Control method of energy storage conversion device, energy storage conversion device and energy storage equipment

Abstract

The present invention discloses a control method for an energy storage conversion device, an energy storage conversion device, and an energy storage device. The energy storage conversion device includes: a first converter, a second converter, an inverter, a first switch, an inductor, and a second switch; one end of the first converter is connected to an energy storage battery, and the other end of the first converter is connected to the second converter; the second switch is connected in parallel to both ends of the second converter; the inverter is connected to the second converter; the first switch and the inductor are connected in series and then in parallel between the midpoints of the two bridge arms of the full bridge of the first converter; the energy storage conversion device is configured to execute the control method. By using the present invention, the energy storage conversion device has high power density and working efficiency, low cost, extremely strong off-grid load adaptability, and high reliability.

Description

Technical Field

[0001] The present invention relates to the field of energy storage conversion control, and in particular to a control method for an energy storage conversion device, an energy storage conversion device, and an energy storage device. Background Art

[0002] With the rapid development of power electronics technology and the gradual consensus on global energy crisis awareness, photovoltaic and energy storage conversion technologies are developing rapidly in parallel to meet the needs of household energy storage devices. At the same time, increasingly higher requirements are placed on the working efficiency, power density, and reliability of household energy storage devices.

[0003] Currently, household energy storage devices in off-grid scenarios generally use a three-stage converter structure to achieve coordinated control of the battery energy storage unit, photovoltaic conversion unit, and inverter unit. However, this structure suffers from low efficiency, low power density, and high cost. While a two-stage converter structure significantly improves converter efficiency and power density and reduces costs, it also leads to weak load adaptability in off-grid scenarios, severely limiting the energy storage device's ability to replace the grid.

[0004] Therefore, existing household energy storage devices have technical problems in achieving compatibility between working efficiency, power density, cost and off-grid load adaptability. Summary of the Invention

[0005] The embodiments of the present invention provide a control method for an energy storage conversion device, an energy storage conversion device, and an energy storage device, so as to realize that the energy storage conversion device has high power density and working efficiency, low cost, and at the same time has extremely strong off-grid load adaptability and high reliability.

[0006] In order to solve the above technical problems, an embodiment of the present application provides a control method for an energy storage conversion device, wherein the energy storage conversion device is used in an energy storage device, and the energy storage conversion device includes: a first converter, a second converter, and an inverter;

[0007] The first converter is a bidirectional LLC resonant converter, and the second converter is a bidirectional Buck-Boost converter or a bidirectional Half-Bridge converter;

[0008] In an off-grid or grid-connected state, when the energy storage device needs to be charged, the first converter operates in a constant voltage, constant current, or constant power mode to charge the energy storage device, the second converter is in an inoperative state, and the inverter operates in a rectification mode to achieve stable control of the bus voltage;

[0009] In the grid-connected state, when the energy storage device needs to discharge, the first converter operates in a constant voltage mode to achieve stable control of the bus voltage and suppress the twice-power frequency ripple current on the battery side; the second converter is in an inoperative state, and the inverter operates in an inverter mode to achieve stable control of the AC output voltage;

[0010] In the off-grid state, when the energy storage device needs to discharge and the load is in a power-stable state, the first converter operates in a constant voltage mode to achieve stable control of the bus voltage and suppress the twice-power-frequency ripple current on the battery side. The second converter is in an inoperative state, and the inverter operates in an inverter mode to achieve stable control of the AC output voltage.

[0011] In the off-grid state, when the energy storage device needs to discharge and the load suddenly changes from a power stable state to a short-term severe overload state, the first converter switches from the variable frequency closed-loop operating mode to the fixed frequency open-loop control mode, the second converter realizes the stable control of the bus voltage and suppresses the twice power frequency ripple current on the battery side, and the inverter operates in the inverter mode to realize the stable control of the AC output voltage.

[0012] Furthermore, a first switch (Sw1) and an inductor (Lm1) are connected in series and then in parallel between the midpoints of the two arms of the full bridge of the first converter; when the first switch is closed, the first converter operates in a constant voltage mode to achieve stable control of the bus voltage and suppress the twice-power frequency ripple current on the battery side; when the first switch is disconnected, the first converter operates in a constant voltage, constant current, or constant power mode to charge the energy storage device.

[0013] Furthermore, a second switch (Sw2) is connected in parallel at both ends of the second converter; when the second switch is closed, the second converter is in an inoperative state; when the second switch is disconnected, the second converter achieves stable control of the bus voltage and suppresses twice the power frequency ripple current on the battery side.

[0014] Furthermore, in the off-grid state, when the energy storage device needs to discharge and the load suddenly changes from a stable power state to a short-term severe overload state, the second switch is in a closed state, and the second converter short-circuits the second switch through a normally closed power device, so that the second converter can achieve stable control of the bus voltage and suppress the twice-power frequency ripple current on the battery side.

[0015] Furthermore, the LLC operating frequency of the first converter is set to be higher than the LLC resonant frequency point of the first converter.

[0016] In order to solve the above technical problems, an embodiment of the present application further provides an energy storage conversion device, which includes: a first converter, a second converter, an inverter, a first switch (Sw1), an inductor (Lm1) and a second switch (Sw2);

[0017] One end of the first converter is connected to the energy storage battery, and the other end of the first converter is connected to the second converter; the second switch is connected in parallel to both ends of the second converter; and the inverter is connected to the second converter;

[0018] The first switch and the inductor are connected in series and then in parallel between the midpoints of the two bridge arms of the full bridge of the first converter;

[0019] The energy storage conversion device is configured to execute the above-mentioned control method for the energy storage conversion device.

[0020] Furthermore, the first converter includes: a first switching device, a second switching device, a third switching device, a fourth switching device, a fifth switching device, a sixth switching device, a seventh switching device, an eighth switching device, a transformer, a first inductor, and a first capacitor;

[0021] The first switching device, the second switching device, the third switching device and the fourth switching device constitute two bridge arms of the left full bridge of the first converter;

[0022] The fifth switching device, the sixth switching device, the seventh switching device and the eighth switching device constitute two bridge arms of the right full bridge of the first converter;

[0023] The transformer, the first inductor, the first capacitor, the first switch, and the inductor constitute the resonant cavity parameters of the first converter.

[0024] Furthermore, the second converter is composed of a two-switch Buck-Boost converter, including a ninth switching device, a tenth switching device, a second capacitor, and a second inductor;

[0025] The ninth switching device and the tenth switching device constitute a bridge arm of the second converter, and are connected to the first converter in parallel with the second capacitor;

[0026] The second inductor is connected to the midpoint of the bridge arm of the second converter and the inverter;

[0027] The inverter output voltage is a L / N two-wire system.

[0028] Furthermore, the second converter is composed of a two-switch Buck-Boost converter, including a ninth switching device, a tenth switching device and a second inductor;

[0029] The ninth switching device and the tenth switching device constitute a bridge arm of the second converter, and are connected to the inverter;

[0030] The second inductor is connected to the midpoint of the bridge arm of the second converter and the first converter;

[0031] The inverter consists of two phases and three bridge arms, and the output voltage is a three-wire system of L1 / L2 / N.

[0032] Furthermore, the second converter is composed of a two-switch Buck-Boost converter, including a ninth switching device, a tenth switching device, a second capacitor, and a second inductor;

[0033] The ninth switching device and the tenth switching device constitute a bridge arm of the second converter and are connected to the inverter;

[0034] The second inductor is connected to the midpoint of the bridge arm of the second converter and is connected to the first converter in parallel with the second capacitor;

[0035] The inverter is composed of a full-bridge converter, and the output voltage is a L / N two-line.

[0036] In order to solve the above technical problems, the embodiment of the present application further provides an energy storage device, comprising: an energy management module, a power distribution module, and an energy storage module; the power distribution module includes an energy storage conversion device;

[0037] The energy management module controls the energy storage conversion device to execute the above-mentioned control method for the energy storage conversion device.

[0038] The control method, energy storage conversion device, and energy storage equipment provided by the embodiments of the present invention operate in a two-stage topology structure of a first converter and an inverter in a grid-connected mode or an off-grid mode with a stable load, and the second converter does not operate. At this time, the energy storage conversion device only has losses in the first converter and the inverter, and the overall working efficiency is high. In the event of a short-term severe overload in the off-grid mode, the second converter is switched into operation to form a three-stage structure. At the same time, the first converter switches from closed-loop variable frequency control to fixed-frequency open-loop control. At this time, the reliable operation of the energy storage conversion device can be effectively guaranteed, and it has extremely strong off-grid load adaptability. Since the second converter is only switched into operation for a relatively short time, the selection of the power device of the second converter and the design of the magnetic core device can be greatly simplified, which has the advantages of effectively improving the power density of the energy storage conversion device and reducing the cost, so that the energy storage conversion device has high power density and working efficiency, low cost, and extremely strong off-grid load adaptability and high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0040] Figure 1 This is a schematic diagram of the energy storage conversion device of the present application in a two-stage conversion structure;

[0041] Figure 2 This is a schematic diagram of the energy storage conversion device of the present application in a three-stage conversion structure;

[0042] Figure 3 This is another structural diagram of the energy storage conversion device of the present application;

[0043] Figure 4 1 is a structural diagram of an embodiment of a control method for an energy storage conversion device according to the present application;

[0044] Figure 5 1 is a structural diagram of an embodiment of a control method for an energy storage conversion device according to the present application;

[0045] Figure 6 1 is a structural diagram of an embodiment of a control method for an energy storage conversion device according to the present application;

[0046] Figure 7 1 is a structural diagram of an embodiment of a control method for an energy storage conversion device according to the present application;

[0047] Figure 8 1 is a structural diagram of an embodiment of a control method for an energy storage conversion device according to the present application;

[0048] Figure 9 is a structural schematic diagram of an embodiment of an energy storage conversion device according to the present application;

[0049] Figure 10 is another structural schematic diagram of an embodiment of the energy storage conversion device according to the present application;

[0050] Figure 11 is another structural schematic diagram of an embodiment of the energy storage conversion device according to the present application;

[0051] Figure 12 is another structural schematic diagram of an embodiment of the energy storage conversion device according to the present application;

[0052] Figure 13 is another structural schematic diagram of an embodiment of the energy storage conversion device according to the present application;

[0053] Figure 14 It is a structural diagram of the energy storage device of this application.

[0054] Reference numerals:

[0055] A first converter 10, a second converter 20, and an inverter 30;

[0056] A first switch Sw1, a second switch Sw2, and an inductor Lm1;

[0057] a first switching device Q1, a second switching device Q2, a third switching device Q3, a fourth switching device Q4, a fifth switching device Q5, a sixth switching device Q6, a seventh switching device Q7, an eighth switching device Q8, a ninth switching device Q9, a tenth switching device Q10, a transformer T1, a first inductor Lr, a first capacitor Cr, a second capacitor C2, and a second inductor L4. DETAILED DESCRIPTION

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of the application are for the purpose of describing specific embodiments only and are not intended to limit this application. The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, not to describe a specific order.

[0059] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0060] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0061] An embodiment of the present invention provides a control method for an energy storage conversion device. The energy storage conversion device is used in an energy storage device. The energy storage conversion device includes: a first converter 10 , a second converter 20 , and an inverter 30 .

[0062] The first converter 10 is a bidirectional LLC resonant converter, and the second converter 20 is a bidirectional Buck-Boost converter or a bidirectional Half-Bridge converter.

[0063] In an off-grid or grid-connected state, when the energy storage device needs to be charged, the first converter 10 operates in a constant voltage, constant current, or constant power mode to charge the energy storage device, the second converter 20 is in an off-grid state, and the inverter 30 operates in a rectification mode to achieve stable control of the bus voltage.

[0064] In the grid-connected state, when the energy storage device needs to discharge, the first converter 10 operates in a constant voltage mode to achieve smooth control of the bus voltage and suppress the twice-power frequency ripple current on the battery side. The second converter 20 is in a non-working state, and the inverter 30 operates in an inverter mode to achieve smooth control of the AC output voltage.

[0065] In the off-grid state, when the energy storage device needs to discharge and the load is in a power stable state, the first converter 10 operates in a constant voltage mode to achieve smooth control of the bus voltage and suppress the twice-power frequency ripple current on the battery side. The second converter 20 is in a non-working state, and the inverter 30 operates in an inverter mode to achieve smooth control of the AC output voltage.

[0066] In the off-grid state, when the energy storage device needs to discharge and the load suddenly changes from a power stable state to a short-term severe overload state, the first converter 10 switches from the variable frequency closed-loop operating mode to the fixed frequency open-loop control mode, the second converter 20 realizes stable control of the bus voltage and suppresses the twice-power frequency ripple current on the battery side, and the inverter 30 operates in the inverter mode to realize stable control of the AC output voltage.

[0067] Specifically, if Figure 1 As shown, Figure 1 Schematic diagram of the energy storage conversion device in a two-stage conversion structure when the second converter 20 is in an inoperative state.

[0068] When the energy storage device needs to be charged in an off-grid or grid-connected state, or when the energy storage device needs to be discharged in a grid-connected state, or when the energy storage device needs to be discharged in an off-grid state and the load is in a power stable state, the second converter 20 is in an inoperative state, and the energy storage conversion device is in a secondary conversion structure.

[0069] like Figure 2 As shown, Figure 2 Schematic diagram of the energy storage conversion device in a three-stage conversion structure when the second converter 20 is switched into operation.

[0070] In the off-grid state, when the energy storage device needs to discharge and the load suddenly changes from a power stable state to a short-term severe overload state, the second converter 20 enters the working state to achieve stable control of the bus voltage and suppress the twice-power frequency ripple current on the battery side. The energy storage conversion device is in a three-level conversion structure.

[0071] By operating the energy storage conversion device in a two-stage topology of a first converter and an inverter in a grid-connected mode or an off-grid mode with a stable load, and the second converter not operating, the energy storage conversion device only has losses in the first converter and the inverter, and the overall working efficiency is high. In the event of a short-term severe overload in the off-grid mode, the second converter is switched on to form a three-stage structure, and at the same time, the first converter is switched from closed-loop frequency conversion control to fixed-frequency open-loop control. At this time, the reliable operation of the energy storage conversion device can be effectively guaranteed, and it has extremely strong off-grid load adaptability. Since the second converter is only switched on for a relatively short time, the selection of the second converter power device and the design of the magnetic core device can be greatly simplified, which has the advantages of effectively improving the power density of the energy storage conversion device and reducing costs, so that the energy storage conversion device has high power density and working efficiency, low cost, and extremely strong off-grid load adaptability and high reliability.

[0072] Furthermore, if Figure 3 As shown, the first switch Sw1 and the inductor Lm1 are connected in series and then in parallel between the midpoints of the two arms of the full bridge of the first converter 10; when the first switch Sw1 is closed, the first converter 10 operates in a constant voltage mode to achieve stable control of the bus voltage and suppress the twice-power frequency ripple current on the battery side; when the first switch Sw1 is disconnected, the first converter 10 operates in a constant voltage, constant current or constant power mode to charge the energy storage device.

[0073] By controlling the first switch, the switching of the bidirectional charging and discharging modes of the first converter is achieved, ensuring that the energy storage conversion device operates in a two-stage topology structure of the first converter and the inverter by switching the first switch and the second switch in a grid-connected mode or an off-grid mode with stable load, thereby improving the working efficiency of the energy storage conversion device.

[0074] Furthermore, if Figure 3 As shown, the second switch Sw2 is connected in parallel at both ends of the second converter 20; when the second switch Sw2 is closed, the second converter 20 is in a non-working state; when the second switch Sw2 is disconnected, the second converter 20 achieves stable control of the bus voltage and suppresses the twice-power frequency ripple current on the battery side.

[0075] By controlling the second switch, the second converter is controlled to switch into the state of the energy storage conversion device, ensuring that the energy storage conversion device operates in a two-stage topology structure of the first converter and the inverter by switching the first switch and the second switch in a grid-connected mode or an off-grid mode with stable load, thereby improving the working efficiency of the energy storage conversion device.

[0076] Specifically, the first switch Sw1 and the second switch Sw2 implement state switching between different operating modes of the energy storage conversion device. The first switch Sw1 and the second switch Sw2 can be formed by mechanical switches or electronic switches. Mechanical switches include but are not limited to relays, and electronic switches include but are not limited to thyristors, IGBTs, and MOSFETs.

[0077] The output of the inverter 30 includes but is not limited to a L1 / L2 / N three-wire system and a L / N two-wire system. The schematic diagram of the embodiment of the present application takes the L1 / L2 / N three-wire system as an example for explanation.

[0078] like Figure 4 As shown, in the off-grid or grid-connected state, when the energy storage device needs to be charged, the second switch Sw2 is closed, the first switch Sw1 is disconnected, and the first converter 10 operates in a constant voltage, constant current, or constant power mode to charge the energy storage device to achieve energy storage. The second converter 20 is in an inoperative state, and the inverter 30 operates in a rectification mode to achieve stable control of the bus voltage.

[0079] like Figure 5 As shown, in the grid-connected state, when the energy storage device needs to discharge, the second switch Sw2 is closed, the first switch Sw1 is closed, the first converter 10 operates in the constant voltage mode to achieve stable control of the bus voltage and suppress the twice-power frequency ripple current on the battery side, the second converter 20 is in the non-operating state, and the inverter 30 operates in the inverter mode to achieve stable control of the AC output voltage.

[0080] like Figure 6 As shown, in the off-grid state, when the energy storage device needs to discharge and the load is in a power stable state, the first switch Sw1 is closed or the second switch Sw2 is closed, the first converter 10 operates in a constant voltage mode to achieve stable control of the bus voltage and suppress the twice-power frequency ripple current on the battery side, the second converter 20 is in a non-operating state, and the inverter 30 operates in an inverter mode to achieve stable control of the AC output voltage.

[0081] like Figure 7As shown, in the off-grid state, when the energy storage device needs to discharge and the load suddenly changes from a power stable state to a short-term severe overload state, such as a sudden addition of an ultra-high power compressor / resistive load on the output side, the first switch Sw1 or the second switch Sw2 is switched from a closed state to an open state, and the first converter 10 is switched from a variable frequency closed-loop operating mode to a fixed frequency open-loop control mode. The LLC operating frequency of the first converter 10 is higher than the LLC resonant frequency point of the first converter 10. The second converter 20 achieves stable control of the bus voltage and suppresses twice the power frequency ripple current on the battery side. The inverter 30 operates in the inverter mode to achieve stable control of the AC output voltage.

[0082] The first converter 10 switches from a variable-frequency closed-loop operating mode to a fixed-frequency open-loop control mode, effectively preventing the first converter 10 from entering the capacitive range, which could cause the inverter 30 bus voltage to lose control. This also prevents abnormal failure of power switches Q1 through Q8 due to entering the capacitive range. When the output load of the energy storage conversion device switches to within the rated load power, the energy storage conversion device switches to an off-grid state, requiring the energy storage device to discharge and the load to operate in a stable power state.

[0083] Furthermore, if Figure 8 As shown, in the off-grid state, when the energy storage device needs to discharge and the load suddenly changes from a power stable state to a short-term severe overload state, the second switch Sw2 is in a closed state, and the second converter 20 short-circuits the second switch Sw2 through a normally closed power device, so that the second converter 20 can achieve stable control of the bus voltage and suppress the twice-power frequency ripple current on the battery side.

[0084] In an off-grid discharge scenario, if the second switch Sw2 is a mechanical switch, when the energy storage conversion device switches between different modes due to a short-term severe overload of the output load, there is a problem of deterioration in the output voltage waveform due to an internal factor confirming the on / off state of the mechanical switch, resulting in an increased mode switching delay. To optimize the problem of deterioration in the output voltage waveform within a short period of time, the second switch Sw2 is closed and the first switch Sw1 is opened. The second converter 20 short-circuits the second switch Sw2 via a normally closed power device, so that the second converter 20 operates in constant voltage mode to achieve stable control of the bus voltage and suppress the double power frequency ripple current on the battery side. The inverter 30 operates in inverter mode to achieve stable control of the AC output voltage.

[0085] In this operating mode, when the output of the energy storage conversion device is severely overloaded for a short time, the state transition is quickly completed through the action of the internal switching device of the second converter 20, which can reduce the state switching time of the second switch Sw2. However, this operating mode will cause additional losses due to the conduction loss of the normally closed power device inside the second converter 20.

[0086] In an embodiment of the present invention, in a grid-connected mode or an off-grid mode with a stable load, the energy storage conversion device operates in a two-stage topology structure of a first converter and an inverter, and the second converter does not operate. At this time, the energy storage conversion device only has losses in the first converter and the inverter, and the overall working efficiency is high. In the case of a short-term severe overload in the off-grid mode, the second converter is switched to work to form a three-stage structure. At the same time, the first converter is switched from closed-loop frequency conversion control to fixed-frequency open-loop control. At this time, the reliable operation of the energy storage conversion device can be effectively guaranteed, and it has extremely strong off-grid load adaptability. Since the second converter only works for a short time, the selection of the power device of the second converter and the design of the magnetic core device can be greatly simplified, which has the advantages of effectively improving the power density of the energy storage conversion device and reducing costs, so that the energy storage conversion device has high power density and working efficiency, low cost, and extremely strong off-grid load adaptability and high reliability.

[0087] In order to solve the above technical problems, the embodiment of the present invention further provides an energy storage conversion device, such as Figure 9 As shown, the energy storage conversion device includes: a first converter 10, a second converter 20, an inverter 30, a first switch Sw1, an inductor Lm1 and a second switch Sw2.

[0088] One end of the first converter 10 is connected to the energy storage battery, and the other end of the first converter 10 is connected to the second converter 20 ; the second switch Sw2 is connected in parallel at both ends of the second converter 20 ; and the inverter 30 is connected to the second converter 20 .

[0089] The first switch Sw1 and the inductor Lm1 are connected in series and then in parallel between the midpoints of the two bridge arms of the full bridge of the first converter 10 .

[0090] The energy storage conversion device is configured to execute the above-mentioned control method for the energy storage conversion device.

[0091] By switching the first switch and the second switch, the energy storage conversion device operates in a two-stage topology of a first converter and an inverter. In the event of a short-term severe overload in the off-grid mode, the second converter switches into operation to form a three-stage structure, thereby improving the working efficiency of the energy storage conversion device, effectively ensuring the reliable operation of the energy storage conversion device, and having extremely strong off-grid load adaptability.

[0092] Furthermore, if Figure 10 As shown, the first converter 10 includes: a first switching device Q1, a second switching device Q2, a third switching device Q3, a fourth switching device Q4, a fifth switching device Q5, a sixth switching device Q6, a seventh switching device Q7, an eighth switching device Q8, a transformer T1, a first inductor Lr and a first capacitor Cr.

[0093] The first switching device Q1 , the second switching device Q2 , the third switching device Q3 and the fourth switching device Q4 constitute two arms of the left full bridge of the first converter 10 .

[0094] The fifth switching device Q5 , the sixth switching device Q6 , the seventh switching device Q7 and the eighth switching device Q8 constitute two arms of the right full bridge of the first converter 10 .

[0095] The transformer T1 , the first inductor Lr, the first capacitor Cr, the first switch Sw1 , and the inductor Lm1 constitute the resonant cavity parameters of the first converter 10 .

[0096] The first converter can operate in constant voltage, constant current or constant power mode to charge the energy storage device. When the energy storage device needs to discharge, the first converter operates in constant voltage mode to achieve stable control of the bus voltage and suppress the twice-power frequency ripple current on the battery side. In the off-grid state, when the energy storage device needs to discharge and the load suddenly changes from a power stable state to a short-term severe overload state, the first converter switches from a variable frequency closed-loop operating mode to a fixed frequency open-loop control mode, which can effectively ensure the reliable operation of the energy storage conversion device.

[0097] In some optional implementations of this embodiment, such as Figure 11 As shown, the second converter 20 is composed of a two-switch Buck-Boost converter, including a ninth switching device Q9, a tenth switching device Q10, a second capacitor C2 and a second inductor L4.

[0098] The ninth switching device Q9 and the tenth switching device Q10 constitute a bridge arm of the second converter 20 , and are connected to the first converter 10 in parallel with the second capacitor C2 .

[0099] The second inductor L4 connects the midpoint of the bridge arm of the second converter 20 and the inverter 30 .

[0100] The output voltage of the inverter 30 is a L / N two-wire system.

[0101] Specifically, the output voltage of the inverter 30 is a L / N two-wire system, and the second converter 20 is a two-switch Buck-Boost converter, which is in Buck mode in the discharge mode and in Boost mode in the charge mode.

[0102] In some optional implementations of this embodiment, such as Figure 12 As shown, the second converter 20 is composed of a two-switch Buck-Boost converter, including a ninth switching device Q9, a tenth switching device Q10 and a second inductor L4.

[0103] The ninth switching device Q9 and the tenth switching device Q10 constitute a bridge arm of the second converter 20 and are connected to the inverter 30 .

[0104] The second inductor L4 connects the midpoint of the bridge arm of the second converter 20 and the first converter 10 .

[0105] The inverter 30 is composed of two phases and three bridge arms, and the output voltage is a three-wire system of L1 / L2 / N.

[0106] Specifically, the inverter 30 is composed of two phases and three bridge arms, and the output voltage is a three-wire system of L1 / L2 / N. The second converter 20 is composed of a two-switch Buck-Boost converter, which is a Boost mode in the discharge mode and a Buck mode in the charging mode.

[0107] In this embodiment of the present invention, since the second switch Sw2 is connected in parallel across the second converter 20, when the energy storage conversion device switches between different switching states, when the second switch Sw2 is closed, the ninth switch device Q9 is connected and operated, and when the second switch Sw2 is disconnected, the ninth switch Q9 is disconnected and operated. By controlling the switching state of the second switch Sw2, the operation of the ninth switch device Q9 can be effectively ensured that the second switch Sw2 achieves zero voltage switching (ZVS), effectively ensuring the reliability of the operation of the second switch Sw2. Therefore, this control method can effectively improve the power density and operating efficiency of the energy storage conversion device while effectively ensuring the reliability and longevity of the entire device.

[0108] In some optional implementations of this embodiment, such as Figure 13 As shown, the second converter 20 is composed of a two-switch Buck-Boost converter, including a ninth switching device Q9, a tenth switching device Q10, a second capacitor C2 and a second inductor L4.

[0109] The ninth switching device Q9 and the tenth switching device Q10 constitute a bridge arm of the second converter 20 and are connected to the inverter 30 .

[0110] The second inductor L4 is connected to the midpoint of the bridge arm of the second converter 20 , and is connected to the first converter 10 in parallel with the second capacitor C2 .

[0111] The inverter 30 is composed of a full-bridge converter, and the output voltage is a L / N two-line.

[0112] In this embodiment of the present invention, since the second switch Sw2 is connected in parallel across the second converter 20, when the energy storage conversion device switches between different switching states, when the second switch Sw2 is closed, the ninth switch device Q9 is connected and operated, and when the second switch Sw2 is disconnected, the ninth switch Q9 is disconnected and operated. By controlling the switching state of the second switch Sw2, the operation of the ninth switch device Q9 can be effectively ensured that the second switch Sw2 achieves zero voltage switching (ZVS), effectively ensuring the reliability of the operation of the second switch Sw2. Therefore, this control method can effectively improve the power density and operating efficiency of the energy storage conversion device while effectively ensuring the reliability and longevity of the entire device.

[0113] In order to solve the above technical problems, Figure 14 As shown, an embodiment of the present invention further provides an energy storage device, including: an energy management module 101, a power distribution module 102, and an energy storage module 103. The power distribution module 102 includes an energy storage conversion device 1021, and the energy management module 101 controls the energy storage conversion device 1021 to execute the above-mentioned energy storage conversion device control method.

[0114] The power distribution module 102 is connected to the energy management module 101 and is configured to supply power to the energy management module 101 .

[0115] The energy storage module 103 is connected to the energy management module 101 and the power distribution module 102 respectively, and is configured to store electrical energy.

[0116] The energy management module 101 controls the energy storage conversion device 1021 to execute the control method of the energy storage conversion device.

[0117] The energy storage conversion device 1021 includes a first converter, a second converter and an inverter.

[0118] The energy storage conversion device 1021 is configured as follows: in an off-grid or grid-connected state, when the energy storage device needs to be charged, the first converter operates in a constant voltage, constant current or constant power mode to charge the energy storage device, the second converter is in an off-grid state, and the inverter operates in a rectification mode to achieve smooth control of the bus voltage.

[0119] In the grid-connected state, when the energy storage device needs to discharge, the first converter operates in a constant voltage mode to achieve smooth control of the bus voltage and suppress the twice-power frequency ripple current on the battery side. The second converter is in a non-working state, and the inverter operates in an inverter mode to achieve smooth control of the AC output voltage.

[0120] In the off-grid state, when the energy storage device needs to discharge and the load is in a power stable state, the first converter operates in a constant voltage mode to achieve smooth control of the bus voltage and suppress the twice-power frequency ripple current on the battery side. The second converter is in a non-working state, and the inverter operates in an inverter mode to achieve smooth control of the AC output voltage.

[0121] In the off-grid state, when the energy storage device needs to discharge and the load suddenly changes from a power stable state to a short-term severe overload state, the first converter switches from the variable frequency closed-loop operating mode to the fixed frequency open-loop control mode, the second converter realizes the stable control of the bus voltage and suppresses the twice power frequency ripple current on the battery side, and the inverter operates in the inverter mode to realize the stable control of the AC output voltage.

[0122] Obviously, the embodiments described above are only some of the embodiments of the present application, rather than all of the embodiments. The preferred embodiments of the present application are given in the accompanying drawings, but they do not limit the patent scope of the present application. The present application can be implemented in many different forms. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive. Although the present application has been described in detail with reference to the aforementioned embodiments, for those skilled in the art, it is still possible to modify the technical solutions described in the aforementioned specific embodiments, or to make equivalent replacements for some of the technical features therein. Any equivalent structure made using the contents of the present application specification and the accompanying drawings, directly or indirectly used in other related technical fields, is also within the scope of patent protection of the present application.

Claims

1. A control method for an energy storage conversion device, wherein the energy storage conversion device is used in an energy storage device, and the energy storage conversion device comprises: A first converter, a second converter, and an inverter; The first converter is a bidirectional LLC resonant converter, and the second converter is a bidirectional Buck-Boost converter or a bidirectional Half-Bridge converter, characterized in that: In an off-grid or grid-connected state, when the energy storage device needs to be charged, the first converter operates in a constant voltage, constant current, or constant power mode to charge the energy storage device, the second converter is in an inoperative state, and the inverter operates in a rectification mode to achieve stable control of the bus voltage; In the grid-connected state, when the energy storage device needs to discharge, the first converter operates in a constant voltage mode to achieve stable control of the bus voltage and suppress the twice-power frequency ripple current on the battery side; the second converter is in an inoperative state, and the inverter operates in an inverter mode to achieve stable control of the AC output voltage; In the off-grid state, when the energy storage device needs to discharge and the load is in a power-stable state, the first converter operates in a constant voltage mode to achieve stable control of the bus voltage and suppress the twice-power-frequency ripple current on the battery side. The second converter is in an inoperative state, and the inverter operates in an inverter mode to achieve stable control of the AC output voltage. In the off-grid state, when the energy storage device needs to discharge and the load suddenly changes from a stable power state to a short-term severe overload state, the first converter switches from the variable frequency closed-loop operation mode to the fixed frequency open-loop control mode. The second converter realizes stable control of the bus voltage and suppresses the double power frequency ripple current on the battery side. The inverter operates in the inverter mode to realize stable control of the AC output voltage. The first switch and the inductor are connected in series and then in parallel between the midpoints of the two bridge arms of the full bridge of the first converter; when the first switch is closed, the first converter operates in a constant voltage mode to achieve stable control of the bus voltage and suppress the twice-power frequency ripple current on the battery side; when the first switch is open, the first converter operates in a constant voltage, constant current, or constant power mode to charge the energy storage device; The second switch is connected in parallel at both ends of the second converter; when the second switch is closed, the second converter is in an inoperative state; when the second switch is disconnected, the second converter achieves stable control of the bus voltage and suppresses twice the power frequency ripple current on the battery side.

2. The control method of the energy storage conversion device according to claim 1, characterized in that: In the off-grid state, when the energy storage device needs to discharge and the load suddenly changes from a stable power state to a short-term severe overload state, the second switch is in a closed state, and the second converter short-circuits the second switch through a normally closed power device, so that the second converter can achieve stable control of the bus voltage and suppress the twice-power frequency ripple current on the battery side.

3. The control method of the energy storage conversion device according to claim 1, characterized in that: The LLC operating frequency of the first converter is set to be higher than the LLC resonant frequency point of the first converter.

4. An energy storage conversion device, characterized in that: The energy storage conversion device includes: a first converter, a second converter, an inverter, a first switch, an inductor and a second switch; One end of the first converter is connected to the energy storage battery, and the other end of the first converter is connected to the second converter; the second switch is connected in parallel to both ends of the second converter; and the inverter is connected to the second converter; The first switch and the inductor are connected in series and then in parallel between the midpoints of the two bridge arms of the full bridge of the first converter; The energy storage conversion device is configured to execute the control method according to any one of claims 1 to 3.

5. The energy storage conversion device according to claim 4, characterized in that: The first converter includes a first switching device, a second switching device, a third switching device, a fourth switching device, a fifth switching device, a sixth switching device, a seventh switching device, an eighth switching device, a transformer, a first inductor, and a first capacitor; The first switching device, the second switching device, the third switching device and the fourth switching device constitute two bridge arms of the left full bridge of the first converter; The fifth switching device, the sixth switching device, the seventh switching device and the eighth switching device constitute two bridge arms of the right full bridge of the first converter; The transformer, the first inductor, the first capacitor, the first switch, and the inductor constitute the resonant cavity parameters of the first converter.

6. The energy storage conversion device according to claim 4, characterized in that: The second converter is composed of a two-switch Buck-Boost converter, including a ninth switching device, a tenth switching device, a second capacitor, and a second inductor; The ninth switching device and the tenth switching device constitute a bridge arm of the second converter, and are connected to the first converter in parallel with the second capacitor; The second inductor is connected to the midpoint of the bridge arm of the second converter and the inverter; The inverter output voltage is a L / N two-wire system.

7. The energy storage conversion device according to claim 4, characterized in that: The second converter is composed of a two-switch Buck-Boost converter, including a ninth switching device, a tenth switching device and a second inductor; The ninth switching device and the tenth switching device constitute a bridge arm of the second converter, and are connected to the inverter; The second inductor is connected to the midpoint of the bridge arm of the second converter and the first converter; The inverter consists of two phases and three bridge arms, and the output voltage is a three-wire system of L1 / L2 / N.

8. The energy storage conversion device according to claim 4, characterized in that: The second converter is composed of a two-switch Buck-Boost converter, including a ninth switching device, a tenth switching device, a second capacitor, and a second inductor; The ninth switching device and the tenth switching device constitute a bridge arm of the second converter and are connected to the inverter; The second inductor is connected to the midpoint of the bridge arm of the second converter and is connected to the first converter in parallel with the second capacitor; The inverter is composed of a full-bridge converter, and the output voltage is a L / N two-line.

9. An energy storage device comprising: Energy management module, power distribution module, energy storage module; the power distribution module includes an energy storage conversion device; It is characterized in that the energy management module controls the energy storage conversion device to execute the control method described in any one of claims 1 to 3.

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