Microgrid Inverter Firming Control for Fast Voltage Support
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Solution Overview
Problem
Existing energy storage systems struggle to efficiently manage power transfer between energy storage systems and power grids, particularly in transitioning between different operating modes to meet changing grid requirements.
Innovation Solution
A system comprising a direct current (DC) link, an energy storage system (ESS), and a load manager with a DC-to-alternate current (AC) inverter and an output filter, which includes a first inductor, a second inductor, and a capacitor. This system operates in a firming mode, where the load controller regulates active and reactive power by controlling the second and first axis components of the capacitor voltage vector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing energy storage systems use conventional operating modes for power transfer, then the system structure is simple, but the system cannot rapidly respond to changing grid requirements and maintain stability during transitions
Solution Approach 1:
The patent implements dynamic operating mode transitions between following mode, firming mode, and forming mode based on real-time grid conditions. The control system dynamically adjusts the capacitor voltage vector components (d-axis and q-axis) to regulate active and reactive power, enabling the system to adapt to changing grid requirements and maintain stability during transitions between different operating states
Solution Approach 2:
The patent changes the control parameters from conventional current control to capacitor voltage vector control. By controlling the d-axis component for active power and q-axis component for reactive power, the system achieves faster response to grid disturbances. The parameter transformation between different reference frames (abc to dq0) enables precise control of power flow while maintaining system stability
2Adaptability or versatility
If the system transitions between different operating modes to meet changing grid requirements, then the system adaptability improves, but the transition response time increases and stability during transition is compromised
Solution Approach 1:
The patent prepares the system for mode transitions by continuously monitoring grid conditions and pre-calculating the required capacitor voltage vector adjustments. The control system maintains readiness to switch between following mode, firming mode, and forming mode by keeping the control algorithms for all modes available and synchronized, enabling instantaneous transition without stability compromise
Solution Approach 2:
The patent implements a feedback control mechanism that continuously monitors the actual power output and compares it with the reference values. The error signals are used to adjust the capacitor voltage vector components in real-time, ensuring smooth and rapid mode transitions. The feedback loop maintains system stability during transitions by detecting deviations and correcting them immediately
Data Source
AI summary
A system for managing power transfer with a power grid can include a DC-to-alternate current (AC) inverter, an output filter, and a load controller. The DC-to-alternate current (AC) inverter can be configured to output an output voltage (VOUT). The output filter can be configured to receive an output voltage (VOUT) and generate a capacitor voltage vector (VCAP) across a capacitor, the capacitor voltage vector (VCAP) including a second axis component capacitor voltage and a first axis component capacitor voltage. The load controller can be operable to regulate an active power supplied to the power grid by controlling the second axis component capacitor voltage and a reactive power supplied to the power grid by controlling the first axis component capacitor voltage, the load controller regulates the active power by altering a phase angle and a magnitude of the second axis component capacitor voltage of the capacitor voltage vector (VCAP).