# Performance Tuning for Power Electronic Interfaces Under VSG Control
## 7 Conclusion  
Based on the quantitative analysis of performance indices, this paper proposes a parameter tuning method for VSG-PEIs performing frequency control. From the above analysis, the following conclusions are made:  
(1) From the perspective of the time scale and the activation, the frequency control is divided into two parts: the frequency response including IR and PFR, and the frequency regulation including SFR. Two dynamic systems are formed in different parts. (2) By the effects of the dominant poles and zeros, the dynamic systems of the VSG-based PEIs in both parts are simplified into approximation models with second-order transfer functions. The performance indices are deduced from the reduced-order models. (3) Different stages of frequency control kick in chronological order. In the proposed algorithm, the inertia constant is considered first for the ROCOF standard in the inertial response stage. Then the inertia constant and the speed droop are designed by checking the requirements of the nadir, the settling time, and settling frequency. (4) In frequency regulation, the parameter of inertia and speed droop are inherited or readjusted from the previous part. The integral coefficient is determined according to the standard of SFR delivery time. (5) The proposed algorithm can be utilized in two scenarios: (1) the parameter determination for the dominated PEIs in a stand-alone system, and (2) the equivalent parameter determination for a synchronous area with different units with inertia properties. By the simulation results, the proposed method can fully satisfy typical performance standards. **Author Contributions:** This study was carried out by [PERSON] under the supervision of [PERSON]. The editing was mostly done by [PERSON] All authors have read and agreed to the published version of the manuscript. **Funding:** This research was funded by National Natural Science Foundation of China-Hebei on the project of \"Research on inertia characteristics and control strategy for primary frequency and voltage regulation of DFIG\" (no. E201802134). **Conflicts of Interest:** The authors declare no conflict of interest. **Nomenclature**  
_1. Acronyms_  
AGC  Automatic generation control  
APR  Active power reserve  
IBG  Inverter-based generation  
IR  Inertial response  
MPP  Maximum power point  
PEI  Power electronic interfaces  
FFR  Primary frequency response  
RG  Renewable generation unit  
ROCOF  Rate of change of frequency  
SFR  Secondary frequency response  
SG  Synchronous generator  
SO  System operator  
TFR  Tertiary frequency response  
VSG  Virtual synchronous generator  
VSI  Voltage-sourced inverter2. _Sets and indices_  
ROCOF  
Rate of change of frequency  
\(t_{\rm peak}\)  
Peak time  
\(f_{\rm peak}\)  
Peak frequency  
\(f_{\rm ss}\)  
Steady-state frequency  
\(\sigma\)  
Overshoot  
\(t_{\rm s}\)  
Settling time  
SG  
Set of synchronous generators  
RG  
Set of renewable generation  
3. _Variables_  
\(\omega_{\tau}\)  
Angular speed of rotor  
\(H_{\rm vir}\)  
Virtual inertia constant  
\(f_{\rm vir}\)  
Virtual moment of inertia  
\(\omega_{m}\)  
Virtual angular speed  
\(P_{m}\)  
Virtual mechanical power  
\(P_{e}\)  
Electrical power  
\(\gamma\)  
Valve position  
4.