CN115622376A - Cascade type energy storage converter system with function of inhibiting leakage current and control method - Google Patents

Cascade type energy storage converter system with function of inhibiting leakage current and control method Download PDF

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Publication number
CN115622376A
CN115622376A CN202211432187.3A CN202211432187A CN115622376A CN 115622376 A CN115622376 A CN 115622376A CN 202211432187 A CN202211432187 A CN 202211432187A CN 115622376 A CN115622376 A CN 115622376A
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switch tube
tube
switching tube
type
module
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CN115622376B (en
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刘亚涛
刘永奎
廖正军
曹立航
李江江
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Xi'an Singularity Energy Co ltd
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Xi'an Singularity Energy Co ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • H02M1/123—Suppression of common mode voltage or current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/28—Arrangements for balancing of the load in a network by storage of energy
    • H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
    • H02M7/68—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters
    • H02M7/72—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/79—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/797—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

Abstract

The invention discloses a cascade energy storage converter system with leakage current inhibition function and a control method thereof, belonging to the technical field of new energy storage, and comprising the following steps: the system comprises an I type DC/AC module topological system, a II type DC/AC module topological system and a III type DC/AC module topological system which are sequentially connected in series; the type I DC/AC module topology system comprises: a plurality of I-type DC/AC modules connected in series; the type II DC/AC module topology system comprises: a plurality of type II DC/AC modules connected in series; the type III DC/AC module topology system comprises: a plurality of type III DC/AC modules connected in series. According to the invention, an additional switch tube and a matched inductance capacitor are added under the traditional H-bridge topological structure, and the common-mode voltage change of the battery and a direct-current bus to the ground is reduced and the circulation path of part of common-mode current is cut off by the matching of the switch tube, the S1 switch tube, the S2 switch tube, the S3 switch tube and the S4 switch tube, so that the overall leakage current level of the system is reduced.

Description

Cascade type energy storage converter system with function of inhibiting leakage current and control method
Technical Field
The invention relates to the technical field of new energy storage, in particular to a cascade energy storage converter system capable of inhibiting leakage current.
Background
The cascaded energy storage PCS has the characteristic of high efficiency, but all power sub-modules need to be insulated, and as the battery modules are large in size, the battery modules and connecting cables thereof introduce large parasitic capacitance, so that common-mode current paths exist among all power sub-modules of the PCS, and the requirements of battery units on ground insulation and the existence of common-mode current in a system bring challenges to practical engineering.
In the traditional photovoltaic inverter industry, leakage current is restrained through a HERIC topology, an NPC topology and an H6 topology at present, but the technical scheme cannot be applied to a cascade energy storage and conversion system due to the characteristics of three phases and a non-cascade structure. In addition, because the application time of the medium-high voltage cascade energy storage topology is short, no technical discussion in the aspect of targeted leakage current suppression is seen at present. In recent two years, medium-high voltage cascade energy storage systems have been tried, but the problem is weakened by adopting the traditional optimized cell arrangement and structural design in the specific product design, but the effect is limited in the mode, the occupied area is greatly increased, and the power density is reduced.
Disclosure of Invention
In one aspect, the present invention is directed to the above problem, and provides a cascaded energy storage converter system with leakage current suppression.
The technical scheme adopted by the invention is as follows: a cascaded energy storage converter system with leakage current suppression, comprising: the system comprises an I type DC/AC module topological system, a II type DC/AC module topological system and a III type DC/AC module topological system which are sequentially connected in series;
the type I DC/AC module topology system comprises: a plurality of I-type DC/AC modules connected in series;
the type I DC/AC module includes: the H-bridge circuit, the S5 switch tube and the S6 switch tube;
the S5 switch tube is connected between the anode of the support capacitor and the positive direct current bus of the H-bridge circuit, and the S6 switch tube is connected between the cathode of the support capacitor and the negative direct current bus of the H-bridge circuit;
the type II DC/AC module topology system comprises: a plurality of type II DC/AC modules connected in series;
the type II DC/AC module includes: the H-bridge circuit, the S5 switch tube and the S6 switch tube;
the S5 switch tube and the S6 switch are connected between the anode of the support capacitor and a positive direct current bus of the H-bridge circuit, and the S5 switch tube and the S6 switch tube are connected in series in a reverse direction;
the type III DC/AC module topology system comprises: a plurality of type III DC/AC modules connected in series;
the type III DC/AC module includes: the H-bridge circuit, the S5 switch tube and the S6 switch tube;
the S5 switch tube and the S6 switch are connected between the positive electrode of the supporting capacitor and the negative direct-current bus of the H-bridge circuit, and the S5 switch tube and the S6 switch tube are connected in series in a reverse direction.
Further, in the I-type DC/AC module, a base electrode of the S5 switch tube or a cathode of the anti-parallel diode is connected with an output port of the anode of the battery pack, and an emitter electrode of the S5 switch tube or an anode of the anti-parallel diode is connected with the anode of the supporting capacitor of the H-bridge circuit;
and the base electrode of the S6 switch tube or the cathode of the anti-parallel diode is connected with the output port of the cathode of the battery pack, and the emitter electrode of the S6 switch tube or the anode of the anti-parallel diode is connected with the cathode of the supporting capacitor of the H-bridge circuit.
Furthermore, in the type ii DC/AC module, the base or the anti-parallel diode cathode of the S5 switch tube is connected to the positive output port of the battery pack, the emitter or the anti-parallel diode anode of the S5 switch tube is connected to the emitter or the anti-parallel diode anode of the S6 switch tube, and the emitter or the anti-parallel diode anode of the S6 switch tube is connected to the emitter or the anti-parallel diode anode of the S5 switch tube.
Furthermore, in the type iii DC/AC module, the emitter of the S5 switch tube or the anode of the anti-parallel diode is connected to the output port of the negative electrode of the capacitor, and the base of the S5 switch tube or the cathode of the anti-parallel diode is connected to the base of the S6 switch tube or the cathode of the anti-parallel diode;
and the emitting electrode or the anode of the anti-parallel diode of the S6 switch tube is connected with the negative direct current bus of the H-bridge circuit, and the emitting electrode or the anode of the anti-parallel diode of the S6 switch tube is connected with the base electrode or the cathode of the anti-parallel diode of the S5 switch tube.
On the other hand, the scheme provides a method for inhibiting leakage current of a cascade energy storage converter system, and the method adopts a unipolar sectional control strategy:
in the discharging stage, keeping the S6 switching tube turned off, and modulating the S1 switching tube, the S2 switching tube, the S3 switching tube, the S4 switching tube and the S5 switching tube;
and in the charging stage, keeping the S5 switching tube turned off, and modulating the S1 switching tube, the S2 switching tube, the S3 switching tube, the S4 switching tube and the S6 switching tube.
Further, in the discharging stage, under the positive polarity of the modulation wave, the S1 switching tube is continuously turned on, the S4 switching tube and the S5 switching tube are kept synchronously turned on and off, and the turning-on actions of the S4 switching tube and the S5 switching tube are judged by comparing the modulation wave with the carrier wave; specifically, a high level is output when the amplitude of the modulated wave is larger than the carrier wave, or a low level is output when the amplitude of the modulated wave is smaller than the carrier wave;
and under the negative polarity of the modulated wave, the S3 switching tube is continuously conducted, the S2 switching tube and the S5 switching tube are kept synchronously on and off, and the actions of the S2 switching tube and the S5 switching tube are judged by comparing the modulated wave with the carrier wave.
Furthermore, in the charging stage, under the positive polarity of the modulation wave, the S1 switching tube is continuously turned on, and the S4 switching tube and the S6 switching tube are kept synchronously turned on and off, wherein the on-state actions of the S4 switching tube and the S6 switching tube are judged by comparing the modulation wave with the carrier wave;
and under the negative polarity of the modulation wave, the S3 switching tube is continuously conducted, the S2 switching tube and the S6 switching tube are kept synchronously on and off, and the switching actions of the S2 switching tube and the S6 switching tube are judged by comparing the modulation wave with the carrier wave.
The invention has the beneficial effects that:
by adding an additional switching tube and a matched inductance capacitor under the traditional H-bridge topological structure, the matching of the tube and an S1 switching tube, an S2 switching tube, an S3 switching tube and an S4 switching tube reduces the common-mode voltage change of a battery and a direct-current bus to the ground and cuts off the circulation path of part of common-mode current, further reduces the overall leakage current level of the system, and provides an energy storage system control and leakage current suppression modulation strategy matched with the optimized system structure and suitable for multi-level cascade connection, thereby integrally improving the field operation index of equipment.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification.
FIG. 1a is a schematic diagram of a type I modified cascaded PCS control process according to an embodiment of the present invention;
FIG. 1b is a schematic diagram of a type II modified cascaded PCS control process according to an embodiment of the present invention;
FIG. 1c is a schematic diagram of a modified cascading PCS control process of type III in accordance with an embodiment of the present invention;
fig. 2 is a schematic diagram of leakage current of a single-phase H-bridge inductor arranged on both sides according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of an S5 pulse blocking leakage current loop according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a type I DC/AC modular system in accordance with an embodiment of the present invention;
FIG. 5 is a schematic diagram of a type II DC/AC module system according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a type III DC/AC module system according to an embodiment of the present invention;
fig. 7 is a schematic carrier distribution diagram of a two-module cascade system according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of the switch states of the module cascade discharge process according to the embodiment of the present invention;
FIG. 9 is a schematic diagram of the voltage at the H-bridge port and the common and differential mode voltages at two modules according to an embodiment of the present invention;
fig. 10 is a schematic diagram of a single-phase full-bridge inverter topology with single inductor filtering according to an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example one
Referring to fig. 1a to 1c, a cascaded energy storage converter system with leakage current suppression comprises: the system comprises a type I DC/AC module topology system, a type II DC/AC module topology system and a type III DC/AC module topology system which are sequentially connected in series;
the type I DC/AC module topology system comprises: a plurality of I-type DC/AC modules connected in series;
the type I DC/AC module includes: the H-bridge circuit, the S5 switch tube and the S6 switch tube;
the S5 switch tube is connected between the anode of the support capacitor and the positive direct-current bus of the H-bridge circuit, and the S6 switch tube is connected between the cathode of the support capacitor and the negative direct-current bus of the H-bridge circuit;
the type II DC/AC module topology system comprises: a plurality of type II DC/AC modules connected in series;
the type II DC/AC module comprises: the H-bridge circuit, the S5 switch tube and the S6 switch tube;
the S5 switch tube and the S6 switch are connected between the anode of the support capacitor and a positive direct current bus of the H-bridge circuit, and the S5 switch tube and the S6 switch tube are reversely connected in series;
the type III DC/AC module topology system comprises: a plurality of type III DC/AC modules connected in series;
the type III DC/AC module includes: the H-bridge circuit, the S5 switch tube and the S6 switch tube;
the S5 switch tube and the S6 switch are connected between the positive electrode of the support capacitor and the negative direct-current bus of the H-bridge circuit, and the S5 switch tube and the S6 switch tube are connected in series in a reverse direction.
It should be noted that, the invention aims to develop 3 different DC/AC module topologies on the basis of a basic topology by slightly increasing the number of switches under the existing control system and architecture, and to connect the developed DC/AC modules in series to form a cascaded energy storage converter system with leakage current suppression capability, thereby reducing the problem that the common-mode leakage current of the system under the existing H-bridge cascaded energy storage scheme exceeds the standard and improving the field operation index of the equipment.
Referring to fig. 4, in the type i DC/AC module according to an embodiment of the present invention, a base or an anti-parallel diode cathode of the S5 switching tube is connected to an output port of an anode of a battery pack, and an emitter or an anti-parallel diode anode of the S5 switching tube is connected to an anode of a supporting capacitor of the H-bridge circuit;
and the base electrode of the S6 switch tube or the cathode of the anti-parallel diode is connected with the output port of the cathode of the battery pack, and the emitter electrode of the S6 switch tube or the anode of the anti-parallel diode is connected with the cathode of the supporting capacitor of the H-bridge circuit.
Referring to fig. 5, in the type ii DC/AC module according to an embodiment of the present invention, a base or an anti-parallel diode cathode of the S5 switch tube is connected to an anode output port of a battery pack, an emitter or an anti-parallel diode anode of the S5 switch tube is connected to an emitter or an anti-parallel diode anode of the S6 switch tube, and an emitter or an anti-parallel diode anode of the S6 switch tube is connected to an emitter or an anti-parallel diode anode of the S5 switch tube.
Referring to fig. 6, in an embodiment of the present invention, in the type iii DC/AC module, an emitter of the S5 switching tube or an anti-parallel diode anode is connected to a capacitor cathode output port, and a base of the S5 switching tube or an anti-parallel diode cathode is connected to a base of the S6 switching tube or an anti-parallel diode cathode;
and the emitting electrode or the anode of the anti-parallel diode of the S6 switch tube is connected with the negative direct current bus of the H-bridge circuit, and the emitting electrode or the anode of the anti-parallel diode of the S6 switch tube is connected with the base electrode or the cathode of the anti-parallel diode of the S5 switch tube.
Example two
It is worth mentioning that, referring to fig. 10, the reason for affecting the leakage current is as follows;
in order to analyze the problem of current leakage under a full-bridge cascade system, the common-mode voltage condition of a single-phase full-bridge inverter is firstly analyzed:
Figure 814977DEST_PATH_IMAGE001
known as u from the above formula cm =u bn So that its common mode currentI cm Comprises the following steps:
Figure 718211DEST_PATH_IMAGE002
wherein, U an Is the voltage at the two ends of the S2 tube of the left bridge arm, U bn Is the voltage at the two ends of the S4 tube of the right bridge arm, U L And U g For the inductor voltage and the grid phase voltage, U cm Is a common mode voltage, C, in the converter p Is the equivalent parasitic capacitance.
In the above structure, due to the high frequency operation of the switching tube,
Figure 992198DEST_PATH_IMAGE003
will jump at high frequency between 0 and the battery voltage and thus generate a large common mode current.
How to eliminate the leakage current:
this patent suppresses the thinking of leakage current and does: the expression of the common-mode voltage under different working conditions and the common-mode voltage in the follow current stage are ensured to be unchanged. In order to ensure that the common-mode voltage is unchanged in the follow current stage, the combined switch tube is operated to cut off a charge-discharge loop of the common-mode capacitor.
According to the characteristics of a full-bridge module and a cascade system, the method is improved on the basis of the existing basic topology, a similar double-Buck circuit structure is constructed by additionally arranging 2 switching tubes on an H-bridge direct-current bus, and the pulse modulation mode is further expanded aiming at the structure.
Referring to fig. 2, the inductance of the h-bridge module is arranged bilaterally
Voltage loop equation:
Figure 389812DEST_PATH_IMAGE004
obtaining:
Figure 698434DEST_PATH_IMAGE005
consider that
Figure 772569DEST_PATH_IMAGE006
For the grid voltage, the frequency is relatively low, the influence of the grid voltage on the common-mode voltage is ignored, and the common-mode voltage can be ensured to be:
Figure 533852DEST_PATH_IMAGE007
the alternating current measurement capacitor mainly solves the EMC problem and is an optional configuration. When the number of the cascade modules is large, the problem of high-frequency electromagnetic interference can be ignored, the capacitor does not need to be arranged, and when the number of the cascade modules is small, the cascade modules are assembled according to the requirement of product specifications.
An additional switching device is arranged on the direct current bus:
the added switch can cut off a common mode current loop under partial working conditions on one hand, and can solve the problem of overhigh switching frequency of an S2 switching tube and an S4 switching tube on the other hand. After a new switch tube is introduced, the S2 switch tube and the S4 switch tube work in a power frequency state, so that the condition that the S2 switch tube and the S4 switch tube work in a power frequency state is ensured
Figure 735157DEST_PATH_IMAGE008
And
Figure 163864DEST_PATH_IMAGE003
less frequently. The newly added switch tube double configuration ensures the power bidirectional flow requirement.
The detailed analysis process is as follows:
referring to fig. 3, for example, in the discharging condition, the common mode voltage is at S1 switch tube, S4 switch tube, S5 switch tube working state
Figure 408901DEST_PATH_IMAGE009
(ii) a When the S1 switch tube and the S3 switch tube are connected with the diodes in parallel in the working state, the pulse of the S5 switch tube is blocked to ensure that the direct-current bus and the battery are/is protectedThe common mode loop between the capacitors is turned off.
In order to adapt to the module cascade energy storage system, the improved design adopts a conventional cascade PCS control framework, and combines a leakage current inhibition idea on the basis of the carrier phase shift control to optimally design a module modulation link.
The control mode adopts the basic idea of unipolar modulation, and is realized by the following steps: the S1 switching tube and the S3 switching tube are ensured to operate at a power frequency switching frequency, the S2 switching tube, the S4 switching tube, the S5 switching tube and the S6 switching tube alternately operate at a carrier switching frequency, and the switching frequency is basically equal to the switching frequency in the conventional multi-module cascade design. Compared with bipolar modulation and unipolar modulation applied to a cascade topology, the switching efficiency is higher under the modulation mode.
The method adopts unipolar subsection control on the control realization, for example, the S1 switching tube is continuously conducted under the positive polarity of the modulation wave, and the S4 switching tube and the S5 switching tube are kept synchronously on and off; and the S3 switching tube is continuously conducted under the negative polarity of the modulation wave, and the S2 switching tube and the S5 switching tube are synchronously switched on and off.
Specifically, in the discharging stage, the S6 switching tube is kept turned off, and the S1 switching tube, the S2 switching tube, the S3 switching tube, the S4 switching tube and the S5 switching tube are modulated;
under the positive polarity of the modulation wave, the S1 switching tube is continuously conducted, the S4 switching tube and the S5 switching tube are kept synchronously on and off, and the switching-on actions of the S4 switching tube and the S5 switching tube are judged by comparing the modulation wave with the carrier wave; specifically, a high level is output when the amplitude of the modulated wave is larger than the carrier wave, or a low level is output when the amplitude of the modulated wave is smaller than the carrier wave;
and under the negative polarity of the modulated wave, the S3 switching tube is continuously conducted, the S2 switching tube and the S5 switching tube are kept synchronously on and off, and the actions of the S2 switching tube and the S5 switching tube are judged by comparing the modulated wave with the carrier wave.
And in the charging stage, keeping the S5 switching tube turned off, and modulating the S1 switching tube, the S2 switching tube, the S3 switching tube, the S4 switching tube and the S6 switching tube.
Under the positive polarity of the modulation wave, the S1 switching tube is continuously conducted, the S4 switching tube and the S6 switching tube are kept synchronously on and off, and the switching-on actions of the S4 switching tube and the S6 switching tube are judged by comparing the modulation wave with the carrier wave;
and under the negative polarity of the modulated wave, the S3 switching tube is continuously conducted, the S2 switching tube and the S6 switching tube are kept synchronously on and off, and the switching actions of the S2 switching tube and the S6 switching tube are judged by comparing the modulated wave with the carrier wave.
Referring to FIG. 7, (1) when unipolar modulation is used, the equivalent switching frequency requirement of the cascaded PCS system is assumed to be
Figure 188638DEST_PATH_IMAGE010
If the number of the single-phase cascade modules is N, the triangular carrier frequency is set to be N
Figure 52689DEST_PATH_IMAGE011
The carrier lag time between adjacent modules is:
Figure 211269DEST_PATH_IMAGE012
；
(2) When adopting unipolar frequency multiplication modulation, the equivalent switching frequency requirement of the cascading PCS system is assumed to be
Figure 768152DEST_PATH_IMAGE010
If the number of the single-phase cascade modules is N, the triangular carrier frequency is set to be N
Figure 628661DEST_PATH_IMAGE013
The carrier lag time between adjacent modules is:
Figure 296402DEST_PATH_IMAGE014
。
the method for generating the triangular carrier specifically comprises the following steps:
each phase of N modules generates 2N triangular carriers, wherein the N triangular carriers comprise N positive triangular carriers and N negative triangular carriers, and the amplitude of the carrier is 1. Each module corresponds to a positive carrier and a negative carrier, which are symmetrically distributed on both sides of the X axis with a 180 ° difference, and the distribution of the two-module system carriers is shown in fig. 7, taking unipolar modulation as an example:
after the triangular carrier is realized, amplitude values of the modulation wave and the triangular wave are compared, and a control pulse is generated according to the magnitude relation of the modulation wave and the triangular wave. Wherein the modulated wave is generated for upper layer control.
In order to further explain the common-mode current suppression and pulse modulation process, the modulation and pulse generation process of the 2-module cascade system discharge is described by taking the example (at this time, the S1 switching tube and the S6 switching tube are turned off).
Referring to fig. 8-9, S11, S12, S13, S14, S15, and S16 (S16 = S26= 0) respectively correspond to the S1 switch tube, the S2 switch tube, the S3 switch tube, the S4 switch tube, the S5 switch tube, and the S6 switch tube of the 1 st module in the cascade system. Wherein
Figure 434123DEST_PATH_IMAGE015
And
Figure 37274DEST_PATH_IMAGE016
is the forward modulated wave of the module 1, 2,
Figure 260444DEST_PATH_IMAGE017
and
Figure 856511DEST_PATH_IMAGE018
is a reverse modulated wave of the module 1, 2, wherein
Figure 848738DEST_PATH_IMAGE019
And with
Figure 622790DEST_PATH_IMAGE020
Are symmetrically distributed at two sides of the X axis with a 180-degree difference,
Figure 333257DEST_PATH_IMAGE021
and with
Figure 342801DEST_PATH_IMAGE022
The phase difference is 180 degrees, the two sides of the X axis are symmetrically distributed,
Figure 845327DEST_PATH_IMAGE023
and with
Figure 649335DEST_PATH_IMAGE024
With a 180 deg. difference in the X-axis (carrier delay under multiple modules)
Figure 112677DEST_PATH_IMAGE025
). Modulated wave
Figure 535699DEST_PATH_IMAGE026
And a triangular carrier
Figure 502518DEST_PATH_IMAGE027
And
Figure 602061DEST_PATH_IMAGE028
comparing the modulated pulse signals generated from S11 to S15 to generate a modulated wave
Figure 552700DEST_PATH_IMAGE026
And a triangular carrier
Figure 779413DEST_PATH_IMAGE029
And
Figure 866317DEST_PATH_IMAGE030
comparing and generating modulation pulse signals of S21-S25, wherein the generation processes of S11-S15 pulses are as follows:
the positive half period S11 of the modulation wave remains on and S12 remains off. At the same time when
Figure 277707DEST_PATH_IMAGE031
When the modulated wave is on, S14 and S15 are on, S13 is off
Figure 309117DEST_PATH_IMAGE032
When the signal is received, S14 and S15 are turned off, and S13 is turned on.
The negative half cycle S13 of the modulation wave remains on and S14 remains off. At the same time when
Figure 198576DEST_PATH_IMAGE033
<
Figure 280932DEST_PATH_IMAGE034
When S12 and S15 are on, S11 is off
Figure 597644DEST_PATH_IMAGE035
When the signal is received, S12 and S15 are switched off, and S11 is switched on;
and (3) keeping the switch tube of S5 off in the charging process, and calculating the switching actions of S11, S12, S13, S14 and S16 by adopting similar logic judgment.
When the n unit modules are cascaded, the voltages at the two ends of the parasitic capacitor are the same as those of the single module during operation, and are the sum of the voltages at the two ends of the parasitic capacitor in the high-frequency equivalent model and the voltages at the two ends of the parasitic capacitor in the low-frequency equivalent model. By optimizing the modulation scheme, the voltage across the parasitic capacitance is constant
Figure 257296DEST_PATH_IMAGE036
。
In order to meet the charging condition of the energy storage system, the method constructs an additional S6 switching tube, the working process and the common-mode voltage analysis process of the switching tube are similar to those described above, and the single-module structure is shown in FIG. 4.
Analyzing the operation mode of the S6 switching tube, the type 2 and type 3 DC/AC module structures can be evolved, see FIGS. 5 and 6.
The added S6 switch tube action logic is determined by the power direction, when the direction is the charging direction, the S6 switch performs the switching action, and the switch tube keeps the off state in the discharging process; when the direction is the discharging direction, the S5 switching tube performs switching action, and the off state is kept in the charging process. The operation logics of the S5 switch tube and the S6 switch tube in the I, II and III type DC/AC module systems are the same.
EXAMPLE III
The backward process of the method is used to support the method conclusion of the invention:
the recursion process realized by the method comprises the following steps:
write voltage loop equations according to the columns of FIG. 10:
Figure 75079DEST_PATH_IMAGE037
obtaining:
Figure 870997DEST_PATH_IMAGE038
when single-inductor filtering is adopted, due to the limitation of a topological structure, the constant common-mode voltage cannot be ensured no matter unipolar modulation or bipolar modulation is adopted;
and carrying out bilateral symmetrical distribution on the inductors, constructing a second inductor loop, and setting the unilateral inductor of the second inductor loop to be L/2.
Write voltage loop equations according to the columns of FIG. 4:
Figure 765134DEST_PATH_IMAGE039
obtaining:
Figure 646503DEST_PATH_IMAGE040
consider that
Figure 2398DEST_PATH_IMAGE041
For the grid voltage, its frequency is relatively low, so its effect on the common mode voltage is neglected:
Figure 918401DEST_PATH_IMAGE042
in a conventional H-bridge topology, when unipolar modulation is employed, there are 3 modes in the positive half-cycle of the grid voltage: (common mode Voltage case under conventional topology)
When S1 is conducted and S4 is turned off, current freewheels through a diode connected in parallel with S3,
Figure 842495DEST_PATH_IMAGE043
whereinu bat Is the battery voltage;
when S1 and S4 are conducted, the common mode voltage
Figure 74807DEST_PATH_IMAGE044
；
When S4 is conducted and current freewheels through the diode connected in parallel with S2,
Figure 109759DEST_PATH_IMAGE045
；
the common-mode voltage is 0,
Figure 4903DEST_PATH_IMAGE046
、
Figure 99898DEST_PATH_IMAGE047
And the excitation generates a common mode current.
In a conventional H-bridge topology, when bipolar modulation is employed, there are 2 modes:
when S1 and S4 are turned on and S2 and S3 are turned off,
Figure 831224DEST_PATH_IMAGE048
；
when S1 and S4 are turned off and S2 and S3 are turned on,
Figure 669867DEST_PATH_IMAGE049
；
it can be seen that the common mode voltage is maintained unchanged by adding inductance in the original circuit (fig. 3) and matching with an appropriate modulation mode, so that the common mode current can be effectively suppressed. However, in the bipolar modulation mode, 4 switching tubes are required to operate at a high switching frequency, and the switching loss is large, so that the circuit structure and the control mode are further optimized, a 1-type cascade system topology is designed by adding matched port inductors and capacitors to a mature topology structure and assisting in a proper modulation mode, and a single-phase system connection diagram is shown in fig. 5.
In the topology and unipolar control mode mentioned in the present embodiment, taking discharge as an example, there are 4 working modes, and the common mode voltages corresponding to the modules are:
in the working mode 1, the switching tubes 1, 4 and 5 are switched on, and the switching tubes 2 and 3 are switched off,
Figure 294884DEST_PATH_IMAGE050
；
in the working mode 2, the switch tube 1 is switched on, the switch tubes 2, 3, 4 and 5 are switched off, the current flows through the 3-tube freewheeling diode, at the moment, the parasitic capacitance can not form a charge-discharge loop, the capacitance voltage is approximately considered to keep the previous mode unchanged,
Figure 685414DEST_PATH_IMAGE051
；
in the working mode 3, the switching tubes 2, 3 and 5 are switched on, the switching tubes 1 and 4 are switched off,
Figure 28670DEST_PATH_IMAGE052
；
in the working mode 4, the switch tube 3 is continuously conducted, the switch tubes 1, 2, 4 and 5 are switched off, the current flows through the diode connected in parallel with the switch tube 1, at the moment, the parasitic capacitor cannot form a charge-discharge loop, the capacitor voltage is approximately considered to keep the last mode unchanged,
Figure 546371DEST_PATH_IMAGE053
；
through the comparison, the topology and the control method disclosed by the patent can suppress the common-mode voltage and further reduce the common-mode current.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and should not be taken as limiting the scope of the present invention, which is intended to cover any modifications, equivalents, improvements, etc. within the spirit and scope of the present invention.

Claims (7)

1. A cascaded energy storage converter system with leakage current suppression, comprising: the system comprises an I type DC/AC module topological system, a II type DC/AC module topological system and a III type DC/AC module topological system which are sequentially connected in series;
the type I DC/AC module topology system comprises: a plurality of I-type DC/AC modules connected in series;
the type I DC/AC module includes: the H-bridge circuit, the S5 switch tube and the S6 switch tube;
the S5 switch tube is connected between the anode of the support capacitor and the positive direct-current bus of the H-bridge circuit, and the S6 switch tube is connected between the cathode of the support capacitor and the negative direct-current bus of the H-bridge circuit;
the type II DC/AC module topology system comprises: a plurality of type II DC/AC modules connected in series;
the type II DC/AC module includes: the H-bridge circuit, the S5 switch tube and the S6 switch tube;
the S5 switch tube and the S6 switch are connected between the anode of the support capacitor and a positive direct current bus of the H-bridge circuit, and the S5 switch tube and the S6 switch tube are connected in series in a reverse direction;
the type III DC/AC module topology system comprises: a plurality of type III DC/AC modules connected in series;
the type III DC/AC module includes: the H-bridge circuit, the S5 switch tube and the S6 switch tube;
the S5 switch tube and the S6 switch are connected between the positive electrode of the support capacitor and the negative direct-current bus of the H-bridge circuit, and the S5 switch tube and the S6 switch tube are connected in series in a reverse direction.
2. The cascade energy storage converter system capable of suppressing leakage current according to claim 1, wherein in the type i DC/AC module, the base or anti-parallel diode cathode of the S5 switch tube is connected to the positive output port of the battery pack, and the emitter or anti-parallel diode anode of the S5 switch tube is connected to the positive electrode of the support capacitor of the H-bridge circuit;
and the base electrode of the S6 switch tube or the cathode of the anti-parallel diode is connected with the output port of the cathode of the battery pack, and the emitter electrode of the S6 switch tube or the anode of the anti-parallel diode is connected with the cathode of the supporting capacitor of the H-bridge circuit.
3. The cascade energy storage converter system capable of suppressing leakage current according to claim 1, wherein in the type ii DC/AC module, the base or anti-parallel diode cathode of the S5 switch tube is connected to the positive output port of the battery pack, the emitter or anti-parallel diode anode of the S5 switch tube is connected to the emitter or anti-parallel diode anode of the S6 switch tube, and the emitter or anti-parallel diode anode of the S6 switch tube is connected to the emitter or anti-parallel diode anode of the S5 switch tube.
4. The cascaded energy storage converter system with leakage current suppression function according to claim 1, wherein in the type iii DC/AC module, the emitter or the anti-parallel diode anode of the S5 switch tube is connected to the capacitor cathode output port, and the base or the anti-parallel diode cathode of the S5 switch tube is connected to the base or the anti-parallel diode cathode of the S6 switch tube;
and the emitting electrode or the anode of the anti-parallel diode of the S6 switch tube is connected with the negative direct current bus of the H-bridge circuit, and the emitting electrode or the anode of the anti-parallel diode of the S6 switch tube is connected with the base electrode or the cathode of the anti-parallel diode of the S5 switch tube.
5. A method for suppressing leakage current of a cascaded energy storage converter system, which is characterized in that the system of any one of claims 1 to 4 is adopted for suppressing the leakage current of the cascaded energy storage converter system, and the method adopts a single-polarity segmented control strategy:
in the discharging stage, keeping the S6 switching tube turned off, and modulating the S1 switching tube, the S2 switching tube, the S3 switching tube, the S4 switching tube and the S5 switching tube;
and in the charging stage, keeping the S5 switching tube turned off, and modulating the S1 switching tube, the S2 switching tube, the S3 switching tube, the S4 switching tube and the S6 switching tube.
6. The method for suppressing the system leakage current of the cascaded energy storage converter according to claim 5, wherein in the discharging phase, under the positive polarity of the modulation wave, the S1 switch tube is continuously turned on, the S4 switch tube and the S5 switch tube are kept synchronously turned on and off, wherein the turning-on actions of the S4 switch tube and the S5 switch tube are determined by the comparison between the modulation wave and the carrier wave; specifically, a high level is output when the amplitude of the modulated wave is larger than the carrier wave, or a low level is output when the amplitude of the modulated wave is smaller than the carrier wave;
and under the negative polarity of the modulated wave, the S3 switching tube is continuously conducted, the S2 switching tube and the S5 switching tube are kept synchronously on and off, and the actions of the S2 switching tube and the S5 switching tube are judged by comparing the modulated wave with the carrier wave.
7. The method for suppressing the system leakage current of the cascaded energy storage converter according to claim 5, wherein in the charging phase, under the positive polarity of the modulation wave, the S1 switch tube is continuously turned on, and the S4 switch tube and the S6 switch tube are kept synchronously turned on and off, wherein the turning-on actions of the S4 switch tube and the S6 switch tube are determined by the comparison between the modulation wave and the carrier wave;
and under the negative polarity of the modulated wave, the S3 switching tube is continuously conducted, the S2 switching tube and the S6 switching tube are kept synchronously on and off, and the switching actions of the S2 switching tube and the S6 switching tube are judged by comparing the modulated wave with the carrier wave.
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