This paper analyzes the effect of unbalanced voltage on voltage rise for a grid-connected photovoltaic (PV) system, and proposes a voltage rise mitigation strategy which injects negative-sequence currents to compensate the unbalanced voltage aiming especially to reduce the voltage rise. The paper also discusses how the averaged powers related to the injected negative-sequence currents are measured by the power meter. Simulation result confirms the superior performance of the proposed strategy over the classical method which suppresses the voltage rise by adjusting the power factor.