## 5 Conclusions
\begin{tabular}{l l} \(\Delta f_{LV}\) & Output from the \(f_{LV}(f_{MV})\) droop controller \\ \(\Delta iESS_{ref}\) & Output from the \(P(f_{MV})\) droop controller \\ \(\Delta P\) & Output from the \(V_{LV}(f_{MV})\) Droop and \(P(f_{LV})\) Droop Controllers \\ \(\Delta V_{LC}\) & Compensation component for the Voltage drop in the LC filter \\ \(\Delta VAC_{LV}\) & Output from the \(V_{LV}(f_{MV})\) droop controller \\ \(\Delta Y^{-}/\Delta Y^{+}\) & Maximum negative/positive variation of Y in the droop controller around \(Y_{os}\) \\ \(\Delta VDC_{MV}\) & Output from the \(VDC(f_{MV})\) droop controller \\ \(\phi\) & Phase-shift between the square waveforms applied to the HFT \\ \(C\) & Capacitance of the coupling filter \\ \(C_{LV}\) & Capacitance of the ST's LV DC bus \\ \(C_{MV}\) & Capacitance of the ST's MV DC bus \\ \(f_{c}\) & Cut-off frequency of the coupling filter \\ \(f_{LV}\) & Reference frequency for the ST's LV inverter \\ \(f_{LV}(f_{MV})\) & Frequency (AC LV grid) - frequency (AC MV grid) droop \\ \(f_{MV}\) & Frequency measured in the MV AC network \\ \(I_{ESS}\) & Current in the local ESS \\ \(Ia_{LV},Ib_{LV},Ic_{LV}\) & AC currents in the ST's LV inverter, each phase \\ \(Ia_{MV},Ib_{MV},Ic_{MV}\) & AC currents in the ST's MV inverter, each phase \\ \(Id\) & Measured active current in the ST's MV inverter \\ \(Id_{ref},Id^{*}_{ref}\) & Reference for the active current in the ST's MV inverter \\ \(IDAB_{LV}\) & DC current in the secondary stage of the isolated DC/DC converter \\ \(IDAB_{MV}\) & DC current in the primary stage of the isolated DC/DC converter \\ \(IDC_{LVg}\) & Current exchanged between \(C_{LV}\) and the ST's LV DC network \\ \(IDC_{LVinv}\) & Current exchanged between the ST's LV inverter and the ST's LV DC bus \\ \(IDC_{MVg}\) & Current exchanged between \(C_{MV}\) and the ST's MV DC network \\ \(IDC_{MVinv}\) & Current exchanged between the ST's MV inverter and the ST's MV DC bus \\ \(IES_{ref}\) & MV side equivalent for the reference current for the local ESS \\ \(ILV_{avg}\) & Current flowing to the capacitance \(C_{LV}\) \\ \(IMV_{cap}\) & Current flowing to the capacitance \(C_{MV}\) \\ \(IMVmax_{p}\) & Maximum AC current peak value of the ST's MV inverter \\ \(Iq\) & Measured reactive current in the ST's MV inverter \\ \(Iq_{ref},Iq^{*}_{ref}\) & Reference for the reactive current in the ST's MV inverter \\ \(L\) & Inductance of the coupling filter \\ \(m_{d}\) & Slope of the droop controller \\ \(N\) & Transformation ratio of the isolated DC-DC converter \\ \(P(f_{LV})\) & Active power-frequency (AC LV grid) droop \\ \(P(f_{MV})\) & Active power-frequency (AC MV grid) droop \\ \(P(VDC)\) & Active power - DC voltage droop \\ \(P_{ref}\) & Reference active power for the ST's MV inverter \\ \(PDC_{LV}\) & Power output of the isolated DC/DC converter in the LV side \\ \(PDC_{MV}\) & Power output of the isolated DC/DC converter in the MV side \\ \(PES_{ref}\) & Active power set-point for the local ESS \\ \(PLV_{Inv}\) & Active power in the ST's LV inverter \\ \(PMV_{Inv}\) & Active power exchanged between the ST and the upstream MV AC grid \\ \(V_{LV}(f_{MV})\) & Voltage (AC LV grid) - frequency (AC MV grid) droop \\ \(Va_{LV},Vb_{LV},Vc_{LV}\) & AC voltages in the ST's LV inverter, each phase \\ \(Va_{MV},Vb_{MV},Vc_{MV}\) & AC voltages in the ST's MV inverter, each phase \\ \(Vabc_{LV}\) & Reference three-phase voltage for the ST's LV inverter \\ \(VAC_{LVinv}\) & Reference for the three-phase AC voltage in the ST's LV inverter \\ \end{tabular}