Power supply equipment

Abstract

The invention discloses power supply equipment, and belongs to the technical field of power supply equipment. According to the power supply equipment, one end of a first charging circuit is connected with a direct-current bus capacitor, the other end of the first charging circuit is used for being connected with a power grid, and a control unit is used for controlling the first charging circuit to charge voltage of the direct-current bus capacitor to first target voltage in a first pre-charging stage. The first charging circuit is controlled to charge the voltage of the direct current bus capacitor to a second target voltage in a second pre-charging stage, the first pre-charging stage is before the second pre-charging stage, the first target voltage is smaller than the second target voltage, and the second target voltage is larger than the voltage of the power grid; and the control unit is also used for controlling the power conversion circuit to perform inversion output under the condition that the voltage of the direct current bus capacitor reaches the second target voltage so as to start the power supply equipment. According to the power supply equipment, the bus capacitor voltage can be effectively increased, the risk of insufficient inverter voltage in the inverter phase-locked grid connection process is effectively reduced, and safe and reliable alternating current pre-charging starting of the power supply equipment is achieved.

Description

Technical Field

[0001] This application belongs to the technical field of power supply equipment, and particularly relates to a power supply equipment. Background Art

[0002] The AC pre-charge start technology of power supply equipment such as photovoltaic inverters and energy storage converters is one of the important means to ensure the safe operation of the equipment. By introducing grid AC power to pre-charge the capacitor on the DC bus of the power supply equipment, the capacitor voltage is raised to close to the grid voltage level, and then the power supply equipment is started to reduce the impact of the inrush current, so that the system can operate more efficiently and reliably, and significantly improve the overall performance and safety.

[0003] The current AC pre-charge start technology has limited ability to raise the bus capacitor voltage. After the bus capacitor voltage is pre-charged, it may be lower than the grid AC peak voltage. After the grid-connected relay is closed, a rectification inrush current may be formed, and there is a risk of insufficient inverter voltage during the inverter phase-locked grid connection process. Summary of the Invention

[0004] This application aims to solve at least one of the technical problems existing in the prior art. For this reason, this application proposes a power supply equipment that can effectively raise the bus capacitor voltage and achieve safe and reliable AC pre-charge start.

[0005] This application provides a power supply equipment, including:

[0006] A power conversion circuit, the input end of the power conversion circuit is connected in parallel with a DC bus capacitor, and the output end of the power conversion circuit is used to connect to the grid;

[0007] A first charging circuit, one end of the first charging circuit is connected to the DC bus capacitor, and the other end is used to connect to the grid;

[0008] A control unit, the control unit is connected to the first charging circuit and the power conversion circuit, the control unit is used to control the first charging circuit to charge the voltage of the DC bus capacitor to a first target voltage in a first pre-charge stage, and control the first charging circuit to charge the voltage of the DC bus capacitor to a second target voltage in a second pre-charge stage, the first pre-charge stage is before the second pre-charge stage, the first target voltage is less than the second target voltage, and the second target voltage is greater than the voltage of the grid;

[0009] The control unit is further used to control the power conversion circuit to perform inverter output to start the power supply equipment when the voltage of the DC bus capacitor reaches the second target voltage.

[0010] According to the power supply device of the present application, the control unit controls the first charging circuit to charge the DC bus capacitor according to the first pre-charging stage and the second pre-charging stage, gradually increasing the voltage of the bus capacitor in stages, and pre-charging the voltage of the DC bus capacitor to a second target voltage higher than the grid voltage, which can effectively raise the voltage of the bus capacitor, effectively reduce the risk of insufficient inverter voltage during the inverter phase-locked grid connection process, and achieve safe and reliable AC pre-charging startup of the power supply device.

[0011] According to an embodiment of the present application, the first charging circuit includes a boost circuit, the input end of the boost circuit is connected to the photovoltaic power generation module, and the power supply device is used to convert the direct current generated by the photovoltaic power generation module into alternating current; a input end capacitor is connected in parallel at the input end of the boost circuit;

[0012] The control unit is used to control the first charging circuit to charge the input end capacitor and the DC bus capacitor in the first pre-charging stage, and the control unit is further used to control the boost circuit to perform boost conversion when the voltage of the input end capacitor reaches the first target voltage, and charge the voltage of the DC bus capacitor to the second target voltage through the input end capacitor in the second pre-charging stage.

[0013] In the embodiment of the present application, in the first pre-charging stage, the voltage of the DC bus capacitor is charged in a current-limiting manner to the first target voltage. In the second pre-charging stage, the boost circuit is started to perform boost, and the voltage of the DC bus capacitor is charged from the first target voltage to the second target voltage. After the boost circuit starts to boost, the current-limiting resistor in the first charging circuit can be bypassed to prevent the current-limiting resistor from overheating due to continuous power loss. The boost circuit boosts to make the voltage of the DC bus capacitor adjustable. The boost circuit takes the input end capacitor as the input and is less affected by grid fluctuations, which can effectively raise the bus voltage, reduce the risk of damage to the DC bus capacitor, and improve the grid adaptation ability of the power supply device.

[0014] According to an embodiment of the present application, the first charging circuit further includes a rectification module, the rectification module is arranged between the boost circuit and the grid, and the rectification module is used to convert the alternating current output by the grid into direct current to charge the input end capacitor and the DC bus capacitor.

[0015] According to an embodiment of the present application, the first charging circuit further includes a first current-limiting charging device, and the first current-limiting charging device is arranged between the boost circuit and the grid.

[0016] According to an embodiment of the present application, a first unidirectional conduction device is arranged between the photovoltaic power generation module and the boost circuit, and the conduction direction of the first unidirectional conduction device is from the photovoltaic power generation module to the boost circuit.

[0017] According to an embodiment of the present application, a first switching device is provided between the photovoltaic power generation module and the boost circuit, and the first switching device is used to control the on / off of the line between the photovoltaic power generation module and the boost circuit.

[0018] According to an embodiment of the present application, the first charging circuit includes a charge pump circuit, the charge pump circuit has a charge pump capacitor, the switching period of the charge pump circuit includes a charging stage and a discharging stage. In the charging stage, the power grid charges the charge pump capacitor, and in the discharging stage, the power grid and the charge pump capacitor charge the DC bus capacitor.

[0019] The control unit is configured to control the charge pump circuit to be connected between the DC bus capacitor and the power grid when the voltage of the DC bus capacitor reaches the first target voltage, and charge the voltage of the DC bus capacitor to the second target voltage through the charge pump capacitor in the second pre-charging stage.

[0020] In the embodiment of the present application, in the first pre-charging stage, the voltage of the DC bus capacitor is charged to the first target voltage in a current-limiting manner by using a charge pump circuit or a second current-limiting charging device. In the second pre-charging stage, the charge pump circuit is used for boosting, and the voltage of the DC bus capacitor is charged from the first target voltage to the second target voltage. The second current-limiting charging device only works in part of the pre-charging stage, which can prevent the current-limiting resistor from overheating due to continuous power loss. The charge pump capacitor of the charge pump circuit can provide the charge quantity for charging the voltage of the DC bus capacitor to a value higher than the peak value of the power grid voltage, which can effectively boost the bus voltage. There are no high-loss devices in the charge pump circuit itself, and the bus voltage can be balanced according to the charge relationship during the grid connection stage, so as not to drop rapidly, providing sufficient control time for inversion and grid connection, improving the success rate of grid connection, and improving the grid adaptation ability of the power supply equipment.

[0021] According to an embodiment of the present application, the control unit is configured to control the first charging circuit to charge the voltage of the DC bus capacitor to the first target voltage through the charge pump circuit in the first pre-charging stage.

[0022] According to an embodiment of the present application, the first charging circuit has a second current-limiting charging device, and the control unit is configured to control the first charging circuit to charge the voltage of the DC bus capacitor to the first target voltage through the second current-limiting charging device in the first pre-charging stage.

[0023] According to an embodiment of the present application, a voltage limiter is connected in parallel with the DC bus capacitor, and the voltage limiter is used to balance the charge quantity input to the DC bus capacitor by the charge pump capacitor in the discharging stage to limit the voltage of the DC bus capacitor.

[0024] According to an embodiment of the present application, the charge pump capacitor is the same capacitor as the AC filtering capacitor of the power supply device.

[0025] According to an embodiment of the present application, the DC bus capacitor includes a first half bus capacitor and a second half bus capacitor connected in series, and the first half bus capacitor and the second half bus capacitor are connected to the midpoint of the bus capacitor;

[0026] The power supply device further includes:

[0027] A second charging circuit, one end of the second charging circuit is connected to the midpoint of the bus capacitor, and the other end is used to be connected to the power grid. The second charging circuit is provided with an insulation impedance detection circuit grounded.

[0028] The control unit is connected to the second charging circuit. The control unit is used to control the first charging circuit and the second charging circuit to first charge the first half bus capacitor, and then charge the first half bus capacitor and the second half bus capacitor, and perform insulation impedance detection through the insulation impedance detection circuit.

[0029] In the embodiment of the present application, by using the first charging branch and the second charging branch for pre-charging the DC bus capacitor, without the need to increase many resistors and relays, through the first charging circuit and the second charging circuit, the first half bus capacitor and the second half bus capacitor can be independently charged, and the charging of the upper and lower half bus capacitors is decoupled. By first charging the first half bus capacitor to form a voltage difference between the two half bus capacitors, the insulation impedance detection between the bus and the ground can be realized in the pre-charging stage, and problems such as insulation aging and damage can be detected in time, avoiding serious accidents such as electric leakage, short circuit and even fire caused by insulation failure, prolonging the service life of the equipment, and ensuring the safety of personnel and equipment.

[0030] According to an embodiment of the present application, the control unit is used to control the second charging circuit to disconnect when the voltage of the first half bus capacitor reaches the first target voltage, and obtain the first detection data of the first half bus capacitor and the insulation impedance detection circuit;

[0031] The control unit is further used to control the second charging circuit to disconnect when the voltages of the first half bus capacitor and the second half bus capacitor both reach the first target voltage, and obtain the second detection data of the first half bus capacitor, the second half bus capacitor and the insulation impedance detection circuit. The first detection data and the second detection data are used to determine the insulation impedance detection result.

[0032] According to an embodiment of the present application, the first charging circuit is further provided with a third current-limiting charging device.

[0033] Additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present application. Description of the Drawings

[0034] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, where:

[0035] Figure 1 is one of the schematic structural diagrams of the power supply device provided by the embodiment of the present application;

[0036] Figure 2 is another schematic structural diagram of the power supply device provided by the embodiment of the present application;

[0037] Figure 3 is Figure 2 the schematic equivalent circuit diagram of

[0038] Figure 4 is one of the schematic flow diagrams of the AC side startup of the power supply device provided by the embodiment of the present application;

[0039] Figure 5 is the third schematic structural diagram of the power supply device provided by the embodiment of the present application;

[0040] Figure 6 is the fourth schematic structural diagram of the power supply device provided by the embodiment of the present application;

[0041] Figure 7 is the fifth schematic structural diagram of the power supply device provided by the embodiment of the present application;

[0042] Figure 8 is the sixth schematic structural diagram of the power supply device provided by the embodiment of the present application;

[0043] Figure 9 is the schematic diagram of the bus capacitor voltage curve of the AC side startup of the power supply device provided by the embodiment of the present application;

[0044] Figure 10 is the seventh schematic structural diagram of the power supply device provided by the embodiment of the present application;

[0045] Figure 11 is Figure 10 the schematic equivalent circuit diagram of

[0046] Figure 12 is Figure 11 the schematic diagram of the current flow direction in the charging half cycle of the charge pump capacitor in

[0047] Figure 13 is Figure 11Schematic diagram of the current flow direction during the capacitor discharge half-cycle of the charge pump in

[0048] Figure 14 It is the second schematic diagram of the process for starting the AC side of the power supply device provided by an embodiment of the present application;

[0049] Figure 15 It is the eighth schematic diagram of the structure of the power supply device provided by an embodiment of the present application;

[0050] Figure 16 It is the ninth schematic diagram of the structure of the power supply device provided by an embodiment of the present application;

[0051] Figure 17 It is the tenth schematic diagram of the structure of the power supply device provided by an embodiment of the present application;

[0052] Figure 18 It is the eleventh schematic diagram of the structure of the power supply device provided by an embodiment of the present application;

[0053] Figure 19 It is the twelfth schematic diagram of the structure of the power supply device provided by an embodiment of the present application;

[0054] Figure 20 It is Figure 19 The equivalent topology diagram of the first state for insulation detection of the power supply device of

[0055] Figure 21 It is Figure 19 The equivalent topology diagram of the second state for insulation detection of the power supply device of

[0056] Figure 22 It is the third schematic diagram of the process for starting the AC side of the power supply device provided by an embodiment of the present application;

[0057] Figure 23 It is the thirteenth schematic diagram of the structure of the power supply device provided by an embodiment of the present application.

[0058] Reference numerals:

[0059] Power conversion circuit 100, DC input terminal 110, DC bus capacitor 200, first half-bus capacitor 210, second half-bus capacitor 220, bus capacitor midpoint 230, first charging circuit 10,

[0060] Boost circuit 310, photovoltaic power generation module 320, input terminal capacitor 330, rectification module 340, first current-limiting charging device 350, first unidirectional conduction device 360,

[0061] Charge pump circuit 410, charge pump capacitor 420, second current-limiting charging device 430, voltage limiting device 440,

[0062] Power grid 600, second charging circuit 710, insulation impedance detection circuit 720, third current-limiting charging device 730. Detailed implementation manners

[0063] The following will clearly describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application belong to the scope of protection of the present application.

[0064] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, rather than to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of the same type, and the number of objects is not limited. For example, the first object can be one or multiple. In addition, "and / or" in the specification and claims means at least one of the connected objects, and the character " / " generally means an "or" relationship between the associated objects before and after.

[0065] The following will, with reference to the accompanying drawings, describe in detail the power supply device provided in the embodiments of the present application through specific embodiments and their application scenarios.

[0066] It should be noted that the power supply device in the embodiments of the present application has a power conversion circuit 100, and the power conversion circuit 100 can realize DC-AC conversion. The power supply device can be devices such as a photovoltaic inverter and an energy storage converter.

[0067] The power supply device in the embodiments of the present application includes: a power conversion circuit 100, a first charging circuit 10, and a control unit.

[0068] Among them, the input end of the power conversion circuit 100 is connected in parallel with a DC bus capacitor 200, and the output end of the power conversion circuit 100 is used to be connected to the power grid 600.

[0069] In this embodiment, one end of the first charging circuit 10 is connected to the DC bus capacitor 200, and the other end is used to be connected to the power grid 600. The first charging circuit 10 can utilize the AC-side energy of the power grid 600 to charge the DC bus capacitor 200 in a current-controllable manner.

[0070] The control unit of the power supply device is connected to the first charging circuit 10 and the power conversion circuit 100. The control unit can control the first charging circuit 10 to charge the DC bus capacitor 200 according to a preset charging strategy. The control unit can also control the power conversion circuit 100 to operate when the voltage of the DC bus capacitor 200 reaches the required value.

[0071] In this embodiment, the preset charging strategy includes a first pre-charging stage and a second pre-charging stage. The control unit is used to control the first charging circuit 10 to charge the voltage of the DC bus capacitor 200 to a first target voltage in the first pre-charging stage, and control the first charging circuit 10 to charge the voltage of the DC bus capacitor 200 to a second target voltage in the second pre-charging stage. The first pre-charging stage is before the second pre-charging stage. The first target voltage is less than the second target voltage, and the second target voltage is greater than the voltage of the power grid 600.

[0072] In actual implementation, the first target voltage and the second target voltage can be set according to the AC peak voltage of the power grid 600. Charging the voltage of the DC bus capacitor 200 to the second target voltage can ensure that the voltage of the DC bus capacitor 200 is not lower than the amplitude of the AC peak voltage, reducing the probability of rectifier impact current formed after the grid-connected relay of the power supply device is closed.

[0073] In the first pre-charging stage, the first charging circuit 10 charges the voltage of the DC bus capacitor 200 from the starting voltage value (0V) to the first target voltage, and the first target voltage can be less than the voltage of the power grid 600.

[0074] In the second pre-charging stage, the first charging circuit 10 charges the voltage of the DC bus capacitor 200 from the first target voltage to the second target voltage. The first charging circuit 10 can use the energy on the AC side to boost the voltage and charge the voltage of the DC bus capacitor 200 to the second target voltage higher than the voltage of the power grid 600.

[0075] It should be noted that the first charging circuit 10 has a boosting function. The control unit can control whether the first charging circuit 10 boosts the voltage by controlling the switching devices at other positions in the first charging circuit 10 or the power supply device, thereby controlling the first pre-charging stage and the second pre-charging stage in which the power supply device starts using the energy on the AC side.

[0076] In this embodiment, the control unit is also used to control the power conversion circuit 100 to perform an inverter output to start the power supply device when the voltage of the DC bus capacitor 200 reaches the second target voltage.

[0077] It can be understood that when the voltage of the DC bus capacitor 200 reaches the second target voltage, the power conversion circuit 100 of the power supply device reaches the starting condition. The control unit controls the power conversion circuit 100 to perform an inverter output to start the power supply device.

[0078] In actual implementation, after starting the power supply device, before closing the grid-connected relay of the power supply device, the AC filter capacitor voltage of the power supply device can be controlled to follow, so as to avoid the contact adhesion of the grid-connected relay caused by the closing of the high voltage difference.

[0079] In the related art, the ability to boost the bus capacitor voltage is limited. After the bus capacitor voltage is pre-charged, it may be lower than the 600 AC peak voltage of the power grid, resulting in the risk of insufficient inverter voltage during the inverter phase-locked grid connection process; some schemes using high-voltage charging have a faster speed and a stronger resistive pre-charging power capacity, and are prone to the risk of bus overshoot damage.

[0080] In the embodiment of the present application, the DC bus capacitor 200 is charged by the first charging circuit 10 according to the first pre-charging stage and the second pre-charging stage. In the first pre-charging stage, the voltage of the DC bus capacitor 200 is charged from the starting voltage value to the first target voltage. In the second pre-charging stage, the voltage is boosted and the voltage of the DC bus capacitor 200 is charged from the first target voltage to the second target voltage. The first charging circuit 10 has a boosting function, and the bus capacitor voltage is increased in stages. The boosting process is flexible and controllable, and can effectively boost the bus capacitor voltage, so that the pre-charged bus capacitor voltage is higher than the 600 AC peak voltage of the power grid, preventing the formation of rectifier impact current when the relay closes during the subsequent grid connection process, and effectively reducing the risk of insufficient inverter voltage during the inverter phase-locked grid connection process.

[0081] According to the power supply device provided by the embodiment of the present application, the control unit controls the first charging circuit 10 to charge the DC bus capacitor 200 according to the first pre-charging stage and the second pre-charging stage, increases the bus capacitor voltage in stages, and pre-charges the voltage of the DC bus capacitor 200 to the second target voltage higher than the 600 voltage of the power grid, which can effectively boost the bus capacitor voltage, effectively reduce the risk of insufficient inverter voltage during the inverter phase-locked grid connection process, and realize the safe and reliable AC pre-charging start of the power supply device.

[0082] In the embodiment of the present application, the first charging circuit 10 may be a boosting circuit 310, a charge pump circuit 410 and other circuits with a boosting function. The following will specifically describe the embodiment of the present application from two different implementation perspectives.

[0083] 1. The first charging circuit 10 includes a boosting circuit 310.

[0084] In some embodiments, the first charging circuit 10 includes a boosting circuit 310. The input end of the boosting circuit 310 is connected to the photovoltaic power generation component 320. The power supply device is used to convert the direct current generated by the photovoltaic power generation component 320 into alternating current. The input end of the boosting circuit 310 is connected in parallel with the input end capacitor 330.

[0085] In this embodiment, the boost circuit 310 that the power supply device such as a photovoltaic inverter itself has is used as the boost function module of the first charging circuit 10 to boost the voltage of the bus capacitor, so that the bus capacitor voltage can be adjusted within a certain range, without introducing additional high-power devices, thus realizing adjustable pre-charge voltage, making the bus capacitor voltage after pre-charge higher than the AC peak voltage of the power grid 600, and effectively reducing the hardware cost of the AC startup of the power supply device.

[0086] It can be understood that, as Figure 1 shown, for power supply devices such as photovoltaic inverters, multiple boost circuits 310 can be set to achieve maximum power point (MPPT) tracking. The boost circuit 310 can adjust the operating point of the photovoltaic power generation module 320 to make its output maximum power, effectively improving the power generation efficiency of the photovoltaic power generation module 320.

[0087] In this embodiment, the control unit is used to control the first charging circuit 10 to charge the input terminal capacitor 330 and the DC bus capacitor 200 in the first pre-charge stage. The control unit is also used to control the boost circuit 310 to perform a boost conversion when the voltage of the input terminal capacitor 330 reaches the first target voltage, and charge the voltage of the DC bus capacitor 200 to the second target voltage through the input terminal capacitor 330 in the second pre-charge stage.

[0088] In the first pre-charge stage, the first charging circuit 10 can use the AC side energy to charge the input terminal capacitor 330 connected in parallel to the input end of the boost circuit 310 and the DC bus capacitor 200 at the same time. The input terminal capacitor 330 connected in parallel to the boost circuit 310 performs passive rectification pre-charge, and the voltages of the input terminal capacitor 330 and the DC bus capacitor 200 are monitored in real time. When the voltage of the input terminal capacitor 330 reaches the first target voltage, the boost circuit 310 can achieve the boost function, that is, the control unit can control the first charging circuit 10 to enter the second pre-charge stage.

[0089] In actual execution, when the voltage of the input terminal capacitor 330 reaches the first target voltage, the first target voltage can be the AC peak voltage of the power grid 600 minus a set threshold, and the set threshold can be within 20V.

[0090] It can be understood that the input terminal capacitor 330 is connected in parallel to the input end of the boost circuit 310, and the DC bus capacitor 200 is connected in parallel to the output end of the boost circuit 310. In the first pre-charge stage, the boost circuit 310 is not started, the voltage of the input terminal capacitor 330 is charged to the first target voltage, and the DC bus capacitor 200 can also be charged to the first target voltage.

[0091] In the second pre-charging stage, the control unit controls the boost circuit 310 to perform a boost conversion, and realizes the boost control of the bus capacitor voltage through the input capacitor 330. The boost circuit 310 performs an active boost pre-charging to charge the voltage of the DC bus capacitor 200 to the second target voltage. After that, the control unit can control the power conversion circuit 100 to perform an inversion output, phase-lock the voltage of the power grid 600, and close the grid-connected relay to realize the AC startup of the power supply device.

[0092] As Figure 9 shown, in the first pre-charging stage, the first charging circuit 10 can use the AC-side energy to charge the input capacitor 330 connected in parallel to the input end of the boost circuit 310 and the DC bus capacitor 200 simultaneously. When the voltage of the input capacitor 330 reaches V1, it enters the second pre-charging stage; in the second pre-charging stage, the control unit controls the boost circuit 310 to perform a boost conversion, and realizes the boost control of the bus capacitor voltage through the input capacitor 330, and charges the voltage of the DC bus capacitor 200 to the second target voltage V2.

[0093] Among them, the second target voltage V2 is slightly higher than the voltage V4 of the power grid 600. After the power conversion circuit 100 is started, the voltage of the DC bus capacitor 200 can be stabilized at V4.

[0094] It can be understood that between the AC output end of the power grid 600 and the boost circuit 310, there may also be devices such as a rectification module 340, a first current-limiting charging device 350, and a switching device, constituting the first charging circuit 10 that realizes boosting through the boost circuit 310 to realize the pre-charging of the DC bus capacitor 200.

[0095] In some embodiments, the first charging circuit 10 may further include a rectification module 340.

[0096] In this embodiment, the rectification module 340 is arranged between the boost circuit 310 and the power grid 600. The rectification module 340 is used to convert the alternating current output by the power grid 600 into direct current to charge the input capacitor 330 and the DC bus capacitor 200.

[0097] In some embodiments, the first charging circuit 10 further includes a first current-limiting charging device 350.

[0098] In this embodiment, the first current-limiting charging device 350 is arranged between the boost circuit 310 and the power grid 600. The first current-limiting charging device 350 can limit the current for charging the input capacitor 330 and the DC bus capacitor 200.

[0099] As Figure 2As shown, the first charging circuit 10 includes a boost circuit 310, an input terminal capacitor 330, a rectification module 340, and a first current-limiting charging device 350. Among them, the rectification module 340 may include diodes D1 and D2. Through the cooperation of D1 and D2, it allows current to pass unidirectionally and converts alternating current into direct current.

[0100] The first current-limiting charging device 350 may include resistors R1 and R2, and the input terminal capacitor 330 and the DC bus capacitor 200 are charged with current limited by R1 and R2.

[0101] As Figure 3 shown, the output terminal of the boost circuit 310 is connected in parallel with the DC bus capacitor 200, and the input terminal of the boost circuit 310 is connected in parallel with the input terminal capacitor 330. The alternating current of the power grid 600 passes through the first current-limiting charging device 350 and the rectification module 340 to achieve current-limiting charging of the input terminal capacitor 330 and the DC bus capacitor 200.

[0102] In some embodiments, a first unidirectional conduction device 360 is provided between the photovoltaic power generation module 320 and the boost circuit 310, and the conduction direction of the first unidirectional conduction device 360 is from the photovoltaic power generation module 320 to the boost circuit 310.

[0103] In this embodiment, as Figure 1 shown, setting the first unidirectional conduction device 360 with the conduction direction from the photovoltaic power generation module 320 to the boost circuit 310 between the photovoltaic power generation module 320 and the boost circuit 310 can prevent the output terminal of the photovoltaic power generation module 320 corresponding to the boost circuit 310 from being charged, and avoid damaging the photovoltaic power generation module 320.

[0104] In some other embodiments, a first switching device may be provided between the photovoltaic power generation module 320 and the boost circuit 310, and the first switching device is used to control the on-off of the line between the photovoltaic power generation module 320 and the boost circuit 310.

[0105] Among them, the first switching device may be a mechanical switch or a semiconductor switch.

[0106] In this embodiment, by setting the first switching device that can control the on-off of the line between the photovoltaic power generation module 320 and the boost circuit 310, when charging the DC bus capacitor 200 through the boost circuit 310, the line between the photovoltaic power generation module 320 and the boost circuit 310 is disconnected to protect the photovoltaic power generation module 320.

[0107] It can be understood that one or more switching devices may be provided in the first charging circuit 10, and the control unit controls the actions of these switching devices to achieve the control of the first pre-charge stage and the second pre-charge stage of the power supply device.

[0108] Taking the power supply device as an inverter as an example, a specific embodiment will be introduced below.

[0109] As Figure 2 shown, the power supply device includes four relays K8, K9, K10, and K11. The rectification module 340 may include diodes D1 and D2. The first current-limiting charging device 350 may include resistors R1 and R2. K10 is connected in parallel with R1, K11 is connected in parallel with R2, K8 is connected in series with R1, and K9 is connected in series with R2.

[0110] The grid-connected relays of the power supply device include K1, K2, K3, K4, K5, and K6. One end of a branch of the first charging circuit 10 is connected between K2 and K5, and the other end of the other branch is connected between K3 and K6.

[0111] As Figure 4 shown, close the relays K2, K3, K8, and K9 to conduct the line between the power grid 600 and the first charging circuit 10, and perform current-limiting charging on the input capacitor 330 and the DC bus capacitor 200 through R1, R2, D1, and D2 to achieve rapid preliminary charging in the first pre-charge stage.

[0112] When the voltage of the input capacitor 330 reaches the amplitude of the AC peak voltage minus the first preset value (i.e., the first target voltage), close K10 and K11 to bypass R1 and R2. The first charging circuit 10 forms a low-impedance pre-charge channel. Closing K10 and K11 can reduce the heat capacity of R1 and R2, and reduce the device volume and cost.

[0113] It can be understood that K10 and K11 are optional switches.

[0114] Start the MPPT circuit (i.e., the boost circuit 310) for pre-charge boost to achieve the boost conversion from the input capacitor 330 to the DC bus capacitor 200, and make the voltage of the DC bus capacitor 200 reach a second preset voltage value higher than the pre-charge rectification (i.e., a second target voltage higher than the voltage of the power grid 600). This second preset voltage value is suitable for the inverter control of the power conversion circuit 100.

[0115] Start the inverter, drive the output port voltage of the inverter to follow the voltage of the power grid 600 to achieve phase locking. At the same time, detect the voltages on both sides of the grid-connected relays (the remaining unclosed K1, K4, K5, and K6). When the instantaneous voltage difference between the two is less than the preset value, close K1, K4, K5, and K6 to achieve grid connection.

[0116] Turn off the MPPT drive, control the boost circuit 310 to stop boosting, and disconnect all the pre-charge related relays K8, K9, K10, and K11.

[0117] It should be noted that the AC input port of the first charging circuit 10 is flexible in power taking. It can be two phase lines or one phase line plus one N line.

[0118] In some embodiments, the AC input of the first charging circuit 10 takes power from the N phase of the power grid 600. As Figure 5 shown, the line where R2 is located takes power from the N phase of the power grid 600; as Figure 6 shown, the DC output of the line where R2 is located can also be connected to the positive DC bus.

[0119] In some embodiments, as Figure 7 shown, the rectification module 340 can be a full-wave passive rectification circuit.

[0120] In some other embodiments, the rectification module 340 can also be a full-wave active rectification circuit.

[0121] It can be understood that the rectification module 340 can realize the conversion from alternating current to direct current, and the selected circuit can be determined according to the specific type of the power supply device.

[0122] In some embodiments, as Figure 8 shown, components such as the inductor of the boost circuit 310 can also be located on the negative DC bus, that is, different types of boost circuits 310 are all adapted to charge the DC bus capacitor 200.

[0123] In the related art, there is a problem that the current-limiting resistor continuously bears power loss during the inverter phase-locked grid connection process. When the voltage stability of the power grid 600 is not good, there are many harmonics, or the grid connection judgment time is long, the current-limiting resistor is prone to overheat and damage; at the same time, the bus voltage is not adjustable, greatly affected by the fluctuation of the power grid 600, the ability to boost the bus voltage is limited or the boost is too high, there is a risk of damaging the bus capacitor, which hinders the grid adaptation ability of the power supply device.

[0124] In the embodiments of the present application, in the first pre-charge stage, the voltage of the DC bus capacitor 200 is charged in a current-limited manner to the first target voltage. In the second pre-charge stage, the boost circuit 310 is started to boost the voltage, and the voltage of the DC bus capacitor 200 is charged from the first target voltage to the second target voltage. After the boost circuit 310 starts to boost, the current-limiting resistor in the first charging circuit 10 can be bypassed to prevent the current-limiting resistor from overheating due to continuous power loss. The boost circuit 310 boosts the voltage so that the voltage of the DC bus capacitor 200 is adjustable. The boost circuit 310 takes the input capacitor 330 at the input end, is less affected by the fluctuation of the power grid 600, can effectively boost the bus voltage, reduce the damage risk of the DC bus capacitor 200, and improve the grid adaptation ability of the power supply device.

[0125] Second, the first charging circuit 10 includes a charge pump circuit 410.

[0126] In some embodiments, the first charging circuit 10 includes a charge pump circuit 410. The charge pump circuit 410 has a charge pump capacitor 420. The switching cycle of the charge pump circuit 410 includes a charging stage and a discharging stage. In the charging stage, the power grid 600 charges the charge pump capacitor 420. In the discharging stage, the power grid 600 and the charge pump capacitor 420 charge the DC bus capacitor 200.

[0127] Among them, the charge pump circuit 410 is a circuit that uses capacitors and switching elements to achieve voltage conversion, and can increase or decrease the input voltage through periodic charging and discharging operations.

[0128] As Figure 10 shown, one end of the charge pump circuit 410 is connected to the power grid 600, and the other end is connected to the DC bus capacitor 200. In the charging stage, the power grid 600 charges the charge pump capacitor 420. In the discharging stage, the power grid 600 and the charge pump capacitor 420 charge the DC bus capacitor 200.

[0129] It can be understood that the DC bus capacitor 200 is arranged between the DC input end 110 of the power supply device and the power conversion circuit 100. The DC input end 110 can be connected to devices such as a photovoltaic power generation module 320 and an energy storage unit.

[0130] The control unit is used to control the charge pump circuit 410 to be connected between the DC bus capacitor 200 and the power grid 600 when the voltage of the DC bus capacitor 200 reaches a first target voltage, and charge the voltage of the DC bus capacitor 200 to a second target voltage through the charge pump capacitor 420 in the second pre-charging stage.

[0131] In the first pre-charging stage, the first charging circuit 10 can charge the DC bus capacitor 200 using the AC side energy, and monitor the voltage of the DC bus capacitor 200 in real time. When the voltage of the DC bus capacitor 200 reaches the first target voltage, the charge stored in the charge pump capacitor 420 during the positive half-cycle (or negative half-cycle) of the AC power grid 600 can be used to achieve the boosting function of the charge pump circuit 410, that is, the control unit can control the first charging circuit 10 to enter the second pre-charging stage.

[0132] In actual implementation, when the voltage of the DC bus capacitor 200 reaches the first target voltage, the first target voltage can be the AC peak voltage of the power grid 600 minus a set threshold, and the set threshold can be 10V - 20V.

[0133] In the second pre-charging stage, the control unit controls the charge pump capacitor 420 to discharge, and charges the DC bus capacitor 200 with the charge provided by the charge pump capacitor 420 to achieve the boosting function, so that the voltage of the DC bus capacitor 200 can be charged to a second target voltage higher than the voltage of the power grid 600.

[0134] In this embodiment, through the charge pump circuit 410, the boost pre-charging of the bus is simply and reliably realized. The resistive loss generated by the charge pump circuit 410 when maintaining the voltage of the bus is much smaller than that of a conventional pre-charging current-limiting resistor. The power supply device is not limited by the heat capacity of the conventional current-limiting resistor method and can continuously withstand power loss without device damage, reducing the time limit in the inverter grid-connection stage and relaxing the power loss requirement in the pre-charging stage, making the inverter grid-connection control of the power supply device more flexible.

[0135] In some embodiments, the first charging circuit 10 has a second current-limiting charging device 430, and the control unit is configured to control the first charging circuit 10 to charge the voltage of the DC bus capacitor 200 to a first target voltage through the second current-limiting charging device 430 in the first pre-charging stage.

[0136] In this embodiment, in the first pre-charging stage, the charging of the DC bus capacitor 200 is achieved through the current-limiting charging loop formed by the second current-limiting charging device 430, and the voltage of the DC bus capacitor 200 can be safely and quickly charged to the first target voltage. After the voltage of the DC bus capacitor 200 reaches the first target voltage, the control unit then switches the switch to introduce the charge pump capacitor 420 of the charge pump circuit 410 to achieve boosting to the second target voltage in the second pre-charging stage.

[0137] In actual implementation, the second current-limiting charging device 430 can be a device such as a resistor that can achieve current-limiting charging.

[0138] It should be noted that the second current-limiting charging device 430 can be disposed in the charge pump circuit 410. In the first pre-charging stage, the second current-limiting charging device 430 is connected between the power grid 600 and the DC bus capacitor 200 to charge the DC bus capacitor 200 using the energy on the AC side. In the second pre-charging stage, through the switching of the switch, the second current-limiting charging device 430 is cut out from between the power grid 600 and the DC bus capacitor 200, and the charge pump capacitor 420 is used for boosting.

[0139] In some embodiments, the control unit is configured to control the first charging circuit 10 to charge the voltage of the DC bus capacitor 200 to a first target voltage through the charge pump circuit 410 in the first pre-charging stage.

[0140] In this embodiment, in the first pre-charging stage, the voltage of the DC bus capacitor 200 is charged to the first target voltage through the charge pump circuit 410, which is applicable to power supply devices that cannot add current-limiting charging devices such as resistors. After the voltage of the DC bus capacitor 200 reaches the first target voltage, the control unit then switches the switch to introduce the charge pump capacitor 420 of the charge pump circuit 410 to achieve boosting to the second target voltage in the second pre-charging stage.

[0141] In some embodiments, a voltage limiter device 440 is connected in parallel with the DC bus capacitor 200. The voltage limiter device 440 is used to balance the amount of charge input to the DC bus capacitor 200 by the charge pump capacitor 420 during the discharge phase, so as to limit the voltage of the DC bus capacitor 200.

[0142] In this embodiment, a voltage limiter device 440 is connected in parallel with the DC bus capacitor 200 to limit the maximum charging voltage that the DC bus capacitor 200 can be charged to. When the voltage of the DC bus capacitor 200 rises, the voltage limiter device 440 generates a higher discharge current, which can offset the amount of charge pumped into the bus by the charge pump from the perspective of cycle average, so that the DC bus capacitor 200 will not experience overvoltage when the AC grid 600 is at a high voltage, providing a passive and safe boost pre-charging method.

[0143] In actual implementation, the voltage limiter device 440 can be an additional resistor, or power-consuming devices such as an auxiliary source and a sampling resistor connected in parallel to the DC bus.

[0144] It should be noted that according to the charge pump principle, the charge pump circuit 410 can provide a limited and controllable amount of charge in each power frequency cycle. The amount of charge Qc provided by the charge pump circuit 410 in each power frequency cycle is determined according to the capacitance C of the charge pump capacitor 420, the effective value Vac of the AC waveform voltage of the grid 600, and the voltage Vbus of the DC bus capacitor 200.

[0145] Taking the voltage limiter device 440 as a resistor Rd as an example, the amount of charge Qd released in the power frequency cycle is related to the voltage Vbus of the DC bus capacitor 200 and the resistance value of the voltage limiting resistor Rd. By adjusting the resistance value of the resistor Rd according to the amount of charge Qc, it is possible to prevent the DC bus capacitor 200 from being overcharged even when the effective value Vac of the AC waveform voltage is too high.

[0146] At the same time, the setting of the resistance value of the resistor Rd is such that when the effective value Vac of the AC waveform voltage is at its minimum, the maximum voltage that the charge pump circuit 410 can pre-charge is greater than the second target voltage.

[0147] In some embodiments, the charge pump capacitor 420 and the AC filter capacitor of the power supply device are the same capacitor.

[0148] In this embodiment, the charge pump capacitor 420 used by the charge pump circuit 410 can be shared with the AC filter capacitor of the power supply device. By using the original AC filter capacitor of the power supply device, the voltage of the DC bus capacitor 200 is lifted, so that the voltage of the pre-charged bus capacitor is higher than the AC peak voltage of the grid 600, which is beneficial to reducing the volume of the circuit and the cost.

[0149] Next, taking the power supply device as an inverter as an example, a specific embodiment will be introduced.

[0150] As Figure 10 shown, one end of the charge pump circuit 410 is connected to the power grid 600, and the other end is connected to the DC bus capacitor 200. The resistor Rd, which serves as the voltage limiter 440, is connected in parallel with the DC bus capacitor 200.

[0151] As Figure 11 shown, the charge pump circuit 410 includes C1 as the charge pump capacitor 420, and R1, which serves as the second current-limiting charging device 430, is disposed in the charge pump circuit 410. The charge pump circuit 410 may further include switching devices such as K1, K2, and K3, and unidirectional conduction devices such as diodes D1 and D2 that control the current flow direction.

[0152] As Figure 14 shown, in the first pre-charging stage, when Kg1, Kg2, K1, and K2 are closed, a resistor current-limiting pre-charging path is formed by D1, D2, and R1, and the voltage of the DC bus capacitor 200 can be charged to the peak AC voltage minus the first preset voltage (10V - 20V), reaching the V1 voltage value (i.e., the first target voltage) in the waveform diagram as shown in Figure 9 shown.

[0153] In actual implementation, due to the limitation of the current by the charge pump capacitor 420, the charge pump capacitor 420 can be used to charge the DC bus capacitor 200 in the first pre-charging stage and the second pre-charging stage. At this time, the role of R1 is to damp the oscillating current of C1, which is different from the pre-charging resistor.

[0154] K2 is disconnected and K3 is closed, and C1 is connected to the charging circuit. As Figure 12 shown, C1 and D2 form a charge pump charging circuit, and C1 can be charged to the peak AC voltage during the negative half-cycle of the AC power grid 600. Here, Cbus represents the DC bus capacitor 200.

[0155] K3 is disconnected. As Figure 13 shown, C1, D1, and the DC bus capacitor 200 form a charge pump discharging circuit, and C1 charges the DC bus capacitor 200 during the positive half-cycle of the AC power grid 600, which can achieve the boosting effect. Here, Cbus represents the DC bus capacitor 200.

[0156] According to the charge pump principle, the charge pump circuit 410 can pre-charge the voltage of the DC bus capacitor 200 to 2 times the peak AC voltage. The boosting of the charge pump circuit 410 is to prepare for the inversion, phase locking, and grid connection of the power supply device. When the voltage of the DC bus capacitor 200 is pre-charged to Figure 9 the V2 (i.e., the second target voltage) as shown in

[0157] shown, the inversion and grid connection control can be started in terms of control. If the inversion does not start after the voltage of the DC bus capacitor 200 reaches V2, the voltage of the DC bus capacitor 200 will followFigure 9 The middle dotted line continues to rise until it stops rising after reaching the V3 voltage controlled by Rd.

[0158] In actual implementation, Rd does not have to be an additional resistor. It can be various power-consuming devices such as auxiliary power sources and sampling resistors connected in parallel to the bus.

[0159] After the voltage of the DC bus capacitor 200 is charged to the preset value V2, the inverter is started, and the voltage at the output port of the inverter is driven to follow the voltage of the power grid 600 to achieve phase locking. At the same time, the voltages on both sides of the grid-connected relay are detected. When the instantaneous voltage difference between the two is less than the preset value, the grid-connected relay is closed to achieve grid connection of the inverter.

[0160] It can be understood that since there are no high-loss devices in the charge pump circuit 410 itself, it is not necessary to turn off the pre-charging related switches during the grid connection stage. The bus voltage can be balanced according to the charge relationship and will not drop rapidly, providing sufficient control time for inversion and grid connection and improving the success rate of grid connection.

[0161] During inversion, the voltage at the output end of the power conversion circuit 100 is gradually boosted. When the voltages on both sides of the three phases are boosted to the same level, that is, when the voltage difference between both sides of the grid-connected relays Kg1, Kg2, Kg3, Kg4, Kg5, Kg6 is close to 0, the remaining unclosed grid-connected relays Kg3, Kg4, Kg5, Kg6 are closed, and the grid-connected relay closing operation can be performed to complete the grid connection step.

[0162] Finally, all pre-charging related relays K1, K2, K3 are disconnected to end the pre-charging process.

[0163] It can be understood that the charge pump circuit 410 has a flexible configuration. For example, Figure 15 as shown, an R2 can also be added to the charge pump circuit 410 as the second current-limiting charging device 430. During the first pre-charging stage, the DC bus capacitor 200 is charged by R1 and R2.

[0164] In some embodiments, for example, Figure 16 as shown, C1 is both the charge pump capacitor 420 and the AC filter capacitor of the power supply device. The charge pump capacitor 420 used in the charge pump circuit 410 can be shared with the AC filter capacitor of the power supply device, which is beneficial to reducing the volume of the circuit and the cost.

[0165] In some embodiments, for example, Figure 17 as shown, C1 is the charge pump capacitor 420. The boosting of the DC bus capacitor 200 by the charge pump circuit 410 is also applicable to single-phase inverters.

[0166] In the related art, during the process of inverter phase-locked grid connection, there is a problem that the current-limiting resistor continuously bears power loss. When the grid voltage stability is poor, there are many harmonics, or the grid connection judgment time is long, the current-limiting resistor is prone to overheat and damage; at the same time, the bus voltage is not adjustable, is greatly affected by the grid voltage fluctuation, has limited ability to boost the bus voltage or boosts too high, and there is a risk of damaging the bus capacitor, which hinders the grid voltage adaptation ability of the system.

[0167] In the embodiment of the present application, in the first pre-charge stage, the voltage of the DC bus capacitor 200 is current-limitingly charged to the first target voltage by using the charge pump circuit 410 or the second current-limiting charging device 430. In the second pre-charge stage, the charge pump circuit 410 is used for boosting, and the voltage of the DC bus capacitor 200 is charged from the first target voltage to the second target voltage. The second current-limiting charging device 430 only works in part of the pre-charge stage, which can prevent the current-limiting resistor from overheating due to continuously bearing power loss. The charge pump capacitor 420 of the charge pump circuit 410 can provide the charge quantity for charging the voltage of the DC bus capacitor 200 to be higher than the peak value of the grid voltage, which can effectively boost the bus voltage. There is no high-loss device in the charge pump circuit 410 itself. During the grid connection stage, the bus voltage can be balanced according to the charge relationship and will not drop rapidly, providing sufficient control time for inversion and grid connection, improving the success rate of grid connection, and improving the grid voltage adaptation ability of the power supply device.

[0168] Insulation impedance detection between the power supply device and the ground is a key step to ensure the safe operation of the power system. By detecting the insulation impedance between the power supply device and the ground, problems such as insulation aging and damage can be detected in time, and serious accidents such as electric leakage, short circuit, and even fire caused by insulation failure can be avoided. Good insulation performance can also improve the working efficiency of the power supply device, extend the service life of the device, and ensure the safety of personnel and equipment.

[0169] In the related art, for insulation impedance detection, detection methods such as unbalanced bridges are usually adopted, which require adding more resistors and relays.

[0170] The power supply device in the embodiment of the present application can not only meet the AC start pre-charge requirements, but also perform insulation detection during the pre-charge stage of the DC bus capacitor 200 without adding more resistors and relays. After the pre-charge and insulation detection are completed, a low-impedance voltage-holding circuit is constructed, and the lowest bus voltage is used for inverter phase-locking, and finally the grid connection relay is closed to realize the grid connection of the power supply device.

[0171] In some embodiments, the DC bus capacitor 200 includes a first half-bus capacitor 210 and a second half-bus capacitor 220 connected in series, and the first half-bus capacitor 210 and the second half-bus capacitor 220 are connected to the bus capacitor midpoint 230.

[0172] In this embodiment, as Figure 18 shown, the power supply device further includes a second charging circuit 710. One end of the second charging circuit 710 is connected to the midpoint 230 of the bus capacitor, and the other end is used to be connected to the power grid 600. The second charging circuit 710 is provided with an insulation impedance detection circuit 720 grounded.

[0173] The control unit is connected to the second charging circuit 710. The control unit is used to control the first charging circuit 10 and the second charging circuit 710 to first charge the first half bus capacitor 210, and then charge the first half bus capacitor 210 and the second half bus capacitor 220, and perform insulation impedance detection through the insulation impedance detection circuit 720.

[0174] In this embodiment, through the first charging circuit 10 and the second charging circuit 710, the first half bus capacitor 210 and the second half bus capacitor 220 can be independently charged, and the charging of the upper and lower half bus capacitors is decoupled. By first charging the first half bus capacitor 210 to form a voltage difference between the two half bus capacitors, the bus-to-ground insulation impedance detection is realized in the pre-charging stage.

[0175] In actual implementation, the first charging circuit 10 can provide a voltage holding path with a lower impedance during the inverter grid connection process, so that the voltage of the DC bus capacitor 200 will not drop rapidly, ensuring the normal execution of phase locking and grid connection relay closing.

[0176] In some embodiments, the first charging circuit 10 is further provided with a third current-limiting charging device 730.

[0177] Among them, the third current-limiting charging device 730 can be a device such as a resistor that can achieve current-limiting charging.

[0178] In actual implementation, the third current-limiting charging device 730 can also be connected in parallel with a switching device. After the first half bus capacitor 210 and the second half bus capacitor 220 are pre-charged to the target voltage, the switching device connected in parallel with the third current-limiting charging device 730 can be closed to reduce the loop impedance of the AC port supplying power to the DC bus during the subsequent grid connection control process, ensure the safety of the third current-limiting charging device 730, and eliminate the operation time limit of the subsequent inverter and grid connection control steps.

[0179] It can be understood that the first charging circuit 10 and the second charging circuit 710 draw power from two to three ports of the power grid 600. The first charging circuit 10 and the second charging circuit 710 can form a loop for separately charging the first half-bus capacitor 210, or they can also form a loop for charging the first half-bus capacitor 210 and the second half-bus capacitor 220. The charging process of the half-bus capacitor is independently controllable. The first charging circuit 10 and the second charging circuit 710 can form a decoupled charging path to meet the requirements of ground insulation impedance detection.

[0180] In actual implementation, the second charging circuit 710 can be provided with devices such as current-limiting charging devices and switching devices, and cooperate with the first charging circuit 10 to form a decoupled charging path.

[0181] In some embodiments, the control unit is configured to control the second charging circuit 710 to disconnect when the voltage of the first half-bus capacitor 210 reaches the first target voltage, and obtain first detection data of the first half-bus capacitor 210 and the insulation impedance detection circuit 720.

[0182] The control unit is further configured to control the second charging circuit 710 to disconnect when the voltages of the first half-bus capacitor 210 and the second half-bus capacitor 220 both reach the first target voltage, and obtain second detection data of the first half-bus capacitor 210, the second half-bus capacitor 220, and the insulation impedance detection circuit 720. The first detection data and the second detection data are used to determine the insulation impedance detection result.

[0183] It can be understood that the insulation impedance detection circuit 720 can include sensors for measuring data such as voltage and current. By collecting data such as voltage and current, the first detection data and the second detection data are obtained, and the insulation impedance detection result of the power supply device is obtained.

[0184] In this embodiment, the control unit first controls the switching devices on the first charging circuit 10 and the second charging circuit 710 to form a charging loop from the power grid 600 to the first half-bus capacitor 210, and charges the first half-bus capacitor 210. When the voltage of the first half-bus capacitor 210 reaches the first target voltage, the control unit controls the second charging circuit 710 to disconnect, that is, disconnects the charging loop from the power grid 600 to the first half-bus capacitor 210, and performs the first insulation impedance detection through the insulation impedance detection circuit 720 to obtain the first detection data corresponding to the first half-bus capacitor 210.

[0185] The control unit then forms a charging loop from the power grid 600 to the DC bus capacitor 200 (including the first half bus capacitor 210 and the second half bus capacitor 220 connected in series) by controlling the switching devices on the first charging circuit 10 and the second charging circuit 710, and charges the first half bus capacitor 210 and the second half bus capacitor 220 simultaneously. When the voltages of both the first half bus capacitor 210 and the second half bus capacitor 220 reach the first target voltage, the control unit disconnects the second charging circuit 710, that is, disconnects the charging loop from the power grid 600 to the DC bus capacitor 200, and performs a second insulation impedance detection through the insulation impedance detection circuit 720 to obtain the second detection data corresponding to the first half bus capacitor 210 and the second half bus capacitor 220.

[0186] In this embodiment, the insulation impedance of the power supply device is calculated by integrating the first detection data and the second detection data, and the ground insulation detection of the power supply device can be realized during the pre-charging stage of the DC bus capacitor 200 without adding many resistors and relays.

[0187] It should be noted that for the DC bus capacitor 200, the ground insulation detection of the power supply device can be realized in the first pre-charging stage. First, the first half bus capacitor 210 is independently charged. When the voltage of the first half bus capacitor 210 reaches the first target voltage, the first insulation detection is performed to obtain the first detection data. Then, the first half bus capacitor 210 and the second half bus capacitor 220 are charged. When both the first half bus capacitor 210 and the second half bus reach the first target voltage (i.e., the voltage of the DC bus capacitor 200 reaches the first target voltage in the first pre-charging stage), the second insulation detection is performed to obtain the second detection data. Subsequently, in the second pre-charging stage, the first half bus capacitor 210 and the second half bus capacitor 220 are boosted and charged to charge the voltage of the DC bus capacitor 200 to a second target voltage higher than the voltage of the power grid 600.

[0188] Next, taking the power supply device as an inverter as an example, a specific embodiment is introduced.

[0189] As Figure 19 shown, the power supply device includes a first charging circuit 10 and a second charging circuit 710. The first charging circuit 10 is provided with Rp1 and Rp2 as the third current-limiting charging devices 730. Rp1 is connected in parallel with the switch Kk1, and Rp2 is connected in parallel with the switch Kk2. The branch where Rp1 is located is connected in series with the switch Kp1, and the branch where Rp2 is located is connected in series with the switch Kp2.

[0190] The branch where Rp1 is located is also provided with a diode Dp1, and the branch where Rp2 is located is also provided with a diode Dp2 to limit the current direction between the power grid 600 and the DC bus capacitor 200 through Dp1 and Dp2.

[0191] The second charging circuit 710 is provided with switches Kn1 and Kn2 connected in series. One end of the second charging circuit 710 is connected to the power grid 600, and the other end is connected to the midpoint 230 of the bus capacitor.

[0192] The DC bus capacitor 200 of the power supply device includes Cb2 as the first half bus capacitor 210 and Cb1 as the second half bus capacitor 220. Cb2 and Cb1 are connected to the midpoint 230 of the bus capacitor.

[0193] The second charging circuit 710 is provided with a grounded insulation impedance detection circuit 720. One end of the insulation impedance detection circuit 720 is grounded, and the other end is connected between Kn1 and Kn2. The insulation impedance detection circuit 720 includes a resistor Rt.

[0194] As Figure 22 shown, at the initial stage of charging, Kn1 and Kn2 are closed to turn on the second charging circuit 710, Kp2 and the grid-connected relay Kg2 are closed to turn on a branch of the first charging circuit 10, forming a current-limiting pre-charging channel for the AC power grid 600 to charge Cb2 via Rp2 and Dp2, that is, to charge the first half bus capacitor 210 first.

[0195] The pre-charging cut-off voltage of Cb2 is the AC peak voltage minus the first preset voltage (10V - 20V). When the voltage of Cb2 is charged to the AC peak voltage minus the first preset voltage, that is, when the voltage of the first half bus capacitor 210 reaches the first target voltage, Kn1 and Kp2 are disconnected, and the voltage across the Rt resistor and the voltage of Cb2 are synchronously measured and recorded to form the first data set for insulation impedance calculation, that is, the first detection data.

[0196] After that, Kn1 is closed to turn on the second charging circuit 710 again, Kp2, Kp1 and the grid-connected relay Kg1 are closed to turn on two branches of the first charging circuit 10, and Cb1 and Cb2 are pre-charged through Rp1, Dp1, Rp2 and Dp2, that is, Cb1 and Cb2 are pre-charged, and the pre-charging cut-off voltage is the AC peak voltage minus the first preset voltage.

[0197] When the capacitor voltages of Cb1 and Cb2 reach the AC peak voltage minus the first preset voltage of their respective corresponding phases, it indicates that the charging in the first pre-charging stage is completed, and the DC bus capacitor 200 has been charged to the first target voltage.

[0198] Kn1, Kp1 and Kp2 are disconnected, that is, the first charging circuit 10 and the second charging circuit 710 are disconnected, and the voltage across the Rt resistor and the voltages of Cb1 and Cb2 are synchronously measured and recorded to form the second data set for insulation impedance calculation, that is, the second detection data, and the insulation impedance is calculated in combination with the first data set.

[0199] When performing the first insulation detection, after the voltage Vc1 of Cb2 is charged to the AC peak voltage minus the first preset voltage, disconnect Kn1 and Kp2, and synchronously measure and record the voltage across the Rt resistor and the voltage of Cb2. The equivalent topology of the first state of the insulation detection is as Figure 20 shown, where Rx is the insulation impedance of the positive bus to ground, and Ry is the insulation impedance of the negative bus to ground.

[0200] When performing the second insulation detection, after the voltages Vc2 of Cb1 and Vc3 of Cb2 are both charged to the AC peak voltage minus the first preset voltage, disconnect Kn1, Kp1, and Kp2, and synchronously measure and record the voltage across the Rt resistor and the voltages of Cb1 and Cb2. The equivalent topology of the second state of the insulation detection is as Figure 21 shown, where Rx is the insulation impedance of the positive bus to ground, and Ry is the insulation impedance of the negative bus to ground.

[0201] According to Vc1, Vc2, Vc3, and the voltage across the Rt resistor, the insulation impedance of the positive bus of the power supply device to ground and the insulation impedance of the negative bus to ground can be calculated through the equivalent topology, completing the insulation impedance detection of the power supply device to ground.

[0202] It should be noted that Figure 19 Db1 and Db2 shown are anti-reverse bypass diodes of the DC bus capacitor 200. Generally, this diode is inherent in the power topology. If it is not available, it needs to be added additionally, and only diodes with a current capacity of several amperes are required.

[0203] After completing the insulation impedance detection to ground, Kn1, Kp2, and Kp1 can be closed to pre-charge Cb1 and Cb2 to compensate for the voltage that may be lost by the DC bus capacitor 200 during the insulation impedance detection. The pre-charge cut-off voltage is the AC peak voltage minus the first preset voltage, that is, the first target voltage. Then, close the Kk1 and Kk2 relays to form a low-impedance channel and constitute a low-impedance rectification circuit between the AC grid 600 and the DC bus, preparing for the next step of the inverter operation of the power conversion circuit 100.

[0204] After the DC bus capacitor 200 is pre-charged, the inverter can be started. Adopt a low dead-time control method or a modulation method with high bus voltage utilization rate to drive the output port voltage of the inverter to follow the voltage of the grid 600 to achieve phase locking. At the same time, detect the voltages on both sides of the grid-connected relay. When the instantaneous voltage difference between the two is less than the preset value, close the grid-connected relays Kg3, Kg4, Kg5, and Kg6 to achieve inverter grid connection.

[0205] When the power conversion circuit 100 performs inversion, the SPWM modulation method can be used, and a relatively small dead time can be adopted, so that the voltage difference between the DC bus voltage and the peak value of the inverted AC is not higher than 10V (the dead time accounts for about 2% in the switching cycle, and the maximum closing voltage difference of the relay is within 10V), meeting the closing condition of the grid-connected relay.

[0206] In addition, Kn1 and Kn2 can also be disconnected to disconnect the connection between the N line and the DC bus, and modulation methods that improve the utilization rate of the bus voltage, including but not limited to DPWM or SVPWM, etc., can be adopted to achieve complete follow-up of the inverted voltage and the grid voltage of 600, meeting the closing condition of the grid-connected relay.

[0207] Finally, disconnect all pre-charge related relays Kp1, Kp2, and Kn2.

[0208] It can be understood that the configuration of the first charging circuit 10 is flexible. As Figure 23 shown, the third current-limiting charging device 730 of the first charging circuit 10 is Rp, Rp is connected in parallel with the switch Kk, and one end of Rp close to the DC bus capacitor 200 is divided into two branches, a first branch in which Dp1 and Kp1 are connected in series, and a second branch in which Dp2 and Kp2 are connected in series. At the initial stage of charging, Kn1 and Kn2 are closed, the second charging circuit 710 is turned on, Kp2 is closed, and the second branch of the first charging circuit 10 is turned on, forming a current-limiting pre-charge channel for charging Cb2 via Rp and Dp2 from the AC grid 600, that is, first charging the first half bus capacitor 210.

[0209] In the related art, for insulation impedance detection, detection methods such as unbalanced bridges are usually adopted, which require adding more resistors and relays.

[0210] In the embodiments of the present application, by using the first charging branch and the second charging branch for pre-charging the DC bus capacitor 200, without adding more resistors and relays, through the first charging circuit 10 and the second charging circuit 710, the first half bus capacitor 210 and the second half bus capacitor 220 can be independently charged, the charging of the upper and lower half bus capacitors is decoupled, and by first charging the first half bus capacitor 210 to form a voltage difference between the two half bus capacitors, insulation impedance detection between the bus and the ground can be realized during the pre-charge stage, problems such as insulation aging and damage can be detected in time, serious accidents such as electric leakage, short circuit, and even fire caused by insulation failure can be avoided, the service life of the equipment can be extended, and the safety of personnel and equipment can be guaranteed.

[0211] In the description of the present application, "the first feature", "the second feature" may include one or more of such features.

[0212] In the description of the present application, the meaning of "a plurality of" is two or more.

[0213] In the description of the present application, a first feature being "on" or "under" a second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through additional features therebetween.

[0214] In the description of this specification, the description of reference terms such as "an embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0215] Although the embodiments of the present application have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A power supply device, characterized in that: include: A power conversion circuit, wherein an input end of the power conversion circuit is connected in parallel to a DC bus capacitor, and an output end of the power conversion circuit is used to be connected to a power grid; a first charging circuit, wherein one end of the first charging circuit is connected to the DC bus capacitor, and the other end of the first charging circuit is used to be connected to the power grid; a control unit, the control unit being connected to the first charging circuit and the power conversion circuit, the control unit being used to control the first charging circuit to charge the voltage of the DC bus capacitor to a first target voltage in a first pre-charging stage, and to control the first charging circuit to charge the voltage of the DC bus capacitor to a second target voltage in a second pre-charging stage, the first pre-charging stage being before the second pre-charging stage, the first target voltage being less than the second target voltage, and the second target voltage being greater than the voltage of the power grid; The control unit is further configured to control the power conversion circuit to perform inverter output when the voltage of the DC bus capacitor reaches the second target voltage, so as to start the power supply device.

2. The power supply device according to claim 1, characterized in that: The first charging circuit includes a boost circuit, the input end of the boost circuit is connected to the photovoltaic power generation component, and the power supply device is used to convert the direct current generated by the photovoltaic power generation component into alternating current; the input end of the boost circuit is connected in parallel with the input end capacitor; The control unit is used to control the first charging circuit to charge the input capacitor and the DC bus capacitor in the first pre-charging stage. The control unit is also used to control the boost circuit to perform a boost conversion when the voltage of the input capacitor reaches the first target voltage, and to charge the voltage of the DC bus capacitor to the second target voltage through the input capacitor in the second pre-charging stage.

3. The power supply device according to claim 2, characterized in that: The first charging circuit also includes a rectifier module, which is arranged between the boost circuit and the power grid, and is used to convert the alternating current output by the power grid into direct current to charge the input capacitor and the DC bus capacitor.

4. The power supply device according to claim 2, characterized in that: The first charging circuit further includes a first current limiting charging device, which is arranged between the boost circuit and the power grid.

5. The power supply device according to any one of claims 2 to 4, characterized in that: A first unidirectional conductive device is provided between the photovoltaic power generation component and the boost circuit, and the conducting direction of the first unidirectional conductive device is from the photovoltaic power generation component to the boost circuit.

6. The power supply device according to any one of claims 2 to 4, characterized in that: A first switch device is provided between the photovoltaic power generation component and the boost circuit, and the first switch device is used to control the on-off of the circuit between the photovoltaic power generation component and the boost circuit.

7. The power supply device according to claim 1, characterized in that: The first charging circuit includes a charge pump circuit, the charge pump circuit has a charge pump capacitor, and a switching cycle of the charge pump circuit includes a charging phase and a discharging phase. In the charging phase, the power grid charges the charge pump capacitor, and in the discharging phase, the power grid and the charge pump capacitor charge the DC bus capacitor. The control unit is used to control the charge pump circuit to be connected between the DC bus capacitor and the power grid when the voltage of the DC bus capacitor reaches the first target voltage, and to charge the voltage of the DC bus capacitor to the second target voltage through the charge pump capacitor in the second pre-charging stage.

8. The power supply device according to claim 7, characterized in that: The control unit is used to control the first charging circuit to charge the voltage of the DC bus capacitor to the first target voltage through the charge pump circuit in the first pre-charging stage.

9. The power supply device according to claim 7, characterized in that: The first charging circuit has a second current limiting charging device, and the control unit is used to control the first charging circuit to charge the voltage of the DC bus capacitor to the first target voltage through the second current limiting charging device in the first pre-charging stage.

10. The power supply device according to any one of claims 7 to 9, characterized in that: The DC bus capacitor is connected in parallel with a voltage limiting device, and the voltage limiting device is used to balance the amount of charge input from the charge pump capacitor to the DC bus capacitor during the discharge phase, so as to limit the voltage of the DC bus capacitor.

11. The power supply device according to any one of claims 7 to 9, characterized in that: The charge pump capacitor and the AC filter capacitor of the power supply device are the same capacitor.

12. The power supply device according to claim 1, characterized in that: The DC bus capacitor comprises a first half bus capacitor and a second half bus capacitor connected in series, wherein the first half bus capacitor and the second half bus capacitor are connected to a midpoint of the bus capacitor; The power supply device also includes: a second charging circuit, one end of the second charging circuit being connected to the midpoint of the bus capacitor, and the other end being used to be connected to the power grid, and the second charging circuit being provided with a grounded insulation impedance detection circuit; The control unit is connected to the second charging circuit, and the control unit is used to control the first charging circuit and the second charging circuit, first charging the first half-bus capacitor, then charging the first half-bus capacitor and the second half-bus capacitor, and performing insulation impedance detection through the insulation impedance detection circuit.

13. The power supply device according to claim 12, characterized in that: The control unit is used for controlling the second charging circuit to be disconnected when the voltage of the first half-bus capacitor reaches the first target voltage, and obtaining first detection data of the first half-bus capacitor and the insulation impedance detection circuit; The control unit is further used to control the second charging circuit to disconnect when the voltages of the first half-bus capacitor and the second half-bus capacitor reach the first target voltage, and to obtain second detection data of the first half-bus capacitor, the second half-bus capacitor and the insulation impedance detection circuit, wherein the first detection data and the second detection data are used to determine the insulation impedance detection result.

14. The power supply device according to claim 12 or 13, characterized in that: The first charging circuit is also provided with a third current limiting charging device.

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