| Electromechanical oscillations in power systems are essentially dynamic processes caused by power disturbance.Compared with the traditional power system,the "double high" power system has more uncertain disturbance and less inertia,and electromechanical oscillation phenomenon is more likely to occur,which has become one of the important problems to be solved urgently in modern power system.In the power system with a high proportion of photovoltaic power generation,the photovoltaic system is adopted to suppress the electromechanical oscillation of the system,which requires no additional investment in hardware equipment and can be adjusted quickly.Therefore,this paper first analyzes the mechanism of PV system to suppress electromechanical oscillation based on the conventional control strategy.Then a new control strategy is proposed to minimize the frequency deviation and frequency change rate in the first time.Main work contents include:(1)A single infinite machine system model including photovoltaic power generation system is established,and the corresponding mathematical model is established.The analysis shows that the photovoltaic inverter can change its own output active and reactive power to adjust the electromagnetic power of the synchronous machine,so as to suppress the electromechanical oscillation.(2)Through the electrical torque method,the mechanical and electrical time scales to suppress the electromechanical oscillation power grid,photovoltaic power generation system for the mechanism analysis,and analyze the PV permeability,photovoltaic power station location,speed loop or Angle loop feedback proportional,integral and differential controller gain has what impact on the pv suppression system electromechanical oscillation.(3)This paper proposes a grid frequency as the feedback signal of fast control strategy of reactive power support,this strategy can make full use of the residual capacity of photovoltaic inverter,at the instant of the oscillation occurred to maximize the reactive power output to reduce the power grid frequency deviation to the greatest extent and frequency variation,and thus more quickly and efficiently suppress the electromechanical oscillation power grid,the model can restrain in the frequency offset and frequency variation is superior to the traditional droop,the inertia control. |
