All-working-condition operation control method and system for HCC converter

Abstract

The invention provides a full-working-condition operation control method and system for an HCC converter. The method comprises the following steps: providing a control signal to control operation of a full-control switching device in the HCC converter in a conduction trigger stage, a steady-state injection stage and a turn-off stage; wherein the control signal comprises a current signal and a voltage signal. The invention provides a device-level fine control implementation scheme for the HCC converter, so that efficient operation and energy-saving operation of the HCC converter can be realized.

Description

Technical Field

[0001] The present invention belongs to the field of ultra-high / ultra-high voltage direct current transmission, and in particular relates to a full-operation condition operation control method and system for an HCC converter. Background Art

[0002] With the rapid development of the power grid, the electricity consumption has been rising year by year, and the requirement to reduce carbon emissions has made clean energy increasingly dominant. In practical applications, the distribution areas of major clean energy such as hydropower and photovoltaic power are often far away from the distribution areas of major power loads. Therefore, the power grid development model with UHV as the main power grid is the guarantee for the safe and stable operation of the power grid, especially the development of UHV DC transmission is the best solution to achieve cross-regional energy optimization and accelerate the transformation of resource advantages into economic advantages.

[0003] There are two types of DC transmission technologies: line-commutated converter (LCC) and voltage source converter (VSC). LCC commutator valves use thyristor technology. Thyristor is a semi-controlled device that can only be turned on but not turned off. When a fault occurs on the inverter side of the DC transmission system, the thyristor commutator valve has the risk of commutation failure.

[0004] Commutation failure is a relatively serious fault in the DC transmission system. Theoretically, any fault in the power system may lead to commutation failure. A single commutation failure will cause a voltage drop, current increase, and reduced transmission power for several cycles. It may not have much impact on civilian electricity, but for a multi-terminal DC feed-in transmission system, once a commutation failure occurs, it will not only cause a sudden drop in transmission power, but also cause a power outage in the large power grid in severe cases. The commutation failure problem affects the planning and development of UHV DC transmission systems.

[0005] There are many research directions at home and abroad for the problem of commutation failure, which can be divided into two categories. One is to optimize the control strategy in order to enhance the system's ability to resist commutation failure from the secondary side; the other is to study the commutation equipment, including capacitor commutated converter (CCC), controlled series capacitor converter (CSCC) and new converter based on semi-controlled H-bridge submodule. However, these control strategies and switching of commutation equipment need to be based on accurate and timely predictive control systems. Through real-time monitoring of current and voltage, possible commutation failures can be predicted to adjust the control strategy or control the switching of capacitors. However, the existing prediction systems have a certain delay, and the prediction of commutation failure is not advanced, and there is a possibility of misjudgment. The commutation failure resistance measures that rely on prediction are not effective. Therefore, a more robust and reliable method for suppressing commutation failure is needed. The converter based on fully controlled devices is an effective means to suppress commutation failure in DC transmission systems.

[0006] Flexible DC transmission technology can suppress the commutation failure of the thyristor commutator valve on the inverter side. It adopts the technical route of voltage source converter, but the one-time investment is too large, the equipment occupies a large area and the cost is high, the economy is poor, and the reliability is not as good as the thyristor valve. At present, only the demonstration project in China adopts LCC on the rectifier side and VSC on the inverter side. The other is the commutator valve technical route based on integrated gate commutated thyristors (IGCT). This method has the advantages of large current, high blocking voltage, low on-state voltage drop, high switching speed, high reliability, etc., so it is a better choice than IGBT in fully controlled devices.

[0007] The construction of a DC transmission system based on IGCT fully-controlled HCC converter (Hybrid Commutated Converter) can effectively suppress inverter commutation failure, reduce equipment costs and improve reliability. It is of great significance for the construction of new power grids and the research of new power systems.

[0008] The prior art lacks refined control on / off strategies for fully controlled HCC converters. Summary of the invention

[0009] In view of the above problems, the present invention provides a method for controlling the full-operation condition operation of an HCC converter, comprising: controlling the operation of a fully controlled switching device in the HCC converter in a conduction triggering stage, a steady-state injection stage and a shutdown stage by providing a control signal;

[0010] The control signal includes a current signal and a voltage signal.

[0011] Further, the HCC converter includes one or more IGCTs connected in series, and a corresponding control unit, and the method includes:

[0012] The control signal is provided to the IGCT by the control unit.

[0013] Further, the HCC converter includes an HCC single valve, the HCC single valve includes a saturable reactor component and an IGCT component connected in series, the IGCT component includes one or more IGCT level control units connected in series, the IGCT level control unit includes a control branch and a switch branch connected in parallel, the switch branch includes an IGCT, the control branch includes the control unit for controlling the corresponding IGCT,

[0014] Methods include:

[0015] The control unit outputs a control signal to control the operation of the corresponding IGCT.

[0016] Further, the method comprises:

[0017] In the conduction triggering stage, a turn-on current signal is output to the fully controlled switching device, so that the HCC converter is turned on and current flows.

[0018] Further, the method comprises:

[0019] In the steady-state injection stage, the control signal is converted into a stable current signal and injected into the fully controlled switching device to keep the HCC converter continuously triggered and turned on.

[0020] Further, the method comprises:

[0021] During the shutdown phase, the control signal is converted to output a shutdown voltage signal to the fully controlled switching device to shut down the HCC converter valve.

[0022] Further, the method comprises:

[0023] In the steady-state injection stage, the control signal is converted into a stable current signal, that is, the steady-state injection current signal is injected into the fully controlled switching device to keep the HCC continuously triggered and turned on, and after the specified time T, the steady-state injection current signal is canceled.

[0024] Further, the method comprises:

[0025] The steady state injection current signal is removed before receiving the system shutdown command.

[0026] The present invention also provides a full-operation condition operation control system for an HCC converter, comprising a fully-controlled switch device and a corresponding control unit arranged in the HCC converter.

[0027] The control unit is used to provide a control signal to control the operation of the fully controlled switch device in the conduction triggering stage, the steady-state injection stage and the shutdown stage;

[0028] The control signal includes a current signal and a voltage signal.

[0029] Further, the HCC converter includes an HCC single valve;

[0030] The HCC single valve includes a saturated reactor component and an IGCT component connected in series;

[0031] The IGCT assembly includes one or more IGCT level control units connected in series;

[0032] The IGCT level control unit comprises a control branch and a switch branch connected in parallel;

[0033] The switch branch includes a fully-controlled switch device IGCT, and the control branch includes the control unit for controlling the corresponding IGCT.

[0034] The HCC converter full-operating condition operation control method and system of the present invention provide a device-level refined control implementation plan for the HCC converter, which can meet the operating condition requirements of the HCC converter during the operation of the ultra-high / ultra-high voltage direct current transmission system, including startup operating conditions, locking operating conditions, fault process resistance to commutation failure conditions, maximum continuous triggering voltage conditions, maximum continuous recovery voltage conditions, maximum transient operating load conditions (triggering angle 90°) operating conditions, minimum delay angle conditions, minimum shutdown angle conditions, transient undervoltage conditions, intermittent DC current conditions and fault surge high current conditions.

[0035] Furthermore, the fine control scheme provided by the present invention facilitates the expansion and adjustment of control steps and parameters, and realizes efficient operation and energy-saving operation of high-efficiency converters, which is of great significance for the wide application of HCC and achieving greater benefits.

[0036] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 A schematic structural diagram of an HCC converter valve according to an embodiment of the present invention is shown;

[0039] Figure 2 It shows a schematic structural diagram of an IGCT level control unit according to an embodiment of the present invention;

[0040] Figure 3 A schematic diagram of the HCC single valve signal control relationship according to an embodiment of the present invention is shown;

[0041] Figure 4 A schematic diagram of a full-operating signal waveform of a HCC single valve according to an embodiment of the present invention is shown;

[0042] Figure 5 A schematic diagram of signal waveforms under the HCC single valve full-operating condition high-efficiency conduction strategy according to an embodiment of the present invention is shown;

[0043] Figure 6 A schematic diagram of signal waveforms under the HCC single-valve all-condition low-power operation strategy according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] An embodiment of the present invention provides a method for controlling the full-operating-condition operation of an HCC converter. The HCC converter includes one or more HCC single valves. When multiple HCC single valves are included, they are respectively arranged on different bridge arms of the HCC converter. The HCC single valve includes one or more IGCTs connected in series and a control unit for controlling each IGCT. The method for controlling the full-operating-condition operation of the HCC converter realizes the full-operating-condition operation control of the HCC converter by controlling the control signal of the control unit.

[0046] Without loss of generality, the HCC converter includes 6 bridge arms. The 6 bridge arms include 3 upper bridge arms and 3 lower bridge arms, one end of the 3 upper bridge arms is connected to the positive electrode port, and the other end is respectively connected to the A phase AC port, the B phase AC port and the C phase AC port, and one end of the 3 lower bridge arms is connected to the negative electrode port, and the other end is respectively connected to the A phase AC port, the B phase AC port and the C phase AC port. A HCC single valve can be set on each bridge arm.

[0047] like Figure 1 As shown, the HCC single valve includes a saturated reactor component and an IGCT component connected in series. The reactor component is used to suppress the excessive di / dt in the initial stage of device opening, and protect the device from opening safely and reliably. Specifically, the HCC single valve includes a first saturated reactor component, an IGCT component, and a second saturated reactor component connected in series in sequence. Among them, the IGCT component includes one or more IGCT level control units connected in series.

[0048] For example, Figure 2 As shown, the IGCT level control unit includes a parallel control branch, a switch branch and a voltage equalizing branch. The control branch includes a control unit for adjusting the switch device of the switch branch to be turned on or off. The switch branch includes a fully controlled switch device IGCT, which is used to be turned on or off under the action of a control signal. The voltage equalizing branch is used to provide commutation voltage equalization for the switch branch. The voltage equalizing branch is used to evenly distribute the voltage across the device. Since the IGCT valve is connected in series with multiple stages, during the operation of the converter, a non-convergent voltage difference will occur, and even damage to the device. The embodiment of the present invention solves this problem through a voltage equalizing branch. And it can keep the voltage difference of each stage of the IGCT device of the series valve within the error range.

[0049] Specifically, the control branch includes a damping resistor Rs, a damping capacitor Cs and a control unit connected in series. The voltage-equalizing branch includes a voltage-equalizing resistor Rp. The main function of the control unit is to control the opening, closing and stable operation of the IGCT device, and output a control signal Sa. The control signal includes a current control signal, a voltage control signal and a current signal in steady-state operation as an electrical signal.

[0050] like Figure 3 As shown, the multiple control units and control signals in the HCC single-valve IGCT assembly are the same, thereby ensuring simultaneous control opening, simultaneous control closing and steady-state operation of the multiple IGCT stages.

[0051] like Figure 4As shown in the figure, the operation of the HCC converter mainly executes the instructions of the system, including the opening instruction, the closing instruction and the steady-state injection process. These three processes include all the operating conditions of the HCC converter: starting operation condition, locking operation condition, fault process to resist commutation failure condition, maximum continuous trigger voltage condition, maximum continuous recovery voltage condition, maximum transient operating load condition (trigger angle 90°) operating condition, minimum delay angle condition, minimum shutdown angle condition, transient undervoltage condition, intermittent DC current condition and fault surge high current condition.

[0052] like Figure 5 As shown, the method of the embodiment of the present invention includes controlling the current signal and voltage signal of the IGCT at different stages by providing a control signal. Specifically, in the conduction triggering stage, after the control unit receives the system opening command, it outputs the opening current signal to turn on the HCC converter to flow current; in the steady-state injection stage, that is, after the HCC converter is turned on, the control signal Sa is converted into a stable current signal (steady-state injection current signal) and injected into the IGCT (between the gate and the cathode) to keep the HCC continuously triggered and turned on; when the HCC converter valve needs to be turned off (the control unit receives the system shutdown command and enters the shutdown stage), the control signal Sa is converted into an output shutdown voltage signal, which is loaded into the switching device to quickly turn off the HCC converter valve. The embodiment of the present invention realizes the refined control of the HCC converter device level. On this basis, the IGCT can be turned on more efficiently by controlling the application of the control signal.

[0053] Among them, the turn-on current signal is an instantaneous current signal (Ia), the steady-state injection current signal is a continuous stable current signal (Ib), and the turn-off voltage signal (U) is a continuous stable voltage. The turn-on current signal current is greater than the steady-state injection current signal. Without loss of generality, the steady-state injection current signal continues from the output of the turn-on current signal until the system shutdown command is received. The turn-off voltage signal continues from the receipt of the system shutdown command until the system turn-on command is received.

[0054] Furthermore, if Figure 6 As shown, the HCC converter control opening adopts the control signal Sa to output current, so that the HCC converter is turned on and current flows through. After the HCC converter is turned on, the control signal Sa is converted into a stable current injection method to keep the HCC continuously triggered and turned on, and after the specified time T, the steady-state injection current signal is cancelled. When the HCC converter valve needs to be turned off, the control signal Sa is converted to output a shutdown voltage signal to quickly turn off the HCC converter valve. Specifically, the steady-state injection current signal is cancelled before receiving the system shutdown command. That is, the duration of the steady-state injection current signal occupies a part of the IGCT opening cycle (from receiving the opening command to receiving the closing command), such as less than 1 / 2. By canceling the steady-state injection current, low-power device conduction control is achieved.

[0055] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling the full-operation operation of an HCC converter, characterized in that: include: Controlling the operation of the fully controlled switching devices in the HCC converter in the conduction triggering stage, the steady-state injection stage and the shut-down stage by providing control signals; The control signal includes a current signal and a voltage signal.

2. The HCC converter full-operation control method according to claim 1, characterized in that: The HCC converter includes one or more IGCTs connected in series, and a corresponding control unit, and the method includes: The control signal is provided to the IGCT by the control unit.

3. The HCC converter full-operation control method according to claim 2, characterized in that: The HCC converter comprises an HCC single valve, wherein the HCC single valve comprises a saturable reactor component and an IGCT component connected in series, wherein the IGCT component comprises one or more IGCT-level control units connected in series, wherein the IGCT-level control unit comprises a control branch and a switch branch connected in parallel, wherein the switch branch comprises the IGCT, and wherein the control branch comprises the control unit for controlling the corresponding IGCT. Methods include: The control unit outputs a control signal to control the operation of the corresponding IGCT.

4. The HCC converter full-operation condition operation control method according to any one of claims 1 to 3, characterized in that: include: In the conduction triggering stage, a turn-on current signal is output to the fully controlled switching device, so that the HCC converter is turned on and current flows.

5. The HCC converter full-operation condition operation control method according to any one of claims 1 to 3, characterized in that: include: In the steady-state injection stage, the control signal is converted into a stable current signal and injected into the fully controlled switching device to keep the HCC converter continuously triggered and turned on.

6. The HCC converter full-operation control method according to any one of claims 1 to 3, characterized in that: include: During the shutdown phase, the control signal is converted to output a shutdown voltage signal to the fully controlled switching device to shut down the HCC converter valve.

7. The HCC converter full-operation control method according to claim 5, characterized in that: include: In the steady-state injection stage, the control signal is converted into a stable current signal, that is, the steady-state injection current signal is injected into the fully controlled switching device to keep the HCC continuously triggered and turned on, and after the specified time T, the steady-state injection current signal is canceled.

8. The HCC converter full-operation control method according to claim 7, characterized in that: include: The steady state injection current signal is removed before receiving the system shutdown command.

9. A full-operation control system for HCC converters, characterized in that: It includes a fully controlled switch device and a corresponding control unit arranged in the HCC converter, The control unit is used to provide a control signal to control the operation of the fully controlled switch device in the conduction triggering stage, the steady-state injection stage and the shutdown stage; The control signal includes a current signal and a voltage signal.

10. The HCC converter full-operation condition operation control system according to claim 9, characterized in that: The HCC converter includes an HCC single valve; The HCC single valve includes a saturated reactor component and an IGCT component connected in series; The IGCT assembly includes one or more IGCT level control units connected in series; The IGCT level control unit comprises a control branch and a switch branch connected in parallel; The switch branch includes a fully-controlled switch device IGCT, and the control branch includes the control unit for controlling the corresponding IGCT.

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