Bidirectional converter for battery management systems

Abstract

The present invention relates to a battery management system for an electric vehicle, including a high-voltage battery, a low-voltage battery, and a bidirectional converter. The bidirectional converter is configured to connect the high-voltage battery to a low-voltage battery and to generate a power flow between the high-voltage battery and the low-voltage battery. The bidirectional converter is further configured to monitor a first voltage associated with the high-voltage battery and a second voltage associated with the low-voltage battery, and to control the voltage ratio between the first voltage and the second voltage to remain within a predetermined range by controlling the power flow between the high-voltage battery and the low-voltage battery.

Description

[Technical Field]

[0001] The present invention relates to a vehicle battery management system, a method for controlling a battery management system, and a computer-implemented method for controlling a bidirectional converter. [Background Art]

[0002] The market for electric and / or hybrid vehicles (cars, motorcycles, boats, ...) is booming. An example of a hybrid vehicle is a vehicle that requires energy input from at least two different types of energy sources, for example an electric power source or electric engine and a fuel power source or combustion engine. The electric power source can be, for example, a solar power source, and can be integrated into the vehicle itself, for example by integrating photovoltaic solar cells into the vehicle. Vehicle performance strongly depends on energy storage capacity, for example batteries. One of the important factors is the management of energy storage that enhances the efficiency and performance of these systems.

[0003] In the present system, electric and / or hybrid vehicles can include a high-voltage energy storage device and a low-voltage energy storage device, wherein an energy converter is connected between the high-voltage energy storage device and the low-voltage energy storage device. The energy converter is configured to transfer energy from one to the other. For example, when the vehicle is stationary and a plurality of auxiliary machines, such as audio, air conditioning, ..., consume power via the low-voltage battery, the converter can extract energy from the high-voltage source and transfer it to the low-voltage battery.

[0004] Since battery voltage varies significantly with the state of charge, energy converters in this system usually have to operate over a wide input voltage range. However, a wide operating range results in that the converter cannot always operate in an optimal manner. [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] The object of the present invention is to provide a battery management system for a vehicle. The battery management system is ● High-voltage battery and, ● Low-voltage battery and, ●A bidirectional converter configured to connect a high-voltage battery to a low-voltage battery and to generate a power flow between the high-voltage battery and the low-voltage battery, wherein the bidirectional converter ○ Monitor the first voltage associated with the high-voltage battery and the second voltage associated with the low-voltage battery. ○By controlling the power flow between the high-voltage battery and the low-voltage battery, the voltage ratio between the first voltage and the second voltage is controlled to remain within a predetermined range. ○When the voltage ratio exceeds a predetermined range, power is generated from the high-voltage battery to the low-voltage battery. ○The system is further configured to generate power flow from the low-voltage battery to the high-voltage battery when the voltage ratio falls below a predetermined range. [Means for solving the problem]

[0006] Because battery voltage fluctuates significantly with charge levels, battery management systems must operate across a wide input voltage range. However, this wide operating range means that the bidirectional converter in the battery management system cannot always operate in zero-voltage switching (ZVS) and zero-current switching (ZCS). The bidirectional converter cannot be optimized for a single fixed operating point. In this system, this can be solved by varying the switching frequency to change the voltage gain. However, this process is often complex and inefficient.

[0007] The introduction of the present invention can alleviate the aforementioned problems through simpler control and improved efficiency of the bidirectional converter in the battery management system.

[0008] Furthermore, the present invention provides a bidirectional converter for a battery management system, wherein the bidirectional converter comprises a first terminal for connecting to a high-voltage battery and a second terminal for connecting to a low-voltage battery, wherein the bidirectional converter is configured to connect the high-voltage battery to the low-voltage battery and to generate a power flow between the high-voltage battery and the low-voltage battery, and the bidirectional converter ● Monitor the first voltage associated with the high-voltage battery and the second voltage associated with the low-voltage battery. ●By controlling the power flow between the high-voltage battery at the first terminal and the low-voltage battery at the second terminal, the voltage ratio between the first voltage and the second voltage is controlled to remain within a predetermined range. ●When the voltage ratio exceeds a predetermined range, power is generated from the high-voltage battery to the low-voltage battery. ●The system is further configured to generate power flow from the low-voltage battery to the high-voltage battery when the voltage ratio falls below a predetermined range.

[0009] The battery management system according to the present invention can be applied to electric vehicles, for example, electric vehicles that can be at least partially charged by on-board solar panels. The on-board solar panels may be integrated into the roof of the vehicle. Furthermore, the electric vehicle may be equipped with in-wheel motors.

[0010] Generally, the high-voltage and low-voltage batteries in a battery management system are used to power one or more electric propulsion motors and low-voltage operating devices, such as car audio systems, airbags, and seat heaters. Typically, high voltage is above 60 volts. High voltage is usually defined as a voltage in the range of 300V to 430V, while low voltage refers to operating at a safety voltage, typically 12 volts, 24 volts, or 48 volts.

[0011] The battery management system is configured to connect a high-voltage battery to a low-voltage battery and further comprises a bidirectional converter configured to generate power flow between the high-voltage and low-voltage batteries, and vice versa. In this way, the high-voltage battery can supply power to the low-voltage battery, for example, when the low-voltage battery's state of charge (SOC) becomes low. SOC is the level of battery charge relative to its capacity. SOC can be expressed, for example, as a percentage.

[0012] In one embodiment, the high-voltage battery may be configured to be charged by a photovoltaic device. The photovoltaic device may be a solar cell grouped into a module and integrated into or mounted on the roof of an electric vehicle.

[0013] Furthermore, the bidirectional converter is configured to monitor a first voltage associated with a high-voltage battery and a second voltage associated with a low-voltage battery. The first and second voltages may correspond, for example, to the voltages at the terminals of the high-voltage and low-voltage batteries, respectively. The first and second voltages are related to the respective energy states (SoE) of each voltage battery. Generally, since battery voltages fluctuate significantly with SoE, the bidirectional converter must operate over a wide input voltage range.

[0014] The bidirectional converter according to the present invention further controls the voltage ratio of the first voltage to the second voltage so that it remains within a predetermined range. To remain within the predetermined range, the bidirectional converter controls the power flow between the high-voltage battery and the low-voltage battery. The most suitable conditions for operating the bidirectional converter are when the voltage ratio is substantially fixed. By introducing a predetermined range, it is avoided that the bidirectional converter is working continuously to control the voltage ratio to a fixed point. To make this more practical, there is a small margin in which the voltage ratio fluctuates within the predetermined range. For example, the predetermined range has an upper limit of +10 percent and a lower limit of -10 percent with respect to the nominal or reference voltage ratio. Suppose the reference or nominal voltage on the high-battery side is 200V and the reference or nominal voltage on the low-battery side is 50V. Thus, the nominal voltage ratio is 4. The predetermined range can be specified therein, for example, as ranging from 3.6 to 4.4 (i.e., a range of +10% to -10% compared to the nominal voltage ratio).

[0015] By introducing a predetermined range, the impractical and inefficient requirement for a bidirectional converter to operate continuously by controlling the voltage ratio is avoided. It can be noted that the predetermined range may relate to the minimum power the bidirectional converter must deliver. Thus, the bidirectional converter is only turned on when it must deliver a minimum power, for example, between 50 and 200 watts, e.g., 100 watts. Various possibilities exist for controlling the voltage ratio by the bidirectional converter. This will become clear in further explanation.

[0016] The bidirectional converter is further configured to generate a power flow from the high-voltage battery to the low-voltage battery when the voltage ratio exceeds a predetermined range. For example, when a stationary vehicle is turned on and some of the vehicle's functional subsystems (radio system, climate control system, lighting system, etc.) are in use, the state of charge (SOC) of the low-voltage battery obviously drops rapidly compared to the SOC of the high-voltage battery. Therefore, the second voltage may steadily decrease while the first voltage remains largely unchanged. To control the voltage ratio between the high-voltage and low-voltage batteries, the bidirectional converter can extract power from the high-voltage battery and supply it to the low-voltage battery.

[0017] Similarly, a bidirectional converter can be configured to generate a power flow from a low-voltage battery to a high-voltage battery when the voltage ratio (i.e., the ratio of the voltage in the high-voltage battery to the voltage in the low-voltage battery) falls below a predetermined range. This situation can occur, for example, during extreme weather conditions.

[0018] An advantage of the present invention is that it enables the bidirectional converter to operate with substantially fixed voltage gain or essentially at a fixed frequency. As a result, the converter operates more efficiently in ZVS and ZCS across the entire SoE range without the need for complex movements or procedures. Another advantage is that the peak current is lower and therefore the power loss is lower.

[0019] Note that the voltage ratio can also be the ratio of the voltage associated with the low-voltage battery to the voltage associated with the high-voltage battery.

[0020] In one embodiment, the battery management system is configured to maintain a substantially constant voltage ratio. Preferably, the voltage ratio is an integer or a fraction of an integer, such as 4 or 1 / 4. Assuming both batteries have similar chemical properties, the state of charge (SOC) will also remain similar. Choosing an integer voltage ratio can reduce inductor costs and leakage.

[0021] In one embodiment, the bidirectional converter is an LLC converter or a CCL converter. Both types of converters are resonant converters. A characteristic feature of these converters is that the voltage gain is fixed at the resonant frequency regardless of load fluctuations. The LLC converter uses magnetizing inductance to induce resonance. An advantage of LLC resonant converters is a narrow frequency variation range over a wide load range. Even zero-voltage switching (ZVS) is possible under no-load conditions. A disadvantage of current LLC converters is that it is difficult to optimize performance for a wide input voltage range. However, according to the present invention, this problem can be mitigated.

[0022] Besides LLC converters, the present invention is applicable to CCL converters. This converter operates in a similar manner to an LLC converter, however, instead of using magnetizing inductance for resonance, the CCL converter uses a separate parallel inductor for resonance.

[0023] In one embodiment, the bidirectional converter operates at a fixed switching frequency when power flow is generated between a low-voltage battery and a high-voltage battery. Operating at a fixed frequency basically means operating at a fixed voltage gain. The state of charge (SOC) of both batteries is maintained similarly. An advantage of this embodiment is that the converter can operate efficiently with ZVS and zero-current switching (ZCS).

[0024] In one embodiment, the bidirectional converter includes a first terminal for connecting to a high-voltage battery and a second terminal for connecting to a low-voltage battery. As described above, the high-voltage battery can be configured to be charged by a photovoltaic device, and the high-voltage battery can be connected to a photovoltaic device, such as a vehicle-mounted solar panel. Alternatively, the low-voltage battery can be charged by the photovoltaic device. Optionally, the photovoltaic device is configured to charge both the high-voltage battery and the low-voltage battery.

[0025] In one embodiment, the bidirectional converter may comprise a control unit that monitors the voltage ratio, for example, on a substantially continuous basis. Based on the monitored voltage ratio and a predetermined range, the control unit controls the bidirectional converter to generate the required or desired power flow as soon as the voltage ratio deviates outside the predetermined range, for example. Various options exist for regulating the bidirectional converter and generating power flow.

[0026] A first possible option is that the bidirectional converter generates a power flow only when the voltage ratio deviates outside the predetermined range. The bidirectional converter is actually passive or inactive when the voltage ratio remains, for example, substantially constant, or when the voltage ratio stays within the predetermined range. Resuming the above example, the (nominal) voltage ratio is 4, and the limits of the predetermined range are 3.6 to 4.4. At the moment when the voltage ratio exceeds 4.4 and increases to, for example, 4.5, the bidirectional converter generates a power flow from the high voltage side to the low voltage side until the voltage ratio reaches the upper limit of the predetermined range.

[0027] The disadvantage of this regulation is that the efficiency of the bidirectional converter is not optimal in situations where one of the battery sources supplies a significant amount of power. In such cases, the voltage ratio steadily progresses towards a value outside the predetermined range. As a result, the bidirectional converter is active most of the time.

[0028] Another option is that as soon as the voltage ratio deviates outside the predetermined range, the bidirectional converter generates a power flow between the high voltage battery and the low voltage battery. The bidirectional converter controls the power flow such that the voltage ratio is restored to the nominal voltage ratio. In other words, the bidirectional converter does not stop immediately as soon as the voltage ratio returns to within the predetermined range, but remains active until the nominal voltage ratio is reached.

[0029] To resume the above example, the (nominal) voltage ratio is 4, and the limit of the given range is 3.6 to 4.4. At the moment the voltage ratio exceeds 4.4 and increases to, for example, 4.5, the bidirectional converter generates a power flow from the high-voltage side to the low-voltage side until the voltage ratio reaches the nominal voltage ratio of 4. The advantage is that the active control time of the bidirectional converter is reduced, especially when the voltage ratio increases or decreases systematically.

[0030] It can be noted that the transfer of power may be a function of both the voltage difference between the two batteries and the power consumption associated with the power supply of the high-voltage and / or low-voltage batteries. The rate at which the battery voltage decreases is a measure of the battery's power supply. When the rate of decrease becomes sufficiently high, it is a sign that the battery is supplying power predominantly. By monitoring the voltage fluctuations of the high-voltage and / or low-voltage batteries as a function of time, and thus the power consumption, the battery management system is configured to predict the moment when the voltage ratio may fall outside a given range. The system is configured to predict even faster with respect to deviations in the voltage ratio.

[0031] A variation of the above voltage ratio adjustment is that the bidirectional converter remains active for a predetermined period of time by maintaining the voltage ratio at the nominal voltage ratio at the moment the voltage ratio is restored to the nominal voltage ratio.

[0032] To resume the above example, the (nominal) voltage ratio is 4, and the limit of a given range is 3.6 to 4.4. At the moment the voltage ratio exceeds 4.4 and increases to, for example, 4.5, the bidirectional converter generates a power flow from the high-voltage side to the low-voltage side until the voltage ratio reaches the nominal voltage ratio of 4. The bidirectional converter remains active by regulating the power flow between the high-voltage and low-voltage batteries for a predetermined period, for example, 1 second, in order to maintain a voltage ratio of 4.

[0033] Alternatively, if the voltage ratio falls outside a predetermined range, the bidirectional converter controls the power flow so that the voltage ratio is restored to the furthest limit of the predetermined range.

[0034] To resume the above example, the (nominal) voltage ratio is 4, and the limit of the given range is 3.6 to 4.4. At the moment the voltage ratio exceeds 4.4 and increases to, for example, 4.5, the bidirectional converter generates a power flow from the high-voltage side to the low-voltage side until the voltage ratio reaches the lower limit of the given range of 3.6.

[0035] In one embodiment, the bidirectional converter is configured to monitor a first voltage associated with a high-voltage battery and a second voltage associated with a low-voltage battery by receiving a first voltage signal associated with the first voltage and a second voltage signal associated with the second voltage, and to control the power flow based on the first voltage signal and the second voltage signal.

[0036] In an alternative embodiment, the bidirectional converter may include a voltage measuring device. The voltage measuring device may be connected to a first voltage battery and / or a low voltage battery. The voltage measuring device is configured to measure a first voltage and / or a second voltage. Subsequently, the voltage measuring device supplies the bidirectional converter with a first voltage signal associated with the first voltage and / or a second voltage signal associated with the second voltage.

[0037] In accordance with the present invention, the present invention further relates to a method for controlling a battery management system for an electric vehicle comprising a high-voltage battery, a low-voltage battery, a bidirectional converter configured to connect the high-voltage battery to the low-voltage battery, and to generate a power flow between the high-voltage battery and the low-voltage battery, the method being: ● A step of monitoring a first voltage associated with a high-voltage battery and a second voltage associated with a low-voltage battery, ● The steps include controlling the power flow between the high-voltage battery and the low-voltage battery so that the voltage ratio of the first voltage to the second voltage remains within a predetermined range, ●When the voltage ratio is higher than a predetermined range, a step is made to generate a power flow from the high-voltage battery to the low-voltage battery, ●Includes the step of generating a power flow from a low-voltage battery to a high-voltage battery when the voltage ratio is below a predetermined range.

[0038] In the method according to the present invention, a first voltage associated with a high-voltage battery and a second voltage associated with a low-voltage battery are monitored. The high-voltage battery and the low-voltage battery can be connected via a bidirectional converter. By monitoring the first voltage and the second voltage, a voltage ratio is determined. For example, both voltages may be determined by voltage measurement via a control unit. The control unit may be part of the bidirectional converter. Alternatively, there may be a distributed control unit that determines the voltages of both batteries, and the control unit controls the bidirectional converter.

[0039] The next step in the method according to the present invention is to control the voltage ratio of the first voltage to a second voltage that remains within a predetermined range. Thereafter, the bidirectional converter controls the power flow between the high-voltage battery and the low-voltage battery. Power flow occurs from the high-voltage battery to the low-voltage battery when the voltage ratio is above a predetermined range. For example, when a stationary vehicle is turned on and several functional subsystems of the vehicle (radio system, climate control system, lighting system, etc.) are in use, the state of charge (SOC) of the low-voltage battery obviously drops rapidly compared to the SOC of the high-voltage battery. Therefore, the second voltage may decrease steadily while the first voltage remains largely unchanged. To control the voltage ratio between the high-voltage battery and the low-voltage battery, power is drawn from the high-voltage battery and supplied to the low-voltage battery.

[0040] Similarly, power flow occurs from low-voltage batteries to high-voltage batteries when the voltage ratio falls below a predetermined range. This situation can occur, for example, during extreme weather conditions.

[0041] The specified range includes, for example, upper and lower limits during which the voltage ratio must be controlled. The following example will illustrate this.

[0042] Assume the desired voltage ratio is 4, meaning the states of charge (SOC) of each battery are equal. In this example, the given range has an upper limit of 4.4 and a lower limit of 3.6. In other words, there is a built-in deviation of 10 percent from the desired voltage ratio. During operation, the bidirectional converter monitors the first and second voltages. A high load on the high-voltage battery results in a higher power demand for the high-voltage battery compared to the low-voltage battery. This disrupts the balance between the two batteries, and the voltage ratio drops below 4. When the voltage ratio reaches the lower limit of the given range, i.e., 3.6, the bidirectional converter converts power from the low-voltage battery to the high-voltage battery. The power flow ensures that the voltage ratio remains within the given range.

[0043] The present invention is described in further detail below with reference to the figures, which illustrate illustrative embodiments of the invention in a non-limiting manner. The same reference numerals in different figures indicate the same feature in different figures. [Brief explanation of the drawing]

[0044] [Figure 1] This figure schematically illustrates a battery management system according to one embodiment of the present invention, which includes a high-voltage battery, a low-voltage battery, and a bidirectional converter. [Figure 2] This diagram schematically illustrates a bidirectional converter for a battery management system, which includes a first terminal for connecting to a high-voltage battery and a second terminal for connecting to a low-voltage battery. [Figure 2a] This figure schematically illustrates one embodiment of a bidirectional converter, in which the bidirectional converter has an LLC configuration. [Figure 3a] This diagram schematically illustrates various control methods for controlling the voltage ratio between a first voltage and a second voltage to remain within a predetermined range by controlling the power flow between a high-voltage battery and a low-voltage battery. [Figure 3b]This diagram schematically illustrates various control methods for controlling the voltage ratio between a first voltage and a second voltage to remain within a predetermined range by controlling the power flow between a high-voltage battery and a low-voltage battery. [Figure 3c] This diagram schematically illustrates various control methods for controlling the voltage ratio between a first voltage and a second voltage to remain within a predetermined range by controlling the power flow between a high-voltage battery and a low-voltage battery. [Figure 4] This diagram schematically illustrates one embodiment of a flowchart for a computer implementation method for controlling a bidirectional converter according to the present invention. [Modes for carrying out the invention]

[0045] Figure 1 schematically illustrates the electrical plan of a solar car, where the battery management system 120 is illustrated to include a high-voltage battery 122, a low-voltage battery 130, and a bidirectional converter 126. The battery management system 120 is applied to an electric vehicle that is at least partially rechargeable by an on-board solar panel equipped with solar cells. Typically, the solar cells are integrated into the roof of the electric vehicle.

[0046] First, Figure 1 illustrates several groups of solar cells 102, each of which is connected to an associated distributed maximum power point tracker 104. The groups 102 are connected in series, thereby forming a string, the output of which is connected to a string voltage bus 106.

[0047] One side of each distributed maximum power point tracker 104, the primary side, is connected to the group associated with that distributed maximum power point tracker. The other side, the secondary side, is connected to the energy exchange bus 108. For other possible uses, such as diagnostics and current monitoring, the distributed maximum power point trackers indicate the communication bus 110. The string voltage bus 106 is connected via the DC / DC converter 112.

[0048] A distributed maximum power point tracker controller 134 controls the distributed maximum power point tracker 104 via the communication bus 110 to disable group 102, for example, during service or error conditions (indicated by, for example, an deployed airbag). A DC / DC converter 112 loads the string bus 106.

[0049] A motor controller 116, connected to a high-voltage bus, is also shown, which generates voltage for an (electric) traction motor 118, such as a permanent magnet motor. It should be noted that two or more motors may be used (typically each motor having its own motor controller). It should also be noted that the motor may be any type of motor, such as brushed or brushless, for propelling a vehicle (or boat), as long as it is an electric motor.

[0050] Please note that most of the above components are optional in relation to this invention.

[0051] A bidirectional converter 126 connects a high-voltage battery 122 to a low-voltage battery 130. The bidirectional converter is configured to generate a power flow between the high-voltage and low-voltage batteries. The low-voltage battery 130 (typically a lead-acid battery) powers a number of low-voltage users 132 (air conditioners, audio systems, lighting, etc.). Typically, high voltage is defined as higher than 60 volts. Typically, high voltage is defined as a voltage in the range of 300V to 430V. Low voltage means operating at a safety voltage, typically 12 volts or 24 volts.

[0052] The bidirectional converter 126 is configured to supply power from the high-voltage battery 122 to the low-voltage battery 130, for example, when the low-voltage battery requests a load, or vice versa. The high-voltage battery and / or low-voltage battery are configured to be charged by solar cells.

[0053] Figure 2 schematically illustrates a bidirectional converter for a battery management system according to the present invention. The bidirectional converter 202 includes a first terminal 204 for connecting to a high-voltage battery 201 and a second terminal 205 for connecting to a low-voltage battery 203. The bidirectional converter 202 is configured to connect the high-voltage battery 201 to the low-voltage battery 203 and to generate a power flow (indicated by arrows 201a, 201b, 203a, and 203b) between the high-voltage battery 201 and the low-voltage battery 203. The transfer of power from the high-voltage battery 201 to the low-voltage battery 203 through the bidirectional converter 202 is illustrated by arrows 201a and 203a. The transfer of power from the low-voltage battery 203 to the high-voltage battery 201 is illustrated by arrows 203b and 201b.

[0054] The bidirectional converter 202 is configured to monitor a first voltage associated with a high-voltage battery 201 at a first terminal 204 and a second voltage associated with a low-voltage battery 203 at a second terminal 205. The bidirectional converter receives a first signal 207 corresponding to the first voltage 207 and a second signal 208 corresponding to the second voltage 208. The first and second voltages may correspond, for example, to the voltages at the terminals of a high-voltage battery and a low-voltage battery, respectively. The first and second voltages are associated with the respective SOCs of each voltage battery.

[0055] The bidirectional converter 202 further controls the voltage ratio of the first voltage to the second voltage so that it remains within a predetermined range. To remain within the predetermined range, the bidirectional converter controls the power flow between the high-voltage battery 201 and the low-voltage battery 203. The most appropriate conditions for operating the bidirectional converter are when the voltage ratio is substantially fixed. By introducing a predetermined range, it is avoided that the bidirectional converter must work continuously to control the voltage ratio to a fixed point. To make this more practical, there is a small margin in which the voltage ratio fluctuates within the predetermined range. By introducing a predetermined range, it is avoided that the bidirectional converter must operate continuously by controlling the voltage ratio, which is impractical and inefficient.

[0056] The bidirectional converter is further configured to generate a power flow from the high-voltage battery to the low-voltage battery when the voltage ratio exceeds a predetermined range. For example, when a stationary vehicle is turned on and some of the vehicle's functional subsystems (radio system, climate control system, lighting system, etc.) are in use, the state of charge (SOC) of the low-voltage battery obviously drops rapidly to zero compared to the SOC of the high-voltage battery. The second voltage steadily decreases while the first voltage remains largely unchanged. To control the voltage ratio between the high-voltage and low-voltage batteries, the bidirectional converter can extract power from the high-voltage battery to the low-voltage battery.

[0057] On the other hand, a bidirectional converter is configured to generate a power flow from a low-voltage battery to a high-voltage battery when the voltage ratio falls below a predetermined range. This situation can occur, for example, during extreme weather conditions.

[0058] In Figure 2, the bidirectional converter includes a control unit 206 that constantly monitors the voltage ratio. The control unit 206 receives a first signal 207 representing a first voltage and a second signal 208 representing a second voltage to determine the voltage ratio. Based on the monitored voltage ratio and a predetermined range, the control unit 206 controls the bidirectional converter 202 to generate the required power flow, for example, as soon as the voltage ratio falls outside the predetermined range. There are various options for adjusting the bidirectional converter 202 and generating the power flow. In one embodiment, the control unit may be a separate controller or control unit, i.e., a controller or control unit located away from the bidirectional converter. Such a separate control unit may be, for example, the vehicle's central master control unit, which controls the bidirectional converter.

[0059] An advantage of the present invention is that the converter can be made to operate with a fixed voltage gain, or essentially at a fixed frequency. As a result, the converter will operate more efficiently in ZVS and ZCS without the need for complex movements or procedures. Another advantage is that the peak current will be lower, and therefore the power loss will be lower.

[0060] Figure 2a illustrates one embodiment of a bidirectional converter, called an LLC resonant converter. A characteristic of these converters is that the voltage gain is fixed at the resonant frequency regardless of load variations. LLC converters use magnetization inductance to induce resonance. The advantage of LLC resonant converters is their narrow frequency variation range over a wide load range. Even zero-voltage saturation (ZVS) is possible without load conditions. Another possible configuration is the CCL resonant converter, which is exactly the same as the LLC resonant converter.

[0061] Figures 3a to 3c schematically illustrate various control methods that control the power flow between a high-voltage battery and a low-voltage battery so that the voltage ratio between the first voltage and the second voltage remains within a predetermined range. The ratio of the first voltage VH to the second voltage VL is described as a function of time t.

[0062] The bidirectional converter according to the present invention is configured to monitor a first voltage VH associated with a high-voltage battery and a second voltage VL associated with a low-voltage battery. The first and second voltages may correspond, for example, to the voltages at the terminals of the high-voltage battery and the low-voltage battery, respectively.

[0063] The bidirectional converter controls the voltage ratio Vrat of the first voltage VH to the second voltage VL so that it remains within a predetermined range. This predetermined range is specified by an upper limit Ulim and a lower limit Llim. The voltage ratio Vrat and the predetermined range are set on the vertical axis in Figures 3a and 3c.

[0064] In Figures 3a and 3c, the predetermined range is defined symmetrically with respect to the voltage ratio, meaning that the voltage ratio is the center of the predetermined range. As an example, the nominal value of the first voltage VH on the high battery side may be, for example, 200V, and the nominal value of the second voltage VL on the low battery side may be, for example, 50V. Therefore, the nominal or desired voltage ratio Vrat is set to 4. The predetermined range has an upper limit of +10 percent and a lower limit of -10 percent, determined from the voltage ratio. The upper limit Ulim is therefore specified to 4.4, and the lower limit Llim is specified to 3.6. By introducing the predetermined range, the impractical and inefficient requirement that the bidirectional converter must operate continuously by controlling the voltage ratio is avoided.

[0065] The bidirectional converter monitors the voltage ratio VH / VL. As soon as the voltage ratio falls outside a predetermined range, the bidirectional converter generates a power flow between the high-voltage and low-voltage batteries. In Figure 3a, the voltage ratio is assumed to increase and reach its upper limit at time t1. Consequently, at time t2, the bidirectional converter begins generating a power flow from the high-voltage side to the low-voltage side until the voltage ratio VH / VL reaches a voltage ratio Vrat of 4. During the period t1-t2, the low-voltage battery is therefore receiving power from the high-voltage battery. In the example shown in Figure 3a, the bidirectional converter stops the power flow once the voltage ratio Vrat reaches its nominal value.

[0066] Therefore, in Figure 3a, the active control period of the bidirectional converter is during the time intervals t1-t2, t3-t4, t5-t6, and t7-t8. The advantage of generating power flow only during specific time intervals is that the active control time of the bidirectional converter is reduced, especially when the voltage ratio increases or decreases systematically.

[0067] Another option is for the bidirectional converter to generate power flow only when the voltage ratio falls outside a predetermined range. This mode of adjustment is visualized in Figure 3b. The bidirectional converter is, in practice, passive or inactive when the voltage ratio remains substantially constant, for example, or when the voltage ratio stays within a predetermined range. Returning to the example in Figure 3a, the (nominal) voltage ratio Vrat is 4, and the limits of the predetermined range Llim, Ulim are 3.6 to 4.4. At time t1, the voltage ratio exceeds 4.4 and increases to, for example, 4.5, meaning that the low-voltage battery is supplying power more favorably than the high-voltage side. As a result, the bidirectional converter generates power flow from the high-voltage side to the low-voltage side until the voltage ratio reaches the upper limit Ulim of the predetermined range. In Figure 3b, it is assumed that the low-voltage battery continuously uses power, such that the second voltage associated with the low-voltage battery steadily decreases during the time interval t1 to t8, while the first voltage associated with the high-voltage battery remains largely unchanged. The bidirectional converter continues to transfer power from the high-voltage battery to the low-voltage battery in order to stay within the upper limit of a predetermined range.

[0068] The disadvantage of this adjustment is that the bidirectional converter is not optimally efficient when one of the battery sources is supplying significant power. As a result, the bidirectional converter is active for most of the time. The active control period of the bidirectional converter is between time intervals t1 and t8. The adjustment in Figure 3b is less efficient compared to the situation in Figure 3a.

[0069] Alternatively, if the voltage ratio falls outside a predetermined range, the bidirectional converter controls the power flow so that the voltage ratio is restored to the furthest limit of the predetermined range. This control scheme is visualized in Figure 3c.

[0070] Revisiting the example in Figures 3a-3b, the (nominal) voltage ratio Vrat is 4, and the limits Llim and Ulim within a given range are 3.6-4.4. In Figure 3c, at time t1, the voltage ratio exceeds 4.4 and increases to, for example, 4.5, and the bidirectional converter generates a power flow from the high-voltage side to the low-voltage side until the voltage ratio reaches the lower limit Llim of the given range, 3.6.

[0071] As can be seen from Figure 3c, the active control period of the bidirectional converter is during the time intervals t1-t2, t4-t5, and t7-t8. During these intervals, the bidirectional converter controls the power flow from the high-voltage battery to the low-voltage battery until the voltage ratio reaches the lower limit Llim. This type of adjustment is very efficient in situations where only one battery source is supplying significant power, and the voltage associated with the other battery source remains largely unchanged, for example, when the battery source is not supplying power or is being charged by solar power, for example.

[0072] Alternatively, power transfer may be a function of both the monitored voltage and operational data associated with the battery. Operational data is related to all different types of data, such as power consumption associated with the power supply of high-voltage and / or low-voltage batteries, vehicle usage, GPS data, etc. For example, power consumption is a measure of the rate at which the battery voltage decreases. When the rate of decrease becomes sufficiently high, it is a sign that the battery is supplying power preferentially. By monitoring the voltage fluctuations of the high-voltage and / or low-voltage batteries as a function of time, and thus power consumption, the battery management system is configured to predict the moment when the voltage ratio may fall outside a given range. The system is configured to predict even faster with respect to deviations in the voltage ratio.

[0073] In one embodiment, the vehicle or controller logs operational data. Based on the operational data, the system is configured to select the most efficient control mechanism for the bidirectional converter. The system is configured to anticipate voltage ratio deviations more accurately and quickly.

[0074] Figure 4 schematically illustrates a flowchart of one embodiment of a computer implementation method according to the present invention for controlling a bidirectional converter. The bidirectional converter is configured to generate a power flow between a high-voltage battery and a low-voltage battery. The bidirectional converter is further configured to connect the high-voltage battery to the low-voltage battery.

[0075] A computer implementation method according to the present invention includes step 401 of receiving a first voltage signal representing a first voltage associated with a high-voltage battery.

[0076] In step 402, a second voltage signal is received, representing a second voltage associated with the low-voltage battery. Note that the sequence in which steps 401 and 402 occur may be modifiable and therefore not fixed. Both steps 401 and 402 may be performed simultaneously.

[0077] The first and second voltage signals can be derived from the voltages by monitoring the first and second voltages, for example, using a voltage measuring system or device. Such voltage measurement or monitoring can be performed, for example, by a voltage measuring device associated with a bidirectional converter. The voltage measuring device may have an output or output terminal from which a signal representing the measured voltage can be obtained, for example. In one embodiment, the bidirectional converter may include a control unit configured to control the voltage measuring device. In one embodiment, the voltage measuring device is configured to measure the first voltage and / or the second voltage. The voltage measuring device may generate a first voltage signal associated with the first voltage and / or a second voltage signal associated with the second voltage.

[0078] The computer implementation method further includes a step 403 of determining a voltage ratio based on a first voltage signal and a second voltage signal. The voltage ratio represents the ratio of the first voltage to the second voltage.

[0079] The computer implementation method further includes step 404 of determining a control signal for controlling a bidirectional converter. The control signal is based on a voltage ratio. In one embodiment, the control signal is set to control the operation of the bidirectional converter so that the voltage ratio is controlled toward a target value or maintained within a predetermined range.

[0080] The computer implementation method according to the present invention further includes, in step 405, outputting a control signal. The control signal may be output directly to the bidirectional converter. For example, the control signal can ensure that the bidirectional converter generates the necessary or desired power flow between the high-voltage battery and the low-voltage battery when the voltage ratio deviates from its nominal or target value.

[0081] It should be understood that the embodiment disclosed in Figure 4 can also be implemented as a method for controlling a battery management system according to the present invention. Such a battery management system can be used, for example, in a vehicle and may comprise a high-voltage battery, a low-voltage battery, and a bidirectional converter configured to connect the high-voltage battery to the low-voltage battery and to generate a power flow between the high-voltage battery and the low-voltage battery. Such a battery management system may further comprise, for example, a control unit for controlling the bidirectional converter. Such a control unit may have, for example, one or more input terminals for receiving voltage signals in steps 401 and 402 shown, for example in Figure 4, and one or more output terminals for outputting a control signal determined, for example in step 404. Such a control unit may further comprise a computer implementation method according to the present invention. In such an embodiment, the control unit may comprise, for example, a memory unit and a processing unit. In such an embodiment, the memory unit may be configured, for example, to store the received voltage signal and optionally to store any further operational data to be received. The processing unit of such a control unit may be configured, for example, to process the stored data, for example, the voltage signal, and to determine, based on the voltage signal, a voltage ratio and a control signal to be output to control the bidirectional converter.

[0082] It should be understood that the disclosed embodiments are for illustrative purposes only, and that the present invention may be implemented in other forms. Therefore, the specific structural configurations disclosed herein should be considered not as limiting the present invention, but merely as the basis for the claims and for enabling implementation by those skilled in the art.

[0083] Furthermore, the various terms used in this description should be interpreted not as limitations, but rather as a comprehensive description of the present invention.

[0084] As used herein, the word "a" means one or more unless otherwise specified. The phrase "plural" means two or more. The words "comprising" and "having" constitute an open language and do not exclude the presence of further elements.

[0085] The reference figures in the claims should not be construed as limiting the invention. It is not necessary for a particular embodiment to achieve all the objectives described.

[0086] The mere fact that certain technical means are specified in various dependent claims further allows for the possibility that combinations of these technical means may be advantageously applied. [Explanation of symbols]

[0087] 102 Solar Cells 104 Distributed Maximum Power Point Tracker 106-string voltage bus 108 Energy exchange bus 110 Communications Bus 112 DC / DC Converters 116 Motor Controller 118. Motor for driving 120 Battery Management System 122 High-Voltage Battery 126 Bidirectional Converters 130 Low Voltage Battery 132 Low-voltage users 134 Distributed Maximum Power Point Tracker Controller 201 High-Voltage Battery 201a, 201b power flow 202 Bidirectional Converter 203 Low-voltage battery 203a, 203b power flow 204 First terminal 205 Second terminal 206 Control Unit 207 First voltage, first signal 208 Second voltage, second signal

Claims

1. A battery management system for electric vehicles, ● High-voltage battery and, ● Low-voltage battery and, ●A bidirectional converter configured to connect the high-voltage battery to the low-voltage battery and to generate a power flow between the high-voltage battery and the low-voltage battery, wherein the bidirectional converter ○ Monitor the first voltage associated with the high-voltage battery and the second voltage associated with the low-voltage battery, ○By controlling the power flow between the high-voltage battery and the low-voltage battery, the voltage ratio between the first voltage and the second voltage is controlled to remain within a predetermined range. ○When the voltage ratio exceeds the predetermined range, the power flow is generated from the high-voltage battery to the low-voltage battery. ○When the voltage ratio falls below the predetermined range, the power flow is generated from the low-voltage battery to the high-voltage battery. ○The power flow is further configured to control the voltage ratio so that it returns to the nominal voltage ratio. Battery management system.

2. The battery management system according to claim 1, wherein the voltage ratio is the value obtained by dividing the first voltage by the second voltage.

3. The battery management system according to claim 1, wherein the voltage ratio is constant.

4. The battery management system according to claim 1, wherein the voltage ratio is an integer.

5. The battery management system according to claim 1, wherein the predetermined range is between -10 and 10 percent of the voltage ratio.

6. The battery management system according to claim 1, wherein the photovoltaic device is integrated into the roof of the vehicle.

7. The battery management system according to claim 1, wherein the low-voltage battery operates in the range of 12 to 48 volts, and the high-voltage battery operates at more than 60 volts.

8. The battery management system according to claim 1, wherein the bidirectional converter operates in ZVS and / or ZCS.

9. The battery management system according to claim 1, wherein the bidirectional converter is an LLC converter or a CCL converter.

10. The battery management system according to claim 1, wherein the bidirectional converter operates at a fixed switching frequency when the power flow is generated between the low-voltage battery and the high-voltage battery.

11. The aforementioned bidirectional converter ● A first terminal for connecting to the high-voltage battery, ● A second terminal for connecting to the low-voltage battery and A battery management system according to claim 1, comprising:

12. A vehicle equipped with the battery management system described in claim 1.

13. The vehicle according to claim 12, further comprising solar panels and in-wheel motors.

14. A bidirectional converter for a battery management system, wherein the bidirectional converter comprises a first terminal for connecting to a high-voltage battery and a second terminal for connecting to a low-voltage battery, and the bidirectional converter is configured to connect the high-voltage battery to the low-voltage battery and to generate a power flow between the high-voltage battery and the low-voltage battery, and the bidirectional converter, ● Monitor the first voltage associated with the high-voltage battery and the second voltage associated with the low-voltage battery. ●By controlling the power flow between the high-voltage battery at the first terminal and the low-voltage battery at the second terminal, the voltage ratio between the first voltage and the second voltage is controlled to remain within a predetermined range. ●When the voltage ratio exceeds the predetermined range, the power flow is generated from the high-voltage battery to the low-voltage battery. ●When the voltage ratio falls below the predetermined range, the power flow is generated from the low-voltage battery to the high-voltage battery. ● A bidirectional converter further configured to control the power flow so as to return the voltage ratio to the nominal voltage ratio.

15. The bidirectional converter according to claim 14, wherein the bidirectional converter is configured to monitor the first voltage associated with the high-voltage battery and the second voltage associated with the low-voltage battery by receiving a first voltage signal associated with the first voltage and a second voltage signal associated with the second voltage, and to control the power flow based on the first voltage signal and the second voltage signal.

16. The bidirectional converter according to claim 15, wherein the bidirectional converter includes a voltage measuring device, the voltage measuring device is configured to measure the first voltage and / or the second voltage, and to supply the bidirectional converter with a first voltage signal associated with the first voltage and / or a second voltage signal associated with the second voltage.

17. A method for controlling a battery management system for an electric vehicle comprising a high-voltage battery, a low-voltage battery, a bidirectional converter configured to connect the high-voltage battery to the low-voltage battery, and to generate a power flow between the high-voltage battery and the low-voltage battery, ● A step of monitoring a first voltage associated with the high-voltage battery and a second voltage associated with the low-voltage battery, ● A step of controlling the power flow between the high-voltage battery and the low-voltage battery so that the voltage ratio between the first voltage and the second voltage remains within a predetermined range, ●When the voltage ratio is higher than the predetermined range, the step of generating the power flow from the high-voltage battery to the low-voltage battery, ●When the voltage ratio is lower than the predetermined range, the step of generating the power flow from the low-voltage battery to the high-voltage battery, A method comprising the step of controlling the power flow so that the voltage ratio is returned to the nominal voltage ratio.

18. The method according to claim 17, wherein the low-voltage battery operates in the range of 12 to 48 volts, and the high-voltage battery operates at more than 60 volts.

19. The method according to claim 17, wherein the monitoring step includes providing a voltage ratio signal to the bidirectional converter based on the first voltage and the second voltage.

20. The method according to claim 17, wherein the first voltage and the second voltage are determined by voltage measurement.

21. The method according to claim 17, wherein the voltage ratio is constant.

22. The method according to claim 17, wherein the voltage ratio is an integer.

23. The method according to claim 17, wherein the predetermined range is between -10 and 10 percent of the voltage ratio.

24. A computer implementation method for controlling a bidirectional converter configured to generate a power flow between a high-voltage battery and a low-voltage battery, ● The step of receiving a first voltage signal representing a first voltage associated with the high-voltage battery, ● The step of receiving a second voltage signal representing a second voltage associated with the low-voltage battery, ● A step in which a voltage ratio is determined based on the first voltage signal and the second voltage signal, and the voltage ratio represents the ratio of the first voltage to the second voltage, ● Determine a control signal for controlling the bidirectional converter, and the control signal is based on the voltage ratio, in steps, A method comprising the step of outputting a control signal configured to control the power flow of the bidirectional converter in order to maintain the voltage ratio of the first voltage to the second voltage within a predetermined range, wherein the control signal is configured to control the power flow of the bidirectional converter in order to return the voltage ratio to the nominal voltage ratio.

25. A computer program comprising, when the program is executed by a computer, an instruction causing the computer to carry out the method of claim 24.

26. A controller for a bidirectional converter, configured to carry out the method of claim 24.

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