EP-4738637-A1 - MODULATION METHOD AND APPARATUS FOR CASCADED ENERGY STORAGE SYSTEM

EP4738637A1EP 4738637 A1EP4738637 A1EP 4738637A1EP-4738637-A1

Abstract

The present application provides a modulation method and apparatus for a cascaded energy storage system. The cascaded energy storage system comprises N sub-modules which are connected in cascade, wherein N is greater than or equal to 2. The modulation method comprises: in an odd period, according to a first correspondence, using N carriers to modulate waveform signals output by the N sub-modules; and in an even period, according to a second correspondence, using the N carriers to modulate the waveform signals output by the N sub-modules, wherein in the first correspondence and the second correspondence, the N carriers are in one-to-one correspondence with the N sub-modules, and the first correspondence is different from the second correspondence. The modulation method provided by the present application can solve the problem of SOC imbalance of energy storage batteries of sub-modules in phases of the cascaded energy storage system in a phase-shifted carrier modulation method.

Inventors

CHEN, XIAOBO
FAN, Mingshan
LIU, Youwei
HU, Lu

Assignees

Contemporary Amperex Technology Co., Limited

Dates

Publication Date: 20260506
Application Date: 20231025

Claims (11)

A modulation method for a cascaded energy storage system, wherein the cascaded energy storage system comprises N submodules connected in cascade, wherein N ≥ 2, and the modulation method comprises: modulating, during an odd-numbered cycle, waveform signals output by the N submodules using N carriers according to a first correspondence relationship; and modulating, during an even-numbered cycle, the waveform signals output by the N submodules using the N carriers according to a second correspondence relationship, wherein in the first correspondence relationship and the second correspondence relationship, the N carriers correspond one-to-one to the N submodules, and the first correspondence relationship is different from the second correspondence relationship.
The modulation method according to claim 1, wherein the submodule corresponding to each carrier in the first correspondence relationship and the second correspondence relationship is different.
The modulation method according to claim 1, wherein the submodules corresponding to a portion of the carriers in the first correspondence relationship and the second correspondence relationship are the same.
The modulation method according to any one of claims 1 to 3, wherein an i th carrier in the first correspondence relationship and an (N+1-i) th carrier in the second correspondence relationship correspond to the same submodule, wherein a larger value of i indicates a larger initial phase angle of the i th carrier, and i is any positive integer not greater than N.
The modulation method according to any one of claims 1 to 3, wherein the N carriers are sorted in an ascending order of initial phase angles and then divided into M carrier groups, wherein a quantity of carriers comprised in each carrier group is the same and greater than 1, and M is an even number; carriers in an i th carrier group in the first correspondence relationship and carriers in an (M+1-i) th carrier group in the second correspondence relationship correspond to the same submodule, wherein i is any positive integer not greater than M.
The modulation method according to any one of claims 1 to 3, wherein an initial phase angle of an i th carrier in the N carriers is (2π/N) × i, or the initial phase angle of the i th carrier in the N carriers is (π/N) × i, wherein i is any positive integer not greater than N.
The modulation method according to any one of claims 1 to 3, wherein each submodule comprises energy storage batteries disposed in parallel, an absorption capacitor, and a converter.
The modulation method according to any one of claims 1 to 3, wherein the cascaded energy storage system comprises a cascaded H-bridge or a cascaded half-bridge.
The modulation method according to any one of claims 1 to 3, wherein the carrier comprises a triangular carrier or a trapezoidal carrier.
A modulation apparatus for a cascaded energy storage system, wherein the cascaded energy storage system comprises N submodules connected in cascade, wherein N ≥ 2, and the modulation apparatus comprises: a first modulation unit, configured to modulate, during an odd-numbered cycle, waveform signals output by the N submodules using N carriers according to a first correspondence relationship; and a second modulation unit, configured to modulate, during an even-numbered cycle, the waveform signals output by the N submodules using the N carriers according to a second correspondence relationship, wherein in the first correspondence relationship and the second correspondence relationship, the N carriers correspond one-to-one to the N submodules, and the first correspondence relationship is different from the second correspondence relationship.
A computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and the computer program, when running on an electronic device, causes the electronic device to perform the modulation method according to any one of claims 1 to 9.

Description

The present application claims priority to Chinese Patent Application No. 2023108088433, filed with China National Intellectual Property Administration on July 04, 2023 and entitled "MODULATION METHOD AND APPARATUS FOR CASCADED ENERGY STORAGE SYSTEM", which is incorporated herein by reference in its entirety. TECHNICAL FIELD The present application relates to the technical field of energy storage systems, and in particular, to a modulation method and a modulation apparatus for a cascaded energy storage system. BACKGROUND In a large-capacity battery energy storage system, a cascaded H-bridge energy storage system has advantages such as strong expandability, a large capacity, a high voltage, and a small harmonic content of an output voltage current, and therefore has a wide application prospect. A modulation strategy commonly used in a cascaded H-bridge battery energy storage system is a carrier phase shifted-pulse width modulation (PS-PWM) strategy. This modulation strategy has advantages such as high quality of output electric energy, capability of outputting a relatively high equivalent switching frequency at a relatively low carrier frequency, ease of controlling an output power of each unit, and ease of implementing modular distributed control. In the PS-PWM modulation method, a control signal is output by comparing a triangular carrier with amodulation wave, that is, a PS-PWM signal output by each submodule is generated by comparing a triangular carrier with a sinusoidal wave. Because initial phase angles of carriers corresponding to the respective submodules are slightly different, output or input powers of different submodules are not completely consistent. Consequently, states of charge (SOCs) of energy storage batteries of different submodules are unbalanced. This shortens the service life of the energy storage system and reduces the use efficiency of the system. Technical Problem An objective of the present application is to provide a modulation method and a modulation apparatus for a cascaded energy storage system, so as to solve a problem of imbalance of SOCs of energy storage batteries between intra-phase submodules of the cascaded energy storage system in a carrier phase-shifted modulation method. Technical Solution The technical solutions adopted in embodiments of the present application are as follows: In a first aspect, provided is a modulation method for a cascaded energy storage system, which includes: the cascaded energy storage system includes N submodules connected in cascade, where N ≥ 2, and the modulation method includes: modulating, during an odd-numbered cycle, waveform signals output by the N submodules using N carriers according to a first correspondence relationship; and modulating, during an even-numbered cycle, the waveform signals output by the N submodules using the N carriers according to a second correspondence relationship, where in the first correspondence relationship and the second correspondence relationship, the N carriers correspond one-to-one to the N submodules, and the first correspondence relationship is different from the second correspondence relationship. In a possible implementation, the submodule corresponding to each carrier in the first correspondence relationship and the second correspondence relationship is different. In a possible implementation, the submodules corresponding to a portion of the carriers in the first correspondence relationship and the second correspondence relationship are the same. In a possible implementation, an ith carrier in the first correspondence relationship and an (N+1-i)th carrier in the second correspondence relationship correspond to the same submodule, where a larger value of i indicates a larger initial phase angle of the ith carrier, and i is any positive integer not greater than N. In a possible implementation, the N carriers are sorted in an ascending order of initial phase angles and then divided into M carrier groups, where a quantity of carriers included in each carrier group is the same and greater than 1, and M is an even number (e.g., 2, 4, or 6); carriers in an ith carrier group in the first correspondence relationship and carriers in an (M+1-i)th carrier group in the second correspondence relationship correspond to the same submodule, where i is any positive integer not greater than M. In a possible implementation, an initial phase angle of an ith carrier in the N carriers is (2π/N) × i, or the initial phase angle of the ith carrier in the N carriers is (π/N) × i, where i is any positive integer not greater than N. In a possible implementation, each submodule includes energy storage batteries disposed in parallel, an absorption capacitor, and a converter. In a possible implementation, the cascaded energy storage system includes a cascaded H-bridge or a cascaded half-bridge. In a possible implementation, the carrier includes a triangular carrier or a trapezoidal carrier. In a second aspect, provided is a modula