阅读说明：本技术 特高压混合直流输电vsc交流断面失电识别方法及装置 (Extra-high voltage hybrid direct current transmission VSC alternating current section power loss identification method and device ) 是由 彭忠 李泰� 刘旭辉 范子强 吴庆范 曹森 赵静 荆雪记 苏进国 胡永昌 李艳梅 于 2019-11-19 设计创作，主要内容包括：本发明提供了一种特高压混合直流输电VSC交流断面失电识别方法及装置,属于电力电子技术与直流输电技术领域,通过检测并计算VSC解锁状态下,联接变压器原边侧交流电压、电流有效值、逆变站极母线的直流电流,以及VSC有功功率实际值与参考值的偏差与对应的判据定值的关系,判断VSC是否发生交流断面失电故障。有效解决了现有VSC交流断面识别方式准确度低、可靠性差的问题。(The invention provides a method and a device for identifying the power failure of an alternating current section of a VSC (voltage source converter) in extra-high voltage hybrid direct current transmission, belonging to the technical field of power electronics and direct current transmission. The problem that the current VSC exchanges section identification mode degree of accuracy low, the reliability is poor has effectively been solved.)

1. An extra-high voltage hybrid direct current transmission VSC alternating current section power loss identification method is characterized by comprising the following steps:

1) measuring and calculating a fault component: the fault components comprise alternating voltage and current effective values at the primary side of the connecting transformer, direct current of a transformer station pole bus and deviation of an actual value and a reference value of VSC active power;

2) setting a fault criterion constant value: setting an alternating current voltage criterion fixed value, an alternating current criterion fixed value, an inversion station pole bus current criterion fixed value and an active power criterion fixed value;

3) and under the unlocking state of the VSC, judging whether the VSC has an alternating current section power-off fault according to the relation between each fault component and the corresponding criterion constant value.

2. The method for identifying the AC fault section of the extra-high voltage hybrid DC transmission VSC according to claim 1, characterized in that when the relation between each fault component and the corresponding criterion constant value meets the following fault criterion in the unlocked state of the VSC, the AC fault section of the VSC is determined to occur:

in the formula of U_asSFor coupling the effective value, Δ, of the AC voltage at the primary side of the transformer₁Determining a constant value for the alternating voltage; i is_acSFor coupling the effective value, Δ, of the AC current on the primary side of the transformer₂Determining a constant value for the alternating current; i is_dLThe direct current of the bus of the inversion station is used, and b is a current criterion constant value of the bus of the inversion station; p_acrefIs the active power reference value, P, of the VSC_acIs the actual value of the active power, Delta, of the VSC₃And for the fixed value of the active power criterion, dblk is 1 to indicate that the VSC is in an unlocked state.

3. The method for identifying the AC fracture surface loss of the VSC in the extra-high voltage hybrid DC transmission according to claim 2, wherein I is_dLThe value of b is 0.08, which is the per unit value of the direct current of the pole bus of the inversion station.

4. An extra-high voltage hybrid direct current transmission VSC alternating current section power failure recognition device is characterized by comprising a processor and a memory, wherein the memory stores a computer program, and the processor executes the computer program to realize the following steps:

1) measuring and calculating a fault component: the fault components comprise alternating voltage and current effective values at the primary side of the connecting transformer, direct current of a transformer station pole bus and deviation of an actual value and a reference value of VSC active power;

2) setting a fault criterion constant value: setting an alternating current voltage criterion fixed value, an alternating current criterion fixed value, an inversion station pole bus current criterion fixed value and an active power criterion fixed value;

3) and under the unlocking state of the VSC, judging whether the VSC has an alternating current section power-off fault according to the relation between each fault component and the corresponding criterion constant value.

5. The device for identifying the AC fault plane loss of the VSC in the UHV hybrid DC transmission according to claim 4, wherein in the VSC unlocking state, when the relation between each fault component and the corresponding criterion constant value meets the following fault criterion, the VSC is judged to have the AC fault plane fault:

in the formula of U_asSFor coupling the effective value, Δ, of the AC voltage at the primary side of the transformer₁Determining a constant value for the alternating voltage; i is_acSFor coupling the effective value, Δ, of the AC current on the primary side of the transformer₂Determining a constant value for the alternating current; i is_dLThe direct current of the bus of the inversion station is used, and b is a current criterion constant value of the bus of the inversion station; p_acrefIs the active power reference value, P, of the VSC_acIs the actual value of the active power, Delta, of the VSC₃And for the fixed value of the active power criterion, dblk is 1 to indicate that the VSC is in an unlocked state.

6. The device for identifying the AC section power loss of the VSC in the UHV hybrid DC transmission according to claim 5, wherein I is_dLThe value of b is 0.08, which is the per unit value of the direct current of the pole bus of the inversion station.

Technical Field

The invention provides an extra-high voltage hybrid direct current transmission VSC alternating current section power loss identification method and device based on an extra-high voltage hybrid direct current transmission system with an inversion station high-end LCC and a plurality of low-end VSCs cascaded, and belongs to the technical field of power electronics and direct current transmission.

Background

A conventional extra-high voltage direct current transmission system uses a power grid phase-change type converter (LCC), so that the problem of system transmission power interruption caused by phase-change failure cannot be solved. A voltage source type converter VSC or a combination of LCC and VSC is used for an inverter station of the hybrid direct current transmission system. The voltage source type converter has no commutation failure, and the active power and the reactive power can be independently controlled without configuring an alternating current filter. The combination of the LCC and the VSC can prevent commutation failure to a certain extent and restrain the occurrence of system power interruption caused by commutation failure. At present, a hybrid direct-current power transmission system becomes a research hotspot and has wide application prospect.

However, for the ultra-high voltage hybrid dc transmission system, under the high-power operation condition, after the VSC has an ac section power loss (the three-phase incoming line on the primary side of the coupling transformer is disconnected), the power on the dc side of the VSC is higher than that on the ac side, which causes the capacitor voltage of the sub-module to increase, and the primary side of the coupling transformer has an overvoltage. Under the operating condition of low power, after the VSC generates the AC section power loss, the other converters generally can not cause DC overvoltage through transferring power. Thus, accurate detection of a loss of power in the VSC ac section may not be possible in some cases by way of overvoltage detection.

In order to effectively identify the condition of the power loss of the VSC alternating-current section of the extra-high voltage direct-current transmission system, a method for identifying the power loss of the VSC section of the extra-high voltage direct-current transmission system is urgently needed.

Disclosure of Invention

The invention aims to provide a method and a device for identifying the loss of power of an alternating current section of a VSC (voltage source converter) in extra-high voltage hybrid direct current transmission, and solves the problems of poor accuracy and low reliability of identification of the alternating current section of the VSC in the prior art.

In order to achieve the purpose, the technical scheme of the invention is as follows: the invention provides an identification method for the loss of power of an alternating current section of a VSC (voltage source converter) in extra-high voltage hybrid direct current transmission, which comprises the following steps:

1) measuring and calculating a fault component: the fault components comprise alternating voltage and current effective values at the primary side of the connecting transformer, direct current of a transformer station pole bus and deviation of an actual value and a reference value of VSC active power;

2) setting a fault criterion constant value: setting an alternating current voltage criterion fixed value, an alternating current criterion fixed value, an inversion station pole bus current criterion fixed value and an active power criterion fixed value;

3) and under the unlocking state of the VSC, judging whether the VSC has an alternating current section power-off fault according to the relation between each fault component and the corresponding criterion constant value.

According to the invention, whether the VSC has an AC section power failure is judged by detecting and calculating the AC voltage at the primary side of the coupling transformer, the current effective value, the DC of the bus of the inversion station pole and the deviation of the actual value of the active power of the VSC and the reference value under the unlocking state of the VSC, and respectively judging the relation between the actual value and the corresponding criterion fixed value. On one hand, the accuracy and the reliability of the VSC alternating-current section identification mode are improved; on the other hand, the method is simple, and the fault judgment efficiency is improved.

Further, under the unlocking state of the VSC, when the relation between each fault component and the corresponding criterion constant value meets the following fault criterion, the VSC is judged to have an alternating current section fault:

in the formula of U_asSFor coupling the effective value, Δ, of the AC voltage at the primary side of the transformer₁Determining a constant value for the alternating voltage; i is_acSFor coupling the effective value, Δ, of the AC current on the primary side of the transformer₂Determining a constant value for the alternating current; i is_dLThe direct current of the bus of the inversion station is used, and b is a current criterion constant value of the bus of the inversion station; p_acrefIs the active power reference value, P, of the VSC_acIs the actual value of the active power, Delta, of the VSC₃And for the fixed value of the active power criterion, dblk is 1 to indicate that the VSC is in an unlocked state.

Further, I_dLThe value of b is 0.08, which is the per unit value of the direct current of the pole bus of the inversion station.

The invention also provides an extra-high voltage hybrid direct current transmission VSC alternating current section power failure recognition device, which comprises a processor and a memory, wherein the memory is stored with a computer program, and the processor executes the computer program to realize the following steps:

1) measuring and calculating a fault component: the fault components comprise alternating voltage and current effective values at the primary side of the connecting transformer, direct current of a transformer station pole bus and deviation of an actual value and a reference value of VSC active power;

2) setting a fault criterion constant value: setting an alternating current voltage criterion fixed value, an alternating current criterion fixed value, an inversion station pole bus current criterion fixed value and an active power criterion fixed value;

3) and under the unlocking state of the VSC, judging whether the VSC has an alternating current section power-off fault according to the relation between each fault component and the corresponding criterion constant value.

According to the invention, whether the VSC has an AC section power failure is judged by detecting and calculating the AC voltage at the primary side of the coupling transformer, the current effective value, the DC of the bus of the inversion station pole and the deviation of the actual value of the active power of the VSC and the reference value under the unlocking state of the VSC, and respectively judging the relation between the actual value and the corresponding criterion fixed value. On one hand, the accuracy and the reliability of the VSC alternating-current section identification mode are improved; on the other hand, the method is simple, and the fault judgment efficiency is improved.

Further, under the unlocking state of the VSC, when the relation between each fault component and the corresponding criterion constant value meets the following fault criterion, the VSC is judged to have an alternating current section fault:

in the formula of U_asSFor coupling the effective value, Δ, of the AC voltage at the primary side of the transformer₁Determining a constant value for the alternating voltage; i is_acSFor coupling the effective value, Δ, of the AC current on the primary side of the transformer₂Determining a constant value for the alternating current; i is_dLThe direct current of the bus of the inversion station is used, and b is a current criterion constant value of the bus of the inversion station;P_acrefis the active power reference value, P, of the VSC_acIs the actual value of the active power, Delta, of the VSC₃And for the fixed value of the active power criterion, dblk is 1 to indicate that the VSC is in an unlocked state.

Further, I_dLThe value of b is 0.08, which is the per unit value of the direct current of the pole bus of the inversion station.

Drawings

Fig. 1 is a topology structure diagram of an extra-high voltage hybrid direct-current transmission system in an embodiment of the invention.

Detailed Description

Embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. It should be emphasized that the following description is merely exemplary in nature and is not intended to limit the scope of the invention or its application.

The embodiment of the identification method comprises the following steps:

fig. 1 is a topological structure diagram of an extra-high voltage hybrid direct-current transmission system provided by the invention. The rectifying station of the extra-high voltage hybrid direct-current transmission system is the same as a conventional extra-high voltage, a power grid phase conversion type converter LCC is adopted, a high-end valve bank of the inverter station uses the power grid phase conversion type converter LCC, and a low-end valve bank is formed by connecting three VSC valve banks in parallel. The direct current side of the VSC valve group is connected with a controllable lightning arrester in parallel. In fig. 1, ACF: ac filter, DCF: and a DC filter. However, the present invention is not limited to the above topology, and the method proposed by the present invention is applicable to any extra-high voltage hybrid dc transmission system composed of LCC and VSC in combination.

In the embodiment, the detection of the power failure of the VSC alternating section is realized through the detection of each fault component of the VSC and the corresponding criterion. The failure determination process is described in detail below:

1) the fault component is measured and calculated.

The VSC alternating current section power failure identification needs to avoid the interference of system start and stop, VSC switch-on and switch-off, alternating current system fault and direct current line ground fault. In the embodiment, the accurate detection of the power failure of the VSC alternating-current section is realized by measuring the alternating-current voltage, the current effective value and the direct current of the inverter station pole bus of the connecting transformer, calculating the deviation between the actual value and the reference value of the VSC active power and comprehensively judging the detection fault components.

2) Setting a fault criterion constant value: and setting an alternating current voltage criterion fixed value, an alternating current criterion fixed value, an inversion station pole bus current criterion fixed value and an active power criterion fixed value.

3) And under the unlocking state of the VSC, simultaneously judging the relationship between each fault component and the corresponding criterion constant value to judge whether the VSC has the AC section power failure.

The criterion for recognizing the power loss of the alternating-current section of the VSC in the ultra-high voltage hybrid direct-current transmission provided by the embodiment is shown as the following formula.

In the formula of U_asSFor coupling the effective value, Δ, of the AC voltage at the primary side of the transformer₁For determining the constant value of the AC voltage, I_acSFor coupling the effective value, Δ, of the AC current on the primary side of the transformer₂For determining a constant value for the alternating current, I_dLIn this embodiment, the criterion fixed value of the dc current of the inverter station pole bus is set to 0.08, and as other embodiments, the criterion fixed value may be set according to actual conditions; p_acrefIs the active power reference value, P, of the VSC_acIs the actual value of the active power, Delta, of the VSC₃For the active power criterion constant value, dblk is the unlocking state of the VSC, and dblk is 1 to indicate that the VSC is in the unlocking state.

And when the criterion is completely met, indicating that the VSC has an alternating current section power failure.

Among the criteria given in this example, U_acS＞Δ₁The criterion can eliminate serious fault interference of the alternating current system when the effective value of the alternating current voltage at the network side is larger than a fixed value. And the influence of auxiliary voltage limiting control and steady-state minimum alternating voltage is needed when the criterion fixed value is protected and set and needs to be avoided when the power is too small. I is_acS＜Δ₂For the fact that the effective value of the alternating current on the network side is smaller than the threshold value, the criterion can eliminate serious fault interference of an alternating current system. Protection setting needs to avoid line capacitive current after line breakage. I is_dLIf the pole bus current per unit value is more than 0.08pu, the criterion can eliminate the interference of the direct current line ground fault.

For the deviation of the VSC active power reference value and the actual value, the interference of slight faults of an alternating current system, system start and stop and VSC valve group switching can be eliminated by the criterion. dblk is 1, which is the unlocking state of the VSC, and the criterion can eliminate the interference of power impact when the VSC is charged.

The embodiment of the identification device comprises:

the invention also provides a device for identifying the VSC section power loss of the UHV hybrid direct-current power transmission system, which comprises a processor, a memory and a computer program, wherein the computer program is stored in and run on the memory, the processor can be realized by adopting a single chip microcomputer, an FPGA, a DSP, a PLC, an MCU or the like, the memory can be an RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable disk, a CD-ROM or any other form of storage medium known in the art, and the storage medium can be coupled to the processor so that the processor can read information from the storage medium, or can be a component of the processor.

When the processor executes the computer program, the following method for identifying the power loss of the VSC section of the ultra-high voltage hybrid direct current transmission system is realized:

1) measuring and calculating a fault component: the fault components comprise alternating voltage on the primary side of the connecting transformer, an effective current value, direct current of an inversion station pole bus and deviation of an actual value and a reference value of VSC active power;

2) setting a fault criterion constant value: setting an alternating current voltage criterion fixed value, an alternating current criterion fixed value, an inversion station pole bus current criterion fixed value and an active power criterion fixed value;

3) and under the unlocking state of the VSC, judging whether the VSC has an alternating current section power-off fault according to the relation between each fault component and the corresponding criterion constant value.

The specific implementation manner of each step has been described in detail in the embodiment of the identification method, and is not described herein again.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.