UPFC Benchmark Results

UPFC

4.3.4 UPFC Benchmark Results

The left hand side of Fig. 4.11 shows the dynamic response of the UPFC to changes in commanded series injection voltage Vdq

*

and relative angle ~, as simulated using the EMTP model of Sen [27], whereas the right hand side of Fig. 4.11 shows the simulated results of the UPFC to the same changes using the detailed PSCADIEMTDC model presented in this chapter.

Fig. 4.12 (a) shows the simulated results of STATCOM inverter's voltage, eia, phase a of the line voltage, Via, and the phase a shunt current, lia, in EMTDC; Fig. 4.12 (b) shows the simulated results of SSSC inverter output voltage, e2a, phase a of the voltage across the series coupling transformer reactance, V₁₂^a> and the phasea line current,la' in EMTDC

(a) 1_1q:Sen EMTP

0.5 0.5

...

_Q)

a.

...

_Q)

a.

-0.5 -0.5

-1L-_~_ _~_~_----:~-,

o ^{0.1 0.2 0.3 0.4 -1}o^{L-_~0.1_ _0.2.L-.-_~0.3_ _0.4~-'}

(b)Vdc:Sen EMTP

2~---,

Vdc:EMTDC

2~-~---,

1.5!Vv"\fl.lv'-

Q)...

a.

...

_Q)

a.

0.5 0.5

o^{L-.-_~_ _~ _ ~_ _~---J}

o

0.1 0.2 0.3 0.4 0.1 0.2 0.3 0.4

(c)P,:Sen EMTP P:EMTDC_I

...Q)

a.

0.5

o ^~

...

_Q)^c

a.

0.5

o

-0.5 -0.5

-1 L-.-_~_ _~_ _.L-.-_~~

o ^{0.1 0.2 0.3 0.4 -1}

o

^L-_~0.1^{_ _}0.2^{~_ _}0.3^~_~-.J0.4

0.2 0.3 0.4 Time(5) 0.1

o

Q,:EMTDC

-1L.-_~_ _~_ _~ _ ~ _

o

0.5

-0.5

...

Q)

a.

0.2 0.3 0.4 Time(5) 0.1

o

(d)Q,:Sen EMTP

-1L.-_~_ _~_ _~ _ ~ _

o

0.5

-0.5

FigA.JI: Peiformanee of a UPFC with a 24-pulse three-level inverter, as modelled in EMTP [27J and PSCAD/EMTDC: (a) I1q; (b) V_DC; (e) Pr; (d) Q,.

(e)Pin,,:Sen EMTP Pin,,:EMTDC

0.5 0.5

'c l 'c A. ^A

~

...

_Cl> 0 J ^~

...

0 /

r ^Cl>

a.. a..

-0.5 -0.5

-1 -1

0 0.1 0.2 0.3 0.4 0 0.1 0.2 0.3 0.4

(f)Qin,,:Sen EMTP Qin,,:EMTDC

0.5 0.5

'c~ 0 ^A. v1 lA 'c^::::> 0

•

VV¹ l.

t

...

_{Cl> v}

a.. a..

-0.5 -0.5

-1 -1

0 0.1 0.2 0.3 0.4 0 0.1 0.2 0.3 0.4

(g)e_1e:Sen EMTP e

1e:EMTDC

0.5 'c::::>

...

0

Cl>

a..

-0.5 -1

0 0.1 0.2 0.3 0.4

0.5 'c::::> 0 a..4i

-0.5 -1

0 0.1 0.2 0.3 0.4

0.5

:g

~ 0 a..t

-0.5 -1

0 0.1

(h)Vle:Sen EMTP

0.2 0.3

Time(5)

0.4

0.5 'c::::>

...

_Cl> 0 a..

-0.5 -1

0 0.1

v_1e:EMTDC

0.2 0.3

Time(5)

0.4

Fig.4.JJ(continued): Performance of a UP FC with a 24-pulse three-level inverter, as modelled in EMTP[27]and PSCADIEMTDC: (e) P/NV; (f) Q/NV; (g) ela; (h) V1a•

(i)lIs:Sen EMTP

0.5 0.5

"- Cl>

a.

o~-III",'vwIIJVII\I\I\!r.AI\I\JV'W~11111111/1/11"

-0.5 -0.5

-1L-_~_ _~_ _~_~---,

o ^{0.1 0.2 0.3 0.4 -1L.-_~_ _}~_~_---:~-,

o ^{0.1 0.2 0.3 04}

0.5 0.5

o~----,IIIII

·c:::>

"- Cl>

a.

o

I---,~

_{n~ I~}^All11

H

^1\11/

\I~

^,1\1\/\1

-0.5 -0.5

-1L.-_~_ _~ _ ~_ _~-,

o ^{0.1 0.2 0.3 0.4 -1}o^L.-_~0.1^{_ _}0.2^{~ _ ~}0.3^{_ _}0.4^~-,

(k)V12s:Sen EMTP V

I2S:EMTDC

0.5 0.5

·c:::>

"- Cl>

a.

-0.5 -0.5

0.3 04 0.1 0.2

-1L..._~_ _~_ _~ _ ~ _

o

-1 L-_~ ~_ _~_~---J

o ^{0.1 0.2 0.3 0.4}

(I) Is:Sen EMTP

0.5

o

~

111/1111/11"1'

"- Cl>

a.

0.5

o

-0.5 -0.5

0.2 0.3 04 Time(5) 0.4 0.1

0.2 0.3

Time(5) 0.1

-1L-_~_ _~_~~_~-.l

o

FigA.J1(continued): Performance of a UP FC with a 24-pulse three-level inverter, as modelled in EMTP [27] and PSCAD/EMTDC: (i) fla; (j)e2a; (k) V12a; (l) fa.

~

^{...-ete n}

V

\

\ ~ (\ I ^{r r} I

L

\1\, ^1/\ 1\

J

^{v, !\ . lA}

~ ^'"

^.~

^{r .}

~ ~ ^\

^v

H

0.5

o

-0.5 -1

o ^{0.05 0.1 0.15 0.2 0.25 0.3}

Time (s)

(b)e_{2e, V12e}andle:EMTDC

0.35 0.4 0.45

0.45 0.4

0.35 0.3

0.1 0.15

o 0.05 0.2 0.25

Time (s)

Fig.4.12: Peiformance of a UPFC with a 24-pulse three-level inverter, as modelled in PSCADIEMTDC: (a) elw Vlw la; (b) e2w V/2w la'

0.8 0.6 0.4

Q; 0.2

e:-

o..

~ 0

W

~ ^-0.2

"Cl>

::: ~:::

^1\,

-0.8 -1

I _I ^I

^{I 0.80.6}

0.4 'c 0.2 ::::>

e:-

Ci:i

O

g

t-:2 -0.2 w

.'.,

;;-

-0.4 -0.6 -0.8 -1

o ^{0.05 0.1 0.15 0.2 0.25}

Time (s)

0.3 0.35 0.4 0.45

Fig.4.13: The line voltage, VIa: EMTP [27J vs. PSCADIEMTDC.

Ineach case the sending and receiving end voltages in the transmission line are kept at constant magnitude and the transmission angle (phase between Vs and Vr) remains fixed. The UPFC is then used to vary the active and reactive power flow in the line by changing the commanded series injection voltage Vdq*and relativeangle~. The commanded quadrature shunt current,I^1q*, remains zero throughout this study; in other words, the STATCOM is not injecting or absorbing reactive current from the line.

From the time t

=

^{0 to t}

=

50ms in Fig. 4.11, switch SI remains open so that the STATCOM is disconnected from the transmission system; switch S2 is closed but the SSSC does not inject any voltage; due to the inductance of the transformer T4, reactive power is exchanged at the point of connection; the dc capacitor is pre-charged before t

=

^O.

At t

=

50ms, SI closes and the commanded quadrature current is set to I1q

* =

O. As a result of this command, the magnitudes of the STATCOM inverter voltage, ^eIa,and the system voltage, ^VIa, are same, as shown in Fig. 4.12(a). This is achieved, as shown in Fig. 4.5, by allowing active power to be transferred between the STATCOM and the line and as a result the dc capacitor voltage, VDC, settles into a new steady state value.

At t

=

lOOms, the desired series injection voltage Vdq

*

is set to 0.2 pu and the commanded relative angle is set to ~

=

120° leading. The dc capacitor voltage settles to a new magnitude keeping the STATCOM output voltage, ^eIa, the same magnitude as the line voltage, ^VIa' This new set of reference inputs causes the series injection voltage, e2a> to lead the line current, la, by an angle<j>,

as shown in Fig. 4.12(b) meaning that the injected voltage vector is in the inductive domain.

The reactive power, QJNV, at the point of SSSC connection remains positive as shown in Fig.

4. 11 (f). Furthermore, because the angle <j> is larger than 90°, the SSSC is also emulating a negative resistance, requiring active power to be injected in series with the line, such that P_JNV is now negative as shown in Fig. 4.11(e), and the source of this active power flow is from bus 1, through the STATCOM. This is evident in Fig. 4.12(a) which shows that the STATCOM output voltage, el a, is almost 180° out of phase with the shunt current, IIa, so that active power may be absorbed at the STATCOM terminals. Fig. 4.11(c) shows that the active power, P" at the receiving end of the line decreases. Fig. 4.11 (d) shows that the reactive power, Q" that flows to the receiving end of the line is now inductive.

With the injected voltage magnitude V_dq

*

kept constant at 0.2 pu, the desired relative angle ~ is now stepped down to 60° at t

=

200ms. The series injected voltage, e2a> still leads the line current, la> at this new operating point, which means that the injecting voltage vector remains in the inductive domain. The reactive power, QJNV, at the point of SSSC connection stays positive

as shown in Fig. 4. 11(f). However, the angle <l> is now smaller than 90°, which means that the SSSCis emulating a positive resistance. This requires active power to be absorbed from the line by the SSSC such that, P/NVis now positive as shown in Fig. 4.11(e), and this real power flows to bus 1 via the STATCOM. This can be seen in Fig. 4.12(a) which shows that the STATCOM output voltage, e/a , is now in phase with the shunt current, I/a , so that active power is released from the UPFC. This new_~ setting further decreases the real power,Pr, transferred down to the receiving end of the line as shown in Fig. 4.11(c), and the reactive power, Q" that flows to the receiving end of the line is now capacitive.

At t

=

300 ms, the relative angle ~ is maintained at 60° while the injected voltage magnitudeV^dq

*

is stepped up to 0.4 pu. The effect of this new setting is that the series injected voltage, e2a.now lags the line current,la' as shown in Fig. 4.l2(b), which suggests that SSSC is partially emulating a capacitive reactance. The reactive power, Q/NV, at the point of SSSC connection is now negative as shown in Fig. 4. 11(f). With the angle <l> still smaller than 90°, the SSSC is still emulating a positive resistance and therefore absorbs active power from the line. P/NV has increased due to the increase in the injected voltage magnitude. Fig. 4.12(a) also shows that more shunt current, I/a , is flowing out to the line. With this new Vdq

*

setting the direction of the active power flow in the transmission line itself now reverses as shown in Fig. 4.11 (c), while the reactive power,Q"remains capacitive.

A close comparison between the results in Fig. 4.11 has shown that the response predicted by Sen's EMTP model in [27] and that predicted by the detailed PSCADIEMTDC model developed this thesis are virtually identical, thus confirming the correctness of the latter model. Fig. 4.13 illustrates this close agreement for one particular system variable: the transmission line voltage

V/a at bus 1 predicted by each of the models is plotted on the same axes in Fig. 4.13 for comparison.