Energy storage converter, pre-charging circuit and pre-charging method thereof and energy storage system
By designing a series-connected switch module and current limiting module precharge circuit in the energy storage converter, the problem of circuit devices damage during precharge of the energy storage converter is solved, and the effect of current current limiting and cost reduction is achieved.
Patent Information
- Application Number
- CN202510229019.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-27
- Publication Date
- 2025-05-06
AI Technical Summary
Existing energy storage converters are prone to damage to circuit devices during pre-charging, because the direct suction current is too large, and the pre-charging circuit uses many devices and is costly.
Design a pre-charge circuit for an energy storage converter, which is located on the branch of the bus capacitor and is connected in series with the bus capacitor, including a switching module and a current limiting module. The switch module bypasses the current limiting module when it is turned on, and when it is turned off, the current limiting module is connected in series with the bus capacitor, and the current limiting module is used to limit the current current.
It effectively avoids damage to circuit devices due to high current impact, reduces the devices used in pre-charge circuits, and reduces the cost of energy storage converters.
Smart Images
Figure CN119944780A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of energy storage technology, and in particular to an energy storage converter and a pre-charging circuit, a pre-charging method and an energy storage system thereof. Background Art
[0002] Energy storage converters have many working modes, such as grid-connected and off-grid. These two modes need to be started from the DC side. Before normal operation, the DC side needs to be connected to the DC power of the battery to pre-charge the internal bus capacitor. For the constant voltage output mode, it needs to be started from the AC side. Before normal operation, the AC side needs to be connected to pre-charge the internal bus capacitor.
[0003] In order to smooth the bus voltage, the energy storage converter will be equipped with a bus capacitor with a large capacitance. The pre-charging of the bus capacitor needs to be current limited, otherwise directly closing the (AC or DC) contactor to power the bus capacitor will cause a large impact current, which may easily damage the components in the circuit.
[0004] Therefore, current energy storage converters are equipped with pre-charging circuits to ensure the safety of the pre-charging process. However, in related technologies, the pre-charging circuits often include pre-charging sub-circuits configured on the AC side and the DC side of the energy storage converter. The pre-charging circuits use many components and are relatively expensive. Summary of the invention
[0005] The main purpose of the present application is to propose an energy storage converter and a pre-charging circuit, a pre-charging method and an energy storage system, aiming to reduce the devices used in the pre-charging circuit.
[0006] To achieve the above-mentioned purpose, in a first aspect, the present application provides a pre-charging circuit of an energy storage converter, wherein the pre-charging circuit is located on a branch where a bus capacitor of the energy storage converter is located, and the pre-charging circuit is connected in series with the bus capacitor; the pre-charging circuit comprises: a switch module and a current limiting module;
[0007] The first end of the switch module is connected to the first end of the current limiting module respectively, and the second end of the switch module is connected to the second end of the current limiting module;
[0008] Wherein, when the switch module is in the on state, the current limiting module is bypassed; when the switch module is in the off state, the current limiting module is connected in series with the bus capacitor.
[0009] In one embodiment, the switch module includes: a pre-charging relay, a first end of the pre-charging relay is connected to a first end of the current limiting module, and a second end of the pre-charging relay is connected to a second end of the current limiting module.
[0010] In one embodiment, the current limiting module includes: a current limiting resistor, a first end of the current limiting resistor is connected to a first end of the switch module, and a second end of the current limiting resistor is connected to a second end of the switch module.
[0011] In one embodiment, the current limiting resistor is a cement resistor, a carbon film resistor, an aluminum shell resistor, a chip resistor or a negative temperature coefficient thermistor.
[0012] In a second aspect, the present application further provides an energy storage converter, the energy storage converter comprising: a bus capacitor, an inverter circuit, an AC filter circuit, a control circuit and a pre-charging circuit as described in the first aspect;
[0013] The bus capacitor is connected in series with the pre-charging circuit, a first end of the pre-charging circuit is connected to a first input end of the inverter circuit, and is connected to one pole of a battery via a first DC contactor, and a second end of the pre-charging circuit is connected to a first end of the bus capacitor;
[0014] The second end of the bus capacitor is connected to the second input end of the inverter circuit, and is connected to the other pole of the battery via a second DC contactor;
[0015] The AC filter circuit is connected to the output end of the inverter circuit, and is connected to the power grid or the AC load via the AC contactor on the AC output branch;
[0016] The control circuit is used to control the on and off of the switch module, the first DC contactor, the second DC contactor and each of the AC contactors.
[0017] In one embodiment, the control circuit is also used to control the first DC contactor and the second DC contactor to be turned on and control the switch module to remain in a disconnected state when a DC pre-charging instruction is received; and control the switch module to be turned on when it is detected that the difference between the pre-charging voltage on the bus capacitor and the DC side battery voltage is less than or equal to a first preset threshold.
[0018] In one embodiment, the control circuit is also used to control each of the AC contactors to be turned on and control the switch module to remain in a disconnected state when an AC pre-charging instruction is received, so that the AC power can complete uncontrolled rectification through the power switch of the inverter circuit, and the rectified voltage after rectification charges the bus capacitor through the pre-charging resistor on the bus; when it is detected that the difference between the pre-charging voltage and the rectified voltage on the bus capacitor is less than or equal to a second preset threshold, the switch module is controlled to be turned on.
[0019] In a third aspect, the present application further provides a pre-charging method, which is applied to the energy storage converter as described in the second aspect, and the pre-charging method comprises:
[0020] Controlling the on / off states of the switch module, the first DC contactor, the second DC contactor and each of the AC contactors according to the received instruction, and turning on the pre-charging circuit of the bus capacitor;
[0021] When it is detected that the difference between the pre-charge voltage on the bus capacitor and the reference voltage is within a preset range, the switch module is controlled to be turned on.
[0022] In one embodiment, the reference voltage is a DC side battery voltage; and controlling the on / off state of the switch module, the first DC contactor, the second DC contactor, and each of the AC contactors according to the received instruction includes:
[0023] In response to the DC pre-charging instruction, the first DC contactor and the second DC contactor are controlled to be turned on, and the switch module is controlled to remain in an off state.
[0024] In one embodiment, the reference voltage is a rectified voltage; and controlling the on / off state of the switch module, the first DC contactor, the second DC contactor, and each of the AC contactors according to the received instruction includes:
[0025] In response to the AC pre-charging instruction, the AC contactors on each AC output branch are controlled to be turned on, and the switch module is controlled to remain in the disconnected state.
[0026] In a fourth aspect, the present application also provides an energy storage system, comprising:
[0027] The energy storage converter as described in the second aspect;
[0028] At least one battery pack, each of the battery packs is connected to the energy storage inverter respectively.
[0029] The above-mentioned pre-charging circuit is located on the branch where the bus capacitor of the energy storage converter is located, and the pre-charging circuit is connected in series with the bus capacitor; the pre-charging circuit includes a switch module and a current limiting module; the first end of the switch module is respectively connected to the first end of the current limiting module, and the second end of the switch module is connected to the second end of the current limiting module, that is, the switch module and the current limiting module are connected in parallel, then in the process of pre-charging the bus capacitor, the switch module is kept disconnected, so that the current limiting module can be connected in series with the bus capacitor, and the current of the branch where the bus capacitor is located is limited by the current limiting module, thereby preventing the components on the circuit from being damaged by a large current shock. After the pre-charging is completed, the current limiting module on the bus capacitor branch is bypassed by turning on the switch module, which will not affect the function of the circuit during normal operation, thereby ensuring the normal operation of the energy storage converter. Since the pre-charging circuit is connected in series with the bus capacitor, the pre-charging circuit can be used as a common circuit for pre-charging the bus capacitor on the AC side and the DC side, so that there is no need to set up corresponding pre-charging sub-circuits for the AC side and the DC side, respectively, which can reduce the components used in the pre-charging circuit and reduce the cost of the energy storage converter.
[0030] The energy storage converter and energy storage system include a bus capacitor, an inverter circuit, an AC filter circuit, a control circuit, and a pre-charging circuit as in the first aspect. The control circuit can control the on-off of the switch module, the first DC contactor, the second DC contactor, and each AC contactor. In the DC pre-charging process, the control circuit can control the on-off of the switch module, the first DC contactor, and the second DC contactor to control the bus capacitor to be connected in series with the current limiting module, and the current limiting module is used to limit the current of the branch where the bus capacitor is located, thereby preventing the components on the circuit from being damaged by a large current impact; in the AC pre-charging process, the control circuit can control the on-off of the switch module and each AC contactor to control the bus capacitor to be connected in series with the current limiting module, thereby preventing the components on the circuit from being damaged by a large current impact. After the pre-charging is completed, the control circuit can control the on-switch module to bypass the current limiting module on the bus capacitor branch, which will not affect the function of the circuit during normal operation, thereby ensuring the normal operation of the energy storage converter. Moreover, the control circuit can control the on and off of the switch module, the first DC contactor and the second DC contactor in the above manner, so that the pre-charging circuit can be used as a common circuit for pre-charging the bus capacitor on the AC side and the DC side, thereby eliminating the need to separately set up corresponding pre-charging sub-circuits for the AC side and the DC side, thereby reducing the number of devices used in the pre-charging circuit and reducing the cost of the energy storage current device.
[0031] The above-mentioned pre-charging method is applied to the energy storage converter of the second aspect. Then, according to the received instruction, the switch module, the first DC contactor, the second DC contactor and the on-off state of each AC contactor are controlled, and the pre-charging circuit of the bus capacitor on the DC side or the AC side can be turned on, so that the pre-charging circuit can be used as a common circuit for the AC side and the DC side to pre-charge the bus capacitor, so that there is no need to set up corresponding pre-charging sub-circuits for the AC side and the DC side respectively, which can reduce the devices used in the pre-charging circuit and reduce the cost of the energy storage current device. By limiting the current of the branch where the bus capacitor is located by the current limiting module, the devices on the circuit can be prevented from being damaged by large current shocks. When it is detected that the difference between the pre-charging voltage and the reference voltage on the bus capacitor is within a preset range, the switch module is controlled to be turned on, and the current limiting module on the bus capacitor branch can be bypassed by the switch module, so that the current limiting module does not affect the function of the circuit when it is working normally, ensuring that the energy storage converter can work normally. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.
[0033] Figure 1 This is a structural schematic diagram of a pre-charging circuit in an embodiment of the present application;
[0034] Figure 2 This is a structural schematic diagram of a pre-charging circuit in another embodiment of the present application;
[0035] Figure 3 This is a schematic diagram of the circuit structure of an energy storage converter in one embodiment of the present application;
[0036] Figure 4 This is one of the circuit structure examples of the energy storage converter in the related art;
[0037] Figure 5 This is the second example of the circuit structure of the energy storage converter in the related art;
[0038] Figure 6 Schematic diagram of a pre-charging method in one embodiment of the present application.
[0039] Description of Figure Numbers:
[0040] 1-pre-charging circuit, 11-switch module, 12-current limiting module, 2-inverter circuit, 3-AC filter circuit.
[0041] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION
[0042] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0043] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.
[0044] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.
[0045] As described in the background technology, the energy storage converter has many working modes, such as grid-connected and off-grid. These two modes need to be started from the DC side. Before normal operation, the DC side needs to be connected to the DC power of the battery to pre-charge the internal bus capacitor. For the constant voltage output mode, it needs to be started from the AC side. Before normal operation, the AC side needs to be connected to pre-charge the internal bus capacitor.
[0046] In order to smooth the bus voltage, the energy storage converter will be equipped with a bus capacitor with a large capacitance. The pre-charging of the bus capacitor needs to be current limited, otherwise directly closing the (AC or DC) contactor to power the bus capacitor will cause a large impact current, which may easily damage the components in the circuit.
[0047] Therefore, current energy storage converters are equipped with pre-charging circuits to ensure the safety of the pre-charging process. However, in related technologies, the pre-charging circuits often include pre-charging sub-circuits configured on the AC side and the DC side of the energy storage converter. The pre-charging circuits use many components and are relatively expensive.
[0048] Based on this, Figure 1 As shown, the present application provides a pre-charging circuit 1 of an energy storage inverter. The pre-charging circuit 1 is located on the branch where the bus capacitor C0 of the energy storage inverter is located. The pre-charging circuit 1 is connected in series with the bus capacitor C0. The pre-charging circuit 1 includes: a switch module 11 and a current limiting module 12.
[0049] The first end of the switch module 11 is respectively connected to the first end of the current limiting module 12, and the second end of the switch module 11 is connected to the second end of the current limiting module 12. When the switch module 11 is in the on state, the current limiting module 12 is bypassed; when the switch module 11 is in the off state, the current limiting module 12 is connected in series with the bus capacitor C0.
[0050] It can be understood that the switch module 11 is connected in parallel with the current limiting module 12. When the switch module 11 is turned on, the resistance of the branch where the switch module 11 is located is much smaller than the resistance of the branch where the current limiting module 12 is located, and the current limiting module 12 is bypassed. When the switch module 11 is disconnected, the branch where the switch module 11 is located is in an open circuit state, and the current limiting module 12 is connected in series with the bus capacitor C0. The current limiting module 12 can limit the current of the branch where the bus capacitor C0 is located, which can prevent the components on the circuit from being damaged by large current shocks.
[0051] In the application, some working modes need to use the DC power of the DC side battery to pre-charge the internal bus capacitor C0. For the constant voltage output mode, it is necessary to start from the AC side, and the AC side needs to be powered on before normal operation to pre-charge the internal bus capacitor C0. In the DC pre-charging process (the process of pre-charging the internal bus capacitor C0 with the DC power of the DC side battery), and in the AC pre-charging process (the process of pre-charging the internal bus capacitor C0 with the power of the AC side), the current limiting module 12 is required for current limiting. The pre-charging circuits of the DC pre-charging process and the AC pre-charging process both include the branch where the bus capacitor C0 is located. On this basis, by connecting the pre-charging circuit 1 in series to the branch where the bus capacitor C0 is located, the pre-charging circuit 1 can be used as a common circuit for the DC pre-charging process and the AC pre-charging process. During the DC pre-charging process and the AC pre-charging process, the switch module 11 is kept disconnected, so that the current limiting module 12 can be connected in series with the bus capacitor C0, and the current limiting module 12 is used to limit the current of the branch where the bus capacitor C0 is located, thereby preventing the components on the circuit from being damaged by large current shocks. After the pre-charging is completed, the current limiting module 12 on the bus capacitor C0 branch can be bypassed by turning on the switch module 11, which will not affect the function of the circuit during normal operation, thereby ensuring the normal operation of the energy storage converter.
[0052] The above-mentioned pre-charging circuit 1 is located in the branch where the bus capacitor C0 of the energy storage converter is located, and the pre-charging circuit 1 is connected in series with the bus capacitor C0; the pre-charging circuit 1 includes a switch module 11 and a current limiting module 12; the first end of the switch module 11 is respectively connected to the first end of the current limiting module 12, and the second end of the switch module 11 is connected to the second end of the current limiting module 12, that is, the switch module 11 and the current limiting module 12 are connected in parallel, then in the process of pre-charging the bus capacitor C0, the switch module 11 is kept disconnected, so that the current limiting module 12 can be connected in series with the bus capacitor C0, and the current of the branch where the bus capacitor C0 is located is limited by the current limiting module 12, thereby preventing the components on the circuit from being damaged by large current shocks. After the pre-charging is completed, the current limiting module 12 on the bus capacitor C0 branch is bypassed by turning on the switch module 11, which will not affect the function of the circuit during normal operation, thereby ensuring the normal operation of the energy storage converter. Since the pre-charging circuit 1 is connected in series with the bus capacitor C0, the pre-charging circuit 1 can be used as a common circuit for pre-charging the bus capacitor C0 on the AC side and the DC side, so there is no need to set up corresponding pre-charging sub-circuits separately for the AC side and the DC side, which can reduce the devices used in the pre-charging circuit 1 and reduce the cost of the energy storage current device.
[0053] In one embodiment, Figure 2 As shown, the switch module 11 includes: a pre-charging relay S1 . A first end of the pre-charging relay S1 is connected to a first end of the current limiting module 12 , and a second end of the pre-charging relay S1 is connected to a second end of the current limiting module 12 .
[0054] Among them, the relay contacts can withstand relatively high voltages and large currents. Therefore, the use of the pre-charging relay S1 in parallel with the current limiting module 12 can improve the reliability of the pre-charging circuit 1. In addition, by using the pre-charging relay S1 as a switch, the weak current signal output by the corresponding control circuit passes through the pre-charging relay S1, which can safely control the strong current circuit and avoid interference and damage to the weak current control circuit by the strong current, thereby helping to improve the anti-interference ability and reliability of the energy storage converter circuit.
[0055] In addition, during the DC pre-charging process and the AC pre-charging process, the switch module 11 needs to be kept disconnected so that the current limiting module 12 is connected in series with the bus capacitor C0, and the current of the branch where the bus capacitor C0 is located is limited by the current limiting module 12. In the application, the pre-charging relay S1 will be in a disconnected state after power failure. When the energy storage converter is powered on and enters the pre-charging process, the pre-charging relay S1 is in a disconnected state, and the current will charge the bus capacitor C0 through the current limiting module 12. The current of the branch where the bus capacitor C0 is located is limited by the current limiting module 12 to prevent the components in the circuit from being damaged by large current shocks.
[0056] In one embodiment, Figure 2As shown, the current limiting module 12 includes: a current limiting resistor R1 . A first end of the current limiting resistor R1 is connected to a first end of the switch module 11 , and a second end of the current limiting resistor R1 is connected to a second end of the switch module 11 .
[0057] It can be understood that the first end of the current limiting resistor R1 is connected to the first end of the switch module 11, and the second end of the current limiting resistor R1 is connected to the second end of the switch module 11, then the current limiting resistor R1 is connected in parallel with the switch module 11, and the resistance of the current limiting resistor R1 is relatively large, then when the switch module 11 is disconnected, the current limiting resistor R1 is connected in series with the bus capacitor C0, and the current limiting resistor R1 can limit the current of the branch where the bus capacitor C0 is located, which can prevent the components on the circuit from being damaged by large current shocks. When the switch module 11 is turned on, since the resistance of the current limiting resistor R1 is much greater than the resistance of the branch where the switch module 11 is located, the current mainly flows through the branch where the switch module 11 is located, and the current limiting resistor R1 is bypassed, so that the current limiting resistor R1 will hardly affect the discharge of the bus capacitor C0, and thus will not affect the function of the energy storage converter when it is working normally, thereby ensuring the normal operation of the energy storage converter.
[0058] It should be noted that when the switch module 11 includes a pre-charging relay S1, the first end of the current limiting resistor R1 is connected to the first end of the pre-charging relay S1, and the second end of the current limiting resistor R1 is connected to the second end of the pre-charging relay S1, that is, the current limiting resistor R1 is connected in parallel with the pre-charging relay S1.
[0059] In one embodiment, the current limiting resistor R1 is a cement resistor, a carbon film resistor, an aluminum shell resistor, a chip resistor or a negative temperature coefficient thermistor.
[0060] Among them, cement resistors are made by winding resistor wire on non-alkali heat-resistant porcelain, adding heat-resistant, moisture-resistant and corrosion-resistant materials to protect and fix it, and putting the wound resistor body into a square porcelain frame, which is filled and sealed with special non-flammable heat-resistant cement. Carbon film resistors are a type of film resistor. High-temperature vacuum coating technology is used to tightly attach carbon to the surface of the porcelain rod to form a carbon film, and then appropriate joints are cut and epoxy resin is coated on the surface for sealing and protection. Aluminum shell resistors are usually wire-wound resistors. They are made by winding the resistor wire on non-alkali heat-resistant porcelain, adding an aluminum shell on the outside and filling it with materials with good thermal conductivity. Chip resistors are a form of metal glass uranium resistors. They are made by mixing metal powder and glass uranium powder and printing them on a substrate using screen printing. Negative temperature coefficient (NTC) thermistors are resistor elements whose resistance value decreases as temperature increases.
[0061] It should be noted that the current limiting resistor R1 can be selected according to the requirements and is not limited to the type in the above examples. In applications, the current limiting resistor R1 can also be other types of resistors.
[0062] The present application also provides an energy storage converter, such as Figure 3 As shown, the energy storage converter includes: a bus capacitor C0, an inverter circuit 2, an AC filter circuit 3, a control circuit (not shown) and a pre-charging circuit 1 as in any of the above schemes.
[0063] The pre-charging circuit 1 is arranged on the busbar and connected in series with the busbar capacitor C0. The first end of the pre-charging circuit 1 is connected to the first input end of the inverter circuit 2 and is connected to one pole of the battery via the first DC contactor S11. The second end of the pre-charging circuit 1 is connected to the first end of the busbar capacitor C0. The first DC contactor S11 and the second DC contactor S12 can be relays. The second end of the busbar capacitor C0 is connected to the second input end of the inverter circuit 2 and is connected to the other pole of the battery via the second DC contactor S12.
[0064] It can be understood that when the first DC contactor S11 and the second DC contactor S12 are turned on, the battery, the pre-charging circuit 1 and the bus capacitor C0 form a pre-charging loop. By disconnecting the switch module 11 of the pre-charging circuit 1, the battery, the current limiting module 12 and the bus capacitor C0 can form a pre-charging loop, and the current limiting module 12 can be used to limit the current of the branch where the bus capacitor C0 is located, thereby preventing the components on the circuit from being damaged by large current shocks.
[0065] The AC filter circuit 3 is connected to the output end of the inverter circuit 2 and is connected to the power grid or the AC load via the AC contactor S2 on the AC output branch. The AC filter circuit 3 can filter the AC signal.
[0066] For example, Figure 3 As shown, each AC contactor S2 may include a first AC contactor S21 provided at the U phase, a second AC contactor S22 provided at the V phase, and a first AC contactor S23 provided at the W phase. Each AC contactor S2 may be a relay.
[0067] The AC filter circuit 3 may include a filter unit arranged on each AC output branch, and the filter unit may be a T-shaped LC filter circuit formed by two inductors and one capacitor. Figure 3 As shown, the AC filter circuit 3 may include a first filter unit, a second filter unit and a third filter unit. The first filter unit includes a first inductor L11, a second inductor L12 and a first capacitor C11. The second filter unit includes a third inductor L21, a fourth inductor L22 and a second capacitor C21. The third filter unit includes a fifth inductor L31, a sixth inductor L32 and a third capacitor C31.
[0068] When the AC contactor S2 is turned on, the power grid, the pre-charging circuit 1 and the bus capacitor C0 can form a pre-charging loop. By disconnecting the switch module 11 of the pre-charging circuit 1, the power grid, the current limiting module 12 and the bus capacitor C0 can form a pre-charging loop, and the current limiting module 12 can be used to limit the current of the branch where the bus capacitor C0 is located, thereby preventing the components on the circuit from being damaged by large current shocks.
[0069] The control circuit is used to control the on and off of the switch module 11, the first DC contactor S11, the second DC contactor S12 and each AC contactor S2. By controlling the on and off of the switch module 11, the first DC contactor S11, the second DC contactor S12 and each AC contactor S2, the energy storage converter can be controlled to enter the DC pre-charging process or the AC pre-charging process. After the pre-charging is completed, the control circuit can control the on-switch module 11 to bypass the current limiting module 12 on the bus capacitor C0 branch, so that the current limiting module 12 will not affect the discharge of the bus capacitor C0, thereby not affecting the function of the circuit during normal operation, and ensuring that the energy storage converter can work normally.
[0070] In related technologies, such as Figure 4 and Figure 5 As shown, the pre-charging circuit includes a first sub-circuit distributed on the DC side and a second sub-circuit distributed on the AC side. Figure 4 As shown, the first subcircuit includes two DC pre-charging relays S10 and two DC pre-charging resistors R10, and the second subcircuit includes a rectifier diode D1, two AC pre-charging relays S20 and two AC pre-charging resistors R20. Figure 5 As shown, the first sub-circuit includes two DC pre-charging relays S10 and two DC pre-charging resistors R10, and the second sub-circuit includes three AC pre-charging relays S20 and three AC pre-charging resistors R20.
[0071] contrast Figures 3 to 5 , it can be found that Figure 3 In the embodiment, the pre-charging circuit 1 can be used as a common circuit for pre-charging the bus capacitor C0 on the AC side and the DC side, so there is no need to separately set corresponding pre-charging sub-circuits for the AC side and the DC side. Figure 3 The pre-charge circuit in Figure 4 and Figure 5 The pre-charging circuit reduces the number of circuit components and reduces the cost of the energy storage current device. Therefore, the solution of this embodiment can reduce the number of components used in the pre-charging circuit 1 and reduce the cost of the energy storage current device.
[0072] The above-mentioned energy storage converter includes a bus capacitor C0, an inverter circuit 2, an AC filter circuit 3, a control circuit and a pre-charging circuit 1 as any of the above schemes. The control circuit can control the on-off of the switch module 11, the first DC contactor S11, the second DC contactor S12 and each AC contactor S2. In the DC pre-charging process, the control circuit can control the on-off of the switch module 11, the first DC contactor S11 and the second DC contactor S12 to control the bus capacitor C0 to be connected in series with the current limiting module 12, and the current of the branch where the bus capacitor C0 is located is limited by the current limiting module 12, thereby preventing the components in the circuit from being damaged by large current impact; in the AC pre-charging process, the control circuit can control the on-off of the switch module 11 and each AC contactor S2 to control the bus capacitor C0 to be connected in series with the current limiting module 12, thereby preventing the components in the circuit from being damaged by large current impact. After the pre-charging is completed, the control circuit can control the switch module 11 to bypass the current limiting module 12 on the bus capacitor C0 branch, which will not affect the function of the circuit during normal operation, thereby ensuring the normal operation of the energy storage converter. Moreover, the control circuit can control the on and off of the switch module 11, the first DC contactor S11 and the second DC contactor S12 in the above manner, so that the pre-charging circuit 1 can be used as a common circuit for pre-charging the bus capacitor C0 on the AC side and the DC side, so that there is no need to set up corresponding pre-charging sub-circuits for the AC side and the DC side respectively, which can reduce the devices used in the pre-charging circuit 1 and reduce the cost of the energy storage current transformer.
[0073] In one embodiment, the control circuit is also used to control the first DC contactor S11 and the second DC contactor S12 to be turned on when receiving a DC pre-charge instruction, and control the switch module 11 to remain in the disconnected state; when it is detected that the difference between the pre-charge voltage on the bus capacitor C0 and the DC side battery voltage is less than or equal to the first preset threshold, the switch module 11 is controlled to be turned on. That is, the pre-charge voltage is V1, the DC side battery voltage is V2, and the first preset threshold is V10. When V2-V1≤V10, the switch module 11 is controlled to be turned on. Among them, the value of V10 can be set according to actual needs, for example, it can be set to a value in 8V-15V, and further, for example, it can be 8V, 9V, 10V, 11V, 12V, 13V, 14V, 15V. It should be noted that the above numerical values are only examples for explanation and do not constitute a limitation on the present application. In the application, the value of V10 is not limited to the above example, and V10 can be a value other than 8V-15V.
[0074] It can be understood that after the DC side is powered on, after the control circuit receives the DC pre-charge instruction, it will control the first DC contactor S11 and the second DC contactor S12 to be turned on, and keep the switch module 11 in the disconnected state. At this time, the battery, the current limiting module 12 and the bus capacitor C0 form a pre-charging circuit, and the DC power charges the bus capacitor C0 through the pre-charging resistor, and the current of the branch where the bus capacitor C0 is located is limited by the pre-charging resistor, thereby preventing the components on the circuit from being damaged by large current shocks. When the control circuit detects that the difference between the pre-charge voltage on the bus capacitor C0 and the DC side battery voltage is less than or equal to the first preset threshold, the control circuit can determine that the DC pre-charging process has been completed. Next, the energy storage converter needs to work normally. In this case, the control circuit controls the switch module 11 to be turned on, so that the current limiting resistor R1 is bypassed, and the current limiting resistor R1 will hardly affect the discharge of the bus capacitor C0, thereby not affecting the function of the energy storage converter when it works normally, and ensuring that the energy storage converter can work normally.
[0075] In applications, based on charging efficiency considerations, it is often considered that the DC pre-charging is completed when the difference between the pre-charging voltage on the bus capacitor C0 and the DC side battery voltage is less than or equal to a first preset threshold. The first preset threshold can be determined according to actual needs.
[0076] It should also be noted that the above-mentioned implementation method of pre-charging judgment is an optional implementation method of the present application. In the application, other implementation methods can also be adopted. In one example, when the control circuit detects that the ratio of the pre-charging voltage V1 on the bus capacitor C0 and the DC side battery voltage V2 is greater than or equal to the first preset value Y1, that is, V1 / V2≥Y1, the control circuit can determine that the DC pre-charging process has been completed and control the switch module 11 to turn on. The first preset value Y1 can be determined according to actual needs.
[0077] In one embodiment, the control circuit is also used to control each AC contactor S2 to be turned on when receiving an AC pre-charge instruction, and control the switch module 11 to remain in the disconnected state, so that the AC power completes uncontrolled rectification through the power switch of the inverter circuit 2, and the rectified voltage after rectification charges the bus capacitor C0 through the pre-charge resistor on the bus; when it is detected that the difference between the pre-charge voltage and the rectified voltage on the bus capacitor C0 is less than or equal to the second preset threshold, the switch module 11 is controlled to be turned on. With the pre-charge voltage as V1, the rectified voltage as V3, and the first preset threshold as V20, when V3-V1≤V20, the switch module 11 is controlled to be turned on. The value of V20 can be set according to actual needs, for example, it can be set to a value between 8V-15V, and further, for example, it can be 8V, 9V, 10V, 11V, 12V, 13V, 14V, 15V. It should be noted that the above numerical values are only examples for illustration and do not constitute limitations to the present application. In applications, the value of V20 is not limited to the above examples, and V20 can be a value other than 8V-15V.
[0078] It can be understood that after the AC side is powered on, the control circuit receives an AC pre-charge instruction (such as a constant voltage mode working command), and will control the AC contactor S2 on the three-phase AC output branch of the AC side U, V, and W to be turned on, and keep the switch module 11 in the disconnected state. At this time, the AC power is uncontrolled rectified through the anti-parallel diode of the IGBT in the inverter circuit, and the rectified voltage is charged through the pre-charge resistor on the bus. The current of the branch where the bus capacitor C0 is located is limited by the pre-charge resistor, thereby preventing the components in the circuit from being damaged by large current shocks. When it is detected that the difference between the pre-charge voltage and the uncontrolled rectifier voltage on the bus capacitor C0 is less than or equal to the second preset threshold, the control circuit can determine that the AC pre-charge process has been completed. In this case, the control circuit controls the switch module 11 to be turned on, and the pre-charge process of the DC bus from the AC side is completed.
[0079] In applications, based on the consideration of charging efficiency, it is often considered that the AC pre-charging is completed when the difference between the pre-charging voltage on the bus capacitor C0 and the DC side battery voltage is less than or equal to the second preset threshold. The second preset threshold can be determined according to actual needs.
[0080] It should also be noted that the above-mentioned implementation method of pre-charging judgment is an optional implementation method of the present application, and other implementation methods can also be used in the application. In one example, when the control circuit detects that the ratio V3 of the pre-charging voltage V1 and the rectified voltage on the bus capacitor C0 is greater than or equal to the second preset value Y2, that is, V1 / V3≥Y2, the control circuit can determine that the DC pre-charging process has been completed and control the switch module 11 to turn on. The second preset value Y2 can be determined according to actual needs.
[0081] In one embodiment, the control module is also used to control the switch module 11 to be in an off state when receiving a shutdown command, so that the switch module 11 is in an off state when powered on next time, avoiding a large impact current when the switch module 11 is turned on when powered on.
[0082] The present application also provides a pre-charging method, which is applied to the energy storage converter of any of the above solutions. Figure 6 As shown, the pre-charging method includes the following steps S601 to S602.
[0083] S601: Control the on / off states of the switch module, the first DC contactor, the second DC contactor and each AC contactor according to the received instruction, and turn on the pre-charging circuit of the bus capacitor.
[0084] S602: When it is detected that the difference between the pre-charge voltage on the bus capacitor and the reference voltage is within a preset range, the switch module is controlled to be turned on.
[0085] The above-mentioned pre-charging method is applied to the energy storage converter of any of the above schemes. According to the received instruction, the switch module, the first DC contactor, the second DC contactor and the on-off state of each AC contactor are controlled, and the pre-charging circuit of the DC side or the AC side to the bus capacitor can be turned on, so that the pre-charging circuit can be used as a common circuit for the AC side and the DC side to pre-charge the bus capacitor, so that there is no need to set up corresponding pre-charging sub-circuits for the AC side and the DC side respectively, which can reduce the devices used in the pre-charging circuit and reduce the cost of the energy storage current device. By limiting the current of the branch where the bus capacitor is located by the current limiting module, the devices on the circuit can be prevented from being damaged by large current shocks. When it is detected that the difference between the pre-charging voltage and the reference voltage on the bus capacitor is within a preset range, the switch module is controlled to be turned on, and the current limiting module on the bus capacitor branch can be bypassed by the switch module, so that the current limiting module will not affect the function of the circuit when it is working normally, ensuring that the energy storage converter can work normally.
[0086] In one embodiment, the reference voltage is the DC side battery voltage; the on / off states of the switch module, the first DC contactor, the second DC contactor and each AC contactor are controlled according to the received instructions, including: responding to the DC pre-charging instruction, controlling the first DC contactor and the second DC contactor to be turned on, and controlling the switch module to remain in the off state.
[0087] It can be understood that after the DC side is powered on, after receiving the DC pre-charge instruction, the first DC contactor and the second DC contactor are controlled to be turned on in response to the DC pre-charge instruction, and the switch module is kept in the disconnected state. At this time, the battery, the current limiting module and the bus capacitor form a pre-charge circuit, and the DC power charges the bus capacitor through the pre-charge resistor, and the current of the branch where the bus capacitor is located is limited by the pre-charge resistor, thereby preventing the components in the circuit from being damaged by large current shocks. When it is detected that the difference between the pre-charge voltage on the bus capacitor and the DC side battery voltage is less than or equal to the first preset threshold value (for example, 15V), it can be determined that the DC pre-charge process has been completed, and the energy storage converter needs to work normally next. In this case, the switch module is controlled to be turned on, so that the current limiting resistor is bypassed, and the current limiting resistor will hardly affect the discharge of the bus capacitor, thereby not affecting the function of the energy storage converter during normal operation, ensuring that the energy storage converter can work normally.
[0088] In applications, based on charging efficiency considerations, it is often considered that the DC pre-charging is completed when the difference between the pre-charging voltage on the bus capacitor and the DC side battery voltage is less than or equal to a first preset threshold. The first preset threshold can be determined according to actual needs.
[0089] In one embodiment, the reference voltage is a rectified voltage; the on / off states of the switch module, the first DC contactor, the second DC contactor and each AC contactor are controlled according to the received instructions, including: responding to the AC pre-charging instruction, controlling the AC contactors on each AC output branch to be turned on, and controlling the switch module to remain in the off state.
[0090] It can be understood that after the AC side is powered on, an AC pre-charge instruction (such as a constant voltage mode working command) is received, and the AC contactor on the three-phase AC output branch of U, V, and W on the AC side is controlled to be turned on in response to the AC pre-charge instruction, and the switch module is kept in the disconnected state. At this time, the AC power is uncontrolled rectified through the anti-parallel diode of the IGBT in the inverter circuit, and the rectified voltage is charged through the pre-charge resistor on the bus, and the current of the branch where the bus capacitor is located is limited by the pre-charge resistor, thereby preventing the devices in the circuit from being damaged by large current shocks. It is detected that the pre-charge voltage on the bus capacitor reaches and the uncontrolled rectifier voltage is less than the second preset threshold value (for example, 15V), and then the switch module on the pre-charge circuit is turned on, so as to complete the pre-charge process of the DC bus from the AC side.
[0091] In applications, similarly, based on considerations of charging efficiency, it is often considered that the AC pre-charging is completed when the difference between the pre-charging voltage on the bus capacitor and the DC side battery voltage is less than or equal to the second preset threshold. The second preset threshold can be determined according to actual needs.
[0092] The embodiment of the present application further provides an energy storage system, comprising: at least one battery pack and an energy storage converter according to any of the above solutions. Each battery pack is connected to the energy storage converter respectively.
[0093] The beneficial effects of the energy storage system of this embodiment relative to the related technology are the same as the beneficial effects of the above-mentioned energy storage converter relative to the related technology, and will not be repeated here.
[0094] The above description is only an exemplary embodiment of the present application and does not limit the patent scope of the present application. All equivalent structural changes made by using the contents of the present application specification and drawings under the technical concept of the present application, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present application.
Claims
1. A pre-charging circuit for an energy storage converter, characterized in that: The pre-charging circuit is located on the branch where the bus capacitor of the energy storage converter is located, and the pre-charging circuit is connected in series with the bus capacitor; the pre-charging circuit includes: a switch module and a current limiting module; The first end of the switch module is connected to the first end of the current limiting module respectively, and the second end of the switch module is connected to the second end of the current limiting module; Wherein, when the switch module is in the on state, the current limiting module is bypassed; when the switch module is in the off state, the current limiting module is connected in series with the bus capacitor.
2. The precharge circuit according to claim 1, wherein: The switch module comprises: a pre-charging relay, a first end of the pre-charging relay is connected to a first end of the current limiting module, and a second end of the pre-charging relay is connected to a second end of the current limiting module.
3. The precharge circuit according to claim 1, wherein: The current limiting module comprises: a current limiting resistor, a first end of the current limiting resistor is connected to a first end of the switch module, and a second end of the current limiting resistor is connected to a second end of the switch module.
4. The precharge circuit as claimed in claim 3, characterized in that The current limiting resistor is a cement resistor, a carbon film resistor, an aluminum shell resistor, a chip resistor or a negative temperature coefficient thermistor.
5. An energy storage converter, characterized in that: The energy storage converter comprises: a bus capacitor, an inverter circuit, an AC filter circuit, a control circuit and a pre-charging circuit as claimed in any one of claims 1 to 4; The bus capacitor is connected in series with the pre-charging circuit, a first end of the pre-charging circuit is connected to a first input end of the inverter circuit, and is connected to one pole of a battery via a first DC contactor, and a second end of the pre-charging circuit is connected to a first end of the bus capacitor; The second end of the bus capacitor is connected to the second input end of the inverter circuit, and is connected to the other pole of the battery via a second DC contactor; The AC filter circuit is connected to the output end of the inverter circuit, and is connected to the power grid or the AC load via the AC contactor on the AC output branch; The control circuit is used to control the on and off of the switch module, the first DC contactor, the second DC contactor and each of the AC contactors.
6. The energy storage converter according to claim 5, characterized in that: The control circuit is also used to control the first DC contactor and the second DC contactor to be turned on and control the switch module to remain in an off state when a DC pre-charging instruction is received; and control the switch module to be turned on when it is detected that the difference between the pre-charging voltage on the bus capacitor and the DC side battery voltage is less than or equal to a first preset threshold.
7. The energy storage converter according to claim 5, characterized in that: The control circuit is also used to control each of the AC contactors to be turned on and control the switch module to remain in a disconnected state when an AC pre-charging instruction is received, so that the AC power can complete uncontrolled rectification through the power switch of the inverter circuit, and the rectified voltage after rectification charges the bus capacitor through the pre-charging resistor on the bus; when it is detected that the difference between the pre-charging voltage and the rectified voltage on the bus capacitor is less than or equal to a second preset threshold, the switch module is controlled to be turned on.
8. A pre-charging method, characterized in that: Applied to the energy storage converter according to any one of claims 5 to 7, the pre-charging method comprises: Controlling the on / off states of the switch module, the first DC contactor, the second DC contactor and each of the AC contactors according to the received instruction, and turning on the pre-charging circuit of the bus capacitor; When it is detected that the difference between the pre-charge voltage on the bus capacitor and the reference voltage is within a preset range, the switch module is controlled to be turned on.
9. The energy storage converter according to claim 8, characterized in that: The reference voltage is the DC side battery voltage; the on-off state of the switch module, the first DC contactor, the second DC contactor and each AC contactor is controlled according to the received instruction, including: In response to the DC pre-charging instruction, the first DC contactor and the second DC contactor are controlled to be turned on, and the switch module is controlled to remain in an off state.
10. The energy storage converter according to claim 8, characterized in that: The reference voltage is a rectified voltage; the on-off state of the switch module, the first DC contactor, the second DC contactor and each AC contactor is controlled according to the received instruction, including: In response to the AC pre-charging instruction, the AC contactors on each AC output branch are controlled to be turned on, and the switch module is controlled to remain in the disconnected state.
11. An energy storage system, characterized in that: include: The energy storage converter according to any one of claims 5 to 7; At least one battery pack, each of the battery packs is connected to the energy storage inverter respectively.