Controller for inverter

Abstract

A controller for an inverter, the inverter including a plurality of switches, the controller configured to generate a control signal, where the control signal operates the plurality of switches in a first switching mode or a second switching mode.

Description

[0001] The present disclosure relates to a controller for an inverter. In particular, the present disclosure relates to a controller for an inverter and a configuration of switches in an inverter for an electric vehicle power system. Background

[0002] Inverters are used for DC / AC power conversion. In particular, traction inverters are commonly used in electric vehicle power systems and for driving electric motors or for DC / AC conversion.

[0003] Overview

[0004] In the increasing electrification of vehicles, it is desirable to design efficient and cost-effective electric vehicle systems while also increasing the power density from battery to wheels.

[0005] According to a first aspect of the present disclosure, there is provided a controller for an inverter, the inverter including a plurality of switches, the controller being configured to generate a control signal, wherein the control signal operates the plurality of switches in a first switching pattern or a second switching pattern.

[0006] Optionally, the controller is configured to receive a first input and / or a second input.

[0007] Optionally, if the first input is less than the second input, the control signal operates the plurality of switches in the first switching pattern.

[0008] Optionally, if the first input is greater than the second input, the control signal operates the plurality of switches in the second switching pattern.

[0009] Optionally, the inverter is configured to operate in a first phase and a second phase.

[0010] Optionally, when operating the plurality of switches in the first switching pattern, the current flowing through the inverter switches between a first current path and a second current path.

[0011] Optionally, during the first phase, the current flowing through the inverter flows from the battery to the output, and during the second phase, the current flowing through the inverter flows from the output to the battery.

[0012] Optionally, the first current path includes a first switch and a second switch, and the second current path includes a third switch and a fourth switch.

[0013] Optionally, the generated control signal causes the current to switch between the first current path and the second current path by alternately switching the second switch and the fourth switch between an on state and an off state.

[0014] Optionally, the first current path includes a first switch and a second switch, and the second current path includes the second switch and a third switch.

[0015] Optionally, the generated control signal causes the current flow to switch between the first current path and the second current path by alternately switching the first switch and the third switch between an on state and an off state.

[0016] Optionally, when the plurality of switches are arranged in a second switch mode, the current flowing through the inverter switches between a third current path and a fourth current path.

[0017] Optionally, during a first phase, the current flowing through the inverter flows from the battery to the output terminal, and during a second phase, the current flowing through the inverter flows from the output terminal to the battery.

[0018] Optionally, the third current path includes a first switch, a second switch, and a capacitor, and the fourth current path includes the second switch, a third switch, a fourth switch, and a capacitor.

[0019] Optionally, the generated control signal alternately switches the first switch and the third switch and the fourth switch between an on state and an off state, such that the third switch and the fourth switch are always in the same state, thereby causing the current flow to switch between the third current path and the fourth current path.

[0020] Optionally, the third current path includes a first switch, a second switch, and a capacitor.

[0021] Optionally, during the second phase, the fourth current path includes the first switch and the third switch, and during the first phase, the fourth current path includes the second switch, the fourth switch, and a capacitor.

[0022] Optionally, during the second phase, the generated control signal causes the current flow to switch between the third current path and the fourth current path by alternately switching the second switch and the third switch between an on state and an off state, and wherein during the first phase, the generated control signal causes the current flow to switch between the third current path and the fourth current path by alternately switching the first switch and the fourth switch between an on state and an off state.

[0023] According to a second aspect of the present disclosure, there is provided an apparatus including an inverter and a controller for the inverter, the inverter including a plurality of switches, the controller being configured to generate a control signal, wherein the control signal operates the plurality of switches in a first switch mode or a second switch mode.

[0024] Optionally, the apparatus is an electric vehicle power system.

[0025] It will be understood that the apparatus of the second aspect may include the features as set forth with respect to the first aspect and may incorporate other features described herein.

[0026] According to a third aspect of the present disclosure, there is provided a method of controlling an inverter including a plurality of switches, the method including generating a control signal using a controller to operate the plurality of switches in a first switching mode or a second switching mode.

[0027] It will be understood that the method of the third aspect may include providing and / or using the features as set forth in the first aspect and / or the second aspect and may incorporate other features as described herein. Brief Description of the Drawings

[0028] The description will now be more particularly described, by way of example only, and with reference to the accompanying drawings, in which:

[0029] Figure 1 is a schematic diagram of a controller for an inverter according to the present disclosure;

[0030] Figure 2(a) is a first exemplary embodiment of an inverter that can be used with Figure 1 the controller, and Figure 2(b) is a second exemplary embodiment of an inverter that can be used with Figure 1 the controller;

[0031] Figure 3(a) is a schematic diagram of a first switching mode in a first exemplary embodiment of the inverter, and Figure 3(b) is a schematic diagram of a first switching mode in a second exemplary embodiment of the inverter;

[0032] Figure 4(a) is a schematic diagram of a second switching mode in a first exemplary embodiment of the inverter, and Figure 4(b) is a schematic diagram of a second switching mode in a second exemplary embodiment of the inverter;

[0033] Figure 5 is a schematic diagram of an electric vehicle power system including the controller of the present disclosure;

[0034] Figure 6(a) is an exemplary embodiment of the controller of the present disclosure for an electric vehicle power system;

[0035] Figure 6(b) is another exemplary embodiment of the controller of the present disclosure for an electric vehicle power system;

[0036] Figure 7 is a graph showing the relationship between the first switching mode, the second switching mode, the first input, and the second input;

[0037] Figure 8 is a graph showing the effect of the second switching mode on the switching losses of the inverter; and

[0038] Figure 9 It is a schematic diagram showing the benefits of providing the same power to an electric vehicle power system at half the current. Detailed description

[0039] In an electric vehicle (EV) power system, a two-level inverter architecture is commonly used.

[0040] To improve the efficiency and power performance of such a system, many methods have been implemented. For example, it may be advantageous to implement a battery with a higher voltage in the EV power system. It allows for the development of smaller and cheaper electric motors. However, when considering the entire EV power system, this is an expensive solution because it requires a more complex battery management system, and other components in the EV power system (such as the switches in the inverter) need to have a higher rated voltage. Additionally, increasing the battery voltage causes other problems. Specifically, the inverter suffers from increased switching losses, which affects the driving range of the EV and may lead to thermal management issues.

[0041] Another challenge when using a two-level inverter in an EV power system is that a higher switching frequency is preferred to improve the performance of the electric motor in the vehicle. However, for a two-level inverter, an increase in the switching frequency results in an increase in switching losses. Therefore, there is a limit to how much the switching frequency can be increased.

[0042] Figure 1 It is a schematic diagram of a controller 110 for an inverter 130 according to the present disclosure. The inverter 130 includes a plurality of switches, and the controller 110 is configured to generate a control signal CS1, where the control signal operates the plurality of switches in a first switching mode or a second switching mode. The controller 110 sends the control signal CS1 to a driver 120. The driver 120 processes the signal to operate the plurality of switches within the inverter 130. The driver 120 may include, for example, one or more gate driver units (GDUs). The number of GDUs may be equal to the number of switches within the inverter 130.

[0043] In a particular embodiment, the controller 110 is configured to receive a first input IN1 and / or a second input IN2.

[0044] One or both of the inputs IN1, IN2 may be received from an external location of the controller 110, or may be provided internally within the controller 110.

[0045] For example, the controller 110 may be configured to receive the first input IN1 from an external location and the second input IN2 from an internal location.

[0046] For example, a second input IN2 can be received from a memory element within the controller 110. The memory element can be pre-programmed with a look-up table, where at least a portion of the data within the look-up table is provided as the second input IN2.

[0047] The values of the first input IN1 and the second input IN2 determine in which switching mode the control signal CS1 operates the plurality of switches. If the first input IN1 is less than the second input IN2, the control signal CS1 operates the plurality of switches in a first switching mode. If the first input IN1 is greater than the second input IN2, the control signal CS1 operates the plurality of switches in a second switching mode.

[0048] FIG. 2(a) shows a first exemplary embodiment of an inverter 130a that can be controlled by Figure 1 the controller 110. The inverter 130a includes a battery 210 coupled to a capacitor DC link. Depending on the use of the inverter, the capacitor DC link can have a voltage, for example, ranging from 400 volts to 800 volts. The inverter 130a also includes one or more legs 220a, 230a, 240a that include a plurality of switches. Within each leg, the plurality of switches are arranged in the same configuration.

[0049] Each leg 220a is arranged as follows. There is a first branch between points U1 and N1, and this first branch includes two nodes P1 and S1. A switch M11 is coupled between nodes P1 and S1, and a switch M12 is coupled between node S1 and point N1. A capacitor C is arranged in a second branch that is in parallel with the first branch and extends only between nodes P1 and S1. The path from P1 to the capacitor C includes a switch M15. Finally, a third branch arranged in parallel with the first and second branches includes switches M13 and M14 coupled in series. Between switches M13 and M14, there is a third node U leading to the output of the inverter 130a.

[0050] Leg 230a includes switches M16, M17, M18, M19, M20; and leg 240a includes switches M21, M22, M23, M24, M25. Legs 230a and 240a include the same switch arrangement as leg 220a. This configuration of the first exemplary inverter 130a does not require an additional control loop. This means that the inverter 130a can respond more quickly to changes in the control signal CS1, and the circuit complexity of the inverter 130a is reduced.

[0051] The inverter 130a includes a plurality of switches operated by Figure 1 the control signal CS1 generated by the controller 110. The inverter 130a is configured to operate in a first phase and a second phase.

[0052] FIG. 2(b) shows what can be byFigure 1 Second exemplary embodiment of inverter 130b controlled by controller 110. Inverter 130b includes battery 210 coupled to a capacitor DC link. Inverter 130b also includes one or more leg arms 220b, 230b, 240b that include a plurality of switches. Within each leg arm, the plurality of switches are arranged in the same configuration.

[0053] Each leg arm 220b is arranged as follows. There is a first branch between points U1 and N1, and this first branch includes two nodes P1 and S1. Switch M11 is coupled between nodes P1 and S1, and switch M12 is coupled between node S1 and point N1. Capacitor C is arranged in a second branch in parallel with the first branch and extends only between nodes P1 and S1. The path from P1 to capacitor C includes diode D. Diode D can be, for example, a passive diode. Finally, a third branch arranged in parallel with the first and second branches includes switches M13 and M14 coupled in series. Between switches M13 and M14, there is a third node U leading to the output terminal of inverter 130b.

[0054] Leg arms 230b and 240b include the same configuration as leg arm 220b. Replacing switches with diodes D in the second embodiment of inverter 130b reduces the number of GDUs required in driver 120. This configuration of the second exemplary inverter 130b results in charge accumulation on capacitor C, which may increase the ripple effect across capacitor C. Therefore, the use of inverter 130b is only applicable to devices where the ripple effect caused is negligible compared to the benefit of reducing the number of GDUs in driver 120.

[0055] Inverter 130b includes a plurality of switches operated by control signal CS1 generated by Figure 1 controller 110. Inverter 130b is configured to operate in a first phase and a second phase.

[0056] Figure 3(a) is a schematic diagram showing how controller 110 operates a plurality of switches in a first switching mode of first exemplary inverter 130a. The first phase of inverter 130a is shown in row 310, and the second phase of inverter 130a is shown in row 320. Although shown for leg arm 220a, it should be understood that, as would be understood by a person skilled in the art, the switching mode shown in Figure 3(a) can additionally or alternatively be applied to leg arm 230a and / or leg arm 240a.

[0057] When operating the plurality of switches in the first switching mode, in each of the first phase and the second phase, the current I flowing through inverter 130a 相 in the first current path I 第一 and the second current path I 第二Switch between them. During the first phase, the current flowing in the inverter flows from the battery to the output terminal. During the second phase, the current flowing in the inverter flows from the output terminal to the battery.

[0058] For the first switching mode of inverter 130a, the first current path I 第一 and the second current path I 第二 are the same for both the first and second phases of inverter 130a. The first current path I 第一 of inverter 130a includes the first switch M15 and the second switch M13. The second current path I 第二 of inverter 130a includes the third switch M12 and the fourth switch M14. The control signal CS1 generated by the controller 110 causes the current to alternate between the first current path I 第一 and the second current path I 第二 by alternately switching the second switch M13 and the fourth switch M14 between the on state and the off state. In other words, when the second switch M13 is in the on state, the fourth switch M14 is in the off state. When the second switch M13 is in the off state, the fourth switch M14 is in the on state. The switching is hard switching and the capacitor C is trickling charged.

[0059] In an alternative embodiment of the first switching mode in inverter 130a, the switches M11 and M14 can be alternately switched between the on state and the off state, and the switches M12, M13 and M15 remain in the off state, where the capacitor C is floating. In another alternative embodiment of the first switching mode in inverter 130a, the switches M12, M13 and M14 can be alternately switched between the on state and the off state, M11 remains in the off state and the switch M15 remains in the on state. In this embodiment, the capacitor C can be said to be in the "power path".

[0060] Figure 3(b) is a schematic diagram showing how the controller 110 operates multiple switches in the first switching mode of the second exemplary inverter 130b. The first phase of inverter 130b is shown in row 330, and the second phase of inverter 130b is shown in row 340. Although shown for leg 220b, it should be understood that, as understood by those skilled in the art, the switching mode shown in Figure 3(b) can be additionally or alternatively applied to leg 230b and / or leg 240b.

[0061] When operating the multiple switches in the first switching mode, in each of the first and second phases, the current I flowing through inverter 130b相 Switch between the first current path I 第一 and the second current path I 第二 During the first phase, the current flowing in the inverter 130b flows from the battery to the output terminal. During the second phase, the current flowing in the inverter flows from the output terminal to the battery.

[0062] For the first switching mode of the inverter 130b, the first current path I 第一 and the second current path I 第二 are the same for both the first and second phases of the inverter 130b. The first current path I of the inverter 130b 第一 includes the first switch M11 and the second switch M14. The second current path I of the inverter 130b 第二 includes the second switch M14 and the third switch M12. The control signal CS1 generated by the controller 110 causes the current to flow between the first current path I 第一 and the second current path I 第二 by alternately switching the first switch M11 and the third switch M12 between the on state and the off state. In other words, when the switch M11 is in the on state, the switch M12 is in the off state. When the switch M11 is in the off state, the switch M12 is in the on state. The switching is hard switching and the capacitor C is trickle charged.

[0063] In an alternative embodiment of the first switching mode of the inverter 130b, the switches M13 and M14 can be alternately switched between the on state and the off state, the switch M12 remains in the on state and the switch M11 is in the off state. In this embodiment, the capacitor C will be trickle charged to commutate a current I greater than zero 相 to VDD.

[0064] Figure 4(a) is a schematic diagram showing how the controller 110 operates multiple switches in the second switching mode of the first exemplary inverter 130a. The first phase of the inverter 130a is shown in row 410, and the second phase of the inverter 130a is shown in row 420. Although shown for the leg 220a, it should be understood that, as understood by those skilled in the art, the switching mode shown in Figure 4(a) can be additionally or alternatively applied to the leg 230a and / or the leg 240a.

[0065] When operating multiple switches in the second switching mode, in each of the first and second phases, the current I flowing through the inverter 130a 相 is in the third current path I 第三 and the fourth current path I 第四Switch between them. During the first phase, the current flowing in the inverter flows from the battery to the output terminal. During the second phase, the current flowing in the inverter flows from the output terminal to the battery.

[0066] For the second switching mode of the inverter 130a, the third current path I 第三 and the fourth current path I 第四 are the same for both the first and second phases of the inverter 130a. The third current path I 第三 of the inverter 130a includes the first switch M11, the second switch M13, and the capacitor C. The fourth current path I 第四 of the inverter 130a includes the second switch M13, the third switch M12, the fourth switch M15, and the capacitor C. The control signal CS1 generated by the controller 110 causes the current to alternate between the third current path I 第三 and the fourth current path I 第四 by alternately switching the first switch M11 and the third switch M12 and the fourth switch M15 between the on state and the off state. In other words, when the first switch M11 is in the on state, the third switch M12 and the fourth switch M15 are in the off state. When the first switch M11 is in the off state, the third switch M12 and the fourth switch M15 are in the on state. For the switches M15 and M11, the switching is hard switching. The switch M12 has a hard switching that only becomes in the on state, and the capacitor C is charged in the current path.

[0067] In an alternative embodiment of the second switching mode in the inverter 130a, the switches M11 and M14 are alternately switched between the on state and the off state, and the switches M12, M13, and M15 are in the off state. In this embodiment, the capacitor C is floating for commutation to VDD.

[0068] FIG. 4(b) is a schematic diagram showing how the controller 110 operates multiple switches in the second switching mode of the second example inverter 130b. The second phase of the inverter 130b is shown in row 430, and the first phase of the inverter 130b is shown in row 440. Although shown for the leg 220b, it should be understood that, according to the understanding of those skilled in the art, the switching mode shown in FIG. 4(b) can be additionally or alternatively applied to the leg 230b and / or the leg 240b.

[0069] When operating multiple switches in the second switching mode, in each of the first and second phases, the current I 相 flowing through the inverter 130b is in the third current path I 第三 and the fourth current path I 第四Switch between them. During the first phase, the current flowing in the inverter flows from the battery to the output terminal. During the second phase, the current flowing in the inverter flows from the output terminal to the battery.

[0070] For the second switching mode of the inverter 130b, the third current path I 第三 Is the same for both the first and second phases of the inverter 130b. The fourth current path I 第四 Is different for the first and second phases of the inverter 130b. The third current path I of the inverter 130b 第三 Includes the first switch M11, the second switch M13, and the capacitor C. During the second phase 430, the fourth current path I of the inverter 130b 第四 Includes the first switch M11 and the third switch M14. During the second phase, the charge in the capacitor C accumulates. During the first phase 440, the fourth current path I of the inverter 130b 第四 Includes the second switch M13, the fourth switch M12, and the capacitor C. During the first phase, the charge stored in the capacitor C returns to the load. During this phase, the current may not flow through the diode D at all. The switching mode in this phase increases the ripple across the capacitor C. The control signal CS1 generated by the controller 110 causes the current to alternate between the third current path I 第三 And the fourth current path I 第四 During the second phase by alternately switching the second switch M13 and the third switch M14 between the on state and the off state. In other words, when the second switch M13 is in the on state, the third switch M14 is in the off state. When the second switch M13 is in the off state, then the third switch M14 is in the on state. The switch M14 has a hard switching, and the capacitor C is in the current path. The control signal CS1 generated by the controller 110 causes the current to alternate between the third current path I 第三 And the fourth current path I 第四 During the first phase by alternately switching the first switch M11 and the fourth switch M12 between the on state and the off state. In other words, when the switch M11 is in the on state, then the switch M12 is in the off state. When the switch M11 is in the off state, then the switch M12 is in the on state. The switch M11 has a hard switching, while the switch M12 has only a hard turn-on switch. The capacitor C is in the power supply path.

[0071] In an alternative embodiment of the second switching mode in the inverter 130b, the switches M11 and M14 are alternately switched between the on state and the off state. The switches M12, M13, and M15 are in the off state, and the capacitor C is floating for commutation to VDD.

[0072] Figure 5FIG. 0 is a schematic diagram of an electric vehicle power system (EVPS) 500 including the controller 110 of the present disclosure. The EVPS 500 also includes a driver 120 and an inverter 130 and is configured to drive an electric motor 140. The inverter 130 includes a plurality of switches. The inverter 130 can be, for example, the inverter 130a of FIG. 2(a) or the inverter 130b of FIG. 2(b). The controller 110 is configured to generate a control signal CS1, where the control signal operates the plurality of switches in a first switching mode or a second switching mode. The controller 110 sends the control signal CS1 to the driver 120. The driver 120 processes the signal to operate the plurality of switches within the inverter 130. The driver 120 can include, for example, a plurality of GDUs. The number of GDUs is equal to the number of switches within the inverter 130.

[0073] The controller 110 is configured to receive a first input IN1. For the EVPS 500, the first input IN1 received by the controller 110 is from the electric motor 140 and is related to the revolutions per minute (RPM) of the motor. For the EVPS 500, a second input IN2 is pre-programmed onto the controller 110. The second input IN2 is a look-up table that includes the voltage that needs to be applied across the inverter 130 for the electric motor 140 to operate at a given RPM and torque value. The maximum voltage that can be applied is limited by the maximum peak in the voltage sine wave. For example, if the inverter 130 operates in a two-level operation, the maximum voltage is limited to the voltage stored in the battery 210.

[0074] In other embodiments, the controller 110 can be configured to receive the second input IN2 from a location external to the controller 110 during operation.

[0075] The value of the RPM IN1 is used to find the operating voltage from the look-up table IN2, and these two values determine in which switching mode the control signal CS1 operates the plurality of switches. For example, if the inverter 130 operates as a two-level inverter and the operating voltage required from the look-up table IN2 for the RPM IN1 is greater than the voltage across the battery 210, the control signal CS1 will operate the plurality of switches in a three-level inverter operation. During the three-level operation of the inverter 130, the maximum voltage is limited to twice the voltage stored in the battery 210. Thus, during this operation of the plurality of switches, the inverter 130 is able to provide the voltage required for the RPM of the electric motor.

[0076] Figures 6(a) and 6(b) are example embodiments of the controller 110 and the driver 120 for the EVPS 500. In Figure 6(a), the driver 120 drives the inverter 130a of Figure 2(a), while in Figure 6(b), the driver 120 drives the inverter 130b of Figure 2(b). The controller 110 in this embodiment is a micro unit controller (MCU). The MCU generates a first switching mode and a second switching mode according to the relationship between torque and RPM in the operating region. At low RPM values of the motor 140, the MCU will generate a control signal CS1 to implement the first switching mode. In this example embodiment, the first switching mode is the switching mode of two-level inverter operation. At RPM values where a voltage greater than the charge (battery voltage) stored in the capacitor DC link is required, the MCU generates a control signal CS1 to implement the second switching mode as three-level inverter operation. During three-level operation, up to twice the capacitor DC link charge can be delivered to the motor 140. According to the understanding of those skilled in the art, the boundary between two-level inverter operation and three-level inverter operation depends on the specific EVPS configuration. For example, it depends on the motor used, the gear ratio, the voltage of the DC link, the weight of the vehicle, and other factors. In this way, all components in the EVPS 500 only need a rated voltage equal to the voltage stored across the capacitor DC link, because only the motor experiences twice the charge.

[0077] Figure 7 Graph 700 shows when the controller 110 of the EVPS 500 switches between the two-level inverter switching mode and the three-level inverter switching mode.

[0078] For Figure 5 the embodiment of the EVPS 500 shown, it should be understood that the system can operate with the same power P 出 and use half the current I 相 value and double the switching frequency. This is Figure 5 the proposed optimal use of the EVPS 500, however other usage scenarios can be achieved. When compared with a prior art two-level inverter with a certain power, the configuration of the switches in the controller 110 and the inverters 130a and 130b of the present disclosure allows the EVPS 500 to provide the same power to the motor 140 as that for which a traditional two-level inverter is designed, but with half the current I 相(Since the motor 140 operates at twice the voltage) and doubles the inverter switching frequency. Thus, the overhead from the inverter 130 is kept to a minimum. Specifically, the overhead due to the additional switches and additional floating capacitors in the power module is minimized. By doubling the DC link voltage and increasing the power density of the motor 140 at a negligible cost to the overall EVPS 500, the overall cost is reduced and the driving range of the electric vehicle is increased. Using the controller 110 of the present disclosure, up to 75% of the conduction losses can be saved in the motor 140 windings, and potentially up to 50% of the theoretical switching losses can also be saved. Doubling the switching frequency of the inverter 130 and saving the switching losses improves the performance of the motor 140 (finer torque control, faster dynamics, optimization of magnetic materials, lower distortion and electromagnetic interference (EMI)).

[0079] The improved efficiency of the EVPS 500 allows for savings in the EV's cooling system. All of these are reflected in savings (or improved range) of the battery 210, with the potential for cost savings that offset the additional cost from the inverter 130.

[0080] The power P supplied to the motor 140 出 is proportional to the phase voltage V 相 multiplied by the phase current I 相 In a conventional two-level inverter, the maximum V 相 ideally is the voltage across the capacitor DC link (in other words, the battery 210 voltage). Since the controller 110 for the inverter 130 is able to double it, the same power can be maintained while supplying half the current I 相 to each phase.

[0081]

[0082] This can be achieved while keeping the maximum rate of change dv / dt of the phase voltage V 相 across each of the multiple switches constant over time. Thus, the switching time can be halved, with the same EMI performance as a two-level inverter. Since the rate of change (di / dt) of the phase current I 相 across each switch also halves over time, this means the switching power loss is:[[]]

[0083]

[0084] where I pk is the peak of I 相 and f sw is the switching frequency, and tr is the switching time.

[0085] Thus, the switching frequency can be doubled while achieving approximately 50% reduction in switching losses. In practice, when the inverter 130 is controlled in three-level operation, the saved switching losses are slightly less because the losses and switching patterns from the floating capacitor itself are considered.

[0086] Figure 8 is a graph 800 showing the effect of three-level operation on the switching losses of the inverter 130a in FIG. 2(a). For the second switching pattern shown in FIG. 4(a), the graph is divided into a first phase and a second phase, which shows the three-level switching operation. Except that M12 is hard-switched on, the number of hard-switching events is the same as in the two-level operation case, and thus occurs at f sw / 8. In this transition, M12 is turned on to charge the floating capacitor C. Therefore, the switching loss depends on the RC time constant and the peak current I pk .

[0087] The floating capacitor undergoes hard charge / discharge cycles at fsw / 4:

[0088]

[0089] where Cfloat is the value of the floating capacitor C, and ΔV is the ripple on the floating capacitor.

[0090] In the simulation example, where the controller 110 and the inverter 130a of the present disclosure are compared with a conventional two-level inverter providing 100 kW, having a 400 VDC link, tr = 200 nSec (and where Cfloat = 100 uF results in a maximum ΔV of 10 V), this ratio is 0.625. This is equivalent to saving approximately 40% of the switching losses.

[0091] Figure 9 is a schematic diagram showing the benefit of using the controller 110 of the present disclosure to provide the same power to an electric vehicle power system at half the current. The conventional two-level inverter is shown on the left hand side 910, and the inverter 130 that can be used with the controller 110 is shown on the right hand side 920.

[0092] The power module of the two-level traction inverter 910 is designed to utilize a certain number 2*M of parallel SiC / IGBT wafers per switch to provide a certain amount of power. The wafers can be reconfigured into the inverter 920, so the current density / thermal performance will remain exactly the same for half the current. For example, if M = 4, then 16 wafers are required for each leg in the conventional two-level inverter 910, but only 20 wafers are required for the controller 110 and the inverter 130 of the present disclosure.

[0093] The control signal CS1 generated by the controller 110 of the present disclosure operates two series switches at each commutation. For 2*M parallel wafers with an RDSon resistance, the resistance of two series switches is 2*RDSon for 920. The RMS of the phase current I RMS is halved, so the conduction loss remains unchanged:

[0094]

[0095] If the motor 140 is driven with half of the phase current I 相 the conduction loss in the windings of the motor 140 can be reduced by up to 75% (ignoring other effects when the switching frequency is doubled):

[0096]

[0097] where R w is the resistance in the windings of the motor 140.

[0098] Alternatively, a smaller winding can be selected for the motor 140, where the winding has a smaller cross-section. This can save cost and reduce the total cross-section of the motor 140 and make it lighter.

[0099] If the switching frequency is doubled, it can be assumed that the DC link capacitor value can be halved to maintain the same ripple performance at the input of the inverter 130. Half of the saved DC link capacitor can be used to implement the three floating capacitors required to generate the three-level inverter 130. For example, the typical DC link capacitance of a 100kW, 400V two-level conventional inverter is about 500uF - 600uF. A 100uF capacitance for the floating capacitors of the controller 110 and inverter 130 of the present disclosure will keep the ripple across the floating capacitors within 10V and leave 200uF to 300uF for the DC link capacitance without performance degradation.

[0100] When implemented in an electric vehicle power system (EVPS) such as Figure 5 shown, the controller 110 of the present disclosure can be used to provide more power to the motor 140 without the need to upgrade the entire electric vehicle system. For example, if the controller 110 and inverter 130 of the present disclosure are used to provide the same current to each phase, approximately twice the power is provided to the motor 140. This example implementation may result in a larger overhead.

[0101] It should be understood that the optimal use of the EVPS 500 of the present disclosure is to provide the same output power for half of the phase current I 相 and double the switching frequency. Although not explicitly disclosed here, other uses of the system are possible. Several examples are provided here, and the list is not exhaustive.

[0102] Another example usage is to use half of the phase current I 相 to provide the same output power to the motor without doubling the switching frequency. More switching losses are saved, but the bill of materials (BOM) increases because the capacitor DC link cannot be saved / or higher ripple on the capacitor DC link is not acceptable. The third example is to provide higher output power with a reduced phase current I 相 and a constant switching frequency for a moderate saving of switching losses and a moderate saving of motor winding conduction losses, and still increasing the BOM because the capacitor DC link cannot be saved / or higher ripple on the DC link is not acceptable and the number of dies in the power module increases. Or providing double the power, with the disadvantages shown above.

[0103] The controller 110 of the present disclosure allows the inverter 130 to provide the same power to the motor 140 with half of the phase current I of the prior art 相 and double the switching frequency. This results in a smaller hardware overhead and allows for the optimization of certain components such as the cooling system, the motor, and (if the range is to be kept constant) the battery pack of, for example, an electric vehicle. Embodiments of the controller 110 and the inverters 130a and 130b of the present disclosure can also provide a higher voltage to the motor without the need to upgrade other components in the EV power system to high-rated voltage components (other than the motor itself) and with a relatively small overhead. Thus, embodiments of the present disclosure avoid the cost of upgrading the entire EV power system (including the battery pack) to a higher voltage or using a complex and expensive DC / DC converter between the battery and the inverter. This is achieved with minimal complexity and without a control loop, which means that the dynamic performance is not affected. Additionally, embodiments of the present disclosure achieve a higher voltage provided to the motor without increasing the actual rate of change of voltage dv / dt experienced by the switching elements or the motor windings. Thus, there is no loss of switching losses, EMI, or reliability.

[0104] It should be understood that the inverter of the present disclosure can be a traction inverter for a passenger EV. Further embodiments can relate to inverters for other applications and for other input voltages, as would be understood by a person skilled in the art.

[0105] Various improvements and modifications can be made without departing from the scope of the present disclosure.

[0106] A person skilled in the art will understand that variations of the disclosed arrangements are possible without departing from the present disclosure. Thus, the above description of specific embodiments is made by way of example only and not for the purpose of limitation. It will be clear to a person skilled in the art that minor modifications can be made without significantly altering the described operation.

Claims

1. A controller for an inverter, the inverter comprising a plurality of switches, the controller being configured to generate a control signal, wherein: The control signal operates the plurality of switches in a first switching mode or a second switching mode.

2. The controller according to claim 1, wherein: The controller is configured to receive a first input and / or a second input, wherein: If the first input is less than the second input, the control signal operates the plurality of switches in the first switching mode.

3. The controller according to claim 2, wherein: If the first input is greater than the second input, the control signal operates the plurality of switches in the second switching mode.

4. The controller according to claim 3, wherein: The inverter is configured to operate in a first phase and a second phase.

5. The controller according to claim 4, wherein: When the plurality of switches are operated in the first switching pattern, current flowing through the inverter is switched between a first current path and a second current path.

6. The controller according to claim 5, wherein: During the first phase, the current flowing through the inverter flows from the battery to the output terminal, and during the second phase, the current flowing through the inverter flows from the output terminal to the battery.

7. The controller according to claim 6, wherein: The first current path includes a first switch and a second switch; and The second current path includes a third switch and a fourth switch, wherein: The generated control signal switches the current flow between the first current path and the second current path by alternately switching the second switch and the fourth switch between an on state and an off state.

8. The controller according to claim 6, wherein: The first current path includes a first switch and a second switch; and The second current path includes the second switch and a third switch, wherein the generated control signal switches the current flow between the first current path and the second current path by alternately switching the first switch and the third switch between an on state and an off state.

9. The controller according to claim 5, wherein: When the plurality of switches are arranged in the second switching pattern, current flowing through the inverter is switched between a third current path and a fourth current path.

10. The controller according to claim 9, wherein: During the first phase, the current flowing through the inverter flows from the battery to the output terminal, and during the second phase, the current flowing through the inverter flows from the output terminal to the battery.

11. The controller according to claim 10, wherein: The third current path includes a first switch, a second switch and a capacitor; and The fourth current path includes the second switch, the third switch, the fourth switch and the capacitor, wherein: The generated control signal switches the current flow between the third current path and the fourth current path by alternately switching the first switch and the third and fourth switches between an on state and an off state so that the third and fourth switches are always in the same state.

12. The controller according to claim 10, wherein: The third current path includes a first switch, a second switch and a capacitor; and wherein: During the second phase, the fourth current path includes the first switch and a third switch; and During the first phase, the fourth current path includes the second switch, a fourth switch, and the capacitor.

13. The controller according to claim 12, wherein: During the second phase, the generated control signal switches the current flow between the third current path and the fourth current path by alternately switching the second switch and the third switch between an on state and an off state, and wherein, during the first phase, the generated control signal switches the current flow between the third current path and the fourth current path by alternately switching the first switch and the fourth switch between an on state and an off state.

14. An apparatus comprising: an inverter including a plurality of switches; as well as A controller for the inverter is configured to generate a control signal, wherein the control signal operates the plurality of switches in a first switching mode or a second switching mode.

15. A method of controlling an inverter comprising a plurality of switches, the method comprising: A controller is used to generate control signals to operate the plurality of switches in a first switching mode or a second switching mode.

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