Feedback Control for Voltage Source Converters in Weak Grids
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Solution Overview
Problem
Weak grid power systems experience stability issues due to coupling between power delivery and voltage, leading to inefficiencies in wind-based energy transmission to the power grid, particularly exacerbated by 4 Hz and 30 Hz oscillations.
Innovation Solution
Implementing mechanism-based feedback control for vector control-based voltage source converters (VSCs) that modulate either the power order or the dc-link voltage order using the d-axis current or PCC voltage as input signals to reduce coupling between power and voltage, enhancing system stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If power delivery is increased in weak grid power systems, then energy transmission efficiency is improved, but PCC voltage reduction occurs leading to system instability
Solution Approach 1:
The patent implements a feedback control mechanism where the PCC voltage is continuously monitored and used to adjust the active power delivery from the wind farm. When PCC voltage drops below a reference threshold, the controller reduces active power delivery to allow voltage recovery, preventing instability. This closed-loop feedback system dynamically balances power delivery and voltage stability.
Solution Approach 2:
The control system dynamically changes operating parameters based on grid conditions. The active power delivery parameter is adjusted in response to PCC voltage measurements, allowing the system to adapt to varying grid strength and maintain stability during different operating conditions including weak grid scenarios.
2Stability of the object's composition
If feedback control is implemented to reduce coupling between power and voltage, then system stability is improved, but control complexity increases
Solution Approach 1:
A feedback control loop is established where PCC voltage measurements are fed back to the wind farm controller. The controller compares the measured voltage with a reference value and adjusts active power delivery accordingly, creating a simple yet effective stability mechanism.
Solution Approach 2:
The control system acts as an intermediary between the wind farm power delivery and the weak grid. By introducing this control layer, the system mediates the interaction between variable wind power output and the weak grid's voltage requirements, reducing harmful coupling effects.
3Productivity
If oscillations are suppressed through feedback control, then delivery efficiency is enhanced, but the coupling between power and voltage requires active management
Solution Approach 1:
The feedback mechanism detects oscillations in PCC voltage and responds by adjusting active power delivery. This automatic response suppresses oscillations and prevents them from growing into instability, thereby maintaining high delivery efficiency even in weak grid conditions.
Solution Approach 2:
The control system operates continuously with periodic measurement and adjustment cycles. By constantly monitoring PCC voltage and making incremental adjustments to power delivery, the system prevents oscillations from developing while maintaining efficient energy transmission.
Data Source
AI summary
Devices and methods for mechanism-based feedback controller employed in a wind powered power system are provided. A controller can include a vector control-based voltage source converter with feedback control circuitry. The feedback control circuitry is configured to modulate either a power order or a dc-link voltage order to control coupling between voltage and power. The controller can be connected to a wind-based turbine generator of a wind farm and regulate power deployed to a power grid.