Curve tracker

Abstract

Embodiments of the present disclosure relate to a curve tracker and system for testing PV modules. The I-V curve tracker may include a switched mode power converter (SMPC) circuit. The I-V curve tracker may be configured to scan for an I-V curve of the PV circuit. Related devices, systems, and methods are also possible.

Description

[0001] Cross-references to related applications This application claims priority to U.S. Provisional Patent Application No. 63 / 499795, filed May 3, 2023, the disclosure of which is hereby incorporated in its entirety. Technical Field

[0002] Embodiments of this disclosure relate to curve trackers and associated systems, devices, circuits, and methods. Background Technology

[0003] Photovoltaic (PV) systems are a ubiquitous contributor to energy production worldwide. PV systems use solar modules or solar panels to convert incident sunlight into electricity, which can then be fed into the grid via an inverter, stored in battery banks, or consumed locally. Attached Figure Description

[0004] Although this disclosure concludes with claims that particularly point out and clearly claim protection for particular embodiments, various features and advantages of embodiments within the scope of this disclosure may be more readily apparent from the following description when read in conjunction with the accompanying drawings, wherein: Figure 1 The illustration shows an example system in which various aspects of this disclosure can be implemented; Figure 2 The illustration shows a model of a PV battery; Figure 3 A portion of a type of curve tracker using a capacitive load is depicted; Figure 4 This is a flowchart illustrating a method for measuring the IV curve of a capacitive load; Figure 5 An example switch is depicted; Figure 6 It is a graph that includes the IV curve; Figure 7 A block diagram of a PV system with modular electronic devices is depicted. Figure 8 Devices including a curve tracker are described according to various embodiments of the present disclosure; Figure 9 This is a flowchart depicting various embodiments of the methods according to this disclosure; Figure 10 This is a flowchart depicting another method according to various embodiments of the present disclosure; Figure 11 This is a flowchart depicting another method according to various embodiments of the present disclosure; Figure 12 Devices including a curve tracker are described according to various embodiments of the present disclosure; Figure 13 The diagram illustrates a "bleeder" circuit for a switch-mode power converter (SMPC) according to various embodiments of the present disclosure; Figure 14 Devices including an SMPC curve tracker according to various embodiments of the present disclosure are described; Figure 15 The illustration shows the quadrants of operation of power conversion circuits according to various embodiments of the present disclosure, including SMPC as a possible type; Figure 16 A C'uk converter is described; Figure 17 Various embodiments of the SMPC according to this disclosure are described; Figure 18 This is a flowchart depicting another method according to various embodiments of the present disclosure; Figure 19 Another C'uk SMPC is depicted according to various embodiments of this disclosure; Figure 20 Another C'uk SMPC is depicted according to various embodiments of this disclosure; Figure 21 Devices including a curve tracker are described according to various embodiments of the present disclosure; Figure 22 It is a graph of IV curves according to various embodiments of the present disclosure; Figure 23 Various timing diagrams are depicted according to various embodiments of the present disclosure; Figure 24 It is a graph showing the current and voltage over time according to various embodiments of the present disclosure; Figure 25 This is a flowchart describing another method according to various embodiments of the present disclosure; and Figure 26 Devices including curve trackers according to various embodiments of the present disclosure are described. Detailed Implementation

[0005] In the following detailed description, reference is made to the accompanying drawings, which form a part of this detailed description and illustrate specific embodiments of the present disclosure that can be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it should be understood that other embodiments can be utilized and structural, logical, and electrical changes can be made within the scope of this disclosure.

[0006] In this description, specific implementations are shown and described by way of example only and should not be construed as the only way to implement this disclosure unless otherwise specified herein. It will be readily apparent to those skilled in the art that various embodiments of this disclosure can be practiced with a variety of other partitioning solutions. For most parts, details regarding timing considerations and such details have been omitted, which are not essential for obtaining a complete understanding of this disclosure and are within the capabilities of those skilled in the art.

[0007] Various embodiments of the present disclosure are illustrated with reference to the following description and accompanying drawings to illustrate their structure and operation. Common elements of the illustrated embodiments may be designated using similar reference numerals. It should be understood that the presented drawings are not intended to be an illustration of actual views of any particular part of the actual structure or method, but are merely intended to more clearly and fully depict an idealized representation of the invention as defined by the following claims.

[0008] It should be understood and appreciated that information and signals can be represented using any of a wide variety of different techniques and methods. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be mentioned throughout the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or particles, light fields or particles, or any combination thereof. For clarity of presentation and description, some accompanying drawings may illustrate signals as single signals. Those skilled in the art will understand that signals can represent signal buses, where buses can have a wide variety of bit widths, and embodiments of this disclosure can be implemented on any number of data signals, including single data signals.

[0009] It should be further understood and appreciated that the various illustrative logic blocks, modules, circuits, and algorithmic actions described in connection with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or a combination of both. To clearly illustrate this interchangeability between hardware and software, the various illustrative components, blocks, modules, circuits, and actions are generally described in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. Those skilled in the art can implement the described functionality in varying ways for each specific application; however, such implementation decisions should not be construed as causing a departure from the scope of the embodiments described herein.

[0010] The various illustrative logic blocks, modules, and circuits described in conjunction with the embodiments disclosed herein can be implemented or performed using a general-purpose processor, a special-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but alternatively, it may be any conventional processor, controller, microcontroller, or state machine, or a combination of such elements. A general-purpose processor can be considered a special-purpose processor, which executes instructions (e.g., software code) stored on a computer-readable medium. The processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration.

[0011] When executed as firmware or software, instructions for performing the procedures described herein may be stored on a computer-readable medium. Computer-readable media include, but are not limited to, non-transitory storage media, such as magnetic and optical storage devices, such as disk drives, magnetic tapes, CDs (compact discs), DVDs (digital versatile discs or digital video discs); and semiconductor devices, such as RAM, DRAM, ROM, EPROM, flash memory, or other volatile or non-volatile storage components.

[0012] It should be understood that any references to elements herein using terms such as "first," "second," etc., do not limit the number or order of those elements unless such limitation is explicitly stated. Rather, these designations may be used herein as a convenient way to distinguish two or more elements or instances of elements. Therefore, references to first and second elements do not imply that only two elements can be used there, or that the first element must somehow precede the second element. Moreover, unless otherwise stated, a set of elements may include one or more elements.

[0013] Assessing the health of a PV system is a crucial part of ensuring its proper functioning. The assessment may be the first step in determining what actions, if any, must be taken to improve the PV system's performance. Current-voltage (IV) curve trackers are used to assess the health of PV systems, but various challenges exist when using IV curve trackers to evaluate PV system health.

[0014] One challenge may be the heat generated by the IV curve tracker, such as heat generated by the resistor. This heat may cause the IV curve tracker to shut down, limiting its operating time, which may require continuous operation in thermal environments. Another challenge associated with IV curve trackers may be accurately measuring high-efficiency (HE) PV modules, which may generate initial high currents (“surge current” or “surge current transients”), which may damage the IV curve tracker or distort the measurement. Yet another challenge associated with IV curve trackers may be that the rate of change of voltage over time (dV / dt) during an IV scan may cause measurement results to differ from those obtained from “steady-state” measurements (e.g., static or slowly changing resistive loads) at any given point on the IV curve. Yet another challenge associated with IV curve trackers may be their implementation using module-level electronics (“MLE” or “MLPE”) that may shut down during an IV scan, thereby interrupting the IV curve tracker measurement. Yet another challenge associated with IV curve trackers is that the energy captured during measurement may be dissipated as heat, which can accumulate with repeated measurements. Furthermore, some IV curve trackers can only be used with systems that produce relatively low amounts of power. As will be apparent, these are just some of the challenges that may arise when using IV curve trackers to evaluate PV systems.

[0015] The aspects of this disclosure address at least some of these challenges. For example, in some embodiments, the IV curve tracker includes switch-mode power converter (SMPC) circuitry and storage capacitors. This configuration can lead to various technical advantages. In some embodiments, the IV curve tracker disclosed herein can adjust its scan rate without dissipating significant energy during IV scanning. By doing so, the IV curve tracker can reduce the heat generated, thereby enabling continuous operation and operation in hot environments. In some embodiments, such an IV curve tracker can scan slowly enough to avoid errors caused by the capacitance of the HE module, but scan fast enough to avoid errors caused by solar ramps, thereby improving the overall accuracy of the IV curve tracker. However, given their configurations, the IV curve trackers disclosed herein can handle PV systems with relatively higher power than previous IV curve trackers. However, in some embodiments, the IV curve trackers disclosed herein can accurately measure the HE module using one of a variety of techniques, including, for example, SMPC circuitry or surge shunt circuitry. However, in some embodiments, the IV curve tracker disclosed herein can accurately measure PV systems including MLE devices by efficiently adjusting the power-on and power-off behavior of the MLE device (such as measuring at least a portion of the IV curve). Other technical improvements provided by various aspects of this disclosure are also possible, as will be understood by those skilled in the art.

[0016] Figure 1 An example system 100 in which various aspects of the present disclosure can be implemented is illustrated. In the example shown, system 100 includes PV circuitry 102, which may include PV modules or module arrays, measuring device 104, connector 106, combiner box 108, combiner box circuitry 109, IV curve tracker 110, connector 112, clip 114, network (which may be physical, WiFi, or similar) 116, user 118, and computing device 120.

[0017] PV circuit 102 may include one or more PV cells, which are part of a PV module (such as...) Figure 2 The system 100 includes a PV battery 200, and the PV circuit can be connected to multiple PV modules. User 118 can use the components depicted in system 100 to evaluate the performance of the PV circuit 102 and any PV modules connected thereto. Examples of such evaluations and how they are performed are further described herein.

[0018] The measuring device 104 may be an instrument for measuring one or more attributes associated with the PV circuit 102. For example, when the PV circuit 102 is a PV circuit under test, the measuring device 104 may measure one or more attributes associated with the PV circuit 102. For example, the measuring device 104 may measure one or more of irradiance, module temperature, or array tilt. In some embodiments, the measuring device 104 is attached to the PV circuit 102, and the measuring device 104 may include external sensor devices coupled to different parts of the PV circuit 102 or the PV module for collecting sensor data associated with the PV circuit 102. Furthermore, based on the collected sensor data, the measuring device 104 may determine one or more attributes associated with the PV circuit 102. The measuring device 104 may be communicatively coupled to the IV curve tracker 110, and the measuring device 104 may provide the measurements associated with the PV circuit 102 to the IV curve tracker 110 via a wired or wireless connection. The IV curve tracker 110 may then use these measurements as part of generating an IV curve trajectory. In some embodiments, the measuring device 104 and the IV curve tracker 110 are communicatively coupled to the network 116.

[0019] Connector 106 can electrically couple PV circuit 102 to combiner box 108. Connector 106 may include one or more of leads, wires, cables, wire harnesses, and other materials for electrically coupling PV circuit 102 to combiner box 108.

[0020] Combiner box 108 can be electrically coupled to PV circuit 102, which may include multiple PV modules. For example, combiner box 108 may include combiner box circuit 109, which receives current / voltage from PV circuit 102 via connector 106. Furthermore, combiner box circuit 109 may receive an electrical connection from IV curve tracker 110. In this way, combiner box circuit 109 can electrically couple PV circuit 102 to IV curve tracker 110.

[0021] IV curve tracker 110 is a device that can be used to test and evaluate the performance of PV circuit 102. Example embodiments of IV curve tracker 110 are described herein. As shown, IV curve tracker 110 can be electrically coupled to combiner box circuit 109 via, for example, connector 112 and clip 114. The IV curve tracker can be electrically coupled to PV circuit 102 via combiner box circuit 109. In some embodiments, IV curve tracker can be directly electrically connected to PV circuit 102 without using combiner box 108.

[0022] In some embodiments, the IV curve tracker 110 is communicatively coupled to the measurement device 104 and the computing device 120. In some embodiments, the IV curve tracker 110 may form a network 116, and the IV curve tracker 110, the measurement device 104, and the computing device 120 may be communicatively coupled via the network 116. In some embodiments, the IV curve tracker 110 is a hotspot in the network 116.

[0023] Connector 112 can electrically couple IV curve tracker 110 to combiner box 108. Connector 112 may include one or more of the following: leads, wires, cables, wire harnesses, clips 114, and other materials for electrically coupling PV circuit 102 to combiner box 108.

[0024] Network 116 can be a wireless, wired, optical, or other communication network. In some embodiments, network 116 is a Wi-Fi network generated by IV curve tracker 110. In some embodiments, network 116 can implement different network protocols, such as Bluetooth.

[0025] User 118 may be a person using components of system 100 to evaluate PV circuit 102. In some embodiments, user 118 is a technician or engineer. In some embodiments, user 118 is maintaining or debugging PV circuit 102.

[0026] The computing device 120 may be one or more of a laptop computer, tablet, mobile phone, or other computing device. The computing device 120 may include a processor and a display. In some embodiments, the processor is configured to present the real-time progress of at least a portion of the IV curve on the display. For example, the computing device 120 may include software programs for evaluating the PV circuit 102. Based on data received from the IV curve tracker 110, the computing device 120 may generate and display data, such as the real-time test progress of at least a portion of the IV curve associated with the PV circuit 102. In some embodiments, the software application may include features for editing operating parameters of the IV curve tracker 110.

[0027] System 100 may include more Figure 1 The examples depict more or fewer components. For example, PV circuit 102 may be a PV circuit comprising a single PV module or multiple PV modules connected in series or in parallel, or both. Certain embodiments of some of the components described in system 100 are further described herein.

[0028] The electrical model of PV battery 200 is in Figure 2 As shown in the diagram, when exposed to sunlight, the current source 202 can generate a photocurrent I. LUnder no load, the current I L The main current flows into diode D204 (parasitic shunt resistance R) sh 208 is large, and the parasitic series resistance R s 210 small), therefore I D Approximately equal to I L The voltage V is essentially equal to the open-circuit voltage (“Voc”). When a short circuit is connected to the PV cell 200, the steady-state current I is essentially equal to the short-circuit current (“Isc”). The PV cell 200 may also have an associated capacitance C. jct 206.

[0029] As those skilled in the art will appreciate, a PV module may include multiple (e.g., many) cells in series, and sometimes may also have parallel cell strings. PV strings or arrays may include series and / or parallel combinations of PV modules. Cells, modules, strings, and arrays (individually or collectively referred to as “PV circuits”) have electrical characteristics such as current-voltage (“IV”) curves. IV curves are a decisive indicator of the performance and integrity of a solar module and can be used to detect even subtle degradation of the solar module within a PV system. A load applied to a PV circuit under solar irradiation may result in a combination of voltage and current on the IV curve of the PV circuit. A static resistive load R applied to a PV circuit may result in current and voltage, where I = V / R. An IV curve tracker can measure or “scan” the IV curve by varying the load applied to the PV circuit. IV curves are sometimes described as “scans” from 0 volts to Voc, from Voc to 0 volts, from 0 amps to Isc, from Isc to 0 amps, from Voc to Isc, or from Isc to Voc. Any of these scans can produce IV curve data. For example, Warner et al. disclosed IV curve measurement in U.S. Patent 4,456,880 entitled “I-VCurve Tracer Employing Parametric Sampling”.

[0030] Some IV curve trackers use capacitive loads CL (also referred to as "load capacitors" in this article), such as Figure 3As shown in device 300, it includes a PV circuit 302 and a curve tracker 304. A curve tracker controller 314 can be configured to control other elements of the curve tracker 304, such as switches S1 306 and S2 308. A capacitive load, which may be a capacitor CL 310, can include a single capacitor or multiple capacitors connected in series and / or parallel combinations. The capacitive load can include one or more capacitors, which can be switched on or off by the curve tracker controller to achieve a variety of different load capacitor values ​​depending on the PV circuit under test or the desired scan rate (or desired scan time). The load capacitor must be large enough to store the energy accumulated during the IV scan. The stored energy increases with increasing voltage and scan time. The scan time increases with decreasing current and increasing capacitance. For example, when scanning the IV curve of a PV circuit with a Voc of 1500V and an Isc of 10-30A, and when the desired scan time is 200ms or more, the load capacitor can be 850uF to 3400uF or larger, and must be rated for a maximum voltage of 1500V. The curve tracker 304 can be operated by connecting the PV circuit 302 to a capacitor CL 310 via a switch 306 (e.g., a software-controlled electronic switch, such as a transistor) S1, which is initially fully discharged to have an initial capacitor voltage of zero volts. The current from the PV circuit 302 then charges the capacitor CL 310 until the voltage of the capacitor CL 310 is substantially equal to the open-circuit voltage of the PV circuit 302. While the capacitor CL is charging, the curve tracker 304 uses a current sensing element M... I 318 (e.g., sensing resistors, sensing amplifiers, and analog-to-digital converters (“ADCs”)) and voltage sensing elements M V 316 (e.g., voltage dividers, sense amplifiers, and ADCs) measure current (I) and voltage (V) at multiple points along the path. Current and voltage are typically measured simultaneously. There is usually a time interval between subsequent samples (sampling interval delay). This can lead to issues such as... Figure 6 The characteristic IV curve is shown in the figure. At the end of the IV scan, switch S1 306 can be opened, and the energy stored in capacitor CL 310 can be dissipated during discharge or discharge mode. This can be accomplished, for example, by a resistive bleeder element Rb 312 (“resistive bleeder”) (e.g., a power resistor). For example, switch S2 308 can be closed, and energy flows from capacitor CL 310 to resistive bleeder element Rb 312.

[0031] As an example, in Figure 4 The flowchart 400 illustrates a typical algorithm for measuring IV curves using a capacitive load curve tracker (e.g., curve tracker 304).

[0032] Other curve trackers use switched resistive loads or active loads (such as transistors) to measure individual points on the IC curve. These types of loads may dissipate energy during IV scans in these devices. Some curve trackers (e.g., within 2 ms) apply pulses to the resistive or active load to minimize heat dissipation. Current and voltage can be measured during the pulse.

[0033] Figure 5 The diagram illustrates an example switch 500. Switch 500 is capable of... Figure 3 , Figure 8 and Figure 12 This document provides an example of the circuit implementation of the switches used in the C'uk converter. In switch 500, the floating drive output can be isolated from the control input current. In some embodiments, one or more of the switches described herein can be implemented using the design of switch 500.

[0034] Limitations—Heat Dissipation For safety reasons, resistive bleeder elements are typically housed within a casing (e.g., the product housing). This may isolate the user from any internal high voltage or high temperature. Heat from the resistive bleeder element can accumulate within the IV curve tracker housing, eventually causing the device to reach a temperature that, when exceeded, shuts down the curve tracker (e.g., to protect itself). This may limit the IV curve tracker's operating time or scan-to-scan time. Continuous use of IV curve trackers is often expected throughout the day and in hot environments (e.g., during commissioning of a large utility-scale PV plant in the desert, where each PV string is measured). Minimizing the amount of energy dissipated within the curve tracker's housing may be desirable, allowing for short scan-to-scan times and long continuous operating times.

[0035] One approach is to install a resistive bleeder element outside the enclosure, but then the wires must then exit the enclosure. It may be desirable to minimize the amount of wires or conductive material leaving the enclosure to minimize the risk of exposing the user to high voltage, especially in the event of a fault inside the enclosure (e.g., a wire detaches inside the enclosure and short-circuits with other wires or metal, eventually finding its way out of the enclosure).

[0036] Another approach is to mount a resistive bleeder element to a heatsink, with a portion of the heatsink inside the housing and a portion outside. Heatsinks are typically conductive metals, so this configuration may have the same drawbacks as configurations that include wires extending beyond the housing (i.e., as mentioned above), and potentially expose the user to high voltages. Heatsinks can be made of highly thermally conductive but non-conductive materials such as ceramics; however, this can increase cost and may result in fragility. Fans may be included to actively cool the bleeder element and / or the heatsink; however, this also increases cost and further reduces battery life (i.e., for fan operation) and has moving parts that may fail in dusty environments (as is common for curve trackers). Furthermore, the power to drive such a fan will typically be via wires, which could be at dangerous voltages if they extend beyond the housing (e.g., the product casing).

[0037] Limitations—Surge Current PV modules generate DC current and may also have AC or dynamic characteristics (primarily derived from PV cell capacitors, e.g., see...). Figure 2 C in jct These characteristics come into play when the operating point changes rapidly. In addition to a moderate amount of parallel-plate junction capacitance, there is diffusion capacitance associated with the large amount of charge stored in the forward-biased junction of the PV cell (i.e., the forward-biased diode of each cell). Diffusion capacitance increases with cell voltage and with irradiance (i.e., photocurrent), and can also increase rapidly with cell efficiency (i.e., the efficiency of the PV cell in converting light per unit area into electrical power). High-efficiency (“HE”) modules consist of HE cells. For example, the SunPower SPR-X22 and REC 400AA have efficiencies of approximately 22%. For HE modules, the diffusion capacitance of the PV circuit can range from tens of microfarads or higher. At the moment an IV scan begins, shorting the PV circuit, free charge in the cell can surge into the associated curve tracker, potentially causing current overload errors or damaging the curve tracker circuitry. Many IV curve trackers cannot withstand the inrush currents associated with HE modules and will either be damaged, produce errors, or become incapable of measurement. Some curve trackers will use pulsed loads, which can cause surge current transients, where each pulse involves a large change in the current in the PV circuit.

[0038] For an IV curve tracker, accurate and successful measurement of the HE module is likely desirable.

[0039] Typically, when measuring the IV curve of a string, the string is first disconnected from any inverter it might otherwise be connected to. However, if a user makes a mistake and attempts to measure the IV curve of a PV string connected to the inverter input, a high inrush current may enter the associated IV curve tracker. PV inverters typically have large input capacitances several orders of magnitude larger than the capacitance of the PV modules, and this has been observed to cause very large inrush currents. This large inrush current can damage the IV curve tracker, cause it to become inaccurate, and / or otherwise malfunction it, making measurement impossible. When this occurs, protection circuitry may be needed to protect the measurement circuitry (i.e., the IV curve tracker's measurement circuitry). However, it can be difficult to distinguish between an inrush current due to an incorrect inverter connection (in which case the protection circuitry is expected to stop the measurement) and a string of HE modules (in which case the measurement should still be performed).

[0040] If connected to an inverter, it is desirable to have an IV curve tracker that accurately and successfully measures the HE module, while preventing damage caused by unintentional measurements.

[0041] Limitations – Accuracy of measuring high-efficiency modules Another challenge presented by HE modules is that, in addition to large inrush currents, the rate of change of voltage over time (dV / dt) during an IV scan can cause measurements to differ from those obtained from “steady-state” measurements at any given point on the IV curve (e.g., static or slowly changing resistive loads). When an HE module scans from Voc to Isc or from Isc to Voc to generate an IV curve, the measured shape of the resulting IV curve may be inaccurate due to the rapidly changing voltage. The error in the IV curve shape depends on how fast the IV curve is scanned. The faster the scan, the larger the error. Moreover, the higher the efficiency of the cell, the larger the error. This is due to the charge stored in the forward bias junction of the PV cell and is roughly analogous to the nonlinear capacitance in each PV junction. To minimize the measurement error of the HE module, it may be necessary to scan the IV curve slowly enough to minimize this effect. However, some IV curve trackers are not able to scan slowly enough or adjust their scan times in a flexible manner. For example, the scan time of a capacitive load IV curve tracker is a function of the load capacitor and the current and voltage of the PV circuit under test. Other curve trackers cannot scan slowly because they use active or resistive loads that dissipate energy during IV scans. Other curve trackers apply pulses to the active or resistive load to minimize heat dissipation in the load element, but the pulses themselves are very fast (e.g., 2 ms), and the dynamic response of the HE module associated with the capacitor may make its measurement challenging or impossible.

[0042] An IV curve tracker that allows for arbitrary adjustment of its scan rate while not dissipating a large amount of energy during IV scans would be desirable.

[0043] Limitations—Module-level Electronics Figure 7 A schematic block diagram of a PV system 700 including multiple PV modules 702 comprising PV circuitry is illustrated. Each PV module is electrically coupled to module-level electronics (“MLE”) or module-level power electronics (“MLPE”), which are depicted as multiple MLPE 704 devices. MLPE 704 may include components that improve the performance of the associated PV module 702, thereby more generally improving the performance of the PV circuitry. In some embodiments, MLPE 704 may include a microinverter or a DC power optimizer. In some embodiments, MLPE 704 may include performance or diagnostic monitoring features. In some embodiments, MLPE 704 may have a fast shutdown device that can rapidly reduce or stop the current or voltage from the associated PV module 702.

[0044] When attempting to scan a PV module 702 or a module string (where the module is equipped with an MLPE 704), a scan starting from a short circuit (and therefore zero voltage) may cause the MLPE 704 electronics to shut down, which typically also disconnects the module from the string. There may not be sufficient voltage for the electronics to operate, and therefore the electronics may shut down. The electronics may not re-energize for several seconds, and IV measurements may be inaccurate.

[0045] It may be expected that the IV curve tracker will be able to measure at least a portion of the IV curves of the module and module string using the MLPE 704.

[0046] Limitations—Existing Switching Mode Approaches In some instances, resistive elements can be used as loads for the SMPC. This means that the energy transferred from the PV circuit via the SMPC must be dissipated as heat. What is needed is a way to scan the IV curve with the SMPC without having to dissipate energy as heat. While some curve trackers in existing systems have relatively low power handling capabilities, field measurements of utility-scale PV systems require the ability to handle higher power levels. For example, PV strings in utility-scale systems can have voltage levels up to 1500V and currents of 30 amps or more. What is needed is an SMPC IV curve tracker with significantly higher power handling capabilities (e.g., 15kW to 45kW or higher).

[0047] Surge diversion As discussed above, the HE module has high capacitance, which has been observed to cause large inrush currents when the IV scan from Isc to Voc begins or when the array is short-circuited during pulsed load measurements. For a nominal 30A Isc array, this inrush current can be on the order of, for example, 400 amps, and can last for, for example, approximately 100-600 µs. See, for example, Figure 24 Surge current pulses can occur. Damage to internal electronic components not rated for this type of surge current can occur. However, components rated for such high currents are expensive and generally bulky. (Reference) Figure 8 The device 800 includes a PV circuit 801 and a curve tracker 802. In some embodiments of this disclosure, the curve tracker 802 includes a surge shunt circuit (“shunt”) 804 configured to clamp or shunt surge current away from associated measurement circuitry, thereby preventing surge current from propagating into other parts of the curve tracker 802. This configuration allows other internal components to have relatively low current ratings, and thus saves cost.

[0048] Shunt 804 may include a current sensing circuit (not shown) that detects an increase in current entering curve tracker 802, which indicates the start of an IV scan, or it may detect a high inrush current. This current sensing circuit then causes shunt controller 810 to turn on electronic switch S3 805 (e.g., an insulated-gate bipolar transistor (“IGBT”) or other high-current, high-voltage switching device), which instantaneously transfers current to... Figure 8In the short circuit shown, or alternatively, the current is transferred to a load such as a resistor or capacitor. Switch S3 805 can be controlled by shunt controller 810. After the surge current has been shunted for a certain amount of time Ts (e.g., 600µs), shunt controller 810 can open switch S3 805, thereby releasing the circuit. Normal IV curve scanning can then continue (starting with a short circuit). For example, curve tracker controller 806 first enables or equips the shunt controller, which then begins monitoring the current. Then, curve tracker controller 806 closes switch S1 816, initiating current flow from PV circuit 801 into load capacitor CL 820, which is initially zero volts and subsequently begins charging. When shunt controller 810 detects current flow, it closes switch S3 805 for a period of time Ts, and then opens S3 805. Load capacitor CL 820 continues charging to Voc, while current and voltage are measured at multiple points on the IV curve. When the IV curve scan is complete, the curve tracker controller 806 opens switch S1 816 and then closes S2 818 to discharge the voltage on the load capacitor CL 820, and then opens S2 818 again. In another example, S3 805 is closed for a period of time Ts and then opened. After S3 805 is opened, the curve tracker controller 806 can then close switch S1 816 to begin the IV scan. Current from the PV circuit 801 can then flow into the load capacitor CL 820, which is initially at zero volts and subsequently charged to Voc, while current and voltage are measured at multiple points on the IV curve. At the end of the scan, switch S1 816 opens and switch S2 818 closes to release the energy stored in the load capacitor CL 820 via the resistive bleeder Rb 822. This method in Figure 9The flowchart 900 illustrates this. In another example, switch S3 805 can be closed to allow current to flow from PV circuit 801 into the surge shunt, and then switch S1 816 closes to allow current from PV circuit 801 to also flow into load capacitor CL 820, which is initially at zero volts and subsequently begins to charge. Switch S3 805 is then opened either after a predetermined amount of time (e.g., reaching time period TS2) or when the surge current transient has been fully or partially shunted. As the current and voltage of PV circuit 801 are measured at multiple points on the IV curve, load capacitor CL 820 continues to charge to Voc (or close to Voc). Then, when the IV curve is complete, S1 816 opens and S2 818 closes to discharge the voltage across load capacitor CL 820, and then S2 818 opens. The current and voltage of the PV circuit 801 can be measured during the time switch S3 805 is closed, during the time switch S1 816 is closed, and at any other time during the operation of the IV curve tracker. This method... Figure 25 The flowchart 2500 is shown.

[0049] Segmented scanning of capacitive loads As discussed above, when attempting to scan a PV circuit with a capacitive load curve tracker, where the module is equipped with an "optimizer" or "fast-shutdown" electronics ("module-level electronics" or "MLE"), a scan starting from a short circuit (and therefore zero voltage) may cause the MLE to shut down, which typically also disconnects the module from the associated curve tracker. When this occurs, a typical curve tracker may be unable to perform IV measurements. However, the MLE typically does not shut down immediately upon a short circuit. The MLE may be able to remain on and operate for a period of time (e.g., 10-100 ms) before being de-energized. During this time, a portion of the IV curve can be scanned even if the scan started at the short circuit. During this time, a certain amount of charge is transferred from the PV circuit to the load capacitor. If the curve tracker load is removed (i.e., switch S1 returns to on), the MLE will typically be re-energized after a period of time (e.g., 1-10 seconds). In some embodiments, the controller is configured to scan the first portion of the IV curve from the open-circuit voltage to a non-zero voltage below the open-circuit voltage. In some embodiments, the controller is configured to scan a first portion of the IV curve from a first voltage below the open-circuit voltage to a second voltage below the first voltage. In some embodiments, the controller is configured to scan a first portion of the IV curve from zero volts to a higher voltage below the open-circuit voltage. In some embodiments, the controller is configured to scan a first portion of the IV curve from a first voltage above zero volts to a second voltage above the first voltage.

[0050] In one embodiment, the IV curve is scanned, and charge flows from the PV circuit to the load capacitor C1, charging it to a voltage below Voc, until the MLE is turned off and current stops flowing. The stored charge may remain in the load capacitor C1 (unlike it would typically be removed by a discharge circuit after an IV scan). Then, when the MLE is powered on again, another scan is performed. Since the load capacitor C1 has already been charged to a voltage above zero, the IV scan begins at that voltage, and the voltage continues to increase as more charge enters the load capacitor C1. This may continue until the MLE is turned off again. And again, the charge remains in the load capacitor C1 and is not discharged. This process can be repeated until the voltage across the load capacitor C1 reaches Voc. As a result, the complete IV curve is constructed from a series of partial IV curves. This method in Figure 10 The flowchart 1000 illustrates this. In one example, the controller is configured to bring the voltage on the load capacitor to the open-circuit voltage by repeating a connection-disconnection cycle having connection and disconnection steps, wherein the connection step includes connecting the load capacitor to the PV circuit under test via a module-level electronics (MLE) until the MLE is de-energized, and the disconnection step includes disconnecting the load capacitor from the PV circuit under test until the MLE is energized.

[0051] Typically, in IV curve scanning, switch S1 (see...) Figure 3 The switch S1 closes for the entire duration of the scan, and charge flows into the load capacitor CL until the voltage on the load capacitor CL reaches Voc (or until the MLE is de-energized, as discussed above). In another embodiment, switch S1 is repeatedly pulsed throughout the scan. During each pulse, a small amount of charge flows from PV circuit 302 into the load capacitor CL, slightly charging the voltage on the load capacitor CL. The pulses can continue until the voltage on the load capacitor CL reaches Voc. In some examples, if the pulses are short (e.g., 1-10 ms), the MLE may not turn off in response to the pulsed load (e.g., a short circuit), and therefore, by repeatedly pulsed to the load, the IV curve can be completed without energizing the MLE. This process in Figure 11 The flowchart 1100 is shown.

[0052] MLE devices may require activation signals for normal operation (e.g., rapid device shutdown). In the embodiments described above, when activation signals are required, this can be supplied by an IV curve tracker or a separate device.

[0053] SMPC Blower In various embodiments, during the discharge mode, resistive elements are used to discharge the voltage across the load capacitor to near zero volts after the IV curve scan is complete. As discussed above, a challenge with resistive elements is that they dissipate heat, thereby increasing the internal temperature within the curve tracker. Various embodiments can minimize the amount of heat accumulated within the housing. In one embodiment, during the discharge mode, the discharger may include circuitry that transfers energy stored in the load capacitor CL back to the PV circuit, where the energy is dissipated over a large area of ​​the PV module. One advantage of this approach is minimal heat dissipation within the curve tracker housing. Typically, the PV circuit is a power source (i.e., it converts solar energy into electrical energy), and current and power flow from the PV circuit to the inverter or IV curve tracker as a load. The novel SMPC discharger embodiment reverses this energy flow (i.e., the PV circuit becomes the load, and the curve tracker becomes the source of power and energy). Figure 2 In the battery model shown, power flows back to the PV circuit and diode D, where most of the power is dissipated as heat. One or more PV modules may become slightly hot as they dissipate the energy transferred to them. Because PV modules have a very large surface area (e.g., relative to the curve tracker discharge resistor), they can easily dissipate energy with minimal temperature rise.

[0054] Electricity can be fed into PV circuits in a variety of ways. In various embodiments, a switch-mode power converter (“SMPC”) circuit can be used. An SMPC circuit can be considered a way of transferring power or energy from one place to another with minimal losses or heat dissipation within the SMPC itself. An SMPC circuit can transfer energy from one circuit (e.g., a source) operating with one current and voltage to another circuit (e.g., a load) operating with a different current and voltage, provided that the amount of power from the source is the same as the amount of power entering the load at any given time (ignoring actual losses and timing in the SMPC circuit). In other words, an ideal SMPC circuit can convert power P at voltage V1 and current I1 into power P at a different voltage V2 and current I2.

[0055] refer to Figure 12 The diagram depicts a device 1200 including a PV circuit 1202 and a curve tracker 1204. According to various embodiments, an SMPC discharger 1206 can be constructed using an SMPC circuit to transfer charge energy stored in a load capacitor CL 1216 to the PV circuit 1202. The PV circuit 1202 can be under testing. The curve tracker includes a voltage sensing element Mv 1210 and a current sensing element M... IDuring the scan, the curve tracker controller 1208 can close switch S1 1214 to transfer energy to the load capacitor CL 1216. The SMPC circuit includes a feedback control loop that adjusts the duty cycle of the switch to achieve a target current. This design can use an inductor, and the SMPC controller can control the output current so that the output voltage can naturally adapt to any voltage required to force current into the PV circuit 1202.

[0056] Curve tracker controller 1208 can turn on SMPC bleeder 1206 instead of turning on switch S2 (see...). Figure 3 The curve tracker controller 1208 can be coupled to the SMPC circuitry of the SMPC bleeder 1206 and the load capacitor CL 1216 to remove stored charge (and therefore energy) from the load capacitor CL. In some embodiments, the curve tracker controller 1208 can perform operations described as being performed by other controllers described herein, such as one or more of curve tracker controller 314, curve tracker controller 806, shunt controller 810, SMPC bleeder controller 1302, curve tracker controller 1414, SMPC controller 1618, SMPC controller 1702, SMPC controller 1918, or curve tracker controller 2110. Furthermore, in some embodiments, other controllers described herein can perform one or more of the operations described as being performed by curve tracker controller 1208. More generally, in some embodiments, operations described herein as being performed by a first controller can be performed by different second controllers described herein. In some embodiments, curve tracker controller 1208 is a digital controller. In some embodiments, curve tracker controller 1208 includes analog circuitry.

[0057] The curve tracker controller 1208 can be configured to scan the IV curve of the PV circuit 1202 in scan or scan mode, and the curve tracker controller 1208 can be configured to transfer energy from the load capacitor CL1216 to the PV circuit 1202 in discharge mode.

[0058] For example, in scan mode, switch 1214 can be configured to be closed, which may charge load capacitor CL 1216. This charging of load capacitor CL 1216 can transfer energy from PV circuit 1202 to load capacitor CL 1216. In some embodiments, curve tracker controller 1208 scans the IV curve from open-circuit voltage to zero volt or from zero volt to open-circuit voltage. In some embodiments, curve tracker controller 1208 scans a first portion of the IV curve from open-circuit voltage to a non-zero voltage below the open-circuit voltage. In some embodiments, curve tracker controller 1208 scans a first portion of the IV curve from a first voltage below the open-circuit voltage to a second voltage below the first voltage. In some embodiments, energy is transferred to load capacitor CL 1216 during the scanning of the first portion of the IV curve. Furthermore, in some embodiments, curve tracker controller 1208 is configured to transfer energy from load capacitor CL 1216 to PV circuit 1202 before scanning a second portion of the IV curve. The second portion of the IV curve may be different from the first portion of the IV curve.

[0059] In discharge mode, switch 1214 can be configured to be in the open state to discharge load capacitor CL 1216. Discharging load capacitor CL 1216 transfers energy from load capacitor CL 1216 to PV circuit 1202. In some embodiments, curve tracker controller 1208 can control switch 1214.

[0060] In another embodiment, the curve tracker circuit is as follows: Figure 26 It is configured as shown in the diagram, which simplifies the connection between the SMPC drain 2606 and the PV circuit 2602. Figure 26 Includes curve tracker 2604. The first side of load capacitor CL 2616 is connected to the first input of SMPC discharger 2606 and switch S1 2614. The second side of load capacitor CL 2616 is connected to switch S2 2618. For example, in scan mode, switch S2 2618 can be configured as follows: Figure 26As shown, the second side of the load capacitor CL 2616 is connected to one side of the PV circuit 2602. Switch S1 2614 can be configured to close, allowing the load capacitor CL 2616 to be charged. This charging of the load capacitor CL 2616 transfers energy from the PV circuit 2602 to the load capacitor CL 2616, while Mv and Mi measure the voltage and current of the PV circuit 2602 at multiple points. Switch S1 2614 is then opened. In discharge mode, switch S2 2618 can be switched to another configuration, connecting the second side of the load capacitor CL 2616 to the second input of the SMPC discharger 2606 to discharge the load capacitor CL 2616. Discharging the load capacitor CL 2616 transfers energy from the load capacitor CL 2616 to the PV circuit 2602. In some embodiments, the SMPC controller 2608 is configured to control one or more other components of the curve tracker 2604, such as one or more of the switch S1 2614, switch S2 2618, or SMPC vent 2606.

[0061] One type of SMPC bleeder circuit 1300 uses a flyback converter, such as Figure 13 A simplified conceptual diagram is shown. Figure 13This includes an input voltage Vi 1318 and an output voltage Vo 1320. In some embodiments, the SMPC bleeder circuit 1300 causes the load capacitor CL 1216 to release current into the PV circuit 1202. The SMPC bleeder controller 1302 switches switch S 1304 at a relatively high frequency (e.g., 50-500kHz). When switch S 1304 is closed, the primary winding of the two-winding inductor (e.g., transformer) L 1306 is directly connected to the input voltage Vi 1318. The primary current and magnetic flux in the two-winding inductor L 1306 increase, storing energy in the two-winding inductor L 1306. The voltage induced in the secondary winding V2 is negative, so diode D 1308 is reverse biased (i.e., blocked). When switch S 1304 is open, the primary current Is stops. The secondary voltage V2 becomes positive, forward biasing diode D 1308 and allowing current to flow from the transformer secondary winding L to the output (e.g., to the PV circuit). In this example of a flyback topology, what is controlled is the current (and therefore the energy) in the primary winding. Therefore, an output capacitor is not required (unlike some flyback converters). The input voltage Vi 1318 can be the voltage across the input (e.g., the load capacitor). The SMPC controller 1302 can monitor the input current and voltage as well as the output current and voltage, and repeatedly closes and opens switch S1304 with varying duty cycles in a feedback loop targeting one or more current and voltage setpoints. This type of SMPC bleeder can be referred to as an "SMPC bleeder" or a "flyback bleeder".

[0062] exist Figure 13 In the embodiment depicted, the SMPC bleeder circuit 1300 includes an optional LC EMI filter 1316 and an additional diode D2 1314. The optional LC EMI filter 1316 includes a capacitor 1310 and an inductor 1312. The purpose of D2 1314 is to prevent large inrush currents (similar to the capacitive current of a PV array) generated by the discharge of C2 during scanning.

[0063] refer to Figure 12 After the IV scan, the load capacitor CL 1216 can be at the Voc of the PV circuit 1202. To allow current to flow from the load capacitor CL 1216 back into the PV string, the output Vo can be sufficiently higher than the Voc of the PV string. Due to the output of the flyback converter (e.g., Figure 13(However, ignoring the optional EMI filter) is a dual-winding inductor L1306 that stores energy. This inductor will "ring back" with a sufficient voltage to push current into the PV circuit 1202. As the charge on the load capacitor CL 1216 is discharged into the PV circuit 1202, the voltage on the load capacitor CL 1216 drops until the load capacitor voltage reaches near zero volts. At this point, any residual charge (and therefore residual energy) in the load capacitor CL 1216 can be easily discharged, where the power dissipation of a simple resistor (not shown) is much lower than that of a simple resistive (sole) bleeder.

[0064] Two-quadrant SMPC curve tracker As discussed above, the most common existing techniques for IV curve tracker architectures include capacitive loads, resistive loads, or active transistor loads. With these methods, the load “sees” the same voltage and current as the PV circuit under test. A novel alternative approach to achieving IV scanning of a PV circuit is to use a switch-mode power converter (“SMPC”) architecture as a variable load.

[0065] As discussed above, an SMPC circuit can be considered a way to transfer energy from one place to another. For example, it can transfer energy from a PV circuit to a resistive load. However, using a resistive load leads to heat dissipation in the IV curve tracker. The present invention instead uses an SMPC to transfer energy from a PV circuit to a storage element such as a load capacitor, inductor, battery, or spinning mass during a scan or scan mode. Using a storage element allows the present invention to handle power of 15 kW or higher because the scan of the IV curve during measurement can be decoupled from the energy dissipation in the storage element. An IV curve scan can be performed quickly (e.g., 200 milliseconds), while the energy dissipation (discharge) in the storage element may take longer (e.g., 6 seconds). Switching electronics do not need to dissipate much energy, and the discharge circuit may take longer to dissipate the stored energy. As long as the amount of power from the PV circuit at any given time is the same as the amount of power entering the storage element (ignoring "real-world" losses and timing in the SMPC circuit), the SMPC circuit can transfer energy from a PV circuit operating at one voltage and current to a storage element, such as a storage capacitor, which is at different voltages and charged with different currents.

[0066] In various embodiments of this disclosure, the IV curve tracker includes an SMPC circuit that can present an associated PV circuit with an arbitrary load and can vary the load to scan the IV curve, thereby transferring energy from the PV circuit to a storage element, such as a storage capacitor.

[0067] Figure 14A system 1400 is depicted, including a PV circuit 1402 and an SMPC curve tracker 1404. The SMPC curve tracker 1404 includes a storage capacitor CS 1412, an SMPC circuit 1406, and a curve tracker controller 1414, which controls other components of the SMPC curve tracker 1404. The SMPC curve tracker 1404 further includes a current sensing element M. I 1408, voltage sensing element Mv 1410, and storage capacitor CS 1412. The benefits of using embodiments of the SMPC circuit in this manner may include one or more of the following: 1. The ability to scan the IV curve in a controlled manner from open-circuit voltage (Voc) to short-circuit current (Isc) or vice versa; 2. Minimum energy dissipation during IV scan; 3. The ability to transfer energy from the PV circuit to the storage element during IV scan and then reverse that process during discharge mode and push the stored energy back from the storage element to the PV circuit (i.e., instead of dissipating the energy within the curve tracker using a discharge resistor) is conceptually similar to the flyback discharge described above. 4. The ability to arbitrarily control the start current and / or end current of the scan (within the limitations of the PV circuit); 5. The ability to arbitrarily set the start and / or end voltage of the scan (within the limitations of the PV circuit); 6. The ability to arbitrarily set the point-to-point scanning speed and timing; and / or 7. Prevention of overcurrent events.

[0068] Scanning from Voc to Isc (or equivalently, scanning from Voc to 0 volts or from 0 amps to Isc) allows the curve tracker to eliminate or reduce inrush currents in the HE module because there is no current flow when the scan begins at Voc, and therefore no rapid and potentially large current changes are likely to occur at any point during the scan. It also allows the curve tracker to stop scanning at voltages above zero and before module-level electronics (“MLEs”) shut down—such as power optimizers or fast-shutdown devices.

[0069] The ability to arbitrarily control scan speed and point-to-point timing can have several advantages. The SMPC curve tracker 1404 can limit the rate of voltage change (dV / dt) from the PV circuit. As discussed above, when dV / dt becomes faster, the "diodes" of the PV cell (e.g., Figure 2The charge stored in dV / dt can cause discrepancies between scanned IV measurements and a series of slower or "static" (e.g., resistive) I-V measurements. This can introduce measurement error into the IV curve measurements. This source of measurement error can be reduced by constraining dV / dt to a maximum value (which may depend on the Voc of the PV circuit).

[0070] Alternatively, the SMPC curve tracker 1404 can accelerate the scan to minimize the "solar slope," where changes in solar irradiance during IV scans cause errors in the shape of the IV curve. The SMPC curve tracker 1404 may be able to optimize the scan speed to balance two desired measurement objectives: 1) scans slowly enough to avoid significant errors caused by the capacitance of the HE module, and 2) scans fast enough to avoid significant errors caused by the solar slope during IV scans.

[0071] The SMPC curve tracker 1404 can also vary the sampling timing during different segments of the IV curve. For example, the SMPC curve tracker 1404 can scan the flat and vertical portions of the IV curve more quickly, while slowing down during the "inflection point" around the maximum power point ("MPP"). This can result in higher accuracy of the overall curve. The capacitance of the HE module increases significantly to approximately 75% above Voc. Therefore, in some cases, it may be preferable to use a faster scan time at approximately 75% below Voc and a slower scan time at approximately 75% above Voc. Alternatively, a more continuously varying scan speed can be used, where the point-to-point timing changes from one point to the next. For example, the point-to-point timing may be slow at the start of the scan at Voc and then increase as the scan progresses toward Isc. The varying point-to-point timing can be controlled, for example, linear, polynomial, exponential, or can follow any arbitrary contour.

[0072] The SMPC curve tracker 1404 overcomes the limitations of the prior art, including the following: 1) As discussed above, active load curve tracker circuits cannot scan the curve slowly enough to avoid errors caused by the capacitance of the HE module without generating excessive heat in the transfer transistor; 2) Pulsed loads are essentially very fast single-point measurements repeated at different load points, but as discussed above, they cannot remain long enough to avoid errors caused by the capacitance of the HE module without generating excessive heat in the transfer transistor; and 3) Capacitive load IV curve tracker circuits cannot scan from Voc to Isc and the IV scan speed cannot be easily and arbitrarily set.

[0073] During the scan, the PV circuit voltage can be monitored, and the scan can be terminated when the PV circuit "short-circuit" condition (PV circuit voltage is zero) has been met. This is typically done at a current less than the maximum measurement current allowed by the curve tracker circuit (e.g., 30 amps). By starting from zero current and ramping towards the maximum current, and stopping the scan when the maximum current has been reached or when the PV voltage reaches zero, problems such as users applying excessive current (e.g., attempting to measure four 10-amp strings in parallel with a device rated only 30A) or forgetting to disconnect from the inverter during the scan can be avoided.

[0074] Various embodiments of this disclosure use a "two-quadrant" SMPC topology to control energy transfer from PV circuits to storage elements in a low-loss manner. Figure 15 The diagram illustrates four possible operating quadrants. The two-quadrant SMPC is a subset of the four-quadrant SMPC and can replace the four-quadrant SMPC wherever it is used.

[0075] Because the SMPC circuit is capable of bi-quadrant operation, after the IV scan, during the discharge mode, the SMPC circuit can then switch direction and transfer the energy stored in the storage capacitor back to the PV circuit at a rate that does not damage the measurement circuit, the PV cell, or other components in the PV circuit. This “reverse transfer” is conceptually the same as how the previously described SMPC discharge circuit can operate. As a result, the SMPC circuit described above can include a 2-quadrant SMPC circuit configured to enable bi-directional energy transfer between the PV circuit under test and the load capacitor.

[0076] There are five basic SMPC topologies in the current art, from which almost all SMPC methods originate: buck, boost, buck-boost, Sepic, and C'uk. The "flyback" converter discussed earlier is a variant of the boost converter. The various converter topologies have input and output current characteristics and limitations, which makes them more or less suitable for two-quadrant operation with continuous current and minimal ripple current on the input, as is desirable for this disclosure.

[0077] For embodiments of this disclosure, the C'uk converter is an attractive topology because both the input and output currents are continuous, in contrast to other topologies where the input current, output current, or in some cases both are pulsed. Figure 16The diagram illustrates a basic C'uk schematic circuit 1600. The basic C'uk schematic circuit 1600 includes a voltage source Vs 1602, an inductor L1 1604, a switch 1606, a capacitor C1 1608, an inductor L2 1612, a capacitor C2 1614, a resistor 1616, an SMPC controller 1618, and an output voltage Vo 1620. The SMPC controller 1618 can be configured to control the switch 1606.

[0078] One embodiment of this disclosure can be used as follows: Figure 17 The second switching element 1710 shown in circuit 1700 enables the converter to operate in either the forward or reverse direction (i.e., both quadrants) to control the current between the PV circuit under test and the load capacitor. Note that the above description... Figure 16 The diode D1610 in the image only allows current to flow in one direction. This is different from... Figure 17 The ideal switch S2 1710 shown is such that current can flow in both directions when the switch is closed. In some embodiments, the switch may be a transistor (e.g., a BJT, MOSFET, IGBT, or other suitable switching element) and may include an internal anti-parallel diode.

[0079] This pair of switching elements S1 1706 and S2 1710 (see...) Figure 17 They operate in a complementary manner. When switching element S11706 is closed, switching element S2 1710 is open, and vice versa. This allows circuit 1700 to operate in continuous conduction mode in two of the four quadrants of input-to-output (meaning the current in inductors L1 and L2 is always continuous, not pulsed). In this way, depending on the input and output voltages and duty cycles supplied to switching elements S1 1706 and S2 1710 by SMPC controller 1702, it can be either a "charger" or a "discharger" circuit. This bi-quadrant behavior allows a curve tracker with a single SMPC circuit block to either scan the output of the PV circuit (i.e., as a load) or, after scanning, push the stored energy back into the PV circuit in a controlled manner.

[0080] Figure 17 The C'uk converter shown in the diagram reverses the voltage polarity from the input to the output. Figure 17 This includes the input voltage Vi1716 and the output voltage Vo1718. Since the input and output polarities are not strictly required to be the same in this application, one embodiment uses a "floating" drive circuit (not shown) for the second switching device; this allows both switch S1 and switch S2 to have NPN or N-channel transistors. Such devices offer better switching performance than if they were PNP or P-channel devices.

[0081] A non-limiting operation of circuit 1700 is as follows: In the case of a polarity-reversed C'uk topology, the switching of switch S1 is initiated by SMPC controller 1702, which turns on switch S1 1706. The current through switch S1 1706 is monitored by a high-bandwidth current sensing circuit (not shown), which can be any of a variety of common circuit elements, to name just two examples, including a current-sensing transformer or a current-sensing resistor. When the sensed current reaches a desired threshold, switch S1 1706 is then turned off. As mentioned above, switch S2 1710 operates in the opposite manner to switch S1 1706, such that when switch S1 1706 is on, switch S2 1710 is off, and when switch S1 1706 is off, switch S2 1710 is on. When switch S1 1706 is on, the current in inductor L1 1704 ramps up. Essentially simultaneously, current can also flow through capacitor C1 1708 to switch S1 1706, and this current can also flow through inductor L2 1712 to switch S1 1706. Then, when switch S1 1706 is open and switch S2 1710 is closed, the current in inductor L1 1704 can flow from switch S1 1706 through capacitor C1 1714 to switch S2 1710. Simultaneously, the current in inductor L2 1712 can flow to switch S2 1710. Note that in this configuration of switches S1 1706 and S2 1710, the current flowing through capacitor C1 1714 reverses its previous direction. Due to the current direction in inductor L2 1712, capacitor C2 1714 charges to a negative voltage. All of this generates a negative potential on the output side of the converter, which is why the basic C'uk converter circuit reverses the voltage direction between the input and output. The SMPC controller 1702 can monitor input current and voltage as well as output current and voltage, and repeatedly closes and opens switches S1 1706 and / or switch S2 1710 with varying duty cycles in a feedback loop targeting one or more current and voltage setpoints. Those skilled in the art of switch-mode power conversion and C'uk converter topologies will understand the above operation.

[0082] The SMPC controller 1702 can consist of analog circuitry, including one or more analog feedback loops, but it can also be a computer, processor, or digital signal processor (DSP) running software or firmware. Alternatively, the SMPC controller 1702 can be an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or any other digital circuitry. Alternatively, the SMPC controller 1702 can be analog circuitry or a mixed analog / digital circuitry. Generally, the SMPC controller 1702 can be any circuitry or device capable of controlling the SMPC to deliver power or to have one or more currents and / or voltages at its inputs and / or outputs.

[0083] In various embodiments, the SMPC controller 1702 may be a feedback loop that servos (or controls) the current (e.g., it may adjust the switch duty cycle to achieve a specific input (or output) current). Alternatively, the SMPC controller 1702 may servo the input (or output) voltage. Alternatively, the SMPC controller 1702 may servo the change in input (or output) voltage over time (i.e., dv / dt) or the change in current over time (i.e., di / dv). Servoosizing dv / dt can be useful in an IV curve tracker because one of the important variables to control is the scan time, or more importantly, the rate of change of voltage over time. This is particularly important for control near the maximum power point of the IV curve. The rate of change of voltage at any given point on the IV curve is the dv / dt at that point.

[0084] The SMPC controller 1702 may include multiple control feedback loops or loops within loops. In some embodiments, the SMPC controller 1702 is configured to implement combination Figure 18 One or more of the control feedback loops described. For example, the SMPC controller 1702 may be configured to implement a control loop to control the rate of change of the voltage of the measured PV circuit with respect to time within a predetermined range. For example, an internal control loop 1806 may be present, which receives an input current target and then adjusts the switching duty cycle to achieve that target, as discussed above. In some embodiments, the SMPC controller 1702 is a digital controller. In some embodiments, the SMPC controller 1702 includes analog circuitry.

[0085] In some embodiments, the switches used with circuits 1600 and 1700 can be implemented using switch 500 of Figure 500. For example, in the switches of a C'uk converter, the floating drive output may be isolated from the control input current.

[0086] exist Figure 18In this circuit, the external feedback control loop 1804 receives a dv / dt target from the IV scan loop 1802 and then adjusts the current target to achieve that dv / dt target. The external loop feeds the current target to the internal loop. The external loop can be an analog control loop or a digital (processor-controlled) control loop, such as the well-known proportional-integral-derivative (“PID”) algorithm, or a more complex control loop based on the z-transform method implemented via software or firmware in the controller, or any other type of controller suitable for electronic feedback loops. The dv / dt target of the external loop can be a target that it receives from a third controller, or it can follow a predetermined set of targets. For example, the first part of the IV curve (i.e., high dv / dt) can be scanned rapidly from Voc down to 0.8 Voc, then the IV curve can be scanned slowly from 0.8 Voc down to 0.6 Voc, and then the IV curve can be scanned rapidly from 0.6 Voc down to Isc. This involves rapid scanning through the IV curve to minimize storage requirements and / or heat dissipation, while slow scanning through the maximum power point to minimize curve distortion around the critical point.

[0087] As an example, Figure 18 Flowchart 1800 illustrates the algorithm of an SMPC controller 1702 with multiple control feedback loops.

[0088] In another embodiment of the SMPC circuit 1406 using the C'uk topology, it may be desirable to maintain the polarity between the input and output. This can be achieved by adding a suitable transformer, such as a polarity-maintaining transformer L 1908, which ensures that the circuit has the same voltage polarity on both the input and output sides. Figure 19 A polarity-preserving two-quadrant C'uk converter is shown. Note that adding a transformer makes it possible to "stack" two (or more) switching transistors in such a way that the switching voltage is allowed to be higher than the rated voltage of any single device.

[0089] In various embodiments, the SMPC curve tracker 1404 applies a load starting at Voc voltage and zero current, then changes the load such that the voltage drops from Voc to zero during time period t1. For example, the SMPC curve tracker 1404 can use an SMPC curve tracker to apply a variable load during the scan. (Note that there will be many SMPC control loop cycles during time period t1. The switching cycle of the SMPC process is much shorter than time t1). During time period t1, the load capacitor is charged, and the current and voltage are sampled at a sufficiently high sampling rate (e.g., 100 current / voltage pairs are generated at t1 / 100, or 1000 pairs are generated at t1 / 1000). Then, the SMPC circuit 1406 changes direction (becomes a source) and discharges the load capacitor, transferring energy back to the associated PV circuit during time period t2. During time period t2, while the SMPC circuit 1406 is pushing energy into the PV circuit, the voltage in the PV circuit may be higher than Voc.

[0090] Simple C'uk topologies (and almost all other SMPC topologies) will have "ripple current" in the inductors used. This can make high-resolution current and voltage measurements difficult during IV scans, and therefore the ripple current may be filtered out. According to various embodiments, the input ripple current can be diverted to a portion of the topology where it is harmless for the purpose of scanning the PV circuit. This can be achieved by using a "coupled inductor" method (e.g., ...) on the input and output inductors. Figure 20 As indicated in the document, this is achieved by managing the "leakage inductance" between the two inductors, as those skilled in the art will understand, and as described in textbooks on SMPC converters and in several papers by C'uk and Middlebrook describing the operation of the C'uk converter with coupled inductors.

[0091] In another embodiment, a polarity-maintaining transformer L 1908 (see...) is used. Figure 19 This can make the ripple current in both the input and output windings of the coupled inductor zero. Figure 19 It includes circuit 1900, inductor L1 1902, switch S1 1904, capacitor C1 1906, inductor L3 1908, capacitor C2 1910, switch S2 1912, inductor L2 1914, capacitor C3 1916, SMPC controller 1918, input voltage 1920 and output voltage 1922.

[0092] Generally, all SMPC topologies, except for "buck" topologies, can have "right-half-plane zeros" in their transfer functions. The presence of such right-half-plane zeros can make closed control loops challenging to stabilize. In this disclosure, the control loop for the SMPC circuit can be controlled in an unconventional manner to achieve the desired IV scan characteristics. The basic element of the control loop is that it is controlled via a (accepted) "current-mode programming" method, where the control loop's "target" current value is "scanned" over a controllable duration from zero current to the maximum measured current of the IV curve tracker (e.g., 30 amps or greater). Taking into account the dv / dt of the PV circuit output, the target current for the control loop can be generated by the SMPC controller (e.g., under processor control) to prevent scanning too quickly and causing measurement errors. As part of this same control loop, scanning can be stopped when the measured voltage of the PV circuit reaches zero, or when the maximum permissible current of the SMPC curve tracker is reached. By stopping the scan when the maximum permissible current is reached, problems such as attempting a scan while the PV circuit is still connected to the inverter input can be avoided, as the current will increase in a controlled manner until the maximum permissible current is reached. The voltage at which the (aborted) scan terminates can be anywhere on the IV curve. Undesirable voltage transients can be minimized by ramping the current back to zero in a properly controlled manner.

[0093] Once the scan is complete, the energy stored in the storage capacitor can be pumped back into the PV circuit. This dissipates the energy stored over the large surface area of ​​the PV circuit and avoids internal heating of the curve tracker. This is similar to the operation of a flyback topology SMPC bleeder circuit as described above. The advantage here is that no additional circuitry is required; everything needed already exists in the C'uk converter topology. Only a suitable control algorithm executed by the existing processor is required.

[0094] A typical capacitive load curve tracker may have a capacitor selection switch matrix for selecting different series and parallel combinations of capacitors to achieve appropriate rated voltages and scan speeds. Various embodiments of this disclosure using the SMPC method can avoid the capacitor bank switch matrix, thereby allowing the use of fewer switching transistor elements and thus saving costs.

[0095] The capacitor in a typical capacitive load curve tracker may be large enough to hold all the charge from a complete IV scan. This energy is the power-time integral of the power-time curve. In one embodiment of this disclosure, the SMPC storage capacitor is also sized to store all the energy from the entire IV scan. In this case, the SMPC curve tracker scans the entire IV curve at once during the “loading” phase and then pushes the charge back into the PV circuit during the “discharging” phase to discharge the capacitor.

[0096] When the SMPC reaches the end of the IV curve scan, the voltage across the PV array is at or near zero volts. In practice, it is difficult to push the voltage all the way to zero volts with an SMPC. However, one of the important measurements of an IV curve tracker is the short-circuit current (“Isc”) where the voltage is 0V. Various embodiments of the invention include a bias circuit. The bias circuit enables the SMPC IV curve tracker to measure the true Isc by biasing the negative output of the PV array to a moderately positive voltage relative to the negative (“circuit common”) rail of the SMPC IV curve tracker. This is done to compensate for conduction losses in the SMPC IV curve tracker circuitry, allowing the voltage across the PV array to be driven to zero. This bias can be done with a power supply or from a battery. Alternatively, this can be done by tapping a small amount of switching energy from the SMPC. One way to tap a small amount of energy to the bias circuit is to have an added winding on the polarity-reversing transformer in the C'uk implementation. The winding has its own C'uk capacitor and inductor, as well as a separately controlled switch for regulating the bias circuit voltage. Note that... Figure 20 The diagram shows a PNP transistor Q3 2038, but other circuit topologies including NPN or MOSFETs can also be used. During the discharge of the storage capacitor, this separate circuit does not push its energy back into the PV array. Figure 20 An example of this is shown. Figure 20 The illustration shows an example C'uk SMPC. Figure 20 The illustration shows an example PV array 2002, inductor L1 2004, capacitor C1 2006, capacitor C2 2008, inductor L2 2010, capacitor C3 2012, resistor R3 2014, resistor R2 2016, transistor Q1 2018, diode D1 2020, inductor L3 2022, inductor L4 2024, diode D2 2026, transistor Q2 2028, resistor R1 2030, inductor L5 2032, capacitor C5 2034, diode D4 2036, transistor Q3 2038, diode D5 2040, inductor L8 2042, capacitor C6 2044, and bias adjustment unit 2046. Figure 20The upper part of the diagram is a detailed schematic of the C'uk converter. The bias circuit is located in the lower right part of the diagram, and it shows one possible example of independent bias voltage adjustment. Other methods are, of course, also possible. Note that this diagram illustrates an example of the "coupled inductor" concept in the C'uk converter, which is useful for diverting unwanted ripple current from the input inductor away from the input inductor and towards the output inductor. In the output inductor, the ripple current is harmless in terms of measuring "noise".

[0097] Two-quadrant SMPC curve tracker without storage capacitors exist Figure 21 In another embodiment of the device 2100 shown, two independent PV circuits (e.g., two separate strings) are connected to the SMPC curve tracker 2102. One PV circuit, “PV circuit 2112”, is the source, and the other PV circuit, “PV circuit 2114”, is the load. The SMPC curve tracker 2102, including SMPC 2104, scans the IV curve of PV circuit 2112 and simultaneously transfers energy to PV circuit 2114. The SMPC curve tracker 2102 further includes a voltage sensing element Mv 2106 and a current sensing element M I 2108 and curve tracker controller 2110. An advantage of this embodiment is that a storage capacitor may not be necessary, and a discharge mode may not be required. This reduces measurement time and saves cost, space, and weight on the SMPC curve tracker 2102. After the IV curve of PV circuit 2112 is scanned and energy is fed into PV circuit 2114, the SMPC curve tracker 2102 can then reverse direction and scan the IV curve of PV circuit 2114 and feed energy into PV circuit 2112. In this mode, PV circuit 2114 becomes the source, and PV circuit 2112 becomes the load. This has the advantage that the user can connect two PV circuits to the curve tracker once, and both PV circuits can scan their IV curves without changing the connections, thus allowing for faster characterization of PV circuits (e.g., in solar power plants).

[0098] Two-quadrant SMPC curve tracker with segmented IV scan In another embodiment, the SMPC curve tracker scans a sub-segment of the IV curve (e.g., 25% or 50% of the full curve energy). The curve tracker may start at Voc and scan down to a voltage less than Voc but substantially above 0 V, then stop. Alternatively, the curve tracker may start at a voltage substantially less than Voc and scan down to 0 V. Alternatively, the curve tracker may start at any first voltage and scan up or down to any second voltage. In some embodiments, the SMPC curve tracker scans a sub-segment of the IV curve in a scan mode, then pushes the charge back into the PV circuit (or a different PV circuit as described above) in a discharge mode, and then scans different segments of the IV curve and pushes that charge back into the array (or a different PV circuit). This can be repeated until the entire IV curve has been scanned.

[0099] For example, an SMPC curve tracker can scan the first portion of the IV curve from the open-circuit voltage to a non-zero voltage below the open-circuit voltage. As another example, an SMPC curve tracker can scan the first portion of the IV curve from a first voltage below the open-circuit voltage to a second voltage below the first voltage. Furthermore, in some embodiments, the SMPC curve tracker is configured to transfer energy to the PV circuit under test (or to a different PV circuit) before scanning the second portion of the IV curve. The second portion of the IV curve may differ from the first portion of the IV curve.

[0100] One advantage of this approach is that the storage capacitor can have a lower capacitance, thus saving cost, space (e.g., volume), and weight. For example, if 50% of the IV curve energy is scanned, and then the storage capacitor is discharged, and then the other 50% is scanned, then in this case, the storage capacitor can be approximately half the size compared to the storage capacitor required for a single scan of 100% of the IV curve.

[0101] The IV curve has a corresponding PV (power versus voltage) curve 2202, such as Figure 22 As shown in the graph. Maximum power is... Figure 22 Point 2204 on the curve is indicated. The energy transferred from the PV circuit to the IV curve tracker is the integral of the PV curve 2202 over time. The power fed into the storage capacitor follows the PV curve as the IV curve is scanned. It begins at zero at the start of the IV scan at Voc (i.e., at...). Figure 22The curve (on the right side of the graph) slopes upwards as the voltage decreases to a maximum "Pmax" (point 2204), which is equal to the maximum power voltage multiplied by the maximum power current around the "inflection point" in the IV curve, before sloping back to zero at the end of the IV curve at Isc. The energy stored in the storage capacitor is the power integrated over time during the IV scan, as discussed above.

[0102] One challenge of scanning the IV curve in segments (e.g., 50% at a time) is that when the IV curve scan is interrupted and then restarted, current flow is interrupted and then restarted again. During the time between the two segments, when the storage capacitor is discharged, if the discharge occurs by pushing energy back into the PV circuit, the PV circuit returns to Voc or above Voc. Then the curve scan resumes, and current flows back into the curve tracker and storage capacitor. When current flow restarts rapidly, inrush currents from the HE module capacitors can occur if a low-impedance load in the curve tracker is applied to the PV circuit very quickly. Therefore, in various embodiments of the SMPC curve tracker, a smoother current ramp can be controlled. This can disperse the inrush current pulse over time, reduce the peak current, and make it easier to handle in the circuit. However, this may result in more energy being stored in the capacitor.

[0103] refer to Figure 23 In one example, the SMPC curve tracker applies a load that starts at voltage Voc and zero current (i.e., open circuit), and then the load can be varied such that the voltage decreases from Voc at time t0 to 0.5Voc at time t1. Figure 23 The voltages of the PV circuit and storage capacitor are shown as an illustrative example (not to scale). During the time interval from t0 to t1, the storage capacitor is charged, and the current and voltage are sampled at a sufficiently high sampling rate (e.g., (t1-t0) / 100 to generate 100 current-voltage pairs, or (t1-t0) / 1000 to generate 1000 pairs). Note that the time between each sample pair is different from the cycle time of the SMPC circuit; they are independent. Then, starting at time t1, the SMPC circuit reverses direction and discharges the storage capacitor, transferring energy from the storage capacitor back to the PV circuit. During the time interval from t1 to t2, while the SMPC circuit is pushing energy into the PV circuit, the voltage of the PV circuit may be higher than Voc. Next, the SMPC circuit reverses direction again, picking up where it stopped at 0.5Voc. It can quickly change the load from Voc to 0.5Voc (e.g., within 1µs), or it can change the load more slowly to limit the inrush current, such as... Figure 23The process from time t2 to t3 is illustrated. Returning to 0.5Voc generally wouldn't take as long as the time interval from t0 to t1, because if it did, the storage capacitor would recharge before the voltage could make any progress beyond 0.5Voc. However, it could be a portion of the time interval from t0 to t1, such as 10% or 1% of the time interval from t0 to t1, which would (preferably) transfer only a small amount of energy to the storage capacitor. Then, at time t3, the SMPC circuit continues to reduce the voltage from 0.5Voc to 0 at time t4, while measuring the current and voltage at a sufficiently high sampling rate. Then, at time t4, the SMPC circuit changes direction again and transfers the energy from the storage capacitor back to the PV circuit during the time interval from t4 to t5. Then, at time t5, the PV circuit returns to Voc.

[0104] exist Figure 23 In the example, the IV scan is decomposed into five time periods, with two of the time periods having a Voc fraction from 0.5 to 0, and then from 0.5 to 0. However, in other examples, the IV curve can be decomposed into any number of time periods, and the voltage fraction of the IV curve can be any fraction from 0 to 1. Furthermore, the voltage fractions of the IV curve scanned during the various time periods can be the same number of fractions or different numbers of fractions. Moreover, the voltage fractions can be less than... Figure 23 Instead of increasing linearly as shown, it can follow an exponential curve or other shapes. Furthermore, in this example, the IV curve is divided by voltage (i.e., a fraction of Voc), but it could also be divided by the transferred energy, as discussed above. It could also be divided by current or some other parameter. The energy or other parameter can increase linearly or exponentially, or follow any contour.

[0105] In one embodiment of the invention, the SMPC curve tracker is controlled to slowly and / or repeatedly scan specific narrow regions of the IV curve. This can help to excite problems in the PV circuit that might not appear in a normal IV curve scan, such as ground faults or arcing faults, which are more likely to occur under load and specific voltages. For example, the region directly below Voc may be more likely to detect problems triggered by high voltages such as ground faults or arcing faults. For example, the SMPC curve tracker may slowly (e.g., over 500 ms) scan from 0.9 Voc to Voc. Alternatively, it may scan it repeatedly, slowly (e.g., over 500 ms) moving the voltage from Voc to a lower voltage (e.g., 0.9 Voc), then reversing the direction and slowly scanning back to Voc from the lower voltage. As another example, the scan speed can be adjusted as the SMPC curve tracker repeatedly scans back and forth between Voc and the lower voltage. The invention includes a dual-channel simultaneous sampling high-speed ADC (e.g., 50-100 MSPS), enabling the detection of rapidly changing current or voltage events that may indicate ground faults, arcing faults, or other problems in the PV circuit.

[0106] In another example, the region around the maximum power point (MPP) is repeatedly scanned (e.g., from 0.6 Voc to 0.8 Voc), but each time at a different rate (dv / dt). By analyzing the measured current at different dv / dt rates, the efficiency of the module under test can be determined. Higher-efficiency modules exhibit higher capacitance and also more distorted I-V curves. When scanning from Isc to Voc, as dv / dt increases, a high-efficiency module will generate increasingly lower currents around the MPP. When scanning in the opposite direction from Voc to Isc, as dv / dt increases, a high-efficiency module will generate increasingly higher currents around the MPP.

[0107] Figure 24 An example trajectory 2400 illustrating the changes in current and voltage over time is shown, which can be detected and tracked by the IV curve tracker described herein or by an external oscilloscope. In example trajectory 2400, the current exhibits an inrush current transient 2402.

[0108] As used herein, the term “substantially” refers to the meaning of a given parameter, property, or condition and includes the degree to which a person skilled in the art would understand that a given parameter, property, or condition is satisfied with a small degree of variation, such as within acceptable manufacturing tolerances. For example, a parameter that is substantially satisfied could be satisfied with at least about 90%, at least about 95%, or even at least about 99%.

[0109] As used herein, the terms "module" or "component" may refer to a specific hardware implementation configured to perform the actions of a module or component and / or a software object or software routine that may be stored on and / or executed by general-purpose hardware of a computing system (e.g., computer-readable media, processing devices, but not limited thereto). In some embodiments, the different components, modules, engines, and services described herein may be implemented as objects or processes (e.g., as separate threads) that execute on a computing system. While some of the systems and methods described herein are generally described as being implemented in software (stored on and / or executed by general-purpose hardware), specific hardware implementations or combinations of software and specific hardware implementations are also possible and contemplated.

[0110] As used in this disclosure, the term "combination" referring to multiple elements can include any combination of all elements or any of a variety of different sub-combinations of some of the elements. For example, the phrase "A, B, C, D or a combination thereof" can refer to any one of A, B, C or D; a combination of each of A, B, C and D; and any sub-combination of A, B, C or D, such as A, B and C; A, B and D; A, C and D; B, C and D; A and B; A and C; A and D; B and C; B and D; or C and D.

[0111] The terminology used in this disclosure, and especially in the appended claims (e.g., the body of the appended claims), is generally intended to be “open-ended” terms (e.g., the term “comprising” should be interpreted as “including, but not limited to”, the term “having” should be interpreted as “at least having”, the term “comprising” should be interpreted as “including, but not limited to”, etc.).

[0112] Furthermore, if there is an intent to introduce a specific number of claim statements, this intent will be explicitly stated in the claims, and if no such statements are present, then no such intent exists. For example, to aid understanding, the appended claims may include the use of introductory phrases “at least one” and “one or more” to introduce claim statements. However, the use of such phrases should not be construed as implying that a claim statement introduced by the indefinite article “a” or “an” limits any particular claim containing such an introductory claim statement to some embodiments containing only one such statement, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and / or “an” should be interpreted as meaning “at least one” or “one or more”); the same applies to the use of definite articles used to introduce claim statements.

[0113] Furthermore, even if the specific number of claims introduced is explicitly stated, those skilled in the art will recognize that such a statement should be interpreted as referring to at least a number of claims (e.g., the simple statement "two claims" without other modifiers means at least two claims, or two or more claims). Moreover, in instances where conventions such as "at least one of A, B, and C" or "one or more of A, B, and C" are used, such constructive intent generally includes A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B, and C together, etc.

[0114] Furthermore, any extractive terms or phrases presenting two or more alternative terms, whether in the specification, claims, or drawings, should be understood to contemplate the possibility of including one, any, or both terms. For example, the phrase "A or B" should be understood to include the possibility of including "A" or "B" or "A and B".

[0115] While this disclosure has been described herein with reference to certain illustrated embodiments, those skilled in the art will recognize and understand that the invention is not limited thereto. Rather, many additions, deletions, and modifications can be made to some of the illustrated and described embodiments without departing from the scope of the invention as claimed below, along with its legal equivalents. Furthermore, features from one embodiment can be combined with features from another embodiment while still being covered within the scope of the invention as envisioned by the inventors.

[0116] All aspects of this disclosure Some aspects of the invention are listed below. One aspect is an apparatus for tracking a current-voltage (IV) curve. The apparatus includes a switch-mode power converter (SMPC) circuit, a load capacitor coupled to the SMPC circuit, and a controller coupled to the SMPC circuit and the load capacitor. The controller can be configured to scan the IV curve of a PV circuit under test in a scan mode and optionally control the SMPC circuit to transfer energy from the load capacitor to the PV circuit under test in a discharge mode. The apparatus optionally includes a switch coupled to the load capacitor, configured to be closed in a scan mode to charge the load capacitor and open in a discharge mode to discharge the load capacitor. The SMPC circuit optionally includes a flyback power converter to allow current to flow from the load capacitor into the PV circuit under test. The SMPC circuit is optionally configured to transfer energy from the PV circuit under test to the load capacitor in a scan mode and optionally to transfer energy from the load capacitor to the PV circuit under test in a discharge mode. The SMPC circuit optionally includes a two-quadrant SMPC circuit configured to enable bidirectional energy transfer between the PV circuit under test and the load capacitor. The SMPC circuit optionally includes a C'uk converter configured to operate in either a forward or reverse direction to control the current flow between the PV circuit under test and the load capacitor. The controller is optionally configured to scan a first portion of the IV curve from the open-circuit voltage to a non-zero voltage below the open-circuit voltage, or from a first voltage below the open-circuit voltage to a second voltage below the first voltage. The controller is optionally configured to transfer energy from the load capacitor to the PV circuit under test before scanning a second portion of the IV curve that differs from the first portion. The controller is optionally configured to implement a control loop to control the rate of change of the voltage of the PV circuit under test relative to time within a predetermined range. The controller is optionally a digital controller, or optionally includes analog circuitry.

[0117] On the other hand, there is a tracker for tracking IV curves. This tracker includes a controller and measurement circuitry, and optionally a surge shunt circuitry, wherein the controller, coupled to the measurement circuitry and the surge shunt circuitry, can be configured to charge a load capacitor in scan mode in part based on shunting surge current from the measurement circuitry through the surge shunt circuitry. The tracker optionally includes a discharge circuit, wherein the controller is further optionally configured to discharge the load capacitor in discharge mode in part based on the discharge circuitry. The surge shunt circuitry optionally includes an electronic switch, which is closed for a period of time by the shunt controller in scan mode. The surge shunt circuitry optionally includes an electronic switch, and the controller is optionally configured to close the electronic switch for a period of time in scan mode. The tracker optionally includes a load capacitor coupled to the surge shunt circuitry. The controller is optionally configured to apply the load capacitor to the measured PV circuit using a module-level electronics (MLE) until the MLE is de-energized, remove the load capacitor until the MLE is energized; reapply the load capacitor until the MLE is de-energized; and remove the load capacitor again until the MLE is energized. The controller is optionally configured to repeatedly: (i) apply a load capacitor to a photovoltaic (PV) circuit including a module-level electronics (MLE) until the MLE is de-energized; (ii) remove the load capacitor until the MLE is energized; and (iii) repeat steps (i) and (ii) until the voltage across the load capacitor reaches the open-circuit voltage. The controller is optionally configured to scan the IV curve of the PV circuit including the module-level electronics (MLE) by repeatedly applying the load capacitor to the PV circuit using a pulse switch until the voltage across the load capacitor reaches a predetermined voltage.

[0118] On the other hand, there is a system for testing photovoltaic (PV) modules. This system includes a device for tracking an IV curve and optionally includes an instrument for measuring properties associated with the PV module having the PV circuitry under test. The system optionally includes a processor or a display. The processor is optionally configured to present real-time test progress of at least a portion of the IV curve on the display. The instrument optionally includes multiple sensors coupled to different parts of the PV module to collect sensor data associated with the PV module, and the instrument is further optionally configured to determine properties associated with the PV module based on the sensor data. These properties may include one or more measurements of irradiance, module temperature, or array tilt associated with the PV module. The instrument is optionally configured to transmit one or more measurements to the device via a wired or wireless connection. The device is optionally configured to form a wireless network for communication between the instrument and the device.

[0119] On the other hand, there is a method for tracking a current-voltage (IV) curve. This method may include the steps of: scanning the IV curve using a switch-mode power converter (SMPC) circuit to transfer energy from a photovoltaic (PV) circuit under test to a storage element, and transferring energy stored in the storage element to the PV circuit. Alternatively, the method may include the step of using a switch-mode power converter (SMPC) circuit in a tracker to perform bidirectional energy transfer between the PV circuit under test and the energy storage element in the tracker. Alternatively, the method may include the step of performing a bidirectional energy transfer process between the PV circuit under test and the energy storage element in the tracker based on a switch-mode power converter (SMPC) circuit in the tracker. Alternatively, the method may include the steps of: scanning the PV circuit under test using a switch-mode power converter (SMPC) circuit to transfer energy from the PV circuit to a storage element; and optionally transferring energy stored in the storage element to the PV circuit. The method may optionally include scanning the PV circuit under test, including controlling the scan speed. During the scan, the method may optionally include controlling one or more of a starting current or an ending current; or setting one or more of a starting voltage or an ending voltage. The method may optionally include monitoring the voltage of the PV circuit; or terminating the scanning of the PV circuit when the voltage of the PV circuit is zero. The method may optionally include implementing a control loop to control the rate of change of voltage over time. The control loop may optionally be configured to receive a target rate of change of voltage over time, or to adjust a current target to achieve the target rate of change of voltage over time. The control loop may optionally include an external control loop configured to provide a current target to an internal control loop configured to adjust the switching duty cycle based on the current target. During the scan, the SMPC circuit may be used to apply a variable load. The storage element may be a storage or load capacitor.

Claims

1. An apparatus for tracking a current-voltage (I-V) curve, comprising: a switched mode power converter (SMPC) circuit; a load capacitor coupled to the SMPC circuit; and a controller coupled to the SMPC circuit and the load capacitor, configured to scan the I-V curve of a PV circuit under test in a scan mode, and to control the SMPC circuit to transfer energy from the load capacitor to the PV circuit under test in a bleed mode.

2. The apparatus of claim 1, further comprising: a switch coupled to the load capacitor, configured to be in a closed state to charge the load capacitor in the scan mode, and in an open state in the bleed mode.

3. The apparatus of claim 1 or 2, wherein the SMPC circuit comprises a flyback power converter for causing current to flow from the load capacitor into the PV circuit under test.

4. The apparatus of claim 1 or 2, wherein the SMPC circuit is configured to transfer energy from the PV circuit under test to the load capacitor in the scan mode, and to transfer energy from the load capacitor to the PV circuit under test in the bleed mode.

5. The apparatus of claim 4, wherein the SMPC circuit comprises a 2-quadrant SMPC circuit configured to enable bidirectional energy transfer between the PV circuit under test and the load capacitor.

6. The apparatus of claim 4, wherein the SMPC circuit comprises a C'uk converter configured to operate in a forward or reverse direction to control current flow between the PV circuit under test and the load capacitor.

7. The apparatus of any one of claims 4 to 6, wherein the controller is configured to scan a first portion of the I-V curve from an open circuit voltage to a non-zero voltage below the open circuit voltage, or from a first voltage below the open circuit voltage to a second voltage below the first voltage.

8. The apparatus of claim 7, wherein the controller is further configured to transfer energy from the load capacitor to the PV circuit under test prior to scanning a second portion of the I-V curve different from the first portion of the I-V curve.

9. The apparatus of any one of the preceding claims, wherein the controller is configured to implement a control loop to control a rate of change of voltage of the PV circuit under test with respect to time to be within a predetermined range.

10. The apparatus of any one of the preceding claims, wherein the controller is a digital controller, or the controller comprises an analog circuit.

11. A system for testing a photovoltaic (PV) module, comprising: the apparatus of any one of the preceding claims; and an instrument coupled to the apparatus for measuring a property associated with the PV module as part of the PV circuit under test.

12. The system of claim 11, further comprising: a computing device having a processor and a display, wherein the processor is configured to present a real-time test progress of at least a portion of the I-V curve on the display. ​ ​ 13. The system of any of the preceding claims, wherein the instrument includes a plurality of sensors coupled to different portions of the PV module to collect sensor data associated with the PV module, and the instrument is further configured to determine a property associated with the PV module based on the sensor data.

14. The system of any of the preceding claims, wherein the property includes one or more measurements of irradiance, module temperature, or array tilt associated with the PV module, and the instrument is configured to transmit the one or more measurements to the device via a wired or wireless connection.

15. The system of any of the preceding claims, wherein the device is configured to form a wireless network for the instrument to communicate with the device.

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