State estimation in power system
Regarding state estimation in electrical power grid, does the voltage
  phasor magnitude at each bus(P-Q bus and P-V bus) considered as a
  static state variable or a dynamic state?


Dynamic state, it changes over time.


  If we consider those bus voltages as static state, can we use dynamic
  state estimation techniques to get an estimation of those voltage or
  we only use static state estimation?


The bus voltages fluctuate usually by a few percent, so you could call the bus voltage fixed or it could be measured. If it isn't measured and the current is measured then use the current to estimate your load and power consumed. 


  If I want to plot the magnitude and phase angle at each bus over time,
  are there network dynamic models I can use to do so? For example a
  differential equation of the voltage with parameters such as reactive,
  real power etc...


Yes if you get the right meter. You may want to read this. It also depends on if you want 3-phase or 1-phase. Look for power meters, most measure reactive and real power.