HCC converter valve current measurement strategy

Abstract

The present invention relates to the technical field of HCC novel high-voltage direct-current converters, and specifically relates to an HCC converter valve current measurement strategy, comprising: providing a current transformer acquisition device on each bridge arm of a current transformer configuration topology to measure a converter bridge arm current; and connecting both a valve control device and a pole control device to the current transformer acquisition device, the valve control device measuring a direct-current bus current and a converter transformer valve side alternating current to perform active turn-off determination, and the pole control device measuring all of the bridge arm current, the direct-current bus current, and the converter transformer valve side alternating current to perform in-valve fault determination. The strategy meets the current measurement requirements of a composite HCC novel high-voltage direct-current converter, and allows for device control strategy determination and apparatus protection determination, thereby ensuring the normal operation of a converter.

Description

A Current Measurement Strategy for HCC Converter Valve Technical Field

[0001] This invention belongs to the technical field of novel HCC high-voltage DC converters, specifically relating to an HCC converter valve current measurement strategy. Background Technology

[0002] With the development of power systems, high-voltage direct current (HVDC) transmission technology has gained popularity due to its advantages in long-distance and large-capacity power transmission. Among them, the traditional grid-commutated converter based high voltage direct current (LCC-HVDC) technology has even more obvious advantages in this regard. However, due to the use of thyristors, a semi-controlled device, commutation failures can occur on the inverter side in LCCs. Continuous commutation failures can lead to DC blockage, causing fluctuations in grid voltage and power. To solve the inherent problem of commutation failure, some scholars have proposed a new turn-off converter topology. The difference between this converter and the traditional grid-commutated converter is that each arm of the converter is composed of a series of turn-off thyristors, as shown in Figure 6 of the specification, forming a series structure of turn-off devices and thyristors. The turn-off devices include, but are not limited to, gate turn-off thyristors (GTOs) and integrated gate commutated thyristors (IGCTs). To realize the function of this type of switchable converter, it is necessary to collect current for equipment operation control and protection. For example, when the converter is working in inverter mode, if commutation failure occurs, it is necessary to determine the time of commutation failure based on the current criterion in order to prevent commutation failure. If the converter current cannot be accurately measured, the system will experience commutation failure, which is very unstable and unreliable for system operation. Summary of the Invention

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

[0004] The technical solution of this invention is:

[0005] A method for measuring current in an HCC converter includes the following steps:

[0006] A current transformer acquisition device is installed on each arm of the current transformer configuration topology to measure the converter arm current.

[0007] The current transformer acquisition device is connected to both a valve control device and a polar control device. The valve control device measures the DC bus current and the AC current on the converter transformer valve side to determine active shutdown. The polar control device simultaneously measures the bridge arm current, the DC bus current, and the AC current on the converter transformer valve side to determine internal valve faults.

[0008] Specifically, the polar control device includes multiple main control units.

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

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

[0011] Specifically, the conditions for judging the valve internal fault include overcurrent in the bridge arm, AC overcurrent on the converter transformer valve side, and DC bus overcurrent.

[0012] The beneficial effects of this invention are: the method provided by this invention equips each bridge arm with a current transformer acquisition device, and the active shutdown strategy also measures the DC bus current and the AC current on the converter transformer valve side. Valve faults also simultaneously measure the bridge arm current, DC bus current, and AC current on the converter transformer valve side. Attached Figure Description

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

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

[0015] Figure 3 is a schematic diagram of valve internal fault conditions;

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

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

[0018] Figure 6 is a schematic diagram of the existing technology of a switchable converter topology.

[0019] 1. IGCT valve mixing assembly; 2. IGCT valve failure status; 3. saturated reactor assembly; 4. composite valve bridge arm; 5. HCC converter unit. Detailed Implementation

[0020] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0021] Referring to Figures 1-5, a current transformer acquisition device is installed on each arm of the current transformer configuration topology to measure the converter arm current. The current transformer acquisition device is connected to both a valve control device and a pole control device. The valve control device measures the DC bus current and the AC current on the converter transformer valve side to make active shutdown judgments. The pole control device simultaneously measures the arm current, the DC bus current, and the AC current on the converter transformer valve side to make valve fault judgments.

[0022] The active shutdown strategy requires measuring the converter arm current, so a current measuring transformer is installed on each arm. The active shutdown strategy also measures the DC bus current and the AC current on the converter transformer valve side. In case of an internal valve fault, the arm current, DC bus current, and AC current on the converter transformer valve side are also measured simultaneously.

[0023] The valve control system acquires AC current and DC bus current values ​​in real time. Based on the CP signal and bushing current, the valve control system calculates the bridge arm current, and the inflow and outflow currents of the Y and D valves. Taking valves D4 and D5 as conducting as an example, when there is no additional path or no conducting loop within the valve, the bridge arm current ID4 equals the bushing current IDA, and the bridge arm current ID5 equals IDC. The correspondence between the converter valve bridge arm current, the D / Y valve inflow and outflow currents, and the bushing current is shown in Figure 5. The correspondence between the CP signal, bushing current value, and valve inflow and outflow currents is shown in the table below (IDA is the bushing current of phase A of valve D).

[0024]

[0025] The valve controller monitors the valve current value according to a preset strategy. When the valve controller determines one of the following conditions, it considers that a fault has occurred in the converter valve and should exit the active shutdown function.

[0026]

[0027] The criteria for the active shutdown strategy mainly include two aspects: one is the judgment of normal zero-crossing shutdown of the bridge arm during normal operation; the other is that if commutation failure occurs and the bridge arm current does not cross zero, the active shutdown strategy will be executed.

[0028] To increase the reliability of data acquisition, each current measurement point adopts a dual-redundancy method, as shown in Figure 4. The data collected by the current transformer is input into current transformer acquisition device 1 and current transformer acquisition device 2 respectively, and then input into main control unit A and main control unit B through the data acquisition device, thereby realizing the valve control device's data acquisition of dual-redundant channels.

[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A current measurement strategy for HCC converter valves, characterized in that, Includes the following steps: A current transformer acquisition device is installed on each arm of the current transformer configuration topology to measure the converter arm current. The current transformer acquisition device is connected to both a valve control device and a polar control device. The valve control device measures the DC bus current and the AC current on the converter transformer valve side to determine active shutdown. The polar control device simultaneously measures the converter arm current, the DC bus current, and the AC current on the converter transformer valve side to determine internal valve faults.

2. The HCC converter valve current measurement strategy according to claim 1, characterized in that, The current transformer data acquisition device has multiple components.

3. The HCC converter valve current measurement strategy according to claim 1, characterized in that, The aforementioned polar control device includes multiple 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 outflow value of the Y valve and D valve based on 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 two aspects: first, the judgment of normal zero-crossing shutdown of the bridge arm during normal operation; second, the active shutdown is executed when 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 valve internal fault include overcurrent in the bridge arm, AC overcurrent on the converter transformer valve side, and DC bus overcurrent.

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