Power converter, controller, power supply system, and midpoint voltage offset control method

Abstract

The application provides a power converter, a controller, a power supply system and a midpoint voltage deviation control method, which are applied to the technical field of power electronics, and the power converter comprises a power conversion module, a main control module and at least two DC bus capacitors, each DC bus capacitor is connected in series between the positive electrode of a DC bus and the negative electrode of the DC bus, and since the midpoint voltage deviation suppression strategy in the related art can only achieve good midpoint deviation suppression effect when the bus voltage is high, the main control module increases the bus voltage when the voltage deviation between the capacitance voltage of at least one DC bus capacitor and the target capacitance voltage is greater than the first preset deviation threshold, thereby providing guarantee for the midpoint voltage deviation suppression strategy to achieve better midpoint deviation suppression effect, improving the midpoint deviation suppression effect and significantly improving the stability of the power supply system.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, specifically to a power converter, controller, power supply system, and a method for controlling midpoint voltage offset. Background Technology

[0002] In practical applications, power converters such as inverters often adopt multi-level circuit topologies. At least two DC bus capacitors are set on the DC side of the power conversion circuit. Ideally, the capacitor voltages of each DC bus capacitor are equal, that is, the midpoint voltage is balanced.

[0003] However, factors such as grid harmonics and unbalanced loads can easily cause neutral point voltage deviation, affecting the reliable operation of power converters and even the entire power supply system. The neutral point voltage deviation suppression strategies provided by related technologies are greatly affected by the operating state of the power converter, and often fail to achieve the expected suppression effect, resulting in low stability of the power converter. Summary of the Invention

[0004] In view of this, this application aims to provide a power converter, controller, power supply system and midpoint voltage offset control method to solve the problem of poor midpoint voltage offset suppression effect of power converter in related technologies, which affects the operating stability of power converter.

[0005] In a first aspect, this application provides a power converter, comprising: a power conversion module, a main control module, and at least two DC bus capacitors, wherein... The first side of the power conversion module serves as the first side of the power converter, and the second side of the power conversion module serves as the second side of the power converter; The positive terminal of the first side of the power converter is used to connect to the positive terminal of the DC bus, and the negative terminal of the first side of the power converter is used to connect to the negative terminal of the DC bus. The at least two DC bus capacitors are connected in series between the positive terminal and the negative terminal of the DC bus; The main control module is configured to: acquire the capacitor voltage of each DC bus capacitor; if the voltage deviation between the capacitor voltage of at least one DC bus capacitor and the target capacitor voltage is greater than a first preset deviation threshold, execute preset adjustment measures, the preset adjustment measures including: controlling the power conversion module to increase the bus voltage of the DC bus or controlling the power conversion module to decrease the output power.

[0006] In one optional implementation, the main control module is further configured to: When the voltage deviation between the capacitor voltage of each DC bus capacitor and the target capacitor voltage is less than or equal to the first preset deviation threshold, a preset recovery measure is executed. The preset recovery measure includes: controlling the power conversion module to reduce the bus voltage of the DC bus or controlling the power conversion module to increase the output power.

[0007] In one optional implementation, the main control module is specifically configured as follows: Obtain the bus voltage of the DC bus and the output power of the power conversion module; When the voltage deviation between the DC bus voltage and the minimum operating voltage is less than a second preset deviation threshold, or when the output power of the power conversion module is less than a preset power threshold, the capacitor voltage of each DC bus capacitor is obtained, wherein the minimum operating voltage is the minimum bus voltage required for the power conversion module to output the target AC voltage.

[0008] In one alternative implementation, the target capacitor voltage is determined based on the rated bus voltage of the DC bus and the total number of DC bus capacitors.

[0009] In one optional embodiment, the power conversion module includes a DC / AC conversion circuit, the DC side of which is connected to the DC bus and the connection point between each DC bus capacitor. The main control module is specifically configured to control the DC / AC conversion circuit to reduce the output power in order to increase the bus voltage of the DC bus.

[0010] In one optional implementation, the power conversion module includes a DC / DC conversion circuit and a DC / AC conversion circuit, wherein, The input side of the DC / DC converter circuit is used to connect to a DC power supply, and the output side of the DC / DC converter circuit is connected to one end of the DC bus. The other end of the DC bus and the connection point between each DC bus capacitor are respectively connected to the DC side of the DC / AC conversion circuit. The main control module is specifically configured to either control the DC / DC conversion circuit to increase the output voltage, or control the DC / AC conversion circuit to decrease the output power, thereby increasing the bus voltage of the DC bus.

[0011] In one optional implementation, the main control module includes a first controller and a second controller, wherein, The first controller is connected to the DC / DC conversion circuit, and the second controller is connected to the DC / AC conversion circuit; The first controller is communicatively connected to the second controller; The first controller is configured to: acquire the capacitor voltage of each of the DC bus capacitors; if the voltage deviation between the capacitor voltage of at least one of the DC bus capacitors and the target capacitor voltage is greater than the first preset deviation threshold, control the DC / DC conversion circuit to increase the output voltage, or output a first control signal to the second controller; The second controller is configured to control the DC / AC conversion circuit to reduce its output power in response to the first control signal.

[0012] In one optional implementation, the main control module includes a first controller and a second controller, wherein, The first controller is connected to the DC / DC conversion circuit, and the second controller is connected to the DC / AC conversion circuit; The first controller is communicatively connected to the second controller; The second controller is configured to: acquire the capacitor voltage of each of the DC bus capacitors; if the voltage deviation between the capacitor voltage of at least one of the DC bus capacitors and the target capacitor voltage is greater than the first preset deviation threshold, control the DC / AC conversion circuit to reduce the output power, or output a second control signal to the first controller. The first controller is configured to control the DC / DC converter circuit to increase the output voltage in response to the second control signal.

[0013] Secondly, this application provides a midpoint voltage offset control method applied to a power converter, the method comprising: The capacitor voltage of each DC bus capacitor in the power converter is obtained. The power converter includes a power conversion module and at least two DC bus capacitors. The first side of the power conversion module serves as the first side of the power converter, and the second side of the power conversion module serves as the second side of the power converter. The positive terminal of the first side of the power converter is used to connect to the positive terminal of the DC bus, and the negative terminal of the first side of the power converter is used to connect to the negative terminal of the DC bus. Each DC bus capacitor is connected in series between the positive terminal and the negative terminal of the DC bus. If the voltage deviation between the capacitor voltage of at least one of the DC bus capacitors and the target capacitor voltage is greater than a first preset deviation threshold, a preset adjustment measure is executed. The preset adjustment measure includes: controlling the power conversion module to increase the bus voltage of the DC bus or controlling the power conversion module to decrease the output power.

[0014] In an optional embodiment, the midpoint voltage offset control method provided in the second aspect of this application further includes: When the voltage deviation between the capacitor voltage of each DC bus capacitor and the target capacitor voltage is less than or equal to the first preset deviation threshold, a preset recovery measure is executed. The preset recovery measure includes: controlling the power conversion module to reduce the bus voltage of the DC bus or controlling the power conversion module to increase the output power.

[0015] In one optional implementation, obtaining the capacitor voltage of each DC bus capacitor in the power converter includes: Obtain the bus voltage of the DC bus and the output power of the power conversion module; When the voltage deviation between the DC bus voltage and the minimum operating voltage is less than a second preset deviation threshold, or when the output power of the power conversion module is less than a preset power threshold, the capacitor voltage of each DC bus capacitor is obtained, wherein the minimum operating voltage is the minimum bus voltage required for the power conversion module to output the target AC voltage.

[0016] Thirdly, this application provides a controller including a memory, a processor, and a computer program stored in the memory and executed by the processor, wherein the processor executes the computer program to implement the steps of the midpoint voltage offset control method provided in any embodiment of the second aspect of this application.

[0017] Fourthly, this application provides a power supply system including a power converter as provided in any embodiment of the first aspect of this application.

[0018] Based on the above, the power converter provided in this application includes a power conversion module, a main control module, and at least two DC bus capacitors. The first side of the power conversion module serves as the first side of the power converter, and the second side of the power conversion module serves as the second side of the power converter. The positive terminal of the first side of the power converter is connected to the positive terminal of the DC bus, and the negative terminal of the first side of the power converter is connected to the negative terminal of the DC bus. Each DC bus capacitor is connected in series between the positive and negative terminals of the DC bus. The main control module acquires the capacitor voltage of each DC bus capacitor. If the voltage deviation between the capacitor voltage of at least one DC bus capacitor and the target capacitor voltage is greater than a first preset deviation threshold, the main control module controls the power conversion module to increase the DC bus voltage or controls the power conversion module to decrease the output power. Since the midpoint voltage offset suppression strategy in related technologies can only achieve a good midpoint offset suppression effect when the bus voltage is high, the power converter provided in this application can increase the DC bus voltage by executing preset adjustment measures, thereby ensuring a better midpoint offset suppression effect for the midpoint voltage offset suppression strategy, improving the midpoint offset suppression effect, and significantly improving the operational stability of the power converter and the power supply system. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a structural block diagram of the first power converter provided in the embodiments of this application.

[0021] Figure 2 This is a structural block diagram of the second type of power converter provided in the embodiments of this application.

[0022] Figure 3 This is a structural block diagram of the third type of power converter provided in the embodiments of this application.

[0023] Figure 4 This is a structural block diagram of the fourth type of power converter provided in the embodiments of this application.

[0024] Figure 5 This is a structural block diagram of the fifth power converter provided in the embodiments of this application.

[0025] Figure 6 This is a flowchart of a midpoint voltage offset control method provided in an embodiment of this application.

[0026] Figure 7 This is a flowchart of another midpoint voltage offset control method provided in the embodiments of this application. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] As mentioned earlier, when the DC or AC voltage levels are high, power converters such as inverters often employ multi-level circuit topologies. Taking a common three-level inverter as an example, it has an inverter circuit and two series-connected DC bus capacitors on the DC side of the inverter circuit. Each DC bus capacitor carries half of the bus voltage, and the connection point of the two DC bus capacitors serves as the virtual midpoint of the inverter circuit. Ideally, the capacitor voltages of all DC bus capacitors are equal, and the midpoint voltage of the virtual midpoint is 0V. Correspondingly, when the capacitor voltages of each DC bus capacitor deviate significantly and the midpoint voltage is not 0V, a midpoint voltage offset occurs. This midpoint voltage offset will affect the reliable operation of the power converter and even the entire power supply system. Related technologies employ preset midpoint voltage offset suppression strategies to maintain midpoint voltage balance and ensure the stability of the power supply system.

[0029] Research has found that the midpoint voltage offset suppression strategy provided by related technologies is greatly affected by the operating state of the power converter, specifically by the bus voltage level of the DC bus in the power converter. When the bus voltage is greater than the minimum operating voltage of the power converter, the midpoint voltage offset suppression strategy can achieve a better midpoint offset suppression effect. Correspondingly, the higher the bus voltage, the better the midpoint offset suppression effect. Based on this, this application provides a power converter that increases the DC bus voltage when the capacitor voltages of each DC bus capacitor in the power converter deviate significantly, i.e., when midpoint voltage offset occurs. This ensures that the midpoint voltage offset suppression strategy achieves a better midpoint offset suppression effect, effectively suppresses the midpoint offset of the power converter, and significantly improves the stability of the power supply system.

[0030] Based on the above, this application provides a power converter, see [link to relevant documentation]. Figure 1 The power converter provided in this embodiment includes: a power conversion module 10, a main control module 20, and at least two DC bus capacitors. Figure 1 The figure is represented by n DC bus capacitors, where n ≥ 2.

[0031] Combination Figure 1As shown, the first side of the power conversion module 10 serves as the first side of the power converter. The positive terminal of the first side of the power converter is connected to the positive terminal of the DC bus (i.e., the positive DC bus BUS+), and the negative terminal of the first side of the power converter is connected to the negative terminal of the DC bus (i.e., the negative DC bus BUS-). The other side of the DC bus is connected to the DC power supply 30, that is, the DC power supply 30 is connected to the power conversion module 10 through the DC bus. The second side of the power conversion module 10 serves as the second side of the power converter and is used to connect to the power grid 40. The power conversion module 10 is used to convert the DC power provided by the DC power supply 30 into AC power and finally output it to the power grid 40. Each DC bus capacitor (C1-Cn) is connected in series between the positive and negative terminals of the DC bus. At the same time, the connection point of any two adjacent DC bus capacitors is connected to the power conversion module 10. Figure 1 (shown as dashed lines in the image) The main control module 20 can collect the capacitor voltage of each DC bus capacitor and the DC bus voltage, and control the operation of the power conversion module 10.

[0032] In practical applications, the DC power supply 30 can be selected from various options. In one optional embodiment, the DC power supply 30 can be a photovoltaic module; in another optional embodiment, the DC power supply 30 can also be an energy storage battery. Of course, the DC power supply 30 can also be other power sources capable of providing DC power, which will not be listed here.

[0033] Generally, the capacitance values ​​of all DC bus capacitors are equal. Therefore, ideally, the target capacitor voltages corresponding to each DC bus capacitor are also the same. It can be understood that the target capacitor voltage mentioned in this embodiment refers to the capacitor voltage corresponding to each DC bus capacitor under the condition of midpoint voltage balance. Based on this, as an optional implementation method, the main control module 20 determines the target capacitor voltage of each DC bus capacitor based on the rated bus voltage of the DC bus and the total number of DC bus capacitors. Specifically, the rated bus voltage is divided by the total number of DC bus capacitors, and the result is the target capacitor voltage of each DC bus capacitor.

[0034] Based on the above, the main control module 20 acquires the capacitor voltage of each DC bus capacitor, calculates the difference between the capacitor voltage of each DC bus capacitor and the target capacitor voltage, obtains the voltage deviation corresponding to each DC bus capacitor, and compares the voltage deviation of each DC bus capacitor with the first preset deviation threshold. If the voltage deviation of at least one DC bus capacitor is greater than the first preset deviation threshold, it indicates that the power converter has experienced a midpoint offset. The main control module 20 then controls the power conversion module 10 to execute preset adjustment measures. Specifically, the preset adjustment measures mentioned in this embodiment include: controlling the power conversion module 10 to increase the DC bus voltage, or controlling the power conversion module 10 to decrease the output power. Both of these measures can achieve the purpose of increasing the DC bus voltage.

[0035] As mentioned earlier, the preset midpoint offset suppression strategy has a better midpoint offset suppression effect when the bus voltage is high. Based on this, as an optional implementation, the main control module 20 executes the preset midpoint offset suppression strategy while controlling the power conversion module 10 to perform preset adjustment measures. This reduces the midpoint voltage based on the midpoint offset suppression strategy. As the suppression process proceeds, the deviation between the capacitor voltage of each DC bus capacitor and the target capacitor voltage gradually decreases. When the voltage deviation between the capacitor voltage of each DC bus capacitor and the target capacitor voltage is less than or equal to the first preset deviation threshold, the preset adjustment measures are stopped. Of course, in practical applications, the preset midpoint offset suppression strategy can also be executed by other control modules besides the main control module 20. As for the specific content of the midpoint offset suppression strategy, it can be implemented with reference to relevant technologies, and this application does not make specific limitations on it.

[0036] As can be seen from the foregoing, the first preset deviation threshold is used to identify whether the power converter has experienced a midpoint shift. If the voltage deviation between the voltage of at least one DC bus capacitor and the target capacitor voltage is greater than the first preset deviation threshold, a midpoint shift is determined to have occurred. If the voltage deviation between the voltage of each DC bus capacitor and the target capacitor voltage is less than or equal to the first preset deviation threshold, the midpoint is determined to be balanced. Therefore, in practical applications, the specific value of the first preset deviation threshold needs to be determined by considering factors such as the control precision of the power converter's midpoint shift and the power converter's operating environment (e.g., electromagnetic interference), which will not be elaborated here.

[0037] In summary, the power converter provided in this application embodiment allows the main control module to acquire the capacitor voltage of each DC bus capacitor. If the voltage deviation between the capacitor voltage of at least one DC bus capacitor and the target capacitor voltage is greater than a first preset deviation threshold, the main control module controls the power conversion module to increase the DC bus voltage or control the power conversion module to decrease the output power. Since the midpoint voltage offset suppression strategy in related technologies can only achieve a good midpoint offset suppression effect when the bus voltage is high, the power converter provided in this application can increase the DC bus voltage by executing preset adjustment measures, thereby ensuring a better midpoint offset suppression effect for the midpoint voltage offset suppression strategy, improving the midpoint offset suppression effect, and significantly improving the operational stability of the power converter and the power supply system.

[0038] It should be noted that the power converter provided in this application adopts a multi-level circuit topology. With two DC bus capacitors, it is a three-level circuit topology; with four DC bus capacitors, it is a five-level circuit topology, and so on. These will not be detailed here. In subsequent embodiments, a power converter using a three-level circuit topology will be used as an example to illustrate the operation of the power converter provided in this application.

[0039] See Figure 2 The power converter provided in this application includes a power conversion module 10, a main control module 20, a first DC bus capacitor C1, and a second DC bus capacitor C2, wherein the DC bus includes a positive DC bus BUS+ and a negative DC bus BUS-.

[0040] Combination Figure 2 As shown, one end of the first DC bus capacitor C1 is connected to the positive terminal of the DC bus (i.e., the positive DC bus BUS+), and the other end of the first DC bus capacitor C1 is connected to one end of the second DC bus capacitor C2. The other end of the second DC bus capacitor C2 is connected to the negative terminal of the DC bus (i.e., the negative DC bus BUS-). That is, the first DC bus capacitor C1 and the second DC bus capacitor C2 are connected in series between the positive DC bus BUS+ and the negative DC bus BUS-. The connection point of the first DC bus capacitor C1 and the second DC bus capacitor C2 is the midpoint of the DC bus, which is also the virtual midpoint of the power converter. Figure 2 Point O is shown in the middle.

[0041] One end of the DC bus is connected to the DC power supply 30, and the other end of the DC bus is connected to the DC side of the power conversion module 10. The AC side of the power conversion module 10 is used to connect to the power grid 40. The power conversion module 10 is used to convert the DC power provided by the DC power supply 30 into AC power and finally output it to the power grid 40.

[0042] In practical applications, the DC power supply 30 includes a positive output terminal and a negative output terminal. Correspondingly, the power conversion module 10 includes a positive input terminal and a negative input terminal. The positive and negative input terminals of the power conversion module 10 serve as the first side of the power conversion module 10, that is, as the first side of the power converter. Figure 2 As shown, one end of the positive DC bus BUS+ is connected to the positive output terminal of the DC power supply 30, and the other end is connected to the positive input terminal of the power conversion module 10. One end of the negative DC bus BUS- is connected to the negative output terminal of the DC power supply 30, and the other end is connected to the negative input terminal of the power conversion module 10. The midpoint O of the DC bus is connected to the midpoint of the power conversion module 10, but the specific connection method will vary depending on the implementation of the power conversion module 10. Figure 2 The connection between the two is shown by a dashed line. The specific connection method will be explained in detail in subsequent embodiments, and will not be described here.

[0043] The main control module 20 is connected to the power conversion module 10, and is also connected to the DC bus, the first DC bus capacitor C1, and the second DC bus capacitor C2 (not shown in the figure). The main control module 20 can obtain the bus voltage of the DC bus and the capacitor voltages of the first DC bus capacitor C1 and the second DC bus capacitor C2.

[0044] Combination Figure 2 As shown, the first DC bus capacitor C1 and the second DC bus capacitor C2 are connected in series between the positive DC bus BUS+ and the negative DC bus BUS-. Therefore, the sum of the capacitor voltages of the first DC bus capacitor C1 and the second DC bus capacitor C2 is the bus voltage of the DC bus. In general, the capacitance values ​​of the first DC bus capacitor C1 and the second DC bus capacitor C2 are equal. Therefore, ideally, the target capacitor voltages corresponding to the first DC bus capacitor C1 and the second DC bus capacitor C2 are also the same.

[0045] Based on the above, the main control module 20 acquires the capacitor voltage of each DC bus capacitor, calculates the difference between the capacitor voltage of each DC bus capacitor and the target capacitor voltage, obtains the voltage deviation corresponding to each DC bus capacitor, and compares the voltage deviation of each DC bus capacitor with the first preset deviation threshold. If the voltage deviation of at least one DC bus capacitor is greater than the first preset deviation threshold, it indicates that the power converter has experienced a midpoint offset. The main control module 20 then controls the power conversion module 10 to execute preset adjustment measures. As mentioned above, the preset adjustment measures described in this embodiment include: controlling the power conversion module 10 to increase the DC bus voltage, or controlling the power conversion module 10 to decrease the output power. Both of these measures can achieve the purpose of increasing the DC bus voltage. As mentioned above, the preset midpoint offset suppression strategy has a better midpoint offset suppression effect when the bus voltage is high. Based on this, as an optional implementation method, the main control module 20 executes the preset midpoint offset suppression strategy while controlling the power conversion module 10 to perform preset adjustment measures, thereby reducing the midpoint voltage based on the midpoint offset suppression strategy. As for the specific content of the midpoint offset suppression strategy, it can be implemented with reference to relevant technologies, and this application does not make specific limitations on it.

[0046] In summary, the power converter provided in this application embodiment allows the main control module to acquire the capacitor voltage of each DC bus capacitor. If the voltage deviation between the capacitor voltage of at least one DC bus capacitor and the target capacitor voltage is greater than a first preset deviation threshold, the main control module controls the power conversion module to increase the DC bus voltage or control the power conversion module to decrease the output power. Since the midpoint voltage offset suppression strategy in related technologies can only achieve a good midpoint offset suppression effect when the bus voltage is high, the power converter provided in this application can increase the DC bus voltage by executing preset adjustment measures, thereby ensuring a better midpoint offset suppression effect for the midpoint voltage offset suppression strategy, improving the midpoint offset suppression effect, and significantly improving the operational stability of the power converter and the power supply system.

[0047] Based on the working principle of the power converter, it is known that increasing the DC bus voltage will affect the normal operation of the power converter. In order to restore the operating state of the power converter as soon as possible, after increasing the DC bus voltage, it is necessary to continue to monitor the midpoint offset of the power converter.

[0048] Specifically, after increasing the DC bus voltage, the preset midpoint offset suppression strategy will gradually reduce the midpoint voltage. Based on this, as an optional implementation, the main control module monitors the changes in the capacitor voltage of each DC bus capacitor. When the voltage deviation between the capacitor voltage of each DC bus capacitor and the target capacitor voltage is less than or equal to the first preset deviation threshold, that is, when the midpoint offset is restored to the midpoint balance, the preset recovery measures are executed. Referring to the aforementioned preset adjustment measures, the preset recovery measures provided in this application embodiment include: controlling the power conversion module to reduce the DC bus voltage, or controlling the power conversion module to increase the output power, until the power converter returns to normal operation.

[0049] It should be noted that during the process of the main control module controlling the power conversion module to reduce the bus voltage, the midpoint offset may occur again. At this time, the main control module can control the power conversion module to perform preset adjustment measures according to the control logic provided in the aforementioned embodiment, so that the midpoint offset suppression strategy can further adjust the midpoint voltage of the DC bus. When the voltage deviation between the capacitor voltage of each DC bus capacitor and the target capacitor voltage is less than or equal to the first preset deviation threshold, the main control module can continue to control the power conversion module to perform preset recovery measures. This process is repeated until the midpoint balance is achieved.

[0050] This application embodiment further provides another power converter, see [link to documentation]. Figure 3 As shown, in the power converter provided in this embodiment, the power conversion module includes a DC / AC conversion circuit 110. As for the other components in the power converter and the interconnection between them, please refer to the relevant content of the foregoing embodiment, which will not be repeated here.

[0051] Combination Figure 3 As shown, the DC side of the DC / AC converter circuit 110 is connected to the DC bus and the connection points of the first DC bus capacitor C1 and the second DC bus capacitor C2, respectively. Specifically, the positive input terminal of the DC / AC converter circuit 110 is connected to the positive DC bus BUS+, the negative input terminal is connected to the negative DC bus BUS-, and the midpoint is connected to the midpoint O of the DC bus. The AC side of the DC / AC converter circuit 110 is connected to the power grid 40. The specific circuit topology of the DC / AC converter circuit 110 can be implemented with reference to relevant technologies and will not be detailed here.

[0052] The main control module 20 acquires the capacitor voltage of each DC bus capacitor. If the voltage deviation between the capacitor voltage of at least one DC bus capacitor and the target capacitor voltage exceeds a first preset deviation threshold, the main control module 20 controls the DC / AC conversion circuit 110 to reduce its output power. Based on the operating principle of the DC / AC conversion circuit, reducing the output power can increase its DC-side voltage, thereby increasing the bus voltage of the DC bus. As mentioned above, as an optional implementation, when the bus voltage increases, the main control module 20 can further execute a preset midpoint offset suppression strategy to reduce the midpoint voltage.

[0053] Furthermore, as the midpoint offset improves, the voltage deviation between the DC bus capacitor voltage and the target capacitor voltage gradually decreases. When the voltage deviation between the DC bus capacitor voltage and the target capacitor voltage is less than or equal to the first preset deviation threshold, the main control module 20 further controls the DC / AC conversion circuit 110 to increase the output power, thereby forcing the bus voltage to decrease until the power converter returns to normal operation.

[0054] Similar to the aforementioned embodiments, during the process of the main control module 20 controlling the DC / AC conversion circuit 110 to increase the output power and reduce the bus voltage, the midpoint offset may occur again. At this time, the main control module 20 can control the DC / AC conversion circuit 110 to reduce the output power according to the control logic provided in the aforementioned embodiments, so that the midpoint offset suppression strategy can further adjust the midpoint voltage of the DC bus. When the voltage deviation between the capacitor voltage of each DC bus capacitor and the target capacitor voltage is less than or equal to the first preset deviation threshold, the main control module 20 can continue to control the DC / AC conversion circuit 110 to increase the output power, and so on, until the power converter returns to normal operation.

[0055] This application also provides another power converter, see [link to example]. Figure 4 As shown, in the power converter provided in this embodiment, the power conversion module includes a DC / AC conversion circuit 110 and a DC / DC conversion circuit 120.

[0056] Combination Figure 4As shown, the input side of the DC / DC converter 120 is connected to the DC power supply 30, and the output side of the DC / DC converter 120 is connected to one end of the DC bus. The other end of the DC bus is connected to the DC side of the DC / AC converter 110. Furthermore, the midpoint of the DC side of the DC / AC converter 110 is also connected to the connection point of the first DC bus capacitor C1 and the second DC bus capacitor C2. The main control module 20 is connected to the control terminals of both the DC / AC converter 110 and the DC / DC converter 120. The main control module 20 can also acquire the bus voltage of the DC bus and the capacitor voltages of the first DC bus capacitor C1 and the second DC bus capacitor C2. As for the other components of the power converter and their interconnections, please refer to the relevant content of the foregoing embodiments; they will not be repeated here.

[0057] Based on the above connection relationship, if the voltage deviation between the voltage of at least one DC bus capacitor and the target capacitor voltage is greater than the first preset deviation threshold, the main control module 20 determines that the power converter has experienced a midpoint offset, that is, controls the DC / DC conversion circuit 120 to increase the output voltage. Since the DC bus is directly connected to the output terminal of the DC / DC conversion circuit 120, the bus voltage of the DC bus can be directly increased. Alternatively, the main control module 20 controls the DC / AC conversion circuit 110 to reduce the output power, which can also increase the bus voltage of the DC bus.

[0058] In summary, the power converter provided in this embodiment includes a DC / DC conversion circuit and a DC / AC conversion circuit. The main control module can control the DC / DC conversion circuit or the DC / AC conversion circuit to increase the bus voltage according to the actual situation. Since the midpoint voltage offset suppression strategy in related technologies can only achieve a good midpoint offset suppression effect when the bus voltage is high, increasing the DC bus voltage can provide a guarantee for the midpoint voltage offset suppression strategy to achieve a better midpoint offset suppression effect, improve the midpoint offset suppression effect, and significantly improve the stability of the power supply system.

[0059] Furthermore, for Figure 4The power converter provided in the illustrated embodiment, when using photovoltaic modules as the DC power source, typically employs an MPPT (Maximum Power Point Tracking) control strategy to fully utilize the output power of the photovoltaic modules. Further research reveals that under weak sunlight conditions, the output voltage of the photovoltaic modules decreases. To achieve maximum power output, the MPPT control strategy usually reduces the DC bus voltage, causing it to approach the minimum operating voltage of the power converter. This severely limits the midpoint offset suppression effect of the related technology's midpoint offset suppression strategy. In other words, when the DC bus voltage approaches the minimum operating voltage of the power converter, the control strategy provided in this application needs to be executed to increase the bus voltage, ensuring a better midpoint offset suppression effect for the midpoint offset suppression strategy.

[0060] As mentioned above, the output power of the power conversion module will also affect the DC bus voltage. Based on this, in one possible application scenario, it can be determined whether the control strategy provided in this application needs to be executed based on the output power of the power conversion module, so as to ensure that the midpoint offset suppression strategy achieves a better midpoint offset suppression effect.

[0061] Based on the above, the main control module can obtain the bus voltage of the DC bus and the output power of the power conversion module. When the voltage deviation between the DC bus voltage and the minimum operating voltage is less than the second preset deviation threshold, or when the output power of the power conversion module is less than the preset power threshold, the module obtains the capacitor voltage of each DC bus capacitor and then determines whether to execute preset adjustment measures based on the deviation of the capacitor voltage of each DC bus capacitor from the target capacitor voltage.

[0062] The minimum operating voltage mentioned above refers to the minimum bus voltage required for the power conversion module to output the target AC voltage. The target AC voltage is an AC voltage determined based on the grid voltage that meets the grid connection requirements of the power converter. The specific determination processes for the target AC voltage and the minimum operating voltage can be implemented with reference to relevant technologies, and this application does not limit their specific values. Regarding the second preset deviation threshold, since it measures the closeness between the bus voltage and the minimum operating voltage and is related to the midpoint offset suppression effect of the midpoint offset suppression strategy in relevant technologies, in practical applications, it can be mainly determined by referring to the minimum operating voltage and the specific implementation of the midpoint offset suppression strategy. This application does not limit the specific value of the second preset deviation threshold. Correspondingly, the preset power threshold is used to measure the output power of the power conversion module. In practical applications, it can be determined by combining the design parameters of the power converter and the load conditions of the power supply system to which the power converter belongs. This application does not limit the specific value of the preset power threshold.

[0063] This application also provides another power converter, see [link to example]. Figure 5 As shown, in the power converter provided in this embodiment, the main control module includes a first controller 210 and a second controller 220. The first controller 210 is connected to the control terminal of the DC / DC conversion circuit 120 and is used to control the operation of the DC / DC conversion circuit 120. The second controller 220 is connected to the control terminal of the DC / AC conversion circuit 110 and is used to control the operation of the DC / AC conversion circuit 110. Furthermore, the first controller 210 and the second controller 220 are communicatively connected. As for the other components of the power converter and the interconnections between them, please refer to the relevant content of the foregoing embodiments, which will not be repeated here.

[0064] based on Figure 5 As can be seen from the power converter structure shown, the control process in the aforementioned embodiments, in which the main control module executes preset adjustment measures, can be implemented by the first controller 210 or by the second controller 220.

[0065] Based on the above, as an optional implementation, the first controller 210 controls the power conversion module to perform preset adjustment measures. Specifically, the first controller 210 acquires the DC bus voltage and the output power of the power conversion module. When the voltage deviation between the DC bus voltage and the minimum operating voltage is less than a second preset deviation threshold, or when the output power of the power conversion module is less than a preset power threshold, the first controller 210 acquires the capacitor voltage of each DC bus capacitor. When the voltage deviation between the capacitor voltage of at least one DC bus capacitor and the target capacitor voltage is greater than the first preset deviation threshold, the first controller 210 controls the DC / DC conversion circuit 120 to increase the output voltage, or outputs a first control signal to the second controller 220. In response to the first control signal, the second controller 220 controls the DC / AC conversion circuit 110 to decrease the output power to increase the DC bus voltage. Furthermore, after the bus voltage is increased, the preset midpoint offset suppression strategy will gradually reduce the midpoint voltage. The first controller 210 monitors the capacitor voltage of each DC bus capacitor. When the voltage deviation between the capacitor voltage of each DC bus capacitor and the target capacitor voltage is less than or equal to the first preset deviation, the DC / DC conversion circuit 110 is further controlled to reduce the DC bus voltage or the second controller 220 is notified to control the DC / AC conversion circuit 120 to increase the output power. Both methods can achieve the purpose of reducing the bus voltage. As the bus voltage decreases, the output power of the power conversion module will gradually increase until the power converter returns to normal operation.

[0066] Furthermore, in another optional embodiment, the second controller 220 controls the power conversion module to perform preset adjustment measures. Specifically, the second controller 220 acquires the DC bus voltage and the output power of the power conversion module. If the voltage deviation between the DC bus voltage and the minimum operating voltage is less than a second preset deviation threshold, or if the output power of the power conversion module is less than a preset power threshold, the second controller 220 acquires the capacitor voltage of each DC bus capacitor. If the voltage deviation between the capacitor voltage of at least one DC bus capacitor and the target capacitor voltage is greater than a first preset deviation threshold, the second controller 220 controls the DC / AC conversion circuit 110 to reduce the output power to increase the DC bus voltage. Alternatively, the second controller 220 outputs a second control signal to the first controller 210, which, in response to the second control signal, controls the DC / DC conversion circuit 120 to increase the output voltage. Furthermore, after the bus voltage is increased, the preset midpoint offset suppression strategy will gradually reduce the midpoint voltage. The second controller 220 monitors the capacitor voltage of each DC bus capacitor. When the voltage deviation between the capacitor voltage of each DC bus capacitor and the target capacitor voltage is less than or equal to the first preset deviation, the second controller 220 further controls the DC / AC conversion circuit 120 to increase the output power or notifies the first controller 210 to control the DC / DC conversion circuit 120 to reduce the DC bus voltage until the power converter returns to normal operation.

[0067] This application further provides a midpoint voltage offset control method, which is applied to the power converter provided in any of the foregoing embodiments, specifically to the main control module in the power converter. Of course, in some cases, it can also be executed by other controllers outside the power converter.

[0068] See Figure 6 The midpoint offset control method provided in this application embodiment may include the following steps.

[0069] S100: Obtain the capacitor voltage of each DC bus capacitor in the power converter.

[0070] Based on the foregoing, the first side of the power conversion module serves as the first side of the power converter. The positive terminal of the first side of the power converter is connected to the positive terminal of the DC bus, and the negative terminal of the first side of the power converter is used to connect to the negative terminal of the DC bus. The other side of the DC bus is connected to the DC power supply, i.e., the DC power supply is connected to the power conversion module through the DC bus. The second side of the power conversion module serves as the second side of the power converter and is used to connect to the AC power grid. Each DC bus capacitor is connected in series between the positive and negative terminals of the DC bus. The power conversion module is connected to the DC bus. At the same time, the connection point of any two adjacent DC bus capacitors is connected to the power conversion module. The main control module can collect the capacitor voltage of each DC bus capacitor and control the operation of the power conversion module.

[0071] Furthermore, when a power converter is connected to a photovoltaic module, in order to fully utilize the electrical power output by the photovoltaic module, an MPPT control strategy is typically used to control the operation of the power converter. Under weak sunlight conditions, the output voltage of the photovoltaic module decreases. In order to achieve maximum power output, the MPPT control strategy usually reduces the DC bus voltage, causing the DC bus voltage to approach the minimum operating voltage of the power converter. This situation severely limits the midpoint offset suppression effect of the midpoint offset suppression strategy provided by related technologies. In other words, when the DC bus voltage approaches the minimum operating voltage of the power converter, it is necessary to drive the control strategy provided in this application to increase the bus voltage to ensure a better midpoint offset suppression effect for the midpoint offset suppression strategy.

[0072] Based on this, the main control module can determine whether to increase the bus voltage based on the relationship between the bus voltage and the minimum operating voltage of the DC bus. Specifically, the main control module obtains the bus voltage and the minimum operating voltage, calculates the voltage deviation between the bus voltage and the minimum operating voltage, and if the obtained voltage deviation is less than the second preset deviation threshold, it means that the bus voltage is close to the minimum operating voltage, and the main control module obtains the midpoint voltage of the DC bus.

[0073] Furthermore, the output power of the power conversion module will also affect the DC bus voltage. Based on this, in one possible application scenario, it can be determined whether the control strategy provided in this application needs to be executed based on the output power of the power conversion module, so as to ensure that the midpoint offset suppression strategy achieves a better midpoint offset suppression effect.

[0074] Based on the above, the main control module can obtain the bus voltage of the DC bus and the output power of the power conversion module. When the voltage deviation between the DC bus voltage and the minimum operating voltage is less than the second preset deviation threshold, or when the output power of the power conversion module is less than the preset power threshold, the module obtains the capacitor voltage of each DC bus capacitor and then determines whether to execute preset adjustment measures based on the deviation of the capacitor voltage of each DC bus capacitor from the target capacitor voltage.

[0075] S110. If the voltage deviation between the capacitor voltage of at least one DC bus capacitor and the target capacitor voltage is greater than a first preset deviation threshold, a preset adjustment measure is executed.

[0076] After the main control module obtains the capacitor voltage of each DC bus capacitor, it calculates the difference between the capacitor voltage of each DC bus capacitor and the target capacitor voltage to obtain the voltage deviation of each DC bus capacitor. It then compares the voltage deviation of each DC bus capacitor with the first preset deviation threshold. If the voltage deviation of at least one DC bus capacitor is greater than the first preset deviation threshold, it indicates that the power converter has experienced a midpoint offset. The main control module then controls the power conversion module to execute preset adjustment measures. Specifically, the preset adjustment measures described in this embodiment include: controlling the power conversion module to increase the DC bus voltage, or controlling the power conversion module to decrease the output power. Both of these measures can achieve the purpose of increasing the DC bus voltage.

[0077] As mentioned earlier, the preset midpoint offset suppression strategy has a better midpoint offset suppression effect when the bus voltage is high. Based on this, as an optional implementation method, the main control module executes the preset midpoint offset suppression strategy while controlling the power conversion module to perform preset adjustment measures, thereby reducing the midpoint voltage based on the midpoint offset suppression strategy. As the suppression process proceeds, the deviation between the capacitor voltage of each DC bus capacitor and the target capacitor voltage gradually decreases. When the voltage deviation between the capacitor voltage of each DC bus capacitor and the target capacitor voltage is less than or equal to the first preset deviation threshold, the preset adjustment measures are stopped.

[0078] In summary, the midpoint voltage offset control method provided in this application involves the main control module acquiring the capacitor voltage of each DC bus capacitor. If the voltage deviation between the capacitor voltage of at least one DC bus capacitor and the target capacitor voltage exceeds a first preset deviation threshold, the power conversion module is controlled to either increase the DC bus voltage or decrease the output power. Since the midpoint voltage offset suppression strategy in related technologies can only achieve a good midpoint offset suppression effect when the bus voltage is high, the power converter provided in this application can increase the DC bus voltage by executing preset adjustment measures, thereby ensuring a better midpoint offset suppression effect for the midpoint voltage offset suppression strategy, improving the midpoint offset suppression effect, and significantly improving the operational stability of the power converter and the power supply system.

[0079] This application also provides another method for controlling midpoint voltage offset, see [link to relevant documentation]. Figure 7 The specific steps are shown below.

[0080] S200: Obtain the capacitor voltage of each DC bus capacitor in the power converter.

[0081] In one alternative implementation, the specific implementation of S200 can be referred to Figure 6 The details of S100 in the illustrated embodiment will not be repeated here.

[0082] S210. If the voltage deviation between the capacitor voltage of at least one DC bus capacitor and the target capacitor voltage is greater than a first preset deviation threshold, a preset adjustment measure is executed.

[0083] In one alternative implementation, the specific implementation of S210 can be referred to Figure 6 The details of S110 in the illustrated embodiment will not be repeated here.

[0084] S220. When the voltage deviation between the capacitor voltage of each DC bus capacitor and the target capacitor voltage is less than or equal to the first preset deviation threshold, a preset recovery measure is executed.

[0085] Based on the working principle of the power converter, it is known that increasing the DC bus voltage will affect the normal operation of the power converter. In order to restore the operating state of the power converter as soon as possible, after increasing the DC bus voltage, it is necessary to continue to monitor the midpoint offset of the power converter.

[0086] Specifically, after increasing the DC bus voltage, the preset midpoint offset suppression strategy will gradually reduce the midpoint voltage. Based on this, as an optional implementation, the main control module monitors the changes in the capacitor voltage of each DC bus capacitor. When the voltage deviation between the capacitor voltage of each DC bus capacitor and the target capacitor voltage is less than or equal to the first preset deviation threshold, that is, when the midpoint offset is restored to the midpoint balance, the preset recovery measures are executed. Referring to the aforementioned preset adjustment measures, the preset recovery measures provided in this application embodiment include: controlling the power conversion module to reduce the DC bus voltage, or controlling the power conversion module to increase the output power, until the power converter returns to normal operation.

[0087] In summary, the midpoint voltage offset control method provided in this embodiment improves the midpoint voltage offset suppression effect by increasing the DC bus voltage, thus ensuring a better midpoint offset suppression effect. Furthermore, after the midpoint voltage is balanced, the power conversion module is controlled to reduce the DC bus voltage and increase the output power of the power conversion module, ensuring that the power converter returns to normal operation as soon as possible and minimizing power loss.

[0088] This application also provides a controller, including a memory, a processor, and a computer program stored in the memory and executed by the processor. When the processor executes the computer program, it implements the steps of the midpoint voltage offset control method provided in any of the foregoing embodiments of this application.

[0089] This application also provides a power supply system, which includes the power converter provided in any of the foregoing embodiments.

[0090] Those skilled in the art will understand that the contents disclosed herein can be varied and modified in many ways. For example, the various devices or components described above can be implemented in hardware, or in software, firmware, or a combination of some or all of the three.

[0091] Furthermore, while this disclosure makes various references to certain elements of systems according to embodiments of this disclosure, any number of different elements may be used and operated on clients and / or servers. Elements are merely illustrative, and different aspects of the system and method may use different elements.

[0092] This disclosure uses flowcharts to illustrate the steps of a method according to embodiments of this disclosure. It should be understood that the preceding or following steps are not necessarily performed in exact order. Instead, the steps can be processed in reverse order or simultaneously. Furthermore, other operations can be added to these processes.

[0093] Those skilled in the art will understand that all or part of the steps in the above methods can be implemented by a computer program instructing related hardware, and the program can be stored in a computer-readable storage medium, such as a read-only memory. Optionally, all or part of the steps in the above embodiments can also be implemented using one or more integrated circuits. Accordingly, each module / unit in the above embodiments can be implemented in hardware or as a software functional module. This disclosure is not limited to any particular combination of hardware and software.

[0094] Unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It should also be understood that terms such as those defined in a common dictionary should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and not as having an idealized or highly formalized meaning, unless expressly defined herein.

[0095] The foregoing description is intended to illustrate the present disclosure and should not be construed as limiting it. While several exemplary embodiments of the present disclosure have been described, those skilled in the art will readily understand that many modifications may be made to the exemplary embodiments without departing from the novel teachings and advantages of the present disclosure. Therefore, all such modifications are intended to be included within the scope of the present disclosure as defined by the claims. It should be understood that the foregoing description is intended to illustrate the present disclosure and should not be construed as limiting it to the specific embodiments disclosed, and modifications to the disclosed embodiments and other embodiments are intended to be included within the scope of the appended claims. The present disclosure is defined by the claims and their equivalents.

Claims

1. A power converter, characterized in that, include: The system includes a power conversion module, a main control module, and at least two DC bus capacitors. The first side of the power conversion module serves as the first side of the power converter, and the second side of the power conversion module serves as the second side of the power converter; The positive terminal of the first side of the power converter is used to connect to the positive terminal of the DC bus, and the negative terminal of the first side of the power converter is used to connect to the negative terminal of the DC bus. The at least two DC bus capacitors are connected in series between the positive terminal and the negative terminal of the DC bus; The main control module is configured to: acquire the capacitor voltage of each DC bus capacitor; if the voltage deviation between the capacitor voltage of at least one DC bus capacitor and the target capacitor voltage is greater than a first preset deviation threshold, execute preset adjustment measures, the preset adjustment measures including: controlling the power conversion module to increase the bus voltage of the DC bus or controlling the power conversion module to decrease the output power.

2. The power converter according to claim 1, characterized in that, The main control module is also configured to: When the voltage deviation between the capacitor voltage of each DC bus capacitor and the target capacitor voltage is less than or equal to the first preset deviation threshold, a preset recovery measure is executed. The preset recovery measure includes: controlling the power conversion module to reduce the bus voltage of the DC bus or controlling the power conversion module to increase the output power.

3. The power converter according to claim 1, characterized in that, The main control module is specifically configured as follows: Obtain the bus voltage of the DC bus and the output power of the power conversion module; When the voltage deviation between the DC bus voltage and the minimum operating voltage is less than a second preset deviation threshold, or when the output power of the power conversion module is less than a preset power threshold, the capacitor voltage of each DC bus capacitor is obtained, wherein the minimum operating voltage is the minimum bus voltage required for the power conversion module to output the target AC voltage.

4. The power converter according to claim 1, characterized in that, The target capacitor voltage is determined based on the rated bus voltage of the DC bus and the total number of DC bus capacitors.

5. The power converter according to claim 1, characterized in that, The power conversion module includes a DC / AC conversion circuit, the DC side of which is connected to the DC bus and the connection point between each DC bus capacitor. The main control module is specifically configured to control the DC / AC conversion circuit to reduce the output power in order to increase the bus voltage of the DC bus.

6. The power converter according to claim 1, characterized in that, The power conversion module includes a DC / DC conversion circuit and a DC / AC conversion circuit, wherein, The input side of the DC / DC converter circuit is used to connect to a DC power supply, and the output side of the DC / DC converter circuit is connected to one end of the DC bus. The other end of the DC bus and the connection point between each DC bus capacitor are respectively connected to the DC side of the DC / AC conversion circuit. The main control module is specifically configured to either control the DC / DC conversion circuit to increase the output voltage, or control the DC / AC conversion circuit to decrease the output power, thereby increasing the bus voltage of the DC bus.

7. The power converter according to claim 6, characterized in that, The main control module includes a first controller and a second controller, wherein... The first controller is connected to the DC / DC conversion circuit, and the second controller is connected to the DC / AC conversion circuit; The first controller is communicatively connected to the second controller; The first controller is configured to: acquire the capacitor voltage of each of the DC bus capacitors; if the voltage deviation between the capacitor voltage of at least one of the DC bus capacitors and the target capacitor voltage is greater than the first preset deviation threshold, control the DC / DC conversion circuit to increase the output voltage, or output a first control signal to the second controller; The second controller is configured to control the DC / AC conversion circuit to reduce its output power in response to the first control signal.

8. The power converter according to claim 6, characterized in that, The main control module includes a first controller and a second controller, wherein... The first controller is connected to the DC / DC conversion circuit, and the second controller is connected to the DC / AC conversion circuit; The first controller is communicatively connected to the second controller; The second controller is configured to: acquire the capacitor voltage of each of the DC bus capacitors; if the voltage deviation between the capacitor voltage of at least one of the DC bus capacitors and the target capacitor voltage is greater than the first preset deviation threshold, control the DC / AC conversion circuit to reduce the output power, or output a second control signal to the first controller. The first controller is configured to control the DC / DC converter circuit to increase the output voltage in response to the second control signal.

9. A method for controlling midpoint voltage offset, characterized in that, Applied to a power converter, the method includes: The capacitor voltage of each DC bus capacitor in the power converter is obtained. The power converter includes a power conversion module and at least two DC bus capacitors. The first side of the power conversion module serves as the first side of the power converter, and the second side of the power conversion module serves as the second side of the power converter. The positive terminal of the first side of the power converter is used to connect to the positive terminal of the DC bus, and the negative terminal of the first side of the power converter is used to connect to the negative terminal of the DC bus. Each DC bus capacitor is connected in series between the positive terminal and the negative terminal of the DC bus. If the voltage deviation between the capacitor voltage of at least one of the DC bus capacitors and the target capacitor voltage is greater than a first preset deviation threshold, a preset adjustment measure is executed. The preset adjustment measure includes: controlling the power conversion module to increase the bus voltage of the DC bus or controlling the power conversion module to decrease the output power.

10. The midpoint voltage offset control method according to claim 9, characterized in that, Also includes: When the voltage deviation between the capacitor voltage of each DC bus capacitor and the target capacitor voltage is less than or equal to the first preset deviation threshold, a preset recovery measure is executed. The preset recovery measure includes: controlling the power conversion module to reduce the bus voltage of the DC bus or controlling the power conversion module to increase the output power.

11. The midpoint voltage offset control method according to claim 9, characterized in that, Obtaining the capacitor voltage of each DC bus capacitor in the power converter includes: Obtain the bus voltage of the DC bus and the output power of the power conversion module; When the voltage deviation between the DC bus voltage and the minimum operating voltage is less than a second preset deviation threshold, or when the output power of the power conversion module is less than a preset power threshold, the capacitor voltage of each DC bus capacitor is obtained, wherein the minimum operating voltage is the minimum bus voltage required for the power conversion module to output the target AC voltage.

12. A controller comprising a memory, a processor, and a computer program stored in the memory and executed by the processor, characterized in that, When the processor executes the computer program, it implements the steps of the midpoint voltage offset control method as described in any one of claims 9 to 11.

13. A power supply system, characterized in that, include: The power converter as described in any one of claims 1 to 8.

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