A method for calculating power loss of power devices of MMC-BESS

Abstract

The application relates to a power device power loss calculation method of an MMC-BESS, the relationship between virtual inertia and power devices of the MMC-BESS under VSG control is researched by considering the constraint of the power device of the internal battery submodule of the topology, the additional loss of MOSFET and IGBT in the transient process under different equivalent virtual inertia is deduced, the power consumption increment of the MOSFET is larger when the virtual inertia can be fully utilized, and the power consumption increment of the MOSFET depends on its own parameters when the virtual inertia cannot be fully utilized, so that the power device selection and control parameter design can be guided.

Description

Technical Field

[0001] This invention relates to a method for calculating the power loss of power devices in MMC-BESS, belonging to the field of battery energy storage technology. Background Technology

[0002] With the increasing use of new energy equipment, especially distributed power sources, the proportion of kinetic energy stored in the rotor of synchronous generators has decreased significantly, leading to a decline in the system's anti-interference capability. Simultaneously, due to the fast response speed of grid-connected converters, the transient dynamic behavior and mechanisms of power electronic equipment under large disturbances remain unclear, potentially jeopardizing the transient stability and relay protection of traditional power systems. In power grids where power electronic equipment accounts for an increasingly larger proportion, grid-based control is more suitable. Grid-based control employs a power synchronization strategy similar to that of synchronous generators, achieving synchronization without the need for phase-locked loops. If the grid-connected converter contains energy storage elements, it can also add inertia and damping to the system, thereby enhancing its stability and reliability. Energy storage technology can suppress large fluctuations in new energy power, improve the utilization rate of new energy sources, and support grid power, improving system stability and security, making it widely used in the field of new energy grid connection. The power conversion system in battery energy storage systems using MMC can be applied to AC grids, DC grids, and AC / DC hybrid grids, offering smooth waveforms, good scalability, and high modularity. The grid-type control MMC-BESS has broad application prospects in many situations such as new energy grid connection and AC / DC hybrid power grid.

[0003] VSG (Virtual Inertia Generation) is a common grid-type control strategy, developed from the concept of a Static Synchronous Generator (SSG). In 2007, Professor K. Visscher of KU Leuven, Belgium, proposed the "VSG" control technology. This initial control strategy gave the converter primary frequency regulation and inertial characteristics, but lacked the excitation characteristics of a synchronous generator; it was essentially still current control and could not effectively support the system voltage. Therefore, researchers both domestically and internationally proposed VSG based on voltage control, gradually improving the control strategy to give the converter characteristics similar to those of a traditional synchronous generator, including primary frequency regulation, inertia, and damping. Current research on VSG mainly focuses on the selection principles of virtual inertia and damping coefficients, adaptive control strategies, and applications in energy storage converters. Regarding the selection principles of virtual inertia and damping coefficients, design methods for virtual inertia and damping coefficients can be obtained by constructing a small-signal model of the VSG converter.

[0004] For MMC-BESS, domestic and international scholars have focused their research on topology, modulation strategies, battery state-of-charge (SOC) equalization control strategies, fault location, fault-tolerant control, and heat dissipation design. Regarding MMC-BESS topology, it can be divided into centralized and distributed access based on the battery connection method. The centralized access topology uses battery modules connected in series directly to the common DC bus of the MMC, or connected via a DC / DC converter. While simple, this series structure means that a failure in one battery module can affect the entire DC-side voltage, and the SOC dispersion of individual battery modules can cause overcharging and over-discharging of individual cells, jeopardizing system stability. The distributed access topology uses battery modules directly connected to the DC side of the battery sub-modules, or connected via a DC / DC converter. Compared to centralized access, this method avoids the entire system failing due to a single battery failure. Furthermore, the SOC dispersion can be addressed by power transfer across individual battery groups, improving system reliability.

[0005] Currently, the selection of control parameters in VSG-controlled MMCs is mostly based on the active power transfer function of the virtual synchronous generator input and output. Parameter values ​​are selected according to the influence of different parameters on the system's dynamic response to achieve optimal transfer characteristics. However, the selection of VSG control parameters does not consider the constraints of the battery submodule's power devices; that is, it does not study the relationship between virtual inertia, transient process energy, and power devices. During the transient process of actual MMC-BESS operation, power devices generate additional power consumption, and the choice between MOSFETs and IGBTs results in different additional power consumption. Current literature does not examine the relationship between virtual inertia and the additional power consumption of power devices, thus failing to provide guidance for device selection.

[0006] Some literature has studied the design and selection of inertial parameters J and damping coefficient D for VSG control, and proposed various adaptive virtual rotational inertia control strategies based on the power angle curve of synchronous generators. These strategies aim to meet the requirements of small active power and frequency overshoot and fast dynamic response by rationally selecting the virtual rotational inertia. For example, one adaptive virtual rotor inertia control scheme is determined by the rate of change of the VSG virtual rotor angular velocity and the difference between the virtual rotor angular velocity and the grid angular velocity. However, these control strategies do not consider the internal structure of the topology or the actual operating conditions of the power devices in the MMC-BESS battery submodule, and therefore offer no guidance for the selection of physical power device types and power ratings. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention proposes a method for calculating the power loss of MMC-BESS power devices.

[0008] The technical solution of the present invention is as follows: On the one hand, the present invention provides a method for calculating the power loss of power devices in MMC-BESS, including the following steps: Calculate the rated current flowing through the power devices of the battery submodule when the MMC-BESS under VSG control is in rated operating condition. When the grid frequency experiences a transient disturbance, the MMC-BESS needs to absorb or release electrical energy to share the power deficit in the grid. Construct a formula to calculate the change in current flowing through the power devices of the battery submodule during the current transient process compared to the rated current flowing through the power devices of the battery submodule in rated operating condition. A formula for calculating the loss factor of VSG virtual inertia is constructed. The virtual inertia loss factor of MMC-BESS is calculated by the formula, and the virtual inertia loss factor is used to reflect whether the virtual inertia is fully utilized. Based on the above formula for calculating current change, the current change of the power devices in the MOSFET and IGBT battery sub-modules is calculated respectively. At the same time, the difference between the maximum allowable current of the MOSFET and IGBT battery sub-modules and the rated current of the corresponding type of battery sub-module power device under the rated operating condition of MMC-BESS is also calculated. Based on the current variation of the MOSFET and IGBT battery submodule power devices and the difference between the maximum allowable current of the MOSFET and IGBT battery submodule power devices and the rated current of the corresponding type of battery submodule power devices under the rated operating conditions of MMC-BESS, the power loss of the MOSFET and IGBT battery submodule power devices under the conditions of full and non-full utilization of virtual inertia is calculated.

[0009] As a preferred embodiment of the present invention, the formula for calculating the rated current flowing through the power devices of its battery submodule when the MMC-BESS under VSG control is in its rated operating state is as follows:

[0010] in: This refers to the current flowing through the power device when the MMC-BESS is in its rated operating condition. This is the rated current flowing through the battery submodule.

[0011] As a preferred embodiment of the present invention, the specific steps for constructing the formula for calculating the change in current flowing through the power devices of the battery submodule during the transient process of grid frequency disturbance compared to the rated current flowing through the power devices of the battery submodule under rated operating conditions are as follows: Calculate the difference between the maximum allowable current flowing through the power devices of the battery submodule during normal operation and the current flowing through the power devices of the battery submodule when the MMC-BESS is in rated operating condition. As shown in the following formula:

[0012] in: This is the maximum current value that the power devices in the battery submodule are allowed to flow through when they are operating normally. Current change The size depends on the amount of electrical energy that each battery submodule of MMC-BESS needs to absorb or release. Size, Size and absorption or release of each battery submodule The time required for a large amount of electrical energy The magnitude of the change in current is constructed based on the above relationship. The calculation formula is as follows:

[0013] in: This refers to the rated voltage of the battery submodule; , The larger, The larger; The larger, The smaller; Based on the above formula, we get: when At that time, the current change of the power device in the battery submodule is That is, the power devices of the battery submodule provide When the current is of a certain magnitude, the virtual inertia of the VSG is fully utilized; when At that time, the current change of the power device in the battery submodule is That is, the maximum current that the power devices in the battery submodule can provide is At this time, the current provided by the power devices of the battery submodule is less than the current provided by the power devices of the battery submodule. The required current size means that the virtual inertia of the VSG is not fully utilized at this point.

[0014] In a preferred embodiment of the present invention, the virtual inertia loss coefficient The specific calculation formula is as follows:

[0015] Combined with the change in current The calculation formula is used to obtain the result when When the virtual inertia loss factor is 0, the VSG's virtual inertia is fully utilized; when At that time, the virtual inertia loss factor is At this time, the virtual inertia of VSG is not fully utilized.

[0016] In a preferred embodiment of the present invention, the current variation of the MOSFET-type and IGBT-type battery submodule power devices , The specific calculation formula is as follows:

[0017]

[0018] in: The current flowing through the power devices of the MMC-BESS using MOSFET-type battery submodule power devices during the transient process; The current flowing through the power devices of the MMC-BESS using IGBT-type battery submodules during a transient process; The current flowing through the power devices of the MMC-BESS using MOSFET-type battery submodules under rated operating conditions; The current flowing through the power devices of the MMC-BESS battery submodule when the battery submodule power device is in rated operating condition using IGBT type battery submodule power devices.

[0019] In a preferred embodiment of the present invention, the difference between the maximum allowable current of the MOSFET and IGBT type battery submodule power devices and the rated current of the corresponding type of battery submodule power devices under rated operating conditions of the MMC-BESS is... and The calculation formulas are as follows:

[0020]

[0021] in: This refers to the maximum allowable current flowing through the power devices in the MOSFET-type battery submodule. This refers to the maximum allowable current flowing through the power devices in the IGBT-type battery submodule.

[0022] As a preferred embodiment of the present invention, under the condition of fully utilizing virtual inertia, the specific calculation steps for the power loss of the MOSFET-type and IGBT-type battery submodule power devices are as follows: Assuming that the maximum allowable current of the MOSFET-type battery submodule power device and the IGBT-type battery submodule power device are equal, and the time required for the corresponding battery submodule to absorb or release the same amount of electrical energy is also equal, then the MMC-BESS using the MOSFET-type battery submodule power device and the MMC-BESS using the IGBT-type battery submodule power device have the same loss factor. Under the condition of fully utilizing virtual inertia, i.e., the loss factor At the same time, the power loss calculation formulas for MOSFET-type battery submodule power devices and IGBT-type battery submodule power devices are constructed as follows:

[0023]

[0024]

[0025]

[0026] in: The power loss of the MOSFET-type battery submodule power devices under rated operating conditions in MMC-BESS; The power loss of the IGBT-type battery submodule power devices under rated operating conditions in MMC-BESS; This refers to the equivalent resistance between the drain and source of the MOSFET-type battery submodule power device in the on-state. This refers to the on-state voltage drop between the collector and emitter of the power device in the IGBT-type battery submodule. The power loss of the MOSFET-type battery submodule power devices in MMC-BESS during transient processes; The power loss of the IGBT-type battery submodule power devices in MMC-BESS during transient processes; Compared to the power losses of MOSFET and IGBT battery submodule power devices in MMC-BESS under rated operating conditions, calculate the additional power losses of MOSFET and IGBT battery submodule power devices in MMC-BESS during transient processes:

[0027]

[0028] in: This is to account for the additional power loss of the MOSFET-type battery submodule power devices in the MMC-BESS during transient processes. This is to account for the additional power loss of the IGBT-type battery submodule power devices in MMC-BESS during transient processes. Based on the above formula, the ratio of the additional power loss of the MOSFET and IGBT battery submodule power devices in the MMC-BESS during transient processes to the power loss of the MOSFET and IGBT battery submodule power devices in the MMC-BESS under rated operating conditions is calculated as follows:

[0029]

[0030] in: The ratio of the additional power loss of the MOSFET-type battery submodule power device in the MMC-BESS during transient processes to the power loss of the MOSFET-type battery submodule power device in the MMC-BESS under rated operating conditions. The ratio of the additional power loss of the IGBT-type battery submodule power device in MMC-BESS during transient processes to the power loss of the IGBT-type battery submodule power device in MMC-BESS under rated operating conditions. When the MMC-BESS uses MOSFET or IGBT type battery submodule power devices under rated operating conditions Furthermore, the current change of the power devices in the MOSFET-type battery submodule is the same as that in the IGBT-type battery submodule, i.e. ,at this time and The following relationship exists:

[0031] The above formula shows that when the virtual inertia is fully utilized and the maximum allowable current of the MOSFET-type battery submodule power device and the IGBT-type battery submodule power device are equal, the additional power loss of MMC-BESS using the MOSFET-type battery submodule power device during transient processes is greater than the additional power loss using the IGBT-type battery submodule power device.

[0032] In a preferred embodiment of the present invention, when the virtual inertia is not fully utilized, the specific calculation steps for the power loss of the MOSFET and IGBT type battery submodule power devices are as follows: Assuming that the maximum allowable current of the MOSFET-type battery submodule power device and the IGBT-type battery submodule power device are equal, and the time required for the corresponding battery submodule to absorb or release the same amount of electrical energy is also equal, then the MMC-BESS using the MOSFET-type battery submodule power device and the MMC-BESS using the IGBT-type battery submodule power device have the same loss factor. In the case of non-full utilization of virtual inertia, i.e., the loss factor hour, , Construct power loss calculation formulas for MOSFET-type and IGBT-type battery submodule power devices:

[0033]

[0034] The above formula shows that when the virtual inertia is not fully utilized and the maximum allowable current of the MOSFET-type battery submodule power device and the IGBT-type battery submodule power device are equal, the power loss of the MMC-BESS using the MOSFET-type and IGBT-type battery submodule power devices depends on the parameters of the MOSFET-type and IGBT-type battery submodule power devices themselves.

[0035] On the other hand, the present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the method as described in any embodiment of the present invention.

[0036] In another aspect, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described in any embodiment of the present invention.

[0037] The present invention has the following beneficial effects: 1. This invention studies the relationship between virtual inertia and power devices in MMC-BESS under VSG control, taking into account the constraints of power devices in the battery submodule within the topology. It derives the additional losses of MOSFET and IGBT transient processes under different equivalent virtual inertia. When the virtual inertia can be fully utilized, the power consumption increment of MOSFET is larger. When the virtual inertia cannot be fully utilized, its power consumption increment depends on its own parameters. This can provide guidance for power device selection and control parameter design. Attached Figure Description

[0038] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] It should be understood that the step numbers used in the text are for ease of description only and are not intended to limit the order in which the steps are performed.

[0041] It should be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0042] The terms “comprising” and “including” indicate the presence of the described feature, whole, step, operation, element and / or component, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0043] The term “and / or” refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes these combinations.

[0044] Example 1: See Figure 1 A method for calculating the power loss of MMC-BESS power devices includes the following steps: Calculate the rated current flowing through the power devices of the battery submodule when the MMC-BESS under VSG control is in rated operating condition. When the grid frequency experiences a transient disturbance, the MMC-BESS needs to absorb or release electrical energy to share the power deficit in the grid. Construct a formula to calculate the change in current flowing through the power devices of the battery submodule during the current transient process compared to the rated current flowing through the power devices of the battery submodule in rated operating condition. A formula for calculating the loss factor of VSG virtual inertia is constructed. The virtual inertia loss factor of MMC-BESS is calculated by the formula, and the virtual inertia loss factor is used to reflect whether the virtual inertia is fully utilized. Based on the above formula for calculating current change, the current change of the power devices in the MOSFET and IGBT battery sub-modules is calculated respectively. At the same time, the difference between the maximum allowable current of the MOSFET and IGBT battery sub-modules and the rated current of the corresponding type of battery sub-module power device under the rated operating condition of MMC-BESS is also calculated. Based on the current variation of the MOSFET and IGBT battery submodule power devices and the difference between the maximum allowable current of the MOSFET and IGBT battery submodule power devices and the rated current of the corresponding type of battery submodule power devices under the rated operating conditions of MMC-BESS, the power loss of the MOSFET and IGBT battery submodule power devices under the conditions of full and non-full utilization of virtual inertia is calculated.

[0045] As a preferred embodiment of this example, the formula for calculating the rated current flowing through the power devices of the battery submodule when the MMC-BESS under VSG control is in its rated operating state is as follows:

[0046] in: This refers to the current flowing through the power device when the MMC-BESS is in its rated operating condition. This is the rated current flowing through the battery submodule; When the grid frequency experiences disturbances, as mentioned earlier, the grid-connected MMC-BESS needs to absorb / release energy to share the power deficit of the grid. At this time, the current flowing through the power devices in the battery submodule will increase / decrease accordingly. The change in current flowing through the power devices during this transient process compared to the current flowing through the power devices in the grid-connected MMC-BESS under rated operating conditions is... It can be calculated using the following formula:

[0047] in: This refers to the current flowing through the power devices of the MMC-BESS battery submodule during the transient process.

[0048] As a preferred embodiment of this invention, the specific steps for constructing the formula for calculating the change in current flowing through the power devices of the battery submodule during the transient process of grid frequency disturbance compared to the rated current flowing through the power devices of the battery submodule under rated operating conditions are as follows: Calculate the difference between the maximum allowable current flowing through the power devices of the battery submodule during normal operation and the current flowing through the power devices of the battery submodule when the MMC-BESS is in rated operating condition. As shown in the following formula:

[0049] in: This is the maximum current value that the power devices in the battery submodule are allowed to flow through when they are operating normally. Current change The size depends on the amount of electrical energy that each battery submodule of MMC-BESS needs to absorb or release. Size, Size and absorption or release of each battery submodule The time required for a large amount of electrical energy The magnitude of the change in current is constructed based on the above relationship. The calculation formula is as follows:

[0050] in: This refers to the rated voltage of the battery submodule; , The larger, The larger; The larger, The smaller; Based on the above formula, we get: when At that time, the current change of the power device in the battery submodule is That is, the power devices of the battery submodule provide When the current is of a certain magnitude, the virtual inertia of the VSG is fully utilized; when At that time, the current change of the power device in the battery submodule is That is, the maximum current that the power devices in the battery submodule can provide is At this time, the current provided by the power devices of the battery submodule is less than the current provided by the power devices of the battery submodule. The required current size means that the virtual inertia of the VSG is not fully utilized at this point.

[0051] As a preferred embodiment of this example, the virtual inertia loss coefficient The specific calculation formula is as follows:

[0052] Combined with the change in current The calculation formula is used to obtain the result when When the virtual inertia loss factor is 0, the VSG's virtual inertia is fully utilized; when At that time, the virtual inertia loss factor is At this time, the virtual inertia of VSG is not fully utilized.

[0053] Based on the above formula, the equivalent virtual inertia of the network-type MMC-BESS can be obtained. :

[0054] in: The selected VSG virtual inertia.

[0055] As a preferred embodiment of this invention, the current variation of the MOSFET-type and IGBT-type battery submodule power devices is described. , The specific calculation formula is as follows:

[0056]

[0057] in: The current flowing through the power devices of the MMC-BESS using MOSFET-type battery submodule power devices during the transient process; The current flowing through the power devices of the MMC-BESS using IGBT-type battery submodules during a transient process; The current flowing through the power devices of the MMC-BESS using MOSFET-type battery submodules under rated operating conditions; The current flowing through the power devices of the MMC-BESS battery submodule when the battery submodule power device is in rated operating condition using IGBT type battery submodule power devices.

[0058] In a preferred embodiment of this invention, the difference between the maximum allowable current flowing through the MOSFET and IGBT type battery submodule power devices and the rated current of the corresponding type of battery submodule power devices under rated operating conditions of the MMC-BESS is... and The calculation formulas are as follows:

[0059]

[0060] in: This refers to the maximum allowable current flowing through the power devices in the MOSFET-type battery submodule. This refers to the maximum allowable current flowing through the power devices in the IGBT-type battery submodule.

[0061] In a preferred embodiment of this invention, under the condition of fully utilizing virtual inertia, the specific calculation steps for the power loss of the MOSFET-type and IGBT-type battery submodule power devices are as follows: Assuming that the maximum allowable current of the MOSFET-type battery submodule power device and the IGBT-type battery submodule power device are equal, and the time required for the corresponding battery submodule to absorb or release the same amount of electrical energy is also equal, then the MMC-BESS using the MOSFET-type battery submodule power device and the MMC-BESS using the IGBT-type battery submodule power device have the same loss factor. Under the condition of fully utilizing virtual inertia, i.e., the loss factor At the same time, the power loss calculation formulas for MOSFET-type battery submodule power devices and IGBT-type battery submodule power devices are constructed as follows:

[0062]

[0063]

[0064]

[0065] in: The power loss of the MOSFET-type battery submodule power devices under rated operating conditions in MMC-BESS; The power loss of the IGBT-type battery submodule power devices under rated operating conditions in MMC-BESS; This refers to the equivalent resistance between the drain and source of the MOSFET-type battery submodule power device in the on-state. This refers to the on-state voltage drop between the collector and emitter of the power device in the IGBT-type battery submodule. The power loss of the MOSFET-type battery submodule power devices in MMC-BESS during transient processes; The power loss of the IGBT-type battery submodule power devices in MMC-BESS during transient processes; Compared to the power losses of MOSFET and IGBT battery submodule power devices in MMC-BESS under rated operating conditions, calculate the additional power losses of MOSFET and IGBT battery submodule power devices in MMC-BESS during transient processes:

[0066]

[0067] in: This is to account for the additional power loss of the MOSFET-type battery submodule power devices in the MMC-BESS during transient processes. This is to account for the additional power loss of the IGBT-type battery submodule power devices in MMC-BESS during transient processes. Based on the above formula, the ratio of the additional power loss of the MOSFET and IGBT battery submodule power devices in the MMC-BESS during transient processes to the power loss of the MOSFET and IGBT battery submodule power devices in the MMC-BESS under rated operating conditions is calculated as follows:

[0068]

[0069] in: The ratio of the additional power loss of the MOSFET-type battery submodule power device in the MMC-BESS during transient processes to the power loss of the MOSFET-type battery submodule power device in the MMC-BESS under rated operating conditions. The ratio of the additional power loss of the IGBT-type battery submodule power device in MMC-BESS during transient processes to the power loss of the IGBT-type battery submodule power device in MMC-BESS under rated operating conditions. When the MMC-BESS uses MOSFET or IGBT type battery submodule power devices under rated operating conditions Furthermore, the current change of the power devices in the MOSFET-type battery submodule is the same as that in the IGBT-type battery submodule, i.e. ,at this time and The following relationship exists:

[0070] The above formula shows that when the virtual inertia is fully utilized and the maximum allowable current of the MOSFET-type battery submodule power device and the IGBT-type battery submodule power device are equal, the additional power loss of MMC-BESS using the MOSFET-type battery submodule power device during transient processes is greater than the additional power loss using the IGBT-type battery submodule power device.

[0071] In a preferred embodiment of this invention, when the virtual inertia is not fully utilized, the specific calculation steps for the power loss of the MOSFET and IGBT battery submodule power devices are as follows: Assuming that the maximum allowable current of the MOSFET-type battery submodule power device and the IGBT-type battery submodule power device are equal, and the time required for the corresponding battery submodule to absorb or release the same amount of electrical energy is also equal, then the MMC-BESS using the MOSFET-type battery submodule power device and the MMC-BESS using the IGBT-type battery submodule power device have the same loss factor. In the case of non-full utilization of virtual inertia, i.e., the loss factor hour, , Construct power loss calculation formulas for MOSFET-type and IGBT-type battery submodule power devices:

[0072]

[0073] The above formula shows that when the virtual inertia is not fully utilized and the maximum allowable current of the MOSFET-type battery submodule power device and the IGBT-type battery submodule power device are equal, the power loss of the MMC-BESS using the MOSFET-type and IGBT-type battery submodule power devices depends on the parameters of the MOSFET-type and IGBT-type battery submodule power devices themselves.

[0074] In this embodiment, a VSG-controlled MMC battery energy storage system is designed, whose system virtual inertia... ; set up , The change in current flowing through the power device during the transient process compared to the current flowing through the power device under rated operating conditions of the MMC-BESS is... ; set up , ,but: when hour, , ; , .

[0075] ; .

[0076] ; .

[0077]

[0078] That is, when the virtual inertia can be fully utilized, if the MOSFET and IGBT have the same current, the power consumption increment of the MOSFET is greater than that of the IGBT during the transient process.

[0079] when At that time, set , ,but: ; .

[0080] That is, when the virtual inertia cannot be fully utilized, the power loss of both MOSFET and IGBT is a constant value, the magnitude of which depends on the parameters of the MOSFET or IGBT itself.

[0081] Example 2: This embodiment proposes an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the method described in any embodiment of the present invention.

[0082] Example 3: This embodiment proposes a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the method described in any embodiment of the present invention.

[0083] In this application embodiment, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent the existence of A alone, A and B simultaneously, or B alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, at least one of a, b, and c can represent: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, and c can be single or multiple.

[0084] Those skilled in the art will recognize that the units and algorithm steps described in the embodiments disclosed herein can be implemented using electronic hardware, computer software, or a combination of electronic hardware and software. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0085] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0086] In the several embodiments provided in this application, any function, if implemented as a software functional unit and sold or used as an independent product, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0087] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for calculating the power loss of power devices in MMC-BESS, characterized in that, Includes the following steps: Calculate the rated current flowing through the power devices of the battery submodule when the MMC-BESS under VSG control is in rated operating condition. When the grid frequency experiences a transient disturbance, construct a formula to calculate the change in current flowing through the power devices of the battery submodule during the current transient process compared to the rated current flowing through the power devices of the battery submodule in rated operating condition. A formula for calculating the loss factor of VSG virtual inertia is constructed. The virtual inertia loss factor of MMC-BESS is calculated by the formula, and the virtual inertia loss factor is used to determine whether the virtual inertia is fully utilized. Based on the above formula for calculating current change, the current change of the power devices in the MOSFET and IGBT battery sub-modules is calculated respectively. At the same time, the difference between the maximum allowable current of the MOSFET and IGBT battery sub-modules and the rated current of the corresponding type of battery sub-module power device under the rated operating condition of MMC-BESS is also calculated. Based on the current variation of the MOSFET and IGBT battery submodule power devices and the difference between the maximum allowable current of the MOSFET and IGBT battery submodule power devices and the rated current of the corresponding type of battery submodule power devices under the rated operating conditions of MMC-BESS, the power loss of the MOSFET and IGBT battery submodule power devices under the conditions of full and non-full utilization of virtual inertia is calculated respectively. The formula for calculating the rated current flowing through the power devices of the battery submodule when the MMC-BESS under VSG control is in rated operating condition is as follows: in: This refers to the current flowing through the power device when the MMC-BESS is in its rated operating state; This is the rated current flowing through the battery submodule; The specific steps for constructing the formula for calculating the change in current flowing through the power devices of the battery submodule during the transient process of grid frequency disturbance compared to the rated current flowing through the power devices of the battery submodule under rated operating conditions are as follows: Calculate the difference between the maximum allowable current flowing through the power devices of the battery submodule during normal operation and the current flowing through the power devices of the battery submodule when the MMC-BESS is in rated operating condition. As shown in the following formula: in: This is the maximum current value that the power devices in the battery submodule are allowed to flow through when they are working normally. Current change The size depends on the amount of electrical energy that each battery submodule of MMC-BESS needs to absorb or release. Size, Size and absorption or release of each battery submodule The time required for a large amount of electrical energy The magnitude of the change in current is constructed based on the above relationship. The calculation formula is as follows: in: This refers to the rated voltage of the battery submodule; , The larger, The larger; The larger, The smaller; Based on the above formula, we get: when At that time, the current change of the power device in the battery submodule is That is, the power devices of the battery submodule provide When the current is of a certain magnitude, the virtual inertia of the VSG is fully utilized; when At that time, the current change of the power device in the battery submodule is That is, the maximum current that the power devices in the battery submodule can provide is At this time, the current provided by the power devices of the battery submodule is less than the current provided by the power devices of the battery submodule. The required current size means that the virtual inertia of the VSG is not fully utilized at this point.

2. The method for calculating power loss of MMC-BESS power devices according to claim 1, characterized in that, The virtual inertia loss coefficient The specific calculation formula is as follows: Combined with the change in current The calculation formula is used to obtain the result when When the virtual inertia loss factor is 0, the VSG's virtual inertia is fully utilized; when At that time, the virtual inertia loss factor is At this time, the virtual inertia of VSG is not fully utilized.

3. The method for calculating power loss of MMC-BESS power devices according to claim 2, characterized in that, Current variation of the power devices in the MOSFET and IGBT battery submodules , The specific calculation formula is as follows: in: The current flowing through the power devices of the MMC-BESS using MOSFET-type battery submodule power devices during the transient process; The current flowing through the power devices of the MMC-BESS using IGBT-type battery submodules during a transient process; The current flowing through the power devices of the MMC-BESS using MOSFET-type battery submodules under rated operating conditions; The current flowing through the power devices of the MMC-BESS battery submodule when the battery submodule power device is in rated operating condition using IGBT type battery submodule power devices.

4. The method for calculating the power loss of MMC-BESS power devices according to claim 3, characterized in that, The difference between the maximum allowable current of the MOSFET and IGBT type battery submodule power devices and the rated current of the corresponding type of battery submodule power devices under rated operating conditions of MMC-BESS and The calculation formulas are as follows: in: This refers to the maximum allowable current flowing through the power devices in the MOSFET-type battery submodule. This refers to the maximum allowable current flowing through the power devices in the IGBT-type battery submodule.

5. The method for calculating the power loss of MMC-BESS power devices according to claim 4, characterized in that, Under the condition of fully utilizing virtual inertia, the specific calculation steps for the power loss of the power devices of the MOSFET type and IGBT type battery submodule are as follows: Assuming that the maximum allowable current of the MOSFET-type battery submodule power device and the IGBT-type battery submodule power device are equal, and the time required for the corresponding battery submodule to absorb or release the same amount of electrical energy is also equal, then the MMC-BESS using the MOSFET-type battery submodule power device and the MMC-BESS using the IGBT-type battery submodule power device have the same loss factor. Under the condition of fully utilizing virtual inertia, i.e., the loss factor At the same time, the power loss calculation formulas for MOSFET-type battery submodule power devices and IGBT-type battery submodule power devices are constructed as follows: in: The power loss of the MOSFET-type battery submodule power devices under rated operating conditions in MMC-BESS; The power loss of the IGBT-type battery submodule power devices under rated operating conditions in MMC-BESS; This refers to the equivalent resistance between the drain and source of the MOSFET-type battery submodule power device in the on-state. This refers to the on-state voltage drop between the collector and emitter of the power device in the IGBT-type battery submodule. The power loss of the MOSFET-type battery submodule power devices in MMC-BESS during transient processes; The power loss of the IGBT-type battery submodule power devices in MMC-BESS during transient processes; Compared to the power losses of MOSFET and IGBT battery submodule power devices in MMC-BESS under rated operating conditions, calculate the additional power losses of MOSFET and IGBT battery submodule power devices in MMC-BESS during transient processes: in: This is to account for the additional power loss of the MOSFET-type battery submodule power devices in the MMC-BESS during transient processes. This is to account for the additional power loss of the IGBT-type battery submodule power devices in MMC-BESS during transient processes. Based on the above formula, the ratio of the additional power loss of the MOSFET and IGBT battery submodule power devices in the MMC-BESS during transient processes to the power loss of the MOSFET and IGBT battery submodule power devices in the MMC-BESS under rated operating conditions is calculated as follows: in: The ratio of the additional power loss of the MOSFET-type battery submodule power device in the MMC-BESS during transient processes to the power loss of the MOSFET-type battery submodule power device in the MMC-BESS under rated operating conditions. The ratio of the additional power loss of the IGBT-type battery submodule power device in MMC-BESS during transient processes to the power loss of the IGBT-type battery submodule power device in MMC-BESS under rated operating conditions. When the MMC-BESS uses MOSFET or IGBT type battery submodule power devices under rated operating conditions Furthermore, the current change of the power devices in the MOSFET-type battery submodule is the same as that in the IGBT-type battery submodule, i.e. ,at this time and The following relationship exists: The above formula shows that when the virtual inertia is fully utilized and the maximum allowable current of the MOSFET-type battery submodule power device and the IGBT-type battery submodule power device are equal, the additional power loss of MMC-BESS using the MOSFET-type battery submodule power device during the transient process is greater than the additional power loss using the IGBT-type battery submodule power device.

6. The method for calculating power loss of MMC-BESS power devices according to claim 5, characterized in that, When the virtual inertia is not fully utilized, the specific calculation steps for the power loss of the MOSFET and IGBT battery submodule power devices are as follows: Assuming that the maximum allowable current of the MOSFET-type battery submodule power device and the IGBT-type battery submodule power device are equal, and the time required for the corresponding battery submodule to absorb or release the same amount of electrical energy is also equal, then the MMC-BESS using the MOSFET-type battery submodule power device and the MMC-BESS using the IGBT-type battery submodule power device have the same loss factor. In the case of non-full utilization of virtual inertia, i.e., the loss factor hour, , Construct power loss calculation formulas for MOSFET-type and IGBT-type battery submodule power devices: The above formula shows that when the virtual inertia is not fully utilized and the maximum allowable current of the MOSFET-type battery submodule power device and the IGBT-type battery submodule power device are equal, the power loss of the MMC-BESS using the MOSFET-type and IGBT-type battery submodule power devices depends on the parameters of the MOSFET-type and IGBT-type battery submodule power devices themselves.

7. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the method as described in any one of claims 1 to 6.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the method as described in any one of claims 1 to 6.

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