Pre-charge control system

Abstract

Aspects of the present invention relate to a pre-charge control system. A control system (150) for pre-charging a high voltage system (140) of a vehicle, the system (150) configured to: receive a pre-charge signal (152) indicative of a request to pre-charge a voltage across a first node (142) and a second node (144) of the high voltage system (140); output one or more control signals (154), in dependence on the received pre-charge signal, to control each of a first DC-DC converter (120) and a second DC-DC converter (130) to: convert electrical power received at an input of the respective DC-DC converter from a low voltage power source (110) to a higher voltage that increases over time; and output the converted electrical power at the higher voltage from an output of the respective DC-DC converter to the high voltage system (140), wherein the converted electrical power output from both the first DC-DC converter (120) and the second DC-DC converter (130) is applied across the first node (142) and the second node (144) of the high voltage system (140).

Description

[0001] PRE-CHARGE CONTROL SYSTEM

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a pre-charge control system. Aspects of the invention relate to a control system for controlling pre-charging of a high voltage system of a vehicle, to a system comprising the control system, to a vehicle, to a method for operating a control system for controlling precharging of a high voltage system of a vehicle and to computer readable instructions.

[0004] BACKGROUND

[0005] It is known to provide both high voltage and low voltage systems and components in vehicles. When a vehicle has not been used, for example powered down for a period of time, the high-voltage system may be substantially discharged, such that the voltage across the nodes of the high voltage system may be zero or substantially zero. If the high-voltage system comprises energy storage devices, such as energy storage capacitors or parasitic capacitors, coupled between the input nodes of the high-voltage system, coupling a high voltage to these energy storage devices may result in a large inrush or surge current. To prevent this, the high voltage system may be pre-charged, using pre-charge resistors. However, pre-charge resistors, which may be referred to as passive pre-charge resistors, lead to higher power losses in the resistors as well as increased system size to accommodate large passive components that can dissipate the power losses.

[0006] It is an aim of the present invention to address one or more of the disadvantages associated with the prior art.

[0007] SUMMARY OF THE INVENTION

[0008] Aspects and embodiments of the invention provide a control system for controlling pre-charging of a high voltage system of a vehicle, to a system comprising the control system, to a vehicle, to a method for operating a control system for controlling pre-charging of a high voltage system of a vehicle and to computer readable instructions as claimed in the appended claims.

[0009] According to an aspect of the present invention there is provided a control system for controlling pre-charging of a high voltage system of a vehicle, the control system configured to output one or more control signals to control each of a first DC-DC converter and a second DC-DC converter to: convert electrical power received from a low voltage source at an input voltage across an input of the respective DC-DC converter to a higher voltage that increases over time; and output the converted electrical power at the higher voltage across an output of the respective DC-DC converter to the high voltage system, wherein the converted electrical power output from both the first DC-DC converter and the second DC-DC converter is applied across the first node and the second node of the high voltage system.

[0010] According to an aspect of the present invention, there is provided a control system for controlling pre-charging of a high voltage system of a vehicle, the control system configured to: receive a pre-charge signal indicative of a request to pre-charge a voltage across a first node and a second node of the high voltage system, and in response to receiving the pre-charge signal: output one or more control signals to control each of a first DC-DC converter and a second DC-DC converter to: convert electrical power received from a low voltage power source at an input voltage across an input of the respective DC-DC converter to a higher voltage that increases over time; and output the converted electrical power at the higher voltage across an output of the respective DC-DC converter to the high voltage system, wherein the converted electrical power output from both the first DC-DC converter and the second DC-DC converter is applied across the first node and the second node of the high voltage system.

[0011] Pre-charging comprises supplying electrical power to a system such that an energy storage device, capacitance or parasitic capacitance of the system are charged. This limits the inrush or surge current that charges those capacitances.

[0012] Supplying electrical power across the first node and the second node comprises applying an output voltage from the first DC-DC converter and the second DC-DC converter across the first node and the second node. This may comprise a series or parallel connection of the outputs of the first DC-DC converter and the second DC-DC converter.

[0013] When a vehicle has not been used, for example powered down for a period of time, the high-voltage system may be substantially discharged, such that the voltage across the nodes of the high voltage system may be zero or substantially zero. If the high-voltage system comprises energy storage devices, such as energy storage capacitors or parasitic capacitors, coupled between the input nodes of the high-voltage system, coupling a high voltage to theseenergy storage devices may result in a large inrush or surge current. Coupling a power source to the energy storage device to charge the energy storage devices should be carefully controlled to ensure that the peak current drawn does not exceed current ratings of the system or a current limit set by an electronic power distribution system or fusebox.

[0014] The high voltage system of the vehicle may comprise a high voltage battery and one or more high voltage loads that are coupled or couplable to the first node and the second node of the high voltage system. During operation of the vehicle, the high voltage battery may be coupled to and may provide power to the one or more high voltage loads, such as air conditioning systems or vehicle motors. Directly coupling a high-voltage battery of the vehicle across the first node and second node of the high voltage system on start-up may result in the large surge current being drawn. To prevent this, the voltage across the first node and second node of the high voltage system may be pre-charged over time using the low voltage power system.

[0015] By supplying a voltage that increases over time across the first node and the second node, the voltage across those nodes also increases over time. The voltage supplied across the first node and second node may initially be less than a voltage that the high voltage system normally operates at, such as a voltage of a high voltage battery. The voltage may increase as the charge stored in the energy storage devices of the high-voltage system increases. This charges, or pre-charges, any energy storage devices that are coupled between those nodes. The lower increasing voltage results in a lower surge or inrush current. The voltage may increase in a linear fashion or exponentially. An exponentially increasing voltage may provide a system that precharges faster.

[0016] The inputs of the first DC-DC converter and the second DC-DC converter may be coupled to the low voltage power system. The inputs of the first DC-DC converter and the second DC-DC converter may be coupled to the low voltage power system. The outputs of the first DC-DC converter and the second DC-DC converter may be coupled across the first node and second node of the high voltage system. The outputs of the first DC-DC converter and the second DC-DC converter may be coupled in series. The first DC-DC converter and the second DC-DC converter may receive the same control signal, and may provide the same output voltage. The voltage output of each of the two converters may be half that of when a single converter is used to achieve the same voltage across the nodes of the high-voltage system, reducing the voltage stress applied to the converters. Further, each of the converters may be smaller, due to reduced magnetics needed in each of the converters, and operate at a higher efficiency.

[0017] The first node and second node of the high voltage system may be referred to as input nodes of the high voltage system.

[0018] The first DC-DC converter and the second DC-DC converter may be bi-directional DC-DC converters. As such, where individual inputs and outputs of the DC-DC converters are referenced, it should be understood that each may act as either an input or an output, depending on the use at the time. The DC-DC converters may comprise any suitable DC-DC converter topology. The DC-DC converters may comprise a switch implemented H-bridge, and the control information may comprise control schemes indicating how the switches or transistors are controlled.

[0019] The low voltage power supply may comprise a low voltage battery.

[0020] The high voltage system may comprise a high voltage bus. The high voltage bus may be couplable to a high voltage battery and / or one or more high voltage vehicle systems.

[0021] Receiving a pre-charge signal indicative of a request to pre-charge a voltage across the first node and the second node of the high voltage system may comprise receiving a signal from a system external to the control system. This may be in response to the vehicle entering a startup mode or being powered on from an off state.

[0022] According to an aspect of the present invention, the control system may be configured to output at least one control signal to couple the output of the first DC-DC converter and the output of the second DC-DC converter in series, and to couple the series connection of DC-DC converter outputs between the first node and the second node of the high voltage system.

[0023] The outputs of the first and second converters may be coupled in series, and this series combination may be coupled between the first node and the second node of the high voltage system. This results in the voltage supplied across the first node and second node being a result of the addition of the voltage output by the first DC-DC converter and the voltage output by the second DC-DC converter. This reduces the voltage stress applied to each of the converters.According to an aspect of the present invention, the control system may be configured to output at least one control signal to couple the input of the first DC-DC converter and the input of the second DC-DC converter in parallel, and to couple the parallel inputs of the DC-DC converters to the low voltage power source.

[0024] Coupling both of the DC-DC converters to the same low voltage power supply in parallel results in both converters receiving the same voltage input. This allows the converters to be controlled in the same manner.

[0025] According to an aspect of the present invention, the control system may be configured to control the first DC-DC converter to output the respective converted electrical power at a first output voltage that increases over time; and the second DC-DC converter to output the respective converted electrical power at a second output voltage that increases over time, the second output voltage being substantially equal to the first output voltage.

[0026] Outputting the same output voltage using both converters results in the current drawn by the high voltage system being split between the two converters. The voltage may be the same or substantially the same, allowing for tolerances in the two converters.

[0027] According to an aspect of the present invention, the control system may be configured to receive a voltage signal indicative of the voltage across the first node and the second node of the high voltage system; determine, in dependence on the received voltage signal, whether the voltage across the first node and the second node of the high voltage system has reached a reference voltage; and output, in dependence on a determination that the voltage across the first node and the second node of the high voltage system has reached the reference voltage, one or more control signals to control each of the first DC-DC converter and the second DC-DC converter to stop increasing the higher voltage over time.

[0028] When the voltage that is provided across the first node and the second node reaches a reference voltage, pre-charging may be complete. As such, the voltage supplied to high voltage system by the DC-DC converters no longer has to increase.

[0029] In a situation where the ambient temperature of the vehicle is low, for example, less than -10°C, -15°C, -20°C, -25°C a high voltage battery may not be capable of operating to connect to the high voltage system. For example, a number of contactors or relays that couple the high voltage battery to the high voltage system may not operate below certain ambient temperatures. As such, before the high voltage battery is coupled to the high voltage system, a heater included in the vehicle may be used to raise the temperature of the battery and / or contactors. Once the first DC-DC converter and second DC-DC converter raised the voltage of the high voltage system such that it reaches a voltage at which the heater can operate, the system may stop increasing the voltage applied between the first and second nodes of the high voltage system, and instead maintain a substantially constant voltage. The substantially constant voltage may be 400v, 450v, 500v, 550v, 600v amongst other voltages. This allows the heater to raise the temperature of the vehicle and its components.

[0030] According to an aspect of the present invention, the high voltage system may comprise a high voltage battery system, and wherein the reference voltage is an operating voltage of the high voltage battery system.

[0031] When the voltage across the first node and the second node is the same as the voltage of the high voltage battery system, then there is no need to further pre-charge any capacitances that may be present, at least because coupling the battery to the first node and second node would not change the current drawn. The voltage of the high voltage battery system may be a predetermined or programmed voltage indicating the designed voltage of the battery. Alternatively, the voltage of the high voltage battery system may be determined periodically or continuously through voltage measurement apparatus. This may allow the system to compensate for minor changes in the voltage of the high voltage battery. The battery system may comprise one or more battery packs. For example, there may be two battery packs within the battery system. The battery system may be an 800v system (or substantially 800v). As such, where two battery packs are used, each battery pack may be a 400v battery pack, that when coupled in series provide an 800v battery system.

[0032] According to an aspect of the present invention, the control system may be configured to: output, in dependence on the voltage signal indicating the voltage across the first node and the second node of the high voltage system reaching the operating voltage of the high voltage battery system, a battery control signal to couple the high voltage battery system to the first node and the second node of the high voltage system.

[0033] Coupling the high voltage battery system to or across the first node and second node of the high voltage system allows the high voltage battery system to power any loads included within the high voltage system. When the voltage across the first node and the second node is the same as the voltage ofthe high voltage battery system, then there is no need to further pre-charge any capacitances that may be present, as the current drawn would not change.

[0034] According to an aspect of the present invention, the one or more control signals may control the first DC-DC converter and the second DC-DC converter to operate in an interleaved manner.

[0035] The first DC-DC converter and second DC-DC converter may be any suitable converter topology. The first DC-DC converter and second DC-DC converter may comprise switching DC-DC converters. For example, the DC-DC converters may comprise switches or transistors, such as an H-bridge. The control signals may operate to control such switching DC-DC converters to operate in an interleaved manner. When the converters are interleaved, they are operated in anti-phase to one another, such that the control signals or switches are substantially 180 degrees out of phase. This results in the current drawn by the two converters also being in 180 degrees out of phase, resulting in a lower peak current being drawn from the low voltage power supply. This allows the low voltage power supply to be rated for a lower current draw.

[0036] According to an aspect of the present invention, the high voltage system may comprise one or more capacitances coupled between the first node and the second node, and wherein the control system may be configured to control the first DC-DC converter and the second DC-DC converter to convert the electrical power received from the low voltage power source to the respective higher voltages that increase over time such that a current drawn by the one or more capacitances is below an output current threshold.

[0037] The output current threshold relates to the current drawn on the output side of the first DC-DC converter and the second DC-DC converter. Limiting this current draw results in a lower surge current being drawn. Increasing the voltage over time allows the output current drawn by the energy storage devices to be controlled, and may be kept substantially constant. The output current threshold may be any suitable threshold that is below a desired current draw at the output of the converters.

[0038] According to an aspect of the present invention, the high voltage system may comprise one or more capacitances coupled between the first node and the second node, and wherein the control system may be configured to control the first DC-DC converter and the second DC-DC converter to convert the electrical power received from the low voltage power source to the respective higher voltages that increase over time such that a current drawn by the, or each of the, first DC-DC converter and the second DC-DC converter from the low voltage power source is below an input current threshold. The current supplied by the low voltage power supply may be subject to various limits or thresholds. Limiting this current draw results in a lower surge current being drawn, ensuring that the current drawn whilst pre-charging does not exceed these thresholds. The threshold may be any suitable threshold, for example 10A, 20A, 50A, 100A, 150A, 200A, 250A, 500A etc.

[0039] According to an aspect of the present invention, there is provided a system comprising the control system described herein, a power system, the power system comprising: the low voltage power source; the first DC-DC converter; the second DC-DC converter; and the high-voltage system.

[0040] According to an aspect of the present invention, the first DC-DC converter may comprise a first output node and a second output node; the second DC-DC converter may comprise a first output node and a second output node; the power system may further comprise: a first switch coupled between the first output node of the first DC-DC converter and the second output node of the second DC-DC converter, the first switch configurable to couple the first DC-DC converter and the second DC-DC converter in series; wherein the first output node of the second DC-DC converter is coupled to a first node of the high voltage system; wherein the second output node of the first DC-DC converter is coupled to a second node of the high voltage system.

[0041] According to an aspect of the present invention, there is provided a method for operating a control system for controlling pre-charging of a high voltage system of a vehicle wherein the method comprises: receiving a pre-charge signal indicative of a request to pre-charge a voltage across a first node and a second node of the high voltage system, and in response to receiving the pre-charge signal: outputting one or more control signals to control each of the first DC-DC converter and the second DC-DC converter to: convert electrical power received from a low voltage power source at an input voltage across an input of the respective DC-DC converter to a higher voltage that increases over time; and output the converted electrical power at the higher voltage across an output of the respective DC-DC converter to the high voltage system; wherein the converted electrical power from both the first DC-DC converter and the second DC-DC converter is applied across the first node and the second node of the high voltage system.According to an aspect of the present invention, there is provided computer readable instructions which, when executed by a computer, are arranged to perform the method.

[0042] BRIEF DESCRIPTION OF THE DRAWINGS

[0043] One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a power system of a vehicle in accordance with an embodiment of the invention;

[0044] Figure 2 shows a power system of a vehicle comprising low voltage and high voltage battery modules in accordance with an embodiment of the invention; Figure 3 shows a first flow chart showing a method of controlling pre-charging of a high-voltage system of a vehicle in accordance with an embodiment of the invention;

[0045] Figure 4 shows a graph of the voltage and current waveforms of the power system of Figure 2 in accordance with an embodiment of the invention; Figure 5 shows a second flow chart showing a method of controlling pre-charging of a high-voltage system of a vehicle in accordance with an embodiment of the invention;

[0046] Figure 6 shows a power system of a vehicle comprising high voltage battery modules in accordance with an embodiment of the invention;

[0047] Figure 7 shows a third flow chart showing a method of controlling pre-charging of a high-voltage system of a vehicle in accordance with an embodiment of the invention;

[0048] Figure 8 shows a fourth flow chart showing a method of controlling pre-charging of a high-voltage system of a vehicle in accordance with an embodiment of the invention;

[0049] Figure 9 shows a fifth flow chart showing a method of controlling pre-charging of a high-voltage system of a vehicle in accordance with an embodiment of the invention;

[0050] Figure 10 shows a graph of the voltage and current waveforms of the power system of Figure 6 in accordance with an embodiment of the invention; Figure 11 shows a control system of a vehicle in accordance with an embodiment of the invention; and

[0051] Figure 12 shows a vehicle in accordance with an embodiment of the invention.

[0052] DETAILED DESCRIPTION

[0053] The present disclosure relates to controlling the pre-charging of a high voltage system using two or more DC-DC converters coupled between a low voltage system and the high voltage system.

[0054] The high voltage system may be used to supply power to components of the vehicle that require a high voltage, or have a high current draw, such as an electric motor of a battery electric vehicle (BEV) or hybrid electric vehicle or an air conditioning system. When a vehicle has not been used, for example powered down, for a period, the high-voltage system may be substantially discharged, such that the voltage across the input nodes of the high voltage system may be zero or substantially zero. High voltage systems typically comprise energy storage devices, such as energy storage capacitors or parasitic capacitors, coupled between the input nodes of the high voltage system. These may also be referred to as DC-link capacitors, and act to smooth the voltage of the high voltage system in periods of high current draw. During normal operation of the vehicle, a high voltage battery module or system is coupled to the input nodes of the high voltage system, powering the components or sub-systems of the high voltage system.

[0055] However, coupling the high voltage battery module or system to the input nodes of the high-voltage system when the voltage across the input nodes is zero or substantially zero may result in a large inrush or surge current. The current drawn by the energy storage devices whilst charging is dependent on the voltage across the energy storage devices. When the capacitors are discharged and a high voltage is applied across the capacitors, the currentdraw is very high. As the charge stored in the capacitances increases, the current drawn to charge them decreases. As such, on vehicle startup when the energy storage devices are discharged, a high current is drawn (an in-rush current) when a power source is connected to the energy storage capacitor. An inrush or surge current may exceed the limits set by a fuse box or electronic power distribution unit of the vehicle. Further, to accommodate the large inrush or surge currents, conductors, connections or components of the vehicle may need to be substantially larger than would otherwise be required if the surge current were not present. T o prevent the inrush current exceeding limits of the vehicle, the high-voltage system may be pre-charged, by limiting the current that is supplied or increasing the voltage that is supplied to the high voltage system over time (rather than supplying a high voltage to the discharged capacitances straight away).

[0056] In some cases, a passive pre-charge system may be implemented in which a resistor is coupled between the power source and high voltage system during pre-charging, limiting the current. Alternatively, a DC-DC converter may be used with the output of the DC-DC converter coupled to the high voltage system and configured to increase the supplied voltage over time. This limits the inrush current of the high voltage system by reducing the voltage, allowing the capacitances to charge over a longer period of time.

[0057] However, the use of a pre-charge system in this manner leads to high power losses and a large power system in the case of a passive pre-charge system, or high peak currents being drawn by the DC-DC converter and high voltage stress on switching devices of the DC-DC converter. Further, as the initial current draw on startup to charge the one or more capacitors may exceed the current limit of the fuse or electronic power distribution system, the vehicle may never be able to charge the energy storage devices. This may prevent certain loads from operating correctly.

[0058] As such, it is desirable to pre-charge the high voltage system in a more efficient manner, whilst reducing the system size and reducing voltage stress on the system.

[0059] Figure 1 shows a power system 100 of a vehicle. The power system 100 comprises a low voltage power source 110. The low voltage power source 110 may comprise any suitable low voltage power supply, such as a low voltage battery module of the power system 100. The low voltage power source 100 may be used to power or supply one or more low voltage loads 160 of the power system. The low voltage power source may additionally or alternatively power or supply one or more other electrical components of the vehicle (not shown). The low voltage power source 110 may be a low voltage battery system, comprising one or more battery modules. The low voltage power source 110 may be a 12v, 24v or 48v system.

[0060] The low voltage power source 110 is coupled to inputs of a first DC-DC converter 120 and a second DC-DC converter 130. The input of the first DC-DC converter 120 is coupled in parallel with the input of the second DC-DC converter 130, and this parallel coupling of the inputs is coupled to the outputs of the low voltage power source 110. It should be understood that whilst Figure 1 shows the inputs of the DC-DC converters coupled in parallel, they may instead be coupled in series. Whilst two DC-DC converters are shown, it should be understood that two or more DC-DC converters may be provided. Further, each DC-DC converter may be replaced with two or more DC-DC converters coupled in parallel.

[0061] The outputs of the first DC-DC converter 120 and the second DC-DC converter 130 are coupled to a high voltage system 140 of the power system 100. The outputs of the first DC-DC converter 120 are coupled in series with the outputs of the second DC-DC converter 130, and this series coupling of the outputs is coupled to the first node 142 and second node 144 of the high voltage system 140. It should be understood that whilst Figure 1 shows the outputs of the DC-DC converters coupled in series, they may instead be coupled in parallel.

[0062] Whilst specific terminals of the DC-DC converters may be referred to here as inputs and outputs, it should be understood that the DC-DC converters may be bi-directional DC-DC converters, and as such the inputs and outputs may be input / output (i / o) terminals or nodes. Further, where each system or component is shown as having two input or output nodes or terminals, it should be understood that one of the terminals may be an input or output terminal, and the other terminal may be a ground or common reference terminal.

[0063] A control system 150 is configured to output one or more control signals 154 to control the operation of each of the first DC-DC converter 120 and the second DC-DC converter 130. The control system 150 may be any suitable control system, for example, as described with respect to figure 11. The first DC-DC converter 120 and the second DC-DC converter 130 are controlled by the control system 150. Any suitable DC-DC converter topology may be used, such as a DC-DC converter based around an H-Bridge design, comprising two or more transistors or switches, or four or more transistorsor switches. The DC-DC converters may be any suitable switching DC-DC converter, comprising one or more switches. The control signals output by the control system 150 may be any suitable control signal, with the type of control signal being dependent on the converter topology used.

[0064] The control system 150 is configured to receive a pre-charge signal 152 indicative of a request to pre-charge a voltage across a first node 142 and a second node 144 of the high voltage system 140 and in response to receiving the pre-charge signal, the control system 150 is configured to control the operation of the first DC-DC converter 120 and the second DC-DC converter 130 to pre-charge the high voltage system 140 by modifying the voltage coupled across the first node 142 and the second node 144 of the high voltage system 140. The first node 142 and second node 144 of the high voltage system 140 may also be referred to as input nodes of the high voltage system 140, acting as a high voltage bus of the high voltage system 140. Components or loads of the high voltage system 140 (such as DC-link capacitors and other loads such as electric motors or air conditioning systems, which are not shown) may be coupled between the input nodes 142, 144.

[0065] The low voltage power source 110 is selectively coupled to the high voltage system 140 via the first DC-DC converter 120 and the second DC-DC converter 130 to pre-charge the high voltage system 140 (such as the components of the high voltage system 140 that are coupled between the first node 142 and second node 144 of the high voltage system 140). The first DC-DC converter 120 and the second DC-DC converter 130 are controlled to receive an input voltage from the low voltage power source 110 and generate a higher voltage at their outputs that increases over time. By supplying a voltage that increases over time across the first node 142 and the second node 144, the voltage across those nodes also increases over time. The voltage supplied across the first node 142 and second node 144 may initially be less than a voltage that the high voltage system 140 normally operates at, such as a voltage of a high voltage battery (not shown). The voltage may increase as the charge stored in the energy storage devices of the high-voltage system increases. This charges, or pre-charges, any energy storage devices that are coupled between those nodes. The lower increasing voltage results in a lower surge or inrush current, as the current draw is related to the voltage applied across the capacitance and the charge state of the capacitance. The voltage may increase in a linear fashion or exponentially. An exponentially increasing voltage may provide a system that pre-charges faster.

[0066] Figure 2 shows a power system 200 according to an embodiment of the present invention. The power system 200 includes a number of components also shown in the power system 100 of Figure 1 . Like components are referred to with like reference numerals, and it should be understood that the discussion relating to Figure 1 also applies to Figure 2. The power system 200 includes a number of additional or further components not shown in the power system 100.

[0067] Power system 200 comprises a high voltage battery system comprising a first high voltage battery module 270 and a second high voltage battery module 280. Whilst Figure 2 shows two battery modules, the high voltage battery system may comprise one battery module (for example the first battery module 270). The high voltage battery system may comprise two or more battery modules. The high voltage battery system may be an 800v system (or substantially 800v). As such, where two battery modules are used, each battery module may be a 400v battery module. When coupled in series, the series connection of battery modules provides an 800v battery system. Any other voltage suitable for powering components of a vehicle may be used. The power system 200 further comprises a plurality of switches or switching devices 282-298. These switches or switching devices 282-298 may be relays, transistors or contactors, arranged to selectively couple the different components of the power system 200. During normal use, the high voltage battery modules 270, 280, may be coupled across or between the nodes 142, 144 of the high voltage system 140, supplying electrical power to the one or more loads of the high voltage system. To aid with pre-charging, as discussed above, the high voltage battery modules 270, 280 may be decoupled or disconnected from the high voltage system 140 using the plurality of switching devices, and the low voltage power source 110 used to pre-charge the high voltage system 140 via the DC-DC converters.

[0068] First switch 282 and second switch 284 allow selective coupling of the output of the low voltage power source 110 and the inputs of the first DC-DC converter 120 and the second DC-DC converter 130. Third switch 286, fourth switch 288, fifth switch 290 and sixth switch 292 allow selective coupling of the first battery module 270 and the second battery module 280 to the high voltage system 140. Seventh switch 294, eighth switch 296 and ninth switch 298 allow selective coupling of the outputs of the first DC-DC converter 120 and second DC-DC converter 130 and the battery modules 270, 280 to the input nodes 142, 144 of the high voltage system 140.

[0069] Figure 3 illustrates a method 300 according to an embodiment of the present invention. The method 300 of Figure 3 may be performed by the control system 150 of Figure 1 or Figure 2.The method 300 comprises receiving, in step 310, a pre-charge signal 152 indicative of a request to pre-charge a voltage across the first node 142 and the second node 144 of the high voltage system 140. Receiving a pre-charge signal indicative of a request to pre-charge a voltage across the first node 142 and the second node 144 of the high voltage system may comprise receiving a signal from a system external to the control system 150. This may be in response to the vehicle entering a startup mode or being powered on from an off state, or in response to the vehicle being placed in a mode that requires use of one or more of the high voltage loads of the high voltage system 140. Alternatively, the pre-charge signal may be generated by the control system 150, based on a pre-set condition being met.

[0070] In response to receiving the pre-charge signal 152, the method further comprises outputting in step 320, one or more control signals 154 to control each of the first DC-DC converter 120 and the second DC-DC converter 130 to convert electrical power, received by the first DC-DC converter 120 and the second DC-DC converter 130 from the low voltage power source at an input voltage across an input of the DC-DC converters, to a high voltage that increases over time. The input voltage may be the voltage of the low voltage power source 110.

[0071] Once the electrical power has been converted, the method comprises outputting in step 330, the converted electrical power, at the high voltage across an output of the DC-DC converters, to the high voltage system 140. The outputs of both DC-DC converters are coupled to the nodes of the high voltage system 140, resulting in the converted electrical power output from the first DC-DC converter 120 and the second DC-DC converter 130 being applied across the first node 142 and the second node 144 of the high voltage system 140. As shown in Figure 1 , where the outputs of the first DC-DC converter 120 and the second DC-DC converter 130 are coupled in series, the voltage applied between the first node 142 and second node 144 of the high voltage system is equal to the sum or combination of the output voltages of the first DC-DC converter 120 and the second DC-DC converter 130. If the outputs of the DC-DC converters were coupled in parallel, the voltage applied across the first node 142 and the second node 144 would be equal to the voltage output of the DC-DC converters.

[0072] By controlling the DC-DC converters to increase their output voltage over time, the voltage supplied between the first node 142 and the second node 144 is lower than if it was coupled to a higher voltage initially. This reduces the surge or in-rush current. After the voltage has increased to be substantially or almost the same as the voltage of the high voltage battery, there will be limited inrush current if the high voltage battery is coupled between the first node 142 and the second node 144. The use of two DC-DC converters, coupled as shown in Figure 1 , splits the current draw between the two converters. Further, as the outputs are coupled in series, each converter need be capable of only a portion of the maximum voltage across the first node 142 and second node 144 of the high voltage system 140. This reduces the voltage stress on the switches within the converters, and also allows the converters to have smaller magnetic systems (inductors or capacitors) than would otherwise be required.

[0073] Figure 4 illustrates a graph 400 according to an embodiment of the present invention. An x-axis of the graphs represents a time, in seconds, from 0-0.45s. The graph shows the voltage 410 (in volts) applied between the first node 142 and second node 144 of the high voltage system 140. The y-axis for line 410 shows the voltage, in volts, from -200 to 10OOv. The graph shows the current 420 (in amps) supplied to the high voltage system 140. The y-axis for the current 420 represents a current in amps, from -5A to 10A. The graph shows the current 430 (in amps) drawn from the low voltage power system 110. The y-axis for the current 430 represents a current in amps, from -200A to 200A.

[0074] As can be seen , the voltage output from the first DC-DC converter 120 and the second DC-DC converter 130 that is supplied between the first node 142 and second node 144 of the high voltage system 140 increases over time. The graph shows the voltage increasing from substantially Ov or a low voltage to 800-900v. Increasing the voltage in this fashion ensures that the peak current, shown by graph 420, drawn by the high voltage system 140 (to charge the capacitances) is limited to a suitable level or limit. Further, the current 430 drawn from the low voltage system 110 can also be limited to an acceptable level. The rate at which the voltage supplied between the first node 142 and the second node 144 is increased may be dependent on a desired current draw or current limit of either the low voltage power source 110, the high voltage system 140 or the DC-DC converters is not exceeded.

[0075] For example, the first DC-DC converter 120 and the second DC-DC converter 130 may convert the electrical power received from the low voltage power source 110 to the respective higher voltages that increase over time such that a current drawn by the one or more capacitances coupled between the first node 142 and second node 144 of the high voltage system 140 is below an output current threshold. The output current threshold relates to the current drawn on the output side of the first DC-DC converter 120 and the second DC-DC converter 130. Limiting this current draw results in a lower surge current being drawn. The output current may be determined by measuring the output current using a current sensor. Increasing the voltage over time allows the output current drawn by the capacitances to be controlled, and may be kept substantially constant. The output current threshold may be any suitable threshold that is below a desired current draw at the output of the converters.The output current of the first DC-DC converter and the second DC-DC converter may be primarily limited by the ability of the low voltage power source to supply current. As such, alternatively, or in addition, the first DC-DC converter 120 and the second DC-DC converter 130 may convert the electrical power received from the low voltage power source 110 to the respective higher voltages that increase over time such that a current drawn by the, or each of the, first DC-DC converter 120 and the second DC-DC converter 130 from the low voltage power source 110 is below an input current threshold. The input current may be determined by measuring the input current using a current sensor. The current supplied by the low voltage power supply source may be subject to various limits or thresholds. Limiting this current draw results in a lower surge current being drawn, ensuring that the current drawn whilst pre-charging does not exceed these thresholds. The threshold may be any suitable threshold, for example 10A, 20A, 50A, 100A, 150A, 200A, 250Aetc.

[0076] The switches 282-298 shown in Figure 3 are just one example of how the different components of the power system may be selectively coupled. Any arrangement of switches or permanent connections that allows coupling of the respective components is considered suitable. The switches 282-298 may be selectively controlled by the control system 150 through the output of one or more switch control signals (not shown). Alternatively, the switches may be controlled by one or more separate control systems.

[0077] During the pre-charging operation, the switches may be selectively controlled as shown in Table 1 :

[0078]

[0079] This switching arrangement results in the high voltage battery modules 270, 280 being disconnected from the high voltage system. The low voltage power source 110 is coupled to the inputs of the first DC-DC converter 120 and second DC-DC converter 130 (with the DC-DC converters coupled in parallel at the inputs). The outputs of the first DC-DC converter 120 and the second DC-DC converter 130 are coupled in series, and across the nodes 142, 144 of the high voltage system.

[0080] To provide the switching configuration described here, the control system 150 may output one or more control signals. For example, the control system 150 may output at least one control signal to couple the output of the first DC-DC converter 120 and the output of the second DC-DC converter 130 in series, and to couple the series connection of DC-DC converter outputs between the first node 142 and the second node 144 of the high voltage system 140. This results in the voltage supplied across the first node 142 and second node 144 being a result of the addition of the voltage output by the first DC-DC converter 120 and the voltage output by the second DC-DC converter 130. Further, the control system 150 may output at least one control signal to couple the input of the first DC-DC converter 120 and the input of the second DC-DC converter 130 in parallel, and to couple the parallel inputs of the DC-DC converters to the low voltage power source 110. Coupling both of the DC-DC converters to the same low voltage power source 110 in parallel results in both converters receiving the same voltage input (or substantially the same voltage dependent on parasitic component voltage drops within the system).

[0081] The first DC-DC converter 120 and second DC-DC converter 130 may operate in substantially the same fashion. For example, the control signals 154 output by the control system 150 to the first DC-DC converter 120 and the second DC-DC converter 130 may be the same control signal / s, or substantially the same control signal / s. This allows the system to operate with minimal complexity, and a simple to implement control scheme.

[0082] The first DC-DC converter 120 may output the respective converted electrical power at a first output voltage that increases over time and the second DC-DC converter 130 may output the respective converted electrical power at a second output voltage that increases over time. The series combination of these voltages is applied between the first node 142 and the second node 144 of the high voltage system 140 (as shown in Figure 4, 410). The second output voltage may be substantially equal to the first output voltage, resulting in both of the DC-DC converters providing substantially half of the voltage that is applied between the first node 142 and second node 144 of the high voltage system 140. As the DC-DC converters are coupled in series at their outputs, the entire current drawn flows through both DC-DC converters. Further, the voltage stress applied to the switching devices of each converter issubstantially halved compared to a situation where only a single converter is used. This allows the DC-DC converters to be smaller. The voltage outputs of the two converters may be the same or substantially the same, allowing for tolerances in the two converters. Further, using two DC-DC converters allows the system to continue to operate even if one of the DC-DC converters breaks, becomes non-operable, or develops a fault. This allows the system to pre-charge using one of the two DC-DC converters.

[0083] Alternatively, the first output voltage and the second output voltage may be different, such that each DC-DC converter provides a different portion of the voltage applied between the first node 142 and the second node 144 of the high voltage system 140. This may be particularly beneficial where the DC-DC converters are specified to different levels of efficiency, have different current limits or different voltage limits.

[0084] The system may continue, as described with respect to step 330 of method 300, controlling the DC-DC converters to increase their output voltage over time, until a certain voltage level or limit is reached. When the voltage level or limit has been reached, the DC-DC converters may be controlled to stop increasing the output voltage at that level.

[0085] Figure 5 illustrates a method 500 according to an embodiment of the present invention. The method 500 of Figure 5 may be performed by the control system 150 of Figure 1 or Figure 2. When the voltage that is provided across the first node 142 and the second node 144 reaches a reference voltage, pre-charging may be complete - this may occur when the voltage that is across the first node 142 and the second node 144 is the same as an operating voltage of the high voltage system, or an operating voltage of the series combination of the first battery module 270 and second battery module 280. Above this level, the battery modules 270, 280 or any high voltage power source may be coupled to the first node 142 and second node 144 of the high voltage system 140 without causing a surge or inrush current, as the capacitances between the nodes have been pre-charged. As such, the voltage supplied to the high voltage system by the DC-DC converters no longer has to increase.

[0086] To determine when to stop increasing the voltage output by the first DC-DC converter 120 and second DC-DC converter 130, the control system 150 may receive in step 510, a voltage signal indicative of the voltage across the first node 142 and the second node 144 of the high voltage system 140 and determine in step 520, in dependence on the received voltage signal, whether the voltage across the first node 142 and the second node 144 of the high voltage system has reached a reference voltage. The reference voltage may be an operating voltage of the high voltage battery system (the voltage provided by a series connection of the first battery module 270 and second battery module 280). When the voltage across the first node 142 and the second node 144 is the same as the operating voltage of the high voltage battery system, then there is no need to further pre-charge any capacitances that may be present, at least because coupling the battery to the first node 142 and second node 144 would not change the current drawn. The voltage of the high voltage battery system may be a predetermined or programmed voltage indicating the designed voltage of the battery. Alternatively, the voltage of the high voltage battery system may be determined periodically or continuously through voltage measurement apparatus. This may allow the system to compensate for minor changes in the voltage of the high voltage battery.

[0087] The operating voltage may be the normal or rated battery voltage (e.g. 400v individual / parallel battery voltage or 800v series battery voltage) or could be a lower operating voltage at which the HV battery can be safely coupled to the nodes (e.g. 350 / 750 volts) or can safely operate. The reference voltage may be substantially the same as the operating voltage of the battery, for example within 100, 50, 10, or 5v of the operating voltage.

[0088] The reference voltage 412 shown in Figure 4 shows the voltage at which the DC-DC converters may stop increasing their output voltage, and thus stop increasing the voltage 410 applied between the first node 242 and second node 244 of the high voltage system 240.

[0089] Following a determination that the voltage across the first node 142 and second node 144 has reached the reference voltage, the control system may output in step 530, one or more control signals to control each of the first DC-DC converter 120 and the second DC-DC converter 130 to stop increasing the respective higher voltage over time. The method 500 may take place following the method shown in Figure 3, and the determination as to whether the voltage across the first node 142 and second node 144 has reached the reference voltage may take place continuously or periodically whilst the DC-DC converters are increasing their output voltage.

[0090] Once the voltage output of the first DC-DC converter 120 and the second DC-DC converter has stopped increasing in step 540 of method 500, the first battery module 270 and second battery module 280 may be coupled in series and the series combination coupled between the first node 142 and the second node 144 of the high voltage system. This may comprise the control system outputting, in dependence on the voltage signal indicating the voltage across the first node 142 and the second node 144 of the high voltage system 140 has reached the operating voltage of the high voltage battery system, a battery control signal to couple the high voltage battery system to the first node 142 and the second node 144 of the high voltage system 140.Coupling the high voltage battery system to or across the first node 142 and second node 144 of the high voltage system 140 allows the high voltage battery system to power any loads included within the high voltage system 140. When the voltage across the first node 142 and the second node 144 is the same as the operating voltage of the high voltage battery system, then there is no need to further pre-charge any capacitances that may be present, as the current draw would not change. The high voltage battery system may also be coupled to the first node 142 and the second node 144 of the high voltage system at a voltage below the rated voltage or operating voltage of the high voltage battery, for example so that the high voltage battery can be used to raise the voltage between the first node 142 and second node 144 during the last part of the pre-charging process. At this point, the risk of high in-rush current is significantly reduced.

[0091] As noted, the first DC-DC converter 120 and the second DC-DC converter 130 may operate in the same manner, based on the same control signal 155 from the control system 150. The first DC-DC converter 120 and the second DC-DC converter 130 may instead operate in an interleaved fashion. The control system 150 may output control signals 155 that cause the DC-DC converters, and particularly the switches of the DC-DC converters to operate in an interleaved manner. When the converters are interleaved, they are operated in anti-phase to one another, such that the control signals or switches are substantially 180 degrees out of phase. This results in the current drawn by the two converters also being in 180 degrees out of phase, resulting in a lower peak current being drawn from the low voltage power source. This allows the low voltage power source to be rated for a lower current draw. As noted, the system may operate the DC-DC converters such that their output voltages increase over time until a threshold or operative voltage of the battery modules 270, 280 is reached. In a situation where the ambient temperature of the vehicle is low, for example, less than -10°C, -15°C, -20°C, -25°C a high voltage battery may not be capable of operating to connect to the high voltage system. For example, a number of contactors or relays that couple the high voltage battery to the high voltage system 140 may not operate below certain ambient temperatures. As such, before the high voltage battery is coupled to the high voltage system 140, a heater included in the vehicle may be used to raise the temperature of the battery and / or contactors. Once the first DC-DC converter 120 and second DC-DC converter 130 raised the voltage of the high voltage system 140 such that it reaches a voltage at which the heater can operate, a heater threshold voltage, the system may stop increasing the voltage applied between the first 142 and second 144 nodes of the high voltage system 140, and instead maintain a substantially constant voltage. The substantially constant voltage may be 400v, 450v, 500v, 550v, 600v amongst other voltages. This allows the heater to raise the temperature of the vehicle and its components. After this, once the vehicle or system temperature has risen to a temperature at which the battery contactors can close or the battery can operate, the voltage may continue to be increased until the reference voltage is met.

[0092] Low Voltage Battery Not Present:

[0093] In some situations, it is desirable to omit the low voltage power source 110 from the vehicle. In this situation, one or more low voltage loads of the vehicle may be coupled to a low voltage bus and powered by the high voltage battery (stepped down in voltage using one or more DC-DC converters). In other situations the low voltage battery may not work, be missing, or be faulty. It is still desirable in this situation to allow pre-charging of the high-voltage system so that the one or more high voltage loads can operate, and further to allow use of the low voltage loads.

[0094] Figure 6 shows a power system 600 according to an embodiment of the present invention. The power system 600 includes a number of components also shown in the power system 100 of Figure 1 and power system 200 of Figure 2. Like components are referred to with like reference numerals, and it should be understood that the discussion relating to Figure 1 and Figure 2 also applies to Figure 6.

[0095] The power system 600 comprises a low voltage power source 610. The low voltage power source 610 may be a passive system, such as a low voltage bus, connection or coupling. The low voltage power source 610 is coupled to the inputs of the first DC-DC converter 120 and the second DC-DC converter 130. The low voltage power source 610 is also coupled to the one or more low voltage loads 160.

[0096] The low voltage power source 610 may comprise a low voltage battery, even though it is not required for pre-charging the high voltage system 140. The low voltage power source 610 may be a 12v, 24v or 48v system, configured to power one or more low voltage loads.

[0097] The remaining components of the power system 600 are the same as the power system 100 and the power system 200. It is desirable to pre-charge the high voltage system 140 in an efficient manner without the use of a low voltage battery, where the low voltage battery is faulty, non-operable or not present.The first DC-DC converter 120 and the second DC-DC converter 130 are controlled by the control system 150. The control system 150 is configured to receive a pre-charge signal 152 indicative of a request to pre-charge a voltage across a first node 142 and a second node 144 of the high voltage system 140 and in response to receiving the pre-charge signal, the control system 150 is configured to control the operation of the first DC-DC converter 120 and the second DC-DC converter 130 to pre-charge the high voltage system 140 by modifying the voltage coupled across the first node 142 and the second node 144 of the high voltage system 140.

[0098] As noted previously, the first DC-DC converter 120 and second DC-DC converter 130 may be bi-directional DC-DC converters. In this embodiment, the nodes of the first DC-DC converter 120 that are coupled to the first high voltage battery module 270 may be referred to as an input of the first DC-DC converter 120 and the nodes of the first DC-DC converter 120 that are coupled to the low voltage power source 610 may be referred to as an output of the first DC-DC converter. The nodes of the second DC-DC converter 130 that are coupled to the low voltage power source 610 may be referred to as an input of the second DC-DC converter 130 and the nodes that are coupled to the second high voltage battery module 280 and the nodes of the high voltage system 140 may be referred to as an output of the second DC-DC converter 130. This naming convention is for ease of understanding, and it should be understood that some or all of the nodes may be input / output nodes.

[0099] The first high voltage battery module 270, which may also be referred to as a first high voltage power source, is selectively coupled to the inputs of the first DC-DC converter 120. The first DC-DC converter 120 is controlled to receive an input voltage from the first high voltage battery module 270 and convert the electrical power received from the first high voltage battery module 270 to electrical power having a low or lower voltage. The first DC-DC converter 120 down converts the input voltage to a low voltage, and provides this to the low voltage power source 610. The second DC-DC converter 130 is controlled to receive a second input voltage from the low voltage power source 610 and convert this to a first higher voltage that increases over time. The second DC-DC converter 130 outputs the converted electrical power at the first higher voltage, such that the first higher voltage is applied across the first node 142 and second node 144 of the high voltage system.

[0100] In this manner, the first DC-DC converter 120 acts to down-convert the output of the first high voltage battery module 270 and the second DC-DC converter 130 acts to up-convert the output of the first DC-DC converter 120 in an increasing manner. This allows the voltage applied across or between the first node 142 and second node 144 of the high voltage system 140 to be increased over time using a high voltage battery module 270. This removes the need for a low-voltage battery whilst also allowing pre-charging of the high voltage system 140. Further, the high voltage battery module 270 can be used to power or supply the one or more low voltage loads 160 coupled to the low voltage power source 610 even whilst pre-charging is occurring. Figure 7 illustrates a method 700 according to an embodiment of the present invention. The method 700 of Figure 7 may be performed by the control system 150 of Figure 7.

[0101] The method 700 comprises receiving, in step 710, a pre-charge signal 152 indicative of a request to pre-charge a voltage across the first node 142 and the second node 144 of the high voltage system 140. Receiving a pre-charge signal indicative of a request to pre-charge a voltage across the first node 142 and the second node 144 of the high voltage system 140 may comprise receiving a signal from a system external to the control system 150. This may be in response to the vehicle entering a startup mode or being powered on from an off state, or in response to the vehicle being placed in a mode that requires use of one or more of the high voltage loads of the high voltage system 140. Alternatively, the pre-charge signal may be generated by the control system 150, based on a pre-set condition being met.

[0102] In response to receiving the pre-charge signal 152, the method further comprises outputting in step 720, one or more control signals 154 to control the first DC-DC converter 120 to convert electrical power received from a first high voltage battery module 270 at an input voltage across an input of the first DC-DC converter 120 to a lower voltage and output the converted electrical power at the lower voltage across an output of the first DC-DC converter to a low voltage power source 610.

[0103] Following, or at the same time as outputting in step 720, the method comprises outputting in step 730, one or more second control signals to control the second DC-DC converter 130 to convert electrical power received from the low voltage power source 610 at a second input voltage across an input of the second DC-DC converter 130 to a first higher voltage that increases over time and output the converted electrical power at the first higher voltage across an output of the second DC-DC converter 130 such that the converted electrical power at the first higher voltage from the second DC-DC converter 130 is applied across the first node 142 and the second node 144 of the high voltage system 140. The second input voltage of the second DC-DC converter 130 is from the low voltage power source 610, and thus may be the same voltage as the low voltage output by the first DC-DC converter 120.Utilising both a first DC-DC converter 120 and a second DC-DC converter 130 to pre-charge the high voltage system 140 allows the voltage of the high voltage power source, for example a high voltage battery module 270, to be stepped-down and then stepped-up in an increasing manner to pre-charge the high-voltage system 140. This results in the current drawn by any components across the first node 142 and second node 144 of the high voltage system 140 being reduced, reducing any surge current. No low voltage battery is needed in the vehicle, and as such the vehicle may comprise only the high voltage battery. The first DC-DC converter 120 and second DC-DC converter 130 may be used to power low voltage loads that form part of the low voltage system. As such, re-using the DC-DC converters to pre-charge the high voltage system removes the need for further converters to be included for this task, or for a low voltage battery to pre-charge the high voltage system 140.

[0104] Method 700 may describe a first stage of the pre-charging operation. During the first stage of the pre-charging operation, the switches may be selectively controlled by the control system 150 as shown in Table 2.

[0105]

[0106] Figure 8 illustrates a method 800 according to an embodiment of the present invention. The method 800 of Figure 8 may be performed by the control system 150 of Figure 6. The method 800 includes steps 710-730 as described with respect to the method 700.

[0107] In step 840 of method 800, the method may comprise receiving a voltage signal indicative of a voltage across the first node 142 and the second node 144 of the high voltage system 140 reaching a threshold voltage. The threshold voltage may be a maximum voltage that the second DC-DC converter 130 is capable of outputting, or a voltage substantially similar (for example within a range) to the maximum voltage that the second DC-DC converter 130 is capable of outputting or converting to. The threshold voltage may also be a voltage substantially equal to a rated or operating voltage of the first high voltage battery module 270. Once this voltage is reached, the second DC-DC converter 130 can no longer increase the voltage coupled between the nodes 142 and 144 of the high voltage system 140. If the high voltage system 140 has a node reached a voltage at which the capacitances are suitably pre-charged, then further increases to the voltage supplied between the first node 142 and the second node 144 may not be required.

[0108] Rather than the voltage signal being indicative of the voltage across the first node 142 and second node 144 reaching a threshold, the voltage signal may be indicative of the actual voltage across the first node 142 and 144. Step 840 may then include a further step of determining whether the voltage across the first node 142 and second node 144 of the high voltage system has reached the threshold. The threshold may be an operating voltage of the first high voltage battery module 270.

[0109] Following step 840, the method may enter a second stage of the pre-charging operation.

[0110] In step 850, the control system may output a third control signal to couple the first high voltage battery module 270 in series with the output of the second DC-DC converter 130 between the first node 142 and second node 144 of the high voltage system 140. This allows the output voltage of the second DC-DC converter 130 to be applied on top of the voltage of the first high voltage battery module 270. This allows a greater voltage to be applied to the high voltage system 140, allowing further pre-charging of the capacitances.

[0111] During the second stage of the pre-charging operation, the switches may be selectively controlled as shown in Table 3.

[0112]

[0113] This switching arrangement results in the first high voltage battery module 270 being coupled to both the inputs of the first DC-DC converter 120 and in series with the output of the second DC-DC converter 130. To provide the switching configuration described here, the control system 160 may output one or more control signals to the switches.

[0114] After the first high voltage battery module 270 has been coupled in series with the output of the second DC-DC converter 130, or at the same time as the first high voltage battery module 270 is coupled in series with the output of the second DC-DC converter 130, the conversion of the second DC-DC converter 130 may be modified such that the output voltage of the second DC-DC converter 130 is reduced, for example to zero volts or a lower voltage than the system was previously operating at. This results in the voltage coupled across the first node 142 and second node 144 of the high voltage system 140 being equal to the voltage of the first high voltage battery module 270. As the output of the second DC-DC converter 130 may be substantially the same as the voltage of the first high voltage battery module 270 at the time the first high voltage battery module 270 is coupled in series with the output of the first high voltage battery module 270, the voltage across the first node 142 and second node 144 of the high voltage system 140 does not change substantially. This results in no inrush current, or only a minor inrush current during this operation.

[0115] The output voltage of the second DC-DC converter 130 may then be increased again over time in the same manner as the initial operation. The first high voltage power source or battery 270 acts as an offset that increases the output voltage coupled between the first node 142 and second node 144 of the high voltage system.

[0116] Figure 9 illustrates a method 900 according to an embodiment of the present invention. The method 900 of Figure 9 may be performed by the control system 150 of Figure 6. The method 900 includes steps 710-730 and steps 840-850 as described with respect to the method 800.

[0117] In response to receiving the voltage signal indicative of the voltage across the first node 142 and the second node 144 of the high voltage system 140 has reached the threshold voltage or the determination that the voltage across the first node 142 and the second node 144 of the high voltage system 140 has reached the operating voltage of the first high voltage battery module 270, the method comprises in step 960, outputting a further control signal to control the second DC-DC converter 130 to initially reduce the voltage to which the electrical power received from the low voltage power source 110 is converted. This may comprise reducing the voltage to zero or substantially zero. Step 960 may take place at the same time, before or after step 850. Following the reduction in the output voltage of the second DC-DC converter 130, the second DC-DC converter 130 converts 970 the electrical power received from the low voltage power source 610 to a second higher voltage that increases over time. This voltage may increase in the same manner as in step 720.

[0118] In step 970, the second DC-DC converter 130 outputs the converted electrical power at the second increasing voltage across the output of the second DC-DC converter 130 to the high voltage system 140, such that the converted electrical power from the second DC-DC converter 130 is applied in series with the first high voltage battery module 270, between the first node 142 and the second node 144 of the high voltage system 140.

[0119] Following a determination that the voltage across the first node 142 and second node 144 has reached a reference voltage, the control system may output in step 980 one or more control signals to control the second DC-DC converter 130 to stop increasing the respective second higher voltage over time. The reference voltage may be the operating, actual or rated voltage of a series connection of the first high voltage battery module 170 and the second high voltage battery module 180. When the voltage across the first node 142 and the second node 144 is the same as or similar to the voltage of the high voltage battery system, then there is no need to further pre-charge any capacitances that may be present, at least because coupling the first battery module 270 and second battery module 280 to the first node 142 and second node 144 would not change the current drawn. The voltage of the high voltage battery system may be a predetermined or programmed voltage indicating the designed voltage of the battery. Alternatively, the voltage of the high voltage battery system may be determined periodically or continuously through voltage measurement apparatus. This may allow the system to compensate for minor changes in the voltage of the high voltage power sources or batteries. The battery system may comprise one or more battery modules. For example, there may be two battery modules within the battery system. The battery system may be an 800v system (or substantially 800v). As such, where two battery modules are used, each battery module may be a 400v battery module, that when coupled in series provide an 800v battery system.

[0120] The reference voltage may be as described earlier with respect to the system comprising the low voltage battery, such that when the voltage that is provided across the first node 142 and the second node 144 reaches a reference voltage, pre-charging may be complete. As such, the voltage supplied to high voltage system 140 by the DC-DC converters no longer has to increase.In step 990, following the determination that the voltage across the first node 142 and second node 144 of the high voltage system 140 has reached the reference voltage or operating voltage of the first high voltage battery module 270 and second high voltage battery module 280 coupled in series, the first high voltage battery module 270 and second high voltage battery module 280 may be coupled in series and between the first node 142 and the second node 144 of the high voltage system 140. Coupling the high voltage battery system to or across the first node 142 and second node 144 of the high voltage system 140 allows the high voltage battery system to power any loads included within the high voltage system 140.

[0121] Figure 10 shows a graph. An x-axis of the graphs represents a time, in seconds, from 0-0.8s. The graph shows the voltage 1010 between the first node 142 and second node 144 of the high voltage system 140 and the current drawn by the high voltage system 140. The y-axis for voltage 1010 shows the voltage, in volts, from -200v to 800v. The y-axis for the current 1020 shows the current, in amps, from -5A to 25A. The first stage of the pre-charging process, in which the first battery module is not coupled in series with the output of the second DC-DC converter 130, occurs for a first period 1030. The second stage of the pre-charging process, in which the first high voltage battery module 270 is coupled in series with the output of the second DC-DC converter occurs for a second period 1040. As can be seen, the voltage across the first node 142 and second node 144 of the high voltage system 140 increases during both periods. At the transition between the two periods, when the first high voltage battery 270 is coupled in series with the output of the second DC-DC converter 130 and the output voltage of the second DC-DC converter 130 is reduced, there may be a surge current or current spike caused by the transition period. However, this current spike or surge is significantly lower than it would be if the high voltage battery modules 270, 280 were directly coupled to the high voltage system 140 without pre-charging.

[0122] The methods 700, 800 or 900 may be used in a system where there is no low voltage battery, and the low voltage power source 610 comprises a direct connection or low voltage bus. Alternatively, the methods 700, 800 or 900 may be used in a system where a low voltage battery is present (for example as shown in Figures 1 or 2). In particular, the methods 700, 800, or 900 may take place when the low voltage battery is faulty, not present, discharged or otherwise inoperable. The control system 150 may receive a fault signal indicating a fault associate with the low voltage battery 110 and perform the methods 700, 800 or 900 in response to this fault signal. The fault signal may be received from the low-voltage battery, a different control system of the vehicle or determined through the control system 150 testing the low voltage battery and determining the presence of the fault. This allows the system to operate the high voltage and low voltage loads even without the low voltage battery.

[0123] The rate or type of increase in the output of the second DC-DC converter 130 may be determined so that a current drawn by the high voltage system 140, and in particular a current drawn to charge one or more capacitances remains below an output current threshold. The output current threshold relates to the current drawn on the output side of the second DC-DC converter 130, which is the current drawn by the high voltage system 140. Limiting this current draw results in a lower surge current being drawn. Increasing the voltage over time allows the output current drawn by the energy storage devices to be controlled, and may be kept substantially constant. The output current threshold may be any suitable threshold that is below a desired current draw at the output of the converters. The increase in voltage may be a linear, exponential or other type of increase, and the gradient of the increase may be any suitable gradient.

[0124] The output of the first DC-DC converter 120 may be a substantially constant or constant voltage. The output of the first DC-DC converter 120 is coupled to the low voltage power source 610. The low voltage power source 610 may be a 12v, 24v or 48v system, configured to power one or more low voltage loads 160. As these loads require a substantially constant voltage, the output of the first DC-DC converter 160 may be substantially constant. This allows the low voltage loads to be powered or used whilst the high voltage system 140 is being pre-charged.

[0125] A control system 1100 in accordance with an embodiment of the present invention is described herein with reference to the accompanying Figure 11. The control system 1100 may be used in place of the control system 150 shown in Figures 1 , 2, or 6. The control system 1100 may be installed in a vehicle 1200 shown in Figure 12. The control system 1100 may perform the method of any of Figures 3, 5, 7, 8 or 9.

[0126] The control system 1100 is configured to receive a pre-charge signal 1165 indicative of a request to pre-charge a voltage across a first node 142 and a second node 144 of the high voltage system 140. The control system 1100 may then output one or more control signals 1155 to one or more DC-DC converters to control the DC-DC converters to pre-charge the high voltage system 140 and components coupled between the first node 142 and second node 144 of the high voltage system 140.

[0127] The control system 1100 as illustrated in Figure 11 comprises one controller 1110, although it will be appreciated that this is merely illustrative, and one or more controllers may be used. The controller 1110 comprises processing means 1120 and memory means 1130. The processing means 1120 maybe one or more electronic processing devices 1120 which operably execute computer-readable instructions. The memory means 1130 may be one or more memory devices. The memory means 1130 is electrically coupled to the processing means 1120. The memory means 1130 is configured to store instructions, and the processing means 1120 is configured to access the memory means 1130 and execute the instructions stored thereon.

[0128] The controller 1110 comprises an input means 1140 and an output means 1150. The input means 1140 may comprise an electrical input of the controller 1110. The output means 1150 may comprise an electrical output of the controller 1110. The input 1140 is arranged to receive the pre-charge signal from any suitable device 1160. The pre-charge signal 1165 is an electrical signal. The output 1150 is arranged to output one or more control signals 1155 to the one or more DC-DC converters 120, 130.

[0129] Instead of a digital control system 1100, the control system 1100 may be any suitable analog or Boolean logic implemented control system.

[0130] Figure 12 illustrates a vehicle 1200 according to an embodiment of the present invention. The vehicle 1200 comprises a control system 150 or 1100 operable to control the pre-charging of a high voltage system 140 of the vehicle 1200. The vehicle 1200 may comprise the power system 100, 200 or 600.

[0131] The vehicle 1200 may be a hybrid electric vehicle (HEV). A HEV may be characterised by being arranged to receive electrical energy from an external source, such as via a connection to mains electricity. A HEV may therefore comprise an external electrical connection for charging the battery in addition to a combustion engine. The vehicle 1200 may be a battery electric vehicle (BEV) in which the vehicle is driven solely by electric motors and a battery, with no combustion engine. Vehicle 1200 may be an EGO vehicle, i.e. , a vehicle that is equipped with autonomous or semi-autonomous driving technology and is capable of sensing and navigating its environment without direct input from a human driver.

[0132] It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

CLAIMS1. A control system for controlling pre-charging of a high voltage system of a vehicle, the control system configured to:receive a pre-charge signal indicative of a request to pre-charge a voltage across a first node and a second node of the high voltage system, and in response to receiving the pre-charge signal:output one or more control signals to control each of a first DC-DC converter and a second DC-DC converter to:convert electrical power received from a low voltage power source at an input voltage across an input of the respective DC-DC converter to a higher voltage that increases over time; andoutput the converted electrical power at the higher voltage across an output of the respective DC-DC converter to the high voltage system,wherein the converted electrical power output from both the first DC-DC converter and the second DC-DC converter is applied across the first node and the second node of the high voltage system.

2. The control system according to claim 1 , wherein the control system is configured to:output at least one control signal to couple the output of the first DC-DC converter and the output of the second DC-DC converter in series, and to couple the series connection of DC-DC converter outputs between the first node and the second node of the high voltage system.

3. The control system according to any preceding claim, wherein the control system is configured to:output at least one control signal to couple the input of the first DC-DC converter and the input of the second DC-DC converter in parallel, and to couple the parallel inputs of the DC-DC converters to the low voltage power source.

4. The control system according to any preceding claim, wherein the control system is configured to control:the first DC-DC converter to output the respective converted electrical power at a first output voltage that increases over time; and the second DC-DC converter to output the respective converted electrical power at a second output voltage that increases over time, the second output voltage being substantially equal to the first output voltage.

5. The control system according to any preceding claim, wherein the control system is configured to:receive a voltage signal indicative of the voltage across the first node and the second node of the high voltage system; determine, in dependence on the received voltage signal, whether the voltage across the first node and the second node of the high voltage system has reached a reference voltage; andoutput, in dependence on a determination that the voltage across the first node and the second node of the high voltage system has reached the reference voltage, one or more control signals to control each of the first DC-DC converter and the second DC-DC converter to stop increasing the higher voltage over time.

6. The control system according to claim 5, wherein the high voltage system comprises a high voltage battery system, and wherein the reference voltage is an operating voltage of the high voltage battery system.

7. The control system according to claim 6, wherein the control system is configured to:output, in dependence on the voltage signal indicating the voltage across the first node and the second node of the high voltage system reaching the operating voltage of the high voltage battery system, a battery control signal to couple the high voltage battery system to the first node and the second node of the high voltage system.

8. The control system according to any preceding claim, wherein the one or more control signals control the first DC-DC converter and the second DC-DC converter to operate in an interleaved manner.

9. The control system according to any preceding claim, wherein the high voltage system comprises one or more capacitances coupled between the first node and the second node, and wherein the control system is configured to control the first DC-DC converter and the secondDC-DC converter to convert the electrical power received from the low voltage power source to the respective higher voltages that increase over time such that a current drawn by the one or more capacitances is below an output current threshold.

10. The control system according to any of claims 1 -8, wherein the high voltage system comprises one or more capacitances coupled between the first node and the second node, and wherein the control system is configured to control the first DC-DC converter and the second DC-DC converter to convert the electrical power received from the low voltage power source to the respective higher voltages that increase over time such that a current drawn by the, or each of the, first DC-DC converter and the second DC-DC converter from the low voltage power source is below an input current threshold.

11. A system comprising:the control system of any preceding claim;a power system, the power system comprising:the low voltage power source;the first DC-DC converter;the second DC-DC converter; andthe high-voltage system.

12. The system according to claim 11 , wherein:the first DC-DC converter comprises a first output node and a second output node;the second DC-DC converter comprises a first output node and a second output node;the power system further comprises:a first switch coupled between the first output node of the first DC-DC converter and the second output node of the second DC-DC converter, the first switch configurable to couple the first DC-DC converter and the second DC-DC converter in series;wherein the first output node of the second DC-DC converter is coupled to a first node of the high voltage system; wherein the second output node of the first DC-DC converter is coupled to a second node of the high voltage system.

13. A vehicle comprising the system of claim 11 or 12 or the control system of claims 1-10.

14. A method for operating a control system for controlling pre-charging of a high voltage system of a vehicle wherein the method comprises:receiving a pre-charge signal indicative of a request to pre-charge a voltage across a first node and a second node of the high voltage system, and in response to receiving the pre-charge signal: outputting one or more control signals to control each of the first DC-DC converter and the second DC-DC converter to:convert electrical power received from a low voltage power source at an input voltage across an input of the respective DC-DC converter to a higher voltage that increases over time; andoutput the converted electrical power at the higher voltage across an output of the respective DC-DC converter to the high voltage system; wherein the converted electrical power from both the first DC-DC converter and the second DC-DC converter is applied across the first node and the second node of the high voltage system.

15. Computer readable instructions which, when executed by a computer, are arranged to perform a method according to claim 14.

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