Sensitivity-Partitioned Switching Control of Pole-Mounted Capacitor-Reactor Devices in PV-Rich Distribution Feeders

High photovoltaic (PV) penetration can cause bidirectional voltage violations in distribution feeders, with evening undervoltage and midday overvoltage requiring opposite reactive power responses. This paper proposes a sensitivity-partitioned switching control method for pole-mounted capacitor-reactor devices. A voltage-dependent signed discrete feasible region is formulated to represent capacitive and inductive operating states subject to mechanical interlocking. Voltage-reactive power sensitivity fingerprints are used to partition devices into control zones, in which finite-state switching candidates are screened locally and subsequently verified using nonlinear forward–backward sweep power flow. An operation count penalty is incorporated to reduce mechanical switching. The analysis starts with a fixed-compensation, capacitor-only setup as the baseline, then switches to a full capacitor-reactor controller with both positive and negative adjustment capability on a balanced IEEE 33-bus feeder with 160% PV penetration. The uncompensated feeder exhibits 16.00% undervoltage and 4.01% overvoltage violations. Sensitivity partitioning reduces the aggregate screening space from 27,000 full-feeder combinations to 215 zonal candidates and the mean per-step computation time from 7405 ms to 89 ms. The proposed controller eliminates both types of voltage violations with 14 daily switching actions, compared with 33 for local threshold control. The capacitor-only ablation retains 4.01% overvoltage violations, confirming the necessity of inductive reactive power absorption for the considered high-PV operating condition.