Vehicle battery charger and its operation

Abstract

Vehicle that features: a traction battery; and a battery charger configured to receive power from a remote power distribution circuit and to detect whether a load other than the battery charger is electrically connected to the power distribution circuit and to charge the traction battery at a rate chosen in response to whether a load other than the battery charger is electrically connected to the power distribution circuit.

Description

[0001] Active power is the ability of a circuit to operate within a given time period. Apparent power is the product of the current and voltage of the circuit. Apparent power can be greater than active power due to energy stored in the load and returned to the source, or due to a non-linear load that distorts the waveform of the current drawn from the source.

[0002] The power factor of an AC electrical power system can be defined as the ratio of the active power flowing to the load to the apparent power (a number between 0 and 1).

[0003] In an electrical power system, a load with a low power factor draws more current than a load with a high power factor to deliver the same amount of power. These higher currents can increase energy loss in the distribution system and may require larger wires and other equipment. Due to the cost of larger equipment and wasted energy, utility companies can charge customers with a low power factor higher rates.

[0004] In a purely resistive AC circuit, voltage and current waveforms are in phase and change their polarity at the same time in each cycle. If reactive loads are present, such as capacitors or inductors, the energy stored in the loads introduces a time difference (phase) between the current and voltage waveforms. This stored energy returns to the source and is not available to work on the load. Therefore, a circuit with a low power factor requires higher currents to transfer a given amount of active power compared to a circuit with a high power factor.

[0005] An alternating current power flow has three components: active power (P), measured in watts (W); apparent power (S), measured in volt-amperes (VA); and reactive power (Q), measured in volt-amperes reactive (VAr). The power factor can therefore be defined as P / S

[0006] In the case of a perfectly sinusoidal waveform, P, Q, and S can be expressed as vectors that form a vector triangle, such that the following holds: S2=P2+Q2

[0007] If θ is the phase angle between current and voltage, the power factor is equal to |cos θ|, and P=S*|cos θ|

[0008] When the power factor is 0, the energy flow is completely blind, and energy stored in the load returns to the source in each cycle. When the power factor is 1, all the energy supplied by the source is consumed by the load. Power factors can be specified as "leading" or "lagging" to indicate the sign of the phase angle.

[0009] When a purely resistive load is connected to a power supply, the current and voltage reverse their polarity and phase, the power factor is one, and electrical energy flows through the network in a single direction during each cycle. Inductive loads, such as transformers and motors, consume power, with the current waveform lagging the voltage. Capacitive loads, such as capacitor banks or underground cables, cause reactive power flow, with the current waveform leading the voltage. Both types of loads absorb energy during part of the AC cycle, which is stored in the magnetic or electric field of the device, only to release this energy back to the source during the remainder of the cycle. For example, to obtain 1 kW of active power when the power factor is one, 1 kVA of apparent power must be transferred (1 kW ÷ 1 = 1 kVA).At low power factor values, more apparent power must be transmitted to obtain the same active power. To obtain 1 kW of active power at a power factor of 0.2, 5 kVA of apparent power must be transmitted (1 kW ÷ 0.2 = 5 kVA).

[0010] US 2010 / 0 259 229 A1 describes a battery charger that can receive power from a power distribution circuit with a fuse that reduces reactive power caused by another load. US 2010 / 0 259 218 A1 describes a battery charger that provides reactive power in a power distribution circuit in response to a demand.

[0011] A vehicle according to claim 1 comprises a traction battery and a battery charger. The battery charger can receive power from a remote power distribution circuit and detect whether a load other than the battery charger is electrically connected to the power distribution circuit, and charge the traction battery at a rate selected in response to whether a load other than the battery charger is electrically connected to the power distribution circuit.

[0012] A battery charger can receive power from a power distribution circuit that includes a neutral conductor and earth, and operate based on a measured voltage between the neutral conductor and earth. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a circuit diagram of a power distribution circuit. Fig. 2 is a block diagram of the battery charger of the Fig. 1. Fig. Figure 3 is a block diagram of a power distribution system. Fig. Figure 4 is a block diagram of a battery charger. DETAILED DESCRIPTION

[0013] Here, embodiments of the present disclosure are described; however, it is understood that the disclosed embodiments are only examples, and other embodiments may take different and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed here are not to be understood as limiting, but only as a representative basis to suggest to a person skilled in the art the use of the present invention in various ways. As a person skilled in the art understands, various features illustrated and described with reference to any of the figures can be combined with features illustrated in one or more other figures to create embodiments that are not explicitly illustrated or described.The combinations of illustrated devices provide representative embodiments for typical applications. However, various combinations and modifications of the features, consistent with the teachings of this disclosure, may be desirable for particular applications or embodiments.

[0014] Now, referring to Fig. 1 can include a power distribution circuit 10, power lines (phase conductors) 12, 12', return lines (neutral conductors) 14, 14', and an earth conductor (ground) 16, and in some embodiments can be similar to power distribution circuits found in residential or commercial buildings. A fuse box 18, the battery charger 20, and other loads 22 are electrically connected to the distribution circuit 10. (The battery charger 20 can, for example, be a stationary unit or integrated into a vehicle.) The phase conductor 12 and the neutral conductor 14 are the section of the circuit 10 that is electrically connected between the fuse box 18 and the loads 22. The phase conductor 12' and the neutral conductor 14' are the section of the circuit 10 that is electrically connected between the charger 20 and the loads 22. The fuse box 18 contains a fuse 23, which is electrically connected to the live conductor 12. A power storage unit 24, e.g.a vehicle traction battery can be electrically connected to (and charged by) the battery charger 20.

[0015] As the average professional knows, power from a power source 25, e.g., the mains supply, etc., is supplied to the distribution circuit 10 (and thus to the battery charger 20 and the loads 22) via the fuse box 18. Attempts to draw current from the distribution circuit 10 that exceed its capacity can trip fuses in the fuse box 18.

[0016] In the embodiment of the Fig. 1. The loads 22 (such as a cooling compressor, etc.) can have both active and reactive power components, resulting in an alternating current that lags the alternating voltage. This lagging current, if present, leads to a flow of reactive power between the loads 22 and the power source 25. This reactive power flow results in a current through the fuse 23 that is higher than the current through the fuse 23 in the absence of this reactive power flow. The loads 22 can lower the power factor associated with the distribution circuit 10 and thus reduce the active power available for a given amount of apparent power.

[0017] Now, referring to the Fig. 1 and Fig. 2. An embodiment of the battery charger 20 can include a bridge rectifier 26, a power factor (PF) controlled boost controller (up-converter) 28, a buck controller (down-converter) 30, and a microprocessor 32. The battery charger 20 can, of course, have any suitable configuration. The bridge rectifier 26 can be electrically connected to the live conductor 12', the neutral conductor 14', and ground 16 of the distribution circuit 10. The PF-controlled boost controller 28 is electrically connected to the bridge rectifier 26 and the buck controller 30. The buck controller 30 can be electrically connected to the power storage unit 24. The PF-controlled boost controller 28 and the buck controller 30 are under the command / control of the microprocessor 32.

[0018] The battery charger 20 can also include voltage sensors 34, 36 and a current sensor 38. The voltage sensor 34 measures the voltage between the live conductor 12' and the neutral conductor 14'. The sensor 36 measures the voltage between the neutral conductor 14' and earth 16. As is clear to the average person, this voltage depends on the current through the neutral conductors 14, 14'. The sensor 38 measures the current through the neutral conductor 14'. The sensors 34, 36, and 38 are connected to the microprocessor 32.

[0019] When the charger 20 is not in operation, the entire load current due to the loads 22 passes through the neutral conductor 14. The neutral conductor 14, which has an internal resistance R 14The loads 22 experience a voltage drop between them and the fuse box 18, which is proportional to the current through the loads 22 and in phase. This voltage drop can be measured in the charger 20 by one of the sensors 34 or 36. Thus, a voltage measured by sensor 36 indicates the presence of the loads 22; a change in the voltage measured by sensor 34 indicates the presence of the loads 22. If the loads 22 contain a reactive component, the voltage measured by sensor 36 is phase-shifted relative to the voltage measured by sensor 34. From equation (5) (discussed below), the power factor can then be calculated.

[0020] If the loads 22 were not present, the charger 20 could produce the same voltage drop by charging at a rate that causes a current through the neutral conductors 14, 14' equal to ((R14+R14′)*I charger) / R14 is, where R 14'the internal resistance of the neutral conductor 14' and I Ladegerät the current through the charger 20 (the current through the sensor 38) is.

[0021] The charger 20 can charge the power storage unit 24 at a speed that depends on whether the presence of loads 22 is detected. For example, if loads 22 are detected, the charger 20 can charge the power storage unit 24 at a speed of 600 W. If loads 22 are not detected, the charger can charge the power storage unit 24 at a speed of 1200 W. In other examples, the charging speed can be inversely proportional to the voltage as measured by sensor 36 or to the voltage change associated with sensor 34.

[0022] When the charger 20 is in operation and the loads 22 are present, the power reactive component due to these combined loads has an associated current that can be determined based on the measured voltage 36. Because of this current component, the measured voltage waveform at sensor 36 (V NG ) phase-shifted relative to the measured voltage waveform at sensor 34 (V LN ). If the charger 20 is ordered to operate as a load with such reactive power that the measured voltage waveform at sensor 36 is substantially aligned with the measured voltage waveform at sensor 34, the power in fuse box 18 has little or no reactive component.

[0023] From (4), if R 14' regarding R 14 The small value is the charger current required to charge the phase of V. NG with V LNto correct and align, approximately equal to the current and phase of the example above, where the charger 20 is not operating and thus the entire load current due to the loads 22 passes through the neutral conductor 14. If R 14' regarding R 14 Even if the power is not small, a reactive power component can still be observed in fuse box 18.

[0024] The microprocessor 32 can determine the power factor (and thus the phase differences between the voltage and the current) of the distribution circuit 10 based on information from sensors 34 and 36. For example, the microprocessor 32 can determine the power factor based on the period, T, of the voltage waveform as measured by sensor 34 and the phase between the voltage waveforms as measured by sensors 34 and 36. However, other suitable techniques can also be used.

[0025] To find T, for example, the microprocessor 32 can determine the time between two consecutive zero crossings of the voltage waveform as measured by sensor 34 and multiply this time by a factor of 2. Alternatively, the microprocessor 32 can determine the time between alternating zero crossings of the voltage waveform as measured by sensor 34. Other models are also possible. To find the phase between the voltage waveforms as measured by sensors 34 and 36, the microprocessor 32 can determine the time, t, between a zero crossing of the voltage waveform as measured by sensor 34 and an immediately following zero crossing of the voltage waveform as measured by sensor 36. The microprocessor 32 can then find the power factor of the distribution circuit 10 as PF = cos((t / T)*360)

[0026] The microprocessor 32 can communicate this power factor to the power factor-controlled boost circuit 28. The power factor-controlled boost circuit 28 (which may take the form of a circuit arrangement described in the UNITRODE application note "UC3854 Controlled Power Factor Correction Circuit Design" by Philip C. Todd, 1999, or any other known and / or suitable form) can control the power drawn to correct reactive power caused by the loads 22. This control can be achieved, for example, by adding a digital or analog lead / lag of the current measured by sensor 38 (or by a lag / lead of the voltage measured by sensor 34) before the signal is processed by the power factor-controlled boost circuit 28.In this example, a lag in the current signal produces a corresponding lead in the power factor at the input of the charger 20, and the power factor-controlled boost circuit 28 no longer accepts a power factor of one at its input, as originally intended. Conversely, a lead leads to a corresponding lag in the power factor at the input of the charger 20, and so on.

[0027] If the loads 22 are, for example, motors, they typically have an inductive reactance, X I , which causes a lagging power factor. A leading power factor is equivalent to a capacitive reactance, X c , can be delivered, so that X applies c ≈ X IWith this approximate correspondence, little or no reactive power flows on the phase conductor 12 and neutral conductor 14, and instead flows on the phase conductor 12' and neutral conductor 14'. If the reactive power required to correct reactive power caused by the loads 22 is known, the PF-controlled boost controller 28 can be instructed to generate the required (complementary) reactive power. Alternatively, taking into account (4) and the above discussion of current-generated voltages at sensor 36, for small values ​​of R 14' regarding R 14 , there is little or no reactive power flow through the phase conductor 12, the neutral conductor 14 and the fuse 23, and V NG is in phase with V LN Even for larger values ​​of R 14' , if V NG with V LNWhen the system is in phase, the reactive power flow through the phase conductor 12, the neutral conductor 14, and the fuse 23 is reduced. If, of course, the reactive power of the loads 22 is known, the current generated by reactive power can be directly calculated and controlled.

[0028] Control signal inputs to the PF-controlled boost circuit 28 can be based on the (rectified) voltage between the phase conductors 12', 14' and the voltage amplitude between the phase conductors 14', 16, which is naturally proportional to the current through the neutral conductors 14, 14'. As can be seen by the average person, the above control signal input model allows the PF-controlled boost circuit 28 to essentially correct the power factor of the distribution circuit 10, unlike the battery charger 20 alone.

[0029] The boost circuit 28 can measure the alternating voltage rectified by the bridge rectifier 26 in a known manner and control the current, i, through its inductance in a known manner such that the instantaneous value of the magnitude of i is proportional to the instantaneous value of the magnitude of the voltage between the outer conductors 14', 16.

[0030] If the battery charger 20 is the only load on the distribution circuit 10, the phase conductor 12 has a power factor of approximately one. Since the current, i, is proportional to the AC voltage on the phase conductor 12 (they are in phase), the power factor of the distribution circuit 10 is one. However, if there are additional loads, such as the loads 22, with reactive components, the distribution circuit 10 also has a power factor of approximately one at the fuse box 18 due to the control input model discussed above.

[0031] Assuming that the microprocessor 32 finds the power factor for the distribution circuit 10 as discussed above, it can control the power factor-controlled boost circuit 28 such that it generates reactive power that is sufficiently equal to (and of opposite sign to) the reactive power caused by the loads 22. Thus, the reactive power generated by the power factor-controlled boost circuit 28 cancels out the reactive power of the distribution circuit 10 and increases the active power for a given amount of apparent power.

[0032] From (2) and (3), and assuming a lagging power factor of 0.8 and an apparent power of 375 VA for the distribution circuit 10, the active power is approximately 300 W, and the reactive power is approximately 225 VAr (in this example, the current lags the voltage). The PF-controlled boost circuit 28 can thus operate to generate approximately 225 VAr (current leads the voltage) and drive the apparent power to a value of 300 VA. The operation of the battery charger 20 can thus increase the efficiency with which power is delivered by the distribution circuit 10 under conditions where non-power-factor-corrected loads, such as those in Fig. Figure 1 illustrates the loads 22, which are electrically connected to the distribution circuit 10. In this example, the distribution circuit 10 would need to supply 3.125 A at 120 V to deliver the 375 VA of power. With the reactive power component essentially eliminated, the distribution circuit 10 would only need to supply 2.5 A at 120 V to deliver the 300 W of power. Thus, an additional 0.6 A of active current could be drawn from the battery charger 20 without changing the amount of apparent current flowing through the fuse 23.

[0033] Now, referring to Fig. 3, in the same reference symbols, same descriptions as in Fig. A power distribution system 140 contains a power source 125 and several power distribution circuits 110n (110a, 110b, 110c, etc.). The power source 125 of the Fig. 3 is configured to supply power to the distribution circuits 110n. Reactive loads electrically connected to the distribution system 140 via the distribution circuits 110n can cause leading or lagging nominal reactive power. As discussed above, this nominal reactive power can cause power delivery weaknesses within the distribution system 140.

[0034] In the embodiment of the Fig. 3. The power source 125 may require compensation for the (leading or lagging) reactive power that will be produced / generated by any battery chargers similar to those referred to in Fig. 2 described and are electrically connected to the distribution circuits 110n. In other embodiments, the power source 125 may require compensation of the reactive power that will be produced / generated by other suitably controlled loads or added power sources capable of changing the power factor of the distribution circuits 110n on demand in a manner similar to the battery chargers described herein. Such loads or added power sources may, for example, have an architecture and input control model similar to the battery charger 20 of the Fig. 2 have.

[0035] The power source 125 can, for example, contain a wireless transmitter / receiver or modulator (for data transmission via power line) to transmit such reactive power requirements (and to receive information from battery chargers, as described below). However, any suitable information transmission technology can be used.

[0036] Now, referring to the Fig. 3 and Fig. 4, in which the same reference symbols are used for similar descriptions as in Fig. 2. An embodiment of a battery charger 120 can include a bridge rectifier 126, a power factor-controlled boost controller 128, a buck controller 130, a microprocessor 132, and a transceiver 133. The microprocessor 132 communicates with the transceiver 133. The battery charger 120 can also include voltage sensors 134, 136, and a current sensor 138.

[0037] The transceiver 133 is configured to transmit and / or receive radio signals in a known manner. For example, the transceiver 133 can receive requests / commands for reactive power (of a specific sign) transmitted wirelessly by the power source 125 in a known manner. These requests / commands can then be forwarded to the microprocessor 132 for processing. In other embodiments, the battery charger 120 may incorporate a HOMEPLUG-like (or identical) technology for wired reception and / or wired transmission of communications to and / or from the power source 125. As is clear to the person skilled in the art, such a HOMEPLUG module would be electrically connected to the power lines and return lines 112', 114'. As is known in the art, HOMEPLUG involves superimposing information on AC power lines at specific frequencies.With a suitable circuit arrangement, this information can be read on the receiving side.

[0038] The microprocessor 132 can use the requested / commanded reactive power as a target with which the reactive power of the distribution circuit 110n is “tuned”.For example, if a total reactive power (current leading with respect to voltage) of 5 VAr is required to significantly correct the power factor of the distribution system 140, and the microprocessor 132, using the techniques described herein, has determined that 1 VAr (current leading with respect to voltage) is available to be generated by the charger 120, the microprocessor 132 can, in response to a reactive power (current leading with respect to voltage) request from the power source 125, control the PF-controlled boost regulator 128 to generate 1 VAr of reactive power (current leading with respect to voltage) by, for example, controlling the digital or analog lead / lag of the current measured by sensor 138 (or the lag / lead of the voltage measured by sensor 134) as discussed above, thereby reducing the reactive power of the distribution circuit 110n to 4 VAr (voltage leading with respect to current). is powered.

[0039] The microprocessor 132 can also determine the ability of the battery charger 120 to cause the presence of a specified reactive power in the distribution circuit 110 and communicate this information to the power source 125, for example, via the transmitter-receiver 133. The power source 125 can collect this information from all such battery chargers electrically connected to the power distribution system 140 and accordingly output reactive power requirements (e.g., based on the total capacity).

[0040] Based on the apparent power and power factor of distribution circuit 110n from (1) and (2), the active and reactive powers can be found. The available incremental reactive power can then be found using the power / current ratings of distribution circuit 110n, which can be assumed, determined, or entered by a user. For example, if the active and reactive powers are 10.6 W and 10.6 VAr (current leading with respect to voltage), respectively, and the power rating of distribution circuit 110n is 15 W, the battery charger 120 cannot generate any additional leading reactive power (current leading with respect to voltage) because, from (2), the apparent power is equal to the power rating of distribution circuit 110n. However, a person of average skill would recognize that the battery charger 120 can still generate lagging reactive power if necessary. For example, if the active and reactive powers are 0 W and 10.6 VAr (current leading with respect to voltage), respectively, the battery charger 120 can generate 0 W of additional incremental reactive power if needed.Since the reactive power is 0 VAr, and the available power rating of the distribution circuit 110n is 15 W, the battery charger 120 has the ability to generate 15 VAr of reactive power with both signs.

[0041] In certain embodiments, the power source 125 can measure the power factor (PF) and determine, using any suitable technique, whether the voltage leads or lags the current, and send a command to all battery chargers to generate, for example, 1 VAr of reactive power with a sign opposite to the nominal reactive power. The power source 125 can then periodically measure the PF and send commands to all battery chargers to increase the generated reactive power (with the opposite sign to the nominal reactive power) until the nominal reactive power in the distribution system 140 has been sufficiently reduced and / or eliminated.In other embodiments, such as those with two-way communication between the power source 125 and any battery chargers 120, the power source 125 can, in a known manner, require each battery charger 120 to produce / generate different amounts of reactive power (based on their respective capacities), provided, of course, that each battery charger that specifies its capacity also provides a recognition signal that can distinguish it from others. Other control scenarios are also possible.

[0042] While exemplary embodiments have been described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the description are descriptive rather than limiting, and it is understood that various modifications can be made without departing from the scope of the disclosure and the claims. As described above, the features of different embodiments can be combined to form further embodiments of the invention that are not explicitly described or illustrated.While various embodiments may have been described as offering advantages or being preferable to other embodiments or designs of the prior art with respect to one or more desired properties, the average person skilled in the art recognizes that one or more features or characteristics can be combined to obtain desired overall system characteristics, which depend on the specific application and design. These characteristics may include, but are not limited to: cost, strength, service life, life-cycle costs, marketability, appearance, packaging, size, ease of use, weight, manufacturability, ease of assembly, etc.As such, embodiments which are described as less desirable with respect to one or more properties than other embodiments or designs of the prior art are not outside the scope of the disclosure and may be desirable for certain applications.

Claims

[1] Vehicle that has: a traction battery; and a battery charger configured to receive power from a remote power distribution circuit and to detect whether a load other than the battery charger is electrically connected to the power distribution circuit, and to charge the traction battery at a rate selected in response to whether a load other than the battery charger is electrically connected to the power distribution circuit. [2] The vehicle of claim 1, wherein the battery charger is further configured to charge the traction battery at a first rate when a load other than the battery charger is electrically connected to the power distribution circuit, and to charge the traction battery at a second rate greater than the first rate when no load other than the battery charger is electrically connected to the power distribution circuit. [3] The vehicle of claim 1, wherein the power distribution circuit includes a neutral wire and ground, and wherein the battery charger is further configured to detect whether a load other than the battery charger is electrically connected to the power distribution circuit based on a voltage between the neutral wire and ground. [4] The vehicle of claim 3, wherein the battery charger is further configured to measure the voltage between the neutral conductor and ground. [5] The vehicle of claim 1, wherein the power distribution circuit includes a line conductor and a neutral conductor, and wherein the battery charger is further configured to detect whether a load other than the battery charger is electrically connected to the power distribution circuit based on a voltage change between the line conductor and the neutral conductor.

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