Embodiments of the present disclosure provide a voltage stabilizing circuit and a DC microgrid. The voltage stabilizing circuit includes: a first input terminal and a second input terminal for receiving power input; a switch unit including a first switch and a second switch, a first end of the first switch being connected to the first input terminal, and a first end of the second switch being connected to the second input terminal; an isolation unit including a first inductor and a second inductor, a first end of the first inductor being connected to a second end of the first switch, and a first end of the second inductor being connected to a second end of the second switch; an adjustment unit connected to second ends of the first inductor and the second inductor, the adjustment unit being capable of storing electric energy of the power input and providing a regulated power input; and a first output terminal and a second output terminal, the first output terminal being connected to a node between the adjustment unit and the first inductor, and the second output terminal being connected to a node between the adjustment unit and the second inductor to output the regulated power input.

A dual-source facility power system includes a first electrical interface configured to receive DC power from at least one photovoltaic panel; a second electrical interface configured to receive AC power from an electric utility grid; a third electrical interface configured to deliver AC power to one or more branch circuits or appliances; and a controller. The controller is configured to monitor characteristics of AC power received from the electric utility grid. When one or more such characteristics fail to meet one or more predetermined specifications, the controller is further configured to disconnect the second electrical interface; deliver, to one or more branch circuits or appliances, AC power derived from DC power received from the at least one photovoltaic panel; and individually monitor AC current delivered to one or more of the branch circuits or appliances.

A method and circuit arrangement is described for start-up and shut-down of high power DC to AC inverters which limits inrush current for capacitor charging, reduces input and output relay contact stress and discharges internal capacitors upon shut down. A preferred inrush limiting component has a higher resistance when hot than when cold, such as an incandescent filament lamp.

A DC to AC inverter for solar energy installations is configured to convert DC input power at a first voltage to a desired AC output power waveform. The inverter includes multilevel circuitry configured to define a plurality of different levels, wherein each level is defined by lower and upper voltage values; a jittering controller configured to jitter between the lower and upper voltage values in each level in order to generate a preliminary AC waveform by producing waveform values between the lower and upper voltage values within each level; and a low pass filter configured to filter the preliminary AC waveform to remove the jittering in order to provide a smooth output AC waveform.

A DC to AC converter for solar energy installations is configured to convert DC input power at a first voltage from a floating DC source to a desired AC output power waveform. The converter is configured to cause an AC output waveform at a first repetition frequency and having a voltage relative to one of at least one ground, neutral, or reference potential terminals to appear with a unique phase at each of a number N at least equal to one of a set of live AC output terminals; and a common-mode voltage waveform at a second repetition frequency to appear relative to one of the ground, neutral, or reference potential terminals and in the same phase on both of positive and negative DC input terminals, varying alike in voltage while maintaining a substantially constant differential voltage between them, the variation in voltage having substantially the same common waveform on both the positive and negative DC input terminals and transitioning between a greatest negative and a greatest positive value at a frequency equal to N times the output AC waveform first repetition frequency.

A photovoltaic system providing both grid-tie and back-up operation comprises an inverter having a first, voltage-controlled output for powering appliances, and a second, current-controlled output for grid back-feed. The second output may have a current-controlled mode when connected to the grid and a voltage-controlled mode otherwise. The first and second outputs comprise independent switching transistors, which however may be driven by the same switching control signals, such that the voltage controlled-output mimics the voltage on the current-controlled output when it is connected to the grid, and therefore tracks the grid voltage. Grid isolation relays disconnect the current-controlled inverter output from the grid if it fails. A connection bypassing the grid isolation relay is monitored by the controller for the presence and stability of the grid supply when it resumes. Both outputs follow the voltage on the voltage-controlled output when the current-controlled output is not connected to the grid.

A retention amount management system includes a detector that detects an amount of retention and a server that adjusts an amount of production of hydrogen in a production facility such that the amount of retention of hydrogen retained in the retention facility for a predetermined period attains to a target amount of retention. The server sets the target amount of retention such that a first amount of hydrogen corresponding to an amount of surplus electric power during a stable period during which electric power generated per prescribed period by using renewable energy is higher than a threshold value is larger than a second amount of hydrogen corresponding to the amount of surplus electric power during an ordinary period.

A retention amount management system includes a detector that detects an amount of retention and a server that adjusts an amount of production of hydrogen in a production facility such that the amount of retention of hydrogen retained in a retention facility for a predetermined period attains to a target amount of retention. The server sets the target amount of retention such that an amount of hydrogen corresponding to an amount of surplus electric power during a preparation period during which electric power generated per prescribed period by using renewable energy is higher than a threshold value is larger than an amount of hydrogen corresponding to the amount of surplus electric power during an ordinary period.