Hybrid AC HVDC Grid Dispatch Using Successive Linear Approximation
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Solution Overview
Problem
Conventional power flow analysis methodologies for hybrid AC and HVDC systems are inadequate, as they often overlook converter losses, control laws, grounding schemes, and bipole configurations, leading to incomplete modeling and complex optimization processes.
Innovation Solution
A method for Security Constrained Economic Dispatch (SCED) in hybrid power systems using successive linear programming, where the objective function and constraints are approximated as piecewise linear problems, allowing for linear programming to optimize AC and DC grid interactions without exposing proprietary DC grid modeling details.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If detailed DC grid modeling is used for power flow analysis, then modeling accuracy is improved, but proprietary information is exposed and device complexity increases
Solution Approach 1:
The patent segments the hybrid power system into separate AC grid and DC grid portions, allowing independent analysis of each subsystem. The DC grid is modeled separately with its own power flow equations and constraints, while the AC grid analysis remains unaffected by proprietary DC details. This segmentation enables accurate DC grid modeling without exposing sensitive information to the overall system analysis.
Solution Approach 2:
The patent introduces an intermediary approach by using equivalent models and interface variables at the connection points between AC and DC grids. Instead of directly coupling detailed DC grid models with AC grid analysis, the methodology uses intermediate representations that capture essential DC grid behavior (power injections, voltage magnitudes) without requiring full exposure of proprietary DC grid modeling details.
2Reliability
If converter losses, control laws, grounding schemes, and bipole configurations are included in the model, then modeling completeness is improved, but processing complexity increases
Solution Approach 1:
The patent transforms the complex non-linear power flow equations into linearized forms by changing the mathematical parameters and representation. Converter losses, control laws, and other non-linear elements are incorporated through linearization techniques and iterative solution methods, converting an intractable complex problem into a series of manageable linear programming problems that maintain modeling completeness while reducing processing complexity.
3Measurement precision
If simultaneous optimization of AC and DC grids is performed, then solution accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent applies segmentation by separating the optimization problem into distinct AC grid and DC grid components that can be solved independently or in a coordinated sequential manner. Each grid portion has its own objective function and constraints, allowing for specialized optimization techniques to be applied to each subsystem while maintaining overall system optimality through interface coordination.
Solution Approach 2:
The patent introduces dynamic iterative solution procedures that alternate between optimizing AC and DC grid portions. Rather than attempting static simultaneous optimization, the methodology dynamically iterates between the two subsystems, updating interface variables and converging to a globally optimal solution. This dynamic approach breaks down the computationally intensive simultaneous optimization into a series of simpler iterative steps.
Data Source
AI summary
The teachings herein disclose an advantageous method and apparatus for performing Security Constrained Economic Dispatch (SCED) for a hybrid power system that includes one or more AC grids interconnected with one or more multi-terminal High Voltage DC (HVDC) grids. The teachings include optimizing a non-linear objective function, subject to a set of constraints that include AC and DC grid constraints, for determining the SCED solution using successive linear approximation. The linear programming model used in the linear approximations is advantageously augmented with a DC grid portion in a manner that accounts for the effects of the DC grid on the AC grid, but which does not require exposing proprietary DC grid modeling details, and which conforms the resultant SCED solution to all applicable AC and DC grid constraints, including AC grid line flow constraints, AC grid power balance constraints, DC grid line flow constraints, and DC grid power balance constraints.