The overheat of water walls is serious in ultra-supercritical 2 × 600 MW unit boilers in a power plants. After low NOx burner transformation

the fluctuation of main steam and reheat steam temperature became large. To solve this problem

the original water coal ratio control strategy(coal following water) was modified(the new logic is water following coal). On this basis

optimization on control strategy of the unit coordinated control system was carried out. Variable parameters were set in variable load process

the dynamic and steady state control strategy was separated

and the load rise/descend control parameters were set independently. After the optimization

the overheat of the boiler water walls was drastically reduced

the main steam and reheat steam temperature control quality was improved

and the main steam pressure changed smoothly

which can provide references for the optimization of control strategies for the same type units.