A power converter including a three-input direct current converter capable of performing maximum power point tracking on three power inputs, a step down converter capable of voltage step down of the three power inputs, a bus capacitor and a balance circuit utilizing switches and transformers utilized to balance voltages of the bus capacitor, a three-level inverter capable of creating alternating current voltages for the alternating current grid, an output filter electrically coupled to the three-level inverter, a contactor capable of disconnecting the bus capacitor and the balance circuit from the alternating current grid, and a parameter sensor and a field programmable gate array controller electrically coupled to the power converter, capable of controlling a plurality of power switches based on at least one sensed parameters.

A system includes a central analysis station and a display. The central analysis station may be configured to receive a unique identifier and performance data from each of a plurality of solar panels. The central analysis station may detect a problem in at least one of the plurality of solar panels based on the performance data. A display may be configured to display a status of the at least one of the plurality of solar panels based on the detected problem.

Circuits integrated or integrable with a photovoltaic panel to provide built-in functionality to the photovoltaic panel including safety features such as arc detection and elimination, ground fault detection and elimination, reverse current protection, monitoring of the performance of the photovoltaic panel, transmission of the monitored parameters and theft prevention of the photovoltaic panel. The circuits may avoid power conversion, for instance DC/DC power conversion, may avoid performing maximum power tracking to include a minimum number of components and thereby increase overall reliability.

Distributed maximum power point tracking systems, structures, and processes are provided for power generation structures, such as for but not limited to a solar panel arrays. In an exemplary solar panel string structure, distributed maximum power point tracking (DMPPT) modules are provided, such as integrated into or retrofitted for each solar panel. The DMPPT modules provide panel level control for startup, operation, monitoring, and shutdown, and further provide flexible design and operation for strings of multiple panels. The strings are typically linked in parallel to a combiner box, and then toward and enhanced inverter module, which is typically connected to a power grid. Enhanced inverters are controllable either locally or remotely, wherein system status is readily determined, and operation of one or more sections of the system are readily controlled. The system provides increased operation time, and increased power production and efficiency, over a wide range of operating conditions.

In large PV power plants, grounding of individual PV modules may lead to problems. The present invention overcomes such problems. The basis for the invention is a PV power plant comprising one or more PV generators, each comprising a PV string and an inverter with a DC input and an AC output. The PV string comprises at least one PV module and is electrically connected to the DC input of the inverter. The inverter comprises means for controlling the DC potential at the DC input depending on the DC potential at the AC output. The AC outputs of the inverters are coupled in parallel. The novel feature of the invention is that the PV power plant further comprises an offset voltage source, which controls the DC potential at the AC outputs. Thereby, the DC potential at the DC input will be indirectly controlled, and it is thus possible to ensure that the potentials with respect to ground at the terminals of the PV modules are all non-negative or all non-positive without grounding the PV modules. Ground loops can be avoided, and there is no need for the use of transformer-based inverters.

A method for detecting a potential-induced degradation (PID) of PV modules of a PV installation includes operating a PV generator at a maximum power point (MPP), at a first generator voltage (U.sub.1) and first generator current (I.sub.1), and at a second generator voltage (U.sub.2) and second generator current (I.sub.2), where a first power (P.sub.1) at the first generator voltage (U.sub.1) is in a predefined first ratio V.sub.1=P.sub.1/P.sub.MPP and V.sub.1≤1, with the power (P.sub.MPP) at the maximum power point (MPP) of the PV generator, and where a second power (P.sub.2) at the second generator voltage (U.sub.2) is in a predefined second ratio V.sub.2=P.sub.2/P.sub.1 and V.sub.2<1, with the first power (P.sub.1) of the PV generator, and where a quantity Y that characterizes a progress of the potential-induced degradation (PID) is determined from the values of the voltages (U.sub.1, U.sub.2) and/or the currents (I.sub.1, I.sub.2).

A method and associated apparatus for feeding electric power from a photovoltaic system via a grid connection point into an AC grid having a low short-circuit power is disclosed. The method includes connecting a DC voltage side of at least one first inverter of the photovoltaic system to a photovoltaic generator and an AC voltage side of the at least one first inverter to the grid connection point, wherein the at least one first inverter is operated as a current source, and connecting an AC voltage side of a second inverter of the photovoltaic system to the grid connection point, wherein the second inverter is operated as a voltage source based on measurement values of an AC voltage measured in the region of the photovoltaic system and a predefined characteristic curve. For a first total short-circuit power of all first inverters operated as a current source, and a second total short-circuit power of the AC grid and of the second inverter operated as a voltage source, a ratio of the second total short-circuit power to the first total short-circuit power is greater than or equal to 2.

Aspects of the present invention relate to a method of controlling a hybrid power plant connected to a power network. The hybrid power plant comprises at least two types of renewable energy generator having an active power reserve for supplying additional active power. The method comprises, during a frequency event detected on the power network: determining an additional amount of active power to be provided to the power network to provide fast frequency response; calculating, based on a preset configuration and the active power reserve of the generators, a contribution from each of the at least two types of generator for supplying the additional amount of active power; and generating and dispatching active power requests to the generators for supplying the additional amount according to the calculated contributions.

A serial-parallel converter protection system includes a controller, a drive, a first switching transistor, and a second switching transistor. An input terminal of a converter is connected to an output terminal of the converter through the first switching transistor. The output terminal of the converter is connected in parallel with the second switching transistor. When an output voltage of the converter is greater than a first threshold, the controller controls the first switching transistor to be turned off and controls the second switching transistor to be turned on. In some embodiments, when the output voltage of the converter is greater than the first threshold, the controller controls the first switching transistor to be turned off and controls the second switching transistor to be turned on, so that the converter is bypassed, thereby preventing a voltage and a current from impacting a component inside the converter.

A photovoltaic power generation system and a method and a device for detecting an earth fault of a photovoltaic string. The controller obtains a terminal voltage of each photovoltaic string before voltage disturbance, where the terminal voltage is a voltage to earth of a positive electrode or negative electrode of the photovoltaic string; performs voltage disturbance on each photovoltaic string and obtains a terminal voltage of each photovoltaic string after the voltage disturbance; determines a photovoltaic string with an earth fault based on the terminal voltage of each photovoltaic string before and after the voltage disturbance; obtains a photovoltaic panel with an earth fault by using the terminal voltage and an output voltage of the photovoltaic string before the voltage disturbance, or obtains a photovoltaic panel with an earth fault by using the terminal voltage and an output voltage of the photovoltaic string after the voltage disturbance.