A kind of DC transmission system determines voltage control method
Technical field
The present invention relates to a kind of voltage control method, specifically relate to a kind of DC transmission system and determine voltage control method.
Background technology
High voltage direct current transmission is large with transmission line capability, fed distance is far away, control the advantage such as flexible be used widely in delivery of electrical energy field and play great function, converter is the device realizing electrical energy form AC-DC conversion function in HVDC (High Voltage Direct Current) transmission system, electric energy is called rectifier from exchanging the converter becoming direct current, the converter that electrical energy form becomes interchange from direct current is called inverter, by the direct voltage that the Trigger Angle adjusting converter can regulate converter to export, the adjustment of rectifier and inverter cooperatively interacts and just can realize the flexible control of DC transmission system.Usually, in DC transmission system, control direct voltage by inverter, control direct current by rectifier; At present; the mode of the DC transmission engineering many employings inverter gamma kick put into operation is to control direct voltage; because extinguish angle is steady state value; the adjustment of direct voltage can only realize by regulating the mode of converter transformer tap; because the adjustment of converter transformer tap can only be realized by mechanical mechanism; therefore the response speed of DC voltage regulation slowly, weakens DC transmission system and control advantage flexibly.
Summary of the invention
For the deficiencies in the prior art, the object of this invention is to provide a kind of DC transmission system and determine voltage control method, the method is according to direct voltage set point, Inverter Station converter transformer valve-side alternating voltage effective value, system dc electric current, equivalent commutating resistance determination inverter extinguish angle; Again by inverter extinguish angle determination inverter Trigger Angle, thus determine inverter output dc voltage, the method in good time being adjusted Trigger Angle by rectifier tracing system curent change regulates to realize rectifier voltage.
The object of the invention is to adopt following technical proposals to realize:
The invention provides a kind of DC transmission system and determine voltage control method, its improvements are, described method comprises the steps:
(1) current conversion station inverter extinguish angle is determined;
(2) current conversion station inverter Trigger Angle is determined;
(3) determine rectifier Trigger Angle, carry out determining closed-loop current control to rectifier, regulate rectifier voltage.
Further, in described step (1), in described step (1), according to direct voltage set point, Inverter Station converter transformer valve-side alternating voltage effective value, DC transmission system DC electric current and equivalent commutating resistance determination current conversion station inverter extinguish angle; Direct voltage set point is DC transmission system inverter output dc voltage value; Obtain Inverter Station converter transformer valve-side alternating voltage effective value by the voltage transformer real-time sampling being installed in converter transformer valve-side, obtain DC transmission system DC electric current by the DC current transformer real-time sampling be installed on DC bus; Converter transformer leakage reactance determines equivalent commutating resistance;
If direct voltage set point is U
d0, Inverter Station converter transformer valve-side alternating voltage effective value is U
ac, DC transmission system DC electric current is I
d, equivalent commutating resistance is d
x, then current conversion station inverter extinguish angle λ
0for:
①。
Further, in described rapid (2), by current conversion station inverter extinguish angle determination inverter Trigger Angle, thus inverter output dc voltage is determined; Adopt extinguish angle-Trigger Angle conversion method, when direct current system direct current changes, ensure that inverter output voltage and electric current change according to positive slope, avoid occurring that multiple stable operating point causes control to get muddled;
If direct current setting value is I under nominal operating conditions
doif now system dc electric current equals I
do, inverter extinguish angle is γ
o, it is β that inverter triggers angle of advance
o, the unloaded direct voltage of inverter is U
dio, then the direct voltage U of inverter output
dofor:
U
do=U
diocosβ
o+d
xI
do
②;
=U
diocosγ
o-d
xI
do
If direct current drops to I
d, the direct voltage U of now inverter output
dfor:
U
d=U
diocosβ+d
xI
d③;
Require the decline along with direct current, the direct voltage that inverter exports declines according to slope k, if direct current rated value is I
dcN, by 2., 3. two formulas subtract each other, have:
④;
:
⑤;
On the right side of above formula, last is very little, ignores, then show that direct current drops to I
dtime inverter Trigger Angle α
ifor:
⑥;
Above-mentioned steps determination current conversion station inverter Trigger Angle, makes inverter output dc voltage according to set point change.
Further, in described step (3), rectifier Trigger Angle is adjusted by rectifier tracing system curent change, and closed-loop current control mode is determined in employing, according to inverter output dc voltage and DC transmission system DC current setting value determination rectifier Trigger Angle, realize the adjustment of rectifier DC voltage;
If direct current actual value is I
dc, DC power transmission line resistance is R
l, rectifier output dc voltage is U
dc-R, inverter output dc voltage is U
dc-I, then have:
⑦;
Direct current set point is I
dc0, direct current set point and actual value get difference DELTA I
dc, have:
ΔI
dc=I
dc-I
dc0=-(I
dc0-I
dc)⑧;
Δ I
dcrectifier Trigger Angle α is converted to through proportional integral link
r, have α
r∝ Δ I
dc, then rectifier output dc voltage U
dc-Rfor:
⑨;
Known, U
dc-Rwith α
rincrease and reduce;
When the disturbance due to the external world causes I
dcduring increase, Δ I
dcincrease, α thereupon
rincrease, U thereupon
dc-Rreduce to make I thereupon
dcreduce, after overregulating, I
dcfinally be stabilized in I
dc0, according to the direct voltage that the direct current change of DC transmission system regulates rectifier to export automatically.
Compared with the prior art, the beneficial effect that the present invention reaches is:
1, according to direct voltage set point, Inverter Station converter transformer valve-side alternating voltage effective value, system dc electric current, equivalent commutating resistance determination inverter extinguish angle, ensure that the accurate control of direct voltage;
2, devise a kind of novel extinguish angle-Trigger Angle conversion method, ensure that inverter output voltage and electric current are according to the relationship change of positive slope, avoid occurring that multiple stable operating point causes control to get muddled;
3, the method in good time being adjusted Trigger Angle by rectifier tracing system curent change regulates to realize rectifier voltage, ensures that direct current is stabilized in set point.
Accompanying drawing explanation
Fig. 1 is the flow chart that DC transmission system provided by the invention determines voltage control method;
Fig. 2 provided by the inventionly determines voltage control simulation waveform figure;
Fig. 3 is that inverter output voltage provided by the invention and electric current change schematic diagram according to positive slope;
Fig. 4 is DC transmission system simplified electrical circuit diagram provided by the invention;
Fig. 5 is rectifier voltage Principles of Regulation figure provided by the invention.
Embodiment
Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described in further detail.
Determining voltage control for realizing DC transmission system, setting up DC transmission system and determining voltage control method, the invention provides a kind of direct current transportation and determine voltage control method.The adjustment of customary DC transmission system by regulating the Trigger Angle of converter to realize voltage, simultaneously in order to ensure the stable operation of direct current system, maintain stable power delivery, voltage-regulation also will ensure that system power maintains certain value, for this reason, present invention employs following methods to what realize DC transmission system determines voltage control, and its flow chart as shown in Figure 1, comprises the steps:
(1) current conversion station inverter extinguish angle is determined:
According to direct voltage set point, Inverter Station converter transformer valve-side alternating voltage effective value, system dc electric current, equivalent commutating resistance determination inverter extinguish angle, direct voltage set point is direct current system inverter output dc voltage value, can directly set, Inverter Station converter transformer valve-side alternating voltage effective value is drawn by the voltage transformer real-time sampling being installed in converter transformer valve-side, system dc electric current is drawn by the DC current transformer real-time sampling be installed on DC bus, and equivalent commutating resistance is determined by converter transformer leakage reactance.
If direct voltage set point is U
d0, Inverter Station converter transformer valve-side alternating voltage effective value is U
ac, DC transmission system DC electric current is I
d, equivalent commutating resistance is d
x, then current conversion station inverter extinguish angle λ
0for:
①。
(2) current conversion station inverter Trigger Angle is determined:
By inverter extinguish angle determination inverter Trigger Angle, thus determine inverter output dc voltage; Because inverter triggering signal is inverter Trigger Angle, only can not determine inverter triggering signal by inverter extinguish angle, the present invention devises a kind of novel extinguish angle-Trigger Angle conversion method, when direct current system direct current changes, as shown in Figure 3, ensure inverter output voltage and the electric current relationship change according to positive slope, avoid occurring that multiple stable operating point causes control to get muddled, after determining inverter Trigger Angle according to direct voltage set point, the direct voltage that inverter exports just can according to set point change.
If direct current setting value is I under nominal operating conditions
doif now system dc electric current equals I
do, inverter extinguish angle is γ
o, it is β that inverter triggers angle of advance
o, the unloaded direct voltage of inverter is U
dio, then the direct voltage U of inverter output
dofor:
U
do=U
diocosβ
o+d
xI
do
②;
=U
diocosγ
o-d
xI
do
If direct current drops to I
d, the direct voltage U of now inverter output
dfor:
U
d=U
diocosβ+d
xI
d③;
Require that, along with the decline of direct current, the direct voltage that inverter exports declines according to the slope k of AB section in Fig. 3, subtracted each other by two formulas above, have:
④;
:
⑤;
On the right side of above formula, last is very little, ignores, then show that direct current drops to I
dtime inverter Trigger Angle α
ifor:
⑥;
By above-mentioned steps determination current conversion station inverter Trigger Angle, make inverter output dc voltage according to set point change.
(3) determine rectifier Trigger Angle, carry out determining closed-loop current control to rectifier, realize rectifier voltage and regulate:
The method in good time being adjusted Trigger Angle by rectifier tracing system curent change regulates to realize rectifier voltage; After inverter output voltage determines, also must determine rectifier output dc voltage, the present invention devises a kind of closed loop control method, determines to adjust rectifier Trigger Angle in good time, thus realize the adjustment of rectifier voltage according to inverter output dc voltage and system dc current setting value.
As shown in Figure 4, rectifier output dc voltage must could realize energy higher than inverter output dc voltage and input inverter from rectifier DC transmission system simplified electrical circuit diagram.
For realizing rectifier tracing system curent change adjustment rectifier Trigger Angle, ensure normal power delivery, design rectifier voltage Principles of Regulation figure as shown in Figure 5.
If direct current actual value is I
dc, DC power transmission line resistance is R
l, rectifier output dc voltage is U
dc-R, inverter output dc voltage is U
dc-I, then have:
⑦;
Direct current set point is I
dc0, direct current set point and actual value get difference DELTA I
dc, have:
ΔI
dc=I
dc-I
dc0=-(I
dc0-I
dc)⑧;
Δ I
dcrectifier Trigger Angle α is converted to through proportional integral link
r, have α
r∝ Δ I
dc, then rectifier output dc voltage U
dc-Rfor:
⑨;
Known, U
dc-Rwith α
rincrease and reduce;
When the disturbance due to the external world causes I
dcduring increase, Δ I
dcincrease, α thereupon
rincrease, U thereupon
dc-Rreduce to make I thereupon
dcreduce, after overregulating, I
dcfinally be stabilized in I
dc0, according to the direct voltage that the direct current change of DC transmission system regulates rectifier to export automatically.
Embodiment
For certain DC transmission engineering, show that converter transformer valve-side alternating voltage effective value is 178kV by the voltage transformer real-time sampling of converter transformer valve-side, DC current transformer on the DC bus DC current values drawn of sampling is 5000A, setting direct voltage rated value is 200kV, equivalent commutating resistance is 4.65 Ω, then show that corresponding inverter extinguish angle is according to direct voltage set point:
When direct current system direct current changes, ensure that inverter output voltage and electric current change according to positive slope, as shown in Figure 3, avoid occurring that multiple stable operating point causes control to get muddled, in figure, AB section line segment slope can be specified as required, and line specifies this section of line segment slope to be 1.
Then the Trigger Angle of inverter is:
According to above-mentioned two formulas, inverter can according to direct voltage command value adjustment inverter output dc voltage.
DC power transmission line resistance is R
l=5 Ω, rectifier output dc voltage is U
dc-R, inverter output dc voltage is U
dc-I, then have:
Direct current set point is 5, and direct current set point and actual value get difference △ I
dc, have:
ΔI
dc=5-I
dc0=-(I
dc0-5)
△ I
dcrectifier Trigger Angle α is converted to through proportional integral link
r, have α
r∝ △ I
dc, and rectifier output dc voltage U
dc-Rfor:
Can show that DC voltage regulation waveform is as shown in Fig. 2 (a), (b) He (c), wherein, Maxoder is direct voltage inverter Trigger Angle when being rated value, inverter Trigger Angle during Maxlim for a change direct voltage instruction, DCVoltage is inverter direct-current voltage actual value, V_A_P is inverter direct-current voltage command value, and DCCurrent is direct current actual value; From Fig. 2 (a), (b) and (c), when reducing inverter direct-current voltage command value, control system reduces inverter Trigger Angle automatically, due to the reduction of inverter output dc voltage, DC transmission system DC electric current increases, rectifier reduces output voltage values automatically, makes direct current be stabilized in command value; When increasing inverter direct-current voltage command value, inverter direct-current voltage changes according to command value, and rectifier still can make system dc current stabilization in command value; Visible, The inventive method achieves the voltage control function of DC transmission system.
Finally should be noted that: above embodiment is only in order to illustrate that technical scheme of the present invention is not intended to limit; although with reference to above-described embodiment to invention has been detailed description; those of ordinary skill in the field still can modify to the specific embodiment of the present invention or equivalent replacement; these do not depart from any amendment of spirit and scope of the invention or equivalent replacement, are all applying within the claims of the present invention awaited the reply.