A substation simulation power transmission device and control method thereof

Abstract

The present invention relates to a substation simulation power transmission device and a control method thereof. The power transmission device comprises a front stage and a rear stage. The front stage is a three-phase rectifier, which is connected to a three-phase power supply and used to convert three-phase alternating current into direct current. The rear stage is a three-phase inverter, which is connected to the three-phase rectifier and used to convert the direct current output by the front stage into the required three-phase alternating current and output it. The control method performs power feedforward deadbeat control based on the short-circuit impedance of the transformer on the power transmission device, and utilizes the low voltage of the power transmission device to simulate the substation power transmission, which can not only reduce the impact on the primary equipment of the substation, but also detect the faults of the primary equipment and secondary equipment of the substation, thereby reducing the defect rate in the formal power transmission process, improving the power transmission pass rate of the newly built substation, and facilitating the safe and reliable operation of the power system.

Description

Technical Field

[0001] The invention belongs to the technical field of power electronics, and in particular relates to a substation simulation power transmission device and a control method thereof. Background Art

[0002] At present, transformers in newly built substations mostly use high-voltage side rated voltage direct impact to transmit power, which not only cannot perform loop inspection on the primary system, but also is not conducive to the verification of CT, PT and signal loops in the secondary system. When there is a short circuit or grounding in the primary equipment, the use of direct rated voltage impact to transmit power will generate a huge short-circuit current, which will seriously affect the service life of the primary equipment. When the secondary system has a CT secondary open circuit, a PT secondary short circuit and a virtual connection in the signal loop, the use of direct rated voltage impact to transmit power may cause the relay protection to malfunction, which will seriously affect the correct action rate of the relay protection and is not conducive to the safe and reliable operation of the power system. Summary of the invention

[0003] The object of the present invention is to provide a substation simulation power transmission device and a control method thereof, wherein the power transmission device and the control method thereof are conducive to improving the reliability of power transmission and the safety of power grid operation.

[0004] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a substation simulation power transmission device, including a front stage and a rear stage, the front stage is a three-phase rectifier, the three-phase rectifier is connected to a three-phase power supply, and is used to convert three-phase alternating current into direct current, and the rear stage is a three-phase inverter, the three-phase inverter is connected to the three-phase rectifier, and is used to convert the direct current output by the front stage into the required three-phase alternating current and output it.

[0005] Furthermore, the three-phase rectifier is mainly composed of six power switch tubes T a1 , T b1 , T c1 , T a2 , T b2 , T c2 And two DC side voltage stabilizing capacitors C1 and C2, the a phase of the three-phase power supply is connected to T a1 The emitter, T a2 The collector of phase b is connected to T b1 The emitter, T b2 The collector of phase c is connected to T c1 The emitter, T c2 The collector, T a1 , T b1 , T c1 The collector of the three-phase rectifier is connected as the positive electrode, T a2 , T b2 , T c2The emitter of is connected as the negative electrode of the three-phase rectifier, and the capacitors C1 and C2 are connected in parallel between the positive and negative electrodes of the three-phase rectifier, and C1 = C2.

[0006] Furthermore, the power switch tube T a1 , T b1 , T c1 , T a2 , T b2 , T c2 For IGBT modules.

[0007] Furthermore, the three-phase inverter is mainly composed of six power switch tubes T1, T2, T3, T4, T5, and T6. The positive pole of the three-phase rectifier is respectively connected to the collectors of T1, T3, and T5, and the negative pole is respectively connected to the emitters of T2, T4, and T6. The emitter of T1 is connected to the collector of T2 as the A-phase output of the three-phase inverter, the emitter of T3 is connected to the collector of T4 as the B-phase output of the three-phase inverter, and the emitter of T5 is connected to the collector of T6 as the C-phase output of the three-phase inverter.

[0008] Furthermore, the power switch tubes T1, T2, T3, T4, T5, and T6 are IGBT modules.

[0009] The present invention also provides a control method for a simulated power transmission device of a substation, which performs power feedforward deadbeat control on the power transmission device based on the short-circuit impedance of the transformer, specifically:

[0010] Applying Kirchhoff's voltage law to model the power transmission device, we have:

[0011]

[0012] Where V Sa 、V Sb 、V Sc is the three-phase power supply voltage, i Sa 、i Sb 、i Sc is the input current of the power transmission device, V Ha 、V Hb 、V Hc is the output voltage of the power transmission device, i Ha 、i Hb 、i Hc is the output current of the power transmission device, L1 and L2 are the filter reactances of the power transmission device;

[0013] Get high center short-circuit impedance Z 1-2 %、High to low short circuit impedance Z 1-3 %, thus the short-circuit power of the high pair is:

[0014]

[0015] In the formula, i hk is the output current of the power transmission device, k = a, b, c;

[0016] The short-circuit power of high to low is:

[0017]

[0018] Assuming the input power of the front stage of the power transmission device is P, according to the principle of energy conservation:

[0019] (3U m I m cosθ) / 2=P (4)

[0020] Where U m is the peak value of the input voltage of the front stage of the power transmission device, I m is the peak current of the front stage of the power transmission device, θ is the power factor angle; ignoring the leakage reactance of the transformer, that is, cosθ=1, the command signal of the peak current of the front stage of the power transmission device is obtained:

[0021] I m =2P / (3U m ) (5)

[0022] When the transformer is unloaded, there are:

[0023]

[0024] When the rated current flows into the high voltage side of the transformer, the three phases on the medium voltage side are short-circuited, and the low voltage side is open, there are:

[0025]

[0026] When the rated current flows into the high voltage side of the transformer, the medium voltage side is open circuit, and the three phases on the low voltage side are short circuited, there are:

[0027]

[0028] In order to ensure the stability of the DC side voltage of the power transmission device, a PI regulator is used to adjust the DC side voltage outer loop:

[0029] I out =K P ΔU dc +K I ∫ΔU dc dt (9)

[0030] In the formula, I out is the output command signal of the PI regulator, K P and K I are the proportional and integral coefficients of the PI regulator, ΔU dcis the difference between the DC side reference voltage and the real-time voltage;

[0031] The input current component of the front stage of the power transmission device is obtained as follows:

[0032] I P =I m +I out (10)

[0033] According to the law of conservation of energy, the input power P of the power transmission device is equal to the output power P', thus the output voltage of the power transmission device is obtained:

[0034]

[0035] Where: V hk is the output voltage of the power transmission device, k = a, b, c;

[0036] When the transformer is unloaded, the output power of the power transmission device is 0. Therefore, for the post-stage control of the power transmission device, it is only necessary to stabilize its outer loop voltage without considering energy compensation.

[0037] When the rated current flows into the high voltage side of the transformer, the three phases on the medium voltage side are short-circuited, and the low voltage side is open, there are:

[0038]

[0039] When the rated current flows into the high voltage side of the transformer, the medium voltage side is open circuit, and the three phases on the low voltage side are short circuited, there are:

[0040]

[0041] Compared with the prior art, the present invention has the following beneficial effects: a device for simulating power transmission in a newly built substation and a control method thereof are provided. The device simulates power transmission in a substation through dynamic continuous low voltage, which can not only reduce the impact on the primary equipment of the substation, but also detect the faults of the primary equipment and secondary equipment of the substation, thereby reducing the defect rate in the formal power transmission process, improving the power transmission pass rate of the newly built substation, and facilitating the safe and reliable operation of the power system. The control method is a power feedforward error beat control method based on transformer characteristics, which realizes the rapid tracking and stable output of the current and voltage of the power transmission device by utilizing the short-circuit characteristics of the transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a topological diagram of a simulated power transmission device of a substation according to an embodiment of the present invention.

[0043] Figure 2 It is an equivalent model diagram of a simulated power transmission device of a substation according to an embodiment of the present invention. DETAILED DESCRIPTION

[0044] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0045] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0046] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0047] The present embodiment provides a substation simulation power transmission device, which includes a front stage and a rear stage, wherein the front stage is a three-phase rectifier, which is connected to a three-phase power supply and is used to convert three-phase alternating current into direct current, and the rear stage is a three-phase inverter, which is connected to the three-phase rectifier and is used to convert the direct current output by the front stage into the required three-phase alternating current and output it.

[0048] Figure 1 : is a topological diagram of the simulated power transmission device of the substation in this embodiment. Sa 、V Sb 、V Sc is the three-phase power supply voltage; L1 and L2 are the filter reactances of the power transmission device; i Sa 、i Sb 、i Sc is the input current of the power transmission device; T a1 , T b1 , T c1 , T a2 , T b2 , T c2 , T1, T2, T3, T4, T5, T6 are power switch tubes; C1, C2 are DC side voltage stabilizing capacitors; u dc is the DC side voltage; i Ha 、i Hb 、i Hc is the output current of the power transmission device; V Ha 、V Hb 、V Hc is the voltage on the high voltage side of the transformer, V Ma 、V Mb 、V Mc is the voltage on the medium voltage side of the transformer, V La 、V Lb 、VLc is the voltage on the low voltage side of the transformer.

[0049] like Figure 1 As shown, the three-phase rectifier mainly consists of six power switch tubes T a1 , T b1 , T c1 , T a2 , T b2 , T c2 And two DC side voltage stabilizing capacitors C1 and C2, the a phase of the three-phase power supply is connected to T a1 The emitter, T a2 The collector of phase b is connected to T b1 The emitter, T b2 The collector of phase c is connected to T c1 The emitter, T c2 The collector, T a1 , T b1 , T c1 The collector of the three-phase rectifier is connected as the positive electrode, T a2 , T b2 , T c2 The emitter of the three-phase rectifier is connected as the negative electrode of the three-phase rectifier, and the capacitors C1 and C2 are connected in parallel between the positive and negative electrodes of the three-phase rectifier, and C1 = C2. The three-phase inverter is mainly composed of six power switch tubes T1, T2, T3, T4, T5, and T6. The positive electrode of the three-phase rectifier is connected to the collector of T1, T3, and T5 respectively, and the negative electrode is connected to the emitter of T2, T4, and T6 respectively. The emitter of T1 is connected to the collector of T2 as the A phase output of the three-phase inverter, the emitter of T3 is connected to the collector of T4 as the B phase output of the three-phase inverter, and the emitter of T5 is connected to the collector of T6 as the C phase output of the three-phase inverter.

[0050] In this embodiment, the power switch tube T a1 , T b1 , T c1 , T a2 , T b2 , T c2 , T1, T2, T3, T4, T5, and T6 use IGBT modules.

[0051] This embodiment also provides a control method for the above-mentioned substation simulated power transmission device, which performs power feedforward deadbeat control on the power transmission device based on the transformer short-circuit impedance, specifically:

[0052] Applying Kirchhoff's voltage law to model the power transmission device, we have:

[0053]

[0054] According to formula (1), the equivalent model of the substation simulation power transmission device is obtained, as follows: Figure 2 shown.

[0055] As can be seen from the transformer nameplate, the high-center short-circuit impedance Z 1-2 %、High to low short circuit impedance Z 1-3 %, thus the short-circuit power of the high pair is:

[0056]

[0057] In the formula, i hk is the output current of the power transmission device, k=a, b, c.

[0058] The short-circuit power of high to low is:

[0059]

[0060] Assume that the input power of the front stage of the power transmission device is P. Ideally, the switching loss of the system is considered to be 0. According to the principle of energy conservation, we have:

[0061] (3U m I m cosθ) / 2=P (4)

[0062] Where U m is the peak value of the input voltage of the front stage of the power transmission device, I m is the peak current of the front stage of the power transmission device, θ is the power factor angle; ignoring the leakage reactance of the transformer, that is, cosθ=1, the command signal of the peak current of the front stage of the power transmission device is obtained:

[0063] I m =2P / (3U m ) (5)

[0064] When the transformer is unloaded, there are:

[0065]

[0066] When the rated current flows into the high voltage side of the transformer, the three phases on the medium voltage side are short-circuited, and the low voltage side is open, there are:

[0067]

[0068] When the rated current flows into the high voltage side of the transformer, the medium voltage side is open circuit, and the three phases on the low voltage side are short circuited, there are:

[0069]

[0070] In order to ensure the stability of the DC side voltage of the power transmission device, a PI regulator is used to adjust the DC side voltage outer loop:

[0071] Iout =K P ΔU dc +K I ∫ΔU dc dt (9)

[0072] In the formula, I out is the output command signal of the PI regulator, K P and K I are the proportional and integral coefficients of the PI regulator, ΔU dc It is the difference between the DC side reference voltage and the real-time voltage.

[0073] The input current component of the front stage of the power transmission device is obtained as follows:

[0074] I P =I m +I out (10)

[0075] According to the law of conservation of energy, the input power P of the power transmission device is equal to the output power P', thus the output voltage of the power transmission device is obtained:

[0076]

[0077] Where: V hk is the output voltage of the power transmission device, k=a, b, c.

[0078] When the transformer is unloaded, the output power of the power transmission device is 0. Therefore, for the subsequent control of the power transmission device, it is only necessary to stabilize its outer loop voltage without considering energy compensation.

[0079] When the rated current flows into the high voltage side of the transformer, the three phases on the medium voltage side are short-circuited, and the low voltage side is open, there are:

[0080]

[0081] When the rated current flows into the high voltage side of the transformer, the medium voltage side is open circuit, and the three phases on the low voltage side are short circuited, there are:

[0082]

[0083] The present invention provides a substation simulation power transmission device based on a power feedforward error beat control method of transformer short-circuit impedance, which can quickly and stably realize the control of the power transmission device, and realize the rapid tracking and output of voltage and current. By utilizing the low-voltage simulation power transmission function of the power transmission device, not only can the impact on the primary equipment of the substation be reduced, but also the failure of the primary equipment and secondary equipment of the substation can be detected, thereby reducing the defect rate in the formal power transmission process, improving the power transmission pass rate of the newly built substation, and facilitating the safe and reliable operation of the power system.

[0084] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A control method for a simulated power transmission device of a substation, characterized in that: The substation simulation power transmission device includes a front stage and a rear stage, wherein the front stage is a three-phase rectifier, which is connected to a three-phase power supply and used to convert three-phase alternating current into direct current, and the rear stage is a three-phase inverter, which is connected to the three-phase rectifier and used to convert the direct current output by the front stage into the required three-phase alternating current and output it; The power transmission device is subjected to power feedforward deadbeat control based on the transformer short-circuit impedance, specifically: Applying Kirchhoff's voltage law to model the power transmission device, we have: Where V Sa 、V Sb 、V Sc is the three-phase power supply voltage, i Sa 、i Sb 、i Sc is the input current of the power transmission device, V Ha 、V Hb 、V Hc is the output voltage of the power transmission device, i Ha 、i Hb 、i Hc is the output current of the power transmission device, L1 and L2 are the filter reactances of the power transmission device; Get high center short-circuit impedance Z 1-2 %、High to low short circuit impedance Z 1-3 %, thus the short-circuit power of the high pair is: In the formula, i hk is the output current of the power transmission device, k = a, b, c; The short-circuit power of high to low is: Assuming the input power of the front stage of the power transmission device is P, according to the principle of energy conservation: (3U m I m cosθ) / 2=P (4) Where U m is the peak value of the input voltage of the front stage of the power transmission device, I m is the peak current of the front stage of the power transmission device, θ is the power factor angle; ignoring the leakage reactance of the transformer, that is, cosθ=1, the command signal of the peak current of the front stage of the power transmission device is obtained: I m =2P / (3U m ) (5) When the transformer is unloaded, there are: When the rated current flows into the high voltage side of the transformer, the three phases on the medium voltage side are short-circuited, and the low voltage side is open, there are: When the rated current flows into the high voltage side of the transformer, the medium voltage side is open circuit, and the three phases on the low voltage side are short circuited, there are: In order to ensure the stability of the DC side voltage of the power transmission device, a PI regulator is used to adjust the DC side voltage outer loop: In the formula, I out is the output command signal of the PI regulator, K P and K I are the proportional and integral coefficients of the PI regulator, ΔU dc is the difference between the DC side reference voltage and the real-time voltage; The input current component of the front stage of the power transmission device is obtained as follows: I P =I m +I out (10) According to the law of conservation of energy, the input power P of the power transmission device is equal to the output power P', thus the output voltage of the power transmission device is obtained: Where: V hk is the output voltage of the power transmission device, k = a, b, c; When the transformer is unloaded, the output power of the power transmission device is 0. Therefore, for the post-stage control of the power transmission device, it is only necessary to stabilize its outer loop voltage without considering energy compensation. When the rated current flows into the high voltage side of the transformer, the three phases on the medium voltage side are short-circuited, and the low voltage side is open, there are: When the rated current flows into the high voltage side of the transformer, the medium voltage side is open circuit, and the three phases on the low voltage side are short circuited, there are:

2. A control method for a substation simulated power transmission device according to claim 1, characterized in that: The three-phase rectifier consists of six power switch tubes T a1 , T b1 , T c1 , T a2 , T b2 , T c2 And two DC side voltage stabilizing capacitors C1 and C2, the a phase of the three-phase power supply is connected to T a1 The emitter, T a2 The collector of phase b is connected to T b1 The emitter, T b2 The collector of phase c is connected to T c1 The emitter, T c2 The collector, T a1 , T b1 , T c1 The collector of the three-phase rectifier is connected as the positive electrode, T a2 , T b2 , T c2 The emitter of is connected as the negative electrode of the three-phase rectifier, and the capacitors C1 and C2 are connected in parallel between the positive and negative electrodes of the three-phase rectifier, and C1 = C2.

3. A control method for a substation simulated power transmission device according to claim 2, characterized in that: The power switch tube T a1 , T b1 , T c1 , T a2 , T b2 , T c2 For IGBT modules.

4. The control method of a substation simulated power transmission device according to claim 1, characterized in that: The three-phase inverter is composed of six power switch tubes T1, T2, T3, T4, T5, and T6. The positive pole of the three-phase rectifier is connected to the collectors of T1, T3, and T5 respectively, and the negative pole is connected to the emitters of T2, T4, and T6 respectively. The emitter of T1 is connected to the collector of T2 as the A-phase output of the three-phase inverter, the emitter of T3 is connected to the collector of T4 as the B-phase output of the three-phase inverter, and the emitter of T5 is connected to the collector of T6 as the C-phase output of the three-phase inverter.

5. A control method for a substation simulated power transmission device according to claim 4, characterized in that: The power switch tubes T1, T2, T3, T4, T5 and T6 are IGBT modules.

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