Adaptive Inverter Control for High Short-Circuit Fault Current
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Solution Overview
Problem
Microgrids face challenges in protecting against short-circuit faults due to limited short-circuit current from inverter-based distributed energy resources, leading to difficulties in coordinating conventional protective devices and the need for cost-prohibitive solutions that require extensive installation of relays and sensors.
Innovation Solution
An inverter system with an overrated semiconductor-based power module, saturable inductive grid filter, and adaptive controller gain adjustments to maintain stability during high-current operations, enabling increased short-circuit current capacity and stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional protective devices (fuses, relays) are used in islanded microgrids, then protection coordination is required, but the limited short-circuit current from inverter-based resources prevents proper operation of these devices
Solution Approach 1:
The patent changes the current magnitude parameter by using an overrated semiconductor power module that can deliver higher short-circuit current (e.g., 6-10 times rated current) compared to conventional inverters. This parameter change enables conventional protective devices to operate reliably in islanded mode without requiring complex alternative protection schemes.
Solution Approach 2:
The patent implements dynamic control of the inverter output current through adaptive controller gain adjustments. The controller dynamically increases the current magnitude during fault conditions while maintaining stability, allowing the system to provide sufficient short-circuit current for protection device operation only when needed, rather than continuously.
2Quantity of substance
If inverter power module is overrated to increase short-circuit current capacity, then protection device operation is enabled, but controller stability during high-current operation becomes challenging
Solution Approach 1:
The patent uses dynamic adaptive controller gain adjustment to maintain stability during high-current operation. The controller gains are modified based on operating conditions, allowing the system to stabilize at different current levels including the elevated short-circuit current levels required for protection device operation.
Solution Approach 2:
The patent implements feedback control mechanisms that continuously monitor system state and adjust controller parameters accordingly. This feedback ensures that the overrated power module operates stably even at high current levels by detecting saturation conditions and adjusting control signals to prevent instability.
3Object-generated harmful factors
If saturable inductive grid filter is used to filter AC signal, then grid compatibility is improved, but controller stability is affected when the filter saturates at high current operation
Solution Approach 1:
The patent accounts for the dynamic saturation behavior of the saturable inductive grid filter by implementing adaptive controller gain adjustments. When the filter saturates at high currents, its inductance changes, and the controller dynamically adjusts gains to compensate for this change and maintain stability.
Solution Approach 2:
The patent changes the controller parameters (gains) based on the operating point of the saturable inductive filter. By detecting filter saturation conditions and adjusting controller parameters accordingly, the system maintains stability across the full range of operating conditions including high-current fault scenarios.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables the use of affordable overcurrent devices like fuses and relays, improves fuse-relay coordination, and reduces reliance on costly synchronous condensers, enhancing microgrid protection and stability with minimal hardware modifications.
Implementation Method 1
a semiconductor-based power module that is overrated by a factor f1 having a value greater than two and configured to receive a DC signal and convert the DC signal into an AC signal
Implementation Method 2
a saturable inductive grid filter configured to filter the AC signal
Implementation Method 3
a saturable inductive grid filter configured to filter the AC signal
Data Source
AI summary
Methods and systems comprising an inverter comprising: a semiconductor-based power module that is overrated by a factor f1 having a value greater than two and configured to receive a DC signal and convert the DC signal into an AC signal; a saturable inductive grid filter configured to filter the AC signal; at least one sensor configured to produce a current measurement and a voltage measurement from the AC signal output from the saturable inductive grid filter; and a processor configured to compute adaptive controller gain values using at least the current measurement and temperature, and cause an adjustment to a gain of an inverter controller in accordance with the adaptive controller gain values to maintain stability when the saturable inductive grid filter saturates at high current operations.