CN110058128B - Method, system, equipment and storage medium for detecting steady-state operation range of flexible-straight system - Google Patents
Method, system, equipment and storage medium for detecting steady-state operation range of flexible-straight system Download PDFInfo
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Abstract
The invention discloses a method for detecting a steady-state operation range of a flexible-straight system, which comprises the following steps: configuring a voltage sequence of a connection transformer network side voltage of the flexible direct current system; presetting a steady-state operation range calculation equation of the flexible direct-current system, wherein constraint conditions of the steady-state operation range calculation equation at least comprise constraint aiming at the overload capacity of the flexible direct-current system and constraint aiming at the pressure resistance capacity of primary equipment; and detecting the steady-state operation range of the flexible direct current system under each voltage level of the voltage sequence based on a steady-state operation range calculation equation under the constraint condition. By applying the scheme, the steady-state operation range of the flexible and straight system which is more consistent with the actual engineering can be determined, the estimation of the active power and reactive power output capacity of the flexible and straight system which is more accurate and has more practical application value is carried out, and the full application of the overload capacity is facilitated. The application also discloses a system, equipment and storage medium for detecting the steady-state operation range of the flexible-straight system, and the system, equipment and storage medium have corresponding effects.
Description
Technical Field
The invention relates to the technical field of flexible-straight system detection, in particular to a method, a system, equipment and a storage medium for detecting the steady-state operation range of a flexible-straight system.
Background
The flexible direct-current transmission technology is a third generation direct-current transmission technology based on a voltage source converter technology, and the adopted converter element is a bidirectional controllable power electronic device which can be controlled to be switched on and switched off, and is typically represented by an Insulated Gate Bipolar Transistor (IGBT). The development of the Modular Multilevel Converter can be divided into a two-level/three-level voltage source Converter based on a pulse width modulation theory and an MMC (Modular Multilevel Converter) based on step wave approximation, the MMC is a main development trend at the present stage, and the flexible direct-current system is an MMC.
The control method of the flexible direct current connection variable-branch joint can be divided into two categories of manual control and automatic control, the common mode is an automatic control mode, the control method can be divided into two control modes of fixed voltage control and fixed modulation ratio control, and the fixed voltage control mode is adopted in actual operation. Under specific operation conditions, the flexible direct-current coupling and variable-division joint needs to be fixed at a certain specific gear, so that the safety and stability of the operation of the flexible direct-current system are ensured. Therefore, there is a need to evaluate the effect of the prescribed coupling tap gear on the dc system operating characteristics, including the steady state operating range of the flexible dc system.
Referring to fig. 1, a conventional method for studying a steady-state operation range of a flexible direct-current system is a theoretical calculation method, and a simultaneous equation is solved by calculating a power relationship among a PCC point, a v point and a diff point and by using a constraint condition of a current converter in actual operation. U shapesFor system voltage, the PCC point is a common connection point, i.e., the connection point of the converter station connecting the transformer side and the AC system, UpccIs the PCC point voltage, δpccIs the PCC point voltage phase angle; point v is the side of the connecting variable valve, UvIs the voltage at v point, deltavIs the voltage phase angle at v. The diff point is the equivalent point of the non-common connecting end of the bridge arm reactor, and the point is equipotential under the equivalent circuit of the fundamental wave, namely Udiff＝Epk＝Enk，δdiffIs the voltage phase angle of diff point, EpkFor the voltage at the non-common connection end of the upper bridge arm reactor, EnkThe voltage is the voltage of the non-common connecting end of the lower bridge arm reactor. u. ofpkIs the upper bridge arm voltage unkIs lower bridge arm voltage, UdcIs a dc interelectrode voltage. i.e. ipkFor upper arm current, inkIs the lower bridge arm current, IdcIs a direct current icirkIs a bridge arm circulating current.
Zsys＝Rsys+XsysIs the system impedance, XTFor equivalent leakage reactance of transformer fundamental wave, XL0Is the bridge arm reactance at fundamental frequency, Xac＝Xsys+XTIs an equivalent reactance of an AC system, Xlink＝XT+XL0/2 is the connection impedance between the PCC point and the diff point, XΣIs the sum of the reactances of equal value.
Ps+jQsFor the power flowing into the AC system at the PCC point, Pv+jQvFor the power flowing into the transformer on the valve side of the transformer, Pdiff+jQdiffEquivalent power flowing into the bridge arm reactor is supplied to the converter. The simultaneous equations are:
the constraint conditions are as follows:
m is the output voltage modulation ratio, I, of modular multilevel converter MMCvNIs the MMC AC side-group wave current rating.
However, the foregoing analysis only obtains the output range of the active power and the reactive power of the flexible direct current after the tap is fixed theoretically, and only stays at the theoretical analysis level without the support of simulation or actual operation data. This is because in practical applications, the flexible dc system usually sets overload logic, and even if the IBGT has a lower current capacity than the thyristor, a certain current capacity margin and a short-time current capacity are still left during engineering design. It can be seen that, because overload logic is not considered in the conventional scheme, it is not beneficial to accurately determine the steady-state operation range of the straightening and smoothing system, and it is also not beneficial to fully apply the overload capacity.
In summary, how to determine the steady-state operation range of the flexible dc system that better conforms to the reality and achieve the full application of the overload capacity is a technical problem that needs to be solved urgently by those skilled in the art.
Disclosure of Invention
The invention aims to provide a method, a system, equipment and a storage medium for detecting the steady-state operation range of a flexible direct-current system, so as to determine the steady-state operation range which is more consistent with the actual steady-state operation range of the flexible direct-current system and realize the full application of overload capacity.
In order to solve the technical problems, the invention provides the following technical scheme:
a steady-state operation range detection method for a flexible-straight system comprises the following steps:
configuring a voltage sequence of a connection transformer network side voltage of the flexible direct current system;
presetting a steady-state operation range calculation equation of the flexible direct current system, wherein constraint conditions of the steady-state operation range calculation equation at least comprise constraint aiming at the overload capacity of the flexible direct current system and constraint aiming at the pressure resistance capacity of primary equipment;
and detecting the steady-state operation range of the flexible direct current system under each voltage level of the voltage sequence based on the steady-state operation range calculation equation under the constraint condition.
Preferably, the steady-state operation range calculation equation is:
wherein, Ps+jQsThe power flowing into the alternating current system from the PCC point is the connection point of the converter station connecting with the transformer side and the alternating current system; pv+jQvThe power flowing into the transformer from the valve side of the transformer, point v is the connection point between the transformer and the transformer network, PvActive power, Q, flowing into the transformer for the valve side of the transformervTo transform into a voltageReactive power, U, flowing into the transformer on the valve sidevIs the voltage at v point; xTFor equivalent leakage reactance of transformer fundamental wave, XL0Is the bridge arm reactance at fundamental frequency; pdiff+jQdiffEquivalent power flowing into a bridge arm reactor for the converter;
the constraint conditions of the steady state operating range calculation equation are:
wherein m is the output voltage modulation ratio, I, of the modular multilevel converter MMCvNFor MMC AC side-group wave current rating, IvdIs the d-axis component of the transformer valve-side current, IvqIs the q-axis component of the transformer valve side current, IvdmaxIs the maximum allowable value of d-axis current when the flexible direct current system has overload capacity, IvqmaxIs the maximum allowable value, U, of the q-axis current of the flexible direct current system when the flexible direct current system has overload capacityvmaxIs the maximum withstand voltage of the primary device.
Preferably, the detecting the steady-state operation range of the flexible direct current system at each voltage level of the voltage sequence based on the steady-state operation range calculation equation under the constraint condition includes:
and based on the steady-state operation range calculation equation under the constraint condition, detecting the steady-state operation range of the flexible direct current system for the capacity of sending rated reactive power, the capacity of absorbing rated reactive power and the capacity of sending active power under each voltage level of the voltage sequence.
Preferably, the detecting the steady-state operation range of the flexible direct current system with respect to the capability of generating rated reactive power based on the steady-state operation range calculation equation under the constraint condition at each voltage level of the voltage sequence includes:
adjusting a connected grid-side voltage of the flexible direct current system from an allowable maximum value to a maximum value in the voltage sequence;
setting the active power of the flexible direct current system as rated power, and setting the reactive power to send out rated reactive power;
adjusting the voltage of the connection transformer network side of the flexible direct current system to a target voltage value, wherein the target voltage value is the maximum value selected from the current voltage values to be measured of the voltage sequence;
judging whether the flexible direct current system has overload capacity or not;
if the overload capacity is not available, recording that the flexible direct current system is not in a stable running range in the current state, and recording current running data of the flexible direct current system;
if the flexible direct current system has overload capacity, judging whether the flexible direct current system is in a steady-state operation range or not through the steady-state operation range calculation equation under the constraint condition, and recording a judgment result and current various operation data of the flexible direct current system;
after the operation data are recorded, marking the current target voltage value as a measured voltage value, and judging whether a voltage value to be measured exists in the voltage sequence or not;
if not, ending the detection of the steady-state operation range of the capacity of the flexible direct current system for generating rated reactive power;
if so, adjusting the flexible direct current system to a steady-state operation range and have load capacity, and returning to the step of adjusting the voltage of the connection transformer network side of the flexible direct current system to a target voltage value to select the next target voltage value from the voltage sequence.
Preferably, the detecting the steady-state operation range of the flexible direct current system for absorbing the rated reactive power capability at each voltage level of the voltage sequence based on the steady-state operation range calculation equation under the constraint condition includes:
adjusting a connected grid-side voltage of the flexible direct current system from an allowable maximum value to a maximum value in the voltage sequence;
setting the active power of the flexible direct current system as rated power, and setting the reactive power as absorbing rated reactive power;
adjusting the voltage of the connection transformer network side of the flexible direct current system to a target voltage value, wherein the target voltage value is the maximum value selected from the current voltage values to be measured of the voltage sequence;
judging whether the flexible direct current system has overload capacity or not;
if the overload capacity is not available, recording that the flexible direct current system is not in a stable running range in the current state, and recording current running data of the flexible direct current system;
if the flexible direct current system has overload capacity, judging whether the flexible direct current system is in a steady-state operation range or not through the steady-state operation range calculation equation under the constraint condition, and recording a judgment result and current various operation data of the flexible direct current system;
after the operation data are recorded, marking the current target voltage value as a measured voltage value, and judging whether a voltage value to be measured exists in the voltage sequence or not;
if not, ending the detection of the steady-state operation range of the flexible direct current system for absorbing the rated reactive power;
if so, adjusting the flexible direct current system to a steady-state operation range and have load capacity, and returning to the step of adjusting the voltage of the connection transformer network side of the flexible direct current system to a target voltage value to select the next target voltage value from the voltage sequence.
Preferably, the detecting the steady-state operation range of the active power capability of the flexible direct current system at each voltage level of the voltage sequence based on the steady-state operation range calculation equation under the constraint condition includes:
adjusting a connected grid-side voltage of the flexible direct current system from an allowable maximum value to a maximum value in the voltage sequence;
setting the active power of the flexible direct current system as rated power and the reactive power as 0;
adjusting the voltage of the connection transformer network side of the flexible direct current system to a target voltage value, wherein the target voltage value is the maximum value selected from the current voltage values to be measured of the voltage sequence;
judging whether the flexible direct current system has overload capacity or not;
if the overload capacity is not available, recording that the flexible direct current system is not in a stable running range in the current state, and recording current running data of the flexible direct current system;
if the flexible direct current system has overload capacity, judging whether the flexible direct current system is in a steady-state operation range or not through the steady-state operation range calculation equation under the constraint condition, and recording a judgment result and current various operation data of the flexible direct current system;
after the flexible direct current system is determined not to be in a steady-state operation range in the current state and operation data are recorded, the flexible direct current system is adjusted to be in the steady-state operation range through voltage regulation and has load capacity, a voltage critical value of a steady-state operation range calculation equation meeting the constraint condition is determined through gradually reducing the voltage, all operation data of the flexible direct current system are recorded at the voltage critical value, and the detection of the steady-state operation range of the active power capacity of the flexible direct current system is finished;
after the flexible direct current system is determined to be in a steady-state operation range in the current state and operation data are recorded, marking the current target voltage value as a measured voltage value, and judging whether a voltage value to be measured exists in the voltage sequence or not;
if not, ending the detection of the steady-state operation range of the active power capability of the flexible direct current system;
if so, adjusting the flexible direct current system to a steady-state operation range and have load capacity, and returning to the step of adjusting the voltage of the connection transformer network side of the flexible direct current system to a target voltage value to select the next target voltage value from the voltage sequence.
A system for detecting a steady-state operating range of a straightening system, comprising:
the voltage sequence configuration module is used for configuring a voltage sequence of the connection transformer network side voltage of the flexible direct current system;
the system comprises a steady-state operation range calculation equation and constraint condition setting module, a steady-state operation range calculation equation and a constraint condition setting module, wherein the steady-state operation range calculation equation and the constraint condition setting module are used for presetting the steady-state operation range calculation equation of the flexible direct current system, and the constraint condition of the steady-state operation range calculation equation at least comprises constraint aiming at the overload capacity of the flexible direct current system and constraint aiming at the pressure resistance capacity of primary equipment;
and the detection module is used for detecting the steady-state operation range of the flexible direct current system under each voltage level of the voltage sequence based on the steady-state operation range calculation equation under the constraint condition.
Preferably, the steady-state operation range calculation equation is:
wherein, Ps+jQsThe power flowing into the alternating current system from the PCC point is the connection point of the converter station connecting with the transformer side and the alternating current system; pv+jQvThe power flowing into the transformer from the valve side of the transformer, point v is the connection point between the transformer and the transformer network, PvActive power, Q, flowing into the transformer for the valve side of the transformervFor reactive power, U, flowing into the transformer on the valve side of the transformervIs the voltage at v point; xTFor equivalent leakage reactance of transformer fundamental wave, XL0Is the bridge arm reactance at fundamental frequency; pdiff+jQdiffEquivalent power flowing into a bridge arm reactor for the converter;
the constraint conditions of the steady state operating range calculation equation are:
wherein m is the output voltage modulation ratio, I, of the modular multilevel converter MMCvNFor MMC AC side-group wave current rating, IvdIs the d-axis component of the transformer valve-side current, IvqIs the q-axis component of the transformer valve side current, IvdmaxIs the maximum allowable value of d-axis current when the flexible direct current system has overload capacity, IvqmaxIs the maximum allowable value, U, of the q-axis current of the flexible direct current system when the flexible direct current system has overload capacityvmaxIs the maximum withstand voltage of the primary device.
A soft straight system steady state operating range detection apparatus comprising:
a memory for storing a computer program;
a processor for executing the computer program to implement the steps of the method for detecting steady-state operating range of a flexible direct system as described in any one of the above.
A computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the steps of the method of any of the above-described systems steady state operating range detection.
The technical scheme provided by the embodiment of the invention comprises the following steps: configuring a voltage sequence of a connection transformer network side voltage of the flexible direct current system; presetting a steady-state operation range calculation equation of the flexible direct-current system, wherein constraint conditions of the steady-state operation range calculation equation at least comprise constraint aiming at the overload capacity of the flexible direct-current system and constraint aiming at the pressure resistance capacity of primary equipment; and detecting the steady-state operation range of the flexible direct current system under each voltage level of the voltage sequence based on a steady-state operation range calculation equation under the constraint condition.
Under the condition of overload capacity, the flexible direct current system has a wider limiting range for the current on the valve side, namely a wider steady-state operation range. Therefore, the constraint aiming at the overload capacity of the flexible direct current system and the constraint aiming at the pressure resistance of the primary equipment are added in the constraint condition, a wider steady-state operation range can be determined, the range is more consistent with the flexible direct current system in the practical engineering, namely, the method can evaluate the output capacity of the active power and the reactive power of the flexible direct current system more accurately and has more practical application value, and is also favorable for fully applying the overload capacity.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic diagram of a steady state operation range theoretical calculation method for a flexible-straight system;
FIG. 2 is a flowchart illustrating a method for detecting a steady-state operation range of a flexible-straight system according to the present invention;
FIG. 3 is a flow chart illustrating the implementation of the present invention for detecting the rated reactive power capability of a flexible direct current system;
FIG. 4 is a flow chart of an embodiment of the present invention for detecting active power capability of a flexible direct current system;
fig. 5 is a schematic structural diagram of a system for detecting a steady-state operation range of a flexible-straight system according to the present invention.
Detailed Description
The core of the invention is to provide a method for detecting the steady-state operation range of the flexible direct-current system, which can determine the steady-state operation range of the flexible direct-current system which is more in line with the actual steady-state operation range and realize the full application of the overload capacity.
In order that those skilled in the art will better understand the disclosure, the invention will be described in further detail with reference to the accompanying drawings and specific embodiments. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 2, fig. 2 is a flowchart illustrating an implementation of a method for detecting a steady-state operating range of a flexible-direct system according to the present invention, where the method for detecting the steady-state operating range of the flexible-direct system includes the following steps:
step S101: and configuring a voltage sequence of the connection transformer network side voltage of the flexible direct current system.
The flexible direct current system described in the present application is also referred to as a flexible direct current system, and is all MMC. When configuring the voltage sequence of the connection transformer side voltage of the flexible direct current system, the number of voltages included in the voltage sequence and the voltage magnitude of each voltage can be set and adjusted according to the need, and the implementation of the present invention is not affected, for example, in a specific occasion, the voltage sequence includes: 500V, 480V, 450V, 430V and 400V.
Step S102: a steady-state operation range calculation equation of the flexible direct current system is preset, and constraint conditions of the steady-state operation range calculation equation at least comprise constraint aiming at the overload capacity of the flexible direct current system and constraint aiming at the pressure resistance capacity of the primary equipment.
The applicant considers that the overload logic is the calculated overload capacity under the current ambient temperature condition, considering whether the backup cooling device is available, the converter valve current capacity, the current temperature and other factors, and limits the current command output by the direct current power control or the direct current control. The overload logic facilitates full utilization of the overload capability without undesirable shutdown due to overstress of the equipment. Therefore, the scheme of the application aims at the fact that overload logic is equipped in practical application, namely the scheme aims at a flexible direct current system with overload capacity. However, it should be noted that, in practical applications, the flexible dc system usually sets overload logic, and even if the IBGT has a lower current capacity than the thyristor, a certain current capacity margin and a short-time current capacity are left during engineering design, so the flexible dc system in practical applications is usually suitable for the scheme of the present application.
Although overload logics of the flexible direct current system in practical application are different, under the condition of overload capacity, the limiting range of the flexible direct current system on the valve side current is wider, the overload logics are not considered in the traditional scheme, the limiting on the valve side current is narrower, and the steady-state operation range is influenced. That is, the soft straight system has a wider steady state operating range when considering the overload logic.
Therefore, in step S102, the constraint condition of the steady-state operation range calculation equation includes an overload capability constraint for the flexible dc system. And, considering that the overload logic is to clip the current, a voltage limiting condition is added to the constraint condition, namely the voltage endurance capacity of the primary equipment is considered in the constraint condition of the steady-state operation range calculation equation. Because the constraint condition is based on the overload capacity of the flexible direct current system and the pressure resistance of the primary equipment, the method and the device can evaluate the output capacity of the active power and the reactive power of the flexible direct current system more accurately and have more practical application value.
In one embodiment, the steady state operation range calculation equation in step S102 may be:
wherein, Ps+jQsThe power flowing into the alternating current system from the PCC point is the connection point of the converter station connecting with the transformer side and the alternating current system; pv+jQvThe power flowing into the transformer from the valve side of the transformer, point v is the connection point between the transformer and the transformer network, PvActive power, Q, flowing into the transformer for the valve side of the transformervFor reactive power, U, flowing into the transformer on the valve side of the transformervIs the voltage at v point; xTFor equivalent leakage reactance of transformer fundamental wave, XL0Is the bridge arm reactance at fundamental frequency; pdiff+jQdiffEquivalent power flowing into the bridge arm reactor is supplied to the converter.
The constraint condition of the steady-state operation range calculation equation based on the overload capacity of the flexible direct-current system and the pressure resistance capacity of the primary equipment can be as follows:
wherein m is the output voltage modulation ratio of MMC, IvNFor MMC AC side-group wave current rating, IvdIs the d-axis component of the transformer valve-side current, IvqIs the q-axis component of the transformer valve side current, IvdmaxIs the maximum allowable value of d-axis current when the flexible direct current system has overload capacity, IvqmaxIs the maximum allowable value of q-axis current, U, of the flexible direct current system when the system has overload capacityvmaxIs the maximum withstand voltage of the primary device. U shapevdAnd UvqAre respectively UvA d-axis component and a q-axis component.
In such an embodiment of the present invention, the first,
i.e. constraint for overload capability of the flexible dc system, Uv≤UvmaxIs a constraint on the pressure resistance of the primary equipment.
E.g. when considering overload capacity, Ivdmax＝2.933kA，Ivqmax＝0.8kA，IvN2.922 kA. While overload capability is not considered in the conventional scheme, Ivdmax＝2.820kA，Ivqmax＝0.769kA，IvN2.922 kA. When considering overload capability, assume IvqWhen the value is 0, then IvdCan reach an upper limit value IvN2.922 kA; when overload capability is not considered in the conventional scheme, IvdCan only reach Ivdmax2.820 kA. As another example, when considering overload capabilities, assume
Then IvqCan reach an upper limit value Ivqmax0.8 kA; while overload capability is not considered in the conventional scheme, IvqCan only reach Ivqmax0.769 kA. It can be seen that there is a certain difference in the steady state operation range of the flexible direct current system in the scheme and the traditional scheme.
Step S103: and detecting the steady-state operation range of the flexible direct current system under each voltage level of the voltage sequence based on a steady-state operation range calculation equation under the constraint condition.
Generally, the detection of the steady state operation range can be performed on the rated reactive power emitting capacity, the rated reactive power absorbing capacity and the active power emitting capacity of the flexible direct current system. During detection, the theoretical value of the steady-state operation range of the flexible direct current system may be calculated in advance according to the constraint condition determined in step S102, and then the detection of the steady-state operation range of the flexible direct current system is realized based on the detection data.
The technical scheme provided by the embodiment of the invention comprises the following steps: configuring a voltage sequence of a connection transformer network side voltage of the flexible direct current system; presetting a steady-state operation range calculation equation of the flexible direct-current system, wherein constraint conditions of the steady-state operation range calculation equation at least comprise constraint aiming at the overload capacity of the flexible direct-current system and constraint aiming at the pressure resistance capacity of primary equipment; and detecting the steady-state operation range of the flexible direct current system under each voltage level of the voltage sequence based on a steady-state operation range calculation equation under the constraint condition.
Under the condition of overload capacity, the flexible direct current system has a wider limiting range for the current on the valve side, namely a wider steady-state operation range. Therefore, the constraint aiming at the overload capacity of the flexible direct current system and the constraint aiming at the pressure resistance of the primary equipment are added in the constraint condition, a wider steady-state operation range can be determined, the range is more consistent with the flexible direct current system in the practical engineering, namely, the method can evaluate the output capacity of the active power and the reactive power of the flexible direct current system more accurately and has more practical application value, and is also favorable for fully applying the overload capacity.
Referring to fig. 3, in an embodiment of the present invention, based on a steady-state operation range calculation equation under a constraint condition, a process of detecting a steady-state operation range of a flexible dc system in a power generation capacity of generating rated reactive power at each voltage level of a voltage sequence may specifically include the following steps:
step S301: the voltage on the connection transformer network side of the flexible direct current system is adjusted from the maximum value allowed to the maximum value in the voltage sequence.
Step S302: the active power of the flexible direct current system is set to be rated power, and the reactive power is set to be rated reactive power.
It should be noted that before step S301 is executed, if the overload logic of the system is triggered due to a fault or the like and the detection is executed when the overload capability of the system is not recovered, an erroneous detection result may be obtained. Therefore, before step S301 is executed, the recording may be observed to determine whether the system has overload capability, and if not, step S301 may be executed after the system recovers the overload capability, which is beneficial to avoiding the occurrence probability of false detection, and this is also true when the test of absorbing the rated reactive power capability and sending out the active power capability is executed in the subsequent embodiment.
At the same power level, the higher the AC voltage, IvdAnd IvqThe lower the probability of triggering the overload logic, the lower the probability of the overload logic, and therefore the application first adjusts the network-side voltage of the flexible dc system from the maximum value allowed to the maximum value in the voltage sequence, i.e. the detection of the maximum voltage value in the voltage sequence is performed first. And the active power of the flexible direct current system is set as rated power, and the reactive power is set to send out rated reactive power. It should be noted that, in some cases, the maximum value in the voltage sequence is equal to the maximum value allowed by the voltage on the side of the connected transformer of the flexible dc system.
Step S303: and regulating the voltage of the connection transformer network side of the flexible direct current system to a target voltage value, wherein the target voltage value is the maximum value selected from the current voltage values to be measured of the voltage sequence.
When the detection process starts, each voltage value in the voltage sequence is a voltage value to be detected, namely, each voltage value does not execute the detection process. For example, in one particular case, the voltage sequence includes: 500V, 480V, 450V, 430V and 400V, the voltage of the connection transformer side of the flexible direct current system is adjusted to 500V when the step S303 is executed for the first time.
Step S304: and judging whether the flexible direct current system has overload capacity or not.
If the overload capability is not available, step S305 is executed: and recording that the flexible direct current system is not in a steady-state operation range in the current state, and recording current operation data of the flexible direct current system.
If the overload capability is available, step S306 is executed: and judging whether the flexible direct current system is in the steady-state operation range or not through a steady-state operation range calculation equation under the constraint condition, and recording a judgment result and current various operation data of the flexible direct current system.
Detection data obtained by sampling and limit value I related to overload logicvdmax、IvqmaxTo determine whether the flexible dc system has overload capability. It should be noted that, since the constraint conditions in the solution of the present application include constraints for the overload capability of the flexible dc system and constraints for the pressure-resistant capability of the primary equipment, when it is determined in step S304 that the flexible dc system does not have the overload capability, it is not necessary to determine whether the constraint conditions are satisfied, but step S305 is directly performed: and recording that the flexible direct current system is not in a steady-state operation range in the current state, and recording current operation data of the flexible direct current system.
When the overload capacity is available, whether the flexible direct current system is in the steady-state operation range or not can be judged through the steady-state operation range calculation equation under the constraint condition determined in the step S102, and the judgment result and various current operation data of the flexible direct current system are recorded.
In this embodiment, the flexible dc system is not in the steady-state operation range, and there are generally two possibilities: one is that the voltage of the connection transformer valve side exceeds the primary equipment tolerance voltage value due to the fact that the voltage of the connection transformer network side is too high; and the other is that the overload logic of the flexible-direct system is triggered due to the fact that the voltage of the connection transformer network side is too low, and the flexible-direct system cannot fully generate reactive power under rated active power. In any two cases, current various operating data of the flexible direct current system need to be recorded, and the recorded operating data may include actual active power, reactive power, system voltage, voltage at the side of the connection transformer network, voltage at the side of the connection transformer valve, and other key operating data.
Step S307: after the operation data are recorded, marking the current target voltage value as a measured voltage value, and judging whether the voltage value to be measured exists in the voltage sequence.
If the voltage does not exist, ending the detection of the steady-state operation range of the rated reactive power capability of the flexible direct current system;
if so, step S308 is performed: the flexible dc system is adjusted to the steady state operating range and has load capacity, and then returns to step S303 to select the next target voltage value from the voltage sequence.
For example, the voltage sequence includes: 500V, 480V, 450V, 430V and 400V. After a round of detection is performed by selecting 500V as the target voltage value, it can be determined in step S307 that there are 4 voltage values to be detected in the voltage sequence.
It is emphasized that after step S307, before returning to step S303 to select the next target voltage value from the voltage sequence, the flexible dc system needs to be adjusted to the steady-state operation range and have load capacity, i.e. step S308 needs to be performed. Of course, if the flexible dc system is already in the steady state operating range and has load capacity, no adjustment is naturally necessary. The adjustment manner of step S308 is usually voltage adjustment.
For example, after 500V is selected as the target voltage value and the detection is performed, the flexible dc system has overload capability, and when S306 is performed, it is determined that the flexible dc system is in the steady-state operation range under the condition that the voltage on the link transformer side of the flexible dc system is 500V through the steady-state operation range calculation equation under the constraint condition, step S303 may be performed, and 480V is selected as the target voltage value of the second round. Assuming that the flexible dc system is not in the steady-state operation range when step S306 is executed under the condition of 480V, the flexible dc system is restored to the steady-state operation range and has the load capacity by voltage adjustment in step S308, that is, the voltage may be adjusted from 480V to 500V, and after the flexible dc system is restored to the steady-state operation range and has the load capacity, the operation of step S303 is executed again to reduce the voltage from 500V to 450V, that is, 450V is selected as the target voltage value of the third round.
For another example, in one case, when the 500V detection is performed, it is detected that the system has overload capability and is in the steady-state operation range, and after the voltage is adjusted from 500V to 480V, it is also detected that the system has overload capability and is in the steady-state operation range, and after the voltage is continuously adjusted from 480V to 450V, it is detected that the system is not in the steady-state operation range. When the 430V detection is performed, the voltage of 450V needs to be increased, for example, the voltage may be increased to 480V or 500V, and the system waits for overload capability and is in a steady-state operation range, and then step S303 is performed to decrease the voltage to 430V to perform the 430V detection.
Since it is determined that the flexible direct current system is in the steady-state operation range and has the load capacity, and then step S303 is executed, it is beneficial to avoid the hidden troubles of triggering overload logic and calculating the steady-state operation range by mistake, which may be caused by a wrong test method.
When the voltage sequence does not have the voltage value to be detected, the detection of the steady-state operation range of the flexible direct current system capable of generating rated reactive power can be finished after the voltage values in the voltage sequence are detected.
In a specific embodiment of the present invention, based on a steady-state operation range calculation equation under a constraint condition, the process of detecting the steady-state operation range of the flexible dc system for absorbing the rated reactive power capability at each voltage level of the voltage sequence may specifically include:
adjusting the voltage of the connection transformer network side of the flexible direct current system from an allowable maximum value to a maximum value in a voltage sequence;
setting the active power of the flexible direct current system as rated power, and setting the reactive power as absorbing rated reactive power;
adjusting the voltage of the connection transformer network side of the flexible direct current system to a target voltage value, wherein the target voltage value is the maximum value selected from the current voltage values to be measured of the voltage sequence;
judging whether the flexible direct current system has overload capacity or not;
if the overload capacity is not provided, recording that the flexible direct current system is not in a stable state operation range in the current state, and recording current operation data of the flexible direct current system;
if the overload capacity is possessed, judging whether the flexible direct current system is in the steady-state operation range or not through a steady-state operation range calculation equation under the constraint condition, and recording a judgment result and current various operation data of the flexible direct current system;
after the operation data are recorded, marking the current target voltage value as a measured voltage value, and judging whether a voltage value to be measured exists in a voltage sequence or not;
if not, ending the detection of the steady-state operation range of the flexible direct current system for absorbing the rated reactive power;
if so, adjusting the flexible direct current system to a steady-state operation range and have load capacity, and returning to the step of adjusting the voltage of the connection transformer network side of the flexible direct current system to the target voltage value to select the next target voltage value from the voltage sequence.
The process of detecting the steady-state operation range of the flexible direct-current system for absorbing the rated reactive power capability can be referred to in correspondence with the embodiment of detecting the rated reactive power capability of the flexible direct-current system.
In this embodiment, the active power of the flexible dc system is set to the rated power and the reactive power is set to absorb the rated reactive power. When the flexible direct current system is judged not to be in the steady-state operation range through the steady-state operation range calculation equation under the constraint condition, two possibilities exist: one is thatBecause the voltage of the connected transformer network side is low, overload logic is not triggered at the moment, although IvqThe maximum value is reached, but the rated reactive power cannot be absorbed; and the other is that the overload logic of the flexible direct system is triggered due to the fact that the voltage of the connection transformer network side is lower, and the flexible direct system cannot absorb rated reactive power under rated active power. In any two cases, current various operating data of the flexible direct current system need to be recorded, and the recorded operating data may include actual active power, reactive power, system voltage, voltage at the side of the connection transformer network, voltage at the side of the connection transformer valve, and other key operating data. And when all the voltages in the voltage sequence are detected, namely all the voltages are marked as the measured voltage values, the detection of the reactive power absorption capacity of the system is finished.
Referring to fig. 4, in an embodiment of the present invention, the detecting the steady-state operation range of the active power capability of the flexible dc system at each voltage level of the voltage sequence by using the steady-state operation range calculation equation under the constraint condition includes:
step S401: adjusting the voltage of the connection transformer network side of the flexible direct current system from an allowable maximum value to a maximum value in a voltage sequence;
step S402: setting the active power of the flexible direct current system as rated power and the reactive power as 0;
step S403: adjusting the voltage of the connection transformer network side of the flexible direct current system to a target voltage value, wherein the target voltage value is the maximum value selected from the current voltage values to be measured of the voltage sequence;
step S404: judging whether the flexible direct current system has overload capacity or not;
if the overload capability is not available, step S405 is executed: recording that the flexible direct current system is not in a stable state operation range in the current state, and recording current operation data of the flexible direct current system;
if the overload capability is available, step S406 is executed: judging whether the flexible direct current system is in a steady-state operation range or not through a steady-state operation range calculation equation under a constraint condition, and recording a judgment result and current various operation data of the flexible direct current system;
after determining that the flexible dc system is not in the steady-state operation range in the current state and recording the operation data, executing step S407: the flexible direct current system is adjusted to a steady-state operation range through voltage regulation and has load capacity, a voltage critical value of a steady-state operation range calculation equation meeting the constraint condition is determined through gradually reducing the voltage, various operation data of the flexible direct current system are recorded at the voltage critical value, and the detection of the steady-state operation range of the active power capacity of the flexible direct current system is finished;
after determining that the flexible dc system is in the steady-state operation range in the current state and recording the operation data, executing step S408: marking the current target voltage value as a measured voltage value, and judging whether a voltage value to be measured exists in the voltage sequence;
if not, ending the detection of the steady-state operation range of the active power capability of the flexible direct current system;
if so, step S409 is executed: the flexible dc system is adjusted to the steady state operating range and has load capacity, and returns to step S403 to select the next target voltage value from the voltage sequence.
In the foregoing embodiment, when the rated reactive power capability of the flexible dc system and the rated reactive power absorbing capability of the flexible dc system are detected, no matter whether the flexible dc system is detected to be in steady-state operation or not, the next voltage value is detected until all the voltage values in the voltage sequence are detected. In the embodiment, when the active power capability of the flexible direct current system is detected, as long as it is determined that the flexible direct current system is not in the steady-state operation range under a certain voltage value, the voltage critical value is directly found out, various operation data of the flexible direct current system are recorded under the condition of the voltage critical value, and the detection of the steady-state operation range of the active power capability of the flexible direct current system is finished.
For example, the voltage sequence includes: 500V, 480V, 450V, 430V and 400V. In the issue of flexible and straight system isWhen the work power capability is detected to be 500V, the system is detected to have overload capability and be in a steady-state operation range, the system is also detected to have overload capability and be in the steady-state operation range after the voltage is adjusted from 500V to 480V, and the system is detected not to be in the steady-state operation range after the voltage is continuously adjusted from 480V to 450V. The reason can be that the soft direct network side voltage is too low, the overload logic of the soft direct system is triggered, and the soft direct system cannot fully generate rated active power. After recording the actual active power, reactive power, system voltage, voltage on the side of the interconnection transformer network, voltage on the side of the interconnection transformer valve and other key operation data, step S407 is executed to determine a voltage critical value. Specifically, the voltage on the side of the connected transformer network can be increased firstly, so that the system is in a steady-state operation range and has overload capacity, and the voltage can be increased to 480V, for example. Then slowly reducing the voltage of the connection variable network side from 480V to enable IvdSuccessive approximation IvdmaxUntil a voltage critical value on the converter transformer network side is determined by the constraint, for example, 465V. In other words, in the process that 480V is reduced to 465V, the flexible-straight system meets the calculation equation of the steady-state operation range under the constraint condition, the flexible-straight system is in the steady-state operation range, when the flexible-straight system is lower than 465V, the flexible-straight system is confirmed to not meet the calculation equation of the steady-state operation range through the constraint condition, namely the flexible-straight system is not in the steady-state operation range, and 465V can be determined as the voltage critical value. And recording various operating data of the flexible direct current system at 465V and finishing the detection of the steady-state operating range of the active power sending capability of the flexible direct current system. Above the voltage critical value, the flexible direct current system has the capability of fully generating active power.
Corresponding to the above method embodiments, the embodiments of the present invention further provide a system for detecting a steady-state operation range of a flexible-straight system, which can be referred to above in correspondence with each other
Referring to fig. 5, the system for detecting the steady-state operation range of the flexible direct-current system may include the following modules:
a voltage sequence configuration module 501, configured to configure a voltage sequence of a connection transformer side voltage of the flexible dc system;
a steady-state operation range calculation equation and constraint condition setting module 502, configured to preset a steady-state operation range calculation equation of the flexible direct current system, where constraint conditions of the steady-state operation range calculation equation at least include constraints for overload capacity of the flexible direct current system and constraints for voltage withstanding capacity of the primary equipment;
and the detection module 503 is configured to detect the steady-state operation range of the flexible direct-current system at each voltage level of the voltage sequence based on the steady-state operation range calculation equation under the constraint condition.
Specifically, the steady state operating range calculation equation is:
wherein, Ps+jQsThe power flowing into the alternating current system from the PCC point is the connection point of the converter station connecting with the transformer side and the alternating current system; pv+jQvThe power flowing into the transformer from the valve side of the transformer, point v is the connection point between the transformer and the transformer network, PvActive power, Q, flowing into the transformer for the valve side of the transformervFor reactive power, U, flowing into the transformer on the valve side of the transformervIs the voltage at v point; xTFor equivalent leakage reactance of transformer fundamental wave, XL0Is the bridge arm reactance at fundamental frequency; pdiff+jQdiffEquivalent power flowing into a bridge arm reactor for the converter;
the constraint conditions of the steady-state operation range calculation equation are as follows:
wherein m is the output voltage modulation ratio, I, of the modular multilevel converter MMCvNFor MMC AC side-group wave current rating, IvdIs the d-axis component of the transformer valve-side current, IvqIs the q-axis component of the transformer valve side current, IvdmaxIs the maximum allowable value of d-axis current when the flexible direct current system has overload capacity, IvqmaxIs a flexible DC systemMaximum allowable q-axis current value, U, of system with overload capabilityvmaxIs the maximum withstand voltage of the primary device.
In an embodiment of the present invention, the detecting module 503 is specifically configured to:
based on a steady-state operation range calculation equation under the constraint condition, under each voltage level of the voltage sequence, the detection of the steady-state operation range is carried out on the capacity of sending rated reactive power, the capacity of absorbing rated reactive power and the capacity of sending active power of the flexible direct-current system.
Corresponding to the above method and system embodiments, the present invention further provides a device for detecting a steady-state operation range of a flexible direct system and a computer readable storage medium, which can be referred to in correspondence with the above.
The soft straight system steady state operation range detection device may include:
a memory for storing a computer program;
a processor for executing a computer program to implement the steps of the method for detecting the steady-state operation range of the flexible direct system in any of the above embodiments.
The computer readable storage medium has stored thereon a computer program, which when executed by a processor implements the steps of the method for detecting the steady-state operation range of the flexible direct system in any of the above embodiments. A computer-readable storage medium as referred to herein may include Random Access Memory (RAM), memory, Read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The principle and the implementation of the present invention are explained in the present application by using specific examples, and the above description of the embodiments is only used to help understanding the technical solution and the core idea of the present invention. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
Claims (8)
1. A steady-state operation range detection method for a flexible-straight system is characterized by comprising the following steps:
configuring a voltage sequence of a connection transformer network side voltage of the flexible direct current system;
presetting a steady-state operation range calculation equation of the flexible direct current system, wherein constraint conditions of the steady-state operation range calculation equation at least comprise constraint aiming at the overload capacity of the flexible direct current system and constraint aiming at the pressure resistance capacity of primary equipment;
based on the steady-state operation range calculation equation under the constraint condition, detecting the steady-state operation range of the flexible direct current system under each voltage level of the voltage sequence;
the steady state operating range calculation equation is as follows:
wherein, Ps+jQsThe power flowing into the alternating current system from the PCC point is the connection point of the converter station connecting with the transformer side and the alternating current system; pv+jQvThe power flowing into the transformer from the valve side of the transformer, point v is the connection point between the transformer and the transformer network, PvActive power, Q, flowing into the transformer for the valve side of the transformervTo transform into a voltageReactive power, U, flowing into the transformer on the valve sidevIs the voltage at v point; xTFor equivalent leakage reactance of transformer fundamental wave, XL0Is the bridge arm reactance at fundamental frequency; pdiff+jQdiffEquivalent power flowing into a bridge arm reactor for the converter;
the constraint conditions of the steady state operating range calculation equation are:
wherein m is the output voltage modulation ratio, I, of the modular multilevel converter MMCvNFor MMC AC side-group wave current rating, IvdIs the d-axis component of the transformer valve-side current, IvqIs the q-axis component of the transformer valve side current, IvdmaxIs the maximum allowable value of d-axis current when the flexible direct current system has overload capacity, IvqmaxIs the maximum allowable value, U, of the q-axis current of the flexible direct current system when the flexible direct current system has overload capacityvmaxIs the maximum withstand voltage of the primary device.
2. The method for detecting the steady-state operation range of the flexible direct current system according to claim 1, wherein the step of detecting the steady-state operation range of the flexible direct current system at each voltage level of the voltage sequence based on the steady-state operation range calculation equation under the constraint condition comprises the following steps:
and based on the steady-state operation range calculation equation under the constraint condition, detecting the steady-state operation range of the flexible direct current system for the capacity of sending rated reactive power, the capacity of absorbing rated reactive power and the capacity of sending active power under each voltage level of the voltage sequence.
3. The method for detecting the steady-state operation range of the flexible direct current system according to claim 2, wherein the step of detecting the steady-state operation range of the flexible direct current system for generating rated reactive power capability at each voltage level of the voltage sequence based on the steady-state operation range calculation equation under the constraint condition comprises the following steps:
adjusting a connected grid-side voltage of the flexible direct current system from an allowable maximum value to a maximum value in the voltage sequence;
setting the active power of the flexible direct current system as rated power, and setting the reactive power to send out rated reactive power;
adjusting the voltage of the connection transformer network side of the flexible direct current system to a target voltage value, wherein the target voltage value is the maximum value selected from the current voltage values to be measured of the voltage sequence;
judging whether the flexible direct current system has overload capacity or not;
if the overload capacity is not available, recording that the flexible direct current system is not in a stable running range in the current state, and recording current running data of the flexible direct current system;
if the flexible direct current system has overload capacity, judging whether the flexible direct current system is in a steady-state operation range or not through the steady-state operation range calculation equation under the constraint condition, and recording a judgment result and current various operation data of the flexible direct current system;
after the operation data are recorded, marking the current target voltage value as a measured voltage value, and judging whether a voltage value to be measured exists in the voltage sequence or not;
if not, ending the detection of the steady-state operation range of the capacity of the flexible direct current system for generating rated reactive power;
if so, adjusting the flexible direct current system to a steady-state operation range and have load capacity, and returning to the step of adjusting the voltage of the connection transformer network side of the flexible direct current system to a target voltage value to select the next target voltage value from the voltage sequence.
4. The method for detecting the steady-state operation range of the flexible direct current system according to claim 2, wherein the step of detecting the steady-state operation range of the flexible direct current system for absorbing rated reactive power at each voltage level of the voltage sequence based on the steady-state operation range calculation equation under the constraint condition comprises the following steps:
adjusting a connected grid-side voltage of the flexible direct current system from an allowable maximum value to a maximum value in the voltage sequence;
setting the active power of the flexible direct current system as rated power, and setting the reactive power as absorbing rated reactive power;
adjusting the voltage of the connection transformer network side of the flexible direct current system to a target voltage value, wherein the target voltage value is the maximum value selected from the current voltage values to be measured of the voltage sequence;
judging whether the flexible direct current system has overload capacity or not;
if the overload capacity is not available, recording that the flexible direct current system is not in a stable running range in the current state, and recording current running data of the flexible direct current system;
if the flexible direct current system has overload capacity, judging whether the flexible direct current system is in a steady-state operation range or not through the steady-state operation range calculation equation under the constraint condition, and recording a judgment result and current various operation data of the flexible direct current system;
after the operation data are recorded, marking the current target voltage value as a measured voltage value, and judging whether a voltage value to be measured exists in the voltage sequence or not;
if not, ending the detection of the steady-state operation range of the flexible direct current system for absorbing the rated reactive power;
if so, adjusting the flexible direct current system to a steady-state operation range and have load capacity, and returning to the step of adjusting the voltage of the connection transformer network side of the flexible direct current system to a target voltage value to select the next target voltage value from the voltage sequence.
5. The method for detecting the steady-state operation range of the flexible direct current system according to claim 2, wherein the step of detecting the steady-state operation range of the flexible direct current system for generating the active power capability at each voltage level of the voltage sequence based on the steady-state operation range calculation equation under the constraint condition comprises:
adjusting a connected grid-side voltage of the flexible direct current system from an allowable maximum value to a maximum value in the voltage sequence;
setting the active power of the flexible direct current system as rated power and the reactive power as 0;
adjusting the voltage of the connection transformer network side of the flexible direct current system to a target voltage value, wherein the target voltage value is the maximum value selected from the current voltage values to be measured of the voltage sequence;
judging whether the flexible direct current system has overload capacity or not;
if the overload capacity is not available, recording that the flexible direct current system is not in a stable running range in the current state, and recording current running data of the flexible direct current system;
if the flexible direct current system has overload capacity, judging whether the flexible direct current system is in a steady-state operation range or not through the steady-state operation range calculation equation under the constraint condition, and recording a judgment result and current various operation data of the flexible direct current system;
after the flexible direct current system is determined not to be in a steady-state operation range in the current state and operation data are recorded, the flexible direct current system is adjusted to be in the steady-state operation range through voltage regulation and has load capacity, a voltage critical value of a steady-state operation range calculation equation meeting the constraint condition is determined through gradually reducing the voltage, all operation data of the flexible direct current system are recorded at the voltage critical value, and the detection of the steady-state operation range of the active power capacity of the flexible direct current system is finished;
after the flexible direct current system is determined to be in a steady-state operation range in the current state and operation data are recorded, marking the current target voltage value as a measured voltage value, and judging whether a voltage value to be measured exists in the voltage sequence or not;
if not, ending the detection of the steady-state operation range of the active power capability of the flexible direct current system;
if so, adjusting the flexible direct current system to a steady-state operation range and have load capacity, and returning to the step of adjusting the voltage of the connection transformer network side of the flexible direct current system to a target voltage value to select the next target voltage value from the voltage sequence.
6. A system for detecting a steady-state operation range of a flexible-straight system is characterized by comprising:
the voltage sequence configuration module is used for configuring a voltage sequence of the connection transformer network side voltage of the flexible direct current system;
the system comprises a steady-state operation range calculation equation and constraint condition setting module, a steady-state operation range calculation equation and a constraint condition setting module, wherein the steady-state operation range calculation equation and the constraint condition setting module are used for presetting the steady-state operation range calculation equation of the flexible direct current system, and the constraint condition of the steady-state operation range calculation equation at least comprises constraint aiming at the overload capacity of the flexible direct current system and constraint aiming at the pressure resistance capacity of primary equipment;
the detection module is used for detecting the steady-state operation range of the flexible direct current system under each voltage level of the voltage sequence based on the steady-state operation range calculation equation under the constraint condition;
the steady state operating range calculation equation is as follows:
wherein, Ps+jQsThe power flowing into the alternating current system from the PCC point is the connection point of the converter station connecting with the transformer side and the alternating current system; pv+jQvThe power flowing into the transformer from the valve side of the transformer, and the v point is that the transformer connects the valve side of the transformer with the transformerConnection points on the machine side, PvActive power, Q, flowing into the transformer for the valve side of the transformervFor reactive power, U, flowing into the transformer on the valve side of the transformervIs the voltage at v point; xTFor equivalent leakage reactance of transformer fundamental wave, XL0Is the bridge arm reactance at fundamental frequency; pdiff+jQdiffEquivalent power flowing into a bridge arm reactor for the converter;
the constraint conditions of the steady state operating range calculation equation are:
wherein m is the output voltage modulation ratio, I, of the modular multilevel converter MMCvNFor MMC AC side-group wave current rating, IvdIs the d-axis component of the transformer valve-side current, IvqIs the q-axis component of the transformer valve side current, IvdmaxIs the maximum allowable value of d-axis current when the flexible direct current system has overload capacity, IvqmaxIs the maximum allowable value, U, of the q-axis current of the flexible direct current system when the flexible direct current system has overload capacityvmaxIs the maximum withstand voltage of the primary device.
7. A gentle straight system steady state operating range check out test set characterized in that includes:
a memory for storing a computer program;
a processor for executing the computer program to implement the steps of the method of detecting steady state operating range of a flexible direct system as claimed in any one of claims 1 to 5.
8. A computer-readable storage medium, having stored thereon a computer program which, when executed by a processor, carries out the steps of the method of steady state operating range detection for a flexible direct system as claimed in any one of claims 1 to 5.
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| Title |
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| "多端柔性直流输电系统直流电压自适应下垂控制策略研究";罗永捷等;《中国电机工程学报》;20160520;第2592页 * |
| "考虑新能源集群孤网接入的柔直换流站稳态运行区间研究";刘莹等;《华北电力技术》;20171231;第9-12页 * |
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