Grid-Forming Inverter Control Under Real-Time Capacity Constraints

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Solution Overview

Problem

Grid-forming inverters face challenges in maintaining power synchronization and stability under capacity constraints during transient AC grid disturbances, leading to poor ride-through performance and instability due to their vulnerability to fast transients and disturbances.

Innovation Solution

A capacity-optimized grid-forming control system that includes a capacity constrainer to enforce real-time constraints on reference signals, ensuring that the output of grid-forming inverters aligns with their operational limits, thereby maintaining power synchronization and stability by proactively managing deviations from capacity constraints.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If grid-forming inverters operate under capacity constraints during transient disturbances, then power synchronization is maintained, but ride-through performance deteriorates and instability occurs

Engineering Contradiction:

Improvepower synchronizationVSAvoidride-through performance

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The control system dynamically adjusts the inverter output by modulating the current reference signals based on real-time capacity constraints and grid conditions. The controller transitions between different operational modes (current control vs power control) depending on the severity of disturbances and remaining capacity, enabling adaptive response to transient conditions while maintaining stability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes operational parameters (current limits, power references, droop coefficients) in response to capacity constraints and disturbance conditions. By adjusting these parameters dynamically, the controller optimizes the trade-off between maintaining power synchronization and ensuring ride-through capability during transient events.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If real-power output increases to maintain frequency equilibrium, then power synchronization is achieved, but capacity constraints are violated leading to instability

Engineering Contradiction:

Improvefrequency equilibriumVSAvoidreal-power output

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The control system continuously monitors the inverter's actual power output, current magnitude, and capacity utilization. Based on this feedback, the controller adjusts the real-power reference and current limits to ensure frequency equilibrium is maintained without exceeding capacity constraints. The feedback loop prevents instability by detecting approaching constraint violations and adjusting operating points accordingly.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The controller applies partial power transfer during transient synchronization by limiting the rate and magnitude of real-power changes. Instead of allowing full excessive power transfer that would violate constraints, the system uses controlled partial action through modified droop characteristics and current limiting to achieve frequency equilibrium within safe operating boundaries.

Inventive Principle:

Principle #16Partial or excessive action

3Ease of operation

If current limits are enforced to prevent overcurrent during transients, then ride-through performance improves, but power synchronization capability deteriorates

Engineering Contradiction:

Improveride-through performanceVSAvoidpower synchronization

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The system dynamically adjusts current limits based on the operational phase and grid conditions. During normal synchronization, higher current limits enable effective power transfer. During severe transients, reduced current limits protect the inverter while maintaining synchronization through alternative control mechanisms such as voltage regulation and frequency adjustment.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The control strategy segments the current control into different components: a synchronous current component for power transfer and a transient current component for stability. By separately managing these components with different limit enforcement strategies, the system maintains both ride-through capability and synchronization effectiveness.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS12494652B2Capacity-optimized grid-forming control

Publication Date: 2025.12.09 EPC POWER CORP

AI summary

Capacity-optimized grid-forming is provided. A controller includes a power-synchronization model (PSM). The PSM is configured to receive positive and negative sequence symmetrical components of an output voltage and an output current. The PSM is configured to generate current references including a positive and negative sequence current reference. The PSM is configured to generate an internal voltage phase reference and voltage magnitude reference. The controller includes a capacity constrainer to determine, based on the current references and a capacity limit terms, that a device is capacity constrained. The capacity constrainer is configured to determine optimum complex gains to scale the plurality of current references based on the capacity limit terms. The capacity constrainer is configured to, responsive to the determination of constraint, output scaled current reference to cause a power stage to adjust the output voltage/current, the scaled current reference scaled according to the complex gains.