Electrical Converter Harmonic Control via Transformer Damping
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Solution Overview
Problem
High power electrical converter systems generate unwanted harmonics during frequency conversion, which can disrupt distribution grids and require expensive and heavy line filter circuits to manage, posing a challenge in maintaining harmonic distortion within defined limits.
Innovation Solution
An electrical converter system employing optimized pulse patterns and a transformer with frequency-dependent damping behavior to control harmonic magnitudes, allowing the transformer to act as a low-pass filter and reduce the need for additional hardware filters, thereby minimizing harmonic distortion without the need for large line filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If electrical line filter circuits are used to reduce harmonics, then harmonic distortion limits are met, but system cost and weight increase
Solution Approach 1:
The invention extracts the harmonic filtering function from separate line filter circuits and integrates it into the transformer design. The transformer's winding configuration and leakage inductance are specifically designed to provide harmonic attenuation, eliminating the need for additional dedicated filter components and reducing overall system weight.
Solution Approach 2:
The transformer is designed to perform multiple functions simultaneously: voltage transformation and harmonic filtering. By incorporating specific winding configurations (such as delta-wye connections) and optimizing leakage inductance, the transformer serves both its primary purpose of voltage conversion and the secondary purpose of harmonic suppression, reducing the need for separate filter circuits.
2Object-affected harmful factors
If electrical line filter circuits are used to reduce harmonics, then harmonic distortion limits are met, but system cost increases
Solution Approach 1:
The invention merges the harmonic filtering function with the transformer assembly. By designing the transformer windings and magnetic circuit to inherently provide harmonic attenuation characteristics, the system eliminates the need for separate filter circuits, reducing component count, assembly complexity, and overall system cost.
Solution Approach 2:
The transformer is designed to perform multiple functions simultaneously: voltage transformation and harmonic filtering. By incorporating specific winding configurations (such as delta-wye connections) and optimizing leakage inductance, the transformer serves both its primary purpose of voltage conversion and the secondary purpose of harmonic suppression, reducing the need for separate filter circuits.
3Object-affected harmful factors
If optimized pulse patterns are used to control harmonics, then harmonic distortion is reduced, but control complexity increases
Solution Approach 1:
The invention employs periodic pulse width modulation (PWM) switching patterns in the converter circuits. By using regular, repeating switching sequences with optimized duty cycles and timing, the system generates voltage waveforms with reduced harmonic content. The periodic nature of the switching allows for predictable harmonic spectra that can be attenuated by the transformer's fixed impedance characteristics.
4Object-affected harmful factors
If transformer with frequency-dependent damping is used, then harmonics are dampened, but transformer design complexity increases
Solution Approach 1:
The invention applies local quality by designing specific winding configurations and connection schemes (such as delta-wye transformations) that create frequency-dependent impedance characteristics in specific parts of the transformer. The leakage inductance and winding arrangements are optimized to provide enhanced damping at harmonic frequencies while maintaining efficient power transfer at the fundamental frequency.
Solution Approach 2:
The transformer design utilizes parameter changes by optimizing winding configurations, turn ratios, and connection schemes to achieve frequency-dependent damping characteristics. By carefully selecting and adjusting these design parameters, the transformer provides enhanced impedance at harmonic frequencies to suppress harmonic currents, while maintaining low losses at the fundamental operating frequency.
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
The system effectively dampens harmonics within specified thresholds, reducing the need for extensive hardware components, saving costs, space, and installation efforts while meeting grid standards for harmonic limits.
Implementation Method 1
a transformer interconnected with the electrical converter at a secondary side and for transforming the multi-phase converter output voltage into a multi-phase transformer output voltage at a primary side
Implementation Method 2
the transformer has a damping behaviour like a low pass filter between the secondary side and the primary side, which frequency-specific damps the converter output voltage, such that converter output magnitudes of specific harmonics at the secondary side are higher than predefined threshold magnitudes for the specific frequencies and transformer output magnitudes of the specific harmonics at the primary side are lower than the predefined threshold magnitudes
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
An electrical converter system (10) comprises an electrical converter (12) for converting an input voltage into a converter output voltage (20); a transformer (14) interconnected with the electrical converter (12) at a secondary side (28) and for transforming the converter output voltage (20) into a transformer output voltage (30) at a primary side (32); and a controller (16) adapted for switching the electrical converter (12) with optimized pulse patterns (22), such that the electrical converter (12) produces the converter output voltage (20) with a fundamental frequency and a series of harmonics (24). Between the secondary side (28) and the primary side (32), the transformer (14) has a frequency damping behaviour like a low pass filter. The optimized pulse patterns (22) are optimized such that the converter output magnitudes (26) of harmonics (24) in an upper frequency range (68) are higher than those of harmonics (24) in a lower frequency range (66) and such that the converter output magnitudes (26) of the harmonics (24) in the upper frequency range (68) at the secondary side (28) are higher than predefined threshold magnitudes (36, 36a, 36b) for the harmonics (24) in the upper frequency range (68) and transformer output magnitudes (34) of the harmonics (24) in the upper frequency range (68) at the primary side (32), which are damped by the transformer (14), are lower than the predefined threshold magnitudes (36, 36a, 36b).