Photovoltaic power collection system and power adjustment method

Abstract

The application discloses a photovoltaic collection system and a power adjustment method. The photovoltaic collection system comprises at least one photovoltaic system, a direct-current collection device corresponding to each photovoltaic system, an energy storage system and a voltage source converter. Each photovoltaic system comprises at least one photovoltaic unit, and each photovoltaic unit comprises at least two photovoltaic branches connected in series. The output end of each photovoltaic system is connected with the input end of the corresponding direct-current collection device, and the output end of the direct-current collection device is connected with the input end of the energy storage system. The energy storage system is connected in parallel with the voltage source converter. The direct-current collection device is used for collecting the current generated by the at least one photovoltaic unit and outputting the collected current to the energy storage system.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and in particular to a photovoltaic collection system and a power adjustment method. Background Technology

[0002] Current photovoltaic (PV) grid connection technologies typically connect to the grid via AC inverters. However, when the capacity of a PV system reaches megawatts (MW) or higher, the need for multiple voltage boosting steps to medium and high voltage levels results in numerous intermediate steps, leading to lower overall grid connection efficiency for the entire PV system. Furthermore, with the increase in parallel PV grid-connected branches, the problems of circulating currents between these branches and oscillations with the grid become increasingly severe. Summary of the Invention

[0003] In view of this, embodiments of this application provide at least one photovoltaic collection system and a power adjustment method.

[0004] The technical solution of this application embodiment is implemented as follows:

[0005] In a first aspect, embodiments of this application provide a photovoltaic collection system, which includes at least one photovoltaic system, a DC collection device corresponding to each photovoltaic system, an energy storage system, and a voltage source converter valve.

[0006] Each photovoltaic system includes at least one photovoltaic unit, and each photovoltaic unit includes at least two photovoltaic branches connected in series.

[0007] The output of each photovoltaic system is connected to the input of its corresponding DC collector, and the output of the DC collector is connected to the input of the energy storage system; the energy storage system is connected in parallel with the voltage source converter valve; wherein...

[0008] A DC collector is used to collect the current generated by at least one photovoltaic unit and output the collected current to an energy storage system.

[0009] In this embodiment, a DC collection device can collect the current generated by photovoltaic units in at least one photovoltaic system into the energy storage system. This allows for the connection of a high-voltage photovoltaic power source (i.e., a photovoltaic unit comprising at least two series-connected photovoltaic branches) to a DC bus. Compared to related technologies that require step-by-step voltage boosting to medium and high voltage levels for large-capacity photovoltaic systems, this improves the efficiency of photovoltaic grid connection. Furthermore, the photovoltaic system sends current to the AC system through a voltage source converter valve, effectively adding a firewall between the photovoltaic system and the AC system, thus significantly reducing resonance problems between the photovoltaic collection system and the AC system. In addition, the DC collection device in the photovoltaic collection system can separate the photovoltaic system and the energy storage system, making them independent. This not only improves the safety of both systems but also allows for adjustments to the energy storage system without affecting the photovoltaic system, or vice versa, thereby enhancing the adaptability of the photovoltaic collection system to different application scenarios.

[0010] In some embodiments, the two DC collecting devices include a first DC collecting device and a second DC collecting device; wherein, the first output terminal of the first DC collecting device is connected to the positive terminal of the energy storage system, and the second output terminal of the first DC collecting device is connected to the midpoint of the energy storage system; the first output terminal of the second DC collecting device is connected to the midpoint of the energy storage system, and the second output terminal of the second DC collecting device is connected to the negative terminal of the energy storage system.

[0011] In this embodiment, the DC collection device includes a first DC collection device and a second DC collection device. The first output terminal and the second output terminal of the first DC collection device are respectively connected to the positive and midpoints of the energy storage system, and the first output terminal and the second output terminal of the second DC collection device are respectively connected to the midpoint and the negative terminal of the energy storage system. This forms a bipolar bus in the photovoltaic collection system, which allows the positive and negative terminals of the energy storage system to operate independently, improving the flexibility and reliability of the photovoltaic collection system in supplying power to the load.

[0012] In some embodiments, the number of DC collection devices is even, and at least four DC collection devices include at least two first DC collection devices connected in series and at least two second DC collection devices connected in series.

[0013] In this embodiment of the application, the voltage of the energy storage system can be further improved by connecting at least two first DC collecting devices connected in series between the positive and midpoints of the energy storage system, and connecting at least two second DC collecting devices connected in series between the midpoint and negative terminal of the energy storage system.

[0014] In some embodiments, the number of photovoltaic systems is even; each photovoltaic system includes at least two photovoltaic units; and the connection method between the photovoltaic units and the corresponding DC collection devices is the same in different photovoltaic systems.

[0015] In this embodiment, the photovoltaic system with an even number of units includes at least two photovoltaic cells, and the connection method between the photovoltaic cells and the corresponding DC collection device is the same in different photovoltaic systems. This ensures power balance on the DC bus of the photovoltaic collection system, thereby improving the stability of the photovoltaic collection system.

[0016] In some embodiments, the number of DC collection devices is 1; the positive terminal of the energy storage system of the DC collection device is connected, and the second output terminal of the DC collection device is connected to the negative terminal of the energy storage system; or, the first output terminal of the DC collection device is connected to the positive or negative terminal of the energy storage system, and the second output terminal of the DC collection device is grounded.

[0017] In this embodiment, the photovoltaic system is connected to the positive and negative terminals of the energy storage system via a DC collection device, or the photovoltaic system is connected to the positive terminal and grounding terminal of the energy storage system via a DC collection device, or the photovoltaic system is connected to the negative terminal and grounding terminal of the energy storage system via a DC collection device, thus forming a single-pole DC bus in the photovoltaic collection system. This reduces the structural complexity of the photovoltaic collection system, thereby lowering the cost of constructing it.

[0018] In some embodiments, the photovoltaic system includes a first photovoltaic subsystem and a second photovoltaic subsystem; the first photovoltaic subsystem includes at least two first photovoltaic units, and the second photovoltaic subsystem includes at least two second photovoltaic units; the number of first photovoltaic units corresponds to the number of second photovoltaic units; wherein, the first end and the second end of each first photovoltaic unit are respectively connected to a first DC collecting device; the first end and the second end of each second photovoltaic unit are respectively connected to a second DC collecting device.

[0019] In this embodiment, the first end of each first photovoltaic unit in the first photovoltaic subsystem is connected to the positive terminal of the energy storage system via a first DC consolidation device corresponding to the first photovoltaic subsystem; the second end of each first photovoltaic unit in the first photovoltaic subsystem is connected to the midpoint of the energy storage system via the first DC consolidation device corresponding to the first photovoltaic subsystem; the first end of each second photovoltaic unit in the second photovoltaic subsystem is connected to the midpoint of the energy storage system via a second DC consolidation device corresponding to the second photovoltaic subsystem; and the second end of each second photovoltaic unit in the second photovoltaic subsystem is connected to the negative terminal of the energy storage system via the second DC consolidation device corresponding to the second photovoltaic subsystem. Thus, by setting a corresponding number of photovoltaic units for different DC consolidation devices, a bipolar bus can be constructed in the photovoltaic consolidation system, enabling the positive and negative terminals of the energy storage system to operate independently, thereby improving the flexibility and reliability of the photovoltaic consolidation system in supplying power to the load.

[0020] In some embodiments, the first DC collection device includes a first bridge arm isolation component; the second DC collection device includes a second bridge arm isolation component; wherein at least one of the two output terminals of each first photovoltaic unit is connected to the first bridge arm isolation component; the first bridge arm isolation component is connected to the positive terminal and / or the midpoint of the energy storage system; at least one of the two output terminals of each second photovoltaic unit is connected to the second bridge arm isolation component; the second bridge arm isolation component is connected to the midpoint and / or the negative terminal of the energy storage system.

[0021] In this embodiment of the application, by setting a bridge arm isolation component on the connection line between the photovoltaic unit and the energy storage system, the impact of the photovoltaic unit on the energy storage system can be reduced, thereby improving the stability of the photovoltaic collection system.

[0022] In some embodiments, the first DC collection device includes a number of first unit isolation components corresponding to the number of first photovoltaic units; the second DC collection device includes a number of second unit isolation components corresponding to the number of second photovoltaic units; wherein, the first ends of at least two first photovoltaic units are respectively connected to their respective corresponding first unit isolation components; at least two first unit isolation components are connected to the positive terminal of the energy storage system through a first bridge arm isolation component, or at least two first unit isolation components are connected to the positive terminal of the energy storage system; the first ends of at least two second photovoltaic units are respectively connected to their respective corresponding second unit isolation components; at least two second unit isolation components are connected to the midpoint of the energy storage system through a second bridge arm isolation component, or at least two first unit isolation components are connected to the midpoint of the energy storage system.

[0023] In this embodiment, the first end of each photovoltaic unit is connected to the corresponding unit isolation component. Therefore, the impact of a faulty photovoltaic unit on other normally functioning photovoltaic units can be reduced, thereby improving the stability of the photovoltaic collection system.

[0024] In some embodiments, the first DC collection device includes a number of first unit reactor components corresponding to the number of first photovoltaic units; the second DC collection device includes a number of second unit reactor components corresponding to the number of second photovoltaic units; wherein, the first ends of the plurality of first photovoltaic units are respectively connected to their respective first unit isolation components through the first unit reactor components; and the first ends of the plurality of second photovoltaic units are respectively connected to their respective second unit isolation components through the second unit reactor components.

[0025] In this embodiment, a unit reactor component is provided between each photovoltaic unit and the unit isolation component. By providing the unit reactor component, the stability of the photovoltaic collection system can be improved and the probability of oscillation and loss of synchronization in the photovoltaic collection system can be reduced.

[0026] In some embodiments, the photovoltaic collection system further includes a first smoothing reactor and a second smoothing reactor; wherein, the first output terminal of the first DC collection device is connected to the positive terminal of the energy storage system through the first smoothing reactor; and the second output terminal of the second DC collection device is connected to the negative terminal of the energy storage system through the second smoothing reactor.

[0027] In this embodiment, the DC collection device is connected to the energy storage system through a smoothing reactor, which can filter and stabilize the photovoltaic collection system, thereby improving the stability of the photovoltaic collection system.

[0028] Secondly, embodiments of this application provide a power adjustment method, the method comprising:

[0029] Obtain the power demand information of the load of the photovoltaic collection system; wherein, the photovoltaic collection system includes at least one photovoltaic system, a DC collection device corresponding to each photovoltaic system, an energy storage system, and a voltage source converter valve; each photovoltaic system includes at least one photovoltaic unit, and each photovoltaic unit includes at least two photovoltaic branches connected in series; the output terminal of each photovoltaic system is connected to the input terminal of the corresponding DC collection device, and the output terminal of the DC collection device is connected to the input terminal of the energy storage system; the energy storage system and the voltage source converter valve are connected in parallel.

[0030] Based on power demand information, the current output power of the photovoltaic system, and the current output power of the energy storage system, control the photovoltaic system and / or the energy storage system to supply power to the load.

[0031] It should be understood that the above general description and the following detailed description are merely exemplary and explanatory, and are not intended to limit the technical solutions of this application. Attached Figure Description

[0032] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with this application and, together with the specification, serve to explain the technical solutions of this application.

[0033] Figure 1a This is a schematic diagram of the composition structure of a photovoltaic grid connection system in related technologies;

[0034] Figure 1b A schematic diagram of the composition structure of a photovoltaic collection system provided in this application embodiment;

[0035] Figure 2 A schematic diagram of the composition structure of a photovoltaic collection system provided in this application embodiment. Figure 2 ;

[0036] Figure 3 A schematic diagram of the composition structure of a photovoltaic collection system provided in this application embodiment. Figure 3 ;

[0037] Figure 4 A schematic diagram of the composition structure of a photovoltaic collection system provided in this application embodiment. Figure 4 ;

[0038] Figure 5 A schematic diagram of the composition structure of a photovoltaic collection system provided in this application embodiment. Figure 5 ;

[0039] Figure 6 A schematic diagram of the composition structure of a photovoltaic collection system provided in this application embodiment. Figure 6 ;

[0040] Figure 7 A schematic diagram of the composition structure of a photovoltaic collection system provided in this application embodiment. Figure 7 ;

[0041] Figure 8 A schematic diagram of the composition structure of a photovoltaic collection system provided in this application embodiment. Figure 8 ;

[0042] Figure 9 A schematic diagram of the composition structure of a photovoltaic collection system provided in this application embodiment. Figure 9 ;

[0043] Figure 10 A schematic diagram of the composition structure of a photovoltaic collection system provided in this application embodiment. Figure 10 ;

[0044] Figure 11 A schematic diagram of the composition structure of a photovoltaic collection system provided in this application embodiment. Figure 10 one;

[0045] Figure 12 A schematic diagram illustrating the implementation process of a power adjustment method provided in this application embodiment;

[0046] Figure 13 A schematic diagram of the implementation process of a power adjustment method provided in this application embodiment. Figure 2 ;

[0047] Figure 14 This is a schematic diagram illustrating a scenario of DC aggregation technology provided in an embodiment of this application.

[0048] Figure 15 This application provides a schematic diagram of the composition structure of a photovoltaic collection system. Figure 10 two;

[0049] Figure 16 This application provides a schematic diagram of the composition structure of a photovoltaic collection system. Figure 10 three;

[0050] Figure 17 This is a control diagram of an energy management system provided in an embodiment of this application;

[0051] Figure 18 A schematic diagram of the implementation process of a power adjustment method provided in this application embodiment. Figure 3 ;

[0052] Figure 19 A schematic diagram of the energy flow of a photovoltaic collection system provided in this application embodiment;

[0053] Figure 20 A schematic diagram of the energy flow direction of the photovoltaic collection system provided in the embodiments of this application. Figure 2 ;

[0054] Figure 21 A schematic diagram of the energy flow direction of the photovoltaic collection system provided in the embodiments of this application. Figure 3 . Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application are further described in detail below with reference to the accompanying drawings and embodiments. The described embodiments should not be regarded as limitations on this application. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0056] In the following description, references are made to “some embodiments,” which describe a subset of all possible embodiments. However, it is understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0057] The terms “first / second / third” are used merely to distinguish similar objects and do not represent a specific ordering of objects. It is understood that “first / second / third” may be interchanged in a specific order or sequence where permitted, so that the embodiments of this application described herein can be implemented in an order other than that illustrated or described herein.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used herein is for descriptive purposes only and is not intended to limit the scope of this application.

[0059] Currently, new energy batteries are being used more and more widely in daily life and industry. They are not only used in energy storage systems for hydropower, thermal power, wind power, and solar power plants, but also extensively in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in aerospace and other fields. With the continuous expansion of the application areas of power batteries, the market demand is also constantly increasing.

[0060] In this embodiment, the battery in the energy storage system can be a single battery cell. A single battery cell refers to a basic unit capable of converting chemical energy into electrical energy, and can be used to manufacture battery modules or battery packs to supply power to electrical devices. A single battery cell can be a rechargeable battery, which is a battery cell that can be recharged after discharge to reactivate its active materials and continue to be used. The single battery cell can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., but this embodiment is not limited to these types.

[0061] In embodiments of this application, the battery may also be a single physical module comprising one or more battery cells to provide higher voltage and capacity. When there are multiple battery cells, the multiple battery cells are connected in series, parallel, or mixed via a busbar.

[0062] Current photovoltaic (PV) grid connection technologies typically connect to the grid via AC inverters. However, when PV system capacity reaches MW or higher, this method becomes inefficient due to the numerous intermediate steps required to boost voltage to medium and high voltage levels, resulting in lower overall system efficiency. Furthermore, with the increase in parallel PV grid-connected branches, the problems of circulating currents between branches and oscillations with the grid become increasingly severe. Figure 1a As shown, the photovoltaic grid-connected system in the relevant technology includes three parallel branches 1. This can lead to circulating currents between the parallel branches and oscillation instability between the parallel branches and the power grid.

[0063] To address the technical problems existing in related technologies, embodiments of this application provide a photovoltaic collection system. Figure 1b This is a schematic diagram of the composition structure of a photovoltaic collection system provided in an embodiment of this application, as shown in Figure 1. Figure 1b As shown, the photovoltaic collection system 100 includes at least one photovoltaic system 110, a DC collection device 120 corresponding to each photovoltaic system 110, an energy storage system 130, and a voltage source converter valve 140.

[0064] Each photovoltaic system 110 includes at least one photovoltaic unit 111, and each photovoltaic unit 111 includes at least two photovoltaic branches 1111 connected in series.

[0065] The output terminal of each photovoltaic system 110 is connected to the input terminal of the corresponding DC collector 120, and the output terminal of the DC collector 120 is connected to the input terminal of the energy storage system 130; the energy storage system 130 is connected in parallel with the voltage source converter valve 140; wherein,

[0066] DC collecting device 120 is used to collect the current generated by at least one photovoltaic unit 111 and output the collected current to energy storage system 130.

[0067] In this embodiment, the number of photovoltaic systems is related to the type of DC bus in the photovoltaic collection system. For example, when the DC bus is a unipolar bus, the number of photovoltaic systems is 1; when the DC bus is a bipolar bus, the number of photovoltaic systems is at least two, and the number of photovoltaic systems is even.

[0068] In this embodiment, the correspondence between the DC collection device in the photovoltaic collection system and each photovoltaic system means that each photovoltaic system is connected to the energy storage system through its corresponding DC collection device. In other words, the number of DC collection devices in the photovoltaic collection system corresponds to the number of photovoltaic systems. It is understood that because the function of the DC collection device is to collect the current generated by at least one photovoltaic unit in the photovoltaic system and output the collected current to the energy storage system, each photovoltaic system corresponds to at least one DC collection device.

[0069] In this embodiment, each photovoltaic system in at least one photovoltaic system includes at least one photovoltaic unit. The output terminal of each photovoltaic unit is connected to the input terminal of a corresponding DC collecting device, thereby enabling the photovoltaic unit to output its generated current to the DC collecting device. Each photovoltaic unit in each photovoltaic system includes at least two photovoltaic branches connected in series. Thus, by connecting multiple photovoltaic branches in series, the voltage of a single photovoltaic unit can be increased.

[0070] In some embodiments, the photovoltaic branch includes a photovoltaic power generation array and a conversion unit. Exemplarily, the conversion unit can be a non-isolated direct current (DC) / DC unit and / or an isolated DC / DC unit. The topology of the isolated DC / DC unit can be an LLC (Inductor-Inductor-Capacitor) resonant DC-DC converter or a phase-shifted full-bridge DC-DC converter circuit; the topology of the non-isolated DC / DC unit can be a boost power factor correction (Boost PFC) DC-DC boost converter circuit. In this embodiment, the photovoltaic power generation array and the conversion unit are connected to form a photovoltaic branch, and the outputs of at least two photovoltaic branches are connected in series, thereby increasing the DC voltage of a single photovoltaic unit. Exemplarily, the DC voltage of a single photovoltaic unit can be between 10kV and ±35kV. In some embodiments, when the conversion unit is an isolated DC / DC unit, medium-voltage isolation can be achieved within each photovoltaic unit through a transformer.

[0071] In some embodiments, the connection relationship between the photovoltaic units in each photovoltaic system is the same. For example, the connection relationship between the photovoltaic units in each photovoltaic system can be one of the following: series connection, parallel connection, series connection followed by parallel connection, and parallel connection followed by series connection.

[0072] In some embodiments, the energy storage system can be a DC-DC direct-connected energy storage valve, and the voltage source converter valve can be a voltage source converter (VSC). In this embodiment, the voltage source converter valve is used to convert the DC power of the energy storage system into AC power, thereby sending the electrical energy of the energy storage system to the AC system. The AC system includes at least one of the following: a power grid and an AC load.

[0073] In this embodiment, a DC collection device can collect the current generated by photovoltaic units in at least one photovoltaic system into the energy storage system. This allows for the connection of a high-voltage photovoltaic power source (i.e., a photovoltaic unit comprising at least two series-connected photovoltaic branches) to a DC bus. Compared to related technologies that require step-by-step voltage boosting to medium and high voltage levels for large-capacity photovoltaic systems, this improves the efficiency of photovoltaic grid connection. Furthermore, the photovoltaic system sends current to the AC system through a voltage source converter valve, effectively adding a firewall between the photovoltaic system and the AC system, thus significantly reducing resonance problems between the photovoltaic collection system and the AC system. In addition, the DC collection device in the photovoltaic collection system can separate the photovoltaic system and the energy storage system, making them independent. This not only improves the safety of both systems but also allows for adjustments to the energy storage system without affecting the photovoltaic system, or vice versa, thereby enhancing the adaptability of the photovoltaic collection system to different application scenarios.

[0074] In some embodiments, such as Figure 2 As shown, the number of DC collection devices is two, including a first DC collection device 1201 and a second DC collection device 1202; wherein,

[0075] The first output terminal of the first DC collecting device 1201 is connected to the positive terminal of the energy storage system 130, and the second output terminal of the first DC collecting device 1201 is connected to the midpoint of the energy storage system 130.

[0076] The first output terminal of the second DC collecting device 1202 is connected to the midpoint of the energy storage system 130, and the second output terminal of the second DC collecting device 1202 is connected to the negative terminal of the energy storage system 130.

[0077] The first DC collecting device and the second DC collecting device are the same.

[0078] In this embodiment, the DC bus in the photovoltaic collection system is a bipolar bus. Therefore, the number of DC collection devices connected between the positive and midpoints of the energy storage system and between the midpoint and negative points of the energy storage system needs to be symmetrical. Because there is a one-to-one correspondence between the DC collection devices and the photovoltaic system, the number of photovoltaic systems is also an even number. The midpoint in the energy storage system refers to the electrical midpoint. In the scenario of positive and negative DC buses (i.e., the aforementioned bipolar bus), the electrical midpoint is the grounding potential of the energy storage system.

[0079] It is understandable that constructing a bipolar bus allows the positive and negative poles of the energy storage system to operate independently. That is, power can be supplied to the load through the positive and midpoints of the DC bus, and also through the midpoint and negative poles of the DC bus. This improves the stability of the photovoltaic (PV) collection system's power supply to the load. Simultaneously, constructing a bipolar bus also enhances the resilience of the PV collection system. For example, such as... Figure 2 As shown, if the photovoltaic branch 1111 in a photovoltaic unit of the photovoltaic system 110 corresponding to the first DC collection device 1201 malfunctions, the malfunctioning photovoltaic branch 1111 can be disconnected. Then, in order to balance the power between the positive and neutral points and between the neutral and negative poles in the bipolar bus, the photovoltaic branch 1111 in a photovoltaic unit of the photovoltaic system 110 corresponding to the second DC collection device 1202 can be disconnected. At this time, the photovoltaic collection system can still supply power to the load normally.

[0080] In this embodiment, the DC collection device includes a first DC collection device and a second DC collection device. The first output terminal and the second output terminal of the first DC collection device are respectively connected to the positive and midpoints of the energy storage system, and the first output terminal and the second output terminal of the second DC collection device are respectively connected to the midpoint and the negative terminal of the energy storage system. This forms a bipolar bus in the photovoltaic collection system, which allows the positive and negative terminals of the energy storage system to operate independently, improving the flexibility and reliability of the photovoltaic collection system in supplying power to the load.

[0081] In some embodiments, such as Figure 3 As shown, the number of DC collectors is multiple and even. Figure 3 The number of DC collectors shown is 4), and the plurality of DC collectors 120 include at least two first DC collectors 1201 connected in series and at least two second DC collectors 1202 connected in series. Figure 3 The number of first DC collecting devices and second DC collecting devices shown is 2); each first DC collecting device 1201 is connected to a corresponding photovoltaic system 110; each second DC collecting device 1202 is connected to a corresponding photovoltaic system 110; wherein...

[0082] The first end of the starting device in at least two first DC collecting devices 1201 is connected to the positive terminal of the energy storage system 130, and the second end of the starting device is connected to the first end of the adjacent device of the starting device; the first end of the ending device in at least two first DC collecting devices 1201 is connected to the second end of the adjacent device of the ending device, and the second end of the ending device is connected to the midpoint of the energy storage system 130.

[0083] The first end of the starting device in at least two second DC collection devices 1202 is connected to the midpoint of the energy storage system 130, and the second end of the starting device is connected to the first end of the adjacent device of the starting device; the first end of the ending device in at least two second DC collection devices 1202 is connected to the second end of the adjacent device of the ending device, and the second end of the ending device is connected to the negative terminal of the energy storage system 130.

[0084] In this embodiment of the application, for at least two first DC collecting devices between the positive and midpoints, the voltage of the positive terminal in the bipolar bus of the photovoltaic collecting system can be increased because the at least two first DC collecting devices are connected in series. Similarly, for at least two second DC collecting devices between the midpoint and negative terminal, the voltage of the negative terminal in the bipolar bus of the photovoltaic collecting system can also be increased because the at least two second DC collecting devices are connected in series.

[0085] In this embodiment of the application, the voltage of the energy storage system can be further improved by connecting at least two first DC collecting devices connected in series between the positive and midpoints of the energy storage system, and connecting at least two second DC collecting devices connected in series between the midpoint and negative terminal of the energy storage system.

[0086] In some embodiments, the number of photovoltaic systems is even; each photovoltaic system includes at least two photovoltaic units; and the connection method between the photovoltaic units and the corresponding DC collection devices is the same in different photovoltaic systems.

[0087] In this embodiment of the application, each photovoltaic system in an even number of photovoltaic systems is connected to a corresponding DC collection device. For example, as shown... Figure 3 As shown, two first DC collectors and two second DC collectors are each connected to a photovoltaic system, meaning the total number of photovoltaic systems is 4.

[0088] In this embodiment, the connection method between the photovoltaic units and the corresponding DC collection devices in different photovoltaic systems is the same. Specifically, the photovoltaic units in each photovoltaic system can be directly connected to the corresponding DC collection device. For example, each photovoltaic unit in a photovoltaic system includes two photovoltaic branches connected in series, with one branch having a voltage of 5KV, meaning the voltage of each photovoltaic unit in the photovoltaic system is 10KV. Each photovoltaic unit in each photovoltaic system is then connected to the DC collection device, constructing a ±10KV DC bus.

[0089] In some embodiments, the photovoltaic units in each photovoltaic system can be connected in series and then connected to the corresponding DC collection device. For example, each photovoltaic unit in the photovoltaic system includes a photovoltaic branch with a voltage of 5KV, that is, the voltage of each photovoltaic unit in the photovoltaic system is 5KV. Then, two photovoltaic branches are connected in series and then connected to the corresponding DC collection device, which can also construct a ±10KV DC bus.

[0090] In this embodiment, the photovoltaic system with an even number of units includes at least two photovoltaic cells, and the connection method between the photovoltaic cells and the corresponding DC collection device is the same in different photovoltaic systems. This ensures power balance on the DC bus of the photovoltaic collection system, thereby improving the stability of the photovoltaic collection system.

[0091] In some embodiments, such as Figure 1b As shown, the first output terminal of the DC collector 120 is connected to the positive terminal of the energy storage system 130, and the second output terminal of the DC collector 120 is connected to the negative terminal of the energy storage system 130.

[0092] In this embodiment of the application, the number of DC collection devices in the photovoltaic collection system is 1, and correspondingly, the number of photovoltaic systems is also 1. Because the photovoltaic system is connected to the positive and negative poles of the energy storage system through the DC collection devices, a single-pole DC bus from the positive pole to the negative pole is formed in the photovoltaic collection system.

[0093] In some embodiments, when the number of DC collection devices in the photovoltaic collection system is 1, the first output terminal of the DC collection device is connected to the positive terminal of the energy storage system, and the second output terminal of the DC collection device is grounded.

[0094] In this embodiment, since one of the two output terminals of the DC collecting device is connected to the positive terminal of the energy storage system and the other is grounded, a voltage difference can be formed between the positive terminal and the grounding point, thus forming a single-pole DC bus from the positive terminal to the grounding point.

[0095] In some embodiments, when the number of DC collection devices in the photovoltaic collection system is 1, the first output terminal of the DC collection device is connected to the negative terminal of the energy storage system, and the second output terminal of the DC collection device is grounded.

[0096] In this embodiment, because one of the two output terminals of the DC collecting device is connected to the negative terminal of the energy storage system and the other is grounded, a voltage difference can be formed between the grounding point and the negative terminal, thus forming a unipolar DC bus from the grounding point to the negative terminal.

[0097] In this embodiment, the photovoltaic system is connected to the positive and negative terminals of the energy storage system via a DC collection device, or the photovoltaic system is connected to the positive terminal and grounding terminal of the energy storage system via a DC collection device, or the photovoltaic system is connected to the negative terminal and grounding terminal of the energy storage system via a DC collection device, thus forming a single-pole DC bus in the photovoltaic collection system. This reduces the structural complexity of the photovoltaic collection system, thereby lowering the cost of constructing it.

[0098] In some embodiments, such as Figure 4 As shown, the two photovoltaic systems include a first photovoltaic subsystem 1101 and a second photovoltaic subsystem 1102; the first photovoltaic subsystem 1101 includes at least two first photovoltaic units 11011, and the second photovoltaic subsystem 1102 includes at least two second photovoltaic units 11021; the number of first photovoltaic units 11011 corresponds to the number of second photovoltaic units 11021; wherein,

[0099] The first end and the second end of each first photovoltaic unit 11011 are respectively connected to the first DC collection device 1201; the first end and the second end of each second photovoltaic unit 11011 are respectively connected to the second DC collection device 1202.

[0100] In this embodiment of the application, the first end of the first photovoltaic unit is connected to the positive terminal of the energy storage system through a corresponding first DC collecting device. This means that the first end of the first photovoltaic unit is connected to the positive terminal of the energy storage system through a first DC collecting device corresponding to the first photovoltaic subsystem. Similarly, the second end of the first photovoltaic unit is connected to the midpoint of the energy storage system through a first DC collecting device corresponding to the first photovoltaic subsystem. The first end of the second photovoltaic unit is connected to the midpoint of the energy storage system through a second DC collecting device corresponding to the second photovoltaic subsystem, and the second end of the second photovoltaic unit is connected to the negative terminal of the energy storage system through a second DC collecting device corresponding to the second photovoltaic subsystem.

[0101] In this embodiment, to match the voltage at the positive terminal and the voltage at the negative terminal of the energy storage system, the number of photovoltaic branches in each first photovoltaic unit and each second photovoltaic unit must be the same. For example, by connecting multiple photovoltaic branches in series in each first photovoltaic unit and each second photovoltaic unit, the voltage of each first photovoltaic unit and each second photovoltaic unit is 10KV. Then, each first photovoltaic unit is connected to the positive and midpoints of the energy storage system, and each second photovoltaic unit is connected to the midpoint and negative terminal of the energy storage system, resulting in a positive terminal voltage of +10KV and a negative terminal voltage of -10KV for the energy storage system.

[0102] In this embodiment, the first end of each first photovoltaic unit in the first photovoltaic subsystem is connected to the positive terminal of the energy storage system via a first DC consolidation device corresponding to the first photovoltaic subsystem; the second end of each first photovoltaic unit in the first photovoltaic subsystem is connected to the midpoint of the energy storage system via the first DC consolidation device corresponding to the first photovoltaic subsystem; the first end of each second photovoltaic unit in the second photovoltaic subsystem is connected to the midpoint of the energy storage system via a second DC consolidation device corresponding to the second photovoltaic subsystem; and the second end of each second photovoltaic unit in the second photovoltaic subsystem is connected to the negative terminal of the energy storage system via the second DC consolidation device corresponding to the second photovoltaic subsystem. Thus, by setting a corresponding number of photovoltaic units for different DC consolidation devices, a bipolar bus can be constructed in the photovoltaic consolidation system, enabling the positive and negative terminals of the energy storage system to operate independently, thereby improving the flexibility and reliability of the photovoltaic consolidation system in supplying power to the load.

[0103] In some embodiments, the first DC collecting device includes a first bridge arm isolation assembly; the second DC collecting device includes a second bridge arm isolation assembly; wherein...

[0104] At least one end of each first photovoltaic unit is connected to a first bridge arm isolation component; the first bridge arm isolation component is connected to the positive terminal and / or midpoint of the energy storage system.

[0105] At least one end of each second photovoltaic unit is connected to a second bridge arm isolation component; the second bridge arm isolation component is connected to the midpoint and / or negative terminal of the energy storage system.

[0106] For example, such as Figure 5 As shown, the first photovoltaic subsystem includes two first photovoltaic units 11011, and the first DC collection device includes two first bridge arm isolation components 12011; the second photovoltaic subsystem includes two second photovoltaic units 11021, and the second DC collection device includes two second bridge arm isolation components 12021; wherein,

[0107] The first end of each first photovoltaic unit 11011 is connected to the positive terminal of the energy storage system through the first bridge arm isolation component 12011; the second end of each first photovoltaic unit 11011 is connected to the midpoint of the energy storage system through the first bridge arm isolation component 12011.

[0108] The first end of each second photovoltaic unit 11021 is connected to the midpoint of the energy storage system through the second bridge arm isolation component 12021; the second end of each second photovoltaic unit 11021 is connected to the negative terminal of the energy storage system through the second bridge arm isolation component 12021.

[0109] In this embodiment, each port of each photovoltaic unit is connected to the energy storage system via a bridge arm isolation assembly. This bridge arm isolation assembly protects the DC bus power in the photovoltaic aggregation system from reverse flow and reduces the impact of a short-circuit fault at the parallel connection point of the photovoltaic units on the DC bus and the energy storage system. For example, the bridge arm isolation assembly may be a medium voltage (MV) diode valve.

[0110] In some embodiments, the number of first bridge arm isolation components connected to the first photovoltaic unit can be one, that is, the first end of the first photovoltaic unit is connected to the positive electrode of the energy storage system through the first bridge arm isolation component, and the second end of the first photovoltaic unit is connected to the midpoint of the energy storage system; or, the first end of the first photovoltaic unit is connected to the positive electrode of the energy storage system, and the second end of the first photovoltaic unit is connected to the midpoint of the energy storage system through the first bridge arm isolation component; similarly, the number of second bridge arm isolation components connected to the second photovoltaic unit can be one, that is, the first end of the second photovoltaic unit is connected to the midpoint of the energy storage system through the second bridge arm isolation component, and the second end of the second photovoltaic unit is connected to the negative electrode of the energy storage system; or, the first end of the second photovoltaic unit is connected to the midpoint of the energy storage system, and the second end of the second photovoltaic unit is connected to the negative electrode of the energy storage system through the second bridge arm isolation component.

[0111] Understandably, because the bridge arm isolation assembly is used to protect the DC bus power from reverse flow in the photovoltaic (PV) collection system, an abnormal PV unit in the PV system will not cause a failure in the energy storage system. For example, such as... Figure 5 As shown, the first photovoltaic subsystem includes two first photovoltaic units 11011. In the event of a short circuit at location 2, the current generated by the two first photovoltaic units 11011 in the first photovoltaic subsystem flows through the short-circuit branch (i.e., Figure 5 The current (as shown by the dotted line in the diagram) flows back to the first photovoltaic unit 11011, causing a short circuit between the two first photovoltaic units 11011, meaning the first photovoltaic subsystem cannot function properly. However, because a first bridge arm isolation component 12011 is installed on the line connecting the first photovoltaic unit 11011 to the energy storage system 130, the first bridge arm isolation component 12011 can isolate the short-circuit current between the two first photovoltaic units 11011. Therefore, the failure of the first photovoltaic subsystem will not affect the energy storage system 130 and the voltage source converter valve 140.

[0112] In this embodiment of the application, by setting a bridge arm isolation component on the connection line between the photovoltaic unit and the energy storage system, the impact of the photovoltaic unit on the energy storage system can be reduced, thereby improving the stability of the photovoltaic collection system.

[0113] In some embodiments, such as Figure 6As shown, the first DC collection device includes first unit isolation components 12012, the number of which corresponds to the number of first photovoltaic units 11011; the second DC collection device includes second unit isolation components 12022, the number of which corresponds to the number of second photovoltaic units 11021; wherein,

[0114] At least two first photovoltaic units 11011 are connected at their first ends to their respective first unit isolation components 12012; at least two first unit isolation components 12012 are connected to the positive terminal of the energy storage system 130 through the first bridge arm isolation component 12011, or at least two first unit isolation components 12012 are connected to the positive terminal of the energy storage system 130. Figure 6 The diagram shows the first unit isolation component 12012 connected to the positive terminal of the energy storage system 130 via the first bridge arm isolation component 12011.

[0115] At least two second photovoltaic units 11021 are connected at their first ends to their respective second unit isolation components 12022; at least two second unit isolation components 12022 are connected to the midpoint of the energy storage system 130 via second bridge arm isolation components 12021, or at least two first unit isolation components 12021 are connected to the midpoint of the energy storage system 130. Figure 6 The diagram shows two second unit isolation assemblies 12022 connected to the midpoint of the energy storage system 130 via a second bridge arm isolation assembly 12021.

[0116] In this embodiment, the first end of each photovoltaic unit is connected to a unit isolation component. That is, there is a one-to-one correspondence between photovoltaic units and unit isolation components; specifically, at least two first photovoltaic units correspond to at least two first unit isolation components, and at least two second photovoltaic units correspond to at least two second unit isolation components. The unit isolation components are used to reduce the possibility of power backflow between different photovoltaic units and to reduce the impact of abnormal photovoltaic units on other normally functioning photovoltaic units. For example, the unit isolation component can be an MV diode valve, differing from the aforementioned bridge arm isolation component in that the current of the unit isolation component is less than the current of the bridge arm isolation component.

[0117] In this embodiment, because the bridge arm isolation component can be connected to at least one output terminal of the photovoltaic unit, when the bridge arm isolation component is connected to the first terminal of the photovoltaic unit, the first terminal of the photovoltaic unit needs to be connected to the bridge arm isolation component through the unit isolation component (i.e., ...). Figure 6 (As shown); when the bridge arm isolation component is connected to the second end of the photovoltaic unit, the first end of the photovoltaic unit is connected to the unit isolation component, and the unit isolation component is connected to the positive electrode or the midpoint of the energy storage system.

[0118] It is understandable that because each photovoltaic unit is connected to a unit isolation component at its first end, a malfunction in one photovoltaic unit will not affect other photovoltaic units in the photovoltaic system. For example, such as... Figure 6 As shown, the first photovoltaic subsystem includes two first photovoltaic units 11011. In the event of a short circuit at position 3, the current generated by the first photovoltaic unit 11011 corresponding to position 3 flows through the short-circuit branch (i.e., Figure 6 The current (as shown by the dotted line in the diagram) flows back to the first photovoltaic unit 11011, causing a short circuit in the first photovoltaic unit 11011 corresponding to position 3, thus causing a fault in the first photovoltaic unit 11011 corresponding to position 3. Simultaneously, because the first output terminal of the faulty first photovoltaic unit 11011 is connected to the first unit isolation component 12012, the current generated by the other first photovoltaic unit 11011 cannot flow into the short-circuited branch through the first unit isolation component 12012. Therefore, the faulty first photovoltaic unit 11011 will not affect the normal operation of other first photovoltaic units 11011 in the first photovoltaic subsystem.

[0119] In this embodiment, the first end of each photovoltaic unit is connected to the corresponding unit isolation component. Therefore, the impact of a faulty photovoltaic unit on other normally functioning photovoltaic units can be reduced, thereby improving the stability of the photovoltaic collection system.

[0120] In some embodiments, if the first photovoltaic subsystem and the second photovoltaic subsystem each include only one photovoltaic unit, then only one unit isolation component and one bridge arm isolation component may exist. For example, as... Figure 7 As shown, the first end of the first photovoltaic unit 11011 is connected to the positive terminal of the energy storage system through the first bridge arm isolation component 12011, and the second end of the first photovoltaic unit 11011 is connected to the midpoint of the energy storage system through the first bridge arm isolation component 12011; the first end of the second photovoltaic unit 11021 is connected to the midpoint of the energy storage system through the second bridge arm isolation component 12021, and the second end of the second photovoltaic unit 11021 is connected to the negative terminal of the energy storage system through the second bridge arm isolation component 12021.

[0121] In some embodiments, when the number of DC collection devices and the number of photovoltaic systems in the photovoltaic collection system are both 1, and the photovoltaic system includes only one photovoltaic unit, the unit isolation component and the bridge arm isolation component may also have only one. For example, as... Figure 8 As shown, the first end of the first photovoltaic unit 11011 is connected to the positive terminal of the energy storage system through the first bridge arm isolation component 12011, and the second end of the first photovoltaic unit 11011 is connected to the midpoint of the energy storage system through the first bridge arm isolation component 12011.

[0122] In some embodiments, such as Figure 9As shown, each first DC collection device includes a number of first unit reactor components 12013 corresponding to the number of first photovoltaic units 11011; each second DC collection device includes a number of second unit reactor components 12023 corresponding to the number of second photovoltaic units 11021; wherein,

[0123] At least two first photovoltaic units 11011 are connected at their first ends to their respective first unit isolation components 12012 via first unit reactor components 12013.

[0124] The first ends of at least two second photovoltaic units 11021 are respectively connected to their respective second unit isolation components 12022 through second unit reactor components 12023.

[0125] In this embodiment, a unit reactor component is provided between each photovoltaic unit and the unit isolation component. By providing the unit reactor component, the stability of the photovoltaic collection system can be improved and the probability of oscillation and loss of synchronization in the photovoltaic collection system can be reduced.

[0126] In some embodiments, the first end of the first photovoltaic unit is connected to the first bridge arm isolation component through the first unit reactor component, and the first end of the second photovoltaic unit is connected to the second bridge arm isolation component through the second unit reactor component.

[0127] In some embodiments, the first end of the first photovoltaic unit is connected to the positive terminal of the energy storage system through the first unit reactor component, and the first end of the second photovoltaic unit is connected to the midpoint of the energy storage system through the second unit reactor component.

[0128] In some embodiments, such as Figure 10 As shown, the photovoltaic collection system also includes a first smoothing reactor 150 and a second smoothing reactor 160; wherein,

[0129] The first output terminal of the first DC collection device 1201 is connected to the positive terminal of the energy storage system 130 through the first smoothing reactor 150;

[0130] The second output terminal of the second DC collection device 1202 is connected to the negative terminal of the energy storage system 130 through the second smoothing reactor 160.

[0131] In this embodiment of the application, when the photovoltaic unit is connected to the energy storage system through a bridge arm isolation component, the bridge arm isolation component can be connected to a smoothing reactor, and the smoothing reactor is connected to the energy storage system. For example, as shown... Figure 11 As shown, the first bridge arm isolation assembly 12011 is connected to the positive terminal of the energy storage system 130 through the first smoothing reactor 150; the second bridge arm isolation assembly 12021 is connected to the negative terminal of the energy storage system 130 through the second smoothing reactor 160.

[0132] In this embodiment, the DC collection device is connected to the energy storage system through a smoothing reactor, which can filter and stabilize the photovoltaic collection system, thereby improving the stability of the photovoltaic collection system.

[0133] The following is based on Figure 11 Taking the photovoltaic collection system provided in this application embodiment as an example, the current flow is explained as follows: When the first photovoltaic unit 11011 starts working, the current generated by the first photovoltaic unit 11011 flows sequentially through the first unit reactor component 12013, the first unit isolation component 12012, the first bridge arm isolation component 12011, and the first smoothing reactor 150, and flows into the positive terminal of the energy storage system 130. Then the current flows out from the midpoint of the energy storage system 130, passes through the first bridge arm isolation component 12011, and flows into the first photovoltaic unit 11011. Similarly, when the second photovoltaic unit 11021 starts working, the current generated by the second photovoltaic unit 11021 flows sequentially through the second unit reactor component 12023, the second unit isolation component 12022, the second bridge arm isolation component 12021, and the second smoothing reactor 160, and flows into the midpoint of the energy storage system 130. Then the current flows out from the negative terminal of the energy storage system 130, passes through the second bridge arm isolation component 12021, and flows into the second photovoltaic unit 11021.

[0134] This application also provides a power adjustment method, which can be applied to an energy management system, such as... Figure 12 As shown, this power adjustment method can be implemented through steps S901 and S902:

[0135] Step S901: Obtain the power demand information of the load of the photovoltaic collection system.

[0136] The photovoltaic collection system includes at least one photovoltaic system, a DC collection device corresponding to each photovoltaic system, an energy storage system, and a voltage source converter valve; each photovoltaic system includes at least one photovoltaic unit, and each photovoltaic unit includes at least two photovoltaic branches connected in series; the output end of each photovoltaic system is connected to the input end of the corresponding DC collection device, and the output end of the DC collection device is connected to the input end of the energy storage system; the energy storage system and the voltage source converter valve are connected in parallel.

[0137] Here, the load of the photovoltaic collection system can refer to a load that needs to be powered through a voltage source converter valve. This load can be an AC load.

[0138] In this embodiment, a power measurement device is installed between the voltage source converter valve and the load. This power measurement device can collect the power demand information of the load and then send the power demand information to the energy management system. For example, this power measurement device can be a power meter.

[0139] Step S902: Based on power demand information, the current output power of the photovoltaic system and the current output power of the energy storage system, control the photovoltaic system and / or the energy storage system to supply power to the load.

[0140] In this embodiment, the energy management system can determine the relationship between the power demand information, the current output power of the photovoltaic system, and the current output power of the energy storage system, and determine whether the current output power of the photovoltaic system and the energy storage system meets the current power demand of the load.

[0141] In some embodiments, such as Figure 13 As shown, step S902 can be achieved by any one of steps S1001 to S1003:

[0142] Step S1001: If the current output power of the photovoltaic system meets the power demand information, the photovoltaic system is controlled to supply power to the load through the voltage source converter valve by the controller of the photovoltaic system and the controller of the voltage source converter valve.

[0143] In this embodiment of the application, when the current output power of the photovoltaic system is greater than or equal to the power demand information, it can be said that the current output power of the photovoltaic system meets the power demand information. At this time, the energy management system sends a control command to the controller of the photovoltaic system to supply power to the load, so that the photovoltaic system supplies power to the load through the voltage source converter valve.

[0144] If the current output power of the photovoltaic system is greater than the power demand information, it means that the photovoltaic system has surplus electrical energy after supplying power to the load. At this time, the photovoltaic system can be controlled to store the electrical energy in the energy storage system, or the photovoltaic system can be controlled to transmit the electrical energy to the grid system through the voltage source converter valve.

[0145] Step S1002: When the current output power of the photovoltaic system and the current output power of the energy storage system meet the power demand information, the photovoltaic system and the energy storage system are controlled by the controller of the photovoltaic system, the controller of the energy storage system and the controller of the voltage source converter valve to supply power to the load through the voltage source converter valve.

[0146] In this embodiment of the application, when the current output power of the photovoltaic system does not meet the power demand information, and the sum of the current output power of the photovoltaic system and the current output power of the energy storage system meets the power demand information, the photovoltaic system and the energy storage system can be controlled to supply power to the load through the voltage source converter valve.

[0147] Step S1003: If the current output power of the photovoltaic system and the current output power of the energy storage system do not meet the power demand information, a power supply request is sent to the controller of the power grid system, so that the power grid system supplies power to the load. The photovoltaic system and the energy storage system are controlled by the controller of the photovoltaic system, the controller of the energy storage system and the controller of the voltage source converter valve to supply power to the load through the voltage source converter valve.

[0148] In this embodiment of the application, if the sum of the current output power of the photovoltaic system and the current output power of the energy storage system does not meet the power demand information, the grid system can be requested to supply power to the load, and the photovoltaic system and the energy storage system can be controlled to supply power to the load through the voltage source converter valve.

[0149] Current photovoltaic (PV) grid connection technologies typically connect to the grid via AC inverters. When the capacity of a PV system reaches MW or higher, this method requires multiple voltage boosting steps to medium and high voltage levels, resulting in numerous intermediate stages and consequently lower overall system efficiency. Furthermore, with the increase in parallel PV grid-connected branches, the problems of circulating currents between these branches and oscillations and instability with the grid become increasingly severe.

[0150] DC aggregation technology boasts advantages such as low transmission loss, low harmonics, high stability, and no need for reactive power compensation, effectively enabling large-capacity photovoltaic grid connection. By utilizing DC direct-connected energy storage valve technology to directly connect MW-level and above photovoltaic power generation to a DC direct-connected bus, photovoltaic grid connection efficiency will be significantly improved, overcoming the oscillation and instability problems in existing photovoltaic grid connection. More importantly, combined with grid-based control strategies, large zero-carbon generator units will be realized, constructing a medium-voltage DC green power supply, grid, load, and energy storage system with new energy sources as the primary energy source. For example, such as... Figure 14 As shown, the DC bus 20 can be connected to a wind power generation unit 13, an energy storage unit 14, a distributed generation (DG) power source 15, an AC load 16, a photovoltaic power generation unit 17, a power receiving unit 18 (e.g., an electric vehicle), a DC load 19, and a power grid 11 connected through a flexible DC valve 12 (i.e., VSC in the above embodiment), thereby forming a medium-voltage DC green power source, power grid, load, and energy storage system with new energy sources as the main energy source.

[0151] In this embodiment of the application, in order to solve the problems existing in photovoltaic grid connection technology in related technologies, this embodiment of the application proposes a photovoltaic DC collection scheme based on DC direct-connected energy storage valve and flexible DC valve. Figure 15 A block diagram of a 10kV photovoltaic system connected to a DC direct-connected system is shown; as follows: Figure 15As shown, the photovoltaic collection system includes a first photovoltaic subsystem 1101, a second photovoltaic subsystem 1102, a first medium-voltage DC collection system 21, a second medium-voltage DC collection system 22, an energy storage system 130, a first smoothing reactor 150, a second smoothing reactor 160, and a flexible DC valve 12, wherein...

[0152] The output terminal of the first photovoltaic subsystem 1101 is connected to the first medium-voltage DC collection system 21, the first medium-voltage DC collection system 21 is connected to the first smoothing reactor 150, the first smoothing reactor 150 is connected to the positive terminal of the energy storage system 130, and the first medium-voltage DC collection system 21 is also connected to the midpoint of the energy storage system 130; the output terminal of the second photovoltaic subsystem 1102 is connected to the second medium-voltage DC collection system 22, the second medium-voltage DC collection system 22 is connected to the second smoothing reactor 160, the second smoothing reactor 160 is connected to the negative terminal of the energy storage system 130, and the second medium-voltage DC collection system 22 is also connected to the midpoint of the energy storage system 130.

[0153] In this embodiment, a DC bus (e.g., ±10kV) is constructed using a DC direct-connected energy storage valve (i.e., energy storage system) and a VSC flexible DC valve. The VSC flexible DC valve serves to enable bidirectional energy communication with an external three-phase AC system, while the energy storage valve serves to smooth out energy fluctuations.

[0154] In this embodiment, the output of the medium-voltage DC collection system is connected between the DC bus of the DC direct-connected energy storage valve and the ground potential, thus serving as a photovoltaic energy collection system. The medium-voltage DC collection system is connected to the DC direct-connected energy storage valve + VSC flexible DC valve system through DC smoothing reactors (i.e., the first smoothing reactor and the second smoothing reactor).

[0155] Figure 16 A schematic diagram of a 10kV photovoltaic system isolated and connected to a single-sided DC bus is shown, as follows. Figure 16 As shown, the photovoltaic system includes multiple grid-connected units 31, each comprising multiple photovoltaic power generation base branches 311. Multiple photovoltaic power generation base branches 311 are connected in series within each grid-connected unit 31, boosting the voltage to 10kV. The multiple grid-connected units 31 are connected in parallel to the DC input terminal of a medium-voltage DC collection system. Each photovoltaic power generation base branch 311 includes a photovoltaic array and an isolated or non-isolated DC / DC converter. Figure 16 The diagram shows an isolated DC / DC converter.

[0156] In this embodiment, the photovoltaic (PV) power generation array is at a low potential. After the PV power generation array is connected to an isolated or non-isolated DC / DC converter, it forms a PV power generation base branch. The output terminals of multiple PV power generation base branches are connected in series to achieve a 10kV DC voltage. That is, multiple PV power generation base branches adopt the Input-Parallel Output-Series (IPOS) method to obtain a grid-connected unit, thereby further forming a grid-connected unit. If an isolated DC / DC converter is used, 10kV isolation can be achieved internally in each PV power generation base branch through a transformer.

[0157] In some embodiments, the isolated DC / DC converter can adopt commonly used industry topologies, such as LLC resonant DC-DC converters or phase-shifted full-bridge DC-DC converter circuits. The isolated DC / DC converter is used for Maximum Power Point Tracking (MPPT), boost / regulation, and 10kV electrical isolation. The non-isolated DC / DC converter can adopt commonly used industry topologies, such as Boost PFC DC-DC boost converter circuits. The non-isolated DC / DC converter is used for MTTP and boost / regulation. During the design phase, the photovoltaic array can be designed in conjunction with the isolated or non-isolated DC / DC converter to achieve optimal integration.

[0158] like Figure 16 As shown, grid-connected unit 31 is connected to bridge arm MV diode valve 34 via unit connecting reactor 32 and unit MV diode valve 33, and multiple grid-connected units 31 are connected in parallel. The unit MV diode valve 33 reduces the probability of power backflow between multiple parallel grid-connected units. One end of the bridge arm MV diode valve 34 is connected to the DC bus or ground potential, and the other end is connected to the parallel connection point of the grid-connected unit, thus protecting against reverse power flow from the bus.

[0159] like Figure 16 As shown, if a short circuit occurs at short circuit point 35, the current generated by the corresponding grid-connected unit 31 will flow through the short-circuit branch (i.e., Figure 16 The current flows back to grid-connected unit 31 from short-circuit point 35 (the dashed section), causing a short circuit in grid-connected unit 31, thus causing a fault in grid-connected unit 31 corresponding to short-circuit point 35. Simultaneously, because the faulty grid-connected unit 31 is connected to unit MV diode valve 33, the current generated by other grid-connected units cannot flow into the short-circuit branch through unit MV diode valve 33. Therefore, the faulty grid-connected unit 31 will not affect the normal operation of other grid-connected units in the photovoltaic system. If a short circuit occurs at short-circuit point 36, the current generated by all grid-connected units 31 in the photovoltaic system flows through the short-circuit branch (i.e.,... Figure 16The short-circuit current (the dashed section corresponding to short-circuit point 36) flows back to itself, causing all grid-connected units 31 to short-circuit, meaning the photovoltaic system cannot function properly. Simultaneously, because a bridge arm MV diode valve 34 is installed on the line connecting the grid-connected unit 31 and the energy storage system 130, the bridge arm MV diode valve 34 can isolate the short-circuit current of the two first photovoltaic units 11011. Therefore, a fault in the first photovoltaic subsystem will not affect the energy storage system 130 and the voltage source converter valve 140.

[0160] It should be noted that, Figure 16 Only a schematic diagram of the connection between the first photovoltaic subsystem and the positive and midpoints of the energy storage system through the first medium-voltage DC collection system is shown.

[0161] In this embodiment of the application, the efficiency analysis / decomposition of the photovoltaic collection system is as follows:

[0162] Based on isolated DC / DC converters, referencing commonly used LLC resonant DC-DC converters or phase-shifted full-bridge DC-DC converters, the expected DC / DC efficiency is 98%; based on non-isolated DC / DC converters, referencing commonly used Boost PFC DC-DC converters, the expected DC / DC efficiency is 99%.

[0163] The expected efficiency of the MV diode valve and unit connection reactor in the medium-voltage DC collection system is 99.6%.

[0164] In summary, the overall photovoltaic grid connection efficiency of this scheme is expected to be 97.6% for isolated photovoltaic systems and 98.6% for non-isolated photovoltaic systems.

[0165] This application also provides a power coordination method among a photovoltaic power generation system, a DC-connected energy storage valve, and a VSC flexible DC valve, which is implemented through an energy management system. Figure 17 As shown, the energy management system 1401 controls the photovoltaic system 110 to supply power to the load through the photovoltaic control system 1402; the energy management system 1401 controls the DC-connected energy storage valve 1405 to supply power to the load through the energy storage valve control system 1403; the energy management system 1401 controls the flexible DC valve 12 to deliver the electrical energy of the DC-connected energy storage valve 1405 and / or the photovoltaic system 110 to the load through the flexible DC valve control system 1404.

[0166] like Figure 18 As shown, the above power coordination method can be implemented through the following steps:

[0167] Step S1501: Whether the photovoltaic power generation system and energy storage valve meet the load requirements.

[0168] Specifically, if the photovoltaic power generation system and the energy storage valve meet the load requirements, step S1502 is executed; if the photovoltaic power generation system and the energy storage valve do not meet the load requirements, step S1503 is executed.

[0169] Step S1502: Does the photovoltaic power generation system meet the load demand?

[0170] If the photovoltaic power generation system meets the load demand, step S1504 is executed; if the photovoltaic power generation system does not meet the load demand, step S1505 is executed.

[0171] In step S1503, the photovoltaic power generation system, energy storage valve, and AC power grid simultaneously supply power to the load.

[0172] In this embodiment, when the photovoltaic power generation system and energy storage valve cannot meet the load demand, the energy from the photovoltaic power generation system and energy storage valve supplies power to the load via the VSC valve. Simultaneously, the energy management system interacts with the AC grid controller to request the grid to also supply power to the load. Figure 19 As shown, the photovoltaic system 110 and the DC-connected energy storage valve 1405 output electrical energy to form a medium-voltage DC bus 42. The medium-voltage DC bus 42 supplies power to the local AC load 41 through the flexible DC valve 12, while the AC grid 42 supplies power to the local AC load 41.

[0173] In step S1504, the photovoltaic power generation system supplies power to the load, and excess energy is stored in the energy storage valve or sent out.

[0174] In this embodiment, when the photovoltaic power generation system can meet the load demand, the photovoltaic power generation system acts as a separate power source, supplying power to the load via the VSC valve. Excess energy is stored in the energy storage valve or sent to the AC grid via the VSC flexible DC valve. Figure 20 As shown, the photovoltaic system 110 outputs electrical energy to form a medium-voltage DC bus 42. The medium-voltage DC bus 42 supplies power to the local AC load 41 and the AC power grid 42 through the flexible DC valve 12, and also supplies electrical energy to the DC direct-connected energy storage valve 1405 to store electrical energy.

[0175] In step S1505, the photovoltaic power generation system and the energy storage valve simultaneously supply power to the load.

[0176] In this embodiment, when the photovoltaic power generation system and the energy storage valve can simultaneously supply power to meet the load demand, the photovoltaic power generation system serves as the main power source, and the energy storage valve serves as an auxiliary power source. Energy is supplied to the load via the VSC valve. Figure 21 As shown, the photovoltaic system 110 and the DC-connected energy storage valve 1405 output electrical energy to form a medium-voltage DC bus 42. The medium-voltage DC bus 42 supplies power to the local AC load 41 and the AC power grid 42 through the flexible DC valve 12.

[0177] It should be understood that the phrase "one embodiment" or "an embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of this application. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. It should be understood that in the various embodiments of this application, the sequence numbers of the above steps / processes do not imply a sequential order of execution; the execution order of each step / 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. The sequence numbers of the above embodiments of this application are merely descriptive and do not represent the superiority or inferiority of the embodiments.

[0178] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0179] The above are merely embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A photovoltaic collection system, characterized in that, The photovoltaic collection system includes at least one photovoltaic system, a DC collection device, an energy storage system, and a voltage source converter valve; Each of the photovoltaic systems includes at least one photovoltaic unit, and each of the photovoltaic units includes at least two photovoltaic branches connected in series; The output terminal of each photovoltaic system is connected to the input terminal of the corresponding DC collector, and the output terminal of the DC collector is connected to the input terminal of the energy storage system; the energy storage system is connected in parallel with the voltage source converter valve; wherein... The DC collecting device is used to collect the current generated by the at least one photovoltaic unit and output the collected current to the energy storage system.

2. The photovoltaic collection system according to claim 1, characterized in that, The photovoltaic data collection system includes two DC data collection devices; the two DC data collection devices include a first DC data collection device and a second DC data collection device; wherein... The first output terminal of the first DC collector is connected to the positive terminal of the energy storage system, and the second output terminal of the first DC collector is connected to the midpoint of the energy storage system. The first output terminal of the second DC collector is connected to the midpoint of the energy storage system, and the second output terminal of the second DC collector is connected to the negative terminal of the energy storage system.

3. The photovoltaic collection system according to claim 1, characterized in that, The number of DC collection devices is even, and at least four DC collection devices include at least two first DC collection devices connected in series and at least two second DC collection devices connected in series.

4. The photovoltaic collection system according to claim 1, characterized in that, The number of photovoltaic systems is even; each photovoltaic system includes at least two photovoltaic units; the connection method between the photovoltaic units and the corresponding DC collection devices is the same in different photovoltaic systems.

5. The photovoltaic collection system according to claim 1, characterized in that, The number of the DC collection devices is 1; The first output terminal of the DC collector is connected to the positive terminal of the energy storage system, and the second output terminal of the DC collector is connected to the negative terminal of the energy storage system; or... The first output terminal of the DC collector is connected to the positive or negative terminal of the energy storage system, and the second output terminal of the DC collector is grounded.

6. The photovoltaic collection system according to claim 2, characterized in that, The two photovoltaic systems include a first photovoltaic subsystem and a second photovoltaic subsystem; the first photovoltaic subsystem includes at least two first photovoltaic units, and the second photovoltaic subsystem includes at least two second photovoltaic units; the number of first photovoltaic units corresponds to the number of second photovoltaic units; wherein, The first end and the second end of each of the first photovoltaic units are respectively connected to the first DC collecting device; the first end and the second end of each of the second photovoltaic units are respectively connected to the second DC collecting device.

7. The photovoltaic collection system according to claim 6, characterized in that, The first DC-DC converter includes a first arm isolation assembly; the second DC-DC converter includes a second arm isolation assembly; wherein, At least one end of each of the first photovoltaic units is connected to the first bridge arm isolation component; the first bridge arm isolation component is connected to the positive terminal and / or the midpoint of the energy storage system; At least one end of each of the second photovoltaic units is connected to the second bridge arm isolation component; the second bridge arm isolation component is connected to the midpoint and / or negative terminal of the energy storage system.

8. The photovoltaic collection system according to claim 7, characterized in that, The first DC collection device includes first unit isolation components in number corresponding to the number of the first photovoltaic units; the second DC collection device includes second unit isolation components in number corresponding to the number of the second photovoltaic units; wherein... The first ends of the at least two first photovoltaic units are respectively connected to their respective first unit isolation components; the at least two first unit isolation components are connected to the positive electrode of the energy storage system through the first bridge arm isolation component, or the at least two first unit isolation components are connected to the positive electrode of the energy storage system. The first ends of the at least two second photovoltaic units are respectively connected to their respective second unit isolation components; the at least two second unit isolation components are connected to the midpoint of the energy storage system through the second bridge arm isolation components, or the at least two first unit isolation components are connected to the midpoint of the energy storage system.

9. The photovoltaic collection system according to claim 8, characterized in that, The first DC collection device includes first unit reactor components in numbers corresponding to the number of the first photovoltaic units; the second DC collection device includes second unit reactor components in numbers corresponding to the number of the second photovoltaic units; wherein... The first ends of the at least two first photovoltaic units are respectively connected to their respective first unit isolation components through the first unit reactance components; The first ends of the at least two second photovoltaic units are respectively connected to their respective second unit isolation components through the second unit reactor components.

10. The photovoltaic collection system according to any one of claims 2, 6 to 9, characterized in that, The photovoltaic collection system further includes a first smoothing reactor and a second smoothing reactor; wherein... The first end of the first DC collecting device is connected to the positive terminal of the energy storage system through the first smoothing reactor; The second end of the second DC collecting device is connected to the negative terminal of the energy storage system through the second smoothing reactor.

11. A power adjustment method, characterized in that, The method includes: The system acquires power demand information of the load in a photovoltaic (PV) collection system. The PV collection system includes at least one PV system, a DC collection device corresponding to each PV system, an energy storage system, and a voltage source converter valve. Each PV system includes at least one PV unit, and each PV unit includes at least two PV branches connected in series. The output terminal of each PV system is connected to the input terminal of the corresponding DC collection device, and the output terminal of the DC collection device is connected to the input terminal of the energy storage system. The energy storage system is connected in parallel with the voltage source converter valve. Based on the power demand information, the current output power of the photovoltaic system, and the current output power of the energy storage system, control the photovoltaic system and / or the energy storage system to supply power to the load.

12. The method according to claim 11, characterized in that, The step of controlling the photovoltaic system and / or the energy storage system to supply power to the load based on the power demand information, the current output power of the photovoltaic system, and the current output power of the energy storage system includes: When the current output power of the photovoltaic system meets the power demand information, the photovoltaic system is controlled to supply power to the load through the voltage source converter valve by the controller of the photovoltaic system and the controller of the voltage source converter valve. When the current output power of the photovoltaic system and the current output power of the energy storage system meet the power demand information, the photovoltaic system and the energy storage system are controlled by the controller of the photovoltaic system, the controller of the energy storage system and the controller of the voltage source converter valve to supply power to the load through the voltage source converter valve. If the current output power of the photovoltaic system and the current output power of the energy storage system do not meet the power demand information, a power supply request is sent to the controller of the power grid system, so that the power grid system supplies power to the load. The controllers of the photovoltaic system, the energy storage system, and the voltage source converter valve control the photovoltaic system and the energy storage system to supply power to the load through the voltage source converter valve.

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