Patent Application
20100090625
The present invention generally relates to power converters, and more particularly relates to an automotive system and power converter with a braking circuit.
In recent years, advances in technology, as well as ever-evolving tastes in style, have led to substantial changes in the design of automobiles. One of the changes involves the complexity of the electrical systems within automobiles, particularly alternative fuel vehicles, such as hybrid, electric, and fuel cell vehicles. Such alternative fuel vehicles typically use one or more electric motors, perhaps in combination with another actuator, to drive the wheels.
Due to the fact that alternative fuel automobiles typically include only direct current (DC) power supplies (e.g., batteries), direct current-to-alternating current (DC/AC) inverters (or power inverters) are provided to convert the DC power to alternating current (AC) power, which is generally required by the motors. Such vehicles, particularly fuel cell vehicles, also often use two separate voltage sources, such as a battery and a fuel cell, to power the electric motors that drive the wheels. Thus, power converters, such as direct current-to-direct current (DC/DC) converters, are typically also provided to manage and transfer the power from the two voltage sources.
The power converters (both DC/AC inverters and DC/DC converters) may also be used in such a way that allows the electric motors to be used for braking and to recharge the DC power supplies. However, during severe braking events, the voltage generated across the power supplies, and the resulting current flowing into the power supplies, may rise to levels that can cause damage to, and shorten the usable life of, the power supplies. Additionally, the physical characteristics of the power converters may limit the amount of current that can flow from the motor and thus limit the amount of braking force that may be applied. As a result, mechanical friction brakes are also typically included in such vehicles.
Accordingly, it is desirable to provide a power converter with improved performance as related to the braking characteristics described above. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent description taken in conjunction with the accompanying drawings and the foregoing technical field and background.
An automotive system is provided. The automotive system includes an electric motor, a direct current (DC) power supply coupled to the electric motor, a power converter including at least one conversion switch coupled between the electric motor and the DC power supply and a braking circuit coupled between the electric motor and the DC power supply, the braking circuit including a braking resistor and a braking switch, and a controller in operable communication with the electric motor, the DC power supply, the at least one conversion switch, and the braking switch. The controller is configured to operate the at least one conversion switch when the electric motor is mechanically actuated such that current flows from the electric motor to the DC power supply and selectively operate the braking switch when a braking parameter of the automotive system exceeds a predetermined threshold such that at least some of the current from the electric motor flows through the braking resistor.
An automotive drive system is provided. The automotive drive system includes an electric motor comprising a stator and a rotor, a DC power supply coupled to the electric motor, a power converter including a plurality of pairs conversion switches coupled between the electric motor and the DC power supply and a braking circuit coupled between the electric motor and the DC power supply, the braking circuit including a braking resistor and a braking switch, and a controller in operable communication with the electric motor, the DC power supply, the pairs of conversion switches, and the braking switch. The controller is configured to operate the pairs of conversion switches when the rotor is mechanically rotated relative to the stator such that a torque is applied to the rotor and current flows from the electric motor to the DC power supply, wherein the torque opposes the rotation of the rotor relative to the stator and selectively operate the braking switch when a braking parameter of the automotive drive system exceeds a predetermined threshold such that at least some of the current from the electric motor flows through the braking resistor.
A method for controlling an automotive power converter is provided. The automotive power converter includes at least one conversion switch and a braking circuit coupled between an electric motor and a DC power supply. The braking circuit includes a braking resistor and a braking switch. The at least one conversion switch is operated when the electric motor is mechanically actuated such that current flows from the electric motor to the DC power supply. A signal representative of a braking parameter is received. The braking switch is selectively operated when a braking parameter exceeds a predetermined threshold such that at least some of the current from the electric motor flows through the braking resistor.
The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and
The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, and brief summary, or the following detailed description.
The following description refers to elements or features being “connected” or “coupled” together. As used herein, “connected” may refer to one element/feature being mechanically joined to (or directly communicating with) another element/feature, and not necessarily directly. Likewise, “coupled” may refer to one element/feature being directly or indirectly joined to (or directly or indirectly communicating with) another element/feature, and not necessarily mechanically. However, it should be understood that although two elements may be described below, in one embodiment, as being “connected,” in alternative embodiments similar elements may be “coupled,” and vice versa. Thus, although the schematic diagrams shown herein depict example arrangements of elements, additional intervening elements, devices, features, or components may be present in an actual embodiment.
Further, various components and features described herein may be referred to using particular numerical descriptors, such as first, second, third, etc., as well as positional and/or angular descriptors, such as horizontal and vertical. However, such descriptors may be used solely for descriptive purposes relating to drawings and should not be construed as limiting, as the various components may be rearranged in other embodiments. It should also be understood that
The automobile 10 may be any one of a number of different types of automobiles, such as, for example, a sedan, a wagon, a truck, or a sport utility vehicle (SUV), and may be two-wheel drive (2WD) (i.e., rear-wheel drive or front-wheel drive), four-wheel drive (4WD), or all-wheel drive (AWD). The automobile 10 may also incorporate any one of, or combination of, a number of different types of engines, such as, for example, a gasoline or diesel fueled combustion engine, a “flex fuel vehicle” (FFV) engine (i.e., using a mixture of gasoline and alcohol), a gaseous compound (e.g., hydrogen and/or natural gas) fueled engine, a combustion/electric motor hybrid engine (i.e., such as in a hybrid electric vehicle (HEV)), and an electric motor.
In the exemplary embodiment illustrated in
Still referring to
The radiator 26 is connected to the frame at an outer portion thereof and although not illustrated in detail, includes multiple cooling channels therein that contain a cooling fluid (i.e., coolant) such as water and/or ethylene glycol (i.e., “antifreeze”) and is coupled to the engine 28 and the inverter 24. Although the discussion below refers to the power converter assembly 24 as a direct current-to-alternating current (DC/AC) inverter (i.e., a DC-to-AC inverter), it should be understood that in other embodiments, aspects of the present invention may be used in conjunction with direct current-to-direct current (DC/DC) converters, as will be appreciated by one skilled in the art.
Still referring to
Referring to
The switch network comprises three pairs (a, b, and c) of series switches (i.e., conversion switches) with antiparallel diodes 51 (i.e., antiparallel to each switch) corresponding to each of the (e.g., three) phases of the motor 30. Each of the pairs of series switches comprises a first switch, or transistor, (i.e., a “high” switch) 52, 54, and 56 having a first terminal coupled to a positive electrode (or first terminal) 58 of the voltage source 22 and a second switch (i.e., a “low” switch) 60, 62, and 64 having a second terminal coupled to a negative electrode (or second terminal) 66 of the voltage source 22 and a first terminal coupled to a second terminal of the respective first switch 52, 54, and 56. As is commonly understood, each of the switches 52, 54, 56, 60, 62, and 64 may be in the form of individual semiconductor devices such as insulated gate bipolar transistors (IGBTs) within integrated circuits formed on semiconductor (e.g. silicon) substrates (e.g., die).
Still referring to
The module stack 82 is connected to the chassis 80 and includes a direct, or double, bonded copper (DBC) substrate 86 and an electronic component, or microelectronic die 88. The DBC substrate 86 includes a ceramic core 90 and two copper layers 92 formed on opposing sides (i.e., upper and lower) of the ceramic core 90. The microelectronic die 88 includes a semiconductor substrate (e.g., silicon substrate) 94 with an integrated circuit formed thereon that includes one or more of the switches within the inverter 24 (
The atomizer 84 (i.e., a cooling mechanism) is connected to the housing and positioned above the module stack 82, and more particularly, above the microelectronic die 88. The atomizer 84 includes a nozzle 98 that is directed towards the microelectronic die 88 and is in fluid communication with the radiator 26 shown in
During operation, referring to
As will be appreciated by one skilled in the art, in addition to providing power to the wheels 16, while the motor 30 is being mechanically actuated by the wheels 16 (i.e., the movement of the automobile 10), the motor 30 may be used to provide a “negative” torque to the wheels 16 (i.e., torque in a direction opposite the positive torque) that may be used for braking (i.e., slowing the automobile 10) and to charge the battery 22. A user may activate the “braking mode” (or regeneration mode) of operation of the inverter 24 and/or the motor 30 by manually applying pressure to the brake pedal 40, which sends an appropriate signal to the electronic control system 18.
In a manner somewhat similar to that used to provide positive torque to the wheels 16, the controller 46 causes the negative torque to be applied to the wheels 16 by determining the desired motor currents and calculating the voltages across the windings of the motor 30 that will produce the desired currents. As is commonly understood, during the motoring mode of operation, the motor voltage and current are substantially aligned with respect to the synchronous frame of reference (i.e., along the d-axis and q-axis). However, during braking mode of operation, the motor voltage and current are substantially opposite (i.e., 180 degrees apart). Because the conversion switches and the diodes within the inverter 24 each allow current to pass in only one direction, the majority of the current flows through the conversion switches during motoring operation, while the majority of the current flows through the diodes during braking operation. As a result, during braking operation, a voltage is generated across the DC link that causes current to flow into the battery 22, while the negative torque is applied to the wheels 16, thus slowing the automobile 10.
During the braking mode of operation, the electronic control system 18 monitors one or more braking parameter, such as the DC link voltage, the pressure applied to the brake pedal 40, and/or accelerations or decelerations detected by the accelerometer array 36. If one or more (or a combination) of the braking parameters exceeds a predetermined threshold, it may be assumed that the automobile is experiencing a severe braking event, such as the automobile 10 decelerating rapidly or the user attempting to decelerate the vehicle rapidly. During such events, the DC link voltage may increase substantially and cause a large amount of current to flow into the battery 22.
In response to the detection of the braking parameter exceeding the threshold, the electronic control system activates the braking switch 76, using for example, PWM control. When the braking switch is activated (i.e., closed), current from the motor 30 flows into the first leg 70 of the braking circuit 68 and is dissipated by the braking resistor 74. As a result, the DC link voltage is reduced which protects the battery 22 from being overcharged and allows for additional current to flow from the motor 30 such that the negative torque applied to the wheels 16 may be increased, which allows the automobile 10 to be decelerated more rapidly, and may allow the automobile not to include conventional friction brakes for the wheels 16.
Referring to
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof.
