without the need for additional laser power sensors or other auxiliary devices. It has the advantages of a streamlined system structure and the ability to identify online, which is of great significance for improving the reliability of the laser wireless energy transmission system.

[0047] (4) The present invention evaluates the parameter pr chain_k By performing transformation, it is possible to estimate the performance attenuation of the transmission link, realize the status monitoring of the laser transmission process, and provide a basis for subsequent fault prediction and health management.

[0048] (5) Using the proposed method of this application to conduct simulation and experimental research on the performance evaluation and fault location of the distributed structure laser wireless energy transmission system 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 system availability. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A schematic diagram of a process of a laser wireless energy transmission system state monitoring and performance evaluation method provided in an embodiment of the present invention;

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

[0051] Figure 3 A laser f provided in an embodiment of the present invention LD With photovoltaic array f PV Schematic diagram;

[0052] Figure 4 A schematic diagram of a laser power setting provided in an embodiment of the present invention;

[0053] Figure 5 is a link performance evaluation parameter pr provided in an embodiment of the present invention. chain With the threshold pr th (Normal situation) Schematic diagram;

[0054] Figure 6 is a link performance evaluation parameter pr provided in an embodiment of the present invention. chain With the threshold pr th (Laser 1 performance drops by 25%) Schematic diagram;

[0055] Figure 7 is a link performance evaluation parameter pr provided in an embodiment of the present invention. chain With the threshold pr th(Laser 1 performance drops 25%, link reorganization) Schematic diagram;

[0056] Figure 8 A schematic diagram of an estimation result of transmission link performance degradation provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0058] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0060] Example 1

[0061] like Figure 1 As shown, this embodiment provides a laser wireless energy transmission system state monitoring and performance evaluation method, including the following steps:

[0062] 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 performance evaluation parameters of the laser wireless energy transmission link;

[0063] S2: extracting the transmission medium part according to the laser wireless energy transmission link performance evaluation parameters of different energy transmission links; eliminating the transmission medium part of the laser wireless energy transmission link performance evaluation parameters of each energy transmission link, thereby performing a comprehensive performance evaluation of the laser and photovoltaic array group;

[0064] S3: Determine the specific faulty link based on the comprehensive performance evaluation results of each energy transmission link, and determine the specific faulty laser or photovoltaic array by switching the laser and photovoltaic array connected to the faulty link to obtain the fault location result.

[0065] In other words, this method mainly includes three parts: first, according to the laser wireless energy transmission system model, the energy transmission link performance evaluation parameter pr is constructed; then, the energy transmission medium related items are separated by integrating the performance evaluation parameters of each link to obtain the comprehensive performance evaluation result of the laser and photovoltaic array; according to the evaluation result, the comprehensive performance of the laser-photovoltaic array matching group can be judged; by adjusting the laser-photovoltaic array matching relationship, the performance attenuation of each laser and photovoltaic array can be finally obtained to realize fault location.

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

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

[0068]

[0069] Where 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, and i LD ,T LD is the laser current and temperature measurement information, u PV ,i PV ,T PV is the voltage, current and temperature measurement information of the photovoltaic array, f LD With f PV They are the prediction results of laser output power and photovoltaic array irradiation laser power.

[0070] As an optional implementation, f LD With f PV are functions derived from the laser and photovoltaic array model parameters, 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, i LD represents the working current of the laser; in essence, this formula is based on the laser model, collecting the laser current and temperature to calculate the laser output optical power at this time. Under normal working conditions of the laser, f LD (i LD , T LD )≈P LDout, when the laser is in abnormal working condition (performance degradation caused by laser aging or other reasons), f LD (i LD , T LD )>P LDout , where P LDout The above method predicts the laser output power based on the slope efficiency and threshold current of the laser.

[0073] The prediction expression of the laser power irradiated by the photovoltaic array is:

[0074]

[0075] In the formula, i PV Indicates 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 ideal factor of the diode (1≤n≤2); q is the electron charge, q=1.602×10 -19 C; N s is the number of photovoltaic units in series; k is the Boltzmann constant, k = 1.381 × 10 -23 J / K; T PV is the photovoltaic cell temperature (Kelvin K). sc is the short-circuit current; k i is the temperature coefficient of the photocurrent, which is an engineering / empirical parameter; T n is the photovoltaic array temperature corresponding to the standard test conditions; G n (W / m 2 ) is the irradiance of the photovoltaic array corresponding to the standard test conditions. rs is the reverse saturation current under standard test conditions, E g is the bandgap width of the semiconductor material (the bandgap width of gallium arsenide material is about 1.42eV); I sc is the short-circuit current under standard test conditions; S PV is the photovoltaic array area; R s is the equivalent series resistance, T is the operating temperature, R sh is the equivalent parallel resistance.

[0076] When the photovoltaic array is working normally, f PV (u PV ,i PV , T PV )≈P PVin , when the PV array is in abnormal working condition (partial short circuit of the PV array or other reasons leading to performance degradation), f PV (u PV ,i PV , T PV)>P PVin , where P PVin The above method predicts the irradiation power of the photovoltaic array based on the classic five-parameter model of the photovoltaic array.

[0077] As an optional implementation, a data-driven method can be used to predict the laser output power based on the laser test data. For example, a BP neural network fitting method is used, with the laser current and laser temperature as input and the laser output optical power as output. Training is performed based on the test data set, and finally the f in the form of a neural network can be obtained. LD (i LD , T LD ), the internal structure and weights of the neural network contain key information about the laser, and the established f LD (i LD , T LD ) can also be used in this method.

[0078] According to the test data of photovoltaic array, the prediction of photovoltaic array irradiation laser power can be carried out by data-driven method. For example, the BP neural network fitting method is used, the photovoltaic array voltage, current, and operating temperature are taken as input, and the photovoltaic array irradiation laser power is taken as output. Training is performed based on the test data set, and finally the f in the form of neural network can be obtained. PV (u PV ,i PV , T PV ), the internal structure and weights 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 this method.

[0079] As an optional implementation, a photovoltaic array irradiation laser power observer can be designed based on the photovoltaic array model and the state observer design principle. The observer current and the actual photovoltaic array current are closed-loop fed back to finally obtain the observed value of the photovoltaic array irradiation laser power. The f obtained by this method is PV (u PV ,i PV , T PV ) can also be used in this method.

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

[0081] Specifically, when the performance of the laser and photovoltaic array is not degraded and the loss in the laser transmission process is negligible (short-distance transmission), pr approaches 0, indicating that the energy transmission performance is better at this time.

[0082] When the performance of the laser or photovoltaic array deteriorates, or there is a certain loss in the laser transmission process (medium and long distance transmission), PR will gradually increase, indicating that there is additional loss in the energy transmission link and the performance is gradually attenuated.

[0083] When the performance of the laser or photovoltaic array decays significantly, or the laser transmission environment is harsh, PR will increase further.

[0084] When pr-->1, the energy transmission link is in a completely failed state, and no energy is transmitted from the transmitter to the receiver, which corresponds to the complete damage of the laser or photovoltaic array, or the complete blocking of the laser light path.

[0085] The range of pr is [0,1]. The value of pr can reflect the additional loss of the laser wireless energy transmission link, which mainly includes three parts, including the degradation of laser performance, the degradation of photovoltaic array performance and the loss caused by the 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 normal operation at this time; when pr is higher, it can be preliminarily inferred that the medium efficiency may be low (visibility decreases) or there are problems such as aging of optoelectronic devices.

[0087] The proposed method of evaluating the status of a laser wireless energy transfer link based on pr is superior to the end-to-end (or electro-optical-electrical) laser energy transfer efficiency η E-E , is not affected by the laser and photovoltaic array working point at this time, and at different i LD 、u PV 、i PV Evaluation criteria that are consistent across all operating temperatures.

[0088] Among them, the end-to-end laser energy transfer efficiency η E-E It is the product of laser efficiency, medium transmission efficiency and photovoltaic array efficiency, which can be expressed as the photovoltaic array output power divided by the laser input power (P PVout / P LDin ), which can also reflect the state of the energy transmission link. The higher the efficiency, the better the link performance. However, due to the optoelectronic nonlinear characteristics of the laser and 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 photovoltaic array, η E-Ewill be significantly reduced, but at this time the laser and photovoltaic array may still be in normal state, so the end-to-end laser energy transfer efficiency η E-E It cannot be directly used to evaluate the status of the laser wireless energy transmission link.

[0089] In addition, the end-to-end laser energy transfer efficiency η E-E It also fails to take into account the influence of the temperature of the laser and photovoltaic array. In some cases, as the temperature changes, the end-to-end laser energy transfer efficiency η E-E It may also change, but the working status of the laser and photovoltaic array may remain unchanged (health index).

[0090] Step S2 specifically includes the following steps:

[0091] S201: Separate the energy transfer medium related items and construct η=min(pr1,pr2,…,pr M );

[0092] In step S1, the parameter pr that can reflect the state of the energy transmission link can be finally obtained, which mainly includes the influence of three parts: laser, photovoltaic array, and laser transmission medium. For the distributed structure energy transmission system, it has multi-beam transmission characteristics, 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 energy transmission links in the distributed structure, and η represents the performance evaluation parameter of the laser transmission process in the medium.

[0095] The range of η is [0,1]. The closer η is to 1, the greater the dielectric loss is. The closer η is to 0, the smaller the dielectric loss is.

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

[0097] In fact, this formula extracts the common additional loss in each link. For a distributed structure laser wireless energy transmission system, multiple light beams are transmitted together in the medium, and there will be similar medium losses, so it can be extracted using this method.

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

[0099] Furthermore, in very rare cases, the dielectric loss in multi-beam energy transmission may be different. For example, one of the beams may be blocked. This type of problem can be diagnosed through image processing methods. In the laser wireless energy transmission system, the transmitter is equipped with a capture, tracking, and aiming system, and a CCD or CMOS image sensor is used to collect images at the receiving end. The laser spot and the photovoltaic array are identified through target recognition methods to complete the alignment of the laser. This type of problem of a beam being blocked can be identified and diagnosed through image processing algorithms. In actual operation, for safety reasons, the blocked beam will be cut off or the energy transmission process of the link will be terminated. Therefore, it can be considered that each laser beam transmitted simultaneously in the same medium has similar dielectric losses, which can be extracted by this method.

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

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

[0102]

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

[0104] Furthermore, when the performance of the laser and photovoltaic array is not degraded, pr chain_kIt approaches 0, indicating that the energy transfer performance is better at this time.

[0105] When the performance of the laser and photovoltaic array deteriorates, pr chain_k It will gradually rise, indicating that the energy transmission performance is attenuated and the performance of the laser or photovoltaic array is degraded.

[0106] When the performance of laser and photovoltaic array is obviously degraded, pr chain_k Will rise further.

[0107] When pr chain_k -->1, the energy transmission link is in a completely failed state, and no energy is transmitted from the transmitter to the receiver, corresponding to the complete damage of the laser or photovoltaic array.

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

[0109] Preferably, it can be based on pr chain_k The numerical value evaluates the state of the laser wireless energy transmission link at this time. chain_k When it is close to 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 are in normal operation; when pr chain_k When it is high, it is preliminarily inferred that there is a high probability of problems such as aging of optoelectronic devices.

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

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

[0112] Only when pr chain_k Exceeding the preset threshold pr th Step S3 is performed only when it is considered that the laser or photovoltaic array in the link has obvious performance degradation.

[0113] Only when pr chain_k Does not exceed the preset threshold pr th When , it is considered that the laser or photovoltaic array in the link is basically in normal working condition, and there is no need to locate the fault.

[0114] Threshold prth The smaller the setting (the closer to 0), the higher the system sensitivity will be, and the system will react when there is a certain performance degradation in the laser or photovoltaic array.

[0115] Threshold pr th The larger the setting (the closer to 1), the lower the system sensitivity will be, and the system will not react until there is more performance degradation in the laser or photovoltaic array performance.

[0116] Furthermore, 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%, then the threshold pr th It can be set according to the following formula:

[0117]

[0118] 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 transmission process in the medium.

[0119] For example, when η = 0.11, it means that the medium transmission efficiency is about 80%. Taking b = 0.8, it is considered that the performance of the laser or photovoltaic array decreases by about 20% as the threshold. At this time, pr th It can be taken as 0.108. chain_k When the pr is less than 0.108, the overall performance degradation of the laser-photovoltaic array matching group is less than 20%; chain_k When it is greater than 0.108, the overall performance of the laser-photovoltaic array matching group has degraded by more than 20%, and it is necessary to further locate the faulty device as the laser or the photovoltaic array;

[0120] For example, when η = 0.11, it means that the medium transmission efficiency is about 80%. Taking b = 0.7, it is considered that the performance of the laser or photovoltaic array decreases by about 30% as the threshold. At this time, pr th It can be taken as 0.171. chain_k When pr is less than 0.171, the overall performance degradation of the laser-photovoltaic array matching group is less than 30%; chain_k When it is greater than 0.171, the overall performance of the laser-photovoltaic array matching group has degraded by more than 30%, and it is necessary to further locate the faulty device as the laser or the photovoltaic array;

[0121] When pr chain_k Exceeding the preset threshold pr th When the laser-photovoltaic array matching group is attenuated, it is considered that the performance of the laser-photovoltaic array matching group has been greatly degraded, and the specific fault location can be determined by changing the matching laser-photovoltaic array.

[0122] By switching the laser and photovoltaic array connected to the faulty link, the process of determining the specific faulty laser or photovoltaic array is as follows:

[0123] The laser or photovoltaic array of the energy transmission link before or after the faulty link is connected to a laser or photovoltaic array in the faulty link to form multiple groups of new links. The comprehensive performance of each group of new links is evaluated to determine the specific faulty laser or photovoltaic array.

[0124] For example, suppose there are three laser wireless energy transmission links, denoted as links [1-1, 2-2, 3-3]. chain_2 When the preset threshold is exceeded, it is considered that the link energy transmission performance has been significantly degraded, 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 to allow laser 1 to irradiate photovoltaic array 2 to form a new link (*1-2), and laser 2 to irradiate photovoltaic array 1 to form a new link (*2-1). Calculate the pr chain_(*1-2) and pr chain_(*2-1) That is, the performance of the new link can be determined, and finally the specific faulty device can be determined. chain_(*1-2) If the value is significantly higher, it can be judged that PV array 2 has a fault, resulting in a significant performance degradation of the link containing PV array 2, causing the corresponding link performance evaluation parameter pr chain_(2-2) With pr chain_(*1-2) Increase.

[0125] Preferably, in the case where multiple lasers irradiate the same photovoltaic array, the fault location method is similar, and it can be determined whether the laser-photovoltaic array on the link is working normally at this time based on the link performance evaluation parameters. Multiple lasers can be judged one by one, or in batches using methods such as binary search.

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

[0127] 1. For Figure 2 A certain distributed structure laser wireless energy transmission system shown has three energy transmission links, namely M=3, with a total of three lasers and three photovoltaic arrays. The lasers are 808nm semiconductor lasers, and the photovoltaic arrays are quad-junction gallium arsenide photovoltaic arrays.

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

[0129] 3. According to the laser manual data, f can be obtained LD (iLD , T LD )=K(T LD )*(i LD -i th ), use a laser power meter to measure the laser output power, the relationship is as follows Figure 3 As shown in the left figure, it can characterize the laser output power under a specific working state.

[0130] 4. To facilitate the analysis of system failure status, a simulation model of the dispersed structure laser wireless energy transmission system is established and verified by simulation through MATLAB / Simulink. Photovoltaic array f PV (u PV ,i PV , T PV ) The irradiation power of the photovoltaic array is observed by the state observer, and the time domain waveform is observed as follows: Figure 3 As shown, the dotted line is the actual irradiation power, and the solid line is the observer output, which can characterize the irradiation power of the photovoltaic array under a specific working state.

[0131] Note that lasers 1-3 and photovoltaic arrays 1-3 constitute three laser wireless energy transmission links (1-1, 2-2, 3-3). Assume that the laser performance decays at this time, and decays to 98%, 96%, and 97% of the expected performance respectively (simulating the power drop corresponding to the instability of the laser power), the medium transmission efficiency is 82%, 83%, and 86% respectively (the medium efficiency includes the medium scattering absorption part and the additional loss of the alignment link), and the photovoltaic array performance decays, and decays to 97%, 95%, and 97% of the expected performance respectively. The laser power is given (theoretically, the power that the laser should output) as follows Figure 4 As shown. Take b = 0.8, that is, when the performance of the laser or photovoltaic array drops by about 20%, the threshold pr is reached th .

[0132] The corresponding results of this simulation are as follows Figure 5 As shown, pr chain_k (k=1,2,3) are relatively small and less than the threshold pr th , at this time, the performance of the laser-photovoltaic array did not drop by more than 20%. When the power output of laser 1 decayed to 75% in a step at 0.12s, the corresponding simulation results are as follows Figure 6 As shown, it can be seen that pr chain1 Exceeding the threshold pr th, it may be that the performance of the laser or photovoltaic array in link 1 has been significantly degraded. Then, by exchanging the matching relationship between the laser and the photovoltaic array in link 1-2, laser 1 irradiates photovoltaic array 2, and laser 2 irradiates photovoltaic array 1, forming links (chain1-2) and (chain2-1). To ensure that the transmission power of each link remains unchanged, the power of lasers 1 and 2 is given by exchanging.

[0133] The simulation results after the change are as follows Figure 7 As shown, pr chain1-2 Exceeding the threshold pr th , combined with the discrimination information before and after link reorganization, pr chain_1-1 With pr chain_1-2 There is a significant performance degradation, and it can be determined that the performance degradation problem is with Laser-1.

[0134] And, for pr chain_1-2 By transforming, we can obtain an estimate of the transmission link performance degradation at this time. Figure 8 The estimated results are as follows: link 3-3 has almost no attenuation, the medium attenuation is about 19.2%, link 2-1 attenuates about 4.2%, before the failure, link 1-2 attenuates about 5.6%, and after the failure, the attenuation is about 26%.

[0135] In summary, this method constructs the energy transmission link performance evaluation parameter pr, which can evaluate the overall transmission performance of the link. For the dispersed structure laser wireless energy transmission system, the separation medium part is calculated by pr chaink It can evaluate the performance of the laser-photovoltaic array combination in the laser wireless energy transmission link, evaluate the energy transmission performance and carry out related fault location. Its improvement effect is mainly reflected in its insensitivity to the working point and the ability to locate the fault of the laser-photovoltaic array. The reason for the above advantages is that the construction of the performance evaluation parameters can fully take into account the nonlinear characteristics of the laser wireless energy transmission system and the characteristics of simultaneous transmission of multiple beams in the dispersed structure.

[0136] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for state monitoring and performance evaluation of a laser wireless energy transmission system, characterized in that: The following steps are involved: 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 performance evaluation parameters of the laser wireless energy transmission link; According to the laser wireless energy transmission link performance evaluation parameters of different energy transmission links, the transmission medium part is extracted; the transmission medium part is eliminated from the laser wireless energy transmission link performance evaluation parameters of each energy transmission link, so as to conduct a comprehensive performance evaluation of the laser and photovoltaic array group; The specific faulty link is determined based on the comprehensive performance evaluation results of each energy transmission link, and the specific faulty laser or photovoltaic array is determined by switching the laser and photovoltaic array connected to the faulty link to obtain the fault location result.

2. A method for state monitoring and performance evaluation of a laser wireless energy transmission system according to claim 1, characterized in that: The calculation expression of the laser wireless energy transmission link performance evaluation parameter is: … Where 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, and i LD ,T LD is the laser current and temperature measurement information, u PV ,i PV ,T PV is the voltage, current and temperature measurement information of the photovoltaic array, f LD With f PV They are the prediction results of laser output power and photovoltaic array irradiation laser power.

3. A method for state monitoring and performance evaluation of a laser wireless energy transmission system according to claim 2, characterized in that: The prediction expression of the laser output power is: f LD (i LD ,T LD )=K(T LD )*(i LD -i th ) In the formula, K(T LD ) represents the slope efficiency of the laser, i th represents the threshold current of the laser, i LD Indicates the operating current of the laser; The prediction expression of the photovoltaic array irradiation laser power is: In the formula, i PV Indicates 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 ideal factor of the diode; q is the amount of electron charge; N s is the number of photovoltaic units connected in series; 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 photocurrent; T n is the photovoltaic array temperature corresponding to the standard test conditions; G n is the irradiance of the photovoltaic array corresponding to the standard test conditions; I rs is the reverse saturation current under standard test conditions, E g is the bandgap width of the semiconductor material; I sc is the short-circuit current under standard test conditions; S PV is the photovoltaic array area; R s is the equivalent series resistance, T is the operating temperature, R sh is the equivalent parallel resistance.

4. A method for state monitoring and performance evaluation of a laser wireless energy transmission system according to claim 2, characterized in that: In the process of predicting the laser output power, a neural network fitting method is used, with the laser current and laser temperature as input and the laser output optical power as output. Training is performed based on the test data set, and finally the f in the form of a neural network can be obtained. LD (i LD , T LD ); In the prediction process of the photovoltaic array irradiation laser power, a neural network fitting method is used, the photovoltaic array voltage, current, and operating temperature are taken as input, and the photovoltaic array irradiation laser power is taken as output. Training is performed based on the test data set, and finally the f in the form of a neural network can be obtained. PV (u PV ,i PV , T PV ).

5. A method for state monitoring and performance evaluation of a laser wireless energy transmission system according to claim 1, characterized in that: The method also includes evaluating the performance status of the corresponding energy transmission link based on the pre-divided numerical intervals according to the calculation results of the laser wireless energy transmission link performance evaluation parameters of each energy transmission link.

6. A method for state monitoring and performance evaluation of a laser wireless energy transmission system according to claim 1, characterized in that: The extraction expression of the transmission medium part is: η=min(pr1,pr2,…,pr M ) Where η is the performance evaluation parameter of the laser transmission process in the medium, pr is the performance evaluation parameter of the laser wireless energy transmission link, and 1~M are the energy transmission link numbers of the laser wireless energy transmission system.

7. A method for state monitoring and performance evaluation of a laser wireless energy transmission system according to claim 6, characterized in that: The calculation expression of the performance evaluation parameter of the laser-photovoltaic array matching group obtained by eliminating the transmission medium part of the laser wireless energy transmission link performance evaluation parameter of each energy transmission link is: pr chain_k =pr k -η(k=1,2...M) In the formula, pr chain_k is the performance evaluation parameter of the kth energy transmission link.

8. A method for state monitoring and performance evaluation of a laser wireless energy transmission system according to claim 1, characterized in that: The process of determining the specific faulty link according to the comprehensive performance evaluation results of each energy transmission link is specifically as follows: The performance evaluation parameters pr corresponding to each energy transmission link chain_k The values ​​are compared with the preset thresholds respectively. If the preset thresholds are exceeded, it is considered that the laser or photovoltaic array in the corresponding energy transmission link has obvious performance degradation; otherwise, there is no need to locate the fault.

9. A method for state monitoring and performance evaluation of a laser wireless energy transmission system according to claim 8, characterized in that: The threshold setting formula is: pr th =[(1-a*b)*(1+a)-(1+a*b)*(1-a)] / [1+a*b)*(1+a)]; a=(1-η) / (1+η); 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 transmission process in the medium.

10. A method for state monitoring and performance evaluation of a laser wireless energy transmission system according to claim 1, characterized in that: The process of determining the specific faulty laser or photovoltaic array by switching the laser and photovoltaic array connected to the faulty link is specifically as follows: The laser or photovoltaic array of the energy transmission link before or after the faulty link is connected to a laser or photovoltaic array in the faulty link to form multiple groups of new links. The comprehensive performance of each group of new links is evaluated to determine the specific faulty laser or photovoltaic array.

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