Micro-grid bus frequency secondary recovery control method and system

Abstract

The invention provides a micro-grid bus frequency secondary recovery control method and system, and belongs to the field of micro-grid control. The method comprises the following steps: acquiring electrical parameters of a target microgrid; the electrical parameters comprise three-phase output voltage and three-phase output current of the distributed power supply, and equivalent resistance and equivalent inductance of a transmission line between the distributed power supply and a bus; determining a power angle between the bus voltage and the output voltage of the distributed power supply based on the electrical parameters; determining a bus voltage angular frequency based on the power angle and the angular frequency of the output voltage of the distributed power supply; and based on the rated value of the angular frequency of the controller in the target microgrid, the bus voltage angular frequency, the cut-off angular frequency of a low-pass filter in the distributed power supply, and the proportionality coefficient and the integral coefficient of a proportional-integral regulator in the distributed power supply, determining the output quantity of secondary recovery control of the bus frequency of the target microgrid. The control effect of the improved bus frequency secondary recovery control method is good.

Description

Technical Field

[0001] The present invention relates to the field of microgrid control technology, and in particular to a control method and system for secondary recovery of bus frequency in a microgrid. Background Art

[0002] As an independent power system composed of multiple distributed power sources and loads, microgrids can ensure uninterrupted power supply to loads in the region and achieve efficient use of renewable energy while meeting power quality and power supply safety. In microgrids based on droop or virtual synchronous generator (VSG) control, the bus voltage frequency will fluctuate with changes in load, and secondary control is needed to restore the bus frequency to the rated value to improve the bus voltage quality.

[0003] At present, the common bus frequency secondary recovery control method is mainly divided into two methods according to the source of the secondary control frequency feedback: bus frequency secondary recovery control method based on bus voltage sampling and bus frequency secondary recovery control method based on converter port frequency feedback. The bus frequency secondary recovery control method based on bus voltage sampling collects the microgrid bus voltage through a voltage sensor and transmits the bus voltage information to the controller of the distributed power source in the microgrid through a communication line. The bus voltage information is phase-locked by a phase-locked loop in the controller to obtain the bus voltage frequency and then used for bus frequency secondary recovery control. The bus frequency secondary recovery control method based on converter port frequency feedback approximates the distributed power port voltage frequency as the bus voltage frequency, so the distributed power port voltage is sampled to the controller and the bus voltage frequency approximation is obtained through the phase-locked loop as the feedback for bus frequency secondary recovery control.

[0004] However, the bus frequency secondary recovery control method based on bus voltage sampling requires the installation of voltage sensors at the microgrid bus and high-speed communication lines connected to distributed power sources, which is costly and has low reliability. When the bus is far away from the distributed power source, the communication line delay may deteriorate the bus frequency secondary recovery control effect. The bus frequency secondary recovery control method based on converter port frequency feedback does not obtain accurate bus voltage frequency values, so the control effect is poor, which may cause the bus frequency to exceed the limit and thus deteriorate the load power supply. Summary of the invention

[0005] The embodiments of the present invention provide a control method and system for secondary recovery of bus frequency in a microgrid, so as to solve the problem that the current control method for secondary recovery of bus frequency has poor effect.

[0006] In a first aspect, an embodiment of the present invention provides a control method for secondary recovery of a microgrid bus frequency, comprising:

[0007] Obtain the electrical parameters of the target microgrid; the electrical parameters include the three-phase output voltage and three-phase output current of the distributed power source, and the equivalent resistance and equivalent inductance of the transmission line between the distributed power source and the bus;

[0008] Based on the electrical parameters, determine the power angle between the bus voltage and the output voltage of the distributed power source;

[0009] Determine the bus voltage angular frequency based on the power angle and the angular frequency of the output voltage of the distributed power source;

[0010] Based on the rated value of the controller angular frequency in the target microgrid, the bus voltage angular frequency, the cut-off angular frequency of the low-pass filter in the distributed power source, and the proportional coefficient and integral coefficient of the proportional-integral regulator in the distributed power source, the output of the secondary recovery control of the bus frequency of the target microgrid is determined; wherein, the controller in the target microgrid is a proportional-integral regulator, and a low-pass filter is provided in the distributed power source.

[0011] In a possible implementation, determining a power angle between a bus voltage and an output voltage of a distributed power source based on an electrical parameter includes:

[0012] Convert the three-phase output voltage and the three-phase output current of the distributed power source into the output voltage and the output current of the distributed power source in the αβ coordinate system;

[0013] Based on the output voltage and output current of the distributed power source in the αβ coordinate system, the bus voltage in the αβ coordinate system is determined;

[0014] The power angle is determined based on the bus voltage and the distributed generation output voltage.

[0015] In a possible implementation, determining the power angle based on the bus voltage and the output voltage of the distributed power source includes:

[0016] Based on the output voltage and output current of the distributed power source in the αβ coordinate system, determine the active power output by the distributed power source;

[0017] The power angle is determined based on the active power, bus voltage and distributed generation output voltage.

[0018] In a possible implementation, the output voltage and output current of the distributed power supply in the αβ coordinate system are respectively:

[0019]

[0020] The bus voltage in the αβ coordinate system is:

[0021]

[0022] The effective value of bus voltage V in αβ coordinate system PCC for:

[0023]

[0024] The active power P output by the distributed power supply is:

[0025] P=v Cα i Oα +v Cβ i Oβ ;

[0026] Power angle δ i for:

[0027]

[0028] Where: v Ca 、v Cb 、v Cc are the three-phase output voltages of the distributed power supply, i Oa 、i Ob 、i Oc are the three-phase output current of the distributed power supply, R l is the equivalent resistance of the transmission line between the distributed generation and the busbar, L l is the equivalent inductance of the transmission line between the distributed generation and the bus, ω PCC0 is the rated value of the controller angular frequency, V C is the effective value of the distributed power supply output voltage.

[0029] In a possible implementation, the control method further includes:

[0030] The angular frequency of the primary controlled distributed power output is determined based on the low-pass filter cutoff angular frequency, the output of the target microgrid bus frequency secondary recovery control, the active power of the rated output of the distributed power, the rated value of the controller angular frequency and the active power output of the distributed power.

[0031] In a possible implementation, the control method further includes:

[0032] Based on the angular frequency of the primary-controlled distributed power output and the voltage amplitude of the primary-controlled distributed power output, a reference voltage of the primary-controlled distributed power output is determined.

[0033] In a possible implementation, the voltage amplitude output by the distributed power source is calculated based on a reactive primary control loop.

[0034] In a possible implementation, the angular frequency ω of the primary controlled distributed power output is i for:

[0035]

[0036] The reference voltage of the primary controlled distributed power supply output is:

[0037]

[0038] Among them, ω PCC0 is the rated value of the controller angular frequency, P0 is the rated output active power of the distributed power source, ω cω is the cut-off frequency of the low-pass filter, ΔP is the output of the secondary recovery control of the target microgrid bus frequency, P is the active power output of the distributed generation, m is the active droop control coefficient, s is the Laplace operator, E i is the voltage amplitude of the distributed power supply output.

[0039] In one possible implementation, the bus voltage angular frequency ω PCC for:

[0040] ω PCC =ω i -sδ i ;

[0041] The output ΔP of the secondary recovery control of the target microgrid bus frequency is:

[0042]

[0043] Among them, s is the Laplace operator, ω i is the angular frequency of the output voltage of the distributed power supply, δ i is the power angle, ω cω is the low-pass filter cutoff frequency, k p is the proportional integral regulator proportional coefficient, k i is the integral coefficient of the proportional integral regulator, ω PCC0 is the rated value of the controller angular frequency.

[0044] In a second aspect, an embodiment of the present invention provides a control system for secondary recovery of bus frequency of a microgrid, the control system comprising at least one distributed power source, a target microgrid, and a control device for secondary recovery of bus frequency of the target microgrid and the microgrid;

[0045] The distributed power source is connected to the busbar of the target microgrid through a low-pass filter and a transmission line. The voltage loop of the distributed power source adopts a proportional resonant controller, the current loop of the distributed power source adopts a proportional controller, and the output end of the distributed power source is equipped with a voltage sensor and a current sensor;

[0046] The target microgrid and the control device for secondary recovery of the microgrid bus frequency perform control on the target microgrid for secondary recovery of the bus frequency based on the control method for secondary recovery of the microgrid bus frequency of any one of the first aspects.

[0047] The embodiment of the present invention provides a control method and system for secondary recovery of bus frequency of a microgrid. First, the electrical parameters of the target microgrid are obtained. Then, based on the electrical parameters, the power angle between the bus voltage and the output voltage of the distributed power source is determined. Next, based on the power angle and the angular frequency of the output voltage of the distributed power source, the bus voltage angular frequency is determined. Finally, based on the rated value of the controller angular frequency in the target microgrid, the bus voltage angular frequency, the cutoff angular frequency of the low-pass filter in the distributed power source, and the proportional coefficient and integral coefficient of the proportional integral regulator in the distributed power source, the output of the secondary recovery control of the bus frequency of the target microgrid is determined. By collecting the output voltage and current of the distributed power source, and calculating the bus voltage according to the line impedance information, the voltage power angle at both ends of the transmission line is calculated according to the output active power of the distributed power source and the output voltage and bus voltage of the distributed power source, and the power angle is differentiated to obtain the bus voltage angular frequency. And the bus voltage angular frequency is used as a feedback quantity and the rated value of the bus voltage frequency to determine the output of the secondary recovery control of the bus frequency of the target microgrid. Therefore, the output of the secondary recovery control can be used as the compensation amount of the active power of the primary control to realize the secondary recovery control of the microgrid bus frequency. The control method can accurately determine the bus voltage angular frequency, so that the secondary recovery can be performed more accurately without causing the bus frequency to exceed the limit. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0049] Figure 1 This is an application scenario diagram of a control method for secondary recovery of a microgrid bus frequency provided by an embodiment of the present invention;

[0050] Figure 2 It is a flow chart for implementing a control method for secondary recovery of bus frequency of a microgrid provided by an embodiment of the present invention;

[0051] Figure 3 It is a strategy structure block diagram of a control method for secondary recovery of bus frequency of a microgrid provided by an embodiment of the present invention;

[0052] Figure 4It is a semi-physical experimental circuit diagram of bus frequency secondary recovery control of a single-bus structure microgrid composed of four distributed power sources provided by an embodiment of the present invention;

[0053] Figure 5 The embodiment of the present invention provides Figure 4 The estimated value of bus frequency of the four distributed generation units changes after the secondary recovery control of the microgrid bus frequency is started;

[0054] Figure 6 The embodiment of the present invention provides Figure 4 The bus frequency changes when the load increases or decreases after the secondary recovery control of the microgrid bus frequency is started;

[0055] Figure 7 is a structural schematic diagram of a control device for secondary recovery of bus frequency of a microgrid provided by an embodiment of the present invention;

[0056] Figure 8 It is a structural schematic diagram of a control system for secondary recovery of bus frequency of a microgrid provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0057] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0058] In order to make the purpose, technical solutions and advantages of the present invention more clear, specific embodiments will be described below in conjunction with the accompanying drawings.

[0059] Figure 1 This is an application scenario diagram of a single busbar structure microgrid applied in the present invention. Multiple distributed power sources are installed on a single busbar. The distributed power source voltage loop uses a PR controller, the current loop uses a P controller, and the primary control uses a droop control. Each distributed power source passes through an LC output filter (L f Inductor and C f The busbar is connected to the bus with a resistive load to simulate the actual active and reactive loads.

[0060] Please also see Figure 2 and Figure 3 , the implementation flow chart of the control method for secondary recovery of the microgrid bus frequency provided by the embodiment of the present invention is described in detail as follows:

[0061] S210: Obtain electrical parameters of the target microgrid.

[0062] The electrical parameters include the three-phase output voltage v of the distributed power supply Cabc , three-phase output current i Oabc , and the equivalent resistance R of the transmission line between the distributed generation and the bus l and equivalent inductance L l .

[0063] Distributed power supply output voltage v Cabc and the output current i Oabc The data is collected through the voltage sensor and current sensor installed at the output end of the distributed power source itself. There is no need to install a voltage sensor at the microgrid bus, which can reduce the control cost.

[0064] S220. Determine a power angle between a bus voltage and an output voltage of a distributed power source based on electrical parameters.

[0065] Before determining the power angle between the bus voltage and the distributed power output voltage, it is necessary to first determine the bus voltage and the distributed power output voltage. The voltage determination method is:

[0066] First, the three-phase output voltage v of the distributed power supply Cabc And the three-phase output current i Oabc The output voltage v of the distributed power supply converted to the αβ coordinate system Cαβ and the output current i Oαβ .

[0067]

[0068] v Ca 、v Cb 、v Cc are the three-phase output voltages of the distributed power supply, i Oa 、i Ob 、i Oc They are the three-phase output currents of distributed power sources.

[0069] Then, based on the output voltage and output current of the distributed generation in the αβ coordinate system, the bus voltage in the αβ coordinate system is determined.

[0070] Bus voltage v in αβ coordinate system PCCαβ for:

[0071]

[0072] The effective value of bus voltage V in αβ coordinate system PCC for:

[0073]

[0074] R lis the equivalent resistance of the transmission line between the distributed generation and the busbar, L l is the equivalent inductance of the transmission line between the distributed generation and the bus, ω PCC0 is the rated value of the controller angular frequency.

[0075] Next, based on the output voltage and output current of the distributed power source in the αβ coordinate system, the active power P output by the distributed power source is determined.

[0076] P=v Cα i Oα +v Cβ i Oβ ;

[0077] Finally, based on the active power, bus voltage and distributed generation output voltage, the power angle δ is determined. i .

[0078]

[0079] V C is the effective value of the distributed power supply output voltage.

[0080] S230. Determine the bus voltage angular frequency based on the power angle and the angular frequency of the output voltage of the distributed power source.

[0081] ω PCC =ω i -sδ i ;

[0082] Among them, ω i is the voltage angular frequency of the distributed power supply output, and s is the Laplace operator.

[0083] S240, based on the rated value of the controller angular frequency in the target microgrid, the bus voltage angular frequency, the cutoff angular frequency of the low-pass filter in the distributed power source, and the proportional coefficient and integral coefficient of the proportional-integral regulator in the distributed power source, determine the output of the secondary recovery control of the bus frequency of the target microgrid.

[0084] Among them, the controller in the target microgrid is a proportional-integral regulator, and a low-pass filter is provided in the distributed power source.

[0085] The output ΔP of the secondary recovery control of the target microgrid bus frequency is:

[0086]

[0087] ω cω is the low-pass filter cutoff frequency, k p is the proportional coefficient of the PI regulator, k i is the integral coefficient of the PI regulator, s is the Laplace operator, ω iis the angular frequency of the output voltage of the distributed power supply, δ i is the power angle, ω cω is the low-pass filter cutoff frequency, ω PCC0 is the rated value of the controller angular frequency.

[0088] In this embodiment, the frequency secondary recovery controller is in the form of a PI regulator.

[0089] The function of the low-pass filter is to filter out the ripple and noise generated when calculating the bus voltage angular frequency and the distributed power output active power.

[0090] The output of the secondary recovery control based on the target microgrid bus frequency, that is, the compensation amount of the primary control active power, can continue the primary control.

[0091] In some embodiments, the angular frequency of the primary controlled distributed power supply output can also be determined based on the output of the secondary recovery control based on the low-pass filter cutoff angular frequency, the target microgrid bus frequency, the active power of the rated output of the distributed power supply, the rated value of the controller angular frequency and the active power output of the distributed power supply.

[0092] The angular frequency ω of the primary controlled distributed power output i for:

[0093]

[0094] Among them, ω PCC0 is the rated value of the controller angular frequency, P0 is the rated output active power of the distributed power source, ω cω is the cutoff angular frequency of the low-pass filter, ΔP is the output of the secondary recovery control of the bus frequency of the target microgrid, P is the active power output of the distributed generation, m is the active droop control coefficient, and s is the Laplace operator.

[0095] In addition, the angular frequency ω of the distributed power output can also be controlled based on the primary control i The voltage amplitude of the distributed power supply output is used to determine the reference voltage of the distributed power supply output controlled once.

[0096] Specifically, the reference voltage of the primary controlled distributed power supply output is:

[0097]

[0098] E i is the voltage amplitude of the distributed power supply output.

[0099] The voltage amplitude E of the distributed power supply output iIt is calculated by the reactive primary control loop, and the reference voltage of the primary controlled distributed power supply output and the converter voltage and current double closed-loop control generate the modulation wave.

[0100] like Figure 3 As shown, the control strategy of the present invention is to input the output voltage and current of the distributed power supply and the equivalent inductance and equivalent resistance of the transmission line into the controller, calculate the bus voltage angular frequency through the designed frequency observer, and use it as feedback quantity and bus frequency rated value to participate in the secondary frequency recovery control, generate a primary control active power compensation quantity, and obtain the distributed power supply output voltage reference after primary control for use as the inner loop control to generate the modulation wave.

[0101] In order to verify the effectiveness of the control method for secondary recovery of the microgrid bus frequency provided by the present invention, a semi-physical experimental circuit for secondary recovery control of the bus frequency of a single-bus structure microgrid composed of four distributed power sources is used. Figure 4 shown.

[0102] Verification results such as Figure 5 and 6 As shown, from Figure 5 and 6 It can be seen from the figure that after the microgrid bus frequency secondary recovery control is started, the four distributed power sources can correctly estimate the bus frequency according to their port output state quantities and can correctly restore the bus frequency to 50Hz. Figure 5 It can be seen from the figure that the time from the start of secondary control to the basic recovery of frequency is 0.8 seconds to 2.8 seconds, the adjustment time is about 2 seconds and there is no overshoot. Figure 6 It can be seen that when the load changes, the control method can maintain the bus frequency stable, the adjustment time is about from 0.8 seconds to 1.6 seconds, the adjustment time is 0.8s and the frequency does not exceed the limit, which can meet the load power supply requirements. Among them, the grid frequency fluctuation range is 50±0.2Hz.

[0103] The control method for secondary recovery of bus frequency of a microgrid provided by the present invention first obtains the electrical parameters of the target microgrid. Then, based on the electrical parameters, the power angle between the bus voltage and the output voltage of the distributed power source is determined. Next, based on the power angle and the angular frequency of the output voltage of the distributed power source, the bus voltage angular frequency is determined. Finally, based on the rated value of the controller angular frequency in the target microgrid, the bus voltage angular frequency, the cutoff angular frequency of the low-pass filter in the distributed power source, and the proportional coefficient and integral coefficient of the proportional integral regulator in the distributed power source, the output of the secondary recovery control of the bus frequency of the target microgrid is determined. By collecting the output voltage and current of the distributed power source, and calculating the bus voltage according to the line impedance information, the voltage power angle at both ends of the transmission line is calculated according to the output active power of the distributed power source and the output voltage and bus voltage of the distributed power source, and the bus voltage angular frequency is obtained by differentiating the power angle. And the bus voltage angular frequency is used as the feedback amount and the rated value of the bus voltage frequency to determine the output of the secondary recovery control of the bus frequency of the target microgrid. Thus, the output of the secondary recovery control can be used as the compensation amount of the active power of the primary control to realize the control of the secondary recovery of the bus frequency of the microgrid. The control method can accurately determine the bus voltage angular frequency, so that secondary recovery can be performed more accurately without causing the bus frequency to exceed the limit.

[0104] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0105] The following is an embodiment of the device of the present invention. For details not described in detail therein, reference may be made to the corresponding method embodiment described above.

[0106] Figure 7 The structure diagram of the control device for secondary recovery of the bus frequency of a microgrid provided by an embodiment of the present invention is shown. For the convenience of explanation, only the part related to the embodiment of the present invention is shown, which is described in detail as follows:

[0107] like Figure 7 As shown, the control device 700 for secondary recovery of the microgrid bus frequency includes:

[0108] The acquisition module 710 is used to acquire the electrical parameters of the target microgrid; the electrical parameters include the three-phase output voltage and the three-phase output current of the distributed power source, and the equivalent resistance and equivalent inductance of the transmission line between the distributed power source and the bus;

[0109] A first determination module 720 is used to determine a power angle between a bus voltage and an output voltage of a distributed power source based on electrical parameters;

[0110] A second determination module 730 is used to determine the bus voltage angular frequency based on the power angle and the angular frequency of the output voltage of the distributed power source;

[0111] The third determination module 740 is used to determine the output of the secondary recovery control of the bus frequency of the target microgrid based on the rated value of the controller angular frequency in the target microgrid, the bus voltage angular frequency, the cutoff angular frequency of the low-pass filter in the distributed power source, and the proportional coefficient and integral coefficient of the proportional-integral regulator in the distributed power source; wherein the controller in the target microgrid is a proportional-integral regulator, and a low-pass filter is provided in the distributed power source.

[0112] In a possible implementation, the first determination module 720 is used to convert the three-phase output voltage and the three-phase output current of the distributed power source into the output voltage and the output current of the distributed power source in the αβ coordinate system;

[0113] Based on the output voltage and output current of the distributed power source in the αβ coordinate system, the bus voltage in the αβ coordinate system is determined;

[0114] The power angle is determined based on the bus voltage and the distributed generation output voltage.

[0115] In a possible implementation, the first determination module 720 is configured to determine the active power output by the distributed power source based on the output voltage and output current of the distributed power source in the αβ coordinate system;

[0116] The power angle is determined based on the active power, bus voltage and distributed generation output voltage.

[0117] In a possible implementation, the output voltage and output current of the distributed power supply in the αβ coordinate system are respectively:

[0118]

[0119] The bus voltage in the αβ coordinate system is:

[0120]

[0121] The effective value of bus voltage V in αβ coordinate system PCC for:

[0122]

[0123] The active power P output by the distributed power supply is:

[0124] P=v Cα i Oα +v Cβ i Oβ ;

[0125] Power angle δi for:

[0126]

[0127] Where: v Ca 、v Cb 、v Cc are the three-phase output voltages of the distributed power supply, i Oa 、i Ob 、i Oc are the three-phase output current of the distributed power supply, R l is the equivalent resistance of the transmission line between the distributed generation and the busbar, L l is the equivalent inductance of the transmission line between the distributed generation and the bus, ω PCC0 is the rated value of the controller angular frequency, V C is the effective value of the distributed power supply output voltage.

[0128] In one possible implementation, the third determination module 740 is used to determine the angular frequency of the primary controlled distributed power supply output based on the low-pass filter cutoff angular frequency, the output of the secondary recovery control of the target microgrid bus frequency, the rated active power of the distributed power supply output, the rated value of the controller angular frequency and the active power output of the distributed power supply.

[0129] In a possible implementation, the third determination module 740 is configured to determine a reference voltage output by the primary controlled distributed power source based on an angular frequency output by the primary controlled distributed power source and a voltage amplitude output by the distributed power source.

[0130] In one possible implementation, the voltage amplitude output by the distributed power source is calculated based on the reactive primary control loop.

[0131] In a possible implementation, the angular frequency ω of the primary controlled distributed power output is i for:

[0132]

[0133] The reference voltage of the primary controlled distributed power supply output is:

[0134]

[0135] Among them, ω PCC0 is the rated value of the controller angular frequency, P0 is the rated output active power of the distributed power source, ω cω is the cutoff frequency of the low-pass filter, ΔP is the output of the secondary recovery control of the target microgrid bus frequency, P is the active power output of the distributed generation, m is the droop control coefficient, s is the Laplace operator, Ei is the voltage amplitude of the distributed power supply output.

[0136] In one possible implementation, the bus voltage angular frequency ω PCC for:

[0137] ω PCC =ω i -sδ i ;

[0138] The output ΔP of the secondary recovery control of the target microgrid bus frequency is:

[0139]

[0140] Among them, s is the Laplace operator, ω i is the angular frequency of the output voltage of the distributed power supply, δ i is the power angle, ω cω is the low-pass filter cutoff frequency, k p is the proportional integral regulator proportional coefficient, k i is the integral coefficient of the proportional integral regulator, ω PCC0 is the rated value of the controller angular frequency.

[0141] In a third aspect, the present invention further provides a control system for secondary recovery of bus frequency of a microgrid, the control system comprising at least one distributed power source, a target microgrid, and a control device for secondary recovery of bus frequency of the target microgrid and the microgrid;

[0142] The distributed power source is connected to the busbar of the target microgrid through a low-pass filter and a transmission line. The voltage loop of the distributed power source adopts a proportional resonant controller, the current loop of the distributed power source adopts a proportional controller, and the output end of the distributed power source is equipped with a voltage sensor and a current sensor.

[0143] The target microgrid and the control device for secondary recovery of the microgrid bus frequency perform control on the target microgrid for secondary recovery of the bus frequency based on the control method for secondary recovery of the microgrid bus frequency of any one of the first aspects.

[0144] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0145] Those of ordinary skill in the art will appreciate that the templates, units, and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0146] If the module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, it can implement the steps of the embodiment of the evaluation method for the adequacy of the distribution network in which each electric vehicle and distributed photovoltaic participate. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device that can carry the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory, random access memory, electric carrier signal, telecommunication signal and software distribution medium.

[0147] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A control method for secondary recovery of bus frequency of a microgrid, characterized in that: include: Obtaining electrical parameters of the target microgrid; the electrical parameters include the three-phase output voltage and three-phase output current of the distributed power source, and the equivalent resistance and equivalent inductance of the transmission line between the distributed power source and the bus; Based on the electrical parameters, determining a power angle between a bus voltage and an output voltage of a distributed power source; Determining the bus voltage angular frequency based on the power angle and the angular frequency of the output voltage of the distributed power source; Based on the rated value of the controller angular frequency in the target microgrid, the bus voltage angular frequency, the cutoff angular frequency of the low-pass filter in the distributed power source, and the proportional coefficient and integral coefficient of the proportional-integral regulator in the distributed power source, the output of the secondary recovery control of the bus frequency of the target microgrid is determined; wherein, the controller in the target microgrid is a proportional-integral regulator, and a low-pass filter is provided in the distributed power source.

2. The control method for secondary recovery of microgrid bus frequency according to claim 1, characterized in that: The determining the power angle between the bus voltage and the output voltage of the distributed power source based on the electrical parameter includes: Converting the three-phase output voltage and the three-phase output current of the distributed power source into the output voltage and the output current of the distributed power source in the αβ coordinate system; Determine the bus voltage in the αβ coordinate system based on the output voltage and output current of the distributed power supply in the αβ coordinate system; The power angle is determined based on the bus voltage and the output voltage of the distributed power supply.

3. The control method for secondary recovery of microgrid bus frequency according to claim 2, characterized in that: The determining the power angle based on the bus voltage and the distributed power supply output voltage comprises: Determine the active power output by the distributed power source based on the output voltage and output current of the distributed power source in the αβ coordinate system; The power angle is determined based on the active power, the bus voltage and the output voltage of the distributed power supply.

4. The control method for secondary recovery of microgrid bus frequency according to claim 3 is characterized in that: The output voltage and output current of the distributed power supply in the αβ coordinate system are: The bus voltage in the αβ coordinate system is: The effective value V of the bus voltage in the αβ coordinate system PCC for: The active power P output by the distributed power supply is: P=v Cα i Oα +v Cβ i Oβ ; The power angle δ i for: Where: v Ca 、v Cb 、v Cc are the three-phase output voltages of the distributed power supply, i Oa 、i Ob 、i Oc are the three-phase output current of the distributed power supply, R l is the equivalent resistance of the transmission line between the distributed generation and the busbar, L l is the equivalent inductance of the transmission line between the distributed generation and the bus, ω PCC0 is the rated value of the controller angular frequency, V C is the effective value of the distributed power supply output voltage.

5. The control method for secondary recovery of microgrid bus frequency according to claim 1, characterized in that: The control method further comprises: Based on the low-pass filter cutoff angular frequency, the output of the target microgrid bus frequency secondary recovery control, the active power of the rated output of the distributed power source, the rated value of the controller angular frequency and the active power output of the distributed power source, the angular frequency of the primary controlled distributed power source output is determined.

6. The control method for secondary recovery of microgrid bus frequency according to claim 5, characterized in that: The control method further comprises: Based on the angular frequency of the primary-controlled distributed power supply output and the voltage amplitude of the primary-controlled distributed power supply output, a reference voltage of the primary-controlled distributed power supply output is determined.

7. The control method for secondary recovery of microgrid bus frequency according to claim 6, characterized in that: The voltage amplitude output by the distributed power source is calculated based on the reactive primary control loop.

8. The control method for secondary recovery of microgrid bus frequency according to claim 6, characterized in that: The angular frequency ω of the primary controlled distributed power output i for: The reference voltage output by the primary controlled distributed power supply is: Among them, ω PCC0 is the rated value of the controller angular frequency, P0 is the rated output active power of the distributed power source, ω cω is the cut-off angular frequency of the low-pass filter, ΔP is the output of the secondary recovery control of the bus frequency of the target microgrid, P is the active power output of the distributed power source, m is the active droop control coefficient, s is the Laplace operator, E i is the voltage amplitude of the distributed power supply output.

9. The control method for secondary recovery of the microgrid bus frequency according to any one of claims 1 to 8, characterized in that: The bus voltage angular frequency ω PCC for: oh PCC =ω i -sδ i ; The output ΔP of the secondary recovery control of the target microgrid bus frequency is: Among them, s is the Laplace operator, ω i is the angular frequency of the output voltage of the distributed power supply, δ i is the power angle, ω cω is the low-pass filter cutoff frequency, k p is the proportional integral regulator proportional coefficient, k i is the integral coefficient of the proportional integral regulator, ω PCC0 is the rated value of the controller angular frequency.

10. A control system for secondary recovery of bus frequency in a microgrid, characterized in that: The control system includes at least one distributed power source, a target microgrid, and a control device for secondary recovery of the microgrid bus frequency; The distributed power source is connected to the busbar of the target microgrid through a low-pass filter and a transmission line, the voltage loop of the distributed power source adopts a proportional resonant controller, the current loop of the distributed power source adopts a proportional controller, and the output end of the distributed power source is equipped with a voltage sensor and a current sensor; The control device for secondary recovery of the bus frequency of the microgrid controls the secondary recovery of the bus frequency of the target microgrid based on the control method for secondary recovery of the bus frequency of the microgrid described in any one of claims 1 to 9.

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