CN116247724A - Inverter active support power grid control method and system based on power synchronous control - Google Patents

Inverter active support power grid control method and system based on power synchronous control Download PDF

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CN116247724A
CN116247724A CN202310103172.0A CN202310103172A CN116247724A CN 116247724 A CN116247724 A CN 116247724A CN 202310103172 A CN202310103172 A CN 202310103172A CN 116247724 A CN116247724 A CN 116247724A
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power
inverter
output
power grid
frequency
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侯川川
刘澳
朱淼
徐莉婷
蔡旭
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Shanghai Jiaotong 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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • 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
    • H02J3/002—Flicker reduction, e.g. compensation of flicker introduced by non-linear load
    • 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
    • H02J3/01—Arrangements for reducing harmonics or ripples
    • 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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • 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
    • H02M1/0003—Details of control, feedback or regulation circuits
    • 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

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  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Inverter Devices (AREA)

Abstract

The invention provides a method and a system for controlling an inverter active support power grid based on power synchronous control, wherein the method comprises the following steps: the power grid frequency is detected in real time through the power synchronizing ring, the power grid frequency is coupled with the set value of the active current output by the inverter, the adjustment quantity of the set value of the active current output by the inverter is generated according to the fluctuation of the power grid frequency, and the power grid is actively supported by changing the output power of the inverter. The invention utilizes the self characteristics and output of the power synchronizing ring to realize the detection of the power grid frequency, couples the obtained power grid frequency with the given value of the active current output by the inverter in an integral relation on the basis of the detection of the power synchronizing ring, thereby realizing the active power support when the power grid frequency fluctuates.

Description

Inverter active support power grid control method and system based on power synchronous control
Technical Field
The invention relates to the technical field of alternating current power generation, transmission, distribution and power utilization, in particular to an inverter active support power grid control method and system based on power synchronous control.
Background
The power generation internet surfing rate of new energy sources such as wind energy, solar energy and biomass energy shows explosive growth, which is not only beneficial to the adjustment of a primary energy structure of a power system, but also beneficial to the reduction of the carbon emission level of power generation and the promotion of clean grid connection of electric energy. The high-proportion penetration of new energy power generation in a power system becomes a large characteristic of a novel power system, and the part of electric energy is connected into a power grid through power electronic conversion equipment such as an inverter and the like. Therefore, the inverter is used as a main interface for interaction between the new energy and the power grid, and the stable operation and control performance of the inverter directly determine whether the renewable energy can be efficiently utilized.
The inverter is an important device for converting electric energy, and comprises a main circuit and a control part. The control commonly used at present is a follow-net type control strategy, comprising a vector current loop and a phase-locked loop. The vector current loop is used for fast control of output current, the phase-locked loop is used for grid-connected synchronization, the frequency and the phase of the voltage at the machine end can be tracked, and the inverter is used for adjusting the amplitude and the phase of the internal potential according to the current control requirement based on the frequency and the phase of the voltage at the machine end. Thus, the phase locked loop is a key in inverter control. However, the existing researches show that in the following network type control strategy, the introduction of the phase-locked loop inevitably brings negative resistance to the inverter, and subsynchronous oscillation is easy to be initiated, so that the system instability phenomenon is generated.
To solve this problem, phase-locked loop-free networking control strategies are proposed that simulate or partially simulate the characteristics of synchronous machines, including droop control and virtual synchronous machine control (virtual synchronous generator, VSG). The droop control can realize autonomous power distribution among parallel inverters under no communication, and the application time is relatively early. Meanwhile, the VSG realizes analogy of damping and inertia of the synchronous machine by simulating a motion equation of a rotor of the synchronous machine and utilizing a control strategy, and the grid support characteristic is superior to droop control. In addition, the concept of power synchronization control (power synchronous control, PSC) with VSG-like characteristics is also proposed by the academia. The power synchronization control realizes the conversion from power fluctuation to angle deviation by analogy to a motion equation of a rotor of the synchronous machine by utilizing single integration, has higher stability margin, and ensures that the PSC can enhance the stability of the inverter accessing a weak power grid and improve the power control range. The combination of the power synchronous control and the current source control ensures the good stability of the weak power grid and improves the response speed and the transient fault current limiting capacity of the system.
The existing power synchronous inverter control strategy only realizes the power transmission function in a steady state, and when the frequency or voltage of the power grid fluctuates, active or reactive power support cannot be provided for the system, namely the output power of the power synchronous inverter cannot respond to the change of the frequency and voltage state of the power grid, and the capability of providing transient support for the power grid is lacking.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method and a system for controlling an inverter active support power grid based on power synchronous control.
The invention provides a power synchronization control-based inverter active support power grid control method, which comprises the following steps: the power grid frequency is detected in real time through the power synchronizing ring, the power grid frequency is coupled with the set value of the active current output by the inverter, the adjustment quantity of the set value of the active current output by the inverter is generated according to the fluctuation of the power grid frequency, and the power grid is actively supported by changing the output power of the inverter.
Preferably, the real-time detection of the grid frequency by the power synchronization loop includes: the conversion from the power difference value to the frequency difference value is realized by synchronizing the power of the inverter and the power of the power grid by utilizing the power synchronization coefficient of the inverter, the obtained frequency deviation is summed with the power grid frequency given value, and the actual frequency of the power grid is obtained, wherein the power difference is the difference value between the given value of the active power output by the inverter and the actual value of the active power output by the inverter.
Preferably, the inverter comprises a power synchronizing ring and a vector current ring, synchronization information of a power grid is extracted through the power synchronizing ring, and the vector synchronizing ring controls output power of the inverter;
the method comprises the steps of obtaining a component of an inverter port voltage given value under a dq coordinate system through a PI regulator by making a difference between the inverter output current given value and an actual value, obtaining the inverter port voltage given value through theta-dominant Park inverse transformation, sending the value into a PWM module as a modulation wave to obtain an inverter driving signal, and controlling the output current of the inverter, so that the output power of the inverter is regulated.
Preferably, the vector current loop realizes decoupling of the active power and the reactive power output by the inverter by respectively controlling the currents in the dq coordinate system, and changes the active power output by the inverter and the reactive power output by the inverter by adjusting the given values of the d-axis current and the q-axis current output by the inverter.
Preferably, when an increase in grid frequency is detected, the inverter output d-axis current setpoint is reduced by the vector current loop; when the frequency of the power grid is detected to be reduced, the given value of the d-axis current output by the inverter is improved through the vector current loop.
Preferably, the inverter further comprises a saturation module, wherein the saturation module is electrically connected with a current output end of the inverter, and limits a d-axis current given value of the inverter between set upper and lower boundaries.
The invention provides an inverter active support power grid control system based on power synchronous control, which comprises the following modules:
module M1: detecting the frequency of a power grid in real time through a power synchronizing ring;
module M2: the power grid frequency is coupled with the set value of the active current output by the inverter, the adjustment quantity of the set value of the active current output by the inverter is generated according to the fluctuation of the power grid frequency, and the power grid is actively supported by changing the output power of the inverter.
Preferably, the module M1 comprises: the conversion from the power difference value to the frequency difference value is realized by synchronizing the power of the inverter and the power of the power grid by utilizing the power synchronization coefficient of the inverter, the obtained frequency deviation is summed with the power grid frequency given value, and the actual frequency of the power grid is obtained, wherein the power difference is the difference value between the given value of the active power output by the inverter and the actual value of the active power output by the inverter.
Preferably, the inverter comprises a power synchronizing ring and a vector current ring, synchronization information of a power grid is extracted through the power synchronizing ring, and the vector synchronizing ring controls output power of the inverter;
the method comprises the steps of obtaining a component of an inverter port voltage given value under a dq coordinate system through a PI regulator by making a difference between the inverter output current given value and an actual value, obtaining the inverter port voltage given value through theta-dominant Park inverse transformation, sending the value into a PWM module as a modulation wave to obtain an inverter driving signal, and controlling the output current of the inverter, so that the output power of the inverter is regulated.
Preferably, the vector current loop realizes decoupling of the active power and the reactive power output by the inverter by respectively controlling the currents in the dq coordinate system, and changes the active power output by the inverter and the reactive power output by the inverter by adjusting the given values of the d-axis current and the q-axis current output by the inverter;
when the rise of the power grid frequency is detected, the given value of the d-axis current output by the inverter is reduced through the vector current loop; when the frequency of the power grid is detected to be reduced, the given value of the d-axis current output by the inverter is improved through the vector current loop.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention utilizes the self characteristics and output of the power synchronizing ring to realize the detection of the power grid frequency, the power synchronizing ring is used as an indispensable element in the control strategy of the power synchronizing inverter, and the power grid state can be accurately monitored in real time by utilizing the additional function without measuring the element.
2. On the basis of power synchronizing ring detection, the invention couples the obtained power grid frequency with the given value of the active current output by the inverter in an integral relation, thereby realizing active power support when the power grid frequency fluctuates.
Other advantages of the present invention will be set forth in the description of specific technical features and solutions, by which those skilled in the art should understand the advantages that the technical features and solutions bring.
Drawings
Other features, objects and advantages of the present invention will become more apparent upon reading of the detailed description of non-limiting embodiments, given with reference to the accompanying drawings in which:
FIG. 1 is a power synchronizer ring control block diagram of the present invention;
FIG. 2 is a block diagram of an inverter vector current control of the present invention;
FIG. 3 is a graph of load power characteristics of the present invention;
FIG. 4 is a block diagram of a power synchronization loop based frequency support of the present invention;
fig. 5 is a graph of inverter output power ripple for grid frequency voltage dip of the present invention.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the present invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications could be made by those skilled in the art without departing from the inventive concept. These are all within the scope of the present invention.
The invention discloses an inverter active support power grid control method based on power synchronous control, which is characterized in that the actual frequency of a power grid can be detected through the frequency locking characteristic of a power synchronous ring in the power synchronous inverter by researching the structure of the power synchronous ring, and on the basis, the given value of active current output by the inverter is modified, and the active power and the frequency characteristic of the power grid are coupled together to realize the active support of the frequency of the power grid.
The inverter active support power grid control method based on the power synchronous control comprises the following steps: the power grid frequency is detected in real time through the power synchronizing ring, the power grid frequency is coupled with the set value of the active current output by the inverter, the adjustment quantity of the set value of the active current output by the inverter is generated according to the fluctuation of the power grid frequency, and the power grid is actively supported by changing the output power of the inverter.
Specifically, the structure of the power synchronizing ring is shown in fig. 1, in which p ref For the given value of the active power output by the inverter, p is the actual value of the active power output by the inverter, Δp is the difference between the given value and the actual value of the active power output by the inverter, S n For the rated capacity of the inverter Δp * K is the per-unit power difference p As the power synchronization coefficient, Δω is the frequency deviation amount, ω ref For a given value of the power grid frequency, ω is the power grid frequency detected by the power synchronizing ring, s is a frequency domain operation symbol, and θ is the output phase angle of the power synchronizing ring.
Compared with the traditional power synchronization control strategy, the inverter active support power grid control method and system based on the power synchronization control, which are applied by the patent, are based on the power synchronization ring, so that the real-time extraction of the power grid frequency is realized, and the power grid active support function under the condition of no detection element can be realized.
The invention firstly analyzes the structural model and the operation characteristic of the power synchronizing ring to obtain a conclusion that the power synchronizing ring can automatically realize the real-time monitoring of the power grid frequency in the process of locking the power grid phase; and then, on the basis of the measurement of the power synchronizing ring, according to the fluctuation of the power grid frequency, the adjustment quantity of the set value of the output active current of the inverter is given, so that the output power of the inverter is changed, and finally, the active supporting function of the inverter based on the power synchronizing control is realized. The specific implementation means are as follows:
1. real-time detection of grid frequency through a power synchronization loop
The conversion from the power difference value to the frequency difference value is realized by synchronizing the power of the inverter and the power of the power grid by utilizing the power synchronization coefficient of the inverter, the obtained frequency deviation is summed with the power grid frequency given value, and the actual frequency of the power grid is obtained, wherein the power difference is the difference value between the given value of the active power output by the inverter and the actual value of the active power output by the inverter.
The method comprises the following steps: in the transient power transfer process between synchronous motors, the generator transmits energy to the motor through reactance to form an electric energy transmission system, and the power of the system during stable operation can be recorded as:
Figure SMS_1
wherein U is INV For the output voltage of the generator port, U PCC For the voltage at the motor, X is the reactance. Delta is the power angle (i.e. the potential angle between two motors), when U INV Advanced U PCC When delta is positive, the generator supplies power to the motor.
In analogy to the above mechanism, the inverter may also be kept synchronized using a power-mediated control method. At this time, the inverter can be equivalently a generator, and the generated electric energy passes through a reactance (a filter inductance L f ) The synchronous transmission is transmitted to the motor side (namely the power grid side), and the synchronization between the power and the phase angle can be realized through the coupling interaction between the power and the phase angle. Therefore, the power synchronous control is characterized in that the inverter and the power grid are kept synchronous at the power level, and then the real-time phase tracking of the grid connection point is realized. The power synchronization loop structure shown in fig. 1 can be obtained, and the control rule of the output phase of the power synchronization loop is as follows:
Figure SMS_2
wherein p is ref The active power given value is output for the inverter, and the calculation formula is shown as (3); p is the actual value of the active power output by the inverter, and the calculation formula is shown in (4); s is S n For the rated capacity of the inverter, the calculation formula is shown as (5), ω is the power grid frequency detected by the power synchronizing ring, ω ref For a given value of the grid frequency, k p S is a frequency domain operation symbol, and θ is the output phase angle of the power synchronization ring.
Figure SMS_3
Wherein u is d I is the d-axis component of the common coupling node voltage after Park conversion dref Outputting d-axis current to inverterAnd (5) setting values.
p＝u a i a +u b i b +u c i c (4)
Wherein u is a 、u b 、u c As the voltage component of the common coupling node in the abc coordinate axis, i a 、i b 、i c And outputting a current component for the inverter under the abc coordinate axis.
Figure SMS_4
Wherein p is ref For the inverter to output active power given value, q ref And outputting reactive power set values for the inverter.
From (2), the power synchronization loop starts from the power level and uses the power synchronization coefficient k p The conversion from the power difference value to the frequency deviation is realized, the obtained frequency deviation is summed with the given value of the power grid frequency, the actual frequency of the power grid can be obtained, and the output phase of the power synchronous loop is obtained through integration, so that the successful phase locking of the power grid voltage is realized. Therefore, the power synchronous loop completes the phase locking function by integrating the frequency on the basis of successful frequency locking.
Therefore, when the function of locking the phase of the power grid is achieved, the power synchronization ring can actively detect and extract the state information of the power grid, and accurate and rapid measurement of the frequency of the power grid is achieved, so that an additional measurement link is not needed, the structure of the power synchronization ring is not needed to be improved, the on-line evaluation of the state of the power grid can be achieved, and a foundation is provided for subsequent qualitative and quantitative analysis of whether the power grid needs frequency support.
2. Active support of a power grid by varying the output power of an inverter
The inverter of a typical grid-connected inverter control strategy comprises a power synchronous ring and a vector current ring, wherein the power synchronous ring is used as a synchronous ring in the power synchronous inverter to finish the extraction of grid synchronous information, and the structure of the inverter is shown in figure 1. The vector current loop realizes the control of the output power of the inverter, and the specific structure is shown in figure 2, i in the figure dref And i qref Respectively dqCoordinate axis inverter output current setpoint, i d And i q Inverter output current actual values H respectively of dq coordinate axes i (s) is a PI controller, the concrete expression of which is shown as (6), u dref And u qref The voltage given value of the output port of the inverter respectively with dq coordinate axes, q is the output phase angle of the power synchronizing ring, i abc Three-phase currents are output for the inverter. The method comprises the steps that an inverter output current given value is differenced from an actual value, a component of an inverter port voltage given value under a dq coordinate system is obtained through a PI regulator, the inverter port voltage given value is obtained through q-dominant Park inverse transformation and is sent to a PWM module as a modulation wave to obtain an inverter driving signal, and accordingly the inverter output current is controlled to meet requirements.
Figure SMS_5
Wherein k is p For PI regulator scaling factor, k i Integrating the coefficients for the PI regulator.
The vector current loop can realize the rapid control of the amplitude and the phase of the output current of the inverter, and the decoupling of the active power and the reactive power of the output of the inverter can be realized through the respective control of the current under the dq coordinate system. The inverter output active power and reactive power can be written as:
Figure SMS_6
wherein u is d 、u q As voltage component of dq coordinate axis, i d 、i q Is the current component of the dq coordinate axis. From (7), the inverter outputs active power and reactive power which are respectively calculated by i d 、i q And (5) determining. Therefore, if the output power of the inverter is to be adjusted, only the d-axis current set value and the q-axis current set value of the output of the inverter are required to be adjusted respectively.
It is known that in high voltage systems the grid is mainly inductive, where the grid frequency is mainly determined by the active power and the grid voltage is mainly determined by the reactive power. And the system is powered onThe frequency deviation of the net is clearly required, and is usually not more than +/-1 Hz. It is therefore considered that the power system loads are normally operated around the rated frequency. Whereas near the nominal operating point, the active load frequency static characteristic of the load may be equivalently a monotonically increasing straight line. As shown in fig. 3, f represents the grid frequency, P represents the active power required by the load at different frequencies, f N Represents the rated frequency of the power grid, P N Indicating the active power required by the load at the rated frequency and voltage.
Analyzing the static characteristic of the active load frequency of the load, if the active power supplied by the power grid to the load is smaller than the rated power P required by the load at the rated frequency N The working frequency of the power grid is reduced, and the active power required by the load is reduced, namely the active power supply and demand balance under a low frequency level is achieved; if the active power supplied by the power grid to the load is greater than the rated power P required by the load at the rated frequency N The grid operating frequency is caused to rise, at which time the active power required by the load increases to achieve active power balance at high frequency levels.
Thus, if a decrease in grid frequency is detected, meaning that the grid active power is lost, it is desirable for the inverter to be able to increase the active power output; if an increase in grid frequency is detected, meaning that the grid active power is excessive, it is desirable for the inverter to be able to reduce the active power output. While the inverter outputs active power from i d It is decided that the d-axis current setpoint i of the inverter should be increased/decreased when the grid frequency decreases/increases, respectively dref When the frequency of the power grid fluctuates, the inverter supports the active power of the power grid. From this, the inverter output active current setpoint, taking into account grid frequency support, can be written as:
Figure SMS_7
the corresponding frequency support block diagram is shown in fig. 4. I in the figure dini For the initial set value of d-axis current output by the inverter, delta omega is the frequency deviation amount detected by the power synchronous ring, and k i-fre For the frequency adjustment coefficient, i dfre For d-axis current setpoint adjustment, i, due to grid frequency fluctuations dref And s is a frequency domain operation symbol for the actual d-axis current given value of the inverter.
If the actual frequency of the power grid is deviated from the rated frequency, namely delta omega is not 0, the frequency error is accumulated after passing through the frequency adjusting coefficient and the integrating unit, and the accumulated error is added to the d-axis current given value of the inverter, so that the coupling of the power grid frequency state and the active power output by the inverter is realized. However, if the power grid frequency deviates for a long time, the frequency error accumulated may cause the output current of the inverter to be too large, exceeding the rated current of the power electronic switching device, and further threatening the safe and stable operation of the inverter. Therefore, a saturation module is added to play a role in limiting amplitude, the d-axis current given value of the inverter is limited between the upper and lower limits given by people, and the breakdown risk of the switching tube is effectively reduced.
Combining the power synchronization loop of fig. 1 and the vector current loop of fig. 2 with the active support control link of fig. 4, an inverter active support power grid control system based on power synchronization control can be obtained, and power grid active power support without an additional power grid state monitoring link can be realized, and specific analysis is shown in embodiment example 1.
Example 1
The traditional power synchronization type control strategy only has the function of transmitting power in a steady state, and cannot provide power support for a power grid when the power grid frequency fluctuates, and the power synchronization control-based inverter active support power grid control method and system firstly analyze the self output characteristics of a power synchronization ring to obtain a conclusion, realize the phase locking function and simultaneously realize automatic extraction of the power grid frequency, and on the basis, change the given value of the active current output by the inverter in real time according to the fluctuation of the power grid state so as to adjust the output power of the inverter and actively support the power grid frequency. In order to prove the advantages of the invention, experimental verification is carried out, and when the occurrence frequency of the power grid drops, the change of the output active power of the inverter is shown in fig. 5. In the control system, the inverter outputs the initial set value i of the d-axis current dini At the level of 50A,q-axis current set point i qref at-30A, the frequency adjustment coefficient k i-fre 7.5, the upper limit of the saturation module is 65A, the lower limit is 35A, and the rated capacity S of the inverter n Power synchronization coefficient k of 30kVA p 200, grid frequency setpoint ω ref 100 PI, PI regulator scaling factor k p 18.756, integral coefficient k i For 23569.51, the d-axis component u of the common coupling node voltage d 311V. In the initial stage of system operation, the power grid frequency is rated value, and at the moment, the actual d-axis current of the inverter is given value i dref 50A, available from (7), the inverter output active power was 23.3kW. At 0.06s, the grid frequency drops from 50Hz to 49.5Hz, which is obtained by the control system parameters and the given value (8) of the output current taking the active supporting capability of the inverter into consideration, if the grid frequency is constantly maintained at a lower level, namely 49.5Hz, the given value i of the actual d-axis current is caused dref Continuously rising, eventually reaching and maintaining at the saturation module upper bound 65A, at which point the inverter output active power is 30.3kW. The simulation verifies the correctness of theory, and proves that the inverter active power support power grid control method based on power synchronous control can realize active power support of power grid frequency even under the condition of no measuring element.
The inverter active support power grid control method based on the power synchronization control provided by the invention is compared with the traditional power synchronization control strategy, and the power synchronization ring can be utilized to realize real-time extraction of the power grid state. Meanwhile, based on the monitored frequency characteristic of the power grid, the active supporting control strategy of the inverter is combined, and the given value of the active current output by the inverter is adjusted in real time, so that the power grid frequency is supported. The invention provides a brand new design and application thought for the grid-connected inverter active support strategy based on power synchronous control.
The invention also provides a power synchronization control-based inverter active support grid control system, which can be realized by executing the flow steps of the power synchronization control-based inverter active support grid control method, namely, a person skilled in the art can understand the power synchronization control-based inverter active support grid control method as a preferred implementation mode of the power synchronization control-based inverter active support grid control system.
An inverter active support power grid control system based on power synchronous control comprises the following modules:
module M1: and detecting the frequency of the power grid in real time through a power synchronizing ring.
The module M1 includes: the conversion from the power difference value to the frequency difference value is realized by synchronizing the power of the inverter and the power of the power grid by utilizing the power synchronization coefficient of the inverter, the obtained frequency deviation is summed with the power grid frequency given value, and the actual frequency of the power grid is obtained, wherein the power difference is the difference value between the given value of the active power output by the inverter and the actual value of the active power output by the inverter.
Module M2: the power grid frequency is coupled with the set value of the active current output by the inverter, the adjustment quantity of the set value of the active current output by the inverter is generated according to the fluctuation of the power grid frequency, and the power grid is actively supported by changing the output power of the inverter.
The inverter comprises a power synchronizing ring and a vector current ring, synchronization information of a power grid is extracted through the power synchronizing ring, and the vector synchronizing ring controls output power of the inverter.
The method comprises the steps of obtaining a component of an inverter port voltage given value under a dq coordinate system through a PI regulator by making a difference between the inverter output current given value and an actual value, obtaining the inverter port voltage given value through q-dominant Park inverse transformation, sending the value into a PWM module as a modulation wave to obtain an inverter driving signal, and controlling the output current of the inverter, thereby regulating the output power of the inverter.
The vector current loop realizes decoupling of the active power and the reactive power output by the inverter by respectively controlling the currents under the dq coordinate system, and changes the active power output by the inverter and the reactive power output by the inverter by adjusting the given value of the d-axis current and the q-axis current output by the inverter.
When the rise of the power grid frequency is detected, the given value of the d-axis current output by the inverter is reduced through the vector current loop; when the frequency of the power grid is detected to be reduced, the given value of the d-axis current output by the inverter is improved through the vector current loop.
The foregoing describes specific embodiments of the present invention. It is to be understood that the invention is not limited to the particular embodiments described above, and that various changes or modifications may be made by those skilled in the art within the scope of the appended claims without affecting the spirit of the invention. The embodiments of the present application and features in the embodiments may be combined with each other arbitrarily without conflict.

Claims (10)

1. An inverter active support power grid control method based on power synchronous control is characterized by comprising the following steps: the power grid frequency is detected in real time through the power synchronizing ring, the power grid frequency is coupled with the set value of the active current output by the inverter, the adjustment quantity of the set value of the active current output by the inverter is generated according to the fluctuation of the power grid frequency, and the power grid is actively supported by changing the output power of the inverter.
2. The method for controlling the inverter active support power grid based on the power synchronization control according to claim 1, wherein the real-time detection of the power grid frequency through the power synchronization loop comprises: the conversion from the power difference value to the frequency difference value is realized by synchronizing the power of the inverter and the power of the power grid by utilizing the power synchronization coefficient of the inverter, the obtained frequency deviation is summed with the power grid frequency given value, and the actual frequency of the power grid is obtained, wherein the power difference is the difference value between the given value of the active power output by the inverter and the actual value of the active power output by the inverter.
3. The method for controlling an inverter active support power grid based on power synchronization control according to claim 1, wherein the inverter comprises a power synchronization loop and a vector current loop, synchronization information of the power grid is extracted through the power synchronization loop, and the vector synchronization loop controls output power of the inverter;
the method comprises the steps of obtaining a component of an inverter port voltage given value under a dq coordinate system through a PI regulator by making a difference between the inverter output current given value and an actual value, obtaining the inverter port voltage given value through theta-dominant Park inverse transformation, sending the value into a PWM module as a modulation wave to obtain an inverter driving signal, and controlling the output current of the inverter, so that the output power of the inverter is regulated.
4. The method for controlling the inverter to actively support the power grid based on the power synchronous control according to claim 3, wherein the vector current loop realizes decoupling of the active power and the reactive power output by the inverter by controlling the currents under the dq coordinate system respectively, and changes the active power output by the inverter and the reactive power output by the inverter by adjusting the set values of the d-axis current and the q-axis current output by the inverter.
5. The method for controlling an inverter to actively support a power grid based on power synchronization control of claim 4 wherein when an increase in grid frequency is detected, the inverter output d-axis current setpoint is reduced by a vector current loop; when the frequency of the power grid is detected to be reduced, the given value of the d-axis current output by the inverter is improved through the vector current loop.
6. The method of claim 5, wherein the inverter further comprises a saturation module electrically connected to a current output terminal of the inverter to limit a d-axis current setpoint of the inverter between set upper and lower boundaries.
7. An inverter active support power grid control system based on power synchronous control is characterized by comprising the following modules:
module M1: detecting the frequency of a power grid in real time through a power synchronizing ring;
module M2: the power grid frequency is coupled with the set value of the active current output by the inverter, the adjustment quantity of the set value of the active current output by the inverter is generated according to the fluctuation of the power grid frequency, and the power grid is actively supported by changing the output power of the inverter.
8. The power synchronization control-based inverter active support grid control system of claim 7, wherein the module M1 comprises: the conversion from the power difference value to the frequency difference value is realized by synchronizing the power of the inverter and the power of the power grid by utilizing the power synchronization coefficient of the inverter, the obtained frequency deviation is summed with the power grid frequency given value, and the actual frequency of the power grid is obtained, wherein the power difference is the difference value between the given value of the active power output by the inverter and the actual value of the active power output by the inverter.
9. The power synchronization control-based inverter active support grid control system of claim 7, wherein the inverter comprises a power synchronization loop through which synchronization information of a grid is extracted and a vector current loop that controls an output power of the inverter;
the method comprises the steps of obtaining a component of an inverter port voltage given value under a dq coordinate system through a PI regulator by making a difference between the inverter output current given value and an actual value, obtaining the inverter port voltage given value through theta-dominant Park inverse transformation, sending the value into a PWM module as a modulation wave to obtain an inverter driving signal, and controlling the output current of the inverter, so that the output power of the inverter is regulated.
10. The inverter active support power grid control system based on power synchronous control according to claim 7, wherein the vector current loop realizes decoupling of the active power and the reactive power output by the inverter by controlling currents under a dq coordinate system respectively, and changes the active power output by the inverter and the reactive power output by the inverter by adjusting given values of d-axis current and q-axis current output by the inverter;
when the rise of the power grid frequency is detected, the given value of the d-axis current output by the inverter is reduced through the vector current loop; when the frequency of the power grid is detected to be reduced, the given value of the d-axis current output by the inverter is improved through the vector current loop.
CN202310103172.0A 2023-02-10 2023-02-10 Inverter active support power grid control method and system based on power synchronous control Pending CN116247724A (en)

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