Power electronic load as a new experimental simulator of electrical load device not only can simulate a variety of load devices for power products to be tested, and also can bring power back to the grid, so it is a green and energysaving device. However in severe conditions the relationship between PEL dynamic performance and mutation of simulation instruction current, mutation of voltage of DBT, the change of grid voltage is concluded. And the feedforward control strategy based on power balance which is used to restrain the effect of above disturbance on the PEL is put forward. Simulation and experimental results verify the correctness and effectiveness of the control schemes.