Current measurement strategy for HCC converter valve

Abstract

The invention belongs to the technical field of HCC novel high-voltage direct-current converters, and particularly relates to an HCC converter valve current measurement strategy, which comprises the following steps of: arranging a current transformer acquisition device on each bridge arm of a current transformer configuration topology to measure the bridge arm current of the converter; the current transformer acquisition device is connected with a valve control device and a pole control device at the same time, and the valve control device measures a direct current bus current and a converter transformer valve side alternating current so as to carry out active turn-off judgment. The pole control device measures the bridge arm current, the direct current bus current and the converter transformer valve side alternating current at the same time so as to judge faults in the valve. The strategy meets the requirement for current measurement of the novel high-voltage direct-current converter of the composite HCC, control strategy criterion and equipment protection criterion of the device are carried out, and normal work of the converter is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of HCC novel high voltage direct current converters, and in particular relates to a HCC converter valve current measurement strategy. Background Art

[0002] With the development of the power system, high-voltage direct current transmission technology has become popular for its advantages in long-distance and large-capacity transmission. Among them, the traditional grid-commutated converter direct current transmission technology (Line-Commutated Converter based high voltage direct current, LCC-HVDC) has more obvious advantages in this regard. However, due to the use of semi-controlled devices such as thyristors in LCC, commutation failures may occur on the inverter side, and continuous commutation failures will lead to DC locking, causing fluctuations in grid voltage and power. In order to solve the inherent problem of commutation failure, some scholars have proposed a new switchable converter topology. The difference between this converter and the traditional grid-commutated converter is that each bridge arm is composed of a switchable valve string, as shown in the attached manual. Figure 6 As shown, a turn-off device-thyristor series structure is formed, and the turn-off device includes but is not limited to the gate turn-off thyristor GTO, the integrated gate commutation thyristor IGCT, etc. In order to realize the function of this turn-off converter, it is necessary to collect current to control and protect the operation of the equipment. For example, when the converter works in the inverter mode, if a commutation failure occurs, it is necessary to determine the time when the commutation failure occurs according to the current criterion, so as to resist the commutation failure; if the current of the converter cannot be accurately measured, the system will fail to commutate, which is very unstable and unreliable for the system operation. Summary of the invention

[0003] The purpose of the present invention is to provide a HCC converter valve current measurement strategy to address the problems existing in the prior art. The strategy meets the requirements for current measurement of the new HCC high-voltage DC converter, performs control strategy judgment and equipment protection judgment of the device, and ensures the normal operation of the converter.

[0004] The technical solution of the present invention is:

[0005] A method for measuring current of an HCC converter device comprises the following steps:

[0006] A current transformer acquisition device is provided on each bridge arm of the current transformer configuration topology to measure the converter bridge arm current;

[0007] The current transformer acquisition device is connected to a valve control device and a pole control device at the same time. The valve control device measures the DC bus current and the AC current on the converter transformer valve side to make an active shutdown judgment. The pole control device simultaneously measures the bridge arm current, the DC bus current and the AC current on the converter transformer valve side to make a fault judgment inside the valve.

[0008] Specifically, the pole control device includes a plurality of main control units.

[0009] Specifically, the valve control device calculates the bridge arm current value, the inflow current and the outflow value of the Y valve and the D valve according to the CP signal and the bushing current value.

[0010] Specifically, the active shutdown judgment includes: first, the judgment of normal zero-crossing shutdown of the bridge arm during normal operation; second, active shutdown is executed when a commutation failure occurs and the bridge arm current does not cross zero.

[0011] Specifically, the conditions for judging the fault inside the valve include overcurrent of the bridge arm current, overcurrent of the AC converter transformer side and overcurrent of the DC bus current.

[0012] The beneficial effect of the present invention is that the method provided by the present invention is equipped with a current transformer acquisition device on each bridge arm, and the active shutdown strategy also measures the DC bus current and the AC current on the converter transformer valve side. The internal valve fault also measures the bridge arm current, DC bus current and the AC current on the converter transformer valve side at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a structural schematic diagram of the current transformer configuration topology of the present invention;

[0014] Figure 2 It is a schematic diagram of active shutdown execution conditions;

[0015] Figure 3 It is a schematic diagram of the fault condition inside the valve;

[0016] Figure 4 is a schematic diagram of current measurement points;

[0017] Figure 5 It is a schematic diagram of the correspondence between the bridge arm current of the valve control device, the inflow and outflow current of the D / Y valve and the bushing current;

[0018] Figure 6 It is a schematic diagram of the topological structure of a switchable converter in the prior art.

[0019] 1IGCT valve hybrid assembly, 2IGCT valve fault failure state, 3saturated reactor assembly, 4composite valve bridge arm 5HCC converter device. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0021] refer to Figure 1-Figure 5 As shown, a current transformer acquisition device is provided on each bridge arm of the current transformer configuration topology to measure the converter bridge arm current; the current transformer acquisition device is simultaneously connected to a valve control device and a pole control device, the valve control device measures the DC bus current and the converter transformer valve side AC current to make an active shutdown judgment, and the pole control device simultaneously measures the bridge arm current, the DC bus current and the converter transformer valve side AC current to make a valve internal fault judgment.

[0022] The implementation of the active shutdown strategy requires measuring the converter arm current, so a current measurement transformer is configured on each bridge arm. At the same time, the active shutdown strategy also measures the DC bus current and the AC current on the converter transformer valve side. The valve internal fault also measures the bridge arm current, DC bus current and the AC current on the converter transformer valve side.

[0023] The valve control system collects the AC current measurement value and the DC bus current value in real time. The valve control calculates the bridge arm current value, the inflow current and outflow value of the Y valve and the D valve according to the CP signal and the bushing current value. Taking the conduction of valves D4 and D5 as an example, when there is no additional path in the valve or the circuit is not connected, the bridge arm current ID4 is equal to the bushing current IDA, and the bridge arm current ID5 is equal to IDC. The correspondence between the converter valve bridge arm current, the D / Y valve inflow and outflow current and the bushing current is as follows Figure 5 The correspondence between CP signal, bushing current value and valve inflow and outflow current is shown in the following table (IDA is the bushing current of phase A of valve D).

[0024]

[0025] The valve control monitors the current value in the valve according to the preset strategy. When the valve control determines one of the following conditions, it is considered that a fault has occurred in the converter valve, and the active shutdown function should be exited at this time.

[0026] Valve internal fault diagnosis

[0027]

[0028] The criteria for the active shutdown strategy mainly include two aspects. On the one hand, the judgment of the normal zero-crossing shutdown of the bridge arm during normal operation; on the other hand, the active shutdown strategy is executed when a commutation failure occurs and the bridge arm current does not cross zero.

[0029] To increase the reliability of data acquisition, each current measurement point adopts dual redundancy, such as Figure 4The current transformer collected data is input into the current transformer collection device 1 and the current transformer collection device 2 respectively, and then input into the main control unit A and the main control unit B through the data collection device, so as to realize the data collection of the dual redundant channels by the valve control device.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A HCC converter valve current measurement strategy, characterized in that: The steps include: A current transformer acquisition device is provided on each bridge arm of the current transformer configuration topology to measure the converter bridge arm current; The current transformer acquisition device is connected to a valve control device and a pole control device at the same time. The valve control device measures the DC bus current and the AC current on the converter transformer valve side to make an active shutdown judgment. The pole control device simultaneously measures the converter arm current, the DC bus current and the AC current on the converter transformer valve side to make a fault judgment inside the valve.

2. The HCC converter valve current measurement strategy according to claim 1, characterized in that: There are multiple current transformer acquisition devices.

3. The HCC converter valve current measurement strategy according to claim 1, characterized in that: The pole control device comprises a plurality of main control units.

4. The HCC converter valve current measurement strategy according to claim 3, characterized in that: The valve control device calculates the bridge arm current value, the inflow current and the outflow value of the Y valve and the D valve according to the CP signal and the bushing current value.

5. The HCC converter valve current measurement strategy according to claim 1, characterized in that: The active shutdown judgment includes: first, the judgment of normal zero-crossing shutdown of the bridge arm during normal operation; second, active shutdown is executed when a commutation failure occurs and the bridge arm current does not cross zero.

6. The HCC converter valve current measurement strategy according to claim 1, characterized in that: The conditions for judging the fault inside the valve include overcurrent of the bridge arm current, overcurrent of the AC converter transformer side and overcurrent of the DC bus current.

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