The unreasonable planning of the access location and capacity of distributed power generation (DG) can have adverse effects on the distribution network. The flexible distribution unit has the advantages of flexible control of power flow distribution and improvement of voltage. Therefore, this paper proposes a steady-state calculation model and control strategy considering the flexible distribution unit in the planning. To more reasonably locate and size DG, this paper first establishes a comprehensive acceptance standard model based on three indicators: life cycle cost (LCC), network loss, and voltage deviation. Then, an improved sparrow search algorithm (ISSA) is proposed to solve the model, and Gaussian mutation and Tent chaos are introduced in the algorithm to improve the global search ability and convergence speed of the algorithm. Finally, a simulation is carried out using the IEEE 33-node distribution network system as an example, considering two scenarios: no access and access of the flexible distribution unit. The particle swarm optimization (PSO) algorithm, sparrow search algorithm (SSA), and ISSA are used for solving respectively. The results show that considering the flexible distribution unit can effectively control the power flow, improve the operating state of the system after DG configuration, and that the optimization results of ISSA are more efficient and accurate than those of other algorithms.