Abstract: Under the "dual carbon" initiative(namely, carbon peak and carbon neutrality), the integration of numerous distributed energy sources significantly increases harmonic injections in distribution networks, posing considerable challenges to static voltage stability. This paper analyzes the impact of harmonics from distributed generation on static voltage stability and introduces the concept of harmonic static voltage stability limit and margin indices. An improved N-order Fibonacci symmetric search method is proposed to accelerate the analysis of harmonic static voltage stability. Furthermore, a double-layer optimization model for photovoltaic-storage allocation in distribution networks is developed, accounting for harmonic static voltage stability margin. The upper layer optimizes photovoltaic-storage capacity based on annual investment and operational costs, harmonic static voltage stability margin, curtailment rate, and storage benefits, exploring the relationship between photovoltaic-storage capacity and the network's harmonic levels and voltage stability margin. The lower layer simulates typical daily operations, targeting minimal operating costs to evaluate photovoltaic-storage performance and analyze the impact of the planning scheme on real-world operations. Finally, a modified IEEE-33 system validates the effectiveness of the proposed method. Results demonstrate that considering harmonic static voltage stability margin in photovoltaic-storage optimization can prevent harmonic violations under typical scenarios, enhance network operational stability, and reduce costs, thereby guiding the orderly development of photovoltaic-storage integration in distribution networks.