Abstract: Methods and apparatus for detecting the presence of undesirable foreign matter in a region between a wireless power transmission apparatus and a power reception apparatus are described. First and second detection methods, based on different detection schemes, may be used to detect and distinguish the presence of foreign matter from misalignment during power transfer operation. A first detection method may be used before power is transferred to a load in a power reception apparatus, and a second detection method may be used while power is supplied to the load.

Abstract: A system is provided. The system includes a utility, a plurality of uninterruptible power supplies (UPSs), a ring bus, at least one load electrically coupled to the plurality of UPSs and the ring bus, and a controller communicatively coupled to the plurality of UPSs, the controller configured to determine a common reference angle while the utility is disconnected from at least one UPS of the plurality of UPSs, calculate a phase angle for each UPS of the plurality of UPSs, wherein the phase angle for each UPS is calculated relative to the common reference angle, and control operation of each UPS based on the respective calculated phase angles.

Abstract: This invention relates to a supercapacitor assembly having an asymmetric supercapacitor, a diode, and a switch in parallel with the diode. The asymmetric supercapacitor has at least one positive electrode, at least one negative electrode, and at least one separator impregnated with an electrolyte. The diode has an anode and a cathode, the cathode being electrically connected to the supercapacitor.

Abstract: We describe a photovoltaic power conditioning unit for delivering power from multiple photovoltaic panels to an ac mains power supply output, comprising: a dc input for receiving power from multiple photovoltaic panels; an ac output for delivering ac power to the ac supply; a bank of electrolytic energy storage capacitors for storing energy from the dc source for delivery to the ac supply; a dc-to-ac converter coupled to the ac output and having an input coupled to the bank for converting energy stored in the bank to ac power for the ac supply; and further comprising: a plurality of sense and control circuits, one for each capacitor in the bank, wherein each circuit is coupled in series with a capacitor, and is configured to disconnect the associated capacitor from the bank upon detection of a current flow through the associated capacitor of greater than a threshold current value.

Abstract: A power receiving unit includes a communication unit, a control unit, a detecting unit that performs metallic foreign matter detection, and a charge storage unit. The control unit is configured to control charging so electric power is stored in the charge storage unit for consumption by the detecting unit during Q-value measurement when the control unit receives a Q-value measurement command from the power transmitting device through the communication unit.

Abstract: A circuit for an energy collection system is provided that includes one or more strings that are configured to couple to an electrical load. Each of the one or more strings comprises one or more string members that are coupled to each other in series. Each of the one or more string members comprises (i) a connection to receive an output from an energy output device, and (ii) an inverter configured to convert the output of the energy output device into alternating current (AC) energy. The circuit includes a controller that controls the output that is provided by the one or more strings by controlling the individual string member.

Abstract: A wind turbine (8) for controlling power oscillations on a grid of a power system (28). The wind turbine (8) comprises rotor blades (12) for turning by the wind, an electric generator (20) rotatably coupled to the rotor blades (12), a power converter (24) responsive to electricity generated by the electric generator (20), the power converter (24) for converting the generated electricity to a frequency and voltage suitable for supply to the power grid (28), and the power converter for regulating voltage on the grid supplemented by modulating real power for damping the power oscillations.

Abstract: According to one embodiment, a system includes a battery to charge power and discharge a direct-current power to a converter, the converter supplying the converted power to a power system, detectors detecting a voltage at a point between the converter and power system, a current output from the converter and effective power from the voltage value and a current value detected, units computing an angular frequency of the voltage output from the converter, based on an effective power value and an output target value of effective power and an output voltage target value of the converter, based on a current value, a set voltage value and an angular frequency, and a controller controlling the converter according to the output voltage target value.

Abstract: A vehicle includes a transmission, energy storage system (ESS), power inverter module (PIM), and controller. The PIM includes a boost converter having a bypass switch and a first plurality of switches, and also a power inverter having a second plurality of switches. The controller is programmed to execute a method that enables a DC boost converter of the PIM by opening the bypass switch when a speed and a torque of the electric machine are within a predetermined boost range. The controller bypasses the boost converter by transmitting a second switching signal closing the bypass switch when the speed and torque are not within the predetermined boost range. A voltage input to the power inverter is equal to the DC battery voltage whenever the boost converter is bypassed and exceeds the DC battery voltage whenever the boost converter is enabled.

Abstract: A method for improving power factor includes collecting consumption data of at least one appliance, building a consumption profile for each of the at least one appliance based on the consumption data collected, reconstructing reactive power consumption of each of the at least one appliance based on the consumption profile for each of the at least one appliance, and computing a schedule for each of the at least one appliance in accordance the reactive power consumption of each of the at least one appliance to improve power factor while respecting at least one constraint.

Abstract: According to one embodiment, an inverter apparatus includes a power conversion unit, a wireless communication unit and a control unit. The power conversion unit converts input power that is one of DC power and AC power into AC output power. The wireless communication unit wirelessly receives a first synchronization signal. The control unit controls a phase of the output power based on the first synchronization signal.

Abstract: An actuator for the power control of at least one connected load has a load detection device for detecting a magnitude of a load and/or a type of a load of the at least one as a measurement variable relating to the load of the at least one consumer. A communication interface receives at least one manipulated variable for the power control of the at least one consumer and transmits the measurement variable detected by the load detection device. Actuators of this type may be integrated into an energy management system, such as of a building automation system, for example.

Abstract: A power supply device for a nonlinear, time-varying load has a multi-phase power system. The load and a reactive power compensator are connected to the phases of the power system. The reactive power compensator is embodied as a multilevel converter with multiple strands, each connected to one of the power system phases and to the other strands at a common star point. The power supply device has a filter circuit that filters harmonics of load and converter currents. The filter circuit has multiple strands, each connected to one of the power system phases and to the other strands at a common star point of the filter circuit, which is connected to the common star point of the multilevel converter such that the common star point of the multilevel converter is connected to the power system phases both via the strands of the multilevel converter and via the filter circuit.

Abstract: An apparatus and method for burning-in an electronic ballast for a lamp. The apparatus comprises a first stage for emulating an input impedance characteristic of a lamp for the electronic ballast and a second stage connected to the first stage for providing energy feedback to a power supply. An input of the first stage connects in use to the electronic ballast to be burnt-in. An output of the second stage connects in use to the power supply to provide energy feedback to said power supply from the electronic ballast being burnt-in. The energy-recyclable burn-in apparatus can emulate the lamp characteristics from start up to the steady state, process high-frequency ballast output power and recycle the power back into the power grid. The burn-in method includes operating the apparatus for a predetermined period of time such that a voltage applied to the electronic ballast simulates a steady-state operation of a lamp for the electronic ballast.

Abstract: An inverter circuit contains a first and second DC sources for providing a DC voltage, a common step-up converter for boosting the DC voltage, an intermediate circuit capacitor connected between the outputs of the common step-up converter, and an inverter for converting the DC voltage provided by the capacitor into an AC voltage. The common step-up converter contains a series circuit having a first inductance and a first rectifier element and is connected between an output of the first DC source and one side of the intermediate circuit capacitor as well as a series circuit which includes a second inductance and a second rectifier element and is connected between an output of the second DC source and another side of the intermediate circuit capacitor. The common step-up converter further contains a common switching element which is connected between the first and second DC sources.

Abstract: A transmit pad inspection device includes a magnetic coupling device, which includes an inductive circuit that is configured to magnetically couple to a primary circuit of a charging device in a transmit pad through an alternating current (AC) magnetic field. The inductive circuit functions as a secondary circuit for a set of magnetically coupled coils. The magnetic coupling device further includes a rectification circuit, and includes a controllable load bank or is configured to be connected to an external controllable load back. The transmit pad inspection device is configured to determine the efficiency of power transfer under various coupling conditions. In addition, the transmit pad inspection device can be configured to measure residual magnetic field and the frequency of the input current, and to determine whether the charging device has been installed properly.

Abstract: The present invention addresses the problem of avoiding that wind turbine voltage levels within a wind power plant do not exceed predetermined overvoltage and/or undervoltage protection levels. In particular, the present invention relates to shifting of an output voltage level of a wind power plant in order to protect an internal power plant grid against overvoltages.

Abstract: A system for multiple energy storage and management includes a propulsion system includes an electric drive and a direct current (DC) link electrically and a first energy storage system coupled to the electric drive. The first energy storage system includes a low specific-power energy storage device (ESD). A coupling device is coupled to a first terminal of the low specific-power ESD and a second energy storage system, wherein a first terminal of the second energy storage system is electrically coupled to the electric drive through the DC link and a second terminal of the second energy storage system is coupled to the coupling device. A boost converter assembly is coupled to the first and second energy storage systems. The coupling device couples the second terminal of the second energy storage system to the first terminal of the low specific-power ESD in a series connection that bypasses the boost converter assembly.

Abstract: A solar power module, and related method of operation, that protects the bypass diodes in the solar power module from overheating due to partial shading, and also protects firefighters and installer personnel from electrical shock hazard. The solar power module includes active bypass switches, and isolation switches that disconnect the PV cells from the bypass switches when all the bypass switches are closed concurrently, thereby allowing the PV cells to continue supplying power to the control circuitry. The isolation switches are also used to maintain the solar power module in a safe state during installation, or in case of fire.

Abstract: A hybrid engine and battery generator and a method of operating the same. The generator is controlled to operate in at least three modes: a battery-only mode, a battery charging mode, and a boost mode. In the battery-only mode, the engine is off and an internal battery of the generator is used by an inverter to generate AC output. In the battery charging mode, the engine generates DC power, via an alternator and rectifier, which is used to charge the battery and to supply power to the inverter to generate AC output. In the boost mode, the battery and the engine generate DC power that is used by the inverter to generate an AC output with increased wattage, relative to the battery-only mode and battery charging mode. The generator automatically switches between the modes based on battery level and load demand.

Abstract: A power management apparatus and a method of operating the same are disclosed. The power management apparatus includes a power conversion unit, a first sensing unit, a second sensing unit, a switch unit, and a control unit. The power conversion unit converts output power generated from at least one renewable energy generation apparatus. The first sensing unit is provided to sense a first current and a first voltage and the second sensing unit is provided to sense a second current and a second voltage. The control unit acquires an output power generated from the renewable energy generation apparatus and acquires a feedback power to an AC utility according to the currents and the voltages when the control unit turns on the switch unit.

Abstract: An electrical power system includes a power grid and a plurality of power plants connected to the power grid. A central repository including one or more electrical energy storage devices is connected directly to the power grid. The one or more energy storage devices are configured to be connected to the power plants via the power grid. The central repository is operable to draw a portion of a power output produced by one or more of the power plants via the power grid during a first period, for storage therein. The central repository is operable to discharge power to the power grid during a second period shifted in time from the first period. The discharged power is a function of a grid requirement or a function of a power demand notified by an individual power plant of the electrical system.

Abstract: A method for no break power transfer in a variable frequency power generating system, the power generating system comprising a first bus connected to a first generator and a second bus connected to a second generator includes configuring a power transfer device to output power that is synchronized to match a voltage and a frequency of the second bus to the second bus; reconfiguring the power transfer device to output power that is synchronized to match a voltage and a frequency of the first bus to the second bus; and closing a tie switch located between the first bus and the second bus.

Abstract: A propulsion system comprising an electric drive, a DC link electrically coupled to the electric drive, and a first energy storage system electrically coupled to the electric drive, the first energy storage system comprising at least a high specific-power energy storage device is shown. The propulsion system further includes a second energy storage system, wherein a first terminal of the second energy storage system is electrically coupled to the electric drive through the DC link and a second terminal of the second energy storage system is coupled in series with a terminal of the high specific-power energy storage device. A multi-channel bi-directional boost converter is coupled to the first energy storage system and to the second energy storage system, wherein the connection between the terminal of the high specific-power energy storage device and the second terminal of the second energy storage system bypasses the multi-channel bi-directional boost converter.

Abstract: A propulsion system includes an electric drive, a first energy storage system electrically coupled to the electric drive through a DC link, and a second energy storage system electrically coupled to the first energy storage system in a series connection. The first energy storage system comprises a high specific-energy storage device and the second energy storage system comprises a low specific-power storage device. The propulsion system also includes a third energy storage system comprising a high specific-energy storage device electrically coupled to the second energy storage system. A bi-directional boost converter is electrically coupled to the second and third energy storage systems such that a terminal of the third energy storage system is electrically coupled to a low voltage side of the bi-directional boost converter and a terminal of the second energy storage system is coupled to a high voltage side of the bi-directional boost converter.

Abstract: An integrated electronics housing contains both system electronics and power generation circuits for a two-axis tracker assembly having a CPV solar array. The housing contains at least a communication bus, motion control circuits, and inverter circuits, and acts as the local system control point for that tracker mechanism. The inverter circuits generate three-phase AC voltage that is supplied to a grid interface transformer. Each inverter receives a bipolar DC voltage supplied from its own set of CPV cells. The motion control circuits move the CPV cells of the tracker mechanism to angular coordinates resulting from a solar tracking algorithm. The communication bus connects to the motion control circuits and the inverter circuits to facilitate communications of information, including parameters of power being generated by the inverter circuits, between the motion control circuits and the AC inverter circuits to fine tune the AC power generated out of the tracker mechanism.

Abstract: An output ripple voltage average amplitude of a switch mode DC-DC converter is dynamically maintained. The converter has a switch and an output filter. By varying a switching period (TPERIOD) of the switch, VRIPPLE is maintained at a substantially constant value over a first range of converter input voltages and a second range of switch duty cycles. Where the output filter includes an inductor having inductance (L) and a capacitor having capacitance (C) the average amplitude of VRIPPLE is dynamically maintained by varying TPERIOD with respect to switch duty cycle (D) and input voltage (VIN) so as to approximately satisfy the following relationship: TPERIOD=(VRIPPLE*8*L*C)0.5/(VIN*(D?D2)).5.

Abstract: A power converter can include an inverter including, connected in series, switching elements, the inverter circuit being connected to both ends of a DC power source series circuit resulting from connecting in series a DC power source and a DC power source. Also included can be an AC output terminal that is connected to a connection point of the switching element and the switching element, an AC output terminal that is connected to a connection point of the DC power source and the DC power source, a bidirectional switch element one end of which is connected to the AC output terminal and the other end of which is connected to a terminal of an AC power source and a bidirectional switch element one end of which is connected to the AC output terminal and the other end of which is connected to the AC power source.

Abstract: An uninterruptible power supply includes plural power units, plural output capacitor units, a capacitor energy bleeder circuit, plural output units, a detecting unit and a controlling unit. The capacitor energy bleeder circuit is electrically connected to the plural output capacitor units. The plural output units are connected with each other in parallel to issue the output voltage to the power output side and avoid returning electrical energy from the power output side back to the capacitor energy bleeder circuit. The detecting unit is used for detecting operating statuses of the plural power units. The controlling unit is used for controlling operations of the plural power units and the capacitor energy bleeder circuit. In response to a to-be-interrupted status of a specified power unit, the controlling unit controls the capacitor energy bleeder circuit to discharge electrical energy of the output capacitor unit corresponding to the specified power unit.

Abstract: A propulsion system includes an electric drive, a first energy storage system electrically coupled to the electric drive through a DC link, and a second energy storage system electrically coupled to the first energy storage system in a series connection. The first energy storage system comprises a high specific-energy storage device; the second energy storage system comprises a high specific-power storage device. The propulsion system also includes a bi-directional boost converter electrically coupled to the first and second energy storage systems such that a terminal of the first energy storage system is electrically coupled to a low voltage side of the bi-directional boost converter and a first terminal of the second energy storage system is coupled to a high voltage side of the bi-directional boost converter. The series connection bypasses the bi-directional boost converter.

Abstract: An apparatus for perpetually harvesting ambient near ultraviolet to far infrared radiation to provide continual power regardless of the environment, incorporating a system for the harvesting electronics governing power management, storage control, and output regulation. The harvesting electronics address issues of efficiently matching the voltage and current characteristics of the different harvested energy levels, low power consumption, and matching the power output demand. The device seeks to harvest the largely overlooked blackbody radiation through use of a thermal harvester, providing a continuous source of power, coupled with a solar harvester to provide increased power output.

Abstract: The multifunctional power converter apparatus and method includes an input power stage configured to receive a DC input voltage from a DC power source and convert the DC input voltage to an AC or DC output voltage. At least one electrical power conversion electronic circuit is connected to an output of the input power stage, a DC output circuit; an AC output circuit; and a controller configured to control the input power stage, the DC output circuit and the AC output circuit. The controller is configured to automatically control the power converter output voltage based on a preselected user input.

Abstract: According to a preferred embodiment of the invention, the system for managing a power system with a plurality of power components that includes power source components and power consumption components includes a central power bus, a plurality of adaptable connectors that each electrically couple to a power component and to the central power bus, and a control processor that receives the state of each power component from the respective adaptable connector and is configured to balance the voltage and current output from each power source component to provide a desired power to a power consumption component based on the received states.

Abstract: A power conversion apparatus includes: a line breaker that is connected in series to a direct-current power supply; a first capacitor that is connected in parallel to the direct-current power supply through the line breaker; a discharge circuit that includes a resistor and a first switching circuit connected in series and is connected in parallel to the first capacitor; a power converter for driving a synchronous machine; a second capacitor that is connected in parallel to a direct-current side of the power converter; a second switching circuit that is connected in series between the first capacitor and the second capacitor; and a control circuit for controlling the discharge circuit. The control circuit controls the discharge circuit on the basis of the voltage of the first capacitor and the voltage of the second capacitor.

Abstract: Various methods and apparatus are described for a photovoltaic system. In an embodiment, pluralities of three-phase Alternating Current (AC) inverter circuits electrically connect into a common three phase AC output. Each of those inverters receives a bipolar DC voltage supplied from its own set of Concentrated PhotoVoltaic (CPV) modules.

Abstract: The present invention provides an apparatus for easily detecting an abnormal status of power generation of a solar cell panel in a solar cell power generation system having the power generation of 1 MW or higher. The present invention provides an abnormality detecting apparatus for a solar cell power generation system including a plurality of solar cell strings each having a plurality of solar cell modules connected to each other in series and a backflow preventing diode connected to a power output terminal of each of the solar cell strings, characterized in that the abnormality detecting apparatus further includes measuring means for measuring a current flowing in the backflow preventing diode; and that the measuring means is supplied with electric power from both terminals of the backflow preventing diode.

Abstract: A primary device for inductive power transfer to a secondary device is disclosed. The primary device includes a primary coil, the primary device being configured to (i) operate in a first mode during which the primary coil transfers power through inductive coupling to the secondary device, and (ii) operate in a second mode during which a foreign object is detected. The primary device further includes a primary controller configured to operate the primary coil (i) using a first frequency during the first mode, and (ii) using a second frequency during the second mode. A method to detect a foreign object which is in proximity of an inductively coupled environment of a primary device is also disclosed.

Abstract: In a converter of a motor drive control device, one of a first switching element and a second switching element is selected in accordance with a current command value of a current flowing through a reactor. The converter is then controlled so that a drive command for the selected switching element is generated. In this way, the efficiency of the converter is improved while a voltage step-up or step-down operation is performed by the converter.

Abstract: A charging unit comprises a first input connectable to a first power source, a second input connectable to a second power source, and an output for connection to a battery to be charged. The charging unit also comprises a power supply unit operable simultaneously to provide power from the first input and power from the second input to the output.

Abstract: Systems and methods of voltage based switching of a power supply system current are disclosed. In one embodiment, a power supply system includes a power bus to supply electrical power to a system load. A power supply is coupled to the power bus. The power supply provides current to the power bus and generates a voltage ?. In addition, the system includes an additional power supply coupled to the power bus. The additional power supply generates a voltage ? that is lower than the voltage ?. An oring module restricts the additional power supply from providing current to the power bus, until a power bus voltage ? is greater than a threshold voltage.

Abstract: This invention is generally concerned with power supply circuits, and more particularly, with circuits to supply power to a mains supply, such as domestic grid mains, from a photovoltaic device. A photovoltaic power conditioning circuit for providing power from a photovoltaic device to an alternating current mains power supply line, the circuit comprising: a DC input to receive DC power from said photovoltaic device; an AC output configured for direct connection to said AC mains power supply line; a DC-to-AC converter coupled to said DC input and to said AC output to convert DC power from said photovoltaic device to AC power for output onto said power supply line; and an electronic controller directly coupled to said power supply line to measure a voltage of said power supply line and a current in said supply line and to control said DC-to-AC converter responsive to said measuring.

Abstract: An apparatus comprises a first energy storage device configured to output a DC voltage, a first bi-directional voltage modification assembly coupled to the first energy storage device, and a charge bus coupled to the first energy storage device and to the first bi-directional voltage modification assembly. The apparatus also comprises high-impedance voltage source coupleable to the charge bus and a controller configured to monitor a transfer of charging energy supplied from the high-impedance voltage source to the first energy storage device. The controller is also configured to compare the monitored transfer of charging energy with a threshold value and, after the threshold value has been crossed, control the first bi-directional voltage modification assembly to modify one of a voltage and a current of the charging energy supplied to the first energy storage device.

Abstract: A drive circuit comprising a DC bus configured to supply power to a load, a first fuel cell coupled to the DC bus and configured to provide a first power output to the DC bus, and a second fuel cell coupled to the DC bus and configured to provide a second power output to the DC bus supplemental to the first fuel cell. The drive circuit further includes an energy storage device coupled to the DC bus and configured to receive energy from the DC bus when a combined output of the first and second fuel cells is greater than a power demand from a load, and provide energy to the DC bus when the combined output of the first and second fuel cells is less than the power demand from the load.

Abstract: In an uninterruptible power supply apparatus, a common mode current flowing from nodes (N1 to N3) to a line of a ground voltage (GND) through a stray capacitance (41) of a battery (40) is limited by a common mode reactor (34), and the low-level common mode current passing through the common mode reactor (34) is caused to flow to a virtual neutral line (NL) through a common mode capacitor (37). Therefore, the level of noise caused by the common mode current can be reduced.

Abstract: We describe a photovoltaic (PV) panel system comprising a PV panel with multiple sub-strings of connected solar cells in combination with a power conditioning unit (microinverter). The power conditioning unit comprises a set of input power converters, one connected to each sub-string, and a common output power conversion stage, to provide power to an ac mains power supply output. Integration of the micro-inverter into the solar PV module in this way provides many advantages, including greater efficiency and reliability. Additionally, embodiments of the invention avoid the need for bypass diodes, a component with a high failure rate in PV panels, providing lower power loss and higher reliability.

Abstract: A voltage application unit causes switching elements to apply voltage to flow an electric current into corresponding windings to generate a revolving magnetic field. A period derivation unit derives an energization period of the windings. A signal generation unit generates a PWM signal for causing the voltage application unit to activate and deactivate the switching elements, such that a duty ratio decreases gradually in a predetermined time period subsequent to the derived energization period. A period specifying unit specifies a detection period of an electric current, which is supplied from the switching elements presently switched and deactivated, by a predetermined time period between an edge, which is caused when the PWM signal changes in level to deactivate the switching elements, and a time point in advance of the edge in the energization period.

Abstract: A method and apparatus for transmitting data in a wireless communication system are disclosed, which transmit uplink data in consideration of mobile station (MS) consumption power such that a UE can be stably operated at a cell edge. A method for transmitting data by a mobile station (MS) of a wireless communication system includes transmitting, if MS power consumption is higher than limitation of power consumption, data to a base station (BS) with power higher than the limitation of power consumption using power supplied from a primary power-supply unit and a storage unit during a first time, and charging the storage unit using the primary power-supply unit during a second time, wherein the limitation of power consumption indicates maximum power amount capable of being normally supplied from the primary power-supply unit.

Abstract: In a hybrid vehicle including: a first battery; a first boost converter for converting an output voltage of the first battery and outputting the output voltage to a motor generator; a second battery; and a second boost converter for converting an output voltage of the second battery and outputting the output voltage to the motor generator, an ECU performs HV drive control for driving the hybrid vehicle by using driving power of both an engine and the motor generator, and stops the second boost converter, when an SOC(1) that is a value indicating a state of charge of the first battery is smaller than a threshold value ? or when an SOC(2) that is a value indicating a state of charge of the second battery is smaller than a threshold value ?.

Abstract: A photovoltaic power generating device comprising a current collecting box side detector for detecting a ground fault in each of the photovoltaic strings, a switch disposed in correspondence to each of the photovoltaic strings and interposed between the photovoltaic string and a connecting cable, a current collecting box including a control unit providing an on/off control of the switch according to the detection result from the detector, a detector for detecting a ground fault in a connecting cable between the current collecting box and the power conditioner, a switch interposed between the connecting cable and the inverter, and a power conditioner having a control unit providing an on/off control of the switch according to the detection result from the detector.

Abstract: A method of converting a direct voltage generated by a decentralized power supply system into three-phase alternating voltage by means of a plurality of single-phase inverters (WR1-WR3), said alternating voltage being provided for supplying an electric mains, is intended to avoid inadmissible load unbalances using single-phase inverters. This is achieved in that, upon failure of one inverter (WR1-WR3), an asymmetrical power supply distribution is reduced by limiting the output of the other inverters. The method makes it possible to simplify three-phase voltage monitoring.