An illustrative example fuel cell power plant includes a cell stack assembly having a plurality of fuel cells configured to generate electricity based on an electrochemical reaction. The power plant includes a capacitor, a plurality of inverters, and at least one controller that is configured to control the plurality of inverters in a first mode and a second mode. The first mode includes the cell stack assembly associated with at least one of the inverters. A cell stack assembly and the associated inverter provide real power to a load external to the fuel cell power plant in the first mode. The second mode includes at least a second one of the inverters associated with the capacitor. The capacitor and the second one of the inverters selectively provide reactive power to or receive reactive power from a grid external to the fuel cell power plant in the second mode.

An illustrative example fuel cell power plant includes a cell stack assembly having a plurality of fuel cells configured to generate electricity based on an electrochemical reaction. The power plant includes a capacitor, a plurality of inverters, and at least one controller that is configured to control the plurality of inverters in a first mode and a second mode. The first mode includes the cell stack assembly associated with at least one of the inverters. A cell stack assembly and the associated inverter provide real power to a load external to the fuel cell power plant in the first mode. The second mode includes at least a second one of the inverters associated with the capacitor. The capacitor and the second one of the inverters selectively provide reactive power to or receive reactive power from a grid external to the fuel cell power plant in the second mode.

A management apparatus periodically transmits information for setting a first voltage range and a second voltage range smaller than the first voltage range to a distribution power supply apparatus. The distribution power supply apparatus removes, from an interconnection point voltage at an interconnection point with the distribution system, a voltage fluctuation component with a cycle shorter than a cycle in which the information is transmitted from the management apparatus to thereby generate a voltage command value of the interconnection point, and performs reactive power control for eliminating a voltage deviation of the interconnection point voltage with respect to the voltage command value. In the reactive power control, the generation of the reactive power is started when an absolute value of the voltage deviation exceeds the first voltage range, and the reactive power is adjusted until the absolute value falls below the second voltage range.

A management apparatus periodically transmits information for setting a first voltage range and a second voltage range smaller than the first voltage range to a distribution power supply apparatus. The distribution power supply apparatus removes, from an interconnection point voltage at an interconnection point with the distribution system, a voltage fluctuation component with a cycle shorter than a cycle in which the information is transmitted from the management apparatus to thereby generate a voltage command value of the interconnection point, and performs reactive power control for eliminating a voltage deviation of the interconnection point voltage with respect to the voltage command value. In the reactive power control, the generation of the reactive power is started when an absolute value of the voltage deviation exceeds the first voltage range, and the reactive power is adjusted until the absolute value falls below the second voltage range.

A load apparatus is connected to an AC power source and is supplied with power from the AC power source. An operation state control unit controls, based on a target value about a power-source quality including either a power-source power factor of the AC power source or a power-source harmonic of the AC power source and on a present power-source quality, an operation state of the load apparatus.

A utility power regulation system includes a power converter configured to regulate one or more of a voltage and a power factor at the primary side of a step-up transformer, or at a load electrically connected to a load feeder line, based on an estimated primary-side line voltage signal. The system includes a voltage estimation circuit configured to estimate the primary-side line voltage signal from one or more signals received from a secondary-side voltage sensor, regulator line current signal, and a primary-side load feeder-line current sensor.

A utility power regulation system includes a power converter configured to regulate one or more of a voltage and a power factor at the primary side of a step-up transformer, or at a load electrically connected to a load feeder line, based on an estimated primary-side line voltage signal. The system includes a voltage estimation circuit configured to estimate the primary-side line voltage signal from one or more signals received from a secondary-side voltage sensor, regulator line current signal, and a primary-side load feeder-line current sensor.

A controller performs a first control for controlling the power source power factor or a power source harmonic of the harmonic current such that an input power factor of at least one of a plurality of connection devices changes in a direction preceding the power source power factor in a case where the power source power factor changes in a lagging direction, and performs a second control for controlling the power source power factor or the power source harmonic such that the input power factor of at least one of the connection devices changes in a direction lagging behind the power source power factor in a case where the power source power factor changes in a leading direction.

An uninterruptible power supply (UPS) system operable in an energy saver mode includes: a static bypass switch connected between an input connector and an output connector of the UPS system and being activatable to operate the UPS system in the energy saver mode; a plurality power modules, each of the plurality of power modules being connected between the input connector and the output connector of the UPS system and at least some of the plurality of power modules being controllable for a reactive power compensation; and a controller for controlling one or more of the controllable power modules depending on a data input related to a reactive power compensation. The controller controls one or more of the controllable power modules depending on the data input such that a reactive power flow via the UPS system is adjusted.

A power converter converts a medium-voltage output from a solar module to an appropriate voltage to power a solar tracker system. The power converter includes a voltage divider having at least two legs, a first semiconductor switch subassembly coupled in parallel with a first leg of the voltage divider, and a second semiconductor switch subassembly coupled in parallel with a second leg of the voltage divider. The power converter may be a unidirectional or a bidirectional power converter. In implementations, the signals for driving the semiconductor switches of the first and second semiconductor switch subassemblies may be shifted out of phase from each other. In implementations, if the bus voltages to the semiconductor switches are not balanced, the pulse width of the driving signal of the semiconductor switch supplied with the higher bus voltage is decreased for at least one cycle.