Bus voltage pre-charge circuit, bus voltage pre-charge method, and energy storage converter system

Abstract

The application discloses a bus voltage pre-charging circuit, a bus voltage pre-charging method and an energy storage converter system. The bus voltage pre-charging circuit comprises a transformer rectifier circuit, a power supply end connected to a target power grid, and used for converting a power supply voltage of the power supply end into a direct current voltage; a voltage regulating circuit connected to the transformer rectifier circuit and a direct current bus of an energy storage converter respectively, and used for adjusting the direct current voltage into a target voltage and providing the target voltage to the direct current bus for pre-charging; wherein the target voltage is a minimum bus voltage required by the energy storage converter when being incorporated into the target power grid.

Description

Technical Field

[0001] This application relates to the field of energy storage system technology, and in particular to a bus voltage pre-charging circuit, a bus voltage pre-charging method, and an energy storage converter system. Background Technology

[0002] In energy storage systems, there are some special operating conditions that may cause the battery to be over-discharged and the battery's state of charge (SOC) to be too low, i.e., the battery voltage is too low. The existing solution is to set a pre-charging circuit on the DC bus of the power conversion system (PCS) to charge the capacitor on the DC bus.

[0003] Typically, the pre-charge circuit includes a pre-charge relay and a current-limiting resistor connected in series. When a low battery voltage is detected, the pre-charge relay closes, and the battery charges the capacitor on the DC bus through the pre-charge relay and the current-limiting resistor. After the pre-charge circuit operates, the DC bus voltage of the energy storage converter is pre-charged to the battery's voltage value.

[0004] However, even after pre-charging in this way, the DC bus voltage of the energy storage converter may still not meet the minimum bus voltage required for grid connection. This prevents the energy storage converter from entering rectification mode to charge the battery, leading to a risk of battery depletion. Manually replenishing the battery would be too costly and lack automation and intelligence. Summary of the Invention

[0005] The purpose of this application is to provide a bus voltage pre-charging circuit, a bus voltage pre-charging method, and an energy storage converter system to solve the problems existing in the current bus voltage pre-charging.

[0006] To solve the above-mentioned technical problems, this specification is implemented as follows: In a first aspect, a bus voltage pre-charge circuit is provided, comprising: A transformer rectifier circuit, connected to the power supply terminal of the target power grid, is used to convert the power supply voltage of the power supply terminal into DC voltage; A voltage regulation circuit is connected to the DC bus of the transformer rectifier circuit and the energy storage converter, respectively, and is used to adjust the DC voltage to the target voltage and provide it to the DC bus for pre-charging. Wherein, the target voltage is the minimum bus voltage required for the energy storage converter to be connected to the target power grid; The voltage regulation circuit includes a first power switching device, a second power switching device, a first inductor, a first diode, a second diode, and a sixth capacitor; The first terminal of the first power switching device is connected to the sixth capacitor, the second terminal is connected to the first inductor, and the third terminal is connected to the drive circuit of the energy storage converter; the first terminal of the second power switching device is connected to the first inductor, the second terminal is connected to the sixth capacitor, and the third terminal is connected to the drive circuit; the first terminal of the first diode is connected to the first inductor, and the second terminal is connected to the DC bus; the first terminal of the second diode is connected to the sixth capacitor and the DC bus respectively, and the second terminal is connected to the first inductor; the sixth capacitor is connected to the transformer rectifier circuit; When the DC voltage is greater than or equal to the target voltage, the drive circuit controls the first power switch and the second power switch to be turned on or off, so as to control the voltage regulation circuit to adjust the bus voltage of the DC bus to be stable at the target voltage.

[0007] Secondly, an energy storage converter system is provided, comprising: As described in the first aspect, the bus voltage pre-charge circuit; and The energy storage converter, the target power grid, and the power supply equipment.

[0008] Thirdly, a bus voltage pre-charging method is provided, applied to the bus voltage pre-charging circuit as described in the first aspect, the method comprising: When it is detected that the bus voltage of the DC bus does not reach the minimum bus voltage required for the energy storage converter to be connected to the target power grid, the supply voltage of the power supply terminal is converted into DC voltage through the transformer rectifier circuit; The operating mode of the voltage regulation circuit is determined based on the relationship between the DC voltage and the minimum bus voltage. In the operating mode, the voltage regulation circuit adjusts the DC voltage to the minimum bus voltage and provides it to the DC bus for pre-charging.

[0009] In this embodiment, the bus voltage pre-charging circuit, through a transformer rectifier circuit and a voltage regulation circuit, utilizes the supply voltage from the target grid's power supply terminal to convert it into the minimum bus voltage required for the energy storage converter to connect to the target grid. This voltage is then supplied to the DC bus of the energy storage converter for pre-charging, ensuring that the DC bus voltage is pre-charged to the minimum bus voltage value after pre-charging. Therefore, the DC bus voltage of the energy storage converter meets the minimum bus voltage required for connection to the target grid. The energy storage converter can then enter rectification mode to charge the corresponding connected power equipment, achieving automated and intelligent precise pre-charging of the DC bus, reducing pre-charging costs and improving pre-charging efficiency. Attached Figure Description

[0010] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a circuit diagram of the energy storage converter according to an embodiment of this application.

[0011] Figure 2 This is a schematic diagram illustrating an application scenario of a bus voltage pre-charging circuit according to an embodiment of this application.

[0012] Figure 3 This is a schematic diagram of an application scenario for a pre-charging circuit according to another embodiment of this application.

[0013] Figures 4 to 5 This is a schematic diagram of the charging and discharging current path of the bus voltage pre-charging circuit in buck mode according to an embodiment of this application.

[0014] Figure 6 This is a schematic diagram of the current path of the bus voltage pre-charge circuit in the direct-through mode according to an embodiment of this application.

[0015] Figures 7 to 8 This is a schematic diagram of the charging and discharging current path of the bus voltage pre-charging circuit in boost mode according to an embodiment of this application.

[0016] Figures 9 to 10 This is a schematic diagram of the charging and discharging current path of the bus voltage pre-charging circuit in buck-boost mode according to an embodiment of this application.

[0017] Figure 11 This is a schematic diagram of the circuit structure of the control unit in an embodiment of this application; Figure 12 This is a schematic flowchart of the bus voltage pre-charging method according to an embodiment of this application. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. The drawing numbers in this application are only used to distinguish the various steps in the solution and are not used to limit the execution order of the various steps. The specific execution order is subject to the description in the specification.

[0019] Figure 1 This is a circuit diagram of an energy storage converter according to an embodiment of this application. The energy storage converter PCS uses a pre-charge relay K1 and a pre-charge current limiting resistor R1 connected in series to pre-charge the DC bus.

[0020] against Figure 1 The energy storage converter shown in this embodiment of the application detects the voltage of the battery BAT and the voltage of the target grid G. If the battery BAT voltage is too low (e.g., BAT voltage...), the converter is activated. (0.5≤peak value of phase voltage of grid G), but the grid voltage is normal. A pre-charge relay K1 is closed, and battery BAT is pre-charged through the pre-charge relay K1 and the pre-charge current-limiting resistor R1 to charge the first capacitor C1 and the second capacitor C2 that constitute the DC bus. When the difference between the bus voltage and the battery BAT voltage is less than the maximum allowable voltage difference, the pre-charge relay K1 opens, and relay K2 closes.

[0021] If the above method is used for pre-charging, the following problem will occur: the bus voltage of the PCS is pre-charged to the battery BAT voltage value. At this time, the PCS starts to work in off-grid no-load inverter mode and builds AC voltage on capacitors C3 / C4 / C5.

[0022] However, the AC voltage built on capacitors C3 / C4 / C5 is too low, and the difference between it and the voltage of the target grid G ​​does not meet the allowable voltage difference range. If relays K4 / K5 / K6 are closed to connect to the grid at this time, the voltage of the target grid G ​​will first charge capacitors C3 / C4 / C5. The instantaneous surge current may damage relays K4 / K5 / K6 and capacitors C3 / C4 / C5.

[0023] Secondly, due to the low voltage across the first capacitor C1 and the second capacitor C2, the mains voltage may cause the bidirectional DC-AC converter 20 to operate in reverse in uncontrolled rectification mode to charge the capacitors of the DC bus. Since the capacitance of the DC bus capacitors (first capacitor C1 and second capacitor C2) of the PCS is generally very large, the instantaneous current of uncontrolled rectification charging the capacitors of the DC bus will be very large, which will instantly damage the power switching devices (such as metal oxide semiconductor field-effect transistors or insulated gate bipolar transistors) of the bidirectional DC-AC converter 20, causing thermal failure.

[0024] When the battery BAT voltage is too low, even if the modulation ratio of the PCS reaches the maximum allowable value, it cannot complete grid-connected operation in rectification mode. Therefore, when the battery BAT voltage is too low, the PCS drive circuit does not allow the battery BAT to precharge the capacitor of the DC bus or close relays K4 / K5 / K6.

[0025] To address this, a DC voltage that meets the requirements is needed to provide the DC bus of the PCS when the voltage of the power supply device, such as the battery BAT, is too low, so that the PCS can operate in rectification mode to charge the battery BAT.

[0026] Therefore, this application provides a bus voltage pre-charging circuit, including: a transformer rectifier circuit connected to the power supply terminal of the target power grid, used to convert the power supply voltage of the power supply terminal into a DC voltage; a voltage regulation circuit connected to the DC bus of the transformer rectifier circuit and the energy storage converter respectively, used to adjust the DC voltage to a target voltage and provide it to the DC bus for pre-charging; wherein, the target voltage is the minimum bus voltage required for the energy storage converter to be connected to the target power grid.

[0027] like Figure 2 and Figure 3 As shown, the bus voltage pre-charging circuit 10 of this application embodiment includes a transformer rectifier circuit 100 and a voltage regulation circuit 200, wherein the transformer rectifier circuit 100 is connected to the power supply terminal of the target power grid G, and the voltage regulation circuit 200 is connected to the DC bus of the transformer rectifier circuit 100 and the energy storage converter PCS respectively.

[0028] The transformer rectifier circuit 100 is used to convert the supply voltage of the power supply terminal of the target power grid G ​​into DC voltage and provide it to the voltage regulation circuit 200 to adjust the DC voltage to the minimum bus voltage required for the energy storage converter PCS to be connected to the target power grid G. The DC bus is pre-charged by the minimum bus voltage so that the DC bus voltage of the energy storage converter PCS is pre-charged to the minimum bus voltage value after pre-charging.

[0029] Therefore, the DC bus voltage of the energy storage converter PCS is the minimum bus voltage required to connect to the target power grid G. The energy storage converter PCS can enter rectification mode to charge the battery BAT, avoiding the risk of battery depletion. Furthermore, through the bus voltage pre-charging circuit 10, which includes a transformer rectifier circuit 100 and a voltage regulation circuit 200, the DC bus can be pre-charged automatically and intelligently, reducing pre-charging costs and improving pre-charging efficiency.

[0030] In one embodiment, the voltage regulation circuit includes a first power switching device, a second power switching device, a first inductor, a first diode, a second diode, and a sixth capacitor; The first terminal of the first power switch is connected to the first terminal of the sixth capacitor, the second terminal of the first power switch is connected to the first terminal of the first inductor, and the third terminal of the first power switch is connected to the drive circuit of the energy storage converter. The first terminal of the second power switch is connected to the second terminal of the first inductor, the second terminal of the second power switch is connected to the second terminal of the sixth capacitor, and the third terminal of the second power switch is connected to the driving circuit. The first end of the first diode is connected to the second end of the first inductor, and the second end of the first diode is connected to the DC bus; the first end of the second diode is connected to the second end of the sixth capacitor and the DC bus, respectively, and the second end of the second diode is connected to the first end of the first inductor; the sixth capacitor is connected to the transformer rectifier circuit.

[0031] Combination Figure 2 and Figure 3 The voltage regulation circuit 200 includes a first power switch Q1, a second power switch Q2, a first inductor L1, a first diode D1, a second diode D2, and a sixth capacitor C6.

[0032] The first terminals of the first power switch Q1 and the second power switch Q2 correspond to the output terminals, the second terminals of the first power switch Q1 and the second power switch Q2 correspond to the input terminals, and the third terminals of the first power switch Q1 and the second power switch Q2 correspond to the control terminals.

[0033] The first power switching device Q1 and the second power switching device Q2 can be metal-oxide-semiconductor field-effect transistors (MOSFETs) or insulated-gate bipolar transistors (IGBTs).

[0034] As shown in the figure, the first terminal of the first power switch device Q1 is connected to one end of the sixth capacitor C6, the second terminal of the first power switch device Q1 is connected to the first inductor L1 and the second diode D2, and the third terminal of the first power switch device Q1 is connected to the drive circuit of the energy storage converter PCS.

[0035] The first terminal of the second power switch Q2 is connected to the first inductor L1 and the first diode D1, the second terminal of the second power switch Q2 is connected to the other terminal of the sixth capacitor C6, and the third terminal of the second power switch Q2 is connected to the drive circuit of the energy storage converter PCS.

[0036] The two ends of the first diode D1 are connected to the first inductor L1 and the DC bus of the energy storage converter PCS, respectively. The two ends of the second diode D2 are connected to the first inductor L1, the sixth capacitor C6 and the DC bus, respectively.

[0037] The two ends of the sixth capacitor C6 are connected to the transformer rectifier circuit 100, and the DC voltage output by the transformer rectifier circuit 100 can be provided to the sixth capacitor C6.

[0038] Specifically, the DC bus is composed of a first capacitor and a second capacitor connected in series, with the second end of the first capacitor and the first end of the second capacitor connected; the second end of the first diode is connected to the first end of the first capacitor, and the first end of the second diode is connected to the second end of the second capacitor.

[0039] As shown in the figure, the DC bus of the energy storage converter PCS is composed of a first capacitor C1 and a second capacitor C2 connected in series. The end of the first capacitor C1 that is not connected to the second capacitor C2 is the first end, which is connected to the first diode D1. The second end of the first capacitor C1 and the first end of the second capacitor C2 are connected to form the midpoint O of the DC bus.

[0040] Correspondingly, the end of the second capacitor C2 that is not connected to the first capacitor C1 is the second end, which is connected to the second diode D2.

[0041] The voltage regulation circuit 200 with the above circuit structure can adjust the DC voltage output by the transformer rectifier circuit 100 in combination with the magnitude of the minimum bus voltage, and provide it to the DC bus composed of the first capacitor C1 and the second capacitor C2 for pre-charging.

[0042] In one embodiment, the transformer rectifier circuit includes a transformer and a rectifier; the primary side of the transformer is connected to the power supply terminal of the target power grid, and the secondary side of the transformer is connected to the rectifier. The transformer transforms the supply voltage at the power supply terminal to obtain the corresponding AC voltage based on the turns ratio of the primary and secondary sides; the rectifier rectifies the AC voltage into DC voltage and provides it to the sixth capacitor.

[0043] Combination Figure 2 and Figure 3 The transformer rectifier circuit 100 includes a transformer T, which includes a primary side and a secondary side. The primary side is connected to the power supply terminal of the target power grid G, and the secondary side of the transformer T is connected to the rectifier.

[0044] Transformer T is a power frequency transformer with a turns ratio of n (n≥1, adjustable according to requirements), that is, primary side: secondary side = 1:n.

[0045] Transformer T, based on the turns ratio n corresponding to the primary and secondary sides, transforms the supply voltage from the target grid G ​​to obtain the corresponding AC voltage, which is then rectified into DC voltage by a rectifier. The DC voltage is further supplied to the sixth capacitor C6 of the voltage regulation circuit 200, which adjusts it to the minimum bus voltage required for the energy storage converter PCS to be connected to the target grid G.

[0046] In one embodiment, the rectifier includes a third diode and a fourth diode; the first end of the third diode is connected to the first end of the secondary side of the transformer, and the second end of the third diode is connected to the first end of the sixth capacitor; the second end of the fourth diode is connected to the second end of the secondary side of the transformer, and the first end of the fourth diode is connected to the second end of the sixth capacitor.

[0047] Combination Figure 2 and Figure 3 In one embodiment, the rectifier includes a third diode D3 and a fourth diode D4, which are series-connected half-wave rectifier diodes connected to the two ends of the secondary side of the transformer, respectively, to further rectify the AC voltage obtained by the transformer T based on the turns ratio n into DC voltage.

[0048] The third diode D3 is connected between one end of the secondary side of transformer T and the first end of the sixth capacitor C6, and the fourth diode D4 is connected between the other end of the secondary side of transformer T and the second end of the sixth capacitor C6.

[0049] In this embodiment, the third diode D3 and the fourth diode D4 are redundant, so that when either diode breaks down and short-circuits, the other diode can ensure that the circuit works normally.

[0050] Furthermore, in one embodiment, the bus voltage pre-charging circuit further includes a current-limiting resistor and a third relay; the current-limiting resistor is connected between the second terminal of the third diode and the first terminal of the sixth capacitor; the common terminal of the third relay is connected to the second terminal of the third diode, the normally open terminal of the third relay is connected to the first terminal of the sixth capacitor, and the control terminal of the third relay is connected to the drive circuit; wherein, the drive circuit controls the pre-charging of the DC bus to start or stop by controlling the normally open terminal of the third relay to close or open.

[0051] like Figure 2 and Figure 3 As shown, the current-limiting resistor R2 is connected between the second terminal of the third diode D3 and the first terminal of the sixth capacitor C6. The common terminal of the third relay K3 is connected to the second terminal of the third diode D3, the normally open terminal is connected to the first terminal of the sixth capacitor C6, and the control terminal is connected to the drive circuit of the energy storage converter PCS.

[0052] Typically, the sixth capacitor C6 has a large capacitance value. In this embodiment, the charging current on the sixth capacitor C6 is limited by the current-limiting resistor R2 to avoid a large current surge to the sixth capacitor C6. The drive circuit controls the normally open terminal of the third relay K3 to close or open, thereby controlling the transformer rectifier circuit 100 to provide charging current to the sixth capacitor C6, and in turn controlling the bus voltage pre-charging circuit 10 to start or stop the pre-charging of the DC bus of the energy storage converter PCS.

[0053] During the charging process of the DC bus, if the voltage of the sixth capacitor C6 or the DC bus voltage (i.e., the sum of the voltages of the first capacitor C1 and the second capacitor C2 (abbreviated as C1+C2)) suddenly becomes over-voltage or under-voltage due to some fault, the over / under-voltage protection is triggered. If the current of the first inductor L1 suddenly becomes over-current, the overcurrent protection is triggered. The protection is determined by the drive circuit of the energy storage converter PCS. After the protection is triggered, it will immediately control the disconnection of the third relay K3 and stop the operation of the bus voltage pre-charge circuit 10.

[0054] When the bus voltage of the DC bus of the energy storage converter PCS cannot meet the grid connection requirements, the bus voltage pre-charging circuit 10 of this application embodiment can use the power supply voltage of the power supply end of the target power grid G ​​to convert to obtain the minimum bus voltage required for grid connection of the energy storage converter, and pre-charge the DC bus of the energy storage converter PCS.

[0055] The supply voltage at the power supply terminal of the target power grid G ​​is usually fixed, but the supply voltage of the target power grid G ​​varies for different power grid systems. Therefore, the DC voltage obtained by the transformer rectifier circuit 100 will be different. The drive circuit can sample the supply voltage of the target power grid G ​​in real time and calculate the minimum bus voltage required for safe grid connection.

[0056] like Figures 1 to 3 As shown, the energy storage converter PCS includes a bidirectional DC-AC converter 20 and a three-phase LCL filter circuit, which is connected to the three-phase target power grid G.

[0057] Inductor L2, capacitor C3, relay K4, and inductor L5 constitute a single-phase LCL filter circuit. Inductor L3, capacitor C4, relay K5, and inductor L6 constitute a single-phase LCL filter circuit. Inductor L4, capacitor C5, relay K6, and inductor L7 constitute a single-phase LCL filter circuit. N is the neutral point constructed by capacitors C3 / C4 / C5 in the three-phase filter circuit.

[0058] In one embodiment, the target power grid includes a three-phase three-wire power grid or a three-wire four-wire power grid.

[0059] Figure 2 The target power grid G ​​shown is a three-phase three-wire power grid, N The neutral point of the target power grid G ​​is connected. In order to reduce the common-mode voltage during the operation of the energy storage converter PCS and reduce battery compatibility (EMC) noise, the neutral point N on the AC side is connected to the midpoint O of the DC bus.

[0060] Three-phase three-wire power grid with no connection and neutral point N. The primary side of transformer T is connected to any line voltage of the target power grid G.

[0061] Figure 3The target power grid G ​​shown is a three-phase four-wire power grid, with a neutral point N connected. The primary side of transformer T is connected to any phase voltage of the target power grid G.

[0062] The transformer T can not only transform voltage, but also achieve electrical isolation from the target power grid G.

[0063] Below, we describe the minimum bus voltage required for the energy storage converter PCS to be connected to the target power grid G ​​and the corresponding DC voltage converted by the target power grid G, taking into account different power grid systems and different types of power grids.

[0064] (1) 400V power grid system In this power grid system, if the target power grid G ​​is a three-phase three-wire power grid, the sampled line voltage of the target power grid G ​​is around 400V; if the target power grid G ​​is a three-phase four-wire power grid, the sampled phase voltage of the target power grid G ​​is around 230V.

[0065] If the phase voltage is 400V / 1.732≈230V, then the peak phase voltage is 230V. 1.414 ≈ 325V. If the modulation ratio, i.e., the ratio of the peak phase voltage of AC to the half-bus voltage required for grid connection, is taken as 0.85 (the modulation ratio is adjustable according to requirements), then the minimum bus voltage required for the energy storage converter PCS to connect to the grid must meet the following condition: (325V) 2) / 0.85 ≈ 765V.

[0066] If the target power grid G ​​is a three-phase three-wire power grid, and the transformer T has a turns ratio n=1, the peak voltage across the sixth capacitor C6 is 400V. 1.414 ≈ 566V; When the turns ratio n=2 of transformer T, the peak voltage across the sixth capacitor C6 is 400V. 1.414 2≈1132V, and the same applies when n is any other number.

[0067] If the target power grid G ​​is a three-phase four-wire power grid, and the transformer T has a turns ratio n=1, the peak voltage across the sixth capacitor C6 is 230V. 1.414≈325V; When the turns ratio n=2 of transformer T, the peak voltage across the sixth capacitor C6 is 230V. 1.414 2≈650V, and the same applies when n is any other number.

[0068] (2) 690V power grid system In this power grid system, if the target power grid G ​​is a three-phase three-wire power grid, the line voltage of the target power grid G ​​sampled is about 690V; if the target power grid G ​​is a three-phase four-wire power grid, the phase voltage of the target power grid G ​​sampled by the PCS is about 400V.

[0069] The phase voltage is approximately 690V / 1.732≈400V, therefore the peak phase voltage is 400V. 1.414≈566V. If the modulation ratio is 0.85, then the minimum bus voltage required for the energy storage converter PCS to connect to the grid must meet the following requirement: (566V) 2) / 0.85 ≈ 1332V.

[0070] If the target power grid G ​​is a three-phase three-wire power grid, and the transformer T has a turns ratio n=1, the peak voltage across the sixth capacitor C6 is 690V. 1.414≈976V; When the turns ratio n=2 of transformer T, the peak voltage across the sixth capacitor C6 is 690V. 1.414 2≈1952V, and the same applies when n is any other number.

[0071] If the target power grid G ​​is a three-phase four-wire power grid, and the transformer T has a turns ratio n=1, the peak voltage across the sixth capacitor C6 is 400V. 1.414 ≈ 566V; When the turns ratio n=2 of transformer T, the peak voltage across the sixth capacitor C6 is 400V. 1.414 2≈1132V, and the same applies when n is any other number.

[0072] When the drive circuit of the energy storage converter PCS detects that the battery BAT voltage is too low in real time and determines that the PCS grid connection requirements are not met, and the voltage of the target grid G ​​is monitored in real time to ensure it is within the normal fluctuation range (not under grid overvoltage or grid low voltage conditions), the drive circuit controls the third relay K3 to close. Any phase voltage or line voltage of the target grid G ​​is transformed by transformer T to obtain the secondary AC voltage n. V, the third diode D3 and the fourth diode D4 are operating in half-wave rectification mode. Since the capacitance value of the sixth capacitor C6 is relatively large, the current limiting resistor R2 is required to limit the charging current of the sixth capacitor C6. The drive circuit samples the DC voltage on the sixth capacitor C6 in real time and samples the voltage of the target power grid G ​​in real time, and calculates the minimum bus voltage required to safely connect to the target power grid G.

[0073] As can be seen from the above, the DC voltage on the sixth capacitor C corresponding to different power grid systems and / or different types of power grids may have three possible relationships with the minimum bus voltage required for the energy storage converter PCS to be connected to the target power grid G: 1. The DC voltage on the sixth capacitor C is greater than the minimum bus voltage; 2. The DC voltage on the sixth capacitor C is equal to the minimum bus voltage; 3. The DC voltage on the sixth capacitor C is less than the minimum bus voltage.

[0074] To address this, the voltage regulation circuit 200 is needed to adjust the corresponding DC voltage to the minimum bus voltage required for the energy storage converter PCS to connect to the target power grid G ​​under different magnitude relationships, and to provide pre-charging to the DC bus of the energy storage converter PCS so that the bus voltage of the pre-charged DC bus can meet the grid connection requirements of the energy storage converter PCS.

[0075] The principle of controlling the voltage regulation circuit 200 to perform voltage regulation under different size relationships in the driving circuit of the embodiments of this application will be described below.

[0076] In one embodiment, when the DC voltage is greater than the target voltage, the drive circuit is configured to: determine that the operating mode of the voltage regulation circuit is a buck mode, and in the buck mode control the first power switching device to be turned on or off, and control the second power switching device to remain off, so that the bus voltage of the DC bus is stabilized at the target voltage.

[0077] In this embodiment, when the DC voltage provided by the transformer rectifier circuit 100 to the sixth capacitor C6 is greater than the minimum bus voltage required for grid connection, the drive circuit determines that the operating mode of the voltage regulation circuit 200 is the buck mode. The voltage regulation circuit 200 reduces the higher input voltage (i.e., the DC voltage on the sixth capacitor C6) to a lower output voltage (i.e., the minimum bus voltage) for use by the DC bus (i.e., the first capacitor C1 and the second capacitor C2) through the buck mode.

[0078] The drive circuit is based on buck mode. The drive signal provided to the first power switch Q1 of the voltage regulation circuit 200 is a pulse width modulation (PWM) wave to control the first power switch Q1 to turn on or off, and the drive signal provided to the second power switch Q2 of the voltage regulation circuit 200 is a low level to control the second power switch Q2 to remain off. In this way, the voltage regulation circuit 200 can stably reduce the higher DC voltage to the minimum bus voltage, so that the DC bus voltage is stabilized at the minimum bus voltage.

[0079] In one embodiment, when the DC voltage is equal to the target voltage, the drive circuit is used to: If the difference between the current bus voltage of the DC bus and the DC voltage is outside the preset voltage difference range, the operating mode of the voltage regulation circuit is determined to be buck mode, and the first power switch device is controlled to be turned on or off, and the second power switch device is controlled to remain off in the buck mode. If the difference between the current bus voltage of the DC bus and the DC voltage is within a preset voltage difference range, the operating mode of the voltage regulation circuit is determined to be the through mode. In the through mode, the first power switch device is controlled to remain on, and the second power switch device is controlled to remain off, so that the bus voltage of the DC bus is stabilized at the target voltage.

[0080] In this embodiment, when the DC voltage provided by the transformer rectifier circuit 100 to the sixth capacitor C6 is equal to the minimum bus voltage required for grid connection, the drive circuit determines that the voltage regulation circuit 200 first operates in buck mode and then in shoot-through mode.

[0081] When the DC bus is initially pre-charged, the voltage on the first capacitor C1 and the second capacitor C2 is zero. In order to avoid the large charging current from impacting the first capacitor C1 and the second capacitor C2, if the difference between the current bus voltage and the DC voltage is outside the preset voltage difference range, such as exceeding the voltage range of [-5V, +5V], then it is necessary to charge slowly.

[0082] At this time, the voltage regulation circuit 200 reduces the input voltage (i.e., the DC voltage on the sixth capacitor C6) to a lower output voltage for use by the DC bus (i.e., the first capacitor C1 and the second capacitor C2) through the buck mode.

[0083] The driving circuit is based on buck mode. The driving signal provided to the first power switch Q1 of the voltage regulation circuit 200 is a pulse width modulation (PWM) wave to control the first power switch Q1 to turn on or off, and the driving signal provided to the second power switch Q2 of the voltage regulation circuit 200 is a low level to control the second power switch Q2 to remain off. In this way, the voltage regulation circuit 200 can make the DC bus voltage rise slowly, avoiding the impact of large charging current on the first capacitor C1 and the second capacitor C2.

[0084] If, after pre-charging in buck mode, the difference between the current bus voltage and the voltage of the sixth capacitor C6 is within the allowable voltage difference range, such as [-5V, +5V], the drive circuit controls the voltage regulation circuit 200 to operate in shoot-through mode. This means the drive signal of the first power switch Q1 changes from a PWM wave to a high level and remains on, while the drive signal of the second power switch Q2 remains unchanged at a low level. In this state, the first power switch Q1 is always on, and the voltage regulation circuit 200 operates in shoot-through mode. Thus, the DC voltage is directly applied to the minimum bus voltage, thereby stabilizing the bus voltage at the minimum bus voltage.

[0085] In one embodiment, when the DC voltage is less than the target voltage, the drive circuit is used to: If the difference between the current bus voltage of the DC bus and the DC voltage is outside the preset voltage difference range, the operating mode of the voltage regulation circuit is determined to be buck mode, and the first power switch device is controlled to be turned on or off, and the second power switch device is controlled to remain off in the buck mode. If the difference between the current bus voltage of the DC bus and the DC voltage is within the preset voltage difference range, then the operating mode of the voltage regulation circuit is determined to be the through mode, and in the through mode, the first power switch device is controlled to remain on and the second power switch device is controlled to remain off. If the current bus voltage of the DC bus is equal to the DC voltage, the operating mode of the voltage regulation circuit is determined to be boost mode. In boost mode, the first power switch is kept on, and the second power switch is turned on or off, so that the bus voltage of the DC bus is stabilized at the target voltage.

[0086] In this embodiment, when the DC voltage provided by the transformer rectifier circuit 100 to the sixth capacitor C6 is less than the minimum bus voltage required for grid connection, the drive circuit determines that the voltage regulation circuit 200 first operates in buck mode, then in shoot-through mode, and finally in boost mode.

[0087] When the DC bus is initially pre-charged, the voltage on the first capacitor C1 and the second capacitor C2 is zero. In order to avoid the large charging current from impacting the first capacitor C1 and the second capacitor C2, if the difference between the current bus voltage and the DC voltage is outside the preset voltage difference range, such as exceeding the voltage range of [-5V, +5V], then it is necessary to charge slowly.

[0088] At this time, the voltage regulation circuit 200 reduces the input voltage (i.e., the DC voltage on the sixth capacitor C6) to a lower output voltage for use by the DC bus (i.e., the first capacitor C1 and the second capacitor C2) through the buck mode.

[0089] The driving circuit is based on buck mode. The driving signal provided to the first power switch Q1 of the voltage regulation circuit 200 is a pulse width modulation (PWM) wave to control the first power switch Q1 to turn on or off, and the driving signal provided to the second power switch Q2 of the voltage regulation circuit 200 is a low level to control the second power switch Q2 to remain off. In this way, the voltage regulation circuit 200 can make the DC bus voltage rise slowly, avoiding the impact of large charging current on the first capacitor C1 and the second capacitor C2.

[0090] If, after pre-charging in buck mode, the difference between the current bus voltage and the DC voltage is within a preset voltage difference range, such as [-5V, 0] or (0, +5V], the drive circuit controls the voltage regulation circuit 200 to operate in direct-on mode. That is, the drive signal of the first power switch Q1 is changed from a PWM wave to a high level and kept on, while the drive signal of the second power switch Q2 remains unchanged at a low level. At this time, the first power switch Q1 is always on, and the voltage regulation circuit 200 operates in direct-on mode.

[0091] At this time, the voltage regulation circuit 200 directly supplies the DC voltage on the sixth capacitor C6 to the DC bus (i.e., the first capacitor C1 and the second capacitor C2) through the direct-through mode.

[0092] If, after pre-charging in direct mode, the difference between the current bus voltage and the DC voltage is 0, and the current bus voltage is the same as the DC voltage, the voltage regulation circuit 200 will boost the input voltage (i.e., the DC voltage on the sixth capacitor C6) to a higher output voltage for use by the DC bus (i.e., the first capacitor C1 and the second capacitor C2) through boost mode.

[0093] The drive circuit is based on boost mode. It provides a high-level drive signal to the first power switch Q1 in the voltage regulation circuit 200 to keep Q1 on, and a PWM wave drive signal to the second power switch Q2 in the voltage regulation circuit 200 to control Q2 to turn on or off. Thus, the voltage regulation circuit 200 can stably boost a lower DC voltage to the minimum bus voltage, thereby stabilizing the DC bus voltage at the minimum bus voltage.

[0094] In the voltage regulation circuit 200 corresponding to the circuit structure of the embodiment of this application, in the buck mode, when the first power switch device is turned on, the sixth capacitor discharges to charge the first inductor, the first capacitor, and the second capacitor through the first power switch device, and the first inductor stores energy; in the buck mode, when the first power switch device is turned off, the first inductor releases energy to charge the first capacitor and the second capacitor through the first diode and the second diode.

[0095] Figures 4 to 5 The current path for charging and discharging of the voltage regulation circuit 200 in buck mode according to an embodiment of this application is shown, wherein Figure 4 The current path corresponding to the charging of the first inductor L1, Figure 5 The current path corresponding to the discharge of the first inductor L1.

[0096] like Figure 4 As shown, when the first power switch Q1 is turned on, the sixth capacitor C6 discharges, the first inductor L1 is charged, and the first capacitor C1 and the second capacitor C2 are charged at the same time.

[0097] like Figure 5 As shown, when the first power switch Q1 is turned off, the first inductor L1 releases energy to charge the first capacitor C1 and the second capacitor C2. After multiple PWM waves / pulses, the bus voltage corresponding to the sum of the voltages of the first capacitor C1 and the second capacitor C2 gradually increases. Eventually, the duty cycle change of the PWM wave of the first power switch Q1 enters a steady state, and the bus voltage is stabilized at the minimum bus voltage required for grid connection of the energy storage converter PCS.

[0098] In the voltage regulation circuit 200 corresponding to the circuit structure of the embodiment of this application, in the direct mode, when the first power switch device remains on and the second power switch device remains off, the sixth capacitor discharges to charge the first inductor, the first capacitor, and the second capacitor through the first power switch device.

[0099] Figure 6 The current path of the voltage regulation circuit 200 in the direct mode of this application embodiment is shown, wherein the drive signal of the first power switching device Q1 changes from a PWM wave in buck mode to a high level and remains on.

[0100] like Figure 6 As shown, the drive signal of the first power switch Q1 is high, keeping it on; the drive signal of the second power switch Q2 is low, keeping it off. At this time, the sixth capacitor C6 discharges, so as to charge the first inductor L1, the first capacitor C1, and the second capacitor C2 through the first power switch Q1.

[0101] The first power switching device Q1 is always on, and the voltage regulation circuit 200 operates in shoot-through mode.

[0102] In the voltage regulation circuit 200 corresponding to the circuit structure of the embodiment of this application, in the boost mode, when the second power switch is turned on, the sixth capacitor discharges to charge the first inductor through the first power switch and the second power switch, and the first inductor stores energy; in the boost mode, when the second power switch is turned off, the first inductor releases energy to charge the first capacitor and the second capacitor through the first diode and the second diode.

[0103] Figures 7 to 8 This is a schematic diagram of the charging and discharging current path of the bus voltage pre-charge circuit in boost mode according to an embodiment of this application, wherein... Figure 7 The current path corresponding to the charging of the first inductor L1, Figure 8 The current path corresponding to the discharge of the first inductor L1.

[0104] In this process, the drive signal of the first power switch device Q1 changes from a PWM wave in buck mode to a high level and remains on, while the drive signal of the second power switch device Q2 changes from a low level in shoot-through mode and remains off to a PWM wave.

[0105] like Figure 7 As shown, when the second power switch Q2 is turned on, the sixth capacitor C6 discharges and the first inductor L1 is charged, storing energy.

[0106] like Figure 8 As shown, when the second power switch Q2 is turned off, the first inductor L1 releases energy, which charges the first capacitor C1 and the second capacitor C2 through the first diode D1 and the second diode D2. After multiple PWM waves / pulses, the bus voltage corresponding to the sum of the voltages of the first capacitor C1 and the second capacitor C2 gradually decreases. Eventually, the duty cycle change of the PWM wave of the second power switch Q2 enters a steady state, and the bus voltage is stabilized at the minimum bus voltage required for grid connection of the energy storage converter PCS.

[0107] In one embodiment, the drive circuit is configured to: control the first power switching device and the second power switching device to be turned on or off simultaneously in buck-boost mode, so as to stabilize the bus voltage of the DC bus at the target voltage; When the first power switch and the second power switch are simultaneously turned on, the sixth capacitor discharges to charge the first inductor through the first power switch and the second power switch, and the first inductor stores energy. When the first power switching device and the second power switching device are turned off simultaneously, the first inductor releases energy to charge the first capacitor and the second capacitor through the first diode and the second diode.

[0108] In this embodiment, the driving circuit can operate the voltage regulation circuit 200 in buck-boost mode without considering the relationship between the DC voltage and the minimum bus voltage. Therefore, the driving circuit controls the voltage regulation circuit 200 to regulate the voltage based on the buck-boost mode.

[0109] Specifically, the drive circuit controls the first power switch Q1 and the second power switch Q2 of the voltage regulation circuit 200 to simultaneously turn on or off, so as to stabilize the DC bus voltage at the minimum bus voltage. The drive signals for the first power switch Q1 and the second power switch Q2 are the same PWM wave, which are turned on and off simultaneously, and the duty cycle of the PWM wave is automatically controlled by the drive circuit.

[0110] Figures 9 to 10 This is a schematic diagram of the charging and discharging current path of the bus voltage pre-charge circuit in buck-boost mode according to an embodiment of this application, wherein... Figure 9 The current path corresponding to the charging of the first inductor L1, Figure 10 The current path corresponding to the discharge of the first inductor L1.

[0111] like Figure 9 As shown, when the first power switch Q1 and the second power switch Q2 are turned on simultaneously, the sixth capacitor C6 discharges and the first inductor L1 is charged, storing energy.

[0112] like Figure 10 As shown, when the first power switch Q1 and the second power switch Q2 are simultaneously turned off, the first inductor L1 discharges, releasing energy, which charges the first capacitor C1 and the second capacitor C2 through the first diode D1 and the second diode D2. After multiple PWM waves, the duty cycle of the PWM waves enters a steady state, and the bus voltage is stabilized at the minimum bus voltage required for grid connection of the energy storage converter PCS.

[0113] The voltage regulation circuit 200 of this application embodiment can have a variety of different operating modes to realize the pre-charging of the bus voltage, and is applicable to various application scenarios with different magnitudes of DC voltage based on the power grid and minimum bus voltage based on the energy storage converter.

[0114] In one embodiment, the drive circuit includes a control unit and a drive unit; The control unit is used to output control commands based on the target voltage, combined with the real-time acquired bus voltage of the DC bus and the charging current of the first inductor. The drive unit is connected to the control unit and the first power switch and the second power switch respectively, and is used to generate corresponding drive signals based on the control command, and control the first power switch and the second power switch to turn on and off through the drive signals.

[0115] In this embodiment, the control unit monitors the current bus voltage of the DC bus, namely the voltage of the first capacitor C1 and the voltage of the second capacitor C2, and sums them, as well as monitors the charging current of the first inductor L1. Based on the real-time collected bus voltage and the current of the first inductor L, combined with the minimum bus voltage required for the grid connection of the energy storage converter PCS, the control unit outputs control commands.

[0116] The drive unit generates appropriate drive signals according to the control command to control the conduction and cutoff of the first power switch Q1 and the second power switch Q2.

[0117] In one embodiment, the control unit includes: A voltage feedback loop is used to output a corresponding voltage compensation feedback value based on the real-time acquired bus voltage of the DC bus; a current feedback loop is connected to the voltage feedback loop and is used to output a pulse width modulation (PWM) signal based on the real-time acquired charging current of the first inductor and the voltage compensation feedback value; a signal modulation circuit is connected to the current feedback loop and is used to generate a corresponding control command based on the operating mode and the PWM signal modulation.

[0118] Combination Figure 11 The circuit structure of the control unit in an embodiment of this application is shown. The sum of the voltage values ​​collected by the first capacitor C1 and the second capacitor C2, and the inductor current value collected by the first inductor L1, participate in the corresponding loop control in real time.

[0119] like Figure 11 As shown, the voltage feedback loop includes a feedback arithmetic unit 12 and a PI (proportional-integral) controller 1. The negative input terminal of the feedback arithmetic unit 12 is connected to the voltage value of the sum of the first capacitor C1 and the second capacitor C2, which is the current bus voltage value of the DC bus. The positive input terminal of the feedback arithmetic unit 12 is connected to the minimum bus voltage value required for grid connection, which serves as the given reference for the voltage feedback loop. The voltage value can be acquired by setting a differential operational amplifier circuit across the corresponding capacitor.

[0120] The relationship between the minimum bus voltage value and the current bus voltage value is input to the feedback arithmetic unit 12. The output of the feedback arithmetic unit 12 is connected to the PI controller 1, and finally outputs the corresponding voltage compensation feedback value to the current feedback loop.

[0121] The current feedback loop includes a feedback arithmetic unit 22 and a PI controller 2. The voltage compensation feedback value output by the PI controller 1 in the voltage feedback loop is used as the given input value for the current feedback loop. The output of the PI controller 1 and the current value of the first inductor L1 are used as the input of the PI controller 2 after passing through the feedback arithmetic unit 22. The current value can be acquired by a Hall sensor connected in series at one end of each inductor.

[0122] The PI controller 2 of the current feedback loop outputs the corresponding current compensation feedback value, which serves as the input to the signal modulation circuit.

[0123] The signal modulation circuit includes a comparator 3 and a logic operation circuit 5. The positive input terminal of the comparator 3 receives the current compensation feedback value output by the PI controller 2 of the current feedback loop, and the negative input terminal of the comparator 3 is connected to a triangular carrier wave 4.

[0124] The minimum value of the triangular carrier wave 4 is 0, the maximum value is 1, the frequency is fsw (configurable, generally the same as the switching frequency of the bidirectional DC-AC converter 20), and the duty cycle is 0.5. After the current compensation feedback value output by the PI controller 2 and the triangular carrier wave 4 pass through the comparator 3, the comparator 3 outputs a PWM signal.

[0125] When the output value of PI controller 2 is greater than the value of triangular carrier wave 4, comparator 3 outputs a high level; when the output value of PI controller 2 is less than the value of triangular carrier wave 4, comparator 3 outputs a low level. As the output value of PI controller 2 changes, comparator 3 outputs a PWM signal with a frequency of fsw.

[0126] The signal modulation circuit includes a logic operation circuit 5, which modulates the PWM signal output by the comparator 3 based on a selected operating mode, such as Buck mode, pass-through mode, Boost mode, or Buck-Boost mode, to generate a corresponding control command.

[0127] If the drive circuit selects the working mode as Buck after calculation, the logic operation circuit 5 will keep the control command of the first power switch Q1 as a PWM wave signal and set the control command of the second power switch Q2 to a constant low level to keep it off.

[0128] If the driving circuit selects the working mode as the pass-through mode after calculation, the logic operation circuit 5 first processes the control commands of the first power switch Q1 and the second power switch Q2 into the Buck mode. When the difference between the voltage value of C1+C2 and the voltage value of the sixth capacitor C6 is equal within the allowable error voltage range, the control command of the first power switch Q1 is set to a constant high level to keep it on, and the control command of the second power switch Q2 is kept at a constant low level to keep it off.

[0129] If the driving circuit selects the working mode as Boost mode after calculation, the logic operation circuit 5 first processes the control commands of the first power switch Q1 and the second power switch Q2 into Buck mode. When the difference between the voltage value of C1+C2 and the voltage value of the sixth capacitor C6 is equal within the allowable error range, the control command of the first power switch Q1 is set to a constant high level to keep it conducting, and the control command of the second power switch Q2 is kept as a PWM signal.

[0130] If the drive circuit selects the Buck-Boost mode after calculation, the logic operation circuit 5 does not process the control commands of the first power switch Q1 and the second power switch Q2. The control commands of the first power switch Q1 and the second power switch Q2 are the same PWM signals, which remain at the same high and low.

[0131] The logic operation circuit 5 outputs control commands to the drive unit. The drive unit generates corresponding drive signals based on the control commands and controls the first power switch Q1 and the second power switch Q2 to turn on and off through the drive signals.

[0132] In this embodiment, the bus voltage pre-charging circuit, through a transformer rectifier circuit and a voltage regulation circuit, utilizes the supply voltage from the target grid's power supply terminal to convert it into the minimum bus voltage required for the energy storage converter to connect to the target grid. This voltage is then supplied to the DC bus of the energy storage converter for pre-charging, ensuring that the DC bus voltage is pre-charged to the minimum bus voltage value after pre-charging. Therefore, the DC bus voltage of the energy storage converter meets the minimum bus voltage required for connection to the target grid. The energy storage converter can then enter rectification mode to charge the corresponding connected power equipment, achieving automated and intelligent precise pre-charging of the DC bus, reducing pre-charging costs and improving pre-charging efficiency.

[0133] Optionally, embodiments of this application also provide an energy storage converter system, including: Bus voltage pre-charge circuit 10 as described in any of the above embodiments; and The energy storage converter PCS, the target power grid G, and the power supply equipment.

[0134] Power supply devices, such as the battery BAT shown in the figure, may also include power supply electronic power converters, such as bidirectional DC-DC converters and bidirectional AC-DC converters.

[0135] Optionally, the target power grid includes a three-phase three-wire power grid or a three-wire four-wire power grid.

[0136] Optionally, embodiments of this application also provide a bus voltage pre-charging method, applied to the bus voltage pre-charging circuit 10 as described in any of the above embodiments, the method comprising: When it is detected that the bus voltage of the DC bus does not reach the minimum bus voltage required for the energy storage converter to be connected to the target power grid, the supply voltage of the power supply terminal is converted into DC voltage through the transformer rectifier circuit; The operating mode of the voltage regulation circuit is determined based on the relationship between the DC voltage and the minimum bus voltage. In the operating mode, the voltage regulation circuit adjusts the DC voltage to the minimum bus voltage and provides it to the DC bus for pre-charging.

[0137] The bus voltage pre-charge method is executed by the drive circuit of the energy storage converter. Below, in conjunction with... Figure 2 and Figure 12 The flowchart below describes the bus voltage pre-charging method according to an embodiment of this application.

[0138] like Figure 12 As shown, it includes the following steps: Step 202: It is detected that the battery BAT voltage is too low and the DC bus voltage does not meet the grid connection requirements. It is also detected that the voltage of the target grid G ​​to be connected to is normal and meets the grid connection requirements. Step 204: Calculate the minimum bus voltage required to meet grid connection requirements; Step 206: Close the third relay K3 to start the pre-charging of the DC bus; Step 208: After the voltage of the sixth capacitor C6 stabilizes, sample the voltage of the sixth capacitor C6 and compare it with the minimum bus voltage that meets the grid connection requirements. Determine the relationship between the two and determine / select the working mode of the voltage regulation circuit 200. Step 210: By controlling the first power switch Q1 and the second power switch Q2 to be turned on and off, the first power switch Q1 and the second power switch Q2 are made to work, and the first capacitor C1 and the second capacitor C2 are charged to achieve pre-charging; Step 212: It is detected that the bus voltage of C1+C2 meets the minimum bus voltage required for grid connection; Step 214: The energy storage converter PCS starts working in off-grid no-load inverter mode, and builds AC voltage on the three-phase filter capacitors C3, C4, and C5. Step 216: After the AC voltage on capacitors C3, C4, and C5 meets the phase and amplitude requirements for grid connection, close relays K4, K5, and K6, and the energy storage converter PCS switches to grid-connected rectification mode. Step 218: Immediately disconnect the third relay K3 and simultaneously close the relay K2. The first power switch Q1 and the second power switch Q2 stop working, and the drive signal becomes low by default, stopping the pre-charging of the DC bus. Step 220: The energy storage converter PCS starts grid-connected rectification to charge the battery BAT.

[0139] This application embodiment adds a circuit to the energy storage system to form an automatic and controllable PCS bus voltage pre-charging circuit. Without manual intervention, the main control chip of the PCS can automatically pre-charge the capacitor of the DC bus when the voltage of the power equipment is too low, so as to meet the DC bus voltage requirement of the PCS when it is connected to the grid, thereby entering the rectification working mode and using the grid voltage to supplement the power equipment, reducing labor costs and improving the automation and intelligence of the bus voltage pre-charging.

[0140] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0141] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal (which may be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in the various embodiments of this application.

[0142] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A bus voltage pre-charging circuit, characterized in that, include: A transformer rectifier circuit, connected to the power supply terminal of the target power grid, is used to convert the power supply voltage of the power supply terminal into DC voltage; A voltage regulation circuit is connected to the DC bus of the transformer rectifier circuit and the energy storage converter, respectively, and is used to adjust the DC voltage to the target voltage and provide it to the DC bus for pre-charging. Wherein, the target voltage is the minimum bus voltage required for the energy storage converter to be connected to the target power grid; The voltage regulation circuit includes a first power switching device, a second power switching device, a first inductor, a first diode, a second diode, and a sixth capacitor; The first terminal of the first power switching device is connected to the sixth capacitor, the second terminal is connected to the first inductor, and the third terminal is connected to the drive circuit of the energy storage converter; the first terminal of the second power switching device is connected to the first inductor, the second terminal is connected to the sixth capacitor, and the third terminal is connected to the drive circuit; the first terminal of the first diode is connected to the first inductor, and the second terminal is connected to the DC bus; the first terminal of the second diode is connected to the sixth capacitor and the DC bus respectively, and the second terminal is connected to the first inductor; the sixth capacitor is connected to the transformer rectifier circuit; When the DC voltage is greater than or equal to the target voltage, the drive circuit controls the first power switch and the second power switch to be turned on or off, so as to control the voltage regulation circuit to adjust the bus voltage of the DC bus to be stable at the target voltage.

2. The circuit as described in claim 1, characterized in that, The first terminal of the first power switch is connected to the first terminal of the sixth capacitor, the second terminal of the first power switch is connected to the first terminal of the first inductor, and the third terminal of the first power switch is connected to the drive circuit of the energy storage converter. The first terminal of the second power switch is connected to the second terminal of the first inductor, the second terminal of the second power switch is connected to the second terminal of the sixth capacitor, and the third terminal of the second power switch is connected to the driving circuit. The first terminal of the first diode is connected to the second terminal of the first inductor, and the second terminal of the first diode is connected to the DC bus. The first end of the second diode is connected to the second end of the sixth capacitor and the DC bus, respectively, and the second end of the second diode is connected to the first end of the first inductor; The sixth capacitor is connected to the transformer rectifier circuit.

3. The circuit as described in claim 2, characterized in that, The DC bus is composed of a first capacitor and a second capacitor connected in series, with the second end of the first capacitor and the first end of the second capacitor connected together. The second end of the first diode is connected to the first end of the first capacitor, and the first end of the second diode is connected to the second end of the second capacitor.

4. The circuit as described in claim 3, characterized in that, The transformer rectifier circuit includes a transformer and a rectifier; The primary side of the transformer is connected to the power supply terminal of the target power grid, and the secondary side of the transformer is connected to the rectifier. The transformer transforms the supply voltage at the power supply terminal to obtain the corresponding AC voltage based on the turns ratio of the primary and secondary sides. The rectifier rectifies the AC voltage into a DC voltage and provides it to the sixth capacitor.

5. The circuit as described in claim 4, characterized in that, The rectifier includes a third diode and a fourth diode; The first end of the third diode is connected to the first end of the secondary side of the transformer, and the second end of the third diode is connected to the first end of the sixth capacitor. The second end of the fourth diode is connected to the second end of the secondary side of the transformer, and the first end of the fourth diode is connected to the second end of the sixth capacitor.

6. The circuit as described in claim 5, characterized in that, It also includes a current-limiting resistor and a third relay; The current-limiting resistor is connected between the second terminal of the third diode and the first terminal of the sixth capacitor; The common terminal of the third relay is connected to the second terminal of the third diode, the normally open terminal of the third relay is connected to the first terminal of the sixth capacitor, and the control terminal of the third relay is connected to the drive circuit. The drive circuit controls the pre-charging of the DC bus to start or stop by controlling the normally open terminal of the third relay to close or open.

7. The circuit as described in claim 3, characterized in that, When the DC voltage is greater than the target voltage, the driving circuit is used to: The operating mode of the voltage regulation circuit is determined to be buck mode, and in buck mode, the first power switching device is controlled to be turned on or off, and the second power switching device is controlled to remain off, so that the bus voltage of the DC bus is stabilized at the target voltage.

8. The circuit as described in claim 3, characterized in that, When the DC voltage equals the target voltage, the drive circuit is used to: If the difference between the current bus voltage of the DC bus and the DC voltage is outside the preset voltage difference range, the operating mode of the voltage regulation circuit is determined to be buck mode, and the first power switch device is controlled to be turned on or off, and the second power switch device is controlled to remain off in the buck mode. If the difference between the current bus voltage of the DC bus and the DC voltage is within a preset voltage difference range, the operating mode of the voltage regulation circuit is determined to be the through mode. In the through mode, the first power switch device is controlled to remain on, and the second power switch device is controlled to remain off, so that the bus voltage of the DC bus is stabilized at the target voltage.

9. The circuit as described in claim 3, characterized in that, When the DC voltage is less than the target voltage, the drive circuit is used to: If the difference between the current bus voltage of the DC bus and the DC voltage is outside the preset voltage difference range, the operating mode of the voltage regulation circuit is determined to be buck mode, and the first power switch device is controlled to be turned on or off, and the second power switch device is controlled to remain off in the buck mode. If the difference between the current bus voltage of the DC bus and the DC voltage is within the preset voltage difference range, then the operating mode of the voltage regulation circuit is determined to be the through mode, and in the through mode, the first power switch device is controlled to remain on and the second power switch device is controlled to remain off. If the current bus voltage of the DC bus is equal to the DC voltage, the operating mode of the voltage regulation circuit is determined to be boost mode. In boost mode, the first power switch device is kept on, and the second power switch device is turned on or off, so that the bus voltage of the DC bus is stabilized at the target voltage.

10. The circuit as described in any one of claims 7-9, characterized in that, In the buck mode, when the first power switching device is turned on, the sixth capacitor discharges so as to charge the first inductor, the first capacitor, and the second capacitor through the first power switching device, and the first inductor stores energy. In the buck mode, when the first power switching device is turned off, the first inductor releases energy to charge the first capacitor and the second capacitor through the first diode and the second diode.

11. The circuit as described in claim 8 or 9, characterized in that, In the direct-through mode, when the first power switch remains on and the second power switch remains off, the sixth capacitor discharges to charge the first inductor, the first capacitor, and the second capacitor through the first power switch.

12. The circuit as described in claim 9, characterized in that, In the boost mode, when the second power switching device is turned on, the sixth capacitor discharges to charge the first inductor through the first power switching device and the second power switching device, and the first inductor stores energy. In the boost mode, when the second power switching device is turned off, the first inductor releases energy to charge the first capacitor and the second capacitor through the first diode and the second diode.

13. The circuit as described in claim 3, characterized in that, The driving circuit is used for: In buck-boost mode, the first power switching device and the second power switching device are controlled to be turned on or off simultaneously to stabilize the bus voltage of the DC bus at the target voltage. When the first power switch and the second power switch are simultaneously turned on, the sixth capacitor discharges to charge the first inductor through the first power switch and the second power switch, and the first inductor stores energy. When the first power switch and the second power switch are turned off simultaneously, the first inductor releases energy to charge the first capacitor and the second capacitor through the first diode and the second diode.

14. The circuit as described in any one of claims 7-9, characterized in that, The drive circuit includes a control unit and a drive unit; The control unit is used to output control commands based on the target voltage, combined with the real-time acquired bus voltage of the DC bus and the charging current of the first inductor. The drive unit is connected to the control unit and the first power switch and the second power switch respectively, and is used to generate corresponding drive signals based on the control command, and control the first power switch and the second power switch to turn on and off through the drive signals.

15. The circuit as described in claim 14, characterized in that, The control unit includes: The voltage feedback loop is used to output a corresponding voltage compensation feedback value based on the bus voltage of the DC bus acquired in real time. A current feedback loop, connected to the voltage feedback loop, is used to output a pulse width modulation (PWM) signal based on the real-time collected charging current of the first inductor and the voltage compensation feedback value. A signal modulation circuit, connected to the current feedback loop, is used to generate corresponding control commands based on the operating mode and the PWM signal modulation.

16. An energy storage converter system, characterized in that, include: Bus voltage pre-charge circuit as described in any one of claims 1-15; as well as The energy storage converter, the target power grid, and the power supply equipment.

17. The system as claimed in claim 16, characterized in that, The target power grid includes a three-phase three-wire power grid or a three-wire four-wire power grid.

18. A method for pre-charging bus voltage, characterized in that, The method, applied to the bus voltage pre-charge circuit as described in any one of claims 1-15, comprises: When it is detected that the bus voltage of the DC bus does not reach the minimum bus voltage required for the energy storage converter to be connected to the target power grid, the supply voltage of the power supply terminal is converted into DC voltage through the transformer rectifier circuit; The operating mode of the voltage regulation circuit is determined based on the relationship between the DC voltage and the minimum bus voltage. In the operating mode, the voltage regulation circuit adjusts the DC voltage to the minimum bus voltage and provides it to the DC bus for pre-charging.

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