Overvoltage and undervoltage faults are common issues that can significantly affect the performance and stability of an inverter system. These voltage fluctuations, often caused by grid instability or sudden load changes, can lead to equipment damage, unexpected shutdowns, and even safety hazards. To ensure reliable operation, it is crucial to implement effective measures for both overvoltage and undervoltage protection.
1. Overvoltage Fault Resolution Measures
To mitigate the impact of grid overvoltage on the inverter, the primary goal is to manage the excess energy in the DC intermediate loop effectively. This includes both dissipating the surplus energy and preventing it from being fed back into the system. Here are several strategies to achieve this:
1) Install a surge absorbing device or a series reactor as an absorbing device. These components help absorb voltage spikes caused by lightning, switching operations, or capacitor charging. Surge absorbers use semiconductor elements to clamp the voltage at a safe level, while series reactors reduce inrush currents and improve the system's ability to handle short circuits, thus limiting overvoltage peaks.
2) Adjust the inverter’s parameters. Properly setting the deceleration time and other operational parameters can prevent excessive kinetic energy from being dumped into the DC bus. For systems with high inertia loads, increasing the deceleration time allows for a smoother energy release, reducing the risk of overvoltage trips.
3) Increase the bleeder resistance. A bleeder resistor provides a controlled path for excess energy to be dissipated, ensuring the DC bus remains stable. This is especially important in high-power systems where rapid energy release could cause voltage spikes.
4) Add an inverter circuit. An additional inverter can feed excess energy back into the grid, but this solution is more complex and costly compared to other methods.
5) Add a suitable capacitor to the DC bus. A properly sized capacitor helps stabilize the DC voltage and improves the system’s ability to withstand overvoltage events. This is a cost-effective measure that can be implemented during the design phase.
6) Reduce the power supply voltage. If the input voltage is too high, using a transformer tap changer to lower the voltage can help reduce the stress on the DC bus and minimize overvoltage risks.
7) Use multiple inverters sharing a DC bus. By connecting multiple inverters to a shared DC bus, the system can balance the load and maintain a stable voltage. This also allows for energy recovery when one inverter is stopped, further improving efficiency.
8) Leverage control system advantages. Modern control systems can predict and manage load changes, helping to prevent overvoltage by adjusting the inverter’s output before a sudden drop in load occurs. Replacing an uncontrolled rectifier with a semi-controlled or fully controlled one can also improve voltage regulation.
2. Undervoltage Fault Resolution Measures
Undervoltage can cause the inverter to shut down unexpectedly, leading to production interruptions and potential damage. Here are some effective ways to address this issue:
1) Enable the inverter’s automatic restart function. This feature allows the inverter to reset automatically after a brief power loss, minimizing downtime. Some inverters also support power frequency switching, which helps maintain motor operation during short power interruptions.
2) Install a UPS (Uninterruptible Power Supply). A UPS provides continuous power during outages, ensuring the inverter continues operating without interruption. It also helps filter voltage fluctuations and protect sensitive electronics from damage.
3) Adjust the low-voltage protection threshold and extend acceleration time. By fine-tuning these settings, the inverter can better tolerate voltage drops and avoid unnecessary tripping. Extending the acceleration time reduces the initial current draw, which helps prevent voltage sags.
In conclusion, overvoltage and undervoltage issues are critical challenges in inverter systems. By implementing the right combination of hardware solutions, parameter adjustments, and control strategies, these problems can be effectively managed. Ensuring the inverter operates within safe voltage limits not only protects the equipment but also enhances overall system reliability and performance.
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