Energy system

Abstract

This application provides an energy system relating to the field of power conversion technology. The energy system includes: at least one boost converter for boosting the output voltage of a first photovoltaic unit and connecting it to a first DC bus; at least one buck converter for stepping down the output voltage of a second photovoltaic unit and connecting it to a second DC bus; a first charge / discharge module for energy transfer between the first and second DC buses; at least one first energy storage unit connected to the second DC bus and connected to the first DC bus via the first charge / discharge module; and an inverter unit connected to the first DC bus for converting the input DC power into AC power and outputting it to the power grid or a load. This application employs a hybrid bus structure design, which reduces device costs and energy losses, thereby lowering the overall cost of the energy system and improving overall efficiency.

Description

Technical Field

[0001] This application relates to the field of power conversion technology, and more specifically to an energy system. Background Technology

[0002] In a photovoltaic (PV) energy system, PV units are connected to the DC bus via boost or buck DC converters to provide power to the system. Energy storage units are connected to the DC bus via charge / discharge modules for energy storage and release. The PV energy system requires energy dispatching among the PV units, energy storage units, and loads based on load demand.

[0003] In related technologies, photovoltaic energy systems adopt a single bus structure, with all photovoltaic units connected to a single high-voltage DC bus or low-voltage DC bus. This single bus structure has the problem of high system cost in different application scenarios. Utility Model Content

[0004] This application provides an energy system that can reduce the cost of energy systems.

[0005] This application provides an energy system, comprising: at least one boost converter, one end of which is connected to a first photovoltaic unit and the other end to a first DC bus, for boosting the output voltage of the first photovoltaic unit and outputting it to the first DC bus; at least one buck converter, one end of which is connected to a second photovoltaic unit and the other end to a second DC bus, for stepping down the output voltage of the second photovoltaic unit and outputting it to the second DC bus; a first charge / discharge module, one end of which is connected to the first DC bus and the other end to the second DC bus, for energy transfer between the first DC bus and the second DC bus; at least one first energy storage unit, which is connected to the second DC bus and connected to the first DC bus through the first charge / discharge module; and an inverter unit, which is connected to the first DC bus, for converting the input DC power into AC power and outputting it to the power grid or a load.

[0006] Optionally, the energy system further includes a second energy storage unit and a second charging and discharging module, wherein the second energy storage unit is connected to the first DC bus through the second charging and discharging module.

[0007] Optionally, the first photovoltaic unit includes N photovoltaic input channels, which are connected to the first DC bus through the at least one boost converter; the second photovoltaic unit includes M photovoltaic input channels, which are connected to the second DC bus through the at least one buck converter; wherein, the voltage of the first DC bus is higher than the voltage of the second DC bus, and N and M are integers greater than or equal to 1.

[0008] Optionally, the ratio between N and M is approximately equal to the ratio of the first power to the second power; wherein the first power is determined based on the output power of the inverter unit, and the second power is determined based on the difference between the total output power of the first photovoltaic unit and the second photovoltaic unit and the output power of the inverter unit.

[0009] Optionally, the photovoltaic input channel is equipped with a maximum power point tracking control module; the maximum power point tracking control module is used to calculate the maximum power point based on the collected input voltage and input current, and output the corresponding voltage reference value.

[0010] Optionally, the maximum power point tracking control module includes: a voltage sampling circuit for acquiring the input voltage of the photovoltaic input channel; a current sampling circuit for acquiring the input current of the photovoltaic input channel; and a calculation circuit for calculating the maximum power point based on the input voltage and the input current, and outputting a voltage reference value corresponding to the maximum power point.

[0011] Optionally, the boost converter or the buck converter receives the voltage reference value through a controller in the energy system and generates a current reference value based on the voltage reference value; the controller also generates a duty cycle control signal based on the deviation between the current reference value and the actual current.

[0012] Optionally, the first charging and discharging module includes a bidirectional DC-DC converter; the bidirectional DC-DC converter adjusts the phase shift angle through a controller in the energy system.

[0013] Optionally, the inverter unit is regulated by a controller in the energy system to synchronize the phase and frequency with the grid voltage in grid-connected mode.

[0014] Optionally, the boost converter is a boost DC-DC converter, and the buck converter is a buck DC-DC converter.

[0015] In several embodiments provided in this application, a hybrid bus structure design is adopted. The first photovoltaic unit is connected to the first DC bus via a boost converter, and the second photovoltaic unit is connected to the second DC bus via a buck converter. Energy is transferred between the first and second DC buses through a first charging / discharging module. This avoids the low-voltage, high-current operation problem caused by configuring buck converters for all photovoltaic units in a low-voltage bus structure, and also avoids the device cost problem caused by configuring high-power charging / discharging modules in a high-voltage bus structure. This reduces device cost and energy loss, thereby lowering the overall cost of the energy system. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0017] Figure 1 This is a structural schematic diagram of a high-voltage DC bus scheme in related technologies;

[0018] Figure 2 This is a structural schematic diagram of a low-voltage DC bus scheme in related technologies;

[0019] Figure 3 This is a schematic diagram of the structure of an energy system provided in one embodiment of this application.

[0020] Figure 4 This is a schematic diagram of an energy system provided for another embodiment of this application.

[0021] Figure 5 This is a schematic diagram of an energy system provided for another embodiment of this application.

[0022] Figure 6 A control block diagram of a boost converter is provided for one embodiment of this application.

[0023] Figure 7 A control block diagram of a buck converter is provided for one embodiment of this application.

[0024] Figure 8 A control block diagram of a first charge / discharge module provided in one embodiment of this application.

[0025] Figure 9 This application provides a control block diagram of an inverter unit in grid-connected mode, as an embodiment of the present application.

[0026] Figure 10This application provides a control block diagram of an inverter unit in off-grid mode, as an embodiment of the present application. Detailed Implementation

[0027] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0028] In the description of the embodiments of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0029] In a typical photovoltaic (PV) energy system, PV units (such as solar photovoltaic modules) convert solar energy into direct current (DC) power, which is then connected to the DC bus via a boost or buck DC converter to supply power to loads or energy storage units. Energy storage units (such as battery packs) are connected to the DC bus via charge / discharge modules for energy storage and release. The PV energy system dynamically schedules energy among the PV units, energy storage units, and loads based on load demand to achieve power balance and stable operation.

[0030] In related technologies, photovoltaic energy systems employ a single busbar structure, meaning all photovoltaic units are connected to a DC busbar of the same voltage level, and then the electrical energy is output to the AC side via an inverter unit (such as an inverter). Depending on the busbar voltage level, related schemes can be divided into high-voltage busbar schemes and low-voltage busbar schemes. In high-voltage busbar schemes, for example... Figure 1 As shown, the outputs of all photovoltaic units 110 are connected to the high-voltage DC bus 130 after passing through a boost DC converter 120. However, since the energy storage unit 140 typically operates on a low-voltage platform, a high-power charging / discharging module 150 supporting high-voltage side operation is required to achieve energy exchange with the high-voltage DC bus 130. The control strategy for this type of charging / discharging module is complex, and the device selection requirements are high, resulting in a higher overall system cost. In a low-voltage bus solution, for example... Figure 2As shown, the outputs of all photovoltaic units 210 are connected to the low-voltage DC bus 230 via a step-down DC converter 220, sharing the same low-voltage platform with the energy storage unit 240. Since the output voltage of the photovoltaic unit 210 is typically higher than the operating voltage of the energy storage unit 240, a step-down converter is needed for voltage matching with the energy storage unit 240. This results in the step-down DC converter 220 operating under low-voltage, high-current conditions, leading to relatively low conversion efficiency, higher conduction and switching losses in the power devices, and consequently, higher overall system cost.

[0031] In a typical application scenario, assuming the total output power of all photovoltaic units is 2200W, the inverter unit outputs 1600W to the AC side, and the remaining 600W is stored by the energy storage unit. If a high-voltage busbar scheme is adopted, such as... Figure 1 As shown, the energy storage unit 140 needs to interact with the high-voltage DC bus 130 via a high-power charge / discharge module 150. At this time, the charge / discharge module 150 needs to have a processing capacity of 2200W to cope with the power difference between the photovoltaic unit input and the inverter unit output, which leads to capacity redundancy in the energy storage side equipment. If a low-voltage bus solution is adopted, such as... Figure 2 As shown, since the output voltage of the photovoltaic unit 210 is higher than the operating voltage of the energy storage unit 240, voltage matching is required through a step-down converter. During this process, the step-down DC-DC converter 220 operates under low-voltage, high-current conditions, which not only leads to a significant increase in conduction and switching losses, but also increases system costs due to component selection.

[0032] Therefore, how to reduce system costs and improve overall efficiency while meeting power supply and energy storage needs has become a key technical problem that urgently needs to be solved.

[0033] Please see Figure 3 . Figure 3An energy system 300 is provided according to an embodiment of this application. The energy system 300 includes: at least one boost converter 321, one end of which is connected to a first photovoltaic unit 311, and the other end of which is connected to a first DC bus 331, for boosting the output voltage of the first photovoltaic unit 311 and outputting it to the first DC bus 331. At least one buck converter 322, one end of which is connected to a second photovoltaic unit 312, and the other end of which is connected to a second DC bus 332, for bucking the output voltage of the second photovoltaic unit 312 and outputting it to the second DC bus 332. A first charge / discharge module 351, one end of which is connected to the first DC bus 331, and the other end of which is connected to the second DC bus 332, for energy transfer between the first DC bus 331 and the second DC bus 332. The energy system 300 also includes at least one energy storage unit 340 and an inverter unit 360. At least some of the energy storage units are connected to the second DC bus 332 and to the first DC bus 331 via the first charge / discharge module 351. The inverter unit 360 is connected to the first DC bus 331 and is used to convert the input DC power into AC power and output it to the power grid or load.

[0034] In this embodiment, the first photovoltaic unit 311 and the second photovoltaic unit 312 are devices capable of converting solar energy into direct current (DC) power. Each photovoltaic unit may include multiple photovoltaic arrays. The first photovoltaic unit 311 and the second photovoltaic unit 312 are two independently configured units that can be used to collect solar energy resources under different spatial regions or environmental conditions. The number of photovoltaic arrays in the first photovoltaic unit 311 and the second photovoltaic unit 312 can be set according to actual needs. For example, the first photovoltaic unit 311 includes N photovoltaic arrays, each connected to the boost converter 321 through a photovoltaic input channel; the second photovoltaic unit 312 includes M photovoltaic arrays, each connected to the buck converter 322 through a photovoltaic input channel. Specifically, the output voltage of the first photovoltaic unit 311 is boosted by the boost converter 321 and then connected to the first DC bus 331 to increase the voltage output of the first photovoltaic unit 311 to the voltage range required by the first DC bus, thereby achieving efficient energy transmission. The output voltage of the second photovoltaic unit 312 is stepped down by the buck converter 322 and then connected to the second DC bus 332. This reduces the voltage output by the second photovoltaic unit 312 to the voltage range required by the second DC bus, making it suitable for energy storage units or other low-voltage applications. The boost converter 321 can be a boost DC-DC converter, and the buck converter 322 can be a buck DC-DC converter. The first DC bus 331 and the second DC bus 332 are connected by a first charging / discharging module 351. The first charging / discharging module 351 can be, for example, a bidirectional DC-DC converter, used for bidirectional energy transfer between the first DC bus 331 and the second DC bus 332, thereby achieving power regulation and energy complementarity between the two DC buses. The first charging / discharging module 351 can dynamically control the energy flow according to the operating status of the energy system, ensuring stable operation of the energy system under different operating conditions.

[0035] The energy system in this embodiment adopts a hybrid bus structure design. Some photovoltaic (PV) units are connected to the first DC bus (high-voltage DC bus) via a boost converter, while others are connected to the second DC bus (low-voltage DC bus) via a buck converter. Compared to the low-voltage bus structure, this embodiment eliminates the need for buck converters for all PV units, thereby reducing conduction and switching losses under low-voltage, high-current conditions and lowering the selection cost of power devices. Simultaneously, it avoids the need for high-power charging / discharging modules in the high-voltage bus structure to address the power difference between the PV unit input and the inverter unit output. Since the energy storage unit can be directly connected to the low-voltage DC bus without high-power energy exchange with the high-voltage DC bus, the capacity requirements and selection complexity of the charging / discharging modules are reduced, lowering the overall system cost. Furthermore, the charging / discharging module between the high-voltage and low-voltage DC buses enables energy transfer and power coordination between the two voltage platforms, allowing the energy system to adjust energy flow according to actual operating conditions and improving system stability.

[0036] In some embodiments, all energy storage units are connected to the second DC bus and to the first DC bus via the first charging and discharging module.

[0037] In this embodiment, the energy storage unit can be an energy storage device with charging and discharging capabilities, such as a lithium-ion battery pack or a lithium iron phosphate battery pack. The energy storage unit is connected to the second DC bus and can store excess energy when the output power of the photovoltaic unit exceeds the load power, and can also release energy when there is insufficient sunlight or the load power increases, thus maintaining the system's energy balance and stable operation. Simultaneously, the energy storage unit is also connected to the first DC bus via a first charging and discharging module. The first charging and discharging module can be a bidirectional DC-DC converter, with bidirectional transmission functions for charging the energy storage unit from the high-voltage DC bus to the low-voltage DC bus and supplying power to the load from the low-voltage DC bus to the high-voltage DC bus. When the output power of the photovoltaic unit is high and the load power is low, the first charging and discharging module can be controlled to transfer excess energy from the high-voltage DC bus to the low-voltage DC bus to charge the energy storage unit. When the load power is high but the output power of the photovoltaic unit is insufficient, the energy storage unit can discharge in reverse to the high-voltage DC bus through the first charging and discharging module to help maintain continuous power supply to the load. In this embodiment, the energy storage unit can not only directly interact with the low-voltage DC bus, but also achieve bidirectional energy regulation between the high-voltage DC bus and the low-voltage DC bus through the first charging and discharging module, thereby enhancing the system's adaptability under different operating conditions.

[0038] Specifically, with Figure 4 For example. In Figure 4In this system, energy storage unit 440 includes two first energy storage units 441. The first energy storage units 441 are connected to the second DC bus 432. They can store excess electrical energy when the output power of the first photovoltaic unit 411 and the second photovoltaic unit 412 exceeds the load demand, and can also release electrical energy when there is insufficient sunlight or increased load, thus achieving energy balance in the system. Simultaneously, the first energy storage units 441 are also connected to the first DC bus 431 via a first charge / discharge module 451. The first charge / discharge module 451 can be a bidirectional buck-boost converter, supporting bidirectional energy flow between the first DC bus 431 and the second DC bus 432. When the output power of the photovoltaic unit 410 is high and the load power is low, some energy on the first DC bus 431 is transferred to the second DC bus 432 through the first charge / discharge module 451 to charge the energy storage unit 440. When the load power is high and the output power of the photovoltaic unit 410 is insufficient, the energy storage unit 440 can discharge in reverse to the first DC bus 431 through the first charge / discharge module 451 to compensate for the energy gap. This configuration structure enhances the adaptability of the energy system 400 to various operating conditions.

[0039] In some embodiments, some energy storage units are connected to the second DC bus and to the first DC bus via the first charge / discharge module; other energy storage units are connected to the first DC bus via the second charge / discharge module.

[0040] In this embodiment, some energy storage units are connected to the second DC bus and then to the first DC bus via a first charge / discharge module. Other energy storage units are directly connected to the first DC bus via a second charge / discharge module. The energy storage units connected to the second DC bus can, on the one hand, absorb excess energy from the low-voltage DC bus for storage; on the other hand, when the load power increases or the photovoltaic unit's output power is insufficient, they can also discharge to the first DC bus via the first charge / discharge module to provide power support to the load. Energy storage units connected to the first DC bus only via the second charge / discharge module are suitable for energy storage devices with higher operating voltages, such as high-voltage battery clusters. This energy storage unit does not need to exchange energy directly with the high-voltage DC bus without going through the low-voltage DC bus, and its charging and discharging process is controlled by the second charge / discharge module, enabling rapid response to load changes on the high-voltage DC bus side and enhancing the dynamic response capability of the high-voltage DC bus. In this embodiment, the energy system can be flexibly configured according to the voltage level and dynamic characteristics of the energy storage units, allowing different energy storage units to operate collaboratively on different voltage platforms. Meanwhile, through the coordinated operation of different charging and discharging modules, the system can achieve energy scheduling between multiple paths and different voltage levels, improving its adaptability under complex operating conditions and overall energy efficiency.

[0041] Specifically, with Figure 5 For example. In Figure 5In this configuration, energy storage unit 540 includes a first energy storage unit 541 and a second energy storage unit 542. The first energy storage unit 541 is connected to a second DC bus 532 and is also connected to the first DC bus 531 via a first charge / discharge module 551. The second energy storage unit 542 is directly connected to the first DC bus 531 via a second charge / discharge module 552. Specifically, the first energy storage unit 541 can absorb excess electrical energy from the low-voltage DC bus for storage; furthermore, when the load power increases or the photovoltaic unit's output power is insufficient, it can also discharge to the first DC bus 531 via the first charge / discharge module 551 to provide electrical support to the load. The second energy storage unit 542 is connected to the first DC bus 531 only via the second charge / discharge module 552, making it suitable for energy storage devices with higher operating voltages. The second energy storage unit 542 can directly exchange energy with the high-voltage DC bus without going through the low-voltage DC bus. Its charging and discharging process is controlled by the second charging and discharging module 552, thereby achieving rapid response to load changes on the high-voltage DC bus side and enhancing the dynamic response capability of the high-voltage DC bus. Through this configuration, the energy system can be flexibly and distributed according to the voltage level and dynamic characteristics of the energy storage units, enabling different energy storage units to operate collaboratively on different voltage platforms. Simultaneously, through coordinated control between different charging and discharging modules, the system can achieve energy dispatch across multiple paths, improving its adaptability under complex operating conditions and overall energy efficiency.

[0042] In some embodiments, the first photovoltaic unit includes N photovoltaic input channels, which are connected to a first DC bus via a boost converter. The second photovoltaic unit includes M photovoltaic input channels, which are connected to a second DC bus via a buck converter. The ratio between N and M is approximately equal to the ratio of the first power to the second power; the first power is determined based on the output power of the inverter unit, and the second power is determined based on the difference between the total output power of the first and second photovoltaic units and the output power of the inverter unit.

[0043] In this embodiment, the first photovoltaic unit includes N photovoltaic input channels, each of which can be connected to a photovoltaic module or photovoltaic array. Its output voltage is boosted by a boost converter and then connected to the first DC bus. The second photovoltaic unit includes M photovoltaic input channels, each of which can also be connected to a photovoltaic module or photovoltaic array. Its output voltage is stepped down by a buck converter and then connected to the second DC bus. The voltage of the first DC bus is higher than the voltage of the second DC bus. To allocate power reasonably, in the specific implementation, the ratio between N and M is configured according to the ratio of the first power to the second power. Here, N and M are integers greater than or equal to 1. The first power represents the output power of the inverter unit, i.e., the power transmitted by the inverter unit to the AC side; the second power represents the difference between the total output power of the first and second photovoltaic units and the output power of the inverter unit, i.e., the power absorbed or released by the energy storage unit. Since boost converters generally have higher efficiency and lower cost than buck converters, by reasonably configuring the ratio between N and M, the overall cost of the energy system can be reduced and its comprehensive energy efficiency improved while meeting power requirements.

[0044] Specifically, with Figure 4 For example. In Figure 4 In this example, assuming the total output power of photovoltaic unit 410 is 2200W and the output power of inverter unit 460 is 1600W, the power difference between them is 600W, which is absorbed and stored by energy storage unit 440. Under this power condition, if... Figure 4 In the hybrid bus scheme shown, the ratio between the number of photovoltaic input channels N connected to the boost converter and the number of photovoltaic input channels M connected to the buck converter can be approximated by the following formula: N / M ≈ Output power of the inverter unit / (Total output power of the photovoltaic unit - Output power of the inverter unit) ≈ 1600 / 600 ≈ 3. Based on this ratio, more photovoltaic input channels can be connected to the high-voltage DC bus to directly power the inverter unit, meeting the main power requirements of the load. Test results at the same power level show that if... Figure 1 The high-voltage busbar scheme shown requires a 2200W high-power charging and discharging module, high-grade power devices, and significant cost. The total system cost is approximately 529 yuan, with a conversion efficiency of approximately 92.4%. If the following is adopted... Figure 2 In the low-voltage busbar scheme shown, because all photovoltaic input channels require buck converters, losses increase under low-voltage, high-current operation, resulting in a total system cost of approximately 494 yuan and a conversion efficiency of approximately 87.4%. However, using... Figure 4In the hybrid bus scheme shown, only 1 / 4 of the photovoltaic input channels are equipped with buck converters, and the first charge / discharge module only needs to handle a power difference of 600W. The total system cost is approximately 449, and the conversion efficiency reaches 93.6%. Therefore, this embodiment optimizes the power path by rationally configuring the photovoltaic input channels, effectively reducing energy system costs and improving energy efficiency while meeting energy system performance requirements.

[0045] In some embodiments, the photovoltaic input channel is equipped with a maximum power point tracking (MPPT) control module. The MPPT control module calculates the maximum power point based on the acquired input voltage and current, and outputs the corresponding voltage reference value. The boost converter or buck converter receives the voltage reference value through a controller in the energy system and generates a current reference value based on the voltage reference value. The controller also generates a duty cycle control signal based on the deviation between the current reference value and the actual current.

[0046] In this embodiment, the photovoltaic input channel is equipped with a maximum power point tracking (MPPT) control module, which can be used to dynamically track the maximum power point of the photovoltaic input channel under different illumination conditions. The MPPT control module acquires the photovoltaic input voltage and input current, calculates the corresponding optimal operating point voltage based on the MPPT algorithm, and outputs this optimal operating point voltage as a voltage reference value. Specifically, the MPPT control module may include: a voltage sampling circuit for acquiring the input voltage of the photovoltaic input channel; a current sampling circuit for acquiring the input current of the photovoltaic input channel; and a calculation circuit for calculating the maximum power point based on the input voltage and input current, and outputting the voltage reference value corresponding to the maximum power point. Correspondingly, the boost converter or buck converter is equipped with a controller, which can be integrated inside the boost converter or buck converter, or it can be located externally, for example, a system controller of the energy system. The controller further includes a voltage loop and a current loop. The voltage loop receives the voltage reference value, compares it with the actual photovoltaic input voltage, and generates a current reference value based on the voltage deviation through proportional-integral (PI) adjustment or other methods. The current loop further compares the current reference value with the actual output current, calculates the control signal based on the current deviation, and outputs a duty cycle command to adjust the operating state of the boost converter or buck converter. Through this control structure, the energy system can dynamically adjust the boost converter or buck converter according to the current operating state of the photovoltaic modules, ensuring that the photovoltaic units continuously operate at their optimal power point and further improving the system's energy transmission efficiency.

[0047] In some embodiments, the first charging and discharging module includes a bidirectional DC-DC converter; the bidirectional DC-DC converter adjusts the phase shift angle via a controller in the energy system.

[0048] In this embodiment, the first charging and discharging module includes a bidirectional DC-DC converter, which is correspondingly equipped with a controller. The controller can be integrated inside the bidirectional DC-DC converter or located externally, such as using a system controller for the energy system. The controller includes a phase-shift control module, which can precisely control the direction of current transmission and the power amplitude by adjusting the phase shift angle of the voltage waveform between the high-voltage DC bus side and the low-voltage DC bus side. This allows the bidirectional DC-DC converter to be in charging mode (energy is transferred from the first DC bus to the second DC bus) or discharging mode (energy is transferred from the second DC bus to the first DC bus). This control method can flexibly adjust the direction of energy flow and the power magnitude without changing the circuit topology, and has the advantages of fast response speed and high adjustment accuracy, which helps to improve the response capability and stable control of the energy system during dynamic operation.

[0049] In some embodiments, the inverter unit is regulated by a controller in the energy system to synchronize the phase and frequency with the grid voltage in grid-connected mode.

[0050] In this embodiment, the inverter unit is equipped with a corresponding controller. The controller can be integrated inside the inverter unit or located externally, such as using the system controller of the energy system. The controller includes a phase-locked loop (PLL) module. The PLL module can sample the AC voltage signal from the grid side, extract the fundamental component of the voltage waveform and obtain its phase information, and compare it with a local reference signal to generate a phase angle for synchronization control. This phase angle can be used to generate a reference signal for a sinusoidal modulation wave, enabling the AC current output by the inverter unit to accurately track the grid voltage in both frequency and phase, achieving grid-connected operation with unity power factor. Using this PLL control strategy effectively prevents frequency drift or phase shift between the inverter output and the grid voltage, contributing to improved grid-connected stability of the energy system.

[0051] The energy system provided in this application embodiment is widely applicable to various typical application scenarios. The control strategies of the system under different operating conditions are described below.

[0052] Scenario 1: The photovoltaic unit supplies power only to the energy storage unit.

[0053] Specifically, with Figure 4 For example, in this operating scenario, the first photovoltaic unit and the boost converter together form a current source. The output voltage of the first photovoltaic unit is boosted and then supplies power to the first DC bus. The control block diagram of the boost converter at this time is as follows: Figure 6 As shown in the diagram. The second photovoltaic unit and the buck converter together form another current source. The output voltage of the second photovoltaic unit is stepped down and then supplied to the second DC bus. The control block diagram of the buck converter at this time is shown in the diagram. Figure 7As shown. The energy storage unit and the first charging / discharging module together form a voltage source to maintain the stability of the first DC bus voltage and absorb the output power from the first photovoltaic unit and the second photovoltaic unit. The control structure of the first charging / discharging module at this time is as follows. Figure 8 As shown, the inverter unit is in a shutdown state and does not transmit power to the AC load or the power grid.

[0054] Scenario 2: The photovoltaic unit supplies power to both the inverter unit and the energy storage unit simultaneously.

[0055] Specifically, with Figure 4 For example, in this operating scenario, the first photovoltaic unit and the boost converter together form a current source. The output voltage of the first photovoltaic unit is boosted and then supplies power to the first DC bus. The control structure of the boost converter at this time is as follows: Figure 6 As shown in the diagram. The second photovoltaic unit and the buck converter together form another current source. The output of the second photovoltaic unit is converted to a step-down converter and then supplies power to the second DC bus. The control structure of the buck converter at this time is as follows: Figure 7 As shown. The energy storage unit and the first charging / discharging module together form a voltage source to maintain the voltage stability of the first DC bus and dynamically adjust the power absorbed by the energy storage unit according to the output power of the inverter unit. The control structure of the first charging / discharging module at this time is as follows. Figure 8 As shown. When the inverter unit is in operation, and it operates in grid-connected mode, a phase-locked loop (PLL)-based grid-connected control strategy is adopted. The corresponding control structure is as follows: Figure 9 As shown. When the inverter unit operates in off-grid mode, an off-grid control strategy based on a virtual grid voltage reference is adopted, and the corresponding control structure is as follows. Figure 10 As shown.

[0056] Scenario 3: The photovoltaic unit and the energy storage unit jointly supply power to the inverter unit.

[0057] Specifically, with Figure 4 For example, in this operating scenario, the first photovoltaic unit and the boost converter together form a current source. The output voltage of the first photovoltaic unit is boosted and then supplies power to the first DC bus. The control structure of the boost converter at this time is as follows: Figure 6 As shown in the diagram. The second photovoltaic unit and the buck converter together form another current source. The output of the second photovoltaic unit is connected to the second DC bus after being buck-converted. The control structure of the buck converter at this time is as follows. Figure 7 As shown in the diagram. The energy storage unit and the first charging / discharging module together form a voltage source to maintain the voltage stability of the first DC bus and provide power compensation to the first DC bus when the output power of the photovoltaic unit is insufficient. The control structure of the first charging / discharging module at this time is as follows: Figure 8 As shown. When the inverter unit is in operation, and it operates in grid-connected mode, a phase-locked loop (PLL)-based grid-connected control strategy is adopted. The corresponding control structure is as follows: Figure 9As shown. When the inverter unit operates in off-grid mode, an off-grid control strategy based on a virtual grid voltage reference is adopted, and the corresponding control structure is as follows. Figure 10 As shown.

[0058] Scenario 4: Power is supplied to the inverter unit only by the energy storage unit.

[0059] Specifically, with Figure 4 For example, in this operating scenario, both the first and second photovoltaic units are in a no-power-output state, and the energy system relies solely on the energy storage unit for power. The energy storage unit and the first charging / discharging module together form a voltage source, supplying energy to the first DC bus and maintaining its voltage stability. The first charging / discharging module dynamically adjusts the output power of the energy storage unit according to the power demand of the inverter unit. The control structure of the first charging / discharging module at this time is as follows: Figure 8 As shown. When the inverter unit is in operation, and it operates in grid-connected mode, a phase-locked loop (PLL)-based grid-connected control strategy is adopted. The corresponding control structure is as follows: Figure 9 As shown. When the inverter unit operates in off-grid mode, an off-grid control strategy based on a virtual grid voltage reference is adopted, and the corresponding control structure is as follows. Figure 10 As shown.

[0060] Scenario 5: The AC power grid supplies power to the energy storage unit in reverse.

[0061] Specifically, with Figure 4 For example, in this operating scenario, both the first and second photovoltaic units are in a state of no power output, and the energy storage unit has insufficient power, requiring supplemental power from the AC grid. At this time, the inverter unit operates in grid-connected mode as a rectifier, absorbing energy from the AC grid and converting it into DC power for transmission to the first DC bus. The corresponding control structure is as follows: Figure 9 As shown in the diagram. The energy storage unit and the first charging / discharging module together form a voltage source, and the first charging / discharging module absorbs energy from the first DC bus to charge the energy storage unit. The first charging / discharging module dynamically adjusts the direction and amplitude of the current according to the first DC bus voltage and charging power requirements. The control structure of the first charging / discharging module is as follows: Figure 8 As shown.

[0062] Specifically, in Figure 6 In the process, the output voltage u of the first photovoltaic unit is sampled. pv1 and output current i pv1 (i.e., the photovoltaic input voltage and input current of the photovoltaic input channel), and calculate the optimal operating point voltage based on the maximum power point tracking (MPPT) control algorithm to obtain the voltage reference value u. pv1ref The voltage reference value u pv1ref With the actual photovoltaic input voltage u pv1 The difference is input to the voltage loop PI regulator, and the output current reference value i is...o1ref Simultaneously, the output current i of the sampled boost converter is... o1 Compare it with the current reference value i o1ref The comparison is performed, and a corresponding PWM duty cycle signal is generated through the current loop PI regulator to drive the main switching device of the boost converter, thereby realizing closed-loop control of its operating state.

[0063] exist Figure 7 In the process, the output voltage u of the second photovoltaic unit is sampled. pv2 and output current i pv2 The optimal operating point voltage is calculated based on the maximum power point tracking (MPPT) control algorithm, and the voltage reference value u is obtained. pv2ref The voltage reference value u pv2ref With the actual photovoltaic input voltage u pv2 The difference is input to the voltage loop PI regulator, and the output current reference value i is... o2ref Simultaneously, the output current i of the sampling buck converter is measured. o2 Compare it with the current reference value i o2ref The comparison is performed, and a corresponding PWM duty cycle signal is generated through the current loop PI regulator to drive the main switching device of the buck converter, thereby realizing closed-loop control of its operating state.

[0064] exist Figure 8 In the process, the first DC bus voltage u is sampled. bus1 And compare it with the set bus voltage reference value u busref1 The difference signal is compared and input to the voltage loop PI regulator, which outputs the current loop reference value i. o3ref Simultaneously, the output current i of the first charging and discharging module is sampled. o3 and compare it with the current loop reference value i o3ref The difference signal is compared and input to the current loop PI regulator to generate the phase shift angle error. The phase shift angle error With the preset offset phase angle The initial phase shift angle is obtained by adding them together. After mirroring, the final phase shift angle is output. The main switching device is used to drive the first charging and discharging module, thereby achieving closed-loop control of its operating state.

[0065] exist Figure 9 In the grid connection mode shown, the grid voltage u is sampled. g The phase information is extracted using a phase-locked loop (PLL) to generate the sinusoidal component sinθ of the phase-locked angle θ. Based on the current reference i output by the photovoltaic unit... pv and the current reference i output by the energy storage unit bat Synthetic grid-connected current reference value i orefmMultiplying this by the sinusoidal component sinθ yields the grid-connected sinusoidal current reference i. oref At the same time, the actual grid-connected current i of the sampling inverter unit is measured. o Compare it with the sinusoidal current reference i oref The difference signal is compared and input to the proportional-resonant (PR) regulator to generate a corresponding PWM duty cycle signal, which is used to drive the main switching device of the inverter unit to achieve accurate tracking of the AC output current and unity power factor operation.

[0066] exist Figure 10 In the off-grid mode shown, the self-generated virtual grid voltage u gr The phase information is extracted using a phase-locked loop (PLL) to generate the sinusoidal component sinθ of the phase-locked angle θ. The off-grid output voltage amplitude u is then set. orefm Multiplying this by the sinusoidal component sinθ yields the off-grid sinusoidal voltage reference u. oref At the same time, the actual output voltage u of the sampling inverter unit is measured. o Compare it with the sinusoidal voltage reference u oref The difference signal is compared and input to the proportional-resonant (PR) regulator to generate a corresponding PWM duty cycle signal, which is used to drive the main switching device of the inverter unit to achieve stable control of the AC output voltage and optimization of waveform quality.

[0067] Of course, in other embodiments, different system structures or control strategies may be adopted, and this application does not limit them.

[0068] It is understood that the term "connection" in the embodiments of this application can be interpreted as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc. can transmit electrical signals or data to each other.

[0069] It is understood that the specific examples in this document are only intended to help those skilled in the art better understand the embodiments of this application, and are not intended to limit the scope of this utility model.

[0070] It is understood that in the various embodiments of this application, the sequence number of each process does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0071] It is understood that the various embodiments described in this application can be implemented individually or in combination, and the embodiments of this application are not limited in this respect.

[0072] Unless otherwise stated, all technical and scientific terms used in the embodiments of this application have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items. The singular forms "a," "the," and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0073] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0074] The above description is merely a specific embodiment of this application, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the protection scope of this application. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. An energy system, characterized in that, include: At least one boost converter is provided, with one end of the boost converter connected to the first photovoltaic unit and the other end connected to the first DC bus, for boosting the output voltage of the first photovoltaic unit and outputting it to the first DC bus; At least one buck converter is provided, with one end of the buck converter connected to the second photovoltaic unit and the other end connected to the second DC bus, for stepping down the output voltage of the second photovoltaic unit and outputting it to the second DC bus; A first charging and discharging module, one end of which is connected to the first DC bus and the other end of which is connected to the second DC bus, is used to transfer energy between the first DC bus and the second DC bus; At least one first energy storage unit, wherein the at least one first energy storage unit is connected to the second DC bus and is connected to the first DC bus through the first charging and discharging module; An inverter unit, connected to the first DC bus, is used to convert the input DC power into AC power and output it to the power grid or load.

2. The energy system according to claim 1, characterized in that, The energy system further includes a second energy storage unit and a second charging and discharging module, wherein the second energy storage unit is connected to the first DC bus through the second charging and discharging module.

3. The energy system according to claim 1 or 2, characterized in that, The first photovoltaic unit includes N photovoltaic input channels, which are connected to the first DC bus through at least one boost converter; The second photovoltaic unit includes M photovoltaic input channels, which are connected to the second DC bus through the at least one step-down converter; Wherein, the voltage of the first DC bus is higher than the voltage of the second DC bus, and N and M are integers greater than or equal to 1.

4. The energy system according to claim 3, characterized in that, The ratio between N and M is approximately equal to the ratio of the first power to the second power. The first power is determined based on the output power of the inverter unit, and the second power is determined based on the difference between the total output power of the first photovoltaic unit and the second photovoltaic unit and the output power of the inverter unit.

5. The energy system according to claim 3, characterized in that, The photovoltaic input channel is equipped with a maximum power point tracking control module; the maximum power point tracking control module is used to calculate the maximum power point based on the collected input voltage and input current, and output the corresponding voltage reference value.

6. The energy system according to claim 5, characterized in that, The maximum power point tracking control module includes: A voltage sampling circuit is used to acquire the input voltage of the photovoltaic input channel; A current sampling circuit is used to collect the input current of the photovoltaic input channel; The arithmetic circuit is used to calculate the maximum power point based on the input voltage and the input current, and output a voltage reference value corresponding to the maximum power point.

7. The energy system according to claim 5, characterized in that, The boost converter or the buck converter receives the voltage reference value through the controller in the energy system and generates a current reference value based on the voltage reference value; the controller also generates a duty cycle control signal based on the deviation between the current reference value and the actual current.

8. The energy system according to claim 1, characterized in that, The first charging and discharging module includes a bidirectional DC-DC converter; the bidirectional DC-DC converter adjusts the phase shift angle through a controller in the energy system.

9. The energy system according to claim 1, characterized in that, The inverter unit is regulated by the controller in the energy system to synchronize with the phase and frequency of the grid voltage in grid-connected mode.

10. The energy system according to claim 1, characterized in that, The boost converter is a boost DC-DC converter, and the buck converter is a buck DC-DC converter.

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