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EP-4738638-A1 - BATTERY SYSTEM WITH DISTRIBUTED VOLTAGE LEVELS

EP4738638A1EP 4738638 A1EP4738638 A1EP 4738638A1EP-4738638-A1

Abstract

A battery system (300) having a middle bus line (ML), a positive bus line (PL) and a negative bus line (NL) is provided. The battery system (300) comprises: a battery module (310), a multilevel neutral point clamped inverter (320). One or more direct current to direct current converters (DC/DC) and two or more auxiliary loads (L1, L2, ...) are connected either between the positive and negative bus lines (PL, NL), or between the positive and middle bus lines (PL, ML), or between the negative and middle bus lines (NL, ML). The operation of the DC/DC converters is configurable to balance the loads of the battery module (310) and/or control charging/discharging of the battery module (310). The connections of the two or more auxiliary loads (L1, L2, ...) are configurable to balance the loads of the battery module (310).

Inventors

  • Kersten, Anton
  • Mirbagheri, Mina

Assignees

  • Volvo Penta Corporation

Dates

Publication Date
20260506
Application Date
20241030

Claims (15)

  1. A battery system (300, 400) having a middle bus line (ML), a positive bus line (PL) and a negative bus line (NL), wherein the battery system (300, 400) comprises: a battery module (310, 410) having a first tap (TP1), a first terminal (T1) and a second terminal (T2), wherein the first tap (TP1) is connected to the middle bus line (ML), the first terminal (T1) is connected to the positive bus line (PL) and the second terminal (T2) is connected to the negative bus line (NL); a multilevel neutral point clamped, NPC, inverter (320) having a neutral terminal (N I ), an output terminal (Outi), a positive terminal (PT I ) and a negative terminal (NT I ), wherein the neutral terminal (N I ) of the multilevel NPC inverter (320) is connected to the first tap (TP1) of the battery module (310), and the positive and negative terminals (PT I , NTi) of the multilevel NPC inverter (320) are connected to the first and second terminals (T1, T2) of the battery module (310) respectively; and at least one direct current to direct current converter, DC/DC, connected either between the positive and negative bus lines (PL, NL), or between the positive and middle bus lines (PL, ML), or between the negative and middle bus lines (NL, ML), wherein operation of the at least one DC/DC converter is configurable for at least one of balancing loads of the battery module (310, 410) and controlling charging/discharging of the battery module (310, 410); and wherein at least two auxiliary loads (L1, L2, ...) are connected either between the positive and negative bus lines (PL, NL), or between the positive and middle bus lines (PL, ML), or between the negative and middle bus lines (NL, ML), directly or via respective switches (S1, S2...).
  2. The battery system (300, 400) according to claim 1, wherein the operation of the at least one DC/DC converter is configurable by adjusting current flows in the at least one DC/DC converter, thereby regulating at least one of power flows to at least one low voltage system and power flows to and from the battery module (310, 410).
  3. The battery system (300, 400) according to any one of claims 1-2, wherein the at least two auxiliary loads (L1, L2, ...) comprise at least one of fans, heat pumps, motor loads, compressors, heaters, cooling system, climate system and resistive loads.
  4. The battery system (300, 400) according to claim 2, wherein the at least one low voltage system comprises at least one of a 12V system, a 24V system and a 48V system.
  5. The battery system (300, 400) according to any one of claims 1-4, wherein the battery module (410) comprises two or more battery packs (411, 412, ... 41n, 41n+1) stacked and two or more taps (TP1, TP2, ... TPn-1, TPn) placed at respective connection points between any two battery packs.
  6. The battery system (300, 400) according to claim 5, wherein a number of taps is fixed or varied depending on the number of auxiliary loads (L1, L2, ...) and required voltage levels of the auxiliary loads (L1, L2, ...).
  7. The battery system (300, 400) according to claim 6, wherein locations to place the number of taps are fixed or varied depending on the required voltage levels of the auxiliary loads (L1, L2, ...).
  8. The battery system (300, 400) according to any one of claims 5-7, wherein the connections of the middle bus line, the positive bus line and the negative bust line to the battery module (410) are fixed or varied.
  9. The battery system (300, 400) according to claim 8, wherein the positive bus line (PL) is connected to the first terminal (T 1) of the battery module (410), the middle bus line (ML) is connected to any one of the two or more taps (TP1, TP2, ... TPn-1, TPn), and the negative bus line (NL) is connected to the second terminal (T2) of the battery module (410).
  10. The battery system (300, 400) according to claim 8, wherein the positive bus line (PL) is connected to any one of the taps (TP1, TP2, ... TPn-1) except the last tap (TPn), the negative bus line (NL) is connected to the second terminal (T2) or to any one of the taps (TP2, ... TPn) except the first tap (TP1) and the middle bus line ML is connected to any one of the two or more taps (TP1, TP2, ... TPn-1, TPn).
  11. The battery system (300, 400) according to any one of claims 5-7, wherein the battery system (400) comprises at least two middle bus lines (MI,1, ML2, ...), and wherein the positive bus line (PL) is connected to the first terminal (T1) of the battery module (410), the at least two middle bus lines (ML1, ML2, ...) are respectively connected to the two or more taps (TP1, TP2, ... TPn-1, TPn), and the negative bus line (NL) is connected to the second terminal (T2) of the battery module (410).
  12. A vehicle (600) comprises a battery system (300, 400) according to any one of the claims 1-11.
  13. A method (500) for distributing power from a battery system (300, 400) to at least two auxiliary loads (L1, L2, ...) comprising: configuring (510) the battery system (300, 400) to have a positive bus line (PL), a negative bus line (NL) and a middle bus line (ML); providing (520) a battery module (310, 410) having a first tap (TP1), a first terminal (T1) and a second terminal (T2); providing (521) a connection between the first tap (TP1) and the middle bus line (ML), a connection between the first terminal (T1) and the positive bus line (PL) and a connection between the second terminal (T2) and the negative bus line (NL); providing (530) a multilevel neutral point clamped, NPC, inverter (320) having a neutral terminal (N I ), an output terminal (Outi), a positive terminal (PT I ) and a negative terminal (NTi); providing (531) a connection between the neutral terminal (N I ) of the multilevel NPC inverter (320) and the first tap (TP 1) of the battery module (310, 410), a connection between the positive terminal (PT I ) of the multilevel NPC inverter (320) and the first terminal (T1) of the battery module (310, 410), and a connection between the negative terminal (NT I ) of the multilevel NPC inverter (320) and the second terminal (T2) of the battery module (310, 410); providing (540) connections to at least two auxiliary loads (L1, L2, ...) and to at least one direct current to direct current converter (DC/DC), such that the at least two auxiliary loads (L1, L2,...) and the at least one DC/DC converter are connected either between the positive and negative bus lines (PL, NL), or between the positive and middle bus lines (PL, ML), or between the negative and middle bus lines (NL, ML), directly or via respective switches (S1, S2...); and configuring (550) operation of the at least one DC/DC converter for at least one of balancing loads of the battery module (310, 410) and controlling charging/discharging of the battery module (310, 410).
  14. The method according to claim 13, wherein configuring (550) operation of the at least one DC/DC converter comprises adjusting (552) current flows in the at least one DC/DC converters, thereby regulating at least one of power flows to at least one low voltage systems and power flows to/from the battery module (310, 410).
  15. The method according to any one of claims 13-14, further comprising: providing (560) at least two battery packs in the battery module (410); and providing (570) at least two taps (TP1, TP2, ... TPn) placed at respective connection points between any two battery packs.

Description

TECHNICAL FIELD The disclosure relates generally to energy storage systems. In particular aspects, the disclosure relates to battery systems with distributed voltage levels. The disclosure can be applied to any electrical energy storage systems and vehicles using electrical energy storage system, such as heavy-duty vehicles, e.g. trucks, buses, and construction equipment, among other vehicle types. Although the disclosure may be described with respect to a particular vehicle, the disclosure is not restricted to any particular vehicle. BACKGROUND A battery energy storage system (BESS) is a system that stores energy in rechargeable batteries for later use. It's widely used in energy systems to provide backup power and stabilize energy supply. In a typical BESS, power conversion system comprising one or more power electronic stages, e.g. direct current to direct current (DC/DC) converters, direct current to alternating current (DC/AC) inverters, alternating current to direct current (AC/DC) inverters are used to handle bidirectional flow of power, allowing for both charging from a power system or energy sources, e.g. traditional grid, renewable energy sources, motors etc., to the BESS and discharging from the BESS to the power system. Fig.1 shows an example BESS 100 comprising a battery module 110 comprising a battery with a voltage level VDC and a DC link capacitor CDC, a 3-phase DC/AC inverter 120 and a 3-phase AC grid 130. The inverter 120 may operate with a high DC link voltage e.g. 1200V. A higher DC voltage level may reduce a cable cross section on the DC link side so that the cost is reduced if long cables are used for DC link. The inverter 120 is a two-level inverter topology which becomes costly at higher voltage levels. Multilevel Neutral Point Clamped (NPC) inverters are usually used in bidirectional AC/DC converters in electrical systems, particularly in applications such as motor drives in vehicles. NPC inverter is a type of multilevel power inverter known for its ability to produce high-quality output voltage with reduced total harmonic distortion and lower switching losses compared to conventional two-level inverters. Figs. 2 is a schematic block diagram showing an example NPC inverter which comprises a battery module with a neutral point N. The NPC inverter achieves these benefits through its unique topology, which includes multiple power semiconductor switches Sa1, Sa2, ...Sa6 implemented by e.g. Insulated Gate Bipolar Transistors (IGBTs) or Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs), arranged in such a way that they can generate several voltage levels across a load. To save cost and operate with a motor driving system, the NPC inverter needs to operate with high voltage levels. Auxiliary components or loads e.g. fans, heat pumps, compressors etc. in a vehicle may operate with different voltage levels than the high voltage level for the motor driving system. Having different battery packs with different voltage levels for different auxiliary components may not be practical regarding cost and efficiency. A cost-effective solution on the entire system level is needed. SUMMARY According to a first aspect of the disclosure, a battery system having a positive bus line, a negative bus line and a middle bus line is provided. The battery system comprises a battery module having a first tap, a first terminal and a second terminal. The first tap is connected to the middle bus line, the first terminal is connected to the positive bus line and the second terminal is connected to the negative bus line. The battery system further comprises a multilevel NPC inverter having a neutral terminal, an output terminal, a positive terminal and a negative terminal. The neutral terminal of the multilevel NPC inverter is connected to the first tap of the battery module, and the positive and negative terminals of the multilevel NPC inverter are connected to the first and second terminals of the battery module respectively. The battery system further comprises at least direct current to direct current converter (DC/DC) connected either between the positive and negative bus lines, or between the positive and middle bus lines, or between the negative and middle bus lines. The operation of at least one DC/DC converter is configurable for at least one of balancing loads of the battery module and controlling charging/discharging of the battery module. The at least two auxiliary loads are connected either between the positive and negative bus lines, or between the positive and middle bus lines, or between the negative and middle bus lines, directly or via respective switches. The first aspect of the disclosure may seek to provide a battery system which can provide different voltage supplies for auxiliary loads. A technical benefit may include providing different voltage levels for auxiliary components by making the midpoint of the battery system accessible for the auxiliary components, active balancing or pro