Application of power quality online monitoring device and anti-island protection device in Tesla factory distributed photovoltaic project

Abstract: With the increasing global attention to renewable energy, distributed photovoltaic power generation systems have been widely used in recent years. Distributed photovoltaic power generation systems have the advantages of environmental protection and flexibility, and can effectively alleviate energy shortage and environmental pollution problems. At the same time, power quality online monitoring devices and anti-island protection devices also play a vital role in distributed photovoltaic projects. The power quality online monitoring device can monitor the voltage, current and other parameters in the power grid in real time to ensure the stability of the power quality generated by the photovoltaic power generation system. The anti-island protection device can disconnect the grid-connection switch when a power station fails, avoiding damage to personnel and equipment and ensuring the safe operation of the photovoltaic power generation system. It can prevent power system failures, improve power system stability, optimize energy utilization, and provide data support, etc. This article will introduce the application of power quality online monitoring devices and anti-island protection devices in distributed photovoltaic power generation systems.

Keywords: distributed photovoltaic; power quality; voltage deviation; voltage fluctuation; harmonics; anti-island protection.

1. Project Overview

The Shanghai Tesla Factory is a super factory located in Pudong New Area, Shanghai, covering an area of approximately 860,000 square meters. The Shanghai Tesla factory mainly produces Model 3 and Model Y, but also includes power battery and motor assembly workshops and a research and development center. The factory adopts intelligent production lines and new manufacturing technologies. It is a modern factory integrating intelligence and automation, providing important support for Tesla's global development.

This project adds distributed photovoltaic grid connection to the original 10/0.4kV system. The power distribution system originally had 4 high-voltage cabinets, 4 transformers, and 31 low-voltage cabinets. This project adopts 0.4kV grid connection, and designs 1# grid connection point and 2# grid connection point. The photovoltaic grid connection is located at the outlet switch of the original low-voltage distribution cabinet. The power supply system diagram and the location of the grid connection cabinet are shown in Figure 1.

Figure 1 Primary system diagram of power distribution system

2. Project requirements

Photovoltaic power generation is a clean energy source, but its power quality is not stable. The uncertainty of photovoltaic power generation may lead to random fluctuations in output power, which may lead to power quality problems such as grid frequency deviation, voltage surges and dips, short-term voltage interruptions, voltage fluctuations and flickers. At the same time, photovoltaic power generation uses AC and DC inverters. Harmonic problems will occur in this link, and DC components will also flow into the power supply system.

These power quality issues can impact the plant in the following ways:

*Voltage fluctuations and flickers: cause unstable operation of motor equipment and affect the normal operation of the production line.

*Harmonic pollution: interfere with the normal operation of electronic components, causing equipment failure or damage.

*Voltage sags and short-term interruptions: lead to equipment shutdown or damage, affecting the normal operation of the production line.

*Frequency deviation: affect the normal operation of motor equipment and lead to stagnation or damage to the production line.

The online power quality monitoring device can monitor, analyze, and evaluate the power quality of the monitoring point, including real-time monitoring of power quality, power quality event alarm, wave recording, data statistics, evaluation analysis and other functions. In this way, power quality problems can be discovered and solved in time, the efficiency and stability of photovoltaic power generation can be improved, and the safe and stable operation of the power system can be guaranteed.

Islanding Effect is a common problem in photovoltaic projects. When there is a power outage on the grid side, the photovoltaic side is still in a normal power generation state and sends power to the grid side, forming an island effect. This brings a great safety threat to maintenance personnel on the grid side. The anti-island protection device can promptly cut off the connection between the photovoltaic system and the power grid to avoid the island effect, thereby protecting the safety of maintenance personnel. In addition, the anti-island protection device can also quickly cut off the connection between the photovoltaic system and the power grid when the power grid fails to avoid damage to the equipment, and automatically restores the connection to the grid after the fault is resolved, ensuring the stable operation of the photovoltaic project.

This project requires that the grid-connected point has the function of blocking power generation for 0.1s when the low voltage is lower than 50%Un, and automatically connecting to the grid when the voltage is 85%Un. At the same time, the power quality of the grid-connected point can be monitored in real time such as voltage harmonics, DC components, and voltage deviations. It needs to upload the voltage, current, active power, reactive power, anti-island protection related data and power quality data of the 1# grid connection point and 2# grid connection point to the Tesla 220kV substation; and then upload it through the original dispatch data network in the station to the dispatch center.

Based on the requirements of this project and relevant regulations, this distributed photovoltaic grid-connected project will be transformed on the original power supply system. The project added 2 grid-connected cabinets, and installed a Class A power quality online monitoring device APView500PV in each cabinet to monitor the power quality of the grid-connected point in real time. At the same time, an anti-island protection device AM5SE-IS needs to be installed. When the island effect occurs, the circuit breaker of the grid-connected cabinet can be cut off in time to avoid accidents. The specific configuration scheme is shown in Figure 2 and Figure 3.

Figure 2 1# grid-connected cabinet configuration 

Figure 3 2# grid-connected cabinet configuration scheme

The main functions implemented by various types of equipment are as follows:

3. On-site installation pictures

All types of equipment in this project are installed on-site in the switch cabinet. The on-site installation pictures are as follows. The equipment is currently running normally on site.

Figure 4 Picture of on-site installation of the device

4. Conclusion

The power quality monitoring device ensures the stability and reliability of power quality by monitoring the power quality of the photovoltaic power generation system in real time. It can promptly detect and solve potential problems, such as voltage fluctuations, flicker, harmonic pollution, etc., to ensure the normal operation of the photovoltaic power generation system. At the same time, power quality monitoring devices can also provide important basis for the optimization of distributed photovoltaic projects, helping us gain a deeper understanding of the performance of photovoltaic systems, and then take corresponding measures to improve and optimize the system.

Anti-island protection devices are equally important in distributed photovoltaic projects. When there is a power outage on the grid side, the photovoltaic side is still in a normal power generation state and sends power to the grid side, forming an island effect. This brings a great safety threat to maintenance personnel on the grid side. The anti-island protection device can promptly cut off the connection between the photovoltaic system and the power grid to avoid the island effect, thereby protecting the safety of maintenance personnel. In addition, the anti-island protection device can also quickly cut off the connection between the photovoltaic system and the power grid when the power grid fails to avoid damage to the equipment, and automatically restores connection to the grid after the fault is resolved, ensuring the stable operation of the photovoltaic project.

In the future, with the rapid development of renewable energy and the continuous advancement of power grid technology, we are expected to achieve more reliable photovoltaic power generation systems and make greater contributions to promoting the development of green energy and achieving sustainable energy supply. In this process, the application of online power quality monitoring devices and anti-island protection devices is crucial. They ensure the stable operation of the photovoltaic power generation system and the improvement of power quality, and provide an important basis for the optimization of distributed photovoltaic projects. Therefore, the application of power quality online monitoring devices and anti-island protection devices in distributed photovoltaic projects has broad prospects and far-reaching impact.