PQ Decoupling Controller for Power Conversion Systems
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Solution Overview
Problem
Existing solar power conversion systems face challenges in decoupling active and reactive power control due to interaction between these components, leading to instability and difficulty in independent regulation.
Innovation Solution
A power conversion system with a controller that includes an active power regulator, a reactive power regulator, and a PQ decoupling unit, which uses active and reactive power compensation elements to generate phase angle and voltage magnitude compensation signals, respectively, to decouple the interaction between active and reactive power loops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If voltage source control is used to emulate a synchronous generator, then the converter can interface DC power to AC grid, but active and reactive power become coupled due to resistance, making independent control difficult
Solution Approach 1:
The control system is segmented into separate active power and reactive power control loops. The active power regulator independently controls active power by adjusting phase angle, while the reactive power regulator independently controls reactive power by adjusting voltage magnitude. This segmentation eliminates the coupling effect caused by resistance, allowing independent regulation of active and reactive power.
Solution Approach 2:
The patent introduces virtual impedance as an intermediary element in the control loop. This virtual impedance compensates for the resistive coupling between active and reactive power channels. By adding this intermediary component, the system can maintain independent control of active and reactive power despite the presence of real resistance in the circuit.
2Reliability
If virtual impedance is added to enhance system stability, then stability improves, but device complexity increases
Solution Approach 1:
The patent replaces physical impedance elements with software-based virtual impedance in the control algorithm. Instead of adding physical components to the circuit, the virtual impedance is implemented through control software that calculates and applies the compensating effects digitally. This substitution maintains system stability while avoiding the complexity of additional physical hardware.
3Ease of manufacture
If resistance is present in the main circuit, then power conversion is enabled, but active and reactive power interaction occurs, reducing control precision
Solution Approach 1:
The control system employs feedback mechanisms where the actual active and reactive power outputs are continuously measured and fed back to their respective regulators. The active power regulator uses feedback to adjust phase angle commands, and the reactive power regulator uses feedback to adjust voltage magnitude commands. This feedback ensures precise independent control despite the presence of circuit resistance.
Data Source
AI summary
A power conversion system is disclosed including a DC bus for receiving DC power, a power converter for converting the DC power to AC power, and a controller. The controller includes an active power regulator for generating a phase angle command signal, a reactive power regulator for generating a voltage magnitude command, and an active power (P) and reactive power (Q) decoupling unit for decoupling interaction between the active and reactive power regulators. The PQ decoupling unit includes an active power compensation element and a reactive power compensation element. The active power compensation element is used for generating a phase angle compensation signal based on a reactive power error signal, to compensate the phase angle command signal. The reactive power compensation element is used for generating a voltage magnitude compensation signal based on an active power error signal, to compensate the voltage magnitude command signal.