Power Network Modelling for Hardware in the Loop and Real Time Applications

In the paper the approximate model of power system elements adjusted for reactive power flow and voltage simulations is presented and the use of these models is demonstrated. The developed approximate models of power system elements are simple but when used in circuit simulations the fast and accurate reactive power flow solution is obtained. The performed reactive power flow calculations take into account corrections due to predetermined active power flow through circuit branches. The so derived values are accurate enough (error less than 1%) in cases where voltage angle across inductance model is less than 15 deg. The main advantage of the proposed approach is that the solution is directly calculated in one step, rather than using iterations. Due to this the proposed approach is handy and numerically efficient for use in power network modelling for hardware in the loop and real time applications, implemented on industrial grade programmable logic controllers (PLCs). Also the proposed approach can be efficiently used in projective model control applications. To demonstrate the versatility of the proposed modelling approach, these models are used to build up the circuit used for the simulation of voltage area controller operation. The voltage area control is modelled by two voltage control modes. The first one is keeping the area total exchange of reactive power close to zero until pilot node (PN) voltage is within the certain voltage band and the second one is imposing the predetermined the PN voltage reactive droop. Simulation results of area voltage control operating under different external and internal transient reactive sinks are presented and thoroughly explained.