Energy storage converter and energy storage system

Abstract

This application discloses an energy storage converter and energy storage system, belonging to the field of power electronics technology. The energy storage converter includes: a DC bus; at least one isolated switching power supply circuit, the input terminal of which is electrically connected to the energy storage element, and the output terminal of which is electrically connected to the DC bus; and an inverter unit, the DC side of which is electrically connected to the DC bus, and the AC side of which is electrically connected to the power grid. The inverter unit is configured to convert the DC power transmitted from the DC bus into AC power. When the isolated switching power supply circuit is placed between the energy storage element and the DC bus, high- and low-voltage isolation between the energy storage element and the DC bus can be achieved. Using an isolated switching power supply circuit allows for electrical isolation between high and low voltages while achieving DC-DC conversion, improving the safety of the energy storage converter. Furthermore, only one stage of isolated switching power supply circuit is needed to achieve electrical isolation, resulting in lower cost.

Description

Technical Field

[0001] This application belongs to the field of power electronics technology, and in particular relates to an energy storage converter and energy storage system. Background Technology

[0002] A photovoltaic (PV) energy storage inverter is a device that integrates PV power generation, energy storage batteries, and power conversion, and is widely used in grid-connected and off-grid systems. In existing energy storage inverter designs, there is often a lack of effective high- and low-voltage isolation measures between the PV modules and energy storage units and the DC bus. This not only increases the risk of electric shock to the system but may also affect the stable operation of the equipment due to electrical interference.

[0003] In related technologies, in order to achieve electrical isolation between high and low voltage, an additional isolation circuit is usually added between the DC bus and the inverter unit, which is costly. Summary of the Invention

[0004] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes an energy storage converter and energy storage system, which uses an isolated switching power supply circuit, and can achieve electrical isolation between high voltage and low voltage while realizing DC-DC conversion, thereby improving the safety of the energy storage converter.

[0005] In a first aspect, this application provides an energy storage converter, comprising:

[0006] DC bus;

[0007] At least one isolated switching power supply circuit, wherein the input terminal of the isolated switching power supply circuit is used for electrical connection with an energy storage element, and the output terminal of the isolated switching power supply circuit is electrically connected to a DC bus;

[0008] The inverter unit has its DC side electrically connected to the DC bus and its AC side electrically connected to the power grid. The inverter unit is configured to convert the DC power transmitted from the DC bus into AC power.

[0009] According to one embodiment of this application, the energy storage element includes a photovoltaic module, and the isolated switching power supply circuit includes:

[0010] The first isolated switching power supply circuit has an input terminal for electrical connection to the photovoltaic module and an output terminal for electrical connection to the DC bus. The first isolated switching power supply circuit is configured to boost the electrical energy of the photovoltaic module and transmit it to the DC bus.

[0011] According to one embodiment of this application, the isolated switching power supply circuit includes:

[0012] The first transformer, the first end of the primary winding of the first transformer is used for electrical connection with the first end of the photovoltaic module;

[0013] The first switching transistor has its first end electrically connected to the second end of the primary winding of the first transformer, and its second end electrically connected to the second end of the photovoltaic module.

[0014] The rectifier unit has its input terminal electrically connected to the first terminal of the secondary winding of the first transformer.

[0015] The first filter capacitor has its first end electrically connected to the output terminal of the rectifier unit and the DC bus, and its second end electrically connected to the second end of the secondary winding of the first transformer and the DC bus.

[0016] According to one embodiment of this application, the rectifier unit includes:

[0017] The second switching transistor has its first terminal electrically connected to the first terminal of the secondary winding of the first transformer, and its second terminal electrically connected to the first terminal of the first filter capacitor.

[0018] According to one embodiment of this application, the energy storage element includes a battery cell, and the isolated switching power supply circuit includes:

[0019] The second isolated switching power supply circuit has an input terminal for electrical connection to the battery cell and an output terminal for electrical connection to the DC bus. The second isolated switching power supply circuit is configured to either boost the power from the battery cell and transmit it to the DC bus, or step down the power from the DC bus and transmit it to the battery cell.

[0020] According to one embodiment of this application, the second isolated switching power supply circuit includes:

[0021] The first full-bridge circuit has its input side electrically connected to the battery cell.

[0022] The third inductor, the first end of the third inductor is electrically connected to the midpoint of the first bridge arm of the first full-bridge circuit;

[0023] The third transformer has its primary winding first end electrically connected to the second end of the third inductor, and the primary winding second end of the third transformer is electrically connected to the midpoint of the second bridge arm of the first full-bridge circuit.

[0024] The second full-bridge circuit has its input side electrically connected to the secondary winding of the third transformer, and its output side electrically connected to the DC bus.

[0025] According to one embodiment of this application, the second isolated switching power supply circuit further includes:

[0026] The first terminal of the fourth inductor is electrically connected to the second terminal of the third inductor and the first terminal of the primary winding of the third transformer, respectively. The second terminal of the fourth inductor is electrically connected to the second terminal of the primary winding of the third transformer.

[0027] The first resonant capacitor has its first terminal electrically connected to the second terminal of the fourth inductor, and its second terminal electrically connected to the midpoint of the second bridge arm of the first full-bridge circuit.

[0028] According to one embodiment of this application, the second isolated switching power supply circuit further includes:

[0029] The fifth inductor has its first terminal electrically connected to the first terminal of the secondary winding of the third transformer, and its second terminal electrically connected to the midpoint of the first bridge arm of the second full-bridge circuit.

[0030] The second resonant capacitor has its first terminal electrically connected to the second terminal of the secondary winding of the third transformer, and its second terminal electrically connected to the midpoint of the second bridge arm of the second full-bridge circuit.

[0031] According to one embodiment of this application, the inverter unit includes:

[0032] The power factor correction circuit is electrically connected to the DC bus at its input side.

[0033] The inverter circuit has its input side electrically connected to the output side of the power factor correction circuit, and its output side is used to connect to the power grid.

[0034] Secondly, this application provides an energy storage system, including a battery cell and the aforementioned energy storage converter, wherein the DC side of the energy storage converter is electrically connected to the energy storage element assembly, and the AC side of the energy storage converter is electrically connected to the power grid.

[0035] According to several embodiments of the energy storage converter and energy storage system of this application, when the isolated switching power supply circuit is set between the energy storage element and the DC bus, high and low voltage isolation between the energy storage element and the DC bus can be achieved. By selecting the isolated switching power supply circuit, electrical isolation between high voltage and low voltage can be achieved under the premise of DC conversion, thereby improving the safety of the energy storage converter. Moreover, only one stage of isolated switching power supply circuit is required to achieve electrical isolation between the energy storage element and the inverter unit, which is low cost.

[0036] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0037] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0038] Figure 1 This is one of the structural block diagrams of energy storage converters in related technologies;

[0039] Figure 2 This is the second structural block diagram of an energy storage converter in related technologies;

[0040] Figure 3 This is one of the structural schematic diagrams of the energy storage converter provided in the embodiments of this application;

[0041] Figure 4 This is a second schematic diagram of the energy storage converter provided in the embodiments of this application;

[0042] Figure 5 This is the third schematic diagram of the energy storage converter provided in the embodiments of this application;

[0043] Figure 6 This is the fourth schematic diagram of the energy storage converter provided in the embodiments of this application.

[0044] Figure label:

[0045] Energy storage element 10, photovoltaic module 11, battery unit 12, isolated switching power supply circuit 20, first isolated switching power supply circuit 30, rectifier unit 31, second isolated switching power supply circuit 40, first full-bridge circuit 41, second full-bridge circuit 42, inverter unit 50, power factor correction circuit 51, inverter circuit 52, power grid 60, DC bus YC, first to fifth switching transistors Q1 to Q5, first to fourth diodes D1 to D4, first to fifth inductors L1 to L5, first to third filter capacitors Cr1 to Cr3, first to second resonant capacitors Cf1 to Cf2, first to third transformers Tr1 to Tr3, center tap transformer Tr4. Detailed Implementation

[0046] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0047] In the following description, a "circuit" refers to a conductive loop consisting of at least one element or sub-circuit connected by an electrical or electromagnetic link. When an element or circuit is said to be "coupled to" or "connected to" another element, or when an element / circuit is said to be "coupled at" or "connected at" two nodes, it can be directly coupled to or connected to the other element, or there may be intermediate elements. The connection between elements can be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there are no intermediate elements between them.

[0048] In the description, the terms "first," "second," etc., are used to distinguish similar objects, not to describe a specific order or sequence. It should be understood that such numerical descriptors can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class, not limited in number; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0049] Furthermore, the use of terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0050] In related technologies, energy storage converters are typically designed using either a high-voltage bus or a low-voltage bus scheme.

[0051] Reference Figure 1 , Figure 1 This paper illustrates an energy storage converter employing a high-voltage bus design in related technologies. The photovoltaic modules and energy storage section are boosted to the high-voltage bus via a non-isolated DC / DC circuit. The subsequent stage uses a bridge inverter circuit to achieve grid-connected / off-grid output. This circuit is entirely non-isolated, raising safety concerns.

[0052] Reference Figure 2 , Figure 2This diagram illustrates an energy storage converter employing a low-voltage bus design in related technologies. Photovoltaic modules and energy storage units are connected in parallel to the low-voltage bus via a DC / DC circuit. The low-voltage bus then boosts the voltage to the high-voltage bus via an isolated DC / DC circuit, finally achieving grid-connected / off-grid output through an inverter circuit. This circuit has a three-stage structure, which, while achieving electrical isolation between high and low voltages, results in higher overall cost and lower overall efficiency.

[0053] Reference Figure 3 , Figure 3 An embodiment of this application illustrates an energy storage converter. One embodiment of this application proposes an energy storage converter comprising: a DC bus YC, at least one isolated switching power supply circuit 20, and an inverter unit 50. The input terminal of the isolated switching power supply circuit 30 is electrically connected to an energy storage element, and the output terminal of the isolated switching power supply circuit 30 is electrically connected to the DC bus YC; the DC side of the inverter unit 50 is electrically connected to the DC bus YC, and the AC side of the inverter unit 50 is electrically connected to the power grid 60. The inverter unit 50 is configured to convert the DC power transmitted through the DC bus YC into AC power.

[0054] Energy storage element 10 refers to a device or component capable of storing energy and releasing it when needed. The specific type of energy storage element 10 can be selected according to the actual application scenario and is not limited here. For example, energy storage element 10 can be a battery cell 11 or a photovoltaic module 12, etc.

[0055] The DC bus YC is the main conductor in the energy storage converter that carries and transmits DC power. The DC bus YC is mainly used to stably transmit the DC power output from the isolated switching power supply circuit 20 to the subsequent inverter unit 50.

[0056] The input terminal of the isolated switching power supply circuit 20 is electrically connected to the energy storage element. The isolated switching power supply circuit 20 is mainly used to boost the energy released by the energy storage element and transmit it to the DC bus YC.

[0057] In other embodiments, the isolated switching power supply circuit 20 can step down excess electrical energy on the DC bus and then transmit it to the energy storage element.

[0058] The DC power stored in the energy storage element 10 can be efficiently transferred to subsequent circuits, and the output terminal of the isolated switching power supply circuit 20 is closely connected to the DC bus YC. This not only realizes the transmission of electrical energy, but also effectively prevents potential damage to the energy storage element and the entire system from possible fault current or voltage fluctuations through electrical isolation technology, thereby enhancing the safety and reliability of the system.

[0059] The specific type of the isolated switching power supply circuit 20 can be selected according to the actual application scenario, and is not limited here. For example, the isolated switching power supply circuit 20 can be a flyback converter circuit or an LLC circuit, etc.

[0060] Inverter unit 50 is mainly used to convert the DC power on the DC bus YC into AC power suitable for grid connection 60. The specific type of inverter unit 50 can be selected according to the actual application scenario and is not limited here. For example, inverter unit 50 may include inverter circuit 52.

[0061] According to the energy storage converter of this application, when the isolated switching power supply circuit 20 is set between the energy storage element 10 and the DC bus YC, high and low voltage isolation between the energy storage element 10 and the DC bus YC can be achieved. By selecting the isolated switching power supply circuit 20, electrical isolation between high voltage and low voltage can be achieved under the premise of DC conversion, thereby improving the safety of the energy storage converter. Moreover, only one stage of isolated switching power supply circuit 20 is required to achieve electrical isolation between the energy storage element 10 and the inverter unit 50, which is low cost.

[0062] In some embodiments, the energy storage element 10 includes a photovoltaic module 11, and the isolated switching power supply circuit 20 includes a first isolated switching power supply circuit 30. The input terminal of the first isolated switching power supply circuit 30 is electrically connected to the photovoltaic module 11, and the output terminal of the first isolated switching power supply circuit 30 is electrically connected to the DC bus YC. The first isolated switching power supply circuit 30 is configured to boost the electrical energy of the photovoltaic module 11 and transmit it to the DC bus YC.

[0063] When the input side of the first isolated switching power supply circuit 30 is electrically connected to the photovoltaic module 11, the first isolated switching power supply circuit 30 is mainly used to boost the DC power generated by the photovoltaic module 11 to convert the input voltage into the required output voltage. By using the first isolated switching power supply circuit 30, electrical isolation can be achieved between the low voltage output by the photovoltaic module 11 and the high voltage on the DC bus YC, reducing the risk of safety accidents caused by electrical faults.

[0064] The specific type of the first isolated switching power supply circuit 30 can be selected according to the actual application scenario, and is not limited here. For example, the first isolated switching power supply circuit 30 can be a flyback converter circuit or a forward converter circuit, etc.

[0065] Reference Figure 4 , Figure 4An energy storage converter according to an embodiment of this application is illustrated. In some embodiments, a first isolated switching power supply circuit 30 includes: a first transformer Tr1, a first switching transistor Q1, a rectifier unit 31, and a first filter capacitor Cr1. A first end of the primary winding of the first transformer Tr1 is electrically connected to a first end of a photovoltaic module 11; a first end of the first switching transistor Q1 is electrically connected to a second end of the primary winding of the first transformer Tr1, and a second end of the first switching transistor Q1 is electrically connected to a second end of the photovoltaic module 11; an input end of the rectifier unit 31 is electrically connected to a first end of the secondary winding of the first transformer Tr1; a first end of the first filter capacitor Cr1 is electrically connected to the output end of the rectifier unit 31 and the DC bus YC, respectively, and a second end of the first filter capacitor Cr1 is electrically connected to a second end of the secondary winding of the first transformer Tr1 and the DC bus YC, respectively.

[0066] The first transformer Tr1 has a primary winding and a secondary winding. Based on the turns ratio of the primary and secondary windings of the first transformer Tr1, the DC voltage input through the primary winding (i.e., the voltage output by the photovoltaic module 11) can be converted into different output voltages and output through the secondary winding. The primary and secondary windings of the first transformer Tr1 are physically separate, isolated by insulating material, achieving electrical isolation between high and low voltage while realizing energy conversion.

[0067] When the first switch Q1 is turned on, photovoltaic energy is stored in the magnetic circuit of the first transformer Tr1 in the form of magnetic energy; when the first switch Q1 is turned off, the energy stored in the magnetic circuit is released through the secondary winding.

[0068] During the period when the first switch Q1 is turned off, the induced voltage in the secondary winding forward biases the rectifier unit 31, converting the AC current induced in the secondary winding into DC output.

[0069] The specific type of the first switching transistor Q1 can be selected according to the actual application scenario, and is not limited here. For example, the first switching transistor Q1 can be a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or an IGBT (Insulated-Gate Bipolar Transistor), etc.

[0070] The specific type of rectifier unit 31 can be selected according to the actual application scenario, and is not limited here. For example, rectifier unit 31 may include a diode. When rectifier unit 31 is a diode, the first isolated switching power supply circuit 30 in this embodiment is a flyback converter, which has a simple structure and flexible control.

[0071] The first filter capacitor Cr1 is mainly used to smooth the voltage at the output of the rectifier unit 31 and reduce voltage fluctuations and ripples caused by the switching frequency.

[0072] In some embodiments, the rectifier unit 31 includes a second switch Q2. The first terminal of the second switch Q2 is electrically connected to the first terminal of the secondary winding of the first transformer Tr1, and the second terminal of the second switch Q2 is electrically connected to the first terminal of the first filter capacitor Cr1.

[0073] The second switch Q2 is an active device, and its specific type can be selected according to the actual application scenario; there is no limitation here. For example, the second switch Q2 can be a MOSFET, IGBT, SiC (silicon carbide) MOSFET, or GaN (gallium nitride) MOSFET, etc. The following explanation uses a MOSFET as an example for the second switch Q2.

[0074] The rectifier unit 31 uses a second switch Q2. When the first switch Q1 is turned off, the energy of the magnetic core of the first transformer Tr1 is transferred to the secondary side, and the polarity of the secondary winding voltage is reversed. At this time, the body diode of the second switch Q2 is naturally turned on due to forward bias. Then, a drive signal is applied to the gate of the second switch Q2 to make it fully turn on. By actively controlling the turn-on and turn-off timing of the second switch Q2, the passive unidirectional conductivity of the diode can be replaced, thereby significantly reducing the power loss of the rectification stage.

[0075] Reference Figure 5 , Figure 5 An energy storage converter according to an embodiment of this application is shown. In some embodiments, the first isolated switching power supply circuit 30 includes: a second transformer Tr2, a third switching transistor Q3, a first diode D1, a second diode D2, a first inductor L1, and a second filter capacitor Cr2. The first end of the primary winding of the second transformer Tr2 is electrically connected to the first end of the photovoltaic module 11; the first end of the third switch Q3 is electrically connected to the second end of the primary winding of the first transformer Tr1, and the second end of the third switch Q3 is electrically connected to the second end of the photovoltaic module 11; the anode of the first diode D1 is electrically connected to the first end of the secondary winding of the first transformer Tr1; the anode of the second diode D2 is electrically connected to the second end of the secondary winding of the first transformer Tr1, and the cathode of the first diode D1 is electrically connected to the cathode of the second diode D2; the first end of the first inductor L1 is electrically connected to the cathode of the first diode D1 and the cathode of the second diode D2; the first end of the second filter capacitor Cr2 is electrically connected to the second end of the first inductor L1 and the DC bus YC, and the second end of the second filter capacitor Cr2 is electrically connected to the anode of the second diode D2 and the DC bus YC.

[0076] In this embodiment, the second transformer Tr2, the third switch Q3, the first diode D1, the second diode D2, the first inductor L1, and the second filter capacitor Cr2 together constitute a forward converter.

[0077] The structure and function of the second transformer Tr2 can be referred to the first transformer Tr1 mentioned above, and will not be repeated here. The primary winding and secondary winding of the second transformer Tr2 are physically separate, which can achieve electrical isolation between high voltage and low voltage while realizing power conversion.

[0078] The first diode D1 and the second diode D2 have unidirectional conduction characteristics and are mainly used to convert the AC power output from the second transformer Tr2 into DC power.

[0079] The third switch Q3 controls the input and output of electrical energy through periodic switching actions, converting the input DC voltage into a pulse width modulation signal for the transfer and control of electrical energy.

[0080] When the third switch Q3 is turned on, the voltage output across the secondary winding causes the first diode D1 to conduct. Current flows through the first diode D1, the first inductor L1, and the first filter capacitor Cr1 to form a circuit. The current accumulates magnetic lines of force in the inductor core until the first switch Q1 is turned off. When the first switch Q1 is turned off, the first diode D1 is reverse-biased and the first inductor L1 generates a back EMF, causing the second diode D2 to conduct. Current flows through the second diode D2, the first inductor L1, and the first filter capacitor Cr1 to form a circuit.

[0081] The second filter capacitor Cr2 is mainly used to smooth the voltage at the output terminal of the first inductor L1, reducing voltage fluctuations and ripple caused by the switching frequency.

[0082] Reference Figure 6 , Figure 6This illustration shows an energy storage converter provided in an embodiment of this application. In some embodiments, a first isolated switching power supply circuit 30 includes: a center-tapped transformer Tr4, a fourth switch Q4, a fifth switch Q5, a third diode D3, a fourth diode D4, a second inductor L2, and a third filter capacitor Cr3. The center point of the primary winding of the center-tapped transformer Tr4 is electrically connected to the first terminal of the photovoltaic module 11, and the center point of the secondary winding of the center-tapped transformer Tr4 is electrically connected to the DC bus YC; the first terminal of the fourth switch Q4 is electrically connected to the first terminal of the primary winding of the center-tapped transformer Tr4, and the second terminal of the fourth switch Q4 is electrically connected to the grounding node; the first terminal of the fifth switch Q5 is electrically connected to the first terminal of the primary winding of the center-tapped transformer Tr4, and the second terminal of the fifth switch Q5 is electrically connected to the grounding node; the anode of the third diode D3 is connected to the first transformer... The first terminal of the secondary winding of transformer Tr1 is electrically connected; the anode of the fourth diode D4 is electrically connected to the second terminal of the secondary winding of the first transformer Tr1, and the cathode of the third diode D3 is electrically connected to the cathode of the fourth diode D4; the first terminal of the second inductor L2 is electrically connected to the cathodes of the third diode D3 and the fourth diode D4 respectively; the first terminal of the third filter capacitor Cr3 is electrically connected to the second terminal of the first inductor L1 and the DC bus YC respectively, and the second terminal of the third filter capacitor Cr3 is electrically connected to the anode of the second diode D2 and the DC bus YC respectively.

[0083] In this embodiment, the center-tapped transformer Tr4, the fourth switch Q4, the fifth switch Q5, the third diode D3, the fourth diode D4, the second inductor L2, and the third filter capacitor Cr3 together constitute an isolated push-pull circuit.

[0084] The fourth switch Q4 and the fifth switch Q5 are alternately turned on under the drive of the control signal, converting the DC input from the photovoltaic module 11 into high-frequency AC, driving the center-tapped transformer Tr4 to work, and inducing an AC voltage on the secondary winding of the center-tapped transformer Tr4. The turns ratio of the center-tapped transformer Tr4 determines the magnitude of the output voltage of the secondary winding, and at the same time achieves electrical isolation between the photovoltaic module 11 and the DC bus YC.

[0085] The third diode D3 and the fourth diode D4 have unidirectional conduction characteristics and are mainly used to convert the AC power output from the secondary winding of the center-tapped transformer Tr4 into DC power.

[0086] The second inductor L2 can release the stored energy when the fourth switch Q4 and the fifth switch Q5 are turned on alternately, ensuring the continuity and stability of the circuit, thereby reducing output noise and maintaining the stability and safety of the circuit.

[0087] The third filter capacitor Cr3 is mainly used to smooth the voltage at the output terminal of the second inductor L2, reducing voltage fluctuations and ripple caused by the switching frequency.

[0088] In some embodiments, the energy storage element 10 includes a battery cell 12, and the isolated switching power supply circuit 20 includes a second isolated switching power supply circuit 40. The input terminal of the second isolated switching power supply circuit 40 is electrically connected to the battery cell 12, and the output terminal of the second isolated switching power supply circuit 40 is electrically connected to the DC bus YC. The second isolated switching power supply circuit 40 is configured to either boost the electrical energy from the battery cell 12 and transmit it to the DC bus YC, or step down the electrical energy from the DC bus YC and transmit it to the battery cell 12.

[0089] Battery cell 12 can store electrical energy and also release its stored electrical energy to maintain the voltage stability of the power grid 60. The input side of the second isolated switching power supply circuit 40 is electrically connected to battery cell 12. The second isolated switching power supply circuit 40 can both boost the DC power output from battery cell 12 to convert the input voltage into the required output voltage and step down the voltage on the DC bus YC before storing it in battery cell 12. That is, the second isolated switching power supply circuit 40 can realize bidirectional energy transfer between battery cell 12 and DC bus YC.

[0090] The second isolated switching power supply circuit 40 can achieve electrical isolation between the low voltage output of the battery unit 12 and the high voltage on the DC bus YC, reducing the risk of safety accidents caused by electrical faults.

[0091] The specific type of the second isolated switching power supply circuit 40 can be selected according to the actual application scenario, and is not limited here. For example, the second isolated switching power supply circuit 40 can be a dual active bridge circuit or an LLC circuit, etc.

[0092] It should be noted that the energy storage element may include both photovoltaic module 11 and battery unit 12. Photovoltaic module 11 is connected to DC bus YC via a first isolated switching power supply circuit 30, and battery unit 12 is connected to DC bus YC via a second isolated switching power supply circuit 40. When photovoltaic module 11 generates a large amount of electrical energy, the excess electrical energy on DC bus YC can be stored in battery unit 12 after being stepped down by the second isolated switching power supply circuit 40; when photovoltaic module 11 generates a small amount of electrical energy, battery unit 12 can release the stored electrical energy, which is then transmitted to DC bus YC via the second isolated switching power supply circuit 40 to maintain grid voltage stability.

[0093] Continue to refer to Figure 5In some embodiments, the second isolated switching power supply circuit 40 includes: a first full-bridge circuit 41, a third inductor L3, a third transformer Tr3, and a second full-bridge circuit 42. The input side of the first full-bridge circuit 41 is electrically connected to the battery cell 12; the first end of the third inductor L3 is electrically connected to the midpoint of the first bridge arm of the first full-bridge circuit 41; the first end of the primary winding of the third transformer Tr3 is electrically connected to the second end of the third inductor L3, and the second end of the primary winding of the third transformer Tr3 is electrically connected to the midpoint of the second bridge arm of the first full-bridge circuit 41; the input side of the second full-bridge circuit 42 is electrically connected to the secondary winding of the third transformer Tr3, and the output side of the second full-bridge circuit 42 is electrically connected to the DC bus YC.

[0094] In this embodiment, the first full-bridge circuit 41, the third inductor L3, the third transformer Tr3, and the second full-bridge circuit 42 together constitute a dual active full-bridge converter circuit.

[0095] The dual active full-bridge converter circuit enables bidirectional power transmission. The first full-bridge circuit 41, under the control of a drive signal, converts the DC power stored in the battery cell 12 into AC power, and achieves electrical isolation and energy transfer through the third transformer Tr3. The third inductor L3 works in conjunction with the switching devices in the first full-bridge circuit 41 to facilitate soft-switching operation and reduce switching losses. Simultaneously, the third inductor L3 also smooths the current, reducing current fluctuations. The second full-bridge circuit 42 converts the AC power induced in the secondary winding of the third transformer Tr3 into DC power, which is then transmitted to the DC bus YC.

[0096] When the photovoltaic module 11 generates a large amount of electrical energy, the second full-bridge circuit 42 can convert the DC power of the DC bus YC into AC power under the control of the drive signal, and achieve electrical isolation and energy transfer through the third transformer Tr3. The first full-bridge circuit 41 converts the AC power induced by the primary winding of the third transformer Tr3 into DC power and stores it in the battery cell 12.

[0097] The dual active full-bridge converter circuit can realize bidirectional power transfer between battery cell 12 and DC bus YC, and can also realize electrical isolation between battery cell 12 and DC bus YC.

[0098] Continue to refer to Figure 4In some embodiments, the second isolated switching power supply circuit 40 further includes a fourth inductor L4 and a first resonant capacitor Cf1. The first terminal of the fourth inductor L4 is electrically connected to the second terminal of the third inductor L3 and the first terminal of the primary winding of the third transformer Tr3, respectively, and the second terminal of the fourth inductor L4 is electrically connected to the second terminal of the primary winding of the third transformer Tr3; the first terminal of the first resonant capacitor Cf1 is electrically connected to the second terminal of the fourth inductor L4, and the second terminal of the first resonant capacitor Cf1 is electrically connected to the midpoint of the second bridge arm of the first full-bridge circuit 41.

[0099] In this embodiment, a fourth inductor L4 and a first resonant capacitor Cf1 are added to the aforementioned embodiment to form an LLC circuit. Building upon the aforementioned bidirectional energy transfer between the battery cell 12 and the DC bus YC, and the electrical isolation between the battery cell 12 and the DC bus YC, the LLC circuit, by adding the fourth inductor L4 and the first resonant capacitor Cf1, forms a resonant network. This allows the switching transistors in the first full-bridge circuit 41 and the second full-bridge circuit 42 to switch under zero voltage or zero current conditions, thereby significantly reducing switching losses and energy loss.

[0100] Continue to refer to Figure 6 In some embodiments, the second isolated switching power supply circuit 40 further includes a fifth inductor L5 and a second resonant capacitor Cf2. The first terminal of the fifth inductor L5 is electrically connected to the first terminal of the secondary winding of the third transformer Tr3, and the second terminal of the fifth inductor L5 is electrically connected to the midpoint of the first bridge arm of the second full-bridge circuit 42; the first terminal of the second resonant capacitor Cf2 is electrically connected to the second terminal of the secondary winding of the third transformer Tr3, and the second terminal of the second resonant capacitor Cf2 is electrically connected to the midpoint of the second bridge arm of the second full-bridge circuit 42.

[0101] In this embodiment, a fifth inductor L5 and a second resonant capacitor Cf2 are added to the secondary winding side of the aforementioned LLC circuit to form a CLLC circuit, making the primary and secondary circuits of the third transformer Tr3 symmetrical. By adjusting the current of the second resonant capacitor Cf2 to control the output voltage, the soft-switching region is wider, which helps to achieve zero-voltage switching and zero-current turn-off over a wider input voltage range, further reducing switching losses.

[0102] In some embodiments, the inverter unit 50 includes a power factor correction circuit 51 and an inverter circuit 52. The input side of the power factor correction circuit 51 is electrically connected to the DC bus YC; the input side of the inverter circuit 52 is electrically connected to the output side of the power factor correction circuit 51, and the output side of the inverter circuit 52 is used to connect to the power grid 60.

[0103] The voltage of the DC bus YC is obtained by conversion from the first isolated switching power supply circuit 30 and the second isolated switching power supply circuit 40. Both the first isolated switching power supply circuit 30 and the second isolated switching power supply circuit 40 contain capacitors or inductors. The charging and discharging process of these components causes a phase difference between the current and the voltage. The power factor correction circuit 51 can optimize the current waveform, reduce harmonic current, and improve the power factor.

[0104] The inverter circuit 52 receives the stable DC power output from the power factor correction circuit 51 and converts it into high-frequency AC power through the internal DC / AC converter to obtain AC power that meets the requirements and supplies it to the power grid 60 or the load.

[0105] This application embodiment also provides an energy storage system, including a battery unit 12 and the aforementioned energy storage converter. The DC side of the energy storage converter is electrically connected to the battery unit 12 and the photovoltaic module 11, respectively, and the AC side of the energy storage converter is electrically connected to the power grid 60.

[0106] The specific structure of the energy storage converter can be referred to in the aforementioned embodiments, and will not be repeated here.

[0107] According to the energy storage system of this application, when the isolated switching power supply circuit 20 is set between the energy storage element 10 and the DC bus YC, high and low voltage isolation between the energy storage element 10 and the DC bus YC can be achieved. By selecting the isolated switching power supply circuit, electrical isolation between high voltage and low voltage can be achieved under the premise of DC conversion, thereby improving the safety of the energy storage converter. Moreover, only one-stage isolated switching power supply circuit 20 is required to achieve electrical isolation between the energy storage element 10 and the inverter unit 50, which is low cost.

[0108] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. An energy storage converter, characterized by, include: DC bus; A first isolated switching power supply circuit, wherein the input terminal of the first isolated switching power supply circuit is electrically connected to the photovoltaic module, and the output terminal of the first isolated switching power supply circuit is electrically connected to the DC bus, and the first isolated switching power supply circuit is configured to boost the electrical energy of the photovoltaic module and transmit it to the DC bus; The second isolated switching power supply circuit has an input terminal for electrical connection to the battery cell and an output terminal for electrical connection to the DC bus. The second isolated switching power supply circuit is configured to either boost the power of the battery cell and transmit it to the DC bus, or step down the power of the DC bus and transmit it to the battery cell. An inverter unit, wherein the DC side of the inverter unit is electrically connected to the DC bus, and the AC side of the inverter unit is used to be electrically connected to the power grid, and the inverter unit is configured to convert the DC power transmitted by the DC bus into AC power. The first isolated switching power supply circuit includes: A first transformer, wherein a first end of the primary winding of the first transformer is used for electrical connection with a first end of the photovoltaic module; The first switching transistor has a first end electrically connected to the second end of the primary winding of the first transformer, and a second end electrically connected to the second end of the photovoltaic module. A rectifier unit, wherein the input terminal of the rectifier unit is electrically connected to the first terminal of the secondary winding of the first transformer; The first filter capacitor has its first end electrically connected to the output terminal of the rectifier unit and the DC bus, and its second end electrically connected to the second end of the secondary winding of the first transformer and the DC bus.

2. The energy storage converter of claim 1, wherein, The rectifier unit includes: The second switching transistor has its first end electrically connected to the first end of the secondary winding of the first transformer, and its second end electrically connected to the first end of the first filter capacitor.

3. The energy storage converter of claim 1, wherein, The second isolated switching power supply circuit includes: A first full-bridge circuit, wherein the input side of the first full-bridge circuit is electrically connected to the battery cell; The third inductor, the first end of which is electrically connected to the midpoint of the first bridge arm of the first full-bridge circuit; The third transformer has a first end of its primary winding electrically connected to the second end of the third inductor, and the second end of its primary winding electrically connected to the midpoint of the second bridge arm of the first full-bridge circuit. The second full-bridge circuit has its input side electrically connected to the secondary winding of the third transformer, and its output side electrically connected to the DC bus.

4. The energy storage converter of claim 3, wherein, The second isolated switching power supply circuit also includes: The fourth inductor has its first end electrically connected to the second end of the third inductor and the first end of the primary winding of the third transformer, and its second end electrically connected to the second end of the primary winding of the third transformer. A first resonant capacitor, the first end of which is electrically connected to the second end of the fourth inductor, and the second end of which is electrically connected to the midpoint of the second bridge arm of the first full-bridge circuit.

5. The energy storage converter of claim 4, wherein, The second isolated switching power supply circuit also includes: The fifth inductor has its first end electrically connected to the first end of the secondary winding of the third transformer, and its second end electrically connected to the midpoint of the first bridge arm of the second full-bridge circuit. The second resonant capacitor has its first end electrically connected to the second end of the secondary winding of the third transformer, and its second end electrically connected to the midpoint of the second bridge arm of the second full-bridge circuit.

6. The energy storage converter of any one of claims 1-5, wherein, The inverter unit includes: A power factor correction circuit, wherein the input side of the power factor correction circuit is electrically connected to the DC bus; An inverter circuit, wherein the input side of the inverter circuit is electrically connected to the output side of the power factor correction circuit, and the output side of the inverter circuit is used to be electrically connected to the power grid.

7. An energy storage system characterized by, It includes a battery cell and an energy storage converter according to any one of claims 1-6, wherein the DC side of the energy storage converter is electrically connected to the energy storage element, and the AC side of the energy storage converter is electrically connected to the power grid.

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