Island micro-grid control method and system comprising multi-network-construction-type inverter

Abstract

The invention discloses a control method for an island micro-grid containing a multi-construction-grid inverter, and the method comprises the steps: adding an integral control link and a feedforward compensation link into a frequency control loop of each construction-grid inverter, and achieving the frequency indifference adjustment and capacity proportion output of the multi-construction-grid inverter through a capacity weighting power distribution scheme. A self-adaptive damping link is added to a power control loop of each grid-forming inverter; acquiring data information of each network-forming inverter in real time; and realizing cooperative control of dynamic frequency modulation and oscillation suppression of the island micro-grid containing the multi-grid-forming inverter according to the acquired data information. The invention also discloses a system for realizing the control method of the island micro-grid comprising the multi-construction-network-type inverter. According to the invention, the control of the island micro-grid containing the multi-grid inverter is realized, the reliability is higher, the accuracy is better, and the control effect is better.

Description

Technical Field

[0001] The present invention belongs to the field of electrical automation, and in particular relates to an island microgrid control method and system including a multi-grid inverter. Background Art

[0002] With the development of economy and technology and the improvement of people's living standards, electricity has become an indispensable secondary energy source in people's production and life, bringing endless convenience to people's production and life. Therefore, ensuring a stable and reliable supply of electricity has become one of the most important tasks of the power system.

[0003] As environmental issues become increasingly severe, more and more photovoltaic (PV) systems are being integrated into power grids to generate electricity. The fluctuating and random nature of PV output creates numerous challenges for island microgrids containing multi-grid inverters.

[0004] First, in an island microgrid containing a grid-forming converter (GFM), the control process of the GFM is as follows: Figure 1 As shown in the figure, the control process relies on the virtual synchronous machine strategy to simulate the inertia of the synchronous generator; however, due to the continuous fluctuation and difficult to accurately predict characteristics of the load in the isolated microgrid, the frequency deviation accumulates over time; and the existing technology is very likely to cause frequency instability or protection malfunction; from the perspective of power distribution, the power mismatch problem is more prominent under the traditional control strategy; when multiple GFMs are operated in parallel, each inverter distributes power according to the droop characteristics, but the proportional link can only respond to power changes at a fixed ratio. When the load continues to fluctuate, the output power of each inverter is difficult to accurately match the actual load demand, resulting in some inverters being overloaded and some inverters being underloaded, and unbalanced power distribution.

[0005] Then, the existing control scheme for isolated microgrids containing multi-grid inverters generally uses a fixed droop coefficient to distribute power. Due to the differences in the output impedance parameters of multi-grid inverters, such as inconsistent line impedance and filter parameters, there will be a risk of power oscillation between parallel inverters; the differences in hardware parameters and control parameters of different inverters make their output impedance inconsistent, which in turn causes parallel circulating current, thereby increasing line loss, reducing system efficiency, and affecting the normal operation of the inverter; at the same time, impedance mismatch will cause the phase of the power distribution loop to shift. When the load fluctuates or the topology changes (such as when an inverter is connected to or exits the system), the system is prone to excite a low-frequency oscillation mode of 0.1-5Hz; this low-frequency oscillation will cause periodic fluctuations in the inverter output power. In severe cases, it will cause the protection device to malfunction, misjudge the normally operating equipment as a faulty equipment and cut off the power supply, or cause the equipment to be disconnected from the grid, affecting the stable power supply of the isolated microgrid.

[0006] Finally, traditional control strategies do not fully consider the impedance matching characteristics between multiple GFM parallel units, resulting in prominent problems of output impedance mismatch and active power oscillation. In a microgrid system containing multiple GFM islands, the stability of multi-machine collaboration faces severe challenges as the system operating conditions become complex and changeable, such as random increases and decreases in loads and dynamic adjustments to the topology structure. Summary of the Invention

[0007] One of the objectives of the present invention is to provide an island microgrid control method containing multi-grid inverters with high reliability, good accuracy and good effect.

[0008] A second object of the present invention is to provide a system for implementing the island microgrid control method containing a multi-grid inverter.

[0009] The control method of the island microgrid including the multi-grid inverter provided by the present invention comprises the following steps:

[0010] S1. Integral control and feedforward compensation are added to the frequency control loop of each grid-type inverter. A capacity-weighted power allocation scheme is used to achieve frequency-free regulation and capacity-proportional output for multiple grid-type inverters.

[0011] S2. Adding adaptive damping to the power control loop of each grid-connected inverter;

[0012] S3. When operating in an island microgrid containing multiple grid-type inverters, obtain data information from each grid-type inverter in real time;

[0013] S4. Based on the data information obtained in step S3, and based on steps S1 and S2, the coordinated control of dynamic frequency modulation and oscillation suppression of the island microgrid containing multi-grid inverters is realized.

[0014] The integral control described in step S1 specifically includes the following steps:

[0015] The angular frequency ω output by the i-th grid-connected inverter i and rated angular frequency ω N After the difference is obtained, it is processed through the integral control link;

[0016] The transfer function of the integral control link is expressed as where k ii is the proportional parameter of the integral control link.

[0017] The feedforward compensation link described in step S1 specifically includes the following steps:

[0018] The output of the integral control link and the output of the feedforward compensation link are summed and used as the input of the frequency adjustment link;

[0019] The equation of the feedforward compensation link is expressed as

[0020]

[0021] I outputi is the output of the integral control link of the i-th grid-connected inverter; I outputj is the output of the integral control link of the j-th grid-connected inverter.

[0022] The capacity-weighted power allocation scheme described in step S1 specifically includes the following steps:

[0023] According to the rotor equation of the grid-type inverter, the following equation is obtained:

[0024] ω1-ω N =ω2-ω N =…=ω i -ω N

[0025] Where ω i is the angular frequency output by the i-th grid-connected inverter; ω N is the rated angular frequency;

[0026] Thus we get

[0027]

[0028] Where P refn is the active power reference value of the nth grid-connected inverter; k ωn is the frequency regulation coefficient of the frequency regulation link of the nth grid-connected inverter; I outputn is the output of the integral control link of the nth grid-connected inverter; P en is the output power of the nth grid-connected inverter; D n is the virtual damping of the nth grid-connected inverter;

[0029] The rated power of each grid-connected inverter is set to meet the following conditions:

[0030]

[0031] Where J n is the virtual moment of inertia of the nth grid-type inverter; X n is the equivalent impedance of the nth grid-type inverter; α1~α n is the constant obtained by actual calculation;

[0032] According to the rated value of the grid-type inverter, the load power is shared proportionally among the grid-type inverters; the output power of each grid-type inverter must meet

[0033] Pe1 :P e2 :…:P en =α1:α2:…:α n

[0034] Due to the existence In order to ensure that the output power of each grid-connected inverter is proportional, it is also necessary to ensure that

[0035] To ensure It is necessary to ensure that the proportional parameters of the integral control link of each grid-connected inverter are equal, and

[0036] After completing step S1, the active power control equation of the i-th grid-connected inverter is expressed as

[0037] Adding an adaptive damping link to the power control loop of each grid-connected inverter as described in step S2 specifically includes the following steps:

[0038] After adding the adaptive damping link to the power control loop of the i-th grid-type inverter, the rotor equation of the i-th grid-type inverter is expressed as

[0039]

[0040] Where m i is the damping compensation coefficient of the adaptive damping link, and m i0 is the set initial damping compensation coefficient, ΔP osc is the real-time power oscillation amplitude of the system.

[0041] The real-time acquisition of data information of each grid-connected inverter described in step S3 specifically includes the following steps:

[0042] Obtain data information of each grid-connected inverter in real time;

[0043] The data information includes the output terminal voltage, output terminal voltage amplitude, output terminal voltage phase value, output terminal current, output terminal current amplitude and output terminal current phase value of the grid-type inverter.

[0044] According to the data information obtained in step S3, step S4 implements coordinated control of dynamic frequency modulation and oscillation suppression of an island microgrid containing a multi-grid inverter based on steps S1 and S2, specifically including the following steps:

[0045] Calculate the output impedance amplitude and phase parameters of each grid-type inverter based on the data information obtained in step S3;

[0046] According to the obtained output impedance amplitude and phase parameters of each grid-type inverter, the impedance mismatch degree is determined:

[0047] Based on the output impedance amplitude of each inverter |Z out,i | and phase angle θ Z,i , calculate the system reference impedance magnitude |Z ref | and the system reference impedance phase θ Z,ref The mismatch degree:

[0048] Amplitude mismatch Δ|Z i | means:

[0049]

[0050] Phase mismatch Δθ i Expressed as:

[0051] Δθ i =|θ Z,i -θ Z,ref |

[0052] If Δ|Z i | is greater than the set amplitude mismatch threshold, or Δθ i If the phase mismatch value is greater than the set phase mismatch threshold, it is determined that the corresponding inverter has impedance mismatch;

[0053] For the grid-type inverter determined to be impedance mismatched, control is performed in combination with step S1 and step S2;

[0054] For the grid-type inverter that is determined to have no impedance mismatch, its current control parameters (such as the droop coefficient, virtual impedance, damping compensation, etc. set in steps S1 / S2) are maintained, it continues to participate in the system dynamic frequency modulation, and monitors the output impedance changes in real time.

[0055] Finally, the coordinated control of dynamic frequency modulation and oscillation suppression of the island microgrid containing multi-grid inverters is completed.

[0056] The present invention also provides a system for implementing the control method of an island microgrid containing multi-grid inverters, comprising a first regulation module, a second regulation module, a data acquisition module and a collaborative control module; the first regulation module, the second regulation module, the data acquisition module and the collaborative control module are connected in series in sequence; the first regulation module is used to add integral control and feedforward compensation links to the frequency control loop of each grid-type inverter, and realize frequency error-free regulation and capacity-proportional output of the multi-grid inverter through a capacity-weighted power allocation scheme, and upload the data information to the second regulation module; the second regulation module is used to add an adaptive damping link to the power control loop of each grid-type inverter according to the received data information, and upload the data information to the data acquisition module; the data acquisition module is used to obtain data information of each grid-type inverter in real time when the island microgrid containing multi-grid inverters is working, and upload the data information to the collaborative control module; the collaborative control module is used to realize the collaborative control of dynamic frequency modulation and oscillation suppression of the island microgrid containing multi-grid inverters based on the received data information and the acquired data information based on the first regulation module and the second regulation module.

[0057] The control method and system for an island microgrid containing multiple grid-type inverters provided by the present invention not only realizes the control of an island microgrid containing multiple grid-type inverters, but also achieves higher reliability, better accuracy, and better control effect by adding integral control and feedforward compensation links to the frequency control loop of each grid-type inverter, adding an adaptive damping link to the power control loop of each grid-type inverter, and combining it with a capacity-weighted power allocation scheme. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is a schematic diagram of the existing control flow.

[0059] Figure 2 Schematic diagram of the process flow of the present invention.

[0060] Figure 3 Schematic diagram of the control flow of the present invention.

[0061] Figure 4 Schematic diagram of simulation of active power output of each GFM and frequency response of microgrid under the traditional GFM control strategy of the method embodiment of the present invention.

[0062] Figure 5 Schematic diagram of simulation of active power output of each GFM and frequency response of microgrid under traditional secondary frequency modulation GFM control according to an embodiment of the method of the present invention.

[0063] Figure 6This is a schematic diagram of simulation of active power output of each GFM and frequency response of a microgrid under the control of the dynamic secondary frequency modulation GFM of the present invention in an embodiment of the method of the present invention.

[0064] Figure 7 Schematic diagram of simulation of active power output of each GFM and frequency response of microgrid under the method of the present invention embodiment.

[0065] Figure 8 This is a schematic diagram of a simulation of the fault ride-through capability of the method of the present invention for verifying the fault ride-through capability of the method of the present invention.

[0066] Figure 9 This is a simulation diagram for verifying the plug-and-play capability of the method embodiment of the present invention.

[0067] Figure 10 Schematic diagram of the functional modules of the system of the present invention. DETAILED DESCRIPTION

[0068] like Figure 2 The method flow diagram of the present invention is shown as follows: The control method of the island microgrid containing a multi-network inverter disclosed in the present invention includes the following steps:

[0069] S1. Add integral control and feedforward compensation links to the frequency control loop of each grid-type inverter, and realize frequency error-free regulation and capacity-proportional output of multi-grid-type inverters through capacity-weighted power allocation scheme (such as Figure 3 shown);

[0070] In specific implementation, the integral control includes the following steps:

[0071] The angular frequency ω output by the i-th grid-connected inverter i and rated angular frequency ω N After the difference is obtained, it is processed through the integral control link;

[0072] The transfer function of the integral control link is expressed as where k ii is the proportional parameter of the integral control link;

[0073] At this time, the rotor equation can be expressed as

[0074] At this time, the output frequency of the GFM is adjusted without any difference. However, due to the different design parameters of each GFM and the different output line impedance, the output power compensation I of the integral link in the frequency control of each GFM is different. outputi The output power of each GFM is not accurately allocated according to its capacity.

[0075] The feedforward compensation link specifically includes the following steps:

[0076] The output of the integral control link and the output of the feedforward compensation link are summed and used as the input of the frequency regulation link;

[0077] The equation of the feedforward compensation link is expressed as

[0078]

[0079] I outputi is the output of the integral control link of the i-th grid-connected inverter; I outputj is the output of the integral control link of the j-th grid-connected inverter.

[0080] The capacity-weighted power allocation scheme specifically includes the following steps:

[0081] According to the rotor equation of the grid-type inverter, the following equation is obtained:

[0082] ω1-ω N =ω2-ω N =…=ω i -ω N

[0083] Where ω i is the angular frequency output by the i-th grid-connected inverter; ω N is the rated angular frequency;

[0084] Thus we get

[0085]

[0086] Where P refn is the active power reference value of the nth grid-connected inverter; k ωn is the frequency regulation coefficient of the frequency regulation link of the nth grid-connected inverter; I outputn is the output of the integral control link of the nth grid-connected inverter; P en is the output power of the nth grid-connected inverter; D n is the virtual damping of the nth grid-connected inverter;

[0087] The rated power of each grid-connected inverter is set to meet the following conditions:

[0088]

[0089] Where J n is the virtual moment of inertia of the nth grid-type inverter; X n is the equivalent impedance of the nth grid-type inverter; α1~α n is the constant obtained by actual calculation;

[0090] According to the rated value of the grid-type inverter, the load power is shared proportionally among the grid-type inverters; the output power of each grid-type inverter must meet

[0091] P e1 :P e2 :…:P en =α1:α2:…:α n

[0092] Due to the existence In order to ensure that the output power of each grid-connected inverter is proportional, it is also necessary to ensure that

[0093] To ensure It is necessary to ensure that the proportional parameters of the integral control link of each grid-connected inverter are equal, and

[0094] Finally, after completing step S1, the active power control equation of the i-th grid-connected inverter is expressed as

[0095] exist Figure 3 The technical content of this step constitutes the "dynamic secondary frequency modulation control" in the figure; dynamic secondary frequency modulation control not only solves the frequency steady-state deviation problem of the multi-GFM parallel system of the isolated microgrid, but also reasonably enables each GFM to output active power according to its capacity ratio.

[0096] Traditional droop control relies solely on the proportional link to achieve power distribution, but the lack of an integral link prevents the frequency from returning to the rated value, resulting in continuous accumulation of deviations during long-term operation. This invention introduces a dynamic integral link into the control loop to construct a "proportional-integral" composite frequency modulation controller. The proportional link quickly responds to power deviations, and the integral link generates a compensation signal by accumulating historical deviations. The two work together to eliminate frequency steady-state errors, ensuring long-term stable operation of the system at the rated frequency.

[0097] Feedforward compensation strategy: To address the frequency fluctuation caused by sudden load changes, this invention designs a feedforward compensation channel to monitor the load power change in real time and generate a compensation signal proportional to the deviation, which is superimposed on the output of the frequency modulation controller. This strategy significantly improves the system's dynamic response speed to sudden load changes by correcting the control instructions in advance, avoiding frequency overshoot or oscillation.

[0098] Capacity-weighted power allocation: To address the issue of uneven power distribution when multiple machines are connected in parallel, this invention proposes a dynamic power allocation algorithm based on rated capacity. The algorithm generates a weighting coefficient based on the rated capacity of each GFM. Power allocation instructions are then distributed to each unit according to the weighting coefficient, ensuring that power is accurately distributed in proportion to capacity, avoiding overload or underload operation, and improving system economy.

[0099] S2. Adding an adaptive damping element to the power control loop of each grid-connected inverter; specifically, the steps include:

[0100] After adding the adaptive damping link to the power control loop of the i-th grid-type inverter, the rotor equation of the i-th grid-type inverter is expressed as

[0101]

[0102] Where m i is the damping compensation coefficient of the adaptive damping link, and m i0 is the set initial damping compensation coefficient, ΔP osc is the real-time power oscillation amplitude of the system.

[0103] Real-time impedance monitoring and mismatch diagnosis: By acquiring the output voltage and current signals of each GFM and extracting the fundamental component through Fourier transform, the amplitude and phase parameters of the output impedance are calculated. By comparing the impedance characteristics of each unit, the degree of impedance mismatch is diagnosed and the mismatched unit is located. If the impedance difference exceeds the threshold, the adaptive compensation mechanism is triggered.

[0104] Adaptive damping compensation: Based on the impedance mismatch diagnosis results, the GFM system damping is dynamically adjusted to generate a damping compensation signal that is superimposed on the power control loop. This compensation signal corrects the output voltage phase to eliminate parallel circulating currents and power oscillations caused by impedance differences. This strategy significantly improves system transient stability and avoids low-frequency oscillation modes that could cause protection device misoperation or equipment disconnection.

[0105] By adding an adaptive damping compensation link to the active power control loop, the damping of the GFM in the transient process is improved, the overall output impedance of the GFM is changed, and the system damping is appropriately adjusted. As a result, the mutual interference between the GFMs is reduced, the active power oscillation of the island microgrid system is effectively suppressed, and the operation stability is improved.

[0106] S3. When operating in an island microgrid containing multiple grid-type inverters, obtain data information of each grid-type inverter in real time; specifically, the following steps:

[0107] Obtain data information of each grid-connected inverter in real time;

[0108] The data information includes the output terminal voltage, output terminal voltage amplitude, output terminal voltage phase value, output terminal current, output terminal current amplitude and output terminal current phase value of the grid-forming inverter;

[0109] S4. Based on the data information obtained in step S3, based on steps S1 and S2, the coordinated control of dynamic frequency modulation and oscillation suppression of the island microgrid containing multi-grid inverters is realized; specifically, the following steps are included:

[0110] Calculate the output impedance amplitude and phase parameters of each grid-type inverter based on the data information obtained in step S3;

[0111] According to the obtained output impedance amplitude and phase parameters of each grid-type inverter, the impedance mismatch degree is determined:

[0112] Based on the output impedance amplitude of each inverter |Z out,i | and phase angle θ Z,i , calculate the system reference impedance magnitude |Z ref | and the system reference impedance phase θ Z,ref The mismatch degree:

[0113] Amplitude mismatch Δ|Z i | means:

[0114]

[0115] Phase mismatch Δθ i Expressed as:

[0116] Δθ i =|θ Z,i -θ Z,ref |

[0117] If Δ|Z i | is greater than the set amplitude mismatch threshold, or Δθ i If the phase mismatch value is greater than the set phase mismatch threshold, it is determined that the corresponding inverter has impedance mismatch;

[0118] For the grid-type inverter determined to be impedance mismatched, control is performed in combination with step S1 and step S2;

[0119] For the grid-connected inverters that are determined to have no impedance mismatch, their current control parameters (such as the droop coefficient, virtual impedance, damping compensation, etc. set in steps S1 / S2) are maintained, they continue to participate in the system dynamic frequency modulation, and the output impedance changes are monitored in real time;

[0120] Finally, the coordinated control of dynamic frequency modulation and oscillation suppression of the island microgrid containing multi-grid inverters is completed.

[0121] In the method of the present invention, specific parameters in the method, such as moment of inertia, inverter virtual damping, frequency adjustment coefficient, etc., are all adjusted and obtained using a parameter tuning method; among them, the preferred parameter tuning method is a parameter tuning method based on a small signal model, specifically: a small signal model of an island microgrid system containing multiple parallel inverters is established, and its transfer function is obtained. According to the knowledge of control theory, the controller parameters are tuned from the two aspects of stability and dynamic response.

[0122] Collaborative optimization: To ensure the overall performance of the island microgrid system, the control strategies of each converter need to be collaboratively optimized. This includes adjusting control parameters, optimizing control algorithms, and coordinating the interactions between converters. By comprehensively considering factors such as the system's dynamic characteristics, load conditions, and distributed power output, a more efficient and stable control strategy can be designed.

[0123] Verification and testing: Finally, comprehensive verification and testing of the coordinated control method for dynamic frequency modulation and oscillation suppression in an island microgrid containing multi-grid inverters is required. This includes performance testing, stability analysis, and fault simulation in a simulated environment and under actual operating conditions. Through verification and testing, the effectiveness and reliability of the method can be ensured, and its performance can be further optimized.

[0124] The present invention is further described below with reference to an embodiment:

[0125] A simulation model containing three GFMs (capacity ratio 3:2:1) was constructed, and the method of the present invention was verified under three typical scenarios: load switching, equipment failure, and plug-and-play.

[0126] (1) Improved frequency regulation performance and precise power distribution:

[0127] The traditional GFM control strategy lacks a dynamic compensation mechanism in the isolated microgrid, resulting in a frequency steady-state deviation of up to 0.14Hz when the load suddenly changes (e.g. Figure 4 shown), Figure 5 The figure shows the improvement effect of introducing the traditional secondary frequency modulation. Although the traditional secondary frequency modulation method achieves frequency regulation without static error (steady-state frequency 50.00Hz), the power distribution accuracy is significantly reduced: the active power ratio before and after load switching (P e1 :P e2 :P e3 ) are 8.55:6.05:3.40 (theoretical value 9:6:3) and 12.8:9.05:5.15 (theoretical 13.5:9:4.5), respectively. The maximum error is 8.9%, and there is a power oscillation with a period of 0.3s, indicating that it is difficult to strike a balance between accuracy and stability. Figure 6The improvement effect of the dynamic secondary frequency control strategy proposed in this invention is presented. On the basis of ensuring frequency error-free regulation, the active power distribution accuracy is significantly improved: the active power ratio P before load switching is e1 :P e2 :P e3 =9.01:6.01:2.98 (theoretical value 9:6:3), after switching P e1 :P e2 :P e3 =13.5:9.02:4.48, average error <3%.

[0128] (2) Outstanding power oscillation suppression effect:

[0129] Aiming at the periodic power oscillation problem caused by impedance mismatch when multiple GFMs are operated in parallel under the traditional control strategy, the present invention dynamically changes the output impedance of the converter through the adaptive damping compensation module, which significantly improves the system damping characteristics: the simulation results are as follows: Figure 7 As shown; the simulation results show that the active power output P of each GFM is e1 、P e2 、P e3 The peak powers of the two control modes are reduced to 13.51kW, 9.08kW and 4.95kW respectively, the oscillation period is shortened to 0.1s, and the amplitude is reduced by more than 60%. At the same time, the frequency zero-error regulation (steady-state frequency 50.00Hz) and active power distribution accuracy (power distribution accuracy 9:6:3) are maintained. The comprehensive advantages of the proposed collaborative control strategy in dynamic response, steady-state accuracy and oscillation suppression are verified.

[0130] (3) Enhanced system fault ride-through and plug-and-play capabilities:

[0131] In order to evaluate the robustness and scalability of the control strategy, the following experimental scenarios are set: (a) a sudden increase of 9kW load at t = 1s; (b) a sudden fault of GFM3 is simulated to stop operation at t = 2s; Figure 8 As shown, the system maintains accurate power distribution (P e1 :P e2 :P e3 ≈3:2:1); When GFM3 exits, the remaining units complete power redistribution within 0.15s. In steady state, P e1 :P e2 =13.5:9, strictly maintaining a 3:2 ratio, and the frequency is always stable at 50.00±0.005Hz, proving that the system has good fault ride-through capability.

[0132] In order to further study the proposed control strategy and highlight its plug-and-play capability, the simulation settings are as follows: from 0 to 1s, only GFM1-2 is running, t=1s is connected to GFM3, and t=3s is suddenly increased by 9kW load. Figure 9 As shown in the figure, after GFM3 is connected, the system completes power redistribution within 0.2s (steady-state P e1 :P e2 :P e3 =8.99:5.99:3.01); when new load is added, each GFM bears the power increase according to its capacity ratio, the frequency deviation of the whole process is less than 0.003Hz, and the power oscillation amplitude is less than 5%. This confirms the strong adaptability of the proposed control strategy to changes in system topology and meets the operational requirements of flexible expansion of the microgrid.

[0133] The above multi-scenario simulations demonstrate that the proposed solution achieves a power allocation error of less than 3%, a reduction in oscillation amplitude of over 60%, a fault recovery time of less than 0.2 seconds, and a power impact of less than 5% during the plug-and-play process, while maintaining frequency regulation accuracy. This demonstrates significant overall performance improvements over traditional control methods.

[0134] like Figure 10 The figure shows a functional module diagram of the system of the present invention: the system disclosed in the present invention for realizing the control method of the island microgrid containing multi-grid inverters comprises a first regulating module, a second regulating module, a data acquisition module and a collaborative control module; the first regulating module, the second regulating module, the data acquisition module and the collaborative control module are connected in series in sequence; the first regulating module is used to add integral control and feedforward compensation links to the frequency control loop of each grid-type inverter, and realize the frequency difference-free regulation and capacity-proportional output of the multi-grid-type inverter through the capacity-weighted power allocation scheme, and upload the data information to the second regulating module; the second ... The regulation module is used to add an adaptive damping link to the power control loop of each grid-type inverter according to the received data information, and upload the data information to the data acquisition module; the data acquisition module is used to obtain the data information of each grid-type inverter in real time when the island microgrid containing multiple grid-type inverters is working, and upload the data information to the collaborative control module; the collaborative control module is used to realize the collaborative control of dynamic frequency modulation and oscillation suppression of the island microgrid containing multiple grid-type inverters based on the received data information and the acquired data information, based on the first regulation module and the second regulation module.

Claims

1. A control method for an island microgrid including a multi-grid inverter, comprising the following steps: S1. Integral control and feedforward compensation are added to the frequency control loop of each grid-type inverter. A capacity-weighted power allocation scheme is used to achieve frequency-free regulation and capacity-proportional output for multiple grid-type inverters. S2. Adding adaptive damping to the power control loop of each grid-connected inverter; S3. When operating in an island microgrid containing multiple grid-type inverters, obtain data information from each grid-type inverter in real time; S4. Based on the data information obtained in step S3, and based on steps S1 and S2, the coordinated control of dynamic frequency modulation and oscillation suppression of the island microgrid containing multi-grid inverters is realized.

2. The control method for an island microgrid containing a multi-grid inverter according to claim 1 is characterized in that The integral control described in step S1 specifically includes the following steps: The angular frequency ω output by the i-th grid-connected inverter i and rated angular frequency ω N After the difference is obtained, it is processed through the integral control link; The transfer function of the integral control link is expressed as where k ii is the proportional parameter of the integral control link.

3. The control method for an island microgrid containing a multi-grid inverter according to claim 2 is characterized in that The feedforward compensation link described in step S1 specifically includes the following steps: The output of the integral control link and the output of the feedforward compensation link are summed and used as the input of the frequency adjustment link; The equation of the feedforward compensation link is expressed as I outputi is the output of the integral control link of the i-th grid-connected inverter; I outputj is the output of the integral control link of the j-th grid-connected inverter.

4. The control method for an island microgrid containing a multi-grid inverter according to claim 3 is characterized in that The capacity-weighted power allocation scheme described in step S1 specifically includes the following steps: According to the rotor equation of the grid-type inverter, the following equation is obtained: ω1-ω N =ω2-ω N =…=oh i -oh N Where ω i is the angular frequency output by the i-th grid-connected inverter; ω N is the rated angular frequency; Thus we get Where P refn is the active power reference value of the nth grid-connected inverter; k ωn is the frequency regulation coefficient of the frequency regulation link of the nth grid-connected inverter; I outputn is the output of the integral control link of the nth grid-connected inverter; P en is the output power of the nth grid-connected inverter; D n is the virtual damping of the nth grid-connected inverter; The rated power of each grid-connected inverter is set to meet the following conditions: Where J n is the virtual moment of inertia of the nth grid-type inverter; X n is the equivalent impedance of the nth grid-type inverter; α1~α n is the constant obtained by actual calculation; According to the rated value of the grid-type inverter, the load power is shared proportionally among the grid-type inverters; the output power of each grid-type inverter must meet P e1 :P e2 :…:P en =α1:α2:…:α n Due to the existence In order to ensure that the output power of each grid-connected inverter is proportional, it is also necessary to ensure that To ensure It is necessary to ensure that the proportional parameters of the integral control link of each grid-connected inverter are equal, and 5. The control method for an island microgrid containing a multi-grid inverter according to claim 4 is characterized in that After completing step S1, the active power control equation of the i-th grid-connected inverter is expressed as 6. The control method for an island microgrid containing a multi-grid inverter according to claim 5 is characterized in that Adding an adaptive damping link to the power control loop of each grid-connected inverter as described in step S2 specifically includes the following steps: After adding the adaptive damping link to the power control loop of the i-th grid-type inverter, the rotor equation of the i-th grid-type inverter is expressed as Where m i is the damping compensation coefficient of the adaptive damping link, and m i0 is the set initial damping compensation coefficient, ΔP osc is the real-time power oscillation amplitude of the system.

7. The control method for an island microgrid containing a multi-grid inverter according to claim 6 is characterized in that The real-time acquisition of data information of each grid-connected inverter described in step S3 specifically includes the following steps: Obtain data information of each grid-connected inverter in real time; The data information includes the output terminal voltage, output terminal voltage amplitude, output terminal voltage phase value, output terminal current, output terminal current amplitude and output terminal current phase value of the grid-type inverter.

8. The control method for an island microgrid containing a multi-grid inverter according to claim 7, characterized in that According to the data information obtained in step S3, step S4 implements coordinated control of dynamic frequency modulation and oscillation suppression of an island microgrid containing a multi-grid inverter based on steps S1 and S2, specifically including the following steps: Calculate the output impedance amplitude and phase parameters of each grid-type inverter based on the data information obtained in step S3; According to the obtained output impedance amplitude and phase parameters of each grid-type inverter, the impedance mismatch degree is determined: Based on the output impedance amplitude of each inverter |Z out,i | and phase angle θ Z,i , calculate the system reference impedance magnitude |Z ref | and the system reference impedance phase θ Z,ref The mismatch degree: Amplitude mismatch Δ|Z i | means: Phase mismatch Δθ i Expressed as: Dth i =|θ Z,i -θ Z,ref | If Δ|Z i | is greater than the set amplitude mismatch threshold, or Δθ i If the phase mismatch value is greater than the set phase mismatch threshold, it is determined that the corresponding inverter has impedance mismatch; For the grid-type inverter determined to be impedance mismatched, control is performed in combination with step S1 and step S2; For the grid-type inverter determined to have no impedance mismatch, the current control parameters are maintained; Finally, the coordinated control of dynamic frequency modulation and oscillation suppression of the island microgrid containing multi-grid inverters is completed.

9. A system for implementing the control method of an island microgrid containing a multi-grid inverter according to any one of claims 1 to 8, characterized in that The system comprises a first regulation module, a second regulation module, a data acquisition module and a collaborative control module; the first regulation module, the second regulation module, the data acquisition module and the collaborative control module are connected in series in sequence; the first regulation module is used to add integral control and feedforward compensation links to the frequency control loop of each grid-type inverter, and realize frequency error-free regulation and capacity-proportional output of multiple grid-type inverters through a capacity-weighted power allocation scheme, and upload data information to the second regulation module; The second regulation module is used to add an adaptive damping link to the power control loop of each grid-type inverter according to the received data information, and upload the data information to the data acquisition module; The data acquisition module is used to obtain the data information of each grid-type inverter in real time based on the received data information when the island microgrid containing multiple grid-type inverters is working, and upload the data information to the collaborative control module; The collaborative control module is used to realize the collaborative control of dynamic frequency modulation and oscillation suppression of the isolated island microgrid containing multi-network inverters based on the received data information and the acquired data information based on the first regulation module and the second regulation module.

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