## 5 Conclusions
### Nomenclature  
Acronym  
VSPSGM  
Variable-speed pumped-storage generator-motor  
DFIG  
Doubly fed induction generator  
RAM  
Random access memory  
CPU  
Central processing unit  
FFT  
Fast Fourier transform  
Variable/Parameter  
\(i_{\text{a.s}}\)  
The stator current of phase A  
\(i_{\text{b.s}}\)  
The stator current of phase B  
\(i_{\text{c.s}}\)  
The stator current of phase C  
\(I_{\text{s}}\)  
The amplitude of stator phase current  
\(\omega_{\text{s}}\)  
The stator angular frequency  
\(\varphi_{\text{as}}\)  
The stator A-phase current angle  
\(i_{\text{d.s}}\)  
The d-axis current at stator side obtained by Clark transformation  
\(i_{\text{a.r}}\)  
The rotor current of phase A  
\(i_{\text{b.r}}\)  
The rotor current of phase B  
\(i_{\text{c.r}}\)  
The motor current of phase C  
\(I_{\text{r}}\)  
The amplitude of rotor phase current  
\(\omega_{\text{r}}\)  
The rotor angular frequency  
\(\varphi_{\text{ar}}\)  
The rotor A-phase current angle  
\(i_{\text{d.r}}\)  
The d-axis current at rotor side obtained by Clark transformation  
\(i_{\text{q.r}}\)  
The q-axis current at rotor side obtained by Clark transformation  
\(s\)  
The slip ratio  
\(E_{\text{s}}\)  
The amplitudes of the stator winding induced potential  
\(E_{\text{r}}\)  
The amplitudes of the rotor winding induced potential  
\(N_{\text{s}}\)  
The number of series turns of each branch winding on the stator side  
\(N_{\text{r}}\)  
The number of series turns of each branch winding on the rotor side  
\(k_{\text{ws}}\)  
The fundamental wave winding factors of stator side  
\(k_{\text{wr}}\)  
The fundamental wave winding factors of rotor side  
\(I_{e}\)  
The amplitude of short-circuit current  
\(\varphi_{e}\)  
The angle of short-circuit current  
\(N_{e}\)  
The turn number of the short-circuit coils  
\(k_{\text{ck}}\)  
The winding factor of the short-circuit coils  
\(\theta\)  
The space electric angle  
\(p\)  
The number of pole-pairs  
\(k\)  
The harmonic order  
\(I_{\text{r1}}\)  
The amplitude of the positive- and negative-sequence current  
components after the fault  
\(\varphi_{\text{ar1}}\)  
The phase angle of A-phase positive induced current after the fault  
\(I_{+}\)  
The induced-current amplitudes of the \(1+2\,s\) harmonic components  
\(I_{-}\)  
The induced-current amplitudes of the \(1-2\,s\) harmonic components  
\(\varphi_{\text{a+}}\)  
The induced-current phase angles of the \(1+2\,s\) harmonic components  
\(\varphi_{\text{a-}}\)  
The induced-current phase angles of the \(1-2\,s\) harmonic components  
\(p\)  
Differential operator  
\(\mathbf{U_{s}}\)  
The stator branch voltage matrices  
\(\mathbf{U_{r}}\)  
The rotor branch voltage matrices  
\(\mathbf{I_{s}}\)  
The stator branch current matrices  
\(\mathbf{I_{r}}\)  
The rotor branch current matrices  
\(\mathbf{R_{s}}\)  
The stator branch resistance matrices  
\(\mathbf{R_{r}}\)  
The rotor branch resistance matrices  
\(\mathbf{L_{ss}}\)  
The stator inductance matrix  
\(\mathbf{L_{rr}}\)  
The rotor inductance matrix  
\(\mathbf{L_{sr}}\)  
The mutual inductance matrices of stator and rotor  
\(\mathbf{L_{rs}}\)  
The mutual inductance matrices of rotor and stator