Inverter grid-connected operation control method and system based on active power angle droop control

Abstract

The present invention provides an inverter grid-connected operation control method and system based on active phase angle droop control, belonging to the technical field of microgrid operation control. The active power reference value and the actual active power value of the DG unit are collected; the difference between the reference value and the actual value is obtained; by using a coordinate transformation phase angle controller and combining the difference, a coordinate transformation phase angle compensation value is obtained; the coordinate transformation phase angle compensation value is superimposed on the original phase angle value; based on the superimposed phase angle, an inverse Park transformation is performed; the three-phase modulation voltage signal obtained by the inverse Park transformation is used to control the output of the DG unit through the SPWM modulation strategy, thereby adjusting the output active power. By adding a coordinate transformation phase angle controller, the present invention realizes the zero-error adjustment of the active power of each DG while retaining the active phase angle droop control structure.

Description

Technical Field

[0001] The present invention relates to the technical field of microgrid operation control, and particularly to an inverter grid-connected operation control method and system based on active power phase angle droop control. Background Art

[0002] A microgrid (Micro-Grid, MG), also known as a microgrid, refers to a small power generation and distribution system composed of distributed power sources, energy storage devices, energy conversion devices, loads, monitoring and protection devices, etc. A microgrid is an autonomous system that can achieve self-control, protection, and management, and can operate either grid-connected with the external power grid or independently (i.e., island operation). The control strategy during the grid-connected operation of a microgrid is very important for the stable operation of both the large power grid and the microgrid.

[0003] In the existing control technologies, during the off-grid operation of a microgrid, active power phase angle droop control is mostly adopted, and the phase angle is used as the droop amount to control the power output of DG (Distributed Generation, DG). The purpose of adopting droop control is to make the inverter simulate the operating characteristics of a synchronous generator. Similar to the parallel operation or grid-connected operation of synchronous generators, droop control can be used for the parallel operation of multiple inverters to achieve reasonable power distribution between inverters or power distribution between the inverter and the power grid.

[0004] In the control of microgrid grid-connected operation, the mainstream control method is to adopt PQ control with adjustable active and reactive power. This control includes a power outer loop and a voltage and current inner loop. Its purpose is to decouple the control of active and reactive power, make the output power track its reference signal in real time, and the large power grid provides frequency and voltage support, and each DG does not participate in voltage and frequency adjustment. However, when the microgrid switches from off-grid to grid-connected operation, the microgrid adopting active power phase angle droop needs to switch the control to PQ control, and the control structure changes significantly. Summary of the Invention

[0005] The purpose of the present invention is to provide an inverter grid-connected operation control method and system based on active power phase angle droop control that retains the active power phase angle droop control structure and enables the inverter to output active power without error adjustment, so as to solve at least one of the technical problems in the above background art.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] On the one hand, the present invention provides an inverter grid-connected operation control method based on active power phase angle droop control, which retains the control structure of active power phase angle droop and operates grid-connected; the method includes:

[0008] Collect the reference value and actual value of the active power of the DG unit;

[0009] The difference between the reference value and the actual value is obtained to get the difference value;

[0010] Using the coordinate transformation phase angle controller, combined with the difference value, the coordinate transformation phase angle compensation value is obtained;

[0011] The coordinate transformation phase angle compensation value is superimposed on the original phase angle value;

[0012] Based on the superimposed phase angle, the inverse Park transformation is performed;

[0013] The three-phase modulation voltage signal obtained by the inverse Park transformation is used to control the output of the DG unit through the SPWM modulation strategy, and then the output active power is adjusted.

[0014] Preferably, the control structure of active power angle droop is retained for grid-connected operation, including: when operating off-grid, the microgrid adopts the active power angle droop control strategy; when switching to grid-connected operation, the control structure of the microgrid remains unchanged, and the control structure of active power angle droop is retained.

[0015] Preferably, using the coordinate transformation phase angle controller, combined with the difference value, the coordinate transformation phase angle compensation value is obtained, including calculating the coordinate transformation phase angle compensation value according to the following formula:

[0016] θ' = ∫(K P (P refi -P i ) + K I ∫(P refi -P i )dt)dt;

[0017] Among them, θ' is the compensated phase angle value, K P and K I are the proportional gain coefficient and integral gain coefficient of the coordinate transformation phase angle controller respectively, P refi represents the active power reference value of the i-th DG unit, P i represents the actual active power value output by the i-th DG unit, and t represents time.

[0018] Preferably, the coordinate transformation phase angle compensation value is superimposed on the original phase angle value according to the following formula:

[0019]

[0020] Among them, θ is the phase angle reference value of the inverse Park transformation, θ 0 is the original phase angle value of the system, and f is the standard frequency of 50Hz.

[0021] Preferably, the inverse Park transformation is performed using the phase angle reference value according to the following formula:

[0022]

[0023] Among them, V a , V b , V c are respectively the voltages in the three-phase stationary coordinate system, and V d , V q , V 0 are respectively the voltages in the synchronous rotating coordinate system.

[0024] Preferably, the obtained three-phase modulated voltage signal controls the output of the DG unit through the SPWM modulation strategy, and further adjusts the output active power, including: during grid-connected operation, if the active power reference value of the DG is not equal to the actual value of the output, the difference is obtained through the coordinate transformation phase angle controller to obtain the coordinate transformation phase angle compensation value, which is compensated to the original coordinate transformation phase angle value. If the difference is positive, the coordinate transformation phase angle reference value is made larger, and the three-phase voltage modulation signal after the Park inverse transformation controls the output of the DG through the SPWM modulation strategy, so that the output active power becomes larger. On the contrary, if the difference is negative, the coordinate transformation phase angle reference value becomes smaller, and the active power output by the DG becomes smaller until there is no difference in active power.

[0025] In a second aspect, the present invention provides an inverter grid-connected operation control system based on active phase angle droop control, which retains the control structure of active phase angle droop for grid-connected operation; the system includes:

[0026] An acquisition module for acquiring the active power reference value and the actual value of the active power of the DG unit;

[0027] A difference module for obtaining the difference by subtracting the reference value from the actual value;

[0028] A compensation module for using the coordinate transformation phase angle controller and combining the difference to obtain the coordinate transformation phase angle compensation value;

[0029] A superposition module for superposing the coordinate transformation phase angle compensation value on the original phase angle value;

[0030] A transformation module for performing the Park inverse transformation based on the superposed phase angle;

[0031] A control module for controlling the output of the DG unit through the SPWM modulation strategy for the three-phase modulated voltage signal obtained by the Park inverse transformation, and further adjusting the output active power.

[0032] In a third aspect, the present invention provides a non-transitory computer-readable storage medium, and the non-transitory computer-readable storage medium is used to store computer instructions, and when the computer instructions are executed by a processor, the inverter grid-connected operation control method based on active phase angle droop control as described above is implemented.

[0033] Fourthly, the present invention provides a computer program product, including a computer program which, when running on one or more processors, is used to implement the inverter grid-connected operation control method based on active phase angle droop control as described above.

[0034] Fifthly, the present invention provides an electronic device, including: a processor, a memory, and a computer program; wherein, the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device runs, the processor executes the computer program stored in the memory, so that the electronic device executes an instruction for implementing the inverter grid-connected operation control method based on active phase angle droop control as described above.

[0035] Advantages of the present invention: By adding a coordinate transformation phase angle controller, while retaining the active phase angle droop control structure, the active power of each DG can be adjusted without error.

[0036] The advantages of the additional aspects of the present invention will be more clearly given in the following description part, or can be learned through the practice of the present invention. Description of the Drawings

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0038] Figure 1 It is a flowchart of the inverter grid-connected operation control method based on active phase angle droop control described in Embodiment 3 of the present invention.

[0039] Figure 2 It is a control block diagram of the inverter grid-connected operation control method based on active phase angle droop control described in Embodiment 3 of the present invention.

[0040] Figure 3 It is a schematic diagram of a microgrid of the inverter grid-connected operation control method based on active phase angle droop control described in Embodiment 3 of the present invention.

[0041] Figure 4 It is a schematic diagram of a microgrid of the inverter grid-connected operation control method based on active phase angle droop control described in Embodiment 4 of the present invention.

[0042] Figure 5 It is a diagram of the change of the output active power of the inverter grid-connected operation control method based on active phase angle droop control described in Embodiment 4 of the present invention. Detailed Embodiments

[0043] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

[0044] Those skilled in the art of the present technology can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of those of ordinary skill in the art to which the present invention pertains.

[0045] It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with their meaning in the context of the prior art, and will not be interpreted in an idealized or overly formal sense unless defined as herein.

[0046] Those skilled in the art of the present technology can understand that, unless specifically stated otherwise, the singular forms "a", "an", "the", and "said" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the specification of the present invention means the presence of the described features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, and / or their groups.

[0047] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. Moreover, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, without conflict, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples.

[0048] For ease of understanding the present invention, the present invention will be further explained below with reference to the accompanying drawings by means of specific embodiments, and the specific embodiments do not constitute a limitation on the embodiments of the present invention.

[0049] Those skilled in the art should understand that the drawings are only schematic diagrams of the embodiments, and the components in the drawings are not necessarily essential for implementing the present invention.

[0050] Embodiment 1

[0051] Embodiment 1 of the present invention provides an inverter grid-connected operation control system based on active phase angle droop control, retaining the control structure of active phase angle droop for grid-connected operation; the system includes:

[0052] The acquisition module is used to acquire the reference value and the actual value of the active power of the DG unit;

[0053] The difference-making module is used to subtract the actual value from the reference value to obtain a difference value;

[0054] The compensation module is used to utilize the coordinate transformation phase angle controller and combine the difference value to obtain the coordinate transformation phase angle compensation value;

[0055] The superposition module is used to superpose the coordinate transformation phase angle compensation value onto the original phase angle value;

[0056] The transformation module is used to perform the inverse Park transformation based on the superposed phase angle;

[0057] The control module is used to control the output of the DG unit by means of the SPWM modulation strategy for the three-phase modulation voltage signal obtained from the inverse Park transformation, and thus adjust the output active power.

[0058] In the first embodiment, by using the above system, an inverter grid-connected operation control method based on active power phase angle droop control is realized, and the grid-connected operation is carried out while retaining the control structure of active power phase angle droop; it includes:

[0059] Utilize the acquisition module to acquire the reference value and the actual value of the active power of the DG unit;

[0060] Utilize the difference-making module to subtract the actual value from the reference value to obtain a difference value;

[0061] Utilize the compensation module to utilize the coordinate transformation phase angle controller and combine the difference value to obtain the coordinate transformation phase angle compensation value;

[0062] Utilize the superposition module to superpose the coordinate transformation phase angle compensation value onto the original phase angle value;

[0063] Utilize the transformation module to perform the inverse Park transformation based on the superposed phase angle;

[0064] Utilize the control module to control the output of the DG unit by means of the SPWM modulation strategy for the three-phase modulation voltage signal obtained from the inverse Park transformation, and thus adjust the output active power.

[0065] Among them, the grid-connected operation while retaining the control structure of active power phase angle droop includes: when operating off-grid, the microgrid adopts the active power phase angle droop control strategy; when switching to grid-connected operation, the microgrid does not change the control structure and retains the active power phase angle droop control structure.

[0066] Utilize the coordinate transformation phase angle controller and combine the difference value to obtain the coordinate transformation phase angle compensation value, including calculating the coordinate transformation phase angle compensation value according to the following formula:

[0067] θ' = ∫(K P(P refi -P i ) + K I ∫(P refi -P i )dt)dt;

[0068] where θ' is the compensated phase angle value, K P and K I are the proportional gain coefficient and integral gain coefficient of the coordinate transformation phase angle controller respectively, P refi represents the active power reference value of the i-th DG unit, and P i represents the actual active power output by the i-th DG unit, and t represents time.

[0069] The coordinate transformation phase angle compensation value is superimposed on the original phase angle value according to the following formula:

[0070]

[0071] where θ is the phase angle reference value of the Park inverse transformation, and θ 0 is the original phase angle value of the system, and f is the standard frequency of 50 Hz.

[0072] The Park inverse transformation is performed using the phase angle reference value according to the following formula:

[0073]

[0074] where V a , V b , V c are the voltages in the three-phase stationary coordinate system respectively, and V d , V q , V 0 are the voltages in the synchronous rotating coordinate system respectively.

[0075] The transformed three-phase modulation voltage signal controls the output of the DG unit through the SPWM modulation strategy, and further adjusts the output active power, including: during grid-connected operation, if the active power reference value of the DG is not equal to the actual value of the output, the difference is obtained through the coordinate transformation phase angle controller to obtain the coordinate transformation phase angle compensation value, which is compensated to the original coordinate transformation phase angle value. If the difference is positive, the coordinate transformation phase angle reference value is made larger, and the three-phase voltage modulation signal after the Park inverse transformation controls the output of the DG through the SPWM modulation strategy, so that the output active power becomes larger. Conversely, if the difference is negative, the coordinate transformation phase angle reference value becomes smaller, and the active power output by the DG becomes smaller until there is no difference in active power.

[0076] Embodiment 2

[0077] In this Embodiment 2, a grid-connected operation control method for an inverter based on active phase angle droop control is provided, including the following steps:

[0078] Keep the control structure of active phase angle droop for grid-connected operation;

[0079] Collect the difference between the reference value and the actual output value of the active power of the DG unit;

[0080] Input the difference into the coordinate transformation phase angle controller to obtain the coordinate transformation phase angle compensation value;

[0081] Superimpose the coordinate transformation phase angle compensation value on the original phase angle value as the phase angle input for Park inverse transformation;

[0082] The transformed three-phase modulation voltage signal controls the output of the DG unit through the SPWM modulation strategy, thereby adjusting the output active power.

[0083] The so-called keeping the control structure of active phase angle droop for grid-connected operation means that when operating off-grid, the microgrid adopts the active phase angle droop control strategy. When switching to grid-connected operation, the microgrid does not change the control structure and retains the active phase angle droop control structure.

[0084] When inputting the difference into the coordinate transformation phase angle controller to obtain the coordinate transformation phase angle compensation value, the coordinate transformation phase angle controller is a proportional-integral controller, and the coordinate transformation phase angle compensation value is calculated according to the following formula:

[0085] Use the proportional-integral controller to obtain the coordinate transformation phase angle compensation value according to formula (1):

[0086] θ' = ∫(K P (P refi - P i ) + K I ∫(P refi - P i )dt)dt (1)

[0087] Where θ' is the compensated phase angle value, K P and K I are the proportional gain coefficient and integral gain coefficient of the coordinate transformation phase angle controller respectively.

[0088] When superimposing the coordinate transformation phase angle compensation value on the original phase angle value as the phase angle input for Park inverse transformation, it includes the following calculation formula:

[0089] The coordinate transformation phase angle compensation value is superimposed on the original phase angle value according to formula (2):

[0090]

[0091] Perform the Park inverse transformation according to the formula (3) using the phase angle reference value:

[0092]

[0093] where θ is the phase angle reference value for the Park inverse transformation, θ 0 is the original phase angle value of the system, f is the standard frequency of 50 Hz, V a 、V b 、V c are the voltages in the three-phase stationary coordinate system respectively, and V d 、V q 、V 0 are the voltages in the synchronous rotating coordinate system respectively.

[0094] The three-phase modulated voltage signals obtained by the above transformation are used to control the output of the DG unit through the SPWM modulation strategy, and then the output active power is adjusted, including:

[0095] During grid-connected operation, if the active power reference value of the DG is not equal to the actual value of the output, the difference is obtained as the coordinate transformation phase angle compensation value after passing through the coordinate transformation phase angle controller and compensated to the original coordinate transformation phase angle value. If the difference is positive, the coordinate transformation phase angle reference value is made larger, and the three-phase voltage modulation signals after the Park inverse transformation are used to control the output of the DG through the SPWM modulation strategy, so that the output active power becomes larger. Conversely, if the difference is negative, the coordinate transformation phase angle reference value becomes smaller, and the active power output by the DG becomes smaller until there is no difference in active power.

[0096] Embodiment 3

[0097] In this Embodiment 3, a grid-connected operation control method for an inverter based on active power phase angle droop control is provided, aiming to add a coordinate transformation phase angle controller to the coordinate transformation control part of each DG. The regulator adjusts the coordinate transformation phase angle reference value of each DG according to the difference between the active power reference value and the actual value to control the output of the active power, so that the inverter can achieve the zero-difference regulation of the active power.

[0098] Refer to Figure 1 、 Figure 2 and Figure 3 As shown, the method described in this embodiment includes the following steps:

[0099] Step S1: Retain the control structure of the active power phase angle droop for grid-connected operation. The control structure is as Figure 3 shown, which means that when operating off-grid, the microgrid adopts the active power phase angle droop control strategy. When switching to grid-connected operation, the microgrid does not change the control structure. The active power phase angle droop control includes the following calculation according to the formula:

[0100] The droop formula calculates the active phase angle reference value and the reactive voltage reference value according to formula (4):

[0101]

[0102] Calculate the d-axis reference value and q-axis reference value of the voltage according to formula (5):

[0103]

[0104] where, δ oi , V oi are the phase angle reference value and voltage reference value of the i-th DG under no-load respectively, δ i , V i are the phase angle reference value and voltage reference value of the i-th DG respectively, m i , n i are the active droop coefficient and reactive droop coefficient of the i-th DG respectively, P i , Q i are the actual active power value and reactive power value output by the i-th DG respectively, V drefi is the d-axis reference value of the voltage of the i-th DG, V qrefi is the q-axis reference value of the voltage of the i-th DG.

[0105] Step S2: Collect the difference between the active power reference value of the DG unit and the actual value of the output

[0106] Step S3: Input the difference into the coordinate transformation phase angle controller to obtain the coordinate transformation phase angle compensation value. The coordinate transformation phase angle controller is also divided into a proportional controller and a proportional-integral controller, and the control structure is as Figure 2 shown, including calculating the coordinate transformation phase angle compensation value according to the following formula:

[0107] Use the proportional-integral controller to obtain the coordinate transformation phase angle compensation value according to formula (1):

[0108] θ' = ∫(K P (P refi -P i ) + K I ∫(P refi -P i )dt)dt (1)

[0109] where, θ' is the compensated phase angle value, K P and K I are the proportional gain coefficient and integral gain coefficient of the coordinate transformation phase angle controller respectively.

[0110] Step S4: Superimpose the coordinate transformation phase angle compensation value on the original phase angle value as the phase angle input for the Park inverse transformation, and the control structure is as Figure 2As shown, it is calculated according to the following formula:

[0111] The coordinate transformation phase angle compensation value is superimposed on the original phase angle value according to formula (3):

[0112]

[0113] Use the phase angle reference value to perform the inverse Park transformation according to formula (4):

[0114]

[0115] Among them, θ is the phase angle reference value of the inverse Park transformation, θ 0 is the original phase angle value of the system, f is the standard frequency of 50 Hz, V a 、V b 、V c are the voltages in the three-phase stationary coordinate system respectively, V d 、V q 、V 0 are the voltages in the synchronous rotating coordinate system respectively.

[0116] Step S5: The three-phase modulated voltage signal obtained by the transformation controls the output active power through the SPWM modulation strategy. Specifically, that is: during grid-connected operation, if the reference value of the active power of the DG is not equal to the actual output value, the difference is passed through the coordinate transformation phase angle controller to obtain the coordinate transformation phase angle compensation value, which is compensated to the original coordinate transformation phase angle value. If the difference is positive, the coordinate transformation phase angle reference value is made larger, and the three-phase voltage modulation signal after the inverse Park transformation controls the output of the DG through the SPWM modulation strategy, so that the output active power becomes larger. Conversely, if the difference is negative, the coordinate transformation phase angle reference value becomes smaller, and the active power output by the DG becomes smaller until there is no difference in active power.

[0117] Example 4

[0118] In this Example 4, a microgrid system containing two DGs is used as an example to verify the effectiveness of the inverter grid-connected operation control method based on active power phase angle droop control. The schematic diagram of the microgrid of the inverter grid-connected operation control method provided by Example 4 is as Figure 4 shown. The results of verifying the effectiveness of the present invention come from the Simulink simulation software. The microgrid design parameters are as follows:

[0119] The lines are all impedance-type lines, with a resistance value of 0.14 Ω and an inductive reactance value of 0.4082 Ω; Load 1 is 10 kW + 10 kVar, Load 2 is 10 kW + 10 kVar, Load 3 is 20 kW, and Load 4 is 25 kW + 25 kVar; The set output active powers of the DGs are P ref1 = 35 kW, Pref2 = 33 kW.

[0120] The total system simulation time is 9 seconds. Figure 5 This is the output active power variation diagram of the inverter grid-connected operation control method based on active power angle droop control provided in Embodiment 2 of the present invention.

[0121] Refer to Figure 5 , grid connection occurs at 2 seconds, the proportional-integral control method is switched in, the grid frequency is 50 Hz, and the active powers output by the two DGs are P 1 = 35 kW, P 2 = 33 kW, and both accurately track the reference value; at 4 seconds, the grid frequency suddenly changes to 49.9 Hz, and it can be seen that the active powers output by the DGs are still P 1 = 35 kW, P 2 = 33 kW after tracking and adjustment; at 6 seconds, the grid frequency suddenly changes to approximately 50.1 Hz, and the active powers output by the DGs are still P 1 = 35 kW, P 2 = 33 kW after tracking and adjustment. It can be seen that the proportional-integral control can achieve the zero-error regulation of the active power, and even if there is an offset in the grid frequency, zero-error regulation can still be achieved.

[0122] Embodiment 5

[0123] Embodiment 5 of the present invention provides a non-transitory computer-readable storage medium, which is used to store computer instructions. When the computer instructions are executed by a processor, the inverter grid-connected operation control method based on active power angle droop control is implemented. This method includes:

[0124] Collect the active power reference value and the actual active power value of the DG unit;

[0125] Subtract the actual value from the reference value to obtain a difference;

[0126] Use the coordinate transformation phase angle controller, combined with the difference, to obtain the coordinate transformation phase angle compensation value;

[0127] Superimpose the coordinate transformation phase angle compensation value on the original phase angle value;

[0128] Based on the superimposed phase angle, perform the Park inverse transformation;

[0129] Control the output of the DG unit through the SPWM modulation strategy with the three-phase modulation voltage signal obtained by the Park inverse transformation, and then adjust the output active power.

[0130] Embodiment 6

[0131] Embodiment 6 of the present invention provides a computer program (product), including a computer program which, when running on one or more processors, is used to implement an inverter grid-connected operation control method based on active phase angle droop control. The method includes:

[0132] Collect the reference value and actual value of the active power of the DG unit;

[0133] Subtract the actual value from the reference value to obtain a difference;

[0134] Use a coordinate transformation phase angle controller, combined with the difference, to obtain a coordinate transformation phase angle compensation value;

[0135] Superimpose the coordinate transformation phase angle compensation value on the original phase angle value;

[0136] Perform an inverse Park transformation based on the superimposed phase angle;

[0137] Control the output of the DG unit through the SPWM modulation strategy with the three-phase modulation voltage signal obtained by the inverse Park transformation, and further adjust the output active power.

[0138] Embodiment 7

[0139] Embodiment 7 of the present invention provides an electronic device, including: a processor, a memory, and a computer program; wherein, the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device runs, the processor executes the computer program stored in the memory so that the electronic device executes instructions for implementing an inverter grid-connected operation control method based on active phase angle droop control. The method includes:

[0140] Collect the reference value and actual value of the active power of the DG unit;

[0141] Subtract the actual value from the reference value to obtain a difference;

[0142] Use a coordinate transformation phase angle controller, combined with the difference, to obtain a coordinate transformation phase angle compensation value;

[0143] Superimpose the coordinate transformation phase angle compensation value on the original phase angle value;

[0144] Perform an inverse Park transformation based on the superimposed phase angle;

[0145] Control the output of the DG unit through the SPWM modulation strategy with the three-phase modulation voltage signal obtained by the inverse Park transformation, and further adjust the output active power.

[0146] In summary, for the inverter grid-connected operation control method based on active phase angle droop control described in the embodiments of the present invention, the phase angle droop control structure is retained, and the dq-axis voltage reference value is calculated through active phase angle droop, avoiding a significant change in the control structure during off-grid to on-grid transition; a coordinate transformation phase angle controller is added. By calculating the difference between the reference value and the actual value of the active power, the compensation value of the coordinate transformation phase angle is obtained. After being superimposed on the original phase angle value and undergoing Park inverse transformation, the three-phase voltage modulation signal controls the DG output through the SPWM modulation strategy, achieving the function of zero-error regulation of the active power of the DG unit at different operating frequencies. The effectiveness of this method is verified in a microgrid system containing 2 DGs and 4 loads.

[0147] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can be implemented in the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can be implemented in the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0148] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate means for realizing the functions specified in Figure 1 one or more of the processes Figure 1 or multiple processes and / or blocks

[0149] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including instruction means for realizing the functions specified in Figure 1 one or more of the processes Figure 1 or multiple processes and / or blocks

[0150] These computer program instructions can also be loaded onto a computer or other programmable data processing device, and a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide for realizing the functions in the processFigure 1 One process or multiple processes and / or boxes Figure 1 Steps of functions specified in one box or multiple boxes.

[0151] Although the specific implementation manners of the present invention have been described above in conjunction with the accompanying drawings, they are not limitations on the protection scope of the present invention. Those skilled in the art should understand that, based on the technical solutions disclosed in the present invention, various modifications or deformations that can be made by those skilled in the art without creative efforts should be covered within the protection scope of the present invention.

Claims

1. A control method for the grid-connected operation of an inverter based on active phase angle droop control, which retains the control structure of active phase angle droop for grid-connected operation; Characterized in that, Comprising: Collect the reference value and the actual value of the active power of the DG unit; Subtract the actual value from the reference value to obtain a difference; Using a coordinate transformation phase angle controller, combine the difference to obtain a coordinate transformation phase angle compensation value, including: calculate the coordinate transformation phase angle compensation value according to the following formula: θ' = ∫(K P (P refi - P i ) + K I ∫(P refi - P i )dt)dt; Among them, θ' is the compensated phase angle value, K P and K I are the proportional gain coefficient and integral gain coefficient of the coordinate transformation phase angle controller respectively, P refi represents the active power reference value of the i-th DG unit, P i represents the actual active power value output by the i-th DG unit, and t represents time; Superimpose the coordinate transformation phase angle compensation value on the original phase angle value, including: the coordinate transformation phase angle compensation value is superimposed on the original phase angle value according to the following formula: where θ is the phase angle reference value of the Park inverse transformation, and θ 0 is the original phase angle value of the system, f is the standard frequency of 50 Hz; Based on the superimposed phase angle, perform an inverse Park transformation, including: Among them, V a , V b , V c are the voltages in the three-phase stationary coordinate system respectively, and V d , V q , V 0 are the voltages in the synchronous rotating coordinate system respectively; Control the output of the DG unit through the SPWM modulation strategy with the three-phase modulation voltage signal obtained by the inverse Park transformation, so as to adjust the output active power; including: control the output of the DG unit through the SPWM modulation strategy with the three-phase modulation voltage signal obtained by the transformation, so as to adjust the output active power, including: in grid-connected operation, if the reference value of the active power of the DG is not equal to the actual value of the output, the difference is obtained through the coordinate transformation phase angle controller to obtain the coordinate transformation phase angle compensation value, which is compensated to the original coordinate transformation phase angle value; if the difference is positive, the coordinate transformation phase angle reference value is made larger, and the three-phase voltage modulation signal after the inverse Park transformation is used to control the output of the DG through the SPWM modulation strategy, so that the output active power becomes larger. On the contrary, if the difference is negative, the coordinate transformation phase angle reference value becomes smaller, and the active power output by the DG becomes smaller until there is no difference in active power; Retain the control structure of active phase angle droop for grid-connected operation, including: in off-grid operation, the microgrid adopts the active phase angle droop control strategy; when switching to grid-connected operation, the microgrid does not change the control structure and retains the active phase angle droop control structure.

2. A control system for the grid-connected operation of an inverter based on active phase angle droop control, which retains the control structure of active phase angle droop for grid-connected operation; Characterized in that, Comprising: A collection module for collecting the reference value and the actual value of the active power of the DG unit; A difference-making module for subtracting the actual value from the reference value to obtain a difference; A compensation module for using a coordinate transformation phase angle controller to combine the difference to obtain a coordinate transformation phase angle compensation value, including calculating the coordinate transformation phase angle compensation value according to the following formula: θ' = ∫(K P (P refi -P i ) + K I ∫(P refi -P i )dt)dt; where θ' is the compensated phase angle value, K P and K I are the proportional gain coefficient and integral gain coefficient of the coordinate transformation phase angle controller respectively, P refi represents the active power reference value of the i-th DG unit, P i represents the actual value of the active power output by the i-th DG unit, and t represents time; A superimposing module for superimposing the coordinate transformation phase angle compensation value on the original phase angle value, including: the coordinate transformation phase angle compensation value is superimposed on the original phase angle value according to the following formula: where θ is the phase angle reference value of the Park inverse transformation, and θ 0 is the original phase angle value of the system, f is the standard frequency of 50 Hz; A transformation module for performing an inverse Park transformation based on the superimposed phase angle, including: Among them, V a , V b , V c are the voltages in the three-phase static coordinate system respectively, and V d , V q , V 0 are the voltages in the synchronous rotating coordinate system respectively; A control module, which is used to control the output of the DG unit through the SPWM modulation strategy with the three-phase modulation voltage signal obtained by the Park inverse transformation, and further adjust the output active power; it includes: controlling the output of the DG unit through the SPWM modulation strategy with the three-phase modulation voltage signal obtained by the transformation, and further adjusting the output active power, including: during grid-connected operation, if the active power reference value of the DG is not equal to the actual value of the output, the difference is obtained through a coordinate transformation phase angle controller to get a coordinate transformation phase angle compensation value, which is compensated to the original coordinate transformation phase angle value; if the difference is positive, the coordinate transformation phase angle reference value is made larger, and the three-phase voltage modulation signal after the Park inverse transformation is used to control the output of the DG through the SPWM modulation strategy, so that the output active power becomes larger. Conversely, if the difference is negative, the coordinate transformation phase angle reference value becomes smaller, and the active power output by the DG becomes smaller until there is no difference in active power.

3. A non-transitory computer-readable storage medium, characterized in that, the non-transitory computer-readable storage medium is used to store computer instructions, and when the computer instructions are executed by a processor, it realizes the grid-connected operation control method of the inverter based on active power phase angle droop control as described in claim 1 or 2.

4. A computer program product, characterized in that, it includes a computer program, and when the computer program runs on one or more processors, it is used to realize the grid-connected operation control method of the inverter based on active power phase angle droop control as described in claim 1.

5. An electronic device, characterized in that, it includes: a processor, a memory, and a computer program; wherein, the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device runs, the processor executes the computer program stored in the memory, so that the electronic device executes the instruction to realize the grid-connected operation control method of the inverter based on active power phase angle droop control as described in claim 1.

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