2140 results about "Photovoltaic inverter" patented technology

A method to convert direct current (DC) power generated by a photovoltaic (PV) arrays to alternating current (AC) power using a PV inverter, the method includes: applying the DC power generated the PV array to the PV inverter; boosting the DC power from the PV array from a predetermined voltage level to a predetermine DC link voltage, wherein the PV array is regulated by the boosting to output a voltage at the predetermined voltage level; converting the boosted DC power to AC power, and disabling the boost of the power generated by the PV array after the array has a predetermined voltage level at least as great as the DC link voltage.

A power inverter system includes a DC to AC inverter configured to convert DC voltage from a DC power source to AC voltage. A DC link couples the DC power source and the inverter. An inverter pre-charger operates to pre-charge the inverter to achieve a desired DC link voltage prior to connecting the power inverter system to an AC power grid. A phased lock loop synchronizes the pre-charged inverter to the AC power grid prior to connecting the power inverter system to the AC power grid. The pre-charged inverter regulates the DC link voltage to about the minimum voltage level that allows control of AC grid currents via the inverter subsequent to connecting the power inverter system to the AC grid. The inverter operates in a maximum power point tracking control mode only subsequent to a first voltage transient caused by connecting the DC power source to energize the power inverter system.

The present invention relates to a photovoltaic three phase synchronization control method realizing maximum power tracking swiftly and stably, which belongs to the technical field photovoltaic power generating control. The method includes the steps as follows: judging the DeltaP/DeltaV value according to the power difference DeltaP between the current time k and the previous time and the voltage difference DeltaV; working out the Iref(k) when the photovoltaic array produces the maximum power; using the Iref(k) to adjust the uq* under the coordinates in vectorial synchronous rotation with the electric network voltage; acquiring six ways of space vectorial SVPWM impulse series according to the rotation angle degree Theta of the three phase electric network voltage, with the aim to control the inverter in order to ensure that the output current of the photovoltaic inverter has the same phase position as that of the mains voltage while ensuring the photovoltaic array is realizing the maximum power output tracking. The power factor is 1. The present invention also can adjust the Idref(k) according to local load requirements, therefore achieving adjustment to the power factor, with low synchronization current harmonic wave distortion factor.

A photovoltaic (PV) inverter system operates continuously in a buck converter mode to generate a sum of full wave rectified sine wave currents at a current node common to a plurality of buck converters in response to a plurality of full wave rectified sine wave currents generated via the plurality of buck converters. The PV inverter system increases the level of the voltage sourcing each buck converter when a corresponding DC power source voltage is lower than the instantaneous voltage of a utility grid connected to the PV inverter system.

A photovoltaic system, method and apparatus are disclosed. In an exemplary embodiment, the system includes a first and second inputs adapted to couple to a first and second rails of a photovoltaic array; an inverter configured to convert DC power from the photovoltaic array to AC power; and an interface portion coupled to the first and second inputs and the inverter, the interface portion configured to isolate at least one of the first and second inputs from the inverter and to modulate an application of a voltage from the photovoltaic array to the inverter so as to increase a load on the photovoltaic array and to reduce the voltage applied from the photovoltaic array to the inverter.

The invention relates to a three-phase four-wire three-level photovoltaic grid-connected inverter and a control method thereof. In the inverter, voltage input from a solar panel is filtered by a filter capacitor; the input voltage is boosted by a boosting circuit to form direct-current bus voltage serving as input voltage of a post inversion circuit; the bus voltage is inverted by a three-phase four-wire inversion circuit to form three-phase voltage; after being filtered by a filtering circuit, the three-phase voltage is output to a power grid; a controller detects the voltage and output current of the solar panel, the three-phase voltage of the power grid and three-phase current output by the three-phase four-wire inversion circuit; a boosting converter and an inversion controller in thecontroller 101 respectively generate driving pulses of the boosting circuit and the three-phase four-wire inversion circuit to control the operation of the integral inverter. A three-phase four-wire power supply system is formed by the addition of a neutral line, so the inverter can be connected with symmetrically-balanced three-phase loads, and also can be connected with single-phase loads. The application field of the photovoltaic inverter is broadened while the safety of the power supply system is improved.

The invention discloses a device and method for detecting faults of a solar power generation system. The solar power generation system comprises a plurality of solar cell panel set strings and a photovoltaic inverter. The device comprises a plurality of fault detecting units, a current converging device, a control system and an auxiliary power source. Each fault detecting unit comprises a control switch, the input ends of the fault detecting units are connected with the solar cell panel set strings respectively, the output ends of the fault detecting units are connected with the input end of the current converging device, and the fault detecting units are used for detecting the relevant parameters of the solar cell panel set strings, wherein the relevant parameters comprise the working voltage and the working current or the open-circuit voltage and the short-circuit current. The current converging device is used for collecting the direct currents output by the fault detecting units. The control system is connected with the fault detecting units, and is used for comparing the relevant parameters with the history parameters of each solar cell panel set string, analyzing the fault situation and controlling the on-off state of the control switches according to the fault situation. The auxiliary power source is used for supplying electricity to the fault detecting units and the control system. The device can directly detect the open-circuit voltage and the short-circuit current, and a fuse is prevented from being replaced.

The invention discloses a reactive voltage control method of a photovoltaic power station, which uses a photovoltatic power station synchronization point as a control target and reactive power as a regulating quantity. According to the reactive demand of the photovoltaic power station, a reactive power supply of the photovoltaic power station is integrally planed, the reactive output of each photovoltaic inverter and reactive compensating device in the photovoltaic power station is determined, and coordination control of the photovoltaic inverters and the reactive compensating devices in the photovoltaic power station is realized; and protection restraint conditions of the photovoltaic inverters and the reactive compensating devices are fully considered, and the photovoltaic inverters and the reactive compensating devices, which do not meet the restraint conditions, do not participate in the reactive voltage control. The control method provided by the invention can ensure that the reactive output of the photovoltaic power station synchronization point meets the system load change and inhibits the bus voltage fluctuation caused by load change, and has the function of maintaining the voltage of the photovoltaic power station synchronization point to be stable.

The invention discloses an overrunning virtual synchronous generator (VSG+) method with rotary inertia and damping self-optimization-trending. The method comprises the following steps: step one, a mechanical equation and an electromagnetic equation of a virtual synchronous generator (VSG) are established; step two, the rotary inertia J and damping D in a VSG model are increased as |delta f| is increased, wherein delta f is an absolute value of a difference between a power network rated frequency and the actual frequency of the VSG; and step three, according to self-adjustment of the rotary inertia J and the damping D, closed-loop control is performed on the |delta f|, and finally, grid connection of a distributed photovoltaic power generation system is realized. According to the VSG+ method with the rotary inertia and damping self-optimization-trending, provided by the invention, the rotary inertia J and the damping D in the VSG are adaptively adjusted as the |delta f| changes, the rotary inertia J and the damping D after adjustment then perform feedback regulation on the |delta f|, and finally, zero impact during grid connection of photovoltaic inverters is realized, such that the acceptance capability of a power network for the distributed photovoltaic power generation system is improved.

The invention discloses a method for detecting an island of a photovoltaic grid-connected inverter. The method comprises the following steps of: 1), detecting a voltage frequency at a common coupling point of the inverter and a power grid, wherein when the voltage frequency is between f11 and f12, a phase position of output current of the inverter is the same to that of voltage at the coupling point; and, by modifying the phase position between the output current of the inverter and the voltage at the coupling point, compared with the voltage at the coupling point, the output current is ahead of time in theta degrees (when fgrid is more than f12 and less than f22) or lags in theta degrees (when fgrid is more than f21 and less than f11); and 2), to compensate a dead zone appeared in frequency detection, judging whether an island effect exists by modifying an amplitude value of the output current of the inverter within one power frequency period after every four power frequency periods and recovering the amplitude value of the output current into an original value after the period. According to the method, harmonic waves output by the inverter to the power grid can be effectively reduced; the detection time is short; the calculation method is simple; and the computing resource of a control chip can be saved.

A photovoltaic power generation system is disclosed, which can allow a user to easily acquire information on a photovoltaic inverter, easily control the photovoltaic inverter, and save electric charges.

The invention relates to a current foldback circuit of photovoltaic inverters which comprises a main current foldback circuit, an overcurrent protection driving circuit and an overcurrent protection control circuit. The main current foldback circuit is connected with the overcurrent protection control circuit by the output terminals of IT1M, IT2-A and IT2-B; the overcurrent protection control circuit is connected with the overcurrent protection driving circuit by the terminals of IDRV+ and IDRV-; and the overcurrent protection driving circuit is connected with the main current foldback circuit by the terminals of IG and IE. The DC side current sensor IT1 in the main current foldback circuit samples the current in the DC busbar, the AC side current sensor IT2 samples the AC output current, the two sample values are output to the overcurrent protection control circuit which sends out the control signals to the overcurrent protection driving circuit by logistic judgment, the overcurrent protection driving circuit transforms the control signal to the signal for driving an overcurrent protection switching tube IGT1, so as to control on and off of the switching tube IGT1.

The invention relates to a photovoltaic system for feeding three-phase current to a power grid that includes several monophase or three-phase photovoltaic inverters that can be connected to the power grid at the output end and are each fitted with a disconnecting device at the output end. The system includes several photovoltaic generators that are connected to the input end of the photovoltaic inverters. A central control and monitoring unit is connected between the photovoltaic inverters and the power grid. The control and monitoring unit has a grid monitoring device at the feeding point to the grid to measure one or more grid parameters. At least one communication link is provided between the individual photovoltaic inverters or the individual disconnecting devices and the connected central control and monitoring unit such that the connecting devices can disconnect the individual photovoltaic inverters from the power grid by means of a control instruction signal of the communication link. The central control and monitoring unit includes a load unbalance recognition component and a load unbalance regulation component, wherein the regulation includes limiting the power variation between the individual phases to a predetermined value.

The invention discloses a cascaded photovoltaic grid-connected inverter and a control method. The cascaded photovoltaic grid-connected inverter has the advantages of high voltage level, high power level, high power quality and the like, and can realize direct high voltage grid connection without any transformer to save cost and an occupied area. The inverter comprises a photovoltaic array and a plurality of cascaded unit bodies. The photovoltaic array comprises a plurality of photovoltaic units of which each is connected with the input side of a corresponding unit body. Each unit body is a single-stage single-phase photovoltaic grid-connected inverter which comprises a DC bus capacitor and an H bridge inverter circuit, wherein the DC bus capacitor is connected in parallel to the input endof the single-stage single-phase photovoltaic grid-connected inverter; and the H bridge inverter circuit is connected in parallel with the DC bus capacitor.

The invention discloses a solar parking shed capable of charging automobiles. The solar parking shed comprises a sun shield, a solar battery pack structure and a control system, wherein the sun shield is supported by a plurality of props, and the solar battery pack structure comprises a plurality of solar panels; the solar panels are connected with a photovoltaic array shunt box through wires; the photovoltaic array shunt box is connected with a photovoltaic system controller through a DC circuit breaker; the photovoltaic system controller is connected with a storage battery; the storage battery is connected with a plurality of charging piles capable of charging the automobiles orderly through an independent photovoltaic inverter and a dual-power change-over switch; the charging piles are connected with a cable of the urban electric network through a dual-power change-over switch; the solar electric power generation is parallel in the urban electric network; and the solar battery pack structure is also improved. The invention can be used for charging the parked automobiles and incorporate the excess electric energy into the urban electric network, and the electric energy of the urban electric network can be automatically supplied to the charging piles, thereby greatly increasing the utilization ratio of the electric energy.

The invention discloses an electric arc fault detection method and device for a photovoltaic inverter and a photovoltaic inverter. The electric arc fault detection method comprises steps of obtaining a photovoltaic inverter DC side current signal, obtaining a current signal frequency spectrum characteristic according to the current signal, determining whether the current signal frequency spectrum characteristic has an arc spectrum characteristic, shutting down the photovoltaic inverter if the current signal spectrum characteristic has the electric arc spectrum characteristic, obtaining first input voltage when the photovoltaic inverter is shut down and obtaining second input voltage since the shutting down until after preset time, calculating voltage drop between the first input voltage and the second input voltage, and determining whether an arc fault happens according to the voltage drop. The arc fault detection method and device for the photovoltaic inverter and the photovoltaic inverter can effectively reduce misjudgment on the arc fault because of interference of the inverter and solves a false triggering problem of the corresponding protection device.

The invention discloses a reactive power and voltage control method for grid-connected inverters of a large photovoltaic power station. The method comprises steps as follows: a voltage reference unit gives reference voltage uref to a voltage control point; a reactive power setting unit is used for comparing actual voltage of the voltage control point with the reference voltage to obtain voltage deviation, and reactive power reference quantity Qref required by maintaining voltage of the voltage control point is automatically acquired through a PID (proportional-integral-derivative) controller; a reactive power distribution unit automatically performs reactive power distribution between SVG (scalable vector graphics) and each photovoltaic power generation unit; the grid-connected inverters in the photovoltaic power generation units adopts distribution in equal proportion of reactive capacity. According to the method, coordinated control of a reactive power compensation device of the photovoltaic power station and the photovoltaic inverters is sufficiently utilized, grid-connected point voltage fluctuation of the photovoltaic power station is reduced, reactive power support is provided for a power grid, and voltage stability of a weak grid is improved; meanwhile, reactive power is distributed according to line loss of the photovoltaic power generation units, and active loss of the photovoltaic power station is reduced; therefore, the reactive power and voltage control method facilitates safe, economic and stable operation of the large photovoltaic power station accessing the weak grid.

The application provides a distributed photovoltaic inverter system and a power-limiting control method thereof. An inverter generates and outputs a power difference value according to a preset power limit value and a grid-connected main power obtained by real-time collection; and when the power difference value meets a preset power-limiting condition, power adjusting modules in N independent power optimizers adjust PV voltages at respective input sides synchronously until the power difference value does not meet the preset power-limiting condition. Therefore, power-limiting control of the distributed photovoltaic inverter system is realized without the need to limit the grid-connected current of the inverter. Besides, because the PV voltages at respective input sides of all power optimizers are adjusted synchronously until the power difference value does not meet the preset power-limiting condition, the output limiting on the total output power of the whole inverter system is realized, so that problems in the prior art are solved.

The invention discloses a low-voltage ride-through method for a photovoltaic inverter. The method comprises the following steps of: acquiring a power grid bus side voltage by using a voltage sensor, causing the power grid bus side voltage to pass through a conditioning circuit and transmitting the power grid bus side voltage into a digital signal processor; capturing and calculating a standard voltage amplitude value by using the digital signal processor; judging whether the standard voltage amplitude value is less than a set lower low-voltage limit or not; if the standard voltage amplitude is less than the set lower low-voltage limit, disconnecting the inverter from a contactor of a power grid; on the contrary, judging the duration of the standard voltage amplitude at the lower limit, keeping the inverter connected with the power grid if the duration is less than a standard, and on the contrary, disconnecting the inverter from the power grid; judging whether a power grid voltage unit value is less than a set upper voltage limit or not; performing grid-connection normally on the inverter if the power grid voltage unit value is greater than the set upper voltage limit; on the contrary, judging the duration of the power grid voltage unit value at the upper limit, keeping the inverter connected with the power grid if the duration is less than the standard, and on the contrary, disconnecting the inverter from the power grid; adopting the internally set voltage reference amplitude of the digital signal processor; and realizing inversion by taking the voltage reference amplitude as an inverter reference voltage.