CN112383080B

CN112383080B - Combined loop control method and device for AC/DC hybrid operation power grid

Info

Publication number: CN112383080B
Application number: CN202011384788.2A
Authority: CN
Inventors: 蔡建逸; 林裕新; 白浩; 陈伟翔; 陈琪烽; 廖绍谦; 李奕武; 陈楠; 刘晓枫; 朱俊樾; 林晓慧; 沈伟; 高永键
Original assignee: Guangdong Power Grid Co Ltd; Shantou Power Supply Bureau of Guangdong Power Grid Co Ltd
Current assignee: Guangdong Power Grid Co Ltd; Shantou Power Supply Bureau of Guangdong Power Grid Co Ltd
Priority date: 2020-11-30
Filing date: 2020-11-30
Publication date: 2023-06-30
Anticipated expiration: 2040-11-30
Also published as: CN112383080A

Abstract

The embodiment of the invention discloses a loop closing control method and a device of an AC/DC hybrid operation power grid, wherein the loop closing control method of the AC/DC hybrid operation power grid comprises the following steps: acquiring a wiring diagram and line data of a power grid; determining a loop closing current constraint condition, a loop closing power constraint condition and a power flow equation of each node of a line where a target loop closing point is located according to a wiring diagram and line data of a power grid; taking the loop closing current constraint condition, the loop closing power constraint condition and the power flow equation as a loop closing current constraint model; determining the size of loop closing boundary parameters in different simulated loop closing states based on a loop closing current constraint model; and determining a control strategy of the safety loop closing according to the size of the loop closing boundary parameter, and controlling the loop closing operation of the power grid based on the control strategy. The loop closing control method and device for the AC/DC hybrid operation power grid, provided by the embodiment of the invention, can ensure the safety and reliability of loop closing operation.

Description

Combined loop control method and device for AC/DC hybrid operation power grid

Technical Field

The embodiment of the invention relates to a power grid loop closing technology, in particular to a loop closing control method and device for an AC/DC hybrid operation power grid.

Background

In an electric power system, when equipment needs to be overhauled or a line is in fault, in order to ensure the continuity of power supply, loop closing operation is generally carried out on a power grid, and normal power supply of a non-overhauling section or a non-fault section is ensured. The ring closing operation can realize uninterrupted switching, and the power failure times and power failure time of a user can be greatly reduced, so that the ring closing operation is carried out on the power grid during line maintenance or faults, and the continuous power supply of the power grid is ensured.

At present, the existing loop closing control method of the AC/DC hybrid operation power grid can generally perform loop closing operation when the phase sequences and phases of voltages at two sides of a loop closing point are consistent, but for the AC/DC hybrid power grid with a power flow control strategy, if the voltage levels are more, only the phases and the phase sequences are checked, the power flow can be caused to be roundabout, and then the equipment is overloaded or tripped, so that the safe operation of the power grid is seriously threatened.

Disclosure of Invention

The embodiment of the invention provides a loop closing control method and device for an alternating current/direct current hybrid operation power grid, so as to ensure the safety and reliability of loop closing operation.

In a first aspect, an embodiment of the present invention provides a combined loop control method for an ac/dc hybrid operation power grid, including:

acquiring a wiring diagram and line data of a power grid;

determining a loop closing current constraint condition, a loop closing power constraint condition and a power flow equation of each node of a line where a target loop closing point is located according to a wiring diagram and line data of a power grid;

taking the loop closing current constraint condition, the loop closing power constraint condition and the power flow equation as a loop closing current constraint model;

determining the size of loop closing boundary parameters in different simulated loop closing states based on a loop closing current constraint model;

and determining a control strategy of the safety loop closing according to the size of the loop closing boundary parameter, and controlling the loop closing operation of the power grid based on the control strategy.

Optionally, determining the loop closing current constraint condition according to the wiring diagram and the line data of the power grid includes:

according to the wiring diagram and line data of the power grid, determining an overcurrent I section protection fixed value I of the line where the target loop closing point is located _{i overcurrent I} ；

Will I _M ≤I _{i overcurrent I} As a closed loop transient current constraint condition; wherein I is _M And i is the instantaneous value of the maximum current after the circuit with the target ring closing point is closed, and i is the circuit nodes at the two sides of the target ring closing point.

according to the wiring diagram and line data of the power grid, determining an overcurrent II-section protection fixed value I of the line where the target loop closing point is located _{i overcurrent II} ；

Will I _i ≤I _{i overcurrent II} As a closed loop transient current constraint condition; wherein I is _i And i is the line nodes at the two sides of the target loop closing point, which is the steady-state current after the loop closing of the line where the target loop closing point is located.

Optionally, determining the loop closing power constraint condition according to the wiring diagram and the line data of the power grid includes:

determining power thresholds at two ends of a transformer substation connected with a line where a target loop closing point is located according to a wiring diagram and line data of a power grid;

and taking the power thresholds at two ends of the transformer substation as loop closing power constraint conditions.

Optionally, determining the magnitude of the loop closing boundary parameter in different simulated loop closing states based on the loop closing current constraint model includes:

when the power grid model fitting ring operates, obtaining the impedance of a transformer substation side connected with a circuit where a ring closing point is positioned in each simulated ring closing state, the power output by the transformer substation to a power utilization load branch circuit and the bus voltage at two sides of the ring closing point;

and substituting the impedance of the transformer substation side, the power of the transformer substation output to the power load branch and the bus voltage of the two sides of the loop closing point into a loop closing current constraint model to obtain the size of the loop closing boundary parameters.

Optionally, determining a control policy of the safety loop closing according to the parameter size of the loop closing boundary parameter, and controlling the loop closing operation of the power grid based on the control policy, including:

according to the parameter of the loop closing boundary parameter, the voltage difference at two sides of the loop closing point, the output power of the circuit connecting the loop closing point with the power supply and the direct current output power are all adjusted to be smaller than the parameter value of the corresponding parameter in the loop closing boundary parameter.

Optionally, the security ring closing control strategy includes: adjusting the pressure difference at two sides of the ring closing point to be smaller than the pressure difference in the ring closing boundary parameter, and determining the switch closure at the ring closing point; determining that the direct current output power of the circuit where the loop closing point is positioned and connected with the power supply is smaller than the direct current power in the loop closing boundary parameter; before the ring closing operation, regulating the pressure difference at two sides of the ring closing point to be smaller than the pressure difference in the ring closing boundary parameters; the fan output of the line where the loop closing point is located and connected with the wind power plant is adjusted before the loop closing operation and is smaller than the fan output power in the loop closing boundary parameters.

Optionally, the power flow equation is represented by a PQ decomposition method of the voltage of each node of the line where the target loop closing point is located, where the power flow equation of the PQ decomposition method is:

wherein, -B' is a modified susceptance matrix without parallel branches, and θ and V are the phase and amplitude of the voltage, respectively.

Optionally, the loop closing boundary parameters include a differential pressure at two sides of the loop closing point, impedance at two sides of the loop closing point, and output power of a line where the loop closing point is located and connected with a power supply.

In a second aspect, an embodiment of the present invention further provides a combined loop control device for an ac/dc hybrid operation power grid, including:

the data acquisition module is used for acquiring a wiring diagram and line data of the power grid;

the constraint condition determining module is used for determining a loop closing current constraint condition, a loop closing power constraint condition and a power flow equation of each node of the line where the target loop closing point is located according to the wiring diagram and line data of the power grid;

the constraint model determining module is used for taking the loop closing current constraint condition, the loop closing power constraint condition and the power flow equation as a loop closing current constraint model;

the boundary parameter determining module is used for determining the size of the closed-loop boundary parameters in different simulated closed-loop states based on the closed-loop current constraint model;

and the loop closing control module is used for determining a control strategy of the safety loop closing according to the size of the loop closing boundary parameter and controlling the loop closing operation of the power grid based on the control strategy.

According to the loop closing control method and device for the AC/DC hybrid operation power grid, loop closing current constraint conditions, loop closing power constraint conditions and a power flow equation of each node of a line where a target loop closing point is located are determined according to the acquired wiring diagram and line data of the power grid; and taking the loop closing current constraint condition, the loop closing power constraint condition and the power flow equation as a loop closing current constraint model; determining the size of loop closing boundary parameters in different simulated loop closing states based on a loop closing current constraint model; and determining a control strategy of the safety loop closing according to the size of the loop closing boundary parameter, and controlling the loop closing operation of the power grid based on the control strategy. According to the loop closing control method and device for the AC/DC hybrid operation power grid, which are provided by the embodiment of the invention, the loop closing operation of the power grid is controlled based on the size of the loop closing boundary parameter determined by the loop closing current constraint model, and the pressure difference of two sides of the loop closing point, the output power of a circuit where the loop closing point is positioned and the DC output power are all smaller than the parameter values of corresponding parameters in the loop closing boundary parameter, so that the starting probability of the circulating power and the power flow control strategy in a loop is reduced, the loop closing operation is prevented from generating power flow roundabout, and the safety and the reliability of the loop closing operation are ensured.

Drawings

Fig. 1 is a schematic diagram of a line transmission power direction of a normal operation of an ac/dc hybrid operation power grid in the prior art;

fig. 2 is a schematic diagram of a transmission power direction of a circuit of a combined loop operation of an ac/dc hybrid operation power grid in the prior art;

fig. 3 is a flowchart of a loop control method for an ac/dc hybrid operation power grid according to an embodiment of the present invention;

fig. 4 is a flow chart of a loop control method for an ac/dc hybrid operation power grid according to a second embodiment of the present invention;

fig. 5 is a schematic diagram of a line transmission power direction of a loop-closing operation of an ac/dc hybrid operation power grid according to a second embodiment of the present invention;

fig. 6 is a schematic diagram of an equivalent circuit of a loop-closing operation of an ac/dc hybrid operation power grid provided in a second embodiment of the present invention;

fig. 7 is a schematic diagram of an optimal loop closing of an ac/dc hybrid operation power grid according to a second embodiment of the present invention;

fig. 8 is a block diagram of a combined loop control device for an ac/dc hybrid operation power grid according to a third embodiment of the present invention.

Detailed Description

The invention is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting thereof. It should be further noted that, for convenience of description, only some, but not all of the structures related to the present invention are shown in the drawings.

Fig. 1 is a schematic diagram of a line transmission power direction of a normal operation of an ac/DC hybrid operation power grid in the prior art, where lines WJ, LJ, SH, JH1 and JH2 shown in fig. 1 are all ac transmission lines, and lines DC1, DC2 and DC3 are all DC transmission lines. As shown in fig. 1, during normal operation of the ac/dc hybrid operation power grid, the 100, 500, 600 switches (loop closing points) of the substation 1 are all in the open positions, and the generated power of the wind farm 2 is transmitted through the ac line WJ and the dc channel of the converter station 2, respectively. The converter station 2 can control the active power output of the converter thereof, so that all the active power of the wind farm 2 is transmitted through the direct current line after being balanced in situ, and the active power of the alternating current line WJ is close to zero. When the generated power of the wind farm 2 increases to cause the active power of the line WJ to exceed ±5MW, the converter station 2 will adjust the conduction angle of the converter, increase the active power transmitted by the dc line, and decrease the active power transmitted by the line WJ (make the active power of the line WJ close to zero). Similarly, the converter station 1 can control the active power of the converter to output to the line JH1, and balance the active power of the wind farm 1 in situ, so that the active power remaining after the active power of the ac line LJ approaches zero is all transmitted through the dc line.

Fig. 2 is a schematic diagram of a transmission power direction of a circuit of a loop-closing operation of an ac/dc hybrid operation power grid in the prior art, as shown in fig. 2, when a loop-closing point of a transformer substation 1 is closed like 100 switches are closed, a wind farm 2 is connected with the outside, and not only an ac circuit WJ and a dc channel of a converter station 2, but also an ac circuit LJ and a dc channel of the converter station 1 are added. At this time, when the

wind power plants

1 and 2 increase the output power, the power is continuously transmitted to the converter station 2, and the residual power is output from the line WJ and rises to more than 5MW, in this way, the converter station 2 adjusts the conduction angle of the converter, and the active power transmitted by the direct current line (through the alternating current line SH of the converter station 3) is continuously increased until the

converter stations

1 and 2 are fully loaded; meanwhile, as the current flows from the converter station 3 to the transformer substation 4 to the transformer substation 5 to the transformer substation 1, when the input power of the line LJ is increased and exceeds-5 MW, the converter station 1 is caused to adjust the conduction angle of the converter, the power of the remaining direct current channel is continuously injected into the I bus of the transformer substation 1 through the alternating current line JH1 and flows to the line WJ and the line JH2 through the II bus, and the current flows into the direct current channel again to form the current roundabout, and the current roundabout can cause overload or tripping of equipment to seriously threaten the safe operation of a power grid.

Example 1

Fig. 3 is a flowchart of a loop closing control method of an ac/dc hybrid operation power grid, which is provided in an embodiment of the present invention, and the method may be implemented by a loop closing control device of the ac/dc hybrid operation power grid, and the device may be implemented by software and/or hardware, and the device may be integrated in an electronic device, such as a computer, having a loop closing control function of the ac/dc hybrid operation power grid, where the method specifically includes the following steps:

and 110, acquiring a wiring diagram and line data of a power grid.

The wiring diagrams of the power grid are shown in fig. 1 and 2, and the line data may include a maximum transmission current of the line, a power threshold value of a line connection transformer, a line overcurrent protection fixed value, and the like. The wiring diagram and the line data of the power grid can be stored in a power grid control system, and the loop closing control device of the AC/DC hybrid operation power grid can acquire the wiring diagram and the line data in the power grid control system through an input interface which is arranged by the loop closing control device and is electrically connected with the power grid control system, so that constraint conditions can be determined.

And 120, determining a loop closing current constraint condition, a loop closing power constraint condition and a power flow equation of each node of the line where the target loop closing point is located according to the wiring diagram and the line data of the power grid.

The loop closing current constraint condition may include a loop closing transient current constraint condition and a loop closing steady state current constraint condition, for example, the loop closing transient current constraint condition may be that a maximum current instantaneous value of a line where a target loop closing point is located after loop closing does not exceed an overcurrent section I protection constant value of the line where the target loop closing point is located. As shown in fig. 2, the loop closing point is at the 100 switch, the 100 switch is closed to realize loop closing operation, and the constraint condition of loop closing current, that is, the maximum current instantaneous value of the line where the 100 switch is located, needs not to exceed the overcurrent I-section protection fixed value of the line. The loop closing power constraint condition can be a power threshold value at two ends of a transformer substation connected by a line where a target loop closing point is located, a power flow equation of each node of the line where the target loop closing point is located can be calculated based on a power system power flow, and the power flow equation is determined according to a wiring diagram and line data of a power grid so as to establish a loop closing current constraint model.

And 130, taking the loop closing current constraint condition, the loop closing power constraint condition and the power flow equation as a loop closing current constraint model.

Specifically, the loop closing current constraint model is a model formed by a power flow equation and a plurality of constraint conditions such as a loop closing current constraint condition, a loop closing power constraint condition and the like, so that the size of loop closing boundary parameters of an alternating current-direct current hybrid running power grid in different simulated loop closing states, such as a simulated loop closing state corresponding to 100 switch closing, 500 switch closing or 600 switch closing, in a line shown in fig. 1 and 2, is determined based on the loop closing current constraint model.

And 140, determining the magnitude of the loop closing boundary parameters in different simulated loop closing states based on the loop closing current constraint model.

The loop closing current constraint model comprises loop closing boundary parameters, and the loop closing boundary parameters can comprise pressure difference at two sides of a loop closing point, impedance at two sides of the loop closing point, output power of a circuit where the loop closing point is positioned and connected with a power supply, and the like in constraint conditions and a power flow equation. If the 100 switch in the line shown in fig. 2 is closed, at this time, the simulated loop closing state of the power grid, that is, the simulated loop closing state corresponding to the closing state of the 100 switch, the line parameters of the power grid running in the simulated loop closing state are substituted into the loop closing current constraint model, so that the magnitude of the loop closing boundary parameters can be obtained; if the 500 switch in the line shown in fig. 2 is closed, at this time, the simulated loop closing state of the power grid, that is, the simulated loop closing state corresponding to the 500 switch is closed, and the line parameters of the power grid running in the simulated loop closing state are substituted into the loop closing current constraint model, so that the magnitude of the loop closing boundary parameters can be obtained; the sizes of the loop closing boundary parameters in different simulation loop closing states are different, so that the loop closing operation of the power grid is controlled according to the sizes of the loop closing boundary parameters in different simulation loop closing states.

And 150, determining a control strategy of the safety loop closing according to the size of the loop closing boundary parameter, and controlling the loop closing operation of the power grid based on the control strategy.

The control strategy of the safety loop can comprise: adjusting the pressure difference at two sides of the ring closing point to be smaller than the pressure difference in the ring closing boundary parameter, and determining the switch closure at the ring closing point; determining that the direct current output power of the circuit where the loop closing point is positioned and connected with the power supply is smaller than the direct current power in the loop closing boundary parameter; before the ring closing operation, regulating the pressure difference at two sides of the ring closing point to be smaller than the pressure difference in the ring closing boundary parameters; the fan output of the line where the loop closing point is located and connected with the wind power plant is adjusted before the loop closing operation and is smaller than the fan output power in the loop closing boundary parameters.

Specifically, according to the parameter of the loop closing boundary parameter, the voltage difference at two sides of the loop closing point, the output power of the line connected with the power supply where the loop closing point is positioned and the direct current output power are all smaller than the parameter values of the corresponding parameters in the loop closing boundary parameter, which is beneficial to reducing the circulating power in a loop and the starting probability of a power flow control strategy, and preventing the loop closing operation from generating power flow roundabout, thereby ensuring the safety and reliability of the loop closing operation.

According to the loop closing control method for the AC/DC hybrid operation power grid, loop closing operation of the power grid is controlled based on the size of the loop closing boundary parameter determined by the loop closing current constraint model, and according to the parameter size of the loop closing boundary parameter, the pressure difference of two sides of an integrated loop point, the output power of a circuit connected with a power supply where the loop closing point is positioned and the DC output power are all smaller than the parameter values of corresponding parameters in the loop closing boundary parameter, so that the starting probability of circulating power and a power flow control strategy in a loop is reduced, the loop closing operation is prevented from generating power flow roundabout, and the safety and the reliability of the loop closing operation are ensured.

Example two

Fig. 4 is a flowchart of a loop closing control method for an ac/dc hybrid power grid, which is provided by the second embodiment of the present invention, and the method may be implemented by a loop closing control device for an ac/dc hybrid power grid, and the device may be implemented by software and/or hardware, and the device may be integrated in an electronic device, such as a computer, having a loop closing control function of the ac/dc hybrid power grid, where the method specifically includes the following steps:

step 210, acquiring a wiring diagram and line data of a power grid.

The wiring diagrams of the power grid are shown in fig. 1 and 2, and the line data may include a maximum transmission current of the line, a power threshold value of a line connection transformer, a line overcurrent protection fixed value, and the like. The wiring diagram and the line data of the power grid can be stored in a power grid control system, and the loop closing control device of the AC/DC hybrid operation power grid can acquire the wiring diagram and the line data in the power grid control system through an input interface which is arranged on the loop closing control device and is electrically connected with the power grid control system.

Step 220, determining an overcurrent I section protection fixed value I of the line where the target loop closing point is located according to the wiring diagram and line data of the power grid _{i overcurrent I} 。

Wherein, the overcurrent I section protects the fixed value I _{i overcurrent I} The specific numerical values of (2) may be set according to actual conditions, and are not limited herein.

Step 230, step I _M ≤I _{i overcurrent I} As a closed loop transient current constraint.

Wherein I is _M And i is the instantaneous value of the maximum current after the circuit with the target ring closing point is closed, and i is the circuit nodes at the two sides of the target ring closing point. Fig. 5 is a schematic diagram of a transmission power direction of a circuit of an ac/dc hybrid operation power grid loop operation provided in a second embodiment of the present invention, and fig. 5 is obtained by equivalently using a wind farm 1 and a converter station 1 in fig. 2 as a power source 1, a wind farm 2 as a power source 2, a converter station 2 as a load 2, and a converter station 3 as a power source 3 on the basis of fig. 2. Fig. 6 is a schematic diagram of an equivalent circuit of a loop closing operation of an ac/dc hybrid operation power grid provided in a second embodiment of the present invention, fig. 6 is an equivalent schematic diagram of fig. 5, and, in combination with fig. 5 and fig. 6, one end of a loop closing point i.e. an I parent side of a 100 switch or a 500 switch or a 600 switch is taken as a transformer station a, transmission power is Sa, electric power used on the side is S2, one end of a loop closing point II parent side is taken as a transformer station b, transmission power is Sb, electric power used on the side is S3, wherein an S0 source continuously flows to a converter station 1, and the node is taken as a load end. Because the power flow control strategy of the power grid operation is started to form power flow detouring, the power of the power supply 2 is the adjustable injection power Sw2, the

power supplies

1 and 3 continuously output the power Sw1 and Sw3, and the power flow flows from the loop closing point I parent to the loop closing point II parent, so that an equivalent diagram shown in fig. 6 is obtained.

Specifically, the maximum current instantaneous value will appear about half a period after closing the loop, and when the closing point is 500 switches or 600 switches, the two main transformer switches and the loop power grid switch of the loop are exceededThe protection fixed value of the section I of the current is influenced (the nodes 5-10 shown in figure 6 are influenced, the loop closing point is not subjected to overcurrent protection and is not influenced, and when the loop closing point is 100 switches, the line switch on the 110kV loop is not subjected to overcurrent protection and is not influenced), I _{i overcurrent I} The protection constant value of the overcurrent I section of each node switch of the loop is ensured, and the constraint condition of the loop closing transient current is as follows:

wherein R, L is equivalent resistance and inductance of the ring closing point, I _m For the closed loop steady state current amplitude,

step 240, determining an overcurrent II section protection fixed value I of the line where the target loop closing point is located according to the wiring diagram and line data of the power grid _{i overcurrent II} 。

It should be noted that the overcurrent II section protection constant value I _{i overcurrent II} The numerical value of (2) may be specifically set according to the actual situation, and is not limited herein.

Step 250, step I _i ≤I _{i overcurrent II} As a closed loop transient current constraint.

Wherein I is _i And i is the line nodes at the two sides of the target loop closing point, which is the steady-state current after the loop closing of the line where the target loop closing point is located. When the loop closing point is 500 switches or 600 switches, the steady-state current after loop closing is smaller than the overcurrent II-section protection fixed value of each node switch on the loop (the same as the I-section protection principle, only the main transformer and the distribution network switch are affected), and the loop closing steady-state current constraint formula is as follows:

wherein S is _i 、U _i 、I _i Loop injection power, line voltage, line current, respectively.

And 260, determining power thresholds at two ends of the transformer substation connected with the line where the target loop closing point is located according to the wiring diagram and the line data of the power grid.

The specific value of the power threshold values at two ends of the transformer substation connected by the line where the target loop closing point is located can be set according to actual conditions, and the specific value is not limited herein.

Step 270, taking power thresholds at two ends of the transformer substation as loop closing power constraint conditions.

Specifically, with reference to fig. 5 and fig. 6, output power at two ends of the ring closing point can be obtained according to the distribution rule of ring network power

The method comprises the following steps:

wherein Z is ₁₂ 、Z ₂₃ 、Z ₃₄ The impedance between node 1 and node 2, the impedance between node 2 and node 3, the impedance between node 3 and node 4,

for cyclic power, Σz ^* ＝(Z ₁₂ +Z ₂₃ +Z ₃₄ ) Is the loop impedance phasor sum. Z when the closing point is adjusted to be 100/500/600 switch ₂₃ Is in growth change, U _N For the busbar voltage at two sides of the ring closing point, +.>

And determining the flow direction of the tide for the voltage phase difference at two sides of the loop closing point. The starting condition of the power flow control strategy of the power grid operation is that the power of the alternating current two ends of the transformer substation 1 is not more than +/-5 MW according to the following conditions/>

Representing the duplicate power +.>

Taking the real part P, the closed loop power constraint condition is:

or (b)

It should be noted that the above power ±5mw is only schematically illustrated, and the specific power value may be set according to the actual situation, which is not limited herein.

And 280, determining a tide equation of each node of the line where the target loop closing point is located according to the wiring diagram and the line data of the power grid.

Specifically, the power flow equation is represented by a PQ decomposition method of the voltage of each node of the line where the target loop closing point is located, and the power flow equation of the PQ decomposition method is:

Step 290, using the loop closing current constraint condition, the loop closing power constraint condition and the power flow equation as a loop closing current constraint model.

Specifically, according to the above constraint conditions and the expression of the power flow equation, the loop closing current constraint model may be expressed as:

wherein, the liquid crystal display device comprises a liquid crystal display device,

U _N in practice, the change is small, and the influence on the target value is small, and the target value can be regarded as a fixed amount. />

Is an independent variable +.>

Z ₂₃ By changing the switch of the closing point, < >>

The output power is regulated by the

power supply

1, 2 to be changed, < >>

By adjusting the difference of the voltage phases on both sides of the closed loop point, ->

Is a dependent variable.

And 291, when the power grid model fitting ring operates, acquiring the impedance of the transformer substation side connected with the line where the ring closing point is positioned in each simulated ring closing state, the power output by the transformer substation to the power utilization load branch circuit and the bus voltage at the two sides of the ring closing point.

Specifically, when the grid model fitting ring is operated as 500 switches are closed or 600 switches are closed, the parameter Z in the closed-loop current constraint model in the closed-loop state is simulated ₁₂ 、Z ₃₄ 、

U _N Specific numerical values are assigned. The above-mentioned simulated loop closing operation can be implemented in a simulated loop closing operation system, when the ac/dc hybrid operation power grid is implemented to implement die fitting loop, the simulated loop closing operation system can store parameter Z ₁₂ 、Z ₃₄ 、/>

U _N The loop closing control device of the AC/DC hybrid operation power grid can acquire the parameter Z through an input interface which is arranged by itself and is electrically connected with the analog loop closing operation system ₁₂ 、Z ₃₄ 、/>

U _N To determine the magnitude of the closed loop boundary parameter.

And 292, substituting the impedance of the transformer substation side, the power output by the transformer substation to the power load branch and the bus voltage at the two sides of the loop closing point into a loop closing current constraint model to obtain the size of the loop closing boundary parameters.

Wherein the boundary parameter of the closed loop is the independent variable Z ₂₃ 、

Parameter Z ₁₂ 、Z ₃₄ 、/>

U _N The numerical value of (2) is substituted into the closed loop current constraint model to obtain the closed loop boundary parameter Z ₂₃ 、/>

And controlling the loop closing operation of the power grid according to the parameter of the loop closing boundary parameter.

And 293, adjusting the pressure difference at two sides of the loop closing point, the output power of the circuit connected with the power supply where the loop closing point is positioned and the direct current output power to be smaller than the parameter values of corresponding parameters in the loop closing boundary parameters according to the parameter values of the loop closing boundary parameters.

Specifically, through the loop closing boundary parameters, a security loop closing management and control strategy can be obtained:

(1) And regulating the pressure difference (not exceeding the boundary parameter value) at two sides of the integrated loop point, determining that a certain switch loop closing operation is closed, and enabling a power flow control strategy not to be started, wherein the loop closing operation is safe.

(2) And controlling the direct current output power (not exceeding the boundary parameter value) and controlling the pressure difference (not exceeding the boundary parameter value) at the two ends of the loop closing point, wherein the power flow control strategy cannot be started, and the loop closing operation of closing a certain switch is safe.

(3) The pressure difference (not exceeding the boundary parameter value) on both sides of the closing point should be regulated before the closing operation, and when the limit value of the pressure difference is reached, the circulating power in the loop is reduced, especially in the case of the sum of the fan output (exceeding the boundary parameter value).

(4) The fan output (not exceeding the boundary parameter value) of the

wind power plants

1 and 2 can be adjusted and reduced before closing the rings, which is beneficial to reducing the starting probability of the power flow control strategy and the circulating power in the closed loop.

(5) The high-voltage side loop closing (namely the loop closing point 100 is used for switching the loop closing), although the tripping of a line is not caused, the winding of power flow causes the increase of power transmission line loss, and if the loop closing can be safely performed on the distribution network side, the loop closing operation by using the high-voltage side switch is not recommended in the aspect of benefit.

Fig. 7 is a schematic diagram of an optimal closed loop of an ac/dc hybrid operation power grid according to a second embodiment of the present invention, and fig. 7 is a model fitting loop operation based on the equivalent circuit of fig. 6, when the parameter Z ₂₃ 、U _a -U _b When the sum of the alternating current output power of the converter station 3 and the output power of the

wind power plants

1, 2 is shaded in fig. 7, the corresponding ring closing operation is the optimal ring closing operation, U shown in fig. 7 _a -U _b For the pressure difference between two ends of the ring closing point, the specific ring closing operation is controlled as follows:

(1) Under the normal operation state of the AC/DC hybrid operation power grid, when the pressure difference of two sides of the ring closing point is-0.7 kV or less U _a -U _b When the voltage is less than or equal to 0.4kV, under any mode, the 600 switch is closed to perform loop closing operation, and a power flow control strategy of the AC/DC hybrid operation power grid cannot be started, so that the loop closing operation is safe.

(2) Controlling the alternating current output power of the converter station 3 to be smaller than or equal to 60MW, and controlling the pressure difference between two ends of the loop closing point to be-0.7 kV and less than or equal to U _a -U _b And the voltage is less than or equal to 0.3kV, at the moment, the power flow control strategy is not started, and the 600 switch or the 500 switch is closed to perform the loop closing operation, so that the safety is ensured.

(3) Before the ring closing operation, the pressure difference between two ends of the ring closing point should be regulated, when U _a Less than U _b When the total output of the fans exceeds 80MW, the circulating power in the loop is reduced.

(4) The fan output of the

wind power plants

1 and 2 can be adjusted before closing the rings and respectively does not exceed 38.6MW and 41.44MW, which is beneficial to reducing the starting probability of a power flow control strategy and the circulating power in a closed loop.

(5) The loop closing operation is performed by switching the loop with a loop closing point 100, and although the tripping of a line is not caused, the winding of power flow causes the increase of power transmission line loss, and if the loop closing operation can be performed safely on the 10kV side, the loop closing operation with the 100 switch is not recommended in the aspect of benefit.

It should be noted that the pressure difference U between the two ends of the above-mentioned ring closing point _a -U _b The specific numerical ranges of the converter station 3 ac output power and the fan output of the

wind farms

1, 2 may be set according to actual conditions, and are not limited herein.

According to the loop closing control method for the AC/DC hybrid operation power grid, when the power grid model is fitted to the loop operation, the obtained impedance of the transformer substation side, the power output to the power load branch and the busbar voltage at the two sides of the loop closing point are substituted into the loop closing current constraint model to obtain the size of the loop closing boundary parameter, the loop closing operation of the power grid is controlled based on the size of the loop closing boundary parameter determined by the loop closing current constraint model, and according to the parameter size of the loop closing boundary parameter, the pressure difference at the two sides of the loop closing point, the output power of the circuit where the loop closing point is positioned and the DC output power are smaller than the parameter values of corresponding parameters in the loop closing boundary parameter, so that the starting probability of the circulating power and the power flow control strategy in the loop is reduced, the loop closing operation is prevented from generating power flow roundabout, and the safety and reliability of the loop closing operation are ensured.

Example III

Fig. 8 is a block diagram of a loop control device for an ac/dc hybrid operation power grid according to a third embodiment of the present invention, where the device includes a data acquisition module 310, a constraint condition determination module 320, a constraint model determination module 330, a boundary parameter determination module 340, and a loop control module 350; the data acquisition module 310 is configured to acquire a wiring diagram and line data of a power grid; the constraint condition determining module 320 is configured to determine a loop closing current constraint condition, a loop closing power constraint condition, and a power flow equation of each node of the line where the target loop closing point is located according to the wiring diagram and line data of the power grid; the constraint model determining module 330 is configured to take the closed loop current constraint condition, the closed loop power constraint condition and the power flow equation as a closed loop current constraint model; the boundary parameter determining module 340 is configured to determine the magnitude of the closed-loop boundary parameter in different simulated closed-loop states based on the closed-loop current constraint model; the loop closing control module 350 is configured to determine a control policy of the safety loop closing according to the magnitude of the loop closing boundary parameter, and control the power grid loop closing operation based on the control policy.

On the basis of the above embodiment, the constraint condition determining module 320 includes an overcurrent I-segment protection constant value determining unit and a loop closing transient current constraint condition determining unit; the overcurrent I section protection fixed value determining unit is used for determining an overcurrent I section protection fixed value I of a line where a target loop closing point is located according to a wiring diagram and line data of a power grid _{i overcurrent I} The method comprises the steps of carrying out a first treatment on the surface of the The loop closing transient current constraint condition determining unit is used for determining I _M ≤I _{i overcurrent I} As a closed loop transient current constraint condition; wherein I is _M And i is the instantaneous value of the maximum current after the circuit with the target ring closing point is closed, and i is the circuit nodes at the two sides of the target ring closing point.

Preferably, the constraint condition determining module 320 includes an overcurrent section ii protection constant value determining unit and a loop closing transient current constraint condition determining unit; the overcurrent II-section protection fixed value determining unit is used for determining an overcurrent II-section protection fixed value I of a line where a target loop closing point is located according to a wiring diagram and line data of a power grid _{i overcurrent II} The method comprises the steps of carrying out a first treatment on the surface of the The loop closing transient current constraint condition determining unit is used for determining I _i ≤I _{i overcurrent II} As closed loop transient current constraintsConditions; wherein I is _i And i is the line nodes at the two sides of the target loop closing point, which is the steady-state current after the loop closing of the line where the target loop closing point is located.

In one embodiment, the constraint condition determining module 320 includes a substation two-terminal power threshold determining unit and a loop closing power constraint condition determining unit; the power threshold determining unit at two ends of the transformer substation determines the power threshold at two ends of the transformer substation connected with the line where the target loop closing point is located according to a wiring diagram and line data of the power grid; the loop closing power constraint condition determining unit is used for taking power thresholds at two ends of the transformer substation as loop closing power constraint conditions.

Preferably, the boundary parameter determining module 340 includes a data acquiring unit and a loop closing boundary parameter determining unit; the data acquisition unit is used for acquiring the impedance of the transformer substation side connected with the circuit where the loop closing point is positioned in each simulated loop closing state, the power output by the transformer substation to the power load branch and the bus voltage at the two sides of the loop closing point when the power grid model fitting loop operates; the loop closing boundary parameter determining unit is used for substituting the impedance of the transformer substation side, the power output to the power load branch by the transformer substation and the bus voltages at the two sides of the loop closing point into the loop closing current constraint model to obtain the size of the loop closing boundary parameter.

Preferably, the loop closing control module 350 includes a loop closing control unit, and the loop closing control unit is configured to adjust, according to the parameter of the loop closing boundary parameter, the differential pressure between two sides of the loop closing point, the output power of the line connection power source where the loop closing point is located, and the dc output power to be smaller than the parameter value of the corresponding parameter in the loop closing boundary parameter.

Preferably, the control strategy of the safety closing ring comprises: adjusting the pressure difference at two sides of the ring closing point to be smaller than the pressure difference in the ring closing boundary parameter, and determining the switch closure at the ring closing point; determining that the direct current output power of the circuit where the loop closing point is positioned and connected with the power supply is smaller than the direct current power in the loop closing boundary parameter; before the ring closing operation, regulating the pressure difference at two sides of the ring closing point to be smaller than the pressure difference in the ring closing boundary parameters; the fan output of the line where the loop closing point is located and connected with the wind power plant is adjusted before the loop closing operation and is smaller than the fan output power in the loop closing boundary parameters.

Preferably, the power flow equation is represented by a PQ decomposition method of the voltage of each node of the line where the target loop closing point is located, and the power flow equation of the PQ decomposition method is:

Preferably, the loop closing boundary parameters comprise the pressure difference at two sides of a loop closing point, the impedance at two sides of the loop closing point and the output power of a circuit where the loop closing point is positioned and connected with a power supply.

The loop control device for the ac/dc hybrid operation power grid provided by the embodiment and the loop control method for the ac/dc hybrid operation power grid provided by any embodiment of the present invention belong to the same inventive concept, and have corresponding beneficial effects, and technical details not shown in detail in the embodiment of the present invention are not shown in detail in the loop control method for the ac/dc hybrid operation power grid provided by any embodiment of the present invention.

Note that the above is only a preferred embodiment of the present invention and the technical principle applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, and that various obvious changes, rearrangements, combinations, and substitutions can be made by those skilled in the art without departing from the scope of the invention. Therefore, while the invention has been described in connection with the above embodiments, the invention is not limited to the embodiments, but may be embodied in many other equivalent forms without departing from the spirit or scope of the invention, which is set forth in the following claims.

Claims

1. The combined loop control method for the AC/DC hybrid operation power grid is characterized by comprising the following steps of:

acquiring a wiring diagram and line data of a power grid;

determining a loop closing current constraint condition, a loop closing power constraint condition and a power flow equation of each node of a line where a target loop closing point is located according to a wiring diagram and line data of the power grid;

determining the magnitude of loop closing boundary parameters in different simulated loop closing states based on the loop closing current constraint model;

determining a control strategy of the safety loop closing according to the size of the loop closing boundary parameter, and controlling the loop closing operation of the power grid based on the control strategy;

the method for determining the control strategy of the safety loop closing according to the parameter size of the loop closing boundary parameter and controlling the loop closing operation of the power grid based on the control strategy comprises the following steps:

and regulating the pressure difference at two sides of the loop closing point, the output power of the circuit connected with the power supply where the loop closing point is positioned and the direct current output power according to the parameter size of the loop closing boundary parameter, wherein the output power and the direct current output power are smaller than the parameter values of corresponding parameters in the loop closing boundary parameter.

2. The loop closing control method of an ac/dc hybrid operation power grid according to claim 1, wherein the determining a loop closing current constraint condition according to a wiring diagram and line data of the power grid comprises:

3. The loop closing control method of an ac/dc hybrid operation power grid according to claim 1, wherein the determining a loop closing current constraint condition according to a wiring diagram and line data of the power grid comprises:

4. The loop closing control method of an ac/dc hybrid operation power grid according to claim 1, wherein the determining a loop closing power constraint condition according to a wiring diagram and line data of the power grid comprises:

determining power thresholds at two ends of a transformer substation connected with a line where a target loop closing point is located according to a wiring diagram and line data of the power grid;

and taking the power thresholds at the two ends of the transformer substation as loop closing power constraint conditions.

5. The loop closing control method of an ac/dc hybrid operating power grid according to claim 1, wherein determining the magnitude of the loop closing boundary parameter in different simulated loop closing states based on the loop closing current constraint model comprises:

and substituting the impedance of the transformer substation side, the power output to the power load branch circuit by the transformer substation and the bus voltages at the two sides of the loop closing point into the loop closing current constraint model to obtain the size of the loop closing boundary parameters.

6. The loop closing control method of an ac/dc hybrid operation power grid according to claim 1, wherein the control strategy of the safety loop closing comprises: adjusting the pressure difference at two sides of the ring closing point to be smaller than the pressure difference in the ring closing boundary parameter, and determining the switch closure at the ring closing point; determining that the direct current output power of a circuit connected with a power supply where the loop closing point is positioned is smaller than the direct current power in the loop closing boundary parameter; before the ring closing operation, regulating the pressure difference at two sides of a ring closing point to be smaller than the pressure difference in the boundary parameters of the ring closing; and adjusting the output power of the fan connected with the wind power plant by the line where the loop closing point is positioned before the loop closing operation to be smaller than the output power of the fan in the loop closing boundary parameters.

7. The loop closing control method of an ac/dc hybrid operating power grid according to claim 1, wherein the power flow equation is represented by a PQ decomposition method of a voltage of each node of a line where a target loop closing point is located, and the power flow equation of the PQ decomposition method is:

8. The loop closing control method of the ac/dc hybrid operation power grid according to claim 1, wherein the loop closing boundary parameters include a differential pressure of two sides of a loop closing point, impedance of two sides of the loop closing point, and output power of a line where the loop closing point is located and connected with a power supply.

9. The utility model provides a close ring management and control device of alternating current-direct current hybrid operation electric wire netting which characterized in that includes:

the constraint condition determining module is used for determining a loop closing current constraint condition, a loop closing power constraint condition and a power flow equation of each node of a line where a target loop closing point is located according to a wiring diagram and line data of the power grid;

the loop closing control module is used for determining a control strategy of the safety loop closing according to the size of the loop closing boundary parameter and controlling the loop closing operation of the power grid based on the control strategy;

the loop closing control module comprises a loop closing control unit, and the loop closing control unit is used for adjusting the pressure difference at two sides of a loop closing point, the output power of a circuit connection power supply where the loop closing point is positioned and the direct current output power according to the parameter size of the loop closing boundary parameter to be smaller than the parameter value of the corresponding parameter in the loop closing boundary parameter.