CN110854868B - Direct current static power limit value calculation method considering influence of new generation phase modulator - Google Patents

Abstract

A direct current static power limit value calculation method considering the influence of a new generation phase modulator comprises the steps of (1) establishing a correlation model between overpasses and direct current systems; (2) calculating the phase-in operation and phase-lag operation sending limit values of the phase modifier; (3) calculating a direct current commutation angle and parameters related to an inversion side under a rated condition; (4) solving the potential of the equivalent alternating current system and the direct current bus voltage power angle; (5) solving each related electrical quantity by taking the direct current as a variable; (6) judging whether the reactive power provided by the phase modulator is in the range of the reactive power allowed to be sent out by the phase modulator; if the direct current is within the range, the direct current is taken as an independent variable, and the direct current power is solved; otherwise, entering the step (7); (7) and (5) replacing the reactive power value sent by the phase modulator by the reactive power limit value which can be sent by the phase modulator, and returning to the step. The invention makes the limit value of the direct current transmission power more consistent with the actual value, and provides an important reference for improving the direct current transmission capability in the actual operation.

Description

Direct current static power limit value calculation method considering influence of new generation phase modulator

Technical Field

The invention belongs to the technical field of power systems, and particularly relates to a direct-current static power limit value calculation method considering the influence of a new generation phase modulator.

Background

Because of the outstanding advantages of ultra-high voltage direct current transmission engineering in the aspects of technology, economy, safety and the like, China has become the country with the widest application prospect of remote direct current transmission worldwide. However, with the increasingly prominent problem of 'strong direct current and weak direct current' of the power grid of a company, the extra-high voltage direct current transmission project puts higher demands on dynamic reactive support of the power grid, so that a new generation of large phase modulators with the characteristics of high-capacity bidirectional dynamic reactive support and the like are produced in response to operation, and the phase modulators are deployed on the extra-high voltage power grid in a large scale. However, since the new generation phase modulator has a large dynamic reactive power supporting capability, which will have an important effect on the dc static power transmission limit, the existing research lacks consideration of the effect of phase modulator access on the dc static power transmission limit.

Aiming at the situation, the invention provides a direct current static power limit value calculation method considering the influence of a new generation phase modulator under the background that the extra-high voltage direct current transmitting end and the receiving end both have the new generation phase modulator, and provides important theoretical support for analysis of a power grid system, analysis of direct current transmission limit capacity and the like.

Disclosure of Invention

Aiming at the defects or improvement requirements of the prior art and aiming at the scene that a new generation phase modulator is deployed at a direct current sending end and a receiving end, the invention provides a direct current static power limit value calculation method considering the influence of the new generation phase modulator, so that the direct current transmission power limit value is more consistent with the reality, and an important reference is provided for improving the direct current transmission capability in the actual operation.

To achieve the above object, according to an aspect of the present invention, there is provided a method for calculating a dc quiescent power limit value considering the influence of a new generation phase modulator, comprising the following steps:

(1) establishing a correlation model between the interchange and the direct current system;

(2) calculating the phase-in operation and phase-lag operation sending limit values of the phase modifier;

(3) calculating a direct current commutation angle mu and an inversion side correlation parameter K under a rated condition;

(4) establishing an alternating current system equation simultaneously, and solving the potential of the equivalent alternating current system and the direct current bus voltage power angle;

(5) taking the direct current as a variable, enabling the direct current bus voltage U to be 1p.u, and solving each related electrical quantity;

(6) judging whether the reactive power provided by the phase modulator is in the range of the reactive power allowed to be sent out; if the direct current is within the range, the direct current is taken as an independent variable, and the direct current power is solved; otherwise, entering the step (7);

(7) replacing the reactive power value sent by the phase modulator by the reactive power limit value which can be sent by the phase modulator, and returning to the step (5);

(8) and (6) ending.

Further, the step (1) specifically comprises:

establishing an operation characteristic equation of the direct current inversion station based on the direct current inversion side,

in the formula, C and K are two constants related to the rectifier side converter transformer parameter and the direct current system reference value respectively, U is the voltage of a direct current bus at the transmitting end, and alpha is a trigger delay angle; mu is a commutation angle, Q_cFor reactive compensation capacity, B_cThe equivalent admittance of the alternating current filter at the rectification side and the reactive compensation capacitor; a and b are constants and represent the proportion converted by the converter; u shape_iConverting the bus voltage for the receiving end; gamma is the arc extinguishing angle of the receiving-end inverter station; x_dIs the impedance of the DC transmission line, P_dIs direct current active power, Q_dIs direct current reactive power; i is_dIs direct current; i Z < theta is equivalent impedance of the alternating current system; e and delta are equivalent potential and a power angle of the alternating current system; p_acThe power is applied to an alternating current system; q_acFor ac system idle, U_dIs a direct-current voltage, and the voltage is,

reactive power increment delta Q emitted by phase modulator_scComprises the following steps:

ΔQ_sc＝Q_{cx_SC max}-Q_{inv_SC0} (2)

wherein Q is_{cx_SCmax}For phase-lag operation limit reactive power, Q, of phase modulators_{inv_SC0}The initial operation reactive value of the phase modulator on the direct current inversion side is obtained.

Further, the step (2) specifically comprises:

according to the electromagnetic equation and control system of the phase modulator unit and the control requirement, the reactive power expression sent out by the phase modulator is obtained by combining the direct current bus voltage U, and the phase-lag operation limit Q of the phase modulator is further obtained_{cx_SCmax}And phase advance operating limit Q_{jx_SCmax}：

Wherein, X_dFor phase-modifier stator inductive reactance, S_NRated capacity, k, for phase-modulators_fmThe strong excitation multiple of the phase modulator, Kc the short-circuit ratio of the phase modulator, E₀And (4) the rated potential of the unit.

Further, the formula for calculating the commutation angle μ of the direct current under the rated condition and the parameter K related to the inversion side in the step (3) is as follows:

where α is the triggered delay angle, P_dIs the DC active power, c is the converter transformer parameter at the rectifier side, U is the DC bus voltage, I_dIs a direct current, mu is a commutation angle.

Further, the step (4) specifically comprises:

according to the six equations 4, 5, 6, 7, 8 and 9 in the formula (1), solving and considering the alternating current potential E and the direct current bus voltage power angle delta of the initial reactive power output of the phase modulator;

further, the step (5) specifically comprises: let U equal to 1p.u, calculate each electric quantity P_d,Q_d,U_d,Q_c,P_ac,Q_acAnd Δ Q_scAccording to Δ Q_sc＝Q_{cx_SC max}-Q_{inv_SC0}To obtain Q_{inv_SC0}，Q_{inv_SC0}Is straightAnd the phase modulator on the current inversion side initially operates at a reactive value.

Further, the step (6) specifically comprises:

judgment of Q_{inv_SC0}Whether or not it is within the variation range of the normal operation of the phase modulator (Q)_SC1,Q_SC2) Wherein Q is_SC1Typical values are-100 Mvar, Q_SC2A typical value is 100Mvar, and if the phase modulator initial output is within a given range, the phase modulator is substituted for the 7 th equation in equation (1) with the order

Solving the direct current I_dSo that the DC transmission power reaches the maximum value P_dmaxIf Q is_{inv_SC0}Out of the range of variation of normal operation of the phase-modifier (Q)_SC1,Q_SC2) Then step (7) is entered.

Further, the step (7) specifically comprises:

judgment of Q_{inv_SC0}Less than Q_SC1Or is greater than Q_SC2If Q is_{inv_SC0}Less than Q_SC1Then Q is asserted_{inv_SC0}＝Q_SC1Substituting the equation into the 7 th equation in the formula (1), and returning to the step (5); otherwise, order Q_{inv_SC0}＝Q_SC2Substituting the equation into the 7 th equation in the formula (1), and returning to the step (5).

The invention considers the influence of the phase modifier on the promotion of the limit value of the direct current transmission power, provides theoretical basis and reference for the promotion of the direct current transmission power in system analysis, has important promotion effect on the consumption of the renewable energy source at the sending end, ensures that the limit value of the direct current transmission power is more consistent with the actual value, and provides important reference for the promotion of the direct current transmission power in the actual operation.

Drawings

Fig. 1 is a schematic flowchart of a method for calculating a dc static power limit value considering the influence of a new generation phase modulator according to an embodiment of the present invention;

fig. 2 is a schematic diagram of different initial reactive power and direct current transmission power of the phase modulator under different initial reactive power output conditions and different direct current conditions.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The following specifically explains the calculation method of the direct current static power limit value considering the influence of the new generation phase modulator provided by the invention with reference to the embodiment; the flow of the method for calculating the direct-current static power limit value considering the influence of the new generation phase modulator provided by the embodiment is shown in fig. 1, and the method specifically comprises the following steps:

step 1: establishing a correlation model between the interchange and the direct current system;

establishing an operation characteristic equation of the direct current inversion station based on the direct current inversion side,

in the formula, C and K are two constants related to the rectifier side converter transformer parameter and the direct current system reference value respectively, U is the voltage of a direct current bus at the transmitting end, and alpha is a trigger delay angle; mu is a commutation angle, Q_cFor reactive compensation capacity, B_cThe equivalent admittance of the alternating current filter at the rectification side and the reactive compensation capacitor; a and b are constants and represent the proportion converted by the converter; u shape_iConverting the bus voltage for the receiving end; gamma is the arc extinguishing angle of the receiving-end inverter station; x_dIs the impedance of the DC transmission line, P_dIs direct current active power, Q_dIs direct current reactive power; i is_dIs direct current; i Z < theta is equivalent impedance of the alternating current system; e and delta are equivalent potential and a power angle of the alternating current system; p_acThe power is applied to an alternating current system; q_acFor ac system idle, U_dIs a direct-current voltage, and the voltage is,

reactive power increment delta Q emitted by phase modulator_scComprises the following steps:

ΔQ_sc＝Q_{cx_SC max}-Q_{inv_SC0} (2)

wherein Q is_{cx_SCmax}For phase-lag operation limit reactive power, Q, of phase modulators_{inv_SC0}The initial operation reactive value of the phase modulator on the direct current inversion side is obtained.

Step 2: calculating the phase-in operation and phase-lag operation sending limit values of the phase modifier;

according to the electromagnetic equation and control system of the phase modulator unit and the control requirement, the reactive power expression sent by the phase modulator is obtained by combining the direct-current bus voltage U, and further the phase-lag operation limit Q of the phase modulator can be obtained_{cx_SCmax}And phase advance operating limit Q_{jx_SCmax}：

Wherein, X_dFor phase-modifier stator inductive reactance, S_NRated capacity, k, for phase-modulators_fmThe strong excitation multiple of the phase modulator, Kc the short-circuit ratio of the phase modulator, E₀And (4) the rated potential of the unit.

And step 3: calculating a direct current commutation angle mu and an inversion side correlation parameter K under a rated condition;

wherein, I_dIs a dc current and U is a dc bus voltage.

Further, K is a constant related to an inversion side system, so that the constant can be determined according to I under a rated working condition_dAnd calculating the value of K through the formula (5) according to the value of U, alpha and mu, and using the value of K for subsequent calculation.

And 4, step 4: establishing an alternating current system equation simultaneously, and solving the potential of the equivalent alternating current system and the direct current bus voltage power angle;

according to the six equations 4, 5, 6, 7, 8 and 9 in the formula (1), the alternating current potential E and the direct current bus voltage power angle delta of the initial reactive power output of the phase modulator are considered to be solved.

And 5: taking the direct current as a variable, enabling the direct current bus voltage U to be 1p.u, and solving each related electrical quantity;

let U equal to 1p.u, calculate each electric quantity P_d,Q_d,U_d,Q_c,P_ac,Q_acAnd Δ Q_scAccording to Δ Q_sc＝Q_{cx_SCmax}-Q_{inv_SC0}Can obtain Q_{inv_SC0}，Q_{inv_SC0}The initial operation reactive value of the phase modulator on the direct current inversion side is obtained.

Step 6: judging whether the reactive power provided by the phase modulator is in the range of the reactive power allowed to be sent out; if the current is within the range, the direct current is taken as an independent variable, and the limit value of the direct current static power is solved; otherwise, entering step 7;

judgment of Q_{inv_SC0}Whether or not it is within the variation range of the normal operation of the phase modulator (Q)_SC1,Q_SC2) Wherein Q is_SC1Typical values are-100 Mvar, Q_SC2A typical value is 100 Mvar. If the initial output of the phase modulator is within the given range, the value of the phase modulator is substituted for the 7 th equation in formula (1) to order

Solving the direct current I_dSo that the DC transmission power reaches the maximum value P_dmaxIf Q is_{inv_SC0}Out of the range of variation of normal operation of the phase-modifier (Q)_SC1,Q_SC2) Then step 7 is entered.

And 7: and replacing the reactive power value sent by the phase modulator by the reactive power limit value which can be sent by the phase modulator, and returning to the step 5.

Judgment of Q_{inv_SC0}Less than Q_SC1Or is greater than Q_SC2If Q is_{inv_SC0}Less than Q_SC1Then Q is asserted_{inv_SC0}＝Q_SC1Substituting the equation into the 7 th equation in the formula (1), and returning to the step (5); otherwise, order Q_{inv_SC0}＝Q_SC2Substituting the equation into the 7 th equation in the formula (1), and returning to the step (5).

And 8: and (6) ending.

The direct current static power limit value calculation method considering the influence of the new generation phase modulator considers the influence of the phase modulator on the increase of the direct current transmission power limit value, provides theoretical basis and reference for the increase of the direct current transmission power in system analysis, and has an important promotion effect on the consumption of the sending-end renewable energy.

Fig. 1 is a schematic diagram showing steps of a method for calculating a dc static power limit value considering the influence of a new generation phase modulator. Fig. 2 is a schematic diagram of different initial reactive power and direct current transmission power of the phase modulator under different initial reactive power output conditions and different direct current conditions, and it can be seen from the diagram that the maximum direct current transmission power value under different direct current conditions is related to the initial reactive power output of the phase modulator, and the maximum direct current transmission power value is affected when the initial reactive power of the phase modulator is larger or smaller.

The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (4)

1. A direct current static power limit value calculation method considering the influence of a new generation phase modulator is characterized by comprising the following steps:

(1) establishing a correlation model between the interchange and the direct current system;

(2) calculating the phase-in operation and phase-lag operation sending limit values of the phase modifier;

(3) calculating a direct current commutation angle mu and an inversion side correlation parameter K under a rated condition;

(4) establishing an alternating current system equation simultaneously, and solving the potential of the equivalent alternating current system and the direct current bus voltage power angle;

(5) taking the direct current as a variable, enabling the direct current bus voltage U to be 1p.u, and solving each related electrical quantity;

(6) judging whether the reactive power provided by the phase modulator is in the range of the reactive power allowed to be sent out; if the direct current is within the range, the direct current is taken as an independent variable, and the direct current power is solved; otherwise, entering the step (7);

(7) replacing the reactive power value sent by the phase modulator by the reactive power limit value which can be sent by the phase modulator, and returning to the step (5);

(8) finishing;

the step (1) specifically comprises the following steps:

establishing an operation characteristic equation of the direct current inversion station based on the direct current inversion side,

in the formula, C and K are two constants related to the rectifier side converter transformer parameter and the direct current system reference value respectively, U is the voltage of a direct current bus at the transmitting end, and alpha is a trigger delay angle; mu is a commutation angle, Q_cFor reactive compensation capacity, B_cThe equivalent admittance of the alternating current filter at the rectification side and the reactive compensation capacitor; a and b are constants and represent the proportion converted by the converter; u shape_iConverting the bus voltage for the receiving end; gamma is the arc extinguishing angle of the receiving-end inverter station; x_dIs the impedance of the DC transmission line, P_dIs direct current active power, Q_dIs direct current reactive power; i is_dIs direct current; i Z < theta is equivalent impedance of the alternating current system; e and delta are equivalent potential and a power angle of the alternating current system; p_acThe power is applied to an alternating current system; q_acFor ac system idle, U_dIs a direct-current voltage, and the voltage is,

phase modulator hairOutput reactive power increment delta Q_scComprises the following steps:

ΔQ_sc＝Q_{cx_SCmax}-Q_{inv_SC0} (2)

wherein Q is_{cx_SCmax}For phase-lag operation limit reactive power, Q, of phase modulators_{inv_SC0}The initial operation reactive value of the phase modulator on the direct current inversion side is obtained;

the step (2) specifically comprises the following steps:

according to the electromagnetic equation and control system of the phase modulator unit and the control requirement, the reactive power expression sent out by the phase modulator is obtained by combining the direct current bus voltage U, and the phase-lag operation limit Q of the phase modulator is further obtained_{cx_SCmax}And phase advance operating limit Q_{jx_SCmax}：

Wherein, X_dFor phase-modifier stator inductive reactance, S_NRated capacity, k, for phase-modulators_fmThe strong excitation multiple of the phase modulator, Kc the short-circuit ratio of the phase modulator, E₀Rated potential for the unit;

in the step (3), the formula for calculating the commutation angle mu of the direct current under the rated condition and the parameter K related to the inversion side is as follows:

where α is the triggered delay angle, P_dIs the DC active power, c is the converter transformer parameter at the rectifier side, U is the DC bus voltage, I_dIs direct current, mu is phase change angle;

the step (4) specifically comprises the following steps:

according to the six equations 4, 5, 6, 7, 8 and 9 in the formula (1), solving and considering the alternating current potential E and the direct current bus voltage power angle delta of the initial reactive power output of the phase modulator;

2. the method of claim 1 for calculating a dc quiescent power limit value that takes into account new generation phase modulator effects, wherein: the step (5) specifically comprises the following steps: let U equal to 1p.u, calculate each electric quantity P_d，Q_d，U_d，Q_c，P_ac，Q_acAnd Δ Q_scAccording to Δ Q_sc＝Q_{cx_SCmax}-Q_{inv_SC0}To obtain Q_{inv_SC0}，Q_{inv_SC0}The initial operation reactive value of the phase modulator on the direct current inversion side is obtained.

3. The method of claim 2 for calculating a dc quiescent power limit value considering the effects of a new generation phase modulator, wherein: the step (6) specifically comprises the following steps:

judgment of Q_{inv_SC0}Whether or not it is within the variation range of normal operation of the phase modulator (Q)_SC1，Q_SC2) Wherein Q is_SC1Typical values are-100 Mvar, Q_SC2A typical value is 100Mvar, and if the phase modulator initial output is within a given range, the phase modulator is substituted for the 7 th equation in equation (1) with the order

Solving the direct current I_dSo that the DC transmission power reaches the maximum value P_dmaxIf Q is_{inv_SC0}Out of the range of variation of normal operation of the phase-modifier (Q)_SC1，Q_SC2) Then step (7) is entered.

4. A method of calculating a dc quiescent power limit value taking into account the effects of a new generation phase modulator as claimed in claim 3, characterized by: the step (7) specifically comprises:

judgment of Q_{inv_SC0}Less than Q_SC1Or is greater than Q_SC2If Q is_{inv_SC0}Less than Q_SC1Then Q is asserted_{inv_SC0}＝Q_SC1Substituting the equation into the 7 th equation in the formula (1), and returning to the step (5); otherwise, order Q_{inv_SC0}＝Q_SC2Substituting the equation into the 7 th equation in the formula (1), and returning to the step (5).

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