Disclosure of Invention
The invention aims to at least solve one of the technical problems in the prior art, and provides a power quality constraint index analysis method of a distributed power generation access system to solve the problems in the prior art.
As an aspect of the present invention, there is provided a power quality constraint index analysis method for a distributed power generation access system, where the power quality constraint index includes a voltage deviation, a harmonic current, a harmonic voltage, and a three-phase imbalance, the power quality constraint index analysis method for the distributed power generation access system includes:
sequencing the power quality constraint indexes to obtain the constraint sequence of the power quality constraint indexes, namely voltage deviation, harmonic current, harmonic voltage and three-phase unbalance;
performing first planning of distributed photovoltaic absorption capacity aiming at voltage deviation constraint indexes of all nodes, wherein the first planning result of the ith node is set as Si,1And temporarily setting the planning result of the ith node as Si=Si,1I is a natural number not less than 1;
with the planning result S of the ith nodeiFor capacity limit, harmonics for individual nodesCarrying out secondary planning on the distributed photovoltaic absorption capacity by the wave current constraint index, wherein the secondary planning result of the ith node is set as Si,2If S isi,2<SiAnd temporarily setting the planning result of the ith node as Si=Si,2Else SiKeeping the same;
with the planning result S of the ith nodeiPerforming third planning of distributed photovoltaic absorption capacity aiming at harmonic voltage constraint indexes of all nodes as capacity limit values, wherein the third planning result of the ith node is set as Si,3(ii) a If Si,3<SiAnd temporarily setting the planning result of the ith node as Si=Si,3Else SiKeeping the same;
with SiAnd/3, setting the single-phase capacity limit value of the ith node, and performing fourth planning on the distributed photovoltaic absorption capacity aiming at the unbalance degree constraint indexes of all the nodes, wherein the planning result of the single-phase capacity of the ith node is Si,4And obtaining the planning result of the ith node that the single-phase capacity of the ith node is not more than SiAnd/3, the difference between the maximum phase capacity and the second maximum phase capacity of the ith node is not more than Si,4。
Preferably, the sorting rule for sorting the power quality constraint indexes includes sorting according to the descending of the weight of each power quality constraint index and sorting from symmetry processing to asymmetry processing.
Preferably, the harmonic voltage constraint index and the harmonic current constraint index are analyzed according to the symmetry of the load.
Preferably, the three-phase unbalance degree constraint index is analyzed according to load asymmetry.
According to the electric energy quality constraint index analysis method of the distributed power generation access system, the power quality indexes of multiple dimensions are constrained, such as voltage deviation, harmonic wave, unbalance degree and the like, to reduce dimensions, the planning result of the former index constraint, namely the digestion capacity, is used as the capacity constraint of the latter index constraint planning, so that the problem of non-convergence of the multidimensional multi-index constraint planning is effectively solved, the planning of the multidimensional power quality index constraint is more conveniently realized, the electric energy quality disturbance source of a distributed photovoltaic power supply is maximally digested under the condition of meeting the electric energy quality index constraint, and the further deterioration of the power quality indexes caused by the disordered access of the disturbance source to a power grid is avoided.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
As an aspect of the present invention, there is provided a power quality constraint index analysis method for a distributed power generation access system, where the power quality constraint index includes a voltage deviation, a harmonic current, a harmonic voltage, and a three-phase imbalance, as shown in fig. 1, the power quality constraint index analysis method for the distributed power generation access system includes:
s110, sequencing the power quality constraint indexes, wherein the obtained constraint sequence of the power quality constraint indexes is voltage deviation, harmonic current, harmonic voltage and three-phase unbalance;
s120, carrying out first planning on the distributed photovoltaic absorption capacity aiming at the voltage deviation constraint index of each node, wherein the first planning result of the ith node is set as Si,1And temporarily setting the planning result of the ith node as Si=Si,1I is a natural number not less than 1;
s130, with the i-th nodePlanning result SiPerforming second planning of distributed photovoltaic absorption capacity aiming at harmonic current constraint indexes of all nodes for capacity limit, wherein the second planning result of the ith node is set as Si,2If S isi,2<SiAnd temporarily setting the planning result of the ith node as Si=Si,2Else SiKeeping the same;
s140, planning result S of the ith nodeiPerforming third planning of distributed photovoltaic absorption capacity aiming at harmonic voltage constraint indexes of all nodes as capacity limit values, wherein the third planning result of the ith node is set as Si,3(ii) a If Si,3<SiAnd temporarily setting the planning result of the ith node as Si=Si,3Else SiKeeping the same;
s150, with SiAnd/3, setting the single-phase capacity limit value of the ith node, and performing fourth planning on the distributed photovoltaic absorption capacity aiming at the unbalance degree constraint indexes of all the nodes, wherein the planning result of the single-phase capacity of the ith node is Si,4And obtaining the planning result of the ith node that the single-phase capacity of the ith node is not more than SiAnd the maximum phase capacity plus the second maximum phase capacity-2 times of the minimum phase capacity of the ith node is not more than Si,4。
According to the electric energy quality constraint index analysis method of the distributed power generation access system, the power quality indexes of multiple dimensions are constrained, such as voltage deviation, harmonic wave, unbalance degree and the like, to reduce dimensions, the planning result of the former index constraint, namely the digestion capacity, is used as the capacity constraint of the latter index constraint planning, so that the problem of non-convergence of the multidimensional multi-index constraint planning is effectively solved, the planning of the multidimensional power quality index constraint is more conveniently realized, the electric energy quality disturbance source of a distributed photovoltaic power supply is maximally digested under the condition of meeting the electric energy quality index constraint, and the further deterioration of the power quality indexes caused by the disordered access of the disturbance source to a power grid is avoided.
Specifically, in order to implement the sorting of multiple power quality constraint indexes, the sorting principle of sorting the power quality constraint indexes includes sorting according to the descending of the weight of each power quality constraint index and sorting from symmetric processing to asymmetric processing.
Preferably, the harmonic voltage constraint index and the harmonic current constraint index are analyzed according to the symmetry of the load.
Preferably, the three-phase unbalance degree constraint index is analyzed according to load asymmetry.
The method for analyzing the power quality constraint index of the distributed power generation access system can be widely applied to the field of planning of the distributed power generation access system based on the power quality constraint.
The following describes in detail the power quality constraint index analysis method of the distributed power generation access system provided by the present invention, taking the schematic diagram of the IEEE33 node power distribution system shown in fig. 2 as an example. As shown in fig. 2, the IEEE33 node power distribution system includes 32 branches and 33 nodes, where node 1 is a system power supply, the system reference voltage is 12.66kV, and the total three-phase power of each node is 5084.26+ j2547.32kva.
Firstly, after the electric energy quality constraint indexes are sequenced, the constraint sequence of the electric energy quality constraint indexes is voltage deviation, harmonic current, harmonic voltage and three-phase unbalance.
The 33 node voltages under the existing load are shown in table 1 below.
Table 1: node voltage under existing load
Secondly, carrying out first planning of distributed photovoltaic absorption capacity aiming at voltage deviation constraint indexes of 33 nodes, and assuming that the voltage deviation constraint of the ith node is as follows: | Δ ViLess than or equal to 7 percent, the power is used as each nodeThe voltage deviation constraint, photovoltaic distributed generation (photovoltaic DG) that each node can accommodate after planning is shown in table 2.
Table 2: photovoltaic DG (kW) capable of being consumed by three phases of each node under voltage deviation constraint
| Node point
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
| Newly added DG
|
0
|
222.89
|
809.51
|
567.66
|
319.56
|
371.36
|
952.33
|
650.2
|
| Node point
|
9
|
10
|
11
|
12
|
13
|
14
|
15
|
16
|
| Newly added DG
|
193.85
|
180.67
|
573.51
|
198.65
|
48.905
|
4.2687
|
96.983
|
23.568
|
| Node point
|
17
|
18
|
19
|
20
|
21
|
22
|
23
|
24
|
| Newly added DG
|
268.95
|
204.53
|
672.44
|
941.4
|
967.49
|
385.58
|
749.08
|
694.84
|
| Node point
|
25
|
26
|
27
|
28
|
29
|
30
|
31
|
32
|
| Newly added DG
|
919.35
|
620.86
|
622.72
|
156.27
|
425.01
|
353.55
|
134.42
|
460.75
|
| Node point
|
33
|
|
|
|
|
|
|
|
| Newly added DG
|
708.45
|
|
|
|
|
|
|
|
Assuming that the main harmonic current spectrum of DG is 3, 5, 11, 13 harmonics, each harmonic current is less than 1% of the rated current, and the capacity obtained by the harmonic current and harmonic voltage constraints is greater than the capacity obtained by the voltage deviation, so that the planned capacity of each node is still the capacity obtained by the voltage deviation so far, that is, the results obtained after performing the second planning of the distributed photovoltaic absorption capability on the harmonic current of each node and performing the third planning of the distributed photovoltaic absorption capability on the harmonic voltage of each node are still the contents shown in table 2.
The three-phase unbalance degree of each node is not more than 2% as constraint, and the single-phase capacity constraint of each node is one third of the capacity of the table 2, so that the single-phase photovoltaic capacity which can be absorbed by each node is obtained and is shown in the table 3.
Table 3: photovoltaic power supply (kW) capable of being consumed by each node in single phase under constraint of unbalance degree
| Node point
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
| Newly-added single-phase DG
|
0.0
|
55.7
|
202.4
|
141.9
|
79.9
|
92.8
|
238.1
|
162.6
|
| Node point
|
9
|
10
|
11
|
12
|
13
|
14
|
15
|
16
|
| Newly added DG
|
48.5
|
45.2
|
143.4
|
49.7
|
12.2
|
1.1
|
24.2
|
5.9
|
| Node point
|
17
|
18
|
19
|
20
|
21
|
22
|
23
|
24
|
| Newly added DG
|
67.2
|
51.1
|
168.1
|
235.4
|
241.9
|
96.4
|
187.3
|
173.7
|
| Node point
|
25
|
26
|
27
|
28
|
29
|
30
|
31
|
32
|
| Newly added DG
|
229.8
|
155.2
|
155.7
|
39.1
|
106.3
|
88.4
|
33.6
|
115.2
|
| Node point
|
33
|
|
|
|
|
|
|
|
| Newly added DG
|
177.1
|
|
|
|
|
|
|
|
Therefore, the planning result for each node is: the photovoltaic power supply capacity which can be absorbed by each node under the constraint of voltage deviation, harmonic wave and unbalance degree is as follows: the single-phase capacity is not more than one third of the capacity of each point in table 2, and simultaneously, the 'maximum phase capacity + second large phase capacity-2 times of the minimum phase capacity' of each node does not exceed the capacity shown in table 3.
It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.