UPS Bidirectional Chopper Control for Grid Frequency Fluctuations
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Solution Overview
Problem
In power systems with a high introduction ratio of distributed power supplies, fluctuations in system frequency occur due to imbalances between generated and demanded power, leading to potential power failures and inefficient utilization of large-capacity power storage devices in uninterruptible power supplies (UPS).
Innovation Solution
An uninterruptible power supply (UPS) is designed with a power conversion device, a frequency detector, and a controller. The power conversion device includes a converter, an inverter, and a bidirectional chopper, which allows for charging and discharging of a power storage device based on detected system frequency fluctuations. The controller adjusts the operation of the bidirectional chopper to compensate for frequency fluctuations by either charging or discharging the power storage device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If distributed power supplies are introduced into the power system, then renewable energy utilization is improved, but system frequency fluctuations increase
Solution Approach 1:
The system employs a frequency detector to continuously monitor system frequency and provides feedback to the controller. The controller adjusts the power storage device's charging/discharging operations based on this feedback, creating a closed-loop control system that automatically compensates for frequency fluctuations caused by distributed power supply variations.
Solution Approach 2:
The power storage device serves dual purposes: it acts as a backup power supply for power failures and simultaneously functions as a frequency regulation device. The system uses its own power storage capability to self-regulate frequency fluctuations without requiring external intervention, enabling the UPS to compensate for imbalances between generated and demanded power.
2Reliability
If large-capacity power storage devices are used for power failure compensation, then power failure backup capability is improved, but utilization efficiency during normal operation deteriorates
Solution Approach 1:
The power storage device is designed to perform multiple functions: it serves as a backup power supply during power failures and simultaneously acts as a frequency regulation device during normal operation. By enabling the same hardware to fulfill both roles, the system maximizes the utilization of the large-capacity power storage device without requiring additional equipment.
Solution Approach 2:
The power storage device operates continuously with useful action throughout both normal and abnormal conditions. During normal operation, it actively participates in frequency regulation through charging and discharging cycles, and during power failures, it seamlessly transitions to backup power supply mode, ensuring continuous useful operation without idle time.
3Productivity
If the bidirectional chopper controls charging and discharging operations, then power storage utilization is improved, but device complexity increases
Solution Approach 1:
The bidirectional chopper is designed to perform multiple functions within a single device structure. It handles both charging operations (storing DC power from the converter) and discharging operations (supplying DC power to the inverter), eliminating the need for separate switching devices for each direction and reducing overall system complexity.
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 proposed UPS effectively compensates for frequency fluctuations in the power system, ensuring stable operation of electrical devices and preventing power failures, while also utilizing the power storage device to balance power imbalances during normal system operation.
Implementation Method 1
The converter converts AC power supplied from the power system into DC power
Implementation Method 2
The inverter converts DC power supplied from the converter or a power storage device into AC power and supplies the AC power to the load
Data Source
AI summary
A bidirectional chopper selectively performs a charging operation and a discharging operation, the charging operation being an operation in which a part of DC power generated by a converter is stored in a power storage device, the discharging operation being an operation in which DC power of the power storage device is supplied to an inverter. A control circuit controls the bidirectional chopper to perform the discharging operation when a power failure of a power system occurs. The control circuit controls the bidirectional chopper based on a system frequency detected by a frequency detector when the power system is normal. The control circuit controls the bidirectional chopper to perform the charging operation in response to an increase in the system frequency, and to perform the discharging operation in response to a decrease in the system frequency.