CN112886628B - Shutoff angle compensation control method for improving stability of LCC-HVDC system - Google Patents
Shutoff angle compensation control method for improving stability of LCC-HVDC system Download PDFInfo
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- CN112886628B CN112886628B CN202110062191.4A CN202110062191A CN112886628B CN 112886628 B CN112886628 B CN 112886628B CN 202110062191 A CN202110062191 A CN 202110062191A CN 112886628 B CN112886628 B CN 112886628B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
- H02M7/68—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters
- H02M7/72—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/75—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
- H02M7/757—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
- H02M7/7575—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only for high voltage direct transmission link
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
- H02J2003/365—Reducing harmonics or oscillations in HVDC
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
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- Power Engineering (AREA)
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Abstract
The invention discloses a shutoff angle compensation control method for improving the stability of an LCC-HVDC system under a weak receiving end condition, which is the core content of the invention and is realized in the following specific mode: q-axis voltage component v output by phase-locked loop of inverter stationqMultiplying by a compensation factor kγcObtaining the compensation amount gamma of the turn-off anglecThen the measured value gamma of the turn-off angle of the inverter valve and the compensation quantity gamma of the turn-off angle are calculatedcAnd adding the two values to obtain a feedback value of the constant-turn-off angle controller. Theoretical analysis shows that the invention can move the pole of the LCC-HVDC system to the left half plane, thereby improving the small signal stability of the LCC-HVDC system under the weak receiving end condition on one hand, and expanding the feasible regions of the fixed turn-off angle controller and the inverter station phase-locked loop parameter on the other hand. The simulation result verifies the effectiveness of the invention.
Description
Technical Field
The invention relates to the field of high-voltage direct-current transmission, in particular to a turn-off angle compensation control method for improving the stability of an LCC-HVDC system under a weak receiving end condition.
Background
In China, a load center and a primary energy center are distributed in the east and west in a reverse mode, and in order to achieve regional balance development, the method for converting primary energy into electric energy and conveying the electric energy to the load center is an economic and environment-friendly measure. LCC-HVDC has the advantages of large transmission capacity, low transmission loss, rapid power transmission power regulation and reversal, strong asynchronous connection capability and the like, has the characteristics of flexible control and capability of realizing asynchronous networking, and is widely applied to the field of long-distance large-capacity power transmission. However, with the rapid development of high-voltage direct-current transmission, the contradiction of 'strong direct current and weak alternating current' of a power grid in a transition period is prominent, and with the improvement of the ratio of direct-current transmission capacity, the interaction between an alternating-current power grid and a direct-current power grid is continuously enhanced, so that the characteristics of a power system are changed, and new challenges are brought to the safe and stable operation of a hybrid power grid. Especially when LCC-HVDC feeds into a weak receiving end power grid, the problems of phase commutation failure, voltage instability, system oscillation and the like are easy to occur in the whole alternating current and direct current system. The small signal stability of the system is one of the necessary conditions for ensuring the stable operation of the alternating current and direct current systems, and if the system oscillates due to the small signal instability, a series of consequences such as phase commutation failure and the like can be caused.
Time domain simulation, a state space equation, an impedance model and an amplitude-phase kinematic model are four main tools for analyzing the stability of the small signal of the LCC-HVDC system. There are many documents that use these tools to analyze the effects of ac system short-circuit ratio, controller parameters, and phase-locked loop parameters on the stability of LCC-HVDC systems. The arrangement of the STATCOM on the circulating current bus of the inverter station is one of measures for improving the stability of an AC/DC system, but the purchase of equipment increases the engineering investment; the controller parameters and the phase-locked loop parameters are reasonably designed, so that the problem of instability predicted in the engineering design stage can be avoided, but the method is difficult to adapt to complicated and variable actual working conditions. The application of the auxiliary control method is a measure with low cost, easy implementation and good effect, however, the prior art does not improve the small signal stability of the LCC-HVDC system under weak receiving end conditions from this aspect.
Disclosure of Invention
The invention aims to solve the technical problem that aiming at the defects of the prior art, the invention provides the shutoff angle compensation control method for improving the stability of the LCC-HVDC system under the weak receiving end condition, and improves the small signal stability of the LCC-HVDC system under the weak receiving end condition.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a shutdown angle compensation control method for improving the stability of an LCC-HVDC system under the condition of a weak receiving end comprises the following steps:
1) measuring the phase voltage v of the current-converting bus of the inverter stationa、vb、vcAnd subjected to per-unit treatment to give v'a、v'b、v'c：
Wherein, VPFor converting the phase voltage amplitude, theta, of the bus of the stationuiIs the phase voltage phase;
2) to v'a、v'b、v'cCarrying out Park conversion to obtain a q-axis voltage component vq；
3) Dividing the q-axis voltage component vqMultiplying by a compensation factor kγcTo obtain the compensation amount gamma of the turn-off anglecThe measured value gamma of the turn-off angle and the compensation gamma of the turn-off angle are comparedcAdding to obtain a turn-off angle feedback value gamma';
4) the turn-off angle feedback value gamma' is processed by a first-order low-pass filter to obtain gammafCommand value gamma of turn-off anglerefAnd gammafThe subtracted difference value delta gamma is sent to a constant off angle control PI controller to obtain a trigger advance angle command beta of an inversion valve of the inversion stationordi。
According to the invention, the q-axis voltage component of the phase-locked loop of the inverter station needs to be introduced into the turn-off angle feedback path, other complex control logics are not needed, the operation is simple and feasible, and the small signal stability of the LCC-HVDC system under the condition of a weak receiving end power grid is greatly improved.
In step 2), v'a、v'b、v'cThe formula for performing Park transformation is:
wherein, thetaplliFor phase-locked loop output phase of the inverter station, and has
ω0Rated frequency, k, of receiving gridppcAnd kipcProportional coefficient and integral coefficient controlled by phase-locked loop PI.
In step 3), the compensation coefficient kγcThe process of changing from 0 to 3 follows kγcThe increase in the number of poles is dominant, the dominant pole of the system is shifted to the left half-plane, indicating that the stability of the system is improved. Thus, the compensation coefficient kγcThe value can be taken within the range of 0-3 according to the conditions of the intensity of a receiving-end alternating current system, the controller and the parameters of the phase-locked loop in the actual engineering. In step 4), triggering advance angle command beta of inverse change valveordiThe calculation formula of (2) is as follows:
wherein Δ γ ═ γref-γf；
TγIs a first order low pass filter time constant, kpγAnd kiγAnd the proportional coefficient and the integral coefficient of the constant turn-off angle control PI controller are respectively.
The invention also provides an LCC-HVDC system, which comprises a rectifier station, a direct current circuit and an inverter station which are connected in sequence; the rectifying station is connected with a transmitting end power grid; the inverter station is connected with a receiving end power grid; also included is a computer device; the computer device is configured or programmed for performing the steps of the above-described method.
The invention also provides a shutdown angle compensation control system for improving the stability of the LCC-HVDC system under the weak receiving end condition, which comprises computer equipment; the computer device is configured or programmed for performing the steps of the above-described method.
Compared with the prior art, the invention has the beneficial effects that: according to the invention, only the q-axis voltage component of the phase-locked loop of the inverter station needs to be introduced into the turn-off angle feedback path, and other complex control logics are not needed, so that the method is simple and feasible; the invention can move the pole of the LCC-HVDC system to the left half plane, thereby improving the small signal stability of the LCC-HVDC system under the condition of weak receiving end on one hand, and expanding the feasible regions of the fixed turn-off angle controller and the inverter station phase-locked loop parameter on the other hand.
Drawings
FIG. 1(a) is a LCC-HVDC system main circuit; FIG. 1(b) shows a structure of constant current control of a rectifier valve; FIG. 1(c) shows a constant turn-off angle control structure of an inverter valve;
FIG. 2 is a block diagram of an implementation of a shutdown angle compensation controller in an embodiment of the present invention;
FIG. 3 is a plot of dominant pole versus compensation factor k for an LCC-HVDC system in an example of the inventionγcTrack at increase;
FIG. 4(a) is a response curve for an LCC-HVDC system with reduced short circuit ratio for an embodiment of the present invention; FIG. 4(b) is a diagram of proportional coefficient k of constant turn-off angle control PI controller according to an embodiment of the present inventionpγThe response curve of the system at increase; FIG. 4(c) is a diagram showing the proportional coefficient k of the phase-locked loop PI controller of the present inventionppcResponse curve of LCC-HVDC system at increase.
Detailed Description
Referring to fig. 1(a) to fig. 1(c), the main circuit and control structure of the LCC-HVDC system in the embodiment of the present invention are shown. FIG. 1(a) is a LCC-HVDC system main circuit; FIG. 1(b) shows a structure of constant current control of a rectifier valve; fig. 1(c) shows an inverse variable valve constant-off angle control structure. The LCC-HVDC system is composed of 9 parts: the system comprises a sending end power grid, a sending end alternating current filter bank, a rectifying station, a rectifying valve constant current controller, a direct current circuit, a receiving end power grid, a receiving end alternating current filter bank, an inverter station and an inverter valve constant turn-off angle controller. The dashed box in fig. 1(c) is the location where the off angle compensation control of the present invention is located.
Referring to fig. 2, a block diagram for implementing the off-angle compensation control of the embodiment of the present invention includes the following calculation steps:
1) measuring the phase voltage v of the current-converting bus of the inverter stationa、vb、vcAnd subjected to per-unit treatment to obtain v'a、v'b、v'c：
2) v'a、v'b、v'cSending the voltage into a conventional three-phase-locked loop to carry out Park conversion to obtain a q-axis voltage component vq；
3) q-axis voltage component vqMultiplying by a compensation factor kγcObtaining the compensation amount gamma of the turn-off anglecThe measured value gamma of the turn-off angle and the compensation gamma of the turn-off anglecAdding to obtain a turn-off angle feedback value γ':
4) the turn-off angle feedback value gamma' is processed by a first-order low-pass filter to obtain gammafCommand value gamma of turn-off anglerefAnd gammafThe subtracted delta gamma value is sent to a constant-off angle control PI controller (Guochun, Jiang, Zhao Cheng Yong, and the like, a dynamic model of an LCC-HVDC system containing the STATCOM and a small signal stability research [ J]The Chinese Motor engineering newspaper 2018,38(14) 4046-4055 DOI 10.13334/j.0258-8013 pcsee.171666) and finally obtains a trigger advance angle instruction beta of the inverse change valveordi：
Controlling a proportional coefficient and an integral coefficient of a PI controller by a fixed turn-off angle;
in step 2), the calculation formula of Park transformation is as follows:
See FIG. 3 for the compensation factor kγcDuring the increase from 0 to 3, the LCC-HVDC system dominates the locus of the poles. From the trajectory trend, it can be seen that with kγcThe dominant pole gradually moves towards the left half-plane, the stability of the system is improved, and the effectiveness of the method is further clarified theoretically.
Referring to FIGS. 4(a) to 4(c), the de-scaling factor k is controlled for the present invention at the short-circuit ratio decreasing and the on-off angle PIpγIncreasing and phase-locked loop PI controller proportionality coefficient kppcAnd increasing simulation graphs of the stability effect of the LCC-HVDC system under the three working conditions. As can be seen from the solid line in FIG. 4(a), without the application of the present invention, the LCC-HVDC system shorts SCR in the receiving gridiAfter decreasing from 2.5 to 1.8, the stabilization is lost, the direct current and the turn-off angle diverge and eventually a commutation failure is initiated. After applying the method (k)γc1.5), the LCC-HVDC system can still stably operate when the short-circuit ratio is reduced, as shown by a dotted line in FIG. 4(a), which shows that the stability of the LCC-HVDC system under the weak receiving end condition can be improved. As can be seen from FIG. 4(b), the PI controller proportional coefficient k is controlled when the turn-off angle is fixedpγWhen the divergence is increased from 0.755 to 1.5, the divergence of the LCC-HVDC system without the method is increased, but the system applying the method can still maintain stable, which shows that the invention can enable k to be increasedpγThe feasible domain of (a) is expanded. As can be seen from the comparison in FIG. 4(c), the invention can also enlarge the proportionality coefficient k of the phase-locked loop of the inverter stationppcCan be used.
Claims (5)
1. A shutdown angle compensation control method for improving the stability of an LCC-HVDC system under the condition of a weak receiving end is characterized by comprising the following steps:
1) measuring the phase voltage v of the current-converting bus of the inverter stationa、vb、vcAnd subjected to per-unit treatment to give v'a、v'b、v'c：
Wherein, VPFor converting the phase voltage amplitude, theta, of the bus of the stationuiIs the phase voltage phase;
2) to v'a、v'b、v'cCarrying out Park conversion to obtain a q-axis voltage component vq；
3) Dividing the q-axis voltage component vqMultiplying by a compensation factor kγcTo obtain the compensation amount gamma of the turn-off anglecThe measured value gamma of the turn-off angle and the compensation gamma of the turn-off angle are comparedcAdding to obtain a turn-off angle feedback value gamma';
4) the turn-off angle feedback value gamma' is processed by a first-order low-pass filter to obtain gammafCommand value gamma of turn-off anglerefAnd gammafThe subtracted difference value delta gamma is sent to a constant off angle control PI controller to obtain a trigger advance angle command beta of an inversion valve of the inversion stationordi。
2. The shutdown angle compensation control method for improving the stability of the LCC-HVDC system in the weak termination condition according to claim 1, wherein v 'is given in step 2)'a、v'b、v'cThe formula for performing Park transformation is:
wherein, thetaplliFor phase-locked loop output phase of the inverter station, and has
ω0Rated frequency, k, of receiving gridppcAnd kipcProportional coefficient and integral coefficient of phase-locked loop PI control.
3. A shutdown angle compensation control method for improving stability of LCC-HVDC system in weak receiving end condition according to claim 1, wherein in step 4), trigger advance angle command β of inverse change valveordiThe calculation formula of (2) is as follows:
wherein Δ γ ═ γref-γf；
TγIs a first order low pass filter time constant, kpγAnd kiγAnd the proportional coefficient and the integral coefficient of the constant turn-off angle control PI controller are respectively.
4. An LCC-HVDC system comprises a rectifier station, a direct current line and an inverter station which are connected in sequence; the rectifying station is connected with a transmitting end power grid; the inverter station is connected with a receiving end power grid; the system is characterized by also comprising computer equipment; the computer device is configured or programmed for carrying out the steps of the method according to one of claims 1 to 3.
5. A shutdown angle compensation control system for improving the stability of an LCC-HVDC system under a weak receiving end condition is characterized by comprising computer equipment; the computer device is configured or programmed for carrying out the steps of the method according to one of claims 1 to 3.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110021949A (en) * | 2018-01-09 | 2019-07-16 | 国家电网公司 | A kind of method and controller inhibiting two layers of inverter while commutation failure |
| CN111786396A (en) * | 2020-07-10 | 2020-10-16 | 国网湖南省电力有限公司 | High-voltage direct-current power transmission system commutation failure suppression method based on energy storage type chain STATCOM |
| CN111864766A (en) * | 2020-07-08 | 2020-10-30 | 华北电力大学 | Control method for additional damping of direct current power transmission system based on angular frequency change rate |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110021949A (en) * | 2018-01-09 | 2019-07-16 | 国家电网公司 | A kind of method and controller inhibiting two layers of inverter while commutation failure |
| CN111864766A (en) * | 2020-07-08 | 2020-10-30 | 华北电力大学 | Control method for additional damping of direct current power transmission system based on angular frequency change rate |
| CN111786396A (en) * | 2020-07-10 | 2020-10-16 | 国网湖南省电力有限公司 | High-voltage direct-current power transmission system commutation failure suppression method based on energy storage type chain STATCOM |
Non-Patent Citations (2)
| Title |
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| 含STATCOM的LCC-HVDC系统的动态模型及小信号稳定性研究;郭春义等;《中国电机工程学报》;20180321(第14期);全文 * |
| 特高压直流分层接入方式下预防换相失败的优化措施;李新年等;《中国电机工程学报》;20181109(第22期);全文 * |
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