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CN113363961A - Current sharing and bus voltage recovery control method for direct-current micro-grid distributed power supply - Google Patents

Current sharing and bus voltage recovery control method for direct-current micro-grid distributed power supply Download PDF

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CN113363961A
CN113363961A CN202110476349.2A CN202110476349A CN113363961A CN 113363961 A CN113363961 A CN 113363961A CN 202110476349 A CN202110476349 A CN 202110476349A CN 113363961 A CN113363961 A CN 113363961A
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distributed power
power supply
current
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CN113363961B (en
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覃姝仪
刘增
刘进军
赵普
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Xian Jiaotong University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J1/00—Circuit arrangements for DC mains or DC distribution networks
    • H02J1/14—Balancing the load in a network
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
    • G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
    • 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
    • H02J1/00—Circuit arrangements for DC mains or DC distribution networks
    • H02J1/10—Parallel operation of DC sources

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Abstract

本发明公开了一种直流微网分布式电源均流及其母线电压恢复控制方法，本发明采用分布式稀疏通信手段进行分布式电源间两两通信，系统可靠性较高，且仅需传输分布式电源的输出电流信息，即可测量出各分布式电源输出端至直流母线间的线路阻抗，通过补偿相应下垂系数使得各分布式电源总输出阻抗相等，进而实现均流的目的，电流均分精度较高。本发明不仅能补偿因下垂系数造成的母线电压跌落，同时还补偿了由线路阻抗压降造成的母线电压跌落，母线电压补偿精度较高。本发明采用的线路阻抗测量方法不受线路阻抗自身大小的影响，同时也不受直流微网系统负载性质的影响，测量误差较小。

Figure 202110476349

The invention discloses a DC micro-grid distributed power supply current sharing and a bus voltage recovery control method. The invention adopts distributed sparse communication means to carry out two-to-two communication between distributed power supplies, the system reliability is high, and only needs to be transmitted and distributed. The output current information of the distributed power supply can be measured to measure the line impedance between the output terminal of each distributed power supply and the DC bus, and the total output impedance of each distributed power supply can be equalized by compensating the corresponding droop coefficient, so as to achieve the purpose of current sharing. High precision. The invention can not only compensate the busbar voltage drop caused by the sag coefficient, but also compensate the busbar voltage drop caused by the line impedance voltage drop, and the busbar voltage compensation accuracy is high. The line impedance measurement method adopted in the present invention is not affected by the size of the line impedance itself, and is also not affected by the load properties of the DC micro-grid system, and the measurement error is small.

Figure 202110476349

Description

Current sharing and bus voltage recovery control method for direct-current micro-grid distributed power supply
Technical Field
The invention belongs to the field of distributed direct-current microgrid coordination control research, and particularly relates to a direct-current microgrid distributed power supply current sharing and bus voltage recovery control method.
Background
The operation control targets of the direct-current micro-grid mainly comprise equipment-level control and system-level control, the equipment-level control mainly comprises some basic control targets of the physical-layer equipment based on local information, and the system-level control is to perform centralized management and energy optimization on the system so as to improve the overall operation efficiency and reliability. From the perspective of optimal operation of the system, how to reasonably distribute the output power/energy of each distributed power supply in the system is one of the key targets in the system-level control of the direct-current micro-grid.
In order to solve the problem of reasonable distribution of output power of distributed power supplies in a direct-current microgrid, students propose a parallel current-sharing control technology, because when the distributed power supplies are operated in parallel, due to the difference of control parameters and the nature of voltage sources of the outputs of the systems, small deviations can cause great difference of output currents. Therefore, when the output voltage is stabilized, the distributed power supplies are required to share the same current, and the output power is consistent. Among the current sharing control means, distributed control means mainly based on droop control has become the focus of research by researchers. Droop control does not require a central controller and all converters are in parallel, peer-to-peer relationship. The droop method is also called an adaptive voltage adjustment method, and adjusts the magnitude of the output current by changing a droop coefficient to decrease the output voltage when the load current increases. The method is simple in control and good in redundancy, and is the simplest multi-source coordination control strategy.
However, the droop control method still has some problems: firstly, the method is provided under the condition of neglecting the line impedance between the output end of the distributed power supply and the direct-current microgrid bus, however, for the actual microgrid system, the line impedance value cannot be neglected, the current sharing precision among the distributed power supplies is reduced due to the existence of the line impedance, and when the load is heavier, the current sharing precision is lower. Secondly, the implementation of droop control will result in a certain bus voltage drop, which will have a direct impact on the power quality of the dc microgrid system. Finally, the current sharing precision and the bus voltage drop problem cannot be considered when droop control is used, namely a lower bus voltage drop can be obtained by setting a smaller droop coefficient, the current sharing precision is lower, the current sharing precision can be improved by setting a larger droop coefficient, and the direct-current bus voltage drop is larger. Therefore, the stability of the bus voltage is ensured while the high current sharing precision is ensured, and the problem to be solved by the current sharing control technology of the distributed power supply of the direct current micro-grid is solved urgently.
Disclosure of Invention
The invention aims to overcome the defects and provides a method for controlling current sharing of a distributed power supply of a direct-current microgrid and bus voltage recovery of the distributed power supply. According to the method, current sharing precision among distributed power supplies can be greatly improved only by transmitting current information, and bus voltage drop caused by droop coefficients and line impedance is accurately compensated, so that the inherent problems of the traditional droop control method are solved.
In order to achieve the above object, the method comprises the following steps:
s1, locally adopting a droop control strategy by the direct-current micro-grid distributed power supply to sample local output current information;
s2, each distributed power supply in the direct-current micro-grid distributed power supplies communicates with an adjacent distributed power supply, and local output current information is sent to the adjacent distributed power supplies;
s3, after each distributed power supply obtains the output current information of the adjacent distributed power supplies, calculating the ratio of the local output current to the output current of the adjacent distributed power supplies;
s4, adjusting droop control coefficients of the direct-current micro-grid distributed power supplies according to the ratio of the local output current to the output current of the adjacent distributed power supplies, repeating the steps S1-S3, and enabling each distributed power supply to obtain the ratio of the local output current after the droop control coefficients are changed to the output current of the adjacent distributed power supplies;
s5, calculating the line impedance between the local output end and the direct current bus by the local controller of each distributed power supply according to the ratio of the local output current before and after the droop control coefficient is changed to the output current of the adjacent distributed power supply;
s6, setting corresponding droop coefficients of the distributed power supplies to enable the total equivalent output impedance of each distributed power supply to be equal;
s7, obtaining the average value of the output current of all the distributed power supplies of the direct-current micro-grid;
and S8, sending the product of the average value of the output current and the total equivalent output impedance as the compensation quantity of the voltage reference value into a voltage control loop of droop control by each distributed power supply local controller.
In S3, the ratio of the local output current to the output current of the adjacent distributed power source is calculated by the local controller.
In S5, the method for measuring the line impedance between the local output terminal and the dc bus includes:
Figure BDA0003047218170000031
wherein R isliThe line impedance value between the distributed power supply i and the direct current bus, k is the increment of the droop coefficient in S4, and RdIs the initial droop coefficient, x, for each distributed power supply in S11，x2And respectively changing the ratio of the output current of the distributed power supply i before and after the change of the droop coefficient to the output current of the adjacent distributed power supply.
In S6, the droop coefficient set for each distributed power supply is such that:
Rdi+Rli＝Rdj+Rlj＝…＝Rdn+Rln＝R
wherein R isdi Rdj,…,RdnThe droop coefficients R are respectively set for the direct current micro-grid distributed power supplies i, j, …, nli,Rlj,…,RlnThe line impedance from the output end of the direct current microgrid distributed power supply i, j, …, n to the direct current bus is respectively, and R is the line impedance from each distributed power supplyThe total equivalent output impedance of the power supply.
In S7, a current observer dynamic expression based on a consistency algorithm is adopted to obtain the average value of the output currents of all the distributed power supplies of the direct-current micro-grid.
In S7, the method for calculating the dynamic expression of the current observer based on the consensus algorithm is as follows:
Figure BDA0003047218170000032
wherein ioiIs the output current value i of the ith distributed power supplyavgi,iavgjObtaining the average value of output currents of the full-system distributed power supplies a for the ith and the jth distributed power supplies respectively by using a local current observerijFor communication weight factors in a communication network topology, a when a distributed power source i is in communication association with a distributed power source j ij1, otherwise, aij＝0。
And calculating the average value of the output current of all the distributed power supplies of the direct-current micro-grid by using a local controller.
In S8, the voltage loop voltage reference value calculating method in droop control is as follows:
Urefi＝(U*-Rdiioi)+Riavgi
wherein, U*,UrefiRespectively, the voltage reference value Ri of the distributed power source i before and after voltage compensationavgiThe amount of voltage compensation for distributed power source i.
Compared with the prior art, the distributed power supplies are communicated pairwise by adopting a distributed sparse communication means, the system reliability is higher, the line impedance between the output end of each distributed power supply and a direct current bus can be measured only by transmitting the output current information of the distributed power supplies, the total output impedance of each distributed power supply is equal by compensating the corresponding droop coefficient, the current equalizing purpose is further realized, and the current equalizing precision is higher. The invention not only can compensate the bus voltage drop caused by the droop coefficient, but also can compensate the bus voltage drop caused by the line impedance voltage drop, and the bus voltage compensation precision is higher. The line impedance measurement method adopted by the invention is not influenced by the size of the line impedance, is not influenced by the load property of the direct-current microgrid system, has small measurement error, and solves the problems that the current sharing precision is influenced by the line impedance and the bus voltage drops in the traditional droop control method.
Drawings
Fig. 1 shows a droop control method adopted for power sharing of a distributed power supply of a direct-current microgrid;
FIG. 2 is a schematic diagram of two droop control equivalent circuits of the distributed power supplies;
fig. 3 is a communication topology diagram of a dc microgrid distributed power supply;
FIG. 4 is a schematic diagram illustrating control of parallel operation of two distributed power supplies;
fig. 5 is a block diagram illustrating current sharing and bus voltage recovery control of a distributed power supply of a dc microgrid;
FIG. 6 is a DC bus voltage simulation waveform diagram when the strategy of the present invention is used for control;
FIG. 7 is a DC bus voltage simulation waveform (before load change) when the inventive strategy is used for control;
FIG. 8 is a DC bus voltage simulation waveform (after load change) when the inventive strategy is employed for control;
FIG. 9 is a simulated waveform diagram of the output current of the distributed power source when the strategy of the invention is adopted for control;
FIG. 10 is a simulation oscillogram of output current of a distributed power supply (before load change) when the strategy of the invention is adopted for control;
FIG. 11 is a simulation oscillogram (after load change) of the output current of the distributed power source when the strategy of the invention is adopted for control;
FIG. 12 is a graph of DC bus voltage waveforms when only droop control is employed;
fig. 13 is a waveform diagram of the output current of the distributed power supply only in the case of droop control.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
The conventional droop control method is shown in fig. 1, and it can be seen that in the voltage loop control of the distributed power supply, through adjustmentSag factor RdCan adjust the output voltage instruction U of the distributed power supplyrefTo adjust the output voltage UoTo adjust the output current i of the distributed power supplyoTo achieve the purpose of controlling the output power of the distributed power supply.
FIG. 2 is an equivalent circuit for droop control for parallel operation of two distributed power sources i, j, where U is*For a given value of the output voltage of the distributed power supply, UbusIs a DC bus voltage value, Uoi，UojThe actual output voltage values i, i of the distributed power supplies i, j respectivelyoi，iojAnd outputting current values for the distributed power supplies i and j respectively. RdFor a virtual resistance at the output of the distributed power supply, i.e. the set droop coefficient, Rli，RljRespectively, the line impedance R between the output end of the distributed power supply and the DC busLThe equivalent load resistance of the direct current microgrid system is obtained. According to kirchhoff's equivalent current-voltage law, the following can be obtained:
Uoi＝U*-Rdioi，Uoj＝U*-Rdioj (1)
Ubus＝Uoi-Rliioi＝Uoj-Rljioj (2)
the equations (1) and (2) are solved simultaneously to obtain:
Figure BDA0003047218170000051
wherein R isi、RjThe equivalent total output impedance of each distributed power source i, j, as can be seen from equation (3), the output current of each distributed power source cannot be proportionally distributed according to a given droop coefficient due to the existence of the line impedance, and meanwhile, as can be seen from equations (1) and (2), the droop coefficient and the existence of the line impedance cause the drop of the bus voltage.
In order to solve the problems of droop control, the invention introduces a method for controlling current sharing of a distributed power supply of a direct-current microgrid and bus voltage recovery of the distributed power supply, and fig. 3 shows a communication topology of the distributed power supply of the direct-current microgrid when the strategy is adopted for control. It can be seen that the control adopts a means of pairwise communication among the distributed power supplies, each distributed power supply only communicates with the adjacent distributed power supplies, and each distributed power supply local controller adopts a consistency algorithm to calculate the average value of the measurement information of the whole system by obtaining the local measurement information and the neighbor node measurement information. The dynamic expression of the current observer based on the consistency algorithm is shown as the following formula:
Figure BDA0003047218170000061
in the formula ioiIs output current information of the ith distributed power supply iavgi，iavgjAnd respectively obtaining the average value of the output current of the full-system distributed power supply by the ith and the jth distributed power supplies by using a local current observer. a isijFor communication weight factors in a communication network topology, a when a distributed power source i is in communication association with a distributed power source jij>0, take aij1, otherwise, aij0. It can be proved that if only one directed spanning tree is included in the communication network topology, when t → ∞
Figure BDA0003047218170000062
And converge at ioiThe arithmetic mean of (a), i.e.:
Figure BDA0003047218170000063
it can be seen that, when the consistency algorithm is adopted for control, when any two distributed power supplies have communication faults or a certain distributed power supply quits operation due to the faults, a cluster of directed spanning trees in the communication network can still be ensured. Therefore, the control method has high reliability, the problem that the whole system cannot normally operate due to the fault of a certain distributed power supply or a certain communication line does not exist, and meanwhile, all the distributed power supplies have the same priority and meet the plug and play requirement of the direct-current micro-grid on the distributed power supplies.
According to the research, the average values of the output voltage and the current of all the distributed power supplies are solved in the local controllers of all the distributed power supplies by using the dynamic expression of the consistency algorithm, and are respectively compared with the instruction voltage and the local output current information, so that the current output voltage and current values of the distributed power supplies are corrected, the current equalizing precision is improved, and the voltage drop of a direct current bus caused by a droop coefficient is compensated. However, no current research considers the influence of the voltage drop caused by the line impedance on the bus voltage drop, and the bus voltage drop caused by the line impedance voltage drop cannot be ignored in the low-voltage dc microgrid or the dc microgrid system with large line impedance. Therefore, the invention provides a line impedance measuring method, which sets corresponding droop coefficients after obtaining the impedance information of each distributed power supply line, so that the total equivalent output impedance of each distributed power supply is equal, and the purpose of current sharing is further achieved. Meanwhile, each distributed power local controller obtains the average value of the output current of each distributed power by using a current observer based on a consistency algorithm, and the product of the average value and the total equivalent output impedance is used as the local voltage compensation quantity, so that the voltage drop of the direct current bus caused by a droop coefficient and line impedance is compensated, and the aim of accurately compensating the bus voltage is fulfilled. The method has the following specific principle:
taking two distributed power supplies i, j as an example, measuring the line impedance, and locally adopting droop control:
Figure BDA0003047218170000071
Ubus＝U*-Riioi＝U*-Rjioj (7)
Ri＝Rd+Rli，Rj＝Rd+Rlj (8)
wherein, U*Is a command power of a distributed power supply i, jAnd pressing the reference value. U shapebusIs a DC bus voltage value, Urefi，UrefjRespectively and actually outputting voltage reference values i, i by the distributed power supplies i, joi，iojRespectively outputting current values, R, for distributed power supplies i, jdFor distributed power droop coefficient, Rli，RljLine impedance R between the output end of the distributed power supply i, j and the DC busi，RjRespectively, the total equivalent output impedance of the distributed power sources i, j. Is easily obtained from the formula (7):
Figure BDA0003047218170000072
each distributed power supply increases k on the original droop coefficient, and the k is as follows:
Figure BDA0003047218170000073
wherein ioi′，ioj' the output current values of the distributed power sources i, j after the droop coefficient is increased, respectively. x is the number of1，x2And increasing the output current ratio of the front distributed power supply i and the rear distributed power supply j for the droop coefficient. The following equations (9) and (10) can be obtained:
Figure BDA0003047218170000074
Rli＝Ri-Rd (12)
namely, the distributed power supply i obtains the current value i before and after the droop coefficient is changed through the communication with the distributed power supply joj，ioj', according to (11) and (12), the line impedance R between the distributed power source i and the DC bus is calculated by the local controllerli。
And carrying out error analysis on the line impedance measurement method:
Figure BDA0003047218170000081
Figure BDA0003047218170000082
as shown in formulas (13) and (14), x ″)1，x2"respectively the output currents ioi，iojRatio and output current ioi′，ioj' measured error value of ratio.
From the formula (13):
Figure BDA0003047218170000083
the line impedance R is known from the formulas (12) and (15)liMeasured error of (2) is represented by RiDenominator term x of1″-x2"and molecular terms kx2"composition, wherein the denominator term x1″-x2"cannot be eliminated, belongs to an uncontrollable factor, and kx is the molecular term2", should have k<1, to avoid amplification errors.
In order to enable the current to be evenly divided under the steady state and the dynamic condition, the droop coefficient of each distributed power supply should be as follows:
Rdi+Rli＝Rdj+Rlj＝…＝Rdn+Rln＝R (16)
so that
ioi＝ioj＝…＝ion (17)
Wherein R isdi Rdj,…,RdnThe droop coefficients i, i are respectively set for the direct current micro-grid distributed power sources i, j, …, noi,ioj,…,ionThe output current values are i, j and …, n, and R is the total equivalent output impedance of the distributed power supply, which should satisfy
Figure BDA0003047218170000084
Wherein, Delta UmaxMaximum voltage drop allowed for bus voltage, INThe rated current of the bus at full load. The droop coefficient R should be made to account for line impedance measurement errorsdiRdj,…,RdnAnd if the voltage is as large as possible, R is also as large as possible, so that the current sharing precision is ensured, and meanwhile, the bus voltage compensation is carried out on the basis. The dynamic expression of the current observer based on the consistency algorithm is shown in a formula (4), namely, each distributed power supply only communicates with the adjacent distributed power supply, the local controller calculates the average value of the output currents of all the distributed power supplies of the direct-current microgrid system according to the formula (4), and at the moment, the voltage compensation quantity of each distributed power supply is
ΔU＝Riavgi＝Riavgj＝…＝Riavgn (19)
The command voltage reference value of the distributed power source i is
Urefi＝(U*-Rdiioi)+Riavgi (20)
Therefore, the method can measure the line impedance between the output end of each distributed power supply and the direct current bus only by transmitting adjacent current information, realizes current sharing, compensates the bus voltage drop caused by the droop coefficient and the line impedance, and is a more accurate bus voltage compensation mode.
Example (b):
two distributed power sources are taken as examples, and the specific implementation mode is explained as follows:
FIG. 4 is a schematic diagram of the control of the parallel operation of two distributed power sources, C1、C2Respectively two distributed power supply output end capacitors, Rl1、Rl2Line impedance i between the output ends of the two distributed power supplies and the DC buso1、io2Respectively output currents, R, for two distributed power suppliesLIs the load equivalent resistance. Each distributed power supply locally adopts droop control, and the two-layer control adopts the control strategy and improves the bus voltage regulation rate, as shown in fig. 5. In MATLAB according to the circuit diagram shown in FIG. 4 and the control method shown in FIG. 5The strategy of the invention is verified by a SIMULINK platform, wherein the rated voltage value of a bus is 80V, and the line resistance R of two distributed power suppliesl1＝2Ω，Rl22.5 Ω, load R L80 Ω. The specific implementation steps are as follows:
1. initially setting the droop coefficient of each distributed power supply to be 2.5 omega, respectively sampling the output current of the local controllers of the two distributed power supplies in a steady state, respectively sampling 5 times of output current values by adopting an average filtering method, simultaneously filtering high-frequency components in the output current by adopting a low-pass filter, and then obtaining the average value of the local output current after 5 times of sampling.
2. And each distributed power supply is communicated with the adjacent distributed power supply, and the local output current average value of each distributed power supply is sent to the adjacent distributed power supply. At this time, each distributed power supply local controller calculates the ratio of the local output current average value to the adjacent distributed power supply output current average value through formula (9), and the ratio is recorded as x1。
3. Adding 0.5 omega to the droop coefficient of each distributed power supply, repeating the step 1 to obtain the output current average value of each distributed power supply after the droop coefficient is changed, repeating the step 2 to obtain the ratio of the local output current average value of each distributed power supply after the droop coefficient is changed to the output current average value of the adjacent distributed power supply, and recording the ratio as x2。
4. The local controller of each distributed power supply can calculate the line impedance from the output end of the distributed power supply to the direct current bus according to the formulas (11) and (12). Experimental calculation to obtain Rl1＝2.0098Ω，Rl2The measurement error from the actual resistance value was 0.49%, 0.43%, respectively, when it was 2.5107 Ω.
5. Uniformly setting the total output impedance R of each distributed power supply to be 5 omega, and calculating the droop coefficients R of the distributed power supplies 1 and 2 by the formula (12)d1＝2.9902Ω，Rd22.4893 Ω. At the moment, the total output impedance of the two distributed power supplies is basically consistent, and the purpose of current sharing is achieved.
6. When the local controller of each distributed power supply communicates with the adjacent distributed power supplies, the two-layer control adopts a current observer based on the formula (4) to obtain the average value of the output current of all the distributed power supplies, and the product of the average value and the total output impedance R is used as the compensation quantity of the voltage reference instruction of the local controller to be sent into a voltage control loop, as shown in the formulas (19) and (20), the purpose of accurately compensating the voltage drop of the bus is achieved.
Fig. 6 to 11 show simulation results in experiments using the above inventive procedure. Fig. 6 shows the simulation results of the dc bus voltage when the inventive control strategy is applied, wherein the load is weighted when t is 1 s. Fig. 7 and 8 are respectively the steady-state values of the dc bus voltage before and after the load is increased, and it can be seen that the steady-state values of the dc bus voltage before and after the load is changed are both rated voltage 80V, so that it can be seen that the method has a relatively accurate dc bus voltage compensation effect.
Fig. 9 shows the output current values of two parallel distributed power supplies when the inventive strategy is employed. Fig. 10 and fig. 11 are steady-state values of output currents of two distributed power supplies before and after load change, respectively, and it can be seen that the output currents of the two distributed power supplies before and after load change almost tend to be consistent, so that it can be seen that the output current sharing accuracy of the distributed power supplies is high when the method is used for controlling.
Fig. 12 and 13 show the dc bus voltage and the output current values of the two distributed power sources when droop control is performed only by using the initial droop coefficient, respectively. It can be seen that when only droop control is adopted, due to the influence of inconsistent line impedance, the current sharing precision is poor, meanwhile, the direct current bus voltage also drops to a certain extent, and meanwhile, when the load is heavier, the current sharing precision is worse, and the direct current bus voltage drop is also larger.
In summary, by comparing the simulation result of the control strategy with the simulation result of only using droop control, it can be seen that the method has higher current sharing accuracy and bus voltage compensation accuracy.

Claims (8)

1.一种直流微网分布式电源均流及其母线电压恢复控制方法，其特征在于，包括以下步骤：1. a DC micro-grid distributed power supply current sharing and its bus voltage recovery control method, is characterized in that, comprises the following steps: S1，直流微网分布式电源本地采用下垂控制策略，对本地输出电流信息进行采样；S1, the DC micro-grid distributed power source adopts the droop control strategy locally to sample the local output current information; S2，直流微网分布式电源中的每台分布式电源与相邻分布式电源进行通信，向相邻分布式电源发送本地输出电流信息；S2, each distributed power supply in the DC micro-grid distributed power supply communicates with the adjacent distributed power supply, and sends local output current information to the adjacent distributed power supply; S3，每台分布式电源获得相邻分布式电源输出电流信息后，计算出本地输出电流与相邻分布式电源输出电流比值；S3, after each distributed power supply obtains the output current information of the adjacent distributed power supply, the ratio of the local output current to the output current of the adjacent distributed power supply is calculated; S4，根据本地输出电流与相邻分布式电源输出电流比值，调整直流微网分布式电源下垂控制系数，重复步骤S1～S3，每台分布式电源获取下垂控制系数改变后的本地输出电流与相邻分布式电源输出电流比值；S4, according to the ratio of the local output current to the output current of the adjacent distributed power supply, adjust the droop control coefficient of the DC micro-grid distributed power supply, and repeat steps S1 to S3, each distributed power supply obtains the local output current after the change of the droop control coefficient and the phase The output current ratio of adjacent distributed power sources; S5，每台分布式电源本地控制器利用下垂控制系数改变前后的本地输出电流与相邻分布式电源输出电流比值，计算出本地输出端至直流母线间的线路阻抗；S5, the local controller of each distributed power source uses the ratio of the local output current before and after the change of the droop control coefficient to the output current of the adjacent distributed power source to calculate the line impedance between the local output terminal and the DC bus; S6，设置各分布式电源的相应下垂系数，使得每台分布式电源总等效输出阻抗相等；S6, setting the corresponding droop coefficient of each distributed power source, so that the total equivalent output impedance of each distributed power source is equal; S7，获得直流微网全部分布式电源输出电流平均值；S7, obtain the average value of output currents of all distributed power sources in the DC microgrid; S8，每台分布式电源本地控制器将输出电流平均值与总等效输出阻抗的乘积作为电压参考值的补偿量，送入下垂控制的电压控制环中。S8, the local controller of each distributed power supply takes the product of the average output current and the total equivalent output impedance as the compensation amount of the voltage reference value, and sends it into the voltage control loop of the droop control. 2.根据权利要求1所述的一种直流微网分布式电源均流及其母线电压恢复控制方法，其特征在于，S3中，本地输出电流与相邻分布式电源输出电流比值通过本地控制器计算。2. A kind of DC micro-grid distributed power supply current sharing and bus voltage recovery control method thereof according to claim 1, it is characterized in that, in S3, the local output current and the adjacent distributed power supply output current ratio are passed through the local controller calculate. 3.根据权利要求1所述的一种直流微网分布式电源均流及其母线电压恢复控制方法，其特征在于，S5中，本地输出端至直流母线间线路阻抗的测量方法如下：3. a kind of DC micro-grid distributed power supply current sharing according to claim 1 and its bus voltage recovery control method, it is characterized in that, in S5, the measuring method of line impedance between local output terminal to DC bus is as follows:
Figure FDA0003047218160000011
Figure FDA0003047218160000011
 其中，Rli为分布式电源i至直流母线间的线路阻抗值，k为S4中下垂系数的增加量，Rd为S1中每台分布式电源的初始下垂系数，x1，x2分别为下垂系数改变前后分布式电源i输出电流与相邻分布式电源输出电流的比值。Among them, R li is the line impedance value between the distributed power source i and the DC bus, k is the increase of the droop coefficient in S4, R d is the initial droop coefficient of each distributed power source in S1, x 1 , x 2 are respectively The ratio of the output current of the distributed power supply i to the output current of the adjacent distributed power supply before and after the droop coefficient is changed. 4.根据权利要求1所述的一种直流微网分布式电源均流及其母线电压恢复控制方法，其特征在于，S6中，各分布式电源所设置的下垂系数应使：4. a kind of DC micro-grid distributed power source current sharing and bus voltage recovery control method thereof according to claim 1, is characterized in that, in S6, the droop coefficient that each distributed power source is set up should make: Rdi+Rli＝Rdj+Rlj＝…＝Rdn+Rln＝R Rdi + Rli = Rdj + Rlj =…= Rdn + Rln =R 其中，Rdi Rdj,…,Rdn分别为直流微网分布式电源i,j,…,n的所设下垂系数，Rli,Rlj,…,Rln分别为直流微网分布式电源i,j,…,n输出端至直流母线间的线路阻抗，R为每台分布式电源总等效输出阻抗。Among them, R di R dj ,…,R dn are the set droop coefficients of the DC micro-grid distributed power sources i,j,…,n respectively, R li ,R lj ,…,R ln are the DC micro-grid distributed power sources, respectively The line impedance between the output end of i,j,…,n and the DC bus, R is the total equivalent output impedance of each distributed power supply. 5.根据权利要求1所述的一种直流微网分布式电源均流及其母线电压恢复控制方法，其特征在于，S7中，采用基于一致性算法的电流观测器动态表达式，获得直流微网全部分布式电源输出电流平均值。5. A kind of DC micro-grid distributed power supply current sharing and bus voltage recovery control method thereof according to claim 1, is characterized in that, in S7, adopts the current observer dynamic expression based on consistency algorithm, obtains DC micro-grid The average value of the output current of all distributed power sources in the network. 6.根据权利要求5所述的一种直流微网分布式电源均流及其母线电压恢复控制方法，其特征在于，S7中，基于一致性算法的电流观测器动态表达式计算方法如下：6. a kind of DC micro-grid distributed power supply current sharing and bus voltage recovery control method thereof according to claim 5, is characterized in that, in S7, the current observer dynamic expression calculation method based on consistency algorithm is as follows:
Figure FDA0003047218160000021
Figure FDA0003047218160000021
 其中，ioi为第i台分布式电源的输出电流值，iavgi,iavgj分别为第i,j台分布式电源利用本地电流观测器获得的全系统分布式电源输出电流平均值，aij为通信网络拓扑中通信权重因子，当分布式电源i与分布式电源j存在通信关联时，aij＝1，否则，aij＝0。Among them, i oi is the output current value of the ith distributed power generation, i avgi , i avgj are the average value of the output current of the whole system of distributed power generation obtained by the i and j th distributed power generation using the local current observer, respectively, a ij is the communication weight factor in the communication network topology, when the distributed power source i and the distributed power source j have a communication association, a ij =1, otherwise, a ij =0. 7.根据权利要求5所述的一种直流微网分布式电源均流及其母线电压恢复控制方法，其特征在于，获得直流微网全部分布式电源输出电流平均值采用本地控制器计算。7 . The DC microgrid distributed power supply current sharing and its bus voltage recovery control method according to claim 5 , wherein a local controller is used to obtain the average value of output currents of all DC microgrid distributed power sources. 8 . 8.根据权利要求1所述的一种直流微网分布式电源均流及其母线电压恢复控制方法，其特征在于，S8中，下垂控制中电压环电压参考值计算方法如下：8. A kind of DC micro-grid distributed power supply current sharing and bus voltage recovery control method thereof according to claim 1, is characterized in that, in S8, the calculation method of voltage loop voltage reference value in droop control is as follows: Urefi＝(U*-Rdiioi)+Riavgi U refi = (U * -R di i oi )+Ri avgi 其中，U*,Urefi分别为电压补偿前后分布式电源i的电压参考值，Riavgi为分布式电源i的电压补偿量。Among them, U * and U refi are the voltage reference values of the distributed power source i before and after voltage compensation respectively, and Ri avgi is the voltage compensation amount of the distributed power source i.
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