Inverter control device

#The present disclosure relates to technology for controlling driving of an alternating current rotating electric machine.

#A high-output alternating current (AC) rotating electric machine used to power an electric automobile, a hybrid automobile, or the like is driven with a high voltage. Since the high-voltage power supply installed in such an automobile is a DC battery, DC power is converted into three-phase alternating current, for example, by an inverter circuit that uses switching elements. The rotating electric machine not only functions as a motor that outputs power for driving the vehicle using electrical energy, but also functions as a generator that generates electricity using kinetic energy from the vehicle, an internal combustion engine, or the like. Electrical power generated by the rotating electric machine is regenerated and stored in a battery.

#Incidentally, there are cases where a switchgear (contactor) is provided between the battery and the rotating electric machine, or more specifically between the battery and the inverter. This contactor is a system main relay (SMR) that is constructed using relays, for example, and the contactor enters a conductive state with closed contact points if the vehicle ignition key (IG key) is in the on state (enabled state), and enters a non-conductive state with open contact points if the IG key is in the off state (non-enabled state). In other words, the battery and the inverter (and the rotating electric machine) are electrically connected when the SMR is in the closed state, and the electrical connection between the battery and the inverter (and the rotating electric machine) is cut off when the SMR is in the open state. During normal operation, the open/closed state of the SMR is also controlled according to the state of the IG key. However, even if the IG key is in the on state, there are cases where the SMR is opened due to a vehicle malfunction, collision, or the like. For example, if the supply of power to the SMR is cut off, if an abnormality occurs in the SMR drive circuit, if the SMR has a mechanical malfunction due to vibration, shock, noise, or the like, or if a disconnection occurs in an SMR peripheral circuit, it is possible for the contact points of the SMR to enter the open state, and for the contactor to enter the open state.

#FIG. 1 is a circuit block diagram schematically showing a system configuration of a rotating electric machine drive device.

#FIG. 2 is a waveform diagram schematically showing an example of control when a contactor is open.

#FIG. 3 is an equivalent circuit diagram showing an example of IGBT control and the flow of current in Phase1.

#Hereinafter, an embodiment of an inverter control device will be described based on the drawings. As shown in FIG. 1, an inverter control device 20 is for controlling a rotating electric machine drive device 1 that includes an inverter 10 and a DC link capacitor 4, and controls driving of a rotating electric machine 80 via the rotating electric machine drive device 1. As will be described later, the inverter 10 is a power conversion device that is connected to a DC power supply (11) via a contactor 9, is connected to the AC rotating electric machine 80, and performs power conversion between direct current and polyphase alternating current (here, three-phase alternating current), and an arm for each alternating current phase is formed by a series circuit including an upper side switching element and a lower side switching element. The DC link capacitor 4 smooths a DC link voltage Vdc, which is the DC-side voltage of the inverter 10. The rotating electric machine 80, which is the target of driving by the rotating electric machine drive device 1 and the inverter control device 20 is a rotating electric machine that is the drive power source of a vehicle such as a hybrid automobile or an electric automobile. The rotating electric machine 80 serving as the drive power source of the vehicle is a rotating electric machine that operates using polyphase alternating current (here, three-phase alternating current), and can function as an electric motor and as a generator.

#Vehicles such as automobiles, which cannot receive a supply of electrical power from an overhead line as with a railroad, are provided with a DC power supply as an electrical power supply for driving the rotating electric machine 80, examples of which include a secondary cell (battery) such as a nickel hydrogen cell or a lithium ion cell, and an electric double layer capacitor. In the present embodiment, a high voltage battery 11 (DC power supply) with a power supply voltage of 200 to 400 [V], for example, is provided as a high-voltage, high-capacity DC power supply for supplying electrical power to the rotating electric machine 80. Since the rotating electric machine 80 is an AC rotating electric machine, the inverter 10 for performing power conversion between direct current and alternating current (here, three-phase alternating current) is provided between the high-voltage battery 11 and the rotating electric machine 80. The voltage across a positive power supply line P and a negative power supply line N on the DC side of the inverter 10 is referred to hereinafter as “DC link voltage Vdc”. The high-voltage battery 11 can supply electrical power to the rotating electric machine 80 via the inverter 10, and can store electrical power obtained due to power generation by the rotating electric machine 80.

#A smoothing capacitor (the DC link capacitor 4) that smooths the voltage across the positive and negative electrodes on the DC side of the inverter 10 (DC link voltage Vdc) is provided between the inverter 10 and the high-voltage battery 11. The DC link capacitor 4 stabilizes the DC voltage (DC link voltage Vdc) that fluctuates according to fluctuations in the power consumption of the rotating electric machine 80. The contactor 9 that can cut the electrical connection between the high-voltage battery 11 and the circuit from the DC link capacitor 4 to the rotating electric machine 80 is provided between the DC link capacitor 4 and the high-voltage battery 11. In the present embodiment, this contactor 9 is a mechanical relay that opens and closes based on instructions from a vehicle ECU (Electronic Control Unit) 90, which is one of the highest ranking control devices of the vehicle, and the contactor 9 is referred to as the system main relay (SMR), for example. The contactor 9 enters a conductive state (connected state) with the SMR contact points closed when the ignition key (IG key) of the vehicle is in the on state (enabled state), and enters a non-conductive state (open state) with the SMR contact points open when the IG key is in the off state (non-enabled state). The inverter 10 is interposed between the high-voltage battery 11 and the rotating electric machine 80 via the contactor 9, the high-voltage battery 11 and the inverter 10 (and the rotating electric machine 80) are electrically connected when the contactor 9 is in the connected state, and the electrical connection between the high-voltage battery 11 and the inverter 10 (and the rotating electric machine 80) is cut off when the contactor 9 is in the open state.