A modified droop control structure for simultaneous power‐sharing and DC voltage oscillations damping in MT‐HVDC grids

Abstract

With increasing energy demand, the use of renewable energy resources is increasing. Renewable energy sources require power electronic converters to get integrated into power grids. Multi‐terminal high voltage direct current (MT‐HVDC) systems are a promising solution for their grid integration. Using droop‐based controller strategies in power converter stations of MT‐HVDC grid, in addition, to providing power‐sharing, can support the frequency of the connected AC grids. However, power changes lead to direct voltage deviations, thereby disrupting the stability of the MT‐HVDC system. Here, a new control structure for the droop controller of the voltage source converter (VSC) controller is proposed which is named modified droop controller (M‐Droop). This method, in addition to power‐sharing, uses an appropriate control action to provide the required voltage stability. Here, analytical studies of the modified control strategy are reported. Moreover, through a developed MATLAB Simulink platform, its performance is verified in the events of transients, consisting of fault, variable load, and change in power generation.

Direct current power system stabilizers for HVDC grids: Current status

“…To address the mentioned issue, a DC‐PSS‐based method to virtually increase the inertia that works alongside the droop controller in a way that does not interrupt the power sharing in the HVDC grid is proposed [46]. Because the basic DC‐PSS does not affect the inertia of the system, a modified droop controller (M‐Droop) method based on the conventional structure of the DC‐PSS is introduced in reference [47] that provides an extra virtual capacity by using the energy stored in the grid, in the event of faults. M‐Droop can supply HVDC grid stability without dependency on the frequency measurement and the PLL.…”

“…Because the basic DC‐PSS has no effect on the inertia of the system, a M‐Droop method based on the conventional structure of the DC‐PSS is introduced in reference [47] that provides an extra virtual capacity by using the energy stored in the grid, in the event of faults. M‐Droop can supply HVDC grid stability without dependency to the frequency measurement and the PLL.…”

“…M‐Droop can supply HVDC grid stability without dependency to the frequency measurement and the PLL. The proposed method in reference [47] can improve the damping for DC voltages of HVDC grids in transient situations. In this structure, the additional signal of the M‐droop controller is used instead of the normal V DC – P droop controller.…”

“…Reference [47] shows that by employing power variations, the M‐droop controller can emulate the behaviour of the virtual capacitor without changing the amount of capacitors of the DC link.…”