阅读说明：本技术 一种含调压器微电网的潮流计算方法和系统 (Load flow calculation method and system of microgrid with voltage regulator ) 是由 彭和平 栾乐 许中 莫文雄 王勇 马智远 王海靖 范伟男 肖天为 刘田 于 2021-08-26 设计创作，主要内容包括：本发明公开了一种含调压器微电网的潮流计算方法和系统,根据系统节点导纳矩阵计算微电网模型的三相不对称潮流,进而计算调压器的控制电压偏差,根据调压器节点导纳矩阵与分接头的关系,确定在调压器分接头动作后系统节点导纳矩阵的变化量,从而利用逐步迭代和修正的方式,每次计算调压器分接头的位置,然后根据分接头位置更新系统节点导纳矩阵,再利用隐Zbus高斯法进行下一次潮流计算,在调压器的控制电压偏差小于预置带宽时,停止迭代,输出三相不对称潮流,在三相不对称潮流的计算速度上,相比于牛顿类算法,具有更好的收敛效果和高效性。(The invention discloses a load flow calculation method and a system of a microgrid with a voltage regulator, wherein three-phase asymmetric load flow of a microgrid model is calculated according to a system node admittance matrix, and then the control voltage deviation of the voltage regulator is calculated, the variable quantity of the system node admittance matrix after the tap joint of the voltage regulator acts is determined according to the relation between the voltage regulator node admittance matrix and the tap joint, so that the position of the tap joint of the voltage regulator is calculated each time by utilizing a gradual iteration and correction mode, then the system node admittance matrix is updated according to the tap joint position, next load flow calculation is carried out by utilizing a hidden Zbus Gauss method, when the control voltage deviation of the voltage regulator is smaller than a preset bandwidth, the iteration is stopped, the three-phase asymmetric load flow is output, and the calculation speed of the three-phase asymmetric load flow has better convergence effect and high efficiency compared with a Newton algorithm.)

1. A load flow calculation method of a microgrid with a voltage regulator is characterized by comprising the following steps:

s1, acquiring a microgrid model containing a voltage regulator;

s2, calculating a system node admittance matrix of the microgrid model;

s3, calculating the three-phase asymmetric power flow of the microgrid model by adopting an implicit Zbus Gaussian method according to the system node admittance matrix;

s4, calculating the control voltage deviation of the voltage regulator according to the result of the three-phase asymmetric power flow;

s5, judging whether the control voltage deviation of the voltage regulator is smaller than a preset bandwidth, if so, jumping to S9, and if not, executing S6;

s6, adjusting the tap joint of the voltage regulator according to the control voltage deviation of the voltage regulator, and updating the transformer node admittance matrix;

s7, updating the system node admittance matrix according to the updated transformer node admittance matrix;

s8, returning to the step S3 to recalculate the three-phase asymmetric power flow of the microgrid model according to the updated system node admittance matrix;

and S9, outputting the three-phase asymmetric power flow of the microgrid model.

2. The method for calculating the power flow of the microgrid with a voltage regulator according to claim 1, wherein the step S2 specifically comprises:

s21, calculating an admittance matrix of each element node of the microgrid model;

and S22, calculating a system node admittance matrix of the microgrid model according to the element node admittance matrixes.

3. The method for calculating the power flow of the microgrid with a voltage regulator, as claimed in claim 1, wherein in step S4, the formula for calculating the deviation of the control voltage of the voltage regulator is as follows:

ΔV_reg＝u/p_tratio-V_drrop-V_reg

wherein u is the node voltage of three-phase asymmetric load flow calculation, p_tratioIs the voltage transformer transformation ratio of a voltage regulator, V_drropFor compensating circuit voltage drop, V, of voltage regulators_regIs the control voltage of the voltage regulator.

4. The method for calculating the power flow of the microgrid with a voltage regulator according to claim 1, wherein the step S6 specifically comprises:

s61, if the control voltage deviation of the voltage regulator is larger than the preset bandwidth and the control voltage deviation of the voltage regulator is larger than zero, controlling a tap joint of the voltage regulator to move downwards by one position, and updating a transformer node admittance matrix;

s62, if the control voltage deviation of the voltage regulator is larger than the preset bandwidth and the control voltage deviation of the voltage regulator is smaller than zero, controlling a tap joint of the voltage regulator to move upwards by one position, and updating a transformer node admittance matrix;

and S63, if the control voltage deviation of the voltage regulator is smaller than the preset bandwidth, the position of a tap of the voltage regulator is not moved, and the transformer node admittance matrix is not updated.

5. The method for calculating the power flow of the microgrid with a voltage regulator according to claim 4, wherein in the step S6, the formula for updating the transformer node admittance matrix is as follows:

wherein Z is_BIs a transformer impedance matrix, B is a matrix representing the relation between current at two sides in the 1V equivalent transformer and equivalent impedance current, N is a matrix representing the relation between current at two ends of the transformer and an equivalent 1V transformer model, A is a matrix representing the relation between node current and branch current, and T is a matrix representing the relation between node current and branch current_agregIs the tap position of the transformer, is KV₁Primary side voltage, KV₂Is the secondary side voltage.

6. A load flow calculation system containing a voltage regulator microgrid is characterized by comprising the following modules:

the model acquisition module is used for acquiring a microgrid model containing a voltage regulator;

the system node admittance matrix calculation module is used for calculating a system node admittance matrix of the microgrid model;

the three-phase asymmetric power flow calculation module is used for calculating the three-phase asymmetric power flow of the micro-grid model by adopting an implicit Zbus Gaussian method according to the system node admittance matrix;

the voltage regulator control voltage deviation calculation module is used for calculating the control voltage deviation of the voltage regulator according to the result of the three-phase asymmetric power flow;

the judging module is used for judging whether the control voltage deviation of the voltage regulator is smaller than a preset bandwidth, if so, the three-phase asymmetric power flow output module is triggered, and if not, the tap joint adjusting module of the voltage regulator is triggered;

the voltage regulator tap adjusting module is used for adjusting the voltage regulator tap according to the control voltage deviation of the voltage regulator and updating the transformer node admittance matrix;

the admittance matrix updating module is used for updating the system node admittance matrix according to the updated transformer node admittance matrix;

the three-phase asymmetric power flow updating module is used for returning to the three-phase asymmetric power flow calculating module to recalculate the three-phase asymmetric power flow of the microgrid model according to the updated system node admittance matrix;

and the three-phase asymmetric power flow output module is used for outputting the three-phase asymmetric power flow of the micro-grid model.

7. The power flow calculation system of the microgrid with a voltage regulator of claim 6, wherein the system node admittance matrix calculation module is specifically configured to:

calculating an admittance matrix of each element node of the microgrid model;

and calculating a system node admittance matrix of the microgrid model according to the element node admittance matrixes.

8. The power flow calculation system of the microgrid with a voltage regulator of claim 6, wherein a formula for calculating the control voltage deviation of the voltage regulator is as follows:

ΔV_reg＝u/p_tratio-V_drrop-V_reg

wherein u is the node voltage of three-phase asymmetric load flow calculation, p_tratioIs the voltage transformer transformation ratio of a voltage regulator, V_drropFor compensating circuit voltage drop, V, of voltage regulators_regIs the control voltage of the voltage regulator.

9. The power flow calculation system of the regulator-included microgrid of claim 6, wherein the regulator tap adjustment module is specifically configured to:

if the control voltage deviation of the voltage regulator is larger than the preset bandwidth and the control voltage deviation of the voltage regulator is larger than zero, controlling a tap joint of the voltage regulator to move downwards by one position, and updating a transformer node admittance matrix;

if the control voltage deviation of the voltage regulator is larger than the preset bandwidth and the control voltage deviation of the voltage regulator is smaller than zero, controlling a tap joint of the voltage regulator to move upwards by one position, and updating a transformer node admittance matrix;

and if the control voltage deviation of the voltage regulator is smaller than the preset bandwidth, the position of a tap joint of the voltage regulator is not moved, and the transformer node admittance matrix is not updated.

10. The power flow calculation system of the microgrid with a voltage regulator of claim 9, wherein the formula for updating the transformer node admittance matrix is as follows:

wherein Z is_BIs a transformer impedance matrix, B is a matrix representing the relation between current at two sides in the 1V equivalent transformer and equivalent impedance current, N is a matrix representing the relation between current at two ends of the transformer and an equivalent 1V transformer model, A is a matrix representing the relation between node current and branch current, and T is a matrix representing the relation between node current and branch current_agregIs the tap position of the transformer, is KV₁Primary side voltage, KV₂Is the secondary side voltage.

Technical Field

The invention relates to the technical field of power grid load flow calculation, in particular to a load flow calculation method and system of a micro-power grid with a voltage regulator.

Background

With the continuous development of the micro-grid, a large number of distributed power supplies and control systems are connected to the grid, and the large number of distributed power supplies connected to the grid can improve the power supply reliability of the system, reduce the grid loss of the system, improve the economy of the system, but also improve the difficulty of system analysis. The distributed power supply can enable the power flow of a system circuit to flow reversely, so that the system is changed from a single power supply mode to a multi-power supply mode, and in order to ensure the voltage stability of a grid-connected point of the distributed power supply, a control element (such as a voltage regulator) is required to control the voltage of the grid-connected point.

Load flow calculation is the basis of distribution network system analysis, and is to solve the steady-state voltage of each node under the condition of a given set of power generation and load conditions. Due to the existence of asymmetric elements in the microgrid, such as three-phase transmission lines and three-phase asymmetric loads, three-phase voltage and currents of the microgrid are not symmetric any more, so that the load flow of only one phase can not be calculated, and the three-phase load flow needs to be calculated. The Newton algorithm is one of three-phase asymmetric power flow algorithms at present, and when solving the micro-grid power flow containing a distributed power supply and a voltage regulator, the Newton algorithm needs to continuously update a Jacobian matrix, so that the calculation speed is low, and the problem of low efficiency exists.

Disclosure of Invention

The invention provides a method and a system for calculating the power flow of a microgrid with a voltage regulator, which are used for solving the technical problems of low convergence speed and low efficiency when a Newton algorithm is used for solving the power flow of the microgrid with a distributed power supply and the voltage regulator in the prior art.

In view of this, the first aspect of the present invention provides a method for calculating a power flow of a microgrid with a voltage regulator, including the following steps:

s1, acquiring a microgrid model containing a voltage regulator;

s2, calculating a system node admittance matrix of the microgrid model;

s3, calculating the three-phase asymmetric power flow of the microgrid model by adopting an implicit Zbus Gaussian method according to the system node admittance matrix;

s4, calculating the control voltage deviation of the voltage regulator according to the result of the three-phase asymmetric power flow;

s5, judging whether the control voltage deviation of the voltage regulator is smaller than a preset bandwidth, if so, jumping to S9, and if not, executing S6;

s6, adjusting the tap joint of the voltage regulator according to the control voltage deviation of the voltage regulator, and updating the transformer node admittance matrix;

s7, updating the system node admittance matrix according to the updated transformer node admittance matrix;

s8, returning to the step S3 to recalculate the three-phase asymmetric power flow of the microgrid model according to the updated system node admittance matrix;

and S9, outputting the three-phase asymmetric power flow of the microgrid model.

Optionally, step S2 specifically includes:

s21, calculating an admittance matrix of each element node of the microgrid model;

and S22, calculating a system node admittance matrix of the microgrid model according to the element node admittance matrixes.

Optionally, in step S4, the formula for calculating the control voltage deviation of the voltage regulator is:

ΔV_reg＝u/p_tratio-V_drrop-V_reg

wherein u is the node voltage of three-phase asymmetric load flow calculation, p_tratioFor regulating the pressureVoltage transformer transformation ratio of transformer_drropFor compensating circuit voltage drop, V, of voltage regulators_regIs the control voltage of the voltage regulator.

Optionally, step S6 specifically includes:

s61, if the control voltage deviation of the voltage regulator is larger than the preset bandwidth and the control voltage deviation of the voltage regulator is larger than zero, controlling a tap joint of the voltage regulator to move downwards by one position, and updating a transformer node admittance matrix;

s62, if the control voltage deviation of the voltage regulator is larger than the preset bandwidth and the control voltage deviation of the voltage regulator is smaller than zero, controlling a tap joint of the voltage regulator to move upwards by one position, and updating a transformer node admittance matrix;

and S63, if the control voltage deviation of the voltage regulator is smaller than the preset bandwidth, the position of a tap of the voltage regulator is not moved, and the transformer node admittance matrix is not updated.

Optionally, in step S6, the formula for updating the transformer node admittance matrix is:

wherein Z is_BIs a transformer impedance matrix, B is a matrix representing the relation between current at two sides in the 1V equivalent transformer and equivalent impedance current, N is a matrix representing the relation between current at two ends of the transformer and an equivalent 1V transformer model, A is a matrix representing the relation between node current and branch current, and T is a matrix representing the relation between node current and branch current_agregIs the tap position of the transformer, is KV₁Primary side voltage, KV₂Is the secondary side voltage.

The invention provides a power flow calculation system with a voltage regulator microgrid, which comprises the following modules:

the model acquisition module is used for acquiring a microgrid model containing a voltage regulator;

the system node admittance matrix calculation module is used for calculating a system node admittance matrix of the microgrid model;

the three-phase asymmetric power flow calculation module is used for calculating the three-phase asymmetric power flow of the micro-grid model by adopting an implicit Zbus Gaussian method according to the system node admittance matrix;

the voltage regulator control voltage deviation calculation module is used for calculating the control voltage deviation of the voltage regulator according to the result of the three-phase asymmetric power flow;

the judging module is used for judging whether the control voltage deviation of the voltage regulator is smaller than a preset bandwidth, if so, the three-phase asymmetric power flow output module is triggered, and if not, the tap joint adjusting module of the voltage regulator is triggered;

the voltage regulator tap adjusting module is used for adjusting the voltage regulator tap according to the control voltage deviation of the voltage regulator and updating the transformer node admittance matrix;

the admittance matrix updating module is used for updating the system node admittance matrix according to the updated transformer node admittance matrix;

the three-phase asymmetric power flow updating module is used for returning to the three-phase asymmetric power flow calculating module to recalculate the three-phase asymmetric power flow of the microgrid model according to the updated system node admittance matrix;

and the three-phase asymmetric power flow output module is used for outputting the three-phase asymmetric power flow of the micro-grid model.

Optionally, the system node admittance matrix calculation module is specifically configured to:

calculating an admittance matrix of each element node of the microgrid model;

and calculating a system node admittance matrix of the microgrid model according to the element node admittance matrixes.

Optionally, the formula for calculating the control voltage deviation of the voltage regulator is:

ΔV_reg＝u/p_tratio-V_drrop-V_reg

wherein u is the node voltage of three-phase asymmetric load flow calculation，p_tratioIs the voltage transformer transformation ratio of a voltage regulator, V_drropFor compensating circuit voltage drop, V, of voltage regulators_regIs the control voltage of the voltage regulator.

Optionally, the regulator tap adjustment module is specifically configured to:

if the control voltage deviation of the voltage regulator is larger than the preset bandwidth and the control voltage deviation of the voltage regulator is larger than zero, controlling a tap joint of the voltage regulator to move downwards by one position, and updating a transformer node admittance matrix;

if the control voltage deviation of the voltage regulator is larger than the preset bandwidth and the control voltage deviation of the voltage regulator is smaller than zero, controlling a tap joint of the voltage regulator to move upwards by one position, and updating a transformer node admittance matrix;

and if the control voltage deviation of the voltage regulator is smaller than the preset bandwidth, the position of a tap joint of the voltage regulator is not moved, and the transformer node admittance matrix is not updated.

Optionally, the formula for updating the transformer node admittance matrix is as follows:

wherein Z is_BIs a transformer impedance matrix, B is a matrix representing the relation between current at two sides in the 1V equivalent transformer and equivalent impedance current, N is a matrix representing the relation between current at two ends of the transformer and an equivalent 1V transformer model, A is a matrix representing the relation between node current and branch current, and T is a matrix representing the relation between node current and branch current_agregIs the tap position of the transformer, is KV₁Primary side voltage, KV₂Is the secondary side voltage.

According to the technical scheme, the embodiment of the invention has the following advantages:

the invention provides a load flow calculation method of a microgrid with a voltage regulator, which is characterized in that three-phase asymmetric load flow of a microgrid model is calculated according to a system node admittance matrix, further, the control voltage deviation of the voltage regulator is calculated, the variable quantity of the system node admittance matrix after the tap joint of the voltage regulator acts is determined according to the relation between the voltage regulator node admittance matrix and the tap joint, therefore, the position of the tap joint of the voltage regulator is calculated each time by utilizing a gradual iteration and correction mode, then the system node admittance matrix is updated according to the tap joint position, next load flow calculation is carried out by utilizing a hidden Zbus Gaussian method, when the control voltage deviation of the voltage regulator is smaller than a preset bandwidth, the iteration is stopped, the three-phase asymmetric load flow is output, and the calculation speed of the three-phase asymmetric load flow has better convergence effect and high efficiency compared with the former Newton algorithm, and the problem that when the load flow of the microgrid with a distributed power supply and the voltage regulator is solved by using the Newton algorithm in the prior art, slow convergence speed and low efficiency.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other related drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic flow chart of a method for calculating a power flow of a microgrid with a voltage regulator according to an embodiment of the present invention;

FIG. 2 is a diagram of a three-phase transformer model provided in an embodiment of the present invention;

fig. 3 is a topology diagram of a voltage regulator model provided in an embodiment of the present invention;

fig. 4 is a schematic structural diagram of a line buck compensator of a voltage regulator according to an embodiment of the present invention;

fig. 5 is a schematic diagram of a tap position of a voltage regulator provided in an embodiment of the present invention;

FIG. 6 is a modified IEEE13 node system topology provided in embodiments of the present invention;

fig. 7 is a schematic structural diagram of a power flow calculation system including a voltage regulator microgrid provided in an embodiment of the present invention.

Detailed Description

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

For easy understanding, referring to fig. 1, an embodiment of a method for calculating a power flow of a microgrid with a voltage regulator according to the present invention includes:

step 101, obtaining a microgrid model containing a voltage regulator.

It should be noted that, in the embodiment of the present invention, a microgrid model including a voltage regulator needs to be obtained first, where the microgrid model includes component models, such as a transmission line model and a transformer model. The model of the transformer with the Y-D connection mode is shown in FIG. 2. The transformer model according to fig. 2 has:

wherein, Y_primThe node admittance matrix of the transformer is calculated by the following steps:

in the formula, Z_BThe short-circuit impedance matrix of the transformer is a 3 x 3 matrix, B represents a relation matrix of equivalent impedance current and current on two sides of the 1V equivalent transformer, is a 6 x 3 matrix, N represents a relation matrix of current on two sides of the transformer and a 1V equivalent transformer model, is a 4 x 2 matrix, and A is related to a transformer wiring mode and represents a matrix of relation between node current and branch current.

And 102, calculating a system node admittance matrix of the microgrid model.

It should be noted that the system node admittance matrix of the microgrid model can be obtained by calculation according to the node admittance matrix of each element, for example, the node admittance matrix of the transmission line, the transformer, the parallel compensation and the series compensation is calculated first, then the connection relationship between the elements is determined through the system topology, and the node admittance matrices of each element are combined through the connection relationship, so as to obtain the system node admittance matrix. This process is prior art and will not be described herein.

And 103, calculating the three-phase asymmetric power flow of the microgrid model by adopting an implicit Zbus Gaussian method according to the system node admittance matrix.

The implicit Zbus Gaussian method is an effective algorithm for three-phase load flow calculation of the power distribution network, iterative calculation is performed on the basis of a node voltage equation, and node injection current in the load flow calculation is obtained by dividing node injection power and node voltage. The network equation of the microgrid system can be expressed as:

I＝Y_busV

where vector V is the node voltage, vector I is the node injection current, Y_busIs a node admittance matrix of the microgrid.

The node types of the microgrid may be divided into: the source point, the P-V nodes (e.g., generators and distributed power sources), and the remaining nodes, and thus, the above equation can be expressed as:

wherein, I₁Injecting a current into the node of the source point, I₂Injecting a current into a node of the P-V node₃Injecting current for nodes of the rest nodes.

The ability of the P-V node type to maintain the reactive power variation has an allowable range, and if the required reactive power is outside this range, the P-V node needs to be converted to a P-Q node in order to maintain a constant voltage. The model of PV-PQ conversion can be used in a power flow meterAnd strengthening in the calculation method. If there is no constant power device in the system, as in the grid load flow calculation method, then I₃Is a known constant injection current, V₃Can be found according to the following formula:

V₃＝Y₃₃ ^-1(I₃(V₃)-Y₃₁V₁-Y₃₂V₂)

v on the right side of the equation₂Estimate V from the latest value of₃Voltage value of, when in an iterative process V₃Is smaller than the prescribed error value, a solution to the equation is obtained.

And 104, calculating the control voltage deviation of the voltage regulator according to the result of the three-phase asymmetric power flow.

It should be noted that, in the embodiment of the present invention, a topology diagram of a voltage regulator model is shown in fig. 3, and a topology diagram of a line step-down compensator in the voltage regulator model is shown in fig. 4. In the regulator model, each time the tap is adjusted, the voltage change amount corresponding to 0.00625, i.e. the voltage transformation ratio, can be calculated by the following formula:

T_R＝1±0.00625·Tap

wherein, T_RFor the regulator ratio, Tap is the Tap (gear) position.

The voltage drop of the compensation circuit can be expressed as:

wherein, V_dropTo compensate for voltage drop of the circuit; r_compΩAnd X_compΩTo compensate for the impedance of the circuit; r_lineΩAnd X_lineΩIs the impedance of a linear equivalent circuit; CT_PIs the current of a linear equivalent circuit; n is a radical of_PTIs the transformation ratio of the voltage transformer.

The voltage regulator typically has 32 taps, 16 taps above neutral and 16 taps below neutral, and the output voltage of the transformer varies by 0.00625 units each time the taps are moved, as shown in fig. 5. The node admittance matrix of the transformer changes with the position of the tap, so the node admittance matrix can be used for reflecting the action of the voltage regulator. Taking a single-phase transformer as an example, when a tap is at a neutral point position, a node admittance matrix of the transformer is:

in the formula, Z_BThe method is characterized in that the method is a transformer impedance matrix, B is a matrix representing the relation between currents on two sides in a 1V equivalent transformer and equivalent impedance currents, N is a matrix representing the relation between the currents on two ends of the transformer and an equivalent 1V transformer model, and A is a matrix representing the relation between node currents and branch currents.

Wherein:

with the adjustment of the secondary side tap of the transformer, the N matrix of the transformer is adjusted as follows:

in the formula, T_agregIs the tap position of the transformer, is KV₁Primary side voltage, KV₂Is the secondary side voltage. The calculation formula of the control voltage deviation of the voltage regulator is as follows:

ΔV_reg＝u/p_tratio-V_drrop-V_reg

in the formula, u is the node voltage of three-phase asymmetric load flow calculation, p_tratioIs the voltage transformer transformation ratio of a voltage regulator, V_drropFor compensating circuit voltage drop, V, of voltage regulators_regIs the control voltage of the voltage regulator.

And 105, judging whether the control voltage deviation of the voltage regulator is smaller than the preset bandwidth, if so, jumping to step 109, and if not, executing step 106.

And 106, adjusting a tap joint of the voltage regulator according to the control voltage deviation of the voltage regulator, and updating the transformer node admittance matrix.

It should be noted that, when the deviation of the control voltage of the voltage regulator is not less than the preset bandwidth, the position of the tap of the voltage regulator needs to be adjusted, so as to update the node admittance matrix of the transformer according to the position of the tap of the voltage regulator, that is, the node admittance matrix Y of the transformer is updated by changing the N matrix_prim。

Specifically, if the control voltage deviation of the voltage regulator is greater than the preset bandwidth and the control voltage deviation of the voltage regulator is greater than zero, the tap joint of the voltage regulator is controlled to move downwards by one position, and the transformer node admittance matrix is updated. And if the control voltage deviation of the voltage regulator is greater than the preset bandwidth and the control voltage deviation of the voltage regulator is less than zero, controlling a tap joint of the voltage regulator to move upwards by one position, and updating the transformer node admittance matrix. And if the control voltage deviation of the voltage regulator is smaller than the preset bandwidth, the position of a tap joint of the voltage regulator is not moved, the transformer node admittance matrix is not updated, and the step 109 is directly skipped to output the three-phase asymmetric power flow of the microgrid model.

And step 107, updating the system node admittance matrix according to the updated transformer node admittance matrix.

It should be noted that the system node admittance matrix is formed by the node admittance matrices of the respective elements, and therefore, when the transformer node admittance matrix is updated, the system node admittance matrix also needs to be updated accordingly.

And 108, returning to the step 103 to recalculate the three-phase asymmetric power flow of the microgrid model according to the updated system node admittance matrix.

And step 109, outputting the three-phase asymmetric power flow of the microgrid model.

In the embodiment of the invention, when the three-phase asymmetric load flow calculation containing the voltage regulator is calculated, the voltage of a bus where the voltage regulator is located is updated by using an implicit Zbus Gaussian method every time, then the control voltage deviation of the voltage regulator is calculated, the position of a tap is determined according to the relation between the control voltage deviation and the bandwidth, a new node admittance matrix of the transformer is determined according to the position of the tap, so that the node admittance matrix of the system is updated, and then the next implicit Zbus Gaussian load flow calculation is carried out until the positions of the taps of all the voltage regulators do not act any more.

The load flow calculation method of the microgrid with the voltage regulator, provided by the embodiment of the invention, is characterized in that the three-phase asymmetric load flow of a microgrid model is calculated according to a system node admittance matrix, further the control voltage deviation of the voltage regulator is calculated, the variable quantity of the system node admittance matrix after the tap joint of the voltage regulator acts is determined according to the relation between the voltage regulator node admittance matrix and the tap joint, so that the position of the tap joint of the voltage regulator is calculated each time by utilizing a gradual iteration and correction mode, then the system node admittance matrix is updated according to the tap joint position, next load flow calculation is carried out by utilizing a hidden Zbus Gaussian method, when the control voltage deviation of the voltage regulator is smaller than a preset bandwidth, the iteration is stopped, the three-phase asymmetric load flow is output, and the calculation speed of the three-phase asymmetric load flow has better convergence effect and high efficiency compared with a Newton algorithm, and the problem that when the load flow of the microgrid with a distributed power supply and the voltage regulator is solved by using the Newton algorithm in the prior art, slow convergence speed and low efficiency.

In order to test and verify the load flow calculation method of the microgrid with the voltage regulator, provided by the embodiment of the invention, the test is carried out by using a modified IEEE13 node system. A modified IEEE13 node system topology is shown in fig. 6. The topology comprises 1 three-phase voltage source, 3 transformers, 3 voltage regulators, 36 distribution network transmission lines and 12 loads, wherein the loads connected with buses 9 and 13 are distributed power supplies, and the control parameters of a main voltage regulator are shown in table 1.

TABLE 1 Main Voltage regulator control parameters

vregReg1/V	bandReg1/V	Ptratio	Rcomp/V	Xcomp/V
					110	3.6/2	20	2.2	9.5

The system is subjected to three-phase asymmetric load flow calculation by using an implicit Zbus Gaussian method, and partial calculation results are shown in Table 2.

Table 2 IEEE13 node system example partial load flow calculation results

The resulting voltage regulator transformation ratio calculation results are shown in table 3:

TABLE 3

Voltage regulator	Transformation ratio
		Reg1	0.95625
Reg2	1.05
		Reg3	1.04375

The voltage regulator reaches a stable state after 10 actions, only 1.1s is needed for the whole calculation process by using matlab, and 2.2s is needed for the calculation by using a Newton method, so that the method has a better convergence effect and a higher calculation speed of the three-phase asymmetric power flow compared with the prior art.

For easy understanding, referring to fig. 7, an embodiment of a power flow calculation system including a voltage regulator microgrid is provided in the present invention, including:

a model obtaining module 201, configured to obtain a microgrid model including a voltage regulator;

a system node admittance matrix calculation module 202, configured to calculate a system node admittance matrix of the microgrid model;

the three-phase asymmetric power flow calculation module 203 is used for calculating the three-phase asymmetric power flow of the microgrid model by adopting an implicit Zbus Gaussian method according to the system node admittance matrix;

the voltage regulator control voltage deviation calculation module 204 is used for calculating the control voltage deviation of the voltage regulator according to the result of the three-phase asymmetric power flow;

a judging module 205, configured to judge whether a control voltage deviation of the voltage regulator is smaller than a preset bandwidth, if so, trigger the three-phase asymmetric power flow output module 209, and if not, trigger the voltage regulator tap adjusting module 206;

the voltage regulator tap adjusting module 206 is configured to adjust the voltage regulator tap according to the control voltage deviation of the voltage regulator, and update the transformer node admittance matrix;

an admittance matrix updating module 207, configured to update the system node admittance matrix according to the updated transformer node admittance matrix;

the three-phase asymmetric power flow updating module 208 is configured to return to the three-phase asymmetric power flow calculation module 203 to recalculate the three-phase asymmetric power flow of the microgrid model according to the updated system node admittance matrix;

and the three-phase asymmetric power flow output module 209 is configured to output a three-phase asymmetric power flow of the microgrid model.

The system node admittance matrix calculation module 202 is specifically configured to:

calculating an admittance matrix of each element node of the microgrid model;

and calculating a system node admittance matrix of the microgrid model according to the element node admittance matrixes.

The formula for calculating the control voltage deviation of the voltage regulator is as follows:

ΔV_reg＝u/p_tratio-V_drrop-V_reg

wherein u is the node voltage of three-phase asymmetric load flow calculation, p_tratioIs the voltage transformer transformation ratio of a voltage regulator, V_drropFor compensating circuit voltage drop, V, of voltage regulators_regIs the control voltage of the voltage regulator.

The regulator tap adjustment module 206 is specifically configured to:

if the control voltage deviation of the voltage regulator is larger than the preset bandwidth and the control voltage deviation of the voltage regulator is larger than zero, controlling a tap joint of the voltage regulator to move downwards by one position, and updating a transformer node admittance matrix;

if the control voltage deviation of the voltage regulator is larger than the preset bandwidth and the control voltage deviation of the voltage regulator is smaller than zero, controlling a tap joint of the voltage regulator to move upwards by one position, and updating a transformer node admittance matrix;

and if the control voltage deviation of the voltage regulator is smaller than the preset bandwidth, the position of a tap joint of the voltage regulator is not moved, and the transformer node admittance matrix is not updated.

The formula for updating the transformer node admittance matrix is as follows:

wherein，Z_BIs a transformer impedance matrix, B is a matrix representing the relation between current at two sides in the 1V equivalent transformer and equivalent impedance current, N is a matrix representing the relation between current at two ends of the transformer and an equivalent 1V transformer model, A is a matrix representing the relation between node current and branch current, and T is a matrix representing the relation between node current and branch current_agregIs the tap position of the transformer, is KV₁Primary side voltage, KV₂Is the secondary side voltage.

The load flow calculation system containing the micro-grid of the voltage regulator, provided by the embodiment of the invention, calculates the three-phase asymmetric load flow of a micro-grid model according to the system node admittance matrix, further calculates the control voltage deviation of the voltage regulator, determines the variation of the system node admittance matrix after the tap joint of the voltage regulator acts according to the relation between the voltage regulator node admittance matrix and the tap joint, thereby calculating the position of the tap joint of the voltage regulator each time by utilizing a gradual iteration and correction mode, then updates the system node admittance matrix according to the tap joint position, then performs the next load flow calculation by utilizing a hidden Zbus Gaussian method, stops iteration and outputs the three-phase asymmetric load flow when the control voltage deviation of the voltage regulator is less than a preset bandwidth, has better convergence effect and high efficiency in the calculation speed of the three-phase asymmetric load flow compared with a Newton algorithm, and solves the problem that when the current technology uses the Newton algorithm to solve the load flow of the micro-grid containing the distributed power supply and the voltage regulator, slow convergence speed and low efficiency.

The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.