CN114928070A - Self-synchronization control method and device of cascade STATCOM system - Google Patents

Self-synchronization control method and device of cascade STATCOM system Download PDF

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CN114928070A
CN114928070A CN202210670257.2A CN202210670257A CN114928070A CN 114928070 A CN114928070 A CN 114928070A CN 202210670257 A CN202210670257 A CN 202210670257A CN 114928070 A CN114928070 A CN 114928070A
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current
voltage
reference quantity
grid
phase angle
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李浪
田鹏
沈仕巡
刘赟
周克
冯华仲
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Moutai University
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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
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H02J3/1821—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators
    • H02J3/1835—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control
    • H02J3/1842—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control wherein at least one reactive element is actively controlled by a bridge converter, e.g. active filters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • H02M1/007—Plural converter units in cascade
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/493—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode the static converters being arranged for operation in parallel
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/10—Flexible AC transmission systems [FACTS]

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Abstract

The invention discloses a self-synchronization control method and a self-synchronization control device of a cascade STATCOM system, wherein the method comprises the following steps: calculating the amplitude reference quantity of grid-connected current according to the reactive power requirement of the power grid, and acquiring the phase angle reference quantity of the grid-connected current according to the acquired phase angle of the power grid, the reactive power requirement and the voltage balance correction value of the maintaining direct current side; acquiring a current reference quantity of a first inverter according to the magnitude and the phase angle of grid-connected current; the remaining inverters acquire local line current information, and obtain voltage references according to reactive power output references and correction of voltage balance maintaining parts on the direct current side; and regulating the corresponding inverters according to the current reference quantity and the voltage reference quantity, controlling the first inverter into a current source, and controlling the other inverters into voltage sources to realize self-synchronizing control. The invention can reduce the dependence on communication when the system operates normally, thereby improving the reliability of the system and reducing the one-time investment cost of the system.

Description

Self-synchronization control method and device of cascade STATCOM system
Technical Field
The invention relates to a self-synchronization control method and device of a cascade STATCOM system, and belongs to the technical field of intelligent control of cascade STATCOM systems.
Background
The cascade STATCOM system is widely applied to medium-high voltage power networks for compensating reactive power required by a power grid. In the past, cascaded STATCOM systems were typically controlled with a centralized control approach based on global information. However, this method relies heavily on a highly processing-capable centralized controller and a high-bandwidth communication network, and when a communication failure or a failure of the centralized controller occurs, the system will not work properly.
In addition, some distributed control methods based on the proximity information are proposed to control the cascaded STATCOM system. Although the distributed control method can realize the control of reactive power and the control of the capacitor voltage on the direct current side, the synchronization of the system still needs communication to be realized. In the prior art, the self-synchronization control method has the outstanding characteristics of not depending on communication, and is more attractive in occasions with higher voltage levels and more cascaded modules.
Therefore, the self-synchronization control method for constructing the cascade STATCOM system has very important significance for improving the operation reliability of the cascade STATCOM system.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the self-synchronization control method and the self-synchronization control device of the cascade STATCOM system are provided to overcome the problem that in the prior art, system synchronization depends on high-bandwidth communication, and when communication failure occurs, the system cannot work normally.
The technical scheme adopted by the invention is as follows: a self-synchronization control method of a cascade STATCOM system comprises the following steps:
step 1: calculating the amplitude reference quantity of grid-connected current according to the reactive power requirement of the power grid, and acquiring the phase angle reference quantity of the grid-connected current according to the acquired phase angle of the power grid, the reactive power requirement and the voltage balance correction quantity of the maintaining direct current side;
step 2: obtaining a current reference quantity of a first inverter according to the amplitude reference quantity of the current and the phase angle reference quantity of the current calculated in the step 1;
and step 3: the other inverters (namely the residual inverters) except the first inverter acquire local line current information, and obtain voltage references according to reactive power output references and correction quantity of a voltage balance part at the direct current side;
and 4, step 4: and regulating the corresponding inverters according to the current reference quantity and the voltage reference quantity, controlling the first inverter into a current source, and controlling the other inverters into voltage sources to realize self-synchronization control of the whole system.
The specific method in the step 1 comprises the following steps:
calculating the magnitude of grid-connected current according to the reactive power requirement of a power grid, wherein the expression is as follows:
Figure BDA0003693069280000021
wherein, K I Coefficient of PI controller, Q g Is the reactive power of the power grid,
Figure BDA0003693069280000022
for the demand of reactive power of the grid, I * I.e. the amplitude reference of the current; s is a complex parameter.
Acquiring a phase angle reference quantity of grid-connected current according to the collected phase angle of the power grid, the reactive power requirement and the voltage balance correction quantity of the direct current side, wherein the expression is as follows:
Figure BDA0003693069280000023
wherein k is P And k I Coefficient of PI controller, δ g In order to collect the phase angle of the power grid,
Figure BDA0003693069280000024
for the DC side capacitor voltage reference, V dc1 For the first inverter dc-side capacitor voltage,
Figure BDA0003693069280000031
i.e. to maintain the dc side voltage balance correction amount,
Figure BDA0003693069280000032
the reference quantity of the phase angle of the grid-connected current is obtained;
Figure BDA0003693069280000033
and the method is a reference quantity for the reactive power demand of the power grid.
In the step 2, the current reference quantity which is used as the vector is synthesized according to the amplitude reference quantity and the phase angle reference quantity of the grid-connected current obtained in the step 1
Figure BDA0003693069280000034
The specific method in the step 3 is as follows: according to the collected local current phase angle information delta of the ith inverter i,line And reactive power reference information Q * Maintaining the DC-side capacitor voltage balance correction
Figure BDA0003693069280000035
Determining the voltage reference which is present as a vector
Figure BDA0003693069280000036
The voltage amplitude reference and the voltage phase angle reference are expressed as follows:
Figure BDA0003693069280000037
Figure BDA0003693069280000038
wherein 1 is<i≤n，Q * ＝Q g N, n is inverterThe number of the cells is equal to or greater than the total number of the cells,
Figure BDA0003693069280000039
for rated grid voltage amplitude, V i * For a reference to the magnitude of the voltage,
Figure BDA00036930692800000310
reference quantity of phase angle of voltage, Q i Is a reactive power, V dci Is the DC side capacitor voltage, K I Is a parameter for PI control.
The first inverter in the step 2 is the inverter closest to the power grid (i.e. the first inverter close to the power grid) in all cascaded STATCOM systems.
A self-synchronization control device of a cascade STATCOM system comprises a current reference quantity acquisition module, a voltage reference quantity acquisition module and a current regulation and voltage regulation module;
the current reference quantity acquisition module is used for acquiring an amplitude reference quantity of grid-connected current of a power grid, a phase angle reference quantity of the grid-connected current and a current reference quantity of the first inverter;
the voltage reference quantity acquisition module respectively acquires voltage reference quantities of the remaining inverters;
the current regulation and voltage regulation module is used for regulating the corresponding inverters according to the obtained current reference quantity and voltage reference quantity, controlling the first inverter into a current source, and controlling other inverters into voltage sources, so that the self-synchronization control of the whole system is realized.
The current regulation module comprises a current reference quantity module, a current loop module and a PWM (pulse-width modulation) module which are sequentially connected (namely, the current reference quantity output by the current reference quantity module is used as the input of the current loop module, and the output of the current loop module is also used as the input of the PWM module); the voltage regulation module comprises a voltage reference quantity module, a voltage outer ring current inner ring module and a PWM (pulse width modulation) module which are sequentially connected (namely, the voltage reference quantity output by the voltage reference quantity module is used as the input of the voltage outer ring current inner ring module, and the output of the voltage reference quantity module is used as the input of the PWM module).
The invention has the beneficial effects that: compared with the prior art, the method aims at the cascade STATCOM system, and obtains the grid-connected current reference quantity according to the reactive power requirement of the power grid, the phase angle of the collected power grid, the reactive power requirement and the voltage balance correction value of the maintaining direct current side; the other inverters except the first inverter acquire local line current information, and obtain voltage references according to reactive power output references and correction of the voltage balance maintaining part at the direct current side; according to the current reference quantity and the voltage reference quantity, the corresponding inverters are regulated, the first inverter is controlled to be a current source, other inverters are controlled to be voltage sources, and the self-synchronization control of the whole system is achieved. According to the self-synchronization control method and the self-synchronization control device of the cascade STATCOM system, each controller is not required to acquire information parameters of a large power grid, and the self-synchronization control can be realized only by acquiring local voltage and current information, so that the dependence on communication during normal operation of the system can be effectively reduced, the communication traffic is greatly reduced, the reliability of the system is improved, and the one-time investment cost is reduced.
Drawings
Fig. 1 is a flowchart of a self-synchronization control method of a cascade STATCOM system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an equivalent circuit structure according to an embodiment of the present invention;
fig. 3 is a first inverter control block diagram according to an embodiment of the present invention;
FIG. 4 is a control block diagram of an inverter other than the first inverter, according to an embodiment of the present invention;
FIG. 5 is a simulated waveform diagram of the voltage and current of the power grid during reactive power absorption according to an embodiment of the invention;
FIG. 6 is a simulated waveform diagram of the voltage and current of the power grid when generating reactive power according to an embodiment of the invention;
fig. 7 is a simulated waveform diagram of the dc-side capacitor voltage under the cascaded STATCOM structure according to an embodiment of the present invention;
fig. 8 is a diagram of a reactive power simulation waveform under a cascaded STATCOM architecture according to an embodiment of the present invention;
fig. 9 is a schematic diagram of a self-synchronization control device of a cascaded STATCOM system according to an embodiment of the present invention.
Detailed Description
The invention is further described with reference to the accompanying drawings and specific embodiments.
Example 1: as shown in fig. 1, a self-synchronization control method of a cascade STATCOM system includes the following steps:
step 1, calculating an amplitude reference quantity of grid-connected current according to the reactive power requirement of a power grid, and acquiring the phase angle reference quantity of the grid-connected current according to the acquired phase angle of the power grid, the reactive power requirement and the voltage balance correction quantity of a maintaining direct current side;
step 2, obtaining a current reference quantity of the first inverter according to the magnitude and the phase angle of the grid-connected current;
step 3, collecting current information of a local line by other inverters except the first inverter, and obtaining voltage reference quantity of the inverters according to reactive power output reference quantity and correction quantity of a voltage balance part at the direct current side;
and 4, regulating the corresponding inverters according to the current reference quantity and the voltage reference quantity, controlling the first inverter into a current source, and controlling other inverters into voltage sources, so as to realize self-synchronization control of the whole system.
The modules are in cascade connection, the first inverter is the inverter closest to the power grid, and therefore power grid data obtained and used are more accurate and reliable.
The self-synchronization control method of the cascade STATCOM system provided by the invention comprises the steps of calculating the amplitude reference quantity of grid-connected current according to the reactive power requirement of a power grid, and obtaining the phase angle reference quantity of the grid-connected current according to the collected phase angle of the power grid, the reactive power requirement and the voltage balance correction quantity of a maintaining direct current side; acquiring a current reference quantity of the first inverter according to the magnitude and the phase angle of the grid-connected current; the other inverters except the first inverter acquire local line current information, and obtain voltage references according to reactive power output references and correction of the voltage balance maintaining part at the direct current side; and regulating the corresponding inverters according to the current reference quantity and the voltage reference quantity, controlling the first inverter into a current source, and controlling the other inverters into voltage sources to realize self-synchronization control of the whole system. According to the self-synchronization control method of the cascade STATCOM system, the dependence of system synchronization on communication can be effectively reduced, the reliability of the system is improved, and the one-time investment cost is reduced.
As an optimal scheme, for a cascade STATCOM system in a grid-connected working mode, according to the demand of reactive power of a power grid, a phase angle of the collected power grid, the demand of reactive power and a voltage balance correction value of a maintaining direct-current side, obtaining an amplitude reference quantity and a phase angle reference quantity of grid-connected current:
wherein, the amplitude reference quantity of the grid-connected current is as follows: to achieve reactive power tracking of the output of the PI controller, i.e.
Figure BDA0003693069280000061
Wherein, K I Coefficient of PI controller, Q g Is the reactive power of the power grid,
Figure BDA0003693069280000062
for the demand of reactive power of the grid, I * I.e. the amplitude reference of the current;
the reference quantity of the phase angle of the grid-connected current is as follows: the phase angle of the network voltage is a reduced number, the sum of the sign function of the network reactive power multiplied by pi/2 and the correction value for maintaining the voltage balance of the direct current side is the difference of the reduced number, i.e. the difference
Figure BDA0003693069280000063
Wherein k is P And k I As a coefficient of the PI controller, δ g In order to collect the phase angle of the power grid,
Figure BDA0003693069280000064
for DC side capacitor voltage reference, V dc1 For the first inverter dc-side capacitor voltage,
Figure BDA0003693069280000071
i.e. to maintain the dc side voltage balance correction amount,
Figure BDA0003693069280000072
is the reference quantity of the phase angle of the grid-connected current.
In summary, according to the obtained amplitude reference quantity and the phase angle reference quantity of the grid-connected current, the current reference quantity serving as the vector is synthesized
Figure BDA0003693069280000073
As a preferred scheme, the voltage amplitude reference is: implementing the output of a reactive power tracking PI controller, i.e.
Figure BDA0003693069280000074
The expression for the phase angle reference of the voltage is:
Figure BDA0003693069280000075
wherein 1 is<i≤n，Q * ＝Q g N, n is the number of inverters,
Figure BDA0003693069280000076
for rated grid voltage amplitude, V i * For the purpose of voltage amplitude reference,
Figure BDA0003693069280000077
reference quantity of phase angle of voltage, Q i Is reactive power, V dci Is the DC side capacitor voltage, K I Is a parameter of the PI controller. And maintaining the voltage balance correction value of the capacitor at the direct current side according to the collected local current phase angle information and the reactive power reference information of the ith inverter, and obtaining the voltage balance correction value as a voltage reference quantity of the vector.
Based on the method provided by the embodiment corresponding to fig. 1, an embodiment of the present invention provides a self-synchronization control method for a tandem STATCOM system. The method comprises the following steps:
101, calculating the amplitude of grid-connected current according to the reactive power requirement of a power grid, and calculating the phase angle of the grid-connected current according to the acquired phase angle of the power grid, the reactive power requirement and the voltage balance correction value of a maintaining direct current side;
102, obtaining a current reference quantity of a first inverter according to the grid-connected current amplitude and the phase angle;
103, collecting local line current information by other inverters except the first inverter, and obtaining voltage reference quantity according to reactive power output reference quantity and correction quantity of a voltage balance part at the direct current side;
and 104, regulating the corresponding inverters according to the current reference quantity and the voltage reference quantity, controlling the first inverter into a current source, and controlling the other inverters into voltage sources to realize self-synchronization control of the whole system.
It should be noted that the method provided by the present invention is applicable to the equivalent circuit structure schematic diagram of the embodiment shown in fig. 2, the control block diagram of the first inverter is shown in fig. 3, and the control block diagrams of the other inverters are shown in fig. 4. The number of inverters included in the cascade STATCOM system is not limited in scope. Specifically, in the present embodiment, the relevant circuit parameter values are as shown in table 1. The cascade STATCOM system comprises 3 inverter modules, and each inverter corresponds to one local controller. The inverter is based on a DC/AC inverter. The front end of each inverter is connected with a direct current capacitor, the outlet of the first inverter is connected with a grid-connected line inductor (the inductor is the grid-connected line inductor, namely the inductor between the first inverter and the power grid), and the outlets of the other inverters are connected with LC filters. The LC filter is connected in series to the grid via a line impedance (inductive). The local controller of the first inverter includes a current reference module, a current loop module, and a PWM modulation module. The other modules except the first inverter comprise a voltage reference module, a voltage outer ring current inner ring module and a PWM modulation module.
TABLE 1
Figure BDA0003693069280000081
In order to construct the current reference of the first inverter, firstly, the reactive power requirement of a power grid, the phase angle of the collected power grid, the reactive power requirement and the voltage balance correction value of a maintaining direct current side are carried out. Specifically, the current reference of the first inverter can be obtained according to the reactive power requirement of the ground grid, the phase angle of the collected power grid and the voltage balance correction value of the maintained direct current side. In this embodiment, the reference quantity of the first inverter current amplitude is:
Figure BDA0003693069280000091
wherein, K I Coefficient of PI controller, Q g Is the reactive power of the power grid,
Figure BDA0003693069280000092
for the demand of reactive power of the grid, I * I.e. the current amplitude reference. The reference for the first inverter current phase angle is:
Figure BDA0003693069280000093
wherein k is P ,k I Coefficient of PI controller, δ g The phase angle of the collected power grid is measured,
Figure BDA0003693069280000094
for the DC side capacitor voltage reference, V dc1 For the first inverter dc-side capacitor voltage,
Figure BDA0003693069280000095
i.e. maintaining the DC side voltage balance correction value delta I* Is the reference quantity of the phase angle of the grid-connected current.
And 102, acquiring a current reference of the first inverter based on the grid-connected current amplitude and the phase angle.
The requirements of the reactive power of the power grid constructed in 101, the phase angle of the collected power grid and the voltage balance correction value of the maintaining direct current side are solved, and the grid-connected current amplitude reference quantity and the phase angle reference quantity of the first inverter can be obtained. In the embodiment, the voltage phase angle delta of the power grid is acquired by a phase-locked loop g According to said grid-connected currentAmplitude reference and current phase angle reference, synthesizing line sinusoidal current reference
Figure BDA0003693069280000096
(i.e. the
Figure BDA0003693069280000097
)。
103, collecting local current phase angle information delta of the ith inverter aiming at other inverters except the first inverter i,line Reference information Q of reactive power * Maintaining the DC-side capacitor voltage balance correction
Figure BDA0003693069280000098
Obtaining the voltage amplitude reference of the ith inverter, wherein the expression is
Figure BDA0003693069280000099
And the voltage phase angle reference of the ith inverter, the expression of which is
Figure BDA00036930692800000910
And synthesizing the sine voltage reference of the ith inverter according to the voltage amplitude reference and the voltage phase angle reference of the ith inverter
Figure BDA00036930692800000911
And 104, regulating the inverter corresponding to the inverter based on the current reference of the first inverter and the voltage references of other inverters. The first inverter is controlled by a current loop, controls grid-connected current to track a given current reference amount and works in a current source mode. And other inverters except the first inverter adopt voltage outer loop current inner loop control to track a given voltage reference quantity and work in a voltage source mode.
According to the self-synchronization control method of the cascade STATCOM system provided by the embodiment, the amplitude reference quantity of the grid-connected current is calculated according to the reactive power requirement of the power grid, and the phase angle reference quantity of the grid-connected current is obtained according to the collected phase angle of the power grid, the reactive power requirement and the voltage balance correction quantity of the maintaining direct current side; acquiring a current reference quantity of the first inverter according to the magnitude and the phase angle of the grid-connected current; the other inverters except the first inverter acquire local line current information, and obtain voltage reference quantity according to reactive power output reference quantity and correction quantity of a voltage balance part at the direct current side; and regulating the corresponding inverters according to the current reference quantity and the voltage reference quantity, controlling the first inverter into a current source, and controlling the other inverters into voltage sources to realize self-synchronization control of the whole system. According to the self-synchronization control method of the cascade STATCOM system, provided by the invention, each controller is not required to obtain information parameters of a large power grid, and the self-synchronization control can be realized only by obtaining local voltage and current information, so that the dependence on communication during normal operation of the system can be effectively reduced, the communication traffic is greatly reduced, the reliability of the system is improved, and the one-time investment cost is reduced.
According to the grid-connected cascade inverter structure adopted in the embodiment, simulation verification is performed according to the reactive power requirement of a power grid of 10000Var and the reactive power requirement of modules except a first inverter of 4000 Var.
A simulation software is adopted to perform an experiment to obtain a simulation oscillogram of the power grid and the current when the power grid works in the reactive power absorption mode in a mode that the reactive power demand of the power grid is 10000Var and the reactive power demand of modules except a first inverter is 4000Var, which is shown in fig. 5. The abscissa is time in units of s, and the ordinate is the amplitude of the corresponding voltage and current in units of V or A.
For the reactive power requirement of 10000Var in the power grid, a simulation oscillogram of the voltage and the current of the power grid when the reactive power is generated, which is obtained by adopting simulation software to carry out experiments, is shown in fig. 6. The abscissa is time in units of s, and the ordinate is the amplitude of the corresponding voltage and current in units of V or a.
For the reactive power requirement of the power grid of 10000Var, a simulation oscillogram of the capacitor voltage at the direct current side obtained by adopting simulation software to perform experiments is shown in fig. 7. The abscissa is time in units of s, and the ordinate is the corresponding voltage amplitude in units of V.
When the reference value of the direct current side capacitor voltage is 200V, the direct current side capacitor voltage of each module is as follows: v dc1 ＝200V,V dc2 ＝200V,V dc3 ＝200V。
Fig. 8 shows a reactive power simulation waveform diagram obtained by performing an experiment with simulation software in a manner that the reactive power demand of the modules except the first inverter is 4000 Var. Wherein, the abscissa is time in units of s, and the ordinate is output reactive power in units of Var.
When the reactive power demand according to the power grid is 10000Var, the output reactive power is: q 1 ＝2650Var,Q 2 ＝4000Var,Q 3 4000Var, the first inverter compensates the reactive power absorbed on the line by 650Var accordingly.
Therefore, the method for acquiring the reference phase angle and the reference voltage provided by the invention realizes the self-synchronous operation of the cascade STATCOM system, namely, the dependence of the system on communication is reduced, and the reliability of the system caused by communication faults is improved.
Example 2: as shown in fig. 9, a self-synchronizing control device of a cascade STATCOM system includes a current reference quantity obtaining module, a voltage reference quantity obtaining module, and a current regulation and voltage regulation module;
the current reference quantity acquisition module is used for acquiring an amplitude reference quantity of grid-connected current of a power grid, a phase angle reference quantity of the grid-connected current and a current reference quantity of a first inverter;
the voltage reference quantity acquisition module respectively acquires voltage reference quantities of the remaining inverters;
the current regulation and voltage regulation module is used for regulating the corresponding inverters according to the obtained current reference quantity and voltage reference quantity, controlling the first inverter into a current source, and controlling other inverters into voltage sources to realize self-synchronization control of the whole system; the current regulation module comprises a current reference quantity module, a current loop module and a PWM (pulse-width modulation) module which are sequentially connected (namely, the current reference quantity output by the current reference quantity module is used as the input of the current loop module, and the output of the current loop module is also used as the input of the PWM module); the voltage regulation module comprises a voltage reference quantity module, a voltage outer ring current inner ring module and a PWM (pulse width modulation) module which are sequentially connected (namely, the voltage reference quantity output by the voltage reference quantity module is used as the input of the voltage outer ring current inner ring module, and the output of the voltage reference quantity module is also used as the input of the PWM module).
The self-synchronizing control device comprises a requirement of reactive power of a power grid, an amplitude reference quantity of grid-connected current is calculated, a phase angle reference quantity of the grid-connected current is obtained according to a phase angle of the collected power grid, the requirement of the reactive power and a voltage balance correction quantity of a maintaining direct current side, and a current reference quantity of a first inverter is obtained according to the size and the phase angle of the grid-connected current; the other inverters except the first inverter acquire local line current information, and obtain voltage references according to reactive power output references and correction of the voltage balance maintaining part at the direct current side; and regulating the corresponding inverters according to the current reference quantity and the voltage reference quantity, controlling the first inverter into a current source, and controlling the other inverters into voltage sources, so as to realize self-synchronization control of the whole system. Specifically, the demand of the reactive power of the power grid, the collected phase angle of the power grid and the correction value for maintaining the voltage balance of the direct current side are used for executing the step 1-2, other inverters except the first inverter collect the current information of the local line, the step 3 is executed according to the reactive power output reference quantity and the correction value for maintaining the voltage balance of the direct current side, and the current regulation and voltage regulation module is used for executing the step 4.
The current regulation module of the first inverter of the current regulation and voltage regulation module comprises a current reference module, a current loop module and a PWM (pulse width modulation) module, so that a closed-loop current source automatic control system is formed; the voltage regulation module except the first inverter comprises a voltage reference quantity module, a voltage outer ring current inner ring module and a PWM (pulse width modulation) module, so that a double-closed-loop voltage source automatic control system is formed.
The self-synchronizing control device of the cascade STATCOM system provided by the invention can realize normal operation, reduce the dependence of system synchronization on communication, ensure that the system can still normally work even when communication faults occur, and improve the reliability of the system.
As a preferred embodiment, the current reference obtaining module is specifically used for a first inverter in a cascade static synchronous compensator (STATCOM) system, calculating an amplitude reference of grid-connected current according to the reactive power requirement of a power grid, and obtaining the phase angle reference of the grid-connected current according to the collected phase angle of the power grid, the reactive power requirement and the voltage balance correction value of a maintaining direct current side; and then obtaining the current reference quantity of the first inverter according to the magnitude and the phase angle of the grid-connected current.
As a preferred embodiment, the voltage reference obtaining module is specifically configured to be used for other inverters except the first inverter in the cascade STATCOM system, and obtain the voltage reference according to the collected local line current information, the reactive power output reference and the correction amount of the voltage balance maintaining part on the dc side.
The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of changes or substitutions within the technical scope of the present invention, and therefore, the scope of the present invention should be determined by the scope of the claims.

Claims (7)

1. A self-synchronization control method of a cascade STATCOM system is characterized in that: the method comprises the following steps:
step 1: calculating the amplitude reference quantity of grid-connected current according to the reactive power requirement of the power grid, and acquiring the phase angle reference quantity of the grid-connected current according to the acquired phase angle of the power grid, the reactive power requirement and the voltage balance correction value of the maintaining direct current side;
step 2: acquiring a current reference of a first inverter according to the amplitude reference of the current and the phase angle reference of the current calculated in the step 1;
and step 3: the other inverters except the first inverter acquire local line current information, and obtain voltage reference quantity according to reactive power output reference quantity and correction quantity of a voltage balance part at the direct current side;
and 4, step 4: and regulating the corresponding inverters according to the current reference quantity and the voltage reference quantity, controlling the first inverter into a current source, and controlling the other inverters into voltage sources to realize self-synchronization control of the whole system.
2. The self-synchronization control method of the cascade STATCOM system as claimed in claim 1, wherein: the specific method in the step 1 comprises the following steps:
calculating the magnitude of grid-connected current according to the reactive power requirement of a power grid, wherein the expression is as follows:
Figure FDA0003693069270000011
wherein, K I Coefficient of PI controller, Q g Is the reactive power of the power grid,
Figure FDA0003693069270000012
for the demand of reactive power of the grid, I * I.e. the amplitude reference of the current; s is a complex parameter;
acquiring a phase angle reference quantity of grid-connected current according to the collected phase angle of the power grid, the reactive power requirement and the voltage balance correction quantity of the direct current side, wherein the expression is as follows:
Figure FDA0003693069270000021
wherein k is P And k I Coefficient of PI controller, δ g In order to collect the phase angle of the power grid,
Figure FDA0003693069270000022
for DC side capacitor voltage reference, V dc1 For the first inverter DC side capacitorThe pressure is applied to the upper part of the cylinder,
Figure FDA0003693069270000023
i.e. to maintain the dc side voltage balance correction amount,
Figure FDA00036930692700000210
the reference quantity of the phase angle of the grid-connected current is obtained;
Figure FDA0003693069270000029
and the reference quantity is needed for the reactive power of the power grid.
3. The self-synchronization control method of the cascade STATCOM system as claimed in claim 2, wherein: in step 2, according to the amplitude reference quantity and the phase angle reference quantity of the grid-connected current obtained in the step 1, synthesizing the current reference quantity as a vector
Figure FDA00036930692700000211
4. The self-synchronization control method of the cascade STATCOM system as claimed in claim 2, wherein: the specific method in the step 3 comprises the following steps: according to the collected local current phase angle information delta of the ith inverter i,line And reactive power reference information Q * Maintaining the DC-side capacitor voltage balance correction
Figure FDA0003693069270000024
Determining the voltage reference which is present as a vector
Figure FDA0003693069270000025
The voltage amplitude reference and the voltage phase angle reference are expressed as follows:
Figure FDA0003693069270000026
Figure FDA0003693069270000027
wherein 1 is<i≤n，Q * ＝Q g N, n is the number of inverters,
Figure FDA0003693069270000028
for nominal grid voltage amplitude, V i * For the purpose of voltage amplitude reference,
Figure FDA00036930692700000212
reference quantity of phase angle of voltage, Q i Is reactive power, V dci Is the DC side capacitor voltage, K I Is a parameter of the PI controller.
5. The self-synchronization control method of the cascade STATCOM system as claimed in claim 1, wherein: in the step 2, the first inverter is the inverter closest to the power grid in all cascaded STATCOM systems.
6. A self-synchronizing control device of a cascade STATCOM system is characterized in that: the device comprises a current reference quantity acquisition module, a voltage reference quantity acquisition module and a current regulation and voltage regulation module;
the current reference quantity acquisition module is used for acquiring an amplitude reference quantity of grid-connected current of a power grid, a phase angle reference quantity of the grid-connected current and a current reference quantity of a first inverter;
the voltage reference quantity acquisition module is used for respectively acquiring voltage reference quantities of the rest inverters;
the current regulation and voltage regulation module is used for regulating the inverters corresponding to each other according to the obtained current reference quantity and voltage reference quantity, controlling the first inverter into a current source, and controlling the other inverters into voltage sources, so that the self-synchronization control of the whole system is realized.
7. The self-synchronizing control device of the cascaded STATCOM system according to claim 6, wherein: the current regulation module comprises a current reference module, a current loop module and a PWM (pulse width modulation) module which are sequentially connected; the voltage regulation module comprises a voltage reference quantity module, a voltage outer ring current inner ring module and a PWM (pulse width modulation) module which are sequentially connected.
CN202210670257.2A 2022-06-14 2022-06-14 Self-synchronization control method and device of cascade STATCOM system Pending CN114928070A (en)

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Publication number Priority date Publication date Assignee Title
CN115483711A (en) * 2022-10-26 2022-12-16 茅台学院 MPPT distributed control method and device for grid-connected cascaded photovoltaic inverter

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115483711A (en) * 2022-10-26 2022-12-16 茅台学院 MPPT distributed control method and device for grid-connected cascaded photovoltaic inverter

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