The invention discloses an islanding detection method in DC microgrids based on MPPT trapezoidal voltage disturbance. The steps are as follows: start the MPPT strategy; set the starting signal threshold of disturbance; measure the output current of PVA at the maximum power; calculate the same environmental factor of PVA with different capacities under the same light intensity and temperature in real time; when the environmental factor is greater than the starting signal threshold of the disturbance, periodic trapezoidal disturbance is carried out to the PVA port voltage reference; if the PCC voltage Upcc exceeds the threshold set by the passive method, it is judged as islanding; otherwise, it is judged whether the change rule of Upcc is consistent with the change rule of the calculated PCC voltage Upccp under the trapezoidal disturbance; If it is consistent, it is judged as islanding; otherwise, it is pseudo islanding.

An electric power supplying device including: a first sensing section that senses a first output current from a first DCDC converter provided between a high-voltage system and an auxiliary device system; a second sensing section that senses a second output current from a second DCDC converter provided between the high-voltage system and the auxiliary device system; a third sensing section that senses a third output current from an auxiliary device battery connected to the auxiliary device system; and a control section that controls output of the second DCDC converter on the basis of results of sensing of output currents by the first sensing section, the second sensing section and the third sensing section.

An electric power supplying device including: a first sensing section that senses a first output current from a first DCDC converter provided between a high-voltage system and an auxiliary device system; a second sensing section that senses a second output current from a second DCDC converter provided between the high-voltage system and the auxiliary device system; a third sensing section that senses a third output current from an auxiliary device battery connected to the auxiliary device system; and a control section that controls output of the second DCDC converter on the basis of results of sensing of output currents by the first sensing section, the second sensing section and the third sensing section.

A power system provides power from a power source to a load via a distribution bus, and includes a DC-DC converter coupled in parallel with a network of switching elements coupled between an output terminal of the power source and the distribution bus. A controller is configured to selectively activate or deactivate the DC-DC converter and each of the switching elements to enable the power source to power the load via the distribution bus. The switching elements may be transistors, and the diodes may be parasitic body diodes of the transistors. The power source may be a battery, such as a rechargeable battery. An output voltage level from the battery may be regulated by the controller as a function of operation of the DC-DC converter and a number of the activated or deactivated transistors.

A power system provides power from a power source to a load via a distribution bus, and includes a DC-DC converter coupled in parallel with a network of switching elements coupled between an output terminal of the power source and the distribution bus. A controller is configured to selectively activate or deactivate the DC-DC converter and each of the switching elements to enable the power source to power the load via the distribution bus. The switching elements may be transistors, and the diodes may be parasitic body diodes of the transistors. The power source may be a battery, such as a rechargeable battery. An output voltage level from the battery may be regulated by the controller as a function of operation of the DC-DC converter and a number of the activated or deactivated transistors.

A power supply system includes: a voltage converter that converts a voltage between first and second power circuits; a power controller that controls charging and discharging of first and second batteries; a cooling output controller that controls cooling output for the second battery; a temperature remaining-capacity acquirer that acquires a temperature remaining-capacity T2_mar; and a cooling remaining-capacity acquirer that acquires a cooling remaining-capacity PC2_mar depending on a difference between maximum cooling output and the cooling output of the second cooler. The power controller is configured to stop the voltage converter in a case where at least one of the temperature remaining-capacity T2_mar and the cooling remaining-capacity PC2_mar is less than an associated one of a threshold value for the temperature remaining-capacity and a threshold value for the cooling remaining-capacity and a potential difference between the first and second batteries is equal to or more than a potential difference threshold value.

A hybrid power-generator system includes an engine, an electric generator, first and second rectifiers, first and second DC-DC voltage converters, a DC bus, an inverter, and one or more controllers. The system provides a unique method of joining two power sources such that the relative proportion utilized can be changed to any value seamlessly, such as to avoid daily and/or seasonal variations in utility charges. Since the AC output portion of the circuit is independent of the utility grid, power can be supplied at variable frequencies to motor loads with significant positive impacts in load efficiency. Power increases required by the load(s) that occur rapidly can utilize the electrical grid to assist for the brief transient, allowing the engine, which is maintained at a fixed and wide-open-throttle position, to continue operation and in a more gradual process to resume its blend target for power generation.

A photovoltaic power generation system and a method for controlling power balance are provided. The system includes at least two photovoltaic arrays, at least one power balance circuit and a power converter. Each of input ports of the power balance circuit is connected with at least one photovoltaic array, and an output port of the power balance circuit is connected with the power converter. The power balance circuit performs power transfer based on a difference between output powers of the two photovoltaic arrays to control a difference between powers of two output terminals of the power balance circuit to be within a preset range.

A photovoltaic power generation system and a method for controlling power balance are provided. The system includes at least two photovoltaic arrays, at least one power balance circuit and a power converter. Each of input ports of the power balance circuit is connected with at least one photovoltaic array, and an output port of the power balance circuit is connected with the power converter. The power balance circuit performs power transfer based on a difference between output powers of the two photovoltaic arrays to control a difference between powers of two output terminals of the power balance circuit to be within a preset range.

System and methods for passive power sharing of parallel sources are provided. Aspects include a first DC power supply including a first generator and a rectifier circuit, a second DC power supply including a second generator and a second rectifier, wherein a first output of the first DC power supply and a second output of the second DC power supply are commonly coupled at a common bus point, a first current sensing device coupled between the first output of the first DC power supply and the common bus point, a first generator controller configured to receive a first current signal from the first current sensing device, analyze the first current signal to determine a first voltage droop value based on the first current signal, and operate the first DC power supply to reduce a first voltage output of the first DC power supply by the first voltage droop value.