Wind Farm Controller Mitigating Electric Unbalance at PCC

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Solution Overview

Problem

Wind farms face challenges in mitigating electric unbalance at the Point of Common Coupling (PCC) between wind turbines and a power grid, leading to poor voltage quality and increased power losses due to harmonic disturbances.

Innovation Solution

A system comprising a measurement device to measure the Voltage Unbalance Factor (VUF) at the PCC and a central wind farm controller that generates a compensation signal to adjust the operation of wind turbines and power converters, reducing electric unbalance by controlling phase offsets and injecting adjustment currents to balance the three-phase current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If wind turbines are connected to the power grid at the PCC, then wind energy can be transmitted to the grid, but electric unbalance occurs leading to poor voltage quality and increased power losses

Engineering Contradiction:

Improvewind energy transmissionVSAvoidpower losses due to harmonic disturbances

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The system continuously measures the Voltage Unbalance Factor (VUF) at the PCC and uses this feedback to dynamically adjust the phase offsets of power converters. This closed-loop control enables real-time mitigation of electric unbalance, improving voltage quality and reducing power losses while maintaining wind energy transmission to the grid.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The invention changes the operating parameters of power converters by dynamically adjusting phase offsets based on measured VUF values. This parameter adjustment allows the system to adapt to varying grid conditions and wind turbine outputs, effectively mitigating electric unbalance and reducing harmonic disturbances without compromising energy transmission.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If wind turbines are connected to the power grid at the PCC, then wind energy can be transmitted to the grid, but voltage quality deteriorates due to electric unbalance

Engineering Contradiction:

Improvewind energy transmissionVSAvoidvoltage quality

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The invention introduces power converters as intermediary devices between the wind turbines and the grid. These converters act as mediators that can actively control phase offsets and inject adjustment currents to counteract electric unbalance, thereby protecting grid voltage quality while allowing wind energy transmission.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of energy

If measurement and control systems are implemented at the PCC to mitigate electric unbalance, then voltage quality and power loss are improved, but system complexity increases

Engineering Contradiction:

Improvepower lossesVSAvoidmeasurement and control system complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The system uses a centralized wind farm controller that performs multiple functions: it controls the operation of multiple wind turbines and simultaneously manages electric unbalance mitigation at the PCC. This multi-functionality reduces the need for separate dedicated control devices, thereby limiting the increase in system complexity while achieving effective unbalance mitigation and power loss reduction.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The invention combines the measurement of VUF, the calculation of compensation signals, and the control of power converter phase offsets into a single integrated control system. By merging these functions, the system achieves effective unbalance mitigation without requiring multiple separate devices, thus limiting the increase in overall system complexity.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentEP2485358B2System and method for mitigating an electric unbalance of a three-phase current at a Point of Common Coupling between a wind farm and a power grid

Publication Date: 2021.12.22 SIEMENS GAMESA RENEWABLE ENERGY AS

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AI summary

It is described a system for mitigating an electric unbalance of a three-phase current at a Point of Common Coupling (120) being located between a wind farm (100) comprising a plurality of wind turbines (110) and a power grid. The system comprises (a) a measurement device (122) for measuring the electric unbalance at the Point of Common Coupling (120) and for providing a measurement signal (122a) being indicative for the measured electric unbalance and (b) a central wind farm controller (130) for controlling the operation of the plurality of wind turbines (110). The central wind farm controller (130) is coupled to the measurement device (122). In response to the measurement signal (122a) the central wind farm controller (130) is configured for providing a control signal (130a) for mitigating the electric unbalance at the Point of Common Coupling (120). It is further described a corresponding method for mitigating an electric unbalance of a three-phase current and a computer program for controlling and/or for carrying out the described method.