CN113363961B - 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 PDFInfo
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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
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- H—ELECTRICITY
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- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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Abstract
The invention discloses a method for current sharing of a distributed power supply of a direct-current micro-grid and bus voltage recovery control method thereof. 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 measuring method adopted by the invention is not influenced by the size of the line impedance, and is also not influenced by the load property of the direct-current microgrid system, and the measuring error is small.
Description
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 an 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 a 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 a local output end and a direct current bus by using the ratio of the local output current before and after the droop control coefficient is changed and the output current of the adjacent distributed power supply by each distributed power supply local controller;
s6, setting corresponding droop coefficients of all distributed power supplies to enable the total equivalent output impedance of all the distributed power supplies to be equal;
s7, obtaining an average value of output currents of all 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 for droop control by each local controller of the distributed power supply.
And in S3, calculating the ratio of the local output current to the output current of the adjacent distributed power supply through a local controller.
In S5, the method for measuring the line impedance between the local output terminal and the dc bus includes:
wherein R is li Is the line impedance value between the distributed power supply i and the direct current bus, k is the increment of the droop coefficient in S4, R d Is the initial droop coefficient, x, of each distributed power supply in S1 1 ，x 2 And 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 coefficients set for each distributed power supply are such that:
R di +R li ＝R dj +R lj ＝…＝R dn +R ln ＝R
wherein R is di R dj ,…,R dn The set droop coefficients R are respectively the droop coefficients of the direct current micro-grid distributed power supplies i, j, …, n li ,R lj ,…,R ln The impedance of a line between an n output end and a direct current bus is respectively the direct current micro-grid distributed power sources i, j, …, and R is the total equivalent output impedance of each distributed power source.
And S7, obtaining the average value of the output current of all the distributed power supplies of the direct-current micro-grid by adopting a dynamic expression of a current observer based on a consistency algorithm.
In S7, the method for calculating the dynamic expression of the current observer based on the consistency algorithm is as follows:
wherein i oi Is the output current value i of the ith distributed power supply avgi ,i avgj Obtaining 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 observer ij For 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 ij =1, otherwise, a ij ＝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 method for calculating the voltage reference value of the voltage loop in droop control is as follows:
U refi ＝(U * -R di i oi )+Ri avgi
wherein, U * ,U refi Respectively, the voltage reference value Ri of the distributed power source i before and after voltage compensation avgi The 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 simulation waveform of DC bus voltage (after load change) when the strategy of the present invention is adopted for control;
FIG. 9 is a simulation waveform diagram of the output current of the distributed power source when the strategy of the present 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, the droop coefficient R is adjusted d Can adjust the output voltage instruction U of the distributed power supply ref To adjust the output voltage U o To adjust the output current i of the distributed power supply o To 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, U bus Is a DC bus voltage value, U oi ，U oj Are respectively distributedThe actual output voltage value, i, of the formula power supply i, j oi ，i oj And outputting current values for the distributed power supplies i and j respectively. R d For a virtual resistance at the output of the distributed power supply, i.e. the set droop coefficient, R li ，R lj Respectively, the line impedance R between the output end of the distributed power supply and the DC bus L The equivalent load resistance of the direct current microgrid system is obtained. According to kirchhoff's equivalent current-voltage law, the following can be obtained:
U oi ＝U * -R d i oi ，U oj ＝U * -R d i oj (1)
U bus ＝U oi -R li i oi ＝U oj -R lj i oj (2)
the equations (1) and (2) are solved simultaneously to obtain:
wherein R is i 、R j The equivalent total output impedance of each distributed power source i, j is shown by 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 line impedance, and meanwhile, the droop coefficient and the existence of line impedance cause the drop of bus voltage as shown by equations (1) and (2).
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:
in the formula i oi For the output current information of the ith distributed power supply, i avgi ，i avgj And 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 is a ij For 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 ij >0, take a ij =1, otherwise, a ij And =0. It can be proved that if only one directed spanning tree is included in the communication network topology, when t → ∞
And converge at i oi The arithmetic mean of (a), i.e.:
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 means 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 requirement of the direct-current micro-grid on plug and play of 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:
U bus ＝U * -R i i oi ＝U * -R j i oj (7)
R i ＝R d +R li ，R j ＝R d +R lj (8)
wherein, U * Is the command voltage reference value of the distributed power source i, j. U shape bus Is a DC bus voltage value, U refi ，U refj Respectively and actually outputting voltage reference values i, i by the distributed power supplies i, j oi ，i oj Respectively outputting current values, R, for distributed power supplies i, j d For distributed power droop coefficient, R li ，R lj Line impedances R between the output end of the distributed power supply i, j and the DC bus respectively i ，R j Respectively, the total equivalent output impedance of the distributed power sources i, j. Is easily obtained from the formula (7):
each distributed power supply increases k on the original droop coefficient, and the k is as follows:
wherein i oi ′，i oj ' the output current values of the distributed power sources i, j after the droop coefficient is increased, respectively. x is the number of 1 ，x 2 And 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:
R li ＝R i -R d (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 j oj ，i oj ', according to (11) and (12), the line impedance R between the distributed power source i and the DC bus is calculated by the local controller li 。
And carrying out error analysis on the line impedance measurement method:
as shown in formulas (13) and (14), x ″) 1 ，x 2 "respectively the output currents i oi ，i oj Ratio and output current i oi ′，i oj ' measured error value of ratio.
From the formula (13):
the line impedance R is known from the formulas (12) and (15) li Is measured with a measurement error of R i Denominator term x of 1 ″-x 2 "and molecular terms kx 2 "composition, wherein the denominator term x 1 ″-x 2 "cannot be eliminated, belongs to an uncontrollable factor, and kx is the molecular term 2 ", 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:
R di +R li ＝R dj +R lj ＝…＝R dn +R ln ＝R (16)
so that
i oi ＝i oj ＝…＝i on (17)
Wherein R is di R dj ,…,R dn The droop coefficients i, i and n are respectively the droop coefficients i, j, …, n of the direct-current micro-grid distributed power supply i, j and … oi ,i oj ,…,i on The output current values are i, j, …, n, and R is the total equivalent output impedance of the distributed power supply, which should satisfy
Wherein, delta U max Maximum voltage drop allowed for bus voltage, I N The rated current of the bus at full load. The droop coefficient R should be made to account for line impedance measurement errors di R dj ,…,R dn And if R is as large as possible, R should be as large as possible, so that the current sharing accuracy 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, and the local controller calculates the direct-current microgrid according to the formula (4)The average value of the output currents of all the distributed power supplies of the system is that the voltage compensation quantity on each distributed power supply is
ΔU＝Ri avgi ＝Ri avgj ＝…＝Ri avgn (19)
The command voltage reference value of the distributed power source i is
U refi ＝(U * -R di i oi )+Ri avgi (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, C 1 、C 2 Are respectively two distributed power supply output end capacitors R l1 、R l2 Respectively the line impedance i between the output ends of the two distributed power supplies and the DC bus o1 、i o2 Respectively output currents, R, for two distributed power supplies L Is the load equivalent resistance. Each distributed power supply adopts droop control locally, and the second-layer control adopts the control strategy and improves the bus voltage regulation rate, as shown in fig. 5. The strategy of the invention is verified on a MATLAB/SIMULINK platform according to the circuit diagram shown in FIG. 4 and the control mode shown in FIG. 5, wherein the rated voltage value of the bus is 80V, and the line resistances R of the two distributed power supplies are R l1 ＝2Ω，R l2 =2.5 Ω, load R L =80 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, the local controller of each distributed power supply calculates the ratio of the average value of the local output current to the average value of the output current of the adjacent distributed power supply according to the formula (9), and the ratio is recorded as x 1 。
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 x 2 。
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 R l1 ＝2.0098Ω，R l2 And the measurement errors of the =2.5107 Ω and the actual resistance value are 0.49% and 0.43%, respectively.
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，R d2 =2.4893 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 is communicated with the adjacent distributed power supply, the two-layer control adopts the current observer based on the formula (4) to obtain the average value of the output currents 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 the 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 at t =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. A method for controlling current sharing and bus voltage recovery of a distributed power supply of a direct-current microgrid is characterized by comprising the following steps:
s1, locally adopting a droop control strategy by a 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, and repeating the steps S1-S3, wherein each distributed power supply obtains 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 a local output end and a direct current bus by using the ratio of the local output current before and after the droop control coefficient is changed and the output current of the adjacent distributed power supply by each distributed power supply local controller;
s6, setting corresponding droop coefficients of all distributed power supplies to enable the total equivalent output impedance of all the distributed power supplies to be equal;
s7, obtaining an average value of output currents of all distributed power supplies of the direct-current micro-grid;
and S8, each distributed power supply local controller takes the product of the average output current value and the total equivalent output impedance as the compensation quantity of the voltage reference value, and sends the compensation quantity into a voltage control loop for droop control.
2. The method according to claim 1, wherein in step S3, a ratio of the local output current to the output current of the adjacent distributed power supplies is calculated by the local controller.
3. The method for current sharing and bus voltage recovery control of the DC microgrid distributed power supply according to claim 1, wherein in S5, a method for measuring line impedance between a local output end and a DC bus is as follows:
wherein R is li Is the line impedance value between the distributed power supply i and the direct current bus, k is the increment of the droop coefficient in S4, R d Is the initial droop coefficient, x, of each distributed power supply in S1 1 ，x 2 The output current of the distributed power supply i before and after the droop coefficient is changed and the output current of the adjacent distributed power supplyThe ratio of the flows.
4. The method according to claim 1, wherein in S6, the droop coefficients set for the distributed power supplies are such that:
R di +R li ＝R dj +R lj ＝…R dn +R ln ＝R
wherein R is di R dj ,…,R dn The droop coefficients R are respectively the droop coefficients of the direct current micro-grid distributed power supplies i, j, …, n li ,R lj ,…,R ln The impedance of the line between the output end of the n output ends and the direct current bus is respectively direct current micro-grid distributed power sources i, j, …, and R is the total equivalent output impedance of each distributed power source.
5. The method according to claim 4, wherein in S7, a dynamic expression of a current observer based on a consistency algorithm is adopted to obtain the average value of the output currents of all the distributed power supplies of the DC microgrid.
6. The method for current sharing and bus voltage recovery control of the DC microgrid distributed power supply according to claim 5, characterized in that in S7, the method for calculating the dynamic expression of the current observer based on the consistency algorithm is as follows:
wherein i oi Is the output current value i of the ith distributed power supply avgi ,i avgj Obtaining 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 observer ij For 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 ij =1, otherwise, a ij ＝0。
7. The method of claim 5, wherein the average value of the output currents of all the distributed power supplies of the DC microgrid is obtained and calculated by a local controller.
8. The method according to claim 6, wherein in S8, the voltage loop voltage reference value calculation method in droop control is as follows:
U refi ＝(U * -R di i oi )+Ri avgi
wherein, U * ,U refi Respectively, the voltage reference value Ri of the distributed power source i before and after voltage compensation avgi Is the voltage compensation quantity, R, of the distributed power supply i di Set droop coefficient, i, for direct current microgrid distributed power supply i oi Is the output current value of the distributed power supply i.
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