Bidirectional DC/DC Converter Control for Wide Voltage Regulation
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Solution Overview
Problem
Existing DC/DC converters are limited to either boosting or bucking operations, restricting flexibility in voltage control between ports and requiring higher voltage rating switches for interfacing energy storage and photovoltaic arrays, which can lead to inefficiencies and increased costs.
Innovation Solution
A bidirectional DC/DC converter system with a control structure that allows voltage magnitude control at one port to be higher than, lower than, or equal to the opposing port, utilizing cascaded half-bridges and inductors or transformers for interfacing energy storage and photovoltaic arrays with lower voltage rating switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a DC/DC converter uses higher voltage rating switches to interface energy storage and photovoltaic arrays, then the voltage control range is improved, but the switching losses increase and costs increase
Solution Approach 1:
The DC/DC converter is divided into two independent conversion stages, each with its own set of switches. This segmentation allows each stage to operate at optimized voltage levels, enabling the use of lower voltage rating switches in each stage while achieving higher overall voltage transformation capability. The first stage converts input voltage to an intermediate voltage, and the second stage converts the intermediate voltage to the output voltage, thereby resolving the contradiction between voltage control range and switching losses.
2Adaptability or versatility
If a DC/DC converter uses higher voltage rating switches to interface energy storage and photovoltaic arrays, then the voltage control range is improved, but the device complexity increases
Solution Approach 1:
The converter is segmented into two stages with distinct functions. The first stage handles voltage matching between the energy storage device and an intermediate bus, while the second stage handles voltage matching between the intermediate bus and the photovoltaic array. This segmentation enables flexible voltage control across a wide range without requiring a single complex high-voltage switch, thereby reducing overall device complexity while maintaining adaptability.
Solution Approach 2:
The bidirectional DC/DC converter system can operate in multiple modes: it can charge the energy storage device from the PV array, discharge the energy storage device to the PV array, or regulate voltages independently. The two-stage architecture provides universal functionality for various operating conditions, achieving high adaptability without requiring overly complex switching arrangements.
3Adaptability or versatility
If a DC/DC converter is designed for bidirectional operation with flexible voltage control, then the adaptability is improved, but the control system complexity increases
Solution Approach 1:
The control system is segmented into two independent control loops, one for each conversion stage. Each control loop independently manages the switching of its respective stage, simplifying the overall control architecture. The first control loop regulates the voltage between the energy storage device and the intermediate bus, while the second control loop regulates the voltage between the intermediate bus and the PV array. This segmented control approach enables bidirectional operation with flexible voltage control while keeping each control module relatively simple.
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
Enables flexible power flow and efficient interfacing of energy storage and photovoltaic arrays with reduced switching losses and lower voltage rating switch requirements, allowing for bidirectional current control and voltage regulation across a wide range of voltages.
Implementation Method 1
The first conversion stage is operative to convert a first voltage at the first port to an output voltage that is output at the second port when the magnitude of the first voltage at the first port is higher than the magnitude of a second voltage at the second port. The second conversion stage is operative to convert the second voltage at the second port to an output voltage that is output at the first port when the magnitude of the second voltage at the second port is greater than the magnitude of the first voltage at the first port.
Data Source
AI summary
A DC/DC converter system includes a bidirectional DC/DC converter converting between voltage levels at first and second ports and a control system for controlling the DC/DC converter. The bidirectional DC/DC converter includes a first conversion stage connected to the first port and a second conversion stage interfaced with the first conversion stage and connected to the second port. The control system includes outer and inner control loops. The outer control loop compares a command for one of a voltage level, a current level or power at one of the first and second ports to an actual value of voltage level, current level or power level and outputs an interface current command based on the comparison. The inner control loop compares the interface current command to an actual interface current at an interface of the first and second conversion stages, and controls a switching signal duty value based on the comparison.