Voltage balancing method and device for optical storage inverter parallel system

Abstract

The invention relates to a voltage balancing method and device for an optical storage inverter parallel system. The method comprises the following steps: acquiring common node voltage information and inverter power information of parallel inverters; constructing a voltage effective value ring based on the common node voltage information; performing adaptive coefficient extraction processing based on the inverter power information to obtain an adaptive power droop coefficient; and importing the voltage effective value ring, the adaptive power droop coefficient and a preset virtual impedance fitting relationship into the optical storage inverter parallel system to realize dynamic voltage balance of the parallel inverter. Power averaging of each module is realized through adaptive droop control, an effective value is calculated through moving average and serves as feedback of an effective value ring, effective value ring calculation is carried out in real time so as to ensure the output voltage stabilization precision and dynamic performance of the inverter voltage, and the effects of accelerating the dynamic response of the inverter voltage, equalizing the inverter power and improving the stability are achieved.

Description

Technical Field This application relates to the field of new energy technology, and in particular to a voltage balancing method and apparatus for a photovoltaic-storage inverter parallel system. Background Technology A photovoltaic (PV) and energy storage (ESS) inverter parallel system is a topology that connects multiple inverters in parallel to operate together, significantly improving the total output power of the system. PV-ESS inverter parallel systems also offer redundancy and increased system reliability. However, in multi-inverter parallel scenarios, hardware differences between individual inverters and line impedance mismatches become particularly prominent, leading to uneven distribution of active and reactive power among the inverters and significant voltage drops at the common node.

[0001] To address the aforementioned issues, existing technologies generally employ traditional droop control methods for summation. However, traditional droop control has the following drawbacks: First, traditional droop control often uses a fixed droop coefficient, making it difficult to dynamically adjust based on real-time operating conditions and the number of parallel inverters. This leads to significant power distribution deviations when parallel inverters experience sudden load increases or decreases. Second, when multiple inverters are connected in parallel, the common node voltage, due to power droop and virtual impedance, results in a relatively large RMS output. Traditional RMS calculation and compensation loops are performed every 20ms, making the RMS calculation too slow. Third, the voltage RMS adjustment time is long and the response is slow during sudden load increases or decreases, resulting in insufficient dynamic performance. Furthermore, existing technologies often use fixed virtual impedance parameters, which cannot adaptively adjust based on the number of parallel inverters or load conditions, leading to low system stability. Summary of the Invention To address the problems in existing technologies, such as the inability of traditional droop control methods to dynamically adjust based on the number of parallel units and operating status, large power distribution deviations when the system is disturbed, large steady-state errors in the common node voltage, insufficient dynamic performance, and fixed virtual impedance.

[0002] In a first aspect, the present invention provides a voltage balancing method for a photovoltaic-storage inverter parallel system, applicable to such a system, wherein the photovoltaic-storage inverter parallel system comprises at least two inverters operating in parallel, including: Obtain common node voltage information and inverter power information of the parallel inverter; A voltage RMS loop is constructed based on the common node voltage information; Based on the inverter power information, adaptive coefficient extraction processing is performed to obtain the adaptive power droop coefficient. The effective voltage value loop, the adaptive power droop coefficient, and the preset virtual impedance fitting relationship are imported into the photovoltaic-storage inverter parallel system to achieve dynamic voltage balance of the parallel inverter.

[0003] Optionally, the step of constructing a voltage RMS loop based on the common node voltage information specifically includes: The common node voltage information is processed by a sliding window to obtain the effective value of the common node voltage; The effective voltage value of the common node is compared with the preset effective voltage value to form a first loop, thus obtaining the effective voltage value loop.

[0004] Optionally, after the step of performing loop construction processing on the effective value of the common node voltage and a preset effective value of voltage to obtain the effective value voltage loop, the method further includes: The effective value of the common node voltage is compared with the preset effective value of the voltage to form a second loop, thus obtaining a voltage compensation loop.

[0005] Optionally, the step of obtaining the inverter power information of the parallel inverter specifically includes: Real-time measurement and processing are performed on all parallel inverters in the photovoltaic-storage inverter parallel system to obtain the active power information and reactive power information of all parallel inverters. The active power information and reactive power information of all parallel inverters are averaged to obtain the inverter power information of the parallel inverters.

[0006] Optionally, the step of performing adaptive coefficient extraction processing based on the inverter power information to obtain the adaptive power droop coefficient specifically includes: Obtain the real-time active power information of each parallel inverter in the photovoltaic-storage inverter parallel system; The inverter power information and the real-time active power information are subjected to hysteresis control, and the droop coefficient is dynamically adjusted to obtain the adaptive power droop coefficient.

[0007] Optionally, the adaptive power droop coefficient includes a rising inverter droop coefficient and a falling inverter droop coefficient. The step of performing hysteresis control on the inverter power information and the real-time active power information and dynamically adjusting the droop coefficient to obtain the adaptive power droop coefficient specifically includes: If the real-time active power information is higher than the inverter power information, the adaptive power droop coefficient is adjusted to decrease the inverter droop coefficient. If the real-time active power information is lower than the inverter power information, the adaptive power droop coefficient is adjusted to increase the inverter droop coefficient.

[0008] Optionally, the step of importing the effective voltage loop, the adaptive power droop coefficient, and the preset virtual impedance fitting relationship into the photovoltaic-storage inverter parallel system to achieve dynamic voltage balance of the parallel inverter includes the following steps: The effective value of the real-time voltage of the common node of the photovoltaic-storage inverter parallel system is obtained and compared with the preset voltage reference value to obtain the voltage deviation. The output of the voltage RMS loop is calculated using the voltage deviation control cycle; The voltage RMS loop is set through its output and voltage output value. Sum the values ​​to obtain the corrected voltage control reference value; The number of all parallel inverters in the photovoltaic-storage inverter parallel system is imported into a preset virtual impedance fitting relationship to obtain the target virtual impedance parameters. The modified voltage control reference value, the adaptive power droop coefficient, and the target virtual impedance parameter are simultaneously applied to the control loops of each parallel inverter in the photovoltaic-storage inverter parallel system to achieve dynamic voltage balance of the parallel inverters.

[0009] Secondly, this aspect provides a voltage balancing device for a photovoltaic-storage inverter parallel system, applied to such a system, wherein the system comprises at least two parallel inverters, including: The acquisition module is used to acquire common node voltage information and inverter power information of the parallel inverter; The construction module is used to construct a voltage RMS loop based on the common node voltage information; The processing module is used to perform adaptive coefficient extraction processing based on the inverter power information to obtain the adaptive power droop coefficient; The dynamic voltage balance module is used to import the effective voltage value loop, the adaptive power droop coefficient, and the preset virtual impedance fitting relationship into the photovoltaic-storage inverter parallel system to achieve dynamic voltage balance of the parallel inverter.

[0010] Thirdly, the present invention provides a computer-readable storage medium storing a computer program that, when executed by a voltage balancing device of a photovoltaic-storage inverter parallel system, implements the voltage balancing method of the photovoltaic-storage inverter parallel system as described above.

[0011] Fourthly, the present invention provides a computer device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the voltage balancing method of the photovoltaic-storage inverter parallel system as described above.

[0012] Fifthly, the present invention provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the voltage balancing method for a photovoltaic-storage inverter parallel system as described above.

[0013] This invention acquires common node voltage information and inverter power information of the parallel inverters; constructs a voltage RMS loop based on the common node voltage information; performs adaptive coefficient extraction processing based on the inverter power information to obtain an adaptive power droop coefficient; and imports the voltage RMS loop, the adaptive power droop coefficient, and a preset virtual impedance fitting relationship into the photovoltaic-storage inverter parallel system to achieve dynamic voltage balance of the parallel inverters. Adaptive droop control achieves power averaging for each module, and the RMS value is calculated using a moving average as feedback for the RMS loop, ensuring real-time RMS loop calculation to guarantee inverter voltage output regulation accuracy and dynamic performance. Attached Figure Description To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a flowchart of the voltage balancing method for a photovoltaic-storage inverter parallel system according to an embodiment of the present invention; Figure 2 This is an overall flowchart of a voltage balancing method for a photovoltaic-storage inverter parallel system according to an embodiment of the present invention; Figure 3 This is a structural block diagram of the voltage balancing device of the photovoltaic-storage inverter parallel system according to an embodiment of the present invention; Figure 4 This is a control diagram of the voltage RMS value loop and voltage compensation loop of the photovoltaic-storage inverter parallel system according to an embodiment of the present invention; Figure 5 This is a logic diagram of the voltage balancing method for a photovoltaic-storage inverter parallel system according to an embodiment of the present invention; Figure 6 This is a structural block diagram of a computer device according to another embodiment of the present invention; Figure 7 This is a structural block diagram of an electronic device according to another embodiment of the present invention. Detailed Implementation The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Well-known modules, units, and their connections, links, communications, or operations are not shown or described in detail. Furthermore, the described features, architectures, or functions can be combined in any way in one or more embodiments. Those skilled in the art should understand that the various embodiments described below are only for illustrative purposes and not for limiting the scope of protection of the present invention. It is also readily understood that the modules, units, or processing methods in the various embodiments described herein and shown in the accompanying drawings can be combined and designed in various different configurations. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0016] The limitations on various terms or methods referred to in the following embodiments are, except where logically impossible, generally defined as broad concepts that can be implemented under the premise of the content disclosed in the embodiments. Under this understanding, all specific subordinate limitations of the terms or methods should be regarded as the inventive content of this invention, and should not be narrowly interpreted or biased on the grounds that the specification does not disclose such specific limitations. For example, when this invention refers to a cloud platform, it includes not only virtual network servers, but also real physical devices, which not only have the ability to store data, but also the ability to perform data processing, intelligent analysis, and reasoning. (Substitution or deletion may be made according to the inventive content.) Similarly, under the premise of logical feasibility, the order of the steps in the method is flexible and varied, and the specific subordinate limitations in the broad concepts of various terms or methods are all within the protection scope of this invention.

[0017] In one embodiment, please refer to Figure 1As shown in the figure, this embodiment proposes a voltage balancing method for a photovoltaic-storage inverter parallel system, which is applied to a photovoltaic-storage inverter parallel system containing at least two inverters operating in parallel, and includes the following steps: S11, obtain common node voltage information and inverter power information of parallel inverters; In this embodiment, the above-mentioned photovoltaic-storage inverter parallel system can be a power conversion system composed of at least two or more photovoltaic-storage hybrid inverters operating in parallel, which includes modules such as photovoltaic array, energy storage battery, DC / DC converter, inverter unit and control unit; The aforementioned parallel inverters can refer to individual photovoltaic-storage hybrid inverters connected to a common AC bus and jointly supplying power to the load in a photovoltaic-storage inverter parallel system. Each inverter has independent power regulation and control functions and communicates with the main control unit. The aforementioned inverter power information can refer to parameters such as active and reactive power output by each parallel inverter during operation, including real-time power value, average power value, phase power factor, and power fluctuation data, which can be uploaded to the control unit via CAN bus or other communication methods for subsequent adaptive droop coefficient extraction and virtual impedance adjustment.

[0018] In this embodiment, the aforementioned common node voltage information refers to the real-time voltage sampling data located at the AC convergence point of each parallel inverter during the operation of the photovoltaic-storage inverter parallel system. This common node voltage information is typically obtained through a voltage sensor, sampling circuit, or measurement module of the control unit, and includes parameters such as instantaneous voltage value, effective value, phase, and waveform information. It can be preprocessed using a sliding window or filtering algorithm to eliminate instantaneous fluctuations, resulting in a stable feedback signal that can be used to construct a voltage effective value loop.

[0019] Specifically, the detailed implementation process for obtaining the inverter power information of the parallel inverter will be described in further detail in the subsequent specific embodiments of this application, and will not be elaborated on here.

[0020] S12, construct the voltage RMS value loop based on the common node voltage information; In this embodiment, the aforementioned voltage RMS loop can refer to a voltage closed-loop control channel constructed based on the RMS voltage of the common node. It uses the RMS voltage of the common node as a feedback signal, compares it with a preset voltage reference value to obtain the voltage deviation, and then calculates the adjustment amount using proportional-integral (PI) or anti-saturation PI adjustment algorithms to correct the inverter output voltage reference value in real time. The voltage RMS loop can operate continuously and dynamically during the operation of the inverter parallel system, rapidly adjusting the steady-state error and transient fluctuations of the common node voltage to ensure stable and consistent voltage output from each parallel inverter, providing a reliable voltage reference for adaptive droop control and virtual impedance adjustment.

[0021] Specifically, the detailed implementation process of constructing the voltage effective value loop based on the common node voltage information will be further described in subsequent specific embodiments of this application, and will not be elaborated on here.

[0022] S13, based on the inverter power information, perform adaptive coefficient extraction processing to obtain the adaptive power droop coefficient; In this embodiment of the invention, the aforementioned adaptive power droop coefficient can refer to a droop control parameter dynamically adjusted based on the difference between the real-time output power of each parallel inverter and the system average power. This coefficient may include an active power droop coefficient and a reactive power droop coefficient, and can be configured with increasing and decreasing adjustment strategies respectively: when the real-time active power of an inverter is higher than the system average power, the droop coefficient automatically decreases (i.e., the droop coefficient decreases), thereby reducing the inverter's output voltage reference value to balance power; when the real-time active power of an inverter is lower than the system average power, the droop coefficient automatically increases (i.e., the droop coefficient increases), thereby increasing the inverter's output voltage reference value to compensate for insufficient power. Through the above adaptive adjustment, power distribution among inverters can be achieved and the dynamic stability of the system can be improved under different numbers of parallel inverters and different load conditions.

[0023] Specifically, the detailed implementation process of the adaptive coefficient extraction process based on inverter power information to obtain the adaptive power droop coefficient will be further described in subsequent specific embodiments of this application, and will not be elaborated on here.

[0024] S14, the effective voltage value loop, adaptive power droop coefficient and preset virtual impedance fitting relationship are imported into the photovoltaic-storage inverter parallel system to realize the dynamic voltage balance of the parallel inverter.

[0025] In this embodiment of the invention, the aforementioned preset virtual impedance fitting can refer to a "parallel unit number - virtual impedance parameter" correspondence curve or mathematical model that is pre-established and stored in the control unit based on a large amount of experimental or simulation data. This fitting relationship can be implemented using polynomial regression, piecewise fitting, table lookup, or interpolation algorithms, enabling the system to automatically match the optimal virtual impedance parameter under different parallel unit numbers and different load conditions.

[0026] Specifically, the implementation process of incorporating the aforementioned voltage RMS loop, adaptive power droop coefficient, and preset virtual impedance fitting relationship into the photovoltaic-storage inverter parallel system to achieve dynamic voltage balance of the parallel inverter will be further described in detail in subsequent specific embodiments of this application, and will not be elaborated on here.

[0027] In this embodiment of the invention, common node voltage information and inverter power information of the parallel inverters are acquired; a voltage RMS loop is constructed based on the common node voltage information; adaptive coefficient extraction is performed based on the inverter power information to obtain an adaptive power droop coefficient; the voltage RMS loop, the adaptive power droop coefficient, and a preset virtual impedance fitting relationship are imported into the photovoltaic-storage inverter parallel system to achieve dynamic voltage balance of the parallel inverters. Adaptive droop control achieves power averaging for each module, and real-time moving average calculation of the RMS value serves as feedback for the RMS loop, ensuring the inverter voltage output regulation accuracy and dynamic performance.

[0028] As a preferred option and not a limitation, step S11 includes the following steps: Real-time measurement and processing are performed on all parallel inverters in the photovoltaic-storage inverter parallel system to obtain the active power information and reactive power information of all parallel inverters. The active power information and reactive power information of all parallel inverters are averaged to obtain the inverter power information of the parallel inverters.

[0029] In this embodiment, the aforementioned active power information may refer to the active power parameters output to the common node by each parallel inverter during operation, such as the instantaneous active power value, average active power value and its fluctuation data obtained in real time through current sensors, voltage sensors and power calculation modules, which are used to reflect the actual work capacity of each inverter. The aforementioned reactive power information refers to the reactive power parameters output to the common node by each parallel inverter during operation. Examples include instantaneous reactive power values, average reactive power values, and their fluctuations, calculated in real-time by current phase, voltage phase, and power factor measurement modules. This data reflects the inverter's ability to maintain voltage support and compensate for reactive power in the line or load. By integrating active and reactive power information, the control unit can extract adaptive droop coefficients and dynamically adjust virtual impedance parameters, thereby ensuring balanced power distribution and stable system operation.

[0030] In one possible embodiment, voltage, current, and phase data are collected in real time at the output of each parallel inverter to calculate the active and reactive power of each inverter. This data is then uploaded to the main control unit via a communication module. The main control unit sums the active and reactive power information of all parallel inverters and takes the average value to obtain the overall average active and reactive power of the system. This generates unified inverter power information and sends it to the control modules of each inverter for subsequent adaptive droop coefficient adjustment and dynamic matching of virtual impedance parameters, thereby achieving power distribution and voltage balance. By performing real-time measurement and averaging of the active and reactive power information of all parallel inverters, the overall power distribution status can be monitored in real time during system operation, and unified inverter power information can be generated. This allows each parallel inverter to adjust its power under a unified benchmark, thereby significantly improving the balance of power distribution, reducing power circulating current caused by inconsistent droop control, improving voltage stability and dynamic response speed, and facilitating the accurate matching and adaptive adjustment of virtual impedance parameters. Overall, this enhances the voltage regulation accuracy and operational reliability of the photovoltaic-storage inverter parallel system.

[0031] As a preferred option and not a limitation, step S12 includes the following steps: The common node voltage information is processed by a sliding window to obtain the effective value of the common node voltage; The effective voltage value of the common node is compared with the preset effective voltage value to form the first loop, thus obtaining the effective voltage value loop.

[0032] In this embodiment, the aforementioned effective value of the common node voltage refers to the root mean square (RMS) value of the voltage obtained by real-time sampling of the common node voltage signal and processing it through a sliding window or filtering algorithm during the operation of the photovoltaic-storage inverter parallel system. This value reflects the stable voltage level of the common node within one or several sampling periods. It is typically calculated using a 10ms sliding window to effectively suppress transient fluctuations and noise interference, obtain a smoother and more reliable voltage feedback signal, and provide a precise control reference for the voltage RMS loop and voltage compensation loop, thereby improving the voltage regulation accuracy and dynamic response performance of the inverter output voltage.

[0033] In this embodiment, the sliding window processing can be implemented by setting a sampling window of fixed length (e.g., 10ms) in the control unit and moving it continuously according to the time sequence. Specifically, the control unit stores the real-time sampled values ​​of the common node voltage or current in segments. Whenever a new sampled value enters the window, the earliest sampled value is removed from the window. The root mean square (RMS) or average value is calculated for all sampled values ​​within the window to obtain the smoothed effective value of the voltage or current at the current moment.

[0034] In one possible embodiment, the process of obtaining the effective value of the common node voltage by performing sliding window processing on the common node voltage information may include: setting a fixed-length sliding sampling window (e.g., 10ms) in the control unit, collecting instantaneous sampled values ​​of the common node voltage in real time, and storing them sequentially in the sampling window according to time sequence; when a new sampled value enters, the earliest sampled value is removed from the window, and the root mean square (RMS) operation is performed on all sampled values ​​within the window to obtain the effective value of the common node voltage at the current moment. Based on this, the effective value of the common node voltage is compared with a preset voltage reference value to obtain the voltage deviation, and the deviation signal is input to a proportional-integral (PI) or anti-saturation PI regulator for calculation and processing to generate an adjustment amount; this adjustment amount is superimposed on the voltage control reference value of the inverter to form a complete voltage effective value loop, realizing closed-loop regulation of the common node voltage. Through this loop control, the voltage output error can be continuously corrected during operation, ensuring the voltage steady-state accuracy and dynamic response performance of the inverter parallel system.

[0035] As a preferred option and not a limitation, the following steps may also be included after step S12: The voltage compensation loop is obtained by constructing a second loop by comparing the effective value of the common node voltage with the preset effective value of the voltage.

[0036] In this embodiment, the aforementioned voltage compensation loop refers to a second closed-loop compensation control channel established after the voltage RMS loop to address the residual error between the common node voltage and the preset voltage reference value. This compensation loop uses the deviation between the RMS common node voltage and the preset reference voltage as an input signal, calculates the compensation amount using proportional-integral (PI), anti-saturation PI, or other adaptive adjustment algorithms, and then superimposes or corrects this compensation amount onto the inverter's voltage control reference value to eliminate steady-state voltage deviations caused by line impedance, load fluctuations, or inverter hardware differences. Through the voltage compensation loop, the steady-state accuracy and dynamic response capability of the inverter output voltage can be further improved, enabling higher-precision control of the common node voltage, reducing the adjustment pressure on the voltage RMS loop, and improving the stability and reliability of the entire photovoltaic-storage inverter parallel system.

[0037] As a preferred option and not a limitation, step S13 includes the following steps: Obtain real-time active power information of each parallel inverter in the photovoltaic-storage inverter parallel system; The inverter power information and real-time active power information are subjected to hysteresis control, and the droop coefficient is dynamically adjusted to obtain the adaptive power droop coefficient.

[0038] This step, "Performing hysteresis control on the inverter power information and real-time active power information, and dynamically adjusting the droop coefficient to obtain an adaptive power droop coefficient," includes the following steps: If the real-time active power information is higher than the inverter power information, the adaptive power droop factor is adjusted to decrease the inverter droop factor. If the real-time active power information is lower than the inverter power information, the adaptive power droop factor is adjusted to increase the inverter droop factor.

[0039] In this embodiment, the aforementioned droop factor of the inverter can refer to the situation where, when the real-time active power of a parallel inverter is higher than the average active power of the system, the control unit automatically reduces the droop factor of the inverter, thereby reducing its output voltage reference value and reducing its output power to approach the average value, thus achieving power distribution. The aforementioned rising inverter droop factor refers to the automatic increase of the inverter's droop factor by the control unit when the real-time active power of a parallel inverter is lower than the system's average active power. This increases the inverter's output voltage reference value, thereby increasing its output power to approach the average value and achieving power distribution. Through these two adaptive adjustment methods (rising and falling), the power output of each inverter can be dynamically balanced under different numbers of parallel inverters and different load conditions, significantly reducing power circulating current and improving the system's dynamic stability and voltage control accuracy.

[0040] In one possible embodiment, current and voltage sensors or power measurement modules are installed at the output of each parallel inverter. A control unit periodically collects and calculates the real-time active power value of each inverter. The control unit then transmits the system average active power (i.e., inverter power information) to the control modules of each inverter via a CAN bus or other communication interface, providing each inverter with a unified power reference. Each inverter control module then compares its own real-time active power value with the received system average active power value to obtain the power difference. When the real-time active power value of an inverter is higher than the system average power value, the control module automatically reduces the droop coefficient of that inverter, adjusting it to a "decreasing inverter droop coefficient" to lower its output voltage reference value, thereby reducing output power. When the real-time active power of a certain inverter is lower than the system average power, the control module automatically increases the droop coefficient of that inverter, adjusting it to an "increasing inverter droop coefficient" to raise its output voltage reference value, thereby increasing the output power. Finally, the adjusted droop coefficient is applied to the inverter control loop in real time, updating the inverter's voltage-power control characteristic curve and achieving dynamic balance of output power among the parallel inverters. Through the above process, each parallel inverter can automatically adjust its droop coefficient according to the actual power deviation, gradually making the power output more consistent, significantly reducing power circulating current and improving system stability.

[0041] As a preferred option and not a limitation, step S14 includes the following steps: The voltage deviation is obtained by comparing the real-time effective value of the common node voltage of the photovoltaic-storage inverter parallel system with the preset voltage reference value. The output of the voltage RMS value loop is calculated by controlling the voltage deviation cycle. The corrected voltage control reference value is obtained by summing the output of the voltage RMS loop and the voltage output value setting. The number of all parallel inverters in the photovoltaic-storage inverter parallel system is imported into a preset virtual impedance fitting relationship to obtain the target virtual impedance parameters; The corrected voltage control reference value, adaptive power droop coefficient, and target virtual impedance parameter are simultaneously applied to the control loops of each parallel inverter in the photovoltaic-storage inverter parallel system to achieve dynamic voltage balance of the parallel inverters.

[0042] In this embodiment, the voltage deviation mentioned above can refer to the deviation signal obtained by the difference between the real-time effective value of the common node voltage and the preset voltage reference value. This deviation signal can reflect the degree of deviation of the current inverter parallel system common node voltage and serve as the input of the voltage effective value loop and voltage compensation loop to correct the inverter output voltage reference value in real time. The aforementioned target virtual impedance parameter can refer to the impedance parameter dynamically calculated based on a preset virtual impedance fitting relationship and the current number of parallel inverters. This parameter typically includes resistive, inductive, and / or capacitive components and can be directly applied to the control loop of each parallel inverter to adjust the inverter's output characteristics under different loads and the number of parallel inverters, thereby achieving better power distribution balance, reducing power circulating current, and improving system stability.

[0043] In one possible embodiment, the common node voltage of the photovoltaic-storage inverter parallel system is sampled at high frequency in real time within the control unit, and its effective value is calculated. The effective value of the real-time voltage is compared with a preset voltage reference value to obtain the voltage deviation. The output of the voltage effective value loop is calculated through the voltage deviation control cycle and used as the input signal for voltage regulation control. The control unit then sums the output of the voltage effective value loop with the voltage output value setting and inputs the voltage effective value loop and voltage compensation loop for summation. The adjustment amount is then calculated through proportional-integral or anti-saturation PI algorithms to correct the voltage control reference value of the inverter. Meanwhile, the control unit counts the number of parallel inverters in the system in real time and substitutes them into the pre-stored virtual impedance fitting relationship curve or lookup table algorithm to dynamically calculate the target virtual impedance parameter. The corrected voltage control reference value, adaptive power droop coefficient and target virtual impedance parameter are sent to the control loop of each parallel inverter to form a real-time closed-loop regulation within each inverter. This enables each inverter to automatically match voltage output and power distribution under different numbers of units and different load conditions, and finally achieves dynamic voltage balance of the entire photovoltaic-storage inverter parallel system. This significantly improves voltage regulation accuracy, reduces power circulating current and enhances system dynamic response and operational stability.

[0044] like Figure 2 As shown, Figure 2This is an overall flowchart of a voltage balancing method for a photovoltaic-storage inverter parallel system according to an embodiment of the present invention. The entire system uses a DC power supply as input, which supplies power to multiple inverter modules (INV1, INV2, INV3). Each inverter receives control commands through a PWM control interface and converts the DC voltage into an AC voltage output, which is then collected at the common point of coupling (PCC). In off-grid operation, the AC output voltage of each inverter is transmitted to the control side in real time through a sampling capture interface. The control side includes a software calculation module that performs real-time calculations on the collected output voltage and current signals of each inverter to obtain the active power Q and the effective value of the common node voltage Vrms. This effective value is further fed into a 10ms sliding window calculation module (10m sliding window moving average calculation) to smooth and filter the data and perform root mean square calculation to obtain a stable feedback signal. Finally, the voltage effective value and power information obtained by the above calculations are fed back to the inverter control unit to adjust the PWM control parameters, thereby achieving dynamic voltage balance and power distribution among multiple inverters under different loads and operating conditions. The overall architecture is compact and covers key aspects such as multi-channel inverter power input, signal acquisition, software calculation, sliding window processing, and feedback control.

[0045] like Figure 3 As shown, the voltage balancing device of the photovoltaic-storage inverter parallel system includes: The acquisition module 301 is used to acquire common node voltage information and inverter power information of the parallel inverter; Construction module 302 is used to construct a voltage RMS loop based on the common node voltage information; Processing module 303 is used to perform adaptive coefficient extraction processing based on the inverter power information to obtain adaptive power droop coefficient; The dynamic voltage balance module 304 is used to import the effective voltage value loop, the adaptive power droop coefficient, and the preset virtual impedance fitting relationship into the photovoltaic-storage inverter parallel system to achieve dynamic voltage balance of the parallel inverter.

[0046] Optionally, the acquisition module 301 includes: The real-time measurement and processing submodule is used to perform real-time measurement and processing on all parallel inverters in the photovoltaic-storage inverter parallel system to obtain the active power information and reactive power information of all parallel inverters. The average calculation and processing submodule is used to perform average calculation and processing on the active power information and reactive power information of all parallel inverters to obtain the inverter power information of the parallel inverters.

[0047] Optionally, building module 302 includes: The sliding window processing submodule is used to perform sliding window processing on the common node voltage information to obtain the effective value of the common node voltage; The first ring construction submodule is used to perform first ring construction processing on the effective value of the common node voltage and the preset effective value of voltage to obtain the effective value of voltage ring.

[0048] Optionally, following module 302, the following may also be included: The second ring construction submodule is used to perform second ring construction processing on the effective value of the common node voltage and the preset effective value of the voltage to obtain the voltage compensation ring.

[0049] Optionally, the processing module 303 includes: The acquisition submodule is used to acquire the real-time active power information of each parallel inverter in the photovoltaic-storage inverter parallel system; The comparison processing submodule is used to perform hysteresis control on the inverter power information and the real-time active power information and dynamically adjust the droop coefficient to obtain the adaptive power droop coefficient.

[0050] Optionally, the comparison processing submodule includes: The first adjustment unit is used to adjust the adaptive power droop coefficient to decrease the inverter droop coefficient if the real-time active power information is higher than the inverter power information. The second adjustment unit is used to adjust the adaptive power droop coefficient to increase the inverter droop coefficient if the real-time active power information is lower than the inverter power information.

[0051] Optional, the dynamic voltage balancing module 304 includes: The deviation calculation submodule is used to obtain the real-time effective value of the common node voltage of the photovoltaic-storage inverter parallel system and compare it with the preset voltage reference value to obtain the voltage deviation. The output submodule is used to calculate the output of the voltage RMS value loop through the voltage deviation control cycle. The correction calculation submodule is used to sum the voltage RMS value loop through the output of the voltage RMS value loop and the voltage output value setting to obtain the corrected voltage control reference value. The import submodule is used to import the number of all parallel inverters in the photovoltaic-storage inverter parallel system into a preset virtual impedance fitting relationship to obtain the target virtual impedance parameters. The dynamic voltage balance submodule is used to simultaneously apply the corrected voltage control reference value, the adaptive power droop coefficient, and the target virtual impedance parameter to the control loops of each parallel inverter in the photovoltaic-storage inverter parallel system, thereby achieving dynamic voltage balance of the parallel inverters.

[0052] In one embodiment, such as Figure 4 As shown, Figure 4 This is the control diagram for the voltage RMS loop and voltage compensation loop of the present invention. As shown in the figure, the voltage RMS loop and voltage compensation loop control diagram of the present invention achieves an organic combination of multi-channel signal acquisition, dual closed-loop control, and PWM drive output: First, through inverter current sampling and power reference issued by the host, the control unit calculates the real-time power information P of each inverter, and obtains the power droop control quantity through PI regulation; at the same time, the preset voltage is compared with the sampled voltage, and the voltage RMS loop is constructed through PI regulation to obtain the voltage reference value Vref; Vref, together with the phase information (Sinθ) and the inverter voltage sampled value, is input into the instantaneous voltage control loop (PI+PR+Repeat control loop) to achieve precise synchronization and rapid adjustment of voltage amplitude and phase; the system also dynamically calculates the virtual impedance curve parameters according to the number of modules, and superimposes the obtained virtual impedance parameters with the voltage control quantity to form a corrected control signal; finally, the corrected signal drives each parallel inverter to output AC voltage to the load through the PWM module, realizing the dynamic balance of active power, reactive power, and voltage. The entire control process utilizes a 10 ms sliding window to calculate Vrms in real time, achieving high-precision voltage regulation and fast response. This ensures power distribution among parallel inverters and significantly improves the dynamic performance and stability of the system.

[0053] In one embodiment, such as Figure 5 As shown, Figure 5 This is a logic diagram of the voltage balancing method for a photovoltaic-storage inverter parallel system according to an embodiment of the present invention.

[0054] like Figure 5 As shown, the control flow of this invention starts from system startup. First, the common node voltage and the current of each inverter are sampled in real time. The node voltage signal is calculated by a sliding window to obtain a stable effective voltage value (RMS), which is then entered into the voltage compensation loop and the effective voltage value loop to adjust the PCC point voltage in real time. The inverter current signal is calculated by reactive power and then works with the droop control module to achieve dynamic distribution of active and reactive power. The system further eliminates the power circulating current caused by multiple parallel inverters through the power circulating current suppression and regulation module. Then, it enters the voltage instantaneous loop to perform fine dynamic control of the voltage, and then enters the current loop to achieve rapid stabilization of the output current. At the same time, the control unit substitutes the number of parallel modules into the fitting curve to dynamically adjust the virtual impedance parameters so that the output impedance matches the system state. Finally, the above adjustment results are combined to form a PWM modulation signal to drive the output of each parallel inverter, realizing full-link closed-loop control and stable output of voltage, current, and power, thereby achieving high-precision voltage regulation, current sharing, and dynamic voltage balance.

[0055] Those skilled in the art can implement the corresponding control logic based on the content of this specification and the illustrations without any creative effort.

[0056] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional modules is used as an example. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. The specific working process of the system, device, and unit described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0057] This invention also provides a computer storage medium storing a computer program that, when executed by a processor, implements the voltage balancing method for the photovoltaic-storage inverter parallel system as described in the above embodiments.

[0058] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the voltage balancing methods for each of the above-described embodiments of a photovoltaic-storage inverter parallel system. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), RAMbus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0059] Alternatively, if the integrated units of the present invention are implemented as software functional modules and sold or used as independent products, they can also be stored in a computer-readable storage medium. Based on this understanding, the technical solutions of the embodiments of the present invention, or the parts that contribute to related technologies, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, terminal, or network device, etc.) to execute all or part of the methods of the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as mobile storage devices, RAM, ROM, magnetic disks, or optical disks.

[0060] Corresponding to the computer storage medium described above, one embodiment also provides a computer device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the voltage balancing method of the photovoltaic-storage inverter parallel system as described in the above embodiments.

[0061] This computer device can be a terminal, and its internal structure diagram can be as follows: Figure 6 As shown, the computer device includes a processor, memory, network interface, display screen, and input devices connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The network interface is used for communication with external terminals via a network connection. When the computer program is executed by the processor, it implements a voltage balancing method for a parallel photovoltaic-storage inverter system. The display screen can be an LCD screen or an e-ink screen. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad on the computer device's casing, or an external keyboard, touchpad, or mouse.

[0062] The electronic device in this application embodiment can be various types of electronic devices, such as a photovoltaic-storage-inverter parallel system, or it can be a component in an electronic device, such as an integrated circuit or a chip. The electronic device can be a terminal or other devices besides a terminal. For example, the electronic device can be a mobile phone, tablet computer, laptop computer, handheld computer, in-vehicle electronic device, mobile internet device (MID), augmented reality (AR) / virtual reality (VR) device, robot, wearable device, ultra-mobile personal computer (UMPC), netbook or personal digital assistant (PDA), etc. It can also be a server, network attached storage (NAS), personal computer (PC), television (TV), ATM or self-service machine, etc. The embodiments of this application do not specifically limit it.

[0063] Optionally, such as Figure 7 As shown, this application embodiment also provides an electronic device 700, including a processor 701, a memory 702, and a program or instructions stored in the memory 702 and executable on the processor 701. When the program or instructions are executed by the processor 701, they implement the various processes of the voltage balancing method embodiment of the above-described photovoltaic-storage inverter parallel system and achieve the same technical effect. To avoid repetition, they will not be described again here.

[0064] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0065] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A voltage balancing method for a photovoltaic-storage inverter parallel system, applied to a photovoltaic-storage inverter parallel system, wherein the photovoltaic-storage inverter parallel system includes at least two inverters operating in parallel, characterized in that, include: Obtain common node voltage information and inverter power information of the parallel inverter; A voltage RMS loop is constructed based on the common node voltage information; Based on the inverter power information, adaptive coefficient extraction processing is performed to obtain the adaptive power droop coefficient. The effective voltage value loop, the adaptive power droop coefficient, and the preset virtual impedance fitting relationship are imported into the photovoltaic-storage inverter parallel system to achieve dynamic voltage balance of the parallel inverter.

2. The voltage balancing method for a photovoltaic-storage inverter parallel system according to claim 1, characterized in that, The step of constructing the voltage RMS loop based on the common node voltage information specifically includes: The common node voltage information is processed by a sliding window to obtain the effective value of the common node voltage; The effective voltage value of the common node is compared with the preset effective voltage value to form a first loop, thus obtaining the effective voltage value loop.

3. The voltage balancing method for a photovoltaic-storage inverter parallel system according to claim 2, characterized in that, After the step of performing loop construction processing on the effective value of the common node voltage and a preset effective value of voltage to obtain the effective value voltage loop, the method further includes: The effective value of the common node voltage is compared with the preset effective value of the voltage to form a second loop, thus obtaining a voltage compensation loop.

4. The voltage balancing method for a photovoltaic-storage inverter parallel system according to claim 1, characterized in that, The step of obtaining the inverter power information of the parallel inverter specifically includes: Real-time measurement and processing are performed on all parallel inverters in the photovoltaic-storage inverter parallel system to obtain the active power information and reactive power information of all parallel inverters. The active power information and reactive power information of all parallel inverters are averaged to obtain the inverter power information of the parallel inverters.

5. The voltage balancing method for a photovoltaic-storage inverter parallel system according to claim 4, characterized in that, The step of performing adaptive coefficient extraction processing based on the inverter power information to obtain the adaptive power droop coefficient specifically includes: Obtain the real-time active power information of each parallel inverter in the photovoltaic-storage inverter parallel system; The inverter power information and the real-time active power information are subjected to hysteresis control, and the droop coefficient is dynamically adjusted to obtain the adaptive power droop coefficient.

6. The voltage balancing method for a photovoltaic-storage inverter parallel system according to claim 5, characterized in that, The adaptive power droop coefficient includes a rising inverter droop coefficient and a falling inverter droop coefficient. The step of performing hysteresis control on the inverter power information and the real-time active power information and dynamically adjusting the droop coefficient to obtain the adaptive power droop coefficient specifically includes: If the real-time active power information is higher than the inverter power information, the adaptive power droop coefficient is adjusted to decrease the inverter droop coefficient. If the real-time active power information is lower than the inverter power information, the adaptive power droop coefficient is adjusted to increase the inverter droop coefficient.

7. The voltage balancing method for a photovoltaic-storage inverter parallel system according to claim 3, characterized in that, The specific steps for importing the effective voltage loop, the adaptive power droop coefficient, and the preset virtual impedance fitting relationship into the photovoltaic-storage inverter parallel system to achieve dynamic voltage balance of the parallel inverter include: The effective value of the real-time voltage of the common node of the photovoltaic-storage inverter parallel system is obtained and compared with the preset voltage reference value to obtain the voltage deviation. The output of the voltage RMS loop is calculated using the voltage deviation control cycle; The voltage RMS loop is set through its output and voltage output value. Sum the values ​​to obtain the corrected voltage control reference value; The number of all parallel inverters in the photovoltaic-storage inverter parallel system is imported into a preset virtual impedance fitting relationship to obtain the target virtual impedance parameters. The modified voltage control reference value, the adaptive power droop coefficient, and the target virtual impedance parameter are simultaneously applied to the control loops of each parallel inverter in the photovoltaic-storage inverter parallel system to achieve dynamic voltage balance of the parallel inverters.

8. A voltage balancing device for a photovoltaic-storage inverter parallel system, applied to a photovoltaic-storage inverter parallel system, wherein the photovoltaic-storage inverter parallel system includes at least two inverters operating in parallel, characterized in that, include: The acquisition module is used to acquire common node voltage information and inverter power information of the parallel inverter; The construction module is used to construct a voltage RMS loop based on the common node voltage information; The processing module is used to perform adaptive coefficient extraction processing based on the inverter power information to obtain the adaptive power droop coefficient; The dynamic voltage balance module is used to import the effective voltage value loop, the adaptive power droop coefficient, and the preset virtual impedance fitting relationship into the photovoltaic-storage inverter parallel system to achieve dynamic voltage balance of the parallel inverter.

9. A computer-readable storage medium, characterized in that, The storage medium stores a computer program, which, when executed by the voltage balancing device of the photovoltaic-storage inverter parallel system, implements the voltage balancing method of the photovoltaic-storage inverter parallel system as described in any one of claims 1 to 7.

10. A computer device, characterized in that, The computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the voltage balancing method for a photovoltaic-storage inverter parallel system as described in any one of claims 1 to 7.

11. An electronic device, characterized in that, include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the steps of the voltage balancing method for a photovoltaic-storage inverter parallel system as described in any one of claims 1 to 7.

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