Reactive Power Coordination for Online Grid Voltage Control
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Solution Overview
Problem
The integration of large-scale renewable energy sources into power grids is hindered by voltage fluctuations and the nonlinearity of reactive power-voltage operations, which are challenging to manage due to the complexity of coordinating continuous and discrete reactive power resources, leading to potential operational inefficiencies and safety concerns.
Innovation Solution
An online voltage control method is developed that constructs a practical model for coordinating multi-type reactive power resources, using linearized equations and mixed-integer quadratic programming to optimize voltage control, considering nodal voltage constraints, generator reactive power, and transformer tap positions, while introducing slack variables to improve computational convergence and avoid unreasonable voltage constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional nonlinear programming methods are used for reactive voltage control, then solution accuracy is maintained, but computational complexity increases and online operation becomes infeasible
Solution Approach 1:
The patent transforms the original nonlinear programming problem into a linear programming problem by changing the mathematical parameters and relationships. Specifically, it linearizes the reactive power-voltage relationship and reformulates the optimization model, enabling efficient online computation while maintaining acceptable solution accuracy for practical power grid operations
Solution Approach 2:
The patent extracts and separates the discrete decision variables (capacitor/reactor switching states) from the continuous optimization variables. By formulating the problem as a mixed-integer linear programming model with clearly defined discrete and continuous components, it enables specialized solution approaches that reduce computational burden while maintaining solution quality
2Ease of operation
If continuous reactive power resources are used for voltage control, then smooth adjustment is achieved, but discrete reactive power resources such as capacitors and reactors cannot be effectively coordinated
Solution Approach 1:
The patent merges continuous and discrete reactive power resources into a unified optimization framework. By formulating a mixed-integer linear programming model that simultaneously handles generator reactive power (continuous) and capacitor/reactor switching (discrete), it achieves coordinated control of all reactive power resources with consistent optimization objectives
Solution Approach 2:
The patent creates a universal control model that can handle multiple types of reactive power resources with different characteristics through a unified mathematical framework. The model accommodates generators, capacitors, reactors, and transformer taps within the same optimization structure, making the system adaptable to various resource configurations
3Reliability
If strict nodal voltage constraints are enforced, then voltage safety is ensured, but unreasonable constraints may lead to no solution and affect online operation reliability
Solution Approach 1:
The patent applies partial enforcement of voltage constraints by introducing slack variables that allow temporary, controlled violations of strict voltage limits. This approach maintains voltage safety through penalty terms in the objective function while avoiding complete constraint violations that would prevent finding any feasible solution, thus ensuring online operation continuity
Data Source
AI summary
An online voltage control method for coordinating multi-type reactive power resources is provided. First, a linearized power flow equation of branch reactive power is established, and an online voltage control model of multi-type reactive power resources including an objective function and constraint conditions is constructed. The constraint conditions includes generator reactive power constraints, reactive power compensator constraints, transformer tap position constraints, a nodal reactive power balance constraint, and slack contained nodal voltage constraints. Then, an optimization result of voltage control is obtained by solving the model. The method makes full use of reactive voltage operation characteristics of a power grid, constructs a practical online solution model for reactive voltage control of large power grid of coordinating multiple reactive power resources, and under a condition of acceptable accuracy loss, takes in account safety of power grid operation, economy of reactive power resource actions and high reliability of online operation.