Series quasi Z source inverter based grid-tied PV control method

Abstract

The present invention discloses a series quasi Z source inverter based grid-tied PV control method. A PV battery inverter system is seen as a virtual synchronous generator, and an integral of an output voltage of a series quasi Z source inverter is taken as a virtual motor magnetic chain. An outer ring is controlled by using a power ring, so that active power transmission and reactive power compensation are realized. An inner ring is a current ring, so that current rapid tracking is realized. PI modulation is performed on the current inner ring, so as to generate a modulated wave signal. Three times of harmonic wave modulation is performed on a modulated signal obtained at a PV side and the modulated wave signal. On and off of an inverter bridge are controlled, so as to realize power adjustment of the grid-tied PV system. According to the method, a virtual synchronous generator quasi direct power control policy is adopted for controlling the system, the virtual magnetic chain directly orients, an alternating current voltage sensor is omitted, system reliability is improved, device cost is saved, quasi direct power control can directly control active power and reactive power of the grid-tied inverter, and the system has the advantages of simple structure and good dynamic response performance.

Description

technical field [0001] The invention relates to a photovoltaic grid-connected control method based on a series quasi-Z source inverter, and belongs to the technical field of photovoltaic grid-connected control. Background technique [0002] In the photovoltaic power generation system, the main problem is how to improve the working efficiency of solar cells. The power electronic conversion in the system is the key to solve this problem. On the one hand, the power conversion link must realize the maximum power point tracking of the solar cell, and on the other hand, it must realize the sine wave output and phase control of the inverter circuit. For two-stage or multi-stage photovoltaic grid-connected systems, these two functions are generally realized in two transformation links. For example, first implement maximum power point tracking (MPPT) control in a DC / DC link, and then implement sinusoidal current output and phase control in a DC / AC link, which is conducive to the rea...

AI Technical Summary

Problems solved by technology

[0008] Option 1 Because the system uses a traditional inverter, there is no direct working state, and the dead time added to the control signal will affect the grid-connected power quality

The voltage vector control based on the dq coordinate system involves trigonometric function transformation, which has a large amount of calculation, poor real-time performance, and complicated programming

[0009] Solution 2: Introducing the Z-source inverter into the photovoltaic grid-connected and reactive power compensation control system can effectively improve the power quality of the system, but the Z-source inverter also mainly adopts the direct current control method of voltage vector orientation. Voltage / input current and DC bus voltage, many sensors and their signal processing circuits bring high cost and complexity

Moreover, photovoltaic grid-connected inverters respond quickly and are difficult to participate in grid regulation, so they cannot provide the necessary voltage and frequency support to the distribution network like a synchronous generator, and lack a "synchronization" mechanism with the distribution network

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