Signal Processor for Inverter Control Using Coordinate Conversion
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Solution Overview
Problem
Designing control systems for interconnection inverter systems is challenging due to the need for quick response times and nonlinear time-varying processes, making it difficult to achieve linear control theory-based designs.
Innovation Solution
A signal processor is developed to perform equivalent fixed-to-rotating and rotating-to-fixed coordinate conversions while maintaining linearity and time-invariance, using specific transfer functions to process input signals and generate PWM signals for power converter circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fixed-to-rotating and rotating-to-fixed coordinate conversions are used for control, then control accuracy is improved, but the system becomes nonlinear and time-varying making linear control theory inapplicable
Solution Approach 1:
The patent inverts the conventional control approach by performing coordinate conversions in the opposite sequence: rotating-to-fixed conversion is applied first to transform rotating coordinate signals to fixed coordinates, then fixed-to-rotating conversion is applied to transform back to rotating coordinates for PWM generation. This inversion maintains signal equivalence while enabling linear control theory application.
Solution Approach 2:
The patent changes the parameter representation by introducing equivalent transfer functions that model the coordinate conversion processes. By representing the conversions as linear time-invariant transfer functions with specific parameters (gain, phase shift), the system maintains control accuracy while becoming amenable to linear control design.
2Measurement precision
If conventional coordinate conversion methods are used, then control precision is maintained, but response time is slow due to complex processing
Solution Approach 1:
The patent extracts the essential control function from the complex coordinate conversion process by identifying and implementing only the critical transformation steps. By separating the necessary conversions from unnecessary processing, the system achieves quick response while maintaining precision.
Solution Approach 2:
The patent performs preliminary coordinate transformations before the main control processing by pre-calculating transfer function parameters and preparing signal transformations in advance. This preliminary action reduces the computational burden during real-time control, enabling faster response times.
3Ease of manufacture
If linear control theory is applied, then system design becomes simpler, but the system must maintain linearity and time-invariance which conflicts with conventional coordinate conversions
Solution Approach 1:
The patent creates a universal control framework that can handle both linear control requirements and coordinate conversion needs through equivalent transfer functions. The same linear control theory apparatus can be applied regardless of the specific coordinate system, providing both simplicity and adaptability.
Solution Approach 2:
The patent introduces equivalent transfer functions as intermediaries between the coordinate conversion processes and the linear control theory application. These transfer functions act as mediators that translate nonlinear coordinate transformations into linear equivalent representations, enabling linear control design while preserving coordinate conversion flexibility.
Data Source
AI summary
A signal processor is configured to perform a process equivalent to performing a series of fixed-to-rotating coordinate conversion, a predetermined process and then rotating-to-fixed coordinate conversion, while maintaining linearity and time-invariance. The signal processor performs a process given by the following matrix G:G=[F(s+jω0)+F(s-jω0)2F(s+jω0)-F(s-jω0)2j-F(s+jω0)-F(s-jω0)2jF(s+jω0)+F(s-jω0)2]where F(s) is a transfer function representing the predetermined process, ω0 is a predetermined angular frequency and j is the imaginary unit.