Integrated Energy Storage Inverters Without Bulky Transformers
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Solution Overview
Problem
Current solar energy harvesting systems require separate power electronic converters for PV and energy storage, leading to inefficiencies, high costs, and limited scalability due to the need for bulky transformers and high voltage energy storage units, which compromise reliability and cost-effectiveness.
Innovation Solution
Integration of energy storage cells into multi-level DC/AC inverters with differential geometric control systems, using half-bridge and full-bridge configurations with semiconductor-based circuit element modules, energy storage sub-circuits, and capacitors to optimize power flow and eliminate the need for low-frequency transformers, allowing for scalable and efficient energy management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two separate power electronic converters are used for PV and energy storage systems, then the system can perform MPPT and convert DC to AC, but the system cost increases and the architecture becomes more complex
Solution Approach 1:
The patent combines the PV inverter and battery inverter into a single integrated power electronic converter. This single converter performs both MPPT for PV panels and DC-AC conversion for battery power, eliminating the need for two separate converters. The integration maintains all necessary functions while reducing system complexity and cost.
Solution Approach 2:
The integrated power electronic converter is designed to perform multiple functions: it acts as a PV inverter for solar power conversion, a battery inverter for energy storage conversion, and enables bidirectional power flow between PV, battery, and grid. This multi-functional design replaces multiple specialized devices with a single universal converter.
2Reliability
If a low frequency transformer is used to provide galvanic isolation and voltage transformation, then the system achieves isolation and voltage matching, but the transformer becomes bulky, heavy, and causes significant losses
Solution Approach 1:
The patent replaces the mechanical low frequency transformer with an electronic isolation mechanism implemented through the integrated power electronic converter. The converter uses high-frequency switching and control circuits to achieve galvanic isolation and voltage transformation without requiring a bulky transformer, thereby eliminating the associated weight and losses.
3Productivity
If the energy storage unit operates at high voltage to eliminate the low frequency transformer, then the system achieves high efficiency and high power density, but the voltage range of energy storage is limited and many battery types cannot be used
Solution Approach 1:
The patent employs a multi-level DC-DC converter stage before the DC-AC inversion that can flexibly adjust the DC voltage level. This converter raises or lowers the battery voltage as needed, allowing low-voltage battery packs to operate effectively in the inverter system. The parameter adjustment capability enables the system to work with various battery types and voltages while maintaining high power density.
4Productivity
If high voltage energy storage is used to eliminate the low frequency transformer, then the system achieves high efficiency, but the reliability decreases due to high voltage requirements
Solution Approach 1:
The patent uses a multi-level DC-DC converter that can adaptively adjust voltage levels based on system conditions. This allows the system to operate at optimal voltage for efficiency while maintaining safe operating parameters for reliability. The flexible voltage control enables the system to achieve high efficiency without being constrained by fixed high voltage requirements that would compromise reliability.
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
This solution enables efficient, cost-effective, and scalable integration of energy storage into PV systems, optimizing power flow and reducing the complexity and cost associated with high voltage requirements, while maintaining reliability and high power density.
Implementation Method 1
Energy storage systems can effectively resolve this issue of intermittent energy from solar energy harvesting systems by storing harvested energy and then releasing that stored energy when needed
Implementation Method 2
a multi-level DC/AC inverter receiving outputs of the plurality of DC/DC converters and producing the AC power
Implementation Method 3
The PV inverter is used to perform MPPT for the PV panels and to convert the harvested energy into an AC form that is compatible with the AC grid
Data Source
AI summary
Systems and circuits relating to the integration of energy storage subsystems into components for use with systems that harvest energy from PV panels and that convert that energy for use with a power grid. Various configurations of inverters that integrate energy storage cells are presented. Half-bridge and full bridge configurations for the inverters are presented. The integrated energy storage cells may be battery cells, supercapacitor cells, or a combination of the two.