In DC transmission systems exporting power from weakly supported renewable energy bases, characteristics such as low inertia, weak damping, and low short-circuit ratio become prominent. Strong coupling between active power and voltage exists, making conventional real-time active power control modes difficult to apply. To address this issue, this paper proposes a real-time active power control method that simultaneously considers static voltage security constraints and the effective regulation space of multi-type resources, ensuring system stability while optimizing resource utilization. First, the coupling mechanism is analyzed, and a sensitivity index is established to quantify coupling degrees under different operating conditions. Then, considering renewable energy uncertainty, a voltage weak point identification method based on probabilistic power flow is proposed by integrating impedance modulus margin. By analyzing the effects of active power outputs of different types of resources on weak-point voltages, a method for quantifying the active power regulation space of multi-type resources under static voltage security constraints is developed. Then, integrating active power-voltage sensitivity and the effective regulation space of multi-type resources, a real-time active power control strategy is designed that accounts for regulation resource selection and differentiated power allocation, thereby meeting active power regulation requirements while reducing adverse impacts on weak-point voltages. Finally, the effectiveness of the proposed method is validated through case studies based on a modified IEEE 30-bus system.