Bidirectional Inverter Control Without Transformer Feedback
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Solution Overview
Problem
Existing power conversion devices face challenges in controlling both AC-DC and DC-AC conversion circuits efficiently, particularly in high-power applications, due to large circuit sizes and the need for transformers, which hinder size reduction and cost effectiveness.
Innovation Solution
A control device is designed to generate a control signal by subtracting a multiplied signal from a reference signal, allowing for efficient control of both AC-DC and DC-AC conversion circuits using a bidirectional inverter with a digital control system, incorporating transistors and capacitors, and employing wide-band-gap semiconductors for reduced losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transformer is provided between the application terminal for the input voltage and the analog control device to generate a control signal commensurate with the input voltage, then the control signal can be generated, but the device size and cost increase
Solution Approach 1:
The patent extracts the voltage-to-current conversion function from a traditional transformer and implements it digitally through ADC sampling and digital signal processing. The control signal is generated by digitally multiplying the sampled input voltage by a reference waveform, eliminating the need for a physical transformer and reducing device size.
Solution Approach 2:
The patent replaces the mechanical/electromagnetic transformer with a digital system consisting of ADC, digital multiplier, and DAC. This substitution eliminates moving parts and magnetic components, significantly reducing device size while maintaining control signal generation capability.
2Reliability
If a transformer is provided between the application terminal for the input voltage and the analog control device to generate a control signal commensurate with the input voltage, then the control signal can be generated, but the cost increases
Solution Approach 1:
The patent extracts the voltage-to-current conversion function from a traditional transformer and implements it digitally through ADC sampling and digital signal processing. The control signal is generated by digitally multiplying the sampled input voltage by a reference waveform, eliminating the need for a physical transformer and reducing device size.
Solution Approach 2:
The patent replaces the mechanical/electromagnetic transformer with a digital system consisting of ADC, digital multiplier, and DAC. This substitution eliminates moving parts and magnetic components, significantly reducing device size while maintaining control signal generation capability.
3Reliability
If PI control is employed in the control device, then negative feedback control is achieved, but large vibration occurs until steady state is reached making control difficult
Solution Approach 1:
The patent implements dynamic control by switching between different control modes based on operating conditions. During transient states, predictive control is used to minimize vibration, while during steady state, PI control maintains accuracy. This dynamic switching resolves the contradiction between rapid response and stability.
Solution Approach 2:
The patent employs periodic sampling and control updates at optimized frequencies that match the system's natural response characteristics. This periodic control action dampens oscillations during transient states while maintaining steady-state accuracy, resolving the vibration issue with PI control.
4Adaptability or versatility
If a bidirectional inverter is used to achieve both AC-DC conversion and DC-AC conversion, then circuit versatility is improved, but control complexity increases
Solution Approach 1:
The patent implements a universal control algorithm that automatically adapts to different operating modes (AC-DC rectification, DC-AC inversion, regenerative braking) through mode detection and parameter switching. A single controller handles all functions by adjusting control parameters, eliminating the need for separate control circuits for each mode and reducing overall complexity.
Solution Approach 2:
The patent implements dynamic control by switching between different control modes based on operating conditions. During transient states, predictive control is used to minimize vibration, while during steady state, PI control maintains accuracy. This dynamic switching resolves the contradiction between rapid response and stability.
Data Source
AI summary
An apparatus includes a control device configured to serve as a principal controlling agent in an electric power conversion device incorporating a switching circuit configured to be a bidirectional inverter. The control device is configured to subtract, from a reference signal that is determined in accordance with an operation mode of the electric power conversion device, a multiplied signal obtained by multiplying a control-target current of the switching circuit by a prescribed coefficient to generate, based on a result of the subtraction, a control signal for controlling the bidirectional inverter.