CN111934572B - Super-large-scale energy storage MMC converter device and energy storage control method - Google Patents

Abstract

The invention discloses an ultra-large-scale energy storage MMC converter device and an energy storage control method, which belong to the technical field of modular multilevel converters. The device of the invention includes: a plurality of bridge arms, each bridge arm includes a plurality of energy storage sub-modules and an inductor; the plurality of energy storage sub-modules are connected in series and connected to the inductor; every two bridge arms pass through the cables of the bridge arms connected as a group of one-phase sub-converters; the one-phase sub-converters include three groups, and the three groups of one-phase sub-converters are connected in parallel; the energy storage sub-modules include: the positive electrode of the energy storage sub-module, the energy storage sub-module Module cathode, first to sixth IGBTs, first to third capacitors, inductor L1, photovoltaic power generation unit, lithium battery pack and diode. The invention can effectively reduce the terminal voltage required by the battery pack and reduce the number of batteries connected in series in the battery pack, thereby improving the reliability of the battery.

Description

A super large-scale energy storage MMC converter device and energy storage control method

technical field

The present invention relates to the technical field of modularized multilevel converters, and more particularly, to a super-large-scale energy storage MMC converter device and an energy storage control method.

Background technique

Today, with the rise of ultra-large-scale energy storage technology, the requirements for energy storage converters are becoming more and more stringent. The ultra-large-scale energy storage station has the characteristics of high voltage and large capacity, and its converter needs to adopt a multi-level structure. Modular multilevel converter (MMC) is a new type of multilevel converter, which is widely used in high-voltage direct current transmission and energy storage converters and other fields. advantage. It can be seen from this that it is a better choice to use multi-level converters in ultra-large-scale energy storage power stations. However, the occurrence of sub-module capacitor voltage balance and each bridge arm circulation problem brings great difficulties to the use of MMC.

SUMMARY OF THE INVENTION

In view of the above problems, the present invention proposes a super large-scale energy storage MMC converter device, including:

Multiple bridge arms, each bridge arm includes multiple energy storage sub-modules and an inductor;

Wherein, the plurality of energy storage sub-modules are connected in series and connected with inductors;

Every two bridge arms are connected by the cables of the bridge arms as a group of one-phase sub-converters; the one-phase sub-converters include three groups, and the three groups of one-phase sub-converters are connected in parallel;

The energy storage sub-module includes: first to sixth IGBTs, first to third capacitors, a lithium battery pack, a positive electrode of the energy storage sub-module, a negative electrode of the energy storage sub-module, an inductor L1, a photovoltaic power generation unit and a diode;

By controlling the turn-off of the control switches of the first to sixth IGBTs, the charging and discharging of the first to third capacitors, and the charging and discharging of the lithium battery pack, the input of current is controlled;

The positive electrode of the energy storage sub-module is connected to the emitter of the first IGBT and the collector of the second IGBT;

The negative electrode of the energy storage sub-module is connected to the emitter of the second IGBT;

The first capacitor and the second capacitor are connected in series, and the anode of the first capacitor is connected to the collector of the first IGBT;

The cathode of the second capacitor is connected to the emitter of the second IGBT;

The emitter of the third IGBT is connected to the collector of the fourth IGBT, and the collector of the third IGBT and the emitter of the fourth IGBT are respectively connected to the positive electrode and the negative electrode of the first capacitor;

The emitter of the fifth IGBT is connected to the collector of the sixth IGBT, and the fifth IGBT

The collector of the IGBT is connected to the emitter of the fourth IGBT and the positive electrode of the second capacitor; the emitter of the sixth IGBT is connected to the negative electrode of the second capacitor;

The anode of the third capacitor is connected to the emitter of the third IGBT, and the cathode of the third capacitor is connected to the emitter of the fifth IGBT;

One end of the inductor L1 is connected to the negative electrode of the third capacitor, and the other end is connected to the positive electrode of the lithium battery pack;

The negative electrode of the lithium battery is connected to the emitter of the sixth IGBT;

The anode of the photovoltaic power generation unit is connected to the collector of the third IGBT through a diode, and the cathode of the photovoltaic power generation unit is connected to the emitter of the sixth IGBT.

Further, the capacitance values of the first to third capacitors are the same and satisfy a preset range.

Further, the device is externally connected to a transformer, an AC power source and a load.

The present invention also proposes an energy storage control method using an ultra-large-scale energy storage MMC converter device, comprising:

Before the ultra-large-scale energy storage MMC converter is put into operation, SOC pre-detection is performed on the lithium battery pack in the energy storage sub-module;

Determine the AC terminal current reference value and the DC terminal voltage reference value of the ultra-large-scale energy storage MMC converter;

Detect the circulating current power of each phase sub-device, convert the circulating current power, obtain the conversion data, and determine the circulating current reference value according to the conversion data and the DC terminal voltage reference value;

Determine the current reference value of each bridge arm according to the circulating current reference value and the AC terminal current reference value;

Perform dq coordinate transformation on the current reference value of each bridge arm, output the dq voltage, perform abc coordinate transformation and SPWM modulation on the dq voltage, obtain the output result, and turn off the first to sixth IGBTs of the energy storage sub-module according to the output result. , the energy storage control is performed by turning off the first to sixth IGBTs.

Optional, SOC pre-detection, including:

Check whether the SOC of each battery of each branch in each lithium battery pack meets the battery input standard;

If each battery meets the battery input standard, the branch circuit will not be disconnected;

If there are multiple batteries that do not meet the battery input standard, the branch circuit will be disconnected, and the capacity and SOC of the lithium battery pack that has been disconnected from the branch circuit will be calculated.

Optionally, the formula for determining the current reference value of the AC terminal is as follows:

为任意一相子装置的参考功率，U_ac为交流电压，

为交流功角。in,

is the reference power of any one-phase sub-device, U _ac is the AC voltage,

is the AC power angle.

Optionally, the formula for determining the DC terminal voltage reference value is as follows:

为任意一相子装置电流直流分量参考值、α_k为电流分配系数、U_dc为直流电压，

为直流端电压参考值、k_dc-pk和k_dc-ik分别为第k相直流分量的比例和积分系数；in,

is the reference value of the current DC component of any one-phase sub-device, α _k is the current distribution coefficient, U _dc is the DC voltage,

is the reference value of the DC terminal voltage, k _dc-pk and k _dc-ik are the proportional and integral coefficients of the k-th phase DC component, respectively;

The formula for determining the current distribution coefficient is as follows:

Among them, Q _k is the total capacity of any one-phase sub-device energy storage sub-module battery pack and Q _all is the total capacity and the determination formula of the current distribution coefficient is as follows:

Optionally, the conversion formula of the commutation power is as follows:

为第一相环流中的交流分量，P_diffa为第一相的环流功率，同理，

为第二相环流中的交流分量，P_diffb为第二相的环流功率，

为第三相环流中的交流分量，P_diffc为第三相的环流功率。in,

is the AC component in the circulating current of the first phase, P _diffa is the circulating current power of the first phase, in the same way,

is the AC component in the second phase circulating current, P _diffb is the circulating current power of the second phase,

is the AC component in the third-phase circulating current, and P _diffc is the circulating power of the third-phase.

Optionally, the formula for determining the current reference value of each bridge arm is as follows:

为任意一相子装置上桥臂参考电流、

为任意一相子装置下桥臂参考电流和为任意一相子装置环流参考值，

为任意一相子装置电流交流端电流参考值。in,

is the reference current of the bridge arm of any one-phase sub-device,

is the reference current of the lower bridge arm of any one-phase sub-device and is the reference value of the circulating current of any one-phase sub-device,

It is the current reference value of the current AC terminal of any phase sub-device.

The invention can effectively reduce the terminal voltage required by the battery pack and reduce the number of batteries connected in series in the battery pack, thereby improving the reliability of the battery. The DC bus voltage is stabilized, the input or output power of each bridge arm is controlled, and the reliability of the operation of the battery pack in the sub-module is improved.

Description of drawings

Fig. 1 is a kind of super-large-scale energy storage MMC converter device structure diagram of the present invention;

Fig. 2 is a structural diagram of an energy storage sub-module of a super-large-scale energy storage MMC converter device of the present invention; Fig. 3 is a flow chart of a method for removing a super-large-scale energy storage MMC converter device of the present invention; Fig. 4 is a super-large energy storage MMC converter device of the present invention. The flow chart of the input method of the large-scale energy storage MMC converter device;

5 is a flowchart of an energy storage control method using a super-large-scale energy storage MMC converter device according to the present invention;

6 is a control block diagram of an energy storage control method using an ultra-large-scale energy storage MMC converter device according to the present invention;

Fig. 7 is a kind of energy storage control method of the present invention that uses the super-large-scale energy storage MMC converter device energy storage sub-module capacitor terminal and battery pack terminal voltage waveform diagram;

8 is a waveform diagram of the three-phase phase voltage on the AC side of an energy storage control method using an ultra-large-scale energy storage MMC converter device according to the present invention;

FIG. 9 is a DC side voltage waveform of an energy storage control method using an ultra-large-scale energy storage MMC converter device according to the present invention.

Detailed ways

Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for the purpose of this thorough and complete disclosure invention, and fully convey the scope of the invention to those skilled in the art. The terms used in the exemplary embodiments shown in the drawings are not intended to limit the invention. In the drawings, the same elements/elements are given the same reference numerals.

Unless otherwise defined, terms (including scientific and technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is to be understood that terms defined in commonly used dictionaries should be construed as having meanings consistent with the context in the related art, and should not be construed as idealized or overly formal meanings.

The present invention proposes an ultra-large-scale energy storage MMC converter device, as shown in Figure 1, comprising:

a plurality of bridge arms, each bridge arm includes a plurality of energy storage sub-modules and an inductor; the plurality of energy storage sub-modules are connected in series and connected to the inductor;

Every two bridge arms are connected by the cables of the bridge arms as a group of one-phase sub-converters; the one-phase sub-converters include three groups, and the three groups of one-phase sub-converters are connected in parallel;

Connect the transformer, AC power supply and load externally to the device.

The energy storage sub-module, as shown in Figure 2, includes: the positive electrode of the energy storage sub-module, the negative electrode of the energy storage sub-module, the first to sixth IGBTs (S1-S6), the first to third capacitors (C1-C3), and the inductance L1, photovoltaic power generation unit, lithium battery pack and diode;

The positive electrode of the energy storage sub-module is connected to the emitter of the first IGBT and the collector of the second IGBT; the negative electrode of the energy storage sub-module is connected to the emitter of the second IGBT;

The first capacitor and the second capacitor are connected in series, and the anode of the first capacitor is connected to the collector of the first IGBT;

The cathode of the second capacitor is connected to the emitter of the second IGBT;

The emitter of the third IGBT is connected to the collector of the fourth IGBT, and the collector of the third IGBT and the emitter of the fourth IGBT are respectively connected to the positive electrode and the negative electrode of the first capacitor;

The emitter of the fifth IGBT is connected to the collector of the sixth IGBT, and the collector of the fifth IGBT is connected to the emitter of the fourth IGBT and the positive electrode of the second capacitor;

The emitter of the sixth IGBT is connected to the negative electrode of the second capacitor;

The anode of the third capacitor is connected to the emitter of the third IGBT, and the cathode of the third capacitor is connected to the fifth

The emitter of the IGBT is connected;

One end of the inductor L1 is connected to the negative electrode of the third capacitor, and the other end is connected to the positive electrode of the lithium battery pack;

The negative electrode of the lithium battery is connected to the emitter of the sixth IGBT;

The anode of the photovoltaic power generation unit is connected to the collector of the third IGBT through a diode, and the cathode of the photovoltaic power generation unit is connected to the emitter of the sixth IGBT.

The energy storage sub-module controls the turn-off of the control switches of the first to sixth IGBTs, controls the cut-off of current, turns off the control switches of the first to sixth IGBTs, charges and discharges the first to third capacitors, and controls the lithium battery The charge and discharge control of the group is input.

As shown in Figure 3, it is the working principle of the two cut-off modes of the energy storage sub-module; the steps of the first cut-off method are:

The switch S1 is controlled by the drive signal to keep off; the switch S2 is controlled by the drive signal to be closed;

At this time, the current flows in from the positive pole of the sub-module, passes through the S2 switch tube, and flows out to the negative pole of the sub-module; the steps of the second cutting method are:

The driving signal controls the switch S1 to keep off; the driving signal controls the switch S2 to turn off;

At this time, the current flows in from the negative pole of the sub-module, passes through the reverse diode T2, and flows out to the positive pole of the sub-module.

As shown in Figure 4, it is the working principle of the two input methods of the energy storage sub-module; the steps of the first input method are:

Switch S2 remains off, switch S1 remains closed, switches S3 and S5 are closed, switches S4 and S6 are open, and current flows in from the positive pole. After T1, S3 charges capacitors C1, C2, C3 and the battery pack; the photovoltaic power generation unit passes through The diode charges the battery.

The steps of the second input method are:

Switch S2 remains off, switch S1 remains closed, switches S4 and S6 are closed, switches S3 and S5 are open, capacitors C1, C2, C3 and the battery pack are discharged, and current flows in from the negative pole, passes through S1, and flows out from the positive pole.

Capacitance values of the first to third capacitors are the same and satisfy a preset range.

Among them, fs is the switching frequency of the IGBT in the sub-module; ron is the on-resistance of the IGBT in the sub-module; rc is the equivalent impedance of the capacitor.

The present invention also proposes an energy storage control method using an ultra-large-scale energy storage MMC converter device, as shown in FIG. 5 , including:

Before the ultra-large-scale energy storage MMC converter is put into operation, SOC pre-detection is performed on the lithium battery pack in the energy storage sub-module;

Determine the AC terminal current reference value and the DC terminal voltage reference value of the ultra-large-scale energy storage MMC converter;

Detect the circulating current power of each phase sub-device, convert the circulating current power, obtain the conversion data, and determine the circulating current reference value according to the conversion data and the DC terminal voltage reference value;

Determine the current reference value of each bridge arm according to the circulating current reference value and the AC terminal current reference value;

Perform dq coordinate transformation on the current reference value of each bridge arm, output the dq voltage, perform abc coordinate transformation and SPWM modulation on the dq voltage, obtain the output result, and turn off the first to sixth IGBTs of the energy storage sub-module according to the output result. , the energy storage control is performed by turning off the first to sixth IGBTs.

As shown in Figure 6, the determination of the upper and lower arm currents of each phase needs to be composed of the AC current of each phase and the circulating current of each phase, and the circulating current of each phase is composed of the DC part and the AC part composition. The DC bus voltage is stabilized by determining the DC bus reference value, and the input active power reference value of the AC part of the MMC converter is set to determine the input power of the converter, and the current distribution coefficient is introduced to allocate each phase according to the capacity of the battery pack connected to each phase. The magnitude of the reference value of the phase DC current controls the charging and discharging power of each battery pack.

SOC pre-detection, including:

Check whether the SOC of each battery of each branch in each lithium battery pack meets the battery input standard;

If each battery meets the battery input standard, the branch circuit will not be disconnected;

If there are multiple batteries that do not meet the battery input standard, the branch circuit will be disconnected, and the capacity and SOC of the lithium battery pack that has been disconnected from the branch circuit will be calculated.

Optionally, the formula for determining the current reference value of the AC terminal is as follows:

为任意一相子装置的参考功率，U_ac为交流电压，

为交流功角。in,

is the reference power of any one-phase sub-device, U _ac is the AC voltage,

is the AC power angle.

The formula for determining the reference value of the DC terminal voltage is as follows:

为任意一相子装置电流直流分量参考值、U_dc为直流电压，α_k为电流分配系数、

为直流端电压参考值、k_dc-pk和k_dc-ik分别为第k相直流分量的比例和积分系数；in,

is the reference value of the current DC component of any phase sub-device, U _dc is the DC voltage, α _k is the current distribution coefficient,

is the reference value of the DC terminal voltage, k _dc-pk and k _dc-ik are the proportional and integral coefficients of the k-th phase DC component, respectively;

The formula for determining the current distribution coefficient is as follows:

Q _k is the total capacity of any one-phase sub-device energy storage sub-module battery pack and Q _all is the total capacity.

The conversion formula of commutation power is as follows:

为第一相环流中的交流分量，P_diffa为第一相的环流功率，同理，

为第二相环流中的交流分量，P_diffb为第二相的环流功率，

为第三相环流中的交流分量，P_diffc为第三相的环流功率。in,

is the AC component in the circulating current of the first phase, P _diffa is the circulating current power of the first phase, in the same way,

is the AC component in the second phase circulating current, P _diffb is the circulating current power of the second phase,

is the AC component in the third-phase circulating current, and P _diffc is the circulating power of the third-phase.

The formula for determining the current reference value of each bridge arm is as follows:

为任意一相子装置上桥臂参考电流、

为任意一相子装置下桥臂参考电流和为任意一相子装置环流参考值，

为任意一相子装置电流交流端电流参考值。in,

is the reference current of the bridge arm of any one-phase sub-device,

is the reference current of the lower bridge arm of any one-phase sub-device and is the reference value of the circulating current of any one-phase sub-device,

It is the current reference value of the current AC terminal of any phase sub-device.

As shown in Figure 7, the voltage at the capacitor of the energy storage sub-module is about 500V, and the voltage at the terminal of the battery pack is about 125V, so the voltage output gain is 4 times. The capacitor voltage of the traditional half-bridge sub-module reaches 500V, which needs to be connected in parallel at the capacitor. 500V battery pack, and the energy storage sub-module topology of the present invention only needs 125V to meet the requirements, which greatly reduces the number of sub-battery that needs to be connected in series in the battery pack, thereby improving the reliability of the battery pack operation.

As shown in Figure 8, the AC side phase voltage waveform of 0-0.4 seconds is recorded, and the phase voltage is a sine wave with a peak value of about 54KV. Because each bridge arm is connected to 50 sub-modules, the MMC converter is a 51-level converter , the generated AC waveform tends to be a sine wave, and the harmonic characteristics are better.

As shown in Figure 9, the voltage waveform of the DC terminal load was recorded for 0-2.5 seconds. The DC voltage is stable at about 135KV after 0.7 seconds, and the voltage stability is good.

The invention can effectively reduce the terminal voltage required by the battery pack and reduce the number of batteries connected in series in the battery pack, thereby improving the reliability of the battery. The DC bus voltage is stabilized, the input or output power of each bridge arm is controlled, and the reliability of the operation of the battery pack in the sub-module is improved.

As will be appreciated by those skilled in the art, the embodiments of the present application may be provided as a method, a system, or a computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein. The solutions in the embodiments of the present application may be implemented in various computer languages, for example, the object-oriented programming language Java and the literal translation scripting language JavaScript, and the like.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It will be understood that each flow and/or block in the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to the processor of a general purpose computer, special purpose computer, embedded processor or other programmable data processing device to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing device produce Means for implementing the functions specified in a flow or flow of a flowchart and/or a block or blocks of a block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory result in an article of manufacture comprising instruction means, the instructions The apparatus implements the functions specified in the flow or flow of the flowcharts and/or the block or blocks of the block diagrams.

These computer program instructions can also be loaded on a computer or other programmable data processing device to cause a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process such that The instructions provide steps for implementing the functions specified in the flow or blocks of the flowcharts and/or the block or blocks of the block diagrams.

While the preferred embodiments of the present application have been described, additional changes and modifications to these embodiments may occur to those skilled in the art once the basic inventive concepts are known. Therefore, the appended claims are intended to be construed to include the preferred embodiment and all changes and modifications that fall within the scope of this application.

Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims (9)

1. A very large scale energy storage MMC converter apparatus, the apparatus comprising:

the bridge arms comprise a plurality of energy storage sub-modules and an inductor;

the energy storage sub-modules are connected in series and connected with an inductor;

each two bridge arms are connected through cables of the bridge arms to serve as a group of one-phase sub-converters; the one-phase sub-converters comprise three groups, and the three groups of the one-phase sub-converters are connected in parallel;

the energy storage sub-module comprises: the photovoltaic power generation system comprises first to sixth IGBTs, first to third capacitors, a lithium battery pack, an energy storage submodule anode, an energy storage submodule cathode, an inductor L1, a photovoltaic power generation unit and a diode;

by controlling the turn-off of the control switches of the first to sixth IGBTs, the charge and discharge of the first to third capacitors and the charge and discharge of the lithium battery pack, controlling the input of current;

the positive electrode of the energy storage sub-module is connected with the emitter of the first IGBT and the collector of the second IGBT;

the negative electrode of the energy storage sub-module is connected with the emitting electrode of the second IGBT;

the first capacitor is connected with the second capacitor in series, and the anode of the first capacitor is connected with the collector of the first IGBT;

the negative electrode of the second capacitor is connected with the emitter of the second IGBT;

the emitter of the third IGBT is connected with the collector of the fourth IGBT, and the collector of the third IGBT and the emitter of the fourth IGBT are respectively connected with the anode and the cathode of the first capacitor;

an emitter of the fifth IGBT is connected with a collector of the sixth IGBT, and the collector of the fifth IGBT is connected with an emitter of the fourth IGBT and a positive electrode of the second capacitor; an emitting electrode of the sixth IGBT is connected with a negative electrode of the second capacitor;

the positive electrode of the third capacitor is connected with the emitter of the third IGBT, and the negative electrode of the third capacitor is connected with the emitter of the fifth IGBT;

one end of the inductor L1 is connected with the negative electrode of the third capacitor, and the other end of the inductor L1 is connected with the positive electrode of the lithium battery pack;

the negative electrode of the lithium battery pack is connected with the emitter of the sixth IGBT;

and the positive electrode of the photovoltaic power generation unit is connected with the collector electrode of the third IGBT through a diode, and the negative electrode of the photovoltaic power generation unit is connected with the emitter electrode of the sixth IGBT.

2. The apparatus of claim 1, wherein the first to third capacitors have the same capacitance value and satisfy a predetermined range.

3. The apparatus of claim 1, externally connected to a transformer, an alternating current power source, and a load.

4. A method of energy storage control using the apparatus of any of claims 1-3, the method comprising:

before the super-large-scale energy storage MMC converter is put into operation, SOC pre-detection is carried out on a lithium battery pack in an energy storage sub-module;

determining an alternating current end current reference value and a direct current end voltage reference value of the super-large-scale energy storage MMC converter;

detecting the circulating current power of each phase of sub-device, converting the circulating current power to obtain conversion data, and determining a circulating current reference value according to the conversion data and a direct-current terminal voltage reference value;

determining a current reference value of each bridge arm according to the circulating current reference value and the alternating-current end current reference value;

and carrying out dq coordinate transformation on the current reference value of each bridge arm, outputting dq voltage, carrying out abc coordinate transformation and SPWM modulation on the dq voltage, obtaining an output result, switching off the first IGBT to the sixth IGBT of the energy storage sub-module according to the output result, and carrying out energy storage control through switching off the first IGBT to the sixth IGBT.

5. The method of claim 4, the SOC pre-detection, comprising:

checking whether the SOC of each battery of each branch in each lithium battery pack meets a battery input standard or not;

if each battery meets the battery input standard, the branch circuit is not broken;

and if a plurality of batteries do not meet the battery input standard, the branch circuit is broken, and the capacity and the SOC of the lithium battery pack of the broken branch circuit are calculated.

6. The method of claim 4, the AC end current reference value

The determination formula of (1) is as follows:

wherein,

is the reference power, U, of any phase sub-device _ac Is an alternating voltage of

Is an ac power angle.

7. The method of claim 4, wherein the dc terminal voltage reference is determined by the following equation:

wherein,

for any phase sub-unit current DC component reference value, alpha _k For distributing coefficient, U, of current _dc Is a direct-current voltage, and the voltage is,

is a reference value k of the voltage at the DC terminal _dc-pk And k _dc-ik Respectively are the proportion and integral coefficient of the kth phase direct current component;

the current distribution coefficient is determined by the following formula:

wherein Q is _k Total capacity and Q of energy storage submodule battery pack for any one-phase submodule _all Is the total capacity.

8. The method of claim 6, wherein the circulating current power is converted again by the following conversion formula:

wherein,

is an alternating component of the first phase circulating current, P _diffa The circulating current power of the first phase is, similarly,

is an alternating component, P, of the second phase circulating current _diffb Is the circulating current power of the second phase,

in a third phase of circulationOf alternating current component, P _diffc Circulating power of the third phase.

9. The method of claim 4, wherein the current reference value of each bridge leg is determined according to the following formula:

wherein,

the reference current of the upper bridge arm of any phase sub-device,

The reference current of the lower bridge arm of any phase sub-device and the circulating current reference value of any phase sub-device,

the reference value is the current reference value of the alternating current end of the current of any phase of the electronic device.

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