Hitachi Information & Telecommunication Engineering, Ltd.

Hitachi Computer Peripherals Co., Ltd.

Kimiaki Taniguchi

Takae Shimada

Hiroyuki Shoji

Yoshihide Takahashi

Fumikazu Takahashi

Masahiro Hamaogi

Yusuke Katsuyama

Akinori Uchida

Susumu Nagafuchi

Akira Kikuchi

Tomoyuki Hatakeyama

Kosuke Abe

Hirofumi Oyamada

Kuniyoshi Watanabe

Daisuke Ishida

A power converter includes a plurality of converters which are connected in parallel to a DC power supply in which an operating point is changed in accordance with an output current or an output voltage. The plurality of converters include maximum power point tracking units for performing maximum power point tracking calculations of the DC power supply. Results of the maximum power point tracking calculations of the plurality of converters are unified between the plurality of converters and the plurality of converters are controlled based on the unified calculation result.

Power converter

A power conversion system is capable of distinguishing easily and clearly between being interconnected to the power system and being in an isolated operation. The power conversion system converts DC power to AC power to interconnect with a power system and injects reactive power into a grid node for determining an isolated operation, including: a voltage detector that detects an output voltage at the grid node; a current detector that detects an output current at the grid node; a frequency measurement unit that measures a frequency of the output voltage at the grid node; a reactive-power measurement unit that measures reactive power at the grid node; and an isolated-operation determination unit that determines whether or not the power conversion system is in an isolated operation as disconnected from the power system. The isolated-operation determination unit includes a reactive-power-fluctuation determination unit that performs a first isolated-operation determination from the reactive power.

Power conversion system and method for detecting isolated operation of the same

A power storage system is provided with charge switches, discharge switches, a bidirectional DC/DC converter and a power storage system controller connecting all the battery packs to an external circuit to achieve parallel charge and discharge, and the power storage system starts the charge by setting a rated charge current value per one battery pack to Iset and setting the rated charge current value Iset as an initial value of a charge current command value Iref(1), thereafter monitor the charge current of each of the battery packs after elapse of a predetermined time so as to subtract its maximum value Ibmax(1) from the charge current command value Iref(1), and add the rated charge current value Iset to result of subtraction Ierr (Iref(1)&#x2212;Ibmax(1)) so as to set as a new charge current command value Iref(2) and carry out pre-charge in such a manner as to carry on the charge.

Power storage system and power source system

In a DC-DC converter, a smoothing capacitor is connected between DC terminals of the switching circuit, and a smoothing capacitor and a voltage clamp circuit are connected between DC terminals of a switching circuit, the voltage clamp circuit including the switching device and the clamp capacitor. The smoothing capacitors are connected to the DC power sources) in parallel, respectively. The winding of the switching circuit is magnetically coupled to the winding of the switching circuit by the transformer. The DC-DC converter performs a discharging operation for discharging the clamp capacitor between at least one of the step-down operation and a step-up operation and a step-up operation performed thereafter.

DC-DC converter, secondary battery charge and discharge system, and method of controlling DC-DC converter

A power storage system is provided with a battery and a battery charger which charges a battery pack having a battery voltage and current detection circuit. A charge circuit is structured such as to acquire terminal voltage information of the battery from a battery voltage detection circuit of the battery pack in a charging process, carry out a constant current charge control in a state in which the terminal voltage of the battery is equal to or lower than a previously determined reference voltage value of the battery, and switch to a constant voltage charge control maintaining the output voltage of the charge circuit in the case that the terminal voltage of the battery goes beyond the reference voltage value, thereby carrying on the charge until the battery is fully charged. Therefore, the power storage system can accurately charge the battery to a prescribed amount safely.

Power storage system with constant current charge control or constant voltage charge control depending on battery terminal voltage in a charging process

A high-efficiency power supply apparatus is provided in light of the reduction of the switching loss. The power supply apparatus connected between the AC power supply and the DC load converts the AC power supplied from the AC power supply to the DC power and supplies it to the DC load. The power supply apparatus comprises the first switching circuit for outputting the switched positive and negative voltages to the primary winding of the transformer, a second switching circuit for supplying the DC power induced in the secondary winding of the transformer and switched to the DC load connected to the second AC terminals, a resonance inductor serial-connected to the primary winding, and a control unit for controlling the switching operations performed by the first and second switching circuits. The control unit substantially short-circuits the second AC terminals by controlling the switching operations performed by the second switching circuit.

Power supply apparatus

Disclosed is a small-size, high-efficiency, isolated, bidirectional DC-DC converter. The bidirectional DC-DC converter includes a transformer in which windings are magnetically coupled, switching circuits, a diode which is connected in parallel with a switch, smoothing capacitors, and a control section. First and second DC power supplies, which are connected in parallel with the smoothing capacitors, respectively, provide bidirectional electrical power transfer. When electrical power is to be transferred from the first DC power supply to the second DC power supply, the switch is maintained in the ON state. When, on the other hand, electrical power is to be transferred from the second DC power supply to the first DC power supply, the switch is maintained in the OFF state to prevent a reverse electrical power flow from the first DC power supply.

Bidirectional DC-DC converter and control method thereof

Bidirectional dc-dc converter and control method thereof

A complex inductor according to the present invention changes its magnetic coupling polarity according to currents flowing its two inductors. The complex inductor includes a first magnetic member, around which first and third windings are formed, and a second magnetic member, around which second and fourth windings are formed. A first inductor is formed by connecting the first winding to the second winding, and a second inductor is formed by connecting the third winding to the fourth winding. The two magnetic members are made of a magnetic material having a magnetic permeability that gradually decreases as its magnetic flux density is increased. When the two windings are interconnected in a direction in which induced voltages generated in these windings by the current flowing in the second inductor weaken each other, the magnetic coupling polarity between the first and second inductors changes according to the current flowing in the inductors. The two inductors are magnetically coupled so that, when one of the two inductors stores energy, the current flowing in the other inductor increases, and when one of the two inductors releases energy, the current flowing in the other inductor decreases.

Complex inductor and power supply unit

A bi-directional DC-DC converter has a transformer for connecting a voltage type full bridge circuit connected to a first power source and a current type switching circuit connected to a second power source. A voltage clamping circuit constructed by switching elements and a clamping capacitor is connected to the current type switching circuit. The converter has a control circuit for cooperatively making switching elements operative so as to control a current flowing in a resonance reactor.

Bi-directional DC-DC converter and method for controlling the same

A bidirectional DC-DC converterhas smoothing capacitors Csand Cs, a smoothing reactor Ls, resonant reactors Lrand Lr, and a resonant capacitor Cr, as well as insulated gate bipolar transistors (IGBTs) Q, Q, and Qto which buffer capacitors C, C, and Care connected in parallel and diodes D, D, and Dare connected in a back-to-back configuration. After part of the energy stored in the smoothing reactor Ls and/or resonant reactors Lrand Lrdraws charges in the buffer capacitor Cand is stored in the resonant capacitor Cr, the energy is stored in the resonant reactors Lrand Lr. The energy is used to draw charges in the buffer capacitors Cand C, achieving soft switching of IGBTs Q, Q, and Q

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Hadano, Japan

Kimiaki Taniguchi