Grid-Connected Inverter Power Decoupling via Amplitude Phase Feedforward
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Solution Overview
Problem
Voltage-controlled grid-connected inverters face challenges in independently controlling active and reactive power due to coupling issues, which are not effectively addressed by existing decoupling methods, especially in large-signal scenarios.
Innovation Solution
A method and apparatus that compute amplitude and phase feedforward amounts based on grid voltage and inverter output voltage differences, allowing for independent control of active and reactive power by using these values to regulate the output power, specifically through equations E ff = ∑(UE sin δ / U cos δ − 2E Δδ / δ ff = −∑ tan δ E ΔE, and applying these to a power regulation module.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If voltage-controlled grid-connected inverters are used to enable island mode operation and provide voltage support, then adaptability and reliability are improved, but power coupling between active and reactive power occurs making independent control difficult
Solution Approach 1:
The patent transforms the control parameters from direct active and reactive power control to amplitude and phase angle control. By changing the control parameters to amplitude feedforward amount and phase feedforward amount, the system achieves independent control of active and reactive power while maintaining voltage-controlled island mode operation capability.
Solution Approach 2:
The patent introduces amplitude feedforward amount and phase feedforward amount as intermediary parameters between the control input and power output. These intermediary parameters decouple the control of active and reactive power, allowing independent adjustment without direct coupling while still operating in voltage-controlled mode.
2Measurement precision
If traditional power control algorithms are used in voltage-controlled inverters, then active and reactive power can be computed, but power coupling causes fluctuations when reference values change
Solution Approach 1:
The patent computes amplitude feedforward amount and phase feedforward amount in advance based on grid voltage and inverter output voltage differences before power regulation. This preliminary computation of decoupling parameters prevents power coupling fluctuations from occurring when reference values change, ensuring stable power output.
3Ease of operation
If existing decoupling methods like inductor current feedforward or vector PI controllers are applied, then power decoupling can be achieved in current-controlled inverters, but these methods cannot be directly applied to voltage-controlled inverters
Solution Approach 1:
The patent fundamentally changes the control parameters from current-based (used in current-controlled inverters with feedforward or PI methods) to voltage-based parameters (amplitude and phase angle). This parameter transformation makes the decoupling method specifically adaptable to voltage-controlled inverters while achieving effective power decoupling control.
Data Source
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AI summary
A method and an apparatus for decoupling output power of an inverter are provided. The method comprises: obtaining voltage amplitude instruction E* and voltage phase instruction θ* according to an output voltage and an output current of the inverter; obtaining an amplitude feedforward amount Eff and a phase feedforward amount δff according to an amplitude U of a grid voltage of the power grid, an amplitude E of the output voltage of the inverter, and a phase difference δ between the output voltage of the inverter and the grid voltage; obtaining a reference voltage amplitude Eref according to the voltage amplitude instruction E* and the amplitude feedforward amount Eff, and obtaining a reference voltage phase θref according to the voltage phase instruction θ* and the phase feedforward amount δff; and regulating the output power of the inverter using the reference voltage amplitude Eref and the reference voltage phase θref.