DC-Coupled Solar PV and Storage Control for Fault and Loss Reduction
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Solution Overview
Problem
Existing power generation and storage systems face challenges such as high fault currents, increased operating costs, control instability, and reduced efficiency due to the complexity of AC-coupled systems, and difficulties in matching voltage ratings for expanded battery storage in DC-coupled architectures, which hinder the effective integration and management of renewable energy sources.
Innovation Solution
A DC-coupled power system with a common DC power bus connecting photovoltaic systems and energy storage, a power inverter for AC conversion, and a control system that manages real-time power adjustments based on system data to balance energy distribution, manage fault events, and optimize energy storage and harvesting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If AC-coupled systems are used to combine energy storage and renewable energy sources, then flexibility in integration is improved, but fault current increases and operating costs increase due to multiple interconnection transformers and independent inverters
Solution Approach 1:
The patent combines the inverter and transformer into a single integrated unit, eliminating the need for separate interconnection transformers. This merging reduces the number of components while maintaining AC-coupled system flexibility, thereby reducing fault current without sacrificing adaptability.
Solution Approach 2:
The integrated inverter-transformer unit performs multiple functions simultaneously: power conversion, voltage transformation, and grid interconnection. This multi-functionality reduces the need for multiple specialized components, lowering overall system complexity and fault current while preserving integration flexibility.
2Adaptability or versatility
If AC-coupled systems use independent inverters and transformers for each energy source, then system modularity is improved, but operating costs increase
Solution Approach 1:
By merging the inverter and transformer into a single integrated unit, the patent reduces the total number of components required in the system. This decreases manufacturing complexity and operating costs while maintaining the modular architecture that allows flexible configuration of multiple energy sources.
3Extent of automation
If AC-coupled systems coordinate multiple inverters for grid commands, then system control capability is improved, but response time to grid commands decreases
Solution Approach 1:
The integrated inverter-transformer unit eliminates the need to coordinate multiple independent inverters, simplifying the control architecture. This single-unit approach maintains full control capability while significantly reducing response time to grid commands by removing coordination delays.
4Stability of the object's composition
If DC-coupled architectures use DC/DC devices on the energy storage system input, then control stability is improved, but equipment efficiency decreases
Solution Approach 1:
The patent removes the DC/DC conversion stage from the energy storage system input by directly connecting the DC-coupled energy storage to the DC bus. This extraction eliminates the efficiency losses associated with DC/DC conversion while maintaining control stability through the simplified direct connection architecture.
5Extent of automation
If DC-coupled architectures use DC/DC devices on the PV input, then maximum power point tracking is improved, but inverter efficiency decreases
Solution Approach 1:
The patent removes the DC/DC conversion stage from the PV input by directly connecting the PV array to the DC bus through the integrated inverter-transformer unit. This extraction eliminates the efficiency losses while maintaining maximum power point tracking capability through the inverter's built-in control algorithms.
6Quantity of substance
If DC-coupled systems expand storage system with additional batteries, then energy storage capacity is improved, but system compatibility decreases due to voltage rating mismatches
Solution Approach 1:
The patent employs DC-DC converters with adjustable voltage transformation ratios that can adapt to different battery voltage ratings. This parameter adjustment capability allows seamless expansion of storage capacity by adding batteries with different voltage ratings without compromising system compatibility.
7Adaptability or versatility
If AC-coupled systems convert energy through multiple devices to charge batteries, then energy source flexibility is improved, but system losses increase
Solution Approach 1:
The patent merges the inverter and transformer into a single integrated unit, reducing the number of conversion stages from multiple devices to a single unified conversion process. This merging maintains the ability to charge batteries from various AC energy sources while minimizing system losses by eliminating intermediate conversion steps.
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 solution enables flexible, cost-effective, and efficient use of renewable energy by reducing system losses, improving response times to grid commands, and ensuring compliance with incentive programs through real-time control of power injection and storage, thereby enhancing the reliability and efficiency of energy management.
Implementation Method 1
a photovoltaic system connected to the DC power bus
Implementation Method 2
a power inverter connected to the DC power bus, the power inverter configured to convert power between the DC power bus and an AC connected load
Data Source
AI summary
An exemplary power system includes a DC power bus and a photovoltaic system connected to the DC power bus. An energy storage system is connected to the DC power bus and stores energy injected to the DC power bus by the photovoltaic system. A power inverter is connected to the DC power bus and converts power between the DC power bus and an AC connected load. The power system also includes a control system that receives power system data from one or more sub-systems and devices connected to the DC power bus, and controls, in real-time, one or more of the power inverter and the energy storage system to act as a load on the DC power bus based on the received power system data.