High voltage ride-through (HVRT) testing verifies that grid-connected energy storage systems, including battery energy storage systems (BESS) and power conversion systems (PCS), can remain connected and continue supporting the grid during temporary overvoltage events. This article explains the technical principles, applicable standards, test samples, test items, testing methods, and practical applications of HVRT evaluation, providing a practical reference for equipment manufacturers, integrators, and plant operators pursuing grid-code compliance.
Technical Overview
High voltage ride-through (HVRT), also referred to as overvoltage ride-through, is the capability of a grid-connected energy storage system to stay connected and continue operating when the voltage at the point of interconnection temporarily rises above its nominal range. Such voltage swells are commonly caused by sudden load rejection, fault clearing on adjacent transmission lines, large capacitor bank switching, or reactive power imbalances in the grid. If a large storage plant disconnects during one of these disturbances, the abrupt loss of power injection or absorption capability can amplify the overvoltage, trigger cascading disconnections of other generation assets, and jeopardize grid stability.
HVRT testing subjects the energy storage system, and in particular its power conversion stage, to a defined voltage-versus-time envelope. Depending on the applicable grid code, a typical requirement is continuous operation at moderately elevated voltage (for example, 1.10 p.u.), sustained connection for several seconds at intermediate levels (for example, 1.20 p.u.), and short-duration withstand at higher magnitudes (for example, 1.30 p.u. for several hundred milliseconds). In addition to simply surviving the event, many standards require the system to provide a dynamic reactive current response, generally absorbing reactive current in proportion to the voltage deviation, to help damp the overvoltage and support network recovery.
HVRT requirements for energy storage systems are specified in national grid codes and international interconnection standards, including GB/T 36547 and GB/T 34120 for storage systems and converters connected to the Chinese power grid, GB/T 19964 for photovoltaic plants with storage interfaces, IEEE 2800 and IEEE 1547 for inverter-based resources in North America, UL 1741 SB for inverter certification, and EN 50549 for generator connections in Europe. Testing is typically performed by accredited third-party laboratories or qualified on-site test teams using calibrated grid-simulation equipment.
Testing Samples
Power Conversion Systems and Energy Storage Inverters
The PCS or grid-tied energy storage inverter is the primary test object for HVRT type testing. Because the converter's control firmware and protection logic determine ride-through behavior, laboratory tests are usually conducted at rated or reduced power on the complete converter, including its control cabinet, filters, and grid-side contactors, to fully reproduce real operating conditions.
Prefabricated Battery Energy Storage Units
Containerized or skid-mounted BESS units, which integrate batteries, a PCS, thermal management, and local controllers, can be tested as complete subsystems. Testing at this level verifies that internal coordination between the battery management system and the converter does not cause nuisance tripping during grid voltage swells.
Complete Energy Storage Stations
Utility-scale storage plants are verified on site before energization or during commissioning. Field testing evaluates the entire chain, including step-up transformers, medium-voltage switchgear, station-level controllers, and protection relays, and confirms that the plant meets the grid operator's connection requirements at the point of common coupling.
Hybrid Renewable-Plus-Storage Plants
For hybrid solar-plus-storage or wind-plus-storage installations, HVRT verification may cover the combined plant response, ensuring that storage converters assist, rather than conflict with, the ride-through behavior of the renewable generating units.
Testing Items
A comprehensive HVRT test program typically covers the following items, adapted to the applicable standard and the characteristics of the device under test:
- Continuous overvoltage operation capability at moderately elevated voltage, for example 1.10 p.u. of nominal voltage.
- Short-duration symmetrical (three-phase) overvoltage ride-through at higher voltage levels, for example 1.20 p.u. and 1.30 p.u., following the voltage-time curve defined by the relevant grid code.
- Asymmetrical overvoltage ride-through, covering single-phase and two-phase voltage swell conditions.
- Dynamic reactive current response during the swell, verifying that the converter absorbs reactive current with the required gain and within the required response time.
- No-trip verification, confirming that converter, transformer, and station protections do not operate during the defined ride-through window.
- Active and reactive power recovery behavior after voltage returns to the normal operating range, including recovery time and rate.
- Power quality during and after the event, including harmonic distortion, flicker, and DC injection.
- Verification of control mode transitions, such as switching between charge and discharge states under elevated grid voltage.
- Coordination with station-level automation, grid dispatch interfaces, and remote monitoring signals during the disturbance.
Testing Methods
Laboratory Type Testing with a Grid Simulator
The reference method for HVRT evaluation uses a programmable grid simulator, or voltage disturbance generator, capable of producing precise, repeatable voltage swells at the converter terminals. The device under test is operated at specified active power levels, typically in both charging and discharging modes, while the simulator applies the required voltage magnitude, duration, and phase-angle characteristics. High-precision power analyzers and synchronized data acquisition systems record three-phase voltages and currents, active and reactive power, and protection status throughout the event.
On-Site Field Testing
For installed plants, HVRT verification can be performed using a medium-voltage test system connected at the point of common coupling, or by coordinated voltage elevation using the substation configuration under the supervision of the grid operator. Field tests follow a documented test plan, agreed risk assessment, and temporary protection setting adjustments to ensure personnel and equipment safety while reproducing realistic grid disturbances.
Typical Test Procedure
Regardless of the test environment, the procedure generally follows these steps:
- Verification of test setup, instrumentation calibration, and communication with the device under test.
- Recording of baseline steady-state operation at the specified pre-event active and reactive power setpoints.
- Application of the voltage swell, with magnitude, duration, and rise time conforming to the standard's voltage-time envelope.
- Measurement of the converter's response, including reactive current absorption, continued power exchange, and absence of protective trips.
- Observation of the post-event recovery transient and confirmation that normal operation resumes within the specified time.
- Repetition of the test sequence across the required voltage levels, phases, and operating points, followed by analysis against the pass criteria.
Pass Criteria
A test is generally considered passed when the system remains connected throughout the required ride-through duration, does not trip or block, provides the specified dynamic reactive support, and restores its pre-event active power exchange within the recovery time allowed by the standard, without exceeding applicable power quality limits.
Applications
HVRT testing serves multiple purposes across the life cycle of an energy storage project:
- Grid interconnection compliance, providing the evidence required by transmission or distribution operators before a storage plant is permitted to connect and operate.
- Type testing and certification of PCS and inverter products, supporting market access in regions governed by GB, IEEE, UL, and EN requirements.
- Factory and site acceptance testing, confirming that delivered equipment and installed plants conform to contracted performance specifications.
- Research, development, and firmware validation, allowing converter manufacturers to refine grid-support control algorithms and protection settings.
- Post-modification verification, demonstrating continued compliance after major hardware replacements, control software updates, or changes to plant configuration.
- Due diligence and financing support, where independent test reports from accredited third-party laboratories strengthen technical risk assessments for investors and insurers.
FAQ
What is high voltage ride-through in an energy storage system?
High voltage ride-through is the ability of a grid-connected energy storage system to remain connected and continue operating safely when grid voltage temporarily rises above nominal levels, rather than disconnecting and worsening the grid disturbance.
How does HVRT differ from LVRT?
LVRT (low voltage ride-through) addresses temporary voltage sags caused by short circuits and faults, and typically requires reactive current injection to support the grid. HVRT addresses temporary voltage swells and typically requires reactive current absorption. Most grid codes require both capabilities for storage systems.
Which standards govern HVRT testing for energy storage systems?
Commonly applied standards and grid codes include GB/T 36547, GB/T 34120, and GB/T 19964 in China, IEEE 2800 and IEEE 1547 with UL 1741 SB in North America, and EN 50549 in Europe. The applicable requirements depend on the grid voltage level, project location, and the connecting utility's rules.
Can HVRT testing be performed on a live storage station?
Yes. On-site HVRT verification is routinely carried out during commissioning using medium-voltage disturbance generators or controlled voltage elevation, always under an approved test plan and in coordination with the grid operator to ensure safety and system security.
How long does an HVRT test campaign take?
A laboratory type test on a PCS usually takes several days, including setup, execution across multiple voltage levels and operating points, and reporting. On-site station-level testing typically ranges from a few days to two weeks, depending on plant size, test scope, and grid scheduling constraints.
What happens if a system fails the HVRT test?
Failures are usually traced to over-sensitive protection settings, control firmware issues, or improper voltage measurement coordination. After corrective action, such as firmware updates or protection recalibration, the affected test points are repeated to demonstrate full compliance before certification or connection approval is granted.