Back-to-Back UPS Inverters for Grid Ancillary Power Quality
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Solution Overview
Problem
Conventional UPS systems face inefficiencies in providing uninterrupted power to critical loads and supporting ancillary services due to high penetration of intermittent renewable-based energy sources and non-linear loads, which adversely affect power quality.
Innovation Solution
A GAUPS device with four-quadrant and unidirectional inverters connected back-to-back on the DC side, allowing for advanced control to provide continuous high-quality power to sensitive loads and support the power grid with ancillary services in various modes, including offline-ancillary, double-conversion-ancillary, grid-connected ancillary, and independent modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If conventional UPS systems are used to provide uninterrupted power to critical loads, then power continuity is maintained, but power quality deteriorates due to high penetration of intermittent renewable-based energy sources and non-linear loads
Solution Approach 1:
The system segments power flow paths by using multiple inverters (grid-side inverter and load-side inverter) connected back-to-back on the DC side, allowing independent control of grid interface and load interface to maintain power quality while ensuring continuity
Solution Approach 2:
The energy storage device acts as an intermediary between the grid and critical loads, buffering power quality disturbances from intermittent renewables and non-linear loads while maintaining stable power supply to sensitive loads
2Object-affected harmful factors
If multiple inverters are used to provide continuous high-quality power and grid support, then power quality and ancillary services improve, but system complexity increases
Solution Approach 1:
The system merges grid support functions and UPS functions into a single integrated GAUPS device with back-to-back inverters sharing a common DC link and energy storage, providing multiple functions (continuous power supply, power quality conditioning, and grid ancillary services) without proportionally increasing complexity
Solution Approach 2:
The GAUPS device is designed as a universal system that can simultaneously provide uninterrupted power to critical loads, condition power quality, and support grid ancillary services through a single integrated architecture with configurable operating modes
3Adaptability or versatility
If energy storage device supplies power to both load and utility grid simultaneously, then system versatility improves, but control difficulty increases
Solution Approach 1:
The system implements dynamic control that allows the energy storage device to flexibly switch between supplying power to the load, supplying power to the utility grid, or absorbing power from the grid, with operating modes that can be configured and changed in real-time based on grid conditions and load requirements
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
The GAUPS device efficiently supplies uninterrupted power to critical loads while simultaneously supporting the grid with ancillary services, enhancing power quality and efficiency by minimizing conversions and adapting to grid conditions.
Implementation Method 1
a first inverter that is coupled between the utility grid and the energy storage device
Implementation Method 2
a second inverter that is coupled between the first inverter and the load
Implementation Method 3
The energy storage device may be coupled between the first inverter and the second inverter
Data Source
AI summary
Methods of operating a grid ancillary service with an uninterruptible power supply (GAUPS) device are provided. A method of operating a GAUPS device includes controlling a switch of the GAUPS device in response to a signal that is generated by the switch, to control efficiency of an inverter and quality of power supplied to a load via the inverter. The switch is coupled between the inverter and the load. Related systems and devices are also provided.