An energy storage apparatus includes: a plurality of energy storage devices connected in series; a voltage detection unit that detects voltages of the plurality of energy storage devices; a discharge circuit that discharges the energy storage devices; and a control unit. The energy storage devices include lithium ion cells. The plurality of energy storage devices is chargeable by an external charger for a lead-acid battery, wherein a charge voltage per cell of the external charger for the lead-acid battery is higher than a maximum voltage of the energy storage device, and wherein the control unit discharges only an energy storage device having a highest voltage out of the plurality of energy storage devices when the plurality of energy storage devices is charged by a charger.

An energy storage apparatus includes: a plurality of energy storage devices connected in series; a voltage detection unit that detects voltages of the plurality of energy storage devices; a discharge circuit that discharges the energy storage devices; and a control unit. The energy storage devices include lithium ion cells. The plurality of energy storage devices is chargeable by an external charger for a lead-acid battery, wherein a charge voltage per cell of the external charger for the lead-acid battery is higher than a maximum voltage of the energy storage device, and wherein the control unit discharges only an energy storage device having a highest voltage out of the plurality of energy storage devices when the plurality of energy storage devices is charged by a charger.

A wireless power transfer system can be achieved at a low cost, can be used as both a power transmission apparatus and a power reception apparatus, and can cope with a change in coupling coefficient of a resonant coil of the power transmission apparatus and a resonant coil of the power reception apparatus. The wireless power transfer system is a power transmission apparatus that is able to perform bidirectional wireless power transmission, and includes the following: a power supply; a switching circuit that includes a plurality of switching devices; a resonator that includes a coil and a capacitor; a drive control circuit that controls an ON/OFF operation of each switching device of the switching circuit; and a detector that detects a resonance current flowing through the switching circuit. The drive control circuit controls the ON/OFF of each switching device of the switching circuit to perform a power transmission operation or a power reception operation based on a resonant current waveform detected by the detector.

A vertical takeoff and landing aircraft system includes a gas turbine engine coupled to a variable pitch propeller. The gas turbine engine is also coupled to a power split device including a first motor generator, a second motor generator, and a planetary module therebetween. The planetary module includes a sun gear, a ring gear, and a planet carrier. The motor generators are coupled to inverters, a DC bus and a battery. The battery is configured to power balance fans disposed on wings and horizontal stabilizers of the aircraft system. The balance fans can be closed off after vertical lift has been achieved.

According to an embodiment, a power supply system for an electric motor car includes a first terminal, a second terminal, and a conversion unit. The first terminal is electrically connected to one of a power storage device and an overhead wire provided within a formation of electric motor cars. The second terminal is electrically connected to a lead wire together with a plurality of electric motors within the formation, a host power supply device, an external power supply device different from the host power supply device. The conversion unit receives first electric power supplied from the plurality of electric motors and the external power supply device via the second terminal and causes a direct current (DC) voltage to be generated at the first terminal according to a regenerative operation of the conversion unit to charge the power storage device in a first operation state and receives second electric power supplied from one of the power storage device and the overhead wire via the first terminal, converts a part of the second electric power into third electric power according to a powered operation of the conversion unit, and outputs the third electric power from the second terminal in a second operation state, thereby converting electric power.

According to an embodiment, a power supply system for an electric motor car includes a first terminal, a second terminal, and a conversion unit. The first terminal is electrically connected to one of a power storage device and an overhead wire provided within a formation of electric motor cars. The second terminal is electrically connected to a lead wire together with a plurality of electric motors within the formation, a host power supply device, an external power supply device different from the host power supply device. The conversion unit receives first electric power supplied from the plurality of electric motors and the external power supply device via the second terminal and causes a direct current (DC) voltage to be generated at the first terminal according to a regenerative operation of the conversion unit to charge the power storage device in a first operation state and receives second electric power supplied from one of the power storage device and the overhead wire via the first terminal, converts a part of the second electric power into third electric power according to a powered operation of the conversion unit, and outputs the third electric power from the second terminal in a second operation state, thereby converting electric power.

An apparatus includes a power converter configured to provide a constant current charge to a capacitor coupled to a high voltage bus through a mechanical contact, an isolation interface configured to receive a pre-charge signal on a primary side of the isolation interface, and convert the pre-charge signal into a bias voltage signal and a control command signal on a secondary side of the isolation interface, and based on the bias voltage signal and the control command signal, a constant current control unit configured to generate a gate drive signal for the power converter.

An apparatus includes a power converter configured to provide a constant current charge to a capacitor coupled to a high voltage bus through a mechanical contact, an isolation interface configured to receive a pre-charge signal on a primary side of the isolation interface, and convert the pre-charge signal into a bias voltage signal and a control command signal on a secondary side of the isolation interface, and based on the bias voltage signal and the control command signal, a constant current control unit configured to generate a gate drive signal for the power converter.

A charging system using a motor driving system, the motor driving system including: a battery and an inverter, the inverter configured to receive and convert a direct current (DC) power stored in the battery into a three-phase alternating current (AC) power and to output the three-phase AC power to a motor when the motor is driven and the motor configured to generate a rotation force using the three-phase AC power output from the inverter, the charging system includes a controller configured to control the inverter to boost a voltage at a neutral point of the motor and to output the boosted voltage to the battery by determining duty values of switching elements in the inverter when an external charging current is provided to the neutral point of the motor.

A charging system using a motor driving system, the motor driving system including: a battery and an inverter, the inverter configured to receive and convert a direct current (DC) power stored in the battery into a three-phase alternating current (AC) power and to output the three-phase AC power to a motor when the motor is driven and the motor configured to generate a rotation force using the three-phase AC power output from the inverter, the charging system includes a controller configured to control the inverter to boost a voltage at a neutral point of the motor and to output the boosted voltage to the battery by determining duty values of switching elements in the inverter when an external charging current is provided to the neutral point of the motor.