3 Comprehensive_control_scheme_for_an_interlinking_converter_in_a_hybrid_AC_DC_microgrid

To manage power flow between DC and AC sources and loads.

It shows better performance in terms of active power, reactive power, AC frequency, and AC voltage.

To eliminate perturbations and quickly track the reference current value.

The lack of accurate control models due to system parameter uncertainties and detection technology limitations.

It is set to deviate from normal 0.005 H to 0.0065 H to simulate parameter perturbations.

TF1 has almost zero overshoot, while TF2 has an overshoot of -0.5.

It often sacrifices nominal performance to achieve better robustness against disturbances.

It indicates the system's response to high-frequency noise and the robustness of the proposed control.

To exponentially converge to the system's actual status, eliminating measurement noise.

It improves disturbance suppression but increases sensitivity to noise.

To suppress transient fluctuations and improve dynamic performance under disturbances.

A load of 40 kW and 40 kVar.

ILCs work in a coordinated way to share power and maintain frequency/voltage.

To present a comprehensive control scheme for the ILC in a hybrid AC/DC microgrid.

{ e_d(t) = w_d(t) - ˆw_d(t), e_q(t) = w_q(t) - ˆw_q(t) }

PSCAD/EMTDC simulation platform.

A combination of outer loop flexible power sharing control and improved robust inner loop control.

It shows the effectiveness of the control strategy under varying conditions.

U d 1 and U q 1, defined as U d 1 = E d − U d − ωL n i q and U q 1 = E q − U q + ωL n i d.

To realize proportional power sharing of the distributed generators (DGs) corresponding to their rated output.

When P_ref > 0, active power flows from AC to DC subgrid; when P_ref < 0, it flows from DC to AC subgrid.

Outer loop flexible power sharing control and improved robust inner loop control.

The errors converge to zero: lim t → ∞ e_d(t) = 0 and lim t → ∞ e_q(t) = 0.

A comprehensive control scheme for an interlinking converter in a hybrid AC/DC microgrid.

Rated frequency of 50 Hz and AC voltage RMS of 380 V.

It realizes autonomous power balance based on a deduced balance state equation.

They are the actual transfer functions in the d-axis and q-axis, respectively.

The frequency is unique in the microgrid and can be expressed as a function of the rated and actual active power outputs of the DGs.

There is a drop in DC bus voltage, generating a positive difference value.

Flexible power sharing of distributed generations (DGs) in the hybrid microgrid.

To eliminate the influence of resultant disturbance terms on the microgrid system.

The output power of the remaining DGs and the transfer power by the interlinking converter is proportionally reallocated.

40 kW and 40 kVar.

It facilitates power exchange and support between AC and DC subgrids.

They represent the lumped disturbance terms that include external disturbances and system parameter uncertainties.

It allows the ILC to manage flexible active power flow between AC and DC subgrids while maintaining stability.

It adjusts power sharing among AC and DC subgrids based on different management objectives.

By suppressing external disturbances and improving dynamic response.

It eliminates the perturbation of w_d on i_d, allowing accurate tracking of the reference value.

Traditional PI control.

Transfers power from the AC to DC subgrid to achieve proportional power sharing.

It allows the utility grid to provide power support to the microgrid.

They are caused by lumped disturbances and the intermediate variables U d 1 and U q 1.

It represents the ratio of sharing between AC and DC distributed generators, allowing for flexible load power sharing.

It relies on coefficients k_ac, k_dc, and λ, requiring proportional DG outputs in each subgrid.

To force the converter current to track the reference value with no steady error.

The voltage and frequency of the AC/DC bus lose stability and become abnormal.

They depict current fluctuations with and without disturbance suppression control.

It results in smaller transients in AC frequency and voltage during disturbances.

They enable load power sharing and eliminate the need for fast communication links.

To track the resultant disturbance terms w d and w q and improve the dynamic response of the control system.

To eliminate steady-state error for the reference command of the ILC.

It maintains the AC bus voltage at rated levels by supplying reactive power to the AC subgrid.

Less energy conversion and lower power loss.

It significantly improves the system’s robust stability under system parameter perturbations.

The unit-step responses of the transfer functions T F_1(s) and T F_2(s).

It suppresses high-frequency measurement noise.

Converter voltage and current, AC bus voltage, DC side current and voltage, equivalent resistance, filter inductance, and filter capacitor.

They are first-order filters used to observe the resultant disturbance terms while avoiding high-frequency noise.

They cause a difference in DG terminal voltages, which can be compensated using the virtual compensation resistance method.

They break the instantaneous power balance state and cause fluctuations in the inner loop current reference.

Hybrid AC/DC microgrid, as it can meet the needs of both AC and DC loads efficiently.

The current fluctuation caused by the disturbance w_d(s).

It results in instability and mess in power sharing.

It depicts the relationship between the observed and actual values of the resultant disturbance term w d.

Globally proportional power sharing according to different DG capacities is realized.

To enhance the robust stability of the microgrid under external or internal disturbance impacts.

Coordinating AC frequency droop characteristics and DC voltage droop characteristics.

It influences the dynamic performance and stability of the microgrid system.

80 kW.

It allows low-frequency dynamics to be close to 1 while attenuating high-frequency dynamics to nearly 0.

As a function of the actual and rated active power outputs of the droop-controlled DGs.

It describes the dynamics of the ILC considering the d and q axis components.

It allows for independent operation of distributed generators without communication.

It addresses issues that cannot be effectively solved by traditional technical methods.

They describe how the actual DC bus voltage relates to the rated values and active power outputs of the DGs.

Because low frequency components dominate system response, and high-order disturbances complicate engineering implementation.

A proper power sharing scheme that aligns with the requirements of the hybrid microgrid.