Energy Storage Converter Overload Control for Grid Fault Support
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Solution Overview
Problem
The increasing proportion of grid-connected new energy-based power generation systems in power systems has led to a decrease in system inertia and short-circuit current, posing instability risks, necessitating improved transient current overload capability in converter grid-forming systems to enhance power grid stability.
Innovation Solution
An energy storage power generation system with power conversion systems that can switch between steady-state and transient-state operating modes, utilizing the short-time overload capability of semiconductor devices to support the power grid during faults, while optimizing system architecture and reducing component costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the quantity of power conversion systems is increased to provide transient current overload capability for grid support, then the power grid stability is improved, but the system complexity and component costs increase
Solution Approach 1:
The power conversion system dynamically switches between steady-state control mode and transient-state control mode based on grid conditions. During normal operation, the system operates in steady-state mode with standard control parameters. When grid instability is detected (voltage deviation exceeds threshold or frequency deviation exceeds threshold), the controller automatically transitions to transient-state mode, adjusting control parameters to enable overload operation. This dynamic adaptation allows the system to provide grid support when needed without requiring permanent oversized capacity, thereby reducing overall system complexity while maintaining reliability.
Solution Approach 2:
The system changes operational parameters between steady-state and transient-state modes. In steady-state mode, the power conversion system operates with nominal current limits and standard power output. When transitioning to transient-state mode, the controller modifies parameters including current thresholds, power output levels, and control loop gains to enable short-term overload operation. This parameter adjustment allows the existing hardware to provide enhanced grid support capability without requiring additional equipment, thus improving reliability without proportionally increasing system complexity.
2Power
If the rated power of power conversion systems is increased to meet transient overload requirements, then the transient current overload capability is improved, but the system costs and device size increase
Solution Approach 1:
The power conversion system is designed to operate at rated power during normal steady-state conditions, but is capable of temporary excessive operation during transient events. The controller enables the system to exceed its rated power output when grid instability is detected, utilizing the transient-state control mode to provide short-term overload capability. This approach allows the system to have just enough capacity for normal operation, rather than being permanently sized for maximum transient requirements, thereby reducing equipment size and costs while still providing necessary grid support during critical events.
3Reliability
If the power conversion system operates in overload state during transient overloading, then the grid support capability is improved, but the risk of equipment damage increases
Solution Approach 1:
The controller is configured with pre-set threshold values for voltage deviation and frequency deviation that trigger the transition to transient-state control mode. These thresholds are established beforehand based on grid code requirements and equipment capabilities. When measurements indicate that the grid is approaching an unstable state (voltage or frequency deviation exceeds the preset threshold), the controller proactively transitions to transient-state mode, enabling the system to provide supportive current before the grid collapses. This beforehand preparation allows the system to respond rapidly to grid disturbances while staying within safe operational limits, thus improving grid support capability without excessive equipment damage risk.
4Device complexity
If the parallel expansion multiple of power conversion systems is reduced below transient overload multiple, then the system costs are reduced, but the ability to support power grid during faults is weakened
Solution Approach 1:
The power conversion system uses dynamic control mode switching to compensate for the reduced number of parallel units. Each power conversion system is equipped with a controller that can switch between steady-state control mode and transient-state control mode. When grid instability is detected, the controllers of the available power conversion systems transition to transient-state mode, adjusting their output to provide the necessary supportive current. This dynamic response allows a smaller number of systems to provide adequate grid support during faults, maintaining reliability while reducing system costs compared to having multiple systems operating continuously at full capacity.
Data Source
AI summary
An energy storage power generation system and a control method thereof. When a transient fault occurs in the power grid, the plurality of power conversion systems may enter a transient-state operating mode from a steady-state operating mode, and a parallel expansion multiple of the energy storage power generation system is less than a transient overload multiple. In embodiments, a physical characteristic of transient overloading and a short-time overload capability of the power conversion system are fully used, and the power grid is supported when a power grid fault is detected. This solution simplifies an architecture of the system and increases efficiency of the system. It is easy to understand that because a quantity of power conversion systems is reduced and costs of the system are also reduced.