CN112467761B - Distributed bus voltage frequency compensation method suitable for micro-grid system - Google Patents

Distributed bus voltage frequency compensation method suitable for micro-grid system Download PDF

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CN112467761B
CN112467761B CN202011454253.8A CN202011454253A CN112467761B CN 112467761 B CN112467761 B CN 112467761B CN 202011454253 A CN202011454253 A CN 202011454253A CN 112467761 B CN112467761 B CN 112467761B
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CN112467761A (en
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贾广宇
陈家伟
侯帅丞
方觅
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Chongqing University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • H02J3/241—The oscillation concerning frequency
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
    • H02J13/00006—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/48—Controlling the sharing of the in-phase component
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/50—Controlling the sharing of the out-of-phase component
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/70—Smart grids as climate change mitigation technology in the energy generation sector
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/12—Monitoring or controlling equipment for energy generation units, e.g. distributed energy generation [DER] or load-side generation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S40/00—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them
    • Y04S40/12—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment

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Abstract

The invention discloses a distributed bus voltage frequency compensation method suitable for a micro-grid system. The invention has the advantage of recovering the bus voltage and frequency to a greater extent without destroying the droop characteristic. Meanwhile, the method adopts a one-way annular low-bandwidth communication mode to form a communication layer without an integrated controller, and has the advantages of high reliability, small communication data volume, low bandwidth, strong expansibility and the like.

Description

Distributed bus voltage frequency compensation method suitable for micro-grid system
Technical Field
The invention relates to the technical field of distributed power generation and micro-grids, in particular to a distributed bus voltage frequency compensation method suitable for a micro-grid system.
Background
With the continuous improvement of the requirements on the capacity and the reliability of the micro-grid, the parallel operation of the distributed power generation units is one of the important ways for solving the requirement of high-power utilization.
Due to the regulation characteristics of voltage frequency-active power and voltage amplitude-reactive power, the droop control is widely applied to a microgrid control system without interconnection lines, so that each distributed power generation unit distributes the active power and the reactive power of the microgrid system according to the rated capacity level of the distributed power generation unit. However, the droop term in the droop control can cause deviation of output voltage and rated value of each distributed power generation unit, and even drop of bus voltage and frequency beyond the allowable range in a serious case can cause operation instability of some sensitive loads, trigger line protection and serious loss.
At present, in order to solve the problem of bus voltage frequency compensation of a microgrid, a plurality of academic papers and patents are studied and a method for modifying a droop coefficient or adding a compensation value in a droop control link of a distributed power generation unit is proposed to offset the deviation caused by a droop item, so that the purpose of reducing the bus voltage and frequency deviation is achieved. For example:
1. liuhaixia et al, in the published article "accurate power distribution and frequency-voltage recovery control in independent microgrid" propose to construct a compensation value containing the average values of the output voltages and frequencies of all distributed power generation units, and the compensation value adjusts the difference between the average value and the rated value of all power generation units to zero through a PI controller, thereby achieving the purpose of compensating the voltage and the frequency. The compensation strategy can reduce the influence of sudden load change on the bus voltage and frequency, but the method needs the centralized controller to calculate the average value of all the distributed power generation units and perform bidirectional communication with each distributed power generation unit to exchange data, so that not only the structure is complex and the communication data amount and the calculation amount are large, but also the structure robustness of the centralized controller is weak, and once the centralized controller fails, the voltage and frequency compensation of the whole system cannot be used.
2. In an article entitled "microgrid voltage and frequency recovery control based on droop characteristics", authors have a juan and a chenxin based on traditional droop control to recover voltage and frequency to near nominal values by changing the droop curve of a large-capacity distributed power generation unit. This method of modifying the droop curve, while reducing voltage to frequency deviations, can make it difficult to apportion power between distributed generation units.
3. "Distributed Secondary Control for Power Allocation and Voltage retrieval in island DC Microgrids," in IEEE Transactions on stable Energy, vol.9, No.4, pp.1857-1869, Oct.2018, published by Guo Fanghong et al, proposes to construct a compensation value containing only the output Voltage values of adjacent generating units, each of which requires bidirectional communication with two adjacent generating units. This approach, while simplifying the communication structure, still brings problems of data redundancy and large communication bandwidth requirements.
4. In a patent of application No. 201910361463.3, entitled "voltage frequency adjustment method and system for islanded microgrid" by wuringing et al, several adjacent distributed power generation units use distributed communication to perform information interaction, transmit two variable information of local voltage deviation and frequency deviation to each other, obtain an average value of the deviation of the adjacent distributed power generation units, and calculate a voltage frequency compensation value by using the average deviation. According to the method, the voltage and frequency adjustment quantity is calculated without acquiring the impedance parameters of the system and the information of the constant power load, but bidirectional communication still needs to be established between each distributed power generation unit in adjacent areas, the communication structure is complex, and the data transmission quantity is still large.
In summary, there is still a lack of a distributed control method with a simple communication architecture to recover bus voltage and frequency.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a distributed bus voltage frequency compensation method suitable for a microgrid system, so as to solve the problem that in the microgrid system in the prior art, when the bus voltage and the frequency deviate from the rated values due to droop control of a distributed power generation unit, the voltage and the frequency of a bus cannot be recovered quickly and efficiently on the premise of ensuring power sharing.
The invention relates to a distributed bus voltage frequency compensation method applicable to a micro-grid system, which comprises the following steps: in an annular communication network formed by communication layers of all distributed power generation units, each distributed power generation unit receives active power and an active droop coefficient and reactive power and a reactive droop coefficient of one distributed power generation unit, a voltage compensation value and a frequency compensation value are obtained after compensation function operation, and the voltage compensation value and the frequency compensation value are added into a droop control equation of a main controller of the distributed power generation units to compensate the voltage and frequency droop of a bus;
the droop control equation is:
Figure GDA0003403137580000031
the compensation function is:
Figure GDA0003403137580000032
the power droop control link containing the voltage compensation value and the frequency compensation value is as follows:
Figure GDA0003403137580000033
in the droop control equation, the power droop control link including the compensation value and the compensation function: f. ofi *A frequency reference value of the ith distributed generation unit; v. ofi *The voltage outer ring reference value of the ith distributed generation unit; f. of0Is a frequency rating; v0Is a voltage rating; Δ fiA frequency compensation value for the ith distributed generation unit; Δ viA voltage compensation value for the ith distributed generation unit; m isiThe active droop coefficient of the ith distributed generation unit is obtained; piActive power of the ith distributed generation unit; n isiThe reactive droop coefficient of the ith distributed generation unit is obtained; qiThe reactive power of the ith distributed generation unit; m isi-1The active droop coefficient of the i-1 th distributed power generation unit is obtained; pi-1The active power of the i-1 th distributed power generation unit; n isi-1The reactive droop coefficient is the reactive droop coefficient of the (i-1) th distributed generation unit; qi-1The reactive power of the (i-1) th distributed generation unit; the subscript i is the serial number of the current distributed power generation unit, i-1 is the serial number of the last distributed power generation unit, and i is 2,3, …, k, where k denotes the number of distributed power generation units contained in the current microgrid system, and when i is 1, i-1 is k.
The invention has the beneficial effects that:
1. when the bus voltage and the frequency of the distributed power generation unit deviate from the rated value due to droop control, the distributed power generation unit is adaptively adjusted according to the compensation function, and the bus frequency and the voltage of the microgrid system can be recovered on the basis of not influencing power uniform division, so that the voltage and the frequency of the alternating current bus are maintained near the rated value, and various loads can be stably operated.
2. The invention is suitable for the distributed bus voltage frequency compensation method of the microgrid system, a communication layer without an integrated controller is formed by adopting a unidirectional annular low-bandwidth communication mode, each distributed power generation unit only needs to obtain the active power, the active droop coefficient, the reactive power and the reactive droop coefficient of the previous distributed power generation unit, and the active power, the active droop coefficient, the reactive power and the reactive droop coefficient are calculated together with relevant parameters of the distributed power generation unit to obtain a frequency compensation value and a voltage compensation value.
Drawings
Fig. 1 is a system configuration block diagram of a distributed microgrid in an embodiment.
Fig. 2 is a block diagram showing the structure and control of each distributed power generation unit in the embodiment.
Fig. 3 is an experimental structure block diagram of the microgrid in the embodiment.
FIG. 4 is a waveform diagram of voltage frequency compensation and before and after load addition and subtraction of the distributed power generation unit in the embodiment.
Detailed Description
The invention is further described below with reference to the figures and examples.
The distributed bus voltage frequency compensation method suitable for the microgrid system in the embodiment comprises the following steps: in an annular communication network formed by communication layers of all distributed power generation units, each distributed power generation unit receives active power and an active droop coefficient and reactive power and a reactive droop coefficient of one distributed power generation unit, a voltage compensation value and a frequency compensation value are obtained after compensation function operation, and the voltage compensation value and the frequency compensation value are added into a droop control equation of a main controller of the distributed power generation units to compensate the voltage and frequency drop of a bus.
The droop control equation is:
Figure GDA0003403137580000051
the compensation function is:
Figure GDA0003403137580000052
the power droop control link containing the voltage compensation value and the frequency compensation value is as follows:
Figure GDA0003403137580000053
in the droop control equation, the power droop control link including the compensation value and the compensation function: f. ofi *A frequency reference value of the ith distributed generation unit for providing a reference phase angle theta to the main controlleri；vi *The voltage outer ring reference value of the ith distributed generation unit; f. of0Is a frequency rating; v0Is a voltage rating; Δ fiA frequency compensation value for the ith distributed generation unit; Δ viA voltage compensation value for the ith distributed generation unit; m isiThe active droop coefficient of the ith distributed generation unit is obtained; piActive power of the ith distributed generation unit; n isiThe reactive droop coefficient of the ith distributed generation unit is obtained; qiThe reactive power of the ith distributed generation unit; m isi-1The active droop coefficient of the i-1 th distributed power generation unit is obtained; pi-1The active power of the i-1 th distributed power generation unit; n isi-1The reactive droop coefficient is the reactive droop coefficient of the (i-1) th distributed generation unit; qi-1The reactive power of the (i-1) th distributed generation unit; the subscript i is the serial number of the current distributed power generation unit, i-1 is the serial number of the last distributed power generation unit, and i is 2,3, …, k, where k denotes the number of distributed power generation units contained in the current microgrid system, and when i is 1, i-1 is k.
In the prior art, an island micro-grid system with a plurality of parallel distributed power generation units generally adopts droop control to distribute active power and reactive power of loads. According to the relationship between the active power P and the voltage frequency f, and the relationship between the reactive power Q and the voltage amplitude V, the droop control equation is obtained as follows:
fi *＝f0-miPi
Figure GDA0003403137580000061
if the main controller is reasonably designed, the output frequency and the output voltage of the power generation unit can quickly reach the reference frequency fi *Sum voltage outer loop reference voltage vi *I.e. fi *And vi *Can be approximately regarded as the output frequency and the output voltage value of the ith distributed generation unit.
From the equation, it can be seen that the output voltage v is due to the presence of the droop terms mP and nQi *And frequency fi *Rated value V of voltage and frequency0And f0There is a difference between them and therefore the droop terms mP and nQ can also be referred to as the drop values. As the load power demand increases, this difference continues to increase, causing the output voltage and frequency to be too low, resulting in the ac bus voltage and frequency dropping outside of acceptable limits. In practice, there is also line impedance between the output node of the distributed power generation unit and the node connected to the bus, but the voltage drop on the line impedance is negligible compared with the voltage drop caused by the droop term, so that v is only required to be measuredi *The compensation to the vicinity of the rated value can ensure that the bus voltage can be compensated to the vicinity of the rated value. While the frequency of the whole microgrid is everywhere equal at steady state, so f will bei *Compensating to the vicinity of the rated value ensures that the bus frequency is also compensated to the vicinity of the rated value. In view of this situation, the distributed bus voltage frequency compensation method applied to the microgrid system in the embodiment adds the compensation value Δ f to the droop control equationiAnd Δ vi：
fi *＝f0-miPi+Δfi
Figure GDA0003403137580000062
Considering that the power equalization state is kept before and after the compensation value is added, for k distributed generation units with different capacities, if the load is distributed in proportion, the following requirements are met:
m1P1＝m2P2＝…＝mkPk
n1Q1＝n2Q2＝…＝nkQk
therefore, if the power sharing state is not damaged after the compensation value is added, the following requirements are met:
m1P1+Δf1＝m2P2+Δf2＝···＝mkPk+Δfk
n1Q1+Δv1＝n2Q2+Δv2＝···＝nkQk+Δvk
the condition for the compensation value can be derived from the above equation:
Δf1＝Δf2＝···＝Δfk
Δv1＝Δv2＝···＝Δvk
in consideration of the communication structure and the data transmission amount, and in combination with the above derivation, the distributed bus voltage frequency compensation method applicable to the microgrid system in the embodiment designs the compensation value as follows:
Figure GDA0003403137580000071
Figure GDA0003403137580000072
the design only needs the local distributed power generation unit to transmit four data of active droop coefficient, active power, reactive droop coefficient and reactive power to the next adjacent distributed power generation unit, the data transmission quantity is small, and the transmission structure is simple and easy to realize. The compensation value tends to converge after being calculated through a plurality of rounds of cycles in the communication, and the compensation value of each distributed power generation unit tends to be consistent in a steady state, so that the condition for the compensation value is met, and the design can ensure that the power distribution of the distributed power generation units is not influenced by a voltage and frequency compensation method.
The working principle and the adjusting process of the distributed voltage and frequency recovery method of the invention are explained in detail below by taking a micro-grid system composed of three distributed power generation units as an example and combining the attached drawings.
The structure of the distributed power generation unit in this embodiment is composed of a direct current source, a three-phase bridge arm, a filter inductor, a filter capacitor, and a connection inductor, and the structure and control block diagram of the ith distributed power generation unit are shown in fig. 2 in the attached drawings of the description. The control part consists of a main controller, a compensation function and a communication layer. The specific process is as follows: output voltage v to ith distributed generation unito(voai、vobi、voci) And an output current io(ioai、iobi、ioci) Sampling, and obtaining a voltage outer ring d-axis feedback voltage value v through dq conversionodiQ-axis feedback voltage value v of sum voltage outer loopoqiAnd performing power calculation to obtain instantaneous active power and reactive power, and filtering by a first-order Low Pass Filter (LPF) to obtain active power P of the ith distributed power generation unitiAnd reactive power Qi(ii) a The communication layer of the ith distributed generation unit receives active power P sent by the adjacent (i-1) th distributed generation uniti-1And active droop coefficient mi-1And reactive power Qi-1And reactive droop coefficient ni-1And the active power P of the selfiAnd active droop coefficient miAnd reactive power QiAnd reactive droop coefficient niSending the data to the (i + 1) th adjacent distributed power generation unit; and calculating a voltage compensation value delta v of the ith distributed generation unit by combining the data and a compensation functioniAnd frequency compensation value deltafi(ii) a Frequency compensation value delta f of ith distributed generation unitiCalculating to obtain the reference frequency f of the ith distributed generation uniti *To thereby derive a voltage phase angle thetai；vi *And-vodiAdd and 0, -voqiAnd adding the signals, sending the signals into the traditional voltage and current double closed-loop control to obtain a modulation wave under a dq coordinate system, and generating a driving signal to drive a three-phase switch bridge arm after Space Vector Pulse Width Modulation (SVPWM).
A block diagram of an experimental structure of the microgrid in the present embodiment is shown in fig. 3. The micro-grid consists of 3 distributed power generation units (DG) with the same capacity1、DG2、DG3) And 2 public loads (public load 1 and public load 2). Wherein, DG1Has a line impedance of (0.1 omega, 0.3Mh), DG2Has a line impedance of (0.1 omega, 1.78mH), DG3Has a line impedance of (0.05 omega, 0.16mH), a power of (15kW,1.8kVar) of the common load 1, a power of (15kW,4.2kVar) of the common load 2, and a DG1、DG2And DG3And forming a communication ring through low-bandwidth communication, and sending the respective active power and active droop coefficient and the reactive power and reactive droop coefficient to the next DG by each DG.
An experimental waveform diagram before and after voltage frequency compensation and load addition and subtraction of the distributed generation unit in the embodiment is shown in fig. 4 in the specification. At the beginning of a stage 1 (t is 0), a common load 1(15kW,1.8kVar) is connected to a bus and keeps a connected state all the time in the whole experiment, three distributed power generation units are started simultaneously, in the stage 1 period (0 < t < 1.4s), the three distributed power generation units respectively bear 5kW of active power and 0.6kVar of reactive power after power sharing, and the power is rapidly increased and always kept in a power sharing state after the power is stabilized. At this stage, the bus voltage and frequency drop obviously, and although the bus voltage and frequency do not exceed the allowable range (10% of the rated value), if the load power is further increased without taking compensation measures, the bus voltage and frequency drop further due to the droop term, and the bus voltage and frequency drop further exceeds the allowable range. When the phase 2 is started (t is 1.4s), the distributed bus voltage frequency compensation method suitable for the microgrid system, which is proposed in the embodiment, is added, during the phase 2 (1.4s < t < 2.4s), the active power and the reactive power output by the three distributed power generation units are basically kept unchanged and are still in an equipartition state, and the bus voltage and the frequency respond quickly and are basically stabilized at the rated values, which shows that the method can effectively compensate the bus voltage and the frequency. At the beginning of phase 3 (t 2.4s), a common load 2(15kW, 4.2kVar) is switched in, with a total load power of 30kW, 6 kVar. During the stage 3 (t is more than 2.4s and less than 3.4s), the power output of the three DGs is correspondingly increased due to the sudden increase of the load and rapidly reaches a steady-state value, the power sharing state is always maintained, and each DG bears 10kW of active load and 2kVar of reactive load in the steady state. The bus voltage and frequency quickly return to near nominal values after a short drop in the event of a sudden load change. The method can realize the compensation of the bus voltage and the frequency without changing the power uniform state when the load suddenly increases; at the beginning of phase 4 (t ═ 3.4s), the common load 2 is switched off and the load suddenly decreases, at which time the total load power decreases to 15kW,1.8 kVar. During the phase 4 (t is more than 3.4s), the power output of the three DGs is correspondingly reduced and rapidly reaches a steady state value, the power sharing state is always maintained, and each DG bears 5kW of active load and 0.6kVar of reactive load in the steady state. The bus voltage and frequency quickly return to near nominal values after a short increase in load surge. The method can still realize the compensation of the bus voltage and the frequency without changing the power average state when the load suddenly decreases.
Finally, the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered in the claims of the present invention.

Claims (1)

1. A distributed bus voltage frequency compensation method suitable for a micro-grid system is characterized by comprising the following steps: in an annular communication network formed by communication layers of all distributed power generation units, each distributed power generation unit receives active power and an active droop coefficient and reactive power and a reactive droop coefficient of one distributed power generation unit, a voltage compensation value and a frequency compensation value are obtained after compensation function operation, and the voltage compensation value and the frequency compensation value are added into a droop control equation of a main controller of the distributed power generation units to compensate the voltage and frequency droop of a bus;
the droop control equation is:
Figure FDA0003403137570000011
the compensation function is:
Figure FDA0003403137570000012
the power droop control link containing the voltage compensation value and the frequency compensation value is as follows:
Figure FDA0003403137570000013
in the droop control equation, the power droop control link including the compensation value and the compensation function: f. ofi *A frequency reference value of the ith distributed generation unit; v. ofi *The voltage outer ring reference value of the ith distributed generation unit; f. of0Is a frequency rating; v0Is a voltage rating; Δ fiA frequency compensation value for the ith distributed generation unit; Δ viA voltage compensation value for the ith distributed generation unit; m isiThe active droop coefficient of the ith distributed generation unit is obtained; piFor the ith distributed transmitterActive power of the electrical unit; n isiThe reactive droop coefficient of the ith distributed generation unit is obtained; qiThe reactive power of the ith distributed generation unit; m isi-1The active droop coefficient of the i-1 th distributed power generation unit is obtained; pi-1The active power of the i-1 th distributed power generation unit; n isi-1The reactive droop coefficient is the reactive droop coefficient of the (i-1) th distributed generation unit; qi-1The reactive power of the (i-1) th distributed generation unit; the subscript i is the serial number of the current distributed power generation unit, i-1 is the serial number of the last distributed power generation unit, and i is 2,3, …, k, where k denotes the number of distributed power generation units contained in the current microgrid system, and when i is 1, i-1 is k.
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