Supplying power to a lv onboard electrical subsystem of a vehicle from the hv onboard electrical subsystem thereof
Patent Information
- Application Number
- EP2023717549
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-05-12
- Filing Date
- 2023-04-06
- Publication Date
- 2025-03-19
AI Technical Summary
Existing methods for supplying a low-voltage (LV) sub-board network from a high-voltage (HV) sub-board network in vehicles are unreliable, especially when using aged batteries or increased impedance, leading to power limitations and potential damage from circulating currents.
A method utilizing galvanically isolated DC-DC converters with adjustable current saturation, where the current saturation value is reduced when input voltage falls below a threshold, and reset when nominal voltage is reached, to ensure reliable power delivery to the LV sub-board network even with power-limited sources.
This approach enhances the reliability of LV sub-board network supply by reducing settling time and overshoot, preventing damage from circulating currents and ensuring stable power delivery even with aged batteries or increased impedance.
Smart Images
Figure 1.1
Abstract
Description
[0001] Supplying a vehicle's low-voltage sub-system from its high-voltage sub-system
[0002] The invention relates to a method for supplying a low-voltage sub-system of a vehicle from its high-voltage sub-system via at least one galvanically isolated DC-DC converter. The invention also relates to a vehicle having an on-board power system with an high-voltage sub-system and an low-voltage sub-system, with at least one galvanically isolated DC-DC converter interposed between them, wherein the vehicle is configured to carry out the method. The invention is particularly advantageously applicable to electric vehicles.
[0003] M. Baumann, Yue Sun, Bert Haj Ali, C. Weissinger, H. Herzog: "Deadzone Compensated Double Integral Sliding Mode Control for Distributed Converters," IEEE Transportation Electrification Conference & Expo (ITEC), June 21–25, 2021, discloses a design method for a so-called "Double Integral Sliding Mode Control" (DISMC) applied to topologies derived from buck converters. The control strategy based on so-called "Voltage Mode Control" (VMC) is extended with a deadzone-compensated current control to stabilize fault conditions such as short circuits. A control concept for distributed converters is derived and verified through test bench-based measurements. DISMC is validated on a prototype 1 kW converter and compared with industry-standard PI-based control designs. Both the settling time and overshoot amplitudes can be reduced by up to 67% and 35%, respectively.
[0004] It is the object of the present invention to at least partially overcome the disadvantages of the prior art and in particular to provide a more reliable supply of an NV sub-system without chemical NV storage from an HV sub-system of a vehicle.
[0005] This object is achieved according to the features of the independent claims. Preferred embodiments can be found in particular in the dependent claims.
[0006] The object is achieved by a method for supplying a low-voltage sub-system of a vehicle from its high-voltage sub-system via at least one galvanically isolated DC-DC converter with an adjustable value of the current saturation, lout, max, in which a
[0007] - an auxiliary voltage, V .th, which is between a nominal voltage, Vj n ,nom, of the HV sub-network and a specified minimum input voltage, Vj n,min, is set,
[0008] - when an input voltage, Vin, measured at the DC-DC converter falls below the value of the auxiliary voltage Vm.th, an input power, P in , on which DC-DC converter is determined and
[0009] - a "performance-adjusted" value, l ou t,max i red, the current saturation is calculated based on the previously determined input power and is set instead of a standard current saturation value, and
[0010] - only when the input voltage Vj n the nominal voltage Vj n ,nom of the HV sub-network is reached again, the current saturation l ou t,max to the default or standard value l ou t,max i def is reset.
[0011] This method offers the advantage that the supply of the low-voltage on-board power system can be provided even with a power-limited source (e.g., an aged high-voltage battery, an increased impedance of the HV sub-system, etc.). This is achieved by adjusting the current saturation l ou t,max is determined using a hysteresis depending on the measured input power. This allows even with a low HV-side input voltage Vj n The DC-DC converter can be used to supply the NV sub-system with a low voltage.
[0012] The low-voltage ("NV") sub-system has a nominal on-board voltage that is lower than the nominal on-board voltage Vj n ,nom of the high-voltage ("HV") sub-system.
[0013] The galvanically isolated DC-DC converter is a DC-DC converter in which the input side, connected to the HV subsystem, is galvanically separated from the output side, connected to the NV subsystem. The galvanic isolation can be implemented in a generally known manner by opposing input and output coils with respective numbers of turns. A turns ratio n is thus given for the DC-DC converter. The input voltage Vj applied to the input side n can be measured by the DC-DC converter itself. The vehicle can be, for example, a motor vehicle with an internal combustion engine, a plug-in hybrid vehicle (PHEV), or a fully electric vehicle (BEV). The vehicle can be a passenger car, truck, motorcycle, aircraft (plane, helicopter, etc.), watercraft (boat, ship, etc.), or a combination thereof.
[0014] The current saturation l out,max corresponds in particular to the current value that can be fed into the low-voltage sub-system by the respective DC-DC converter. The current saturation value l ou t,max is adjustable, particularly via the DC-DC converter itself. The default value can, for example, correspond to the maximum output current value based on the design.
[0015] In particular, in ,nom > V in ,th > in ,min.
[0016] That when the input voltage j n falls below the value of the auxiliary voltage Vm.th, the input power Pj n at the DC-DC converter, a new, "power-adjusted" current saturation value l ou t,max | red and instead of the standard current saturation value l out, max i def is set, includes in particular that in this scenario, which is typically given when there are no transients, first applies and furthermore l ou t,max = lout, max i def applies. Only when, e.g., when a transient occurs, j n below the value of the auxiliary voltage n ,th falls, l becomes ou t,max on l ou t,max i red switched, where l ou t,max | red of the input voltage Pj present at the time of detection of the undershoot n depends and is typically smaller than l ou t,max | def , so l out, max i red (Pin) < l out, max i def . The DC-DC converter then leads to a smaller load on the HV sub-system. The fact that the input voltage V; n below the value of the auxiliary voltage Vj n ,th falls, can - depending on the interpretation - the relationship V; n < n ,th or the relationship V; n < n ,th correspond.
[0017] That the current saturation l ou t,max only then to the standard value l ou t,max i det is reset when the input voltage j n the nominal voltage Vm.nom of the HV sub-network is reached again, corresponds to a hysteresis of the value of the current saturation l ou t,max in the range between Vj n ,th and Vj n ,nom. If the input voltage Vj n between Vj n ,th and n, max, the current value for l remains ou t,max. The input voltage Vj n the nominal voltage Vj n ,nom of the HV sub-network is reached again, can - depending on the design - the relationship Vj n > Vj n ,nom or the relationship Vj n > Vj n ,nom correspond.
[0018] It is a further development that the input power Pj n = Vj n • n with l inthe electrical current flowing through the DC-DC converter on the input side. This input power corresponds to the output power V, neglecting the power loss of the DC-DC converter. ou t • lout at the output side of the DC-DC converter. The input power Pj n can therefore also be calculated using the relationship Vout • lout with or without taking into account the power loss of the DC-DC converter.
[0019] It is a configuration that when the input voltage Vj n below the specified minimum input voltage Vj n ,min falls (ie, depending on the implementation , Vj n < Previous year n ,min or n < Vj n ,min applies), the DC-DC converter switches off and then, when the input voltage Vj n the minimum input voltage Vj n ,min is reached again (ie, depending on the implementation, Vj n > Vj n ,min or Vjn > Vj n ,min applies), the DC-DC converter switches on again.
[0020] The fact that the DC-DC converter switches off includes, in particular, that it switches off its converter functionality and thus does not output a signal on the output side. Analogue includes, in particular, that the DC-DC converter switches on. Other functions and / or components of the DC-DC converter, such as monitoring the input voltage, detecting when various thresholds are reached, and subsequent reactions (e.g., switching the converter functionality on and off), remain unaffected.
[0021] One embodiment involves supplying the low-voltage sub-system from the high-voltage sub-system via multiple DC-DC converters. This offers the advantage that comparatively simple and inexpensive DC-DC converters can be used and, in addition, a particularly high level of reliability and thus security of supply for the low-voltage sub-system is achieved. The method is particularly advantageous for this embodiment because it prevents circulating currents between the distributed DC-DC converters or at least significantly reduces their effects. These circulating currents would otherwise lead to losses and could also damage the DC-DC converters. During a transient load, the input voltages Vj nat the nodes of the individual DC-DC converters, or the total power of DC-DC converters distributed throughout the vehicle may exceed the supply power of the HV sub-system. In the latter case, a DC-DC converter may switch off if V n under j n ,min. This DC-DC converter switches on again immediately when V n the value Vm.min is reached again. The connected DC-DC converter then supplies the low-voltage subsystem again, and the available system power of the high-voltage subsystem is exceeded. Without further measures, this would result in repeated disconnection and reconnection, which, with further repetitions, would place a heavy load on the DC-DC converter electronics, which could even be damaged in the worst case. This electronic load is avoided by adjusting the current saturation value described above.
[0022] As a further development, the above method is carried out independently for each of the DC-DC converters. This is advantageous because the input voltages n of the individual DC-DC converters can differ, for example, when transients occur. As a further development, the input voltage Vin applied to the DC-DC converters is determined individually for each of the DC-DC converters. This also results in the DC-DC converters being switched on and off individually.
[0023] It is a configuration that the minimum input voltage Vj n ,min according to n.min = n • V out,ref is calculated with n being the winding ratio of the DC-DC converter and Vout.ref being a control reference voltage. The (control) reference voltage corresponds specifically to a target control variable of the DC-DC converter at its output terminals. It can be adjusted on the vehicle side and thus adapted to different requirement scenarios, for example. It can generally be higher, lower, or equal to the nominal voltage of the low-voltage sub-system.
[0024] It is a design that the reference voltage V ou t,ref is exchanged between the DC-DC converters on a data line, especially on a CAN bus. This provides the advantage of a simple adjustment of the reference voltage V ou t,ref over several converters and is also practical because this adaptation is not time-critical within typical transmission times of a bus.
[0025] It is a design that the power-adjusted current saturation value l ou t,max | red according to l O ut,max i red = Pj n • n / Vin.th is calculated.
[0026] One design is for the DC-DC converter to be a synchronous rectifier. This offers the advantage of comparatively low losses. This type of rectifier typically does not use components that inherently allow current flow only in one direction; instead, MOSFETs are often used, which are controlled by the DC-DC converter's control electronics to act like semiconductor diodes with a very low forward voltage.
[0027] In a further development, the synchronous rectifier is a push-pull forward converter with full-bridge control. In a further development, the synchronous rectifier is a phase-shifting full-bridge DC-DC converter. This type of converter is particularly well-suited for higher power classes, up to several kilowatts.
[0028] The rectifier can be constructed in particular analogously to the rectifier described in Fig.1(a) of the article "Deadzone Compensated Double Integral Sliding Mode Control for Distributed Converters".
[0029] It is a configuration that the nominal voltage Vm.nom of the HV sub-system lies between 48 V and 1000 V. It is a configuration that the nominal voltage VNv.nom of the NV sub-system lies between 12 V and 60 V. In general, the nominal voltage of the HV sub-system is greater than the nominal voltage of the HV sub-system. Possible examples include Vj n,nom = 48 V, 60 V or 120 V and V iv.nom = 12 V; Vjn.nom = 120 V, 400 V or 800 V and VNv.nom = 48 V or 60 V; etc.
[0030] The object is also achieved by a vehicle having an on-board power system with an HV sub-system and an NV sub-system, between which at least one galvanically isolated DC-DC converter is connected. The vehicle is configured to carry out the method as described above. The vehicle can be designed analogously to the method, and vice versa, and has the same advantages.
[0031] In one embodiment, the vehicle can be a partially or fully electrically powered electric vehicle, e.g. a plug-in hybrid vehicle or a battery-electric vehicle.
[0032] The above-described properties, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following schematic description of an embodiment, which is explained in more detail in connection with the drawings.
[0033] Fig.1 shows a sketch of a section of an on-board power system of a vehicle; and
[0034] Fig.2 shows a possible sequence of the method according to the invention.
[0035] Fig. 1 shows a sketch of a section of an on-board power supply system (EBN) of a vehicle F. The on-board power supply system (EBN) has a low-voltage sub-system (NVN), which can be supplied from a high-voltage sub-system (HVN) via several galvanically isolated DC-DC converters (GSW1, GSW2, GSW3). The DC-DC converters (GSW1, GSW2, GSW3) convert a higher voltage Vj n of the HV sub-network HVN into a lower voltage V out,ref. A respective output voltage V ou t the DC-DC converter GSW1, GSW2, GSW3 is connected to a wiring harness KB of the NV sub-vehicle network NVN, optionally via respective resistors Z, which can be the same or different.
[0036] The DC-DC converters GSW1, GSW2, and GSW3 are connected to a communication channel of the vehicle F, in this case, for example, a CAN bus, and can communicate with each other via this channel. In particular, the DC-DC converters GSW1, GSW2, and GSW3 can be arranged in a master-slave configuration, with the DC-DC converter GSW1 being used as the master and the DC-DC converters GSW2 and GSW3 being used as slaves. A desired value of the reference voltage V ou t,ref of the NV sub-vehicle network can be communicated, for example, via the CAN bus CAN and the DC-DC converters GSW1, GSW2, GSW3.
[0037] Fig.2 shows a possible sequence of a method for supplying the low-voltage sub-network NVN from the high-voltage sub-network HVN by adapting one of the DC-DC converters GSW1, GSW2 or GSW3.
[0038] - the nominal voltage Vj n ,nom of the HV sub-network HVN is greater than the nominal voltage of the NV sub-network NVN;
[0039] - there is an auxiliary voltage Vj n ,th has been specified, which lies between the nominal voltage n.nom of the HV sub-network HVN and the specified minimum input voltage Vj n ,min of the HV sub-network HVN,
[0040] - a standard or default value of the current saturation l ou t,max is at l ou t,max i def.
[0041] For the purpose of further describing the procedure, the following values are assumed purely as examples: Vj n ,nom = 48 V, Vj n ,th = 40 V, VNv.nom and V out,ref = 12 V and n = 3. It follows that Vin.min — n ■ Vhiv.nom — 12 V = 36 V. It also applies that n.nom > n ,th > n.min. Furthermore, it is assumed that at the beginning of the method in step 50, there are no transients or other disturbances and the DC-DC converters GSW1, GSW2, GSW3 are switched on, which is described by their state "ON". The input voltage Vj n is initially above the auxiliary voltage n ,th of 40 V.
[0042] After starting the procedure in step S0, a step S1 checks whether the input voltage Vj n smaller than the auxiliary voltage n ,th. This is usually not the case in a healthy HV sub-network HVN without transients ("N"), in which case it is then queried in a step S2 whether the input voltage Vj nis less than the nominal voltage Vjn.nom of the HV sub-system HVN of 48 V. If this is the case ("Y"), the system branches back to step S1.
[0043] However, if it is determined in step S1 that the input voltage Vj n is smaller than the auxiliary voltage Vjn, th ("J"), i.e. Vjn < Vjn, th, a check is carried out in a step S4 to determine whether the current saturation l ou t,max to the power-adjusted value l ou t,max i red is set. If this is not the case ("N") and the current saturation l ou t,max is still at the default value l ou t,max i def, the process branches to step S5. In step S5, a currently available input power Pj n = Vj n ■ calculated on the input side of the DC-DC converter GSW1, GSW2, GSW3 and from this a power-adjusted current saturation value l ou t,max = lout, max i red := (n ■ P in) I Vm.th, which is now set instead of the standard value lout, max i det on this DC-DC converter GSW1, GSW2, GSW3. Typically, l ou t,max | red < lout, max i det, so that a maximum power transfer from the HV sub-system HVN to the NV sub-system NVN via the DC-DC converter GSW1, GSW2, or GSW3, and thus also overall, is reduced. The system then proceeds to step S6.
[0044] However, if step S4 is answered positively ("Y"), ie that the current saturation l ou t,max already to a performance-adjusted value l ou t,max i red is set, the system branches directly to step S6. This procedure therefore includes keeping the power-adjusted current saturation value lout,max i red unchanged after its setting until it returns to the standard value l ou t,max i det is reset.
[0045] Subsequently, in step S6 it is checked whether the input voltage j n even smaller than the minimum input voltage j n ,min, so if j n < Vm.min applies.
[0046] If this is the case ("Y"), the DC-DC converter GSW1, GSW2 or GSW3 under consideration is switched off individually in step S7, which is indicated by the switching state "OFF".
[0047] After switching off, the process branches back to step S6 and performs the associated query again. As a result, the DC-DC converter GSW1, GSW2 or GSW3 remains switched off until the input voltage j n again greater than or equal to the minimum input voltage j n ,min ("N"). In this case, or if it was already determined in the first query in step S6 that the input voltage jn is greater than or equal to the minimum input voltage j n ,min, the process branches to step S8.
[0048] In step S8, the DC-DC converter GSW1, GSW2 or GSW3 remains or is switched on, and the process branches back to step S1. If the value of the input voltage Vj n in step S1 is still smaller than the auxiliary voltage Vin.th ("J"), the process branches back to step S4. Since the power-adjusted current saturation value l ou t,max i red is set, the process branches directly ("Y") from step S4 to step S6.
[0049] If the value of the input voltage Vj n in step S1 but now greater than or equal to the auxiliary voltage Vm.th ("N"), in step S2 it is again queried whether the input voltage Vj n less than the nominal voltage Vj n ,nom of the HV sub-network HVN. If this is the case ("Y"), the current power-adjusted current saturation value l ou t,max | red is retained and the process returns to step S1.
[0050] Only if the value of the input voltage Vjn the nominal voltage Vj n ,nom has been reached again ("N"), the current saturation l ou t,max to the default value l ou t,max i def reset or reset.
[0051] Of course, the present invention is not limited to the embodiment shown.
[0052] There can be only one DC-DC converter GSW1, only two DC-DC converters GSW1, GSW2 or more than three DC-DC converters GSW1, GSW2, GSW3.
[0053] Furthermore, in general, and in the exemplary embodiment, for example, in steps S1, S2 and / or S6, the conditions "less than" or "greater than" can be queried instead of the conditions "less than" or "greater than" or "greater than".
[0054] In general, "a", "an", etc., can be understood as a singular or a plural, in particular in the sense of "at least one" or "one or more", etc., unless this is explicitly excluded, e.g. by the expression "exactly one", etc.
[0055] A numerical specification may also include the exact number specified as well as a usual tolerance range, as long as this is not explicitly excluded.
[0056] CAN CAN bus
[0057] EBN on-board energy network
[0058] F vehicle
[0059] KB wiring harness
[0060] GSW1 DC-DC converter
[0061] GSW2 DC-DC converter
[0062] GSW3 DC-DC converter n Input current through the DC-DC converter
[0063] HVN HV sub-network HVN lout, max Current saturation lout, max i det Standard value of the current saturation lout, max i red Power-adjusted value of the current saturation n Number of turns ratio
[0064] NVN NV sub-board network
[0065] OFF Switched off state
[0066] ON Switched on state
[0067] P Input power
[0068] S0-S8 procedural steps
[0069] Vn Measured input voltage n.min Minimum input voltage n.nom Nominal voltage of the HV sub-system out.ret Reference voltage
[0070] Vin.th auxiliary voltage
Claims
Patent claims Method (S1 - S8) for supplying a low-voltage (LV) sub-system (NVN) of a vehicle from its high-voltage (HVN) sub-system via at least one galvanically isolated DC-DC converter (GSW1 , GSW2, GSW3) with an adjustable value (lout, max i def, loud, max i red) of the current saturation (lout, max) , at which the DC voltage converter (GSW1 , GSW2, GSW3) - an auxiliary voltage ( n ,th), which is between a nominal voltage (Vj n ,nom) of the HV sub-network (HVN) and a specified minimum input voltage (n.min), is determined (SO), - then, when an input voltage (Vj) measured at the DC voltage converter (GSW1 , GSW2, GSW3) n ) below the value of the auxiliary voltage (Vj) n ,th) falls (S1), an associated input power (Pj) n ) is determined (S5), - a performance-adjusted value (l ou t,max i red) the current saturation (l out,max) based on the previously determined input power (Pj) n ) calculated and instead of a default value (l ou t,max | def) of current saturation (l ou t,max) is set (S5) and - only when the input voltage (Vj n ) the nominal voltage (Vm.nom) of the HV sub-system (HVN) is reached again (S2), the current saturation (l ou t,max) to the standard value (l out,max i def) is reset (S3). Method (S1 - S8) according to claim 1, wherein when the input voltage (Vjn) falls below the minimum input voltage (Vm.min) (S6), the DC-DC converter (GSW1, GSW2, GSW3) switches off (S7) and then, when the input voltage (n) reaches the minimum input voltage (Vm.min) again (S6), the DC-DC converter (GSW1, GSW2, GSW3) switches on again (S8). Method (S1 - S8) according to any of the preceding claims, wherein the low-voltage (LV) sub-system (NVN) is supplied from the high-voltage (HVN) sub-system by means of several DC-DC converters (GSW1, GSW2, GSW3). Method (S1 - S8) according to any of the preceding claims, wherein the minimum input voltage (Vm.min) is determined according to Vm.min = n • V ou t,ref with n a turns ratio of the DC voltage transformer (GSW1 , GSW2, GSW3) and V ou t,ref of a A control reference voltage is calculated at the output side of the DC-DC converter (GSW1, GSW2, GSW3). A method (S1-S8) according to any one of claims 3 to 4, wherein the reference voltage (Vout.ref) is exchanged between the DC-DC converters (GSW1, GSW2, GSW3) on a data line, in particular on a CAN bus (CAN). A method (S1-S8) according to any one of the preceding claims, wherein the power-adapted current saturation value (l) ou t,max) according to l ou t,max = Pin / Vj n ,th • n with Pj n the value of the input power (Pj) n ) and Vj n ,th the value of the auxiliary voltage (Vj n,th) is calculated. Method (S1 - S8) according to any one of the preceding claims, wherein at least one DC-DC converter (GSW1, GSW2, GSW3) is a synchronous rectifier. Method (S1 - S8) according to claim 7, wherein the synchronous rectifier is a phase-shifting full-bridge DC-DC converter. Method (S1 - S8) according to any one of the preceding claims, wherein the nominal voltage (Vm.nom) of the first HV sub-system (HVN) is between 48 V and 1000 V. Method (S1 - S8) according to any one of the preceding claims, wherein the nominal voltage of the LV sub-system (NVN) is between 12 V and 60 V. Vehicle (F) comprising an on-board power supply (EBN) with a high-voltage sub-on-board power supply (HVN) and a low-voltage sub-on-board power supply (NVN), to which at least one galvanically isolated DC voltage converter (GSW1 , GSW2, GSW3) is connected, wherein the vehicle (F) is configured to carry out the method (S1 - S8) according to one of the preceding claims.Vehicle (F) according to claim 11, wherein the vehicle (F) is an electric vehicle.