An energy storage system includes a plurality of bidirectional power converters and a plurality of windings. The plurality of windings shares a magnetic core. A controller transfers energy of a target battery to the magnetic core using a target bidirectional power converter and a target winding at a same time. A voltage of the target battery is greater than those of some or all batteries other than the target battery. As the battery is charged and discharged, the voltage of the battery changes, and the controller only needs to find a new target battery to continue discharging until voltages of all the batteries are equalized, for example, voltage differences between all the batteries are all within a preset voltage range.

A DC/DC converter which includes a first DC link, preferably a first DC link capacitor; a first plurality of N>1 converter bridges connected in parallel to the first DC link; and a transformer, preferably a medium frequency transformer. The transformer includes a primary side and a secondary side, wherein the primary side includes at least one primary winding. The converter further comprises a first plurality of N impedance elements, wherein for each converter bridge, a different one from the first plurality of impedance elements is connected between said converter bridge and the at least one primary winding.

A technology that prevents an encapsulation member encapsulating a semiconductor element from leaking between a resin-made casing and a heat dissipator is provided. A power conversion device includes a heat dissipator that includes a mount surface on which semiconductor elements are mounted, a resin-made casing that includes an intimate-contact surface that intimately contacts the mount surface, and which contains therein the semiconductor elements, and an encapsulation member that encapsulates the semiconductor elements within the casing. A first surrounding portion that surrounds the semiconductor elements is provided on the mount surface of the heat dissipator. A second surrounding portion that surrounds the semiconductor elements is provided on the intimate-contact surface of the casing. The first surrounding portion and the second surrounding portion are fitted with each other in the concavo-convex shape.

A technology that prevents an encapsulation member encapsulating a semiconductor element from leaking between a resin-made casing and a heat dissipator is provided. A power conversion device includes a heat dissipator that includes a mount surface on which semiconductor elements are mounted, a resin-made casing that includes an intimate-contact surface that intimately contacts the mount surface, and which contains therein the semiconductor elements, and an encapsulation member that encapsulates the semiconductor elements within the casing. A first surrounding portion that surrounds the semiconductor elements is provided on the mount surface of the heat dissipator. A second surrounding portion that surrounds the semiconductor elements is provided on the intimate-contact surface of the casing. The first surrounding portion and the second surrounding portion are fitted with each other in the concavo-convex shape.

A drive device drives a motor serving as a load. A first upstream switch is disposed upstream from the motor and a first downstream switch is disposed downstream from the motor in a first current path of current flowing via the motor. A second upstream switch is disposed upstream from the motor and a second downstream switch is disposed downstream from the motor in a second current path of current flowing via the motor. A direction of the current flowing in the motor when current flows in the first current path is different from a direction of the current flowing in the motor when current flows in the second current path. The first upstream drive circuit stops flow of current via the first upstream switch when the current flowing through the first upstream switch becomes greater than or equal to a current threshold.

A drive device drives a motor serving as a load. A first upstream switch is disposed upstream from the motor and a first downstream switch is disposed downstream from the motor in a first current path of current flowing via the motor. A second upstream switch is disposed upstream from the motor and a second downstream switch is disposed downstream from the motor in a second current path of current flowing via the motor. A direction of the current flowing in the motor when current flows in the first current path is different from a direction of the current flowing in the motor when current flows in the second current path. The first upstream drive circuit stops flow of current via the first upstream switch when the current flowing through the first upstream switch becomes greater than or equal to a current threshold.

A device includes at least one isolating transformer. An input is coupled to the at least one isolating transformer and configured to receive input from an energy source. At least one power switch is coupled to the isolating transformer. A diode is coupled to the at least one isolating transformer. An energy storage medium is coupled to the diode. An inverter includes one or more inverter switches, an inverter input, and an inverter output. The inverter input is coupled to the diode and the energy storage medium. The inverter output is configured to be coupled to the power network, and the inverter is configured to create AC power for distribution to the power network. A controller is configured to modulate the at least one power switch to control power flow from the input and to modulate the state of the inverter switches to control power flow to the power network.

In a power converter, an inductance L of a reactor and a capacitance C of a capacitor satisfy a condition of the expression (1) below. In the power converter, a current-limiting circuit between an AC power source and the capacitor is unnecessary. Herein, αm ([A.Math.s]) is a value of a ratio of a maximum rated current squared time product to a maximum rated output current of diodes of a rectifier circuit, Pmax is a maximum power consumption of the motor, Vac is a voltage value of a three-phase AC voltage, and a value of a constant a is 4.3 $\begin{array}{cc}a.Math.C.Math.\sqrt{\frac{C}{L}}.Math.\frac{{\mathrm{Vac}}^3}{P_{\max }}\le {\alpha }_m.& \left(1\right)\end{array}$

An object of the present invention is to effectively reduce vibration or noise caused by a motor. An inverter circuit 300 generates an alternating current from a direct current supplied from a direct current power supply 10 by using a plurality of IGBTs 311 which are switching elements, supplies the generated alternating current to a motor 100, and drives the motor 100. This alternating current includes a fundamental harmonic current corresponding to a rotational speed of the motor 100, and a harmonic current of a switching operation of the IGBTs 311. A controller 200 controls a second phase such that a first phase and the second phase are not superimposed on each other at a predetermined motor rotational speed, the first phase being a phase of an excitation force cyclically produced in the motor 100 by the fundamental harmonic current, and the second phase being a phase of an excitation force cyclically produced in the motor 100 by the harmonic current.

A heater-integrated fuse is provided at a neutral point of a stator coil, and when a short-circuit failure of an inverter is detected, a fuse part of the heater-integrated fuse is cut by heating.