Method and system for testing electrical performance of solar cell panel

Abstract

The invention relates to the technical field of electrical variable measurement, in particular to a method and system for testing the electrical performance of a solar cell panel, and the method comprises the steps: applying symmetric triangular wave voltage excitation to a photovoltaic string, and synchronously collecting the voltage and current of a step-up scanning stage and a step-down scanning stage; carrying out mean value operation on the boost and buck current data based on a symmetry principle to obtain a photovoltaic quiescent current, and carrying out differential operation to obtain a capacitance response current; anchoring a basic reference capacitance current in a low-voltage area, and calculating a difference value between the basic reference capacitance current and a capacitance response current as a capacitance current drop amount; and establishing a linear relation between the capacitance current drop amount and the static conductivity slope, calculating an impedance coupling coefficient, and further obtaining the series resistance and the equivalent capacitance. Measurement of maximum power and quantitative measurement of impedance parameters are simultaneously realized in single millisecond scanning, and the technical problem that in a traditional method, rapid scanning and measurement precision are difficult to consider at the same time is solved.

Description

Technical Field

[0001] This invention relates to the field of electrical variable measurement technology, specifically to a method and system for testing the electrical performance of solar panels. Background Technology

[0002] In the field of photovoltaic power plant operation, maintenance, and testing, the volt-ampere characteristic curve test is the core method for evaluating the power generation performance and electrical connection status of photovoltaic modules. As the voltage level of photovoltaic systems evolves towards 1500 volts, the parasitic capacitance to ground and the internal diffusion capacitance of long series modules increase significantly, causing photovoltaic strings to exhibit strong capacitive load characteristics.

[0003] To avoid measurement errors introduced by fluctuations in light intensity and rise in module junction temperature during testing, millisecond-level rapid voltage scanning must be used in engineering to qualitatively screen and detect high-resistance faults. However, when performing rapid voltage scanning on high-capacitive strings, the drastic rate of voltage change induces a large capacitor charging and discharging current. This capacitor current, superimposed on the photocurrent, causes a significant hysteresis phenomenon in the volt-ampere curve.

[0004] Existing solutions typically face a dilemma: reducing the scan rate to minimize capacitive interference cannot avoid thermal drift errors, leading to inaccurate maximum power measurements; maintaining a fast scan can mask the weak series resistance characteristics reflecting electrical connection quality, resulting in inaccurate impedance parameter measurements. Currently, the industry lacks an engineered testing solution that can simultaneously eliminate capacitive hysteresis interference and effectively extract series resistance characteristics in a single fast scan. Summary of the Invention

[0005] To address the above problems, this invention provides a method and system for testing the electrical performance of solar panels.

[0006] The present invention provides a method and system for testing the electrical performance of solar panels, which adopts the following technical solution: One embodiment of the present invention provides a method for testing the electrical performance of a solar panel, the method comprising the following steps: A triangular wave voltage is applied to the photovoltaic string under test. The triangular wave voltage includes a boost scanning stage and a buck scanning stage with the same scanning rate. The scanning currents of the boost scanning stage and the buck scanning stage are averaged to cancel the capacitive response of the photovoltaic string to obtain the photovoltaic static current. The scanning currents of the boost scanning stage and the buck scanning stage are differentially calculated to cancel the static DC response of the photovoltaic string to obtain the capacitive response current. The average capacitor response current within the preset low-voltage calibration range is denoted as the basic reference capacitor current. The difference between the basic reference capacitor current and the capacitor response current is taken as the capacitor current drop. The rate of change of the capacitor current drop with the static conductivity slope is taken as the impedance coupling coefficient. The static conductivity slope represents the rate of change of the photovoltaic static current with the output voltage of the photovoltaic string. The electrical performance test results of the series resistance of the photovoltaic string are obtained based on the impedance coupling coefficient and the basic reference capacitor current; the electrical performance test results of the equivalent capacitance of the photovoltaic string are obtained based on the basic reference capacitor current and the scan rate.

[0007] Preferably, the specific steps for obtaining the scanning current in the boost scanning phase and the buck scanning phase are as follows: After the triangular wave voltage is applied to the photovoltaic string under test, several voltage data are sampled based on the maximum output voltage of the photovoltaic string and a reference voltage sequence V is formed; for any position index k in the reference voltage sequence V, the voltage corresponding to position index k is denoted as V[k]; During the boost scanning phase, when the output voltage of the photovoltaic string equals V[k], the current sampled on the photovoltaic string is expressed as: During the buck scan phase, when the output voltage of the photovoltaic string is equal to V[k], the current collected on the photovoltaic string is expressed as: ;in , This represents the scanning current obtained under position index k for the boost scanning stage and the buck scanning stage.

[0008] Preferably, the average capacitive response current within the preset low-voltage calibration range is recorded as the basic reference capacitive current, and the specific steps include the following: For position index k, the scanning current of the boost scan phase and the buck scan phase will be... , The capacitive response current obtained by calculating the difference is denoted as... , indicating the capacitor response current obtained from the position index k; For all voltages in the reference voltage sequence V, the index set is formed by the position indices of the voltages that fall within the preset low-voltage calibration interval. ; Index set The average value of the capacitor response current obtained under all position indices is used to obtain the base reference capacitor current.

[0009] Preferably, the rate of change of the capacitor current drop with respect to the static conductance slope is used as the impedance coupling coefficient, where the static conductance slope represents the rate of change of the photovoltaic static current with respect to the output voltage of the photovoltaic string. The specific steps include the following: A regression analysis interval is predefined; for all voltages in the reference voltage sequence V, the indexes of the voltages falling within the regression analysis interval constitute an index set. ; Index set The capacitive response current corresponding to each position index in the index set is used as the dependent variable. The static conductivity slope of the photovoltaic quiescent current corresponding to each position index is used as the independent variable; the index set is then analyzed using the least squares method. All independent and dependent variables are fitted to a linear regression model, and the slope of the linear regression model is used as the impedance coupling coefficient; the intercept of the linear regression model is set to 0. For the voltage at each position index in the reference voltage sequence V, the static conductance slope of the photovoltaic static current corresponding to each position index is equal to the rate of change of the photovoltaic static current at that voltage.

[0010] Preferably, the specific steps for obtaining the electrical performance test results of the photovoltaic string series resistance based on the impedance coupling coefficient and the basic reference capacitor current are as follows: The electrical performance test results of the series resistance of a photovoltaic string are represented by the characteristic value of the series resistance. The characteristic value of the series resistance is positively correlated with the impedance coupling coefficient and negatively correlated with the base reference capacitor current.

[0011] Preferably, the specific steps for obtaining the electrical performance test results of the photovoltaic string equivalent capacitance based on the baseline reference capacitor current and the scan rate are as follows: The electrical performance test results of the equivalent capacitance of a photovoltaic string are represented by the equivalent capacitance characteristic value. The equivalent capacitance characteristic value is positively correlated with the base reference capacitance current and negatively correlated with the scan rate.

[0012] Preferably, the specific steps for obtaining the reference voltage sequence V are as follows: During the boost and buck scanning phases, the output current and voltage of the photovoltaic string are acquired in real time; the ratio of the maximum acquired output voltage to the preset value is recorded as... Starting from 0 volts, The voltage increment sequence with a step size is used as the reference voltage sequence V; All voltages acquired during the boost or buck scanning phase and current For any sequence position index in the reference voltage sequence V In all the collected Search for the two voltages adjacent to voltage V[k], denoted as , making ;in , This represents all voltages collected during the boost or buck scanning phase. The j-th and (j+1)-th voltages in the array; using , Indicates the collected voltage , The current collected at the same time ; Calculate the current value corresponding to the voltage V[k] based on the linear proportional relationship, so that... , The proportional relationship with V[k] and , The calculated current value is proportional to the calculated current value, and is used as the scanning current for the boost or buck scanning phase. or .

[0013] Preferably, the specific steps for obtaining the low-pressure calibration range are as follows: For the photovoltaic quiescent current obtained from all position indices of the reference voltage sequence V, and for position indices where the photovoltaic quiescent current is equal to 0, the voltage corresponding to that position index in the reference voltage sequence V is denoted as the measured open-circuit voltage. The upper and lower limits of the low-voltage calibration range are determined by... Sure.

[0014] Preferably, the specific steps for the regression analysis interval are as follows: For any location index k, the product of the photovoltaic quiescent current at that location index and V[k] is denoted as the power at location index k; the voltage in V corresponding to the location index with the maximum power among all location indices is denoted as... The regression analysis interval is from It is confirmed that the voltage within the regression analysis interval is greater than the voltage within the low-voltage calibration interval.

[0015] Another embodiment of the present invention provides a solar panel electrical performance testing system, the system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement all the steps of the above-described solar panel electrical performance testing method.

[0016] The beneficial effects of the technical solution of the present invention are: This invention fundamentally solves the industry problem of balancing rapid scanning and measurement accuracy in traditional methods by employing a signal separation mechanism based on symmetrical scanning and arithmetic operations. Specifically, the scanning current cancels out the capacitive response of the photovoltaic string by averaging the current, directly utilizing the physical characteristic that the capacitor current has equal amplitude and opposite direction during voltage boosting and bucking. Mathematically, this completely eliminates the superposition interference of capacitor charging and discharging current on the photogenerated current, thereby effectively eliminating the hysteresis loop phenomenon in the volt-ampere curve.

[0017] Furthermore, the resulting photovoltaic quiescent current purely reflects the DC output characteristics of the module under thermal equilibrium, avoiding the capacitance effect errors caused by rapid scanning. This allows for a true and accurate reflection of the photovoltaic string's power generation capacity under current operating conditions. This enables power measurement accuracy comparable to slow scanning, even at the necessary millisecond-level scanning speed.

[0018] In this invention, the difference between the base reference capacitor current and the capacitor response current is used as the capacitor current sag. This process transforms the voltage change rate loss caused by voltage division due to series resistance in the high-voltage region, which is not directly observable, into a current residual signal. This makes the effect of series resistance, which was previously masked, an observable characteristic. Furthermore, by establishing the relationship between the capacitor current sag and the conductance slope (impedance coupling coefficient), it is possible to simultaneously and independently extract the series resistance characteristic value reflecting the electrical connection state and the equivalent capacitance characteristic value reflecting the insulation structure state in a single fast scan. This provides a quantitative basis for identifying high-resistance faults such as connector loose connections and busbar breakage, as well as capacitive anomalies such as PID effect and insulation moisture, making the electrical performance test results of photovoltaic strings more valuable.

[0019] In summary, this invention can simultaneously eliminate capacitive hysteresis interference and effectively extract series resistance and equivalent capacitance characteristics in a single rapid scan, ensuring the reliability and validity of the electrical performance test results of solar panels. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart illustrating the steps of a method for testing the electrical performance of a solar panel, as provided in one embodiment of the present invention. Detailed Implementation

[0022] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a solar panel electrical performance testing method and system proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0024] The following description, in conjunction with the accompanying drawings, details a specific scheme for a solar panel electrical performance testing method and system provided by the present invention.

[0025] Example 1: Please see Figure 1 The diagram illustrates a flowchart of a method for testing the electrical performance of a solar panel according to an embodiment of the present invention. The method includes the following steps: Step S101: Apply a triangular wave voltage to the photovoltaic string under test. The triangular wave voltage includes a boost scanning stage and a buck scanning stage with the same scanning rate.

[0026] A triangular wave voltage excitation is applied across the photovoltaic string under test. This triangular wave voltage is output by an electronic load whose output voltage is controlled. The triangular wave voltage includes a boost scanning phase and a buck scanning phase.

[0027] The boost scan phase includes: the voltage at the electronic load control port increases linearly from zero volts to the termination voltage at a constant positive rate of change +α. .

[0028] The blood pressure reduction scan phase includes: reaching Subsequently, the electronic load immediately controls the port voltage to change at a constant negative rate of change -α from The voltage drops linearly to zero volts.

[0029] It's important to note that the absolute values ​​of the voltage change rates are the same in the boost and buck scanning phases because photovoltaic modules are significantly temperature-sensitive. The solar heating effect during testing causes the module junction temperature to rise (thermal drift), altering its electrical characteristics and introducing measurement errors. To ensure the testing process approximates an isothermal process, millisecond-level rapid voltage scanning is necessary. Simultaneously, the parasitic capacitance of the photovoltaic string generates charging and discharging currents when the voltage changes; the direction of this current depends on the sign of the voltage change rate. To ensure that subsequent steps can mathematically cancel or extract this capacitive current, the absolute values ​​of the voltage change rates in the voltage rise and voltage fall phases must be strictly equal.

[0030] It is a preset voltage, the value of which is higher than the estimated open-circuit voltage; as an example, The voltage is set to 1.1 times the nominal open-circuit voltage of the photovoltaic string under test to ensure that the triangular wave voltage covers the complete volt-ampere curve.

[0031] The scan rate α is also a preset value, and its setting principle needs to balance transient response bandwidth and thermal drift suppression capability. If α is too low (e.g., <100 volts per second), the test time will be too long, resulting in non-negligible thermal drift; if α is too high (e.g., >2000 volts per second), it may exceed the dynamic response bandwidth of the electronic load or excite the transmission line inductance effect of the string. In this embodiment, the preferred range of α is 200–1000 volts per second. As an example, setting α to 500 volts per second, this scan rate can complete a full-range scan of 1500 volts within 3 seconds.

[0032] Step S102: The scanning currents of the boost scanning stage and the buck scanning stage are averaged to offset the capacitor response of the photovoltaic string, thus obtaining the photovoltaic static current. The scanning currents of the boost scanning stage and the buck scanning stage are differentially offset to offset the static DC response of the photovoltaic string, thus obtaining the capacitor response current.

[0033] (1) The current and voltage output of the photovoltaic string are collected in real time using the acquisition card during the boost scanning stage and the buck scanning stage.

[0034] (2) After the triangular wave voltage excitation is applied to the photovoltaic string under test, the voltage range output by the photovoltaic string during the boost scanning stage and the buck scanning stage is sampled at equal intervals (equal step size). All sampled voltage data constitute the reference voltage sequence V. In this embodiment, the voltage contained in the reference voltage sequence V exhibits the characteristic of monotonically increasing from 0 volts as the starting point with a preset step size.

[0035] For any position index k in the reference voltage sequence V, the voltage corresponding to position index k is denoted as V[k], which represents the k-th voltage in the reference voltage sequence V.

[0036] During the boost scanning phase, the current sampled when the output voltage of the photovoltaic string equals V[k] is used as the scanning current during the boost scanning phase (abbreviated as boost scanning current). Its value is represented as During the buck scan phase, the current sampled when the output voltage of the photovoltaic string equals V[k] is used as the scan current for the buck scan phase (abbreviated as buck scan current). Its value is represented as .

[0037] (3) Based on the superposition theorem, the instantaneous current I(t) at the photovoltaic string port at time t is the photovoltaic static current. With capacitor response current The algebraic sum of these inequalities satisfies the formula: .

[0038] Where C represents capacitance. This represents the rate of change of voltage over time. For the voltage at any sequence position index k in the reference voltage sequence V, the rate of change of that voltage is... During the boost and buck processes, the voltages are opposites. Therefore, the magnitudes of the capacitor response current are approximately equal but opposite in sign during both processes, while the photovoltaic quiescent current remains constant. Utilizing this symmetry, the photovoltaic quiescent current and capacitor response current are decoupled point by point.

[0039] Specifically: First, calculate the photovoltaic quiescent current. The photovoltaic quiescent current obtained at position index k is expressed as: This is the kth photovoltaic quiescent current obtained. This process eliminates the hysteresis effect caused by capacitor charging and discharging, restoring the DC output capability of the string under thermal equilibrium. Its calculation utilizes the principle of additive cancellation: .

[0040] Then calculate the capacitor response current. The capacitive response current obtained at position index k is expressed as: This refers to the response current of the k-th capacitor. This process characterizes the amplitude of the dynamic charging and discharging current excited by voltage changes at the k-th voltage point. Its calculation utilizes the subtraction extraction principle: .

[0041] (4) In addition, for all the photovoltaic quiescent currents obtained from the reference voltage sequence V, for the position index where the photovoltaic quiescent current is equal to 0, the voltage corresponding to that position index in the reference voltage sequence V is recorded as the measured open-circuit voltage. .

[0042] Step S103: The average capacitor response current within the preset low-voltage calibration range is recorded as the basic reference capacitor current, and the difference between the basic reference capacitor current and the capacitor response current is used as the capacitor current drop.

[0043] This step aims to utilize the switching characteristics of diodes to convert the resistance effect, which cannot be directly measured in the high-voltage region, into an observable current residual signal. To overcome the uncertainties caused by the nonlinear diffused capacitance in the high-voltage region, this step introduces an engineering-based linear equivalent model and numerical robustness constraints.

[0044] (1) In the low-voltage range far from the maximum power point, the bypass diodes inside the photovoltaic module are in reverse cutoff state, and the dynamic resistance is extremely large. At this time, the current flowing through the series resistor and the voltage drop it generates are close to zero, and the rate of change of voltage applied across the internal equivalent capacitance is actually equal to the scanning rate α of the port voltage. Therefore, the capacitive response current in this range is not modulated by the resistive effect and only reflects the geometric capacitance characteristics of the string.

[0045] Specifically, a low-voltage calibration range is first preset, which includes low-voltage data from the reference voltage sequence V. As an example, the low-voltage calibration range is set to 0.1. ~0.4 .

[0046] For all voltages in the reference voltage sequence V, obtain the position indices of the voltages that fall within the low-voltage calibration interval. These position indices constitute an index set. Defined as the base reference capacitor current. : Where M represents the index set The number of positional indexes in the middle; express The position index i in the middle, This represents the capacitor response current at position index i (or the i-th capacitor response current).

[0047] It should be noted that although the actual capacitance characteristics of photovoltaic modules in the high-voltage region may include a nonlinear diffuse capacitance component (causing the capacitance value to increase with increasing current), in this embodiment, in order to achieve rapid extraction of series resistance characteristics, a linearized equivalent model is adopted, that is, assuming that the geometric capacitance characteristics of the module remain at the level of the low-voltage cutoff region across the entire voltage range. Based on this... The subsequent calculations reflect the degree of impedance deviation relative to this linear benchmark, which is sufficient to meet the qualitative and semi-quantitative screening needs of impedance anomalies (such as loose connections or breaks) in engineering.

[0048] (2) In the high-voltage region close to the open-circuit voltage, the diode conducts exponentially, and the photocurrent flowing through the series resistor changes drastically, leading to a significant increase in the rate of change of voltage drop across the series resistor. This causes the actual rate of change of voltage applied across the internal capacitor to be less than the port scan rate α, thus resulting in the measured voltage drop... Below the ideal benchmark There is a direct physical causal relationship between this loss and the magnitude of the series resistance.

[0049] Iterate through each sequence position index k of the reference voltage sequence V and calculate the capacitor current drop. This represents the difference between the base reference capacitor current and the capacitor response current.

[0050] To prevent numerical anomalies caused by measurement noise floor or diffusion capacitance effects in high-voltage regions (such as measured current exceeding the reference current), nonnegative constraint functions and noise floor tolerances are introduced in other examples. The calculation formula is as follows: The max() function is used to truncate negative values, ensuring that the extracted features always physically represent "fall" or "loss". This is a preset noise floor tolerance used to filter out random fluctuations caused by hardware precision limitations, ensuring that only significant resistance effects are extracted. The preferred value range is 5~10mA, and in this embodiment, it is used as... Let's take an example to illustrate.

[0051] (3) In order to establish the identification equation for the resistance parameter, it is necessary to introduce an equation that can explain the resistance parameter. The changing physical independent variable. Since the rate of change of voltage drop across the resistor is proportional to the rate of change of current flowing through the resistor, this step calculates the photovoltaic quiescent current for any index k of the reference voltage sequence V. The first derivative yields the static conductivity slope. , which represents the rate of change of the photovoltaic static current at position index k with respect to the voltage at position index k in the reference voltage sequence V (i.e., the output voltage of the photovoltaic string).

[0052] Step S104: The rate of change of capacitor current drop with static conductance slope is used as the impedance coupling coefficient.

[0053] This step is based on the differential form of Ohm's law. By utilizing the linear coupling mechanism between the capacitive current drop and the static conductivity slope decoupled in the previous step, the complex electrochemical impedance analysis is simplified into geometric feature regression in a single time-domain scan, thereby achieving robust identification of impedance parameters.

[0054] Since the voltage drop across a series resistor directly depends on the current flowing through it, the resistor impedes the capacitor's charging process (i.e., There is an endogenous positive correlation between the current and the rate of change of voltage (i.e., G). To quantify this association, linear regression analysis needs to be performed: (1) Preset a high-voltage regression analysis interval. As an example, set 0.5 ~ This serves as the interval for the regression analysis. For the maximum power point voltage, as an example, the method for obtaining it is: for any position index k, ... ×V[k] represents the power at position index k. Among all position indices, the position index with the highest power corresponds to the voltage in V. .

[0055] The maximum power value is denoted as the maximum power. . It represents the true power generation potential of the string at the current ambient temperature, eliminating the interference of dynamic capacitance on power measurement during fast scanning.

[0056] The selection of the regression analysis interval is based on the fact that within this range, the diode conduction leads to a significant resistance effect, and the current has not yet entered the region of sharp current drop near the open circuit point (where the derivative is extremely large and nonlinearity is severe), thus the linearity of the signal is the highest.

[0057] (2) For all voltages in the reference voltage sequence V, obtain the position indices of the voltages that fall within the regression analysis interval. These position indices constitute an index set. .

[0058] Before performing regression calculations, statistics Number of elements inside .like If the number of fitting points is less than the preset minimum (e.g., set to 5), it is determined that the current data is insufficient to support reliable statistical inference (possibly due to an excessively fast scan rate or insufficient sampling rate). In this case, the impedance calculation is automatically terminated, and the triangular wave voltage excitation test is marked as "impedance cannot be identified," ending this embodiment. At this point, the scan rate is reduced by 3%, the sampling rate is increased by 10%, the length of the reference voltage sequence V is increased by 8%, and then this embodiment is re-implemented.

[0059] like If the number of fitting points is greater than or equal to the preset minimum number, then Using the static conductivity slope corresponding to all position indices within the range as the x-axis (i.e., the independent variable), The capacitance current drop corresponding to all position indices is used as the ordinate (i.e., dependent variable). Using the least squares method, all the abscissas (i.e., independent variables) and ordinates (i.e., dependent variables) are fitted to form a linear regression model. The slope of this linear regression model is denoted as the impedance coupling coefficient K. In other embodiments, the RANSAC random sampling consensus algorithm can also be used to fit the linear regression model, thereby reducing the impact of noisy data on slope identification.

[0060] It should be noted that in this embodiment, the intercept of the linear regression model is set to 0 (that is, the linear regression model is a straight line passing through the origin). The physical basis for forcing it to pass through the origin is that when the differential conductance of the circuit is zero (i.e., the current is constant), the voltage drop across the series resistor is constant, and no additional voltage change rate loss will be caused. Theoretically, the capacitor current drop must be zero.

[0061] Step S105: Obtain the electrical performance test results of the series resistance of the photovoltaic string based on the impedance coupling coefficient and the basic reference capacitor current; obtain the electrical performance test results of the equivalent capacitance of the photovoltaic string based on the basic reference capacitor current and the scan rate.

[0062] (1) Calculate the characteristic value of the series resistance of the component : in For a preset minimum positive number (e.g.) This parameter In this embodiment, it is defined as an equivalent indicator parameter reflecting the electrical connection loss on the DC side. An abnormal increase in its value usually corresponds to high-resistance faults such as oxidation of the combiner box connector, loose connection of the connector, or broken solder joint of the busbar inside the component.

[0063] It should be noted that the dimension remaining after dividing the numerator and denominator in this formula is the dimension of resistance (i.e., the dimension of ohms or the dimension of volts / amperes). Since the series resistance in a photovoltaic string is non-negative, when K obtained in some embodiments is less than 0, it indicates an error. This error is caused by a hardware failure of the acquisition card or interference that results in the acquisition of incorrect data. In this case, the acquisition card needs to be replaced and this embodiment needs to be reimplemented.

[0064] (2) Calculate the characteristic value of the equivalent capacitance of the component : This parameter This reflects the geometric capacitance characteristics of the module under low-voltage cutoff conditions. Abnormal fluctuations in its value (especially significant deviations from the nominal value) usually correspond to insulation structural abnormalities such as charge buildup in the depletion layer or water accumulation in the module's glass layer caused by the PID (potential-induced decay) effect.

[0065] (3) Maximum power Characteristic value of series resistance of components and component equivalent capacitance characteristic value As part of the electrical performance test results in the test report, , These represent the electrical performance test results under two independent physical quantities: series resistance and equivalent capacitance.

[0066] This concludes the example.

[0067] This embodiment can simultaneously eliminate capacitive hysteresis interference and effectively extract series resistance and equivalent capacitance characteristics in a single fast scan, ensuring the reliability and validity of the electrical performance test results of solar panels.

[0068] Example 2: Step S102 of Embodiment 1 includes: presetting a reference voltage sequence V. As another example, the method for obtaining the reference voltage sequence V includes: To balance testing accuracy and computational efficiency across different voltage levels (e.g., 12V modules to 1500V strings), this embodiment uses a specific step size for the voltage increment within the reference voltage sequence V. It uses a dynamic setting method, rather than a fixed value. The calculation formula is as follows: in, The estimated open-circuit voltage is taken from the maximum voltage value of the photovoltaic string output voltage collected in step S102. The effective number of sampling points (i.e., the length of the reference voltage sequence V, whose value is...) (to ensure sufficient resolution). The minimum voltage resolution (its value in this embodiment is...) This is used to prevent quantization noise from dominating due to excessively small step sizes.

[0069] The reference voltage sequence V is [0 , ,2 3 , ...].

[0070] Furthermore, regarding the current and voltage output from the photovoltaic string, due to the discreteness of sampling and the randomness of triggering time, the voltages sampled during the boost scanning phase and the buck scanning phase are usually not numerically coincident (i.e., there is a spatial phase difference), thus direct point-to-point algebraic operations are not possible. This embodiment utilizes a linear interpolation algorithm to map the collected current and voltage to a reference voltage sequence. Above. Specifically includes: All voltages and currents acquired during the boost scanning phase are represented as follows: and For the reference voltage sequence any sequence position index In all the collected Search and voltage Two adjacent voltages are denoted as , making .in , This represents the j-th and (j+1)-th voltages among all voltages acquired during the boost scanning phase. It lies between these two voltages. Calculate this voltage based on the linear proportional relationship. The corresponding current value will be used as the boost scanning current. .

[0071] As an example, the voltage is calculated based on a linear proportional relationship. The corresponding current values ​​include: Define the proportionality coefficient ;make .

[0072] in , Indicates the collected voltage , The current collected at the same time.

[0073] In special circumstances (e.g., when noise interference is present), when season .

[0074] Among them, when or equal hour, equal or .

[0075] For all voltages and currents acquired during the buck scanning phase, the buck scanning current is obtained using the method described above. .

[0076] Thus, for any given sequence position index k, and All of them strictly correspond to the same voltage value V[k].

[0077] Step S102 of Example 1 includes: calculating the photovoltaic quiescent current. And calculate the capacitor response current In this embodiment, the photovoltaic quiescent current is measured using the following method. and capacitor response current Filtering includes: Since Example 1 involves differential and derivative operations on current data, high-frequency random noise (usually introduced by the switching action of electronic loads or environmental electromagnetic interference) will be significantly amplified during the operation, potentially drowning out the weak resistance characteristic signal. Simultaneously, to accurately calculate the maximum power, the curvature characteristics of the volt-ampere curve at the "knee point" (near the maximum power point) must be fully preserved; excessive smoothing should be avoided to prevent feature clipping.

[0078] Therefore, this embodiment uses a Savitzky-Golay digital filter to filter the boost scan current and the buck scan current at all position indices, respectively, instead of the general moving average algorithm. The Savitzky-Golay filter uses local polynomial least squares fitting, which can smooth noise while keeping the higher-order moments of the signal (such as peak width and height) unchanged.

[0079] In this embodiment, the filter parameters are configured as follows: the window length is set to 11; the fitting order is set to 2.

[0080] This parameter setting effectively suppresses high-frequency noise while ensuring that the curvature of the volt-ampere curve at the knee point remains distorted. The smoothed data after filtering still uses the same sign. and This is represented and used as input for subsequent calculations.

[0081] Step S102 of Example 1 includes: calculating the photovoltaic quiescent current. In this embodiment, Static zero bias subtraction and open-circuit voltage extraction are performed, specifically including: To prevent voltage extraction errors caused by zero-point drift of the hardware acquisition card, a static zero-bias subtraction operation needs to be performed: the average current noise floor value acquired before the acquisition card test (when the voltage is zero and the loop is open) is recorded as follows: Other embodiments may also adopt... The average current at the end of the sequence (much larger than the open-circuit voltage region) is used as... The estimated value (e.g., the mean of the photovoltaic quiescent current corresponding to the last 20 positions of the reference voltage sequence V) is used as... ).Will The value is assigned to the photovoltaic quiescent current. .

[0082] Furthermore, for all location indices of the photovoltaic quiescent current, the photovoltaic quiescent currents of two adjacent location indices with a positive-to-negative transition are located; these two location indices are denoted as... ,satisfy and .

[0083] Furthermore, to ( )and( As two coordinate points, the equation of the line containing these two coordinate points is used. The ordinate corresponding to the equation of this line when the abscissa is 0 is taken as the voltage value when the photovoltaic quiescent current is zero. This voltage value is taken as the measured open-circuit voltage. .

[0084] Step S103 of Example 1 includes: obtaining the static conductivity slope. In this embodiment Specific methods for obtaining them include: For any position index k, a local window centered at k is selected. In this embodiment, the window size is 11. For any position index g within the local window, ... As a sampling point, all sampling points within the window are fitted to a straight line using the least squares method, and the slope of this line is used as the static conductivity slope. .

[0085] After obtaining the electrical performance test results in step S105 of Example 1, according to , The value of the parameter is used to determine potential high-resistance connection hazards and insulation structure abnormalities, specifically including: like If the resistance is greater than the baseline threshold of the photovoltaic strings in the same batch (e.g., the baseline threshold is set to 10Ω), the electrical performance test results will be marked as "high resistance connection abnormality".

[0086] like If the deviation from the nominal value exceeds 15% (e.g., nominal 900nF), the electrical performance test results will be marked as "abnormal insulation structure".

[0087] Example 3: This embodiment provides a solar panel electrical performance testing system. The system includes a photovoltaic string to be tested, an electronic load, and a data acquisition card. The photovoltaic string is composed of several photovoltaic panels (e.g., 28 panels) connected in series. The electronic load is a voltage source with controlled output voltage, which is connected to the terminals at both ends of the photovoltaic string to be tested. The data acquisition card includes a voltmeter and a current meter, which are also connected to the terminals at both ends of the photovoltaic string to be tested, and are used to collect the voltage and current output by the photovoltaic string.

[0088] The system also includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor runs the computer program, it performs all the steps of all the above embodiments by reading the voltage and current acquired by the acquisition card.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of testing the electrical performance of a solar panel, characterized by, The method comprises the following steps: The triangular wave voltage is applied to the photovoltaic string to be measured, and the triangular wave voltage comprises a voltage rising scanning stage and a voltage falling scanning stage with the same scanning speed; the scanning current of the voltage rising scanning stage and the voltage falling scanning stage is used to offset the capacitance response of the photovoltaic string by averaging, so as to obtain a photovoltaic static current; the scanning current of the voltage rising scanning stage and the voltage falling scanning stage is used to offset the static direct current response of the photovoltaic string by difference, so as to obtain a capacitance response current; The average capacitance response current in the preset low-voltage calibration interval is recorded as a basic reference capacitance current, and the difference between the basic reference capacitance current and the capacitance response current is taken as a capacitance current drop amount; the change rate of the capacitance current drop amount with respect to a static conductance slope is taken as an impedance coupling coefficient, and the static conductance slope represents the change rate of the photovoltaic static current with respect to the output voltage of the photovoltaic string; The electrical performance test result of the series resistance of the photovoltaic string is obtained based on the impedance coupling coefficient and the basic reference capacitance current; and the electrical performance test result of the equivalent capacitance of the photovoltaic string is obtained based on the basic reference capacitance current and the scanning speed.

2. The method of claim 1, wherein, The specific acquisition steps of the scanning current of the voltage rising scanning stage and the voltage falling scanning stage are as follows: After the triangular wave voltage is applied to the photovoltaic string to be measured, a plurality of voltage data are sampled based on the maximum voltage output by the photovoltaic string and are used to form a reference voltage sequence V; for any position index k in the reference voltage sequence V, the voltage corresponding to the position index k is recorded as V[k]; The current collected on the photovoltaic string when the voltage output by the photovoltaic string is equal to V[k] in the boost scanning phase is represented as The current collected on the photovoltaic string when the voltage output by the photovoltaic string is equal to V[k] in the boost scanning phase is represented as ; wherein , represents the scanning current obtained in the boost scanning phase and the buck scanning phase at the position index k.

3. The method of claim 2, wherein the step of applying a voltage to the solar panel is performed by applying a voltage to the solar panel using a power supply. The average capacitance response current in the preset low-voltage calibration interval is recorded as a basic reference capacitance current, and the specific steps include the following: For position index k, the scan current of the boost scan phase and the buck scan phase , The capacitance response current obtained by taking the difference is denoted as , indicating the corresponding obtained capacitance response current of position index k; For all voltages in the reference voltage sequence V, the position indexes of the voltages in the preset low-voltage calibration interval among all the voltages constitute an index set ; the index set The average of the corresponding capacitance response currents obtained under all position indexes in the index set is obtained as a basic reference capacitance current.

4. The method of claim 3, wherein the step of applying a voltage to the solar panel is performed by applying a voltage to the solar panel using a power supply. The change rate of the capacitance current drop amount with respect to a static conductance slope is taken as an impedance coupling coefficient, and the specific steps include the following: a regression analysis interval is preset; for all voltages in the reference voltage sequence V, the position indexes of the voltages in the regression analysis interval form an index set ; each position index in the index set corresponds to a capacitance response current as a dependent variable, and a static conductance slope of a photovoltaic static current corresponding to each position index in the index set as an independent variable; all independent variables and dependent variables in the index set are fitted into a linear regression model by using a least square method, and a slope of the linear regression model is taken as the impedance coupling coefficient; wherein, an intercept of the linear regression model is set as 0. For the voltage at each position index in the reference voltage sequence V, the static conductance slope of the photovoltaic static current corresponding to each position index is equal to the change rate of the photovoltaic static current corresponding to each position index at the voltage.

5. The method of claim 1, wherein the method further comprises: The specific steps of obtaining the electrical performance test result of the series resistance of the photovoltaic string based on the impedance coupling coefficient and the basic reference capacitance current include the following: The electrical performance test result of the series resistance of the photovoltaic string is represented by a series resistance characteristic value, and the series resistance characteristic value is positively correlated with the impedance coupling coefficient and is negatively correlated with the basic reference capacitance current.

6. The method of claim 1, wherein, The specific steps of obtaining the electrical performance test result of the equivalent capacitance of the photovoltaic string based on the basic reference capacitance current and the scanning speed include the following: The electrical performance test result of the equivalent capacitance of the photovoltaic string is represented by an equivalent capacitance characteristic value, and the equivalent capacitance characteristic value is positively correlated with the basic reference capacitance current and is negatively correlated with the scanning speed.

7. The method of claim 2, wherein the step of applying a voltage to the solar panel is performed by a power supply. The specific acquisition steps of the reference voltage sequence V are as follows: In the boost scan phase and the buck scan phase, the current and the voltage of the photovoltaic string output are collected in real time; a ratio of a maximum value of the collected output voltage to a preset value is recorded as ; A voltage increasing sequence with 0 volt as starting point and with steps of is used as reference voltage sequence V; for all voltages and currents acquired in the voltage up-scan phase or in the voltage down-scan phase for any sequence position index in the sequence of reference voltages V searching in all voltages acquired for the same sequence position index , for the same sequence position index in the sequence of reference voltages V , denote the j-th and j+1 -th voltages in all voltages , acquired in the voltage up-scan phase or in the voltage down-scan phase ; The current value corresponding to the voltage V[k] is calculated according to a linear proportional relationship, such that , The proportional relationship with V[k] and , The proportional relationship with the calculated current value is the same, and the calculated current value is used as the scan current of the boost scan stage or the step-down scan stage or .

8. The method of claim 3, wherein the step of applying a voltage to the solar panel is performed by a power supply. The specific acquisition steps of the low-voltage calibration interval are as follows: For the photovoltaic static current obtained for all position indexes of the reference voltage sequence V, for the position indexes for which the photovoltaic static current is equal to 0, the voltage corresponding to this position index in the reference voltage sequence V is noted measured open circuit voltage ; The upper and lower limits of the low pressure calibration interval are determined by the following equations:

9. The method of claim 4, wherein the step of applying a voltage to the solar panel is performed by a power supply. The specific steps of the regression analysis interval are as follows: For any one position index k, the product of the photovoltaic static current under the position index and V[k] is recorded as the power of the position index; the voltage corresponding to the position index with the maximum power among all position indexes is taken as V ; the regression analysis interval is determined by , and the voltage within the regression analysis interval is greater than the voltage within the low-voltage calibration interval.

10. A solar panel electrical performance testing system, the system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein, The processor runs the computer program to realize all the steps of the solar cell panel electrical performance test method in any one of claims 1 to 9.

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