Abstract: When islanding operation is to be detected in a power conversion apparatus for converting a DC power into an AC power and outputting the AC power to a system power supply, a plurality of variation generation means for executing, in accordance with different schemes, detection of islanding operation in which power supply from the system power supply is stopped are arranged, and at least one variation generation means is selected by selection means from the plurality of variation generation means and operated.

Abstract: Although increasing the switching frequency is effective to downsize a power supplying apparatus, the switching loss of a switching element increases if the switching frequency is increased. In a power supplying apparatus including a transformer having a very high boosting ratio, and a plurality of switching elements for supplying AC power to the primary side of the transformer, the frequency of the AC power is set to 0.25 to 2 times the self-resonance frequency of the transformer.

Abstract: An AC interconnection apparatus has an input terminal for a commercial power system, a connection terminal to a solar cell, an output terminal connected to a load, an inverter for converting the output voltage of the solar cell into an AC voltage, and a current detector arranged on the load side of an AC connection point for connecting the AC output from the inverter and the commercial power. When a power value calculated on the basis of a current detection value by the current detector and the voltage of the commercial power system is less than the output power of the inverter, the output of the inverter is suppressed, thereby suppressing reverse power flow to the commercial power system. When the current value detected by the current detector exceeds a predetermined value, power supply to the load is stopped using a breaker.

Abstract: In a power supply system for converting the output of a DC power supply having an earth capacitance to AC power, an input voltage from an input-voltage detector and an intermediate voltage from an intermediate-voltage detector are input to an input-ripple controller. The latter calculates the difference between ripple voltages of the two voltages. The input-ripple controller adjusts the size of a ripple command value, which indicates the ripple current that is to be input to a converter circuit, so as to null the difference between the ripple voltages. Furthermore, using a ripple reference waveform having a DC level, the input-ripple controller generates a ripple current waveform so as to null the average value of a full-wave rectified waveform synchronized to the output of an inverter circuit, and outputs the generated ripple current waveform to an output calculator.

Abstract: An AC interconnection apparatus has an input terminal for a commercial power system, a connection terminal to a solar cell, an output terminal connected to a load, an inverter for converting the output voltage of the solar cell into an AC voltage, and a current detector arranged on the load side of an AC connection point for connecting the AC output from the inverter and the commercial power. When a power value calculated on the basis of a current detection value by the current detector and the voltage of the commercial power system is less than the output power of the inverter, the output of the inverter is suppressed, thereby suppressing reverse power flow to the commercial power system. When the current value detected by the current detector exceeds a predetermined value, power supply to the load is stopped using a breaker.

Abstract: When a ground fault occurs in some solar battery string, this solar battery string may be disconnected and operation of a solar power generation system may be continued. If the open-circuit voltage of the solar battery string is high, a safety problem arises. If the open-circuit voltage is decreased, the conversion efficiency decreases. Therefore, an intermediate switch is provided midway along the solar battery string. When a ground fault occurs, this solar battery string where the ground fault has occurred is divided into substrings.

Abstract: In a power generation system including a DC power supply which is connected to a low-voltage distribution system to which a plurality of consumers, each having an earth leakage breaker, are connected and one wire of which is grounded, via a receiving-end earth leakage breaker, and which includes at least a transformerless inverter and an earth floating capacitance, an operational time limit of the receiving-end earth leakage breaker of the power generation system is set to a value larger than an operational time limit of the earth leakage breakers provided in the consumers. The system also includes a ground-direction determination device for determining whether a grounded position is inside or outside the power generation system. Thus, a power generation system in which an unnecessary disconnection of electric power supply does not occur when an accident of external grounding has occurred.

Abstract: An electric power conversion unit 2 for driving a pump 3 run by electric power generated by a solar panel 1, a storage battery 5 connected to the solar panel 1 via the switch 6, and a controller 7 for controlling the electric power conversion unit 2 and the switch 6 are provided. The controller 7 closes the switch 6 during any period when the amount of insolation is large and performs the maximum power point tracking control of the solar panel 1, and otherwise, controls the electric power conversion unit 2 to drive at one of plural fixed frequencies in dependence upon an output voltage from the solar panel 1 by closing the switch 6. Accordingly, it is possible to utilize output from an unstable electric power supply efficiently, such as a solar cell, thereby providing a reliable electric motor driving apparatus having a simple configuration and a control method therefor.

Abstract: As the application range of solar power generation systems widens, a number of relatively compact and lightweight inverters must be installed outdoors. However, an inverter has no burglarproof function at all. A burglarproof device which switches the state of the burglarproof function upon receiving a burglarproof function state change signal, and outputs an alarm signal when the output signal output in the alarm state from a connection detection section indicates that the power supply or load is disconnected is added to the inverter.

Abstract: In a power generation system including a DC power supply which is connected to a low-voltage distribution system to which a plurality of consumers, each having an earth leakage breaker, are connected and one wire of which is grounded, via a receiving-end earth leakage breaker, and which includes at least a transformerless inverter and an earth floating capacitance, an operational time limit of the receiving-end earth leakage breaker of the power generation system is set to a value larger than an operational time limit of the earth leakage breakers provided in the consumers. The system also includes a ground-direction determination device for determining whether a grounded position is inside or outside the power generation system. Thus, a power generation system in which an unnecessary disconnection of electric power supply does not occur when an accident of external grounding has occurred.

Abstract: In a power generation system including a DC power supply which is connected to a low-voltage distribution system to which a plurality of consumers, each having an earth leakage breaker, are connected and one wire of which is grounded, via a receiving-end earth leakage breaker, and which includes at least a transformerless inverter and an earth floating capacitance, an operational time limit of the receiving-end earth leakage breaker of the power generation system is set to a value larger than an operational time limit of the earth leakage breakers provided in the consumers. The system also includes a ground-direction determination device for determining whether a grounded position is inside or outside the power generation system. Thus, a power generation system in which an unnecessary disconnection of electric power supply does not occur when an accident of external grounding has occurred.

Abstract: In a power conversion system having a DC power supply which has an almost fixed DC voltage to ground and a predetermined stray capacitance to ground and outputs a DC power, and a power converter which converts the DC power output from the DC power supply into an AC power by switching, the phase of an AC voltage to ground generated in the DC power supply by switching is detected, the phase of an AC ground fault current that flows through the stray capacitance to ground and the ground fault resistance of the DC power supply is detected, and the difference between the two detected phases is compared with a predetermined threshold value, thereby determining a DC ground fault in the DC power supply. With this arrangement, the ground fault state of the DC power supply can more accurately be detected. In addition, the operation efficiency of the power conversion system can be increased.

Abstract: In the present invention, the temperature of a bypass diode of a solar cell module is measured by a temperature detection means from the exterior of the solar cell module, and the results of temperature detection on each bypass diode are mutually compared to detect the presence or absence of the failure in the solar cell module. Also at least one solar cell in the solar cell module is covered with a light shielding plate, then a current flowing in the bypass diode bypassing to the covered solar cell is detected, and a failed solar cell module is detected from the result of the current detection. Also the solar cell module is provided with a temperature detection means capable of detecting the temperature of the bypass diode and the temperature of an internal portion of the solar cell module other than the bypass diode. By these, it is rendered possible to detect a failure in the solar cell module easily and exactly, and also to detect the short circuit failure in the solar cell.

Abstract: The temperature of a bypass diode of a solar cell module is measured by a temperature detector from the exterior of the solar cell module, and the results of temperature detection of each bypass diode are mutually compared to detect the presence or absence of failure in the solar cell module. Also at least one solar cell in the solar cell module is covered with a light shielding plate, then a current flowing in the bypass diode bypassing to the covered solar cell is detected, and a failed solar cell module is detected from the result of the current detection. Also the solar cell module is provided with a temperature detector capable of detecting the temperature of the bypass diode and the temperature of an internal portion of the solar cell module other than the bypass diode. In this way, it is possible to detect a failure in the solar cell module easily and precisely, and also to detect short circuit failure in the solar cell.

Abstract: In an AC module, if an interconnection relay is provided in an inverter, the inverter increases in size, and disconnection status between the AC module and a system upon occurrence of abnormal condition cannot be easily checked by a user. Accordingly, a plug is connected to an outlet, thereby an output of the inverter is supplied to the system or a load via a coupler. If leakage of direct current, ground fault of a solar cell or the like, a fault or abnormal condition of the inverter, or an abnormal condition of the system is detected, the inverter outputs a signal to separate the plug from the coupler.

Abstract: In a solar power generation apparatus, when power necessary for a control circuit and the like is supplied from the load side of an inverter, a period from when the input voltage becomes lower than a threshold voltage at which the inverter should be stopped to when the inverter is stopped after the elapse of a predetermined time includes a period when power consumed by the inverter become larger than power output from the inverter, i.e., power is wasted. To solve this problem, input power is integrated for a predetermined time to calculate integrated electric energy. The calculated integrated electric energy W1 is compared with a threshold value Y1. If W1<Y1, a gate block signal is output to stop the operation of the inverter. As the threshold value Y1, a value corresponding to the product of the non-load power of the inverter and the predetermined time T1 is set.

Abstract: A general abnormal heating detection method in an electronic device is limited to an object to be monitored, and cannot cope with heating of an object of which overheating is unexpected. To correct this problem, temperature data are acquired from a plurality of temperature sensors distributed in the device to be protected, the parameter indicating temperature distribution pattern in the device is calculated on the basis of the acquired temperature data, and an alarm signal is output when the calculated parameter indicating temperature distribution pattern deviates from a predetermined reference.

Abstract: In a power supply system for converting the output of a DC power supply having an earth capacitance to AC power, an input voltage from an input-voltage detector and an intermediate voltage from an intermediate-voltage detector are input to an input-ripple controller. The latter calculates the difference between ripple voltages of the two voltages. The input-ripple controller adjusts the size of a ripple command value, which indicates the ripple current that is to be input to a converter circuit, so as to null the difference between the ripple voltages. Furthermore, using a ripple reference waveform having a DC level, the input-ripple controller generates a ripple current waveform so as to null the average value of a full-wave rectified waveform synchronized to the output of an inverter circuit, and outputs the generated ripple current waveform to an output calculator.

Abstract: In a solar power generation system which causes a non-insulated type inverter to convert DC power generated by a solar battery into AC power and outputs the AC power to a commercial power system, in detecting a ground fault, the differential current between the output lines of the solar battery is detected, an AC leakage current component due to the capacitance to ground of the solar battery is removed from the differential current, and it is determined whether a ground fault state has occurred by comparing a current value after removal of the AC leakage current component with a predetermined threshold value. With this arrangement, a false ground fault state determination that is caused by the influence of the AC leakage current component due to the electrostatic capacitance although the DC current path can be prevented, and a ground fault state can accurately be determined.

Abstract: Along with the expansion of the application range of solar power generation systems, connection to a single-phase 100-V system is required. To most easily meet this requirement, a non-insulated inverter with a single-phase two-wire 100-V output is used. It is preferable to use an inverter with a single-phase two-wire 200-V output, i.e., a most popular commercially available inverter. For this purpose, a power supplied from a solar battery is converted into a single-phase three-wire 200-V AC power form by the inverter. The output from the inverter with non-insulated inputs and outputs is supplied to a system through a transformer arranged to connect the line of the single-phase three-wire 200-V AC power to a single-phase two-wire 100-V system with one line grounded. To make a ground fault sensor incorporated in the inverter function, the median potential line of the single-phase three-wire 200-V AC power is connected to the ground line of the system.