Fast frequency modulation response communication method for photovoltaic power station with group series inverter

Abstract

The invention discloses a fast frequency modulation response communication method for a photovoltaic power station with a group series inverter. After a frequency regulating system sends a power setting command to a secondary power control device, the secondary power control device calculates the active power target values of all the inverters and broadcasts instructions containing the active power target values of all the inverters. After the inverters receive the instructions, no reply confirmation is required and the active power setting values corresponding to their own communication addresses can be analyzed and executed. A transformer measurement and control device is connected to the secondary power control device through RS485. The secondary power control device directly collects the active power on the transformer side and uploads it to the frequency regulating system. The frequency regulating system performs closed-loop regulation again according to the feedback value. The fast frequency modulation response communication method saves the time for collecting inverter operation data and the time for sequentially issuing instructions.

Description

technical field [0001] The invention relates to the technical field of frequency modulation of a string inverter photovoltaic power station, in particular to a fast frequency modulation response communication method for a string inverter photovoltaic power station. Background technique [0002] With the continuous increase of the installed capacity of photovoltaic power stations, the instability of active power of photovoltaic power stations increases the instability of frequency. According to the requirements of "Technical Regulations for Connecting to Electric Power System", photovoltaic power plants need to participate in the frequency regulation and peak regulation of the power grid. The current regulation method is mainly that after the frequency regulation system receives the frequency regulation command, it calculates the corresponding active power target value and sends it to the secondary power control The device is calculated by the secondary power control device a...

AI Technical Summary

Problems solved by technology

Due to the large number of inverters in the large string inverter photovoltaic power station, in order to reduce the load of the frequency modulation system, the frequency modulation system is connected to the secondary control equipment through optical fiber or network cable, and sends the active power target value to the secondary power control device. The primary power control device redistributes active power to the string inverter. Currently, RS485 or power carrier communication is basically used between the secondary power control device and the string inverter. There are two commonly used communication methods. The first One is to use the broadcast equal sharing method when pursuing control speed, that is, the active power of each string inverter connected to the secondary power control device is the same, and the broadcast is issued, but this method will lead to active power control. The accuracy is low, which is obvious in mountainous photovoltaic power stations. The second type adopts point-to-point rotation mode when pursuing control accuracy, that is, the secondary power control device calculates the active power of each inverter according to the operation status of each inverter. The power is sent point-to-point sequentially, but this method will lead to slow control speed, and the response time of active power adjustment is generally 20s. Since RS485 and power carrier are both bus-type networks, the secondary power control device is querying the inverter. Active power can only be queried sequentially. Due to the transmission bandwidth limitation of RS485 and power carrier network, the time for the secondary power control device to collect the active power data of the inverter generally takes about 15s

[0003] Using the above two adjustment methods can meet the needs of participating in secondary frequency regulation under the traditional AGC system. However, in recent years, with the grid connection and commissioning of large-scale new energy power stations in Northwest China, the proportion of new energy power generation capacity in the Northwest Power Grid has greatly increased. The power grid has put forward higher and higher requirements for the frequency modulation capability of new energy power stations. With the rapid frequency response function of new energy stations vigorously promoted by the Northwest Power Grid, traditional communication methods have been unable to meet the "New Energy Station Fast Frequency Response Performance Requirements" "The parameter requirements of "New Energy Station Fast Frequency Response Performance Requirements" require that the active power adjustment time of the photovoltaic station should not exceed 2s, and the time for the adjustment amount to reach 90% of the target value should not exceed 5s, and the active power should not reach stability. More than 15s, the active power adjustment cycle is not greater than 1s. When the inverter active power setting command is sent in the point-to-point rotation mode, the time to send all the inverter setting commands is much longer than 1s

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