CN114421511A - Control method and device of hybrid direct-current transmission equipment and hybrid direct-current transmission system - Google Patents
Control method and device of hybrid direct-current transmission equipment and hybrid direct-current transmission system Download PDFInfo
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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
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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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
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
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Abstract
The application relates to a control method and a device of hybrid direct-current transmission equipment and a hybrid direct-current transmission system, wherein the control method comprises the following steps: the method comprises the steps of equating a harmonic voltage source for a power grid phase-changing converter, establishing a harmonic current channel equivalent model, setting a tuning filter bank equivalent to a direct current filter to obtain a direct current filter mathematical model, establishing a direct current side harmonic equivalent model according to a phase unit structure of the voltage source converter, calculating direct current side harmonic components of the hybrid direct current transmission equipment based on the models, and controlling the hybrid direct current transmission equipment according to the direct current side harmonic components. The direct current side harmonic component of the hybrid direct current transmission equipment is obtained through calculation and serves as an important basis for controlling the hybrid direct current transmission equipment, and the working reliability of the hybrid direct current transmission equipment can be improved.
Description
Technical Field
The present disclosure relates to the field of power transmission technologies, and in particular, to a method and an apparatus for controlling a hybrid dc power transmission device, and a hybrid dc power transmission system.
Background
The operation and development of the modern society cannot be separated from electric energy, and the use of the electric energy cannot be separated from an efficient and economic power transmission mode. The power transmission technology goes through the development process from early direct current transmission to alternating current transmission at the end of the 19 th century and then to novel high-voltage direct current transmission in the middle of the 20 th century. The development of high-voltage direct-current transmission technology has nearly 70 years of history. Compared with alternating current transmission, the direct current transmission mode has the advantages of low line cost, large transmission capacity, capability of realizing networking among different frequency power grids, no problem of synchronous stability and the like, and is greatly developed for decades.
The traditional Direct Current transmission mode includes a Line Commuted Converter High Voltage Direct Current (LCC-HVDC) transmission technology based on a grid commutation Converter, which is abbreviated as LCC, and also includes a Voltage Source Converter based High Voltage Direct Current (VSC-HVDC) transmission technology based on a fully controlled device, which is abbreviated as VSC.
However, the LCC converter station needs to absorb a large amount of reactive power during operation, and the ac/dc side contains a large amount of harmonics, and needs additional reactive compensation and ac/dc filter devices, which increases the construction cost, and the inverter side has a problem of phase commutation failure, and cannot supply power to the weak ac system/passive network. VSC-HVDC can independently adjust active power and reactive power, can supply power to passive network, does not have commutation failure problem, and area is little, but use cost is higher, and it is not convenient to use. Therefore, the conventional direct-current power transmission apparatus is low in reliability in use.
Disclosure of Invention
In view of the above, it is necessary to provide a method and an apparatus for controlling a hybrid dc power transmission apparatus, and a hybrid dc power transmission system, in order to solve the problem of low reliability in use of a conventional dc power transmission apparatus.
A control method of a hybrid direct current transmission apparatus comprising a grid commutation converter, a direct current filter and a voltage source converter, the grid commutation converter being connected to the direct current filter and the grid commutation converter being connected to the voltage source converter; the control method of the hybrid direct-current transmission equipment comprises the following steps:
equating the harmonic voltage source for the power grid phase change converter, and establishing a harmonic current path equivalent model corresponding to the power grid phase change converter;
setting a tuning filter bank equivalent to the direct current filter to obtain a direct current filter mathematical model corresponding to the direct current filter;
establishing a direct current side harmonic equivalent model corresponding to the voltage source converter according to the phase unit structure of the voltage source converter;
calculating a direct-current side harmonic component of the hybrid direct-current power transmission equipment based on the harmonic current path equivalent model, the direct-current filter mathematical model and the direct-current side harmonic equivalent model;
and controlling the hybrid direct-current transmission equipment according to the direct-current side harmonic component of the hybrid direct-current transmission equipment.
A control apparatus of a hybrid direct current power transmission device, comprising:
the power grid commutation converter modeling module is used for equating a harmonic voltage source for the power grid commutation converter and establishing a harmonic current path equivalent model corresponding to the power grid commutation converter;
the direct current filter modeling module is used for setting a tuning filter bank equivalent to the direct current filter to obtain a direct current filter mathematical model corresponding to the direct current filter;
the voltage source converter modeling module is used for establishing a direct current side harmonic equivalent model corresponding to the voltage source converter according to the phase unit structure of the voltage source converter;
a harmonic component calculation module, configured to calculate a dc-side harmonic component of the hybrid dc power transmission device based on the harmonic current path equivalent model, the dc filter mathematical model, and the dc-side harmonic equivalent model;
and the control module is used for controlling the hybrid direct-current transmission equipment according to the direct-current side harmonic component of the hybrid direct-current transmission equipment.
A hybrid dc power transmission system comprising a hybrid dc power transmission apparatus and a control device for the hybrid dc power transmission apparatus as described above.
The control method and the control device of the hybrid direct-current transmission equipment and the hybrid direct-current transmission system comprise the following steps: the method comprises the steps of equating a harmonic voltage source for the power grid phase change converter, establishing a harmonic current channel equivalent model corresponding to the power grid phase change converter, setting a tuning filter bank equivalent to a direct current filter, obtaining a direct current filter mathematical model corresponding to the direct current filter, establishing a direct current side harmonic equivalent model corresponding to the voltage source converter according to a phase unit structure of the voltage source converter, calculating a direct current side harmonic component of the hybrid direct current transmission equipment based on the harmonic current channel equivalent model, the direct current filter mathematical model and the direct current side harmonic equivalent model, and controlling the hybrid direct current transmission equipment according to the direct current side harmonic component of the hybrid direct current transmission equipment. The hybrid direct-current transmission equipment comprises a power grid commutation converter, a direct-current filter and a voltage source converter, the voltage source converter can reduce the probability of commutation failure of the equipment on an inversion side to a certain extent, reactive transmission and power loss on a line are obviously reduced, investment of a reactive compensation device and a filtering link is reduced, economy is improved, and the power grid commutation converter and the direct-current filter can play a role in fault isolation when a main direct-current line fails. According to the control method of the hybrid direct-current transmission equipment, the direct-current side harmonic component of the hybrid direct-current transmission equipment is calculated by establishing the harmonic current path equivalent model, the direct-current filter mathematical model and the direct-current side harmonic equivalent model and is used as an important basis for controlling the hybrid direct-current transmission equipment, and the working reliability of the hybrid direct-current transmission equipment can be improved.
In one embodiment, the grid commutated converter includes a sending-end grid commutated converter and a receiving-end grid commutated converter, the sending-end grid commutated converter and the receiving-end grid commutated converter are both connected to the dc filter, the receiving-end grid commutated converter is connected to the voltage source converter, the harmonic current path equivalent model includes a first harmonic current path equivalent model and a second harmonic current path equivalent model, and the setting up the grid commutated converter with a harmonic voltage source equivalent to establish a harmonic current path equivalent model corresponding to the grid commutated converter includes:
and equating the transmitting-end power grid commutation converter and the receiving-end power grid commutation converter by using harmonic voltage sources, and establishing the first harmonic current path equivalent model corresponding to the transmitting-end power grid commutation converter and the second harmonic current path equivalent model corresponding to the receiving-end power grid commutation converter.
In one embodiment, the dc filter includes a sending dc filter and a receiving dc filter, the sending grid commutated converter is connected to the sending dc filter, the sending dc filter is connected to the receiving dc filter, the receiving dc filter is connected to the receiving grid commutated converter, the dc filter mathematical model includes a first dc filter mathematical model and a second dc filter mathematical model, and the setting of the tuned filter bank equivalent to the dc filter results in the dc filter mathematical model corresponding to the dc filter, including:
and respectively setting tuning filter banks equivalent to the sending end direct current filter and the receiving end direct current filter to obtain the mathematical model of the first direct current filter corresponding to the sending end direct current filter and the mathematical model of the second direct current filter corresponding to the receiving end direct current filter.
In one embodiment, the establishing a harmonic current path equivalent model corresponding to the power grid commutation converter by equating the power grid commutation converter with a harmonic voltage source includes:
and equating the three-pulse harmonic voltage source for the power grid phase-change converter, and establishing a harmonic current path equivalent model corresponding to the power grid phase-change converter.
In one embodiment, the setting a tuned filter bank equivalent to the dc filter to obtain a mathematical model of the dc filter corresponding to the dc filter includes:
and setting a group of three tuned filters equivalent to the direct current filter to obtain a direct current filter mathematical model corresponding to the direct current filter.
In one embodiment, the establishing a dc-side harmonic equivalent model corresponding to the voltage source converter according to the phase cell structure of the voltage source converter includes:
calculating a harmonic current of the phase unit structure and a harmonic voltage of the phase unit structure;
calculating the equivalent capacitance and the equivalent inductance of the voltage source converter based on the harmonic current of the phase unit structure and the harmonic voltage of the phase unit structure to obtain a direct current side harmonic equivalent model corresponding to the voltage source converter.
In one embodiment, the calculating the dc-side harmonic component of the hybrid dc power transmission apparatus based on the harmonic current path equivalent model, the dc filter mathematical model, and the dc-side harmonic equivalent model includes:
establishing a quantitative calculation model of the direct-current side harmonic of the hybrid direct-current power transmission equipment based on the harmonic current path equivalent model, the direct-current filter mathematical model and the direct-current side harmonic equivalent model;
and calculating the harmonic component on the direct current side of the hybrid direct current transmission equipment according to the quantitative calculation model.
In one embodiment, the calculating the harmonic components on the dc side of the hybrid dc power transmission apparatus according to the quantitative calculation model includes:
and calculating the harmonic component on the direct current side of the hybrid direct current transmission equipment according to the quantitative calculation model and the analysis method of the sine steady-state circuit.
Drawings
Fig. 1 is a block diagram of a hybrid dc power transmission apparatus in one embodiment;
fig. 2 is a flow chart of a control method of a hybrid dc power transmission apparatus according to an embodiment;
FIG. 3 is a circuit diagram of a double tuned filter in one embodiment;
FIG. 4 is a circuit diagram of a triple-tuned filter in one embodiment;
fig. 5 is a flowchart of a control method of a hybrid dc power transmission apparatus according to another embodiment;
fig. 6 is a flowchart of a control method of a hybrid dc power transmission apparatus in yet another embodiment;
FIG. 7 is a diagram of an equivalent model of a harmonic current path corresponding to a grid commutated converter in one embodiment;
FIG. 8 is an equivalent model diagram of the DC side harmonics of the hybrid DC power transmission apparatus in one embodiment;
fig. 9 is a flowchart of a control method of a hybrid dc power transmission apparatus in still another embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described more fully below by way of examples in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
In one embodiment, a control method of a hybrid direct-current power transmission apparatus is provided, which is mainly used for controlling a main power transmission apparatus. Referring to fig. 1, the hybrid dc power transmission apparatus includes a grid commutation converter, a dc filter, and a voltage source converter, the grid commutation converter is connected to the dc filter, and the grid commutation converter is connected to the voltage source converter. The hybrid direct-current transmission equipment comprises the power grid commutation converter and the voltage source converter, and is series-parallel direct-current transmission equipment, the voltage source converter can reduce the probability of commutation failure of the equipment on an inversion side to a certain extent, reactive transmission and power loss on a line are obviously reduced, the investment of a reactive compensation device and a filtering link is reduced, the economy is improved, and the power grid commutation converter and the direct-current filter can play a role in fault isolation when a main direct-current line fails.
Referring to fig. 2, the control method of the hybrid dc power transmission apparatus includes the following steps:
step S100: and equating the harmonic voltage source for the power grid phase change converter, and establishing a harmonic current path equivalent model corresponding to the power grid phase change converter.
Specifically, the power grid commutation converter has the advantages of simple structure, low manufacturing cost, mature technology, high reliability, suitability for long-distance large-capacity electric energy transmission and the like. The type of the grid commutated converter is not exclusive and may be, for example, a 12-pulse converter. The output direct-current voltage of the power grid commutation converter mainly comprises 12k harmonic components, however, higher 6k +3 harmonic components are detected in the grounding electrode current of the actual running direct-current transmission project, and analysis shows that the stray capacitance between the converter transformer and the ground causes the generation of a grounding current branch which plays a very important role in the harmonic current distribution of an electrode line and a grounding line. Therefore, when a harmonic current path equivalent model is established, the harmonic voltage source for the power grid commutation converter is equivalent. According to different types of the power grid commutation converters, different harmonic voltage sources can be set, and the harmonic voltage sources can be specifically selected according to actual requirements, so long as the harmonic voltage sources can be realized by the technical personnel in the field.
Step S300: and setting a tuning filter bank equivalent to the direct current filter to obtain a direct current filter mathematical model corresponding to the direct current filter.
Specifically, the dc filter is generally a passive filter, and when a tuned filter bank equivalent to the dc filter is provided, the type of the selectable tuned filter bank is not unique, for example, a double-tuned filter or a triple-tuned filter may be used, the circuit structure of the double-tuned filter may be shown in fig. 3, and the circuit structure of the triple-tuned filter may be shown in fig. 4. Wherein, the circuit parameters of the direct current filter determine the current frequency which can be filtered by the filter. A set of double tuned filters and triple tuned filters may filter out two and three harmonics of different frequencies, respectively. Taking a power grid commutation converter as a 12-pulse converter as an example, according to actual engineering operation experience, two sets of double-tuned filters or a set of triple-tuned filters are generally used for equivalent dc filters corresponding to the 12-pulse converter, wherein the two sets of double-tuned filters are respectively responsible for filtering 12/24 and 12/36 harmonics, and the one set of triple-tuned filters are responsible for simultaneously filtering 12/24/36 harmonics.
Further, referring to fig. 3, the double-tuned filter includes a first capacitor C1, a second capacitor C2, a first inductor L1, a second inductor L2, a first resistor R1, and a second resistor R2, where the first capacitor C1, the first inductor L1, and the first resistor R1 are sequentially connected in series to form a first series structure, the second inductor L2 and the second resistor R2 are connected to form a second series structure, a first end of the second series structure is connected to a first end of the second capacitor C2, a second end of the second series structure is connected to a second end of the second capacitor C2, the first end of the second series structure is further connected to one end of the first series structure (an end close to the first resistor R1), and the second end of the second series structure is grounded.
Referring to fig. 4, the triple-tuned filter includes a first capacitor C1, a second capacitor C2, a third capacitor, a first inductor L1, a second inductor L2, and a third resistor, wherein the first capacitor C1 and the first inductor L1 are connected to form a first series structure, the second capacitor C2 and the second inductor L2 are connected in parallel to form a first parallel structure, the third capacitor and the third inductor are connected in parallel to form a third parallel structure, a first end of the first parallel structure is connected to one end of the first series structure (the end close to the first inductor L1), a second end of the first parallel structure is connected to the first end of the second parallel structure, and a second end of the second parallel structure is grounded.
Step S500: and establishing a direct current side harmonic equivalent model corresponding to the voltage source converter according to the phase unit structure of the voltage source converter.
Specifically, the voltage source Converter in the field of high voltage transmission generally adopts an MMC (Modular Multilevel Converter) structure. The MMC with high voltage and large capacity has the advantages that the number of cascaded submodules adopted by the MMC with high voltage and large capacity is large, the harmonic content of output direct current voltage and current is low, compared with the LCC with the same voltage grade and transmission capacity, the harmonic on the direct current side generated by the MMC can be ignored, therefore, when the harmonic on the direct current side of a series-parallel LCC-VSC system is analyzed, the VSC can be regarded as a passive element, and in addition, the harmonic content on the direct current side is low, and a filter does not need to be configured on the direct current side of the MMC generally.
According to different phase unit structures of the voltage source converter, the established direct current side harmonic equivalent models are different. According to the current and the voltage of the phase unit structure of the voltage source converter, the equivalent capacitance and the equivalent inductance of the voltage source converter can be obtained through calculation, and therefore a direct current side harmonic equivalent model corresponding to the voltage source converter is obtained. For example, when the phase cell structure of the voltage source converter is such that a plurality of phase cells are connected in parallel, the harmonic current on the dc side of the hybrid dc power transmission apparatus will be equally divided among the plurality of phase cells, so that the harmonic voltage and the harmonic current of any phase cell can be obtained. And then according to the equivalent capacitor and the bridge arm inductance of any phase unit of the voltage source converter, obtaining a direct current side harmonic equivalent model corresponding to the voltage source converter, wherein the direct current side harmonic equivalent model is equivalent to a passive element in a series connection form comprising a capacitor and an inductance.
Step S700: and calculating the direct-current side harmonic component of the hybrid direct-current power transmission equipment based on the harmonic current path equivalent model, the direct-current filter mathematical model and the direct-current side harmonic equivalent model.
After the harmonic current path equivalent model, the direct current filter mathematical model and the direct current side harmonic equivalent model are obtained, the hybrid direct current power transmission equipment comprises a power grid commutation converter, a direct current filter and a voltage source converter, the harmonic current path equivalent model corresponds to the power grid commutation converter, the direct current filter mathematical model corresponds to the direct current filter, and the direct current side harmonic equivalent model corresponds to the voltage source converter, so that a quantitative calculation model of direct current side harmonics corresponding to the whole hybrid direct current power transmission equipment can be obtained. According to the circuit parameters of each equivalent device in the quantitative calculation model of the direct current side harmonic wave, the direct current side harmonic wave of the hybrid direct current power transmission equipment can be quantitatively calculated to obtain each direct current side harmonic wave component.
Step S900: and controlling the hybrid direct-current transmission equipment according to the harmonic component on the direct-current side of the hybrid direct-current transmission equipment.
The direct current harmonic of the hybrid direct current transmission equipment can influence the control protection technology of the new topological structure of the hybrid direct current transmission equipment, so that the control protection technology of the hybrid direct current transmission equipment can be guided by quantitatively analyzing the direct current harmonic, controlling the hybrid direct current transmission equipment according to the direct current side harmonic component of the hybrid direct current transmission equipment. The control of the hybrid direct-current power transmission equipment can be control, protection and the like of each device in the hybrid direct-current equipment, and specific measures can be set according to actual requirements as long as the control can be realized by a person skilled in the art.
In one embodiment, referring to fig. 1, the grid commutation converter includes a transmitting-end grid commutation converter and a receiving-end grid commutation converter, the transmitting-end grid commutation converter and the receiving-end grid commutation converter are both connected to the dc filter, the receiving-end grid commutation converter is connected to the voltage source converter, and the harmonic current path equivalent model includes a first harmonic current path equivalent model and a second harmonic current path equivalent model. At this time, a sending-end power grid phase converter is arranged on the rectification side of the hybrid direct-current transmission equipment, a receiving-end power grid phase converter is arranged on the inversion side of the hybrid direct-current transmission equipment, the receiving-end power grid phase converter is connected with a voltage source converter, and further the receiving-end power grid phase converter on the inversion side is connected with the voltage source converter in series. Referring to fig. 5, step S100 includes step S110.
Step S110: and equating the transmitting-end power grid commutation converter and the receiving-end power grid commutation converter by using harmonic voltage sources, and establishing a first harmonic current path equivalent model corresponding to the transmitting-end power grid commutation converter and a second harmonic current path equivalent model corresponding to the receiving-end power grid commutation converter.
When the number of the power grid phase change converters is two, including the transmitting-end power grid phase change converter and the receiving-end power grid phase change converter, the transmitting-end power grid phase change converter and the receiving-end power grid phase change converter are equivalent by using harmonic voltage sources. The types of the sending-side grid commutation converter and the receiving-side grid commutation converter are not exclusive and may be, for example, 12-pulse converters. The transmitting-end power grid commutation converter and the receiving-end power grid commutation converter can be converters with the same structure and type, and the structures are symmetrical, so that the working stability of the hybrid direct-current equipment is improved.
Taking the transmitting-end power grid commutation converter and the receiving-end power grid commutation converter as an example, both 12-pulse converters are adopted, the output direct-current voltages of the transmitting-end power grid commutation converter and the receiving-end power grid commutation converter mainly contain 12k harmonic components, however, higher 6k +3 harmonic components are detected in the grounding electrode current of the actual running direct-current transmission project, and analysis shows that stray capacitance between a converter transformer and the ground causes the generation of a grounding current branch which plays a very important role in the harmonic current distribution of the polar line and the grounding line. Therefore, when the harmonic current path equivalent model is established, the transmitting-end power grid commutation converter and the receiving-end power grid commutation converter are equivalent by using the harmonic voltage source, and a first harmonic current path equivalent model corresponding to the transmitting-end power grid commutation converter and a second harmonic current path equivalent model corresponding to the receiving-end power grid commutation converter are established. It can be understood that when the transmitting-end power grid commutation converter and the receiving-end power grid commutation converter are identical in structure, the first harmonic current path equivalent model and the second harmonic current path equivalent model are also identical.
In one embodiment, referring to fig. 1, the dc filter includes a sending-end dc filter and a receiving-end dc filter, the sending-end grid commutation converter is connected to the sending-end dc filter, the sending-end dc filter is connected to the receiving-end dc filter, and the receiving-end dc filter is connected to the receiving-end grid commutation converter. The sending end direct current filter is arranged at a direct current side port of the sending end power grid phase change converter, and the receiving end direct current filter is arranged at a direct current side port of the receiving end power grid phase change converter. The dc filter mathematical model includes a first dc filter mathematical model and a second dc filter mathematical model, see fig. 5, and step S300 includes step S310.
Step S310: and respectively setting tuning filter banks equivalent to the sending-end direct-current filter and the receiving-end direct-current filter to obtain a first direct-current filter mathematical model corresponding to the sending-end direct-current filter and a second direct-current filter mathematical model corresponding to the receiving-end direct-current filter.
When the number of the power grid commutation converters is two, including the sending-end power grid commutation converter and the receiving-end power grid commutation converter, the direct current filter includes a sending-end direct current filter and a receiving-end direct current filter, the sending-end direct current filter and the sending-end power grid commutation converter work in a matched mode, and the receiving-end direct current filter and the receiving-end power grid commutation converter work in a matched mode.
The sending end direct current filter and the receiving end direct current filter are both passive filters generally, and when a tuning filter bank equivalent to the sending end direct current filter and the receiving end direct current filter is arranged, the type of the selectable tuning filter bank is not unique, for example, a double tuning filter or a triple tuning filter can be adopted, the circuit structure of the double tuning filter can be shown in fig. 3, the circuit structure of the triple tuning filter can be shown in fig. 4, and the number of the tuning filter banks can be selected according to actual requirements. A set of double tuned filters and triple tuned filters may filter out two and three harmonics of different frequencies, respectively. Taking the example that both the sending-end power grid commutation converter and the receiving-end power grid commutation converter are 12 ripple converters, according to the practical engineering operation experience, for the sending-end direct current filter or the receiving-end direct current filter corresponding to the 12 ripple converter, two sets of double-tuned filters or a set of three-tuned filters are generally used for being equivalent, wherein the two sets of double-tuned filters are respectively responsible for filtering 12/24 and 12/36 harmonics, and the one set of three-tuned filters is responsible for simultaneously filtering 12/24/36 subharmonics. It can be understood that when the transmitting end direct current filter and the receiving end direct current filter have the same structure, the mathematical model of the first direct current filter and the mathematical model of the second direct current filter are also the same.
In one embodiment, referring to fig. 6, step S100 includes step S120.
Step S120: and equating the three-pulse harmonic voltage source for the power grid phase-change converter, and establishing a harmonic current path equivalent model corresponding to the power grid phase-change converter.
Specifically, the grid commutation converter can use a 12-pulse converter as a power transmission unit, the output direct-current voltage of the 12-pulse LCC converter mainly contains 12k harmonic components, however, higher 6k +3 harmonic components are detected in the grounding electrode current of the actual running direct-current transmission project, and analysis shows that the converter transformerStray capacitance to ground results in the creation of ground current branches which play a significant role in the harmonic current distribution of the pole and ground lines. Therefore, the three-pulse harmonic voltage source for the power grid commutation converter can be equivalent, and the established harmonic current path equivalent model corresponding to the power grid commutation converter can be seen in fig. 7. Wherein, C3pRepresents the stray capacitance coupled between the transformer winding and ground, and can be any value within 10-20 nF, L3pHalf of the average value of the phase change inductance of the 6-pulse LCC is shown, and L is L considering that the 6-pulse LCC has phase change once every pi/3 electrical angle and the phase change inductance in the phase change process is 1.5 times of the leakage inductance of the converter transformer (2 times of the leakage inductance of the converter transformer when the phase change is not carried out), thereby3pIs represented by formula (1).
Where μ is the commutation overlap angle (in radians), LTThe leakage inductance of the converter transformer is obtained.
Assuming that the secondary side voltage of a transformer in a star/star connection mode in a 12-ripple LCC power transmission unit is
Wherein, UcIs the amplitude of the phase voltage,
is the initial phase angle of the a-phase voltage.
The output voltage waveform of the 6-pulse LCC two-pole direct current bus is subjected to Fourier series expansion to obtain a three-pulse harmonic voltage source V3p(t) and V3p(T-T/6) (wherein, V3pAnd (T-T/6) is the inverse number of the Fourier series expansion form of the output voltage of the 6-pulse LCC negative direct-current bus, and is shown in a formula (3). One converter valve is divided into 3 phases, and each phase is provided with a positive bridge arm and a negative bridge arm. The output voltage of the negative direct current bus is indicated in the equivalent model of FIG. 7The lower half of (a). The output voltage is a harmonic voltage obtained by fourier series expansion, as shown in fig. 7, with the harmonic voltage being positive on the positive side and negative on the negative side. It should be noted that the two equivalent voltage sources are different in phase by 60 °, because two adjacent thyristor commutation processes of the LCC during normal operation respectively occur in the upper and lower bridge arms, and the phase interval is pi/3.
Where μ is the commutation overlap angle (in radians), α is the flip angle, and the coefficient a3kAnd b3kThe expression of (a) is:
therefore, a harmonic current path equivalent model can be obtained, and circuit parameters corresponding to each equivalent device in the harmonic current path equivalent model can be obtained.
In one embodiment, referring to fig. 6, step S300 includes step S320.
Step S320: and setting a group of three-tuned filters equivalent to the direct current filter to obtain a direct current filter mathematical model corresponding to the direct current filter.
Specifically, the dc filter is generally a passive filter, and when a tuned filter bank equivalent to the dc filter is provided, the type and number of selectable tuned filter banks are not unique. In this embodiment, a set of triple-tuned filters is used to obtain a mathematical model of the dc filter corresponding to the dc filter, and the set of triple-tuned filters can simultaneously filter 12/24/36 th harmonics. It is understood that in other embodiments, other structures of the tuned filter bank and the dc filter can be adopted, as long as the implementation is considered by those skilled in the art.
In one embodiment, referring to fig. 6, step S500 includes step S510 and step S520.
Step S510: harmonic currents of the phase unit structures and harmonic voltages of the phase unit structures are calculated.
Specifically, the harmonic current and harmonic voltage of each phase cell are different according to the phase cell structure of the voltage source converter. Taking the example that the voltage source converter comprises three phase units which are connected in parallel and have the same structure, the harmonic current i on the direct current side of the hybrid direct current transmission equipment is taken into consideration of the symmetry of the structure of the three phase units of the voltage source converter3p_outWill be equally divided among the three phase units, so that for any phase unit there is:
wherein, CphaseFor the equivalent capacitance of any phase unit of the voltage source converter, considering that N sub-modules in 2N sub-modules of each phase unit are conducted at any time (N is the number of bridge arm sub-modules), C can be obtainedphase＝2C0/N，L0Is bridge arm inductance u3p_vscThe harmonic voltage is transmitted to the VSC side from the direct current system structure for the direct current side harmonic of the LCC.
Step S520: and calculating the equivalent capacitance and the equivalent inductance of the voltage source converter based on the harmonic current of the phase unit structure and the harmonic voltage of the phase unit structure to obtain a direct current side harmonic equivalent model corresponding to the voltage source converter.
Similarly, taking as an example that the voltage source converter includes three phase units connected in parallel and having the same structure, equation (5) can be equivalently modified:
therefore, the equivalent model of the harmonic wave on the direct current side corresponding to the voltage source converter can be formed by a value CeqAnd a capacitance of size LeqOf a series form of the inductance of (1), wherein CeqAnd LeqThe expression of (a) is:
in one embodiment, referring to fig. 6, step S700 includes step S710 and step S720.
Step S710: and establishing a quantitative calculation model of the direct-current side harmonic of the hybrid direct-current power transmission equipment based on the harmonic current path equivalent model, the direct-current filter mathematical model and the direct-current side harmonic equivalent model.
Specifically, after obtaining the harmonic current path equivalent model, the dc filter mathematical model, and the dc side harmonic equivalent model, since the hybrid dc power transmission equipment includes the power grid commutation converter, the dc filter, and the voltage source converter, and the harmonic current path equivalent model corresponds to the power grid commutation converter, the dc filter mathematical model corresponds to the dc filter, and the dc side harmonic equivalent model corresponds to the voltage source converter, a quantitative calculation model of the dc side harmonic corresponding to the entire hybrid dc power transmission equipment can be obtained, please refer to fig. 8.
Step S720: and calculating the harmonic component on the direct current side of the hybrid direct current transmission equipment according to the quantitative calculation model.
Specifically, according to the circuit parameters of each equivalent device in the quantitative calculation model of the direct-current side harmonic wave, the direct-current side harmonic wave of the hybrid direct-current power transmission equipment can be quantitatively calculated to obtain each direct-current side harmonic wave component.
In one embodiment, step S720 includes step S722.
Step S722: and calculating the harmonic component on the direct current side of the hybrid direct current transmission equipment according to the quantitative calculation model and the analysis method of the sine steady-state circuit.
Specifically, the quantitative calculation model is shown in fig. 8, where subscripts rec and inv respectively represent a grid commutation converter (a transmitting-end grid commutation converter) on the rectifying side and a grid commutation converter (a receiving-end grid commutation converter) on the inverting side. u. of3p_vscFor harmonic voltages on the DC side of the voltage source converter, u taking into account the harmonic characteristics of the grid commutated converter3p_vscMainly comprising 12k harmonic components. For each frequency harmonic component, the solution can be performed according to the analysis method of the sine steady-state circuit, namely
YU＝I (8)
Where U is a vector formed by voltages (phasor form including amplitude and phase) of all nodes except the ground node in fig. 8, Y is a node admittance matrix, I is a vector formed by injection currents of each node, i.e. a vector such as harmonic current of each node in fig. 8, and the injection currents are node admittance matrices written in positive columns, similar to the network equation.
For a better understanding of the above embodiments, the following detailed description is given in conjunction with a specific embodiment. In one embodiment, a hybrid dc transmission apparatus comprises a grid commutation converter comprising a transmitting side grid commutation converter and a receiving side grid commutation converter, a dc filter comprising a transmitting side dc filter and a receiving side dc filter, and a voltage source converter.
Referring to fig. 9, the control method of the hybrid dc power transmission apparatus includes the steps of:
(1) and (3) establishing different-frequency subharmonic current paths and equivalent models thereof at the direct current side of the LCC, namely current path equivalent models. As shown in fig. 7, in the series-parallel LCC-VSC system, the LCC uses a 12-pulse converter as a power transmission unit, the output dc voltage of the 12-pulse LCC converter mainly contains 12 k-order harmonic component, however, a higher 6k + 3-order harmonic component is detected in the ground electrode current of the actual running dc power transmission project, and it is found through analysis that the stray capacitance between the converter transformer and the ground causes the generation of a ground current branch, which plays a significant role in the harmonic current distribution of the pole line and the ground line. Therefore, in the existing direct current side harmonic analysis method, the 12-pulse LCC converter is generally equivalent to a three-pulse harmonic voltage source, and a current path equivalent model comprises an equivalent voltage source and an equivalent reactance. Wherein, C3pRepresents the stray capacitance coupled between the transformer winding and ground, and has a typical value of 10-20 nF, L3pRepresenting half of the average value of the commutation inductance of a 6-ripple LCC, taking into account that the 6-ripple LCC commutates once every pi/3 electrical angleAnd the commutation inductance during commutation is 1.5 times (2 times) the leakage inductance of the converter transformer when no commutation is performed), so that L is3pIs expressed as
Where μ is the commutation overlap angle (in radians), LTThe leakage inductance of the converter transformer is obtained.
Assuming that the secondary side voltage of a transformer in a star/star connection mode in a 12-ripple LCC power transmission unit is
Wherein, UcIs the phase voltage amplitude, phi0Is the initial phase angle of the a-phase voltage.
The output voltage waveform of the 6-pulse LCC two-pole direct current bus is subjected to Fourier series expansion to obtain a three-pulse harmonic voltage source V3p(t) and V3p(T-T/6) (wherein, V3pAnd (T-T/6) is the inverse number of the Fourier series expansion form of the output voltage of the 6-pulse LCC negative direct-current bus, and is shown in a formula (3). It should be noted that the two equivalent voltage sources are different in phase by 60 °, because two adjacent thyristor commutation processes of the LCC during normal operation respectively occur in the upper and lower bridge arms, and the phase interval is pi/3.
Where μ is the commutation overlap angle (in radians), α is the flip angle, and the coefficient a3kAnd b3kIs expressed as
(2) And (3) establishing an LCC direct current filter mathematical model, namely a direct current filter mathematical model. The conventional LCC dc filter is mainly a passive filter, and usually adopts a double-tuned filter or a triple-tuned filter, and the circuit structure is shown in fig. 3 and 4, wherein the filter circuit parameters determine the current frequency that can be filtered by the filter. According to actual engineering operation experience, two groups of double-tuned filters or one group of three-tuned filters are generally adopted for the 12-pulse converter, wherein the two groups of double-tuned filters are respectively responsible for filtering 12/24 and 12/36 harmonics, and the one group of three-tuned filters are responsible for simultaneously filtering 12/24/36 harmonics.
(3) A direct current side harmonic equivalent model of the VSC is established, and an MMC (Modular Multilevel Converter) structure is generally adopted in the field of high-voltage transmission. The MMC with high voltage and large capacity has the advantages that the number of cascaded submodules adopted by the MMC with high voltage and large capacity is large, the harmonic content of output direct current voltage and current is low, compared with the LCC with the same voltage grade and transmission capacity, the harmonic on the direct current side generated by the MMC can be ignored, therefore, when the harmonic on the direct current side of a series-parallel LCC-VSC system is analyzed, the VSC can be regarded as a passive element, and in addition, the harmonic content on the direct current side is low, and a filter does not need to be configured on the direct current side of the MMC generally.
Considering the symmetry of three phase unit structures of the VSC converter, harmonic current i on the direct current side of the series-parallel LCC-VSC system3p_outWill be equally divided among the three phase units, thereby having for any phase unit
Wherein, CphaseConsidering the conduction of N sub-modules in 2N sub-modules of each phase unit (N is the number of bridge arm sub-modules) at any moment, C can be obtained for the equivalent capacitance of any phase unit of the VSCphase＝2C0/N，L0Is bridge arm inductance u3p_vscThe harmonic voltage is transmitted to the VSC side from the direct current system structure for the direct current side harmonic of the LCC.
Equivalent transformation of the above formula can be obtained
Therefore, the VSC direct current side harmonic analysis model can be composed of a size CeqAnd a capacitance of size LeqOf a series form of the inductance of (1), wherein CeqAnd LeqThe expression of (a) is:
(4) and (3) establishing a quantitative calculation model of the direct-current side harmonic of the series-parallel LCC-VSC system according to the steps (1), (2) and (3) and the topological structure of the series-parallel LCC-VSC system, as shown in FIG. 8. Where the subscripts rec, inv denote the rectifier side and inverter side LCCs, respectively.
In FIG. 8, u3p_vscFor the harmonic voltages on the DC side of the VSC, u takes into account the harmonic characteristics of the LCC3p_vscMainly comprising the 12k harmonic components. For each frequency harmonic component, the solution can be performed according to the analysis method of the sine steady-state circuit, namely
YU＝I (8)
Where U is a vector formed by voltages (phasor form including amplitude and phase) of all nodes except the ground node in fig. 8, Y is a node admittance matrix, I is a vector formed by injection currents of each node, such as a harmonic current vector, of each node in fig. 8, and the injection currents are node admittance matrices written in positive columns, similar to the network equation.
Aiming at the characteristics of a novel topological structure of a receiving-end series-parallel LCC-VSC, firstly establishing different-frequency harmonic current paths and equivalent models of the current paths on the direct current side of the LCC; secondly, establishing an LCC direct current filter mathematical model; then, establishing a VSC direct current side harmonic equivalent model; and finally, obtaining a quantitative calculation method of the direct-current side harmonic of the receiving-end series-parallel LCC-VSC system. The harmonic equivalent model is established by fully considering the topological structures and the conversion characteristics of the traditional LCC, the VSC and the direct current filter, the direct current side harmonic quantitative calculation model is established according to the novel topological structure of the receiving end series-parallel LCC-VSC, the direct current side harmonic quantitative calculation of the receiving end series-parallel LCC-VSC hybrid direct current system can be realized, the gap of harmonic quantitative calculation aiming at the novel topology is filled, and the control protection technology of the receiving end series-parallel LCC-VSC hybrid direct current system is guided.
The control method of the hybrid direct-current transmission equipment comprises a power grid commutation converter, a direct-current filter and a voltage source converter, wherein the power grid commutation converter is connected with the direct-current filter, the power grid commutation converter is connected with the voltage source converter, and the control method of the hybrid direct-current transmission equipment comprises the following steps: the method comprises the steps of equating a harmonic voltage source for the power grid phase change converter, establishing a harmonic current channel equivalent model corresponding to the power grid phase change converter, setting a tuning filter bank equivalent to a direct current filter, obtaining a direct current filter mathematical model corresponding to the direct current filter, establishing a direct current side harmonic equivalent model corresponding to the voltage source converter according to a phase unit structure of the voltage source converter, calculating a direct current side harmonic component of the hybrid direct current transmission equipment based on the harmonic current channel equivalent model, the direct current filter mathematical model and the direct current side harmonic equivalent model, and controlling the hybrid direct current transmission equipment according to the direct current side harmonic component of the hybrid direct current transmission equipment. The hybrid direct-current transmission equipment comprises a power grid commutation converter, a direct-current filter and a voltage source converter, the voltage source converter can reduce the probability of commutation failure of the equipment on an inversion side to a certain extent, reactive transmission and power loss on a line are obviously reduced, investment of a reactive compensation device and a filtering link is reduced, economy is improved, and the power grid commutation converter and the direct-current filter can play a role in fault isolation when a main direct-current line fails. According to the control method of the hybrid direct-current transmission equipment, the direct-current side harmonic component of the hybrid direct-current transmission equipment is calculated by establishing the harmonic current path equivalent model, the direct-current filter mathematical model and the direct-current side harmonic equivalent model and is used as an important basis for controlling the hybrid direct-current transmission equipment, and the working reliability of the hybrid direct-current transmission equipment can be improved.
In one embodiment, a control device of a hybrid direct-current transmission apparatus is provided, which includes a power grid commutation converter modeling module, a direct-current filter modeling module, a voltage source converter modeling module, a harmonic component calculation module, and a control module, wherein the power grid commutation converter modeling module is configured to equate a harmonic voltage source for a power grid commutation converter to establish a harmonic current path equivalent model corresponding to the power grid commutation converter, the direct-current filter modeling module is configured to set a tuning filter bank equivalent to a direct-current filter to obtain a direct-current filter mathematical model corresponding to the direct-current filter, the voltage source converter modeling module is configured to establish a direct-current side harmonic equivalent model corresponding to the voltage source converter according to a phase unit structure of the voltage source converter, the harmonic component calculation module is configured to calculate a direct-current side harmonic component of the hybrid direct-current transmission apparatus based on the harmonic current path equivalent model, the direct-current filter mathematical model, and the direct-current side harmonic equivalent model, the control module is used for controlling the hybrid direct-current transmission equipment according to the direct-current side harmonic component of the hybrid direct-current transmission equipment.
The operation contents of each module in the control device of the hybrid dc power transmission apparatus correspond to the steps of the control method for the hybrid dc power transmission apparatus, and are described in detail in the foregoing, and are not described again here.
The control device of the hybrid direct-current transmission equipment comprises a power grid commutation converter, a direct-current filter and a voltage source converter, the power grid commutation converter is connected with the direct-current filter, the power grid commutation converter is connected with the voltage source converter, the control device of the hybrid direct-current transmission equipment comprises a power grid commutation converter modeling module, a direct-current filter modeling module, a voltage source converter modeling module, a harmonic component calculation module and a control module, and the working process comprises the following steps: the method comprises the steps of equating a harmonic voltage source for the power grid phase change converter, establishing a harmonic current channel equivalent model corresponding to the power grid phase change converter, setting a tuning filter bank equivalent to a direct current filter, obtaining a direct current filter mathematical model corresponding to the direct current filter, establishing a direct current side harmonic equivalent model corresponding to the voltage source converter according to a phase unit structure of the voltage source converter, calculating a direct current side harmonic component of the hybrid direct current transmission equipment based on the harmonic current channel equivalent model, the direct current filter mathematical model and the direct current side harmonic equivalent model, and controlling the hybrid direct current transmission equipment according to the direct current side harmonic component of the hybrid direct current transmission equipment. The hybrid direct-current transmission equipment comprises a power grid commutation converter, a direct-current filter and a voltage source converter, the voltage source converter can reduce the probability of commutation failure of the equipment on an inversion side to a certain extent, reactive transmission and power loss on a line are obviously reduced, investment of a reactive compensation device and a filtering link is reduced, economy is improved, and the power grid commutation converter and the direct-current filter can play a role in fault isolation when a main direct-current line fails. According to the control method of the hybrid direct-current transmission equipment, the direct-current side harmonic component of the hybrid direct-current transmission equipment is calculated by establishing the harmonic current path equivalent model, the direct-current filter mathematical model and the direct-current side harmonic equivalent model and is used as an important basis for controlling the hybrid direct-current transmission equipment, and the working reliability of the hybrid direct-current transmission equipment can be improved.
In one embodiment, a hybrid dc power transmission system is provided, comprising a hybrid dc power transmission apparatus and a control device of the hybrid dc power transmission apparatus as described above.
According to the hybrid direct-current power transmission system, the hybrid direct-current power transmission equipment comprises a power grid commutation converter, a direct-current filter and a voltage source converter, the power grid commutation converter is connected with the direct-current filter, the power grid commutation converter is connected with the voltage source converter, and the control method of the hybrid direct-current power transmission equipment comprises the following steps: the method comprises the steps of equating a harmonic voltage source for the power grid phase change converter, establishing a harmonic current channel equivalent model corresponding to the power grid phase change converter, setting a tuning filter bank equivalent to a direct current filter, obtaining a direct current filter mathematical model corresponding to the direct current filter, establishing a direct current side harmonic equivalent model corresponding to the voltage source converter according to a phase unit structure of the voltage source converter, calculating a direct current side harmonic component of the hybrid direct current transmission equipment based on the harmonic current channel equivalent model, the direct current filter mathematical model and the direct current side harmonic equivalent model, and controlling the hybrid direct current transmission equipment according to the direct current side harmonic component of the hybrid direct current transmission equipment. The hybrid direct-current transmission equipment comprises a power grid commutation converter, a direct-current filter and a voltage source converter, the voltage source converter can reduce the probability of commutation failure of the equipment on an inversion side to a certain extent, reactive transmission and power loss on a line are obviously reduced, investment of a reactive compensation device and a filtering link is reduced, economy is improved, and the power grid commutation converter and the direct-current filter can play a role in fault isolation when a main direct-current line fails. According to the control method of the hybrid direct-current transmission equipment, the direct-current side harmonic component of the hybrid direct-current transmission equipment is calculated by establishing the harmonic current path equivalent model, the direct-current filter mathematical model and the direct-current side harmonic equivalent model and is used as an important basis for controlling the hybrid direct-current transmission equipment, and the working reliability of the hybrid direct-current transmission equipment can be improved.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A control method of a hybrid dc transmission apparatus, characterized in that the hybrid dc transmission apparatus comprises a grid commutation converter, a dc filter and a voltage source converter, the grid commutation converter is connected to the dc filter, the grid commutation converter is connected to the voltage source converter; the control method of the hybrid direct-current transmission equipment comprises the following steps:
equating the harmonic voltage source for the power grid phase change converter, and establishing a harmonic current path equivalent model corresponding to the power grid phase change converter;
setting a tuning filter bank equivalent to the direct current filter to obtain a direct current filter mathematical model corresponding to the direct current filter;
establishing a direct current side harmonic equivalent model corresponding to the voltage source converter according to the phase unit structure of the voltage source converter;
calculating a direct-current side harmonic component of the hybrid direct-current power transmission equipment based on the harmonic current path equivalent model, the direct-current filter mathematical model and the direct-current side harmonic equivalent model;
and controlling the hybrid direct-current transmission equipment according to the direct-current side harmonic component of the hybrid direct-current transmission equipment.
2. The method according to claim 1, wherein the grid commutated converter comprises a transmitting-end grid commutated converter and a receiving-end grid commutated converter, the transmitting-end grid commutated converter and the receiving-end grid commutated converter are both connected to the dc filter, the receiving-end grid commutated converter is connected to the voltage source converter, the harmonic current path equivalent model comprises a first harmonic current path equivalent model and a second harmonic current path equivalent model, and the equating the grid commutated converter with a harmonic voltage source to establish a harmonic current path equivalent model corresponding to the grid commutated converter comprises:
and equating the transmitting-end power grid commutation converter and the receiving-end power grid commutation converter by using harmonic voltage sources, and establishing the first harmonic current path equivalent model corresponding to the transmitting-end power grid commutation converter and the second harmonic current path equivalent model corresponding to the receiving-end power grid commutation converter.
3. The method according to claim 2, wherein the dc filter includes a sending-side dc filter and a receiving-side dc filter, the sending-side grid commutation converter is connected to the sending-side dc filter, the sending-side dc filter is connected to the receiving-side dc filter, the receiving-side dc filter is connected to the receiving-side grid commutation converter, the dc filter mathematical model includes a first dc filter mathematical model and a second dc filter mathematical model, the setting of the tuning filter bank equivalent to the dc filter results in a dc filter mathematical model corresponding to the dc filter, and the method includes:
and respectively setting tuning filter banks equivalent to the sending end direct current filter and the receiving end direct current filter to obtain the mathematical model of the first direct current filter corresponding to the sending end direct current filter and the mathematical model of the second direct current filter corresponding to the receiving end direct current filter.
4. The method according to claim 1, wherein the establishing a harmonic current path equivalent model corresponding to the grid commutation converter with the harmonic voltage source equivalent value for the grid commutation converter comprises:
and equating the three-pulse harmonic voltage source for the power grid phase-change converter, and establishing a harmonic current path equivalent model corresponding to the power grid phase-change converter.
5. The method according to claim 1, wherein the setting a tuned filter bank equivalent to the dc filter to obtain a mathematical model of the dc filter corresponding to the dc filter includes:
and setting a group of three tuned filters equivalent to the direct current filter to obtain a direct current filter mathematical model corresponding to the direct current filter.
6. The method according to claim 1, wherein the establishing a dc-side harmonic equivalent model corresponding to the voltage source converter according to the phase cell structure of the voltage source converter includes:
calculating a harmonic current of the phase unit structure and a harmonic voltage of the phase unit structure;
calculating the equivalent capacitance and the equivalent inductance of the voltage source converter based on the harmonic current of the phase unit structure and the harmonic voltage of the phase unit structure to obtain a direct current side harmonic equivalent model corresponding to the voltage source converter.
7. The method according to claim 1, wherein the calculating a dc-side harmonic component of the hybrid dc power transmission apparatus based on the harmonic current path equivalent model, the dc filter mathematical model, and the dc-side harmonic equivalent model includes:
establishing a quantitative calculation model of the direct-current side harmonic of the hybrid direct-current power transmission equipment based on the harmonic current path equivalent model, the direct-current filter mathematical model and the direct-current side harmonic equivalent model;
and calculating the harmonic component on the direct current side of the hybrid direct current transmission equipment according to the quantitative calculation model.
8. The method according to claim 7, wherein the calculating the harmonic components on the dc side of the hybrid dc power transmission apparatus from the quantitative calculation model includes:
and calculating the harmonic component on the direct current side of the hybrid direct current transmission equipment according to the quantitative calculation model and the analysis method of the sine steady-state circuit.
9. A control device for a hybrid dc power transmission apparatus, comprising:
the power grid commutation converter modeling module is used for equating a harmonic voltage source for the power grid commutation converter and establishing a harmonic current path equivalent model corresponding to the power grid commutation converter;
the direct current filter modeling module is used for setting a tuning filter bank equivalent to the direct current filter to obtain a direct current filter mathematical model corresponding to the direct current filter;
the voltage source converter modeling module is used for establishing a direct current side harmonic equivalent model corresponding to the voltage source converter according to the phase unit structure of the voltage source converter;
a harmonic component calculation module, configured to calculate a dc-side harmonic component of the hybrid dc power transmission device based on the harmonic current path equivalent model, the dc filter mathematical model, and the dc-side harmonic equivalent model;
and the control module is used for controlling the hybrid direct-current transmission equipment according to the direct-current side harmonic component of the hybrid direct-current transmission equipment.
10. A hybrid direct current transmission system comprising a hybrid direct current transmission apparatus and a control device of the hybrid direct current transmission apparatus according to claim 9.
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