The single-phase full-bridge voltage source inverter $$(VSI),$$ shown in figure, has an output frequency of $$50$$ $$Hz$$. It uses unipolar pulse width modulation with switching frequency of $$50$$ $$kHz$$ and modulation index of $$0.7.$$ For
$${V_{in}} = 100\,V\,\,DC,\,\,L = 9.55\,\,mH,\,C = 63.66\,\,\mu F,$$ and $$R = 5\,\Omega ,$$ the amplitude of

A 50 Hz generating unit has H-constant of 2 MJ/MVA. The machine is initially operating in steady state at synchronous speed, and producing 1 pu of real power. The initial value of the rotor angle $$\delta $$ is $${5^ \circ }$$, when a bolted three phase to ground short circuit fault occurs at the terminal of the generator. Assuming the input mechanical power to remain at 1 pu, the value of $$\delta $$ in degrees, 0.02 second after the fault is _____________

Consider a $$HVDC$$ link which uses thyristor based line commutated converters as shown in the figure. For a power flow of $$750$$ $$MW$$ from System $$1$$ to System $$2,$$ the voltages at the two ends, and the current, are given by: $${V_1} = 500\,kV,\,\,{V_2} = 485\,kV\,\,$$ and $$\,{\rm I} = 1.5\,kA.\,\,$$ If the direction of power flow is to be reversed (that is, from System $$2$$ to System $$1$$) without changing the electrical connections, then which one of the following combinations is feasible?

Determine the correctness or otherwise of the following Assertion (a) and the Reason (R).
Assertion (A): Fast decoupled load flow method gives approximate load flow solution because it uses several assumptions.
Reason (R): Accuracy depends on the power mismatch vector tolerance.