CN112425058A - Vehicle-side charging circuit and method for transmitting electrical energy to a vehicle electrical system - Google Patents

Abstract

The vehicle-side charging circuit (LS) is equipped with a controllable multiphase rectifier (GR) having a plurality of controllable half-bridges (B0-B2). The AC voltage side of the rectifier (GR) is connected to an AC voltage terminal (IF). The direct-current voltage side of the rectifier (GR) is connected to the vehicle-mounted power grid terminal (A) in a converter-less manner. The charging circuit has a control device (C) which is operatively connected to the controllable half-bridge (B0-B2). The control device (C) is set up to control a smaller number of controllable half-bridges in a clocked manner in the precharge mode than in the main charging mode. Furthermore, a method for transmitting electrical energy to an on-board electrical system is described.

Description

Vehicle-side charging circuit and method for transmitting electrical energy to a vehicle electrical system

Vehicles with electric drives usually have a battery as energy store for feeding the drive. In many vehicle cases, a charging socket is provided in order to transfer energy from the outside into the battery, for example in the course of a charging process.

Since the terminal voltage of the battery depends on the state of charge, which changes during the course of the charging process, the charging circuit usually comprises a dc voltage converter, the variable conversion ratio of which can be used to adapt the charging voltage to the transient battery voltage. However, such a dc voltage converter is associated with additional costs for the charging circuit.

The object of specifying the possibility with which energy can be introduced into the vehicle electrical system and in particular into the battery provided there in a simple manner with an adaptable variable charging voltage is therefore to be solved.

This object is achieved by the subject matter of the independent claims. Further embodiments, features, characteristics and advantages result from the dependent claims, the description and the drawings.

It is proposed to use a controllable rectifier with a plurality of half bridges in order to adjust the appropriate voltage by means of the number of active half bridges. Thus, in addition to the duty cycle, the number of active half-bridges or phases may be varied in order to thereby achieve an adaptation. Since the link factors of different heights occur with different numbers of active half-bridges, different voltages are obtained by different numbers of half-bridges alone. In the case of a first charging state or in the case of a first number of active half bridges (compared to the nominal value), therefore, a lower voltage can be achieved by the dc voltage converter than in the case of a second charging state or of a second number of active half bridges, which is higher than the first charging state or the first number of active half bridges.

A vehicle-side charging circuit with a controllable multiphase rectifier is proposed. The rectifier has a plurality of controllable half-bridges. Each phase is assigned a (own) controllable half-bridge. The half bridge comprises a series circuit of two switching elements or one switching element and one diode, wherein the switching elements are controllable. The switching element is in particular a semiconductor switch, for example a transistor, such as an IGBT or a MOSFET. The switching element can furthermore consist of two semiconductor switches connected in anti-series with one another, in particular when the semiconductor switches have a body diode. The ends of the series circuit are connected to the dc voltage potential (e.g., + and-) of the rectifier. The coupling point via which the two elements of the series circuit are connected is connected with the (separate) phase terminal. Preferably, this applies for all half bridges. The end of the series circuit or circuits is part of the dc voltage side of the rectifier. The junction between two elements of the series circuit (i.e. switching element-switching element or switching element-diode) is part of the ac voltage side of the rectifier. This also applies to the junction points of the diodes of the diode half-bridge, if present.

The ac voltage side of the rectifier is connected to the ac voltage terminal. The phase terminal is part of an alternating voltage terminal. The dc voltage side of the rectifier is connected to the vehicle electrical system terminals in a converter-less manner. No components which would act in a voltage-converting manner or would change the voltage level are present between the rectifier on the one hand and the vehicle electrical system terminals or the vehicle electrical system connected thereto on the other hand, wherein the filter, the connecting elements and the safety device are not regarded as voltage-converting elements. The connection between the rectifier and the vehicle electrical system terminal is therefore a direct connection. This saves costs for the dc voltage converter connected downstream of the rectifier.

The charging circuit and in particular the rectifier has a control device. The control device is connected in a controlled manner to the rectifier or to the controllable half bridge thereof. The control device is designed to control the rectifier. The control device is set up to control a smaller number of controllable half-bridges in a clocked manner in the precharge mode than in the main charging mode. Thus, there is a precharge mode with a smaller number of active half-bridges than in the main charging mode. The control device is set up to execute the main charging mode after the pre-charging mode. The control device is therefore designed to increase the link factor of the rectifier by increasing the number of active or controlled half-bridges. The control device may have an input, wherein the control device adjusts the number of phases depending on the signal at the input, or alternatively (i.e. depending on the signal) sets one of the mentioned charging modes. The input signal may reflect the number of phases or the rated voltage or the actual voltage. In both cases, the control device comprises a comparator for comparing the voltage with at least one comparison value in order to set the pre-charge mode or the main-charge mode depending on the comparison result.

Preferably, the control device is set up to control the controllable half-bridges, preferably all controllable half-bridges, in a clocked manner in the main charging mode. In this case, the control device can be set up to control the half-bridge according to the phase control or according to a (predefined) duty cycle, in particular according to the phase control. In this way, the effective rectified voltage of the rectifier, i.e., the (pulsating) output voltage, can be set, in particular taking into account the number of active half-bridges (i.e., depending on the link factor) and/or depending on the nominal voltage value.

The control device can be set up to control only one controllable half-bridge in a clocked manner in the precharge mode and to control the remaining controllable half-bridges to be open-circuited. If the rectifier is equipped, for example, with three controllable half-bridges (or three groups of controllable half-bridges), the control means can be set up for actively controlling only one of the half-bridges (or groups of half-bridges) in the precharge mode. In other words, the control device can be set up (in the case of a rectifier with three controllable half-bridges or half-bridge groups) to operate the two half-bridges (or half-bridge groups) as open-circuited in the precharge mode. In the case of an open-circuit actuation of a half bridge, the switchable switching elements of the half bridge are in an open-circuit switching state; the control device is set up to set the switching state by actuation.

Active steering corresponds to clocked steering (in particular clocked steering as mentioned earlier) and vice versa. In the case of active or clocked actuation, according to one specific embodiment, the half bridge concerned or its switchable switching elements are switched (i.e. their switching state is changed) in each phase of the ac voltage to be rectified, in particular in the partial load operating range of the rectifier.

The control device may have an input. The input is preferably connected to the vehicle electrical system terminal in terms of signaling. This input is connected to the vehicle electrical system terminal (or to a battery in the vehicle electrical system connected thereto) such that a signal, for example in the form of a voltage value, is received at the input, which signal characterizes the voltage (of the vehicle electrical system, at the vehicle electrical system terminal, of the battery). Preferably, the control device is set up to compare the value of the voltage applied at the input with a threshold value. For this purpose, the control device can have a comparator. Preferably, the control device is set up for setting the pre-charging mode if the voltage value is below a threshold value and for setting the main-charging mode if the voltage value is above the threshold value. Alternatively, the input can be set up for receiving a switching instruction. In this case, a switching command, which specifies the mode (main charging mode or pre-charging mode), can be transmitted from the superordinate control device to the input. The superordinate control device can be part of the charging circuit or can be arranged externally, wherein the input of the control device of the charging circuit is connected (in a manner to receive commands) to the superordinate control device. In the simplest case, the instruction is a binary signal.

The rectifier may comprise an uncontrollable half-bridge, in particular in the form of a diode half-bridge. Preferably, the non-controllable half bridge has a series circuit of two diodes. The conduction directions of the two diodes are the same. The series circuit is connected like a controllable half bridge. The ac voltage terminal may have a neutral contact which is connected to the uncontrollable half-bridge, in particular to the connection point via which the two diodes are connected to each other. The diodes of the non-controllable half-bridges (and also the diodes of each controllable half-bridge, which preferably have one diode) have a cut-off direction which is directed towards the positive potential of the rectifier (or its direct voltage side). In other words, the diodes of the uncontrollable half-bridges (and also the diodes of each controllable half-bridge, which preferably have one diode) have a cut-off direction which points to the positive potential of the vehicle electrical system terminal.

Furthermore, a method for transmitting electrical energy to an on-board electrical system is described. The energy is transmitted from the multiphase ac voltage source via a vehicle-side controllable and multiphase rectifier to the vehicle electrical system (in particular to a battery located there). In particular via a charging circuit as described herein. This also applies to rectifiers. With the voltage level maintained, the energy is transferred from the rectifier to the vehicle electrical system (or to the vehicle electrical system terminals). No voltage conversion takes place between the rectifier and the vehicle electrical system or the vehicle electrical system terminals. Energy is transmitted between the rectifier and the vehicle electrical system terminals via a direct connection, in particular via a connection without a voltage converter (and without a converter). In the pre-charge mode, a smaller number of controllable half-bridges of the rectifier is controlled in a clocked manner than in the main charge mode. This results in a lower rectified voltage in the precharge mode than in the main charging mode. In other words, in the pre-charge mode, the rectifier is equipped with a lower link factor than in the main charge mode. This can be used to adapt the voltage applied to the vehicle electrical system to the operating state of components of the vehicle electrical system. In this case, the operating state may be a state of charge, a terminal voltage or an idling voltage of a secondary battery representing the component.

In the main charging mode, preferably all controllable half-bridges are controlled in a clocked manner. For example three controllable half-bridges. The ac voltage terminals or the ac voltage source are preferably three-phase. The link factor for sqrt (3) is derived.

In the precharge mode, only one of the controllable half-bridges is operated in a clocked manner. The remaining controllable half-bridges are steered in an open switching state. The remaining controllable half-bridges are inactive in the precharge mode. In the case of a three-phase rectifier, i.e. a rectifier with three half-bridges, the two half-bridges or phases can be inactive, for example in the precharge mode, while one half-bridge or phase is active or controlled in a clocked manner. The clocked actuation corresponds in particular to a phase actuation or to a pulse width modulation.

The actual voltage of the vehicle electrical system is preferably compared with a threshold value. Based on the comparison, either the pre-charge mode or the main charge mode is set (or the entire rectifier is deactivated). Preferably, the pre-charge mode is set when the actual voltage is below a threshold. Preferably, the main charging mode is set when the voltage value is higher than a threshold value. The threshold value characterizes the voltage or state of charge of the accumulator above which the main charging mode results in a rectified voltage which would be permissible for the actual voltage (or for the actual state of charge of the connected accumulator) without resulting in exceeding the maximum charging current of the accumulator (in general: resulting in an overload). Below the threshold value, the rectified voltage may be too high for the charging process of the accumulator in the case of the main charging mode, i.e. the main charging mode may be associated with exceeding the maximum charging current in the case of an actual voltage below the threshold value.

The actual voltage may be a terminal voltage or an idling voltage of a battery which is arranged in the vehicle electrical system and to which energy is transmitted. The actual voltage may furthermore be a voltage at a terminal of the vehicle electrical system, and the threshold value corresponds to a maximum voltage of a component of the vehicle electrical system.

Fig. 1 shows, in overview, a charging circuit according to the invention, which is arranged between a vehicle electrical system and an ac power source and serves to illustrate the operating mode described here by way of example.

In fig. 1, an ac voltage source Q is connected via three phases L1 to L3 and via a neutral line N via an optional filter F to a rectifier GR. The vehicle-side charging circuit LS comprises an optional filter and in particular a rectifier GR. An interface in the form of an ac voltage terminal IF is used on the vehicle side for coupling an ac voltage source Q, for example, via the ac voltage terminal. This ac voltage terminal IF forms an interface, which is arranged on the vehicle side, for example in the form of a (preferably standardized) charging socket for transmitting energy to the rectifier GR. Isolating switches may be provided between the ac voltage terminal IF and the rectifier GR, for example one for each of the phases L1 to L3 and for the neutral line N. These disconnectors can be opened in case of a fault or as a protective measure before and after charging (or feedback).

The rectifier GR comprises three controllable half-bridges B0-B2 and a diode half-bridge DH. The half-bridges B0 to B2 each comprise a series circuit of two switchable transistors. This is two switching elements 01 and 02 in the case of controllable half-bridge B0, switching elements 11 and 12 in the case of controllable half-bridge B1, and switching elements 21 and 22 in the case of controllable half-bridge B2. In each half bridge, the two switching elements mentioned are connected to each other via an intermediate point. In the case of the diode half-bridge DH, the two diodes D1, D2 are connected via an intermediate point. These connection points are furthermore connected (for example via an optional filter) to the alternating voltage terminal IF. The connection points of the two respective switching elements of the half-bridges B0 to B2 are each connected to one phase L1 to L3 of the ac voltage interface IF. As mentioned, the diode half-bridge DH comprises two diodes D1, D2, which are likewise connected to one another in a series circuit. The resulting connection point is connected to the neutral line N.

The half-bridges B0 to B2 and the diode half-bridge DH each have two ends, one of which is connected to the positive voltage bus of the rectifier and the other of which is connected to the negative voltage bus of the rectifier. The voltage bus or the associated potential forms the dc voltage side of the rectifier GR. The voltage bus extends up to the on-board power supply terminal a.

The charging circuit LS furthermore comprises the already mentioned dc voltage terminals a, which comprise terminals for the two mentioned dc voltage potentials. In which the energy storage ES can be connected. The energy store represents, for example, one or more components of an onboard power supply system HB, which is connected to a terminal a. The onboard power supply system HB is in particular a high-voltage onboard power supply system having a nominal voltage of, for example, at least 60V, 100V, 400V or 800V.

The half-bridges B0 to B2 are operated by a control device C, which is shown symbolically, wherein the half-bridges are controllable. To this end, each switching element 01 to 22 of the half-bridges B0 to B2 comprises a control input (connected to the control means), for example a gate. The switching elements can be configured as MOSFETs or IGBTs or also as every other controllable semiconductor element. The control means C is an electric circuit, for example a programmable circuit with a processor or a hard-wired logic circuit.

The control device C is set up to actively control only one of the half-bridges B0 to B2 in the precharge mode. In this case, for example, only half bridge B0 is operated. The half-bridges B1 and B2 are not clocked. In the precharge mode, the control device C actuates the half bridge B0 with a clock control signal in order to generate a pulsating dc voltage at the vehicle electrical system terminal a. The inactive half-bridges (here half-bridges B1 and B2) are steered as open-circuited (off) in the precharge mode. In particular, the non-steered half-bridges B1 and B2 do not contribute to the generation of a clocked dc voltage at the vehicle electrical system terminal a. Since only a plurality of half-bridges, i.e. one half-bridge of a smaller number than the maximum possible number of all half-bridges, is active, a lower link factor (verkenttungfaktor) results than if all half-bridges were active. Thus, since the link factor is lower than in the main charging mode, a reduced direct voltage results at the on-board power supply system terminal a in the pre-charging mode.

In the main charging mode, more half-bridges are actively steered than in the pre-charging mode. In the main charging mode, the more controlled half-bridges B0 to B2 contribute to the generation of a pulsating direct voltage at the vehicle electrical system terminal a. Thus, a higher link factor results in the main charging mode than in the pre-charging mode, and therefore a higher ripple (effective) voltage also results at the vehicle electrical system terminal a. If a smoothing capacitor is provided at the vehicle electrical system terminal a, the consideration of the ripple voltage at the vehicle electrical system terminal a also corresponds to the consideration of the smoothed voltage or to the consideration of the effective voltage at (am) here. If a smoothed voltage is considered as a voltage, the higher the number of half-bridges operated, the higher the (effective) voltage under load.

In the present example, all half-bridges B0 to B2 can be controlled in a clocked manner by the control means C in the main charging mode. Thereby utilizing all three phases L1 to L3. If only bridge B0 is used in precharge mode (and bridges B1 and B2 are inactive), then only phase L1 is utilized. It follows directly that, as a result, less power is available at the vehicle electrical system terminal a and a lower voltage is also available under load. Due to the phase offset between the phases L1 to L3 (specification: L1-L3 are three-phase connections), a higher effective voltage is also obtained at the vehicle electrical system terminal a when using all half-bridges B0 to B2 than when using a smaller number of half-bridges. The rectifier GR shown is constructed in three phases and comprises a diode half-bridge DH for neutral. The control device C specifies whether the rectifier GR is operated in a single-phase or three-phase (or also two-phase) manner. The control device C thus defines the number of active phases and thus also directly defines the link factor of the rectifier, as a result of which a ripple voltage or a direct voltage (which is dependent on the number of phases concerned) is obtained at the vehicle electrical system terminal a.

The dc voltage at the vehicle electrical system terminal a can thus be regulated. For this purpose, the control device C may have an input E, at which either the number of phases or a command that reflects the number of half-bridges to be operated is input directly.

Alternatively, a voltage value signal can be emitted at input E, which signal specifies the voltage at energy store ES or at vehicle electrical system terminal a. In this case, the control means C may comprise a comparator which compares the voltage value with a threshold value and determines the number of phases on the basis of the comparison. If, for example, the voltage value is higher than a threshold value, a higher number of phases is manipulated than would otherwise be the case. For example, the control device may steer all controllable half bridges B0 to B2 if a threshold value is exceeded, and only one of the controllable half bridges, for example half bridge B0, if the voltage value is below the threshold value. The threshold value may depend on an aging value reflecting the aging as a function of the rise and/or may depend on the temperature of the energy store ES. The greater the aging of the energy storage ES, the greater the aging value, for example the inverse or component of the SOH value (SOH — state of health) -the general state of the energy storage ES). The voltage value signal at input E may be a digital signal, for example, a signal of a voltage detection device, which measures an analog voltage at vehicle electrical system terminal a or at energy store ES and transmits it as a digital value. Analog-to-digital converters may be used for this purpose. The input E is preferably connected to the terminal a in terms of signaling in order to obtain a value that reflects its voltage, but is preferably galvanically isolated in order to thus provide a control device that is galvanically isolated from the vehicle electrical system HB. The energy storage ES is preferably designed as a battery.

Claims (10)

1. Vehicle-side charging circuit (LS) having a controllable multiphase rectifier (GR) having a plurality of controllable half bridges (B0-B2), wherein an ac voltage side of the rectifier (GR) is connected to an ac voltage terminal (IF) and a dc voltage side of the rectifier (GR) is connected to a vehicle electrical system terminal (a) in a converter-less manner, wherein the charging circuit has a control device (C) which is connected to the controllable half bridges (B0-B2) in a controlled manner, wherein the control device (C) is set up to control a smaller number of controllable half bridges in a clocked manner in a precharge mode than in a main charging mode.

2. Vehicle-side charging circuit (LS) according to claim 1, in which the control device (C) is set up for operating all controllable half-bridges in a clocked manner in the main charging mode.

3. Vehicle-side charging circuit (LS) according to claim 1 or 2, wherein the control means (C) are set up for operating only one controllable half-bridge and the remaining controllable half-bridges to be open-circuited in a clocked manner in a precharge mode.

4. Vehicle-side charging circuit (LS) according to claim 1 or 2, wherein the control device (C) has an input (E) which is signally connected to the on-board electrical system terminal, wherein the control device is set up for comparing a voltage value applied at the input (E) with a threshold value, wherein the control device is set up for setting the pre-charging mode if the voltage value is below the threshold value and for setting the main-charging mode if the voltage value is above the threshold value.

5. Vehicle side charging circuit (LS) according to one of the preceding claims, wherein the rectifier comprises an uncontrollable half-bridge having a series circuit of two diodes.

6. Method for transmitting electrical energy to a vehicle electrical system, wherein energy is transmitted from a multiphase alternating voltage source (Q) via a vehicle-side controllable and multiphase rectifier (GR) to the vehicle electrical system (HB), wherein the energy is transmitted from the rectifier to the vehicle electrical system while maintaining a voltage level, wherein furthermore in a pre-charge mode a smaller number of controllable half-bridges of the rectifier is controlled in a clocked manner than in a main-charge mode.

7. The method according to claim 6, wherein in the main charging mode all controllable half bridges (B0-B2) are steered in a clocked manner.

8. Method according to claim 6 or 7, wherein in the precharge mode only one of the controllable half-bridges (B0-B2) is clocked and the remaining controllable half-bridges are steered in an open circuit.

9. Method according to claim 6, 7 or 8, wherein the actual voltage of the on-board electrical network is compared with a threshold value, and wherein the pre-charging mode is set if the actual voltage is below the threshold value and the main charging mode is set if the voltage value is above the threshold value.

10. Method according to claim 9, wherein the actual voltage is a terminal voltage or an idling voltage of a battery (ES) which is arranged in the onboard power supply system (HB) and to which the energy is transmitted.

Images