<p>The unified power quality conditioner (UPQC) is an attractive solution for addressing power quality issues, and its combination with renewable energy sources and energy storages has gradually become an application trend. In this paper, the solar photovoltaic (PV) and battery energy storage (BES) are integrated into the dc link of UPQC, thus forming a PV+BES+UPQC (PVB-UPQC) system. From this integrated feature, the PVB-UPQC possesses the dual-source power regulation ability from the grid and dc link. Based on this ability, four operation modes are further developed. But in the conventional control strategy, different control schemes need to be switched between grid-connected and off-grid scenarios. This will increase the burden on the control strategy design, and may even cause the voltage transient issue during the switching of different control schemes. To avoid switching control schemes, in this paper, a multi-mode unified control (MMUC) is proposed to configure the power behaviors between the grid, PV, BES and load. As an advantage, the proposed MMUC can achieve the seamless switching and stable operation for four operation modes using only one set of control scheme. After that, the control functions of MMUC are demonstrated through quantitative multi-mode transition analysis. Finally, an experimental platform based on hardware-in-the-loop is built, and the experimental results demonstrate the feasibility and effectiveness of the proposed MMUC for the PVB-UPQC.</p>