CN113098076B - Control device and control method of alternating current-direct current power supply system and alternating current-direct current power supply system - Google Patents
Control device and control method of alternating current-direct current power supply system and alternating current-direct current power supply system Download PDFInfo
- Publication number
- CN113098076B CN113098076B CN202110289491.6A CN202110289491A CN113098076B CN 113098076 B CN113098076 B CN 113098076B CN 202110289491 A CN202110289491 A CN 202110289491A CN 113098076 B CN113098076 B CN 113098076B
- Authority
- CN
- China
- Prior art keywords
- current
- voltage
- loop
- direct
- converter
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- 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
- H02J5/00—Circuit arrangements for transfer of electric power between ac networks and dc networks
-
- 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
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
-
- 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
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
Abstract
The application discloses controlling means, control method and alternating current-direct current power supply system of alternating current-direct current power supply system, alternating current-direct current power supply system include transmission line, send end converter, receive end converter and a plurality of switch, and controlling means includes: the sending end control unit adopts double closed-loop control of a direct-current voltage outer ring and a current inner ring and is used for controlling the direct-current side voltage of the sending end converter to be constant, and simultaneously introduces neutral point potential closed-loop control based on zero sequence voltage injection to ensure neutral point potential balance of the sending end converter; and the receiving end control unit adopts double closed loop PI control of a voltage outer loop and a current inner loop and is used for controlling alternating current voltage output of the receiving end converter, providing voltage support for a load, and simultaneously introducing current feedback and voltage feedforward and eliminating current coupling and load disturbance voltage influence. By means of the mode, the control device can improve the power supply reliability and effectiveness of the alternating current and direct current power supply system, and the voltage requirement of a terminal user is met.
Description
Technical Field
The application relates to the technical field of power distribution, in particular to a control device and a control method of an alternating current and direct current power supply system and the alternating current and direct current power supply system.
Background
In the initial stage of power grid construction, remote end users are limited by living standards, the power consumption is low, and the power consumption quality requirements are not high, so that the power consumption voltage drop of the users is not obvious, and the power consumption requirements are not strict. However, as the living level of people is increased, household loads are diversified, refined and large in capacity, the centralized starting of large power loads causes obvious voltage drop of a long-distance distribution line, and the problem of voltage drop of a terminal user is obvious. In addition, the starting of various high-power electric loads is often periodic, so that the problem of low terminal voltage occurs periodically, and the problem is remarkably aggravated due to the time concentration, and the daily life and the production and the electricity utilization of residents are influenced.
In order to solve the problem of low voltage at the end, the existing solutions mainly comprise: (1) And a 10kV line and a transformer are added, line transformation is carried out simultaneously, and the power supply radius is shortened. The mode has huge investment, and the line crosses the mountain area, the green vegetation of the mountain grows rapidly, the ground short circuit fault is easy to cause, and great difficulty is brought to the later operation and maintenance work; (2) The photovoltaic power generation device and the energy storage device are arranged at the tail end of the user, namely, a new power supply is arranged on the user side to improve the voltage of the user, the power is prevented from being transmitted for a long distance through the original power transmission line, and the voltage drop can be reduced. However, the photovoltaic energy storage device has high cost and long investment return period, and rural areas face land acquisition problems. (3) Reactive compensation and voltage regulation devices are installed, voltage regulators are connected in series on a line with an overlong power supply radius, and a centralized automatic reactive compensation station is built in an inductive load dense area. Although the voltage can be raised by about 20%, the voltage is still not qualified, and the problem cannot be solved fundamentally.
The inventor finds through research that an alternating current-direct current power supply system can realize low-voltage direct current power distribution by introducing a power electronic converter, solves the problem of insufficient voltage of a terminal user, and can generate a new problem: how to ensure the effectiveness and reliability of the dc power supply mode of the ac/dc power supply system?
Disclosure of Invention
The application provides a control device and a control method of an alternating current-direct current power supply system and the alternating current-direct current power supply system, and aims to solve the problems that in the prior art, the terminal voltage of the alternating current-direct current power supply system is insufficient, and the effectiveness and the reliability of a direct current power supply mode cannot be guaranteed.
In order to solve the technical problem, the present application provides a control device for an ac/dc power supply system, where the ac/dc power supply system includes a power transmission line, a transmitting-end converter, a receiving-end converter and a plurality of switches, and the control device includes: the sending end control unit adopts double closed-loop control of a direct-current voltage outer ring and a current inner ring and is used for controlling the direct-current side voltage of the sending end converter to be constant, and simultaneously introduces neutral point potential closed-loop control based on zero sequence voltage injection to ensure the neutral point potential balance of the sending end converter; and the receiving end control unit adopts double closed loop PI control of a voltage outer loop and a current inner loop and is used for controlling alternating current voltage output of the receiving end converter, providing voltage support for a load, introducing current feedback and voltage feedforward at the same time and eliminating current coupling and load disturbance voltage influence.
Optionally, the sending-end control unit includes: the first PI controller is applied to a direct-current voltage outer ring, can eliminate static error and outputs a command amplitude of current; the phase-locked loop is used for detecting the phase of the voltage of the power grid side to be used as a current instruction phase reference of the power grid side so as to enable the voltage and the current of the power grid side to be in the same phase; the proportion controller is applied to the current inner ring; the sending end control unit also adopts power grid side voltage feedforward to eliminate the interference of the power grid side voltage; and generating a required alternating current side current vector instruction through direct current voltage feedback control of the three-phase rectifier.
Optionally, the sending-end control unit further includes: and the second PI controller is used for determining the injected zero sequence component value so as to balance the midpoint potential of the transmitting-end converter.
Alternatively, when it is assumed that the capacitance values of the two capacitors on the dc side of the sending-end converter are equal, the following results are obtained:
wherein the content of the first and second substances,
taking the average value of the switching function in a switching period by adopting an average state space method:
known as d ik ∈[0，1]Then, the first step is executed,
when U is formed c1 ＞U c2 When the current is in the normal state, the second PI controller superposes a negative current direct-current component; when U is formed c1 ＜U c2 The second PI controller superposes a positive current direct-current component;
wherein C is the capacitance value of the capacitor; u shape c1 、U c2 Are the voltages on the two capacitors, S, respectively ik For the on-off state of the switching tube, i sk Outputting current for the power grid side; i.e. i 2 Outputting current for the direct current side of the sending end converter; τ is a time constant; i represents parameters 1 and 4; k represents any one of three phases of a, b and c of the transmission line; d is a radical of ik As a function of the switching S ik Average value over one switching period.
Optionally, the receiving-end converter is used for controlling three-phase alternating current voltage output and providing voltage support for a load; the receiving end control unit converts the three-phase symmetrical static coordinate system into a coordinate system synchronously rotating at the frequency of the alternating-current side fundamental waves, so that the fundamental wave sine quantity in the three-phase symmetrical static coordinate system is converted into a direct-current variable in the synchronous rotating coordinate system, and the simplified design of a control system is realized.
Optionally, the receiving-end control unit adopts double closed-loop control of a voltage outer loop and a current inner loop, and simultaneously compensates coupling between two phases of currents by using the detected actual current, so that mutual influence between the currents in the two phases of rotating coordinate systems is eliminated, and decoupling control of the currents is realized.
Optionally, when the current inner loop of the receiving-end control unit adopts a PI controller, the following equation is obtained:
wherein k is Pi Is the proportionality coefficient, k, of the current loop controller Ii Is the integral coefficient of the current loop controller;
command value of current inner loop
Is the output of the voltage outer loop controller;
u dn 、u qn d-axis components and q-axis components of the converter output voltage under a rotating coordinate system are respectively; u. of ld 、u lq The d-axis component and the q-axis component of the load terminal voltage under a rotating coordinate system are respectively; i.e. i sq 、i sd The q-axis component and the d-axis component of alternating-current side current of the converter under the rotating coordinate system are respectively; s is a parameter symbol and represents a calculation operator of a time domain function in a frequency domain after Laplace transform;
the voltage outer loop controller also adopts a PI controller:
wherein k is Pu Is the proportionality coefficient, k, of the voltage loop controller Iu Is the integral coefficient of the voltage loop controller;
is a d-axis voltage reference;
is a q-axis voltage reference.
Optionally, when the load-side voltage meets a preset voltage, the alternating current and direct current power supply system directly transmits alternating current through the power transmission line; when the voltage at the load side does not meet the preset voltage, alternating current is rectified into direct current through the transmitting end converter for direct current power transmission, and the direct current is inverted into the alternating current through the receiving end converter and transmitted to the load side.
In order to solve the technical problem, the present application provides a control method for an ac/dc power supply system, where the ac/dc power supply system includes a power transmission line, a transmitting-end converter, a receiving-end converter, and a plurality of switches, and the control method includes: a double closed-loop control mode of a direct-current voltage outer loop and a current inner loop is adopted for a sending end converter to ensure that the voltage of a direct-current side is constant, and meanwhile, midpoint potential closed-loop control based on zero-sequence voltage injection is introduced to ensure midpoint potential balance of the sending end converter; the receiving end converter is controlled by a double closed loop PI of a voltage outer loop and a current inner loop, and is used for controlling alternating voltage output of the receiving end converter, providing voltage support for a load, and simultaneously introducing current feedback and voltage feedforward to eliminate current coupling and load disturbance voltage influence.
In order to solve the technical problem, the application provides an ac/dc power supply system, which includes the above control device.
The application provides a control device, a control method and an alternating current and direct current power supply system, wherein the alternating current and direct current power supply system comprises a power transmission line, a transmitting end converter, a receiving end converter and a plurality of switches, and the control device comprises: the sending end control unit adopts double closed-loop control of a direct-current voltage outer ring and a current inner ring and is used for controlling the voltage of the direct-current side of the sending end converter to be constant, and simultaneously introduces neutral point potential closed-loop control based on zero sequence voltage injection to ensure the neutral point potential balance of the sending end converter; and the receiving end control unit adopts double closed loop PI control of a voltage outer loop and a current inner loop and is used for controlling alternating current voltage output of the receiving end converter, providing voltage support for a load, and introducing current feedback and voltage feedforward at the same time and eliminating current coupling and load disturbance voltage influence. In this way, the control device of the application can realize that the alternating current and direct current power supply system meets the voltage requirement of a terminal user, and guarantees the effectiveness of a direct current power supply mode.
Drawings
In order to more clearly illustrate the technical solution of the present application, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a schematic structural diagram of an embodiment of an AC/DC power supply system according to the present application;
FIG. 2 is a circuit diagram of a sending-end converter after being connected to a power grid in an embodiment;
FIG. 3 is a schematic diagram of a control block of an embodiment of a sending-end converter of the present application;
FIG. 4 is a schematic diagram of a control block of another embodiment of a transmitting side converter of the present application;
FIG. 5 is a schematic diagram of a control block of an embodiment of a receiving end converter of the present application;
FIG. 6 is a schematic flowchart of an embodiment of a control method for an AC/DC power supply system according to the present application;
FIG. 7 is a graph of three phase voltage and current waveforms for a load under a typical application condition of the present application;
FIG. 8 (a) is a graph of the overall waveform of the load side voltage current of an embodiment;
FIG. 8 (b) is a partial enlarged waveform of the load side voltage current of an embodiment;
FIG. 8 (c) is a partial enlarged waveform of voltage and current at a certain point of the power transmission line according to an embodiment;
fig. 8 (d) is a dc-side voltage waveform diagram according to an embodiment.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present application, the following describes the control device, the control method, and the ac/dc power supply system provided in the present application in further detail with reference to the accompanying drawings and specific embodiments.
The application provides a control device of an alternating current and direct current power supply system, which adopts a voltage and current double-loop control scheme of a sending end converter and a receiving end converter, wherein the sending end converter provides a voltage and current double-loop control scheme for introducing neutral point voltage balance control, and the receiving end converter provides a voltage and current double-loop control scheme for introducing real-time detection current to realize current decoupling. The response speed of the alternating current and direct current power supply system can be improved, and the safety and the reliability of the system are improved.
Referring to fig. 1, fig. 1 is a schematic structural diagram of an embodiment of an ac/dc power supply system according to the present application. The ac/dc power supply system 100 may include a transmission line 110, a transmitting-end converter 120, a receiving-end converter 130, and several switches.
The transmission line 110 may be used to connect the grid side and the load side. In this embodiment, the power transmission line 110 may be a three-phase four-wire line.
The transmit-side converter 120 may be connected between the grid side and the transmission line 110. Alternatively, the dc bus voltage rating of the sending side converter 120 may be 750V.
The receiving end converter 130 may be connected between the load side and the transmission line 110. The receiving-side converter 130 may be the same as the transmitting-side converter 120.
When the load side voltage of the ac/dc power supply system 100 meets the preset voltage, ac power transmission is directly performed through the power transmission line 110; when the load-side voltage does not meet the preset voltage, the transmitting-end converter 120 rectifies the alternating current into direct current for direct current power transmission, and the receiving-end converter 130 reversely flows the direct current into alternating current for transmission to the load side.
The preset voltage can be set to 198V, because the national standard power consumption requirement is 198V-231V.
Specifically, first to sixth switches S1 to S6 may be included.
The first switch S1 may be disposed between the input end of the sending-end converter 120 and the power transmission line 110, and the second switch S2 may be disposed between the output end of the sending-end converter 120 and the power transmission line 110; the third switch S3 may be disposed between the output terminal of the receiving-end converter 130 and the transmission line 110; the fourth switch S4 may be disposed between the input terminal of the receiving-end converter 130 and the transmission line 110; the fifth switch S5 may be disposed in the power transmission line 110 between the input end and the output end of the sending-end converter 120; the sixth switch S6 may be disposed in the power transmission line 110 between the input terminal and the output terminal of the receiving-side converter 130.
It should be noted that, since the power transmission line 110 is a three-phase four-wire line, the first to sixth switches S1 to S6 do not refer to a single switch, but refer to a group of switches.
As shown in fig. 1, the sending-side converter 120 includes an input terminal a, an input terminal B, an input terminal C, + output terminal, -output terminal, and N terminal. The input end a, the input end B, the input end C, and the N end are connected to the a-phase line, the B-phase line, the C-phase line, and the N line in the power transmission line 110, respectively, and the + output end and the-output end are connected to two lines that are not adjacent to each other through the first switch S1, for example, the + output end is connected to the a-phase line and the-output end is connected to the C-phase line in fig. 1.
The receiving-side converter 130 is almost the same as the transmitting-side converter 120, except that the input terminal of the receiving-side converter 130 needs to be connected to the transmission line 110 through the third switch S3. And will not be described in detail herein.
In addition, the power transmission line 110 may further include other components to ensure the safety of the power transmission line 110, such as resistance, inductance, and the like.
In this embodiment, the control device may include a sending-end control unit and a receiving-end control unit.
The sending end control unit can adopt double closed-loop control of a direct-current voltage outer ring and a current inner ring and is used for controlling the voltage of the direct-current side of the sending end converter to be constant, and meanwhile, neutral point potential closed-loop control based on zero sequence voltage injection is introduced to ensure the neutral point potential balance of the sending end converter; the receiving end control unit can adopt double closed loop PI control of a voltage outer loop and a current inner loop, is used for controlling alternating current voltage output of the receiving end converter, provides voltage support for a load, and introduces current feedback and voltage feedforward at the same time, and is used for eliminating current coupling and load disturbance voltage influence.
The transmitting end converter and the receiving end converter can adopt a diode clamping type three-level topological structure. Firstly, a low-frequency mathematical model of the diode-clamped three-level converter under a three-phase static coordinate system is established, namely the mathematical model neglects higher harmonics related to the switching frequency. As known from the knowledge of power electronics, PWM control of the power switching devices generates voltage pulse signals containing fundamental wave and high-frequency harmonic components at the ac input terminals a, b, and c of the three-phase bridge. The three-phase alternating-current voltage of the converter is controllable fundamental wave sinusoidal voltage because the filter can filter out high-frequency harmonic components.
Referring to fig. 2, fig. 2 is a circuit structure diagram of a transmitting-end converter after being connected to a power grid in an embodiment. With the current direction of fig. 2 as a reference, an equation of the alternating current side of the rectifier module in the three-phase stationary coordinate system can be obtained according to kirchhoff's voltage law:
in the formula: l is the equivalent inductance value of the filter; i all right angle sk 、u sk -the grid side outputs current and voltage; u. of kn -converter ac output terminal voltage, where k = a, b, c.
The formula (1) shows that the current at the AC output end of the sending-end converter is not only related to the control quantity u kn Related to the grid-side voltage u sk In connection with this, the current controller can be designed to eliminate this effect using a grid side voltage feed forward approach.
And generating a required alternating current side current vector instruction through direct current voltage feedback control of the three-phase rectifier.
The outer ring of the direct current voltage adopts a PI controller which can eliminate the static error, and the output of the PI controller is the instruction amplitude of the current.
In order to achieve unity power factor, i.e. current and voltage are in phase, a phase-locked loop may be used to detect the phase of the grid voltage as the current command phase reference.
Because the current instruction and feedback are both alternating current quantities, namely the current is directly controlled under a three-phase static coordinate system, a current loop adopts a proportional controller. In summary, the control block diagram of the sending-end converter is shown in fig. 3.
For diode-clamped three-level converters, midpoint potential imbalance is an inherent problem. When the converter works, three-phase output current of the converter generates alternating current on a neutral line of the converter through a bridge arm, and the alternating current can cause potential fluctuation of capacitors of an upper bridge arm and a lower bridge arm. In addition, the midpoint voltage drift can be caused by the problems of inconsistent parameters of the capacitor and the switching tube, unbalanced load and the like. And the fluctuation of the midpoint voltage can cause the distortion of the output voltage waveform and the increase of the voltage stress of a power switch device, and can damage the device in serious cases, so that the safety and the reliability of a system are endangered, and therefore, effective measures must be taken to ensure the midpoint potential balance of the converter.
Therefore, the sending end control unit may further include a second PI controller, and the second PI controller is configured to determine the injected zero sequence component value, so that the midpoint potential of the sending end converter is balanced.
Assuming that the capacitance values of two capacitors on the dc side of the transmitting-end converter are equal, i.e. C1= C2= C, analyzing the two capacitors on the dc side according to kirchhoff's current law to obtain:
wherein the content of the first and second substances,
since the defined switching functions are quantized digital quantities, for the purpose of analysis, an average state space method is adopted, and the average value of the average state space method in one switching period is taken as follows:
known as d ik ∈[0，1]Then, the first step is executed,
wherein C is the capacitance value of the capacitor; u shape c1 、U c2 Respectively the voltages on the two capacitors, S ik For the on-off state of the switching tube，i sk Outputting current for the power grid side; i.e. i 2 Outputting current for the direct current side of the sending end converter; τ is a time constant; i represents parameters 1 and 4; k represents any one of three phases of a, b and c of the transmission line; d ik As a function of the switching S ik Average value over one switching period.
According to the formula (4), when U is c1 ＞U c2 In order to reduce the difference between the two, the second PI controller may superimpose a negative current dc component; when U is turned c1 ＜U c2 The second PI-controller may superimpose a positive dc component of the current. Therefore, a control block diagram of the transmitting-end converter added with the neutral point potential balance control based on the zero sequence voltage injection method is shown in fig. 4.
The receiving end converter needs to act as a voltage source to provide voltage support for the load, i.e. for controlling the three-phase alternating voltage output. In a mathematical model of a three-phase static coordinate system, the alternating current side is the time-varying alternating current quantity, which is not beneficial to the design of a control system. For this reason, the receiving-end control unit can also be used for converting the three-phase symmetrical static coordinate system into a coordinate system synchronously rotating at the frequency of the alternating-current side fundamental waves, so that the fundamental wave sine quantity in the three-phase symmetrical static coordinate system is converted into a direct-current variable in the synchronous rotating coordinate system, and the design of a control system is simplified. Obtaining a low-frequency mathematical model under a two-phase (dq) rotating coordinate system after park transformation:
in the formula: i.e. i sd 、i sq -d, q-axis components of the current vector at the ac side of the converter; w is the grid fundamental angular frequency; u. of dn 、u qn -d, q axis components of the converter output voltage vector; u. of ld 、u lq -d, q axis components of the load terminal voltage vector.
Through coordinate transformation, a three-phase state equation under a three-phase coordinate system is changed into two phases, the order of the state equation is reduced, and the design of a controller is facilitated. However, in a two-phase rotating coordinate system, coupling is generated between the state equations, namely, the current change in any one axis direction can cause the current change in the other axis direction.
Therefore, in order to achieve an ideal control effect and reduce the design difficulty of the controller, the receiving-end control unit is also used for compensating the coupling between the two phases of currents by using the detected actual current, so that the mutual influence between the currents is eliminated, and the decoupling control of the currents is realized.
When the receiving end control unit adopts a PI controller, the following equation is obtained:
wherein k is Pi Is the proportionality coefficient, k, of the current loop controller Ii Is the integral coefficient of the current loop controller;
instruction value of current inner loop
Is the output of the voltage outer loop controller;
u dn 、u qn d-axis components and q-axis components of the converter output voltage under a rotating coordinate system are respectively; u. of ld 、u lq The d-axis component and the q-axis component of the load terminal voltage under a rotating coordinate system are respectively; i all right angle sq 、i sd The q-axis component and the d-axis component of alternating-current side current of the converter under the rotating coordinate system are respectively; s is a parameter symbol and represents a calculation operator of a frequency domain after the time domain function is subjected to the Laplace transform;
the voltage outer loop controller also adopts a PI controller:
wherein k is Pu Is the proportionality coefficient, k, of the voltage loop controller Iu Is the integral coefficient of the voltage loop controller.
In summary, a control block diagram of the receiving-end converter is shown in fig. 5, and after current feedback and voltage feed-forward are introduced, current coupling and load disturbance voltage influence can be effectively eliminated.
In fig. 5, w is a given voltage frequency command; and U is a given voltage command in the three-phase static coordinate system.
Based on the control device of the alternating current and direct current power supply system, the application provides a control method of the alternating current and direct current power supply system. Referring to fig. 6, fig. 6 is a schematic flowchart illustrating an embodiment of a control method for an ac/dc power supply system according to the present application. The method specifically comprises the following steps:
s610: a double closed-loop control mode of a direct-current voltage outer loop and a current inner loop is adopted for a sending-end converter to ensure that the voltage of a direct-current side is constant, and meanwhile, neutral-point potential closed-loop control based on zero-sequence voltage injection is introduced to ensure neutral-point potential balance of the sending-end converter.
S620: the receiving end converter adopts double closed loop PI control of a voltage outer loop and a current inner loop, is used for controlling alternating current voltage output of the receiving end converter, provides voltage support for a load, and introduces current feedback and voltage feed forward to eliminate current coupling and load disturbance voltage influence.
Based on above-mentioned alternating current-direct current power supply system's controlling means, this application provides an alternating current-direct current power supply system, including foretell controlling means. The specific principles and structures have been described in detail in the above embodiments and will not be described in detail here.
For example, referring to fig. 7, fig. 7 shows three-phase voltage and current waveforms of a load under a typical application condition of the present application. In the figure, the waveform on the left side of the dotted line is that the user load directly obtains electric energy from the distribution network, namely the existing 400V distribution network power supply mode; the waveform on the right side is the direct current transmission path constructed by the original line provided by the invention. Under the alternating current working mode, the effective value of the voltage of the load end is about 167V and does not meet the requirements of national standards, and under the direct current working mode, the effective value of the voltage is about 220V and the voltage of the user end is qualified.
Fig. 8 shows the main operating waveforms for switching from ac to dc transmission under heavy load. As can be seen from fig. 8 (a) and (b), after the ac mode is switched to the dc mode, the load terminal voltage rises from 269.5V to 310.86V, and the load terminal voltage THD in the dc mode is 0.84%, which meets the requirement. As can be seen from fig. 8 (d), the dc-side voltage is stabilized around 700V during the switching process, and the reliability of the control strategy of the transmitting-side converter is explained.
In summary, when the power transmission is performed by using the conventional ac transmission scheme, the terminal voltage is about 170V at the time of the peak load of the system, and the requirement of the voltage qualification rate is not satisfied. And the DC transmission mode is adopted, and based on the control scheme of the sending-end converter and the receiving-end converter provided by the invention, the voltage of a terminal user can be kept at 220V, and the national standard requirement (198-231V) is met.
Specifically, the voltage and current double-loop control scheme of the sending-end converter with the addition of the neutral-point voltage balance control, which is provided by the application, realizes the stable output of the direct-current voltage in the direct-current power supply mode; the receiving end converter voltage and current double-loop control scheme added with the actual detection current compensation realizes decoupling control of current, stable output of three-phase alternating current voltage in a direct current power supply mode and power supply of an effective support load.
It is to be understood that the specific embodiments described herein are merely illustrative of the application and are not limiting of the application. In addition, for convenience of description, only a part of structures related to the present application, not all of the structures, are shown in the drawings. Step numbers used herein are also for convenience of description only and are not intended as limitations on the order in which steps may be performed. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The terms "first", "second", etc. in this application are used to distinguish different objects, and are not used to describe a particular order. Furthermore, the terms "include" and "have," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements but may alternatively include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.
The above description is only for the purpose of illustrating embodiments of the present application and is not intended to limit the scope of the present application, and all modifications of equivalent structures and equivalent processes, which are made by the contents of the specification and the drawings of the present application or are directly or indirectly applied to other related technical fields, are also included in the scope of the present application.
Claims (7)
1. The control device of the alternating current-direct current power supply system is characterized in that the alternating current-direct current power supply system comprises a power transmission line, a sending end converter, a receiving end converter and a plurality of switches, wherein the sending end converter and the receiving end converter adopt diode-clamped three-level topological structures, and the sending end converter comprises an input end A, an input end B, an input end C, a + output end, an output end and an N end; the input end A, the input end B, the input end C and the N end are correspondingly connected with an A-phase line, a B-phase line, a C-phase line and an N line in the power transmission line, and the + output end and the-output end are connected in two different lines through a first switch S1; when the load side voltage meets the preset voltage, the alternating current and direct current power supply system directly transmits alternating current through the power transmission line; when the voltage of the load side does not meet the preset voltage, rectifying the alternating current into direct current through the transmitting end converter to perform direct current power transmission, and inverting the direct current into the alternating current through the receiving end converter to be transmitted to the load side; the control device includes:
the sending end control unit adopts double closed-loop control of a direct-current voltage outer ring and a current inner ring and is used for controlling the direct-current side voltage of the sending end converter to be constant, and simultaneously introduces neutral point potential closed-loop control based on zero sequence voltage injection to ensure the neutral point potential balance of the sending end converter;
the receiving end control unit adopts double closed loop PI control of a voltage outer loop and a current inner loop and is used for controlling alternating current voltage output of the receiving end converter, providing voltage support for a load, and introducing current feedback and voltage feedforward at the same time and eliminating current coupling and load disturbance voltage influence;
the receiving end converter is used for controlling three-phase alternating current voltage output and providing voltage support for a load;
the receiving end control unit converts a three-phase symmetrical static coordinate system into a coordinate system synchronously rotating at the frequency of an alternating-current side fundamental wave, so that a fundamental wave sine quantity in the three-phase symmetrical static coordinate system is converted into a direct-current variable in a synchronous rotating coordinate system;
the receiving end control unit adopts double closed loop control of a voltage outer loop and a current inner loop, and utilizes detected actual current to compensate coupling between two phases of current, so that mutual influence between the current under a two-phase rotating coordinate system is eliminated, and decoupling control of the current is realized.
2. The control device according to claim 1, wherein the sending-end control unit includes:
the first PI controller is applied to a direct-current voltage outer ring, can eliminate static error and outputs a command amplitude of current;
the phase-locked loop is used for detecting the phase of the voltage on the power grid side to be used as a current instruction phase reference of the power grid side so as to enable the voltage and the current on the power grid side to be in the same phase;
the proportional controller is applied to the current inner ring;
the sending end control unit also adopts power grid side voltage feedforward to eliminate the interference of the power grid side voltage; and generating a required alternating current side current vector instruction through direct current voltage feedback control of the three-phase rectifier.
3. The control device according to claim 2, wherein the sending-end control unit further includes:
and the second PI controller is used for determining the injected zero sequence component value so as to balance the midpoint potential of the sending end converter.
4. The control device according to claim 3,
when the capacitance values of the two capacitors on the direct current side of the sending-end converter are equal, obtaining:
wherein, the first and the second end of the pipe are connected with each other,
taking the average value of the switching function in a switching period by adopting an average state space method:
known as d ik ∈[0,1]Then, if the number of the first time zone is less than the first threshold value,
when U is turned c1 ＞U c2 When the current is in the normal state, the second PI controller superposes a negative current direct-current component; when U is formed c1 ＜U c2 The second PI controller superposes a positive current direct-current component; t is s Is a switching cycle;
wherein C is the capacitance value of the capacitor; u shape c1 、U c2 Are the voltages on the two capacitors, S, respectively ik For the on-off state of the switching tube, i sk Outputting current for the power grid side; i.e. i 2 Outputting current for the direct current side of the sending end converter; τ is a time constant; i represents parameters 1, 4; k represents any one of three phases a, b and c of the transmission line; d is a radical of ik As a function of the switching S ik Average value over one switching period.
5. The control device according to claim 4, wherein when the PI controller is adopted as the current inner loop of the receiving-end control unit, the following equation is obtained:
wherein k is Pi Is the proportionality coefficient, k, of the current loop controller Ii Is the integral coefficient of the current loop controller;
instruction value of current inner loop
Is the output of the voltage outer loop controller; wi (light) sq Where w is the angular frequency, i sq Is the Q-axis current;
u dn 、u qn d-axis components and q-axis components of the converter output voltage under a rotating coordinate system are respectively; u. u ld 、u lq Respectively representing d-axis components and q-axis components of the load terminal voltage under a rotating coordinate system; i.e. i sq 、i sd Q-axis components and d-axis components of alternating-current side current of the converter under a rotating coordinate system are respectively; s is a parameter symbol and represents a calculation operator of a time domain function in a frequency domain after Laplace transform;
the voltage outer loop controller also adopts a PI controller:
wherein k is Pu Is the proportionality coefficient, k, of the voltage loop controller Iu Is the integral coefficient of the voltage loop controller;
is a d-axis voltage reference;
is a q-axis voltage reference.
6. The control method of the alternating current-direct current power supply system is characterized in that the alternating current-direct current power supply system comprises a power transmission line, a sending end converter, a receiving end converter and a plurality of switches, wherein the sending end converter and the receiving end converter adopt diode-clamped three-level topological structures, and the sending end converter comprises an input end A, an input end B, an input end C, a + output end, an output end and an N end; the input end A, the input end B, the input end C and the N end are correspondingly connected with an A-phase line, a B-phase line, a C-phase line and an N line in the power transmission line, and the + output end and the-output end are connected to two different lines through a first switch S1; when the voltage of the load side of the alternating current and direct current power supply system meets the preset voltage, alternating current power transmission is directly carried out through the power transmission line; when the voltage of the load side does not meet the preset voltage, rectifying the alternating current into direct current through the transmitting end converter to perform direct current power transmission, and inverting the direct current into the alternating current through the receiving end converter to be transmitted to the load side; the control method comprises the following steps:
a double closed-loop control mode of a direct-current voltage outer loop and a current inner loop is adopted for the sending end converter to ensure that the voltage of a direct-current side is constant, and meanwhile, neutral point potential closed-loop control based on zero sequence voltage injection is introduced to ensure that the neutral point potential of the sending end converter is balanced;
the receiving end converter is subjected to double closed loop PI control of a voltage outer loop and a current inner loop, and is used for controlling alternating current voltage output of the receiving end converter, providing voltage support for a load, and introducing current feedback and voltage feedforward to eliminate current coupling and load disturbance voltage influence;
the receiving end converter is used for controlling three-phase alternating current voltage output and providing voltage support for a load;
the receiving end control unit converts a three-phase symmetrical static coordinate system into a coordinate system synchronously rotating at the frequency of an alternating-current side fundamental wave, so that a fundamental wave sine quantity in the three-phase symmetrical static coordinate system is converted into a direct-current variable in a synchronous rotating coordinate system;
the double closed-loop control of the voltage outer loop and the current inner loop is adopted, and meanwhile, the coupling between two phases of currents is compensated by using the detected actual current, so that the mutual influence between the currents under a two-phase rotating coordinate system is eliminated, and the decoupling control of the currents is realized.
7. A system for supplying ac and dc power, comprising a control device according to any one of claims 1 to 5.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110289491.6A CN113098076B (en) | 2021-03-17 | 2021-03-17 | Control device and control method of alternating current-direct current power supply system and alternating current-direct current power supply system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110289491.6A CN113098076B (en) | 2021-03-17 | 2021-03-17 | Control device and control method of alternating current-direct current power supply system and alternating current-direct current power supply system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN113098076A CN113098076A (en) | 2021-07-09 |
| CN113098076B true CN113098076B (en) | 2023-01-24 |
Family
ID=76668359
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202110289491.6A Active CN113098076B (en) | 2021-03-17 | 2021-03-17 | Control device and control method of alternating current-direct current power supply system and alternating current-direct current power supply system |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN113098076B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113270941B (en) * | 2021-05-28 | 2022-08-12 | 广东电网有限责任公司 | Low-voltage alternating current-direct current power distribution mode conversion system and time sequence control method and device thereof |
Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101295877A (en) * | 2008-06-05 | 2008-10-29 | 上海交通大学 | Control system of offshore wind power flexible DC power transmission current transformer |
| CN101546913A (en) * | 2009-04-21 | 2009-09-30 | 上海追日电气有限公司 | Multifunctional high-power electronic load and control method thereof |
| CN104410083A (en) * | 2014-12-12 | 2015-03-11 | 山东电力工程咨询院有限公司 | Capacitance midpoint potential balancing device on SVG (Static VAR Generator) direct current side and control method of capacitance midpoint potential balancing device |
| CN108988667A (en) * | 2018-07-19 | 2018-12-11 | 山东大学 | Reduce by the Predictive Control System and method of three level VIENNA rectifier system common-mode voltages |
| CN109495001A (en) * | 2018-12-28 | 2019-03-19 | 山东大学 | Three level Vienna rectifier of modular parallel, control system and method |
| CN109802384A (en) * | 2019-01-29 | 2019-05-24 | 西北工业大学 | A kind of non-equilibrium model predictive control method of star chain type STATCOM |
| CN109861564A (en) * | 2019-01-10 | 2019-06-07 | 中国电力科学研究院有限公司 | A kind of energy storage load net-side rectifier voltage balance control method and system |
| CN110176770A (en) * | 2019-06-10 | 2019-08-27 | 上海电力学院 | The control method of MMC type Active Power Filter-APF when unbalanced source voltage |
| CN112104247A (en) * | 2020-09-08 | 2020-12-18 | 沈阳工业大学 | Neutral-point potential control method for medium-voltage three-level full-power converter of wind generating set |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10439511B2 (en) * | 2018-02-03 | 2019-10-08 | S&C Electric Company | Three phase inverter grid voltage feed forward method under unbalanced operating conditions |
-
2021
- 2021-03-17 CN CN202110289491.6A patent/CN113098076B/en active Active
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101295877A (en) * | 2008-06-05 | 2008-10-29 | 上海交通大学 | Control system of offshore wind power flexible DC power transmission current transformer |
| CN101546913A (en) * | 2009-04-21 | 2009-09-30 | 上海追日电气有限公司 | Multifunctional high-power electronic load and control method thereof |
| CN104410083A (en) * | 2014-12-12 | 2015-03-11 | 山东电力工程咨询院有限公司 | Capacitance midpoint potential balancing device on SVG (Static VAR Generator) direct current side and control method of capacitance midpoint potential balancing device |
| CN108988667A (en) * | 2018-07-19 | 2018-12-11 | 山东大学 | Reduce by the Predictive Control System and method of three level VIENNA rectifier system common-mode voltages |
| CN109495001A (en) * | 2018-12-28 | 2019-03-19 | 山东大学 | Three level Vienna rectifier of modular parallel, control system and method |
| CN109861564A (en) * | 2019-01-10 | 2019-06-07 | 中国电力科学研究院有限公司 | A kind of energy storage load net-side rectifier voltage balance control method and system |
| CN109802384A (en) * | 2019-01-29 | 2019-05-24 | 西北工业大学 | A kind of non-equilibrium model predictive control method of star chain type STATCOM |
| CN110176770A (en) * | 2019-06-10 | 2019-08-27 | 上海电力学院 | The control method of MMC type Active Power Filter-APF when unbalanced source voltage |
| CN112104247A (en) * | 2020-09-08 | 2020-12-18 | 沈阳工业大学 | Neutral-point potential control method for medium-voltage three-level full-power converter of wind generating set |
Non-Patent Citations (2)
| Title |
|---|
| 基于模块化多电平的交直变换系统研究;白天彤;《中国优秀硕士论文电子期刊网》;20170715(第07期);第1-79页 * |
| 维也纳电路中点电压均衡控制与输入电流畸变抑制研究;肖梁乐;《中国优秀硕士论文电子期刊网》;20190415(第04期);第1-87页 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN113098076A (en) | 2021-07-09 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN107611991B (en) | Parameter design method of LC coupling type SVG under unbalanced power grid and control method and system thereof | |
| CN104009486B (en) | The asymmetry compensation current-limiting method of a kind of three-phase three-wire system SVG | |
| CN105743091B (en) | A kind of double close-loop decoupling control method of Active Power Filter-APF | |
| CN104167941B (en) | Three-phase PWM rectifier control method | |
| CN106532749B (en) | A kind of micro-capacitance sensor imbalance power and harmonic voltage compensation system and its application | |
| CN106655843A (en) | Cascaded H-bridge PWM rectification system and control method thereof | |
| CN108512452A (en) | A kind of control system and control method of direct-current grid grid-connection converter electric current | |
| CN110277788B (en) | Composite compensation device for long-distance sparse power supply | |
| CN110212535B (en) | Higher harmonic active stabilization device and method for AC/DC hybrid microgrid | |
| CN112290567B (en) | Three-phase power quality compensation device and method based on half-bridge converter | |
| CN202353232U (en) | High-voltage cascaded inverter power unit grid-connection feedback device | |
| CN110350547A (en) | A kind of more level reactive compensation systems and its control method suitable for unbalanced load | |
| CN106026154A (en) | Modeling method for extra-high-voltage direct-current layered access power transmission system | |
| CN109888829A (en) | Photovoltaic microgrid system based on the sagging control of improvement perception is from grid-connected seamless switch-over system | |
| CN110729909A (en) | Multi-port railway power regulator system and comprehensive control method thereof | |
| CN110266008A (en) | Based on the improved more level active power filters of neutral-point-clamped type | |
| CN106972759A (en) | A kind of power supply of simulating grid disturbance | |
| CN108565892A (en) | A kind of fault ride-through method, device and photovoltaic generating system | |
| CN102496950A (en) | Power unit grid-connected and feedback device for high-voltage concatenated frequency converter | |
| CN113098076B (en) | Control device and control method of alternating current-direct current power supply system and alternating current-direct current power supply system | |
| CN108173443A (en) | A kind of three discontinuous SVPWM methods of level SVG | |
| CN104362759B (en) | Final power quality regulating and controlling device for power distribution network and regulating and controlling method | |
| CN114498718A (en) | Flexible traction substation and control method thereof | |
| CN105529710A (en) | Control method and device based on distribution static synchronous compensator (DSTATCOM) topological structure | |
| CN204290329U (en) | A kind of SVG DC bus capacitor neutral-point potential balance device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |