Differential Geometry DC/DC Converter for PV-Battery Power Flow
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Solution Overview
Problem
Existing solar energy harvesting systems with separate power electronic converters for photovoltaic and energy storage are not cost-effective and lack real-time information exchange, leading to suboptimal power flow, and architectures that eliminate low frequency transformers face limitations in scalability and reliability due to high voltage energy storage requirements.
Innovation Solution
A system using a low voltage DC/DC converter based on differential geometry to converge capacitor voltages to nominal values, coupled with a bi-directional high voltage DC/DC converter and a DC/AC inverter, enabling efficient power conversion and control across components, including a control system for MPPT and charge management, and geometric modulation for semiconductor switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two separate power electronic converters are used for PV and energy storage, then each converter can be optimized for its specific function, but the system cost increases and real-time information exchange between components is lost
Solution Approach 1:
The patent combines the PV converter and battery converter into a single integrated power electronic converter. This single converter handles both PV power processing and battery charge/discharge operations, eliminating the need for two separate converters. The integration maintains functional optimization while reducing system cost and enabling real-time information exchange between PV and battery components through a unified control system.
2Reliability
If a low frequency transformer is used to provide isolation and voltage transformation, then galvanic isolation and voltage matching are achieved, but the transformer becomes bulky, heavy, and causes significant losses
Solution Approach 1:
The patent replaces the traditional low frequency transformer with a high frequency isolated DC-DC converter. This substitution eliminates the bulky, heavy transformer by using high frequency switching technology that achieves the same galvanic isolation and voltage transformation functions with much smaller and lighter components. The high frequency converter also reduces energy losses compared to low frequency transformer operation.
3Productivity
If the energy storage subsystem operates at high voltage to eliminate the transformer, then the architecture achieves high efficiency and power density, but the voltage range is limited and many battery types cannot be used
Solution Approach 1:
The patent employs a wide voltage range DC-DC converter that can adapt to different battery voltage levels. The converter's voltage conversion ratio is dynamically adjustable, allowing it to interface with various battery types operating at different voltages (low voltage, medium voltage, or high voltage). This parameter adaptability enables the system to maintain high efficiency and power density while being compatible with multiple battery chemistries and voltage specifications.
Data Source
AI summary
Systems and methods relating to the conversion of DC power to AC power suitable for an AC power grid. DC power is received from one or more PV panels and is converted into DC power useful for charging an energy storage subsystem. The energy storage subsystem feeds into a DC/DC converter that converts the low voltage DC power into high voltage DC power suitable for a DC/AC inverter. The DC/AC inverter then converts the high voltage DC power into AC power suitable for an AC grid. A low voltage DC/DC converter can be used that is based on a differential geometry approach such that adjustable parameter values for components within the converter converge to nominal values as system parameters evolve.