Neutral-point balancing circuit, control method, power converter, photovoltaic equipment and electric appliance

Abstract

The invention discloses a neutral-point balancing circuit, a control method, a power converter, photovoltaic equipment and an electric appliance. The neutral-point balancing circuit comprises a first switch of which the first end is connected with the first end of the output side of a rectifying circuit of the power converter; the first end of the first resistor is connected with the second end of the first switch, and the second end of the first resistor is connected with the first end of an upper bridge arm capacitor of the direct-current bus; the first end of the second switch is connected between the first switch and the first resistor, and the second end of the second switch is connected with the second end of the upper bridge arm capacitor; the first end of the second resistor is connected with the first end of the lower bridge arm capacitor of the direct current bus, and the second end is connected with the second end of the lower bridge arm capacitor. According to the invention, the function multiplexing of the resistor can be realized, that is, the dual functions of limiting the charging current and balancing the neutral-point voltage are realized through the same resistor, the number of the resistors is reduced, and the cost is reduced and the energy is saved.

Description

Technical Field

[0001] This invention relates to the field of electronic power technology, and more specifically, to a midpoint balancing circuit, a control method, a power converter, a photovoltaic device, and an electrical appliance. Background Technology

[0002] Due to factors such as varying loads and battery voltage changes, the DC voltage output from the grid and the inverter to the bus fluctuates, causing differences in the midpoint potential of the output voltage, resulting in a voltage offset. When this offset exceeds the midpoint voltage tolerance range, the system becomes unbalanced. To ensure a stable midpoint voltage balance, identical resistors are typically added to both half-bridges to balance the voltage offset. Furthermore, in practical applications, an additional pre-charging resistor is usually added to pre-charge the bus capacitor with a small current to prevent overcurrent. The redundant setting of the midpoint balancing resistor and the pre-charging resistor increases the system cost.

[0003] There is currently no effective solution to the problem of increased circuit cost caused by redundant settings of the midpoint balancing resistor and pre-charging resistor in existing power converters. Summary of the Invention

[0004] This invention provides a midpoint balancing circuit, a control method, a power converter, a photovoltaic device, and an electrical appliance to solve the problem of redundant settings of the midpoint balancing resistor and pre-charging resistor in the prior art, which increases circuit cost.

[0005] To solve the above-mentioned technical problems, the present invention provides a midpoint balancing circuit applied to a power converter. The power converter includes a rectifier circuit and an inverter circuit. The output terminal of the inverter circuit is connected to the high line and the low line of the DC bus. An upper bridge arm capacitor and a lower bridge arm capacitor are connected in series between the high line and the low line of the DC bus. The midpoint balancing circuit is characterized by comprising:

[0006] A first switch, the first end of which is connected to the first end of the output side of the rectifier circuit;

[0007] The first resistor has its first end connected to the second end of the first switch, and its second end connected to the first end of the upper bridge arm capacitor.

[0008] The second switch has its first end connected between the first switch and the first resistor, and its second end connected to the second end of the upper bridge arm capacitor.

[0009] The second resistor has its first end connected to the first end of the lower bridge arm capacitor and its second end connected to the second end of the lower bridge arm capacitor.

[0010] Furthermore, the midpoint balancing circuit also includes:

[0011] The third resistor has its first end connected between the first switch and the first resistor;

[0012] The third switch has its first end connected to the second end of the third resistor, and its second end connected to the second end of the second resistor.

[0013] Furthermore, the third switch is a normally closed switch.

[0014] Furthermore, the midpoint balancing circuit also includes:

[0015] Auxiliary power supply, whose input is connected to the AC power grid;

[0016] The fourth resistor has its first end connected to the first output terminal of the auxiliary power supply;

[0017] The fifth resistor has its first end connected to the second end of the fourth resistor, and its second end connected to the second output terminal of the auxiliary power supply.

[0018] The first end of the fourth resistor and the second end of the fifth resistor are also connected to the third switch.

[0019] Furthermore, the midpoint balancing circuit also includes:

[0020] The sixth resistor has its first end connected to the first output terminal of the auxiliary power supply;

[0021] The fourth switch has its first end connected to the second end of the sixth resistor, and its second end connected to the second output terminal of the auxiliary power supply.

[0022] Furthermore, the first switch is a normally open switch; the second switch and the fourth switch are both normally closed switches.

[0023] The present invention also provides a control method applied to the above-mentioned midpoint balancing circuit, the control method comprising:

[0024] After the power converter is started, the first switch is turned on, thereby controlling the upper bridge arm capacitor and the lower bridge arm capacitor to charge, while the second switch is turned off.

[0025] After the upper bridge arm capacitor and the lower bridge arm capacitor have finished charging, the first switch is turned off, and the second switch is turned on.

[0026] Furthermore, after the power converter is started, the control method further includes:

[0027] The fourth switch is turned off, which in turn causes the third switch to turn off;

[0028] Wherein, the first end of the third switch is connected to the second end of the third resistor, the second end of the third switch is connected to the second end of the second resistor, and the first end of the third resistor is connected between the first switch and the first resistor;

[0029] The first end of the fourth switch is connected to the second end of the sixth resistor, and the second end is connected to the second output terminal of the auxiliary power supply; the first end of the sixth resistor is connected to the first output terminal of the auxiliary power supply.

[0030] The input terminal of the auxiliary power supply is connected to the AC power grid, the first end of the fourth resistor is connected to the first output terminal of the auxiliary power supply, the first end of the fifth resistor is connected to the second end of the fourth resistor, and its second end is connected to the second output terminal of the auxiliary power supply; the first end of the fourth resistor and the second end of the fifth resistor are also respectively connected to the third switch.

[0031] Furthermore, after the upper bridge arm capacitor and the lower bridge arm capacitor have been charged, the method further includes:

[0032] The fourth switch is controlled to close, which in turn controls the control voltage of the third switch to decrease, so that the third switch remains open at a lower voltage.

[0033] The present invention also provides a power converter including the above-described midpoint balancing circuit.

[0034] The present invention also provides a photovoltaic device, including the power converter described above.

[0035] The present invention also provides an electrical appliance, including the photovoltaic device described above.

[0036] The present invention also provides a computer-readable storage medium having a computer program stored thereon, characterized in that the program, when executed by a processor, implements the above-described control method.

[0037] The present invention also provides an electronic device, comprising:

[0038] One or more processors;

[0039] A storage device for storing one or more programs, which, when executed by one or more processors, cause the one or more processors to implement the above-described control method.

[0040] By applying the technical solution of this invention, a first resistor is set in the midpoint balancing circuit of the power converter. The first end of the first resistor is connected to the first end of the upper bridge arm capacitor, and the second end is connected to the rectifier circuit through a first switch and to the second end of the upper bridge arm capacitor through a second switch. After the power converter starts up, the first switch is turned on, thereby controlling the charging of the upper and lower bridge arm capacitors, while the second switch is turned off. After the upper and lower bridge arm capacitors have finished charging, the first switch is turned off, while the second switch is turned on, giving the first resistor a dual function. First, it acts as a current-limiting resistor in the pre-charging circuit during power converter startup, limiting the charging current of the upper and lower bridge arm capacitors on the bus. Second, it acts as a voltage balancing resistor for the upper and lower bridge arm capacitors on the DC bus during normal operation of the power converter, ensuring that the voltage of the upper and lower bus capacitors is evenly distributed. Through the above scheme, the function of the first resistor is reused, that is, the dual function of limiting the charging current and balancing the midpoint voltage is achieved through the same resistor, reducing the number of resistors and achieving cost reduction and energy saving. Attached Figure Description

[0041] Figure 1 Here is a structural diagram of an existing midpoint balancing circuit;

[0042] Figure 2 This is a structural diagram of the midpoint balancing circuit according to an embodiment of the present invention;

[0043] Figure 3 A flowchart of a control method according to an embodiment of the present invention;

[0044] Figure 4 This is a schematic diagram of the hardware structure of an electronic device according to an embodiment of the present invention. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0046] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0047] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0048] It should be understood that although the terms first, second, third, etc., may be used to describe resistors in the embodiments of the present invention, these resistors should not be limited to these terms. These terms are only used to distinguish different resistors. For example, without departing from the scope of the embodiments of the present invention, a first resistor may also be referred to as a second resistor, and similarly, a second resistor may also be referred to as a first resistor.

[0049] Depending on the context, the words “if” or “suppose” as used here can be interpreted as “when” or “in response to determination” or “in response to detection.” Similarly, depending on the context, the phrases “if determination” or “if detection (of the stated condition or event)” can be interpreted as “when determination” or “in response to determination” or “when detection (of the stated condition or event)” or “in response to detection (of the stated condition or event).”

[0050] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0051] The optional embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0052] Example 1

[0053] Figure 1 The diagram shows the structure of an existing midpoint balancing circuit. Due to factors such as different loads and battery voltage variations, the DC voltage output from the grid and the inverter to the bus fluctuates, causing differences in the midpoint potential of the output voltage, resulting in a deviation. When the deviation exceeds the midpoint voltage tolerance range, the system becomes unbalanced. To ensure a stable midpoint voltage balance, such as... Figure 1 As shown, identical resistors are typically added to both half-bridges to balance the midpoint voltage offset. Furthermore, in practical applications, an additional pre-charge resistor is usually added to pre-charge the bus capacitor with a small current to prevent overcurrent. The redundant setting of the midpoint balancing resistor and the pre-charge resistor increases the system cost.

[0054] To address the issue of increased circuit cost due to redundant midpoint balancing resistors and pre-charge resistors in existing power converters, this embodiment provides a midpoint balancing circuit. Figure 2 A structural diagram of the midpoint balancing circuit according to an embodiment of the present invention is shown below. Figure 2 As shown, this midpoint balancing circuit is applied to a power converter, which includes a rectifier circuit 1 and an inverter circuit 2. The output terminal of the inverter circuit is connected to the high line and low line of the DC bus. An upper bridge arm capacitor C1 and a lower bridge arm capacitor C2 are connected in series between the high line and the low line of the DC bus. The midpoint balancing circuit includes: a first switch S1, whose first terminal is connected to the first terminal of the output side of the rectifier circuit 1; a first resistor R1, whose first terminal is connected to the second terminal of the first switch S1, and whose second terminal is connected to the first terminal of the upper bridge arm capacitor C2; a second switch S2, whose first terminal is connected between the first switch S1 and the first resistor R1, and whose second terminal is connected to the second terminal of the upper bridge arm capacitor C1; and a second resistor R2, whose first terminal is connected to the first terminal of the lower bridge arm capacitor C2, and whose second terminal is connected to the second terminal of the lower bridge arm capacitor C2.

[0055] After the power converter is started, the first switch S1 is turned on, which in turn controls the upper bridge arm capacitor C1 and the lower bridge arm capacitor C2 to charge, while the second switch S2 is turned off. After the upper bridge arm capacitor C1 and the lower bridge arm capacitor C2 have finished charging, the first switch S1 is turned off, while the second switch S2 is turned on.

[0056] In this embodiment, the midpoint balancing circuit includes a first resistor R1. The first end of R1 is connected to the first end of the upper bridge arm capacitor C1, and the second end is connected to the rectifier circuit 1 via a first switch S1 and to the second end of the upper bridge arm capacitor C1 via a second switch S2. After the power converter starts up, the first switch S1 is turned on, thereby controlling the charging of the upper bridge arm capacitor C1 and the lower bridge arm capacitor C2, while the second switch S2 is turned off. After the upper bridge arm capacitor C1 and the lower bridge arm capacitor C2 have finished charging, the first switch S1 is turned off, while the second switch S2 is turned on. This control scheme gives the first resistor R1 a dual function: firstly, it acts as a current-limiting resistor in the pre-charging circuit during power converter startup, limiting the charging current of the upper and lower bridge arm capacitors on the bus; secondly, it acts as a voltage balancing resistor for the upper and lower bridge arm capacitors on the DC bus during normal operation of the power converter, ensuring that the voltage of the upper and lower bus capacitors is evenly distributed. This scheme achieves functional reuse of the first resistor, that is, using the same resistor to achieve the dual functions of limiting the charging current and balancing the midpoint voltage, reducing the number of resistors and achieving cost reduction and energy saving.

[0057] If the DC bus is under high voltage for an extended period, the electrical energy cannot be discharged, posing a safety hazard and threatening the safety of commissioning and maintenance personnel. To address the issue of the DC bus of the power converter being under high voltage for a long time and unable to quickly discharge electrical energy, such as... Figure 2The midpoint balancing circuit shown also includes: a third resistor R3, the first end of which is connected between the first switch S1 and the first resistor R1; and a third switch S3, the first end of which is connected to the second end of the third resistor R3, and the second end of which is connected to the second end of the second resistor R2.

[0058] In order to disconnect the third resistor R3 from the circuit when the appliance is running and connect the third resistor R3 to the circuit after the appliance is powered off to discharge the DC bus power, the third switch S3 is set as a normally closed switch, that is, it is turned on when the power is off and turned off when the power is on.

[0059] To achieve the on / off control of the third switch S3, such as Figure 2 As shown, the above-mentioned midpoint balancing circuit further includes: an auxiliary power supply 3, whose input terminal is connected to the AC mains; a fourth resistor R4, whose first terminal is connected to the first output terminal of the auxiliary power supply 3; a fifth resistor R5, whose first terminal is connected to the second terminal of the fourth resistor R4, and whose second terminal is connected to the second output terminal of the auxiliary power supply 3; the first terminal of the fourth resistor R4 and the second terminal of the fifth resistor R5 are also respectively connected to a third switch S3. The fourth resistor R4 and the fifth resistor R5 are the negative feedback resistors of the auxiliary power supply. The voltage across the series circuit formed by the fourth resistor R4 and the fifth resistor R5 is the control voltage applied across the third switch S3. When the auxiliary power supply 3 is on, this control voltage can control the third switch S3 to open.

[0060] After the third switch S3 is opened, the control voltage of the third switch S3 is reduced to a minimum voltage sufficient to keep it open, thus minimizing its energy consumption. To achieve this, the aforementioned midpoint balancing circuit further includes: a sixth resistor R6, whose first end is connected to the first output terminal of the auxiliary power supply 3; and a fourth switch S4, whose first end is connected to the second end of the sixth resistor R6, and whose second end is connected to the second output terminal of the auxiliary power supply 3. After the third switch S3 is opened, the fourth switch S4 is turned on, which in turn controls the sixth resistor R6 to be connected to the circuit. The sixth resistor R6, the fourth resistor R4, and the fifth resistor R5 form a series circuit connected in parallel. The resistance of the entire circuit decreases, the voltage output by the auxiliary power supply 3 decreases, and thus the control voltage of the third switch S3 decreases, keeping the third switch S3 open at a lower voltage, achieving energy saving.

[0061] Generally, when multiple switches exist in a circuit, they need to be controlled by multiple control signals. This requires the controller MCU to have multiple signal output terminals, placing high demands on the number of terminals on the chip and making the control scheme more complex. In the application scenario of this application, it is necessary to ensure that when the first switch S1 is on, the second switch S2 and the fourth switch S4 are both off; and when the first switch S1 is off, the second switch S2 and the fourth switch S4 are both on. Therefore, it can be configured as follows: the first switch S1 is a normally open switch, i.e., it is on when the MCU outputs a high level and off when the MCU outputs a low level; the second switch S2 and the fourth switch S4 are both normally closed switches, i.e., they are off when the MCU outputs a high level and on when the MCU outputs a low level. Thus, in the charging state, the MCU outputs a high level, controlling the first switch S1 to be on, and the second switch S2 and the fourth switch S4 to be off. 4. When the circuit is open, the first resistor R1 acts as a current-limiting resistor for charging. At the same time, the fourth switch S4 is open, allowing the auxiliary power supply 3 to output a higher voltage, which in turn turns off the third switch S3 at the higher voltage. After charging is complete, the MCU outputs a low level, controlling the first switch S1 to turn off, while the second switch S2 and the fourth switch S4 are both turned on. This causes the first resistor R1 to be connected in parallel across the upper bridge arm capacitor C1 as a midpoint balancing resistor. Simultaneously, the auxiliary power supply 3 outputs a lower voltage, keeping the third switch S3 off at the lower voltage. The on / off state of the three switches can be controlled through the same control signal, saving on chip interfaces and simplifying the control scheme.

[0062] Example 2

[0063] This embodiment provides another midpoint balancing circuit, the structure of which is shown in the diagram mentioned above. Figure 2 As shown in the diagram, in this embodiment, the power converter is a photovoltaic power converter. 4: the main switch of the photovoltaic power converter device; 1: the inverter circuit (T-NPC, I-NPC, A-NPC, etc., circuit topologies with a midpoint voltage; this embodiment uses the T-NPC topology as an example); 2: the rectifier circuit; 3: the auxiliary power supply. C1 is the upper bridge arm capacitor; C2 is the upper bridge arm capacitor; the first resistor R1 is the upper bridge arm resistor; the second resistor R2 is the lower bridge arm resistor; the third resistor R3 is the bleeder resistor; the sixth resistor R6 is a parallel resistor; the fourth resistor R4 and the fifth resistor R5 are the negative feedback resistors of the auxiliary power supply 3; the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 are all relays, wherein the first switch S1 is a normally open relay, and the second switch S2, the third switch S3, and the fourth switch S4 are all normally closed relays.

[0064] The midpoint balancing resistor network architecture in this embodiment mainly consists of an upper bridge arm resistor R1, a lower bridge arm resistor R2, a bleeder resistor R3, relays S1-S4, and an auxiliary power supply 3. Relay S1 is a normally open relay, and relay S2 is a normally closed relay. Their switching states are complementary and controlled by the same MCU control signal. A high level triggers the state switching action, and a low level restores the initial state. Relay S3, a normally closed relay, is controlled by the power supply state of the auxiliary power supply. During operation, the auxiliary power supply has two output voltage levels, determined by relay S4. When the relay is open, the resistance of the negative feedback circuit of the auxiliary power supply is composed of R4 and R5. When the output voltage reaches 24V, it can drive relay S3 to close. After relay S4 closes, the resistance of the negative feedback circuit of the auxiliary power supply is composed of R4, R5, and R6. When the output voltage drops to 18V, it can keep relay S3 in the open state, thus reducing the power consumption of relay S3. The upper bridge arm resistor R1 also serves two functions: 1. As a current-limiting resistor in the pre-charging circuit during the startup of the photovoltaic power converter, it limits the charging current of the bus capacitor. 2. As a voltage balancing resistor for the upper and lower capacitors on the DC bus during normal operation of the photovoltaic power converter, it ensures that the voltage of the upper and lower bus capacitors is evenly distributed. The resistance values ​​of the upper arm resistor R1 and the lower arm resistor R2 are generally in the kiloohm range, while the voltage discharge resistor R3 is in the hundred ohm range.

[0065] System control and operation process:

[0066] When the appliance is not started, relay S1 is in the open state, relay S2 is in the closed state, the auxiliary power supply has no voltage output, relay S3 is in the closed state, and relay S4 is also in the closed state.

[0067] After the appliance starts and completes its self-test, the MCU outputs a high-level control signal, closing relay S1 and opening relay S2. At this time, the upper bridge arm resistor acts as a current-limiting resistor connected to the pre-charging circuit. The rectifier bridge rectifies the AC to DC, and the DC current is limited by the upper bridge arm resistor to charge the bus capacitor with a small current. Additionally, relay S4 at the auxiliary power supply output terminal operates synchronously according to the MCU's control signal, switching from a closed to an open state. The auxiliary power supply voltage rises to 24V, triggering relay S3 to disconnect the bleeder resistor R3.

[0068] After the bus capacitors have finished charging, the control signal output by the MCU switches from high to low, causing relay S1 to open and relay S2 to close. The upper bridge arm resistor R1 and the lower bridge arm resistor R2 are connected and connected in parallel with the upper and lower bridge arm capacitors between the DC bus, respectively, to balance the bus capacitor voltage. Simultaneously, relay S4 also switches from open to closed according to the change in the MCU's control signal, causing the auxiliary power supply voltage to drop to 18V and keeping relay S3 open to reduce power loss.

[0069] After the appliance is turned off, relay S1 remains open, relay S2 remains closed, and relay S4 remains closed. Because the auxiliary power supply has no voltage output when the equipment is powered off, relay S3 cannot remain open and returns to its initial closed state. The bleeder resistor R3 is connected, forming a voltage bleedering circuit with the upper bridge arm resistor R1 and the lower bridge arm resistor R2. This quickly discharges the voltage of the upper bridge arm capacitor C1 and the lower bridge arm capacitor C2 to a safe voltage level, preventing the DC bus from being under high voltage for an extended period.

[0070] In this embodiment, the midpoint balancing circuit allows the controller MCU to synchronously control the pre-charging circuit, the bus midpoint balancing circuit, and the voltage holding circuit of the auxiliary power supply with just one control signal, saving the MCU's signal interface. In the resistor network architecture, the upper bridge arm resistor can serve as both the current-limiting resistor for the pre-charging circuit and the bus midpoint balancing resistor; that is, the current-limiting resistor for the pre-charging circuit and the upper bridge arm resistor for midpoint balancing share a single resistor, achieving a common material design and solving the problem of needing an additional current-limiting resistor for the pre-charging circuit, thus reducing costs. Simultaneously, after the equipment is powered off, the low-impedance loop automatically connects to the DC bus, enabling rapid discharge of the bus voltage. This solves the problem of the power converter's DC bus being under high voltage for extended periods, preventing rapid energy discharge and ensuring the safety of commissioning and maintenance personnel.

[0071] Example 3

[0072] This embodiment provides a control method applied to the midpoint balancing circuit of the above embodiment. Figure 3 A flowchart of a control method according to an embodiment of the present invention is shown below. Figure 3 As shown, the control method includes:

[0073] S101 controls the first switch S1 to turn on after the power converter starts, thereby controlling the upper bridge arm capacitor and the lower bridge arm capacitor to charge, while controlling the second switch S2 to turn off.

[0074] S102: After the upper bridge arm capacitor and the lower bridge arm capacitor have finished charging, control the first switch S1 to turn off and at the same time control the second switch S2 to turn on.

[0075] As mentioned above Figure 2 As shown, the midpoint balancing circuit includes: a first switch S1, the first end of which is connected to the first end of the output side of the rectifier circuit 1; a first resistor R1, the first end of which is connected to the second end of the first switch S1, and the second end of which is connected to the first end of the upper bridge arm capacitor C2; a second switch S2, the first end of which is connected between the first switch S1 and the first resistor R1, and the second end of which is connected to the second end of the upper bridge arm capacitor C1; and a second resistor R2, the first end of which is connected to the first end of the lower bridge arm capacitor C2, and the second end of which is connected to the second end of the lower bridge arm capacitor C2.

[0076] After the power converter is started, the first switch S1 is turned on, which in turn controls the upper bridge arm capacitor C1 and the lower bridge arm capacitor C2 to charge, while the second switch S2 is turned off. After the upper bridge arm capacitor C1 and the lower bridge arm capacitor C2 have finished charging, the first switch S1 is turned off, while the second switch S2 is turned on.

[0077] The control method of this invention, after the power converter starts up, controls the first switch S1 to turn on, thereby controlling the charging of the upper bridge arm capacitor C1 and the lower bridge arm capacitor C2, while simultaneously controlling the second switch S2 to turn off. After the upper bridge arm capacitor C1 and the lower bridge arm capacitor C2 have finished charging, the first switch S1 is turned off, while the second switch S2 is turned on, giving the first resistor R1 a dual function: firstly, it acts as a current-limiting resistor in the pre-charging circuit during power converter startup, limiting the charging current of the upper and lower bridge arm capacitors on the bus; secondly, it acts as a voltage balancing resistor for the upper and lower bridge arm capacitors on the DC bus during normal operation of the power converter, ensuring that the voltage of the upper and lower bus capacitors is evenly distributed. Through the above scheme, the function of the first resistor is reused, achieving cost reduction and energy saving.

[0078] If the DC bus is under high voltage for an extended period, the electrical energy cannot be discharged, posing a safety hazard and threatening the safety of commissioning and maintenance personnel. To address the issue of the DC bus of the power converter being under high voltage for a long time and unable to quickly discharge electrical energy, such as... Figure 2 The midpoint balancing circuit shown also includes: a third resistor R3, whose first end is connected between the first switch S1 and the first resistor R1; and a third switch S3, whose first end is connected to the second end of the third resistor R3, and whose second end is connected to the second end of the second resistor R2. To ensure that the third resistor R3 is disconnected from the circuit when the appliance is running, and connected to the circuit after the appliance is powered off, thereby discharging DC bus power, the third switch S3 is a normally closed switch, meaning it is open when power is off and open when power is on.

[0079] To achieve the on / off control of the third switch S3, such as Figure 2As shown, the above-mentioned midpoint balancing circuit further includes: an auxiliary power supply 3, whose input terminal is connected to the AC power grid; a fourth resistor R4, whose first terminal is connected to the first output terminal of the auxiliary power supply 3; a fifth resistor R5, whose first terminal is connected to the second terminal of the fourth resistor R4, and whose second terminal is connected to the second output terminal of the auxiliary power supply 3; the first terminal of the fourth resistor R4 and the second terminal of the fifth resistor R5 are also respectively connected to the third switch S3. The fourth resistor R4 and the fifth resistor R5 are the negative feedback resistors of the auxiliary power supply. The voltage across the series circuit formed by the fourth resistor R4 and the fifth resistor R5 is the control voltage applied across the third switch S3. When the auxiliary power supply 3 is on, this control voltage can control the third switch S3 to open. Therefore, after the power converter is started, the above control method also includes: controlling the fourth switch S4 to open, thereby controlling the third switch S3 to open.

[0080] After the third switch S3 is opened, reducing the control voltage of the third switch S3 to a minimum voltage that can keep the third switch S3 open can minimize the energy consumption of the third switch S3. Therefore, after the upper bridge arm capacitor and the lower bridge arm capacitor have finished charging, the above method also includes: controlling the fourth switch S4 to close, thereby controlling the control voltage of the third switch to decrease, so that the third switch S3 remains open at a lower voltage.

[0081] Example 4

[0082] This embodiment provides a power converter, including the midpoint balancing circuit of the above embodiment, which is used to realize the functional reuse of the first resistor, that is, to achieve the dual function of limiting the charging current and balancing the midpoint voltage through the same resistor, thereby reducing the number of resistors and achieving cost reduction and energy saving.

[0083] Example 5

[0084] This embodiment provides a photovoltaic device, including the power converter described in the above embodiment.

[0085] Example 6

[0086] This embodiment describes an electrical appliance, including the photovoltaic equipment described in the above embodiment.

[0087] Example 7

[0088] This embodiment provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the above-described control method.

[0089] Example 8

[0090] This embodiment provides an electronic device, including:

[0091] One or more processors;

[0092] A storage device for storing one or more programs, which, when executed by one or more processors, cause the one or more processors to implement the above-described control method.

[0093] Figure 4 This is a schematic diagram of the hardware structure of an electronic device according to an embodiment of the present invention, such as... Figure 4 As shown, the electronic device includes:

[0094] One or more processors 410 and memory 420, Figure 4 Take a processor 410 as an example.

[0095] The aforementioned electronic device may further include: an input device 430 and an output device 440.

[0096] The processor 410, memory 420, input device 430, and output device 440 can be connected via a bus or other means. Figure 4 Taking the example of a connection between China and Israel via a bus.

[0097] The memory 420, as a non-volatile computer-readable storage medium, can be used to store non-volatile software programs, non-volatile computer-executable programs, and modules, such as the program instructions / modules corresponding to the control method in this embodiment of the invention. The processor 410 executes various functional applications and data processing of the server by running the non-volatile software programs, instructions, and modules stored in the memory 420, thereby implementing the above-described method embodiments.

[0098] The memory 420 may include a program storage area and a data storage area. The program storage area may store application programs required for operating the device and at least one function. The data storage area may store data created based on the use of the anomaly detection device. Furthermore, the memory 420 may include high-speed random access memory and may also include non-volatile memory, such as at least one disk storage device, flash memory device, or other non-volatile solid-state storage device.

[0099] Input device 430 can receive input digital or character information, and generate key signal inputs related to user settings and function control of the electronic device. Output device 440 may include display devices such as a display screen.

[0100] The one or more modules are stored in the memory 420, and when executed by the one or more processors 410, they execute the control method in any of the above method embodiments.

[0101] The aforementioned electronic device can execute the control method provided in the embodiments of the present invention, and possesses the corresponding functional modules and beneficial effects of the method. Technical details not described in detail in this embodiment can be found in the control method provided in the embodiments of the present invention.

[0102] The electronic devices of this invention exist in various forms, including but not limited to:

[0103] (1) Mobile communication devices: These devices are characterized by their mobile communication capabilities and are primarily designed to provide voice and data communication. These terminals include smartphones (e.g., iPhones), multimedia phones, feature phones, and low-end phones.

[0104] (2) Ultra-mobile personal computer devices: These devices fall under the category of personal computers, have computing and processing functions, and generally also have mobile internet access capabilities. These terminals include: PDAs, MIDs, and UMPCs, such as iPads.

[0105] (3) Portable entertainment devices: These devices can display and play multimedia content. This category includes: audio and video players (such as iPods), handheld game consoles, e-books, as well as smart toys and portable car navigation devices.

[0106] (4) Server: A device that provides computing services. The components of a server include a processor, hard disk, memory, device bus, etc. Servers are similar to general computer architectures, but because they need to provide highly reliable services, they have higher requirements in terms of processing power, stability, reliability, security, scalability, and manageability.

[0107] (5) Other electronic devices with data interaction functions, such as televisions, in-vehicle screens, etc.

[0108] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the control methods described in various embodiments or some parts of the embodiments.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A midpoint balancing circuit applied to a power converter, the power converter comprising a rectification circuit and an inverter circuit, an output terminal of the inverter circuit being connected to a DC bus high line and a DC bus low line, an upper bridge arm capacitor and a lower bridge arm capacitor being arranged in series between the DC bus high line and the DC bus low line, characterized in that, The midpoint balancing circuit includes: A first switch, the first end of which is connected to the first end of the output side of the rectifier circuit; The first resistor has its first end connected to the second end of the first switch, and its second end connected to the first end of the upper bridge arm capacitor. The second switch has its first end connected between the first switch and the first resistor, and its second end connected to the second end of the upper bridge arm capacitor. The second resistor has its first end connected to the first end of the lower bridge arm capacitor and its second end connected to the second end of the lower bridge arm capacitor.

2. The midpoint balancing circuit according to claim 1, characterized in that, The midpoint balancing circuit also includes: The third resistor has its first end connected between the first switch and the first resistor; The third switch has its first end connected to the second end of the third resistor, and its second end connected to the second end of the second resistor.

3. The midpoint balancing circuit according to claim 2, characterized in that, The third switch is a normally closed switch.

4. The midpoint balancing circuit according to claim 2, characterized in that, The midpoint balancing circuit also includes: Auxiliary power supply, whose input is connected to the AC power grid; The fourth resistor has its first end connected to the first output terminal of the auxiliary power supply; The fifth resistor has its first end connected to the second end of the fourth resistor, and its second end connected to the second output terminal of the auxiliary power supply. The first end of the fourth resistor and the second end of the fifth resistor are also connected to the third switch.

5. The midpoint balancing circuit according to claim 2, characterized in that, The midpoint balancing circuit also includes: The sixth resistor has its first end connected to the first output terminal of the auxiliary power supply; The fourth switch has its first end connected to the second end of the sixth resistor, and its second end connected to the second output terminal of the auxiliary power supply.

6. The midpoint balancing circuit according to claim 5, characterized in that, The first switch is a normally open switch; Both the second switch and the fourth switch are normally closed switches.

7. A control method applied to the midpoint balancing circuit according to any one of claims 1 to 6, characterized in that, The control method includes: After the power converter is started, the first switch is turned on, thereby controlling the upper bridge arm capacitor and the lower bridge arm capacitor to charge, while the second switch is turned off. After the upper bridge arm capacitor and the lower bridge arm capacitor have finished charging, the first switch is turned off, and the second switch is turned on.

8. The control method according to claim 7, characterized in that, After the power converter starts up, the control method further includes: The fourth switch is turned off, which in turn causes the third switch to turn off; Wherein, the first end of the third switch is connected to the second end of the third resistor, the second end of the third switch is connected to the second end of the second resistor, and the first end of the third resistor is connected between the first switch and the first resistor; The first end of the fourth switch is connected to the second end of the sixth resistor, and the second end is connected to the second output terminal of the auxiliary power supply; the first end of the sixth resistor is connected to the first output terminal of the auxiliary power supply. The input terminal of the auxiliary power supply is connected to the AC power grid, the first end of the fourth resistor is connected to the first output terminal of the auxiliary power supply, the first end of the fifth resistor is connected to the second end of the fourth resistor, and the second end of the fifth resistor is connected to the second output terminal of the auxiliary power supply; the first end of the fourth resistor and the second end of the fifth resistor are also respectively connected to the third switch.

9. The control method according to claim 8, characterized in that, After the upper bridge arm capacitor and the lower bridge arm capacitor have been charged, the method further includes: The fourth switch is controlled to close, which in turn controls the control voltage of the third switch to decrease, so that the third switch remains open at a lower voltage.

10. A power converter, characterized in that, The midpoint balancing circuit includes any one of claims 1 to 6.

11. A photovoltaic device, characterized in that, Includes the power converter as described in claim 10.

12. An electrical appliance, characterized in that, Includes the photovoltaic equipment described in claim 11.

13. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the control method as described in any one of claims 7 to 9.

14. An electronic device, characterized in that, include: One or more processors; A storage device for storing one or more programs, which, when executed by one or more processors, cause the one or more processors to implement the control method as described in any one of claims 7 to 9.

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