Power unit and power electronic conversion device using the same

Abstract

The power unit comprises: a plurality of power conversion circuits, a first output end of one of two adjacent power conversion circuits in the plurality of conversion circuits is connected with a second output end of the other one in sequence; a local controller for outputting a plurality of control signals; a plurality of drive circuits for outputting drive signals to drive the on-off of a plurality of power semiconductor switches according to the plurality of control signals, the control signals corresponding to the power semiconductor switches at the same position in the plurality of power conversion circuits are the same, and the power semiconductor switches at the same position in the plurality of power conversion circuits are turned on and off at the same time. The power unit can share higher voltage, reduce the number of optical fibers, auxiliary power supplies and local controllers, simplify the circuit structure, improve the system reliability, realize the purpose of reducing the number of power units by using low-voltage power devices, save costs, only need to configure a voltage clamping circuit for each power conversion circuit, reduce the number of voltage clamping circuits, reduce costs and improve system reliability.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese application No. 201611170857.3, filed on December 16, 2016, entitled “Power Unit and Power Electronic Conversion Device Using the Power Unit”, the contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of power electronics technology, and in particular to a power unit and a power electronic conversion device using such a power unit. Background Technology

[0004] Due to the voltage withstand capabilities of current power electronic switching devices, a cascaded topology of power units connected in series is a better solution for high-voltage, high-power applications. Traditional cascaded solutions require each power unit to be equipped with an optical fiber, auxiliary power supply, and control board. As voltage levels increase, the number of cascaded power units also increases, leading to a sharp increase in the number of optical fibers, auxiliary power supplies, and control boards. This results in a complex system design, high cost, and reduced system reliability.

[0005] Figure 1 , Figure 2 The diagram shown is a commonly used Static Var Generator (SVG), which includes a three-phase circuit with power units in each phase cascaded together.

[0006] like Figure 1 As shown, each phase circuit of the SVG is composed of multiple power units 1 cascaded together. Each power unit includes a first terminal and a second terminal. The first terminal of the first power unit of each phase circuit is connected to the three-phase lines A, B and C of the three-phase power grid through a filter L. The second terminal of one of two adjacent power units is connected to the first terminal of the other. The second terminals of the last power units of each phase circuit are connected to each other.

[0007] like Figure 2 Each phase circuit of the SVG consists of eight cascaded power units P1 to P8. Each power unit includes a first terminal and a second terminal. The second terminal of one of two adjacent power units is connected to the first terminal of the other. For example, the second terminal of power unit P1 is connected to the first terminal of power unit P2, the second terminal of power unit P2 is connected to the first terminal of power unit P3, and so on. The second terminal of power unit P7 is connected to the first terminal of power unit P8. The first terminals of the three power units P1 in the three-phase circuit are connected to phases A, B, and C of the three-phase power grid G ​​and the load R respectively through a filter circuit (composed of inductors, resistors, and capacitors, such as LCL).load The second ends of the three power units P8 in the three-phase circuit are connected to each other. Each power unit includes four power devices 2, each of which is composed of a power semiconductor switch S and a diode D, the collector of the power semiconductor switch S being connected to the cathode of the diode D, and the emitter of the power semiconductor switch S being connected to the anode of the diode D.

[0008] The single-phase SVG also includes a plurality of power units, each of which includes a first end and a second end, the first end of one of two adjacent power units being connected to the second end of the other.

[0009] Figure 1 The power unit 1 shown can be an H-bridge circuit or other circuit topologies, such as a half-bridge circuit, a three-level conversion circuit, etc. For example, taking the power unit as an H-bridge circuit, the H-bridge circuit includes power semiconductor switches S1-S4 and a bus capacitor C, as shown. Figure 3 The first end of the power semiconductor switch S1 is connected to the positive end of the bus capacitor C and the first end of the power semiconductor switch S3, the second end of the power semiconductor switch S1 is connected to the first end of the power semiconductor switch S4, the second end of the power semiconductor switch S4 is connected to the negative end of the bus capacitor C and the second end of the power semiconductor switch S2, the second end of the power semiconductor switch S3 is connected to the first end of the power semiconductor switch S2, the second end of the power semiconductor switch S1 serves as the first output end O1 of the H-bridge circuit, and the second end of the power semiconductor switch S3 serves as the second output end O2 of the H-bridge circuit.

[0010] The cascaded topologies of the above power units, if applied to a 35KV wind power plant, usually have three implementation schemes, which are described as follows:

[0011] 1. Each power unit adopts an H-bridge circuit, and the power semiconductor switches S1-S4 in the H-bridge circuit can be selected from low-voltage power devices, such as low-voltage IGBTs (Insulated Gate Bipolar Translator).

[0012] Advantages: Low-voltage IGBTs (e.g., 1700V) have a relatively mature process at present, and their market demand is large, so their cost is within an acceptable range. Each power semiconductor switch is composed of an IGBT, and there is no need to consider the voltage balancing problem.

[0013] Disadvantages: Since the voltage of single power device is low (for example, 1700V IGBT, the DC bus voltage across bus capacitor C is about 1000V), about 72 H-bridge circuits are cascaded in each phase circuit. The number of H-bridge circuits is large, and the reliability of the system will be affected. Moreover, each H-bridge circuit is equipped with a set of optical fiber (optical fiber is usually used for signal transmission in high-voltage applications), auxiliary power supply and control board, and each H-bridge circuit needs to be controlled independently. Due to the large number of cascaded H-bridge circuits, this scheme will result in a large number of optical fibers, auxiliary power supplies and control boards, making the control and structural design of the entire system complex, increasing the cost, and reducing the reliability of the system.

[0014] 2. Each power unit adopts an H-bridge circuit, and the power semiconductor switches S1-S4 in the H-bridge circuit can be selected from high-voltage power devices, such as high-voltage IGBT (Insulated Gate Bipolar Translator).

[0015] Advantages: The voltage of single power device is high (for example, 6500V IGBT), and the DC bus voltage across bus capacitor C is about 3000V, so about 18 H-bridge circuits are needed in each phase circuit, reducing the number of cascaded H-bridge circuits; at the same time, the number of optical fibers, auxiliary power supplies and control boards is reduced, which can reduce the cost of these devices in the system, simplify the system control and structural design, and increase the reliability.

[0016] Disadvantages: The cost of high-voltage IGBT is much higher than that of low-voltage IGBT (the cost of 6500V IGBT is more than 4 times the cost of 1700V IGBT), which results in an increase in cost that is much higher than the cost saved by the control board and optical fiber, leading to a significant increase in system cost.

[0017] 3. Each power unit adopts an H-bridge circuit, and the power semiconductor switches S1-S4 in the H-bridge circuit can be selected from low-voltage power devices connected in series.

[0018] Advantages: The number of cascaded H-bridge circuits is reduced, and the number of cascaded H-bridge circuits is the same as in the second scheme, but the power semiconductor switches in each H-bridge circuit are connected in series with multiple low-voltage power devices (for example, 4 1700V IGBTs are connected in series to form an equivalent 6500V IGBT), which reduces the system cost. Compared with the first scheme, the number of cascaded H-bridge circuits is reduced, the number of optical fibers, auxiliary power supplies and control boards is reduced, the cost is reduced, the control and structure are simplified, and the reliability is increased; compared with the second scheme, the cost of connecting multiple low-voltage IGBTs in series to form an equivalent high-voltage power device is lower than that of a single high-voltage power device, and this scheme of connecting low-voltage power devices in series to form an equivalent high-voltage power device has an advantage in total cost.

[0019] Disadvantages: there is an uneven voltage problem in the series application of low-voltage IGBTs. In order to solve this problem, a clamping plate needs to be provided for each low-voltage IGBT, resulting in a large number of clamping plates and reducing the reliability of the system. SUMMARY

[0020] The purpose of the present application is to provide a power unit and a power electronic conversion device using the same, so as to at least partially overcome one or more problems caused by the limitations and defects of the related art.

[0021] Other characteristics and advantages of the present application will become apparent from the following detailed description, or will be learned by practice of the present application.

[0022] According to one aspect of the present application, a power unit is provided, characterized by comprising:

[0023] a plurality of power conversion circuits, each of which comprises at least one bridge arm having a plurality of power semiconductor switches, and each of which comprises a first output end and a second output end, wherein the first output end of one of the adjacent two power conversion circuits in the plurality of conversion circuits and the second output end of the other one are connected in sequence, and the remaining two first output ends and second output ends form a first end and a second end of the power unit;

[0024] a local controller for outputting a plurality of control signals; and

[0025] a plurality of drive circuits coupled to the local controller for receiving the plurality of control signals and outputting respective drive signals according to the plurality of control signals to drive the plurality of power semiconductor switches to turn on or turn off,

[0026] wherein the plurality of power conversion circuits are the same, the number of the plurality of control signals is the same as the number of the power semiconductor switches in each of the power conversion circuits, and the control signals corresponding to the power semiconductor switches at the same position in the plurality of power conversion circuits are the same, so that the power semiconductor switches at the same position in the plurality of power conversion circuits are turned on or turned off at the same time.

[0027] According to one embodiment, the power unit further comprises:

[0028] an auxiliary power supply connected to the local controller for supplying power to the local controller.

[0029] According to one embodiment, the number of the plurality of driving circuits is the same as the number of the power semiconductor switches, and each of the driving circuits drives the corresponding power semiconductor switch to turn on and turn off.

[0030] According to one embodiment, the plurality of driving circuits are directly connected to the local controller, or the plurality of driving circuits are connected to the local controller through a magnetic isolation device, or the plurality of driving circuits are connected to the local controller through an optical isolation device.

[0031] According to one embodiment, the power conversion circuit comprises:

[0032] a bus capacitor connected in parallel across the bridge arms, and a voltage clamping circuit connected in parallel across the bus capacitor.

[0033] According to one embodiment, a bus voltage between the two ends of the bus capacitor is clamped by the voltage clamping circuit within a predetermined range.

[0034] According to one embodiment, the plurality of power conversion circuits are n power conversion circuits, the first output end of a first power conversion circuit is the first end of the power unit, the second output end of the first power conversion circuit is connected to the first output end of a second power conversion circuit, and so on, until the second output end of an (n-1)th power conversion circuit is connected to the first output end of an nth power conversion circuit, and the second output end of the nth power conversion circuit is the second end of the power unit, wherein n is a natural number greater than 1.

[0035] According to one embodiment, the power conversion circuit is an H-bridge circuit, wherein the H-bridge circuit comprises:

[0036] The at least one bridge arm comprises a first bridge arm and a second bridge arm, and the first bridge arm and the second bridge arm each comprise an upper power semiconductor switch and a lower power semiconductor switch, and the connection point of the upper power semiconductor switch and the lower power semiconductor switch of the first bridge arm is the first output end of the power conversion circuit, and the connection point of the upper power semiconductor switch and the lower power semiconductor switch of the second bridge arm is the second output end of the power conversion circuit.

[0037] According to one embodiment, wherein the power conversion circuit is a half bridge circuit, the half bridge circuit comprises the bridge leg, wherein the bridge leg comprises: an upper power semiconductor switch and a lower power semiconductor switch having a first end and a second end, the second end of the upper power semiconductor switch and the first end of the lower power semiconductor switch are connected to a connection point, the connection point is a first output terminal of the power conversion circuit, the second end of the lower power semiconductor switch is a second output terminal of the power conversion circuit.

[0038] According to one embodiment, wherein the power conversion circuit is a diode clamped three-level circuit, the diode clamped three-level circuit comprises:

[0039] the at least one bridge leg, the at least one bridge leg comprises a first bridge leg and a second bridge leg, the first bridge leg and the second bridge leg each comprises a first power semiconductor switch, a second power semiconductor switch, a third power semiconductor switch and a fourth power semiconductor switch, wherein the first power semiconductor switch, the second power semiconductor switch, the third power semiconductor switch and the fourth power semiconductor switch of the first bridge leg are connected in series, a connection point of the second power semiconductor switch and the third power semiconductor switch of the first bridge leg is a first output terminal of the power conversion circuit, the first power semiconductor switch, the second power semiconductor switch, the third power semiconductor switch and the fourth power semiconductor switch of the second bridge leg are connected in series, a connection point of the second power semiconductor switch and the third power semiconductor switch of the second bridge leg is a second output terminal of the power conversion circuit;

[0040] a first bus capacitor and a second bus capacitor, wherein the first bus capacitor and the second bus capacitor are connected in series and are connected in parallel with the first bridge leg and the second bridge leg; and

[0041] a first switch, a second switch, a third switch and a fourth switch, wherein the first switch and the second switch are connected in series and are connected between the connection point of the first power semiconductor switch and the second power semiconductor switch of the first bridge leg and the connection point of the third power semiconductor switch and the fourth power semiconductor switch of the first bridge leg, the third switch and the fourth switch are connected in series and are connected between the connection point of the first power semiconductor switch and the second power semiconductor switch of the second bridge leg and the connection point of the third power semiconductor switch and the fourth power semiconductor switch of the second bridge leg, a connection point of the first switch and the second switch is connected with a connection point of the first bus capacitor and the second bus capacitor, a connection point of the third switch and the fourth switch is connected with the connection point of the first bus capacitor and the second bus capacitor.

[0042] According to one embodiment, wherein the power conversion circuit is a flying capacitor three-level circuit, wherein the flying capacitor three-level circuit comprises:

[0043] the at least one bridge leg, the at least one bridge leg comprising a first bridge leg and a second bridge leg, the first bridge leg and the second bridge leg each comprising a first power semiconductor switch, a second power semiconductor switch, a third power semiconductor switch and a fourth power semiconductor switch, wherein the first power semiconductor switch, the second power semiconductor switch, the third power semiconductor switch and the fourth power semiconductor switch of the first bridge leg are connected in series, a connection point of the second power semiconductor switch and the third power semiconductor switch of the first bridge leg being a first output terminal of the power conversion circuit, the first power semiconductor switch, the second power semiconductor switch, the third power semiconductor switch and the fourth power semiconductor switch of the second bridge leg are connected in series, a connection point of the second power semiconductor switch and the third power semiconductor switch of the second bridge leg being a second output terminal of the power conversion circuit;

[0044] a first bus capacitor and a second bus capacitor, wherein the first bus capacitor and the second bus capacitor are connected in series and are connected in parallel with the first bridge leg and the second bridge leg; and

[0045] a first capacitor and a second capacitor, wherein the first capacitor is connected between a connection point of the first power semiconductor switch and the second power semiconductor switch of the first bridge leg and a connection point of the third power semiconductor switch and the fourth power semiconductor switch of the first bridge leg, the second capacitor is connected between a connection point of the first power semiconductor switch and the second power semiconductor switch of the second bridge leg and a connection point of the third power semiconductor switch and the fourth power semiconductor switch of the second bridge leg.

[0046] According to one embodiment, wherein the power conversion circuit is a neutral point clamped three-level circuit, wherein the neutral point clamped three-level circuit comprises:

[0047] the at least one bridge leg, the at least one bridge leg comprising a first bridge leg and a second bridge leg, the first bridge leg and the second bridge leg each comprising an upper power semiconductor switch and a lower power semiconductor switch, wherein a connection point of the upper power semiconductor switch and the lower power semiconductor switch of the first bridge leg is a first output terminal of the power conversion circuit, a connection point of the upper power semiconductor switch and the lower power semiconductor switch of the second bridge leg is a second output terminal of the power conversion circuit,

[0048] A first bus capacitor and a second bus capacitor, wherein the first bus capacitor and the second bus capacitor are connected in series and then connected in parallel with the first bridge arm and the second bridge arm; and

[0049] A first switch group and a second switch group, wherein the first switch group is connected between the connection point of the upper power semiconductor switch and the lower power semiconductor switch of the first bridge arm and the connection point of the first bus capacitor and the second bus capacitor, and the second switch group is connected between the connection point of the upper power semiconductor switch and the lower power semiconductor switch of the second bridge arm and the connection point of the first bus capacitor and the second bus capacitor.

[0050] According to another aspect of this disclosure, a power electronic conversion device is provided, characterized in that it comprises:

[0051] The main controller is used to output the main control signal; and

[0052] In at least the power unit of the foregoing embodiments, the local controller is coupled to the main controller to receive the main control signal in order to generate the corresponding control signal.

[0053] According to one embodiment, the at least one power unit is a plurality of power units, the second end of one of two adjacent power units is connected to the first end of the other, and the local controller of each power unit is coupled to the main controller.

[0054] According to one embodiment, the local controller is connected to the main controller via an optical fiber, or the local controller is directly electrically connected to the main controller.

[0055] In the first approach of the prior art, each power unit 100 includes only one power conversion circuit 110. Since each power unit 100 corresponds to a set of optical fibers, auxiliary power supply 150, and control board, and there are many power conversion circuits, the power unit 100 of the present invention includes multiple power conversion circuits 110 compared to the first approach of the prior art. This allows for the distribution of higher voltages, and thus the number of power units 100 is reduced. This reduces the number of optical fibers, auxiliary power supply 150, and local controller 120, simplifying the circuit structure and improving system reliability.

[0056] The second approach in the prior art is to use high-voltage power devices to reduce the number of cascaded power units 100, but high-voltage power devices are expensive. The power units 100 in this embodiment of the invention can use low-voltage power devices to achieve the same goal of reducing the number of power units 100, and compared to the second approach in the prior art, this invention saves costs.

[0057] The third solution in the prior art is to connect multiple same power semiconductor switches in series to be equivalent to a high-voltage power device, so as to prevent uneven voltage, and a voltage clamping circuit needs to be configured for each power semiconductor switch. However, the power unit 100 according to the embodiments of the present application only needs to configure a voltage clamping circuit for each power conversion circuit 110, thereby reducing the number of voltage clamping circuits, reducing the cost, and improving the system reliability. BRIEF DESCRIPTION OF DRAWINGS

[0058] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:

[0059] Figure 1 A schematic diagram of a commonly used static var generator (SVG);

[0060] Figure 2 A more specific schematic diagram of a commonly used static var generator;

[0061] Figure 3 A schematic diagram of an H-bridge circuit;

[0062] Figure 4 A schematic diagram of a power unit 100 according to an embodiment of the present application;

[0063] Figure 5 A schematic diagram of a power unit 100 according to another embodiment of the present application;

[0064] Figure 6 A schematic diagram of a power unit 100 according to another embodiment of the present application;

[0065] Figure 7 A schematic diagram of a power unit 100 according to another embodiment of the present application;

[0066] Figure 8 A schematic diagram of a power unit according to another embodiment of the present application;

[0067] Figure 9 A schematic diagram of a power unit according to another embodiment of the present application;

[0068] Figure 10 A schematic diagram of a power unit according to another embodiment of the present application;

[0069] Figure 11 A schematic diagram of a power unit according to another embodiment of the present application; and

[0070] Figure 12 A power electronic conversion device according to the present application. DETAILED DESCRIPTION

[0071] Example implementations are now described with reference to the drawings. Example implementations can, however, be implemented in many different forms and should not be construed as limited to the examples set forth herein; rather, these implementations are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example implementations to those skilled in the art. The drawings are schematic and are not necessarily to scale; like reference characters indicate like structures throughout the several views. Like reference characters do not necessarily indicate the same components or parts in all figures. The drawings provide examples of how example implementations can be assembled, manufactured, and used, and are not intended to limit the present disclosure in any way.

[0072] Moreover, the described features, structures, or characteristics can be combined in any suitable manner in one or more implementations. In the following description, numerous specific details are provided, such as examples of programming, software modules, user selections, network transactions, database queries, database structures, hardware modules, hardware- specific architectures, memory, hardware- specific instructions, data structures, control signaling, and so on. However, one skilled in the relevant art will recognize that the example implementations can be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail in order to avoid obscuring aspects of the example implementations.

[0073] Figure 4 is a power unit 100 according to an embodiment of the present application, comprising a plurality of power conversion circuits 110-1…110-n, a local controller 120, and a plurality of drive circuits 130.

[0074] Each power conversion circuit 110 comprises at least one bridge arm 111 having a plurality of power semiconductor switches (e.g., Q 11 , Q 12 ), and each power conversion circuit 110 comprises a first output terminal O1 and a second output terminal O2, wherein the first output terminal O1 of one of the adjacent two power conversion circuits 110 and the second output terminal O2 of the other are connected in sequence, and the remaining two first output terminals and second output terminals form a first end (e.g., the first output terminal O1 of the first power conversion circuit 110) and a second end (e.g., the second output terminal O2 of the last power conversion circuit 110-n) of the power unit 100. Specifically, the plurality of power conversion circuits is n power conversion circuits, the first output terminal O1 of the first power conversion circuit 110-1 is the first end of the power unit 100, the second output terminal O2 of the first power conversion circuit 110-1 is connected to the first output terminal O1 of the second power conversion circuit 110-2, and so on, until the second output terminal O2 of the (n-1)th power conversion circuit is connected to the first output terminal O1 of the nth power conversion circuit 110-n, and the second output terminal O2 of the nth power conversion circuit 110-n is the second end of the power unit 100, wherein n is a natural number greater than 1.

[0075] The local controller 120 is used to output multiple control signals (not shown).

[0076] Multiple drive circuits 130 are coupled to a local controller 120 to receive the multiple control signals and output individual drive signals according to the multiple control signals to drive the power semiconductor switch (Q in the figure). 11 Q 12 Q 13 ...Q n4 ( ) to turn on or off.

[0077] exist Figure 4 In this configuration, multiple power conversion circuits are identical, and the number of control signals is the same as the number of power semiconductor switches in each power conversion circuit. The drive circuits 130 corresponding to the power semiconductor switches at the same location in the multiple power conversion circuits receive the same control signals, causing the power semiconductor switches at the same location in the multiple power conversion circuits to be simultaneously turned on or off.

[0078] In other words, each power unit 100 includes multiple identical power conversion circuits, and the power semiconductor switches at the same location in each power conversion circuit are controlled by the same control signal. Therefore, the functions of each power conversion circuit 110 in each power unit 100 are the same.

[0079] in Figure 4 The example described uses the power conversion circuit 110-1…110-n as an H-bridge circuit; however, the power conversion circuit 110-1…110-n in the embodiments of the present invention is not limited to the H-bridge circuit.

[0080] Additionally, please see Figure 5 In some embodiments, the power unit 100 further includes an auxiliary power supply 150. The auxiliary power supply 150 is connected to the local controller 120 and is used to power the local controller 120.

[0081] Since each power unit 100 only needs to be equipped with one auxiliary power supply 150, the power electronic conversion device used in the power unit 100 of this embodiment requires fewer auxiliary power supplies 150, saving costs and simplifying the circuit structure.

[0082] In some implementations, the number of drive circuits 130 is the same as the number of power semiconductor switches, and each drive circuit 130 drives a corresponding power semiconductor switch (Q in the figure). 11 Q 12 Q 13 ...Q n4 ( ) to turn on and off.

[0083] That is, each drive circuit 130 is used to transmit a control signal to a specific power semiconductor switch to control its turn-on and turn-off.

[0084] In some embodiments, the plurality of drive circuits 130 are directly electrically connected with the local controller 120.

[0085] In some embodiments, the plurality of drive circuits 130 are connected with the local controller 120 through a magnetic isolation device.

[0086] In some embodiments, the plurality of drive circuits 130 are connected with the local controller 120 through an optical isolation device.

[0087] The use of a magnetic isolation device has the advantages of higher reliability, higher performance, lower power consumption, etc. The use of an optical isolation device has the advantages of one-way signal transmission, complete electrical isolation between the input end and the output end, no influence of the output signal on the input end, strong anti-interference ability, stable operation, long service life, high transmission efficiency, etc.

[0088] In addition, please refer to Figure 6 In some embodiments, the power conversion circuit further comprises a bus capacitor C and a voltage clamping circuit 160, the bus capacitor C is connected in parallel across the bridge arm 111, and the voltage clamping circuit 160 is connected in parallel across the bus capacitor C.

[0089] In the present embodiment, the DC bus voltage between the two ends of the bus capacitor C is clamped within a predetermined range by the voltage clamping circuit 160. The predetermined range here can be various operating voltage ranges known to those skilled in the art, which will not be described here.

[0090] Since in each power unit 100, the first output end of one of the two adjacent power conversion circuits and the second output end of the other are connected in series, in order to avoid the problem of uneven voltage, a voltage clamping circuit 160 can be provided for the two ends of the bus capacitor C of each power conversion circuit, the bus capacitor C and the voltage clamping circuit 160 are connected in parallel, and both are connected in parallel across the bridge arm 111. In this way, the DC bus voltage between the two ends of the bus capacitor C of each power conversion circuit is clamped within a predetermined range, so that each power conversion circuit will not be overvoltage, which is beneficial to protect the power semiconductor switch.

[0091] Since in the power unit 100 of the present embodiment, only the voltage clamping circuit 160 needs to be configured for the two ends of the bus capacitor C of each power conversion circuit, and no voltage clamping circuit needs to be configured for each power semiconductor switch, the number of voltage clamping circuits can be reduced, the cost and circuit complexity can be reduced, and the system reliability can be improved.

[0092] For ease of explanation, it is assumed that in some embodiments, there are n power conversion circuits. The first output terminal O1 of the first power conversion circuit is the first terminal of the power unit 100. The second output terminal O2 of the first power conversion circuit is connected to the first output terminal O1 of the second power conversion circuit, and so on, until the second output terminal O2 of the (n-1)th power conversion circuit is connected to the first output terminal O1 of the nth power conversion circuit. The second output terminal O2 of the nth power conversion circuit is the second terminal of the power unit 100, where n is a natural number greater than 1. Typically, n is much greater than 1.

[0093] The power conversion circuit involved in the power unit 100 of the embodiments of the present invention can adopt different topologies. Several different topologies are described below as optional embodiments. However, the present invention is not limited to the topologies listed below.

[0094] Please see Figure 7 In some embodiments, each power conversion circuit is an H-bridge circuit, which includes at least one bridge arm, comprising a first bridge arm and a second bridge arm, each bridge arm including an upper power semiconductor switch and a lower power semiconductor switch. In this embodiment, taking the first power conversion circuit 110-1 as an example, this power conversion circuit is an H-bridge circuit, including bridge arm 111a and bridge arm 111b. Bridge arm 111a includes an upper power semiconductor switch Q. 11 and the lower power semiconductor switch Q 12 Bridge arm 111b includes an upper power semiconductor switch Q. 13 and the lower power semiconductor switch Q 14 Among them, the high-power semiconductor switch Q 11 and the lower power semiconductor switch Q 12 The connection point is the first output terminal O1 of the H-bridge circuit 110-1. The upper power semiconductor switch Q... 13 and the lower power semiconductor switch Q 14 The connection point is the second output terminal O2 of the H-bridge circuit 110-1.

[0095] In this embodiment, the local controller 120 outputs four control signals. Each H-bridge circuit can correspond to a drive circuit 130. The drive circuit 130 is coupled to the local controller 120 and connected to the upper power semiconductor switch Q. 11 and Q 13 and the lower power semiconductor switch Q 12 and Q 14 The control terminal is connected to receive four control signals output from the local controller 130, and processes the control signals to generate four drive signals to be output to the high-power semiconductor switch Q in the H-bridge circuit. 11 and Q 13and the control end of the lower power semiconductor switch Q 12 and the control end of the lower power semiconductor switch Q 14 , to drive the upper power semiconductor switch Q 11 and the control end of the lower power semiconductor switch Q 13 and the control end of the lower power semiconductor switch Q 12 and the control end of the lower power semiconductor switch Q 14 . The driving circuit 130 can be directly connected with the local controller 120; can also be connected through a magnetic isolation device, such as a transformer; and can also be connected through an optical isolation device, such as an optical coupler or an optical fiber.

[0096] In the embodiment, the local controller 120 outputs 4 control signals, and each H-bridge circuit can correspond to 4 driving circuits. The driving circuits are coupled with the local controller 120 and are connected with the control ends of the power semiconductor switches in the H-bridge circuit one by one, that is, the number of the driving circuits is the same as the number of the power semiconductor switches, to receive a control signal and process the control signal to generate each driving signal output to the control end of the corresponding power semiconductor switch, to drive the conduction or turn-off of the power semiconductor switch.

[0097] In the embodiment, the control signals corresponding to the power semiconductor switches at the same position of each H-bridge circuit are the same. For example, taking the upper power semiconductor switch of the bridge arm 111a of the H-bridge circuit as an example, specifically, the upper power semiconductor switch Q 11 of the bridge arm 111a of the 1st H-bridge circuit, the upper power semiconductor switch Q 21 of the bridge arm 111a of the 2nd H-bridge circuit, and so on, until the upper power semiconductor switch Q n1 of the bridge arm 111a of the nth H-bridge circuit, the control signals corresponding to the power semiconductor switches are the same, so that the upper power semiconductor switches Q 11 , Q 21 …Q n1 are simultaneously turned on or turned off.

[0098] Please refer to Figure 8 In some embodiments, each power conversion circuit is a half-bridge circuit, and the half-bridge circuit includes a bridge arm 111, and the bridge arm 111 includes an upper power semiconductor switch (such as Q 11 ) and a lower power semiconductor switch (such as Q 12), the second end of the upper power semiconductor switch and the first end of the lower power semiconductor switch are connected to a connection point, which is a first output end O1 of the half-bridge circuit, and the second end of the lower power semiconductor switch is a second output end O2 of the half-bridge circuit. In the embodiment, the first output end of one of the two adjacent power conversion circuits and the second output end of the other of the two adjacent power conversion circuits are sequentially connected, specifically, the first output end O1 of the first half-bridge circuit is a first end of the power unit, the second output end O2 of the first half-bridge circuit and the first output end O1 of the second half-bridge circuit are connected, and sequentially, the second output end O2 of the (n-1)th half-bridge circuit and the first output end O1 of the nth half-bridge circuit are connected, and the second output end O2 of the nth half-bridge circuit is a second end of the power unit.

[0099] In the embodiment, the local controller 120 outputs two control signals (not shown), each of which is used to control one of the upper power semiconductor switch and the lower power semiconductor switch of the corresponding bridge arm, and each half-bridge circuit can correspond to a driving circuit 130, which is coupled with the local controller 120 and connected with the control end of the upper power semiconductor switch Q 11 and the lower power semiconductor switch Q 12 of the half-bridge circuit, so as to receive the two control signals output by the local controller 130, process the control signals, and output two driving signals to the control end of the upper power semiconductor switch Q 11 and the lower power semiconductor switch Q 12 of the half-bridge circuit, so as to control the conduction or turn-off of the upper power semiconductor switch Q 11 and the lower power semiconductor switch Q 12 .

[0100] In the embodiment, the control signals corresponding to the power semiconductor switches at the same position of each half-bridge circuit are the same, for example, taking the upper power semiconductor switches of the half-bridge circuits as an example, the control signals corresponding to the upper power semiconductor switch Q 11 of the first half-bridge circuit, the upper power semiconductor switch Q 21 of the second half-bridge circuit, and the upper power semiconductor switch Q n1 of the nth half-bridge circuit are the same, so that the upper power semiconductor switches Q 11 , Q 21 , and Q n1 are simultaneously turned on or turned off.

[0101] Please refer to Figure 9In some embodiments, the power conversion circuit is a diode clamped three-level circuit, which includes at least one bridge arm, and the at least one bridge arm includes a first bridge arm 111a and a second bridge arm 111b. The first bridge arm 111a and the second bridge arm 111b each include a first power semiconductor switch (e.g., Q 11 , 15 a second power semiconductor switch (e.g., Q 12 , 16 a third power semiconductor switch (e.g., Q 13 , 17 and a fourth power semiconductor switch (e.g., Q 14 , 18 . The diode clamped three-level circuit further includes a first bus capacitor C1, a second bus capacitor C2, a first switch D1, a second switch D2, a third switch D3, and a fourth switch D4. The first bus capacitor C1 and the second bus capacitor C2 are connected in series and are connected in parallel with the first bridge arm 111a and the second bridge arm 111b. The first power semiconductor switch Q 11 , the second power semiconductor switch Q 12 , the third power semiconductor switch Q 13 , and the fourth power semiconductor switch Q 14 of the first bridge arm 111a are connected in series. The connection point of the second power semiconductor switch Q 12 and the third power semiconductor switch Q 13 is a first output terminal O1. The first power semiconductor switch Q 15 , the second power semiconductor switch Q 16 , the third power semiconductor switch Q 17 , and the fourth power semiconductor switch Q 18 of the second bridge arm 111b are connected in series. The connection point of the second power semiconductor switch Q 16 and the third power semiconductor switch Q 17 is a second output terminal O2. The first switch D1 and the second switch D2 are connected in series and are connected between the connection point of the first power semiconductor switch Q 11 and the second power semiconductor switch Q 12 and the connection point of the third power semiconductor switch Q 13 and the fourth power semiconductor switch Q 14 of the first bridge arm 111a. The third switch D3 and the fourth switch D4 are connected in series and are connected between the connection point of the first power semiconductor switch Q 16 and the second power semiconductor switch Q 17 and the connection point of the third power semiconductor switch Q 17 and the fourth power semiconductor switch Q 18The connection points of the first switch D1 and the second switch D2 are connected with the connection points of the first bus capacitor C1 and the second bus capacitor C2. The connection points of the third switch D3 and the fourth switch D4 are connected with the connection points of the first bus capacitor C1 and the second bus capacitor C2. In this embodiment, the first switch D1 and the second switch D2 are clamping diodes, and the first power semiconductor switch, the second power semiconductor switch, the third power semiconductor switch and the fourth power semiconductor switch are IGBTs or IGCTs, etc.

[0102] In this embodiment, the first output end of one of the two adjacent power conversion circuits is connected with the second output end of the other one of the two adjacent power conversion circuits in sequence. Specifically, the first output end O1 of the first diode clamped three-level circuit is the first end of the power unit, the second output end O2 of the first diode clamped three-level circuit is connected with the first output end O1 of the second diode clamped three-level circuit, and the second output end O2 of the n-1th diode clamped three-level circuit is connected with the first output end O1 of the nth diode clamped three-level circuit, and the second output end O2 of the nth diode clamped three-level circuit is the second end of the power unit.

[0103] In this embodiment, the local controller outputs eight control signals, each of which is used to control one of the corresponding first power semiconductor switch (such as Q 11 , Q 15 ), the second power semiconductor switch (such as Q 12 , Q 16 ), the third power semiconductor switch (such as Q 13 , Q 17 ) and the fourth power semiconductor switch (such as Q 14 , Q 18 ). The control signals corresponding to the power semiconductor switches at the same position of each diode clamped three-level circuit are the same. For example, taking the first power semiconductor switch of the diode clamped three-level circuit as an example, the control signals corresponding to the first power semiconductor switch Q 11 of the first diode clamped three-level circuit, the first power semiconductor switch Q 21 of the second diode clamped three-level circuit, and so on until the first power semiconductor switch Q n1 of the nth diode clamped three-level circuit are the same, so that the first power semiconductor switch Q 11 , Q 21 and Q n1 are turned on or turned off at the same time.

[0104] Please refer to Figure 10In some embodiments, the power conversion circuit 110 is a flying capacitor three-level circuit. The flying capacitor three-level circuit includes at least one bridge arm, including a first bridge arm 111a and a second bridge arm 111b. The first bridge arm 111a and the second bridge arm 111b each include a first power semiconductor switch (Q 11 15 ), a second power semiconductor switch (Q 12 16 ), a third power semiconductor switch (Q 13 17 ), and a fourth power semiconductor switch (Q 14 18 ). The flying capacitor three-level circuit further includes a first bus capacitor C1, a second bus capacitor C2, a first capacitor C3, and a second capacitor C4. The first bus capacitor C1 and the second bus capacitor C2 are connected in series and are connected in parallel with the first bridge arm 111a and the second bridge arm 111b. The first power semiconductor switch Q 11 12 13 14 of the first bridge arm 111a are connected in series. The connection point of the second power semiconductor switch Q 12 13 is the first output terminal O1. The first power semiconductor switch Q 15 16 17 18 of the second bridge arm 111b are connected in series. The connection point of the second power semiconductor switch Q 16 17 is the second output terminal O2. The first capacitor C3 is connected between the connection point of the first power semiconductor switch Q 11 12 and the second power semiconductor switch Q 13 14 of the first bridge arm 111a. The second capacitor C4 is connected between the connection point of the first power semiconductor switch Q 15 16 and the second power semiconductor switch Q 17 18 of the second bridge arm 111b.

[0105] ​​​​​​​​​​​​​​​​In the embodiment, the first output terminal of one of the two adjacent power conversion circuits is connected with the second output terminal of the other one of the two adjacent power conversion circuits in sequence. Specifically, the first output terminal O1 of the first flying-capacitor three-level circuit is the first terminal of the power unit, the second output terminal O2 of the first flying-capitor three-level circuit is connected with the first output terminal O1 of the second flying-capacitor three-level circuit, and the second output terminal O2 of the n-1th flying-capacitor three-level circuit is connected with the first output terminal O1 of the nth flying-capacitor three-level circuit, and the second output terminal O2 of the nth flying-capacitor three-level circuit is the second terminal of the power unit.

[0106] In the embodiment, the local controller outputs eight control signals, each of which is used to control one of the corresponding first power semiconductor switches (such as Q 11 , Q 15 ), second power semiconductor switches (such as Q 12 , Q 16 ), third power semiconductor switches (such as Q 13 , Q 17 ) and fourth power semiconductor switches (such as Q 14 , Q 18 ). The control signals corresponding to the power semiconductor switches at the same position of each flying-capacitor three-level circuit are the same. For example, taking the first power semiconductor switches of the flying-capacitor three-level circuits as an example, the control signals corresponding to the first power semiconductor switches Q 11 of the first flying-capacitor three-level circuit, the first power semiconductor switches Q 21 of the second flying-capacitor three-level circuit, and so on until the first power semiconductor switches Q n1 of the nth flying-capacitor three-level circuit are the same, so that the first power semiconductor switches Q 11 , Q 21 and Q n1 are turned on or turned off at the same time.

[0107] Please refer to Figure 11 In some embodiments, the power conversion circuit 110 is a neutral-point-clamped three-level circuit. The neutral-point-clamped three-level circuit includes at least one bridge arm, and the at least one bridge arm includes a first bridge arm 111a and a second bridge arm 111b. The first bridge arm 111a and the second bridge arm 111b each include an upper power semiconductor switch (such as Q 11 , Q 15 ) and a lower power semiconductor switch (such as Q 12 , Q 16 ). The neutral-point-clamped three-level circuit further includes a first bus capacitor C1, a second bus capacitor C2, a first switch group (such as Q 13 , Q 14 ) and a second switch group (such as Q 17, Q 18 ). Wherein the first bus capacitor C1 and the second bus capacitor C2 are connected in series and then connected in parallel with the first bridge arm 111a and the second bridge arm 111b. The connection point of the upper power semiconductor switch Q 11 and the lower power semiconductor switch Q 12 of the first bridge arm 111a is the first output end O1. The connection point of the upper power semiconductor switch Q 15 and the lower power semiconductor switch Q 16 of the second bridge arm 111b is the second output end O2. The first switch group (such as Q 13 , Q 14 ) is connected between the connection point of the upper power semiconductor switch Q 11 and the lower power semiconductor switch Q 12 of the first bridge arm 111a and the connection point of the first bus capacitor C1 and the second bus capacitor C2. The second switch group (such as Q 17 , Q 18 ) is connected between the connection point of the upper power semiconductor switch Q 15 and the lower power semiconductor switch Q 16 of the second bridge arm 111b and the connection point of the first bus capacitor C1 and the second bus capacitor C2. In the embodiment, the first switch group is composed of two power semiconductor switches connected in series, wherein the two power semiconductor switches are bidirectional controllable switches.

[0108] In the embodiment, the first output end of one of the adjacent two power conversion circuits and the second output end of the other are connected in turn, specifically, the first output end O1 of the first neutral point clamped three-level circuit is the first end of the power unit, the second output end O2 of the first neutral point clamped three-level circuit is connected with the first output end O1 of the second neutral point clamped three-level circuit, and so on, the second output end O2 of the n-1th neutral point clamped three-level circuit is connected with the first output end O1 of the nth neutral point clamped three-level circuit, and the second output end O2 of the nth neutral point clamped three-level circuit is the second end of the power unit.

[0109] In the embodiment, the local controller outputs 8 control signals, each of which is used to control the corresponding upper power semiconductor switch (such as Q 11 , Q 15 ), lower power semiconductor switch (such as Q 12 , Q 16 ), first switch group (such as Q 13 , Q 14 ) and second switch group (such as Q 17 , Q 18) one of them. The control signals corresponding to the same position of the power semiconductor switches of each neutral-point-clamped three-level circuit are the same, for example, taking the first power semiconductor switch of the neutral-point-clamped three-level circuit as an example, the control signals corresponding to the first power semiconductor switch Q 11 of the first neutral-point-clamped three-level circuit, the control signals corresponding to the first power semiconductor switch Q 21 of the second neutral-point-clamped three-level circuit, and the control signals corresponding to the first power semiconductor switch Q n1 of the nth neutral-point-clamped three-level circuit are the same, so that the first power semiconductor switches Q 11 , Q 21 , and Q n1 are simultaneously turned on or turned off.

[0110] Referring to Figure 12 , the application also provides an electric power electronic conversion device 500, which can comprise:

[0111] a main controller 300 for outputting a main control signal; and at least one power unit 100 according to the embodiments of the application.

[0112] The local controller 120 is coupled to the main controller 300 for receiving and generating a corresponding control signal according to the main control signal.

[0113] In some embodiments, there are a plurality of power units 100, the second end of one of the adjacent two power units 100 is connected to the first end of the other of the adjacent two power units 100, and the local controller 120 of each power unit 100 is coupled to the main controller 300.

[0114] In some embodiments, the local controller 120 and the main controller 300 are connected through an optical fiber 310; or the local controller 120 and the main controller 300 are directly electrically connected.

[0115] In the first prior art scheme, each power unit 100 only includes one power conversion circuit 110, and since each power unit 100 corresponds to a set of optical fibers, auxiliary power supplies 150, control boards, and the like, and there are more power conversion circuits, compared with the first prior art scheme, the power unit 100 of the embodiments of the application includes a plurality of power conversion circuits 110, which can share higher voltage, therefore, the number of power units 100 is less, thereby reducing the number of optical fibers, auxiliary power supplies 150, and local controllers 120, simplifying the circuit structure, and improving the system reliability.

[0116] The second solution of the prior art is to use high-voltage power devices to reduce the number of power units 100, but the high-voltage power devices are expensive. The power unit 100 of the present embodiment can use low-voltage power devices to achieve the purpose of reducing the number of power units 100, and compared with the second solution of the prior art, the present embodiment saves cost.

[0117] The third solution of the prior art is to connect multiple same power semiconductor switches in series to be equivalent to a high-voltage power device, so as to prevent uneven voltage, and a voltage clamping circuit needs to be configured for each power semiconductor switch. However, the power unit 100 of the present embodiment only needs to configure a voltage clamping circuit for each power conversion circuit 110, so as to reduce the number of voltage clamping circuits, reduce cost, and improve system reliability.

[0118] The above specifically shows and describes the exemplary embodiments of the present application. It should be understood that the present application is not limited to the detailed structure, arrangement or implementation method described herein; on the contrary, the present application is intended to cover various modifications and equivalent arrangements within the spirit and scope of the appended claims.

Claims

1. A power unit, characterized by The power unit comprises: a plurality of power conversion circuits, each of the power conversion circuits comprising at least one bridge arm having a plurality of power semiconductor switches, and each of the power conversion circuits comprising a first output terminal and a second output terminal, wherein the first output terminal of one of the adjacent two power conversion circuits and the second output terminal of the other of the adjacent two power conversion circuits are connected in sequence, and the remaining two first output terminals and second output terminals form a first terminal and a second terminal of the power unit; a local controller configured to output a plurality of control signals; and a plurality of drive circuits coupled to the local controller, each of the drive circuits configured to receive the plurality of control signals and output a respective drive signal according to the plurality of control signals to drive the power semiconductor switches to turn on or turn off. The plurality of power conversion circuits are identical, the number of the plurality of control signals is identical to the number of the power semiconductor switches in each of the power conversion circuits, and the control signals corresponding to the power semiconductor switches at the same positions in the plurality of power conversion circuits are identical, so that the power semiconductor switches at the same positions in the plurality of power conversion circuits are simultaneously turned on or turned off. The power unit further comprises:

2. The power unit of claim 1, wherein, an auxiliary power supply connected to the local controller to supply power to the local controller. The number of the plurality of drive circuits is identical to the number of the power semiconductor switches, and each of the drive circuits drives the corresponding power semiconductor switch to turn on or turn off.

3. The power unit of claim 1, wherein, The plurality of drive circuits are directly connected to the local controller, or the plurality of drive circuits are connected to the local controller through a magnetic isolation device, or the plurality of drive circuits are connected to the local controller through an optical isolation device.

4. The power unit of claim 1, wherein, The power conversion circuit comprises:

5. The power unit of claim 1, wherein, a bus capacitor and a voltage clamping circuit, the bus capacitor being connected in parallel across the bridge arm, and the voltage clamping circuit being connected in parallel across the bus capacitor. The bus voltage between the two ends of the bus capacitor is clamped by the voltage clamping circuit within a predetermined range.

6. The power unit of claim 5, wherein, The plurality of power conversion circuits are n power conversion circuits, the first output terminal of the first power conversion circuit is the first terminal of the power unit, the second output terminal of the first power conversion circuit is connected to the first output terminal of the second power conversion circuit, and the connection is sequentially continued until the second output terminal of the (n-1)th power conversion circuit is connected to the first output terminal of the nth power conversion circuit, and the second output terminal of the nth power conversion circuit is the second terminal of the power unit, wherein n is a natural number greater than 1.

7. The power unit of claim 1, wherein, The power conversion circuit is an H-bridge circuit, wherein the H-bridge circuit comprises:

8. The power unit of claim 7, wherein, ​ The at least one bridge arm comprises a first bridge arm and a second bridge arm, the first bridge arm and the second bridge arm each comprise an upper power semiconductor switch and a lower power semiconductor switch, a connection point of the upper power semiconductor switch and the lower power semiconductor switch of the first bridge arm is the first output terminal of the power conversion circuit, and a connection point of the upper power semiconductor switch and the lower power semiconductor switch of the second bridge arm is the second output terminal of the power conversion circuit.

9. The power unit of claim 7, wherein, The power conversion circuit is a half-bridge circuit, and the half-bridge circuit comprises the bridge arm, wherein the bridge arm comprises an upper power semiconductor switch and a lower power semiconductor switch having a first end and a second end, the second end of the upper power semiconductor switch and the first end of the lower power semiconductor switch are connected to a connection point, and the connection point is the first output terminal of the power conversion circuit, and the second end of the lower power semiconductor switch is the second output terminal of the power conversion circuit.

10. The power unit of claim 7, wherein, The power conversion circuit is a diode-clamped three-level circuit, and the diode-clamped three-level circuit comprises: The at least one bridge arm comprises a first bridge arm and a second bridge arm, the first bridge arm and the second bridge arm each comprise a first power semiconductor switch, a second power semiconductor switch, a third power semiconductor switch and a fourth power semiconductor switch, wherein the first power semiconductor switch, the second power semiconductor switch, the third power semiconductor switch and the fourth power semiconductor switch of the first bridge arm are connected in series, a connection point of the second power semiconductor switch and the third power semiconductor switch of the first bridge arm is the first output terminal of the power conversion circuit, the first power semiconductor switch, the second power semiconductor switch, the third power semiconductor switch and the fourth power semiconductor switch of the second bridge arm are connected in series, and a connection point of the second power semiconductor switch and the third power semiconductor switch of the second bridge arm is the second output terminal of the power conversion circuit; a first bus capacitor and a second bus capacitor, wherein the first bus capacitor and the second bus capacitor are connected in series and are connected in parallel with the first bridge arm and the second bridge arm; and a first bus capacitor and a second bus capacitor, wherein the first bus capacitor and the second bus capacitor are connected in series and are connected in parallel with the first bridge arm and the second bridge arm; and a first switch, a second switch, a third switch and a fourth switch, wherein the first switch and the second switch are connected in series between the connection point of the first power semiconductor switch and the second power semiconductor switch of the first bridge arm and the connection point of the third power semiconductor switch and the fourth power semiconductor switch of the first bridge arm, and the third switch and the fourth switch are connected in series between the connection point of the first power semiconductor switch and the second power semiconductor switch of the second bridge arm and the connection point of the third power semiconductor switch and the fourth power semiconductor switch of the second bridge arm, and the connection point of the first switch and the second switch is connected to the connection point of the first bus capacitor and the second bus capacitor, and the connection point of the third switch and the fourth switch is connected to the connection point of the first bus capacitor and the second bus capacitor.

11. The power unit of claim 7, wherein, The power conversion circuit is a flying capacitor three-level circuit, wherein the flying capacitor three-level circuit comprises: The at least one bridge arm comprises a first bridge arm and a second bridge arm, and each of the first bridge arm and the second bridge arm comprises a first power semiconductor switch, a second power semiconductor switch, a third power semiconductor switch and a fourth power semiconductor switch, wherein the first power semiconductor switch, the second power semiconductor switch, the third power semiconductor switch and the fourth power semiconductor switch of the first bridge arm are connected in series, the connection point of the second power semiconductor switch and the third power semiconductor switch of the first bridge arm is the first output terminal of the power conversion circuit, the first power semiconductor switch, the second power semiconductor switch, the third power semiconductor switch and the fourth power semiconductor switch of the second bridge arm are connected in series, and the connection point of the second power semiconductor switch and the third power semiconductor switch of the second bridge arm is the second output terminal of the power conversion circuit. a first bus capacitor and a second bus capacitor, wherein the first bus capacitor and the second bus capacitor are connected in series and are connected in parallel with the first bridge arm and the second bridge arm; and a first capacitor and a second capacitor, wherein the first capacitor is connected between the connection point of the first power semiconductor switch and the second power semiconductor switch of the first bridge arm and the connection point of the third power semiconductor switch and the fourth power semiconductor switch of the first bridge arm, and the second capacitor is connected between the connection point of the first power semiconductor switch and the second power semiconductor switch of the second bridge arm and the connection point of the third power semiconductor switch and the fourth power semiconductor switch of the second bridge arm.

12. The power unit of claim 7, wherein, The power conversion circuit is a neutral point controllable three-level circuit, wherein the neutral point controllable three-level circuit comprises: The at least one bridge arm comprises a first bridge arm and a second bridge arm, the first bridge arm and the second bridge arm each comprise a respective upper power semiconductor switch and a lower power semiconductor switch, wherein a connection point of the upper power semiconductor switch and the lower power semiconductor switch of the first bridge arm is the first output terminal of the power conversion circuit, and a connection point of the upper power semiconductor switch and the lower power semiconductor switch of the second bridge arm is the second output terminal of the power conversion circuit, a first bus capacitor and a second bus capacitor, wherein the first bus capacitor and the second bus capacitor are connected in series and are connected in parallel with the first bridge arm and the second bridge arm; and a first switch group and a second switch group, wherein the first switch group is connected between the connection point of the upper power semiconductor switch and the lower power semiconductor switch of the first bridge arm and the connection point of the first bus capacitor and the second bus capacitor, and the second switch group is connected between the connection point of the upper power semiconductor switch and the lower power semiconductor switch of the second bridge arm and the connection point of the first bus capacitor and the second bus capacitor.

13. A power electronic conversion device, characterized by, comprise: a main controller configured to output a main control signal; and a local controller coupled to the main controller and configured to receive the main control signal and generate a corresponding control signal. The at least one power unit is a plurality of power units, a second terminal of one of the adjacent two power units is connected to a first terminal of the other of the adjacent two power units, and the local controller of each of the power units is coupled to the main controller.

14. The power electronic conversion device of claim 13, wherein, The local controller and the main controller are connected through an optical fiber, or the local controller and the main controller are directly electrically connected.

15. The power electronic conversion device of claim 13, wherein, The at least one bridge arm comprises a first bridge arm and a second bridge arm, the first bridge arm and the second bridge arm each comprise a respective upper power semiconductor switch and a lower power semiconductor switch, wherein a connection point of the upper power semiconductor switch and the lower power semiconductor switch of the first bridge arm is the first output terminal of the power conversion circuit, and a connection point of the upper power semiconductor switch and the lower power semiconductor switch of the second bridge arm is the second output terminal of the power conversion circuit, a first bus capacitor and a second bus capacitor, wherein the first bus capacitor and the second bus capacitor are connected in series and are connected in parallel with the first bridge arm and the second bridge arm; and a first switch group and a second switch group, wherein the first switch group is connected between the connection point of the upper power semiconductor switch and the lower power semiconductor switch of the first bridge arm and the connection point of the first bus capacitor and the second bus capacitor, and the second switch group is connected between the connection point of the upper power semiconductor switch and the lower power semiconductor switch of the second bridge arm and the connection point of the first bus capacitor and the second bus capacitor. comprise: a main controller configured to output a main control signal; and a local controller coupled to the main controller and configured to receive the main control signal and generate a corresponding control signal. The at least one power unit is a plurality of power units, a second terminal of one of the adjacent two power units is connected to a first terminal of the other of the adjacent two power units, and the local controller of each of the power units is coupled to the main controller. The local controller and the main controller are connected through an optical fiber, or the local controller and the main controller are directly electrically connected.

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