Method and system for detecting the absence of a neutral point between a voltage detection OBC and a polyphase mains supply

Abstract

A method and system for detecting the absence of a neutral point between a voltage detection OBC and polyphase mains power are disclosed. A vehicle on-board battery charger (OBC) includes (i) a rail circuit having respective rail controllers and (ii) a main controller. The rail controllers sample the voltage supplied to their rail circuits and send a fault signal to the main controller when a comparison between the sampled voltage and a threshold affirms an inappropriate voltage condition (overvoltage or undervoltage) of the sampled voltage. The main controller, in response to receiving a fault signal from any of the rail controllers, controls all the rail controllers to stop the operation of all the rail circuits. In a variant, the main controller samples the voltage supplied to the rail circuits and stops the operation of all the rail circuits when the comparison between the sampled voltage and the threshold is affirmative.

Description

[0001] Cross - reference to related applications

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 143,222, filed on January 29, 2021, the disclosure of which is hereby incorporated by reference in its entirety. Technical field

[0003] The present invention relates to methods and systems for controlling a multiphase charger (e.g., a multiphase on - vehicle battery charger for an electric vehicle). Background

[0004] An on - vehicle battery charger (OBC) of an electric vehicle (EV) is used to charge the traction battery of the EV. The OBC converts the electric power absorbed from an AC power source into DC electric power and uses the DC electric power to charge the battery.

[0005] Summary

[0006] One objective includes a system and method for controlling an on - vehicle battery charger (OBC) of an electric vehicle (EV) such that when the OBC receives electric power from a charging station (e.g., a mains power source) to charge the traction battery of the EV, the charging operation is stopped during an inappropriate voltage condition (such as an over - voltage condition or an under - voltage condition) of the received electric power.

[0007] In performing at least one of the above - mentioned and / or other objectives, an OBC is provided. The OBC includes a first rail circuit having a first rail controller, a second rail circuit having a second rail controller, and a main controller operably communicating with the rail controllers. The first rail controller is configured to control the operation of the first rail circuit and is further configured to sample a first voltage supplied to the first rail circuit and send a fault signal to the main controller when a comparison between the sampled first voltage and a threshold affirms an inappropriate voltage condition regarding the first voltage. The second rail controller is configured to control the operation of the second rail circuit and is further configured to sample a second voltage supplied to the second rail circuit and send a fault signal to the main controller when a comparison between the sampled second voltage and a threshold affirms an inappropriate voltage condition regarding the second voltage. The main controller is configured to control both rail controllers to stop the operation of both rail circuits in response to receiving a fault signal from either rail controller. The inappropriate voltage condition can be an over - voltage condition or an under - voltage condition.

[0008] The first voltage can be a first - phase voltage supplied by a multiphase mains power source, and the second voltage can be a second - phase voltage supplied by the multiphase mains power source.

[0009] The comparison between the sampled voltage and the threshold may require that successive samples of the sampled voltage being compared to the threshold be positive, such that the comparison is positive.

[0010] The OBC may also include a third rail circuit having a third rail controller operatively communicating with the main controller. The third rail controller is configured to control the operation of the third rail circuit and is further configured to sample a third voltage supplied to the third rail circuit and send a fault signal to the main controller when a comparison between the sampled third voltage and a threshold affirms an inappropriate voltage condition regarding the third voltage. The main controller is further configured to, in response to receiving a fault signal from any rail controller, control all rail controllers to stop the operation of all rail circuits.

[0011] The third voltage may be a third phase voltage supplied by a three-phase mains power supply. The comparison between the sampled voltage and the threshold may require that at least three successive samples of the sampled voltage being compared to the threshold be positive, such that the comparison is positive.

[0012] At least one of the comparisons being positive may be due to a loss of neutral between the OBC and the mains power supply, with voltage being supplied from the mains power supply to the rail circuit, whereby the main controller detects the loss of neutral by receiving a fault signal. A loss of neutral between the OBC and the mains power supply may occur due to a switched connection between the neutral node of the OBC and the neutral line of the mains power supply being open in an external electric vehicle supply equipment (EVSE), while a switched connection between a voltage node of at least one rail circuit and a corresponding voltage line of the OBC is closed in the EVSE.

[0013] At least one of the comparisons being positive may be due to instability between the OBC and the mains power supply, with voltage being supplied from the mains power supply to the rail circuit, whereby the main controller detects the instability by receiving a fault signal.

[0014] The main controller may also be configured to control all rail controllers to resume the operation of all rail circuits after the expiration of a delay after the operation of the rail circuits has stopped, and in response to receiving a fault signal from any rail controller after the operation of all rail circuits has been resumed, control all rail controllers to stop the operation of all rail circuits.

[0015] The OBC may be mounted on an electric vehicle and may be used to charge a traction battery of the electric vehicle.

[0016] In addition, in performing at least one of the above and / or other purposes, a method for use with an OBC is provided. The OBC includes a first rail circuit having a first rail controller, a second rail circuit having a second rail controller, and a main controller operably communicating with the rail controllers. The first rail controller is configured to control the operation of the first rail circuit, and the second rail controller is configured to control the operation of the second rail circuit. The method includes the first rail controller sampling a first voltage supplied to the first rail circuit and, when a comparison between the sampled first voltage and a threshold affirms an inappropriate voltage state regarding the first voltage, sending a fault signal to the main controller. The method further includes the second rail controller sampling a second voltage supplied to the second rail circuit and, when a comparison between the sampled second voltage and the threshold affirms an inappropriate voltage state regarding the second voltage, sending a fault signal to the main controller. At least one of the comparisons between the sampled voltage and the threshold is affirmative, whereby at least one of the rail controllers sends a fault signal to the main controller. The method further includes the main controller, in response to receiving the fault signal, controlling both rail controllers to stop the operation of both rail circuits.

[0017] In addition, in performing at least one of the above and / or other purposes, another OBC is provided. The OBC includes a first rail circuit, a second rail circuit, and a controller. The controller is configured to sample a first voltage supplied to the first rail circuit and stop the operation of both rail circuits when a comparison between the sampled first voltage and a threshold affirms an inappropriate voltage state regarding the first voltage. Brief Description of the Drawings

[0018] Figure 1 A block diagram of an electrical system showing a multi-phase (or multi-rail) on-board battery charger (OBC) is shown;

[0019] Figure 2 A block diagram of an electrical system is shown, where the OBC is described in detail as a three-phase (or three-rail) OBC having three phases (or rails) and also having an input relay between the rails;

[0020] Figure 3 An illustration showing a graph having a first-phase AC voltage, a second-phase AC voltage, and a third-phase AC voltage, which are respectively supplied from a three-phase mains power supply of the electrical system to a first rail, a second rail, and a third rail of the OBC when the OBC and the mains power supply operate properly together;

[0021] Figure 4 As shown in Figure 2Block diagram of the electrical system shown, and illustrations with the following curves: (i) curves of three AC voltage phases supplied from the mains power supply to three rails of the OBC respectively when the OBC and the mains power supply are operating properly together, followed by (ii) curves of three AC voltage phases supplied from the mains power supply to three rails of the OBC respectively when there is a neutral point loss between the OBC and the mains power supply;

[0022] Figure 5 A block diagram of the OBC is shown, in which the corresponding controllers of the rails of the OBC and their communicable arrangements with the main controller of the OBC are depicted;

[0023] Figure 6 A flowchart showing the operation of a method and system for detecting a neutral point loss between the OBC and the mains power supply based on voltage is shown;

[0024] Figure 7A An illustration based on experimental results is shown, which has curves of three AC voltage phases supplied from the mains power supply to the OBC respectively;

[0025] Figure 7B Shows Figure 7A An illustration of an enlarged portion of the illustration shown; and

[0026] Figure 8 Another flowchart is shown, which depicts the operation of a method and system for detecting a neutral point loss between the OBC and the mains power supply based on voltage. Detailed description

[0027] Detailed embodiments of the present invention are disclosed herein; however, it should be understood that the disclosed embodiments are only examples of the present invention that can be embodied in various and alternative forms. The drawings do not have to be to scale; some features may be exaggerated or reduced to show details of specific components. Therefore, the specific structural and functional details disclosed herein should not be construed as restrictive, but only as a representative basis for teaching those skilled in the art to adopt the present invention in different ways.

[0028] Now referring to Figure 1 , a block diagram of an electrical system 10 having an on-board battery charger (OBC) 12 is shown. The OBC 12 is "mounted" on an electric vehicle (EV). In this document, the terms "electric vehicle" and "EV" cover any type of vehicle that uses electric power for vehicle propulsion, including pure battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), etc. The OBC 12 is used to charge the traction battery 14 of the EV. The traction battery 14 is a high-voltage (HV) direct current (DC) traction battery for vehicle propulsion according to the electrical energy requirements.

[0029] The electrical system 10 further includes an alternating current (AC) power source, such as a mains power supply 16 of a power grid. The OBC 12 uses the electrical power from the mains power supply 16 to charge the traction battery 14. The OBC 12 is connected to the mains power supply 16 via an external electric vehicle supply equipment (EVSE) 18 to absorb electrical power from the mains power supply. The OBC 12 converts the electrical power absorbed from the mains power supply 16 into DC electrical power. The OBC 12 outputs the DC electrical power to the traction battery 14 via the vehicle's HV DC bus for charging the traction battery.

[0030] The main controller (“controller”) 20 is associated with the OBC 12. The controller 20 is an electronic device, such as a processor, a microcontroller, or an analogue (e.g., a computer) loaded on the EV (e.g., a vehicle controller). The controller 20 communicates with the OBC 12 to control the operation of the OBC. The controller 20 controls the OBC 12 to convert the electrical power from the mains power supply 16 into DC electrical power and charge the traction battery 14 with the DC electrical power. The controller 20 may be integrated within the OBC unit. The controller 20 may provide general commands as well as communication with other vehicle units and phase (rail)-specific controllers (discussed below) responsible for phase (rail) operation, control, and real-time diagnosis. The controller 20 is also operable to communicate with and control other nodes of the electrical system 10 and the EV, including the nodes involved in the charging application.

[0031] Now referring to Figure 2 and continuing to refer to Figure 1 a block diagram of the electrical system 10 with a detailed depiction of the OBC 12 is shown. The OBC 12 is an N-phase (or N-rail) OBC, where N is an integer greater than 1. Thus, the OBC 12 is a multi-phase (multi-rail) OBC having at least two phases (or rails) (i.e., branches, etc.). For example, as Figure 2 shown, the OBC 12 is a three-phase (or three-rail) OBC having a first rail 22a, a second rail 22b, and a third rail 22c (collectively referred to as “rails 22”) (each labeled as an “inner phase” in Figure 2 ).

[0032] The rails (i.e., the track circuits) 22 have the same electrical circuit system for converting the electrical power from the utility power supply 16 into DC electrical power to charge the traction battery 14. For example, each of the rails 22a, 22b, and 22c has an AC electromagnetic interference (EMI) input filter, followed in sequence by a power factor corrector (PFC), a DC link capacitor, a DC / DC converter, and an output filter (not shown). The controller 20, together with the track controllers of the rails 22 (discussed below), controls the operation of the electrical circuit system of the rails 22, converts the electrical power from the utility power supply 16 into DC electrical power, and delivers the DC electrical power to the traction battery 14. More specifically, in an embodiment, the "main controller" is inside the OBC, and three "in-phase controllers" (or "track controllers") are respectively associated with the three rails 22. The combination of these four controllers can be understood to provide the "controller" function.

[0033] Each of the rails 22a, 22b, and 22c will be connected to the utility power supply 16 via the EVSE 18 so that the rail absorbs electrical power from the utility power supply and converts the absorbed electrical power into DC electrical power for charging the traction battery 14. The rails 22 are connected in parallel between the input terminal of the OBC and the output terminal of the OBC. The input terminal is connected to the utility power supply 16 via the EVSE 18, and the output terminal is connected to the traction battery 14 via the HV DC bus of the vehicle.

[0034] Strictly by way of example, each of the rails 22a, 22b, and 22c can deliver 3.6 kW of electrical power for charging the traction battery 14. Thus, in this example, the OBC 12 can deliver 10.8 kW (3 * 3.6 kW) of electrical power for charging the traction battery 14 (i.e., in this example, the OBC 12 is an "11 kW" OBC).

[0035] The OBC 12 also includes input relays 24a and 24b (collectively referred to as "input relays 24"). The input relay 24a is located between the input terminals of the rails 22a and 22b. The input relay 24b is located between the input terminals of the rails 22a and 22c. Each of the input relays 24a and 24b is switchable between an open state and a closed state. The controller 20 is operable to control the switching of the input relays 24.

[0036] A closed input relay connects the input terminals of the two rails between which the input relay is located. Conversely, an open input relay disconnects the two rails between which the input relay is located. The two input relays 24 are Figure 2Both are shown in the open state. Therefore, when the input relay 24a between rails 22a and 22b is open, the input terminal of rail 22b is not connected to the input terminal of rail 22a. Similarly, when the input relay 24b between rails 22a and 22c is open, rail 22c is not connected to the input terminal of rail 22a.

[0037] The input relays 24 are used to enable the OBC 12 to be used interchangeably with a single-phase mains power supply and a polyphase mains power supply. In either case where the mains power supply is single-phase or polyphase, rail 22a is directly connected to the mains power supply 16 alone via the EVSE 18. When the mains power supply 16 is single-phase, the controller 20 controls the input relay 24 to close. In this case, rails 22b and 22c are combined with rail 22a to connect to the mains power supply 16 using rail 22a. When the mains power supply 16 is polyphase, the controller 20 controls the input relay 24 to open. In this case, in addition to rail 22a being directly connected to the mains power supply 16 alone via the EVSE 18, rails 22b and 22c are also directly connected to the mains power supply via the EVSE alone.

[0038] In an embodiment of the present invention, the mains power supply 16 is a three-phase mains power supply. The OBC 12 is a three-phase (i.e., three-rail) OBC, corresponding to the mains power supply 16 being a three-phase mains power supply. Since the OBC 12 is a three-rail OBC, both input relays 24a and 24b are open, and all three rails 22 of the OBC 12 are directly connected to the mains power supply 16 alone via the EVSE 18. In particular, each of rails 22a, 22b, 22c is directly connected to the corresponding lines L1, L2, L3 of the mains power supply 16 via the respective nodes L 1’ 、L 2’ 、L 3’ of the OBC, and is directly connected to the neutral line N of the mains power supply via the neutral node N' of the OBC.

[0039] As described, an OBC for an EV that can work with single-phase (1-ph) and three-phase (3-ph) AC grids with an available N (neutral line) is typically designed with three internal rails (or modules) 22 that share the neutral node N' of the OBC. In the case of a 1-ph AC grid, rails 22b and 22c can be switched to the L 1’ node of the OBC. As further described, the OBC is not directly connected to the grid, but is connected to the grid by means of the EVSE. The EVSE serves as an additional element to ensure a safe and controlled connection of the OBC to the AC grid. When both the EVSE and the OBC are ready for the charging operation, the EVSE closes its contactor, and the OBC receives an AC voltage supply from the AC grid.

[0040] Now refer to Figure 3 and continue to refer toFigure 1 and Figure 2 shows Diagram 30, which has graphs of a first-phase AC voltage 32a (vL1N), a second-phase AC voltage 32b (vL2N), and a third-phase AC voltage 32c (vL3N) respectively supplied from a three-phase mains power supply 16 to the first rail 22a, the second rail 22b, and the third rail 22c of the OBC 12. As shown in Diagram 30, the AC voltages 32 are phase-shifted from each other by 120°, and have the same sinusoidal shape and the same peak amplitude. Thus, Diagram 30 indicates when the OBC 12 and the mains power supply 16 are operating properly together. When the corresponding switch of the EVSE 18 is properly closed, thereby connecting the nodes L 1’ 、L 2’ 、L 3’ 、N’ of the OBC to the corresponding lines L1, L2, L3, N of the mains power supply, the operation between the OBC 12 and the mains power supply 16 is proper.

[0041] Now refer to Figure 4 , and continue to refer to Figure 1 、 Figure 2 and Figure 3 , which shows Diagram 40 of a block diagram of the electrical system 10 and a graph of the AC voltage supplied from the mains power supply 16 to the OBC with respect to the internal N’ point of the OBC 12 as shown in Figure 2 . Diagram 40 has (i) graphs of the three AC voltage phases 32a, 32b, 32c respectively supplied from the mains power supply 16 to the three rails 22a, 22b, 22c of the OBC 12 when the OBC and the mains power supply are operating properly together, followed by (ii) graphs of the three-phase AC voltages 32a’, 32b’, 32c’ respectively supplied from the mains power supply to the three rails 22a, 22b, 22c of the OBC when there is a neutral point loss between the OBC 12 and the mains power supply 16.

[0042] The neutral point loss between the OBC 12 and the mains power supply 16 is due to the disconnection of the switch connection between the neutral node N’ of the OBC 12 and the neutral line of the mains power supply 16 in the EVSE 18, while the switch connections between one or more nodes L 1’ 、L 2’ 、L 3’ of the OBC and the corresponding lines L1, L2 、L3 of the mains power supply are closed in the EVSE. This neutral point loss occurs in Figure 4is represented by line 44 in the illustration 40, where line 44 indicates the moment when the neutral point loss occurs, which is represented by the dashed line 46 in the illustration 40, and line 44 is further shown in the block diagram of the electrical system 10. This neutral point loss occurs due to the disconnection of the switch between the neutral node N' of the OBC 12 and the neutral line N of the mains power supply 16 in the EVSE 18, as shown by the dashed circle 48. As Figure 4 further shown in this example, in the EVSE, all the nodes L of the OBC 1’ 、L 2’ 、L 3’ and the switch connections between the corresponding lines L1, L2, L3 of the mains power supply are closed.

[0043] Figure 4 The depiction in occurs on some OBCs, where the EVSE 18 disconnects the neutral contactor (N) before disconnecting the line contactor (Lx). This means that if during an emergency stop, where the EVSE 18 decides to disconnect its contactors while the OBC 12 is still processing power, the inner rails L 1’ 、L 2’ 、L 3’ to the internal neutral node N' may start to fluctuate in voltage because the power grid (i.e., the mains power supply 16) no longer applies the line-to-neutral voltage. Therefore, the input voltage of each inner rail 22 of the OBC 12 can increase to 1.73 times the amount for which the inner rail is designed, and thus may damage the OBC. In the case where the internal neutral point N' is floating, the unbalanced condition means that those rails operating in a lower power state (e.g., rails 22a and 22b) will see their input voltage Lx'-N' increase (e.g., the AC voltages 32a' and 32b' in the illustration 40 depict the overvoltage states of the input voltages L1'-N' and L2'-N'), while those rails operating in a higher power state (e.g., rail 22c) will see their input voltage Lx'-N' decrease (e.g., the AC voltage 32c' in the illustration 40 depicts the undervoltage state of the input voltage L3'-N'). This means that it is not possible to perform a selective stop on the inner rails with too high an input voltage because this would make the situation worse.

[0044] Therefore, it is desirable to perform an intelligent stop on all the rails 22 to ensure that the OBC 12 stops processing in all the rails simultaneously, so as not to damage any components in the case of a persistent inappropriate input voltage condition (i.e., in the case of a persistent input overvoltage or undervoltage condition). If the controllers for all the rails 22 are generic, this can be achieved, but due to cost and considering the functional isolation between the rails, each inner rail is typically controlled by its own independent "rail controller" that only sees what is happening on its own rail.

[0045] In summary, the above descriptions regarding Figure 2 , Figure 3 and Figure 4 relate to the neutral point loss protection in the three-phase OBC. The neutral point loss is an issue that needs to be addressed during the charging mode. Under normal conditions, the L1, L2, and L3 phase voltages are relative to the neutral point. However, when the EVSE first disconnects the N relay during disconnection, or due to grid instability, the neutral point may be lost. Without a neutral point reference, the L1, L2, and L3 phase voltages may change due to environmental factors. In this state, damage can occur within a relatively short time (such as 200 milliseconds). The OBC will detect this anomaly and respond quickly to avoid such damage.

[0046] Now referring to Figure 5 , and continuing to refer to the previous figures, a block diagram of the OBC 12 is shown. In this block diagram, separate controllers 52a ("CTRL1"), 52b ("CTRL2"), 52c ("CTRL3") (collectively referred to as "rail controllers 52") of the rails 22a, 22b, 22c of the OBC 12 are shown respectively, and their communicable arrangement with the controller 20 ("MCU") of the OBC.

[0047] According to an embodiment of the present invention, the information from the rail controllers 52 is received by the OBC supervisor MCU (i.e., the controller 20), which is also the controller responsible for commanding what the rail controllers do. In operation, each of the rail controllers 52a, 52b, 52c provides a signal to the controller 20, which indicates the input voltage received by its corresponding rails 22a, 22b, 22c from the mains power supply 16. When the controller 20 sees a continuous inappropriate voltage (i.e., continuous overvoltage or undervoltage) on one or more rails 22, it commands all the rails to stop processing power together. At this time, when the system returns to the natural balance state, all the input voltages will return to "normal". Therefore, further according to an embodiment of the present invention, a retry strategy can be additionally deployed to resume charging in order to prove that the continuous inappropriate voltage state is actually given by the neutral node loss, and set the corresponding DTC (Diagnostic Trouble Code).

[0048] Now referring to Figure 6 , continuing to refer to Figure 5, a flowchart 60 depicting the operation of a method and system for detecting a neutral point loss between an OBC 12 and a mains power supply 16 based on voltage in accordance with an embodiment of the present invention is shown. Referring to block 62, "controller overvoltage detection" of flowchart 60, the operation includes the rail controllers 52 sampling the AC voltage supplied to the input terminals of their associated rails 22, comparing the sampled AC voltage with an overvoltage threshold, and sending a fault signal to the controller 20 when the sampled AC voltage is greater than the overvoltage threshold. For example, the rail controller 52a of rail 22a samples the AC voltage supplied to rail 22a at a given moment, compares the AC voltage sample with the overvoltage threshold, and sends a fault signal to the controller 20 when the AC voltage sample is greater than the overvoltage threshold. (Of course, the operations depicted in flowchart 60 may include an undervoltage threshold instead of the overvoltage threshold.)

[0049] In an embodiment, when three consecutive AC voltage samples are greater than the overvoltage threshold, the rail controller 52 sends a fault signal to the controller 20. For example, referring to block 62, when three consecutive AC voltage samples of rail 22 (each sample acquired by the rail controller 52 of that rail 22 within, for example, 100 microseconds) are greater than an overvoltage threshold of, for example, 380 Vpk, then the rail controller 52 sends a fault signal to the controller 20. Of course, this is just an example, as any predetermined sampling interval other than 100 microseconds and / or any predetermined overvoltage threshold other than 380 Vpk can be used for the determination of the fault signal. (Note that, for compatibility with more AC voltages, the overvoltage threshold can be a variable threshold calculated before each start of charging (or charging retry) (e.g., overvoltage threshold = (AC voltage RMS * 1.735)) (the "1.73" factor has been mentioned above). Also note that the overvoltage threshold may be limited / saturated, such as 399 Vpk, to avoid damage to the OBC input terminals (at the TVS component, as explained below).

[0050] Referring to block 64, "report fault to MCU" of flowchart 60, the operation further includes the controller 20 receiving a fault signal from the rail controller 52 in response to the rail controller detecting an overvoltage condition at the rail 22 of the OBC 12 to which the rail controller belongs. In response to receiving the fault signal, the controller 20 commands all rails 22 to stop processing power. For example, as shown in block 64, the controller 20 sends a zero current setpoint to all rails 22 in response to receiving a fault signal from the rail controller 52. Sending a zero current setpoint is equivalent to the controller 20 instructing phase 22 to stop processing power.

[0051] Referring to block 66, “MCU resets all controllers” of flowchart 60, the operation also includes controller 20 resetting all rail controllers 52. As shown in block 66, once the rail controllers 52 are restarted, rail 22 of OBC 12 is again ready to absorb electric power from the mains power supply 16 and convert the absorbed electric power into DC electric power for charging the traction battery 14.

[0052] Referring to block 68, “MCU starts retry strategy” of flowchart 60, the operation also includes controller 20 starting a retry strategy after a delay after controller 20 resets the rail controllers 52. Generally, a ground loss is not detected until the rail starts working again (energy flow). Then, after a series of “neutral point loss” fault cycles, controller 20 may set a permanent neutral point loss fault status and stop retrying. If the permanent fault is due to a malfunction of the rail controller 52, it is not related to this abnormal detection. Note that when the rail controller 52 is set to “permanent fault”, due to reaching the maximum number of fault attempts (e.g., five times), controller 20 disables the affected rail controllers 52, and the communication between them is disabled. Therefore, the disabled rail controller 52 does not report its AC voltage or new faults to controller 20 (due to its being disabled), and controller 20 will use information from fewer rails 22 / rail controllers 52.

[0053] Now referring to Figure 7A and Figure 7B , and continuing to refer to Figure 5 and Figure 6 , there are shown a diagram 70 according to experimental results (as Figure 7A shown) and a diagram 72 of an enlarged portion 71 of diagram 70 (as Figure 7B shown), diagram 70 having graphs of three AC voltage phases respectively supplied from the mains power supply 16 to the OBC with respect to the internal N’ point of the OBC 12. In particular, both diagrams 70 and 72 have (i) graphs of three AC voltage phases 32a, 32b, 32c respectively supplied from the mains power supply 16 to three rails 22a, 22b, 22c of the OBC 12 when the OBC and the mains power supply are operating properly together, and (ii) graphs of three-phase AC voltages 32a’, 32b’, 32c’ respectively supplied from the mains power supply to the three rails 22a, 22b, 22c of the OBC when there is a neutral point loss between the OBC and the mains power supply.

[0054] According to this experiment, initially, the OBC 12 and the mains power supply 16 operate properly together, where all the rails 22 of the OBC operate at more or less the same power. Then, at a given time, a neutral point loss occurs between the OBC 12 and the mains power supply 16, as shown by the dashed line 74 in illustration 70. The rails 22 then start to become unbalanced due to the neutral point loss. During the initial time period when the rails 22 are unbalanced, none of the AC voltage phases supplied to the rails 22 of the OBC 12 is greater than the overvoltage threshold (or as shown above, at least no three consecutive samples of the AC voltage phases supplied to the rails 22 are detected by the rail controller 52 of that rail 22 as being greater than the overvoltage threshold).

[0055] At a subsequent time, as shown by the dashed line 76 in illustration 72, a significant unbalanced condition is reached (i.e., the unbalance of the rails 22 has reached an actionable level) (there is a risk of unbalance in the input stage). This significant unbalanced condition is reached because the AC voltage phases supplied to the rails 22 of the OBC 12 become greater than the overvoltage threshold (or at least three consecutive samples of the AC voltage phases supplied to the rails 22 are detected by the rail controller 52 of that rail 22 as being greater than the overvoltage threshold). In particular, according to these experimental results, because the AC voltage phase 32c' of the rail 22c supplied to the OBC 12 becomes greater than the overvoltage threshold (or at least three consecutive samples of the AC voltage phase 32c' are greater than the overvoltage threshold), this significant unbalanced condition is reached.

[0056] In response to the comparison between the AC voltage phase 32c' and the overvoltage threshold being positive, the rail controller 52c sends a fault signal indicating continuous overvoltage on the rail 22c to the controller 20. The top and bottom voltage clamping is an indicator that the input transient voltage suppressor (TVS) is activated due to the loss of neutral (LoN). If this condition is not stopped, it may eventually fail due to a short circuit and damage the OBC 12. (For clarity, embodiments of the present invention also contemplate an alternative where sensing is performed at the negative peak, where a negative threshold and negative overvoltage are used for the comparison involving the AC voltage phase. Sensing a "smaller" AC voltage phase signal relative to the threshold can also indicate the loss of neutral.)

[0057] In response to receiving the fault signal from the rail controller 52c, the controller 20 commands all the rails 22 to stop processing power. According to these experimental results, after three consecutive samples of the AC voltage phase 32c' are greater than the overvoltage threshold, the controller 20 sends a stop processing power command signal to the rail controllers 52 of the rails 22. In response to receiving the stop processing power command, the rail controllers 52 control their rails 22 to stop processing power. Then, at the moment indicated by the dashed line 78, all the rails 22 are stopped (the controller 20 stops the charging operation), and then the AC voltage phases return to normal.

[0058] Now refer to Figure 8 and continue to refer to Figure 5 which shows another flowchart 80 that depicts the operation of a method and system for detecting a neutral point loss between the OBC 12 and the mains power supply 16 based on voltage. As will be discussed, the operation includes a retry strategy for retrying the operation of the OBC 12 after stopping the operation of the OBC following a neutral point loss. The operation begins when the OBC 12 receives AC electrical energy from the mains power supply 16 to charge the traction battery 14. During charging, the rail controllers 52 monitor the input voltage of their respective rails 22, as shown at block 82. That is, the input voltage at each of the rails 22a, 22b, and 22c is monitored by the respective rail controllers 52a, 52b, and 52c. Then, as indicated by reference numeral 83, a neutral point loss condition occurs. Due to the neutral point loss condition, the rail controllers 52 detect an overvoltage condition at their rails 22 and notify the controller 20 with a fault signal, as shown at block 84. In response to receiving the fault signal, the controller 20 commands all the rail controllers 52 to stop the operation of their rails 22, as shown at block 86. That is, the overvoltage at each rail can be reported to the controller 20, and then the controller 20 will stop the charging operation.

[0059] After a delay (as shown at block 87), the controller 20 resets the fault indication (retry strategy) to the rail controllers 52, as shown at block 88. The controller 20 and the rail controllers 52 are then used to resume charging (retry strategy), as shown at block 90. That is, the retry strategy is initiated in the event that the anomaly has disappeared.

[0060] As described, many OBCs designed to operate with a 1-ph or 3-ph AC grid are based on three inner rails that share a neutral node, and the expectation for these OBCs is to be connected to an AC grid with an available N (a grid of the star configuration type). The OBC is robust against a neutral point loss or absence in the grid to avoid potential damage. The EVSE can disconnect the N contactor while charging, and this can generate a harmful voltage at the input of one or more of the inner rails of the OBC. A similar situation can occur in the case where the grid actually does not have an available neutral node (such as a grid of the delta configuration type).

[0061] As described, embodiments of the present invention provide an effective method to detect and protect a 3-ph OBC from the absence or lack of a neutral node. Embodiments of the present invention can use software in the OBC digital controller (i.e., rail controller 52) and in the MCU (i.e., controller 20) to implement the detection and protection of the 3-ph OBC from the absence or lack of a neutral node, so the solution is relatively without additional cost. Thus, embodiments of the present invention avoid using an additional analog isolation amplifier that provides the input voltage of the OBC's rail to the MCU. Embodiments of the present invention can also be applied to an arrangement where only one controller directly manages the three rails of the OBC.

[0062] As described, a brief description of embodiments of the present invention includes protecting the OBC in the case of a missing neutral connection during 3-phase AC grid charging; such an anomaly may occur due to grid instability (e.g., temporary grid anomaly) or due to the EVSE disconnecting the N relay before disconnecting the L1-L3 relays. New features of embodiments of the present invention include that the existing input voltage monitoring stage is used to detect overvoltage (or undervoltage) fault states; the fault is transferred to the main microcontroller that commands the charging to stop; the response time is less than 200 milliseconds to avoid damaging the input stage; a retry strategy after a given delay to resume charging in the case of a temporary absence of the neutral connection or temporary grid instability; and only a software algorithm is added. The problems solved by embodiments of the present invention include that the neutral point missing fault may damage the OBC input stage. The techniques for which embodiments of the present invention provide improvements include direct sensing using additional components, which may be faster but more expensive and require a larger PCB area.

[0063] Although the exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the present invention. Instead, the words used in the specification are words of description rather than limitation, and it should be understood that various changes can be made without departing from the spirit and scope of the present invention. Additionally, the features of the embodiments of various implementations can be combined to form additional embodiments of the present invention.

[0064] Aspects of the present disclosure may be implemented in one or more of the embodiments below:

[0065] Item 1): On-board battery charger (OBC), comprising:

[0066] A first rail circuit having a first rail controller;

[0067] A second rail circuit having a second rail controller;

[0068] A main controller operably communicating with the rail controllers;

[0069] Among them, the first rail controller is configured to control the operation of the first rail circuit, and is also configured to sample the first voltage supplied to the first rail circuit, and when the comparison between the sampled first voltage and the threshold affirms an inappropriate voltage state regarding the first voltage, send a fault signal to the main controller;

[0070] The second rail controller is configured to control the operation of the second rail circuit, and is also configured to sample the second voltage supplied to the second rail circuit, and when the comparison between the sampled second voltage and the threshold affirms an inappropriate voltage state regarding the second voltage, send a fault signal to the main controller; and

[0071] The main controller is configured to, in response to receiving a fault signal from either rail controller, control both rail controllers to stop the operation of both rail circuits.

[0072] Item 2): The OBC according to item 1), wherein:

[0073] The inappropriate voltage state is an overvoltage state or an undervoltage state.

[0074] Item 3): The OBC according to item 1), wherein:

[0075] The comparison between the sampled voltage and the threshold requires that consecutive samples of the sampled voltage compared with the threshold are affirmative, so that the comparison is affirmative.

[0076] Item 4): The OBC according to item 1), further comprising:

[0077] A third rail circuit, which has a third rail controller;

[0078] Among them, the main controller is also operably communicable with the third rail controller;

[0079] The third rail controller is configured to control the operation of the third rail circuit, and is also configured to sample the third voltage supplied to the third rail circuit, and when the comparison between the sampled third voltage and the threshold affirms an inappropriate voltage state regarding the third voltage, send a fault signal to the main controller; and

[0080] The main controller is also configured to, in response to receiving a fault signal from any rail controller, control all rail controllers to stop the operation of all rail circuits.

[0081] Item 5): The OBC according to item 4), wherein:

[0082] The first voltage is the first phase voltage supplied by a three-phase mains power supply, the second voltage is the second phase voltage supplied by the three-phase mains power supply, and the third voltage is the third phase voltage supplied by the three-phase mains power supply.

[0083] Item 6): The OBC according to Item 1), wherein:

[0084] The first voltage is the voltage of the first phase supplied by a polyphase mains power supply, and the second voltage is the voltage of the second phase supplied by the polyphase mains power supply.

[0085] Item 7): The OBC according to Item 1), wherein:

[0086] At least one comparison in the comparison is affirmative due to the absence of a neutral point between the OBC and the mains power supply. The voltage is supplied from the mains power supply to the rail circuit, and thus the main controller detects the absence of the neutral point by receiving a fault signal.

[0087] Item 8): The OBC according to Item 7), wherein:

[0088] An absence of a neutral point between the OBC and the mains power supply occurs because a switch connection between the neutral node of the OBC and the neutral wire of the mains power supply in an external electric vehicle supply equipment (EVSE) is disconnected, while a switch connection between the voltage node of at least one rail circuit and the corresponding voltage line of the OBC in the EVSE is closed.

[0089] Item 9): The OBC according to Item 1), wherein:

[0090] At least one comparison in the comparison is affirmative due to instability between the OBC and the mains power supply. The voltage is supplied from the mains power supply to the rail circuit, and thus the main controller detects the instability by receiving a fault signal.

[0091] Item 10): The OBC according to Item 1), wherein:

[0092] The main controller is further configured to control all rail controllers to resume the operation of all rail circuits after the expiration of a delay after the operation of all rail circuits is stopped; and

[0093] The main controller is further configured to, after the operation of all rail circuits is resumed, in response to receiving a fault signal from any rail controller, control all rail controllers to stop the operation of all rail circuits.

[0094] Item 11): The OBC according to Item 1), wherein:

[0095] The OBC is loaded on an electric vehicle and is used to charge the traction battery of the electric vehicle.

[0096] Item 12): A method for use with an on-vehicle battery charger (OBC), the on-vehicle battery charger including a first rail circuit having a first rail controller, a second rail circuit having a second rail controller, and a main controller operably communicating with the rail controllers, wherein the first rail controller is configured to control the operation of the first rail circuit and the second rail controller is configured to control the operation of the second rail circuit, the method comprising:

[0097] Sampling, by the first rail controller, a first voltage supplied to the first rail circuit, and, when a comparison between the sampled first voltage and a threshold affirms an inappropriate voltage state regarding the first voltage, sending a fault signal to the main controller;

[0098] Sampling, by the second rail controller, a second voltage supplied to the second rail circuit, and, when a comparison between the sampled second voltage and a threshold affirms an inappropriate voltage state regarding the second voltage, sending a fault signal to the main controller;

[0099] Wherein at least one of the comparisons between the sampled voltage and the threshold is affirmative, whereby at least one of the rail controllers sends a fault signal to the main controller; and

[0100] In response to the main controller receiving the fault signal, controlling, by the main controller, both rail controllers to stop the operation of both rail circuits.

[0101] Item 13): The method according to item 12), wherein the OBC further includes a third rail circuit having a third rail controller, the main controller is further operably communicating with the third rail controller, and the third rail controller is configured to control the operation of the third rail circuit, the method further comprising:

[0102] Sampling, by the third rail controller, a third voltage supplied to the third rail circuit, and, when a comparison between the sampled third voltage and a threshold affirms an inappropriate voltage state regarding the third voltage, sending a fault signal to the main controller; and

[0103] In response to the main controller receiving the fault signal, controlling, by the main controller, all rail controllers to stop the operation of all rail circuits.

[0104] Item 14): The method according to item 13), wherein:

[0105] The first voltage is a first-phase voltage supplied by a three-phase mains power supply, the second voltage is a second-phase voltage supplied by the three-phase mains power supply, and the third voltage is a third-phase voltage supplied by the three-phase mains power supply.

[0106] Item 15): The method according to item 13), further comprising:

[0107] After the expiration of a delay after the operation of all track circuits has stopped, the master controller controls all track controllers to resume the operation of all track circuits; and

[0108] After the operation of all track circuits has been resumed, in response to receiving a fault signal from any track controller, the master controller controls all track controllers to stop the operation of all track circuits.

[0109] Item 16): A on-vehicle battery charger (OBC), comprising:

[0110] A first track circuit;

[0111] A second track circuit; and

[0112] A controller configured to sample a first voltage supplied to the first track circuit and, when a comparison between the sampled first voltage and a threshold affirms an inappropriate voltage state regarding the first voltage, stop the operation of both track circuits.

[0113] Item 17): The OBC according to item 16), wherein:

[0114] The controller is further configured to sample a second voltage supplied to the second track circuit and, when a comparison between the sampled second voltage and a threshold affirms an inappropriate voltage state regarding the second voltage, stop the operation of both track circuits.

[0115] Item 18): The OBC according to item 17), further comprising:

[0116] A third track circuit; and

[0117] The controller is further configured to sample a third voltage supplied to the third track circuit and, when a comparison between the sampled third voltage and a threshold affirms an inappropriate voltage state regarding the third voltage, stop the operation of all track circuits.

[0118] Item 19): The OBC according to item 18), wherein:

[0119] The first voltage is the first-phase voltage supplied by a three-phase mains power supply, the second voltage is the second-phase voltage supplied by the three-phase mains power supply, and the third voltage is the third-phase voltage supplied by the three-phase mains power supply.

[0120] Item 20): The OBC according to item 18), wherein:

[0121] The master controller is further configured to resume the operation of all track circuits after the expiration of a delay after the operation of all track circuits has been stopped; and

[0122] The master controller is further configured to stop the operation of all track circuits when the comparison between any sampled voltage and a threshold is positive after the operation of all track circuits has been restored.

Claims

1. An on-vehicle battery charger OBC, comprising: A first rail circuit having a first rail controller; A second rail circuit having a second rail controller; A main controller operably communicating with the first rail controller and the second rail controller; Wherein, the first rail controller is configured to control the operation of the first rail circuit, and is further configured to sample a first voltage supplied to the first rail circuit, and when a comparison between the sampled first voltage and a threshold affirms an inappropriate voltage state regarding the first voltage, send a first fault signal to the main controller; The second rail controller is configured to control the operation of the second rail circuit, and is further configured to sample a second voltage supplied to the second rail circuit, and when a comparison between the sampled second voltage and the threshold affirms an inappropriate voltage state regarding the second voltage, send a second fault signal to the main controller; And The main controller is configured to, in response to receiving the first fault signal from the first rail controller or the second fault signal from the second rail controller, control the two rail controllers to stop the operation of the two rail circuits.

2. The OBC according to claim 1, wherein: The inappropriate voltage state is an overvoltage state or an undervoltage state.

3. The OBC according to claim 1, wherein: The comparison between the sampled voltage and the threshold requires that consecutive samples of the sampled voltage compared with the threshold are affirmative, so that the comparison is affirmative.

4. The OBC according to claim 1, further comprising: A third rail circuit having a third rail controller; Wherein, the main controller also operably communicates with the third rail controller; The third rail controller is configured to control the operation of the third rail circuit, and is further configured to sample a third voltage supplied to the third rail circuit, and when a comparison between the sampled third voltage and the threshold affirms an inappropriate voltage state regarding the third voltage, send a third fault signal to the main controller; and The main controller is further configured to, in response to receiving the first fault signal, the second fault signal or the third fault signal from any one of the rail controllers, control all rail controllers to stop the operation of all rail circuits.

5. The OBC according to claim 4, wherein: The first voltage is the first phase voltage supplied by a three-phase mains power supply, the second voltage is the second phase voltage supplied by the three-phase mains power supply, and the third voltage is the third phase voltage supplied by the three-phase mains power supply.

6. The OBC according to claim 1, wherein: The first voltage is the first phase voltage supplied by a polyphase mains power supply, and the second voltage is the second phase voltage supplied by the polyphase mains power supply.

7. The OBC according to claim 1, wherein: At least one comparison in the comparison between the sampled voltage and the threshold is affirmative due to the absence of a neutral point between the OBC and the mains power supply, and the voltage is supplied from the mains power supply to the track circuit, whereby the main controller detects the absence of the neutral point by receiving the first fault signal or the second fault signal.

8. The OBC according to claim 7, wherein: The absence of the neutral point between the OBC and the mains power supply occurs due to the disconnection of the switch connection between the neutral node of the OBC and the neutral wire of the mains power supply in the external electric vehicle supply equipment EVSE, while the switch connection between the voltage node of at least one track circuit and the corresponding voltage line of the OBC in the EVSE is closed.

9. The OBC according to claim 1, wherein: At least one comparison in the comparison between the sampled voltage and the threshold is affirmative due to the instability between the OBC and the mains power supply, and the voltage is supplied from the mains power supply to the track circuit, whereby the main controller detects the instability by receiving the first fault signal or the second fault signal.

10. The OBC according to claim 1, wherein: The main controller is further configured to control all track controllers to resume the operation of all track circuits after the expiration of a delay after the operation of all track circuits is stopped; and The main controller is further configured to, after the operation of all track circuits is resumed, in response to receiving the first fault signal or the second fault signal from any one of the track controllers, control all track controllers to stop the operation of all track circuits.

11. The OBC according to claim 1, wherein: The OBC is installed on an electric vehicle and is used to charge the traction battery of the electric vehicle.

12. A method for use with an on-vehicle battery charger OBC, the on-vehicle battery charger including a first track circuit having a first track controller, a second track circuit having a second track controller, and a main controller operably communicating with the first track controller and the second track controller, wherein the first track controller is configured to control the operation of the first track circuit, and the second track controller is configured to control the operation of the second track circuit, the method comprising: Sampling, by the first track controller, a first voltage supplied to the first track circuit, and sending, by the first track controller, a first fault signal to the main controller when at least one comparison in the comparison between the sampled first voltage and a threshold affirms an inappropriate voltage state regarding the first voltage; Sampling, by the second track controller, a second voltage supplied to the second track circuit, and sending, by the second track controller, a second fault signal to the main controller when at least one comparison in the comparison between the sampled second voltage and the threshold affirms an inappropriate voltage state regarding the second voltage; wherein at least one comparison in the comparison between the sampled voltage and the threshold is affirmative, whereby at least one of the first track controller and the second track controller sends the first fault signal or the second fault signal to the main controller; and In response to the main controller receiving the first fault signal or the second fault signal, the main controller controls two rail controllers to stop the operation of two rail circuits.

13. The method according to claim 12, wherein, The OBC further includes a third rail circuit having a third rail controller, the main controller is also operably communicable with the third rail controller, and the third rail controller is configured to control the operation of the third rail circuit. The method further includes: sampling, by the third rail controller, a third voltage supplied to the third rail circuit, and sending, by the third rail controller, a third fault signal to the main controller when a comparison between the sampled third voltage and the threshold affirms an inappropriate voltage state regarding the third voltage; and In response to the main controller receiving the third fault signal, the main controller controls all rail controllers to stop the operation of all rail circuits.

14. The method according to claim 13, wherein: the first voltage is the first phase voltage supplied by a three-phase mains power supply, the second voltage is the second phase voltage supplied by the three-phase mains power supply, and the third voltage is the third phase voltage supplied by the three-phase mains power supply.

15. The method according to claim 13, further comprising: after a delay period expires after the operation of all rail circuits stops, the main controller controls all rail controllers to resume the operation of all rail circuits; and after the operation of all rail circuits is resumed, in response to receiving the first fault signal, the second fault signal, or the third fault signal from any one of the rail controllers, the main controller controls all rail controllers to stop the operation of all rail circuits.

16. An on-board battery charger OBC, comprising: a first rail circuit, the first rail circuit including a first rail controller; a second rail circuit, the second rail circuit including a second rail controller; and a controller configured to control the first rail controller and the second rail controller to sample a first voltage supplied to the first rail circuit, and to stop the operation of two rail circuits when a comparison between the sampled first voltage and a threshold affirms an inappropriate voltage state regarding the first voltage.

17. The OBC according to claim 16, wherein: the controller is further configured to sample a second voltage supplied to the second rail circuit, and to stop the operation of two rail circuits when a comparison between the sampled second voltage and the threshold affirms an inappropriate voltage state regarding the second voltage.

18. The OBC according to claim 17, further comprising: a third rail circuit; and the controller is further configured to sample a third voltage supplied to the third rail circuit, and to stop the operation of all rail circuits when a comparison between the sampled third voltage and the threshold affirms an inappropriate voltage state regarding the third voltage.

19. The OBC according to claim 18, wherein: The first voltage is the first-phase voltage supplied by a three-phase mains power supply, the second voltage is the second-phase voltage supplied by the three-phase mains power supply, and the third voltage is the third-phase voltage supplied by the three-phase mains power supply.

20. The OBC according to claim 18, wherein: The controller is further configured to resume the operation of all track circuits after the expiration of a delay after the operation of all track circuits has been stopped; and The controller is further configured to stop the operation of all track circuits when a comparison between any sampled voltage and the threshold is positive after the operation of all track circuits has been resumed.

Images