Energy consumption sub-module cooperative hybrid equalization modulation method

Abstract

The application provides a kind of energy consumption submodule collaborative hybrid equalization modulation method, in the whole energy consumption process, energy consumption submodule assumes the dual role of basic energy consumption input and compensation energy consumption input, realizes the collaborative optimization of damping characteristic and energy balance: by dynamic rotation mechanism, each energy consumption submodule is switched to basic energy consumption input and compensation energy consumption input according to preset order, to promote the balanced distribution of energy among energy consumption submodules.The application realizes accurate electromotive force reconstruction by dynamically adjusting the switching combination of energy consumption submodules, effectively dissipates surplus power, suppresses voltage harmonics caused by alternating current fault, and balances heat dissipation distribution through energy consumption submodule polling mechanism, improves the fault ride-through capability and operation stability of high-voltage flexible direct current transmission system under alternating current grid fault conditions, and provides reliable technical support for new energy grid connection and other engineering applications.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of high-voltage direct current transmission, and particularly relates to a kind of energy consumption submodule collaborative hybrid equalization modulation method applied to high-voltage flexible direct current transmission system. BACKGROUND

[0002] In the high-voltage flexible direct current transmission system, the modular multilevel converter (MMC) becomes the core equipment of offshore wind power grid connection and cross-regional power grid interconnection due to its high output waveform quality and low switching frequency. Its typical structure contains hundreds of sub-modules (SM), each of which is composed of an IGBT half-bridge circuit and an energy storage capacitor. In terms of control strategy, the MMC uses the ladder wave synthesis technology to generate a high-purity sine wave, effectively suppressing harmonic pollution and providing high-quality power for sensitive loads. In terms of energy management, through intelligent switching strategy and dynamic voltage balancing algorithm, switching loss is significantly reduced and system efficiency is improved, adapting to high-power density application requirements. The MMC also supports independent regulation of active and reactive power and wide-range operating condition adaptability, suitable for complex scenarios such as weak grid connection and island power supply. It also has the advantage of modular design, with standardized sub-module units facilitating rapid expansion and on-site maintenance, and redundant configuration improving system reliability. In addition, the MMC has good dynamic response capability: in terms of function, it has a millisecond-level fault identification and rapid recovery mechanism to ensure stable operation of the power grid.

[0003] In traditional MMC operation, the modular multilevel converter (MMC) takes on the core function of AC-DC energy conversion. When the AC system fails (such as three-phase short circuit or single-phase grounding), the converter valve and energy consumption device need to quickly adopt fault ride-through control strategy to respond in time to maintain system stability. At this time, the energy consumption submodule as an energy buffer device, its dynamic modulation performance directly affects the fault ride-through capability. However, the existing technology has the following bottlenecks:

[0004] (1) Dynamic modulation technology bottleneck: the existing energy consumption submodule modulation strategy based on the nearest level approximation method (NLM) realizes equivalent damping through discrete switching, which can quickly respond to the energy demand at the fault moment, but its essence is to discretize the continuous electromotive force reconstruction process. This approximate treatment leads to two key defects: first, the equivalent damping has an amplitude deviation from the actual demand, making the additional electromotive force brought by the energy consumption module unable to accurately match the AC voltage loss in the fault transient state, causing converter current waveform distortion; second, the step characteristic of discrete switching causes phase compensation delay, exacerbating the electromagnetic oscillation of the system during the fault. These factors superimposed lead to the decline of the dynamic response performance of the converter, manifested as the extension of voltage recovery time and the increase of current overshoot during fault ride-through, and in severe cases, it may even cause system instability.

[0005] (2) Uneven heat dissipation problem: the traditional sub-module switching strategy uses a specific sub-module group fixedly during the fault period, resulting in that part of the modules continuously operate under high load, while other modules are in idle state. This fixed switching mode causes significant heat distribution imbalance: the continuously operating modules generate a large amount of heat due to energy conversion, while the idle modules do not participate in heat dissipation, resulting in the coexistence of local overheating and overall waste of heat dissipation resources. At the same time, the heat exchange efficiency of the cooling system gradually decreases due to long-term response to the fixed heating area, further exacerbating the temperature difference between the modules. This uneven thermal stress distribution not only affects the reliability of the equipment, but also limits the energy handling capacity of the system during the fault period, which is an important factor restricting the performance improvement of the high-voltage flexible direct current transmission system. SUMMARY

[0006] The purpose of the present application is to overcome the deficiencies in the prior art and provide a kind of energy consumption sub-module cooperative hybrid balanced modulation method, by dynamic adjustment energy consumption sub-module switching combination realizes accurate electromotive force reconstruction, while effectively dissipating surplus power, inhibiting voltage harmonic caused by alternating current fault, and through energy consumption sub-module polling mechanism, the heat dissipation distribution is balanced, the fault ride-through capability and operation stability of high-voltage flexible direct current transmission system under alternating current grid fault condition are improved, and reliable technical support is provided for new energy grid connection and other engineering applications. In order to achieve the above purpose, the solution of the present application is:

[0007] A kind of energy consumption sub-module cooperative hybrid balanced modulation method, in the whole energy consumption process, energy consumption sub-module assumes the dual role of basic energy consumption input and compensation energy consumption input, realizes the cooperative optimization of damping characteristic and energy balance:

[0008] Wherein, based on the damping demand of high-voltage flexible direct current transmission system, the number of energy consumption sub-modules as basic energy consumption input is determined, at least one energy consumption sub-module is selected as compensation energy consumption sub-module for compensation energy consumption input from the total energy consumption sub-modules at the same time, to compensate the equivalent damping resistance value of the energy consumption sub-module of basic energy consumption input and the resistance value deviation of the equivalent damping resistance value R diss Required during high-voltage flexible direct current transmission alternating current low voltage fault ride-through process;Through dynamic rotation mechanism, each energy consumption sub-module is switched to basic energy consumption input and compensation energy consumption input according to preset order, to promote the balanced distribution of energy among energy consumption sub-modules.

[0009] On the basis of the above technical scheme, the present application can also use the following further technical schemes, or use these further technical schemes in combination:

[0010] The compensation energy consumption input state of energy consumption sub-module is dynamically adjusted by pulse width modulation method, wherein the number of energy consumption sub-modules for compensation energy consumption input and modulation parameters are dynamically adjusted according to the resistance value deviation.

[0011] The energy consumption sub-module cooperative hybrid equalization modulation method comprises the following steps:

[0012] S1, according to the actual AC fault condition, obtaining the required input equivalent damping resistance R of the high-voltage flexible AC transmission system during AC low-voltage fault ride-through diss ;

[0013] S2, based on the required input equivalent damping resistance R diss , calculating and determining the basic number N of the energy consumption sub-modules to be input diss ;

[0014] S3, calculating the resistance deviation R between the equivalent damping resistance of the basic number of energy consumption sub-modules determined in step S2 and the required input equivalent damping resistance bias ; in the total energy consumption sub-modules, based on the basic number of energy consumption sub-modules determined in step S2, an additional energy consumption sub-module is used for PWM modulation as a compensation energy consumption sub-module to compensate for the resistance deviation R bias ;

[0015] S4, in order to avoid the significant thermal distribution imbalance effect caused by the traditional fixed switching mode, the application proposes a power regulation strategy based on a dynamic rotation mechanism, which realizes the internal energy equalization distribution of the MMC bridge arm by periodically rotating the switching of the energy consumption sub-modules. The core of this strategy is to optimize the switching timing of each energy consumption sub-module within the control period:

[0016] In the total energy consumption sub-modules, according to the dynamic rotation mechanism, the energy consumption sub-modules are sequentially rotated and switched, and within a rotation period T res , each energy consumption sub-module has an average basic conduction time T in ; according to formula (5):

[0017] (5)

[0018] Where N is the total number of energy consumption sub-modules.

[0019] This formula shows that each energy consumption sub-module will obtain the same basic conduction time within the control period, thereby ensuring the balance of energy distribution, and based on this, the switching mode of periodic sequential rotation is carried out.

[0020] In each switching period in a rotation period T res , the energy consumption sub-modules to be input include the basic number of energy consumption sub-modules and the compensation energy consumption sub-module, and the compensation energy consumption sub-module is one of the basic number of energy consumption sub-modules in the next switching period.

[0021] Further preferably, the energy consumption sub-modules are sequentially numbered, and the switching logic of the dynamic rotation mechanism is as follows:

[0022] Initial switching: put in the i to i+N diss energy consumption sub-modules, a total of 1+N diss energy consumption sub-modules, wherein the last one is a compensation energy consumption sub-module;

[0023] Periodic switching: every time after the average on-time T in of the energy consumption sub-modules, the serial number of the energy consumption sub-modules put in is moved N diss in the whole, the compensation energy consumption sub-module of the last round is used as one of the basic number of energy consumption sub-modules in the current round; that is, the i+N diss to i+2N diss number is the energy consumption sub-module described in step S2, the i+2N diss +1 number is the compensation energy consumption sub-module, and so on.

[0024] Cyclic compensation: when the number of energy consumption sub-modules switched each time exceeds the total number of energy consumption sub-modules, the first energy consumption sub-module is used to cyclically connect and sort.

[0025] In step S2, the basic number of energy consumption sub-modules put in is calculated according to formula (1):

[0026] (1)

[0027] Wherein, R sm is the damping resistance value of a single energy consumption sub-module, and floor is the floor function.

[0028] In actual low-voltage AC fault, R diss cannot be divided by R sm , in step S3, the resistance deviation R bias is calculated by formula (2):

[0029] (2).

[0030] In each switching period, the on-time of the compensation energy consumption sub-module is obtained by formula (3):

[0031] (3)

[0032] Where t on represents the on-time of the compensation energy consumption sub-module, T s represents the switching period of the energy consumption sub-module, and formula (3) is rewritten by using the duty cycle D, and formula (4) is obtained:

[0033] (4).

[0034] The energy consumption sub-module comprises a main through-flow branch, an energy consumption branch and a bypass loop in parallel, wherein: in the main through-flow branch, the half-controlled switch device T1 is connected in reverse parallel with its freewheeling diode D1, and then connected in reverse series with the fully-controlled switch device T2, or the fully-controlled switch device S3 is connected in reverse parallel with its freewheeling diode D1, and then connected in reverse series with the fully-controlled switch device S4; the energy consumption branch comprises a resistor R d ; the bypass loop comprises a bypass switch K.

[0035] The application further provides a high-voltage flexible direct current power transmission system, comprising: a three-phase six-bridge-arm MMC converter valve, each bridge arm comprising M MMC sub-modules and N energy consumption sub-modules; the M energy consumption sub-modules are controlled based on any preceding cooperative hybrid balanced modulation method.

[0036] The application further provides a computer device, comprising: at least one processor, and a memory in communication connection with the at least one processor, wherein the memory stores instructions executed by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to execute the energy consumption sub-module cooperative hybrid balanced modulation method described above to cope with high-voltage flexible direct current power transmission alternating current low-voltage faults.

[0037] The application further provides a computer readable storage medium, which stores computer instructions, and the computer instructions are used to enable the computer to execute the energy consumption sub-module cooperative hybrid balanced modulation method described above to cope with high-voltage flexible direct current power transmission alternating current low-voltage faults.

[0038] Compared with the prior art, the application has the following beneficial effects:

[0039] (1) Compared with the existing energy consumption device, the method of the application can accurately reconstruct the electromotive force by dynamically adjusting the switching combination of the energy consumption sub-modules, effectively compensate for the resistance deviation problem based on the existing nearest level approximation method (NLM), accurately match the missing alternating current voltage under the fault transient state of the converter output voltage, suppress the current waveform distortion of the converter valve, avoid the phase compensation delay and electromagnetic oscillation caused by discrete switching, greatly improve the dynamic response performance of the converter, reduce the voltage recovery time and current overshoot during fault ride-through, enhance the system stability, and reduce the risk of system instability.

[0040] (2) The application can effectively dissipate surplus power while suppressing voltage harmonics caused by alternating current faults, provide better power for the power grid, meet the power demand of sensitive loads, and ensure the stable operation of the power grid.

[0041] (3) The application proposes a power regulation strategy based on a dynamic rotation mechanism, which realizes the balanced distribution of energy in the MMC bridge arm by periodically switching the energy-consuming resistor, thereby avoiding the heat distribution imbalance caused by the traditional fixed switching mode. Balanced heat distribution can reduce local overheating, fully utilize overall heat dissipation resources, improve the heat exchange efficiency of the cooling system, reduce the temperature difference between modules, improve equipment reliability, and enhance the energy processing capacity of the system during failure.

[0042] In summary, the application can significantly improve the fault ride-through capability of the high-voltage flexible DC transmission system under AC grid fault conditions, ensuring that the system can quickly respond and maintain stable operation when faults such as three-phase short circuit and single-phase grounding occur. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 The topology structure of the MMC converter valve based on the energy-consuming sub-module for realizing high-voltage flexible DC transmission AC low-voltage fault ride-through in the application.

[0044] Figure 2 The power electronic topology diagram of the MMC sub-module.

[0045] Figure 3 The power electronic topology diagram of the energy-consuming sub-module.

[0046] Figure 4 The power electronic topology diagram of another energy-consuming sub-module.

[0047] Figure 5 The comparison diagram of the nearest level method (NLM) and the equivalent damping implementation of the application.

[0048] Figure 6 The flowchart of the cooperative hybrid balanced modulation method of the application.

[0049] Figure 7 The example diagram of the power regulation strategy of the dynamic rotation mechanism of the application. DETAILED DESCRIPTION

[0050] The application will be further described in detail below in conjunction with the drawings.

[0051] I. Topology structure of MMC converter valve

[0052] As Figure 1 , Figure 2 , Figure 3 , Figure 4As shown, the two ends of the MMC converter valve are connected to the bus of the high-voltage flexible DC power transmission system through DC circuit breakers. The topology structure of the converter valve is composed of three-phase six bridge arms, each phase including upper and lower bridge arms; wherein, the common point of the three-phase bridge arms is taken as the DC port connected to the DC system, and the midpoints of the upper and lower bridge arms are taken as the AC ports connected to the AC system; each bridge arm contains a bridge arm inductor and M MMC sub-modules SM which are sequentially connected in series and have the same structure, M≥1; between the bridge arm inductor L of each bridge arm and the midpoints of the upper and lower bridge arms, N energy dissipation sub-modules RSM which are sequentially connected in series and have the same structure are arranged, N≥1; the energy dissipation sub-module includes a main current branch, an energy dissipation branch and a bypass loop in parallel; in the main current branch, the half-controlled switch device T1 is connected in reverse parallel with its freewheeling diode D1, and then reversely connected in series with the fully-controlled switch device T2, or the fully-controlled switch device S3 is connected in reverse parallel with its freewheeling diode D1, and then reversely connected in series with the fully-controlled switch device S4; the energy dissipation branch includes an energy dissipation resistor R d , and the bypass branch includes a bypass switch K.

[0053] Wherein, the MMC sub-module can be a half-bridge power module, including two switch power devices with reverse diodes and a capacitor. The half-controlled switch device T1 can be a thyristor, and the fully-controlled switch devices T2, S3 and S4 can be three-terminal semiconductor switch devices (IGBT), and a water-cooled heat dissipation device is arranged outside the energy dissipation resistor R d . In each bridge arm, the number of series connection of the MMC sub-module and the energy dissipation sub-module, and the selection of the capacitor and the switch device are determined by the technical personnel according to the actual situation of the high-voltage flexible DC power transmission system.

[0054] II. Explanation of energy dissipation sub-module cooperative hybrid equalization modulation mode

[0055] Based on the above-mentioned topology structure of the converter valve, the present application proposes an energy dissipation sub-module cooperative hybrid equalization modulation method, which provides a feasible solution for accurate reconstruction of the electromotive force on the AC side at the moment of fault ride-through and equalization of the heat distribution of the energy dissipation sub-module. The present application can accurately reconstruct the electromotive force by dynamically adjusting the switching combination of the energy dissipation sub-module, effectively compensating for the resistance deviation problem of the existing nearest level approximation method (NLM), so that the output voltage of the converter accurately matches the missing AC voltage under the fault transient state, and suppresses the distortion of the current waveform of the converter valve; in terms of heat equalization, a power regulation strategy based on a dynamic rotation mechanism is adopted, and the internal energy of the MMC bridge arm is evenly distributed by periodically switching the energy dissipation sub-module, thereby avoiding the heat distribution imbalance problem caused by the traditional fixed switching mode.

[0056] Figure 5 The above-mentioned topology structure of the converter valve is based on the nearest level approximation method (NLM) and the present application in the implementation of equivalent damping. The required equivalent damping resistance R dissThe relationship between the discrete module switching and the resistance value that can be reached.

[0057] In the traditional nearest level method, if only an integer number of energy consumption sub-modules with a resistance value of R sm are switched to achieve the required input equivalent damping resistance R diss , then:

[0058] The number of modules determined by the floor(R diss / R sm ) method has an equivalent resistance of N diss *R sm , which is usually less than the required R diss . The number of modules determined by the roundup(R diss / R sm ) method (N diss +1) has an equivalent resistance of (N diss +1)*R sm , which is usually greater than the required R diss .

[0059] Because the number of energy consumption sub-modules switched must be an integer, the required input equivalent damping resistance R diss cannot be accurately matched by only this discrete switching, resulting in a deviation between the actual input damping and the required damping. For example, if N diss modules are used, there is a resistance deviation of (as shown by the double-headed arrow in Figure 5 ).

[0060] To solve this problem, the present application uses an additional compensation energy consumption sub-module to finely adjust through PWM (pulse width modulation) on the basis of N diss main energy consumption sub-modules (i.e., floor(R diss / R sm )). The PWM compensation energy consumption sub-module equivalently provides a resistance of R bias , so that the total input equivalent damping resistance can accurately approach and compensate to the required R diss , improving the accuracy of damping control and overcoming the amplitude deviation problem caused by discrete steps in the traditional NLM method.

[0061] The energy consumption sub-module cooperative hybrid equalization modulation method of the present application will be described in detail below with reference to Figure 6 , Figure 7 and Figure 1 and Figure 5 , including the following steps:

[0062] S1, according to the actual AC fault condition, the required input equivalent damping resistance R in the AC low voltage fault ride-through process is obtained diss .

[0063] S2, based on the required input equivalent damping resistance R diss , the basic number of energy consumption sub-modules required to be input is calculated and determined as:

[0064] (1)

[0065] Where N diss is the basic number of energy consumption sub-modules, R sm is the damping resistance of a single energy consumption sub-module, and floor is the floor function.

[0066] S3, in the actual AC low voltage fault, R diss cannot be divided by R sm , therefore, there is a resistance deviation R bias between the input resistance of the basic number of energy consumption sub-modules and the required input equivalent damping resistance R diss , as shown in formula (2): Figure 5

[0067] (2)

[0068] S4, in order to compensate for the resistance deviation, an additional energy consumption sub-module is used for PWM modulation as a compensation energy consumption sub-module, and the conduction time of the compensation energy consumption sub-module in each round is obtained by formula (3):

[0069] (3)

[0070] Where t on represents the conduction time of the compensation energy consumption sub-module, T s represents the switching period of the energy consumption sub-module, and the duty cycle D of the compensation energy consumption sub-module is used to rewrite formula (3), and formula (4) is obtained:

[0071] (4).

[0072] For convenience of understanding, in the specific implementation of the present application, 12 energy consumption sub-modules and 7 switching periods (T1-T7) shown in formula (5) are taken as examples to explain the power regulation strategy based on the dynamic rotation mechanism: Figure 7

[0073] If N diss energy consumption sub-modules are required to be input, according to formula (5), the average basic conduction time T in of each energy consumption sub-module is:

[0074] (5)​​

[0075] N diss =4 as an example; the initial switching is in the order of rotation mechanism, the first to the fourth energy consumption sub-modules (corresponding to the T1 column shadow part in the figure) are put into the T1 switching period, and the fifth energy consumption sub-module is additionally put into PWM modulation as a compensation energy consumption sub-module to compensate for the resistance deviation; the period is switched, after T in time, the fifth to the eighth energy consumption sub-modules (T2 column shadow in the figure) are put into the T2 switching period, and the ninth energy consumption sub-module is additionally put into PWM modulation; in this way, the ninth to the twelfth energy consumption sub-modules (T3 column shadow in the figure) are put into the T3 switching period, and the first energy consumption sub-module is additionally put into PWM modulation; the combination switching of the energy consumption sub-modules is realized through the sequential rotation.

[0076] When the number of energy consumption sub-modules exceeds the total number of energy consumption sub-modules each time (such as the T3 switching period), the first energy consumption sub-module is circularly connected in sequence to ensure the continuity of switching according to the circular compensation mechanism.

[0077] The application realizes accurate electromotive force reconstruction by dynamically adjusting the switching combination of the energy consumption sub-modules, effectively dissipates the surplus power, suppresses the voltage harmonics caused by alternating current faults, balances the heat dissipation distribution through the energy consumption sub-module polling mechanism, improves the fault ride-through capability and operation stability of the high-voltage flexible direct current transmission system under the condition of alternating current grid fault, provides reliable technical support for new energy grid connection engineering application, and has important significance for promoting the rapid development and safety guarantee of the flexible direct current transmission system.

Claims

1. A method for energy-consuming sub-module cooperative hybrid equalization modulation, characterized in that, In the whole energy consumption process, the energy consumption sub-module bears the dual role of basic energy consumption investment and compensation energy consumption investment, realizing the collaborative optimization of damping characteristics and energy balance: The number of energy dissipation sub-modules as the basic energy dissipation input is determined based on the damping requirement of the high-voltage flexible DC power transmission system, at least one energy dissipation sub-module is selected from the total energy dissipation sub-modules as a compensation energy dissipation sub-module for compensation energy dissipation input at the same time, so as to compensate the equivalent damping resistance value deviation of the basic energy dissipation input and the required equivalent damping resistance value R diss of the high-voltage flexible DC power transmission AC low-voltage fault ride-through process; and the dynamic rotation mechanism is used to make each energy dissipation sub-module be switched to the basic energy dissipation input and the compensation energy dissipation input in a preset order, so as to promote the balanced distribution of energy among the energy dissipation sub-modules. The pulse width modulation method is used to dynamically adjust the compensation energy consumption input state of the energy consumption sub-module, wherein the number of compensation energy consumption input energy consumption sub-modules and the modulation parameters are dynamically adjusted according to the resistance deviation.

2. The method of claim 1, wherein the energy-consuming sub-module is a motor. Comprising the following steps: S1, according to the actual AC fault condition, get the required equivalent damping resistance R in the process of high-voltage flexible AC transmission AC low-voltage fault ride through diss ; S2, based on the required input equivalent damping resistance value R diss , calculate and determine the basic number N of energy dissipation sub-modules input diss ; S3, calculating the resistance value deviation R between the equivalent damping resistance value of the basic number of energy dissipation sub-modules determined in step S2 and the required input equivalent damping resistance value bias ; in the total energy dissipation sub-module, on the basis of the basic number of energy dissipation sub-modules determined in step S2, an additional energy dissipation sub-module is used for PWM modulation as a compensation energy dissipation sub-module to compensate for the resistance value deviation R bias ; S4, in the total energy consumption sub-module, according to the dynamic rotation mechanism, sequentially rotate the switching energy consumption sub-module, in a rotation period T res According to formula (5) calculation: in According to formula (5) calculation: Wherein N is the total number of energy consumption sub-modules.

3. The method of claim 2, wherein, In each switching period T res In each switching period, the energy-consuming sub-modules put in include the basic number of energy-consuming sub-modules and compensation energy-consuming sub-modules, and the compensation energy-consuming sub-modules serve as one of the basic number of energy-consuming sub-modules in the next switching period.

4. The method of claim 2, wherein the method comprises: The energy consumption sub-modules are numbered, and the switching logic of the dynamic rotation mechanism is as follows: Initial switching: put in the i to i+N diss energy consumption sub-modules, a total of 1+N diss energy consumption sub-modules, the last one is a compensation energy consumption sub-module; Periodic switching: every time the average basic conduction time T of the energy-consuming submodule is passed in After a period of time, the serial number of the energy-consuming submodule is moved N as a whole diss The serial number of the energy-consuming submodule is moved N as a whole The compensation energy-consuming submodule of the previous round is one of the basic number of energy-consuming submodules in the current round Looping in: the number of energy consumption sub-module switching exceeds the total number of energy consumption sub-modules each time, and the first energy consumption sub-module is looped to connect in sequence.

5. The method of claim 2, wherein the method comprises: In step S2, the basic number of energy consumption sub-modules is calculated according to formula (1): wherein R sm is the damping resistance value of the individual energy-consuming sub-module, and floor is a floor function.

6. The method of claim 2, wherein, In step S3, the resistance deviation R is calculated by formula (2) bias : R bias = R diss -N diss R sm (2) wherein R sm is the damping resistance value of the individual energy-consuming sub-module.

7. The method of claim 2, wherein the method comprises: The duty cycle D of the compensation compensation sub-module of PWM modulation is determined by formula (4): R bias = DR sm (4) wherein R sm is the damping resistance value of the individual energy-consuming sub-module.

8. The method of claim 2, wherein the method is a method of co- mixed equalization modulation of energy-consuming sub-modules, characterized in that, The energy consumption sub-module comprises a main through-flow branch, an energy consumption branch and a bypass loop in parallel, wherein: in the main through-flow branch, a half-controlled switch device T1 is connected in reverse parallel with its freewheeling diode D1, and then connected in reverse series with a fully-controlled switch device T2, or a fully-controlled switch device S3 is connected in reverse parallel with its freewheeling diode D1, and then connected in reverse series with a fully-controlled switch device S4; the energy consumption branch comprises a resistor R d ; and the bypass loop comprises a bypass switch K.

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