A kind of DC transmission system constant voltage control method
Technical field
The present invention relates to a kind of voltage control method, in particular to a kind of DC transmission system constant voltage control method.
Background technique
The advantages that D.C. high voltage transmission is big with transmission line capability, conveying distance is remote, control is flexible obtains in electric energy transmission field
It is widely applied and plays great function, inverter is to realize electrical energy form AC-DC conversion function in HVDC transmission system
Device, electric energy is become the inverter of direct current from exchange and calls rectifier, electrical energy form is become from direct current the change of current of exchange
Device is known as inverter, by adjusting the DC voltage of the adjustable inverter output of Trigger Angle of inverter, rectifier and inversion
The adjusting of device cooperates and can realize the flexible control of DC transmission system.In general, in DC transmission system, by inversion
Device controls DC voltage, by rectifier controls DC current;Currently, the DC transmission engineering to have put into operation mostly uses inversion
Device determines the mode of gamma kick to control DC voltage, and since blow-out angle is steady state value, the adjusting of DC voltage can only pass through
The mode for adjusting converter power transformer tap realizes, due to converter power transformer tap adjusting can only by mechanical mechanism come
It realizes, therefore the response speed of DC voltage regulation is very slow, weakens DC transmission system and controls flexible advantage.
Summary of the invention
In view of the deficiencies of the prior art, the object of the present invention is to provide a kind of DC transmission system constant voltage control method,
This method is according to DC voltage setting value, Inverter Station converter transformer valve-side alternating voltage virtual value, system dc electric current, equivalence
Commutating resistance determines inverter blow-out angle;Inverter Trigger Angle is determined by inverter blow-out angle again, so that it is determined that inverter exports
DC voltage adjusts the method for Trigger Angle by rectifier tracing system curent change to realize that rectifier voltage is adjusted in due course.
The purpose of the present invention is adopt the following technical solutions realization:
The present invention provides a kind of DC transmission system constant voltage control method, it is improved in that the method includes
Following step:
(1) converter station inverter blow-out angle is determined;
(2) converter station inverter Trigger Angle is determined;
(3) it determines rectifier Trigger Angle, constant current closed-loop control is carried out to rectifier, adjusts rectifier voltage.
Further, in the step (1), in the step (1), become according to DC voltage setting value, the Inverter Station change of current
Depressor valve top-cross stream voltage effective value, DC transmission system DC electric current and equivalent commutating resistance determine converter station inverter blow-out
Angle;DC voltage setting value is that DC transmission system inverter exports DC voltage value;By being installed in converter transformer valve-side
Voltage transformer real-time sampling obtains Inverter Station converter transformer valve-side alternating voltage virtual value, by being installed on DC bus
DC current transformer real-time sampling obtains DC transmission system DC electric current;Converter power transformer leakage reactance determines equivalent commutation electricity
Resistance;
If DC voltage setting value is Ud0, Inverter Station converter transformer valve-side alternating voltage virtual value is Uac, direct current transportation
System dc electric current is Id, equivalent commutating resistance is dx, then converter station inverter blow-out angle λ0Are as follows:
①。
Further, in rapid (2), inverter Trigger Angle is determined by converter station inverter blow-out angle, so that it is determined that inverse
Become device and exports DC voltage;Inversion is guaranteed when the variation of direct current system DC current using blow-out angle-Trigger Angle conversion method
Device output voltage and electric current change according to positive slope, and avoiding the occurrence of multiple stable operating points causes control to get muddled;
If DC current setting valve is I under nominal operating conditionsdoIf system dc electric current is equal to I at this timedo, inverter puts out
Arc angle is γo, it is β that inverter, which triggers angle of advance,o, inverter zero load DC voltage is Udio, then inverter output DC voltage
UdoAre as follows:
If DC current falls to Id, the DC voltage U of inverter output at this timedAre as follows:
Ud=Udiocosβ+dxId③;
It is required that the DC voltage of inverter output declines according to slope k, if DC current volume with the decline of DC current
Definite value is IdcN, by 2., 3. two formulas are subtracted each other, have:
④;
:
⑤;
Last very little on the right side of above formula, ignores, it is concluded that DC current falls to IdWhen inverter Trigger Angle αIAre as follows:
⑥;
Above-mentioned steps determine converter station inverter Trigger Angle, make inverter output DC voltage according to set point change.
Further, in the step (3), rectifier Trigger Angle is adjusted by rectifier tracing system curent change, and adopt
With constant current close-loop control mode, determined according to inverter output DC voltage and DC transmission system DC current setting value whole
Device Trigger Angle is flowed, realizes the adjusting of rectifier DC voltage;
If DC current actual value is Idc, DC power transmission line resistance is RL, it is U that rectifier, which exports DC voltage,dc-R, inverse
Become device output DC voltage as Udc-I, then have:
⑦;
DC current setting value is Idc0, DC current setting value and actual value take difference DELTA Idc, have:
ΔIdc=Idc-Idc0=-(Idc0-Idc) ⑧;
ΔIdcRectifier Trigger Angle α is converted to by proportional integration linkR, there is αR∝ΔIdc, then rectifier exports direct current
Voltage Udc-RAre as follows:
⑨;
It is found that Udc-RWith αRIncrease and reduce;
When the disturbance due to the external world causes IdcWhen increase, Δ IdcIt increases with it, αRIt increases with it, Udc-RReducing therewith makes Idc
Reduce, after overregulating, IdcIt is final to stablize in Idc0, automatic adjustment rectification is changed according to the DC current of DC transmission system
The DC voltage of device output.
Compared with the prior art, the beneficial effect that the present invention reaches is:
1, according to DC voltage setting value, Inverter Station converter transformer valve-side alternating voltage virtual value, system dc electric current,
Equivalent commutating resistance determines inverter blow-out angle, ensure that the accurate control of DC voltage;
2, devise a kind of novel blow-out angle-Trigger Angle conversion method, guarantee inverter output voltage and electric current according to
The relationship change of positive slope, avoiding the occurrence of multiple stable operating points causes control to get muddled;
3, the method for Trigger Angle is adjusted by rectifier tracing system curent change to realize that rectifier voltage is adjusted in due course, is protected
DC current is demonstrate,proved to stablize in setting value.
Detailed description of the invention
Fig. 1 is the flow chart of DC transmission system constant voltage control method provided by the invention;
Fig. 2 is constant voltage control simulation waveform provided by the invention;
Fig. 3 is inverter output voltage and electric current provided by the invention according to positive slope variation schematic diagram;
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.
Specific embodiment
Specific embodiments of the present invention will be described in further detail with reference to the accompanying drawing.
To realize the control of DC transmission system constant voltage, DC transmission system constant voltage control method is established, the present invention mentions
A kind of direct current transportation constant voltage control method is supplied.Customary DC transmission system realizes electricity by adjusting the Trigger Angle of inverter
The adjusting of pressure, while the stable operation in order to guarantee direct current system, maintain stable power transmission, voltage adjusting also to guarantee be
System electric current maintains certain value, for this purpose, the constant voltage control of DC transmission system is realized present invention employs following methods,
Flow chart is as shown in Figure 1, include the following steps:
(1) converter station inverter blow-out angle is determined:
According to DC voltage setting value, Inverter Station converter transformer valve-side alternating voltage virtual value, system dc electric current, etc.
Value commutating resistance determines inverter blow-out angle, and DC voltage setting value is that direct current system inverter exports DC voltage value, can be with
It directly sets, Inverter Station converter transformer valve-side alternating voltage virtual value is by being installed in the voltage transformer of converter transformer valve-side
Real-time sampling show that system dc electric current is obtained by the DC current transformer real-time sampling being installed on DC bus, equivalent
Commutating resistance is determined by converter power transformer leakage reactance.
If DC voltage setting value is Ud0, Inverter Station converter transformer valve-side alternating voltage virtual value is Uac, direct current transportation
System dc electric current is Id, equivalent commutating resistance is dx, then converter station inverter blow-out angle λ0Are as follows:
①。
(2) converter station inverter Trigger Angle is determined:
Inverter Trigger Angle is determined by inverter blow-out angle, so that it is determined that inverter exports DC voltage;Due to inverter
Trigger signal is inverter Trigger Angle, only not can determine that inverter trigger signal, the present invention devise one by inverter blow-out angle
The novel blow-out angle-Trigger Angle conversion method of kind, when the variation of direct current system DC current, as shown in figure 3, guaranteeing inverter
According to the relationship change of positive slope, avoiding the occurrence of multiple stable operating points causes control to get muddled for output voltage and electric current,
After inverter Trigger Angle has been determined according to DC voltage setting value, the DC voltage of inverter output can be according to setting value
Variation.
If DC current setting valve is I under nominal operating conditionsdoIf system dc electric current is equal to I at this timedo, inverter puts out
Arc angle is γo, it is β that inverter, which triggers angle of advance,o, inverter zero load DC voltage is Udio, then inverter output DC voltage
UdoAre as follows:
If DC current falls to Id, the DC voltage U of inverter output at this timedAre as follows:
Ud=Udiocosβ+dxId③;
It is required that the DC voltage of inverter output declines according to AB sections in Fig. 3 of slope k with the decline of DC current,
Subtracted each other by two formulas above, had:
④;
:
⑤;
Last very little on the right side of above formula, ignores, it is concluded that DC current falls to IdWhen inverter Trigger Angle αIAre as follows:
⑥;
Converter station inverter Trigger Angle is determined through the above steps, becomes inverter output DC voltage according to setting value
Change.
(3) it determines rectifier Trigger Angle, constant current closed-loop control is carried out to rectifier, realize that rectifier voltage is adjusted:
The method of Trigger Angle is adjusted by rectifier tracing system curent change in due course to realize that rectifier voltage is adjusted;Inversion
After device output voltage has determined, it must also determine that rectifier exports DC voltage, the present invention devises a kind of closed loop control method,
DC voltage is exported according to inverter and system dc current setting value determines adjustment rectifier Trigger Angle in due course, to realize whole
Flow the adjusting of device voltage.
DC transmission system simplified electrical circuit diagram is as shown in figure 4, rectifier output DC voltage must be higher than inverter output directly
Galvanic electricity pressure is just able to achieve energy and inputs inverter from rectifier.
To realize that rectifier tracing system curent change adjusts rectifier Trigger Angle, guarantees normal power transmission, design
Rectifier voltage Principles of Regulation figure is as shown in Figure 5.
If DC current actual value is Idc, DC power transmission line resistance is RL, it is U that rectifier, which exports DC voltage,dc-R, inverse
Become device output DC voltage as Udc-I, then have:
⑦;
DC current setting value is Idc0, DC current setting value and actual value take difference DELTA Idc, have:
ΔIdc=Idc-Idc0=-(Idc0-Idc) ⑧;
ΔIdcRectifier Trigger Angle α is converted to by proportional integration linkR, there is αR∝ΔIdc, then rectifier exports direct current
Voltage Udc-RAre as follows:
⑨;
It is found that Udc-RWith αRIncrease and reduce;
When the disturbance due to the external world causes IdcWhen increase, Δ IdcIt increases with it, αRIt increases with it, Udc-RReducing therewith makes Idc
Reduce, after overregulating, IdcIt is final to stablize in Idc0, automatic adjustment rectification is changed according to the DC current of DC transmission system
The DC voltage of device output.
Embodiment
By taking certain DC transmission engineering as an example, change of current transformation is obtained by the voltage transformer real-time sampling of converter transformer valve-side
Device valve top-cross stream voltage effective value is 178kV, and the DC current values that the DC current transformer sampling on DC bus obtains are
5000A sets DC voltage rated value as 200kV, and equivalent commutating resistance is 4.65 Ω, then is obtained according to DC voltage setting value
Corresponding inverter blow-out angle are as follows:
When the variation of direct current system DC current, guarantee that inverter output voltage and electric current change according to positive slope, such as
Shown in Fig. 3, avoiding the occurrence of multiple stable operating points causes control to get muddled, and AB sections of line segment slopes can according to need finger in figure
Fixed, it is 1 that line, which specifies this section of line segment slope,.
The then Trigger Angle of inverter are as follows:
According to above-mentioned two formula, inverter can adjust inverter according to DC voltage instruction value and export DC voltage.
DC power transmission line resistance is RL=5 Ω, it is U that rectifier, which exports DC voltage,dc-R, inverter output DC voltage
For Udc-I, then have:
DC current setting value is 5, and DC current setting value and actual value take difference △ Idc, have:
ΔIdc=5-Idc0=-(Idc0-5)
△IdcRectifier Trigger Angle α is converted to by proportional integration linkR, there is αR∝△Idc, and rectifier exports direct current
Voltage Udc-RAre as follows:
It can be concluded that shown in DC voltage regulation waveform such as Fig. 2 (a), (b) and (c), wherein Maxoder is DC voltage
Inverter Trigger Angle when for rated value, Maxlim are inverter Trigger Angle when changing DC voltage instruction, and DCVoltage is inversion
Device DC voltage actual value, V_A_P are inverter direct-current voltage instruction value, and DCCurrent is DC current actual value;By Fig. 2
(a), it is found that when reducing inverter direct-current voltage instruction value, control system reduces inverter Trigger Angle automatically by (b) and (c), by
In the reduction of inverter output DC voltage, DC transmission system DC electric current increases, and rectifier reduces output voltage values automatically,
Stablize DC current in instruction value;When increasing inverter direct-current voltage instruction value, inverter direct-current voltage is according to instruction value
Variation, rectifier can still be such that system dc electric current stablizes in instruction value;As it can be seen that the method for the invention realizes DC transmission systems
Voltage control function.
Finally it should be noted that: the above embodiments are merely illustrative of the technical scheme of the present invention and are not intended to be limiting thereof, to the greatest extent
Invention is explained in detail referring to above-described embodiment for pipe, and those of ordinary skill in the art still can be to this hair
Bright specific embodiment is modified or replaced equivalently, these without departing from spirit and scope of the invention any modification or
Equivalent replacement, within the scope of the claims of the invention pending application.