Voltage Ride-Through

Voltage Ride-Through (VRT) refers to a solar inverter’s ability to remain connected and operational during short-term grid voltage disturbances, such as voltage sags, swells, or momentary dips, without disconnecting from the electrical grid.

Modern grid codes require grid-connected solar inverters to stay online during brief instability events to support grid reliability, avoid cascading outages, and ensure continuous renewable energy generation—especially in regions with high solar penetration.

In professional solar designing and engineering workflows, VRT plays a critical role in:

Inverter selection
Utility interconnection approval
Compliance with grid codes
Long-term system stability and uptime

By enabling PV systems to “ride through” abnormal voltage conditions instead of disconnecting, VRT helps stabilize the grid rather than worsen disturbances.

Key Takeaways

VRT ensures inverters stay connected during brief voltage disturbances
Mandatory for modern grid code and interconnection compliance
Includes LVRT, HVRT, and dynamic voltage support
Influences inverter choice, wiring design, and system reliability
Essential for high solar penetration and grid stability

What It Is

Voltage Ride-Through is a grid-support function embedded in advanced inverter control systems. When grid voltage temporarily moves outside nominal limits, a VRT-capable inverter must:

Remain connected to the grid
Operate safely within electrical limits
Provide active or reactive grid support, depending on the event

This behavior prevents large amounts of distributed solar capacity from disconnecting simultaneously—an issue that can severely destabilize modern grids.

VRT works closely with other design parameters such as:

These elements directly influence voltage behavior at the inverter terminals and determine whether the system can comply with LVRT and HVRT requirements.

How It Works

Voltage Ride-Through is executed through inverter firmware and fast-response power electronics that continuously monitor grid conditions.

Step-by-Step Operation

Voltage Sensing: The inverter continuously monitors grid voltage on the AC side—an essential input for accurate modeling in Shadow Analysis and grid-interactive system design.

Event Detection: When voltage deviates beyond defined thresholds (for example, 0.7 pu or 1.2 pu), the inverter detects an abnormal grid condition.

Ride-Through Decision LogicGrid codes define how long the inverter must stay connected at specific voltage levels.Examples include:
0.5 pu for 0.15 seconds
0.7 pu for 0.5 seconds

Reactive Power Response: During the disturbance, the inverter may inject or absorb reactive power to support voltage recovery—closely tied to Power Factor control strategies.

Controlled Power Output: Active power is reduced or limited to stay within thermal and electronic limits.

Return to Normal Operation: Once voltage stabilizes, the inverter ramps output gradually to avoid introducing new disturbances.

This entire process occurs in milliseconds and is mandatory for compliance in Europe, the U.S., Australia, and other regulated solar markets.

Types / Variants

1. Low Voltage Ride-Through (LVRT)

Ability to remain connected during voltage sags below nominal levels.

LVRT is essential to prevent mass inverter disconnection during grid faults.

2. High Voltage Ride-Through (HVRT)

Ability to stay connected during voltage swells above nominal voltage, often caused by switching operations or capacitor banks.

3. Dynamic Voltage Support (DVS)

An advanced VRT capability where the inverter actively injects reactive power to help restore grid voltage.

4. Grid-Code-Specific VRT Profiles

Different regions impose different VRT curves, such as:

IEEE 1547-2018
ENTSO-E (Europe)
CEA guidelines

These profiles define voltage limits, ride-through durations, and reactive power behavior.

How It’s Measured

VRT performance is validated through standardized grid compliance testing.

Key Measurement Parameters

Voltage threshold (pu): Per-unit voltage at which the inverter must remain connected.‍
Ride-through duration (seconds): Time the inverter must stay operational at that voltage level.‍
Reactive power response (VAR): Measures voltage support capability.‍
Current limits: Defines maximum inverter output during grid disturbances.

These parameters are evaluated during utility interconnection studies and grid certification testing.

Practical Guidance (Actionable Steps)

For Solar Designers

Select inverters certified to regional grid codes.
Validate VRT curves during solar designing and compliance reviews.
Use Voltage Drop Calculator and AC Size Calculator to ensure wiring supports stable ride-through behavior.

For EPC Teams

Ensure transformer and MV cable sizing do not introduce excessive voltage drops.
Confirm inverter firmware is updated for grid-support functions.

For Installers

Maintain correct grounding & bonding to avoid false voltage detection.
Document VRT settings for inspections and commissioning.

For Sales Teams

Position VRT compliance as a reliability and grid-readiness advantage, especially for commercial and utility-scale projects.

Real-World Examples

Residential Rooftop (5 kW System)

A short voltage sag occurs due to a nearby fault. The inverter remains connected under LVRT rules, avoiding nuisance shutdowns and improving homeowner experience.

Commercial Carport (400 kW)

A temporary voltage swell from capacitor switching is handled through HVRT, preventing revenue loss and maintaining uptime.

Utility-Scale Plant (25 MW)

A regional fault triggers deep voltage dips. Inverters with LVRT and DVS remain connected, provide voltage support, and comply with ENTSO-E requirements—preventing cascading outages.