CN112769139B - Flexible power distribution network three-phase state estimation method considering SNOP and B-DSTATCOM - Google Patents

Flexible power distribution network three-phase state estimation method considering SNOP and B-DSTATCOM Download PDF

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CN112769139B
CN112769139B CN202010340398.9A CN202010340398A CN112769139B CN 112769139 B CN112769139 B CN 112769139B CN 202010340398 A CN202010340398 A CN 202010340398A CN 112769139 B CN112769139 B CN 112769139B
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phase
node
snop
dstatcom
vsc
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CN112769139A (en
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马鑫
张爽
田蓓
李宏强
张迪
薛飞
王超
周雷
顾雨嘉
张汉花
吴玫蓉
杨慧彪
梁剑
任勇
钱勇
孙尚鹏
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Electric Power Research Institute of State Grid Ningxia Electric Power Co Ltd
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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
    • H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
    • H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
    • 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
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H02J3/1821—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators
    • H02J3/1835—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control
    • H02J3/1842—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control wherein at least one reactive element is actively controlled by a bridge converter, e.g. active filters
    • 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
    • H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
    • 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • 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
    • Y02E40/10—Flexible AC transmission systems [FACTS]
    • 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
    • Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks

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Abstract

The invention provides a flexible power distribution network three-phase state estimation method considering SNOP and B-DSTATCOM, which comprises the following steps: (1) Constructing a power distribution network state estimation model based on a weighted minimum absolute value method; (2) A measurement equation and constraint conditions of an alternating current power distribution network state estimation model are provided; (3) SNOP and B-DSTATCOM state estimation models considering transmission loss and various control modes are provided, and corresponding measurement equations, control pseudo measurement equations and constraint conditions are provided; (4) Calling an original dual interior point method in an IPOPT solver to solve the problem; the invention considers the three-phase imbalance characteristics of the flexible power distribution equipment and the flexible power distribution network, further provides a steady state tidal current measurement equation, a control pseudo measurement equation and an equation constraint thereof, and verifies the applicability and the necessity of a state estimation model to different control modes of SNOP and B-DSTATCOM.

Description

Flexible power distribution network three-phase state estimation method considering SNOP and B-DSTATCOM
Technical Field
The invention relates to the technical field of power grid dispatching automation, in particular to a flexible power distribution network three-phase state estimation method considering SNOP and B-DSTATCOM.
Background
With the continuous access of a distributed power supply and a distributed energy storage system in a power distribution network, the necessary control capacity of the power distribution network is very deficient, and flexible power distribution equipment is required to be installed to improve the active control capacity. The intelligent soft normally open switch (Soft Normally Open Point, SNOP) realizes interconnection between distribution networks with different voltage grades and feeder lines with different phase angles, realizes comprehensive active-reactive regulation and control of the system through four-quadrant control of tide, solves the problem of insufficient power supply capacity of the distribution network, and is one of important equipment for realizing flexible interconnection and load transfer of the distribution network. In addition, the static synchronous compensator (Distribution Static Compensator, DSTATCOM) of the power distribution network can provide rapid and dynamic reactive compensation for the power distribution network, can improve the voltage stability of the power distribution network, perform harmonic filtering and compensate unbalanced load, and is popularized and applied in the medium-low voltage power distribution network. In addition, the DSTATCOM (hereinafter referred to as B-DSTACOM) with the battery energy storage combined with the DSTATCOM can realize four-quadrant control and active-reactive comprehensive regulation and control of tide, and has wider application prospect.
The SNOP, the B-DSTATCOM and other flexible power distribution equipment are put into the power distribution network, so that the economical efficiency and the flexibility of the operation of the power distribution network are greatly improved, and higher requirements are put forward for the operation control of the power distribution network. At present, intensive researches on control strategies, tide calculation, transfer strategies, optimal tide, configuration optimization and the like of a flexible power distribution network containing SNOP and B-DSTACOM are carried out. In the operation mode calculation and control mode adjustment of the flexible power distribution network, the state estimation plays an important role as an important data base. Therefore, it is necessary to study the state estimation method of the flexible power distribution network containing SNOP and B-DSTACOM.
In the existing three-phase state estimation research of the power distribution network, most state estimation methods only perform state estimation on state quantities in a power distribution network part, a distributed power supply and a distributed energy storage system, and a steady state model and corresponding state quantities of flexible power distribution equipment are not considered. For the power flow calculation and the optimal power flow related research of the flexible power distribution equipment SNOP and the B-DSTATCOM, the equivalent modeling is only carried out, the detailed modeling is not carried out, and the influence of the transmission loss and the control mode on the steady-state model is often ignored. The transmission loss of the SNOP and the B-DSTATCOM is about 5% of the transmission power, and is difficult to ignore in state estimation. The invention discloses a flexible power distribution network three-phase state estimation method considering SNOP and B-DSTATCOM transmission loss and control modes, which aims to accurately sense the real-time state of a flexible power distribution network containing SNOP and B-DSTATCOM and obtain a more accurate and practical three-phase unbalanced flexible power distribution network state.
Disclosure of Invention
It is necessary to provide a three-phase state estimation method of a flexible power distribution network, which takes SNOP and B-DSTATCOM into account.
A flexible power distribution network three-phase state estimation method considering SNOP and B-DSTATCOM comprises the following steps:
(1) Constructing a power distribution network state estimation model based on a weighted minimum absolute value method;
(2) A measurement equation and constraint conditions of an alternating current power distribution network state estimation model are provided;
(3) SNOP and B-DSTATCOM state estimation models considering transmission loss and various control modes are provided, and corresponding measurement equations, control pseudo measurement equations and constraint conditions are provided;
(4) And calling a primary dual interior point method in the IPOPT solver to solve the problem.
Preferably, the specific method of the step (1) is as follows:
in general, the weighted minimum absolute value based state estimation problem is described as an optimization problem as follows:
Figure GDA0004268838770000021
wherein: x is a state variable;
Figure GDA0004268838770000022
is a measurement vector; j represents an objective function; />
Figure GDA0004268838770000023
Representing an exact equality constraint, if zero injection power is represented, there is +.>
Figure GDA0004268838770000024
h (x) represents a measurement equation and is typically a nonlinear function; Δz is a measurement residual vector, and the following Δvariable represents the measurement residual of the corresponding measurement; sigma is a standard deviation coefficient matrix.
Preferably, the flexible power distribution network comprising SNOP and B-DSTATCOM is divided into two branches according to the difference of whether the flexible power distribution network is connected with a B-DSTATCOM branch or an SNOP branch or an alternating current power distribution network: a three-phase alternating current power distribution network part, an SNOP branch part and a B-DSTATCOM branch part; the specific method of the step (2) is as follows:
(1) Measurement equation and constraint condition based on state estimation model of three-phase alternating current power distribution network part
Psi phase voltage measurement at node i
Figure GDA0004268838770000025
The following formula is shown:
Figure GDA0004268838770000026
wherein: i. j is the node number, there is i∈N B ，N B Representing a set of power distribution network nodes; subscript ψ is the phase sequence, there is ψ ε ψ, ψ= [ a, b, c ]]Representing a set of node phase sequences; e, e i,ψ 、f i,ψ Representing the real and imaginary parts of the ψ -phase voltage at node i, respectively;
the formation of the jacobian matrix in the formula (2) is complicated, and a state variable U is introduced i,ψ Replacing the part inside the root number in the formula (2) as shown in the formula (3); thus, voltage SCADA measurement
Figure GDA0004268838770000027
As shown in formula (4):
(U i,ψ ) 2 ＝(e i,ψ ) 2 +(f i,ψ ) 2 i∈N B ,ψ∈Ψ (3)
Figure GDA0004268838770000028
the ψ phase on branch ij carries the real part I of the current ij,ψ,x Imaginary part I ij,ψ,y As shown in formula (5);
measurement of the ψ phase transmission current on branch ij
Figure GDA0004268838770000029
As shown in formula (6):
Figure GDA00042688387700000210
Figure GDA0004268838770000031
wherein: g ij,ψ 、b ij,ψ For the phi relative on the branch ij
Figure GDA0004268838770000032
The conductance and susceptance of the phase;
similar to the transformation in voltage measurement, the introduction of state variables
Figure GDA0004268838770000033
As shown in formula (7), the line-transmitted electrical flow measurement is shown in formula (8):
Figure GDA0004268838770000034
Figure GDA0004268838770000035
active power measurement of psi phase transmission on branch ij
Figure GDA0004268838770000036
And reactive power measurement->
Figure GDA0004268838770000037
As shown in formula (9);
psi phase injection active power measurement of node i
Figure GDA0004268838770000038
And reactive power measurement->
Figure GDA0004268838770000039
As shown in formula (10);
Figure GDA00042688387700000310
Figure GDA00042688387700000311
wherein: omega shape i Representing a node set connected with a node i in the alternating current distribution network;
Figure GDA00042688387700000312
psi relative +.about.of branches ij respectively>
Figure GDA00042688387700000319
The real part and the imaginary part corresponding to the admittance matrix are opposite;
(2) Measurement equation based on SNOP branch part state estimation model
The SNOP is usually installed at a tie switch of the power distribution network, and the VSC on two sides is controlled to realize four-quadrant control of the power flow, so that the power flow distribution can be improved, the voltage level can be increased, a psi phase steady-state model is shown in fig. 3, wherein, taking all variables on the node i side as an example,
Figure GDA00042688387700000313
is the psi phase voltage at the node i of the SNOP branch; />
Figure GDA00042688387700000314
The PSI phase fundamental voltage of the VSC at the i side of the SNOP branch node; v (V) S,DC The voltage at the direct current side of the SNOP branch VSC; />
Figure GDA00042688387700000315
The method comprises the steps that the active power and the reactive power of the psi phase are input to the i sides of nodes at two ends of an SNOP branch; />
Figure GDA00042688387700000316
The method comprises the steps that the PSI phase active power and reactive power of the VSC are introduced into the SNOP branch node i side; />
Figure GDA00042688387700000317
The PSI phase current of the VSC flows into the SNOP branch node i side; />
Figure GDA00042688387700000318
An equivalent psi phase admittance matrix of the SNOP branch node i side converter transformer;
the method comprises the steps that the phi-phase voltage measurement at a node i of an SNOP branch and the phi-phase voltage measurement at a node j of the SNOP branch and the phi-phase fundamental voltage measurement of a VSC at a node i side and a node j side of the SNOP branch are in the form of flexible power distribution network node phi-phase voltage measurement equations, and are shown in a formula (3) and a formula (4);
the flow of the node i at two ends of the SNOP branch into the psi phase current of the VSC and the flow of the node j into the psi phase current of the VSC are both in the form of a flexible power distribution network line psi phase transmission electric current measurement equation, as shown in a formula (7) and a formula (8);
the estimation of the state of the SNOP leg requires the introduction of a dc side voltage measurement of the VSC therein
Figure GDA0004268838770000041
AC side voltage measurement
Figure GDA0004268838770000042
State variable V S,DC To perform state estimation as shown in the following formula:
Figure GDA0004268838770000043
wherein N is S Representing a set of alternating current nodes at two ends of an SNOP line; mu is the utilization rate of direct current voltage, and when the modulation mode is SPWM, mu is 0.866;
Figure GDA0004268838770000044
there is +.>
Figure GDA0004268838770000045
The PSI phase input power of the SNOP branch at the node i side and the node j side adopts the node PSI phase injection power form of the flexible power distribution network, as shown in a formula (10); the SNOP branch flows into the PSI phase power of the VSC from the node i and flows into the PSI phase power of the VSC from the node j, and the PSI phase power of the VSC is transmitted in the form of line PSI phase of the flexible power distribution network, as shown in a formula (9);
since the sno leg consists of 2 back-to-back VSC legs, the sno leg transmission loss is often greater than 5% of its transmission power and is therefore not negligible. Therefore, the following relationship exists between the active power of the ψ phase of the sno leg flowing into the VSC from node i and the active power of the ψ phase flowing into the VSC from node j:
Figure GDA0004268838770000046
wherein,,
Figure GDA0004268838770000047
the transmission loss of the psi phase of the node i side and the node j side of the SNOP branch are respectively shown; alpha, beta and gamma are loss coefficients of the VSC in practical application respectively;
the reactive power flowing into the VSC from the two ends of the SNOP branch is directly counteracted by the compensation reactive balance of the VSC;
(3) Measurement equation and constraint condition of state estimation model based on B-DSTATCOM branch part
The battery energy storage can be directly connected in parallel at two sides of the direct current capacitor to form B-DSTATCOM, the two can share one VSC to provide direct current voltage and current, and the PSY steady-state model of the B-DSTATCOM is shown in figure 4 when the VSC is connected to a power grid through a connecting reactor i,ψ Is the psi phase voltage at the node i of the B-DSTATCOM;
Figure GDA0004268838770000048
the PSI phase fundamental voltage of the VSC at the node i side is B-DSTATCOM; v (V) BDS,DC The voltage of the direct current side of the B-DSTATCOM; />
Figure GDA0004268838770000049
The PSI phase power input to the node i side for the B-DSTATCOM; />
Figure GDA00042688387700000410
The PSI phase power of the VSC is flown from the node i side for the B-DSTATCOM; p (P) BDS,DC The output power of the direct current side of the B-DSTATCOM; />
Figure GDA00042688387700000411
The psi phase current of the VSC is streamed to the node i for B-DSTATCOM; />
Figure GDA00042688387700000412
The equivalent psi phase admittance of the converter transformer is B-DSTATCOM;
the voltage measurement of the psi phase of the B-DSTATCOM at the node i and the voltage measurement of the psi phase fundamental wave of the VSC at the node i side are in the form of a flexible power distribution network node psi phase voltage measurement equation, as shown in a formula (3) and a formula (4). The flow measurement of the psi phase current of the B-DSTATCOM flowing into the VSC at the node i adopts the form of a flexible power distribution network line psi phase transmission electric flow measurement equation, as shown in a formula (7) and a formula (8);
the state estimation of B-DSTATCOM requires the introduction of direct current side voltage measurements of VSC therein
Figure GDA0004268838770000051
AC side voltage measurement->
Figure GDA0004268838770000052
State variable V BDS，DC To perform state estimation as shown in the following formula:
Figure GDA0004268838770000053
wherein N is BDS Representing a set of B-DSTATCOM nodes; mu is the utilization rate of direct current voltage, and when the modulation mode is SPWM, mu is 0.866;
Figure GDA0004268838770000054
for the VSC modulation of B-DSTATCOM at node i, there is +.>
Figure GDA0004268838770000055
The PSI phase power input by the B-DSTATCOM at the node i side adopts the form of PSI phase injection power of the power distribution network node, as shown in a formula (10); the power of the psi phase of the B-DSTATCOM flowing into the VSC from node i takes the form of the power distribution network line psi phase transmission power as shown in equation (9).
The following relationship exists between the PSI phase active power of the VSC from the node i side and the B-DSTATCOM direct current side output power:
Figure GDA0004268838770000056
wherein,,
Figure GDA0004268838770000057
transmission loss of the psi phase for B-DSTATCOM;
and the reactive power of the B-DSTATCOM flowing from node i into the VSC is directly balanced by the compensation reactive power of the VSC.
Preferably, the control pseudo measurement equation components of the VSC of the SNOP and B-DSTATCOM are:
(1) active power control on the ac side
Figure GDA0004268838770000058
Wherein,,
Figure GDA0004268838770000059
respectively representing the equivalent psi phase conductance and susceptance of the converter transformer of the corresponding equipment, and the existence of the equivalent psi phase conductance and susceptance
Figure GDA00042688387700000510
(2) Constant ac side reactive power control
Figure GDA00042688387700000511
(3) Constant DC side voltage control
Figure GDA0004268838770000061
(4) Constant ac side voltage control
Figure GDA0004268838770000062
Wherein,,
Figure GDA0004268838770000063
a substitution variable of the VSC fundamental voltage in the formula (3);
(5) fixed frequency control
Figure GDA0004268838770000064
Preferably, the specific method of the step (4) is as follows:
the three-phase state estimation problem of the flexible power distribution network adopts a weighted minimum absolute value method with stronger robust against difference, adopts an OPTI library to model an optimization problem, calls a primary dual interior point method in an IPOPT solver to solve the problem, and finally obtains a state variable result of state estimation.
Preferably, the DSTATCOM provides fast, dynamic reactive compensation and harmonic filtering for flexible distribution networks.
The beneficial effects of the invention are as follows: aiming at the current situation that SNOP and B-DSTATCOM are gradually applied to a flexible power distribution network, the invention provides a flexible power distribution network state estimation model taking SNOP and B-DSTATCOM transmission loss into consideration, and further provides a steady state tidal current measurement equation, a control pseudo measurement equation and an equation constraint thereof by taking three-phase imbalance characteristics of flexible power distribution equipment and the flexible power distribution network into consideration, so that applicability of the state estimation model to different control modes of SNOP and B-DSTATCOM and necessity of taking SNOP and B-DSTATCOM transmission loss into consideration are verified. In addition, the reliability and the practicability of the model in engineering application are ensured by adopting a practical weighted minimum absolute value method.
Drawings
Fig. 1 is a block diagram of a flexible power distribution network including a SNOP and a B-DSTATCOM. The invention only takes SNOP and B-DSTATCOM which are commonly based on voltage source type converters (Voltage Source Converter, VSC) as research objects.
Fig. 2 is a modified IEEE-33 test system topology. The figure contains an SNOP device connected across node 33 and node 18, and two B-DSTATCOM devices at node 8 and node 12, respectively. Aiming at the set flexible power distribution network calculation example, the method is used for carrying out three-phase state estimation of the flexible power distribution network taking SNOP and B-DSTATCOM into account, realizing accurate perception and estimation of three-phase state information of the flexible power distribution network and flexible power distribution equipment, and making a data basis for realizing real-time control of the flexible power distribution network and the flexible power distribution equipment.
Fig. 3 is a schematic diagram of the psiphase steady-state model of SNOP.
Fig. 4 is a schematic diagram of the psiphase steady state model of B-DSTATCOM.
Detailed Description
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
The invention provides a flexible power distribution network three-phase state estimation method considering SNOP and B-DSTATCOM, which comprises the following steps:
(1) Constructing a power distribution network state estimation model based on a weighted minimum absolute value method;
(2) A measurement equation and constraint conditions of an alternating current power distribution network state estimation model are provided;
(3) SNOP and B-DSTATCOM state estimation models considering transmission loss and various control modes are provided, and corresponding measurement equations, control pseudo measurement equations and constraint conditions are provided;
(4) And calling a primary dual interior point method in the IPOPT solver to solve the problem.
Preferably, the specific method of the step (1) is as follows:
in general, the weighted minimum absolute value based state estimation problem is described as an optimization problem as follows:
Figure GDA0004268838770000071
wherein: x is a state variable;
Figure GDA0004268838770000072
is a measurement vector; j represents the orderA standard function; />
Figure GDA0004268838770000073
Representing an exact equality constraint, if zero injection power is represented, there is +.>
Figure GDA0004268838770000074
h (x) represents a measurement equation and is typically a nonlinear function; Δz is a measurement residual vector, and the following Δvariable represents the measurement residual of the corresponding measurement; sigma is a standard deviation coefficient matrix.
Preferably, the flexible power distribution network comprising SNOP and B-DSTATCOM is divided into two branches according to the difference of whether the flexible power distribution network is connected with a B-DSTATCOM branch or an SNOP branch or an alternating current power distribution network: a three-phase alternating current power distribution network part, an SNOP branch part and a B-DSTATCOM branch part; the specific method of the step (2) is as follows:
(1) Measurement equation and constraint condition based on state estimation model of three-phase alternating current power distribution network part
Psi phase voltage measurement at node i
Figure GDA0004268838770000075
The following formula is shown:
Figure GDA0004268838770000076
wherein: i. j is the node number, where i E N exists B ，N B Representing a set of power distribution network nodes; subscript ψ is the phase sequence, there is ψ ε ψ, ψ= [ a, b, c ]]Representing a set of node phase sequences; e, e i,ψ 、f i,ψ Representing the real and imaginary parts of the ψ -phase voltage at node i, respectively;
the formation of the jacobian matrix in the formula (2) is complicated, and a state variable U is introduced i,ψ Replacing the part inside the root number in the formula (2) as shown in the formula (3); thus, voltage SCADA measurement
Figure GDA0004268838770000077
As shown in formula (4):
(U i,ψ ) 2 ＝(e i,ψ ) 2 +(f i,ψ ) 2 i∈N B ,ψ∈Ψ (22)
Figure GDA0004268838770000078
the ψ phase on branch ij carries the real part I of the current ij,ψ,x Imaginary part I ij,ψ,y As shown in formula (5);
measurement of the ψ phase transmission current on branch ij
Figure GDA0004268838770000081
As shown in formula (6):
Figure GDA0004268838770000082
Figure GDA0004268838770000083
wherein: g ij,ψ 、b ij,ψ For the phi relative on the branch ij
Figure GDA0004268838770000084
The conductance and susceptance of the phase;
similar to the transformation in voltage measurement, the introduction of state variables
Figure GDA0004268838770000085
As shown in formula (7), the line-transmitted electrical flow measurement is shown in formula (8):
Figure GDA0004268838770000086
Figure GDA0004268838770000087
transmission of the psi phase on the branches ijPower measurement
Figure GDA0004268838770000088
And reactive power measurement->
Figure GDA0004268838770000089
As shown in formula (9);
psi phase injection active power measurement of node i
Figure GDA00042688387700000810
And reactive power measurement->
Figure GDA00042688387700000811
As shown in formula (10);
Figure GDA00042688387700000812
Figure GDA00042688387700000813
wherein: omega shape i Representing a node set connected with a node i in the alternating current distribution network;
Figure GDA00042688387700000814
psi relative +.about.of branches ij respectively>
Figure GDA00042688387700000815
The real part and the imaginary part corresponding to the admittance matrix are opposite;
(2) Measurement equation based on SNOP branch part state estimation model
SNOP is usually arranged at a tie switch of a power distribution network, and the four-quadrant control of the power flow is realized by controlling VSCs at two sides, so that the power flow distribution can be improved, the voltage level can be increased, a psi phase steady-state model is shown as a figure 3, wherein, taking all variables at the side of a node i as an example, V i,ψ Is the psi phase voltage at the node i of the SNOP branch;
Figure GDA00042688387700000816
the PSI phase fundamental voltage of the VSC at the i side of the SNOP branch node; v (V) S,DC For SNOP branches
Voltage on the VSC dc side;
Figure GDA0004268838770000091
the method comprises the steps that the active power and the reactive power of the psi phase are input to the i sides of nodes at two ends of an SNOP branch; />
Figure GDA0004268838770000092
The method comprises the steps that the PSI phase active power and reactive power of the VSC are introduced into the SNOP branch node i side; />
Figure GDA0004268838770000093
The PSI phase current of the VSC flows into the SNOP branch node i side; />
Figure GDA0004268838770000094
An equivalent psi phase admittance matrix of the SNOP branch node i side converter transformer;
the method comprises the steps that the phi-phase voltage measurement at a node i of an SNOP branch and the phi-phase voltage measurement at a node j of the SNOP branch and the phi-phase fundamental voltage measurement of a VSC at a node i side and a node j side of the SNOP branch are in the form of flexible power distribution network node phi-phase voltage measurement equations, and are shown in a formula (3) and a formula (4);
the flow of the node i at two ends of the SNOP branch into the psi phase current of the VSC and the flow of the node j into the psi phase current of the VSC are both in the form of a flexible power distribution network line psi phase transmission electric current measurement equation, as shown in a formula (7) and a formula (8);
the estimation of the state of the SNOP leg requires the introduction of a dc side voltage measurement of the VSC therein
Figure GDA0004268838770000095
AC side voltage measurement
Figure GDA0004268838770000096
State variable V S,DC To perform state estimation as shown in the following formula:
Figure GDA0004268838770000097
wherein N is S Representing a set of alternating current nodes at two ends of an SNOP line; mu is the utilization rate of direct current voltage, and when the modulation mode is SPWM, mu is 0.866;
Figure GDA0004268838770000098
there is +.>
Figure GDA0004268838770000099
The PSI phase input power of the SNOP branch at the node i side and the node j side adopts the node PSI phase injection power form of the flexible power distribution network, as shown in a formula (10); the SNOP branch flows into the PSI phase power of the VSC from the node i and flows into the PSI phase power of the VSC from the node j, and the PSI phase power of the VSC is transmitted in the form of line PSI phase of the flexible power distribution network, as shown in a formula (9);
since the sno leg consists of 2 back-to-back VSC legs, the sno leg transmission loss is often greater than 5% of its transmission power and is therefore not negligible. Therefore, the following relationship exists between the active power of the ψ phase of the sno leg flowing into the VSC from node i and the active power of the ψ phase flowing into the VSC from node j:
Figure GDA00042688387700000910
wherein,,
Figure GDA00042688387700000911
the transmission loss of the psi phase of the node i side and the node j side of the SNOP branch are respectively shown; alpha, beta and gamma are loss coefficients of the VSC in practical application respectively;
the reactive power flowing into the VSC from the two ends of the SNOP branch is directly counteracted by the compensation reactive balance of the VSC;
(3) Measurement equation and constraint condition of state estimation model based on B-DSTATCOM branch part
The battery energy storage can be directly connected in parallel with the two direct-current capacitorsThe side combination is B-DSTATCOM, the two share one VSC to provide direct current voltage and current, and the PSI phase steady-state model of the B-DSTATCOM is shown in figure 4 when the VSC is connected into a power grid through a connecting reactor, wherein V is shown as the following formula i,ψ Is the psi phase voltage at the node i of the B-DSTATCOM;
Figure GDA0004268838770000101
the PSI phase fundamental voltage of the VSC at the node i side is B-DSTATCOM; v (V) BDS,DC The voltage of the direct current side of the B-DSTATCOM; />
Figure GDA0004268838770000102
The PSI phase power input to the node i side for the B-DSTATCOM; />
Figure GDA0004268838770000103
The PSI phase power of the VSC is flown from the node i side for the B-DSTATCOM;
P BDS,DC the output power of the direct current side of the B-DSTATCOM;
Figure GDA0004268838770000104
the psi phase current of the VSC is streamed to the node i for B-DSTATCOM; />
Figure GDA0004268838770000105
The equivalent psi phase admittance of the converter transformer is B-DSTATCOM;
the voltage measurement of the psi phase of the B-DSTATCOM at the node i and the voltage measurement of the psi phase fundamental wave of the VSC at the node i side are in the form of a flexible power distribution network node psi phase voltage measurement equation, as shown in a formula (3) and a formula (4). The flow measurement of the psi phase current of the B-DSTATCOM flowing into the VSC at the node i adopts the form of a flexible power distribution network line psi phase transmission electric flow measurement equation, as shown in a formula (7) and a formula (8);
the state estimation of B-DSTATCOM requires the introduction of direct current side voltage measurements of VSC therein
Figure GDA0004268838770000106
AC side voltage measurement->
Figure GDA0004268838770000107
State variable V BDS,DC To perform state estimation as shown in the following formula:
Figure GDA0004268838770000108
wherein N is BDS Representing a set of B-DSTATCOM nodes; mu is the utilization rate of direct current voltage, and when the modulation mode is SPWM, mu is 0.866;
Figure GDA0004268838770000109
for the VSC modulation of B-DSTATCOM at node i, there is +.>
Figure GDA00042688387700001010
The PSI phase power input by the B-DSTATCOM at the node i side adopts the form of PSI phase injection power of the power distribution network node, as shown in a formula (10); the power of the psi phase of the B-DSTATCOM flowing into the VSC from node i takes the form of the power distribution network line psi phase transmission power as shown in equation (9).
The following relationship exists between the PSI phase active power of the VSC from the node i side and the B-DSTATCOM direct current side output power:
Figure GDA00042688387700001011
wherein,,
Figure GDA00042688387700001012
transmission loss of the psi phase for B-DSTATCOM;
and the reactive power of the B-DSTATCOM flowing from node i into the VSC is directly balanced by the compensation reactive power of the VSC.
Preferably, the control pseudo measurement equation components of the VSC of the SNOP and B-DSTATCOM are:
the SNOP and the B-DSTATCOM are used as controllable devices, and control target values thereof are generally known when performing state estimation, so that the SNOP and the B-DSTATCOM can be used as pseudo measurement to improve the redundancy of the state estimation.
The SNOP has generally 4 control scenarios, and the scenarios and control modes thereof are shown in table 3. Under normal operation, VSCs at both sides of the sno, one for ensuring the voltage level of the dc bus and the other for regulating the power transmitted by the sno line. When a fault occurs in an alternating-current power distribution network at one side, the VSC at the fault end supplies power to an island of the alternating-current power distribution network, so that the effect of island balance power supply is actually achieved, the potential phase in the converter is directly selected as a voltage selection phase reference point in the island, and the VSC at the non-fault end realizes uninterrupted power supply.
TABLE 3 multiple control modes of SNOP
Figure GDA0004268838770000111
The B-DSTATCOM can respectively provide direct current voltage and direct current based on direct current capacitance and battery energy storage at the direct current side, four-quadrant control of power flow is achieved through controlling the VSC, and comprehensive active and reactive regulation and control of the device are achieved, wherein the control mode is shown in a table 4.
Table 4B-DSTATCOM and various control modes of DSTATCOM
Figure GDA0004268838770000112
Taking VSC on the node i side of the SNOP tributary and VSC of B-DSTATCOM at node i as an example, the following pseudo-measurement equation can be correspondingly added, wherein the variables are as follows
Figure GDA0004268838770000113
Delta *,DC The upper right hand corner of the diagram collectively represents the class of devices for SNOP, B-DSTATCOM.
(1) Active power control on the ac side
Figure GDA0004268838770000114
Wherein,,
Figure GDA0004268838770000115
respectively representing the equivalent psi phase conductance and susceptance of the converter transformer of the corresponding equipment, and the existence of the equivalent psi phase conductance and susceptance
Figure GDA0004268838770000116
(2) Constant ac side reactive power control
Figure GDA0004268838770000117
(3) Constant DC side voltage control
Figure GDA0004268838770000121
(4) Constant ac side voltage control
Figure GDA0004268838770000122
/>
Wherein,,
Figure GDA0004268838770000123
a substitution variable of the VSC fundamental voltage in the formula (3);
(5) fixed frequency control
Figure GDA0004268838770000124
Preferably, the specific method of the step (4) is as follows:
the three-phase state estimation problem of the flexible power distribution network adopts a weighted minimum absolute value method with stronger robust against difference, adopts an OPTI library to model an optimization problem, calls a primary dual interior point method in an IPOPT solver to solve the problem, and finally obtains a state variable result of state estimation.
Preferably, the DSTATCOM provides fast, dynamic reactive compensation and harmonic filtering for flexible distribution networks.
The following example is provided to verify the results of an evaluation using the method of the present invention.
Fig. 2 is a topology of an example flexible distribution network modified from the conventional distribution network example of IEEE 33 node, which includes SNOP devices connected across node 33 and node 18, and two B-DSTATCOM devices at node 8 and node 12, respectively. Aiming at the set flexible power distribution network calculation example, the method is used for carrying out three-phase state estimation of the flexible power distribution network taking SNOP and B-DSTATCOM into account, and the range and the sensing surface of the state estimation of the traditional power distribution network are expanded by considering a steady-state model and corresponding state quantity of flexible power distribution equipment in the state estimation; meanwhile, the influence of the transmission loss and the control mode of the flexible power distribution equipment SNOP and the B-DSTATCOM on the state estimation model is considered, accurate perception and estimation of the three-phase state information of the flexible power distribution network and the flexible power distribution equipment are realized, and a data basis is made for realizing the real-time control of the flexible power distribution network and the flexible power distribution equipment; in addition, the flexible power distribution network state estimation model based on the weighted minimum absolute method is adopted, so that the method can be better guaranteed to have higher efficiency in engineering practice links. In the calculation program, the OPTI library is adopted to model the problem, the original dual interior point method in the IPOPT solver is called to solve the problem, and the calculation convergence requirement is set to be 10 -6 . In addition, the calculation example adopts a full measurement mode, certain random errors are added to the configured measurement data on the basis of the flow calculation true value, and the standard deviation of the random errors is set to be 0.01pu of the true value.
The design scenario is as follows (see appendix for specific set-points) to verify the applicability and correctness of the proposed model to different control modes.
Scenario 1: VSC1 in SNOP branch is U DC U AC Control, VSC2 is P AC Q AC Control, without regard to B-DSTATCOM;
scenario 2: VSC1 in SNOP branch is P AC U AC Control, VSC2 is U DC U AC Control, B-DSTATCOM is U DC U AC Controlling;
scenario 3: VSC1 in SNOP branch is P AC Q AC Control, VSC2 is U DC Q AC Control, B-DSTATCOM is P AC U AC And (5) controlling.
And quantitatively analyzing the state estimation effect of the flexible power distribution network through the set performance indexes. Setting the index of the state estimation filtering performance as the measurement error statistical value S 1 Estimation error statistics S 2 And the statistic value J. Of the objective function are shown in a formula (39) respectively; setting the indexes of the state estimation precision as average estimation errors S respectively 3 Average maximum estimation error S 4 As shown in equation (40); setting an index of state estimation calculation efficiency performance as an average calculation time
Figure GDA0004268838770000137
Figure GDA0004268838770000131
/>
Figure GDA0004268838770000132
Wherein T is the estimated total times; m is the dimension of the measurement vector; n is the dimension of the state variable;
Figure GDA0004268838770000133
representing the measurement value of the i-dimensional measurement vector in the kth estimation; />
Figure GDA0004268838770000134
Expressing a power flow true value of the i-dimensional measurement vector in the kth estimation; r is R ii Representing the weight coefficient corresponding to the i-th dimension measurement vector in the weight coefficient matrix; h is a i,k (x) Representing the result value of the i-dimensional measurement equation in the kth estimation; x is x i,k The estimated result of the i-dimensional state variable in the kth estimation is obtained; />
Figure GDA0004268838770000135
Representing the true value of the i-dimensional state variable.
Setting the total estimated times T as 100 times, and comparing performance indexes of different scenes under the flexible power distribution network calculation example in table 5.
Comparing the first three columns of Table 5, S is known from the literature 1 The method is characterized in that 1, a measurement equation and constraint conditions adopted by a model are described to meet the requirements; s is S 2 <And 1, and J is close to the redundancy of the set measurement value, which shows that the filtering effect of the proposed state estimation model is good. In addition, the state estimation is carried out on the flexible power distribution network under different scenes, the indexes of the three filtering effects are not obviously changed, and the condition that different control modes of SNOP and B-DSTATCOM have no influence on the state estimation filtering effect of the flexible power distribution network is explained.
TABLE 5 comparison of Performance indicators for different scenes
Figure GDA0004268838770000136
Comparing the middle two columns of the table 5, and performing state estimation on the flexible power distribution network under different scenes, S 3 Are all smaller than 2.5X10 -3 ，S 4 Are all smaller than 2X 10 -2 This illustrates the effectiveness and practicality of the proposed flexible power distribution network state estimation model. In addition, the estimation accuracy indexes in different scenes have no obvious change, which indicates that different control modes of SNOP and DSTATCOM have no influence on the state estimation accuracy of the flexible power distribution network.
Comparing the last column of the table 5, carrying out state estimation on the flexible power distribution network under different scenes, wherein the average calculation time of model solving is less than 32ms, and the high efficiency and the practicability of state estimation calculation are ensured.
The model under different conditions considers the influence of SNOP and DSTATCOM transmission loss on state variable errors, and an error table for transmitting active power is shown in table 6. As can be seen from table 6, the relative error of the estimated dc active power flow values is more than 2% before and after considering the transmission loss of the SNOP and DSTATCOM for different control methods. Therefore, the accuracy of the state estimation model of the flexible power distribution network can be improved by considering the transmission loss of the SNOP and the DSTATCOM and the control mode.
Table 6 estimation error of the dc power transmitted by SNOP and B-DSTATCOM
Figure GDA0004268838770000141
To further test the influence of different amounts of bad data on the recognition capability and the calculation efficiency of different algorithms, 0, 50, 100 and 150 bad data are added in the measurement of the scene 2, and the following 3 methods are adopted for solving, so that the results are shown in table 7. The method 1 is a weighted least square method based on orthogonal transformation, the method 2 is a weighted least square method based on a regular equation, and the method 3 is a weighted least absolute method provided by the invention.
TABLE 7 identification capability and computational efficiency of different algorithms under scenario 2
Figure GDA0004268838770000142
As can be seen from comparing the first six columns of Table 7, when there is no bad data in the measurement, S of method 1 and method 2 3 S and S 4 Substantially the same and with a higher accuracy than method 3, indicating that the accuracy of the weighted least squares method is now higher than the accuracy of the weighted least absolute method. When there is bad data in the measurement, S of method 1 and method 2 as the bad data increases 3 S and S 4 Obviously increases, and the method 3 improves the index S of the estimation accuracy along with the quantity of the bad data 3 S and S 4 The increase amplitude is minimum, and the method provided by the invention has better robust capacity than a weighted least square method, and can better ensure that the state estimation of the flexible power distribution network has higher precision and reliability in engineering practice links.
As can be seen from comparison of the last three columns of table 7, when no bad data exists in the measurement, the method 1 adopts orthogonal transformation, the generated hessian matrix has smaller scale, higher calculation efficiency and minimum average calculation time. When bad data exists in measurement, the average calculation time of the method 2 and the method 3 is basically unchanged along with the increase of the bad data, and the average calculation time of the method 1 is obviously improved, because the method 1 needs to identify the bad data one by one, the average calculation time is increased along with the increase of the number of the bad data; the method 2 has no bad data identification link, and bad data has no influence on calculation time; the method 3 can automatically restrain the influence of bad data, and is irrelevant to the quantity of the bad data. Therefore, the calculation time of the method provided by the invention is irrelevant to the quantity of bad data, and the state estimation of the flexible power distribution network can be better ensured to have higher efficiency in engineering practice links.
The foregoing disclosure is merely illustrative of the presently preferred embodiments of the invention, and it is not intended to limit the scope of the invention, which can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present disclosure describes embodiments, not every embodiment is provided with a separate embodiment, and that this description is provided for clarity only, and that the disclosure is not limited to the embodiments described in detail below, and that the embodiments described in the examples may be combined as appropriate to form other embodiments that will be apparent to those skilled in the art.

Claims (4)

1. A flexible power distribution network three-phase state estimation method considering SNOP and B-DSTATCOM, wherein SNOP is an intelligent soft normally open switch, and B-DSTATCOM is a power distribution network static synchronous compensator, and is characterized by comprising the following steps:
(1) Constructing a power distribution network state estimation model based on a weighted minimum absolute value method;
(2) A measurement equation and constraint conditions of an alternating current power distribution network state estimation model are provided;
(3) SNOP and B-DSTATCOM state estimation models considering transmission loss and various control modes are provided, and corresponding measurement equations, control pseudo measurement equations and constraint conditions are provided;
(4) Calling an original dual interior point method in an IPOPT solver to solve the problem;
the flexible power distribution network comprising SNOP and B-DSTATCOM is divided into two branches according to the difference of whether the flexible power distribution network is connected with a B-DSTATCOM branch or an SNOP branch or an alternating current power distribution network: a three-phase alternating current power distribution network part, an SNOP branch part and a B-DSTATCOM branch part; the specific method of the step (2) and the step (3) is as follows:
measurement equation and constraint condition based on state estimation model of three-phase alternating current power distribution network part
Psi phase voltage measurement at node i
Figure FDA0004219983310000011
The following formula is shown:
Figure FDA0004219983310000012
wherein: i. j is the node number, where i E N exists B ，N B Representing a set of power distribution network nodes; subscript ψ is the phase sequence, there is ψ ε ψ, ψ= [ a, b, c ]]Representing a set of node phase sequences; e, e i,ψ 、f i,ψ Representing the real and imaginary parts of the ψ -phase voltage at node i, respectively;
the formation of the jacobian matrix in the formula (2) is complicated, and a state variable U is introduced i,ψ Replacing the part inside the root number in the formula (2) as shown in the formula (3); thus, voltage SCADA measurement
Figure FDA0004219983310000013
As shown in formula (4):
(U i,ψ ) 2 ＝(e i,ψ ) 2 +(f i,ψ ) 2 i∈N B ,ψ∈Ψ (3)
Figure FDA0004219983310000014
the ψ phase on branch ij carries the real part I of the current ij,ψ,x Imaginary part I ij,ψ,y As shown in formula (5);
measurement of the ψ phase transmission current on branch ij
Figure FDA0004219983310000015
As shown in formula (6):
Figure FDA0004219983310000016
Figure FDA0004219983310000017
wherein: g ij,ψ 、b ij,ψ For the phi relative on the branch ij
Figure FDA0004219983310000018
The conductance and susceptance of the phase;
similar to the transformation in voltage measurement, the introduction of state variables
Figure FDA0004219983310000019
As shown in formula (7), the line-transmitted electrical flow measurement is shown in formula (8):
Figure FDA00042199833100000110
Figure FDA00042199833100000111
active power measurement of psi phase transmission on branch ij
Figure FDA00042199833100000112
And reactive power measurement->
Figure FDA00042199833100000113
As shown in formula (9);
psi phase injection active power measurement of node i
Figure FDA00042199833100000114
And reactive power measurement->
Figure FDA00042199833100000115
As shown in formula (10);
Figure FDA0004219983310000021
Figure FDA0004219983310000022
wherein: omega shape i Representing a node set connected with a node i in the alternating current distribution network;
Figure FDA0004219983310000023
psi relative to branches ij
Figure FDA0004219983310000024
The real part and the imaginary part corresponding to the phase in the admittance matrix;
measurement equation based on SNOP branch part state estimation model
SNOP is arranged at a tie switch of the power distribution network, and four-quadrant control of power flow is realized by controlling VSCs at two sides, so that power flow distribution can be improved, voltage level can be improved, and in a psi-phase steady-state model, all variables at the i side of a node are taken as an example, V i,ψ Is the psi phase voltage at the node i of the SNOP branch;
Figure FDA0004219983310000025
the PSI phase fundamental voltage of the VSC at the i side of the SNOP branch node; v (V) S,DC The voltage at the direct current side of the SNOP branch VSC; />
Figure FDA0004219983310000026
The method comprises the steps that the active power and the reactive power of the psi phase are input to the i sides of nodes at two ends of an SNOP branch; />
Figure FDA0004219983310000027
The method comprises the steps that the PSI phase active power and reactive power of the VSC are introduced into the SNOP branch node i side; />
Figure FDA0004219983310000028
The PSI phase current of the VSC flows into the SNOP branch node i side; />
Figure FDA0004219983310000029
An equivalent psi phase admittance matrix of the SNOP branch node i side converter transformer;
the method comprises the steps that the phi-phase voltage measurement at a node i of an SNOP branch and the phi-phase voltage measurement at a node j of the SNOP branch and the phi-phase fundamental voltage measurement of a VSC at a node i side and a node j side of the SNOP branch are in the form of flexible power distribution network node phi-phase voltage measurement equations, and are shown in a formula (3) and a formula (4);
the flow of the node i at two ends of the SNOP branch into the psi phase current of the VSC and the flow of the node j into the psi phase current of the VSC are both in the form of a flexible power distribution network line psi phase transmission electric current measurement equation, as shown in a formula (7) and a formula (8);
the estimation of the state of the SNOP leg requires the introduction of a dc side voltage measurement of the VSC therein
Figure FDA00042199833100000214
AC side voltage measurement->
Figure FDA00042199833100000210
State variable V S,DC To perform state estimation as shown in the following formula:
Figure FDA00042199833100000211
wherein N is S Representing a set of alternating current nodes at two ends of an SNOP line; mu is the utilization rate of direct current voltage, and when the modulation mode is SPWM, mu is 0.866;
Figure FDA00042199833100000212
there is +.>
Figure FDA00042199833100000213
The PSI phase input power of the SNOP branch at the node i side and the node j side adopts the node PSI phase injection power form of the flexible power distribution network, as shown in a formula (10); the SNOP branch flows into the PSI phase power of the VSC from the node i and flows into the PSI phase power of the VSC from the node j, and the PSI phase power of the VSC is transmitted in the form of line PSI phase of the flexible power distribution network, as shown in a formula (9);
because the SNOP branch consists of 2 back-to-back VSC branches, the transmission loss of the SNOP branch is often more than 5% of the transmission power of the SNOP branch, so that the transmission loss of the SNOP branch is not negligible; therefore, the following relationship exists between the active power of the ψ phase of the sno leg flowing into the VSC from node i and the active power of the ψ phase flowing into the VSC from node j:
Figure FDA0004219983310000031
wherein,,
Figure FDA0004219983310000032
the transmission loss of the psi phase of the node i side and the node j side of the SNOP branch are respectively shown; alpha, beta and gamma are loss coefficients of the VSC in practical application respectively;
the reactive power flowing into the VSC from the two ends of the SNOP branch is directly counteracted by the compensation reactive balance of the VSC;
measurement equation and constraint condition of state estimation model based on B-DSTATCOM branch part
The battery energy storage is directly connected in parallel at two sides of the direct current capacitor to form B-DSTATCOM, the two share one VSC to provide direct current voltage and current, and the voltage and current are connected into a power grid through a connecting reactor, and V is in a psi phase steady-state model of the B-DSTATCOM i,ψ Is the psi phase voltage at the node i of the B-DSTATCOM;
Figure FDA0004219983310000033
the PSI phase fundamental voltage of the VSC at the node i side is B-DSTATCOM; v (V) BDS,DC The voltage of the direct current side of the B-DSTATCOM; />
Figure FDA0004219983310000034
The PSI phase power input to the node i side for the B-DSTATCOM; />
Figure FDA0004219983310000035
The PSI phase power of the VSC is flown from the node i side for the B-DSTATCOM; p (P) BDS,DC The output power of the direct current side of the B-DSTATCOM; />
Figure FDA0004219983310000036
The psi phase current of the VSC is streamed to the node i for B-DSTATCOM; />
Figure FDA0004219983310000037
The equivalent psi phase admittance of the converter transformer is B-DSTATCOM;
the voltage measurement of the psi phase of the B-DSTATCOM at the node i and the voltage measurement of the psi phase fundamental wave of the VSC at the node i side are in the form of a flexible power distribution network node psi phase voltage measurement equation, as shown in a formula (3) and a formula (4); the flow measurement of the psi phase current of the B-DSTATCOM flowing into the VSC at the node i adopts the form of a flexible power distribution network line psi phase transmission electric flow measurement equation, as shown in a formula (7) and a formula (8);
the state estimation of B-DSTATCOM requires the introduction of direct current side voltage measurements of VSC therein
Figure FDA00042199833100000312
AC side voltage measurement
Figure FDA00042199833100000313
State variable V BDS,DC To perform state estimation as shown in the following formula:
Figure FDA0004219983310000038
wherein N is BDS Representing a set of B-DSTATCOM nodes; mu is the utilization rate of direct current voltage, and when the modulation mode is SPWM, mu is 0.866;
Figure FDA0004219983310000039
for the VSC modulation of B-DSTATCOM at node i, there is +.>
Figure FDA00042199833100000310
The PSI phase power input by the B-DSTATCOM at the node i side adopts the form of PSI phase injection power of the power distribution network node, as shown in a formula (10); B-DSTATCOM flows into the phase power of the VSC from the node i in the form of distribution network line phase transmission power, as shown in formula (9);
the following relationship exists between the PSI phase active power of the VSC from the node i side and the B-DSTATCOM direct current side output power:
Figure FDA00042199833100000311
wherein,,
Figure FDA0004219983310000041
transmission loss of the psi phase for B-DSTATCOM;
the reactive power of the B-DSTATCOM flowing into the VSC from the node i is directly balanced by the compensation reactive power of the VSC;
the control pseudo measurement equation components of the VSC of the SNOP and the B-DSTATCOM are as follows:
(1) active power control on the ac side
Figure FDA0004219983310000042
Wherein,,
Figure FDA0004219983310000043
respectively representing the equivalent psi phase conductance and susceptance of the converter transformer of the corresponding equipment, and the existence of the equivalent psi phase conductance and susceptance
Figure FDA0004219983310000044
Variable->
Figure FDA0004219983310000045
To (ultra) *,DC The upper right hand corner of the diagram shows the class of device SNOP, B-DSTATCOM, AC, VSC, DC shows the ac side, VSC virtual side, dc side of the device respectively; />
Figure FDA0004219983310000046
Figure FDA0004219983310000047
The real part and the imaginary part of the psi phase voltage at the equipment node i and the virtual side of the VSC are respectively represented; />
Figure FDA0004219983310000048
Figure FDA0004219983310000049
For this device the exchange side and the VSC virtual side branch ij are relatively +.>
Figure FDA00042199833100000410
Mutual conductance and mutual susceptance of the phases;
Figure FDA00042199833100000411
a measurement value representing a fixed value of the active power of the phase psi of the alternating-current side at the equipment node i;
(2) constant ac side reactive power control
Figure FDA00042199833100000412
Wherein,,
Figure FDA00042199833100000413
a measurement value representing a fixed value of the phase psi reactive power of the alternating current side at the equipment node i;
(3) constant DC side voltage control
Figure FDA00042199833100000414
Wherein,,
Figure FDA00042199833100000415
a measurement value representing a constant value of the dc side voltage of the apparatus;
(4) constant ac side voltage control
Figure FDA00042199833100000416
Wherein,,
Figure FDA00042199833100000417
measurement value representing the VSC virtual side ψ phase voltage constant value at the device node i +.>
Figure FDA00042199833100000418
A substitution variable of the VSC fundamental voltage in the formula (3);
(5) fixed frequency control
Figure FDA00042199833100000419
Wherein,,
Figure FDA00042199833100000420
the measurement value of the virtual side psi phase voltage imaginary part fixed value of the VSC at the equipment node i is represented, and if fixed frequency control is adopted, the measurement value is 0.
2. The flexible power distribution network three-phase state estimation method considering SNOP and B-DSTATCOM as claimed in claim 1, wherein the method comprises the following steps of: the specific method of the step (1) is as follows:
the weighted minimum absolute value based state estimation problem is described as an optimization problem as follows:
Figure FDA0004219983310000051
wherein: x is a state variable;
Figure FDA0004219983310000052
is a measurement vector; j represents an objective function; />
Figure FDA0004219983310000053
Representing an exact equality constraint, if zero injection power is represented, there is +.>
Figure FDA0004219983310000054
h (x) represents a measurement equation and is a nonlinear function; Δz is the measurement residual vector, Δz + Absolute value of positive measurement residual error for corresponding measurement, Δz - The following delta-variables represent the corresponding measured measurement residuals for the absolute values of the corresponding measured negative measurement residuals; sigma is a standard deviation coefficient matrix.
3. The flexible power distribution network three-phase state estimation method considering SNOP and B-DSTATCOM as claimed in claim 1, wherein the method comprises the following steps of: the specific method of the step 4) is as follows:
the three-phase state estimation problem of the flexible power distribution network adopts a weighted minimum absolute value method with stronger robust against difference, adopts an OPTI library to model an optimization problem, calls a primary dual interior point method in an IPOPT solver to solve the problem, and finally obtains a state variable result of state estimation.
4. The flexible power distribution network three-phase state estimation method considering SNOP and B-DSTATCOM as claimed in claim 1, wherein the method comprises the following steps of: the B-DSTATCOM provides rapid and dynamic reactive power compensation and harmonic filtering for the flexible power distribution network.
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