Ac coupling control system and control method for hybrid energy storage inverter

Abstract

The application discloses an AC coupling control system and a control method of a hybrid energy storage inverter, and the system comprises a first control module, an inverter current feedforward module, a frequency adjustment module, a second control module, a third control module and an inverter voltage feedforward module which are connected in sequence; wherein the first control module is connected with an inverter voltage output end of the hybrid energy storage inverter, and can output an adjustment signal according to a difference signal of an inverter voltage reference signal and an inverter voltage effective value; the inverter current feedforward module can provide current feedforward compensation for the adjustment signal based on the power direction; the frequency adjustment module can provide voltage frequency compensation for the adjustment signal according to a battery current signal of the hybrid energy storage inverter, and dynamically generate an inverter voltage instantaneous value reference signal, so that the second control module and the third control module obtain a modulation signal under the voltage feedforward compensation of the inverter voltage feedforward module, AC coupling control of the hybrid energy storage inverter is realized, and the system stability is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power electronics, and particularly relates to an AC coupling control system and a control method of a hybrid energy storage inverter. BACKGROUND

[0002] The existing hybrid energy storage inverter often faces the problem of power mismatch in AC coupling applications, especially when the output power of the micro photovoltaic inverter exceeds the battery receiving capacity of the energy storage system, the system is prone to trigger the protection mechanism to cause frequent shutdown and restart.

[0003] Traditional control strategies mostly rely on single loop regulation, such as voltage effective value PI control, but its dynamic response speed is insufficient, and it is difficult to cope with voltage instability caused by sudden changes in light or dramatic fluctuations in load power; in addition, the existing technology also lacks direct closed-loop control of battery current, when the micro-inverter power suddenly increases or the load suddenly changes, the battery current may exceed the safety threshold, causing the bus voltage to rise, the system to be forced to shut down, and even equipment damage. SUMMARY

[0004] The present application aims to at least solve one of the technical problems existing in the prior art, which can dynamically adjust the feedforward compensation according to the power direction through the inverter current feedforward module, reduce the bus voltage fluctuation, and combine the frequency adjustment module to monitor the battery current in real time, avoid battery overload through frequency compensation, dynamically generate a voltage instantaneous value reference signal for control, thereby improving the system stability.

[0005] In a first aspect, the present application provides an AC coupling control system of a hybrid energy storage inverter, the system comprising: a first control module, an inverter current feedforward module, a frequency adjustment module, a second control module, a third control module and an inverter voltage feedforward module connected in sequence; wherein the first control module is connected with an inverter voltage output end of the hybrid energy storage inverter, and is used for outputting a first adjustment signal according to a difference signal of an inverter voltage reference signal and an inverter voltage effective value; the inverter current feedforward module is used for providing current feedforward compensation for the first adjustment signal according to inverter power output by the hybrid energy storage inverter, to obtain a second adjustment signal; the frequency adjustment module is used for providing voltage frequency compensation for the second adjustment signal according to a battery current signal of the hybrid energy storage inverter, to obtain an inverter voltage instantaneous value reference signal; the second control module is used for outputting an inverter current reference signal according to the inverter voltage instantaneous value reference signal and an inverter voltage instantaneous value; the third control module is used for outputting a third adjustment signal according to the inverter current reference signal and an inverter current instantaneous value, and combining a voltage feedforward signal of the inverter voltage instantaneous value reference signal provided by the inverter voltage feedforward module, to obtain a modulation signal used for generating a PWM waveform signal according to the third adjustment signal.

[0006] In some embodiments, the first control module comprises an inverter voltage effective value PI loop, the inverter voltage effective value PI loop is configured to output a first PI loop signal based on an output limit of ±1 according to the difference signal, and the first PI loop signal and the inverter voltage reference signal are added to obtain a first adjustment signal.

[0007] In some embodiments, the inverter current feedforward module is configured to output 80% of the inverter current effective value as a positive feedforward compensation when the inverter power is greater than 0, and output 80% of the inverter current effective value as a negative feedforward compensation when the inverter power is less than 0.

[0008] In some embodiments, the frequency adjustment module comprises a voltage frequency PI loop, the voltage frequency PI loop is configured to perform voltage frequency compensation on a reference voltage frequency of the hybrid energy storage inverter by comparing the battery current signal with a preset maximum allowed current, and when the battery current signal is greater than the maximum allowed current, the output range of the voltage frequency compensation is 0Hz to 5Hz, and the reference voltage frequency is 50Hz.

[0009] In some embodiments, the system further comprises a first calculation unit, and in the process of providing voltage frequency compensation for the second adjustment signal to obtain an inverter voltage instantaneous value reference signal, the first calculation unit is configured to perform the following calculation formula:

[0010] Wherein, InvVoltRealRef is the inverter voltage instantaneous value reference signal, S is the second adjustment signal, f base is the reference voltage frequency, and Δf is the voltage frequency compensation.

[0011] In some embodiments, the second control module comprises an inverter voltage instantaneous value PI loop, the inverter voltage instantaneous value PI loop is configured to output a second PI loop signal based on an output limit of ±1 according to the inverter voltage instantaneous value reference signal and an inverter voltage instantaneous value, and the second PI loop signal is an inverter current reference signal.

[0012] In some embodiments, the third control module comprises an inverter current instantaneous value PI loop, the inverter current instantaneous value PI loop is configured to output a third PI loop signal based on an output limit of ±0.3 according to a difference between the inverter current reference signal and an inverter current instantaneous value, and the third PI loop signal and a voltage feedforward signal of the inverter voltage instantaneous value reference signal provided by the inverter voltage feedforward module are added to obtain a third adjustment signal.

[0013] In some embodiments, the system further comprises a second calculation unit; in a process of obtaining a modulation signal for generating a PWM waveform signal according to the third adjustment signal, the second calculation unit is configured to perform the following calculation: the modulation signal = the third adjustment signal * (1 / Ubus); wherein Ubus is the bus voltage of the hybrid energy storage inverter.

[0014] In some embodiments, the system further comprises a sampling terminal for obtaining an inverter voltage instantaneous value signal, an inverter current instantaneous value signal and an inverter current effective value, and the system is connected to the DC bus of the hybrid energy storage inverter through the sampling terminal.

[0015] In the second aspect, the application provides an AC coupling control method of a hybrid energy storage inverter, which is applied to the AC coupling control system of the hybrid energy storage inverter as described in any one of the first aspect, and the method comprises: outputting, by the first control module, a first adjustment signal according to a difference signal between an inverter voltage reference signal and an inverter voltage effective value; providing, by the inverter current feedforward module, current feedforward compensation for the first adjustment signal according to the direction of power flow of AC coupling to obtain a second adjustment signal; providing, by the frequency adjustment module, voltage frequency compensation for the second adjustment signal according to a battery current signal of the hybrid energy storage inverter to obtain an inverter voltage instantaneous value reference signal; outputting, by the second control module, an inverter current reference signal according to the inverter voltage instantaneous value reference signal and an inverter voltage instantaneous value; outputting, by the third control module, a third adjustment signal according to the inverter current reference signal and an inverter current instantaneous value, and combining a voltage feedforward signal of the inverter voltage instantaneous value reference signal provided by the inverter voltage feedforward module, so as to obtain a modulation signal for generating a PWM waveform signal according to the third adjustment signal.

[0016] The AC coupling control system and control method of the hybrid energy storage inverter have at least the following beneficial effects: the first control module, the inverter current feedforward module, the frequency adjustment module, the second control module, the third control module and the inverter voltage feedforward module are sequentially connected, and AC coupling control of the hybrid energy storage inverter is realized; the first control module is connected with an inverter voltage output end of the hybrid energy storage inverter, and is used for outputting a first adjustment signal according to a difference signal of an inverter voltage reference signal and an inverter voltage effective value; the inverter current feedforward module is used for providing current feedforward compensation for the first adjustment signal according to inverter power output by the hybrid energy storage inverter, and obtaining a second adjustment signal; the frequency adjustment module is used for providing voltage frequency compensation for the second adjustment signal according to a battery current signal of the hybrid energy storage inverter, and obtaining an inverter voltage instantaneous value reference signal; the second control module is used for outputting an inverter current reference signal according to the inverter voltage instantaneous value reference signal and an inverter voltage instantaneous value; the third control module is used for outputting a third adjustment signal according to the inverter current reference signal and an inverter current instantaneous value, and combining a voltage feedforward signal of the inverter voltage instantaneous value reference signal provided by the inverter voltage feedforward module, so as to obtain a modulation signal used for generating a PWM waveform signal. It can be understood that the first control module can perform closed-loop adjustment based on the inverter voltage effective value, and ensure basic voltage stability; the inverter current feedforward module can dynamically adjust feedforward compensation according to a power direction, enhance energy absorption when flowing forward, optimize power supply stability when flowing backward, and significantly reduce bus voltage fluctuation; the frequency adjustment module can monitor the battery current in real time, and through frequency compensation, the frequency is increased to trigger micro-inversion power reduction when exceeding the limit, so as to avoid battery overload, and at the same time, the dynamic generation mechanism of the voltage instantaneous value reference signal is combined, so as to improve the response speed of the system to power mutation; based on the above modules, the hybrid energy storage inverter can still operate stably when micro-inversion power exceeds the limit, load mutates or light fluctuates, so as to eliminate the "hiccup" shutdown problem; through the introduction of direct closed-loop control of the battery current and adaptive compensation of the power direction, the robustness of the system in a complex energy flow scene is significantly enhanced, the battery life is prolonged, and the system stability is improved.

[0017] Additional features and advantages of the application will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of the application. The objectives and other advantages of the application will be realized and attained by the structure particularly pointed out in the description and claims. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings are included to provide a further understanding of the technical scheme of the application, and constitute a part of the specification, and are used to explain the technical scheme of the application together with the embodiments of the application, and do not constitute a limitation on the technical scheme of the application.

[0019] The application will be further described below with reference to the accompanying drawings and embodiments.

[0020] Figure 1 is a schematic diagram of a hybrid energy storage inverter provided by an embodiment of the application;

[0021] Figure 2 is a module schematic diagram of an AC coupling control system of a hybrid energy storage inverter provided by an embodiment of the application;

[0022] Figure 3 is a circuit schematic diagram of an AC coupling control system of a hybrid energy storage inverter provided by an embodiment of the application;

[0023] Figure 4 is a flowchart of an AC coupling control method of a hybrid energy storage inverter provided by an embodiment of the application. DETAILED DESCRIPTION

[0024] This part will describe the specific embodiments of the application in detail, and the preferred embodiments of the application are shown in the accompanying drawings, which serve to supplement the description in the text part of the specification and enable people to intuitively and visually understand each technical feature and the overall technical scheme of the application, but it cannot be understood as a limitation on the protection scope of the application.

[0025] In the description of the application, one or more is meant to be one or more, more than two is meant to be two or more, greater than, less than, more than, etc. are understood as not including the number, above, below, within, etc. are understood as including the number, "any one" means one or more, "at least one of the following" and similar expressions mean any combination of these items, including any combination of single or multiple items. If the first, second, etc. are described, they are only used to distinguish technical features for the purpose, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or implicitly indicating the sequence of indicated technical features.

[0026] It should be noted that the terms such as setting, installing and connecting in the embodiments of the application should be understood broadly, and the person skilled in the art can reasonably determine the specific meaning of the above terms in the embodiments of the application in combination with the specific content of the technical scheme. For example, the term "connection" can be mechanical connection, electrical connection or can communicate with each other; it can be directly connected or indirectly connected through an intermediate medium.

[0027] It should be noted that the technical features involved in each embodiment of the application described below can be combined with each other as long as there is no conflict between them.

[0028] The existing hybrid energy storage inverter often faces the problem of power mismatch in AC coupling applications, especially when the output power of the micro photovoltaic inverter exceeds the battery receiving capacity of the energy storage system, the system is prone to trigger the protection mechanism to cause frequent shutdown and restart; the traditional control strategy mainly depends on single loop regulation, such as voltage effective value PI control, but its dynamic response speed is insufficient, and it is difficult to cope with voltage instability caused by sudden changes in light or sharp fluctuations in load power; in addition, the existing technology also lacks direct closed-loop control of battery current, when the micro-inverter power suddenly increases or the load suddenly changes, the battery current may exceed the safety threshold, causing the bus voltage to rise, the system to shut down forcibly, and even equipment damage.

[0029] Based on this, the purpose of the present application is to at least solve one of the technical problems existing in the prior art, to dynamically adjust the feedforward compensation according to the power direction through the inverter current feedforward module, to reduce the bus voltage fluctuation, and to combine the frequency adjustment module to monitor the battery current in real time, to avoid battery overload through frequency compensation, to dynamically generate the voltage instantaneous value reference signal for control, and to improve the system stability.

[0030] The application scheme will be further described below with reference to the accompanying drawings.

[0031] Reference Figure 1 , Figure 1 is a schematic diagram of a hybrid energy storage inverter provided by an embodiment of the present application; wherein the battery (Bat) is an energy storage unit of the hybrid energy storage inverter, connected to the bus (Vbus) through a Buck-Boost topology; the Buck-Boost topology is a DC-DC converter used to adjust the battery voltage to match the bus voltage; the bus (Vbus) is a DC bus used to connect the battery and the inverter bridge, providing a DC voltage; the inverter bridge is used to convert DC to AC, which can include a one-letter three-level or T-shaped three-level, the input end of the inverter bridge is connected to the bus (Vbus), and the output end is connected to the load and the grid through the inductor L1 and the capacitor C2, the inductor L1 and the capacitor C2 are used to filter out the high-frequency harmonics of the inverter output, and the output is a smooth AC voltage; the load (Load) is a load port connected to the hybrid storage, which can be other electrical appliances; the grid (GridPort) is an output port of the inverter, used to output AC to the external grid or load; the inverter voltage instantaneous value (InvVoltReal) refers to the instantaneous value of the inverter output voltage, the inverter voltage effective value (InvVoltRms) refers to the effective value of the inverter output voltage, and the inverter current instantaneous value (InvCurrReal) refers to the instantaneous value of the inverter output current, which are collected from the output end of the inverter bridge for feedback of the control loop; the battery current (Ibat) refers to the charging and discharging current of the battery, which is collected from the output end of the battery for feedback of the control loop.

[0032] It can be understood that the AC coupling control system in the application can be connected with the hybrid energy storage inverter through a sampling interface to sample various signals and connected with the hybrid energy storage inverter through a control interface to modulate the hybrid energy storage inverter.

[0033] Reference Figure 2 , Figure 2 is a module schematic diagram of an AC coupling control system of a hybrid energy storage inverter provided by an embodiment of the application; in a first aspect, the application provides an AC coupling control system of a hybrid energy storage inverter, which comprises: first control module, inverter current feedforward module, frequency adjustment module, second control module, third control module and inverter voltage feedforward module connected in sequence; wherein the first control module is connected with an inverter voltage output end of the hybrid energy storage inverter, and is used for outputting a first adjustment signal according to a difference signal of an inverter voltage reference signal and an inverter voltage effective value; the inverter current feedforward module is used for providing current feedforward compensation for the first adjustment signal according to inverter power output by the hybrid energy storage inverter to obtain a second adjustment signal; the frequency adjustment module is used for providing voltage frequency compensation for the second adjustment signal according to a battery current signal of the hybrid energy storage inverter to obtain an inverter voltage instantaneous value reference signal; the second control module is used for outputting an inverter current reference signal according to the inverter voltage instantaneous value reference signal and an inverter voltage instantaneous value; the third control module is used for outputting a third adjustment signal according to the inverter current reference signal and an inverter current instantaneous value, and combining a voltage feedforward signal of the inverter voltage instantaneous value reference signal provided by the inverter voltage feedforward module, so as to obtain a modulation signal used for generating a PWM waveform signal according to the third adjustment signal.

[0034] It can be understood that the first control module can perform closed-loop adjustment based on the inverter voltage effective value to ensure the stability of the basic voltage; the inverter current feedforward module can dynamically adjust the feedforward compensation according to the power direction to enhance energy absorption when flowing forward and optimize power supply stability when flowing backward, thereby significantly reducing bus voltage fluctuation; the frequency adjustment module can monitor the battery current in real time, and through frequency compensation, the frequency is increased to trigger micro-inversion power reduction when exceeding the limit to avoid battery overload, and at the same time, the dynamic generation mechanism of the voltage instantaneous value reference signal is combined to improve the response speed of the system to power mutation, so that the second control module and the third control module obtain the modulation signal under the voltage feedforward compensation of the inverter voltage feedforward module, realize AC coupling control of the hybrid energy storage inverter, and thereby improve the system stability. Based on the above modules, the application can still operate stably when the micro-inversion power exceeds the limit, the load mutates or the light fluctuates, so as to eliminate the "hiccup" shutdown problem, and through the introduction of direct closed-loop control of the battery current and adaptive compensation of the power direction, the robustness of the system in complex energy flow scenarios is significantly enhanced, the battery life is prolonged, and thereby the system stability is improved.

[0035] In some embodiments, the first control module comprises an inverter voltage effective value PI loop, the inverter voltage effective value PI loop is used for outputting a first PI loop signal based on the output limit of ±1 according to the difference signal, the first PI loop signal and the inverter voltage reference signal are added to obtain the first adjustment signal.

[0036] It can be understood that the first control module is connected with the inverter voltage output end of the hybrid energy storage inverter, and is used for outputting the first adjustment signal according to the difference signal between the inverter voltage reference signal and the inverter voltage effective value. The module is realized by the inverter voltage effective value PI loop, and can output the first PI loop signal based on the output limit of ±1 according to the difference signal, the signal is added to the inverter voltage reference signal to obtain the first adjustment signal. The function of the first control module is to ensure that the output voltage of the inverter is close to the reference value, and to provide a basic signal for the subsequent control module.

[0037] In some embodiments, specifically, the core of the first control module is the inverter voltage effective value PI loop, the proportional coefficient is set to 1.5, the integral coefficient is 0.03, and the output limit is ±1. This parameter combination can quickly respond when the voltage effective value deviates from the reference value, while avoiding the overshoot problem caused by integral accumulation; for example, when the inverter voltage effective value decreases due to sudden load increase, the proportional coefficient 1.5 can rapidly amplify the error signal to drive the output adjustment; the integral coefficient 0.03 gradually eliminates the steady-state error to ensure that the voltage returns to the set value. The first adjustment signal is obtained by superimposing the PI loop output and the reference voltage, which not only retains the stability of the reference voltage, but also incorporates dynamic correction.

[0038] In some embodiments, the inverter current feedforward module is used for outputting 80% of the inverter current effective value as positive feedforward compensation when the inverter power is greater than 0; and outputting 80% of the inverter current effective value as negative feedforward compensation when the inverter power is less than 0; wherein it can be understood that the inverter current feedforward module further comprises a power direction judgment module, the power direction judgment module is used for detecting the power flow direction, and outputting the feedforward signal polarity as +1 when the power flows from the micro photovoltaic inverter to the hybrid energy storage inverter; and outputting the feedforward signal polarity as -1 when the power flows from the hybrid energy storage inverter to the load.

[0039] It can be understood that the inverter current feedforward module receives the first adjustment signal and provides current feedforward compensation for the first adjustment signal according to the inverter power output by the hybrid energy storage inverter to obtain the second adjustment signal. The module can dynamically adjust the feedforward compensation according to the direction of the inverter power. When the inverter power is greater than 0, 80% of the inverter current effective value is output as positive feedforward compensation; and when the inverter power is less than 0, 80% of the inverter current effective value is output as negative feedforward compensation. The function of the inverter current feedforward module is to reduce the bus voltage fluctuation and improve the dynamic response and stability of the system.

[0040] It can be understood that, in the above-mentioned inverter current feedforward module, when the inverter power is greater than zero (micro-inverted hybrid storage power supply), the module outputs 80% of the effective value of the inverter current as a forward feedforward compensation to accelerate energy absorption; when the inverter power is less than zero (hybrid storage supplies power to the load), 80% of the effective value of the output current is output as a negative compensation to suppress voltage drop; through adaptive judgment of the power direction, the energy flow path is optimized, for example, in the scene of sudden increase of micro-inverted power caused by sudden change of light, the forward compensation can quickly offset the trend of bus voltage rise; and when the hybrid storage discharges due to sudden increase of load, the negative compensation can effectively prevent voltage sag, and the compensation ratio of 80% instead of full compensation ensures the response speed and avoids the risk of oscillation caused by over-compensation.

[0041] In some embodiments, the frequency adjustment module includes a voltage frequency PI loop, which is used to perform voltage frequency compensation on the reference voltage frequency of the hybrid energy storage inverter when the battery current signal is greater than the maximum allowed current by comparing the battery current signal with the preset maximum allowed current, and the output range of the voltage frequency compensation is 0Hz to 5Hz, and the reference voltage frequency is 50Hz.

[0042] It can be understood that the frequency adjustment module receives a second adjustment signal and provides voltage frequency compensation for the second adjustment signal according to the battery current signal of the hybrid energy storage inverter to obtain an inverter voltage instantaneous value reference signal, which is realized by a voltage frequency PI loop, can perform voltage frequency compensation on the reference voltage frequency when the battery current signal is greater than the maximum allowed current by comparing the battery current signal with the preset maximum allowed current, and the compensation range is 0Hz to 5Hz, and the reference voltage frequency is 50Hz. The function of the frequency adjustment module is to avoid battery overload, dynamically generate an inverter voltage instantaneous value reference signal, and improve the stability of the system.

[0043] In some embodiments, the frequency adjustment module further includes a battery current detection module for real-time acquisition of the battery charge and discharge current of the hybrid energy storage inverter and conversion into a battery current signal, and the frequency adjustment module further includes a voltage frequency PI loop, the input end of which is connected to the current feedback signal, and the output end generates a frequency adjustment signal; the output range of the frequency adjustment signal is 50Hz to 55Hz, and the frequency adjustment step is 0.1Hz.

[0044] The voltage frequency PI loop of the frequency adjustment module takes the battery current as the control object, the proportional coefficient can be set to 0.8, the integral coefficient is 0.02, the output amplitude limiting is 0-5Hz, when it is detected that the battery current exceeds the preset maximum allowable value (such as 120% of the rated current of the battery), the PI loop outputs the frequency compensation value, and the reference frequency is proportionally increased from 50Hz to a maximum of 55Hz. For example, if the battery current is over-limit by 20%, the frequency compensation value can reach 2Hz, and the inverter voltage frequency is increased to 52Hz. After the micro-inversion sensing frequency is increased, the over-frequency derating function is automatically started, and the output power is proportionally reduced (such as 10% per 1Hz increase), thereby reducing the input power to the battery and achieving smooth transition when the power is over-limit.

[0045] In some embodiments, the system further comprises a first calculation unit; in the process of providing voltage frequency compensation for the second adjustment signal to obtain the inverter voltage instantaneous value reference signal, the first calculation unit is used to perform the following calculation formula:

[0046]

[0047] Wherein, InvVoltRealRef is the inverter voltage instantaneous value reference signal, S is the second adjustment signal, f base is the reference voltage frequency, and Δf is the voltage frequency compensation.

[0048] In some embodiments, the second control module comprises an inverter voltage instantaneous value PI loop, and the inverter voltage instantaneous value PI loop is used to output a second PI loop signal according to the difference between the inverter voltage instantaneous value reference signal and the inverter voltage instantaneous value based on the output amplitude limiting of ±1, and the second PI loop signal is the inverter current reference signal.

[0049] It can be understood that the second control module receives the inverter voltage instantaneous value reference signal and the voltage feedforward signal of the inverter voltage instantaneous value reference signal provided by the inverter voltage feedforward module, and outputs the inverter current reference signal. This module is realized by the inverter voltage instantaneous value PI loop, and can output a second PI loop signal according to the difference between the inverter voltage instantaneous value reference signal and the inverter voltage instantaneous value based on the output amplitude limiting of ±1, and the second PI loop signal is the inverter current reference signal. The function of the second control module is to ensure that the output current of the inverter meets the expectation and improve the dynamic response and stability of the system.

[0050] The PI loop of the second control module can adopt a high proportional coefficient (2.0) and a medium integral coefficient (0.1), and the output amplitude is limited to ±1. The high proportional coefficient ensures the rapid suppression of voltage transient fluctuations, for example, when the load suddenly changes and causes the voltage to drop, the controller can quickly output a compensation signal. The integral coefficient 0.1 takes into account the steady-state accuracy and avoids high-frequency noise interference. The module combines the instantaneous value reference signal generated by the frequency adjustment module with the feedforward voltage signal to output the inverter current reference value, providing an accurate target for downstream control.

[0051] In some embodiments, the third control module includes an inverter current instantaneous value PI loop, which is used to output a third PI loop signal based on an output amplitude of ±0.3 according to the difference between the inverter current reference signal and the inverter current instantaneous value. The third PI loop signal and the voltage feedforward signal of the inverter voltage instantaneous value reference signal provided by the inverter voltage feedforward module are added to obtain a third adjustment signal.

[0052] It can be understood that the third control module receives the inverter current reference signal and the inverter current instantaneous value, and combines the voltage feedforward signal of the inverter voltage instantaneous value reference signal provided by the inverter voltage feedforward module to output the third adjustment signal. This module is implemented through the inverter current instantaneous value PI loop, which can output a third PI loop signal based on an output amplitude of ±0.3 according to the difference between the inverter current reference signal and the inverter current instantaneous value. The signal is added to the voltage feedforward signal to obtain a third adjustment signal. The function of the third control module is to further adjust the output voltage of the inverter to ensure that it is within a reasonable range, improving the stability and dynamic response of the system.

[0053] The PI loop parameters of the third control module can adopt more targeted numbers, for example, the proportional coefficient is set to 2.5, the integral coefficient is 0.15, and the output amplitude is ±0.3. A higher proportional coefficient can quickly track changes in the current reference value, for example, when the micro-inverter power suddenly drops, the controller can adjust the current output within milliseconds. A narrower output amplitude prevents current overshoot from impacting the inverter bridge. The third adjustment signal is generated by adding the PI output and the feedforward voltage to generate the final modulation signal, which is normalized by the bus voltage to generate a PWM waveform, for example, when the bus voltage is 400V, the modulation signal is scaled in proportion to ensure the accuracy of the PWM duty cycle under different bus voltages.

[0054] In some embodiments, the inverter voltage feedforward module provides a voltage feedforward signal to improve the dynamic response and stability of the system. This module can provide feedforward compensation based on the inverter voltage instantaneous value to reduce errors and improve the response speed and stability of the system. The function of the inverter voltage feedforward module is to assist the control module to ensure that the output voltage and current of the inverter meet the expectations.

[0055] In some embodiments, the system further comprises a second calculation unit; in the process of obtaining a modulation signal for generating a PWM waveform signal according to the third adjustment signal, the second calculation unit is configured to perform the following calculation: modulation signal = third adjustment signal * (1 / Ubus); wherein Ubus is the bus voltage of the hybrid energy storage inverter.

[0056] In some embodiments, the system further comprises a sampling terminal for obtaining the inverter voltage instantaneous value signal, the inverter current instantaneous value signal and the inverter current effective value; the system is connected to the DC bus of the hybrid energy storage inverter through the sampling terminal.

[0057] It can be understood that the system obtains the inverter voltage instantaneous value, current instantaneous value and effective value signals in real time through the sampling terminal, and is directly connected to the DC bus; the sampling terminal can adopt a Hall sensor, ensuring that the control loop responds to the fast-changing power state in real time, so that in complex working conditions (such as cloudy weather leading to frequent fluctuations in photovoltaic power), the multi-module in the application can work cooperatively, the voltage effective value loop maintains basic stability, the current feedforward compensation offsets the directional disturbance, the frequency adjustment module realizes battery protection, the instantaneous value loop quickly tracks dynamic changes, and finally the system maintains a voltage deviation of less than 2% within a power fluctuation range of ±20%, completely eliminating the "hiccup" shutdown problem.

[0058] In summary, the application converts the traditional protection mechanism into active adjustment through the linkage design of the battery current closed loop and the frequency compensation, prolongs the service life of the equipment; further, the power direction adaptive feedforward strategy can be used to optimize the polarity of the energy flow path and improve the dynamic performance; further, the multi-level PI parameter fine configuration can be used to balance the response speed and stability. For example, the medium integral coefficient of the first control module prevents the voltage loop from being saturated, and the high proportional coefficient of the third control module ensures the current tracking accuracy, so as to improve the system stability and system performance.

[0059] Reference Figure 3 , Figure 3 is a circuit schematic diagram of an AC coupling control system of a hybrid energy storage inverter provided by an embodiment of the application; in some embodiments, as Figure 3As shown, InvVoltRmsRef is the inverse voltage reference signal, InvVoltRms is the inverse voltage effective value, InvCurrRms is the inverse current effective value, Pinv is the inverse power, InvCurrRms*0.8 represents 80% of the inverse current effective value (forward feed-forward compensation), and InvCurrRms-0.8* represents 80% of the inverse current effective value (negative feed-forward compensation); in the frequency adjustment module, Ibat represents the battery current signal, Ibat_Max represents the preset maximum allowed current, and a PI loop can also be provided in the frequency adjustment module, which can, when the battery current signal is greater than the maximum allowed current, perform voltage frequency compensation on the reference voltage frequency of the hybrid energy storage inverter, the output range of the voltage frequency compensation is 0Hz to 5Hz, Δf is the voltage frequency compensation, fbase is the reference voltage frequency (50Hz), and "1.414" is an approximate value of InvVoltRealRef is the inverse voltage instantaneous value reference signal.

[0060] Further, the input end of the inverse voltage instantaneous value PI loop and the output end of the inverse current instantaneous value PI loop are both connected with a given feed-forward of the inverse voltage instantaneous value reference signal, that is, an inverse voltage feed-forward module for providing a voltage feed-forward signal of the inverse voltage instantaneous value reference signal; InvVoltRealRef represents the inverse voltage instantaneous value reference signal, InvVoltReal represents the inverse voltage instantaneous value, InvCurrRef represents the inverse current reference signal, InvCurrReal represents the inverse current instantaneous value, and 1 / Ubus represents the inverse of the bus voltage.

[0061] It can be understood that the specific explanations of the signals are as follows:

[0062] Inverse voltage reference signal (InvVoltRmsRef): the inverse voltage reference signal of the inverter, that is, the expected inverse voltage effective value, which is used to compare with the actual inverse voltage effective value to generate an error signal, and then adjust the output voltage of the inverter;

[0063] Inverse voltage effective value (InvVoltRms): the actual effective value of the inverter output voltage, which is used to compare with the inverse voltage reference signal to generate an error signal, and is used to control the output voltage of the inverter;

[0064] Inverse current effective value (InvCurrRms): the actual effective value of the inverter output current, which is used to calculate the inverse power and provide feed-forward compensation according to the power direction;

[0065] Inverse power (Pinv): the output power of the inverter, which is used to determine the power direction and decide the positive and negative directions of the feed-forward compensation;

[0066] Battery current signal (Ibat): the charging and discharging current of the battery, used to monitor the charging and discharging state of the battery, avoid overcurrent or undercurrent, and ensure the safety of the battery;

[0067] Voltage frequency compensation (Δf): the compensation value of the reference voltage frequency, used to compensate the reference voltage frequency when the battery current exceeds the preset maximum allowed current, to avoid battery overload;

[0068] Reference voltage frequency (fbase): the reference voltage frequency of the inverter, usually 50Hz, used as the reference value for frequency compensation to ensure the stability of the output frequency of the inverter;

[0069] Inverter voltage instantaneous value reference signal (InvVoltRealRef): the instantaneous value reference signal of the inverter output voltage; used to compare with the actual inverter voltage instantaneous value to generate an error signal, and then adjust the output voltage of the inverter;

[0070] Inverter voltage instantaneous value (InvVoltReal): the actual instantaneous value of the inverter output voltage, used to compare with the inverter voltage instantaneous value reference signal to generate an error signal, used to control the output voltage of the inverter;

[0071] Inverter current reference signal (InvCurrRef): the reference signal of the inverter output current, used to compare with the actual inverter current instantaneous value to generate an error signal, and then adjust the output current of the inverter;

[0072] Inverter current instantaneous value (InvCurrReal): the actual instantaneous value of the inverter output current, used to compare with the inverter current reference signal to generate an error signal, used to control the output current of the inverter;

[0073] Bus voltage (Ubus): the DC bus voltage of the inverter, used to calculate the voltage modulation signal to ensure that the output voltage of the inverter is within a reasonable range;

[0074] Voltage feedforward signal, a voltage feedforward signal used to improve the dynamic response and stability of the system, providing feedforward compensation in the control loop, reducing error, and improving the response speed and stability of the system;

[0075] Modulation signal, a modulation signal used to generate a PWM waveform signal, the switching devices of the inverter are controlled by the modulation signal to achieve precise control of the inverter output voltage.

[0076] Reference Figure 4 , Figure 4is a flow chart of an AC coupling control method of a hybrid energy storage inverter provided by an embodiment of the present application; in a second aspect, the present application provides an AC coupling control method of a hybrid energy storage inverter, the method being applied to an AC coupling control system of the hybrid energy storage inverter as in any one of the first aspect, and the method comprising the following steps:

[0077] In step S410, a first adjustment signal is output by the first control module according to the difference signal between the inverter voltage reference signal and the inverter voltage effective value;

[0078] In step S420, a current feedforward compensation is provided for the first adjustment signal by the inverter current feedforward module according to the power flow direction of the AC coupling, to obtain a second adjustment signal; a voltage frequency compensation is provided for the second adjustment signal by the frequency adjustment module according to the battery current signal of the hybrid energy storage inverter, to obtain the inverter voltage instantaneous value reference signal;

[0079] In step S430, an inverter current reference signal is output by the second control module according to the inverter voltage instantaneous value reference signal and the inverter voltage instantaneous value;

[0080] In step S440, a third adjustment signal is output by the third control module according to the inverter current reference signal and the inverter current instantaneous value, and in combination with the voltage feedforward signal of the inverter voltage instantaneous value reference signal provided by the inverter voltage feedforward module, to obtain a modulation signal for generating a PWM waveform signal according to the third adjustment signal.

[0081] It can be understood that the first control module generates the first adjustment signal by comparing the inverter voltage reference signal and the inverter voltage effective value, which can be used to preliminarily adjust the output voltage of the inverter to ensure that it is close to the reference value; the inverter current feedforward module provides the current feedforward compensation for the first adjustment signal according to the direction of the inverter power; the frequency adjustment module provides the voltage frequency compensation for the second adjustment signal according to the battery current signal, to ensure the stability of the output frequency of the inverter; the second control module generates the inverter current reference signal according to the inverter voltage instantaneous value reference signal and the voltage feedforward signal. The signal can be used to adjust the output current of the inverter to ensure that it meets the expectation; the third control module generates the third adjustment signal according to the inverter current reference signal and the inverter current instantaneous value. The signal can be added to the voltage feedforward signal to generate a modulation signal for generating a PWM waveform signal, which can be used to control the switching device of the inverter to realize accurate control of the output voltage of the inverter, so as to improve the.

[0082] The embodiments of the present application are described in detail above in combination with the drawings, but the present application is not limited to the above-described embodiments, and various changes can be made within the knowledge range of ordinary skilled in the art without departing from the purpose of the present application.

Claims

1. An AC coupling control system for a hybrid energy storage inverter, the system comprising: The system comprises a first control module, an inverter current feedforward module, a frequency adjustment module, a second control module, a third control module and an inverter voltage feedforward module connected in sequence, wherein The first control module is connected with an inverter voltage output end of the hybrid energy storage inverter, and is configured to output a first adjustment signal according to a difference signal of an inverter voltage reference signal and an inverter voltage effective value; The inverter current feedforward module is configured to provide current feedforward compensation for the first adjustment signal according to inverter power output by the hybrid energy storage inverter, to obtain a second adjustment signal; The frequency adjustment module is configured to provide voltage frequency compensation for the second adjustment signal according to a battery current signal of the hybrid energy storage inverter, to obtain an inverter voltage instantaneous value reference signal; The second control module is configured to output an inverter current reference signal according to the inverter voltage instantaneous value reference signal and an inverter voltage instantaneous value; The third control module is configured to output a third adjustment signal according to the inverter current reference signal and an inverter current instantaneous value, and in combination with a voltage feedforward signal of the inverter voltage instantaneous value reference signal provided by the inverter voltage feedforward module, to obtain a modulation signal for generating a PWM waveform signal according to the third adjustment signal.

2. The AC coupling control system of a hybrid energy storage inverter according to claim 1, wherein, The first control module comprises an inverter voltage effective value PI loop, which is configured to output a first PI loop signal according to the difference signal based on ±1 output limiting, and the first PI loop signal and the inverter voltage reference signal are added to obtain the first adjustment signal.

3. The AC coupling control system of a hybrid energy storage inverter according to claim 2, wherein, The inverter current feedforward module is configured to output 80% of the inverter current effective value as positive feedforward compensation when the inverter power is greater than 0, and output 80% of the inverter current effective value as negative feedforward compensation when the inverter power is less than 0.

4. The AC coupling control system of a hybrid energy storage inverter according to claim 3, wherein, The frequency adjustment module comprises a voltage frequency PI loop, which is configured to perform voltage frequency compensation on a reference voltage frequency of the hybrid energy storage inverter when the battery current signal is greater than a preset maximum allowable current by comparing the battery current signal with the maximum allowable current, and the output range of the voltage frequency compensation is 0Hz to 5Hz, and the reference voltage frequency is 50Hz.

5. The AC coupling control system of a hybrid energy storage inverter according to claim 4, wherein, The system further comprises a first calculation unit, and in the process of providing voltage frequency compensation for the second adjustment signal to obtain the inverter voltage instantaneous value reference signal, the first calculation unit is configured to perform the following calculation formula: Wherein, InvVoltRealRef is the inverse voltage transient value reference signal, S is the second adjustment signal, f base is the reference voltage frequency, and Δf is the voltage frequency compensation.

6. The AC coupling control system of a hybrid energy storage inverter of claim 1, wherein, The second control module comprises an inverter voltage instantaneous value PI loop, which is configured to output a second PI loop signal according to the inverter voltage instantaneous value reference signal and an inverter voltage instantaneous value based on ±1 output limiting, and the second PI loop signal is an inverter current reference signal.

7. The AC coupling control system of a hybrid energy storage inverter of claim 1, wherein, The third control module includes an inverter current instantaneous value PI loop, which is used for output limiting based on ±0.

3. The third PI loop signal is output according to the difference between the inverter current reference signal and the inverter current instantaneous value. The third PI loop signal is added to the voltage feedforward signal of the inverter voltage instantaneous value reference signal provided by the inverter voltage feedforward module to obtain the third adjustment signal.

8. The AC coupling control system of a hybrid energy storage inverter of claim 1, wherein, The system further includes a second calculation unit; during the process of obtaining the modulation signal for generating the PWM waveform signal based on the third adjustment signal, the second calculation unit performs the following calculation: The modulation signal = the third adjustment signal * (1 / Ubus); Wherein, Ubus is the bus voltage of the hybrid energy storage inverter.

9. The AC coupling control system of a hybrid energy storage inverter of any one of claims 1 to 8, wherein, The system also includes a sampling terminal for acquiring the instantaneous value signal of inverter voltage, the instantaneous value signal of inverter current, and the effective value of inverter current. The system is connected to the DC bus of the hybrid energy storage inverter through the sampling terminal.

10. An AC coupling control method of a hybrid energy storage inverter, characterized by, The method is applied to the AC coupling control system of the hybrid energy storage inverter as described in any one of claims 1 to 9, and the method includes: The first control module outputs a first adjustment signal based on the difference signal between the inverter voltage reference signal and the effective value of the inverter voltage. The inverter current feedforward module provides current feedforward compensation for the first adjustment signal based on the power flow direction of AC coupling, thereby obtaining the second adjustment signal; The frequency adjustment module provides voltage frequency compensation to the second adjustment signal based on the battery current signal of the hybrid energy storage inverter, thereby obtaining a reference signal for the instantaneous value of the inverter voltage. The second control module outputs an inverter current reference signal based on the inverter voltage instantaneous value reference signal and the inverter voltage instantaneous value. The third control module outputs a third adjustment signal based on the inverter current reference signal and the instantaneous value of the inverter current, combined with the voltage feedforward signal of the instantaneous value reference signal of the inverter voltage provided by the inverter voltage feedforward module, so as to obtain a modulation signal for generating a PWM waveform signal based on the third adjustment signal.

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