Mild hybrid energy storage system architecture and method for controlling an engine

Abstract

The present invention relates to a mild hybrid energy storage system architecture and a method for controlling an engine. The mild hybrid energy storage system architecture comprises a battery, a supercapacitor connected in parallel with the battery, a passive battery pre-charge circuit connected between terminals of the battery and a DC bus, a battery main contactor connected in parallel with the battery pre-charge circuit between the terminals of the battery and the DC bus, a passive supercapacitor pre-charge circuit connected between terminals of the supercapacitor and the DC bus, a supercapacitor main contactor connected in parallel with the supercapacitor pre-charge circuit between the terminals of the supercapacitor and the DC bus, and a control module configured to independently control operation of the battery pre-charge circuit, the battery main contactor, the supercapacitor pre-charge circuit and the supercapacitor main contactor.

Description

[0001] This application is a divisional application of the invention patent application filed on January 23, 2020, with application number 202080024466.9 (international application number PCT / US2020 / 014736) and titled "Battery-Supercapacitor Hybrid Energy Storage System Architecture for Mild Hybrid Power Systems". Technical Field

[0002] This disclosure generally relates to hybrid energy storage system architectures, and more specifically, to a HESS architecture for mild hybrid powertrain applications, which employs dedicated pre-charge circuitry and main contactors for batteries and supercapacitors. Background Technology

[0003] Low-voltage (e.g., 48 volts) mild hybrid systems are of interest to commercial vehicles because they offer a relatively low cost and provide a reasonable level of fuel savings, resulting in an attractive return on investment. Some mild hybrid systems employ a hybrid energy storage system (“HESS”) that includes a battery and a supercapacitor (“UC”). A UC, sometimes referred to as a supercapacitor, is a high-capacity capacitor with a lower voltage limit, filling the gap between an electrolytic capacitor and a rechargeable battery. Such a UC reduces the load on the battery in a HESS by absorbing rapid voltage and / or current transients and releasing power very quickly (but at a low energy output compared to batteries, which typically have an order of magnitude greater energy storage capacity). The UC essentially smooths the battery's cycle transition, thus improving its thermal behavior and lifespan. A UC can reliably support engine starting functions but cannot on its own support mild hybrid functions with a target level of regenerative energy recovery. Energy storage systems that include batteries such as lithium-ion batteries are required to realize the value of mild hybrid systems.

[0004] Interest in utilizing 48V engine starter motors and the perceived risk of relying entirely on lithium-ion batteries for engine starting have led some manufacturers to add UC (Unified Cell Controller), thus configuring HESS (Heated Safe Energy System). The interconnection between the battery and UC introduces cost and functional trade-offs and can be optimized based on application scenarios and design requirements. To date, powertrain systems employing HESS have either limited operational flexibility to a level insufficient for medium or heavy-duty commercial vehicle applications or required additional components, increasing the cost and complexity of HESS to meet desired operational requirements. Therefore, a low-cost, highly reliable, and high-performance HESS architecture is needed for applications such as mild hybrid applications in commercial vehicles. Summary of the Invention

[0005] According to one embodiment, this disclosure provides a mild hybrid energy storage system architecture, the mild hybrid energy storage system architecture comprising: a battery; a supercapacitor connected in parallel with the battery; a passive battery precharge circuit connected between terminals of the battery and a DC bus; a battery main contactor connected in parallel with the battery precharge circuit between terminals of the battery and the DC bus; a passive supercapacitor precharge circuit connected between terminals of the supercapacitor and the DC bus; a supercapacitor main contactor connected in parallel with the supercapacitor precharge circuit between terminals of the supercapacitor and the DC bus; and a control module configured to independently control the operation of the battery precharge circuit, the battery main contactor, the supercapacitor precharge circuit, and the supercapacitor main contactor. In one aspect of this embodiment, the battery includes at least one lithium-ion battery. In another aspect, the passive battery precharge circuit includes a resistor connected between terminals of the battery and an input terminal of a precharge switch, the output terminal of the precharge switch being connected to the DC bus. In another aspect, the passive supercapacitor pre-charge circuit includes a resistor connected between a terminal of the supercapacitor and an input terminal of a pre-charge switch, the output terminal of which is connected to the DC bus. In another aspect of this embodiment, the battery terminal is a positive terminal and the supercapacitor terminal is a positive terminal. A first voltage sensor is also included, configured to provide a supercapacitor voltage measurement to the control module. A variation of this aspect further includes a second voltage sensor configured to provide a DC bus voltage measurement to the control module. Another variation includes a third voltage sensor configured to provide a battery voltage measurement to the control module. In another aspect of this embodiment, the control module is further configured to: respond to an approximate zero voltage in the supercapacitor by closing the battery pre-charge switch of the passive battery pre-charge circuit to pre-charge the DC bus; after pre-charging the DC bus, activate the engine starter to start the engine; and after activating the engine starter, close the supercapacitor pre-charge switch of the passive supercapacitor pre-charge circuit to charge the supercapacitor. In a variation of this embodiment, the control module is further configured to: shut down the engine; and after shutting down the engine, open the supercapacitor precharge switch and the supercapacitor main contactor to isolate the supercapacitor. In another variation, the control module is further configured to: respond to a voltage exceeding a predetermined threshold voltage by closing the supercapacitor precharge switch and the supercapacitor main contactor, followed by closing the battery precharge switch.In yet another variation, the control module is further configured to respond to a voltage exceeding a predetermined threshold voltage by closing the supercapacitor precharge switch, closing the supercapacitor main contactor, and closing the battery precharge switch approximately simultaneously.

[0006] In another embodiment, this disclosure provides a method for controlling an engine in a mild hybrid system, the method comprising: sensing a voltage of a supercapacitor; pre-charging the DC bus by closing a battery pre-charge switch of a passive battery pre-charge circuit connected between terminals of a battery and a DC bus, responding to a voltage approximately zero, wherein the DC bus is connected to an engine starter; after pre-charging the DC bus, starting the engine starter to start the engine; and after starting the engine starter, closing a supercapacitor pre-charge switch of the passive supercapacitor pre-charge circuit connected between terminals of the supercapacitor and the DC bus to charge the supercapacitor. One aspect of this embodiment further includes: shutting off the engine; and after shutting off the engine, opening the supercapacitor pre-charge switch and a main contactor connected in parallel with the passive supercapacitor pre-charge circuit to isolate the supercapacitor. Another aspect further includes: responding to a voltage higher than a predetermined threshold voltage by closing the supercapacitor pre-charge switch and the main contactor connected in parallel with the passive supercapacitor pre-charge circuit, and then closing the battery pre-charge switch. Another aspect includes responding to a voltage higher than a predetermined threshold voltage by closing the supercapacitor precharge switch, closing the main contactor connected in parallel with the passive supercapacitor precharge circuit, and closing the battery precharge switch approximately simultaneously. Attached Figure Description

[0007] The above-mentioned and other features and advantages of this disclosure, and their implementations, will become clearer and the invention itself will be better understood by referring to the following description of embodiments of the invention in conjunction with the accompanying drawings, wherein:

[0008] Figure 1 This is a schematic diagram of the existing HESS architecture;

[0009] Figure 2 This is a schematic diagram of the HESS architecture, another existing technology;

[0010] Figure 3 This is a schematic diagram of the HESS architecture, another existing technology;

[0011] Figure 4 This is a schematic diagram of the HESS architecture, another existing technology;

[0012] Figure 5 This is a schematic diagram of a HESS architecture according to one embodiment of the present disclosure; and

[0013] Figure 6 This is a table that illustrates comparisons of various HESS architectures relative to certain performance attributes.

[0014] Throughout the various views, corresponding reference numerals indicate the corresponding parts. The examples set forth herein illustrate exemplary embodiments of this disclosure, and such examples are not to be construed as limiting the scope of this disclosure in any way. Detailed Implementation

[0015] For the purpose of promoting an understanding of the principles of this disclosure, reference is now made to the embodiments illustrated in the accompanying drawings described below. The exemplary embodiments disclosed herein are not intended to be exclusive or to limit this disclosure to the precise forms disclosed in the following detailed description. Rather, these exemplary embodiments were chosen and described so that others skilled in the art may utilize their teachings.

[0016] The terms “connected,” “connected,” and variations thereof are used to refer to arrangements in which two or more components are in direct physical contact with each other, as well as arrangements in which two or more components are not in direct contact with each other (e.g., components are “connected” via at least a third component), but still cooperate or interact with each other. Furthermore, the terms “connected,” “connected,” and variations thereof refer to any connection known in the art for machine parts, including but not limited to connections made with bolts, screws, threads, magnets, electromagnets, adhesives, friction clips, welds, snap-fits, clamps, etc.

[0017] Throughout this disclosure and claims, references to various components or features are made using numerical terms such as "first" and "second". Such use is not intended to indicate an order of components or features. Rather, the use of numerical terms is to assist the reader in identifying the referenced components or features and should not be interpreted narrowly as providing a specific order of components or features.

[0018] Those skilled in the art will recognize that the provided implementations can be implemented in hardware, software, firmware, and / or a combination thereof. The programming code according to the implementations can be implemented in any feasible programming language such as C, C++, HTML, XTML, JAVA, or any other feasible high-level programming language or a combination of high-level and low-level programming languages.

[0019] Now refer to Figure 1This illustrates a prior art passive HESS architecture 10. Architecture 10 is an example of certain architectures used in the telecommunications industry, featuring a direct parallel combination of a UC (Unified Voltage Regulator) and a battery such as a lithium-ion battery. Generally, architecture 10 includes a battery 12 connected in parallel with a series-connected carbon-carbon UC 14. The parallel combination is connected to a buck-boost converter 16, which outputs the DC bus voltage to a motor driver 18 connected to a motor 20. In this example, the UC 14 (when properly sized) supplies the majority of the burst power required during transmission (due to its very low equivalent series resistance), while the battery 12 provides virtually all the backup and stored power. No pre-charge circuitry is used in architecture 10 because it utilizes the buck-boost converter 16. Therefore, architecture 10 is relatively complex and expensive.

[0020] Figure 2 An active parallel connection HESS architecture 22 is depicted, comprising a UC group 24, a lithium-ion battery pack 26, and a buck-boost converter 28, all communicating with a monitoring module (“SCM”) 30. Similarly, the use of a buck-boost converter leads to increased complexity and cost. Figure 3 Another prior art HESS architecture 32 configured as a bidirectional DC / DC converter is depicted, which has a battery 34 connected to a first buck-boost converter 36, a plurality of UCs 38 connected between the first buck-boost converter 36 and a second buck-boost converter 40, the output of the second buck-boost converter 40 being connected to a motor driver 42 driving a motor 44. Figure 4 The prior art HESS architecture 46, configured as a bidirectional DC / DC converter, is also depicted, having a battery 48 connected to a first converter 50 and multiple UCs 52 connected to a second converter 54. The positive and negative terminals of converters 50 and 54 are connected together to form a DC bus provided to a motor driver 56 for a drive motor 58. Figure 3 and Figure 4 The configuration is also relatively complex and expensive.

[0021] Now refer to Figure 5This illustration shows a hybrid energy storage system (“HESS”) architecture for mild hybrid powertrain applications according to this disclosure. Architecture 100 generally includes a battery 102, a supercapacitor (“UC”) 104, a DC / DC converter 106, a low-voltage battery 108, a starter 110, a battery management system (“BMS”) 112, and a monitoring module (“SCM”) 114. Since some functions of the BMS 112 and SCM 114 can be performed by either or both of these components, the device may be simply referred to as the “control module”. Architecture 100 also includes a main contactor 116 connected to the positive terminal of the battery 102 and a pre-charge circuit 118 connected in parallel across the main contactor 116. Similarly, a main contactor 120 is connected to the positive terminal of the UC 104, and a pre-charge circuit 122 is connected in parallel across the main contactor 120. Precharge circuit 118 includes resistor 124, one side of which is connected to the positive terminal of battery 102 and the other side to the input of precharge switch 126. The output of precharge switch 126 is connected to the output of main contactor 116, both of which are connected to the positive terminal 128 of the DC bus. Similarly, precharge circuit 122 includes resistor 130, one side of which is connected to the positive terminal of UC 104 and the other side to the input of precharge switch 132. The output of precharge switch 132 is connected to the output of main contactor 120, both of which are connected to the positive terminal 128 of the DC bus. The negative terminals of battery 102 and UC 104 are connected to the negative terminal 134 of the DC bus. As shown, DC / DC converter 106 is connected between the positive terminal 128 and the negative terminal 134 and is configured to provide low-voltage (e.g., 12 volts) power to battery 108. Similarly, starter 110 is connected between positive terminal 128 and negative terminal 134. Positive terminal 128 and negative terminal 134 are then connected to various loads powered by architecture 100.

[0022] Voltage sensor 136 is depicted as being connected to the positive terminal of battery 102. Voltage sensor 136 can be implemented in any of various configurations to measure the voltage of battery 102. Voltage sensor 136 provides the battery voltage measurement to BMS 112. BMS 112 then provides the battery voltage measurement to SCM 114. Similarly, voltage sensor 138 is depicted as being connected to the positive terminal of UC 104. Voltage sensor 138 can also be implemented in any of various configurations to measure the voltage of UC 104. Voltage sensor 138 provides the UC voltage measurement to SCM 114. Another voltage sensor 140 is depicted as being connected to the positive terminal 128 of the DC bus. Voltage sensor 140 can also be implemented in any of various configurations to measure the voltage at the positive terminal 128. Voltage sensor 140 provides the DC bus voltage measurement to SCM 114. As further described herein, SCM 114 is connected to main contactor 116, precharge circuit 118, main contactor 120, and precharge circuit 122, as follows: Figure 5 As indicated by the dashed lines in the diagram. Overall, the SCM 114 uses voltage measurements from voltage sensors 136, 138, and 140 to control the operation of the main contactor 116, the pre-charge circuit 118, the main contactor 120, and the pre-charge circuit 122.

[0023] It should be understood that some supercapacitors may include internal voltage sensors and communication circuitry. If such a supercapacitor is used as UC 104, then voltage sensor 138 would be unnecessary and can be omitted. Additionally, in some embodiments, voltage sensor 140 can be omitted, and alternatively, such as DC / DC converter 106, battery 108, or another power converter / inverter can be used. Figure 5 The voltage sensor already present in the SCM 114 (not shown). Furthermore, the supercapacitor pre-charge function can be implemented externally to the SCM 114 within a local controller that communicates with the SCM 114 at the monitoring level (e.g., in response to connection / disconnect commands and reporting status).

[0024] It should be understood that, in alternative implementations, UC 104 may be directly connected to the positive terminal 128 of the DC bus (i.e., the main contactor 120 and pre-charge circuit 122 would be omitted). However, in such an implementation, it would be necessary to wait for pre-charging of UC 104 by battery 102, which occurs, for example, during engine start-up. With UC 104 at or near 0 volts during start-up, pre-charging by battery 102 can take several minutes (e.g., 20 to 30 minutes). This delay during engine start-up is inconsistent with design considerations taken into account during the development of architecture 100. Architecture 100 is designed to provide DC bus pre-charging and engine start-up functionality within seconds, not minutes.

[0025] In operation, the SCM 114 of architecture 100 is configured to independently control the precharge circuits 118, 122 and the main contactors 116, 120 to achieve the desired performance. For example, when the engine is started and UC 104 is at or near 0 volts (as indicated by the UC voltage measurement provided to SCM 114 by voltage sensor 138), SCM 114 can close only the precharge switch 126 (disconnecting UC 104 from the DC bus) or close both precharge switches 126 and 132. In this way, the battery 102 can quickly charge the DC bus while delaying the precharge of UC 104, which may take longer. Therefore, all loads connected to the DC bus, including starter 110, can be used quickly (e.g., within 1 or 2 seconds). It should be understood that if the pre-charge circuit 122 and the main contactor 120 are not present, a significant delay will be required before any capacitive load connected in parallel with UC 104 can be operated. This delay will correspond to the time required for UC 104 to charge. SCM 114 can be programmed with voltage thresholds to determine when to close and open the pre-charge switches 126, 132 and the main contactors 116, 120.

[0026] It should also be understood from the preceding information that when the engine is off, UC 104 and the DC bus can maintain a non-zero voltage. The DC bus does not need to be de-energized (and therefore no such circuitry is required) because the mild hybrid system is a relatively low-voltage system (e.g., 48 volts), and there are no high-voltage safety concerns. For safety reasons, the battery 102 can be simply disconnected by opening the main contactor 116 via BMS 112 or SCM 114. When the engine is commanded to start, BMS 112 or SCM 114 can sense the voltage of UC 104 using sensor 138 or otherwise, and if the sensed voltage is higher than a predetermined threshold voltage (e.g., 43 volts), BMS 112 or SCM 114 can close the main contactor 116, and the DC bus can quickly reach the desired operating voltage because UC 104 maintains a higher non-zero voltage on the DC bus during engine shutdown.

[0027] Architecture 100 is also configured to address voltage leakage of UC 104 over time. It is known that if UC 104 remains connected to the DC bus for an extended period, the voltage of UC 104 will slowly decrease due to leakage. Therefore, architecture 100 permits SCM 114 to isolate UC 104 by opening switch 132 and main contactor 120 when the engine is off, thereby maintaining the operating voltage of UC 104 for a further extended period. Upon the next engine start, SCM 114 can connect UC 104 to the DC bus (by closing precharge switch 132 followed by main contactor 120) before or simultaneously with connecting battery 102 to the DC bus. Alternatively, battery 102 can be connected to the DC bus first to ensure that all precharge current is provided to the DC bus, thereby enabling rapid use of starter 110 instead of using some of the precharge current for charging UC 104. In this scenario, SCM 114 will keep UC 104 disconnected to utilize the high power supplied by battery 102 to support engine starting. However, it should be understood that under cold start conditions, because the starting current provided by a lithium-ion battery such as battery 102 may be insufficient in very cold weather, SCM 114 may need to connect both battery 102 and UC 104 during startup. In any case, the DC bus pre-charging process supported by architecture 100 is faster compared to alternative systems.

[0028] Figure 6 A table comparing various architectures in terms of many attributes or functional requirements is provided. The first column lists the attribute or functional requirements. The second column shows, for example,... Figure 5 The rating of architecture 100 described in this disclosure is shown. The remainder lists the ratings of various other prior art architectures. As illustrated, with, for example... Figures 1 to 4 Compared to higher-cost active HESS architectures like the one described in the paper, Architecture 100's cost is moderate. While battery-only energy storage systems are low-cost, such systems are unsuitable for mild hybrid applications in commercial vehicles. Architecture 100 has a low rating in assembly and control complexity compared to other architectures (except for battery-only systems). The architecture also provides the ability to isolate the UC104 to reduce leakage and eliminates the need for UC104 pre-charging, as described in this paper. Other architectures offer this feature, but at a higher cost, higher complexity, or both. Architecture 100 also provides very fast DC bus pre-charging and high reliability for engine starting, partly due to the ability to isolate the UC104.

[0029] As should be clear from the foregoing, the architecture 100 according to this disclosure is designed to provide a low component count, partly because a dedicated DC bus discharge circuit is no longer required, resulting in low cost and high reliability. Instead of a dedicated discharge circuit (e.g., a resistor), embodiments of this disclosure utilize the active discharge mechanism supported by the power inverter and DC / DC converter, which are already part of the overall mild hybrid system.

[0030] While the invention has been described as having an exemplary design, further modifications can be made to the invention within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or alterations of the invention using its general principles. Furthermore, this application is intended to cover these deviations from the scope of this disclosure and from known practices or customs falling within the limitations of the appended claims.

[0031] Furthermore, the connecting lines shown in the various figures included herein are intended to represent exemplary functional relationships and / or physical connections between various elements. It should be noted that many alternative or additional functional relationships or physical connections may exist in a real system. However, any benefit, advantage, solution to a problem, and any element that causes any benefit, advantage, or solution to occur or become more significant shall not be construed as a critical, necessary, or essential feature or element. Therefore, the scope is limited only by the appended claims, wherein references to elements in the singular form are not intended to mean "one and only one," but rather "one or more" unless expressly stated otherwise.

[0032] Furthermore, when phrases such as "at least one of A, B or C" are used in the claims, it is intended that the phrase be interpreted as meaning that in an embodiment A may be present alone, in an embodiment B may be present alone, in an embodiment C may be present alone, or in a single embodiment any combination of elements A, B or C may be present; for example, A and B, A and C, B and C or A and B and C.

[0033] Systems, methods, and apparatuses are provided herein. In the specific embodiments described herein, references to “one embodiment,” “implementation,” “exemplary embodiment,” etc., indicate that the described embodiment may include a particular feature, structure, or characteristic, but each embodiment may not necessarily include that particular feature, structure, or characteristic. Furthermore, these phrases do not necessarily refer to the same embodiment. Additionally, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is proposed that such a feature, structure, or characteristic, when combined with other embodiments (whether explicitly described or not), is beneficial to this disclosure and can be implemented within the common knowledge of those skilled in the art. Those skilled in the art will understand how this disclosure can be implemented in alternative embodiments after reading this specification.

[0034] Furthermore, regardless of whether an element, component, or method step in this disclosure is expressly recited in the claims, such element, component, or method step is not intended to be made public. No element of any claim herein should be construed in accordance with 35 U.S.SC §112(f) unless the element is expressly recited using the phrase “means for…”. As used herein, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusions, such that a process, method, article, or apparatus that comprises a list of elements does not necessarily include only those elements, but may include other elements not expressly listed or inherent to the process, method, article, or apparatus.

Claims

1. A mild hybrid energy storage system architecture, the mild hybrid energy storage system architecture comprising: Battery; A supercapacitor, which is connected in parallel with the battery; A battery main contactor, which is connected to the terminals of the battery; A passive battery pre-charging circuit is connected in parallel across the two ends of the battery main contactor; The supercapacitor main contactor is connected to the terminals of the supercapacitor; A passive supercapacitor pre-charge circuit is connected in parallel to the supercapacitor's main contactor; as well as The control module is configured as follows: The engine starting function is provided by commanding the battery to delay the pre-charging of the supercapacitor; as well as The supercapacitor is isolated by opening both the supercapacitor precharge switch of the passive supercapacitor precharge circuit and the supercapacitor main contactor when the engine is off.

2. The lightweight hybrid energy storage system architecture according to claim 1, wherein, When the engine is off, the supercapacitor maintains a non-zero voltage.

3. The lightweight hybrid energy storage system architecture according to claim 1, wherein, The passive battery pre-charge circuit includes a resistor connected between the terminals of the battery and the input terminal of the pre-charge switch, the output terminal of the pre-charge switch being connected to a DC bus.

4. The lightweight hybrid energy storage system architecture according to claim 1, wherein, The passive supercapacitor pre-charge circuit includes a resistor connected between the terminals of the supercapacitor and the input terminal of the supercapacitor pre-charge switch, the output terminal of the supercapacitor pre-charge switch being connected to a DC bus.

5. The lightweight hybrid energy storage system architecture according to claim 1, wherein, The terminal of the battery is the positive terminal of the battery, and the terminal of the supercapacitor is the positive terminal of the supercapacitor.

6. The mild hybrid energy storage system architecture according to claim 1, wherein the mild hybrid energy storage system architecture further comprises a first voltage sensor configured to provide a supercapacitor voltage measurement value to the control module.

7. The mild hybrid energy storage system architecture according to claim 6, wherein the mild hybrid energy storage system architecture further comprises at least one of the following: A second voltage sensor, configured to provide a DC bus voltage measurement value to the control module; and A third voltage sensor is configured to provide battery voltage measurements to the control module.

8. The lightweight hybrid energy storage system architecture according to claim 1, wherein, The control module is also configured to: The battery precharge switch of the passive battery precharge circuit is closed to respond to the voltage of the supercapacitor being approximately zero. Start the engine by activating the engine starter; as well as Close the supercapacitor pre-charge switch of the passive supercapacitor pre-charge circuit to charge the supercapacitor.

9. The mild hybrid energy storage system architecture according to claim 8, wherein, The control module is also configured to perform at least one of the following: The shutdown operation involves turning off the engine and, after turning off the engine, opening the supercapacitor precharge switch and the supercapacitor main contactor to isolate the supercapacitor. A first overvoltage operation, wherein the control module responds to the voltage exceeding a predetermined threshold voltage by closing the supercapacitor precharge switch and the supercapacitor main contactor, and then closing the battery precharge switch; and The second overvoltage operation involves the control module responding to a voltage exceeding a predetermined threshold voltage by closing the supercapacitor precharge switch, closing the supercapacitor main contactor, and approximately simultaneously closing the battery precharge switch.

10. A method for controlling an engine using a control module based on a mild hybrid energy storage system architecture according to any one of claims 1 to 9.

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