Pre-charging method and power system
By charging the bus capacitor with low power while the internal circuit of the inverter is disabled, the problem of excessive auxiliary power during the pre-charging process of the inverter is solved, resulting in faster charging speed and lower energy consumption, while reducing cost and size.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI SIGE DIGITAL TECHNOLOGY CO LTD
- Filing Date
- 2026-03-25
- Publication Date
- 2026-07-14
AI Technical Summary
When existing inverters are pre-charged before grid connection, the auxiliary power supply is too high, which increases cost and size, consumes a lot of energy, and slows down the charging speed.
The bus capacitor is charged while the internal circuit of the inverter is in a disabled state. It is charged using a low-power power supply through a pre-charging device, and the power-on state of the execution circuit is controlled during the charging process to optimize the charging process, reduce power consumption and increase charging speed.
This reduces the energy consumption of the bus capacitor by the internal circuitry, improves the charging speed, enables low-power charging, and reduces cost and size.
Smart Images
Figure CN122394330A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of inverter technology, and in particular relates to a pre-charging method for an inverter and a power system. Background Technology
[0002] Before the grid-connection relay engages, the inverter typically needs to control the voltage difference across its terminals to prevent it from becoming too large and damaging the relay. Therefore, when the inverter connects to the grid without DC power input, it needs to pre-charge the internal bus to reduce the voltage difference across the grid-connection relay. Simultaneously, power is required to power the grid-connection process. Currently, the auxiliary power supply configured for pre-charging the inverter is too high, leading to increased cost and size, as well as high energy consumption. Summary of the Invention
[0003] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a pre-charging method and power system that can reduce the power consumption of the bus capacitor in the internal circuit, improve the charging speed, and also realize low-power charging.
[0004] In a first aspect, this application provides a pre-charging method for an inverter, the inverter including a bus capacitor electrically connected to a pre-charging device, the pre-charging method comprising: When a pre-charge command is detected, the internal circuitry of the control inverter is in a disabled state; The pre-charging device is connected to the power supply, and the power supply is used to charge the bus capacitor.
[0005] According to one embodiment of this application, the pre-charging command includes a grid connection command, and the pre-charging method further includes: During the charging of the bus capacitor, the execution circuit in the inverter corresponding to the grid connection command switches from the disabled state to the powered-on state. The control circuit performs the grid connection action, connecting the inverter to the external power grid.
[0006] According to one embodiment of this application, controlling the execution circuit within the inverter corresponding to the grid connection command to switch from a disabled state to a powered-on state includes: Determine the stage voltage; After the voltage of the bus capacitor reaches the stage voltage, the execution circuit in the inverter corresponding to the grid connection command switches from the disabled state to the powered-on state.
[0007] According to one embodiment of this application, determining the stage voltage includes: If the charging power of the pre-charging device is less than the power consumed by the inverter when the execution circuit is powered on, then the stage voltage is determined to be greater than the voltage of the external power grid; or, If the charging power of the pre-charging device is greater than the power consumed by the inverter when the execution circuit is powered on, the difference between the stage voltage and the voltage of the external power grid is determined to be within a threshold range, which includes both positive and negative values.
[0008] According to one embodiment of this application, the execution circuit includes an auxiliary power supply circuit, the input terminal of which is electrically connected to the bus capacitor. The execution circuit within the inverter corresponding to the grid connection command switches from a disabled state to a powered-on state, including: The auxiliary power supply circuit is switched from a disabled state to a powered-on state.
[0009] According to one embodiment of this application, the grid connection operation includes the grid connection switch being engaged, and the pre-charging method further includes: During the power-on period of the execution circuit, the charging power of the pre-charging device is adjusted so that the difference between the voltage of the bus capacitor and the voltage of the external power grid is within the error range when the grid-connected switch is energized.
[0010] According to one embodiment of this application, the charging power of the pre-charging device is determined according to the following process: Determine the actual voltage of the bus capacitor and the actual charging current of the pre-charging device during the charging process; The target charging current is determined based on the difference between the target reference voltage and the actual voltage. The target adjustment amount is determined based on the difference between the target charging current and the actual charging current; The pre-charging device is driven by a target adjustment amount.
[0011] According to one embodiment of this application, the pre-charging device includes a power supply circuit, the output terminal of which is electrically connected to a bus capacitor. The power supply circuit is driven by a PWM signal, and the pre-charging device is driven based on a target adjustment amount, including: The duty cycle adjustment amount is determined based on the PWM signal determined by the target adjustment amount. The PWM signal of the drive power supply circuit is adjusted according to the duty cycle adjustment.
[0012] Secondly, this application provides a power system including an inverter, the inverter including a bus capacitor, a pre-charging device electrically connected to the bus capacitor, and a controller, the controller being electrically connected to the pre-charging device and configured to implement the pre-charging method according to the foregoing.
[0013] Thirdly, this application provides a power system including an inverter and a pre-charging device. The inverter includes a bus capacitor and a controller. The power output port of the pre-charging device is electrically coupled to the bus capacitor. The controller is communicatively connected to the drive circuit within the pre-charging device via a communication control port. The controller is configured to implement the pre-charging method described above.
[0014] According to the pre-charging method and power system of this application, by charging the inverter's bus capacitor while the inverter's internal circuit is in a disabled state, the power consumption of the internal circuit on the bus capacitor can be reduced, the charging speed can be increased, and low-power charging can also be achieved.
[0015] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description
[0016] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the inverter provided in the embodiments of this application; Figure 2 This is a schematic flowchart of the pre-charging method for the inverter provided in the embodiments of this application; Figure 3 This is a schematic diagram of the bus capacitor voltage change in the inverter in low power mode; Figure 4 This is one of the schematic diagrams illustrating the voltage change of the bus capacitor during the charging process in an embodiment of this application; Figure 5 This is the second schematic diagram of the voltage change of the bus capacitor during the charging process in an embodiment of this application; Figure 6 This application presents a schematic diagram of the voltage control logic in an embodiment.
[0017] Figure label: Solar panel 101, boost circuit 102, bus capacitor 103, DC / AC 104, smart load 105, auxiliary power supply circuit 106, inverter 107, power supply circuit 108, charging circuit 109, pre-charging device 110, communication control interface 111, power grid 112. Detailed Implementation
[0018] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.
[0019] In the following description, a "circuit" refers to a conductive loop consisting of at least one element or sub-circuit connected by an electrical or electromagnetic link. When an element or circuit is said to be "coupled to" or "connected to" another element, or when an element / circuit is said to be "coupled at" or "connected at" two nodes, it can be directly coupled to or connected to the other element, or there may be intermediate elements. The connection between elements can be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there are no intermediate elements between them.
[0020] In the description, the terms "first," "second," etc., are used to distinguish similar objects, not to describe a specific order or sequence. It should be understood that such numerical descriptors can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class, not limited in number; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.
[0021] Furthermore, the use of terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0022] Reference Figure 1 , Figure 1 This is a schematic diagram of the inverter structure provided in an embodiment of this application. One embodiment of this application proposes an inverter. As an example, the inverter 107 includes a boost circuit 102, a bus capacitor 103, a DC / AC converter 104, a smart load 105, and an auxiliary power supply circuit 106. Of course, the inverter 107 may also include other circuit components, such as detection circuits and communication circuits. The bus capacitor 103 is connected between the boost circuit 102 and the DC / AC converter 104. The smart load 105 is used to control the enabling or disabling of the circuit components inside the inverter (including the auxiliary power supply circuit 106). When disabled, the circuit components can reduce power consumption. The input side of the auxiliary power supply circuit 106 is coupled to the bus capacitor, and the output side is connected to the energy-consuming circuit components inside the inverter 107 to provide power.
[0023] The DC side of inverter 107 can be electrically connected to solar panel 101, and the AC side of inverter 107 can be electrically connected to power grid 112. Boost circuit 102 boosts the DC power output from solar panel 101 and transmits it to DC bus (not shown). DC / AC 104 converts the DC power on the DC bus into AC power and transmits it to power grid 112. A bus capacitor 103 is provided on the DC bus.
[0024] exist Figure 1 In this configuration, inverter 107 is electrically connected to pre-charging device 110. Pre-charging device 110 includes a power supply circuit 108 and a charging circuit 109. Power supply circuit 108 provides electrical energy; it can be a flyback switching power supply with a rectifier bridge, a flyback switching power supply drawing power from an external power source such as a battery pack, or other power sources. The output of charging circuit 109 is coupled to bus capacitor 103 within inverter 107, allowing charging circuit 109 to charge bus capacitor 103 using the electrical energy provided by power supply circuit 108. Pre-charging device 110 and inverter 107 are connected via communication control interface 111 for mutual communication, transmission of sampling control signals, and control interaction between the inverter and pre-charging device.
[0025] In other examples, the pre-charging device 110 may also be integrated inside the inverter 107.
[0026] Reference Figure 2 , Figure 2 This is a flowchart illustrating a pre-charging method for an inverter provided in an embodiment of this application. One embodiment of this application proposes a pre-charging method. In this embodiment, the inverter structure can be referenced as described above, and the pre-charging method includes steps 10 and 20.
[0027] Step 10: When a pre-charge command is detected, the internal circuitry of the control inverter 107 is disabled. Step 20: Connect the pre-charging device 110 to the power supply and use the power supply to charge the bus capacitor 103.
[0028] It should be noted that the pre-charging method in this embodiment can be executed by the controller in the aforementioned inverter 107, or by other components with circuit control capabilities. The following description will use the controller in the inverter 107 as the executing entity.
[0029] The controller can be implemented using an MCU (Microcontroller Unit) chip; it can also be based on a DSP (Digital Signal Processor) chip or an FPGA (Field-Programmable Gate Array) chip. The controller can be implemented using a Programmable Gate Array (FPGA) or a custom-designed controller chip; this application does not limit the specific hardware implementation of the controller.
[0030] The pre-charge command can be sent to the inverter 107 by an external device or apparatus. When the controller detects the pre-charge command, it determines that the bus capacitor 103 needs to be charged and begins to execute the pre-charge method. At this time, the controller 107 can control the internal circuit of the inverter 107 to be in a disabled state, so that the inverter 107 enters a low-power mode.
[0031] As an example, the internal circuitry in the disabled state may include load circuits unrelated to the charging process, such as the auxiliary power supply circuit 106 and the grid connection circuit, thereby reducing the overall power consumption of the inverter 107 and enabling the bus capacitor 103 to be charged at a faster rate.
[0032] The input side of the pre-charging device 110 can be electrically connected to any form of external power source, such as an auxiliary power supply, photovoltaic panel, battery pack, or power grid, so that the power supply circuit 108 can be connected to electrical energy. Alternatively, the input terminal of the power supply circuit 108 can be equipped with a switch, the other end of which can be electrically connected to any form of external power source. The controller can control the switch to close, thereby controlling the pre-charging device to connect to the power source.
[0033] In this embodiment, when the inverter 107 is in low-power mode, the pre-charging device 110 begins to output electrical energy to charge the bus capacitor 103. When a capacitor with a fixed capacitance value C is charged with a constant power P, the instantaneous voltage V(t) on the capacitor changes non-linearly with time, specifically following the formula and curve below:
[0034] Where V0 is the initial voltage at the start of charging; P is the constant charging power P of bus capacitor 103; C is the size of inverter bus capacitor; and t is the actual charging required.
[0035] The curve shows that the instantaneous voltage V(t) across the capacitor increases with time in a square root manner, indicating that the charging rate gradually slows down. The higher the capacitor voltage, the less charge is charged per unit time.
[0036] The detailed derivation of the formula is as follows: Definition of constant power:
[0037] The relationship between capacitor circuit and voltage:
[0038] Combining the above two equations, the differential equation for capacitor charging is:
[0039] Separating the variables and integrating, we obtain:
[0040] After integration and transformation, we can obtain:
[0041] Reference Figure 3 , Figure 3 This is a schematic diagram of the bus capacitor voltage change in the inverter under low power mode. When inverter 107 is in low power mode, all irrelevant loads are turned off to reduce the overall power consumption of the system. The overall power consumption at this time is P1, while the constant output power of charging circuit 109 is P0. Therefore, the actual charging power at this time is P = P0 - P1, and the bus capacitor voltage gradually increases.
[0042] According to the pre-charging method of this application, by charging the bus capacitor of the inverter while the internal circuit of the inverter is in a disabled state, the power consumption of the internal circuit to the bus capacitor can be reduced, the charging speed can be increased, and low-power charging can also be achieved.
[0043] In some embodiments, the pre-charge command includes a grid connection command. The pre-charge method further includes: during the charging of the bus capacitor 103, controlling the execution circuit in the inverter 107 corresponding to the grid connection command to switch from a disabled state to a powered-on state; controlling the execution circuit to perform a grid connection action, so that the inverter 107 is connected to the external power grid 112.
[0044] In this embodiment, the inverter 107 needs to be pre-charged by the bus capacitor 103 to achieve grid connection. For example, the inverter 107 can be used as a photovoltaic static var generator (SVG) to achieve reactive power compensation in a solar power plant. During photovoltaic power generation, factors such as weather can lead to output waveform distortion, increased harmonics, and potential problems. Using a photovoltaic SVG allows for dynamic adjustment of the system to control and optimize reactive loads.
[0045] Especially when SVG is applied in nighttime scenarios, because there is no photovoltaic (PV) output at night, the bus capacitor 103 inside the inverter 107 needs to be charged using an external power source. Typically, the inverter 107 can use a battery or auxiliary power supply to pre-charge the internal bus. However, in addition to the circuitry required for grid connection, such auxiliary power supplies also have static power consumption due to dead load circuitry to meet their cross-regulation requirements. This results in a larger size, increased cost, and slower charging speed for these auxiliary power supplies.
[0046] The grid connection process of the inverter 107 in this embodiment can be divided into multiple stages. In the first stage, the voltage of the bus capacitor 103 is rapidly increased by charging the bus capacitor 103 while the inverter 107 is in a low power consumption state. In the second stage, the inverter 107 controls the circuit that executes the grid connection process to be powered on, and the bus capacitor 103 continues to be charged until the grid connection is completed.
[0047] The execution circuit within the inverter 107 corresponding to the grid connection command may include a grid detection sampling circuit, a relay circuit, a grid connection switch, and an inverter drive circuit. In the second stage, the controller powers on these circuits to fulfill basic functions such as activating relays, driving switches, and sampling communication, thereby achieving grid connection control of the inverter 107.
[0048] In some embodiments, controlling the execution circuit in the inverter corresponding to the grid connection command to switch from a disabled state to a powered-on state includes: determining the stage voltage; and after the voltage of the bus capacitor 103 reaches the stage voltage, controlling the execution circuit in the inverter 107 corresponding to the grid connection command to switch from a disabled state to a powered-on state.
[0049] In this embodiment, the controller detects the voltage of the bus capacitor 103 and controls the overall power consumption of the inverter 107 based on the voltage of the bus capacitor 103. The stage voltage is used to set the switching timing of the inverter 107 from the first stage to the second stage.
[0050] The stage voltage can be determined based on the required voltage of bus capacitor 103 for grid connection and the voltage variation trend of bus capacitor 103 in the second stage. The overall power consumption P2 of inverter 107 in the second stage is greater than its overall power consumption P1 in the first stage. The actual charging power of bus capacitor 103 in the second stage is P = P0 - P2.
[0051] As an example, determining the stage voltage may include: when the charging power of the pre-charging device is greater than the power consumed by the inverter when the execution circuit is powered on, the difference between the stage voltage and the voltage of the external power grid is within a threshold range, which includes both positive and negative values.
[0052] The threshold range, including positive and negative values, means that the stage voltage can be greater than, less than, or equal to the voltage of the external power grid 112. When the stage voltage is greater than the voltage of the external power grid 112, the difference is positive; when the stage voltage is less than the voltage of the external power grid 112, the difference is negative. The threshold range needs to be set to ensure that the bus voltage, after the second stage, is within the positive and negative error range of the voltage of the external power grid at the time of grid connection.
[0053] In this example, the voltage of bus capacitor 103 drops during the second stage. The difference between the stage voltage and the external grid voltage remains within a threshold range, ensuring that the voltage of bus capacitor 103 meets grid connection requirements upon completion of grid connection control. For example, the stage voltage can be lower than the voltage of the external grid 112 to allow for voltage rise space during the second stage and shorten the duration of the first stage.
[0054] Reference Figure 4 , Figure 4 This is one of the schematic diagrams illustrating the voltage change of the bus capacitor 103 during the charging process, according to an embodiment of this application. As an example, the first stage is defined as time t decreasing from 0 to 20 seconds, and the second stage is defined as time t increasing from 20 seconds to 40 seconds. Figure 4 In the first stage, the bus capacitor voltage and Figure 3 The same as shown; in the second stage, if P0 is greater than P2, the voltage of bus capacitor 103 rises, but its rate of rise is less than the rate of rise in the first stage. Furthermore, although... Figure 4 The voltage of the intermediate bus capacitor appears flatter in the second stage than in the first stage, but it is still an upward convex curve (the slope continues to decrease slightly as the voltage increases), not a straight line.
[0055] As another example, determining the stage voltage may also include: determining that the stage voltage is greater than the voltage of the external power grid 112 when the charging power of the pre-charging device 110 is less than the power consumed by the inverter 107 when the execution circuit is powered on.
[0056] In this example, the voltage of bus capacitor 103 drops during the second stage. Therefore, to ensure that the voltage of bus capacitor 103 meets the grid connection requirements when grid connection control is completed, the stage voltage needs to be greater than the voltage of the external power grid 112 to reserve space for voltage drop during the second stage.
[0057] Reference Figure 5 , Figure 5 This is the second schematic diagram showing the voltage change of the bus capacitor 103 during the charging process, according to an embodiment of this application. As an example, the first stage is from 0 to 20 seconds, and the second stage is from 20 seconds to 40 seconds. Figure 5 In the first stage, the bus capacitor voltage and Figure 3 The same applies as shown; in the second stage, if P0 is less than P2, the voltage of bus capacitor 103 drops.
[0058] In some embodiments, the execution circuit may include the auxiliary power supply circuit 106 as described above, the input terminal of the auxiliary power supply circuit 106 being electrically connected to the bus capacitor 103; controlling the execution circuit in the inverter 107 corresponding to the grid connection command to switch from a disabled state to a powered state includes: controlling the auxiliary power supply circuit 106 to switch from a disabled state to a powered state.
[0059] The auxiliary power supply circuit 106 can be electrically connected to the DC bus via a switch. The controller can control the switch to open, putting the auxiliary power supply circuit 106 in a disabled state, or control the switch to close, putting the auxiliary power supply circuit 106 from a disabled state to a powered state. The auxiliary power supply circuit 106 can obtain power from the bus capacitor 103 to power other circuits within the inverter 107.
[0060] The auxiliary power supply circuit 106 being in a powered-on state can also mean that it is in a power output state, such as providing voltages of 3.3V, 5V, or 8V. In this case, other circuits within the inverter 107 can obtain power from the auxiliary power supply circuit 106 and operate under the control of the controller. These other circuits can perform pre-grid connection ISO (Isolation Resistance) testing, relay self-testing, and RCD (Residual Current Device) testing.
[0061] In some embodiments, the grid connection action includes the grid connection switch being activated, and the pre-charging method further includes: during the power-on of the execution circuit, adjusting the charging power of the pre-charging device 110 so that the difference between the voltage of the bus capacitor 103 and the voltage of the external power grid 112 is within the error range when the grid connection switch is activated.
[0062] The grid-connection switch can be a switch, such as a relay, installed between the AC side of the inverter 107 and the power grid 112. Closing this grid-connection switch connects the inverter 107 to the power grid 112, typically the final step in grid-connection control. Therefore, before this connection, the voltage difference across the grid-connection switch should not be too large to damage the AC relay. This error range can be ±3%, ±5%, or ±6%, etc.
[0063] In this embodiment, the charging power of the pre-charging device 110 can be conditionally adjusted to control the voltage of the bus capacitor 103. For example, during the detection process before the grid-connected switch is closed, if the controller detects that the voltage of the bus capacitor 103 is greater than the voltage of the external power grid 112 and the difference is large, it can reduce the charging power of the pre-charging device 110 to reduce the voltage of the bus capacitor 103; or if it detects that the voltage of the bus capacitor 103 is less than the voltage of the external power grid 112 and the difference is large, it can increase the charging power of the pre-charging device 110 to increase the voltage of the bus capacitor 103.
[0064] In other embodiments, the voltage of inverter 107 when the grid-connected switch is engaged can be controlled by adjusting the charging time of bus capacitor 103. (As described above...) Figure 4 or Figure 5 As shown in the process, the higher the stage voltage, the higher the voltage of the inverter 107 when the grid-connected switch is energized. Therefore, the voltage control of the inverter 107 when the grid-connected switch is energized can be achieved by setting the stage voltage.
[0065] In some embodiments, the charging power of the pre-charging device 110 is determined according to the following process: determining the actual voltage of the bus capacitor 103 and the actual charging current of the pre-charging device 110 during the charging process; determining the target charging current based on the difference between the target reference voltage and the actual voltage; determining the target adjustment amount based on the difference between the target charging current and the actual charging current; and driving the pre-charging device 110 based on the target adjustment amount.
[0066] In this embodiment, the pre-charging device 110 can achieve voltage regulation control of the bus capacitor 103 through voltage control and current control. Especially during the grid connection process of the inverter 107, the bus capacitor 103 can be controlled to enter the voltage regulation mode to avoid voltage fluctuations in the bus capacitor 103 and cause grid connection abnormalities.
[0067] As an example, the pre-charging device 110 includes a power supply circuit 108, the output of which is electrically connected to the bus capacitor 103. The power supply circuit 108 is driven by a PWM signal. Driving the pre-charging device 110 based on a target adjustment amount includes: determining a duty cycle adjustment amount based on the PWM signal according to the target adjustment amount; and adjusting the PWM signal driving the power supply circuit 108 according to the duty cycle adjustment amount.
[0068] In this example, the power supply circuit 108 uses a flyback switching circuit to implement the charging and voltage regulation control of the bus capacitor 103. In the voltage regulation control, the PWM signal driving the flyback switching circuit is adjusted and corrected through feedback to ensure the voltage of the bus capacitor 103 is stable.
[0069] Reference Figure 6 , Figure 6 A schematic diagram of the voltage control logic of an embodiment of this application is shown. (See attached diagram.) Figure 6 As shown, the controller employs a dual-closed-loop PID control strategy with an outer voltage loop and an inner current loop to achieve dynamic stability of the bus voltage under load fluctuations. The specific process is as follows: The controller may include a sampling module, a voltage PID control unit, a current PID control unit, and a PWM signal generator and driver. The sampling module acquires the DC bus voltage feedback signal Vbus_fb and the switching transistor current feedback signal Ics_fb in the flyback switching circuit in real time.
[0070] The target reference voltage Vref is compared with the actual sampled bus voltage Vbus_fb to calculate the voltage error, which is then input to the voltage PID control unit (typically using PI regulation). The output of the voltage loop serves as the target reference current command Iref for the inner loop. To prevent overcurrent, the I_ref output of the voltage loop is limited to a maximum permissible charging current.
[0071] The target reference current Iref output by the outer voltage loop is compared with the actual sampled current Ics_fb to calculate the current error. This current error is input to the current PID control unit (usually using PI regulation). The output quantity PWMduty of the current loop directly corresponds to the adjustment amount of the PWM duty cycle. The output duty cycle is limited to ensure it remains within a reasonable range (e.g., 0%~95%).
[0072] The PWM signal generator and driver generate a PWM waveform based on the final duty cycle calculated from the inner current loop, and apply it to the gate of the switching transistor in the flyback switching circuit. By adjusting the on-time of the MOSFET at high frequency, the input power and the power consumed by the load are dynamically balanced, ultimately stabilizing the voltage of the bus capacitor 103 near the target reference value Vref to achieve smooth grid-connected operation.
[0073] An embodiment of this application also provides a power system including an inverter 107, the inverter 107 including a bus capacitor 103, a pre-charging device 110 electrically connected to the bus capacitor 103, and a controller electrically connected to the pre-charging device 110, the controller being configured to implement the pre-charging method according to the foregoing.
[0074] In this embodiment, the pre-charging device 110 is integrated inside the inverter 107, and the controller can directly control the power supply circuit 108 and the charging circuit 109 in the pre-charging device 110. The specific process of the pre-charging method can be described in the aforementioned embodiments, and will not be repeated here.
[0075] An embodiment of this application also provides a power system including an inverter 107 and a pre-charging device 110. The inverter 107 includes a bus capacitor 103 and a controller. The power output port of the pre-charging device 110 is electrically coupled to the bus capacitor 103. The controller is communicatively connected to the drive circuit within the pre-charging device 110 via a communication control port 111. The controller is configured to implement the pre-charging method described above.
[0076] In this embodiment, the pre-charging device 110 is independent of the inverter 107, and the pre-charging device 110 and the inverter 107 are connected through a power port and a communication control port 111. The pre-charging device 110 also includes a power supply circuit 108 and a drive circuit for the charging circuit 109. The controller receives control signals from the drive circuit through the communication control port 111, such as the aforementioned adjustment amount of the PWM duty cycle. The specific process of the pre-charging method can be described in the aforementioned embodiments, and will not be repeated here.
[0077] 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. Without further limitation, 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. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.
[0078] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.
Claims
1. A pre-charging method for an inverter, characterized in that, The inverter includes a bus capacitor, which is electrically connected to a pre-charging device. The pre-charging method includes: When a pre-charge command is detected, the internal circuitry of the inverter is controlled to be in a disabled state; The pre-charging device is connected to a power source, and the power source is used to charge the bus capacitor.
2. The pre-charging method according to claim 1, characterized in that, The pre-charging command includes a grid connection command, and the pre-charging method further includes: During the charging of the bus capacitor, the execution circuit in the inverter corresponding to the grid connection command is controlled to switch from the disabled state to the powered-on state; The control circuit performs the grid connection action, connecting the inverter to the external power grid.
3. The pre-charging method according to claim 2, characterized in that, Controlling the execution circuit within the inverter corresponding to the grid connection command to switch from the disabled state to the powered-on state includes: Determine the stage voltage; After the voltage of the bus capacitor reaches the stage voltage, the execution circuit in the inverter corresponding to the grid connection command switches from the disabled state to the powered-on state.
4. The pre-charging method according to claim 3, characterized in that, The determined stage voltage includes: If the charging power of the pre-charging device is less than the power consumed by the inverter when the execution circuit is in the powered-on state, then the stage voltage is determined to be greater than the voltage of the external power grid; or, When the charging power of the pre-charging device is greater than the power consumed by the inverter when the execution circuit is in the powered-on state, it is determined that the difference between the stage voltage and the voltage of the external power grid is within a threshold range, the threshold range including positive and negative values.
5. The pre-charging method according to claim 2, characterized in that, The execution circuit includes an auxiliary power supply circuit, the input terminal of which is electrically connected to the bus capacitor. The control of the execution circuit within the inverter corresponding to the grid connection command to switch from the disabled state to the powered-on state includes: Control the auxiliary power supply circuit to switch from the disabled state to the powered-on state.
6. The pre-charging method according to claim 2, characterized in that, The grid connection action includes the grid connection switch engaging, and the pre-charging method further includes: During the power-on period of the execution circuit, the charging power of the pre-charging device is adjusted so that the difference between the voltage of the bus capacitor and the voltage of the external power grid is within the error range when the grid-connected switch is energized.
7. The pre-charging method according to any one of claims 1-6, characterized in that, The charging power of the pre-charging device is determined according to the following process: Determine the actual voltage of the bus capacitor and the actual charging current of the pre-charging device during the charging process; The target charging current is determined based on the difference between the target reference voltage and the actual voltage; The target adjustment amount is determined based on the difference between the target charging current and the actual charging current; The pre-charging device is driven based on the target adjustment amount.
8. The pre-charging method according to claim 7, characterized in that, The pre-charging device includes a power supply circuit, the output terminal of which is electrically connected to the bus capacitor. The power supply circuit is driven by a PWM signal. Driving the pre-charging device based on the target adjustment amount includes: The duty cycle adjustment amount is determined based on the target adjustment amount using the PWM signal. The PWM signal driving the power supply circuit is adjusted according to the duty cycle adjustment amount.
9. An electric power system, characterized in that, The device includes an inverter, the inverter comprising a bus capacitor, a pre-charging device electrically connected to the bus capacitor, and a controller, the controller being electrically connected to the pre-charging device, the controller being configured to implement the pre-charging method according to any one of claims 1-8.
10. An electric power system, characterized in that, The device includes an inverter and a pre-charging device. The inverter includes a bus capacitor and a controller. The power output port of the pre-charging device is electrically coupled to the bus capacitor. The controller is communicatively connected to the drive circuit within the pre-charging device via a communication control port. The controller is configured to implement the pre-charging method according to any one of claims 1-8.