A power conversion device includes a power switching circuit that supplies AC voltages generated between switching elements operating as upper arms and switching elements operating as lower arms, and a control circuit that generates and supplies to the driver circuit signals for controlling the switching operation of the switching elements by a PWM method in a first operational region in which frequency of an AC power to be outputted is low, and that generates and supplies to the driver circuit signals for controlling the switching operation of the switching elements at timings based upon the phase of the AC power to be outputted in an operational region in which the frequency of the AC power to be outputted is higher than in the first operational region.

Power Conversion Device

A method and apparatus for converting DC input power to AC output power. The apparatus comprises means for storing energy from a DC input current, means for converting the DC input current to AC output current, means for causing the energy to be stored in and drawn from the means for storing during at least one storage and at least one burst period, respectively, the AC output current greater than the DC input current during the at least one burst period; a first means for determining a maximum power point (MPP) and operating the means for converting proximate the MPP; and a second means for determining a difference in a first and a second power measurement, producing an error signal indicative of the difference, and coupling the error signal to the first means to adjust at least one operating parameter of the means for converting to drive toward the MPP.

Method and apparatus for improved burst mode during power conversion

An apparatus and method for converting a DC input power to a DC output power. The apparatus comprises an energy storage module and a burst mode controller. The burst mode controller causes energy to be stored in the energy storage module during at least one storage period, and further causes the energy to be drawn from the energy storage module during at least one burst period. During the at least one burst period, the DC output power is greater than the DC input power. Additionally, the burst mode controller employs a maximum power point tracking (MPPT) technique for operating a device providing the DC input power proximate a maximum power point (MPP).

Method and apparatus for power conversion with maximum power point tracking and burst mode capability

The invention relates to a separate network comprising at least one energy generator using regenerative sources of energy. Preferably, said energy generator is a wind power plant which is provided with a first synchronous generator, an intermediate DC circuit that comprises at least one first rectifier and an inverter, a second synchronous generator, and an internal combustion engine that is coupled to the second synchronous generator. In order to create a separate network in which the internal combustion engine can be entirely shut off as long as the wind power plant generates enough power for all connected users at the highest possible efficiency, a fully regulable wind power plant (10) and an electromagnetic coupler (34) are arranged between the second synchronous generator (32) and the internal combustion engine (30).

Separate network and method for operating a separate network

A five-level inverter that can be reduced in generated loss, and size and cost is provided. The inverter has: first, second, and third arm pairs that are configured by combining in series two arms formed of semiconductor devices with respect to an input DC power source provided with five terminals and having five mutually different voltage levels including zero; and AC switches configured by inverse serially combining arms formed of semiconductor devices. The configuration, in which the number of elements that pass electric current is reduced with respect to that in the conventional circuit, makes it possible to increase the device in efficiency and reduce in size.

Five-level inverter

PROBLEM TO BE SOLVED: To surely smooth fluctuation of output to a power system due to distributed power supply such as a wind power generation system and a solar power generation system by preventing shortage of power accumulation or full charging of a power accumulator. SOLUTION: A distributed power supply system 10 consisting of distributed power supply 9, a power fluctuation smoothing apparatus 1 and a power converter 15 is connected to a power system 12, a controller 4 of the power fluctuation smoothing apparatus 1 is composed of an output detector 5, an accumulated power detector 6, a target value setting device 7 for setting a target output value, and a charge/discharge controller 8 for controlling a charger/ discharger 3. An output of the distributed power supply 9 and amount of accumulated power of a power accumulator 2 are detected. A running average value in the preset period of an output of the distributed power supply 9 is compensated with an output target adjusting value which is preset depending on the amount of accumulated power to set an output target value to the side of the power system 12. When an output of the distributed power supply 9 is larger than the output target value, an extra power is used to charge the power accumulator 2. When an output is smaller than the output target value, shortage is compensated with the power discharged from the power accumulator 2 until the output to the side of power system 12 reaches the output target value. COPYRIGHT: (C)2002,JPO

Power fluctuation smoothing apparatus and method for controlling distributed power supply system comprising the same

PROBLEM TO BE SOLVED: To suppress variation in reverse tidal-current power to a system by allowing a control means to switch and control the charging and discharging of a charging and discharging means by comparing the output of a DC power source with its target value. SOLUTION: A charging and discharging control part 5 is provided at a halfway part of a branch wire 9 to control the charging and discharging of a charging and discharging element 6. Namely, a switching command part of the charging and discharging control part 5 makes a switching judgement between charging operation and discharging operation according to output power information on a solar battery 1 of a DC collection box 2 which is supplied from a power sensor 10 provided between an intermediate point 8a and the output terminal 2a of the DC collection box 2 and switches the charging and discharging switching part 51 according to the judgement. Consequently, variation in the generated power of the DC power source due to variation of the sunshine is absorbed, so that the variation of the reverse tidal-current power to the system can be suppressed.

Direct-current power output device and solar power generation system

PROBLEM TO BE SOLVED: To provide a transformer-less electric power converter for solar power generation, which does not fluctuate the potential of the direct current part of an inverter even in the case of a linkage to a three-phase three-wire system V-phase grounding system SOLUTION: An inverter circuit is provided which has two pairs of series circuits Q1, Q2, Q3, Q4 of two switching elements in it A plurality of capacitors C1, C2 dividing DC voltage are series-connected between the DC input parts of the inverter circuit One output line OL2 is drawn, as one of the three-phase outputs, from the connecting parts C1, C2 of the capacitors Respective two output lines OL1, OL3 are taken out, as other two of the three-phase outputs, from the intermediate points of the respective pairs of switching elements Q1, Q2, Q3, Q4, thereby forming a half-bridge inverter circuit The output line OL2 drawn from the connecting part of the capacitors C1, C2 is connected with the grounded phase COPYRIGHT: (C)2001,JPO

Electric power converter for solar power generation

PROBLEM TO BE SOLVED: To provide a reactive power change system of single operation detector, which can properly detect a single operation without increasing the quantity of input reactive power even when a reactive power load is included in a load.SOLUTION: The single operation detector 6, which detects a single operation state, is provided with a reactive power input unit 61 which periodically inputs a reactive power where a current gains, and a reactive power where a current delays to the output power of an inverter device 2, and a single operation detector 64 which determines whether the phase of an interconnection point voltage signal Vo at an interconnection point (a) has changed. The single operation detector 64 detects the system is in a single operation state when it is determined that the phase of the interconnection point voltage signal Vo has changed. Even when a reactive power load is included in a load B, it can detect a single operation properly because it is determined that the phase of the interconnection point voltage signal Vo has changed in case any reactive power has been input.

Single operation detector, method of detecting single operation, and system-interconnected inverter system equipped with single operation detector

PROBLEM TO BE SOLVED: To reduce a loss of tracking time of maximum power point voltage when returning to MPPT control after switching from the MPPT control to interconnected point voltage suppression control in a system-interconnected inverter device.SOLUTION: A controller 4 comprises: a first voltage command value generation part 401 for controlling an inverter device 3 through MPPT control; a second voltage command value generation part 402 for controlling the inverter device 3 through interconnected point voltage suppression control; and a voltage command value switching part 403 for switching between the MPPT control and the interconnected point voltage suppression control. When the voltage command value switching part 403 switches from the MPPT control to the interconnected point voltage suppression control, the second voltage command value generation part 402 switches from control for increasing output voltage of a solar battery 2 to control for decreasing the output voltage, and searches for a maximum power point of the solar battery 2. When the output voltage of the solar battery 2 reaches voltage at the maximum power point, the second voltage command value generation part 402 ends the interconnected point voltage suppression control, and the first voltage command value generation part 401 starts the MPPT control.

Hiromasa Kubo

Papers

Power fluctuation smoothing apparatus and method for controlling distributed power supply system comprising the same

Direct-current power output device and solar power generation system

Electric power converter for solar power generation

Single operation detector, method of detecting single operation, and system-interconnected inverter system equipped with single operation detector

System-interconnected inverter device