Control method and device of multi-level converter, electronic equipment and medium

Abstract

The invention discloses a control method and device of a multi-level converter, electronic equipment and a medium, and relates to the field of control. According to the number of switching tubes of the multilevel converter, a group of upper bridge arm switching control sequences and a group of lower bridge arm switching control sequences which are mutually dual are determined, and corresponding upper bridge arm PWM waves and lower bridge arm PWM waves are generated to control on and off of the upper bridge arm switching tubes and the lower bridge arm switching tubes. The voltage of the flying capacitor can be balanced by sequentially sending a pair of upper bridge arm PWM waves and a pair of lower bridge arm PWM waves which are mutually paired in adjacent periods, so that the voltage of the flying capacitor is balanced as much as possible by periodically sending the first upper bridge arm PWM waves, the second upper bridge arm PWM waves, the first lower bridge arm PWM waves and the second lower bridge arm PWM waves; the voltage oscillation effect of the multi-level converter when the flying capacitor voltage is in a non-voltage-sharing state is eliminated.

Description

Technical Field

[0001] The present invention relates to the field of control, and in particular to a control method, device, electronic equipment and medium for a multi-level converter. Background Art

[0002] Flying capacitor multi-level converters are gradually gaining attention due to their advantages of high power density and high efficiency. The circuit structure of the N-level flying capacitor multi-level converter is shown in the figure. Figure 1 As shown, it uses multiple switch tubes in series to form the upper bridge arm and the lower bridge arm, and sets a flying capacitor between the nodes of the switch tubes to limit the stress of the switch tubes. However, since the voltage of the flying capacitor must be 1 / (N-1), 2 / (N-1)...(N-2) / (N-1) times the Vbus voltage (bus voltage), that is, to achieve the steady-state natural voltage balancing of the flying capacitor, the stress of each switch tube can be evenly distributed, so the voltage of the flying capacitor must be controlled.

[0003] In general, the control of multi-level converters generally adopts phase-shift PWM (Pulse Width Modulation) with a common duty cycle. Figure 1 In the N-level flying capacitor multi-level converter shown, each switch tube is named S1a, S2a...S(N-1)a in sequence when counting from the middle point of the bridge arm upwards, and each switch tube is named S1b, S2b, ..., S(N-1)b in sequence when counting downwards. The existing multi-level converter control method is that the closing sequence and opening time of the switches in each switching cycle are the same, and the control method of S1b, S2b...S(N-1)b is exactly complementary to S1a, S2a...S(N-1)a, that is, the switching sequence of the upper bridge arm switch tube is opposite to the switching sequence of the lower bridge arm switch tube, for example: the switching sequence of the upper bridge arm in each switching cycle is S1a, S2a...S(N-1)a closed in sequence, and the opening time of each switch is the same. In principle, such a modulation method can realize the steady-state natural voltage balancing of the flying capacitor. However, when the flying capacitor voltage does not meet 1 / (N-1), 2 / (N-1)...(N-2) / (N-1) times the Vbus voltage (bus voltage), the flying capacitor voltage will produce voltage oscillation under the constraints of this control method, and then cause serious overvoltage problems on the switch tube. Therefore, there is an urgent need for a control method to eliminate the voltage oscillation effect of the multi-level converter when the flying capacitor voltage is in an uneven voltage state. Summary of the invention

[0004] The object of the present invention is to provide a control method, device, electronic device and medium for a multi-level converter. When the flying capacitor voltage of the multi-level converter is in an uneven voltage state, the scheme balances the flying capacitor voltage of the multi-level converter as much as possible by periodically sending a first upper bridge arm PWM wave, a second upper bridge arm PWM wave and a first lower bridge arm PWM wave, a second lower bridge arm PWM wave that are dual to each other, so as to eliminate the voltage oscillation effect of the multi-level converter when the flying capacitor voltage is in an uneven voltage state.

[0005] In order to solve the above technical problems, the present invention provides a control method of a multi-level converter, comprising:

[0006] Determining whether the flying capacitor voltage of the multi-level converter is in an uneven voltage state;

[0007] If the flying capacitor of the multi-level converter is in an uneven voltage state, determining the number of first switch tubes in the upper bridge arm and the number of second switch tubes in the lower bridge arm of the multi-level converter;

[0008] Determine a first switch control sequence of an upper bridge arm, a second switch control sequence of an upper bridge arm, a first switch control sequence of a lower bridge arm, and a second switch control sequence of a lower bridge arm according to the first number of switch tubes and the second number of switch tubes, wherein the first switch control sequence of the upper bridge arm is dual to the second switch control sequence of the upper bridge arm, the first switch control sequence of the lower bridge arm is dual to the second switch control sequence of the lower bridge arm, the first switch control sequence of the upper bridge arm is opposite to the first switch control sequence of the lower bridge arm, and the second switch control sequence of the upper bridge arm is opposite to the second switch control sequence of the lower bridge arm;

[0009] Based on the first switch control sequence of the upper bridge arm, the second switch control sequence of the upper bridge arm, the first switch control sequence of the lower bridge arm, the second switch control sequence of the lower bridge arm and the preset duty cycle, the corresponding first upper bridge arm PWM wave, second upper bridge arm PWM wave, first lower bridge arm PWM wave and second lower bridge arm PWM wave are generated, and the first upper bridge arm PWM wave and the second upper bridge arm PWM wave are periodically sent to the upper bridge arm switch tube of the multi-level converter within a preset period range, and the first lower bridge arm PWM wave and the second lower bridge arm PWM wave are periodically sent to the lower bridge arm switch tube of the multi-level converter.

[0010] Optionally, the determining whether the flying capacitor voltage of the multi-level converter is in an uneven voltage state includes:

[0011] Determining a bus voltage of a bus capacitor of the multilevel converter;

[0012] Determining whether the bus voltage is within a preset voltage range;

[0013] If the bus voltage is within the preset voltage range, it is determined that the flying capacitor voltage of the multi-level converter is not in the uneven voltage state;

[0014] If the bus voltage is not within the preset voltage range, it is determined that the flying capacitor voltage of the multi-level converter is in the uneven voltage state.

[0015] Optionally, determining the upper arm first switch control sequence, the upper arm second switch control sequence, the lower arm first switch control sequence, and the lower arm second switch control sequence according to the first switch tube quantity and the second switch tube quantity includes:

[0016] Determine a set of dual phase sequence wheels according to the number of the first switch tubes and the number of the second switch tubes;

[0017] The first switch control sequence of the upper bridge arm, the second switch control sequence of the upper bridge arm, the first switch control sequence of the lower bridge arm, and the second switch control sequence of the lower bridge arm are determined based on the dual phase sequence wheel.

[0018] Optionally, the determining, based on the dual phase sequence wheel, the first switch control sequence of the upper bridge arm, the second switch control sequence of the upper bridge arm, the first switch control sequence of the lower bridge arm, and the second switch control sequence of the lower bridge arm includes:

[0019] Determine N upper bridge arm switch control sequence combinations and N lower bridge arm switch control sequence combinations having a dual phase sequence relationship according to the dual phase sequence wheel;

[0020] Selecting a set of target upper bridge arm switch sequence control combinations from each of the upper bridge arm switch sequence control combinations, and using the upper bridge arm switch sequences corresponding to the target upper bridge arm switch sequence control combinations as the upper bridge arm first switch control sequence and the upper bridge arm second switch control sequence;

[0021] A target lower bridge arm switch sequence control combination opposite to the target upper bridge arm switch sequence control combination is selected from each of the lower bridge arm switch sequence control combinations, and the lower bridge arm switch sequence corresponding to the target lower bridge arm switch sequence control combination is used as the lower bridge arm first switch control sequence and the lower bridge arm second switch control sequence.

[0022] Optionally, after the flying capacitor of the multi-level converter is in an uneven voltage state, the method further includes:

[0023] A corresponding fault report is generated according to the time when the uneven pressure state occurs and the uneven pressure state, and the alarm device is controlled to issue a corresponding alarm.

[0024] Optionally, the periodically sending the first upper arm PWM wave and the second upper arm PWM wave to the upper arm switch tube of the multilevel converter within a preset period range and the periodically sending the first lower arm PWM wave and the second lower arm PWM wave to the lower arm switch tube of the multilevel converter include:

[0025] Determine the preset upper bridge arm PWM wave sending order and the preset lower bridge arm PWM wave sending order;

[0026] Sending the first upper bridge arm PWM wave and the second upper bridge arm PWM wave to the upper bridge arm switch tube in sequence within the preset period range according to the preset upper bridge arm PWM wave sending order;

[0027] Within the preset period range, the first lower bridge arm PWM wave and the second lower bridge arm PWM wave are sent to the lower bridge arm switch tube in sequence according to the preset lower bridge arm PWM wave sending order, and the number of the first upper bridge arm PWM wave, the second upper bridge arm PWM wave, the first lower bridge arm PWM wave and the second lower bridge arm PWM wave is equal.

[0028] Optionally, after periodically sending the first upper arm PWM wave and the second upper arm PWM wave to the upper arm switch tube of the multilevel converter and periodically sending the first lower arm PWM wave and the second lower arm PWM wave to the lower arm switch tube of the multilevel converter within a preset period range, the method further includes:

[0029] Determine whether the upper bridge arm switch tube and the lower bridge arm switch tube perform corresponding switching actions within a preset time;

[0030] If the upper bridge arm switch tube or the lower bridge arm switch tube performs a corresponding switching action within a preset time, it is determined that the upper bridge arm switch tube and the lower bridge arm switch tube are not faulty;

[0031] If the upper bridge arm switch tube or the lower bridge arm switch tube does not perform a corresponding switching action within a preset time, it is determined that the upper bridge arm switch tube or the lower bridge arm switch tube fails, and the alarm device is controlled to issue a corresponding alarm.

[0032] In order to solve the above technical problems, the present invention further provides a control device for a multi-level converter, comprising:

[0033] A judging unit, used for judging whether the flying capacitor voltage of the multi-level converter is in an uneven voltage state;

[0034] A first determining unit, configured to determine the number of first switch tubes in the upper bridge arm and the number of second switch tubes in the lower bridge arm of the multi-level converter when the flying capacitor of the multi-level converter is in an unbalanced voltage state;

[0035] A second determining unit is used to determine, according to the first number of switch tubes and the second number of switch tubes, a first switch control sequence of an upper bridge arm, a second switch control sequence of an upper bridge arm, a first switch control sequence of a lower bridge arm, and a second switch control sequence of a lower bridge arm, wherein the first switch control sequence of the upper bridge arm is dual to the second switch control sequence of the upper bridge arm, the first switch control sequence of the lower bridge arm is dual to the second switch control sequence of the lower bridge arm, the first switch control sequence of the upper bridge arm is opposite to the first switch control sequence of the lower bridge arm, and the second switch control sequence of the upper bridge arm is opposite to the second switch control sequence of the lower bridge arm;

[0036] A sending unit is used to generate a corresponding first upper bridge arm PWM wave, a second upper bridge arm PWM wave, a first lower bridge arm PWM wave and a second lower bridge arm PWM wave based on the first upper bridge arm switch control sequence, the second upper bridge arm switch control sequence, the first lower bridge arm switch control sequence, the second lower bridge arm switch control sequence and a preset duty cycle, and periodically send the first upper bridge arm PWM wave and the second upper bridge arm PWM wave to the upper bridge arm switch tube of the multi-level converter and periodically send the first lower bridge arm PWM wave and the second lower bridge arm PWM wave to the lower bridge arm switch tube of the multi-level converter within a preset period range.

[0037] In order to solve the above technical problems, the present invention further provides an electronic device, comprising:

[0038] Memory for storing computer programs;

[0039] A processor is used to implement the steps of the control method of the multi-level converter as described above when executing the computer program.

[0040] To solve the above technical problem, the present invention further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the control method of the multi-level converter as described above are implemented.

[0041] The object of the present invention is to provide a control method, device, electronic device and medium of a multi-level converter. When the flying capacitor voltage of the multi-level converter is in an uneven voltage state, the scheme determines a group of upper bridge arm switch control sequences and a group of lower bridge arm switch control sequences that are mutually dual according to the number of switch tubes of the multi-level converter, and generates corresponding upper bridge arm PWM waves and lower bridge arm PWM waves to control the opening and closing of the upper bridge arm switch tube and the lower bridge arm switch tube. Because sending a pair of mutually dual upper bridge arm PWM waves and a pair of lower bridge arm PWM waves in sequence in adjacent cycles can balance the flying capacitor voltage, the scheme balances the flying capacitor voltage as much as possible by periodically sending a first upper bridge arm PWM wave, a second upper bridge arm PWM wave, a first lower bridge arm PWM wave and a second lower bridge arm PWM wave, so as to eliminate the voltage oscillation effect of the multi-level converter when the flying capacitor voltage is in an uneven voltage state. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0043] Figure 1 A schematic diagram of the structure of an N-level converter provided by the present invention;

[0044] Figure 2 A process flow chart of a control method for a multi-level converter provided by the present invention;

[0045] Figure 3 A modulation principle diagram of a phase-shift PWM with a common duty cycle provided by the present invention;

[0046] Figure 4 A structural schematic diagram of a flying capacitor five-level converter provided by the present invention;

[0047] Figure 5 The oscillation phenomenon of the voltage of the flying capacitor of the flying capacitor five-level converter provided by the present invention is started from the initial state of non-balanced voltage under the phase sequence of 1234;

[0048] Figure 6 A key mode diagram of a flying capacitor five-level converter provided by the present invention under the control of Seq.1234;

[0049] Figure 7 A flying capacitor five-level converter provided by the present invention corresponds to the modal diagram of Seq.1234;

[0050] Figure 8A key mode diagram of a flying capacitor five-level converter provided by the present invention under the control of Seq.4321;

[0051] Fig. 9 A flying capacitor five-level converter provided by the present invention corresponds to the modal diagram of Seq.4321;

[0052] Fig.10 A schematic diagram of a phase sequence wheel with a phase sequence of 1234 provided by the present invention;

[0053] Fig.11 A schematic diagram of a phase sequence wheel with a phase sequence of 4321 provided by the present invention;

[0054] Fig.12 A schematic diagram of an interlaced phase sequence (1234-1432) modulation provided by the present invention;

[0055] Fig.13 A schematic diagram of a voltage dynamic experiment effect with non-staggered phase sequence provided by the present invention;

[0056] Fig.14 A schematic diagram of another voltage dynamic experimental effect of non-staggered phase sequence provided by the present invention;

[0057] Fig.15 A schematic diagram of three pairs of dual phase sequences of a five-level converter provided by the present invention;

[0058] Fig.16 A schematic diagram of a dual phase sequence wheel of a four-level converter provided by the present invention;

[0059] Fig.17 A schematic diagram of a phase sequence switching in one switching cycle or a phase sequence switching in two switching cycles provided by the present invention;

[0060] Fig.18 A schematic diagram of a triangular wave dual phase sequence modulation provided by the present invention;

[0061] Fig.19 A schematic diagram of the structure of a control device for a multi-level converter provided by the present invention;

[0062] Fig. 20 The present invention provides a schematic structural diagram of an electronic device. DETAILED DESCRIPTION

[0063] The core of the present invention is to provide a control method, device, electronic device and medium for a multi-level converter. When the flying capacitor voltage of the multi-level converter is in an uneven voltage state, the scheme balances the flying capacitor voltage of the multi-level converter as much as possible by periodically sending a first upper bridge arm PWM wave, a second upper bridge arm PWM wave and a first lower bridge arm PWM wave, a second lower bridge arm PWM wave that are dual to each other, so as to eliminate the voltage oscillation effect of the multi-level converter when the flying capacitor voltage is in an uneven voltage state.

[0064] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0065] Please refer to Figure 2 , Figure 2 A process flow chart of a control method for a multi-level converter provided by the present invention. The control method for a multi-level converter includes:

[0066] S11: Determine whether the flying capacitor voltage of the multi-level converter is in an uneven voltage state;

[0067] S12: if the flying capacitor of the multi-level converter is in an uneven voltage state, determining the number of first switch tubes in the upper bridge arm and the number of second switch tubes in the lower bridge arm of the multi-level converter;

[0068] S13: determining a first switch control sequence of an upper bridge arm, a second switch control sequence of an upper bridge arm, a first switch control sequence of a lower bridge arm, and a second switch control sequence of a lower bridge arm according to the first number of switch tubes and the second number of switch tubes, wherein the first switch control sequence of the upper bridge arm is dual to the second switch control sequence of the upper bridge arm, the first switch control sequence of the lower bridge arm is dual to the second switch control sequence of the lower bridge arm, the first switch control sequence of the upper bridge arm is opposite to the first switch control sequence of the lower bridge arm, and the second switch control sequence of the upper bridge arm is opposite to the second switch control sequence of the lower bridge arm;

[0069] S14: Generate corresponding first upper bridge arm PWM wave, second upper bridge arm PWM wave, first lower bridge arm PWM wave and second lower bridge arm PWM wave based on the first switch control sequence of the upper bridge arm, the second switch control sequence of the upper bridge arm, the first switch control sequence of the lower bridge arm, and the preset duty cycle, and periodically send the first upper bridge arm PWM wave and the second upper bridge arm PWM wave to the upper bridge arm switch tube of the multi-level converter and periodically send the first lower bridge arm PWM wave and the second lower bridge arm PWM wave to the lower bridge arm switch tube of the multi-level converter within a preset period range.

[0070] In the present invention, considering that when the flying capacitor voltage of the multi-level converter is in an uneven voltage state, if the upper bridge arm switch tube and the lower bridge arm switch tube of the multi-level converter are controlled in the same switching order in each switching cycle, the multi-level converter will experience voltage oscillation. Therefore, this scheme firstly needs to target the situation where the flying capacitor voltage of the multi-level converter is in an uneven voltage state, and secondly, in this case, the switching order of the upper bridge arm switch tube and the lower bridge arm switch tube of the multi-level converter is changed to eliminate the voltage oscillation phenomenon of the multi-level converter as much as possible. Therefore, this scheme needs to first determine whether the flying capacitor voltage of the multi-level converter is in an uneven voltage state. If so, it is necessary to determine the number of first switch tubes of the upper bridge arm and the number of second switch tubes of the lower bridge arm of the multi-level converter, because the number of switch tubes determines the determination of the actual dual switch tubes, and then determine the mutually dual upper bridge arm first switch control order and upper bridge arm second switch control order according to the first switch tube number and the second switch tube number. The method comprises the following steps: a first switching control sequence of the multi-level converter and a second switching control sequence of the multi-level converter. The first switching control sequence of the multi-level converter and the second switching control sequence of the multi-level converter are used to control the flying capacitor. The first switching control sequence of the multi-level converter and the second switching control sequence of the multi-level converter are used to control the flying capacitor. The first switching control sequence of the multi-level converter and the second switching control sequence of the multi-level converter are used to control the flying capacitor. The first switching control sequence of the multi-level converter and the second switching control sequence of the multi-level converter are used to control the flying capacitor. The first switching control sequence of the multi-level converter and the second switching control sequence of the multi-level converter are used to control the flying capacitor. The flying capacitor voltage is balanced as much as possible to eliminate the voltage oscillation effect of the multi-level converter when the flying capacitor voltage is in an uneven voltage state.

[0071] It should be noted that if Figure 3As shown, PWM modulation requires carrier and modulation wave, where the carriers are named Carrier1~Carrier4 respectively. They are compared with the modulation wave CMP. If the carrier is smaller than CMP at this time, the corresponding PWM is set high, otherwise it is set low. In this way, modulation can generate a PWM signal that drives the carrier signal to shift backward by 180° / (N-1) in sequence. Figure 1 The control methods of the switches S1b, S2b...S(N-1)b in the lower bridge arm of the middle multi-level converter are complementary to the switches S1a, S2a...S(N-1)a in the upper bridge arm of the multi-level converter. In principle, such a modulation method can achieve steady-state natural voltage balancing of the flying capacitor. However, under the dynamic condition of uneven voltage balancing, the flying capacitor voltage will oscillate under the constraints of this control method, thus causing serious overvoltage problems on the switch tube.

[0072] It should also be noted that under the dynamic condition of uneven voltage, the flying capacitor voltage will oscillate under the constraints of this control method, thus causing serious overvoltage problems on the switch tube. Currently, no particularly good control solution for this situation has been investigated. Figure 4 The five-level flying capacitor boost circuit shown in the figure uses Figure 5 The control phase sequence of Seq.1234 shown in the figure is used for control. The so-called Seq.1234 is Figure 3 In this control phase sequence, S1a, S2a, S3a, and S4a are turned on in sequence. Figure 4 An experiment is conducted with a five-level circuit as shown, and the bus voltage is started from an initial state of uneven voltage at a lower voltage. Then, we can see in the experiment that the flying capacitor voltage oscillates, and the oscillation causes overvoltage to the switch tube stress.

[0073] It should also be noted that, taking a five-level circuit as an example, the technical solution of the present application is described, and the so-called dual phase sequence is as follows: Figure 6 Seq.1234 and Figure 8 The key modal diagram of the multi-level circuit corresponding to the two driving sequences of Seq.4321. The characteristics of these two driving sequences are that the dynamic behaviors of the flying capacitor derived from them are completely opposite. The derivation process is as follows:

[0074] Assume that the flying capacitor voltage ripple and input and output voltage ripple are ignored in a switching cycle, and the parasitic parameters such as resistance and inductance in the circuit are ignored. If it is Seq.1234, the corresponding modal diagram is as follows Figure 7 As shown, S1a-S4a are the first switch tube to the fourth switch tube respectively, S1b-S4b are the fifth switch tube to the eighth switch tube respectively, Cf1 is the first flying capacitor, Cf2 is the second flying capacitor, Cf3 is the third flying capacitor, and Cbus is the bus capacitor.

[0075] In the M1 mode, the flying capacitor Cf1 is charged and the inductor current decreases, so the charge of the first flying capacitor Q C1 And the change in inductor current is equal to:

[0076] ; Where D is the duty cycle, Ts is the switching period of the switch tube, V in is the input voltage of the five-level converter, V Cf1 is the voltage value of the first flying capacitor, V Cf2 is the voltage value of the second flying capacitor, V Cf3 is the voltage value of the third flying capacitor, I0-I8 are the current values ​​of the inductor at the input end of the five-level converter at different times, L is the inductance value of the inductor at the input end of the five-level converter, Q C1 is the charge of the first flying capacitor, Q C2 is the charge of the second flying capacitor, Q C3 is the charge of the third flying capacitor, Q D1 is the discharge amount of the first flying capacitor, Q D2 is the discharge amount of the second flying capacitor, Q D3 is the discharge amount of the third flying capacitor;

[0077] In the M2 mode, there is no flying capacitor being charged or discharged, and the inductor current rises. The current change during this period is:

[0078] ;

[0079] In the M3 mode, Cf1 is discharged while Cf2 is charged, and the current flows through the two in series, so the discharge amount of Cf1 is Q D1 Equal to the charge of Cf2, the changing current is equal to:

[0080] ;

[0081] In the M4 mode, there is no flying capacitor being charged or discharged, and the inductor current rises. The current change during this period is:

[0082] ;

[0083] In the M5. mode, Cf2 is discharged while Cf3 is charged, and the current flows through the two in series, so the discharge amount of Cf2 is equal to the charge amount of Cf3, and the changing current is equal to:

[0084] ;

[0085] In the M6 ​​mode, there is no flying capacitor being charged or discharged, and the inductor current rises. The current change during this period is:

[0086] ;

[0087] In the M7 mode, Cf3 is discharged and Cbus is charged, but the general bus voltage is constant, so the discharge amount of Cf3 and the changing current are equal to:

[0088] ; V bus is the voltage of the bus capacitor.

[0089] In the M8 mode, there is no flying capacitor being charged or discharged, and the inductor current rises. The current change during this period is:

[0090] ;

[0091] Based on this modal analysis based on the relationship between volt-seconds and ampere-seconds, the charge change of each flying capacitor can be calculated. , , :

[0092] ;

[0093] For simplicity of calculation, it is assumed that the capacitance of all three flying capacitors is equal and equal to the capacitance Cf of the bus capacitor.

[0094] Then we can deduce:

[0095] ;

[0096] in, , , are voltage values ​​of the first flying capacitor to the third flying capacitor respectively.

[0097] If the same derivation process is used to calculate Seq.4321, the voltage change finally derived is exactly opposite to Seq.1234, and the modal diagram corresponding to Seq.4321 is as follows: Fig. 9 As shown:

[0098] ;

[0099] It should also be noted that the present application defines such two control phase sequences with completely opposite dynamics as dual phase sequences. For dual phase sequences, there are also equivalent phase sequences. For example, for Seq.1234, Seq.2341, Seq.3412, and Seq.4123 also have exactly the same control dynamics, so here we use Fig.10 The wheel shown in the figure represents the phase sequence 1234. The above four phase sequences are all in this wheel, but the starting points on the wheel are different. Fig.11 Then the phase sequence wheel of the corresponding dual phase sequence 4321 is described. It can be found that the rotation direction of the dual phase sequence on the phase sequence wheel is opposite. Since the control dynamics of the dual phase sequence are completely opposite, the two phase sequences can be used to alternate to completely cancel these dynamics. This is the so-called method of achieving dynamic cancellation by staggered phase sequence.

[0100] It should also be noted that if Fig.12 As shown in , this scheme can make a staggered phase sequence of 1234 and 1432 by changing the phase shift of the carrier once in each switching cycle, and 1432 is the equivalent phase sequence of 4321, so such phase sequence staggering can also achieve the effect of dynamic cancellation. Fig.13 and Fig.14 As shown, by comparing the dynamic effects of the staggered phase sequence and the non-staggered phase sequence under the experiment, it can be seen that the staggered dual phase sequence completely eliminates the voltage oscillation of the flying capacitor, which confirms the feasibility of the present application.

[0101] It should also be noted that there are three pairs of dual phase sequences in the five-level multi-level converter circuit, such as Fig.15 As shown in Figure 2, in addition to the five-level multi-level converter, the concept of dual phase sequence also exists for other levels, such as the four-level phase sequence wheel. Fig.16 shown.

[0102] It should also be noted that the phase sequence can be staggered once in one switching cycle or once in multiple switching cycles, such as Fig.17 As shown, for example, the phase sequence is switched once every 1 switching cycle, or once every 2 switching cycles.

[0103] It should also be noted that, in practical applications, the modulation of the staggered phase sequence can be implemented using a sawtooth wave or a carrier wave of other waveforms such as a triangle wave. Fig.18 As shown, if the PWM wave corresponding to the triangular wave carrier is transmitted to each switch tube of the multi-level converter, the adjacent switch tubes corresponding to the adjacent PWM waves will have a time period in which they are in the on state at the same time. As for the actual effects corresponding to other waveforms, this application does not make any special limitations here, and it is only necessary to complete the balanced flying capacitor voltage.

[0104] The present embodiment provides a control method for a multi-level converter. When the flying capacitor voltage of the multi-level converter is in an uneven voltage state, the present scheme determines a set of upper bridge arm switch control sequences and a set of lower bridge arm switch control sequences that are mutually dual according to the number of switch tubes of the multi-level converter, and generates corresponding upper bridge arm PWM waves and lower bridge arm PWM waves to control the opening and closing of the upper bridge arm switch tube and the lower bridge arm switch tube. Because sending a pair of mutually dual upper bridge arm PWM waves and a pair of lower bridge arm PWM waves in sequence in adjacent cycles can balance the flying capacitor voltage, the present scheme balances the flying capacitor voltage as much as possible by periodically sending a first upper bridge arm PWM wave, a second upper bridge arm PWM wave, a first lower bridge arm PWM wave, and a second lower bridge arm PWM wave, so as to eliminate the voltage oscillation effect of the multi-level converter when the flying capacitor voltage is in an uneven voltage state.

[0105] Based on the above embodiments:

[0106] As an optional embodiment, the determining whether the flying capacitor voltage of the multi-level converter is in an uneven voltage state includes:

[0107] Determining a bus voltage of a bus capacitor of the multilevel converter;

[0108] Determining whether the bus voltage is within a preset voltage range;

[0109] If the bus voltage is within the preset voltage range, it is determined that the flying capacitor voltage of the multi-level converter is not in the uneven voltage state;

[0110] If the bus voltage is not within the preset voltage range, it is determined that the flying capacitor voltage of the multi-level converter is in the uneven voltage state.

[0111] In the present invention, considering that whether the flying capacitor voltage of the multi-level converter is in an uneven voltage state is related to the bus voltage of the bus capacitor, this scheme first determines the bus voltage of the bus capacitor of the multi-level converter, and then judges whether the bus voltage is within a preset voltage range. If the bus voltage is within the preset voltage range, it proves that the flying capacitor voltage of the multi-level converter is not in the uneven voltage state; conversely, if the bus voltage is not within the preset voltage range, it proves that the flying capacitor voltage of the multi-level converter is not in the uneven voltage state, thereby ensuring the integrity and accuracy of the uneven voltage state judgment process.

[0112] As an optional embodiment, determining the upper arm first switch control sequence, the upper arm second switch control sequence, the lower arm first switch control sequence, and the lower arm second switch control sequence according to the first switch tube quantity and the second switch tube quantity includes:

[0113] Determine a set of dual phase sequence wheels according to the number of the first switch tubes and the number of the second switch tubes;

[0114] The first switch control sequence of the upper bridge arm, the second switch control sequence of the upper bridge arm, the first switch control sequence of the lower bridge arm, and the second switch control sequence of the lower bridge arm are determined based on the dual phase sequence wheel.

[0115] In the present invention, considering that the first switch control sequence of the upper bridge arm and the second switch control sequence of the upper bridge arm are dual to each other, the first switch control sequence of the lower bridge arm and the second switch control sequence of the lower bridge arm are dual to each other, and the dual phase sequence can determine the corresponding phase sequence wheel according to the number of switch tubes, and then determine the dual switch control sequence, this scheme first determines a set of dual phase sequence wheels according to the first number of switch tubes and the second number of switch tubes, and then determines the first switch control sequence of the upper bridge arm, the second switch control sequence of the upper bridge arm, the first switch control sequence of the lower bridge arm and the second switch control sequence of the lower bridge arm based on the dual phase sequence wheels, thereby ensuring the integrity and accuracy of the dual switch control sequence determination process.

[0116] As an optional embodiment, determining the first switch control sequence of the upper bridge arm, the second switch control sequence of the upper bridge arm, the first switch control sequence of the lower bridge arm, and the second switch control sequence of the lower bridge arm based on the dual phase sequence wheel includes:

[0117] Determine N upper bridge arm switch control sequence combinations and N lower bridge arm switch control sequence combinations having a dual phase sequence relationship according to the dual phase sequence wheel;

[0118] Selecting a set of target upper bridge arm switch sequence control combinations from each of the upper bridge arm switch sequence control combinations, and using the upper bridge arm switch sequences corresponding to the target upper bridge arm switch sequence control combinations as the upper bridge arm first switch control sequence and the upper bridge arm second switch control sequence;

[0119] A target lower bridge arm switch sequence control combination opposite to the target upper bridge arm switch sequence control combination is selected from each of the lower bridge arm switch sequence control combinations, and the lower bridge arm switch sequence corresponding to the target lower bridge arm switch sequence control combination is used as the lower bridge arm first switch control sequence and the lower bridge arm second switch control sequence.

[0120] In the present invention, considering that the number of switch tubes on the upper bridge arm and the number of switch tubes on the lower bridge arm in the multi-level converter determine the number of switch control sequences of the dual phase sequence, and in actual control, only one set of mutually dual switch control sequences needs to be selected to balance the flying capacitor voltage, so this scheme first determines N upper bridge arm switch control sequence combinations and N lower bridge arm switch control sequence combinations with a dual phase sequence relationship according to the dual phase sequence wheel, and then selects a set of target upper bridge arm switch sequence control combinations from each of the upper bridge arm switch sequence control combinations, and uses the upper bridge arm switch sequence corresponding to the target upper bridge arm switch sequence control combination as the upper bridge arm first switch control sequence and the upper bridge arm second switch control sequence; similarly, selects a target lower bridge arm switch sequence control combination opposite to the target upper bridge arm switch sequence control combination from each of the lower bridge arm switch sequence control combinations, and uses the lower bridge arm switch sequence corresponding to the target lower bridge arm switch sequence control combination as the lower bridge arm first switch control sequence and the lower bridge arm second switch control sequence. The selection of a set of mutually dual upper bridge arm switch control sequences and a set of mutually dual lower bridge arm switch control sequences is accurately completed, thereby improving the reliability of the scheme.

[0121] As an optional embodiment, after the flying capacitor of the multi-level converter is in an uneven voltage state, the method further includes:

[0122] A corresponding fault report is generated according to the time when the uneven pressure state occurs and the uneven pressure state, and the alarm device is controlled to issue a corresponding alarm.

[0123] In the present invention, considering that when the flying capacitor of the multi-level converter is in an uneven voltage state, on the one hand, it is necessary to automatically switch the switching sequence, and on the other hand, for the equipment safety of the multi-level converter, it is also necessary for the user or maintenance personnel to observe the voltage oscillation of the multi-level converter in real time. Therefore, after determining that the flying capacitor of the multi-level converter is in an uneven voltage state, the present solution will also generate a corresponding fault report according to the time when the uneven voltage state occurs, so as to facilitate subsequent viewing by users or maintenance personnel. In addition, in order to enable users or maintenance personnel to observe the uneven voltage of the flying capacitor of the multi-level converter in time, the present solution will also control the issuance of corresponding alarms during the alarm period to improve the safety and reliability of the solution.

[0124] As an optional embodiment, the periodic sending of the first upper arm PWM wave and the second upper arm PWM wave to the upper arm switch tube of the multi-level converter within a preset period range and the periodic sending of the first lower arm PWM wave and the second lower arm PWM wave to the lower arm switch tube of the multi-level converter include:

[0125] Determine the preset upper bridge arm PWM wave sending order and the preset lower bridge arm PWM wave sending order;

[0126] Sending the first upper bridge arm PWM wave and the second upper bridge arm PWM wave to the upper bridge arm switch tube in sequence within the preset period range according to the preset upper bridge arm PWM wave sending order;

[0127] Within the preset period range, the first lower bridge arm PWM wave and the second lower bridge arm PWM wave are sent to the lower bridge arm switch tube in sequence according to the preset lower bridge arm PWM wave sending order, and the number of the first upper bridge arm PWM wave, the second upper bridge arm PWM wave, the first lower bridge arm PWM wave and the second lower bridge arm PWM wave is equal.

[0128] In the present invention, considering that sending a pair of mutually dual upper bridge arm PWM waves and a pair of lower bridge arm PWM waves in sequence in adjacent cycles can completely balance the voltage of the flying capacitor, it can be undoubtedly known that whether the voltage of the flying capacitor can be completely balanced within the preset cycle range depends on the number of mutually dual upper bridge arm PWM waves and mutually dual lower bridge arm PWM waves. Therefore, this scheme first determines the preset upper bridge arm PWM wave sending sequence and the preset lower bridge arm PWM wave sending sequence, and then sends the first upper bridge arm PWM wave and the second upper bridge arm PWM wave to the upper bridge arm switch tube in sequence according to the preset upper bridge arm PWM wave sending sequence within the preset cycle range, and at the same time, sends the first lower bridge arm PWM wave and the second lower bridge arm PWM wave to the lower bridge arm switch tube in sequence according to the preset lower bridge arm PWM wave sending sequence within the preset cycle range. However, in order to completely balance the voltage of the flying capacitor, the number of the first upper bridge arm PWM wave, the second upper bridge arm PWM wave, the first lower bridge arm PWM wave and the second lower bridge arm PWM wave are equal, so this scheme can completely eliminate the voltage oscillation effect of the multi-level converter when the flying capacitor voltage is in an uneven voltage state.

[0129] It should be noted that in actual applications, for example: within the preset cycle range, there are four switching cycles, the phase sequence 1234 can be selected in the first switching cycle and the second switching cycle, and the phase sequence 4321 can be selected in the third switching cycle and the fourth switching cycle. As long as the number of the first upper bridge arm PWM wave and the second upper bridge arm PWM wave that are dual to each other within the preset cycle range is consistent, the voltage of the flying capacitor can be completely balanced, thereby completely eliminating the voltage oscillation effect of the multi-level converter when the flying capacitor voltage is in an uneven voltage state.

[0130] As an optional embodiment, after periodically sending the first upper arm PWM wave and the second upper arm PWM wave to the upper arm switch tube of the multi-level converter and periodically sending the first lower arm PWM wave and the second lower arm PWM wave to the lower arm switch tube of the multi-level converter within a preset period range, the method further includes:

[0131] Determine whether the upper bridge arm switch tube and the lower bridge arm switch tube perform corresponding switching actions within a preset time;

[0132] If the upper bridge arm switch tube or the lower bridge arm switch tube performs a corresponding switching action within a preset time, it is determined that the upper bridge arm switch tube and the lower bridge arm switch tube are not faulty;

[0133] If the upper bridge arm switch tube or the lower bridge arm switch tube does not perform a corresponding switching action within a preset time, it is determined that the upper bridge arm switch tube or the lower bridge arm switch tube fails, and the alarm device is controlled to issue a corresponding alarm.

[0134] Please refer to Fig.19 , Fig.19 The present invention provides a schematic diagram of the structure of a control device for a multi-level converter. The control device for the multi-level converter includes:

[0135] A judging unit 11, used to judge whether the flying capacitor voltage of the multi-level converter is in an uneven voltage state;

[0136] A first determining unit 12 is used to determine the number of first switch tubes in the upper bridge arm and the number of second switch tubes in the lower bridge arm of the multi-level converter when the flying capacitor of the multi-level converter is in an unbalanced voltage state;

[0137] A second determining unit 13 is used to determine, according to the first number of switch tubes and the second number of switch tubes, a first switch control sequence of an upper bridge arm, a second switch control sequence of an upper bridge arm, a first switch control sequence of a lower bridge arm, and a second switch control sequence of a lower bridge arm, wherein the first switch control sequence of the upper bridge arm is dual to the second switch control sequence of the upper bridge arm, the first switch control sequence of the lower bridge arm is dual to the second switch control sequence of the lower bridge arm, the first switch control sequence of the upper bridge arm is opposite to the first switch control sequence of the lower bridge arm, and the second switch control sequence of the upper bridge arm is opposite to the second switch control sequence of the lower bridge arm;

[0138] The sending unit 14 is used to generate the corresponding first upper bridge arm PWM wave, second upper bridge arm PWM wave, first lower bridge arm PWM wave and second lower bridge arm PWM wave based on the first upper bridge arm switch control sequence, the second upper bridge arm switch control sequence, the first lower bridge arm switch control sequence, the second lower bridge arm switch control sequence and the preset duty cycle, and periodically send the first upper bridge arm PWM wave and the second upper bridge arm PWM wave to the upper bridge arm switch tube of the multi-level converter and periodically send the first lower bridge arm PWM wave and the second lower bridge arm PWM wave to the lower bridge arm switch tube of the multi-level converter within a preset period range.

[0139] The control device of the multi-level converter provided in this embodiment corresponds to the above method, and thus has the same beneficial effects as the above method. Therefore, for the embodiments of the control device of the multi-level converter, please refer to the description of the embodiments of the method part, which will not be repeated here.

[0140] Please refer to Fig. 20 , Fig. 20 The present invention provides a schematic diagram of the structure of an electronic device. The electronic device includes:

[0141] A memory 20, for storing computer programs;

[0142] The processor 21 is used to implement the steps of the control method of the multi-level converter as described above when executing the computer program.

[0143] The electronic device provided in this embodiment may include but is not limited to a smart phone, a tablet computer, a laptop computer or a desktop computer.

[0144] Among them, the processor 21 may include one or more processing cores, such as a 4-core processor, an 8-core processor, etc. The processor 21 can be implemented in at least one hardware form of a digital signal processor (DSP), a field-programmable gate array (FPGA), and a programmable logic array (PLA). The processor 21 may also include a main processor and a coprocessor. The main processor is a processor for processing data in the awake state, also known as a central processing unit (CPU); the coprocessor is a low-power processor for processing data in the standby state. In some embodiments, the processor 21 may be integrated with a graphics processing unit (GPU), which is responsible for rendering and drawing the content to be displayed on the display screen. In some embodiments, the processor 21 may also include an artificial intelligence (AI) processor, which is used to process computing operations related to machine learning.

[0145] The memory 20 may include one or more computer-readable storage media, which may be non-transitory. The memory 20 may also include a high-speed random access memory, and a non-volatile memory, such as one or more disk storage devices, flash memory storage devices. In this embodiment, the memory 20 is at least used to store the following computer program 201, wherein the computer program can implement the relevant steps of the control method of the multi-level converter disclosed in any of the above embodiments after being loaded and executed by the processor 21. In addition, the resources stored in the memory 20 may also include an operating system 202 and data 203, etc., and the storage method may be temporary storage or permanent storage. Among them, the operating system 202 may include Windows, Unix, Linux, etc. The data 203 may include, but is not limited to, the control method of the multi-level converter, etc.

[0146] In some embodiments, the electronic device may further include a display screen 22 , an input / output interface 23 , a communication interface 24 , a power source 25 , and a communication bus 26 .

[0147] Those skilled in the art will understand that Fig. 20 The structure shown in the figure does not constitute a limitation on the electronic device, and may include more or fewer components than shown in the figure.

[0148] The purpose of this embodiment is to provide an electronic device, in which the memory 20 is used to store computer programs, and the processor 21 is used to implement the steps of the control method of the multi-level converter when executing the computer program, so that the control process is more efficient and accurate.

[0149] The present invention also provides an embodiment corresponding to a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the control method of the multi-level converter as described above are implemented.

[0150] It is understandable that if the method in the above embodiment is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium to execute all or part of the steps of the methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM), random access memory (RAM), disk or optical disk and other media that can store program codes.

[0151] The computer-readable storage medium provided in this embodiment corresponds to the above method, and therefore has the same beneficial effects as the above method. Therefore, for the embodiments of the computer-readable storage medium part, please refer to the description of the embodiments of the method part, which will not be repeated here.

[0152] It should be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0153] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A control method for a multi-level converter, characterized in that: include: Determining whether the flying capacitor voltage of the multi-level converter is in an uneven voltage state; If the flying capacitor of the multi-level converter is in an uneven voltage state, determining the number of first switch tubes in the upper bridge arm and the number of second switch tubes in the lower bridge arm of the multi-level converter; Determine a first switch control sequence of an upper bridge arm, a second switch control sequence of an upper bridge arm, a first switch control sequence of a lower bridge arm, and a second switch control sequence of a lower bridge arm according to the first number of switch tubes and the second number of switch tubes, wherein the first switch control sequence of the upper bridge arm is dual to the second switch control sequence of the upper bridge arm, the first switch control sequence of the lower bridge arm is dual to the second switch control sequence of the lower bridge arm, the first switch control sequence of the upper bridge arm is opposite to the first switch control sequence of the lower bridge arm, and the second switch control sequence of the upper bridge arm is opposite to the second switch control sequence of the lower bridge arm; Based on the first switch control sequence of the upper bridge arm, the second switch control sequence of the upper bridge arm, the first switch control sequence of the lower bridge arm, the second switch control sequence of the lower bridge arm and the preset duty cycle, the corresponding first upper bridge arm PWM wave, second upper bridge arm PWM wave, first lower bridge arm PWM wave and second lower bridge arm PWM wave are generated, and the first upper bridge arm PWM wave and the second upper bridge arm PWM wave are periodically sent to the upper bridge arm switch tube of the multi-level converter within a preset period range, and the first lower bridge arm PWM wave and the second lower bridge arm PWM wave are periodically sent to the lower bridge arm switch tube of the multi-level converter.

2. The control method of the multilevel converter according to claim 1, characterized in that: The determining whether the flying capacitor voltage of the multi-level converter is in an uneven voltage state includes: Determining a bus voltage of a bus capacitor of the multilevel converter; Determining whether the bus voltage is within a preset voltage range; If the bus voltage is within the preset voltage range, it is determined that the flying capacitor voltage of the multi-level converter is not in the uneven voltage state; If the bus voltage is not within the preset voltage range, it is determined that the flying capacitor voltage of the multi-level converter is in the uneven voltage state.

3. The control method of the multi-level converter according to claim 1, characterized in that: The determining, according to the first number of switch tubes and the second number of switch tubes, a first switch control sequence of an upper bridge arm, a second switch control sequence of an upper bridge arm, a first switch control sequence of a lower bridge arm, and a second switch control sequence of a lower bridge arm comprises: Determine a set of dual phase sequence wheels according to the number of the first switch tubes and the number of the second switch tubes; The first switch control sequence of the upper bridge arm, the second switch control sequence of the upper bridge arm, the first switch control sequence of the lower bridge arm, and the second switch control sequence of the lower bridge arm are determined based on the dual phase sequence wheel.

4. The control method of the multi-level converter according to claim 3, characterized in that: The determining of the first switch control sequence of the upper bridge arm, the second switch control sequence of the upper bridge arm, the first switch control sequence of the lower bridge arm, and the second switch control sequence of the lower bridge arm based on the dual phase sequence wheel includes: Determine N upper bridge arm switch control sequence combinations and N lower bridge arm switch control sequence combinations having a dual phase sequence relationship according to the dual phase sequence wheel; Selecting a set of target upper bridge arm switch sequence control combinations from each of the upper bridge arm switch sequence control combinations, and using the upper bridge arm switch sequences corresponding to the target upper bridge arm switch sequence control combinations as the upper bridge arm first switch control sequence and the upper bridge arm second switch control sequence; A target lower bridge arm switch sequence control combination opposite to the target upper bridge arm switch sequence control combination is selected from each of the lower bridge arm switch sequence control combinations, and the lower bridge arm switch sequence corresponding to the target lower bridge arm switch sequence control combination is used as the lower bridge arm first switch control sequence and the lower bridge arm second switch control sequence.

5. The control method of a multi-level converter according to claim 1, characterized in that: After the flying capacitor of the multi-level converter is in an uneven voltage state, the method further includes: A corresponding fault report is generated according to the time when the uneven pressure state occurs and the uneven pressure state, and the alarm device is controlled to issue a corresponding alarm.

6. The control method of a multi-level converter according to claim 1, characterized in that: The method of periodically sending the first upper bridge arm PWM wave and the second upper bridge arm PWM wave to the upper bridge arm switch tube of the multi-level converter within a preset period range and periodically sending the first lower bridge arm PWM wave and the second lower bridge arm PWM wave to the lower bridge arm switch tube of the multi-level converter comprises: Determine the preset upper bridge arm PWM wave sending order and the preset lower bridge arm PWM wave sending order; Sending the first upper bridge arm PWM wave and the second upper bridge arm PWM wave to the upper bridge arm switch tube in sequence within the preset period range according to the preset upper bridge arm PWM wave sending order; Within the preset period range, the first lower bridge arm PWM wave and the second lower bridge arm PWM wave are sent to the lower bridge arm switch tube in sequence according to the preset lower bridge arm PWM wave sending order, and the number of the first upper bridge arm PWM wave, the second upper bridge arm PWM wave, the first lower bridge arm PWM wave and the second lower bridge arm PWM wave is equal.

7. The control method of a multi-level converter according to any one of claims 1 to 6, characterized in that: After periodically sending the first upper bridge arm PWM wave and the second upper bridge arm PWM wave to the upper bridge arm switch tube of the multi-level converter within a preset period range and periodically sending the first lower bridge arm PWM wave and the second lower bridge arm PWM wave to the lower bridge arm switch tube of the multi-level converter, the method further includes: Determine whether the upper bridge arm switch tube and the lower bridge arm switch tube perform corresponding switching actions within a preset time; If the upper bridge arm switch tube or the lower bridge arm switch tube performs a corresponding switching action within a preset time, it is determined that the upper bridge arm switch tube and the lower bridge arm switch tube are not faulty; If the upper bridge arm switch tube or the lower bridge arm switch tube does not perform a corresponding switching action within a preset time, it is determined that the upper bridge arm switch tube or the lower bridge arm switch tube fails, and the alarm device is controlled to issue a corresponding alarm.

8. A control device for a multi-level converter, characterized in that: include: A judging unit, used for judging whether the flying capacitor voltage of the multi-level converter is in an uneven voltage state; A first determining unit, configured to determine the number of first switch tubes in the upper bridge arm and the number of second switch tubes in the lower bridge arm of the multi-level converter when the flying capacitor of the multi-level converter is in an unbalanced voltage state; A second determining unit is used to determine, according to the first number of switch tubes and the second number of switch tubes, a first switch control sequence of an upper bridge arm, a second switch control sequence of an upper bridge arm, a first switch control sequence of a lower bridge arm, and a second switch control sequence of a lower bridge arm, wherein the first switch control sequence of the upper bridge arm is dual to the second switch control sequence of the upper bridge arm, the first switch control sequence of the lower bridge arm is dual to the second switch control sequence of the lower bridge arm, the first switch control sequence of the upper bridge arm is opposite to the first switch control sequence of the lower bridge arm, and the second switch control sequence of the upper bridge arm is opposite to the second switch control sequence of the lower bridge arm; A sending unit is used to generate a corresponding first upper bridge arm PWM wave, a second upper bridge arm PWM wave, a first lower bridge arm PWM wave and a second lower bridge arm PWM wave based on the first upper bridge arm switch control sequence, the second upper bridge arm switch control sequence, the first lower bridge arm switch control sequence, the second lower bridge arm switch control sequence and a preset duty cycle, and periodically send the first upper bridge arm PWM wave and the second upper bridge arm PWM wave to the upper bridge arm switch tube of the multi-level converter and periodically send the first lower bridge arm PWM wave and the second lower bridge arm PWM wave to the lower bridge arm switch tube of the multi-level converter within a preset period range.

9. An electronic device, characterized in that: include: Memory for storing computer programs; A processor, configured to implement the steps of the method for controlling a multi-level converter as claimed in any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the control method of the multi-level converter according to any one of claims 1 to 7 are implemented.

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