Low & High Voltage Ride-Through: Why They Are Essential Stabilization Requirements for New Energy Equipment

As large-scale PV and wind power connect to the grid, new energy sources are gradually replacing traditional generation, becoming the primary power supply unit of the power system. The grid is like a busy energy highway, with power loads fluctuating in real time and frequent abnormal conditions of voltage sags and swells. Low Voltage Ride-Through (LVRT) and High Voltage Ride-Through (HVRT) are the core protection technologies for new energy generation equipment. In simple terms: equipment equipped with both ride-through capabilities will not easily trip offline during grid voltage fluctuations, stabilizing its own operation while assisting the grid in voltage regulation, significantly improving the overall stability of both the equipment and the grid.

Part 1: Low Voltage Ride-Through (LVRT) — Resilience During Grid Low Voltage

1.1 Core Definition

One-sentence summary: The ability of equipment to withstand low voltage and persist in grid-connected operation when grid voltage suddenly drops.

1.2 Common Causes of Voltage Sags

When the grid encounters a sudden fault, the voltage at the point of common coupling can rapidly drop within tens of milliseconds to several seconds, falling as low as 15% of the rated voltage. Common scenarios:

• Grid line short circuits; lightning strikes on lines during thunderstorms.

• Sudden switching of large electrical equipment, abrupt load changes.

1.3 Hazards Without LVRT

New energy inverters are highly sensitive to voltage. Without LVRT capability, when voltage drops, the equipment triggers its self-protection mechanism and directly trips offline.

If a large number of new energy power stations simultaneously disconnect from the grid, the grid's active power suffers a sharp deficit, voltage and frequency continuously deteriorate, small grid faults can easily spread, triggering cascading blackout accidents.

1.4 Core Function of LVRT

• Hold the Grid Connection: During voltage sag, the equipment does not disconnect or shut down.

• Proactive Voltage Regulation: Injects reactive current into the grid, providing momentum for voltage recovery and accelerating the grid's return to normal.

Practical case: A PV power station was struck by lightning; grid voltage instantly dropped to 30% of the rated value. Thanks to the inverter's LVRT function, the equipment continued grid-connected operation for 0.5 seconds. After grid voltage recovered, it smoothly returned to full output, successfully avoiding generation losses from shutdown.

Part 2: High Voltage Ride-Through (HVRT) — Overvoltage Endurance for Grid High Voltage

2.1 Core Definition

One-sentence summary: The ability of equipment to withstand high voltage and suppress overvoltage when grid voltage abnormally rises.

2.2 Common Causes of Voltage Swells

• Large load suddenly disconnects, grid power consumption drops sharply.

• Reactive power compensation device malfunctions, transmission line accidentally opens.

2.3 Hazards Without HVRT

Overvoltage may seem like abundant power, but it is extremely dangerous: it accelerates the aging of inverters and transmission lines, and in severe cases directly burns out generation equipment. It also aggravates grid voltage imbalance, affecting the safety of all power-consuming equipment in the area.

2.4 Core Function of HVRT

• Stable Grid Connection: Under high-voltage conditions, it refuses to trip and continuously maintains grid connection.

• Suppress Overvoltage: Actively absorbs excess reactive power from the grid, moderately reduces active power output, and suppresses continuous voltage rise.

Important New Regulation: The 2024 new national standard explicitly stipulates that HVRT is officially listed as a mandatory requirement for PV power station grid connection, forming a hard threshold for new energy grid connection together with LVRT.

Part 3: Direct Comparison — Core Differences Between LVRT and HVRT

Part 4: Core Reasons — Why Equipment with Ride-Through Capability is More Stable

4.1 Eliminate Mass Disconnections, Prevent Fault Amplification

Equipment without ride-through capability trips offline with the slightest voltage fluctuation, aggravating grid faults. Equipment with ride-through capability holds the grid connection during voltage abnormalities, acting as a stabilizing anchor for the grid and blocking cascading fault reactions.

4.2 Proactively Participate in Voltage Regulation, Empowering Grid Self-Healing

Traditional new energy equipment only generates power and does not participate in grid regulation. Equipment with ride-through capability can proactively inject or absorb reactive power based on voltage changes, transforming from a passive power generator into a grid stability participant, accelerating grid fault recovery.

4.3 Meet National Standards, Ensure Compliant Operation

The state explicitly requires: New energy power stations at 220kV and above must pass LVRT and HVRT capability assessments. Non-compliant stations are prohibited from grid connection and will be judged as power system safety hazards. Ride-through capability is the basic threshold for legal operation.

4.4 Assist O&M Troubleshooting, Reduce Shutdown Losses

Frequent triggering of ride-through protection at power stations is not necessarily a grid problem—it is mostly likely caused by equipment detection deviations, abnormal line impedance, or parameter mismatches. Mastering ride-through principles allows O&M personnel to quickly locate hidden dangers and reduce unplanned shutdown losses.

Part 5: Full Summary

• Low Voltage Ride-Through: Defends the lower voltage limit; holds grid connection during fault low voltage, helping voltage recovery.

• High Voltage Ride-Through: Stabilizes the upper voltage limit; suppresses overvoltage during abnormal high voltage, protecting equipment safety.

LVRT and HVRT are core standard technologies for new energy power stations. They are both the key to equipment self-protection and an important guarantee for the safe and stable operation of the power grid. As power industry standards continue to upgrade and ride-through technology steadily improves, grid resilience will be further enhanced, enabling stable transmission of clean wind and PV power and consolidating the power technology foundation for the national 'Dual Carbon' goal.