At present, the once-through steam generator (OTSG) is widely used in the high-temperature gas-cooled reactor (HTR), integrated pressurized water reactor (IPWR) and other advanced nuclear power plants. At the same time, functions such as extensive load following and automatic start-up put higher requirements on the automatic control of the above-mentioned nuclear power system. Manual control of the above-mentioned nuclear power systems may lead to a mismatch between nuclear power and thermal power, and even to problems such as OTSGs drying and running water that threaten operational control safety, and suitable automatic control strategies are urgently needed. A large-range power automatic control system has been designed for advanced nuclear power systems using OTSGs. The control system uses dynamic model for operational control as the basis for analysis, designs coordinated control strategies based on dissipation, and gives theoretical proof of the system’s progressive stability across the world. In order to verify the effectiveness of the control strategy, a numerical simulation was conducted using the NuScale integrated pressurized water reactor as the subject, thereby confirming the efficacy of the control approach. The results showed that the control strategy maintained a stable length of the superheated steam section of the secondary side of the OTSG during the large-scale power load tracking process while ensuring a matching of nuclear and thermal power. This research work is the basis for the next step in implementing fault-tolerant control and automatic start-up control.