Full-Converter Wind Power Grid Support With Dynamic DC-Link Voltage
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Solution Overview
Problem
Modern wind power plants face limitations in providing effective grid support, especially in low winds, due to restricted capabilities in feeding active and reactive power, which can destabilize the electrical supply grid.
Innovation Solution
The method involves setting a second DC voltage dynamically based on a feed set point value, which includes both active and reactive power components, using a step-up converter or active rectifier to adjust the DC voltage, and employing a tolerance band method for efficient inversion into AC voltage, allowing for optimal grid support and power management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the second DC voltage is kept constant at a high level to enable grid feed-in, then the AC voltage level required for grid connection is achieved, but the wind power plant cannot effectively provide grid support in low winds and switching losses increase
Solution Approach 1:
The patent applies dynamics by making the second DC voltage adjustable rather than fixed. The control device dynamically adapts the second DC voltage based on operating conditions: in low winds, a lower second DC voltage reduces switching losses and improves grid support capability, while in strong winds, a higher second DC voltage enables effective grid feed-in. This dynamic adjustment resolves the contradiction between maintaining grid connection capability and reducing energy losses.
2Adaptability or versatility
If the second DC voltage is increased to improve reactive power feed-in capability, then grid support is enhanced, but the switching losses in the inverter increase
Solution Approach 1:
The patent applies parameter changes by adjusting the second DC voltage level according to the required reactive power feed-in. The control device modifies the second DC voltage parameter to match the grid support requirements: when reactive power support is needed, the second DC voltage is increased to enable adequate reactive power feed-in, while when full load operation occurs, the second DC voltage is reduced to minimize switching losses. This resolves the contradiction between adaptability and energy efficiency.
3Reliability
If the step-up converter controls the generator to achieve the required second DC voltage in low winds, then the AC voltage level is maintained, but the control complexity increases and grid support capability is limited
Solution Approach 1:
The patent applies universality by enabling the step-up converter to perform multiple functions: it not only maintains the required second DC voltage level for grid feed-in but also provides grid support capability by adjusting the second DC voltage according to grid requirements. The control device integrates both grid connection maintenance and grid support functions into a single control system, reducing overall system complexity while achieving multi-functionality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances grid support by allowing wind power plants to contribute more effectively to grid stability, especially in low winds, by dynamically adjusting the second DC voltage to meet grid requirements, improving reactive power feed-in and reducing switching losses, while maintaining a sinusoidal signal quality.
Implementation Method 1
an electrical AC voltage is generated by a generator and rectified into a first DC voltage
Implementation Method 2
This first DC voltage can be stepped up to a second DC voltage by means of a step-up converter
Implementation Method 3
the second DC voltage forms an input for an inverter which generates the electrical power which is to be fed into the electrical supply grid with an AC voltage which is adjusted to the electrical supply grid
Data Source
AI summary
The invention relates to a method for feeding electrical power into an electrical supply grid. The method includes rectifying a first AC voltage of an electrical power, produced by a generator, into a first DC voltage and increasing the first DC voltage to a second DC voltage such that the second DC voltage has a step-up ratio in relation to the first DC voltage. Alternatively, the method includes rectifying the first AC voltage into the second DC voltage without producing the first DC voltage. The method includes inverting the second DC voltage into a second AC voltage for feeding electrical power into the electrical supply grid depending on an feed setpoint value and setting the second DC voltage depending on the feed setpoint value and actual value. The second DC voltage is increased depending on an increase in the feed setpoint voltage or actual value.