Controller for inverter
The controller for the inverter addresses inefficiencies in electric vehicle systems by optimizing switching patterns and frequencies, enhancing power density and motor performance while reducing costs and thermal issues.
Patent Information
- Application Number
- JP2024215206
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-12-26
- Filing Date
- 2024-12-10
- Publication Date
- 2025-07-30
AI Technical Summary
Existing electric vehicle systems face inefficiencies and high costs due to increased switching losses and thermal management issues in two-level inverters, limiting power density and driving range.
A controller for an inverter that operates switches in multiple patterns based on input values, allowing for efficient switching between current paths and reducing switching losses by doubling the DC link voltage and switching frequency.
Improves power density and reduces switching losses by up to 50%, enhances motor performance with precise torque control, and increases driving range while minimizing hardware overhead and costs.
Smart Images
Figure 2025111379000001_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to a controller for an inverter. More particularly, the present disclosure relates to a controller for an inverter and the configuration of switches in an inverter for use in an electric vehicle power system.
Background Art
[0002] An inverter is used for DC / AC power conversion. In particular, a traction inverter is often used not only for driving an electric motor and for DC / AC conversion, but also in an electric vehicle power system.
Summary of the Invention
Problems to be Solved by the Invention
[0003] As the electrification of automobiles progresses, it is desired to design an efficient and cost-effective electric vehicle system and improve the power density from the battery to the wheels.
Means for Solving the Problems
[0004] According to a first aspect of the present disclosure, a controller for an inverter is provided. The inverter includes a plurality of switches. The controller is configured to generate a control signal. The control signal operates the plurality of switches in a first switching pattern or a second switching pattern.
[0005] Optionally, the controller is configured to receive a first input and / or a second input.
[0006] Optionally, when the first input is smaller than the second input, the control signal operates the plurality of switches in the first switching pattern.
[0007] Optionally, when the first input is larger than the second input, the control signal operates the plurality of switches in the second switching pattern.
[0008] Optionally, the inverter is configured to operate in a first phase and a second phase.
[0009] Optionally, when a plurality of switches operate in a first switching pattern, the current flowing through the inverter switches between a first current path and a second current path.
[0010] Optionally, in the first phase, the current flowing through the inverter flows from the battery to the output, and in the second phase, the current flowing through the inverter flows from the output to the battery.
[0011] 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.
[0012] Optionally, 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.
[0013] Optionally, the first current path includes a first switch and a second switch, and the second current path includes a second switch and a third switch.
[0014] Optionally, 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.
[0015] Optionally, when a plurality of switches are arranged in a second switching pattern, the current flowing through the inverter switches between a third current path and a fourth current path.
[0016] Optionally, in the first phase, the current flowing through the inverter flows from the battery to the output, and in the second phase, the current flowing through the inverter flows from the output to the battery.
[0017] Optionally, the third current path includes the first switch, the second switch, and the capacitor, and the fourth current path includes the second switch, the third switch, the fourth switch, and the capacitor.
[0018] Optionally, the generated control signal switches the flow of current between the third current path and the fourth current path by alternately switching the first switch, 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.
[0019] Optionally, the third current path includes the first switch, the second switch, and the capacitor.
[0020] Optionally, in the second phase, the fourth current path includes the first switch and the third switch, and in the first phase, the fourth current path includes the second switch, the fourth switch, and the capacitor.
[0021] Optionally, in the second phase, the generated control signal switches the flow of current 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 in the first phase, the generated control signal switches the flow of current 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.
[0022] According to a second aspect of the present disclosure, an apparatus is provided that includes an inverter including a plurality of switches and a controller for the inverter. The controller is configured to generate a control signal. The control signal operates the plurality of switches in a first switching pattern or a second switching pattern.
[0023] Optionally, the apparatus is a power system for an electric vehicle.
[0024] Note that the device according to the second aspect may include the features as described above in relation to the first aspect, and it should be noted that other features as described in this specification can be incorporated.
[0025] According to a third aspect of the present disclosure, a method for controlling an inverter including a plurality of switches is provided. The method includes generating, using a controller, a control signal for operating the plurality of switches in a first switching pattern or a second switching pattern.
[0026] Note that the method according to the third aspect may include the features as described above in relation to the first aspect and / or the second aspect, and it should be noted that other features as described in this specification can be incorporated.
Brief Description of the Drawings
[0027] Hereinafter, the present invention will be described in more detail by way of example with reference to the accompanying drawings.
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[0028] In an electric vehicle (EV) power system, a two-level inverter architecture is commonly used.
[0029] To improve the efficiency and power performance of such a system, many methods have been implemented. For example, introducing a high-voltage battery into the EV power system can be advantageous. This enables the development of a smaller and less expensive electric motor. However, considering the entire EV power system, a more complex battery management system is required, and high rated voltages are also required for other components within the EV power system (such as the switches of the inverter), so this is an expensive solution. Furthermore, increasing the battery voltage causes another problem. In particular, the inverter suffers from an increase in switching losses that can affect the driving range of the EV and consequently cause thermal management problems.
[0030] Another issue when using a two-level inverter in an EV power system is that in order to improve the performance of the electric motor of the vehicle, it is preferable to increase the switching frequency. However, in the case of a two-level inverter, increasing the switching frequency may increase the switching losses. Therefore, there is a limit to increasing the switching frequency.
[0031] FIG. 1 is a diagram of a controller 110 for an inverter 130 according to the present disclosure. The inverter 130 includes a plurality of switches. The controller 110 is configured to generate a control signal CS1. The control signal operates the plurality of switches in a first switching pattern or a second switching pattern. The controller 110 transmits 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, one or more gate driver units (GDUs). The number of GDUs may be equal to the number of switches within the inverter 130.
[0032] In a specific embodiment, the controller 110 is configured to receive a first input IN1 and / or a second input IN2.
[0033] One or both of the inputs IN1, IN2 may be received from outside the controller 110 or may be provided inside the controller 110.
[0034] For example, the controller 110 may be configured to receive the first input IN1 from outside and the second input IN2 from inside.
[0035] For example, the second input IN2 may be received from a memory element within the controller 110. The memory element may be pre-programmed with a look-up table, and at least a part of the data in the look-up table may be provided as the second input IN2.
[0036] The values of the first input IN1 and the second input IN2 determine in which switching pattern the control signal CS1 operates a plurality of switches. When the first input IN1 is smaller than the second input IN2, the control signal CS1 operates the plurality of switches in the first switching pattern. When the first input IN1 is larger than the second input IN2, the control signal CS1 operates the plurality of switches in the second switching pattern.
[0037] FIG. 2(a) shows a first exemplary embodiment of the inverter 130a controllable by the controller 110 of FIG. 1. The inverter 130a includes a battery 210 coupled to a capacitor DC link. The capacitor DC link can have a voltage of, for example, 400 volts to 800 volts depending on the application of the inverter. The inverter 130a further includes one or more legs 220a, 230a, 240a including a plurality of switches. Within each leg, the plurality of switches are arranged in the same configuration.
[0038] Each leg 220a is arranged as follows. There is a first branch including two nodes P1 and S1 between point U1 and point N1. Switch M11 is coupled between nodes P1 and P2, and switch M12 is coupled between node S1 and point N1. Capacitor C is arranged in a second branch parallel to the first branch extending only between nodes P1 and S1. The path from P1 to capacitor C includes switch M15. Finally, a third branch arranged in parallel with the first and second branches includes switches M13 and M14 coupled in series. There is a third node U between switches M13 and M14 that connects to the output of the inverter 130a.
[0039] Leg 230a includes switches M16, M17, M18, M19, M20, and leg 240a includes switches M21, M22, M23, M24, M25. Legs 230a and 240a are configured with 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 quickly to changes in the control signal CS1 and the complexity of the circuit of the inverter 130a is reduced.
[0040] Inverter 130a includes a plurality of switches that are operated by a control signal CS1 generated by the controller 110 of FIG. 1. Inverter 130a is configured to operate in a first phase and a second phase.
[0041] FIG. 2(b) shows a second exemplary embodiment of an inverter 130b that can be controlled by the controller 110 of FIG. 1. Inverter 130b includes a battery 210 coupled to a capacitor DC link. Inverter 130b further includes one or more legs 220b, 230b, 240b that include a plurality of switches. Within each leg, the plurality of switches are arranged in the same configuration.
[0042] Each leg 220b is arranged as follows. There is a first branch including two nodes P1 and S1 between point U1 and point N1. Switch M11 is coupled between nodes P1 and P2, and switch M12 is coupled between node S1 and point N1. Capacitor C is arranged in a second branch parallel to the first branch that extends only between nodes P1 and S1. The path from P1 to capacitor C includes diode D. Diode D is, 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. There is a third node U between switches M13 and M14 that leads to the output of inverter 130b.
[0043] Legs 230b and 240b have the same configuration as leg 220b. In the second embodiment of inverter 130b, by replacing the switch with diode D, the number of GDUs required for driver 120 is reduced. With this configuration of the second exemplary inverter 130b, charge accumulates in capacitor C, and the ripple effect across the entire capacitor C can be increased. Therefore, the use of inverter 130b is only preferable for devices where the induced ripple effect is negligible compared to the advantage of reducing the number of GDUs in driver 120.
[0044] Inverter 130b includes a plurality of switches that are operated by control signal CS1 generated by controller 110 of FIG. 1. Inverter 130b is configured to operate in a first phase and a second phase.
[0045] FIG. 3(a) is a diagram showing how controller 110 operates a plurality of switches in a first switching pattern for the first exemplary inverter 130a. The first phase of inverter 130a is indicated by reference numeral 310, and the second phase of inverter 130a is indicated by reference numeral 320. Although only leg 220a is shown, it should be noted that the switching pattern as shown in FIG. 3(a) may be additionally or alternatively applied to leg 230a and / or leg 240a according to the understanding of those skilled in the art.
[0046] When the plurality of switches operate in the first switching pattern, in each of the first phase and the second phase, current I flowing through inverter 130a phase is switched between a first current path I first and a second current path I second In the first phase, the current flowing through the inverter flows from the battery to the output. In the second phase, the current flowing through the inverter flows from the output to the battery.
[0047] In the first switching pattern of inverter 130a, the first current path I first and the second current path I secondis the same for both the first and second phases of the inverter 130a. The first current path I of the inverter 130a first includes the first switch M15 and the second switch M13. The second current path I of the inverter 130a second includes the third switch M12 and the fourth switch M14. The control signal CS1 generated by the controller 110 alternately switches the second switch M13 and the fourth switch M14 between the on state and the off state, so that the current is in the first current path I first and the second current path I second to switch between. 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 charging of the capacitor C is trickle charging.
[0048] In an alternative embodiment of the first switching pattern in the inverter 130a, the switches M11 and M14 can alternately switch between the on state and the off state, and the switches M12, M13, and M15 can keep the capacitor C in the floating state and off state. In another alternative embodiment of the first switching pattern in the inverter 130a, the switches M12, M13, and M14 can alternately switch between the on state and the off state, M11 can remain in the off state, and the switch M15 can remain in the on state. The capacitor C in this embodiment can be said to be in the "power path".
[0049] FIG. 3(b) is a diagram showing how the controller 110 operates a plurality of switches in a first switching pattern for the second exemplary inverter 130b. The first phase of the inverter 130b is indicated by reference numeral 330, and the second phase of the inverter 130b is indicated by reference numeral 340. Although only leg 220b is shown, it should be noted that, according to the understanding of those skilled in the art, the switching pattern as shown in FIG. 3(b) may be additionally or alternatively applied to leg 230b and / or leg 240b.
[0050] When the plurality of switches operate in the first switching pattern, in each of the first phase and the second phase, the current I flowing through the inverter 130b phase is the first current path I first and the second current path I second switch between. In the first phase, the current flowing through the inverter 130b flows from the battery to the output. In the second phase, the current flowing through the inverter flows from the output to the battery.
[0051] In the first switching pattern of the inverter 130b, the first current path I first and the second current path I second are the same in both the first phase and the second phase of the inverter 130b. The first current path I first of the inverter 130b includes the first switch M11 and the second switch M14. The second current path I second of the inverter 130b includes the second switch M14 and the third switch M12. The control signal CS1 generated by the controller 110 alternately switches the first switch M11 and the third switch M12 between the on state and the off state, thereby causing the current to flow between the first current path I first and the second current path I second alternately. 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 charging of the capacitor C is trickle charging.
[0052] In an alternative embodiment of the first switching pattern in the inverter 130b, the switches M13 and M14 can alternate between an on state and an off state, the switch M12 can remain in the on state, and the switch M11 can remain in the off state. The capacitor C in this embodiment is trickled for commutation to VDD for a current I greater than zero. phase with respect to the current I, it is trickled for commutation to VDD.
[0053] FIG. 4(a) is a diagram showing how the controller 110 operates a plurality of switches in a second switching pattern for the first exemplary inverter 130a. The first phase of the inverter 130a is indicated by reference numeral 410, and the second phase of the inverter 130a is indicated by reference numeral 420. Although only leg 220a is shown, it should be noted that, according to the understanding of those skilled in the art, the switching pattern as shown in FIG. 4(a) may be additionally or alternatively applied to leg 230a and / or leg 240a.
[0054] When a plurality of switches operate in the second switching pattern, in each of the first phase and the second phase, the current I flowing through the inverter 130a phase is switched between a third current path I third and a fourth current path I fourth In the first phase, the current flowing through the inverter flows from the battery to the output. In the second phase, the current flowing through the inverter flows from the output to the battery.
[0055] In the second switching pattern of the inverter 130a, the third current path I third and the fourth current path I fourth are the same in both the first phase and the second phase of the inverter 130a. The third current path I third of the inverter 130a includes the first switch M11, the second switch M13, and the capacitor C. The fourth current path I fourthincludes a second switch M13, a third switch M12, a fourth switch M15, and a capacitor C. The control signal CS1 generated by the controller 110 alternates the first switch M11, the third switch M12, and the fourth switch M15 between the on state and the off state, thereby causing the current to flow through the third current path I third and the fourth current path I fourth alternately. In other words, when the second switch M13 is in the on state, the third switch M12 and the fourth switch M15 are in the off state. When the second switch M13 is in the off state, the third switch M12 and the fourth switch M15 are in the on state. For switches M15 and M11, the switching is hard switching. The switch M12 only hard switches to the on state, and the charge of the capacitor C is in the power path.
[0056] In an alternative embodiment of the second switching pattern in the inverter 130a, the switches M11 and M14 alternate between the on state and the off state, and the switches M12, M13, and M15 are in the off state. The capacitor C in this embodiment is in a floating state for the current transfer to VDD.
[0057] FIG. 4(b) is a diagram showing how the controller 110 operates a plurality of switches in a second switching pattern for a second exemplary inverter 130b. The second phase of the inverter 130b is indicated by the reference numeral 430, and the first phase of the inverter 130b is indicated by the reference numeral 440. Although only the leg 220b is shown, it should be noted that, according to the understanding of those skilled in the art, the switching pattern as shown in FIG. 4(b) may be additionally or alternatively applied to the leg 230b and / or the leg 240b.
[0058] When a plurality of switches operate in the second switching pattern, in each of the first phase and the second phase, the current I flowing through the inverter 130b phase is the third current path I third and the fourth current path I fourthIt switches between them. In the first phase, the current flowing through the inverter flows from the battery to the output. In the second phase, the current flowing through the inverter flows from the output to the battery.
[0059] In the second switching pattern of the inverter 130b, the third current path I third is the same in both the first and second phases of the inverter 130b. The fourth current path I fourth is different in the first and second phases of the inverter 130b. The third current path I third of the inverter 130b includes the first switch M11, the second switch M13, and the capacitor C. In the second phase 430, the fourth current path I fourth of the inverter 130b includes the first switch M11 and the third switch M14. In the second phase, the charge of the capacitor C accumulates. In the first phase 440, the fourth current path I fourth of the inverter 130b includes the second switch M13, the fourth switch M12, and the capacitor C. In the first phase, the charge stored in the capacitor C is returned to the load. In this phase, there may be no current flowing through the diode D. The switching pattern of this phase increases the ripple of the entire capacitor C. In the second phase, the control signal CS1 generated by the controller 110 alternately switches the second switch M13 and the third switch M14 between the on state and the off state, so that the current is in the third current path I third and the fourth current path I fourth and switches alternately between them. In other words, when the second switch M13 is in the on state, the third switch M12 is in the off state. When the second switch M13 is in the off state, the third switch M14 is in the on state. For the switch M14, the switching is hard switching, and the capacitor C is in the power path. In the first phase, the control signal CS1 generated by the controller 110 alternately switches the first switch M11 and the fourth switch M12 between the on state and the off state, so that the current is in the third current path I third and the fourth current path I fourthThey alternate between each other. In other words, when switch M11 is in the on state, switch M12 is in the off state. When switch M11 is in the off state, switch M12 is in the on state. For switch M11, the switching is hard switching, and switch M12 only hard switches when in the on state. Capacitor C is in the power path.
[0060] In an alternative embodiment of the second switching pattern in inverter 130b, switches M11 and M14 alternate between the on state and the off state. Switches M12, M13, and M15 are in the off state, and capacitor C is in a floating state for commutation to VDD.
[0061] FIG. 5 is a diagram showing an electric vehicle power system (EVPS) 500 including the controller 110 of the present disclosure. Further, EVPS 500 includes a driver 120 and an inverter 130 and is configured to drive a motor 140. Inverter 130 includes a plurality of switches. Inverter 130 can be, for example, inverter 130a of FIG. 2(a) or inverter 130b of FIG. 2(b). Controller 110 is configured to generate a control signal CS1. The control signal operates a plurality of switches in a first switching pattern or a second switching pattern. Controller 110 transmits control signal CS1 to driver 120. Driver 120 processes signals to operate a plurality of switches within inverter 130. Driver 120 can include, for example, a number of GDUs. The number of GDUs is equal to the number of switches within inverter 130.
[0062] The controller 110 is configured to receive a first input IN1. In the case of the EVPS500, the first input IN1 received by the controller 110 is from the motor 140 and is related to the rotational speed (RPM) of the motor. In the case of the EVPS500, the second input IN2 is pre-programmed into the controller 110. The second input IN2 is a look-up table that includes the voltage that needs to be applied across the entire inverter 130 for the motor 140 to operate at a given rotational speed and torque value. The maximum voltage that can be applied is limited by the maximum peak of the voltage sine wave. For example, when the inverter 130 is operating at two levels, the maximum voltage is limited to the voltage stored in the battery 210.
[0063] In other embodiments, the controller 110 may be configured to receive the second input IN2 from outside the controller 110 during operation.
[0064] The value of the rotational speed IN1 is used to obtain the operating voltage from the look-up table IN2. These two values determine in which switching pattern the control signal CS1 operates a plurality of switches. For example, when the inverter 130 is operating in two-level inverter operation and the operating voltage from the look-up table IN2 required for the rotational speed IN1 is greater than the voltage of the entire battery 210, the control signal CS1 operates the plurality of switches in three-level inverter operation. The maximum voltage during the three-level operation of the inverter 130 is limited to twice the voltage stored in the battery 210. Therefore, during the operation of the plurality of switches, the inverter 130 can supply the voltage required for the rotational speed of the motor.
[0065] Figures 6(a) and 6(b) are diagrams showing exemplary embodiments of the controller 110 and the driver 120 for the EVPS500. In Figure 6(a), the driver 120 drives the inverter 130a of Figure 2(a), and 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 pattern and a second switching pattern according to the torque versus rotational speed in the operating region. At low rotational speeds of the motor 140, the MCU generates a control signal CS1 to implement the first switching pattern. In this exemplary embodiment, the first switching pattern is for two-level inverter operation. At rotational speed values that require a voltage greater than the charge (battery voltage) stored in the capacitor DC link, the MCU generates a control signal CS1 to implement the second switching pattern, which is three-level inverter operation. During three-level operation, up to twice the charge of the capacitor DC link can be supplied to the motor 140. The boundary between two-level and three-level inverter operation depends on the specific EVPS configuration, as understood by those skilled in the art. For example, it depends on the motor used, the gear ratio, the voltage of the DC link, the weight of the vehicle, etc. In this way, since only the motor experiences twice the charge, all components of the EVPS500 only need a rated voltage equal to the voltage stored in the entire capacitor DC link.
[0066] Figure 7 is a plot 700 showing the timing at which the controller 110 of the EVPS500 switches between the switching pattern of a two-level inverter and the switching pattern of a three-level inverter.
[0067] Note that in the embodiment of the EVPS500 shown in Figure 5, the system uses half the value of the current I phase and twice the switching frequency to achieve the same power P outIt should be noted that it can operate with . This is the optimal usage of the proposed EVPS500 in FIG. 5, but other usages are also feasible. When compared with a prior art two-level inverter with a specific power, due to the configuration of the switches in the controller 110 and the inverters 130a and 130b of the present disclosure, the EVPS500 can supply the motor 140 with the same power as that designed for a conventional two-level inverter. However, in this case, (since the motor 140 operates at twice the voltage), the power can be supplied to the motor 140 at half the current I phase and twice the inverter switching frequency. Therefore, the overhead from the inverter 130 can be minimized. Specifically, the overhead due to the additional switches and additional floating capacitors in the power module can be minimized. By taking advantage of the benefit of doubling the DC link voltage and improving the power density of the motor 140 at a negligible cost for the entire EVPS500, overall cost reduction and an increase in the driving range of the electric vehicle can be provided. With the controller 110 of the present disclosure, the conduction loss in the windings of the motor 140 can be saved by up to 75%, and theoretically, the switching loss may also be saved by up to 50%. By doubling the switching frequency of the inverter 130 and saving the switching loss, the performance of the motor 140 is improved (more precise torque control, faster dynamics, optimization of magnetic materials, lower distortion and electromagnetic interference (EMI)).
[0068] By improving the efficiency of the EVPS500, savings can be made in the EV's cooling system. All of these are reflected in the savings of the battery 210 (or an increase in the driving range), leading to the possibility of cost reduction that offsets the additional cost due to the inverter 130.
[0069] The power P supplied to the motor 140 out is proportional to the phase voltage V phase × the phase current I phase In a conventional two-level inverter, the maximum V phaseIdeally, it is the voltage across the entire capacitor DC link (in other words, the voltage of the battery 210). Since the controller 110 of the inverter 130 can double this, the same power can be maintained while supplying half the current I phase to each phase.
[0070]
Number
[0071] This can be achieved while keeping the maximum time rate of change dv / dt of the phase voltage V phase across each of the plurality of switches the same. Thus, with the same EMI performance as a two-level inverter, the transition time can be halved. Since the time rate of change (di / dt) of the phase current I phase of each switch is halved, the switching power loss is as follows.
[0072]
Number
[0073] Here, I pk is the peak value of I phase , f sw is the switching frequency, and tr represents the transition time.
[0074] Therefore, the switching frequency can be doubled while reducing the switching loss by approximately 50%. In fact, when the inverter 130 is controlled in three-level operation, the savings in switching loss are slightly less because the losses from the floating capacitor itself and the switching pattern are taken into account.
[0075] FIG. 8 is a plot 800 showing the effect of three-level operation on the switching loss of the inverter 130a in FIG. 2(a). This plot is divided into a first phase and a second phase for the second switching pattern shown in FIG. 4(a) showing three-level switching operation. The number of hard switching events is the same as in the case of two-level operation, except for the hard switch-on of M12, which occurs at f sw / 8. In this transition, M12 switches on and the floating capacitor C is charged. Therefore, the switching loss depends on the RC time constant and the peak current I pk .
[0076] The floating capacitor performs hard charge / discharge cycles at fsw / 4.
[0077] [Number]
[0078] Here, C float is the value of the floating capacitor C, and ΔV represents the ripple of the floating capacitor.
[0079] In a simulation example comparing the controller 110 and the inverter 130a of the present disclosure with a conventional two-level inverter supplying 100 kW at tr = 200 nanoseconds with a 400V DC link, Cfloat = 100 uF and the maximum ΔV is 10V. This ratio is 0.625. This corresponds to a saving of approximately 40% in switching losses.
[0080] FIG. 9 is a diagram showing the advantage that the same power can be supplied at half the current in the electric vehicle power system using the controller 110 of the present disclosure. On the left, a conventional two-level inverter is shown by reference numeral 910, and on the right, the inverter 130 that can be used with the controller 110 is shown by reference numeral 920.
[0081] The power module of the two-level traction inverter 910 is designed to supply a constant power with a fixed number of 2*M parallel SiC / IGBT dies per switch. Since these dies can be reconfigured within the inverter 920, the current density / thermal performance remains unchanged even when the current is halved. For example, when M = 4, the conventional two-level inverter 910 requires 16 dies per leg, while only 20 are needed for the controller 110 and inverter 130 of the present disclosure.
[0082] The control signal CS1 generated by the controller 110 of the present disclosure operates two switches in series for each commutation. Assuming the parallel resistance RDSon of 2*M dies, there are two switches with 2*RDSon in series in 920. The RMS I of the phase current RMS is halved, so the conduction loss remains unchanged.
[0083]
Number
[0084] When the motor 140 is driven with half of the phase current I phase , 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).
[0085]
Number
[0086] Here, R w represents the resistance in the windings of the motor 140.
[0087] Alternatively, for the windings of the motor 140, a smaller one with a smaller cross-sectional area of the windings can be selected. This can save costs and reduce the total cross-sectional area of the motor 140 to achieve weight reduction.
[0088] If the switching frequency is doubled, it can be assumed that the value of the DC link capacitor can be halved in order to maintain the same ripple performance at the input of the inverter 130. Using the saved half of the DC link capacitor, three floating capacitors required to generate the three-level inverter 130 can be realized. For example, the typical capacitance of the DC link capacitor of a conventional two-level inverter of 100 kW and 400 V is about 500 uF to 600 uF. If a capacitance of 100 uF is used for the floating capacitors of the controller 110 and the inverter 130 of the present disclosure, the ripple of the entire floating capacitor can be suppressed within 10 V, and the capacitance of the DC link can be left at 200 uF to 300 uF without degrading the performance.
[0089] When the controller 110 of the present disclosure is implemented in an electric vehicle power system (EVPS) as shown in FIG. 5, it can be used to supply more power to the motor 140 without upgrading the entire electric vehicle system. For example, when the controller 110 and the inverter 130 of the present disclosure are used to supply substantially the same current, about twice the power is supplied to the motor 140. As a result, in this embodiment, the overhead may increase.
[0090] Note that the optimal usage of the EVPS 500 of the present disclosure is to provide the same output power with half of the phase current I phase and twice the switching frequency. It should be noted that other usage of the system is possible even if not explicitly disclosed here. Some examples are shown here, but this list is not exhaustive.
[0091] In another embodiment, without doubling the switching frequency, half of the phase current I phaseIt is used to supply the same output power to the motor. Although more switching losses are saved, the capacitor DC link cannot be saved or a higher ripple of the capacitor DC link cannot be tolerated, so the bill of materials (BOM) increases. The third embodiment reduces the phase current I phase to provide higher output power without changing the switching frequency. However, the capacitor DC link cannot be saved, a higher ripple of the DC link is tolerated, the number of dies of the power module is increased, or twice the power with the above-mentioned drawbacks is provided, so the bill of materials (BOM) also increases here.
[0092] With the controller 110 of the present disclosure, the inverter 130 can supply the same power to the motor 140 at half the phase current I phase of the prior art and twice the switching frequency. Thereby, the hardware overhead is reduced, and optimization of specific components such as a cooling system, an electric motor, and (when keeping the driving distance constant) a battery pack, for example, in an electric vehicle becomes possible. Also, the embodiments of the controller 110 and the inverters 130a and 130b of the present disclosure can supply a higher voltage to the electric motor with a relatively small overhead without upgrading other components in the EV power system to components of a higher rated voltage (apart from the electric motor itself). Therefore, the embodiments of the present disclosure avoid the cost of upgrading the entire EV power system (including the battery pack) to a high voltage and the use of a complex and expensive DC / DC converter between the battery and the inverter. This is achieved with minimal complexity and no control loops. This means that it does not affect the dynamic performance. Furthermore, the embodiments of the present disclosure achieve a high voltage supplied to the motor without increasing the actual rate of change of voltage dv / dt experienced by the switching element or the motor winding. Therefore, there is no disadvantage to switching losses, EMI, or reliability.
[0093] Note that it should be noted that the inverter of the present disclosure may be a traction inverter for a passenger EV. Further embodiments may relate to inverters for other applications and other input voltages, in accordance with the understanding of those skilled in the art.
[0094] Also, various improvements and modifications may be made without departing from the scope of the present disclosure.
[0095] Those skilled in the art will understand that it is possible to make variations to the disclosed arrangements without departing from the present disclosure. Therefore, the above description of specific embodiments is for illustrative purposes only and not for the purpose of limitation. It will be apparent to those skilled in the art that minor changes can be made without making significant changes to the described operations.
Claims
Claim 1 A controller for an inverter, wherein the inverter includes a plurality of switches, and the controller is configured to generate a control signal, and the control signal operates the plurality of switches in a first switching pattern or a second switching pattern. Claim 2 The controller is configured to receive a first input and / or a second input. When the first input is smaller than the second input, the control signal operates the plurality of switches in the first switching pattern. The controller according to claim 1. Claim 3 When the first input is larger than the second input, the control signal operates the plurality of switches in the second switching pattern. The controller according to claim 2. Claim 4 The inverter is configured to operate in a first phase and a second phase. The controller according to claim 3. Claim 5 When the plurality of switches operate in the first switching pattern, the current flowing through the inverter switches between a first current path and a second current path. The controller according to claim 4. Claim 6 In the first phase, the current flowing through the inverter flows from the battery to the output, and in the second phase, the current flowing through the inverter flows from the output to the battery. The controller according to claim 5. Claim 7 The first current path includes a first switch and a second switch. The second current path includes a third switch and a fourth switch. 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. The controller according to claim 6. Claim 8 The first current path includes a first switch and a second switch. The second current path includes the second switch and a third switch. 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. The controller according to claim 6. Claim 9 When the plurality of switches are arranged in the second switching pattern, the current flowing through the inverter switches between a third current path and a fourth current path. The controller according to claim 5.
10. In the first phase, the current flowing through the inverter flows from the battery to the output. In the second phase, the current flowing through the inverter flows from the output to the battery. The controller according to claim 9.
11. The third current path includes a first switch, a second switch, and a capacitor. The fourth current path includes the second switch, a third switch, a fourth switch, and the capacitor. The generated control signal alternately switches the first switch, the third switch, and the fourth switch between an on state and an off state so that the third switch and the fourth switch are always in the same state, thereby switching the flow of the current between the third current path and the fourth current path. The controller according to claim 10.
12. The third current path includes a first switch, a second switch, and a capacitor. In the second phase, the fourth current path includes the first switch and a third switch. In the first phase, the fourth current path includes the second switch, a fourth switch, and the capacitor. The controller according to claim 10.
13. In the second phase, the generated control signal switches the flow of the current 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. In the first phase, the generated control signal switches the flow of the current 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. The controller according to claim 12.
14. An apparatus including an inverter including a plurality of switches and a controller for the inverter. The controller for the inverter. The apparatus is configured to generate a control signal that operates the plurality of switches in a first switching pattern or a second switching pattern. Apparatus.
15. A method for controlling an inverter including a plurality of switches, comprising the step of using a controller to generate a control signal for operating the plurality of switches in a first switching pattern or a second switching pattern, the method.