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: $V_{1} = 500 \text{ kV}, V_{2} = 485 \text{ kV}$ and $I = 1.5 \text{ kA}$. 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?
- $V_{1} = −500 \text{ kV}, V_{2} = −485 \text{ kV}$ and $I = 1.5 \text{ kA}$
- $V_{1} = −485 \text{ kV}, V_{2} = −500 \text{ kV}$ and $I = 1.5 \text{ kA}$
- $V_{1} = 500 \text{ kV}, V_{2} = 485 \text{ kV}$ and $I= −1.5 \text{ kA}$
- $V_{1} = −500 \text{ kV} , V_{2} = −485 \text{ kV} $ and $I = −1.5 \text{ kA}$