With the rapid development of photovoltaic (PV) power generation, the power grid faces new challenges such as insufficient reactive power and voltage fluctuations. Since PV generation is directly affected by changes in light intensity and temperature, the stability of grid voltage is put to the test. As the capacity of photovoltaic power plants expands, their impact on grid stability becomes more significant, making it essential for large-scale PV plants to have adequate low voltage ride-through capability. In the wave of clean energy development, PV plants, as a representative of green energy, are gradually integrating into everyday life. However, ensuring the stable operation and efficient generation of PV plants relies on a key piece of intelligent equipment known as the SVG (Static Var Generator) reactive power compensation device.

1. What is SVG (Static Var Generator)?

SVG, or Static Var Generator, is a device used for reactive power compensation and voltage regulation. It achieves this by precisely controlling the phase and magnitude of the current, allowing for effective regulation of reactive power in the grid, which enhances grid stability and reliability. The core principle behind SVG is the use of power electronics technology to provide the required reactive power quickly and accurately to optimize power quality. SVG devices utilize power electronic converters, such as Insulated Gate Bipolar Transistors (IGBT), to control reactors connected to the AC side. Based on the real-time reactive power demands of the load, the SVG adjusts the reactive output of the reactors, providing effective compensation for reactive power in the system. Additionally, SVGs have a rapid response capability to changes in the grid’s reactive power load, ensuring efficient and stable grid operation.

2. Why Should Photovoltaic Power Plants Use SVG?

National power departments mandate that any installation with a low voltage transformer and large electrical equipment should be equipped with reactive power compensation devices, especially in factories, residential areas, and locations with low power factors. Examples include large asynchronous motors, transformers, welding machines, lathes, air compressors, and cranes. Even residential areas with air conditioners and refrigeration units are significant consumers of reactive power. In rural areas with poor power conditions and fluctuating voltages, reactive power compensation devices are crucial for improving power supply quality and efficiency.

When PV power plants convert solar energy into electricity, they can create power quality issues, including reactive power imbalances when connected to the grid.

3. The Role of SVG in Photovoltaic Power Plants

   SVG plays four key roles in photovoltaic power plants:

• Grid Stability: Reactive power is essential for the stable operation of the grid. Both active and reactive power work together to maintain stable voltage and frequency. Reactive power acts as the “support force” for the grid, ensuring voltage levels remain steady.

• Voltage Regulation: In some cases, photovoltaic power plants may cause voltage fluctuations in the grid. Providing reactive power compensation helps stabilize grid voltage and prevents issues caused by the integration of PV plants.

• Increased Transmission Capacity: Reactive power compensation effectively reduces grid losses and increases the utilization rate of transmission lines, thus enhancing the grid's transmission capacity.

• Reduced Losses: By optimizing the grid's power factor, reactive power compensation helps lower transmission losses, improving overall grid efficiency.

4. Key Points to Consider for SVG Operation in Photovoltaic Power Plants

A. Pre-Operation Checks: 

1. Before powering on the SVG reactive power compensation device, the following checks must be completed:

2. Ensure all internal connections are secure with no loose components.

3. Check that no foreign objects could interfere with the device's operation.

4. Confirm that the control cabinet's closing operation is functional.

5. Verify that data displayed on the touch screen matches backend data with no abnormalities.

6. Observe whether the cooling fan starts normally and listen for any unusual sounds.

7. Ensure that data displayed on the touch screen is normal after startup and that compensation data is accurate.

B. Maintenance of SVG Devices: 

Regular inspections are critical to ensure stable operation, including checking for abnormal sounds, ensuring appropriate temperature and humidity conditions, and monitoring for unusual odors. Every three months, a comprehensive inspection should be conducted, following power-off safety procedures. During the shutdown, check the first and second connections in the cabinet, clean the inside and outside of the cabinet, and ensure insulation and withstand voltage tests are passed with insulation resistance values above 500 MΩ. If the device will not be used for an extended period, ensure the cabinet door is tightly closed to prevent small animals from entering and causing damage.

C. Detailed Operating Steps for Deploying SVG:

1. Confirm that the SVG isolation switch is closed, and the grounding switch is open.

2. Ensure the control device is functioning correctly without alarm signals.

3. Turn on the fan power in the SVG startup cabinet, and check if the cooling fan operates normally.

4. Verify that the bypass contactor in the startup cabinet is open.

5. Set the SVG switch to "self-test" mode.

6. If all conditions are met, the remote signaling page will display a closing allowance. If not, troubleshoot the issue.

7. Close the SVG circuit breaker and monitor the SVG link voltage on the remote measurement page. The voltage should be approximately 610V (±20V depending on bus voltage). Ensure the control device shows no alarm signals.

8. If the bypass contactor is in automatic mode and no issues are detected, it will automatically close. Monitor the system in self-test mode for one minute.

9. Once the SVG is verified to be running correctly, switch the SVG to "engaged" mode and monitor the three-phase DC voltage (approximately 760V ±20V), as well as SVG link voltage, and check for any alarms.

10. If an alarm occurs during operation, switch back to "self-test" mode, identify the cause of the fault, and restart the SVG after resolving the issue.