LCR Filter PCS Voltage Control via SVPWM
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Solution Overview
Problem
Traditional power conversion systems (PCS) for intermittent energy sources like wind and solar face challenges in controlling voltage and frequency, especially in off-grid scenarios, due to complex filtering effects and high DC-side voltage requirements, which complicate control strategies and increase the difficulty of engineering applications.
Innovation Solution
A system and method employing an LCR-type PCS topology with a simplified control strategy using a reference voltage converter, phase-locked loop, grid-side voltage converter, proportional integral controllers, and space vector pulse width modulation (SVPWM) generator, which reduces the complexity of control by employing a single-stage voltage closed-loop control and model reduction techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an LCL filter is used in the PCS to improve filtering effect, then the filtering performance is improved, but the DC-side voltage requirement increases which is adverse to series/parallel connection of DC-side battery components
Solution Approach 1:
The patent changes the filter topology from LCL to LCR, modifying the circuit parameters and structure. This parameter change allows achieving good filtering效果 while reducing the DC-side voltage requirement to 450V, making it suitable for battery series/parallel connections.
2Measurement precision
If an LCL filter or isolating transformer is added to improve output performance, then the output quality is improved, but the mathematical model becomes high-order which increases control complexity
Solution Approach 1:
The patent extracts and eliminates unnecessary control loops from the system. By using the LCR filter topology and simplified control strategy, it removes the need for complex voltage-current double closed-loop control, reducing the number of sensors and PI controllers while maintaining output performance.
Solution Approach 2:
Instead of using complex control strategies to handle high-order models, the patent inverts the approach by selecting a filter topology (LCR) that naturally simplifies the mathematical model, making the control system easier to implement and debug.
3Measurement precision
If traditional voltage-current double closed-loop control is used for high-order PCS model, then the control accuracy is maintained, but more sensors and PI controllers are required making debugging difficult
Solution Approach 1:
The patent removes unnecessary control components (additional sensors and PI controllers) by adopting a simplified control architecture based on the LCR filter topology, which maintains control accuracy while significantly improving debugging convenience.
Data Source
AI summary
The present invention discloses a system and a method for controlling PCS voltage and frequency, wherein the system comprises a reference voltage converter, a phase-locked loop, a grid-side voltage converter, a voltage transformer, a first proportional integral controller, a second proportional integral controller, a coordinate converter and a SVPWM generator; a reference voltage converter is connected to an output terminal of a the phase-locked loop, and the output terminal of the phase-locked loop is further connected to a grid-side voltage converter; the grid-side voltage converter is connected to a high-voltage side of an isolating transformer of the electric grid via the voltage transformer; two output terminals of the grid-side voltage converter are respectively connected to the coordinate converter via two proportional integral controllers; an output terminal of the coordinate converter is connected to the SVPWM generator; an output terminal of the SVPWM generator is connected to a power switch of the electric grid. A PWM control signal for controlling the power switch of the electric grid is generated by the reference voltage converter, the phase-locked loop, the grid-side voltage converter, the voltage transformer, the two proportional integral controllers, the coordinate converter and the SVPWM generator. The system and method for controlling PCS voltage and frequency according to the invention have the advantages that the PCS can realize voltage and frequency buildup in an off-grid state and can stably output an expected voltage and frequency.