MATPOWER 2-bus test cases for OPF relaxations

This data set is composed of two test cases for optimal power flow (power flow optimisation in electrical networks). One test case "case2_parallel", shows a second-order cone relaxation gap when using the canonical branch flow model, but not when using the bus injection model. The other test case "case2_gap" shows a significant relaxation gap without total current constraints, and a much lower one with enforcement of total current limits.本数据集包含两个面向电网最优潮流（optimal power flow，电力网络潮流优化）的测试用例。其中测试用例"case2_parallel"在采用标准支路潮流模型（canonical branch flow model）时会出现二阶锥松弛间隙（second-order cone relaxation gap），而使用节点注入模型（bus injection model）时则无此类间隙。另一测试用例"case2_gap"则表现为：未施加总电流约束（total current constraints）时存在显著的松弛间隙，而在强制执行总电流限值（total current limits）后，松弛间隙将大幅减小。