DFIM Drive Capacity Limits Under Real-Time Operating Conditions
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Solution Overview
Problem
Conventional methods for determining high-level limitations in doubly fed induction machines are conservative, fail to simultaneously address transient and steady-state limitations, and are affected by model inaccuracies, leading to suboptimal performance and potential system overloads or underruns during extreme conditions like wind gusts.
Innovation Solution
A method to dynamically calculate high-level limitations based on actual system operation conditions, including low-level limitations of components and system parameters, while the system is in operation, using a power surfing algorithm that incorporates incremental calculations to account for real-time parameters and adapt to changing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional offline calculation methods with fixed look-up tables are used to determine high-level limitations, then the system operates with predetermined limit values, but the system cannot be optimized for every situation and rotor current dependence as function of machine speed is not considered, leading to underestimation of system capacities at high machine slips
Solution Approach 1:
The patent transitions from static fixed look-up tables to dynamic online calculation of high-level limitations. The system continuously computes limitations based on current operating conditions including rotor speed, grid frequency, and converter currents, allowing the limitations to adapt dynamically to changing system states rather than relying on predetermined fixed values
Solution Approach 2:
The patent changes the approach from using fixed parameter values stored in look-up tables to calculating parameters dynamically based on actual operating conditions. The high-level limitations are recomputed in real-time using current rotor speed, grid frequency, and converter current measurements, allowing the system to optimize for every situation rather than being constrained by predetermined values
2Reliability
If steady-state limitation is used in look-up table generation, then the command is over limited in transient conditions, but if transient limitation is chosen, then the converter generates alarm and disconnects when command exceeds steady-state limitations during extended periods
Solution Approach 1:
The patent implements dynamic differentiation between transient and steady-state limitations through online calculation. The system determines transient limitations for immediate response and steady-state limitations for sustained operation, switching between them based on the duration and nature of the command, thereby handling both transient and steady-state conditions reliably without false alarms or disconnections
Solution Approach 2:
The patent performs preliminary assessment of system state to determine whether transient or steady-state limitation applies before enforcing the limitation. By evaluating the duration and characteristics of power commands in advance, the system prepares the appropriate limitation level, preventing false alarms and ensuring continuous operation during legitimate transient conditions
3Measurement precision
If maximum size look-up table is used to cover operating points, then the accuracy is constrained by discrete LUT points, but reducing LUT size improves computational efficiency, creating a trade-off between accuracy and performance
Solution Approach 1:
The patent replaces the large discrete look-up table with a continuous mathematical model that computes limitations analytically. Instead of storing pre-calculated values at discrete operating points, the system uses equations based on machine parameters and operating conditions to calculate exact limitations for any continuous range of operating points, eliminating the accuracy-resolution trade-off inherent in discrete LUTs
Solution Approach 2:
The patent substitutes the mechanical/numerical approach of storing values in a look-up table with an analytical/mathematical approach using calculation equations. The system replaces the discrete numerical data structure with continuous mathematical relationships that provide infinite resolution without requiring large memory storage
4Reliability
If conventional fixed limitation methods are used, then the system operates conservatively to avoid overloads, but this leads to suboptimal performance and potential system underruns during extreme conditions like wind gusts
Solution Approach 1:
The patent changes the limitation parameters dynamically based on real-time operating conditions rather than using fixed conservative values. By continuously updating high-level limitations according to actual rotor speed, grid frequency, and converter current measurements, the system maintains reliable protection against overloads while allowing optimal performance during extreme conditions such as wind gusts
Data Source
AI summary
It is described a method of determining at least one high-level limitation of a system including a doubly fed induction machine, the method comprising: receiving at least one system operation condition parameter related to the actual operation condition; calculating the high-level limitation based on at least one low-level limitation at least one component of the system and the system operation condition parameter, wherein the method is particular performed, while the system is in operation.