Multi-module electric vehicle battery control system

Abstract

Disclosed are systems and methods for operating a multi-battery module power system that enable safe and efficient operation with multiple batteries having different characteristics, including controlling and connecting the batteries for unidirectional or bidirectional current and power flow to a load, such as a bus or a DC motor. In one embodiment, the system has multi-layer controls that can controllably switch operation of the system, or portions thereof, between multiple (e.g., four) operating quadrants defined by voltage-current characteristics.

Description

[Technical field]

[0001] This application relates to the design and operation of electric battery systems such as those found in electric vehicles. [Background technology]

[0002] There is a need for practical and safe electric battery systems. It is usually not possible or practical to connect multiple batteries of different ratings, chemistries, ages, or other configuration differences in parallel. Batteries of different nature, composition, or usage history may have different internal impedances and voltage outputs. In one aspect, operating multiple but different batteries together, e.g., in parallel, may result in undesirable electrical surges that may cause degradation or damage to the battery itself and / or the load and other connected components. There is also a need for improved battery control for electric vehicles, whether the vehicles are land, sea, air, or space based. Summary of the Invention

[0003] Although the exemplary embodiments described herein have novel features, no single feature is essential or solely responsible for the desired properties. The following description and drawings are intended to describe in detail certain specific implementations of the present disclosure, and to provide some exemplary means for implementing various principles of the present disclosure. However, such specific examples are not exhaustive of the many possible embodiments of the present disclosure. Without limiting the scope of the claims, some of the advantageous features are summarized below. Other objects, advantages, and novel features of the present disclosure are described in the following detailed description of the present disclosure with reference to the drawings, which are intended to specifically illustrate the present invention, but are not intended to limit the present invention.

[0004] One embodiment is a system for powering an electric motor from a battery unit having a plurality of battery module units, each having a battery module and a battery module controller circuit, the plurality of battery module units, and an electrical bus connected to the electric motor, each of the battery module controller circuits having a first side of the battery module controller circuit electrically connected to a respective battery module at a respective battery module voltage Vbatt, and a second side of the battery module controller circuit electrically connected to the electrical bus at a bus voltage Vbus by a bus side connection, and a plurality of battery module controller circuits. and at least one switch in the battery module controller circuit that switches between switching states of its respective battery module controller circuit, wherein each battery module operates in a plurality of operating modes according to the switching state of its respective battery module controller circuit, the operating modes including a first state in which the difference (Vbus-Vbatt) is greater than zero and the bus current is greater than zero, a second state in which the difference (Vbus-Vbatt) is greater than zero but the bus current is less than zero, a third state in which the difference (Vbus-Vbatt) is less than zero and the bus current is less than zero, and a fourth state in which the difference (Vbus-Vbatt) is less than zero but the bus current is greater than zero. [Brief description of the drawings]

[0005] For a fuller understanding of the nature and advantages of the present concepts, reference is made to the detailed description of the preferred embodiment and the accompanying drawings. [Figure 1] FIG. 1 shows a simplified arrangement of multiple battery modules in a system according to an embodiment of the invention. [Diagram 2] FIG. 2 illustrates a four-state or four-quadrant operating space, showing four respective operating conditions or sets of states. [Diagram 3]FIG. 3 shows the main components of an exemplary battery module controller circuit and bidirectional buck-boost converter. [Figure 4] Figure 4 shows the equivalent circuit of the controller when operating in quadrant Q1 or Q2. [Diagram 5] Figure 5 shows the equivalent circuit of the controller when operating in quadrant Q3 or Q4. [Figure 6] FIG. 6 illustrates an embodiment of a battery module controller circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] FIG. 1 illustrates a basic arrangement of multiple battery modules in a system 10 according to an embodiment of the present invention. The battery assembly 100 includes multiple (n) battery module units 102a...102n (generally 102). Each battery module unit 102 includes one or more battery modules 104a...104n (generally 104) that may have multiple battery cells therein, and a respective battery module controller circuit 106a...106n (generally 106), which are described in more detail below. Generally, the multiple modules referred to herein may have reference numbers (e.g., 102, 104, 106, etc.), which are understood to correspond to the individual instance set of numbers referenced for each module in the multiple module system without loss of generality (thus, 102 may correspond to one or more of 102a, 102b,...102n), and such description applies to any or all of such elements. Thus, the accompanying drawings may show an example (eg, 102a or 102n) but this is not intended to be limiting or excluding references to other similarly numbered reference elements.

[0007] The battery assembly 100 is typically used to store electrical energy and / or provide power to electrical loads 110 on demand. For example, the electrical loads may include one or more electric motors, such as a DC motor for propelling an electric vehicle, or they may include domestic loads, such as lighting, communication, and comfort loads in a vehicle with a DC power bus requirement. The system can be used to power alternating current (AC) loads, such as AC motors, by providing bus power through a DC to AC converter to drive the AC load or AC motor.

[0008] The load controller 112 may include a power regulator, a transformer, and / or a converter that can be used to put the bus voltage Vbus into a usable form for driving the load or motor 114. In some examples, the power regulator can include a DC to AC converter, for example if the motor 114 is an AC motor.

[0009] The master controller 130 is disposed in a layer above the battery module controller circuits 106 and the load controllers 112. The master controller 130 is connected to each of the other controllers via a control bus 131, which electrically connects these control units to each other and allows them to exchange control signals between them. The master controller 130 may have electric and / or electronic circuits, including programmable units, one or more processors, and circuits configured and arranged to execute machine-readable instructions for managing and controlling the overall operation of the system 10 and the battery assembly 100 or the battery module controller 106. The master controller 130 may be connected to other components of the system 10 within the battery assembly 100 or external systems and components via a CAN bus. The master controller 130 may programmatically set a power limit (e.g., kilowatts, etc.) for the power provided by the battery assembly 100 or a given battery module unit 102. In one embodiment, the master controller 130 can communicate via the CAN bus with external diagnostic or monitoring systems and computers through communication ports or connections to ascertain the operational and performance or service status of the system 10, upload updated instruction sets, and control the system 10.

[0010] The architecture, as described, is useful for powering and controlling electric vehicles, such as electric cars, buses, trucks, trains, and delivery vehicles, drones, and other watercraft. In particular, the systems and methods can be adapted to control power supply to and from a multi-cell battery unit having multiple replaceable battery modules, such that one or more battery modules can be physically removed from a vehicle without removing other battery modules from the vehicle, e.g., the removed modules can be charged or serviced outside the vehicle body. Thus, the systems and methods can maintain and control battery modules in a vehicle in conjunction with an architecture for servicing the battery modules when they are removed from the vehicle. Thus, in optional embodiments, a communication bus, optionally including a wide area network communication connection, can be established to control and program and / or facilitate the features described herein. In optional aspects, the service station 11 or a data-connected server controller establishes a data communication path 12 (including wireless between two compatible communication transceivers) to manage, monitor, and control the operation of some or all of the on-board master controller 130.

[0011] Each battery module unit 102 can be described by a battery voltage Vbatt_i, which defines the electromotive force obtained from its (i_th) battery module 104. In one embodiment, the voltages Vbatt_i of multiple battery module units 102 can be the same or similar, but according to the present invention, the managed system allows and supports different BM voltage levels while operating multiple BMs 104 in parallel with each other as described herein. In another embodiment, under the present system and method, V_batt may be equal to the DC bus voltage Vbus 120, but is not necessarily equal to it. In this embodiment, Vbatt_i is the terminal voltage of the battery module i, which is typically the voltage potential of the connection port of the BM controller 106. The controller 106i can be considered as a layer that separates each i_th battery from the DC bus 120.

[0012] The design of the system considers both energy storage and power delivery performance. Thus, each battery module controller 106 of each battery module unit 102 can control its individual performance within the context of the master controller 130's settings, including controlling the individual battery module bus current Ibus_i of the (i_th) module, which can be positive or negative, for example, depending on whether a given battery module 104 is in a discharge or charge mode of operation. In general, power (P) is proportional to the product of the system voltage and current in a DC system. If the battery and DC bus powers are represented as Pbatt and Pbus, these are generally obtained using Vbatt*Ibatt or Vbus*Ibus in current notation. The system 10 can include its controller and / or the master controller 130 and can be used to control the battery module current Ibatt_i of each (i_th) battery module.

[0013] Aspects of the present battery module (BM) control layer include voltage control, where the system and method manages the voltage difference between the system battery module and the load or vehicle powertrain voltage, and current control, where the system and method manages bidirectional current flow to allow sufficient current flow along the various circuit paths of the system. As shown in FIG. 2, a four-quadrant scheme 20 showing each of four operating settings, conditions, modes, or states can be defined for voltage and current modes of operation according to those states. The difference between the bus voltage and the battery voltage (Vbus-Vbatt) is defined on the vertical axis 22. The DC current flowing into or out of the main system bus is defined on the horizontal axis 24 and can be positive or negative depending on the direction of the bidirectional flow, for example when charging or discharging the battery. Thus, when Ibus>0 and Vbus-Vbatt>0, a first (I) operating quadrant 202 is identified, when Ibus<0 and Vbus-Vbatt>0, a second (II) operating quadrant 204 is identified, when Ibus<0 and Vbus-Vbatt<0, a third (III) operating quadrant 206 is identified, and when Ibus>0 and Vbus-Vbatt<0, a fourth (IV) operating quadrant 208 is identified.

[0014] The bus current Ibus is the sum of the contributions from each battery module, e.g., Ibus_a+Ibus_b+...+Ibus_n. The total current (Ibus) from the battery to the load can be greater than or less than zero, depending on the net current and its direction. The battery system is a DC system, and the DB system allows bidirectional current movement within the system depending on its mode of operation. For example, current can be defined as "positive" flow in one mode of operation (charging or discharging), or "negative" flow (discharging or charging, respectively). Thus, the examples provided herein are illustrative, and rules regarding current flow can be based on positive or negative charge flow, as desired in a given application. Either rule is within the scope of this disclosure.

[0015] In one embodiment, each battery module controller circuit 106i operates in one of four operating modes (or operating quadrants) as described below and shares a common parameter, the bus voltage Vbus. The operating quadrants are an aspect of the battery module control layer in one embodiment of the present invention. The operating modes and operating quadrants can be set for one or more battery modules to controllably deplete / use all battery modules simultaneously or at the same rate, deplete some battery modules before others, or perform a combination of the two aforementioned operations. Thus, the present invention, in some embodiments, allows for decoupling a battery module from the powertrain of an electric vehicle and / or from other battery modules in the battery assembly and system. This can provide a powerful smart battery architecture for any electric vehicle, including a variety of electric cars, trucks, and other battery-powered vehicles.

[0016] Generally, when in battery charging mode, the system will charge the battery modules by operating in either the second or third quadrant of operation (204, 206). Generally, when in discharge mode, the system will discharge the battery modules by operating in either the first or fourth quadrant of operation (202, 208). Switching between operating states and quadrants is described below.

[0017] Operationally, a pulse width modulator and pulse width modulation scheme can be used to drive the operating modes of the system between the four operating quadrants as previously described. The duty cycle of the switch elements of the control circuit can be used to achieve this switching according to the target operating state as dictated by the master controller 130. For the switch elements, the present invention can use transistors, diodes, or other voltage and / or current controlled semiconductor devices that function as gates or switch components. Other alternative or equivalent elements can be substituted by those skilled in the art without loss of generality, given the disclosure herein.

[0018] FIG. 3 shows an example circuit 30 and major components of a bidirectional converter for controlling a multi-module battery system that may include battery modules of different architectures, chemistries, states of charge, and electrical / chemical states. In one example, the converter may have a buck-boost converter that may have a control circuit characterized by a half-bridge on the battery side 32 characterized by a battery voltage (Vatt), an inductor (L), and a second half-bridge on the bus side 34 characterized by a bus voltage (Vbus). The inductor L maintains a current by storing energy in its magnetic field. The capacitors, e.g., C1, C2, maintain a voltage by storing energy in the electric field between their respective plates. The current flowing into and out of the battery system is labeled Ibatt, and the current flowing into and out of the bus is labeled Ibus. The voltage and current values ​​throughout the circuit 30 follow conventional rules for voltage and current summation (e.g., Kirchhoff's current law at any given circuit node) and principles of power flow in capacitors and inductors.

[0019] The control circuit may include one or more active elements, such as transistors, e.g., (MOSFET) elements S1, S2, S3, S4, that can controllably change the conduction path to pump charge between buffers in the circuit. In one embodiment, the transistors (S1, S2, S3, S4) are controllably switched by the battery module controller 106 of the corresponding battery module unit 102 and / or battery module 104. The speed, frequency, or period of switching may be adjusted as needed to achieve an operating state in any of the four operating quadrants (controlling pulse width modulation) discussed above.

[0020] The control circuit 30 is controlled according to its switching frequency. Various embodiments may use so-called soft switching and / or multi-phase interleaving. In one aspect, soft switching can increase the efficiency of the system at the expense of the circuit. In one aspect, multi-phase interleaving can increase the power rating of the circuit, but at additional cost.

[0021] FIG. 4 shows the equivalent circuit of FIG. 3 when operating in quadrants Q1 or Q2, with transistor switch S2 open and showing no current flowing in that leg of the circuit (as shown by the dashed line).

[0022] FIG. 5 shows the equivalent circuit of FIG. 3 when operating in quadrants Q3 or Q4, with transistor switch S3 open and showing no current flowing in that leg of the circuit (as shown by the dashed line).

[0023] Referring to FIG. 3-5, when switch S3 is open (OFF) and switch S4 is closed (ON), the circuit operates as a synchronous buck converter. Using feedback control, the current can be controlled bidirectionally (increased or decreased from zero, or reversed), and when Vbatt > Vbus, the circuit operates in the third or fourth quadrant (Q3 during charging and Q4 during discharging). On the other hand, when switch S2 is open (OFF) and switch S1 is closed (ON), the operation of the circuit is mirrored, the current becomes bidirectional when Vbatt < Vbus, and the circuit operates in the first and second quadrants (Q1 or Q2).

[0024] FIG. 6 shows an exemplary alternative embodiment of the control circuit 40 used in the present invention. This alternative embodiment has, by way of example, a bidirectional dual active bridge (DAB) converter. The DAB has two full-bridge circuit portions and a transformer T connected thereto. The first full-bridge is arranged on the battery side and connected to the battery voltage Vbatt. The second full-bridge is arranged on the bus side and connected to the bus voltage Vbus. With this design, galvanic insulation can be provided between the two sides of the circuit across the transformer. Design considerations for this embodiment may include the additional size of the transformer T and the additional cost of the additional transistor switches S. Those skilled in the art can implement the control circuit based on the specific requirements of their applications without departing from the scope of the present invention, which can use the specific example shown or equivalent alternative circuit designs that achieve substantially the same results required for those applications. For example, other implementations such as adopting a resonant LLC converter or a Cuk converter may be used.

[0025] In one aspect of the invention, the system and method allows for different voltages between the battery modules and the load bus (e.g., the powertrain of a vehicle) during operation. In other aspects, the system and method allows for voltage differences between the various battery modules themselves. Thus, the system and method controllably isolates the battery modules and battery units from the bus and / or load as needed, allowing for flexible operation under multiple conditions.

[0026] In yet other aspects, the systems and methods enable current scheduling and other operational flexibility between individual battery modules.

[0027] A notable result of using the present system and method is that, thanks to the present controller and control system, including the battery module controller 106, multiple battery modules 104 of various characteristics can be employed and connected in parallel as shown without substantial performance or safety issues. In one embodiment, the battery cells of the battery module 104 may not each have the same inherent electromotive force capacity or voltage Vbatt. In particular, the individual battery cells and battery modules of the multiple battery module units 102 may differ in their individual capacity, age, operational history, charge and discharge characteristics, chemistry, capacity, physical dimensions, and other aspects. Such differences in battery design and operation result in non-identical power performance, availability, and other variations in voltage and current characteristics. If not properly controlled and managed in such a multi-battery system, differences in output voltages can result in voltage differences and unwanted currents within and between the units, which in the worst case, can manifest as a short circuit condition if there is a voltage difference on the common output bus. Such variations can result in electrical and / or thermal properties if not properly controlled and regulated, which can result in damage to electrical and electronic components, damage to the battery cells, and malfunction of the entire power system. Current overload in a battery, battery module, or connected components can, in the worst case, cause thermal runaway of conductors due to resistive losses or dangerous energy or pressure buildup within the battery unit, potentially resulting in the explosion of the battery enclosure.

[0028] The present invention provides flexible, efficient and safe power flow control in a multi-battery module architecture. The system and method can individually and controllably specify how much relative power to draw from each battery module in a multi-battery module system. In one aspect, this allows the battery modules to be controllably depleted, for example, at the same relative rates, if desired by an operator.

[0029] Thus, although several aspects and embodiments of the technology of the present application have been described, it will be understood that various changes, modifications, and improvements will readily occur to those skilled in the art. Such changes, modifications, and improvements are intended to be made within the spirit and scope of the technology described in the present application. For example, those skilled in the art can readily conceive of various other means and / or structures for performing the functions described herein and / or obtaining the results and / or one or more advantages thereof, and each such variation and / or modification is deemed to be within the scope of the embodiments described herein.

[0030] Those skilled in the art will recognize that there are many equivalents to the specific embodiments described herein. Accordingly, it will be understood that the foregoing embodiments have been presented by way of example only, and that, within the scope of the appended claims and their equivalents, the embodiments of the invention may be practiced otherwise than as specifically described. Furthermore, any combination of two or more features, systems, articles, materials, kits, and / or methods described herein is within the scope of the present disclosure, if such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent.

[0031] The above-described embodiments may be implemented in a variety of ways. One or more aspects and embodiments of the present application that relate to the execution of a process or method may use program instructions executable by a device (e.g., a computer, processor, or other device) to perform or control the execution of the process or method.

[0032] In this regard, the various inventive concepts may be embodied as a non-transitory computer-readable storage medium (or multiple non-transitory computer-readable storage media) encoded with one or more programs (e.g., a computer memory, one or more data storage disks, optical disks, magnetic tapes, flash memory, circuitry within a field programmable gate array or other semiconductor device, or other tangible computer storage medium) that, when executed by one or more computers or other processors, perform methods that implement one or more of the various embodiments described above.

[0033] Computer-executable instructions may be used to control one or more processors and circuits used in the invention and may be provided in various forms, such as program modules, for execution by one or more computers or other devices. The functionality of the program modules may be combined or distributed as desired in various embodiments.

[0034] Also, as noted above, some aspects may be embodied as one or more methods. The actions performed as part of the method may be ordered in any suitable manner. Thus, while the described embodiments are shown as a series of actions, embodiments may be constructed to perform actions in an order different from that described, which may include performing some actions simultaneously.

Claims

1. A system for supplying electric power to an electric motor from a battery unit having a plurality of battery module units, a plurality of battery module units, each of which includes a battery module and a battery module controller circuit; an electric bus connected to the electric motor; having Each of the battery module controller circuits comprises: a first side of a battery module controller circuit electrically connected to each battery module at a respective battery module voltage Vbatt, and a second side of the battery module controller circuit electrically connected to the electrical bus at a bus voltage Vbus by a bus side connection; at least one switch in the battery module controller circuit that switches between a plurality of switching states; and each battery module operates in a plurality of operating modes responsive to the switching state of its respective battery module controller circuit, the operating modes including a first state in which the difference (Vbus-Vbatt) is greater than zero and the bus current is greater than zero, a second state in which the difference (Vbus-Vbatt) is greater than zero but the bus current is less than zero, a third state in which the difference (Vbus-Vbatt) is less than zero and the bus current is less than zero, and a fourth state in which the difference (Vbus-Vbatt) is less than zero but the bus current is greater than zero; system.

2. 10. The system of claim 1, wherein each of the battery modules comprises a plurality of battery cells, at least some of the cells being connected in series with each other.

3. 2. The system of claim 1, wherein each of the battery module control circuits has a two-sided design, and each of the two sides is electrically connected to each other through an inductor.

4. 2. The system of claim 1, wherein each of the battery module control circuits has a two-sided design, and each of the two sides is electrically connected to each other via a transformer.

5. 2. The system of claim 1, wherein each of the battery module controller circuits is adapted to operate a respective battery module within a four-quadrant state space having the four operating states.

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