Optical storage system and control method thereof

Abstract

The invention discloses an optical storage system and a control method thereof, the optical storage system comprises a photovoltaic string, an energy storage unit and a load device, the photovoltaic string is connected to a DC bus through a photovoltaic DC / DC circuit, the energy storage unit is connected to the DC bus through an energy storage DC / DC circuit, and the load device and a power grid are connected to the DC bus through a DC / AC circuit; the photovoltaic DC / DC circuit, the energy storage DC / DC circuit and the DC / AC circuit are used for detecting the bus voltage of the DC bus and adjusting the working state of the photovoltaic DC / DC circuit, the energy storage DC / DC circuit and the DC / AC circuit according to the voltage interval of the bus voltage; wherein the voltage interval is set according to a voltage reference value and represents the energy balance state of the optical storage system under the current bus voltage; according to the invention, energy output or input can be automatically triggered and adjusted without depending on a communication system of the optical storage system, so that the energy balance state in the optical storage system is further influenced, and stable control of the bus voltage is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical storage system application, and in particular to an optical storage system and a control method thereof. BACKGROUND

[0002] In the optical storage system, photovoltaic strings are connected to a DC bus through a photovoltaic DC / DC circuit, energy storage modules are connected to the DC bus through an energy storage DC / DC circuit, and a power grid and a load device are connected to the DC bus through a DC / AC circuit. Therefore, the bus voltage of the DC bus can reflect the energy balance state of the optical storage system. Only when the energy flowing into and out of the DC bus is equal, the bus voltage can be stable.

[0003] When the optical storage system is running, the energy consumed or released by each part of the power unit in the system is not a fixed value. Therefore, it is necessary to reasonably control each part of the power unit through the DC bus voltage signal to make the energy in the system as balanced as possible and maintain the stability of the bus voltage. Currently, the working state of the photovoltaic DC / DC circuit, the energy storage DC / DC circuit and the DC / AC circuit is adjusted through communication to regulate the energy flow, thereby maintaining the stability of the bus voltage. However, this method depends on the reliability and speed of communication, and is prone to large fluctuations in the bus voltage under dynamic conditions, or even loss of control. SUMMARY

[0004] The embodiment provides an optical storage system and a control method thereof, which can stabilize the bus voltage without relying on communication.

[0005] In a first aspect, the embodiment of the present application provides an optical storage system, comprising photovoltaic strings, an energy storage unit and a load device, wherein the photovoltaic strings are connected to a DC bus through a photovoltaic DC / DC circuit, the energy storage unit is connected to the DC bus through an energy storage DC / DC circuit, and the load device and a power grid are connected to the DC bus through a DC / AC circuit.

[0006] The photovoltaic DC / DC circuit, the energy storage DC / DC circuit and the DC / AC circuit are all used to detect the bus voltage of the DC bus, and adjust the working state thereof according to the voltage interval in which the bus voltage is located.

[0007] The voltage interval is set according to a voltage reference value, and represents the energy balance state of the optical storage system under the current bus voltage.

[0008] In some embodiments, the optical storage system is provided with a plurality of voltage intervals, and the upper limit value and the lower limit value of each voltage interval are obtained by adjusting the voltage reference value.

[0009] In some embodiments, the voltage interval includes a first voltage interval, a second voltage interval, a third voltage interval, a fourth voltage interval, and a fifth voltage interval.

[0010] The first voltage interval ranges from Udcr-ΔUdc to Udcr+ΔUdc;

[0011] The second voltage interval ranges from Udcr+ΔUdc to Udcr+2ΔUdc;

[0012] The third voltage interval ranges from greater than Udcr+2ΔUdc;

[0013] The fourth voltage interval ranges from Udcr-2ΔUdc to Udcr-ΔUdc;

[0014] The fifth voltage interval ranges from less than Udcr-2ΔUdc;

[0015] Wherein, Udcr is the voltage reference value, and ΔUdc is a voltage adjustment value.

[0016] In some embodiments, the optical storage system includes a double closed-loop space vector pulse amplitude modulation circuit, which includes a transformation module, a voltage outer loop module, a current inner loop module, and a control module. The transformation module is connected to the AC output end of the DC / AC circuit, and is used to perform coordinate conversion on the collected AC signal of the DC / AC circuit. The voltage outer loop module is connected to the DC bus, and is used to obtain a d-axis current given value through PI control according to the bus voltage and the bus voltage given value. The current inner loop module is connected to the output end of the voltage outer loop module and the output end of the transformation module, and is used to obtain a d-axis voltage control signal through PI control according to the d-axis AC current output by the transformation module and the d-axis current given value, and to obtain a q-axis voltage control signal through PI control according to the q-axis AC current output by the transformation module and the q-axis current given value. The control module is connected to the output end of the current inner loop module, and is used to obtain a compensation amount of the operating parameter of the DC / AC circuit according to the d-axis voltage control signal and the q-axis voltage control signal, so as to adjust the output power of the DC / AC circuit.

[0017] In a second aspect, the embodiments of the present application also provide a control method of an optical storage system, applied to the optical storage system of the first aspect, and the control method includes:

[0018] The photovoltaic DC / DC circuit, the energy storage DC / DC circuit, and the DC / AC circuit acquire a bus voltage of the DC bus;

[0019] The photovoltaic DC / DC circuit, the energy storage DC / DC circuit, and the DC / AC circuit adjust their operating states according to the voltage range in which the bus voltage is located.

[0020] The voltage range is set according to the voltage reference value and represents the energy balance state of the photovoltaic energy storage system under the current bus voltage.

[0021] In some embodiments, when the bus voltage is within a first voltage range, the photovoltaic DC / DC circuit, the energy storage DC / DC circuit, and the DC / AC circuit adjust their operating states according to the voltage range in which the bus voltage is located, including:

[0022] The DC / AC circuit operates in inverter mode, and adjusts its output power according to the compensation amount output by the dual closed-loop space vector pulse amplitude modulation circuit so that the bus voltage is maintained within the first voltage range.

[0023] The photovoltaic DC / DC circuit operates in maximum power point tracking mode;

[0024] The energy storage DC / DC circuit adjusts its operating mode according to the power of the energy storage unit;

[0025] The first voltage range is from Udcr-ΔUdc to Udcr+ΔUdc, where Udcr is the voltage reference value and ΔUdc is the voltage adjustment value.

[0026] In some embodiments, when the bus voltage is in a second voltage range, the photovoltaic DC / DC circuit, the energy storage DC / DC circuit, and the DC / AC circuit adjust their operating states according to the voltage range in which the bus voltage is located, including:

[0027] The DC / AC circuit operates in inverter mode;

[0028] The photovoltaic DC / DC circuit operates in maximum power point tracking mode;

[0029] The energy storage DC / DC circuit determines the current power level of the energy storage unit, and operates in charging mode when the power level of the energy storage unit is less than the upper limit of the rechargeable power level.

[0030] The second voltage range is from Udcr+ΔUdc to Udcr+2ΔUdc, where Udcr is the voltage reference value and ΔUdc is the voltage adjustment value.

[0031] In some embodiments, when the bus voltage is in a third voltage range, the photovoltaic DC / DC circuit, the energy storage DC / DC circuit, and the DC / AC circuit adjust their operating states according to the voltage range in which the bus voltage is located, including:

[0032] The DC / AC circuit operates in inverter mode;

[0033] The photovoltaic DC / DC circuit reduces the output power;

[0034] The energy storage DC / DC circuit determines the current power level of the energy storage unit, and operates in charging mode when the power level of the energy storage unit is less than the upper limit of the rechargeable power level.

[0035] The third voltage range is greater than Udcr + 2ΔUdc, where Udcr is the voltage reference value and ΔUdc is the voltage adjustment value.

[0036] In some embodiments, after the energy storage DC / DC circuit determines the current charge of the energy storage unit, the control method further includes:

[0037] If the energy storage unit's charge exceeds the maximum rechargeable capacity, the energy storage DC / DC circuit stops charging the energy storage unit.

[0038] In some embodiments, when the bus voltage is in a fourth voltage range, the photovoltaic DC / DC circuit, the energy storage DC / DC circuit, and the DC / AC circuit adjust their operating states according to the voltage range in which the bus voltage is located, including:

[0039] The DC / AC circuit operates in rectification mode;

[0040] The photovoltaic DC / DC circuit operates in maximum power point tracking mode;

[0041] The energy storage DC / DC circuit determines the current power of the energy storage unit, and operates in discharge mode when the power of the energy storage unit is greater than the lower discharge limit.

[0042] The fourth voltage range is from Udcr-2ΔUdc to Udcr-ΔUdc, where Udcr is the voltage reference value and ΔUdc is the voltage adjustment value.

[0043] In some embodiments, when the bus voltage is in the fifth voltage range, the photovoltaic DC / DC circuit, the energy storage DC / DC circuit, and the DC / AC circuit adjust their operating states according to the voltage range in which the bus voltage is located, including:

[0044] The DC / AC circuit operates in rectification mode and stops the voltage supply to at least a portion of the load devices;

[0045] The photovoltaic DC / DC circuit operates in maximum power point tracking mode;

[0046] The energy storage DC / DC circuit determines the current power of the energy storage unit, and operates in discharge mode when the power of the energy storage unit is greater than the lower discharge limit.

[0047] The fifth voltage range is less than Udcr-2ΔUdc, where Udcr is the voltage reference value and ΔUdc is the voltage adjustment value.

[0048] In some embodiments, the DC / AC circuit stops the voltage supply to at least a portion of the load devices, including:

[0049] The DC / AC circuit acquires the priority of the load device;

[0050] The DC / AC circuit stops the voltage supply to the load device in order of priority from low to high.

[0051] In some embodiments, after the energy storage DC / DC circuit determines the current charge of the energy storage unit, the control method further includes:

[0052] When the energy storage unit's charge is less than the lower limit of its discharge capacity, the energy storage DC / DC circuit stops discharging the energy storage unit.

[0053] The photovoltaic-storage system and its control method in this embodiment have at least the following beneficial effects: the photovoltaic DC / DC circuit, energy storage DC / DC circuit, and DC / AC circuit in the photovoltaic-storage system can all independently detect the bus voltage and determine the voltage range of the bus voltage based on its magnitude. They then adjust their own operating states accordingly based on the voltage range. Since the bus voltage reflects the energy balance state in the photovoltaic-storage system, the photovoltaic DC / DC circuit, energy storage DC / DC circuit, and DC / AC circuit automatically adjust their operating states based on the voltage range of the bus voltage. This allows them to trigger adjustments to energy output or input independently without relying on the communication system of the photovoltaic-storage system, thereby affecting the energy balance state in the photovoltaic-storage system and achieving stable control of the bus voltage.

[0054] Other features and advantages of this application will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the description, claims and drawings. Attached Figure Description

[0055] Figure 1 This is a structural framework diagram of a photovoltaic energy storage system provided in an embodiment of this application;

[0056] Figure 2 This is a schematic diagram of five control modes of a photovoltaic energy storage system provided in an embodiment of this application;

[0057] Figure 3 This is a voltage control block diagram of a dual closed-loop space vector pulse amplitude modulation circuit for bus voltage in a first voltage range, provided in an embodiment of this application.

[0058] Figure 4 This is a schematic flowchart of a control method for a photovoltaic energy storage system provided in an embodiment of this application;

[0059] Figure 5 This is a flowchart illustrating a method for controlling the bus voltage to be in a first range, as provided in an embodiment of this application.

[0060] Figure 6 This is a flowchart illustrating a method for controlling the bus voltage in a second range according to an embodiment of this application.

[0061] Figure 7 This is a flowchart illustrating a method for controlling the bus voltage in a third interval, as provided in an embodiment of this application.

[0062] Figure 8 This is a flowchart illustrating a control method for controlling the energy storage unit's charge level when the bus voltage is in the second or third range, as provided in an embodiment of this application.

[0063] Figure 9 This is a flowchart illustrating a method for controlling the bus voltage in the fourth range according to an embodiment of this application.

[0064] Figure 10 This is a flowchart illustrating a method for controlling the bus voltage in the fifth range according to an embodiment of this application.

[0065] Figure 11 This is a flowchart illustrating a control method for stopping the voltage supply to a load device according to an embodiment of this application;

[0066] Figure 12This is a flowchart illustrating a control method provided in this application embodiment for controlling the energy storage unit's charge level when the bus voltage is in the fourth or fifth interval and the charge level reaches the lower limit. Detailed Implementation

[0067] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various implementations. Simultaneously, the steps or actions described in the method description can be rearranged or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various orders in the specification and drawings are merely for the clear description of a particular embodiment and do not imply a mandatory order, unless otherwise stated that a particular order must be followed.

[0068] In the description of this application, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0069] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages).

[0070] With the continuous advancement of energy conservation, emission reduction and energy transition in countries around the world, renewable energy power generation technology has received increasing attention. Among them, photovoltaic and energy storage systems are widely used in power systems and microgrids due to their technological maturity and economic viability.

[0071] In a photovoltaic-storage system, photovoltaic strings are connected to the DC bus via photovoltaic DC / DC circuits, energy storage modules are connected to the DC bus via energy storage DC / DC circuits, and the power grid and load devices are connected to the DC bus via DC / AC circuits. Therefore, the bus voltage of the DC bus can reflect the energy balance of the system in the photovoltaic-storage system. Only when the energy flowing into and out of the DC bus is equal can the bus voltage remain stable.

[0072] During the operation of a photovoltaic-storage system, the energy consumed or released by each power unit within the system is not a fixed value. Therefore, it is necessary to rationally control each power unit through the DC bus voltage signal to maintain energy balance within the system and stabilize the bus voltage. Currently, energy flow is typically regulated by adjusting the operating states of the photovoltaic DC / DC circuit, energy storage DC / DC circuit, and DC / AC circuit through communication to maintain bus voltage stability. However, this method relies heavily on the reliability and speed of communication, and is prone to large fluctuations or even loss of control of the bus voltage under dynamic conditions.

[0073] Based on this, the present application provides a photovoltaic energy storage system and its control method, which can automatically trigger and adjust the energy output or input without relying on the communication system of the photovoltaic energy storage system, thereby affecting the energy balance state of the photovoltaic energy storage system and realizing stable control of the bus voltage.

[0074] The following description, in conjunction with the accompanying drawings, illustrates a photovoltaic energy storage system and its control method according to embodiments of this application:

[0075] Reference Figure 1 As shown, Figure 1 This is a structural framework diagram of a photovoltaic energy storage system provided in an embodiment of this application.

[0076] This application provides a photovoltaic-storage system, including a photovoltaic string 110, an energy storage unit 120, and a load device 130. The photovoltaic string 110 is connected to a DC bus 160 through a photovoltaic DC / DC circuit 140, the energy storage unit 120 is connected to the DC bus 160 through an energy storage DC / DC circuit 150, and the load device 130 and the power grid 180 are connected to the DC bus 160 through a DC / AC circuit 170. The photovoltaic DC / DC circuit 140, the energy storage DC / DC circuit 150, and the DC / AC circuit 170 are all used to detect the bus voltage of the DC bus 160 and adjust their own operating state according to the voltage range in which the bus voltage is located. The voltage range is set according to a voltage reference value and represents the energy balance state of the photovoltaic-storage system under the current bus voltage.

[0077] It should be noted that the photovoltaic-storage system consists of three main parts: a photovoltaic string 110, an energy storage unit 120, and a load device 130. The photovoltaic string 110 can be composed of multiple photovoltaic circuit boards connected in series. Each photovoltaic panel can convert sunlight into direct current (DC). By superimposing the DC power generated by multiple photovoltaic circuit boards in series, the total output voltage and current are increased, thereby improving the output power and meeting the energy supply or storage needs of the photovoltaic system. The photovoltaic string 110 is connected to a DC bus 160 via a photovoltaic DC / DC circuit 140. The photovoltaic string 110 can effectively capture solar energy and convert it into usable electrical energy, while the photovoltaic DC / DC circuit 140 can convert the DC power generated by the photovoltaic string 110 into DC power suitable for the DC bus 160. The energy storage unit 120 can be used to store and release electrical energy, and is typically composed of a series of batteries or other types of energy storage devices, such as lithium-ion batteries, sodium-sulfur batteries, and supercapacitors. When the electrical energy generated by the photovoltaic string 110 exceeds current demand, the excess electrical energy is stored, and the stored electrical energy is released when the system needs additional energy. Energy storage unit 120 is connected to DC bus 160 via energy storage DC / DC circuit 150, which controls the flow of electrical energy between energy storage unit 120 and DC bus 160. DC / AC circuit 170 is a DC-AC converter. The electrical energy generated in photovoltaic string 110 is in DC form, but many residential and commercial applications require AC power for appliances and equipment. DC / AC circuit 170 converts DC power to AC power by inverting it through a series of electronic components, such as transistors and capacitors. This allows the photovoltaic power generation system to be connected to the grid 180 or to supply AC loads in residential and commercial buildings. Simultaneously, DC / AC circuit 170 can also control the output AC parameters, such as voltage, frequency, and waveform, to ensure they meet the requirements of the receiving equipment. Grid 180 can also rectify the AC power through DC / AC circuit 170 to supplement the supply to DC bus 160.

[0078] In addition, the photovoltaic DC / DC circuit 140, the energy storage DC / DC circuit 150 and the DC / AC circuit 170 detect the bus voltage, and according to the voltage of the DC bus 160, the photovoltaic DC / DC circuit 140 controls the output power of the photovoltaic, the energy storage DC / DC circuit 150 manages the energy flow between the energy storage unit 120 and the DC bus 160, controls the energy storage unit 120 to release the stored electrical energy, and the DC / AC circuit 170 controls the AC power to be rectified into DC power or controls the DC power to be inverted into AC power.

[0079] Furthermore, the photovoltaic DC / DC circuit 140, the energy storage DC / DC circuit 150, and the DC / AC circuit 170 adjust their operating states according to the voltage range of the bus voltage. The voltage range is set according to the voltage reference value, which represents the energy balance state of the photovoltaic and energy storage system under the current bus voltage. When the bus voltage is in different voltage ranges, the photovoltaic DC / DC circuit 140, the energy storage DC / DC circuit 150, and the DC / AC circuit 170 enter different operating states.

[0080] It is understandable that the photovoltaic-storage system independently detects the bus voltage through the photovoltaic DC / DC circuit 140, the energy storage DC / DC circuit 150, and the DC / AC circuit 170, and determines the voltage range of the bus voltage based on its magnitude. It then adjusts its own operating state accordingly. Since the bus voltage reflects the energy balance in the photovoltaic-storage system, the photovoltaic DC / DC circuit 140, the energy storage DC / DC circuit 150, and the DC / AC circuit 170 automatically adjust their operating states based on the voltage range of the bus voltage. This allows them to trigger adjustments to energy output or input independently without relying on the communication system of the photovoltaic-storage system, thereby affecting the energy balance in the system and achieving stable control of the bus voltage.

[0081] In one embodiment of this application, the voltage range of the DC bus 160 of the photovoltaic energy storage system is divided into five voltage ranges: the first voltage range, the second voltage range, the third voltage range, the fourth voltage range, and the fifth voltage range. At the same time, the five voltage ranges correspond one-to-one with the five working modes of the photovoltaic energy storage system: the first working mode, the second working mode, the third working mode, the fourth working mode, and the fifth working mode.

[0082] In some embodiments, the photovoltaic energy storage system is provided with multiple voltage ranges, and the upper and lower bounds of each voltage range are obtained by adjusting based on voltage reference values.

[0083] Understandably, by dividing the voltage range into multiple intervals and adjusting their upper and lower bounds, the system can manage energy more effectively. Based on real-time energy demand and supply, the system can switch between different intervals to maximize the use of available energy and ensure stable system operation.

[0084] Reference Figure 2 As shown, Figure 2 This is a schematic diagram of five control modes of a photovoltaic energy storage system provided in an embodiment of this application.

[0085] In some embodiments, the voltage range includes a first voltage range, a second voltage range, a third voltage range, a fourth voltage range, and a fifth voltage range;

[0086] The first voltage range is from Udcr-ΔUdc to Udcr+ΔUdc;

[0087] The second voltage range is from Udcr+ΔUdc to Udcr+2ΔUdc;

[0088] The range of the third voltage interval is greater than Udcr+2ΔUdc;

[0089] The fourth voltage range is from Udcr-2ΔUdc to Udcr-ΔUdc;

[0090] The range of the fifth voltage interval is less than Udcr-2ΔUdc;

[0091] Where Udcr is the voltage reference value and ΔUdc is the voltage adjustment value.

[0092] Understandably, each voltage range has an upper and a lower bound, which are determined based on voltage reference values ​​and system operating requirements. In practical applications, these voltage range settings can be adjusted according to the system's performance and stability requirements.

[0093] It should be noted that, based on the voltage reference value, i.e. the balance state of the photovoltaic-storage system, the voltage range of the DC bus 160 is adjusted by the voltage adjustment value, resulting in the following: when the bus voltage is in the first voltage range Udcr-ΔUdc to Udcr+ΔUdc, the photovoltaic-storage system switches to the first operating mode; when the bus voltage is in the second voltage range Udcr+ΔUdc to Udcr+2ΔUdc, the photovoltaic-storage system switches to the second operating mode; when the bus voltage is in the third voltage range greater than Udcr+2ΔUdc, the photovoltaic-storage system switches to the third operating mode; when the bus voltage is in the fourth voltage range Udcr-2ΔUdc to Udcr-ΔUdc, the photovoltaic-storage system switches to the fourth operating mode; and when the bus voltage is in the fifth voltage range less than Udcr-2ΔUdc, the photovoltaic-storage system switches to the fifth operating mode. Without relying on the communication system of the photovoltaic-storage system, the system automatically triggers adjustments to energy output or input based on the voltage range of the bus voltage, thereby affecting the energy balance in the photovoltaic-storage system and achieving stable control of the bus voltage.

[0094] Understandably, by setting different voltage ranges based on voltage reference and adjustment values, the photovoltaic-storage system can better cope with the impact of external factors such as grid fluctuations or load changes, thereby improving the system's stability and reliability.

[0095] Reference Figure 3 As shown, Figure 3 This is a voltage control block diagram of a dual closed-loop space vector pulse amplitude modulation circuit for bus voltage in a first voltage range, provided in an embodiment of this application.

[0096] In some embodiments, the optical storage system includes a dual-loop space vector pulse amplitude modulation circuit. The dual-loop space vector pulse amplitude modulation circuit includes a conversion module, a voltage outer loop module, a current inner loop module, and a control module. The conversion module is connected to the AC output terminal of the DC / AC circuit and is used to perform coordinate transformation on the acquired AC signal from the DC / AC circuit. The voltage outer loop module is connected to the DC bus and is used to obtain the d-axis current reference through PI control based on the bus voltage and the bus voltage reference. The current inner loop module is connected to the output terminal of the voltage outer loop module and the output terminal of the conversion module. It is used to obtain the d-axis voltage control signal and the q-axis voltage control signal through PI control based on the d-axis AC current and the d-axis current reference output by the conversion module, and the q-axis voltage control signal based on the q-axis AC current and the q-axis voltage reference output by the conversion module. The control module is connected to the output terminal of the current inner loop module and is used to obtain the compensation amount of the operating parameters of the DC / AC circuit based on the d-axis voltage control signal and the q-axis voltage control signal, so as to adjust the output power of the DC / AC circuit.

[0097] It should be noted that the transformation module is used for coordinate transformation, converting the acquired AC signal from the DC / AC circuit into a dq-axis coordinate system, obtaining the d-axis current feedback id and the q-axis current feedback iq. The dq-axis coordinate system is a rotating coordinate system, where the d-axis is aligned with the rotor flux linkage axis, and the q-axis forms a 90-degree angle with the d-axis and is consistent with the rotor rotation direction. The voltage outer loop module obtains the d-axis current reference value idref based on the feedback and given DC bus voltage through PI control. The current inner loop module connects the output of the voltage outer loop module and the output of the transformation module. Based on the d-axis current feedback id and the d-axis current reference idref, it obtains the d-axis voltage control signal edpwm through PI control decoupling, and obtains the q-axis voltage control signal eqpwm based on the q-axis current feedback iq and the q-axis current reference iqref through PI control decoupling. The SVPWM control module obtains the compensation values ​​Sa, Sb, and Sc of the DC / AC circuit's operating parameters based on the d-axis voltage control signal edpwm and the q-axis voltage control signal eqpwm, and modulates the output power of the DC / AC circuit.

[0098] Reference Figure 3 As shown, Kpu and Kiu are the proportional and integral coefficients of the bus voltage loop, respectively; Kpid and Kiid are the proportional and integral coefficients of the d-axis current loop, respectively; and Kpiq and Kiiq are the proportional and integral coefficients of the q-axis current loop, respectively.

[0099] It should be noted that the dual closed-loop space vector pulse amplitude modulation circuit converts the current of the three-phase AC ABC system into the current of the two-phase orthogonal dq system, obtains the bus voltage Ude and the bus voltage reference value Udcref on the d-axis, and calculates the corresponding d-axis active current based on the difference between the bus voltage Ude and the bus voltage reference value Udcref. Based on the calculated d-axis active current, the pulse amplitude modulation circuit applies the corresponding compensation amount to the DC / AC circuit 170 to adjust its output power. When the bus voltage Udc is higher than the bus voltage reference value Udcref, the actual input current reference value of the grid increases through current compensation, thereby increasing the output power of the grid and causing the bus voltage to drop to the reference value. When the bus voltage Udc is lower than the voltage reference value Udcref, the actual input current reference value of the grid decreases through current compensation, thereby decreasing the output power of the grid and causing the bus voltage to rise to the reference value. This ensures a stable supply of power to household loads, thereby ensuring that the system can operate stably under various working conditions and better adapt to changes in power consumption and load demand fluctuations.

[0100] Understandably, by comparing the voltage information obtained through processing, the dual-closed-loop space vector pulse amplitude modulation circuit can calculate the d-axis active current information, which is used to adjust the operating parameters of the DC / AC circuit 170 to ensure the stability and efficiency of the system under different operating conditions. Based on the calculated d-axis active current information, the dual-closed-loop space vector pulse amplitude modulation circuit can generate corresponding compensation amounts to adjust the output power of the DC / AC circuit 170, ensuring that the system can provide stable power output under various workloads and achieve effective connection to the power grid 180.

[0101] Reference Figure 4 As shown, Figure 4 This is a flowchart illustrating a control method for a photovoltaic energy storage system provided in an embodiment of this application. The method is applied to the photovoltaic energy storage system described above and may include, but is not limited to, the following steps:

[0102] Step S410: The photovoltaic DC / DC circuit, the energy storage DC / DC circuit, and the DC / AC circuit obtain the bus voltage of the DC bus.

[0103] In step S420, the photovoltaic DC / DC circuit, the energy storage DC / DC circuit, and the DC / AC circuit adjust their operating states according to the voltage range in which the bus voltage is located.

[0104] The voltage range is set according to the voltage reference value and represents the energy balance state of the photovoltaic-storage system under the current bus voltage.

[0105] It should be noted that the photovoltaic-storage system consists of three main parts: a photovoltaic string 110, an energy storage unit 120, and a load device 130. The photovoltaic string 110 can be composed of multiple photovoltaic circuit boards connected in series. Each photovoltaic panel can convert sunlight into direct current (DC). By superimposing the DC power generated by multiple photovoltaic circuit boards in series, the total output voltage and current are increased, thereby improving the output power and meeting the energy supply or storage needs of the photovoltaic system. The photovoltaic string 110 is connected to a DC bus 160 via a photovoltaic DC / DC circuit 140. The photovoltaic string 110 can effectively capture solar energy and convert it into usable electrical energy, while the photovoltaic DC / DC circuit 140 can convert the DC power generated by the photovoltaic string 110 into DC power suitable for the DC bus 160. The energy storage unit 120 can be used to store and release electrical energy, and is typically composed of a series of batteries or other types of energy storage devices, such as lithium-ion batteries, sodium-sulfur batteries, and supercapacitors. When the electrical energy generated by the photovoltaic string 110 exceeds current demand, the excess electrical energy is stored, and the stored electrical energy is released when the system needs additional energy. Energy storage unit 120 is connected to DC bus 160 via energy storage DC / DC circuit 150, which controls the flow of electrical energy between energy storage unit 120 and DC bus 160. DC / AC circuit 170 is a DC-AC converter. The electrical energy generated in photovoltaic string 110 is in DC form, but many residential and commercial applications require AC power for appliances and equipment. DC / AC circuit 170 converts DC power to AC power by inverting it through a series of electronic components, such as transistors and capacitors. This allows the photovoltaic power generation system to be connected to the grid 180 or to supply AC loads in residential and commercial buildings. Simultaneously, DC / AC circuit 170 can also control the output AC parameters, such as voltage, frequency, and waveform, to ensure they meet the requirements of the receiving equipment. Grid 180 can also rectify the AC power through DC / AC circuit 170 to supplement the supply to DC bus 160.

[0106] In addition, the photovoltaic DC / DC circuit 140, the energy storage DC / DC circuit 150 and the DC / AC circuit 170 detect the bus voltage, and according to the voltage of the DC bus 160, the photovoltaic DC / DC circuit 140 controls the output power of the photovoltaic, the energy storage DC / DC circuit 150 manages the energy flow between the energy storage unit 120 and the DC bus 160, controls the energy storage unit 120 to release the stored electrical energy, and the DC / AC circuit 170 controls the AC power to be rectified into DC power or controls the DC power to be inverted into AC power.

[0107] Furthermore, the photovoltaic DC / DC circuit 140, the energy storage DC / DC circuit 150, and the DC / AC circuit 170 adjust their operating states according to the voltage range of the bus voltage. The voltage range is set according to the voltage reference value, which represents the energy balance state of the photovoltaic and energy storage system under the current bus voltage. When the bus voltage is in different voltage ranges, the photovoltaic DC / DC circuit 140, the energy storage DC / DC circuit 150, and the DC / AC circuit 170 enter different operating states.

[0108] Reference Figure 5 As shown, Figure 5 This is a flowchart illustrating a method for controlling the bus voltage to be in a first range, as provided in an embodiment of this application. The method may include, but is not limited to, the following steps:

[0109] In step S510, the DC / AC circuit operates in inverter mode. The DC / AC circuit adjusts the output power according to the compensation amount output by the dual closed-loop space vector pulse amplitude modulation circuit so that the bus voltage is maintained within the first voltage range.

[0110] In step S520, the photovoltaic DC / DC circuit operates in maximum power point tracking mode;

[0111] In step S530, the energy storage DC / DC circuit adjusts its operating mode according to the amount of electricity stored in the energy storage unit.

[0112] The first voltage range is from Udcr-ΔUdc to Udcr+ΔUdc, where Udcr is the voltage reference value and ΔUdc is the voltage adjustment value.

[0113] It should be noted that the photovoltaic DC / DC circuit 140, the energy storage DC / DC circuit 150, and the DC / AC circuit 170 detect the bus voltage and compare it with the upper and lower limits of each range. When the bus voltage is in the first voltage range, the bus voltage is stable, that is, the photovoltaic and energy storage system is in an energy balance state. The photovoltaic and energy storage system enters the first working mode. The photovoltaic DC / DC circuit 140 controls the photovoltaic string 110 to maintain the current working state and converts the DC power generated by the photovoltaic string 110 into voltage and current suitable for the DC bus 160. The energy storage DC / DC circuit 150 controls the energy storage unit 120 to maintain the current working state. The DC / AC circuit 170 inverts the DC power to AC power to supply the grid 180 or the AC load of homes and commercial buildings.

[0114] Understandably, closed-loop control allows the inverter to adjust the output voltage in real time according to the actual bus voltage, so as to keep the grid voltage stable within a suitable range, which helps to prevent voltage fluctuations from damaging other equipment and ensures the stable operation of the grid.

[0115] In one embodiment of this application, when the bus voltage is in the first voltage range, the photovoltaic energy storage system enters the first working mode. The photovoltaic DC / DC circuit 140 maintains normal operation and continuously inputs the highest energy into the photovoltaic energy storage system. Since the energy storage unit 120 is in the off mode, the energy storage DC / DC circuit 150 controls the energy storage unit 120 to maintain the current off mode. The DC / AC circuit 170 inverts the DC power to AC power to supply the grid 180 or supply the AC load of homes and commercial buildings.

[0116] Reference Figure 6 As shown, Figure 6 This is a flowchart illustrating a method for controlling the bus voltage to be in a second range, as provided in an embodiment of this application. The method may include, but is not limited to, the following steps:

[0117] Step 610: The DC / AC circuit operates in inverter mode;

[0118] Step 620: The photovoltaic DC / DC circuit operates in maximum power point tracking mode;

[0119] Step 630: The energy storage DC / DC circuit determines the current power level of the energy storage unit, and operates in charging mode if the power level of the energy storage unit is less than the upper limit of the rechargeable power level.

[0120] The second voltage range is from Udcr+ΔUdc to Udcr+2ΔUdc, where Udcr is the voltage reference value and ΔUdc is the voltage adjustment value.

[0121] It should be noted that the photovoltaic DC / DC circuit 140, the energy storage DC / DC circuit 150, and the DC / AC circuit 170 detect the bus voltage and compare it with the upper and lower limits of each range. When the bus voltage is in the second voltage range, i.e., the photovoltaic-energy storage system has sufficient energy and is not within the adjustable range of the DC / AC circuit 170, the photovoltaic DC / DC circuit 140 controls the photovoltaic string 110 to operate normally and converts the DC power generated by the photovoltaic string 110 into voltage and current suitable for the DC bus 160. When the energy storage unit 120's charge is less than 90% of its maximum rechargeable capacity, the energy storage DC / DC circuit 150 controls... The energy storage unit 120 switches to the energy storage mode, storing a portion of the DC power generated by the photovoltaic string 110 into the energy storage unit 120, reducing the DC power generated by the photovoltaic string 110 to within the adjustable range of the DC / AC circuit 170. At this time, the bus voltage is in the first voltage range, and the photovoltaic-energy storage system enters the first working mode. The photovoltaic DC / DC circuit 140 controls the photovoltaic string 110 to maintain normal operation, the energy storage DC / DC circuit 150 controls the energy storage unit 120 to maintain charging, and the DC / AC circuit 170 inverts the remaining DC power to AC power to supply the grid 180 or the AC loads of homes and commercial buildings, thereby ensuring normal power supply.

[0122] Understandably, when the bus voltage is in the second voltage range, the photovoltaic-storage system is in an energy-sufficient state, storing the excess electrical energy supplied by the load device 130 and the grid 180 through the energy storage unit 120. This reduces the bus voltage without wasting energy, bringing the photovoltaic-storage system closer to a balanced state and improving the system's stability and reliability.

[0123] In one embodiment of this application, when the energy storage unit 120 has not reached its charging limit and the photovoltaic DC / DC circuit 140, the energy storage DC / DC circuit 150, and the DC / AC circuit 170 detect that the bus voltage is in the second voltage range, the photovoltaic energy storage system enters a second operating mode. When the grid 180 and the AC load of residential and commercial buildings require maximum supply, the photovoltaic DC / DC circuit 140 is in MPPT mode, i.e., normal operating state, and continuously inputs the maximum energy to the photovoltaic energy storage system. The energy storage DC / DC circuit 150 controls the energy storage unit 120 to store a portion of electrical energy, reducing the DC power generated by the photovoltaic string 110 to the maximum adjustable limit of the DC / AC circuit 170. At this time, the bus voltage drops to the first voltage range, and the photovoltaic-storage system enters the first working mode. The photovoltaic DC / DC circuit 140 controls the photovoltaic string 110 to maintain normal operation, the energy storage DC / DC circuit 150 controls the energy storage unit 120 to maintain the current charging state, and the DC / AC circuit 170 inverts the DC power energy at the maximum adjustment limit into AC power energy suitable for supplying the power grid 180 or supplying households, thereby ensuring normal power supply.

[0124] In one embodiment of this application, when the energy storage unit 120 has not reached its charging limit and the photovoltaic DC / DC circuit 140, the energy storage DC / DC circuit 150, and the DC / AC circuit 170 detect that the bus voltage is in the second voltage range, the photovoltaic-energy storage system enters a second operating mode. When the grid 180 and the AC loads of residential and commercial buildings do not require maximum supply or do not require supply, the photovoltaic DC / DC circuit 140 is in MPPT mode, i.e., normal operating state, and continuously inputs the maximum energy to the photovoltaic-energy storage system. The energy storage DC / DC circuit 150 controls the energy storage unit 120 to store a portion of electrical energy, reducing the DC power generated by the photovoltaic string 110 to meet the maximum adjustable limit of the DC / AC circuit 170. The DC / AC circuit 170 switches to a current-limiting or shut-off state. When the bus voltage drops to the first voltage range, the photovoltaic-storage system enters the first working mode. The photovoltaic DC / DC circuit 140 controls the photovoltaic string 110 to maintain normal operation, the energy storage DC / DC circuit 150 controls the energy storage unit 120 to maintain the current charging state, and the DC / AC circuit 170 remains in the current-limiting or off state, converting the remaining DC power into AC power or shutting it off.

[0125] Reference Figure 7 As shown, Figure 7 This is a flowchart illustrating a control method for a bus voltage in a third interval, as provided in an embodiment of this application. The method may include, but is not limited to, the following steps:

[0126] Step S710: The DC / AC circuit operates in inverter mode;

[0127] Step S720: The photovoltaic DC / DC circuit reduces its output power;

[0128] In step S730, the energy storage DC / DC circuit determines the current power level of the energy storage unit, and operates in charging mode if the power level of the energy storage unit is less than the upper limit of the rechargeable power level.

[0129] The third voltage range is greater than Udcr + 2ΔUdc, where Udcr is the voltage reference value and ΔUdc is the voltage adjustment value. It should be noted that there are two scenarios when the photovoltaic-storage system enters the third operating mode: First, the bus voltage is within the third voltage range, and the system directly enters the third operating mode. Second, when the energy storage unit 120 reaches its maximum rechargeable capacity and the photovoltaic DC / DC circuit 140, energy storage DC / DC circuit 150, and DC / AC circuit 170 detect that the bus voltage is within the second voltage range, the photovoltaic DC / DC circuit 140 is still operating normally, continuously inputting the maximum energy to the photovoltaic-storage system. Since the maximum input energy exceeds the adjustable range of the DC / AC circuit 170, the DC / AC circuit 170 can only convert the maximum adjustable DC power into AC power, resulting in continuous redundancy in the photovoltaic-storage system. The bus voltage continues to increase, gradually exceeding the second voltage range and reaching the third voltage range, thus the photovoltaic-storage system enters the third operating mode.

[0130] Understandably, when the bus voltage is in the third voltage range, the photovoltaic-storage system is in a state of excessive energy. The output power is reduced by the photovoltaic DC / DC circuit 140, and the energy storage DC / DC circuit 150 stores electrical energy as an auxiliary, thereby reducing the bus voltage and bringing the photovoltaic-storage system towards a balanced state, thus improving the stability and reliability of the system.

[0131] In one example of this application, the photovoltaic DC / DC circuit 140, the energy storage DC / DC circuit 150, and the DC / AC circuit 170 detect the bus voltage and compare it with the upper and lower limits of each range. When the bus voltage is in the third voltage range, i.e., the photovoltaic-energy storage system is in a state of sufficient energy and not within the adjustable range of the DC / AC circuit 170, the photovoltaic DC / DC circuit 140 reduces its output power. During the process of converting the DC power generated by the photovoltaic string 110 into DC power suitable for the DC bus 160, the conversion rate decreases. The photovoltaic-energy storage system detects the energy storage unit 120. When the energy storage unit 120 has not reached its upper limit of rechargeable capacity, the energy storage DC / DC circuit 150 can control the energy storage unit 120 to store energy until the bus voltage is reduced to the first voltage range or the energy storage unit 120 reaches its upper limit of rechargeable capacity and charging stops. When the energy storage unit 120 reaches its upper limit of rechargeable capacity, the energy storage DC / DC circuit 150 stops supplying energy to the energy storage unit 120, thereby preventing it from continuing to charge. The photovoltaic DC / DC circuit 140 reduces the output power, and the bus voltage gradually decreases to the first voltage range. The photovoltaic-storage system enters the first working mode. The photovoltaic DC / DC circuit 140 maintains the reduced power output state, the energy storage DC / DC circuit 150 controls the storage unit to maintain the status quo, and the DC / AC circuit 170 inverts the DC power at the maximum adjustment limit into AC power suitable for supplying the power grid 180 or supplying households, thereby ensuring normal power supply.

[0132] Understandably, when the bus voltage is in the third voltage range and the photovoltaic-storage system enters the third operating mode, if the energy storage unit 120 has not reached its maximum rechargeable capacity, the energy storage DC / DC circuit 150 controls the energy storage unit 120 to store energy and the photovoltaic DC / DC circuit 140 to reduce power, thereby lowering the bus voltage. During the process of lowering the bus voltage, if the energy storage unit 120 reaches its maximum rechargeable capacity, the energy storage DC / DC circuit 150 controls the energy storage unit 120 to stop charging, while the photovoltaic DC / DC circuit 140 continues to maintain low power to further reduce the bus voltage. Alternatively, if the energy storage unit 120 never reaches its maximum rechargeable capacity during the process of lowering the bus voltage, and the bus voltage drops to within the first voltage range, the energy storage DC / DC circuit 150 controls the energy storage unit 120 to stop charging.

[0133] Reference Figure 8 As shown, Figure 8 This is a flowchart illustrating a control method for an energy storage unit reaching its upper limit when the bus voltage is in the second or third range, as provided in an embodiment of this application. The method may include, but is not limited to, the following steps:

[0134] Step S810: When the bus voltage is in the second or third range, determine that the energy storage unit has reached its upper limit.

[0135] In step S820, the energy storage DC / DC circuit stops charging the energy storage unit.

[0136] It should be noted that when the photovoltaic energy storage system is in the second working mode and the photovoltaic energy storage system detects that the battery capacity of the energy storage unit 120 is in the range of 90% to 100%, the energy storage DC / DC circuit 150 can stop supplying power to the energy storage unit 120, thereby preventing it from continuing to charge.

[0137] Understandably, exiting charging mode is an important safety function in energy storage systems. It can effectively prevent overcharging and protect the performance and safety of energy storage unit 120, helping to ensure the stability and reliability of the energy storage system during long-term operation.

[0138] In one embodiment of this application, when the energy storage unit 120 reaches its charging limit and the photovoltaic DC / DC circuit 140, the energy storage DC / DC circuit 150, and the DC / AC circuit 170 detect that the bus voltage is in the second voltage range, the photovoltaic DC / DC circuit 140 continuously inputs the maximum energy to the photovoltaic-energy storage system in MPPT mode, i.e., normal operation mode. The energy storage DC / DC circuit 150 controls the energy storage unit 120 to exit the charging mode or maintain a non-charging state. The DC / AC circuit 170 inverts the DC power at the maximum adjustment limit into AC power suitable for supplying the grid 180 or the household, thereby ensuring normal power supply.

[0139] Reference Figure 9 As shown, Figure 9 This is a flowchart illustrating a control method for a bus voltage in a fourth range, provided in an embodiment of this application. The method may include, but is not limited to, the following steps:

[0140] Step 910: The DC / AC circuit operates in rectification mode;

[0141] Step 920: The photovoltaic DC / DC circuit operates in maximum power point tracking mode;

[0142] Step 930: The energy storage DC / DC circuit determines the current charge of the energy storage unit, and operates in discharge mode when the charge of the energy storage unit is greater than the lower discharge limit.

[0143] The fourth voltage range is from Udcr-2ΔUdc to Udcr-ΔUdc, where Udcr is the voltage reference value and ΔUdc is the voltage adjustment value.

[0144] It should be noted that when the DC / AC circuit 170 operates in rectification mode, it converts the DC power supplied by the grid 180 into AC power to increase the bus voltage. This helps maintain the stability of the photovoltaic-energy storage system and ensures the efficient utilization and transmission of energy. Simultaneously, when the charge of the energy storage unit 120 exceeds its discharge limit, the energy storage DC / DC circuit 150 operates in discharge mode, releasing the energy from the energy storage unit 120 to provide additional power to the photovoltaic-energy storage system, thus helping to maintain its operational stability.

[0145] Understandably, when the bus voltage is in the fourth voltage range, the photovoltaic energy storage system is in a state of insufficient energy. The energy storage DC / DC circuit 150 controls the energy storage unit 120 to release electrical energy to increase the bus voltage. At the same time, the DC / AC circuit 170 switches to rectification mode to rectify the AC power of the grid 180 into DC power to supply the load equipment 130 and maintain the operational stability of the photovoltaic energy storage system.

[0146] In one embodiment of this application, the photovoltaic DC / DC circuit 140, the energy storage DC / DC circuit 150, and the DC / AC circuit 170 detect the bus voltage and compare it with the upper and lower limits of each range. When the bus voltage is in the fourth voltage range, i.e., the photovoltaic-storage system is in a state of energy shortage, the photovoltaic DC / DC circuit 140 controls the photovoltaic string 110 to operate normally and converts the DC power generated by the photovoltaic string 110 into a voltage and current suitable for the DC bus 160. When the energy storage unit 120 has a charge capacity greater than 10% of the maximum rechargeable capacity, the energy storage DC / DC circuit 150 controls the energy storage unit 120 to switch to the energy release mode and release the energy in the energy storage unit 120. The DC / AC circuit 170 rectifies the AC power supplied by the grid 180 into DC power and raises the bus voltage to the first voltage range. At this time, the bus voltage is in the first voltage range, the photovoltaic-storage system enters the first working mode, the photovoltaic DC / DC circuit 140 controls the photovoltaic string 110 to maintain normal operation, the energy storage DC / DC circuit 150 controls the energy storage unit 120 to maintain discharge, and the DC / AC circuit 170 rectifies the AC power supplied by the grid 180 into DC power to supply the loads of residential and commercial buildings, thereby ensuring normal power supply.

[0147] Reference Figure 10 As shown, Figure 10 This is a flowchart illustrating a control method for a bus voltage in the fifth interval provided in an embodiment of this application. The method may include, but is not limited to, the following steps:

[0148] In step S1010, the DC / AC circuit operates in rectification mode and stops the voltage supply to at least a portion of the load devices;

[0149] In step S1020, the photovoltaic DC / DC circuit operates in maximum power point tracking mode;

[0150] In step S1030, the energy storage DC / DC circuit determines the current power of the energy storage unit, and operates in discharge mode when the power of the energy storage unit is greater than the lower limit of the dischargeable power.

[0151] The fifth voltage range is less than Udcr-2ΔUdc, where Udcr is the voltage reference value and ΔUdc is the voltage adjustment value.

[0152] It should be noted that there are two scenarios when the photovoltaic-storage system enters the fifth operating mode: The first is when the bus voltage is in the fifth voltage range, in which case the photovoltaic-storage system directly enters the fifth operating mode; the second is when the energy storage unit 120 drops to the minimum discharge limit and the photovoltaic DC / DC circuit 140, energy storage DC / DC circuit 150, and DC / AC circuit 170 detect that the bus voltage is in the fourth voltage range. The DC / AC circuit 170 adjusts the upper limit of the rectified AC power supplied by the grid 180 at its maximum. Since the photovoltaic DC / DC circuit 140 continues to input the maximum energy to the photovoltaic-storage system, the energy of the photovoltaic-storage system is still insufficient. Furthermore, since the energy storage unit 120 drops to the minimum discharge limit and cannot continue to release energy, the bus voltage further decreases. This causes the photovoltaic-storage system to be unable to meet the voltage supply of the load device 130, gradually exceeding the fourth voltage range and reaching the fifth voltage range, thus the photovoltaic-storage system enters the fifth operating mode.

[0153] Understandably, when the bus voltage is in the fifth voltage range, the photovoltaic energy storage system is in a state of severe energy shortage. By shutting down some load devices 130, the supply demand is reduced, the photovoltaic energy storage system tends to a balanced state, and the stability and reliability of the photovoltaic energy storage system are improved.

[0154] In one embodiment of this application, the photovoltaic DC / DC circuit 140, the energy storage DC / DC circuit 150, and the DC / AC circuit 170 detect the bus voltage and compare it with the upper and lower limits of each range. When the bus voltage is in the fifth voltage range, i.e., the photovoltaic-energy storage system is in a state of insufficient energy and is not within the adjustable range of the DC / AC circuit 170, the photovoltaic-energy storage system controls a portion of the load devices 130 to shut down, thereby reducing the voltage supply to the load devices 130. The photovoltaic-energy storage system detects the energy storage unit 120. When the energy storage unit 120 has not reached the lower limit of discharge capacity, the energy storage DC / DC circuit 150 can control the energy storage unit 120 to release electrical energy until the bus voltage is raised to the first voltage range or the energy storage unit 120 reaches the lower limit of discharge capacity and stops discharging. When the energy storage unit 120 reaches the lower limit of discharge capacity, the energy storage DC / DC circuit 150 stops releasing electrical energy to the energy storage unit 120. The photovoltaic DC / DC circuit 140 controls the photovoltaic string 110 to work in MPPT mode, i.e., normal operation. Some load devices 130 are turned off, the first voltage range changes, the bus voltage reaches the first voltage range, the photovoltaic-storage system enters the first working mode, the photovoltaic DC / DC circuit 140 maintains normal state, the energy storage DC / DC circuit 150 controls the storage unit to maintain a stopped charging state, and the DC / AC circuit 170 rectifies the AC power energy at the maximum adjustment limit into DC power energy, thereby ensuring normal power supply.

[0155] Understandably, when the bus voltage is in the fifth voltage range and the photovoltaic-storage system enters the fifth operating mode, if the energy storage unit 120 has not reached its minimum discharge capacity, the energy storage DC / DC circuit 150 controls the energy storage unit 120 to release electrical energy and shut down the load device 130, thereby ensuring that the voltage supply meets the voltage requirements. During the adjustment of the bus voltage, if the energy storage unit 120 reaches its minimum discharge capacity, the energy storage DC / DC circuit 150 controls the energy storage unit 120 to stop discharging. Conversely, if the energy storage unit 120 consistently fails to reach its minimum discharge capacity during the adjustment of the bus voltage, and the bus voltage drops to the first voltage range, the energy storage DC / DC circuit 150 controls the energy storage unit 120 to stop discharging.

[0156] It needs to be explained that different load devices 130 are connected to the photovoltaic energy storage system, which causes the voltage reference value to change, and thus the coefficients of the five voltage ranges also change.

[0157] Reference Figure 11 As shown, Figure 11 This is a flowchart illustrating a control method for stopping the voltage supply to a load device according to an embodiment of this application. The method may include, but is not limited to, the following steps:

[0158] Step S1110: The DC / AC circuit obtains the priority of the load device;

[0159] In step S1120, the DC / AC circuit stops the voltage supply to the load device according to the priority from low to high.

[0160] It should be noted that in photovoltaic-storage systems, to effectively manage energy distribution and ensure stable operation, the priority of load devices (130) is typically used to determine the order in which voltage supply is cut off. This ensures that critical equipment or systems receive priority power supply when power resources are limited or the grid (180) is unstable. By monitoring the power demand and priority of each device in the photovoltaic-storage system in real time, voltage supply can be dynamically adjusted to ensure rational resource utilization and sufficient power support for the most critical devices. This intelligent energy management approach improves the reliability, stability, and efficiency of the photovoltaic-storage system while maximizing the satisfaction of the power needs of different devices.

[0161] Reference Figure 12 As shown, Figure 12 This is a flowchart illustrating a control method for an energy storage unit whose power reaches a lower limit when the bus voltage is in the fourth or fifth range, as provided in an embodiment of this application. The method may include, but is not limited to, the following steps:

[0162] Step S1210: When the bus voltage is in the fourth or fifth range, determine that the energy storage unit's power has reached the lower limit.

[0163] In step S1220, the energy storage DC / DC circuit stops discharging the energy storage unit. It should be noted that when the photovoltaic-energy storage system is in the fourth operating mode and the system detects that the battery capacity of the energy storage unit 120 is less than 10%, the energy storage DC / DC circuit 150 can stop the energy storage unit 120 from releasing electrical energy, thereby preventing it from continuing to discharge.

[0164] Understandably, when the energy storage unit 120's charge drops below its discharge limit, the energy storage DC / DC circuit 150 will exit the discharge mode. This is to avoid over-discharge, prevent damage to the energy storage unit 120, and extend its service life.

[0165] In one embodiment of this application, when the energy storage unit 120 drops to the minimum discharge limit and the photovoltaic DC / DC circuit 140, the energy storage DC / DC circuit 150, and the DC / AC circuit 170 detect that the bus voltage is in the fourth voltage range, the photovoltaic DC / DC circuit 140 is in MPPT mode, i.e., normal operation state, and continuously inputs the maximum energy to the photovoltaic-energy storage system. The energy storage DC / DC circuit 150 controls the energy storage unit 120 to exit the discharge mode or maintain a non-discharge state. The DC / AC circuit 170 rectifies the DC power supplied by the grid 180 into suitable AC power, thereby ensuring normal power supply.

[0166] One embodiment of this application provides a photovoltaic-energy storage system that switches between different operating modes according to different bus voltage ranges. In different operating modes, the inverter, energy storage, and photovoltaic systems operate in different control modes. Stable control of the bus voltage can be achieved through the coordinated operation of each power unit in the system, including:

[0167] In the first operating mode, when the bus voltage is in the first voltage range, the photovoltaic energy storage system enters the first operating mode. The photovoltaic DC / DC circuit 140 maintains normal operation and continuously inputs the maximum energy to the photovoltaic energy storage system. Since the energy storage unit 120 is in the off mode, the energy storage DC / DC circuit 150 controls the energy storage unit 120 to maintain the current off mode. The DC / AC circuit 170 inverts the DC power to AC power to supply the grid 180 or the load equipment 130.

[0168] In the second operating mode, when the bus voltage is in the second voltage range, the photovoltaic-storage system enters the second operating mode. The photovoltaic DC / DC circuit 140 is in MPPT mode, i.e., normal operating state, continuously inputting the maximum energy to the photovoltaic-storage system. The energy storage DC / DC circuit 150 controls the energy storage unit 120 to store a portion of the electrical energy, reducing the DC power generated by the photovoltaic string 110 to the maximum adjustable limit of the DC / AC circuit 170. When the bus voltage drops to the first voltage range, the photovoltaic-storage system enters the first operating mode. The photovoltaic DC / DC circuit 140 controls the photovoltaic string 110 to maintain normal operation, the energy storage DC / DC circuit 150 controls the energy storage unit 120 to maintain the current charging state, and the DC / AC circuit 170 inverts the DC power at the maximum adjustable limit into a form suitable for supplying the grid 180 or the load equipment 130.

[0169] When the energy storage unit 120 reaches its charging limit, the energy storage DC / DC circuit 150 controls the energy storage unit 120 to exit the charging mode or maintain a non-charging state, which can effectively prevent overcharging and protect the performance and safety of the energy storage unit 120.

[0170] In the third operating mode, when the bus voltage is in the third voltage range, i.e., the photovoltaic-storage system has sufficient energy and is not within the adjustable range of the DC / AC circuit 170, the photovoltaic DC / DC circuit 140 reduces its output power. During the process of converting the DC power generated by the photovoltaic string 110 into DC power suitable for the DC bus 160, the conversion rate decreases. The photovoltaic-storage system detects the energy storage unit 120. When the energy storage unit 120 has not reached its upper limit of rechargeable capacity, the energy storage DC / DC circuit 150 can control the energy storage unit 120 to store energy until the bus voltage is reduced to the first voltage range or the energy storage unit 120 reaches its upper limit of rechargeable capacity, at which point charging stops. When the energy storage unit 120 reaches its upper limit of rechargeable capacity, the energy storage DC / DC circuit 150 stops supplying energy to the energy storage unit 120, thereby preventing it from continuing to charge. The photovoltaic DC / DC circuit 140 reduces the output power, and the bus voltage gradually decreases to the first voltage range. The photovoltaic energy storage system enters the first working mode. The photovoltaic DC / DC circuit 140 maintains the reduced power output state, the energy storage DC / DC circuit 150 controls the storage unit to maintain the status quo, and the DC / AC circuit 170 inverts the DC power at the maximum adjustment limit into a form suitable for supplying the power grid 180 or the load equipment 130.

[0171] In the fourth operating mode, when the bus voltage is in the fourth voltage range (i.e., the photovoltaic-storage system is short of energy), the photovoltaic DC / DC circuit 140 controls the photovoltaic string 110 to operate normally and converts the DC power generated by the photovoltaic string 110 into voltage and current suitable for the DC bus 160. When the energy storage unit 120 has a charge capacity greater than 10% of its maximum rechargeable capacity, the energy storage DC / DC circuit 150 controls the energy storage unit 120 to switch to energy release mode, releasing the energy in the energy storage unit 120. The DC / AC circuit 170 rectifies the AC power supplied by the grid 180 into DC power, raising the bus voltage to the first voltage range. At this time, the bus voltage is in the first voltage range, and the photovoltaic-storage system enters the first operating mode. The photovoltaic DC / DC circuit 140 controls the photovoltaic string 110 to maintain normal operation, the energy storage DC / DC circuit 150 controls the energy storage unit 120 to maintain discharge, and the DC / AC circuit 170 rectifies the AC power supplied by the grid 180 into DC power to supply the load device 130.

[0172] When the energy storage unit 120 drops to the minimum discharge limit, the energy storage DC / DC circuit 150 controls the energy storage unit 120 to exit the discharge mode or maintain a non-discharge state, and the DC / AC circuit 170 rectifies the DC power supplied by the grid 180 into suitable AC power, thereby ensuring normal power supply.

[0173] In the fifth operating mode, when the bus voltage is in the fifth voltage range, i.e., the photovoltaic-storage system is short of energy and outside the adjustable range of the DC / AC circuit 170, the photovoltaic-storage system controls a portion of the load devices 130 to shut down, thereby reducing the voltage supply to the load devices 130. The energy storage DC / DC circuit 150 can control the energy storage unit 120 to release electrical energy. The photovoltaic DC / DC circuit 140 controls the photovoltaic string 110 to work in MPPT mode, i.e., normal operation state, shutting down a portion of the load devices 130. The first voltage range changes, the bus voltage reaches the first voltage range, the photovoltaic-storage system enters the first operating mode, the photovoltaic DC / DC circuit 140 maintains normal state, the energy storage DC / DC circuit 150 controls the storage unit to maintain a stopped charging state, and the DC / AC circuit 170 rectifies the AC power at the maximum adjustable upper limit into DC power, thereby ensuring normal power supply.

[0174] The photovoltaic DC / DC circuit, energy storage DC / DC circuit, and DC / AC circuit in the photovoltaic-energy storage system provided in this application embodiment can all independently detect the bus voltage and determine the voltage range of the bus voltage based on its magnitude. They then adjust their operating states accordingly based on the voltage range. Since the bus voltage reflects the energy balance state of the photovoltaic-energy storage system, the photovoltaic DC / DC circuit, energy storage DC / DC circuit, and DC / AC circuit automatically adjust their operating states based on the voltage range of the bus voltage. This allows them to trigger adjustments to energy output or input independently without relying on the communication system of the photovoltaic-energy storage system, thereby affecting the energy balance state of the photovoltaic-energy storage system and achieving stable control of the bus voltage.

[0175] It will be understood by those skilled in the art that all or some of the steps and systems in the methods disclosed above can be implemented as software, firmware, hardware, and suitable combinations thereof. Some or all of the physical components can be implemented as software executed by a processor, such as a central processing unit, digital signal processor, or microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit. Such software can be distributed on a computer-readable medium, which can include computer storage media (or non-transitory media) and communication media (or transient media). As is known to those skilled in the art, the term computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disc (DVD) or other optical disc storage, magnetic cartridges, magnetic tape, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and is accessible to a computer. Furthermore, as is known to those skilled in the art, communication media typically contain computer-readable instructions, data structures, program modules, or other data in modulated data signals such as carrier waves or other transmission mechanisms, and may include any information delivery medium.

[0176] The above is a detailed description of the preferred embodiments of this application. However, this application is not limited to the above embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of this application. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A photovoltaic-storage system, characterized in that, It includes a photovoltaic string, an energy storage unit, and load equipment. The photovoltaic string is connected to a DC bus through a photovoltaic DC / DC circuit, the energy storage unit is connected to the DC bus through an energy storage DC / DC circuit, and the load equipment and the power grid are connected to the DC bus through a DC / AC circuit. The photovoltaic DC / DC circuit, the energy storage DC / DC circuit, and the DC / AC circuit are all used to detect the bus voltage of the DC bus and adjust their own working state according to the voltage range in which the bus voltage is located. The voltage range is set according to the voltage reference value and represents the energy balance state of the photovoltaic energy storage system under the current bus voltage.

2. The photovoltaic energy storage system according to claim 1, characterized in that, The photovoltaic energy storage system is provided with multiple voltage ranges, and the upper and lower bounds of each voltage range are adjusted based on the voltage reference value.

3. The photovoltaic energy storage system according to claim 2, characterized in that, The voltage range includes a first voltage range, a second voltage range, a third voltage range, a fourth voltage range, and a fifth voltage range; The first voltage range is from Udcr-ΔUdc to Udcr+ΔUdc; The second voltage range is from Udcr+ΔUdc to Udcr+2ΔUdc; The range of the third voltage interval is greater than Udcr+2ΔUdc; The range of the fourth voltage interval is from Udcr-2ΔUdc to Udcr-ΔUdc; The range of the fifth voltage interval is less than Udcr-2ΔUdc; Wherein, Udcr is the voltage reference value, and ΔUdc is the voltage adjustment value.

4. The photovoltaic energy storage system according to claim 1, characterized in that, The optical energy storage system includes a dual-loop space vector pulse amplitude modulation circuit. This circuit comprises a conversion module, a voltage outer loop module, a current inner loop module, and a control module. The conversion module is connected to the AC output of the DC / AC circuit and is used to perform coordinate transformation on the acquired AC signal from the DC / AC circuit. The voltage outer loop module is connected to the DC bus and is used to obtain a d-axis current reference based on the bus voltage and a given bus voltage via PI control. The current inner loop module is connected to the output of the voltage outer loop module and the output of the conversion module. It is used to obtain a d-axis voltage control signal based on the d-axis AC current output by the conversion module and the given d-axis current via PI control, and a q-axis voltage control signal based on the q-axis AC current output by the conversion module and the given q-axis current via PI control. The control module is connected to the output of the current inner loop module and is used to obtain compensation amounts for the operating parameters of the DC / AC circuit based on the d-axis voltage control signal and the q-axis voltage control signal, thereby adjusting the output power of the DC / AC circuit.

5. A control method for a photovoltaic energy storage system, characterized in that, The control method, applied to the optical energy storage system according to any one of claims 1 to 5, comprises: The photovoltaic DC / DC circuit, the energy storage DC / DC circuit, and the DC / AC circuit acquire the bus voltage of the DC bus. The photovoltaic DC / DC circuit, the energy storage DC / DC circuit, and the DC / AC circuit adjust their operating states according to the voltage range in which the bus voltage is located. The voltage range is set according to the voltage reference value and represents the energy balance state of the photovoltaic energy storage system under the current bus voltage.

6. The control method according to claim 5, characterized in that, When the bus voltage is within a first voltage range, the photovoltaic DC / DC circuit, the energy storage DC / DC circuit, and the DC / AC circuit adjust their operating states according to the voltage range in which the bus voltage is located, including: The DC / AC circuit operates in inverter mode, and adjusts its output power according to the compensation amount output by the dual closed-loop space vector pulse amplitude modulation circuit so that the bus voltage is maintained within the first voltage range. The photovoltaic DC / DC circuit operates in maximum power point tracking mode; The energy storage DC / DC circuit adjusts its operating mode according to the power of the energy storage unit; The first voltage range is from Udcr-ΔUdc to Udcr+ΔUdc, where Udcr is the voltage reference value and ΔUdc is the voltage adjustment value.

7. The control method according to claim 5, characterized in that, When the bus voltage is in the second voltage range, the photovoltaic DC / DC circuit, the energy storage DC / DC circuit, and the DC / AC circuit adjust their operating states according to the voltage range in which the bus voltage is located, including: The DC / AC circuit operates in inverter mode; The photovoltaic DC / DC circuit operates in maximum power point tracking mode; The energy storage DC / DC circuit determines the current power level of the energy storage unit, and operates in charging mode when the power level of the energy storage unit is less than the upper limit of the rechargeable power level. The second voltage range is from Udcr+ΔUdc to Udcr+2ΔUdc, where Udcr is the voltage reference value and ΔUdc is the voltage adjustment value.

8. The control method according to claim 5, characterized in that, When the bus voltage is in the third voltage range, the photovoltaic DC / DC circuit, the energy storage DC / DC circuit, and the DC / AC circuit adjust their operating states according to the voltage range in which the bus voltage is located, including: The DC / AC circuit operates in inverter mode; The photovoltaic DC / DC circuit reduces the output power; The energy storage DC / DC circuit determines the current power level of the energy storage unit, and operates in charging mode when the power level of the energy storage unit is less than the upper limit of the rechargeable power level. The third voltage range is greater than Udcr + 2ΔUdc, where Udcr is the voltage reference value and ΔUdc is the voltage adjustment value.

9. The control method according to claim 7 or 8, characterized in that, After the energy storage DC / DC circuit determines the current power level of the energy storage unit, the control method further includes: If the energy storage unit's charge exceeds the maximum rechargeable capacity, the energy storage DC / DC circuit stops charging the energy storage unit.

10. The control method according to claim 5, characterized in that, When the bus voltage is in the fourth voltage range, the photovoltaic DC / DC circuit, the energy storage DC / DC circuit, and the DC / AC circuit adjust their operating states according to the voltage range in which the bus voltage is located, including: The DC / AC circuit operates in rectification mode; The photovoltaic DC / DC circuit operates in maximum power point tracking mode; The energy storage DC / DC circuit determines the current power of the energy storage unit, and operates in discharge mode when the power of the energy storage unit is greater than the lower discharge limit. The fourth voltage range is from Udcr-2ΔUdc to Udcr-ΔUdc, where Udcr is the voltage reference value and ΔUdc is the voltage adjustment value.

11. The control method according to claim 5, characterized in that, When the bus voltage is in the fifth voltage range, the photovoltaic DC / DC circuit, the energy storage DC / DC circuit, and the DC / AC circuit adjust their operating states according to the voltage range in which the bus voltage is located, including: The DC / AC circuit operates in rectification mode and stops the voltage supply to at least a portion of the load devices; The photovoltaic DC / DC circuit operates in maximum power point tracking mode; The energy storage DC / DC circuit determines the current power of the energy storage unit, and operates in discharge mode when the power of the energy storage unit is greater than the lower discharge limit. The fifth voltage range is less than Udcr-2ΔUdc, where Udcr is the voltage reference value and ΔUdc is the voltage adjustment value.

12. The control method according to claim 11, characterized in that, The DC / AC circuit stops the voltage supply to at least a portion of the load devices, including: The DC / AC circuit acquires the priority of the load device; The DC / AC circuit stops the voltage supply to the load device in order of priority from low to high.

13. The control method according to claim 10 or 11, characterized in that, After the energy storage DC / DC circuit determines the current power level of the energy storage unit, the control method further includes: When the energy storage unit's charge is less than the lower limit of its discharge capacity, the energy storage DC / DC circuit stops discharging the energy storage unit.

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