WO2015196747A1

WO2015196747A1 - Test system for simulating direct-current bias of converter transformer

Info

Publication number: WO2015196747A1
Application number: PCT/CN2014/093376
Authority: WO
Inventors: 张红跃; 熊章学; 牛志雷; 马玉龙; 黄金海; 宋红涛; 赵艳茹; 徐玉洁; 胡晓静; 刘家军; 杜延辉; 路振宇; 曹雪兰; 王二军; 安友彬
Original assignee: 国家电网公司; 许继集团有限公司; 许继电气股份有限公司; 国网北京经济技术研究院
Priority date: 2014-06-26
Filing date: 2014-12-09
Publication date: 2015-12-30
Also published as: CN104360179A

Abstract

A test system for simulating the direct-current bias of a converter transformer. The test system comprises an RTDS simulation system of a direct-current power transmission system for simulating the direct-current bias operating condition of the converter transformer, wherein the RTDS simulation system is connected to an RTDS real-time digital simulator and a converter transformer protection device; and a bias resistor is connected in series between a neutral point of a star converter transformer of a unipolar and/or bipolar low-end valve group and a direct-current grounding electrode. By connecting the bias resistor in series between the neutral point of the star converter transformer of the unipolar and/or bipolar low-end valve group and the direct-current grounding electrode, the test system introduces a direct current of the grounding electrode to the neutral point of the Vn/V converter transformer to simulate a phenomenon of the direct-current bias of the converter transformer caused by the fact that the direct current invades the converter transformer in an actual direct-current power transmission system. When the system is used to simulate the direct-current bias of the converter transformer, the realization method is simple and reliable, and the realization threshold is relatively low.

Description

Test system for simulating DC bias of converter transformer

Technical field

The present invention relates to a test system and method for simulating DC biasing of a converter transformer.

Background technique

In recent years, UHV DC transmission systems have developed rapidly in China. With the completion and commissioning of HVDC transmission systems, many problems have arisen. The DC transmission line usually starts to be operated in a single pole at the initial stage of operation, and then the bipolar operation is completed. In the event of a failure, in order to prevent the line from being stopped, the unipolar operation is continued. Electrical energy. When the DC transmission system operates in a single-maximum manner, a large ground current causes a certain DC current to flow through the neutral point of the converter transformer or the converter transformer winding, causing DC bias, causing the transformer core to saturate. It works in the nonlinear region of the core saturation curve, causing the transformer excitation current to be distorted in a half-wave period.

As shown in Figure 1, in the figure, i is the magnitude of the excitation current.

For the magnetic flux in the magnetic circuit, the solid line in the figure is the phase voltage when the neutral point is not applied with DC voltage, and the dotted line is the phase voltage after superimposing a forward DC voltage, which is linear due to the phase voltage and the magnetic flux in each phase magnetic circuit. Relationship, so the ordinate in Figure 1 is directly written as magnetic flux per phase

Analysis of the excitation current waveform under DC bias can find that in the negative half cycle, the DC component is opposite to the AC voltage. At this time, the magnetic flux decreases, the saturation is small or not saturated, and the negative half cycle waveform can be regarded as a sine wave. In the positive half cycle, the DC voltage is the same as the AC direction, and the superposition of each other causes the magnetic flux to increase and the saturation degree to be deep, so that the positive half cycle exhibits a cusp wave.

When the DC transformer is DC biased, if the suppression measures are not taken, it may affect the normal operation of the converter transformer and the stable transmission of the DC power of the DC transmission system. In severe cases, the DC will be jeopardized. The stable operation of the system and the safety of the grid. In recent years, a large number of HVDC transmission projects have been completed and put into operation in China, and the influence of DC bias on the converter transformer will be more obvious. Therefore, the analysis and research on the DC bias of the converter transformer is more urgent.

At present, the main method to study the DC bias of the converter transformer is to inject a certain DC current at the neutral point of the converter transformer to simulate the DC component flowing through the converter transformer. This method is mostly used to study a single transformer or multiple model parameters. The same transformer is operated in parallel.

In the converter protection device of the HVDC transmission system, DC saturation protection is arranged at the neutral point of the star, which is specifically used to reflect the DC bias phenomenon of the converter transformer, but in the actual system, the star and the star angle become neutral. The sensed DC current is not the same, so the method of injecting a certain DC current at the neutral point of the converter transformer to simulate the DC component flowing through the converter transformer is not very flexible. There is no way to simulate the star change and the star angle change. Inconsistent point DC current.

Summary of the invention

It is an object of the present invention to provide a test system for simulating DC biasing of a converter transformer to solve the problem that the existing test system cannot actually simulate DC current.

In order to achieve the above object, the technical solution adopted by the present invention is: a test system for simulating DC bias of a converter transformer, comprising a DCDS simulation system for simulating a DC bias operating condition of a converter transformer, The RTDS simulation system is connected with an RTDS real-time digital simulator and a converter transformer protection device; the RTDS simulation system is a single-stage or bipolar DC transmission system composed of two 12-pulse converters in series, corresponding to two The 12-pulse converters constitute the high-end valve group and the low-end valve group of each stage, respectively. The single-stage and/or bipolar low-end valve group has a biasing in series between the neutral point of the star-changing transformer and the DC grounding pole. resistance.

The RTDS simulation system is protected by an interface board and a power amplifier and a converter transformer The connection is used to provide the required voltage and current signals and the status signal of the tap position. The converter transformer protection device feeds the protection trip and alarm signal feedback to the RTDS simulation system.

The value of the biasing resistance is determined by the measured data fitting: when the direct current transmission system is operated at a single maximum, the actual direct current flowing through the converter transformer is matched under different transmission powers, and the resistance value is fitted to It can reflect the actual distribution of DC current in the actual DC transmission system.

The test system for simulating the DC bias of the converter transformer establishes a DCDS simulation system of the DC transmission system which can reflect the DC bias operation condition of the converter transformer, and the simulation system adopts two stages of 12 pulsating converters in each stage. The single-stage or bipolar DC transmission system, the corresponding two 12-pulse converters constitute the high-end valve group and the low-end valve group of each stage, respectively, through the stars in the single-stage and / or bipolar low-end valve group The series biasing resistance between the neutral point of the current transformer and the DC grounding pole is introduced into the neutral point of the Yn/Y converter transformer to simulate the commutation of the DC converter due to the inrush of the DC current into the converter transformer. DC bias phenomenon. The device is simple and reliable in realizing the DC biasing of the converter transformer, and has a low threshold and has a high promotion value.

DRAWINGS

1 is a schematic diagram of DC biasing of a converter transformer of the present invention;

2 is a schematic diagram of a test system of the RTDS test of the present invention;

3 is a schematic diagram of analog DC biasing of the test system of the present invention.

detailed description

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

FIG. 2 is a schematic diagram of an embodiment of a test system for simulating a DC bias of a converter transformer according to the present invention. The system includes a DC transmission system RTDS for simulating a DC bias operating condition of a converter transformer. Simulation system, RTDS simulation system and RTDS real-time digital simulator and commutation The voltage regulator protection device is connected; the RTDS simulation system is a single-stage or bipolar DC transmission system composed of two 12-pulse converters in series at each stage, and the corresponding two 12-pulse converters respectively constitute a high-end valve of each stage. The group and the low-end valve block, the single-stage and / or bipolar low-end valve block, the star commutating transformer neutral point and the DC grounding pole have a biasing resistor in series, as shown in Figure 3.

The RTDS simulation system is connected to the converter transformer protection device through the corresponding interface board and power amplifier to provide the required voltage and current signals and the status signal of the tap position. The converter transformer protection device will protect the trip and The alarm signal is fed back to the RTDS simulation system; the interface board here uses the commercially available GT series interface board to meet the traditional needs of this test.

As shown in Figure 3, in the RTDS simulation system, the converter transformer of the low-end valve group consists of three single-phase transformers, which are composed of three single-phase transformers. The DC current of the grounding pole is introduced into the neutral point of the Yn/Y converter transformer to simulate the actual. In the HVDC transmission system, the DC-transverse magnetic phenomenon caused by the inrush of the DC current into the converter transformer is realized by connecting a resistor R between the Yn/Y commutating neutral point and the DC grounding pole. The value of the resistor R is determined by the field measured data fitting, that is, when the DC power transmission system is operated in a single maximum, the actual DC current flowing through the converter transformer under different transmission powers is fitted, and the resistance value is fitted to It can reflect the actual distribution of DC current in the actual DC transmission system.

The test procedure of the test system for simulating the DC bias of the converter transformer is as follows: (1) Establishing a dual 12-pulse converter valve group RTDS simulation system for the UHV DC transmission system, the converter transformer and its connected external intersection The DC system is simulated in the RTDS real-time digital simulator. The RTDS real-time digital simulator here is a conventional technology in the field, and will not be described here. The converter transformer consists of a single-phase transformer composed of a single-phase transformer, and the RTDS simulation system passes the GT series. The interface board and the power amplifier are connected to the commutation protection device, and provide the state quantity of the voltage, current signal and the tap position of the converter transformer protection in the RTDS real-time digital emulator, and the converter transformer protection device will Guarantee The protection trip and alarm signals are returned to the RTDS simulation system to form a real-time closed-loop test system that meets the RTDS closed-loop test requirements for converter transformer protection; (2) a resistor in series between the Yn/Y commutating neutral point and the DC ground. R, the grounding direct current is introduced into the neutral point of the Yn/Y converter transformer, which is used to simulate the commutation DC bias phenomenon caused by the inrush of the DC current into the converter transformer in the actual DC transmission system, and the value of the resistor R can be Determine according to Table 1.

Table 1 Transformer test data of a converter station in a special high-voltage DC project

It can be seen from the above table that according to the field data, 1000A DC current is provided at the low end of the pole 1 and the pole 1 high-end valve group is in the locked state, but the AC circuit breaker of the pole 1 high-end valve group is provided in the closed state to provide substantially the same DC as the field. The current, the required bias resistance of the magnetoresistance is 12Ω.

The above embodiments are only used to help understand the core idea of the present invention, and the present invention may not be limited thereto. For those skilled in the art, the present invention may be modified or equivalently replaced according to the idea of the present invention. Any modifications made herein are intended to be included within the scope of the invention.

Claims

A test system for simulating a DC bias of a converter transformer, comprising: a DCDS simulation system for simulating a DC bias operating condition of a converter transformer, the RTDS simulation system and RTDS real-time digital simulation The converter is connected to the converter transformer protection device; the RTDS simulation system is a single-stage or bipolar DC transmission system composed of two 12-pulse converters in series, and two corresponding 12-pulse converters respectively constitute each stage. The high-end valve block and the low-end valve block, the single-stage and / or bipolar low-end valve block, the star commutating transformer neutral point and the DC grounding pole have a biasing resistor in series.
A test system for simulating a DC bias of a converter transformer according to claim 1, wherein said RTDS simulation system is connected to a converter transformer protection device through an interface board and a power amplifier for providing the required The voltage and current signals and the status signal of the tap position, the converter transformer protection device will input the protection trip and alarm signal feedback to the RTDS simulation system.
The test system for simulating the DC bias of a converter transformer according to claim 1, wherein the value of the bias magnet is determined by fitting the measured data: when the DC transmission system is operated in a single operation, different In the case of the delivery power, the actual DC current flowing through the converter transformer is fitted to the resistance value to reflect the actual distribution of the DC current in the actual DC transmission system.