Patent Description:
A hybrid vehicle described in <CIT> includes a high-voltage battery having a relatively high voltage (for example, about <NUM> V) and used for a traveling operation and a low-voltage battery having a relatively low voltage (for example, about <NUM> V), charging DC power, and used for vehicle-mounted electrical components. The hybrid vehicle described in <CIT> protects the battery from the risk of overcharge by controlling an upper-limit engine rotation speed via an engine control device and maintaining a counter electromotive force of a motor at a voltage below the overcharge when a main relay provided between the battery and a motor is welded so that a motor inverter fails and the battery has a risk of overcharge. Further, the hybrid vehicle described in <CIT> protects the battery from the risk of overcharge by controlling the upper-limit engine rotation speed via the engine control device, limiting a counter electromotive force of the motor, and maintaining a counter electromotive voltage of the motor at a voltage below the overcharge when the communication of the motor control device is off and the communication of the battery control device is off. <CIT> relates to a vehicle including a motor, an inverter, and a motor controller. <CIT> relates to a fast response failure mode control methodology for a hybrid vehicle having an AC electric machine.

However, in the technique described in <CIT>, since there was no examination on preventing the welding of a contactor (main relay) provided in a high-voltage current path connecting a generator (motor) to the battery, the welding of the contactor could not be prevented. Further, in the technique described in <CIT>, since the power generation voltage of the generator was limited by controlling the upper-limit engine rotation speed when communication abnormality occurs in the communication between the generator and the control device, there was a concern that the traveling could not be continued due to lack of generated electric power.

This invention has been made in view of the above-described problems and an object of this invention is to provide a hybrid vehicle power generation system capable of generating electric power enabling a continuous travel by a generator even when communication abnormality with a control device occurs and preventing an occurrence of a welding of a disconnected contactor provided in a high-voltage current path or a voltage surge of the high-voltage current path.

According to aspects of this invention, there is provided a hybrid vehicle power generation system including: a control device; a generator performing communication with the control device, generating high-voltage electric power according to an instruction of the control device in a normal state without communication abnormality, and autonomously generating high-voltage electric power in an abnormal communication state with communication abnormality; a high-voltage current path connected to the generator and receiving the high-voltage electric power generated by the generator; a contactor switched by the control device to a closed state of connecting the high-voltage current path or an open state of disconnecting the high-voltage current path; a low-voltage current path connected to the generator and supplying low-voltage electric power, having a voltage lower than the high-voltage electric power supplied to the high-voltage current path, to the generator; and a relay switched by the control device to a closed state of connecting the low-voltage current path or an open state of disconnecting the low-voltage current path, wherein the generator stops the autonomous generation of electric power when the relay is switched to the open state to disconnect the low-voltage current path during the autonomous generation of electric power, and wherein the control device switches the relay from the closed state to the open state before the contactor is switched from the closed state to the open state when switching the contactor from the closed state to the open state.

In this way, according to this invention, it is possible to provide a hybrid vehicle power generation system capable of generating electric power enabling a continuous travel by a generator even when communication abnormality with a control device occurs and preventing an occurrence of a welding of a disconnected contactor provided in a high-voltage current path or a voltage surge of the high-voltage current path.

A hybrid vehicle power generation system according to embodiments of this invention includes: a control device; a generator performing communication with the control device, generating high-voltage electric power according to an instruction of the control device in a normal state without communication abnormality, and autonomously generating high-voltage electric power in an abnormal communication state with communication abnormality; a high-voltage current path connected to the generator and receiving the high-voltage electric power generated by the generator; a contactor switched by the control device to a closed state of connecting the high-voltage current path or an open state of disconnecting the high-voltage current path; a low-voltage current path connected to the generator and supplying low-voltage electric power, having a voltage lower than the high-voltage electric power supplied to the high-voltage current path, to the generator; and a relay switched by the control device to a closed state of connecting the low-voltage current path or an open state of disconnecting the low-voltage current path, wherein the generator stops the autonomous generation of electric power when the relay is switched to the open state to disconnect the low-voltage current path during the autonomous generation of electric power, and wherein the control device switches the relay from the closed state to the open state before the contactor is switched from the closed state to the open state when switching the contactor from the closed state to the open state. Accordingly, the hybrid vehicle power generation system according to embodiments of this invention can generate electric power enabling a continuous travel by the generator even when communication abnormality with the control device occurs and prevent an occurrence of a welding of the disconnected contactor provided in the high-voltage current path or a voltage surge of the high-voltage current path.

Hereinafter, a hybrid vehicle power generation system according to embodiments of this invention will be described with reference to the drawings. <FIG> are diagrams showing the hybrid vehicle power generation system according to embodiments of this invention.

In <FIG>, a hybrid vehicle <NUM> equipped with the hybrid vehicle power generation system according to an embodiment of this invention includes an internal combustion engine <NUM>, a generator <NUM> which is connected to the engine <NUM> through a belt <NUM>, a high-voltage current path <NUM> which is connected to the generator <NUM> and to which high-voltage electric power generated by the generator <NUM> is supplied, and a control device <NUM>. The engine <NUM> includes a starter <NUM> and the starter <NUM> starts the engine <NUM>.

The generator <NUM> is connected to a crankshaft (not shown) of the engine <NUM> through the belt <NUM>. The generator <NUM> is an ISG (Integrated Starter Generator) which is a rotary electric machine having a function of generating electric power by the power of the engine <NUM>, a function of applying power to the engine <NUM>, and a function of starting the engine <NUM>. The generator <NUM> generates <NUM> V of electric power. The generator <NUM> is composed of a claw pole type magnet-filled winding field type motor.

The hybrid vehicle <NUM> includes a high-voltage battery <NUM> and the high-voltage battery <NUM> is composed of a Li (lithium ion) battery having a plurality of cells and charges and discharges <NUM> V of electric power. The high-voltage current path <NUM> connects the generator <NUM> to the high-voltage battery <NUM>.

The hybrid vehicle <NUM> includes a contactor 14A. The contactor 14A is provided in the high-voltage battery <NUM>. The contactor 14A is switched by the control device <NUM> to a closed state in which the high-voltage current path <NUM> is connected or an open state in which the high-voltage current path <NUM> is disconnected. The high-voltage battery <NUM> is provided with a BMS (Battery Management System) 14B.

The BMS 14B has a function of preventing overcharge, overdischarge, and overcurrent of the cell, a function of managing the temperature of the cell, a function of determining whether or not the cell is abnormal, a function of calculating the state of charge (SOC), and the like. The BMS 14B switches the contactor 14A to the open state or the closed state according to the instruction from the control device <NUM>.

The hybrid vehicle <NUM> includes low-voltage current paths <NUM>, <NUM>, and <NUM> to which <NUM> V of low-voltage electric power is supplied. The low-voltage current path <NUM> connects a DC-DC converter <NUM> to a lead battery <NUM>. The low-voltage current path <NUM> connects the low-voltage current path <NUM> to a 12V component <NUM>. The low-voltage current path <NUM> connects the low-voltage current path <NUM> to the generator <NUM>. Thus, the low-voltage current path <NUM> supplies low-voltage electric power having a voltage lower than the high-voltage electric power supplied to the high-voltage current path <NUM> to the generator <NUM>. Specifically, the low-voltage current path <NUM> supplies low-voltage electric power from the low-voltage system of the hybrid vehicle <NUM> to the generator <NUM>.

The hybrid vehicle <NUM> includes the lead battery <NUM> which charges and discharges <NUM> V of electric power and the 12V component <NUM> which is connected to the lead battery <NUM> via the low-voltage current paths <NUM> and <NUM> as a low-voltage system. The 12V component <NUM> is an electrical component operated by 12V of electric power. The low-voltage current path <NUM> supplies <NUM> V of low-voltage electric power to the generator <NUM>.

The hybrid vehicle <NUM> includes a relay <NUM>. The relay <NUM> is provided in the low-voltage current path <NUM>. The relay <NUM> is switched by the control device <NUM> to a closed state in which the low-voltage current path <NUM> is connected or an open state in which the low-voltage current path <NUM> is disconnected.

The hybrid vehicle <NUM> includes the DC-DC converter <NUM>. The DC-DC converter <NUM> is connected to the high-voltage current path <NUM> and the low-voltage current path <NUM>. The DC-DC converter <NUM> steps down the high-voltage electric power generated by the generator <NUM> and supplies the stepped down low-voltage electric power to the low-voltage system. Here, the lead battery <NUM> is charged with the low-voltage electric power output from the DC-DC converter <NUM>. Therefore, the DC-DC converter <NUM> steps down <NUM> V of high-voltage electric power supplied from the generator <NUM> via the high-voltage current path <NUM> to <NUM> V of low-voltage electric power and supplies the stepped down low-voltage electric power to the lead battery <NUM> via the low-voltage current path <NUM>.

The hybrid vehicle <NUM> includes ground wires <NUM> and <NUM>. The ground wire <NUM> connects a minus terminal (not shown) of the lead battery <NUM> to the DC-DC converter <NUM>. The ground wire <NUM> connects the minus terminal of the lead battery <NUM> to the generator <NUM>.

The hybrid vehicle <NUM> includes a communication line <NUM> which is used for communication between the control device <NUM> and the generator <NUM> by CAN (Controller Area Network) and a communication line <NUM> which is used for communication between the control device <NUM> and the high-voltage battery <NUM> by CAN. The generator <NUM> communicates with the control device <NUM> via the communication line <NUM>. The BMS 14B of the high-voltage battery <NUM> communicates with the control device <NUM> via the communication line <NUM>.

The control device <NUM> is configured as an ECU (Electronic Control Unit) which includes a microcomputer equipped with a CPU, a RAM, a ROM, an input/output interface, and the like. The CPU uses the temporary storage function of the RAM and performs signal processing according to a program stored in advance in the ROM. The ROM stores various control constants, various maps and the like in advance.

The generator <NUM> communicates with the control device <NUM> and generates high-voltage electric power according to the instruction of the control device <NUM> in a normal state in which no abnormality occurs in communication.

Here, there is a case in which the hybrid vehicle <NUM> cannot continue to travel due to the insufficient electricity when the generator <NUM> is configured to stop the power generation when abnormality occurs in communication between the control device <NUM> and the generator <NUM>. Here, in this embodiment, the generator <NUM> autonomously generates high-voltage electric power in the case of communication abnormality in which abnormality occurs in communication with the control device <NUM> via the communication line <NUM>. That is, the generator <NUM> autonomously generates electric power according to the control contents set in advance in the generator <NUM> when abnormality occurs in communication with the control device <NUM>. Accordingly, the hybrid vehicle <NUM> can continue the power generation by autonomous generation of electric power and can travel to a service base where repairs and the like can be performed.

On the other hand, when the contactor 14A is switched from the closed state to the open state while the high-voltage electric power is supplied to the high-voltage current path <NUM>, the contactor 14A may be welded by arc discharge or a voltage surge (load dump) may occur in the high-voltage current path <NUM>. In order to prevent the welding of the contactor 14A or the voltage surge of the high-voltage current path <NUM>, it is preferable to switch the contactor 14A to the open state while the generation of electric power of the generator <NUM> is stopped. On the other hand, the control device <NUM> cannot control the generator <NUM> to stop the autonomous generation of electric power in the case of communication abnormality with the generator <NUM>.

Here, in this embodiment, the generator <NUM> stops the autonomous generation of electric power when the relay <NUM> is switched to the open state during the autonomous generation of electric power so that the low-voltage current path <NUM> is disconnected. Since the low-voltage current path <NUM> is disconnected so that the supply of the low-voltage electric power to the generator <NUM> is stopped and the supply of electric power to the control unit of the generator <NUM> is stopped, the power supply unit to the field coil inside the generator <NUM> is turned off and the generator <NUM> stops the generation of electric power.

The control device <NUM> switches the relay <NUM> from the closed state to the open state before the contactor 14A is switched from the closed state to the open state when the contactor 14A is switched from the closed state to the open state in response to the request from the BMS 14B of the high-voltage battery <NUM>. In other words, the control device <NUM> switches the relay <NUM> from the closed state to the open state and switches the contactor 14A from the closed state to the open state.

The generator <NUM> includes a high voltage detection unit 13A which detects an actual power generation voltage value of the high-voltage electric power to be generated. The actual power generation voltage value is a voltage which is actually generated when the generator <NUM> generates electric power. The generator <NUM> autonomously generates electric power by setting the actual power generation voltage value detected by the high voltage detection unit 13A before the occurrence of the communication abnormality as a target power generation voltage value during the communication abnormality. Accordingly, since the power generation voltage at the time of the occurrence of the communication abnormality is maintained also in the autonomous generation of electric power, it is possible to extend the traveling life to the service base. The target power generation voltage is a target power generation voltage of the generator <NUM>. Additionally, when electric power is generated above the center (about <NUM>%) of the regular use area of the open circuit voltage (OCV) of the high-voltage battery <NUM> at the time of the occurrence of the communication abnormality, the generator <NUM> sets the target power generation voltage to a predetermined value (constant) stored in the generator <NUM> instead of the actual power generation voltage value at the time of the occurrence of the communication abnormality. Accordingly, even when the communication abnormality occurs during high regeneration of the generator <NUM>, it is possible to prevent the mechanical load from increasing due to the generation of excessive electric power and wasteful consumption of fuel more than the fuel required for extending the traveling life to the service base.

The generator <NUM> includes a low voltage detection unit 13B which detects the voltage of the low-voltage electric power supplied from the low-voltage current path <NUM>. Here, when the DC-DC converter <NUM> functions normally, the normal value of the voltage of the low-voltage current path <NUM> connected to the DC-DC converter <NUM> becomes equal to or higher than a threshold value at the time of normal electric power generation (in this embodiment, <NUM> V). On the other hand, when the DC-DC converter <NUM> does not function normally and the supply of electric power to the low-voltage current path <NUM> is stopped, the normal value of the voltage of the low-voltage current path <NUM> becomes a value lower than <NUM> V. Therefore, the generator <NUM> stops the autonomous generation of electric power when the voltage value detected by the low voltage detection unit 13B during the communication abnormality is equal to or lower than the threshold value (in this embodiment, <NUM> V). It is preferable that the control device <NUM> switches the relay <NUM> from the closed state to the open state when the communication is abnormal and the cell fails.

The configuration and power generation characteristics of the generator <NUM> will be described with reference to <FIG>. In <FIG>, the vertical axis indicates the open circuit voltage (OCV) (written as LiB voltage_OCV in the figure) of the high-voltage battery <NUM> and the horizontal axis indicates the state of charge (in the figure, the state of charge is abbreviated as SOC) of the high-voltage battery <NUM>. In this embodiment, a normally used area of SOC is set in the high-voltage battery <NUM>.

A counter electromotive voltage which is generated by the magnet inside the generator <NUM> is applied to the high-voltage battery <NUM>. Therefore, the amount of magnet and the magnetic circuit of the generator <NUM> are set so that the counter electromotive voltage due to the magnet when the engine <NUM> rotates at the maximum engine rotation speed (the generator <NUM> rotates at the maximum rotation speed) becomes the lower limit of the open circuit voltage in the normal use area of the high-voltage battery <NUM>. A counter electromotive voltage range exists in the counter electromotive voltage due to the magnet of the generator <NUM>. The upper limit value of the counter electromotive voltage range is set to be the lower limit of the open circuit voltage of the normal use area of the high-voltage battery <NUM>.

In <FIG>, when the cell of the high-voltage battery <NUM> fails and the communication abnormality with the generator <NUM> occurs, the control device <NUM> switches the relay <NUM> to the open state so that stops the supply of the low-voltage electric power to the generator <NUM> by the low-voltage current path <NUM>. Since the supply of the low-voltage electric power is stopped, the power supply unit to the field coil of the generator <NUM> is turned off so that the generator <NUM> stops the generation of electric power. Further, even when a counter electromotive voltage is generated due to the rotation of the engine <NUM>, no current flows to the high-voltage battery <NUM> in which the cell fails since that voltage is set to be equal to or lower than the voltage value of the normal specification area of the high-voltage battery <NUM>. Thus, since no current is supplied to the cell of the high-voltage battery <NUM> when the cell of the high-voltage battery <NUM> fails and the communication abnormality with the generator <NUM> occurs, it is possible to protect the high-voltage battery <NUM>.

The operation of the generator <NUM> in the case of communication abnormality will be described with reference to <FIG>. In <FIG>, the generator <NUM> determines whether or not the communication (written as CAN communication in the figure) by CAN is abnormal in step S1. When it is not the abnormal state, the normal control is performed and the current operation ends in step S8. The normal control is a control in which the control device <NUM> and the generator <NUM> communicate with each other and the generator <NUM> generates high-voltage electric power according to the instruction of the control device <NUM>.

When the communication is abnormal in step S1, the generator <NUM> determines whether or not the voltage value of the low-voltage current path is equal to or lower than a threshold value in step S2. When it is determined that the voltage value is not equal to or lower than the threshold value in step S2, the generator <NUM> determines whether or not the target power generation voltage has been set in step S3.

When the target power generation voltage has not been set in step S3, the generator <NUM> acquires the actual power generation voltage value in step S4. Next, the generator <NUM> sets the target power generation voltage to the actual power generation voltage value in step S5. Next, the generator <NUM> starts the autonomous generation of electric power in step S6.

When it is determined that the voltage value is equal to or lower than the threshold value in step S2, the generator <NUM> stops the generation of electric power in step S7. Additionally, the generator <NUM> stops the autonomous generation of electric power when it is determined that the voltage value is equal to or lower than the threshold value also during the autonomous generation of electric power in the case of communication abnormality with the control device <NUM>.

The operation of the control device <NUM> in the case of communication abnormality will be described with reference to <FIG>. In <FIG>, the control device <NUM> determines whether or not the communication (written as CAN communication in the figure) by CAN is abnormal in step S11. When it is not the abnormal state, the normal control is performed in step S15 and the current operation ends. The normal control is a control in which the control device <NUM> and the generator <NUM> communicate with each other and the generator <NUM> generates high-voltage electric power according to the instruction of the control device <NUM>.

When the communication with the generator <NUM> is abnormal in step S11, the control device <NUM> determines whether or not the welding of the contactor 14A or the failure of the cell of the high-voltage battery <NUM> occurs in step S12.

When it is determined that the welding of the contactor 14A or the failure of the cell of the high-voltage battery <NUM> occurs in step S12, the control device <NUM> opens the relay <NUM> and ends the current operation in step S13.

When it is determined that the welding of the contactor 14A or the failure of the cell of the high-voltage battery <NUM> does not occur in step S12, the control device <NUM> determines whether or not there is an open request of the contactor 14A from the BMS 14B of the high-voltage battery <NUM> in step S14.

When there is no open request of the contactor 14A in step S14, the control device <NUM> ends the current operation. When there is an open request of the contactor 14Ain step S14, the control device <NUM> opens the relay <NUM> before opening the contactor 14A in step S13 and ends the current operation. That is, in step S13, the control device <NUM> first opens the relay <NUM> and then opens the contactor 14A.

As described above, in this embodiment, the hybrid vehicle <NUM> includes the low-voltage current path <NUM> which is connected to the generator <NUM> and supplies the low-voltage electric power having a voltage lower than the high-voltage electric power to the generator <NUM> and the relay <NUM> which is switched by the control device <NUM> to the closed state of connecting the low-voltage current path <NUM> or the open state of disconnecting the low-voltage current path <NUM>. The generator <NUM> stops the autonomous generation of electric power when the relay <NUM> is switched to the open state during the autonomous generation of electric power so that the low-voltage current path <NUM> is disconnected.

When the contactor 14A is switched from the closed state to the open state, the control device <NUM> switches the relay <NUM> from the closed state to the open state before the contactor 14A is switched from the closed state to the open state.

Accordingly, the generator <NUM> can generate electric power enabling the continuous travel of the hybrid vehicle <NUM> by the autonomous generation of electric power even when the communication abnormality with the control device <NUM> occurs. Therefore, it is possible to increase the chance that the driver drives the hybrid vehicle <NUM> and brings the vehicle to the service factory even when the communication abnormality occurs.

Further, since the relay <NUM> is switched from the closed state to the open state before the contactor 14A is switched from the closed state to the open state, the contactor 14A can be opened while the autonomous generation of electric power of the generator <NUM> is stopped and the high-voltage electric power is not supplied to the high-voltage current path <NUM>. Accordingly, it is possible to prevent an occurrence of the welding of the disconnected contactor 14A provided in the high-voltage current path <NUM> or the voltage surge (load dump) of the high-voltage current path <NUM>.

As a result, the generator <NUM> can generate electric power enabling the continuous travel even when the communication abnormality with the control device <NUM> occurs and an occurrence of the welding of the disconnected contactor 14A provided in the high-voltage current path <NUM> or the voltage surge of the high-voltage current path <NUM> can be prevented.

Further, in this embodiment, the hybrid vehicle <NUM> includes the DC-DC converter <NUM> which steps down the high-voltage electric power generated by the generator <NUM> and supplies the stepped down low-voltage electric power to the low-voltage system, the low-voltage current path <NUM> supplies the low-voltage electric power from the low-voltage system to the generator <NUM>, and the generator <NUM> includes the high voltage detection unit 13A which detects the actual power generation voltage value of the high-voltage electric power to be generated and performs the autonomous generation of electric power by setting the actual power generation voltage value detected by the high voltage detection unit 13A before the occurrence of the communication abnormality during the communication abnormality to the target power generation voltage value.

Accordingly, since the actual power generation voltage value before the occurrence of the communication abnormality is set to the target power generation voltage during the communication abnormality, the target power generation voltage can be set to an appropriate voltage value and the overcharge or overdischarge of the low-voltage system can be prevented.

Further, since the supply of electric power to the contactor 14A can be suppressed as much as possible when the contactor 14A is welded, it is possible to reduce the possibility of damaging the contactor 14A and to reduce the possibility of red heat or the like of the contactor 14A.

Further, in this embodiment, the generator <NUM> includes the low voltage detection unit 13B which detects the voltage of the low-voltage electric power supplied from the low-voltage current path <NUM> and the generator <NUM> stops the autonomous generation of electric power when the voltage value detected by the low voltage detection unit 13B during the communication abnormality is equal to or lower than the threshold value.

Accordingly, since the generator <NUM> stops the autonomous generation of electric power when the DC-DC converter <NUM> stops the supply of the low-voltage electric power to the low-voltage system, the engine load decreases and the consumption of fuel and electric power is suppressed. Accordingly, the travel distance can be increased and the driver can drive to dealers or repair shops. Further, since the supply of electric power to the DC-DC converter <NUM> is stopped during the failure of the DC-DC converter <NUM>, it is possible to reduce the possibility of red heat or the like of the DC-DC converter <NUM>.

Further, in this embodiment, the hybrid vehicle <NUM> includes the high-voltage battery <NUM> having a plurality of cells and the high-voltage current path <NUM> connects the generator <NUM> to the high-voltage battery <NUM>. Then, the control device <NUM> switches the relay <NUM> from the closed state to the open state when the communication is abnormal and the cell fails.

Accordingly, since the generator <NUM> stops the autonomous generation of electric power by switching the relay <NUM> to the closed state when the communication is abnormal and the cell of the high-voltage battery <NUM> fails, it is possible to protect the high-voltage battery <NUM>.

In this embodiment, the generator <NUM> performs the autonomous generation of electric power by setting the actual power generation voltage value detected by the high voltage detection unit 13A before the occurrence of the communication abnormality to the target power generation voltage value during the communication abnormality.

Additionally, when electric power is generated above the center (for example, <NUM>%) of the regular use area of the high-voltage battery <NUM>, the generator <NUM> may set the target power generation voltage to the constant stored in the generator <NUM> during the communication abnormality.

The autonomous generation of electric power basically maintains the state at the time of the occurrence of the communication abnormality. However, when the communication abnormality occurs during high regeneration of the generator <NUM>, the excessive power generation will increase the mechanical load and waste fuel consumption. Since the target power generation voltage is set to a constant stored in the generator <NUM>, it is possible to extend the traveling life of the vehicle.

Claim 1:
A hybrid vehicle power generation system comprising:
a control device (<NUM>);
a generator (<NUM>) performing communication with the control device (<NUM>), generating high-voltage electric power according to an instruction of the control device (<NUM>) in a normal state without communication abnormality, and autonomously generating high-voltage electric power in an abnormal communication state with communication abnormality;
a high-voltage current path (<NUM>) connected to the generator (<NUM>) and receiving the high-voltage electric power generated by the generator (<NUM>); and
a contactor (14A) switched by the control device (<NUM>) to a closed state of connecting the high-voltage current path (<NUM>) or an open state of disconnecting the high-voltage current path (<NUM>), the hybrid vehicle power generation system being characterized by
a low-voltage current path (<NUM>) connected to the generator (<NUM>) and supplying low-voltage electric power, having a voltage lower than the high-voltage electric power supplied to the high-voltage current path (<NUM>), to the generator (<NUM>); and
a relay (<NUM>) switched by the control device (<NUM>) to a closed state of connecting the low-voltage current path (<NUM>) or an open state of disconnecting the low-voltage current path (<NUM>),
wherein the generator (<NUM>) stops the autonomous generation of electric power when the relay (<NUM>) is switched to the open state to disconnect the low-voltage current path (<NUM>) during the autonomous generation of electric power, and
wherein the control device (<NUM>) switches the relay (<NUM>) from the closed state to the open state before the contactor (14A) is switched from the closed state to the open state when switching the contactor (14A) from the closed state to the open state.