A MMC converter modulation method and device for power router

Abstract

The present disclosure relates to a method and device for modulating an MMC converter for an electric energy router. The method comprises: calculating and generating a first number of modules to be put into operation based on a nearest level approximation modulation strategy of a modular multilevel converter; determining whether the first number of modules to be put into operation is an integer, calculating a module voltage imbalance coefficient, and generating a module compensation number based on the module voltage imbalance coefficient according to the determination result; dividing the module compensation number by a multiplication factor, and summing the result with the first number of modules to generate a second number of modules to be put into operation; using the second number of modules as the real-time number of modules to be put into operation for the upper and lower bridge arms of each phase in the nearest level approximation modulation strategy NLM, thereby completing the modulation of the MMC converter. The present disclosure does not directly increase the number of levels on the AC side of the MMC of the electric energy router, but can increase the number of levels of the module instructions during the modulation process, thereby optimizing the matching process of the number of submodules put into operation, equivalently increasing the number of levels and reducing the harmonic content.

Description

Technical Field

[0001] The present disclosure relates to the field of power electronics technology, and in particular to a method and device for modulating an MMC converter for a power router. Background Art

[0002] Currently, the main modulation strategies used for modular multilevel converters (MMCs) in power routers are NLM modulation and PWM modulation. PWM modulation works well when the number of MMC submodules is small, but when the number of submodules is large, PWM modulation becomes very complex to control, and the switching frequency increases, leading to increased switching losses. As a type of step-wave modulation, NLM modulation offers better modulation performance with high-level MMCs, making it widely used in engineering. However, due to site size and cost constraints, the number of MMC submodules cannot be too large, resulting in some degree of harmonics on the MMC AC side. Therefore, reducing the harmonic content on the MMC AC side without increasing the number of MMC submodules, scale, or cost is an urgent issue.

[0003] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute prior art known to ordinary technicians in the field. Summary of the Invention

[0004] The present disclosure aims to provide a method and apparatus for modulating an MMC converter for a power router, thereby overcoming, at least to some extent, one or more problems caused by limitations and defects of related technologies.

[0005] According to one aspect of the present disclosure, there is provided a method for modulating an MMC converter for a power router, comprising:

[0006] Based on the nearest level approach modulation strategy NLM of the modular multilevel converter MMC, a relationship between the number of upper and lower bridge arm modules including the multiplication factor is generated, and the first number of modules put into operation is calculated;

[0007] Determine whether the first number of modules put into operation is an integer, and calculate the module voltage imbalance coefficient. If the first number of modules put into operation is an integer, match the even number closest to the module voltage imbalance coefficient, and use the even number closest to the module voltage imbalance coefficient as the module compensation number. If the first number of modules put into operation is not an integer, match the odd number closest to the module voltage imbalance coefficient, and use the odd number closest to the module voltage imbalance coefficient as the module compensation number.

[0008] After dividing the module compensation number by the multiplication factor, the sum is added to the first number of modules to generate a second number of modules. The second number of modules is used as the real-time number of modules for each phase upper and lower bridge arms in the nearest level approximation modulation strategy NLM to complete the MMC converter modulation.

[0009] In an exemplary embodiment of the present disclosure, the method further includes:

[0010] Based on the nearest level approach modulation strategy NLM of the modular multilevel converter MMC, the relationship between the number of modules in the upper and lower bridge arms including the multiplication factor is generated.

[0011]

[0012] Among them, n pj With n nj are the first input modules of the upper and lower bridge arms of the MMC, round is the rounding function, u j is the modulation wave voltage, U SM is the capacitance voltage of the neutron modules in the upper and lower bridge arms of the MMC, N is the number of neutron modules in the upper and lower bridge arms of the MMC, and a is the rate coefficient.

[0013] In an exemplary embodiment of the present disclosure, the method further includes:

[0014] The calculation formula for module voltage unbalance coefficient is:

[0015]

[0016] Among them, x′ is the module voltage unbalance coefficient, U dc is the MMC bus voltage, u nj 、u pj They are the upper and lower arm voltages of the MMC respectively.

[0017] In an exemplary embodiment of the present disclosure, the method further includes:

[0018] Determine whether the first number of modules put into operation is an integer, and calculate the module voltage imbalance coefficient. If the first number of modules put into operation is an integer, match the even number closest to the module voltage imbalance coefficient, and use the even number closest to the module voltage imbalance coefficient as the module compensation number x; if the first number of modules put into operation is not an integer, match the odd number closest to the module voltage imbalance coefficient, and use the odd number closest to the module voltage imbalance coefficient as the module compensation number x.

[0019] In an exemplary embodiment of the present disclosure, the method further includes:

[0020] After dividing the module compensation number by the multiplication factor, the sum is added to the first input module number to generate the second input module number.

[0021]

[0022] Among them, n′ pj (t), n′ nj (t) are the number of second input modules of the upper and lower bridge arms of the MMC respectively;

[0023] The second number of modules put into operation is used as the real-time number of modules put into operation of the upper and lower bridge arms of each phase in the nearest level approximation modulation strategy NLM to complete the MMC converter modulation.

[0024] In an exemplary embodiment of the present disclosure, the method further includes:

[0025] The multiplication factor is 2.

[0026] In one aspect of the present disclosure, there is provided an MMC converter modulation device for an electric energy router, comprising:

[0027] A first module number calculation module is configured to generate a relationship between the number of modules put into operation in the upper and lower bridge arms, including a multiplying factor, based on a nearest level approximation modulation strategy NLM of the modular multilevel converter MMC, and calculate and generate a first number of modules put into operation;

[0028] a module compensation number calculation module, configured to determine whether the first number of modules put into operation is an integer and calculate a module voltage imbalance coefficient; if the first number of modules put into operation is an integer, then match the even number closest to the module voltage imbalance coefficient and use the even number closest to the module voltage imbalance coefficient as the module compensation number; if the first number of modules put into operation is not an integer, then match the odd number closest to the module voltage imbalance coefficient and use the odd number closest to the module voltage imbalance coefficient as the module compensation number;

[0029] The converter modulation module is used to divide the module compensation number by the multiplication factor, sum it with the first number of input modules, generate a second number of input modules, and use the second number of input modules as the real-time number of input modules of each phase upper and lower bridge arms in the nearest level approximation modulation strategy NLM to complete the MMC converter modulation.

[0030] In an exemplary embodiment of the present disclosure, a modulation method for an MMC converter for an energy router is disclosed, wherein the method includes: calculating and generating a first number of modules to be put into operation based on a nearest level approximation modulation strategy for a modular multilevel converter; determining whether the first number of modules to be put into operation is an integer, calculating a module voltage imbalance coefficient, and generating a module compensation number based on the module voltage imbalance coefficient according to the determination result; dividing the module compensation number by a multiplication factor, and summing the result with the first number of modules to generate a second number of modules to be put into operation; using the second number of modules as the real-time number of modules to be put into operation for the upper and lower bridge arms of each phase in the nearest level approximation modulation strategy (NLM), thereby completing MMC converter modulation. The present disclosure does not directly increase the number of levels on the AC side of the MMC of the energy router, but rather increases the number of levels of module instructions during the modulation process, thereby optimizing the matching process of the number of submodules put into operation, equivalently increasing the number of levels and reducing harmonic content.

[0031] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and other features and advantages of the present disclosure will become more apparent by describing in detail example embodiments thereof with reference to the accompanying drawings.

[0033] Figure 1 A flow chart of a method for modulating an MMC converter for an electric energy router according to an exemplary embodiment of the present disclosure is shown;

[0034] Figures 2A-2C An MMC topology principle diagram of an MMC converter modulation method for a power router according to an exemplary embodiment of the present disclosure is shown;

[0035] Figure 3 A flowchart of a modulation method for an MMC converter of an electric energy router according to an exemplary embodiment of the present disclosure when the multiplication factor is 2 is shown;

[0036] Figure 4 A schematic block diagram of an MMC converter modulation device for a power router according to an exemplary embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0037] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be embodied in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concepts of the example embodiments to those skilled in the art. Like reference numerals in the drawings represent like or similar parts, and thus repetitive description thereof will be omitted.

[0038] In addition, the described features, structures or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure can be practiced without one or more of the specific details, or other methods, components, materials, devices, steps, etc. can be adopted. In other cases, well-known structures, methods, devices, implementations, materials or operations are not shown or described in detail to avoid obscuring various aspects of the present disclosure.

[0039] The blocks shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically separate entities. Specifically, these functional entities may be implemented in software, or in one or more software-hardened modules, or in different networks and / or processor devices and / or microcontroller devices.

[0040] In this exemplary embodiment, a modulation method for an MMC converter of an electric energy router is first provided; Figure 1 As shown in , the MMC converter modulation method for a power router may include the following steps:

[0041] Step S110: Based on the nearest level approach modulation strategy NLM of the modular multilevel converter MMC, a relational expression for the number of upper and lower bridge arm modules including a multiplication factor is generated, and a first number of modules is calculated.

[0042] Step S120: Determine whether the first number of modules put into operation is an integer, and calculate the module voltage imbalance coefficient. If the first number of modules put into operation is an integer, match the even number closest to the module voltage imbalance coefficient, and use the even number closest to the module voltage imbalance coefficient as the module compensation number. If the first number of modules put into operation is not an integer, match the odd number closest to the module voltage imbalance coefficient, and use the odd number closest to the module voltage imbalance coefficient as the module compensation number.

[0043] Step S130: After dividing the module compensation number by the multiplication factor, the sum is added to the first number of invested modules to generate a second number of invested modules. The second number of invested modules is used as the real-time number of invested modules for the upper and lower bridge arms of each phase in the nearest level approximation modulation strategy NLM to complete the MMC converter modulation.

[0044] In an exemplary embodiment of the present disclosure, a modulation method for an MMC converter for an energy router is disclosed, wherein the method includes: calculating and generating a first number of modules to be put into operation based on a nearest level approximation modulation strategy for a modular multilevel converter; determining whether the first number of modules to be put into operation is an integer, calculating a module voltage imbalance coefficient, and generating a module compensation number based on the module voltage imbalance coefficient according to the determination result; dividing the module compensation number by a multiplication factor, and summing the result with the first number of modules to generate a second number of modules to be put into operation; using the second number of modules as the real-time number of modules to be put into operation for the upper and lower bridge arms of each phase in the nearest level approximation modulation strategy (NLM), thereby completing MMC converter modulation. The present disclosure does not directly increase the number of levels on the AC side of the MMC of the energy router, but rather increases the number of levels of module instructions during the modulation process, thereby optimizing the matching process of the number of submodules put into operation, equivalently increasing the number of levels and reducing harmonic content.

[0045] Next, a modulation method for an MMC converter of a power router in this exemplary embodiment will be further described.

[0046] In step S110, based on the nearest level approach modulation strategy NLM of the modular multilevel converter MMC, a relational expression for the number of upper and lower bridge arm modules including a multiplying factor may be generated, and a first number of modules may be calculated.

[0047] In this exemplary embodiment, the method further includes:

[0048] Based on the nearest level approach modulation strategy NLM of the modular multilevel converter MMC, the relationship between the number of modules in the upper and lower bridge arms including the multiplication factor is generated.

[0049]

[0050] Among them, n pj With n nj are the first input modules of the upper and lower bridge arms of the MMC, round is the rounding function, u j is the modulation wave voltage, U SM is the capacitance voltage of the neutron modules in the upper and lower bridge arms of the MMC, N is the number of neutron modules in the upper and lower bridge arms of the MMC, and a is the rate coefficient.

[0051] In this exemplary embodiment, Figure 2A The MMC topology diagram shows that each phase consists of two bridge arms, and each bridge arm consists of a reactor connected in series with multiple submodules. The submodule consists of an output capacitor, two IGBTs, and two corresponding anti-parallel diodes. Figure 2BAs shown in Figure 1, the output voltage of the submodule can be regulated by controlling the IGBT drive signal in the submodule. Table 1 details the various operating states of the submodule, where 1 and 0 represent the IGBT in the on and off states, respectively. By adjusting the operating state of the MMC submodule, the AC side voltage can be controlled.

[0052]

[0053] Table 1 Working status of half-bridge submodule

[0054] In high-level MMC, NLM modulation strategy is widely used. Figure 2C As shown in the figure, as a type of step wave modulation, the specific implementation of NLM is to measure the instantaneous value of the modulation wave and then adjust the number of sub-modules in the upper and lower bridge arms of each phase in real time to fit the sinusoidal modulation wave. Through deductive reasoning, it is not difficult to derive the relationship between the number of real-time modules in the upper and lower bridge arms of the traditional NLM modulation strategy as follows:

[0055]

[0056] where n pj With n nj They represent the number of submodules put into the upper and lower bridge arms of phase j, round represents the rounding function, and u j Represents the modulation wave voltage, U SM Represents the submodule capacitor voltage.

[0057] In practical NLM applications, a fixed sampling frequency is typically set for discrete control. The above formula calculates the number of upper and lower bridge arm modules in real time during each sampling period, generating corresponding IGBT trigger pulses to control the switching status of each bridge arm submodule. This gradually generates a step wave that fits the modulation wave. As can be seen, as the number of MMC submodules increases, the number of levels also increases, naturally reducing harmonics.

[0058] Increasing the number of submodules can reduce the harmonic content, but its cost and floor space will also increase. This paper proposes an improved NLM modulation strategy for the MMC converter in the power router. Without changing the number of submodules, the number of levels can be increased equivalently, thereby reducing the harmonic content. The modulation expression is:

[0059]

[0060] In the embodiment of this example, the bridge arm voltage can also be used as the input of the modulation model. In this case, the modulation expression is:

[0061]

[0062] where upj Represents the upper bridge arm modulation wave reference voltage, u nj Represents the reference voltage of the lower bridge arm modulation wave.

[0063] In the embodiment of this example, when the bridge arm voltage is used as the input of the modulation model, although the simultaneous increase or decrease in the number of second modules of the upper and lower bridge arms will produce the effect of mismatch between the sum of the voltages of the bridge arm sub-modules of the same phase and the DC side voltage, in the high-level MMC system, the number of second modules is large, so that the voltage shared by the capacitor of each second module is very low. At the same time, the value of x in the formula is generally relatively small, so its impact on the operation of the high-level MMC is very small.

[0064] The present invention introduces a coefficient a into the traditional NLM modulation mode, multiplies the modulation wave in the rounding function by the coefficient a, rounds it up, and then divides it by a. According to the different values ​​of a, n pj With n nj The number of steps in the staircase wave will increase by a times. Although this method does not directly increase the number of levels on the AC side, it can optimize the matching process of the number of submodules input during the modulation process, effectively increasing the number of levels and thus reducing the harmonic content.

[0065] In step S120, it can be determined whether the first number of modules put into operation is an integer, and the module voltage imbalance coefficient is calculated. If the first number of modules put into operation is an integer, the even number closest to the module voltage imbalance coefficient is matched, and the even number closest to the module voltage imbalance coefficient is used as the module compensation number; if the first number of modules put into operation is not an integer, the odd number closest to the module voltage imbalance coefficient is matched, and the odd number closest to the module voltage imbalance coefficient is used as the module compensation number.

[0066] In this exemplary embodiment, the method further includes:

[0067] The calculation formula for module voltage unbalance coefficient is:

[0068]

[0069] Among them, x′ is the module voltage unbalance coefficient, U dc is the MMC bus voltage, u nj 、u pj They are the upper and lower arm voltages of the MMC respectively.

[0070] In this exemplary embodiment, the method further includes:

[0071] Determine whether the first number of modules put into operation is an integer, and calculate the module voltage imbalance coefficient. If the first number of modules put into operation is an integer, match the even number closest to the module voltage imbalance coefficient, and use the even number closest to the module voltage imbalance coefficient as the module compensation number x; if the first number of modules put into operation is not an integer, match the odd number closest to the module voltage imbalance coefficient, and use the odd number closest to the module voltage imbalance coefficient as the module compensation number x.

[0072] In the embodiment of this example, since n pj With n nj The value of is no longer just an integer, but includes both integers and non-integers, which is contrary to the NLM modulation principle. The following combines the MMC circulation suppression strategy to handle non-integer values.

[0073] The MMC circulation is divided into three parts, namely the DC side part, the phase circulation part and the AC side part.

[0074]

[0075] The DC part flowing through the bridge arm inductance will not generate voltage, and due to the symmetry of the bridge arm, the AC current of each phase is evenly divided and in opposite directions between the upper and lower bridge arms, and the inductance voltages generated by them cancel each other out, so the voltage drop on the bridge arm is entirely due to the interphase circulating current. And because the bridge arm inductance is much larger than the bridge arm resistance, after ignoring the bridge arm resistance loss, the voltage calculation formula of the bridge arm inductance can be obtained.

[0076]

[0077] As the above equation shows, the magnitude of the circulating current is entirely dependent on the bridge arm inductor voltage, which is the difference between the DC link voltage and the submodule input voltage. If the MMC submodules are switched on and off strictly so that the sum of the input submodule voltages equals the DC link voltage, no circulating current will be generated. This allows us to derive a circulating current suppression strategy for MMC converters.

[0078] In step S130, the module compensation number can be divided by the multiplication factor and then summed with the first number of invested modules to generate a second number of invested modules. The second number of invested modules is used as the real-time number of invested modules for the upper and lower bridge arms of each phase in the nearest level approximation modulation strategy NLM to complete the MMC converter modulation.

[0079] In this exemplary embodiment, the method further includes:

[0080] After dividing the module compensation number by the multiplication factor, the sum is added to the first input module number to generate the second input module number.

[0081]

[0082] Among them, n′pj (t), n′ nj (t) are the number of second input modules of the upper and lower bridge arms of the MMC respectively;

[0083] The second number of modules put into operation is used as the real-time number of modules put into operation of the upper and lower bridge arms of each phase in the nearest level approximation modulation strategy NLM to complete the MMC converter modulation.

[0084] In this exemplary embodiment, the method further includes:

[0085] The multiplication factor is 2.

[0086] In this exemplary embodiment, Figure 3 The following is a flowchart of the non-integer handling scheme combined with a circulating current suppression strategy during modulation, using a value of 2 as an example. First, the number of modules in the bridge arm is checked to see if it is an integer. If so, the difference between the bridge arm voltage and the DC link voltage and the ratio of the submodule capacitor voltage is determined to be close to an even number. If it is a non-integer, the ratio is determined to be close to an odd number, thereby calculating the number x. The number of submodules in the upper and lower bridge arms is then increased by x / 2. This strategy reduces the difference between the bridge arm voltage and the DC link voltage, suppresses interphase circulating currents based on the voltage calculation formula for the bridge arm inductance, and also resolves the issue of a non-integer number of modules in operation after the introduction of the coefficient a.

[0087] It should be noted that although the steps of the method disclosed herein are depicted in a particular order in the accompanying drawings, this does not require or imply that the steps must be performed in that particular order, or that all steps must be performed to achieve the desired result. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one, and / or one step may be decomposed into multiple steps.

[0088] In addition, in this exemplary embodiment, a MMC converter modulation device for a power router is also provided. Figure 4 As shown, the MMC converter modulation device 400 for an electric energy router may include: a first input module number calculation module 410, a module compensation number calculation module 420, and a converter modulation module 430.

[0089] A first module number calculation module 410 is configured to generate a relationship between the number of modules put into operation in the upper and lower bridge arms, including a multiplying factor, based on the nearest level approximation modulation strategy NLM of the modular multilevel converter MMC, and calculate and generate a first number of modules put into operation;

[0090] The module compensation number calculation module 420 is configured to determine whether the first number of modules put into operation is an integer and calculate the module voltage imbalance coefficient. If the first number of modules put into operation is an integer, the module compensation number is matched with the even number closest to the module voltage imbalance coefficient and the even number closest to the module voltage imbalance coefficient is used as the module compensation number. If the first number of modules put into operation is not an integer, the module compensation number is matched with the odd number closest to the module voltage imbalance coefficient and the odd number closest to the module voltage imbalance coefficient is used as the module compensation number.

[0091] The converter modulation module 430 is used to divide the module compensation number by the multiplication factor, sum it with the first number of input modules, generate a second number of input modules, and use the second number of input modules as the real-time number of input modules of each phase upper and lower bridge arms in the nearest level approximation modulation strategy NLM to complete the MMC converter modulation.

[0092] The specific details of each of the above-mentioned MMC converter modulation device modules for a power router have been described in detail in the corresponding MMC converter modulation method for a power router, and thus will not be repeated here.

[0093] It should be noted that although the above detailed description mentions several modules or units of an MMC converter modulation device 400 for an energy router, this division is not mandatory. In fact, according to embodiments of the present disclosure, the features and functions of two or more modules or units described above can be embodied in a single module or unit. Conversely, the features and functions of a single module or unit described above can be further divided and embodied by multiple modules or units.

[0094] Furthermore, the above-described figures are merely illustrative of the processes included in the method according to exemplary embodiments of the present invention and are not intended to be limiting. It is readily understood that the processes illustrated in the above-described figures do not indicate or limit the temporal order of these processes. Furthermore, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0095] Other embodiments of the present disclosure will readily occur to those skilled in the art after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow from the general principles of the present disclosure and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the present disclosure being indicated by the claims.

[0096] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes can be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A MMC converter modulation method for an electric energy router, characterized in that: The method comprises: Based on the nearest level approach modulation strategy NLM of the modular multilevel converter MMC, a relationship formula for the number of upper and lower bridge arm modules including a multiplication factor is generated, and the first number of modules to be put into operation is calculated; Determine whether the first number of modules put into operation is an integer, and calculate the module voltage imbalance coefficient. If the first number of modules put into operation is an integer, match the even number closest to the module voltage imbalance coefficient, and use the even number closest to the module voltage imbalance coefficient as the module compensation number. If the first number of modules put into operation is not an integer, match the odd number closest to the module voltage imbalance coefficient, and use the odd number closest to the module voltage imbalance coefficient as the module compensation number. After dividing the module compensation number by the multiplication factor, the sum is added to the first number of modules to generate a second number of modules. The second number of modules is used as the real-time number of modules for each phase upper and lower bridge arms in the nearest level approximation modulation strategy NLM to complete the MMC converter modulation.

2. The method according to claim 1, wherein The method further comprises: Based on the nearest level approach modulation strategy NLM of the modular multilevel converter MMC, the relationship between the number of modules in the upper and lower bridge arms including the multiplication factor is generated. Among them, n pj With n nj are the first input modules of the upper and lower bridge arms of the MMC, round is the rounding function, u j is the modulation wave voltage, U SM is the capacitance voltage of the neutron modules in the upper and lower bridge arms of the MMC, N is the number of neutron modules in the upper and lower bridge arms of the MMC, and a is the rate coefficient.

3. The method according to claim 2, wherein The method further comprises: The calculation formula for module voltage unbalance coefficient is: Among them, x′ is the module voltage unbalance coefficient, U dc is the MMC bus voltage, u nj 、u pj They are the upper and lower arm voltages of the MMC respectively.

4. The method according to claim 3, wherein The method further comprises: After dividing the module compensation number by the multiplication factor, the sum is added to the first input module number to generate the second input module number. Among them, n′ pj (t), n′ nj (t) are the number of second input modules of the upper and lower bridge arms of the MMC respectively; The second number of modules put into operation is used as the real-time number of modules put into operation for the upper and lower bridge arms of each phase in the nearest level approximation modulation strategy NLM to complete the MMC converter modulation, where x is the module compensation number.

5. The method according to claim 1, wherein The method further comprises: The multiplication factor is 2.

6. An MMC converter modulation device for an electric energy router, characterized in that: The device comprises: A first module number calculation module is configured to generate a relationship between the number of modules put into operation in the upper and lower bridge arms, including a multiplying factor, based on a nearest level approximation modulation strategy NLM of the modular multilevel converter MMC, and calculate and generate a first number of modules put into operation; a module compensation number calculation module, configured to determine whether the first number of modules put into operation is an integer and calculate a module voltage imbalance coefficient; if the first number of modules put into operation is an integer, then match the even number closest to the module voltage imbalance coefficient and use the even number closest to the module voltage imbalance coefficient as the module compensation number; if the first number of modules put into operation is not an integer, then match the odd number closest to the module voltage imbalance coefficient and use the odd number closest to the module voltage imbalance coefficient as the module compensation number; The converter modulation module is used to divide the module compensation number by the multiplication factor, sum it with the first number of input modules, generate a second number of input modules, and use the second number of input modules as the real-time number of input modules of each phase upper and lower bridge arms in the nearest level approximation modulation strategy NLM to complete the MMC converter modulation.

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