CN103760447B - A kind of alternating-current fault detection method for D.C. high voltage transmission - Google Patents

Abstract

The invention provides an AC fault detection method for high-voltage direct current transmission. The method includes the following steps: respectively obtaining the three-phase voltage of the commutation bus and the three-phase currents on each outgoing line of the commutation bus; The three-phase voltage and the three-phase current on each outgoing line of the commutation bus respectively obtain the voltage zero-sequence component value and rotation vector amplitude of the commutation bus and the current zero-sequence component value and rotation vector amplitude of each outgoing line of the commutation bus; The power zero-sequence component value and the power rotation vector amplitude of each outgoing line of the converter bus; the above-mentioned values are compared with their respective set values to obtain the fault detection result. The detection method is fast and accurate, and meets the fault detection requirements of HVDC transmission, and provides valuable information for the control system of HVDC transmission to prevent commutation failure.

Description

An AC fault detection method for HVDC transmission

technical field

The invention relates to a method in the technical field of power transmission and distribution, in particular to a fault detection method for high-voltage direct current transmission.

Background technique

Since the 1950s, the traditional grid commutated high-voltage direct current (Line-Commutated-Converter High Voltage Direct Current, LCC-HVDC) has developed rapidly around the world due to its large-capacity long-distance transmission and fast controllable active power.

However, since LCC-HVDC uses ordinary thyristors without self-shutoff capability as commutation components, the LCC-HVDC system requires a certain strength of the AC system to achieve commutation, and the commutation voltage needs to be provided by the AC grid. When the power grid fails or the three-phase is seriously asymmetrical, the AC bus voltage will drop, the line voltage zero crossing point may be advanced, the commutation overlap angle of the LCC-HVDC valve arm will increase, and the cut-off angle will decrease, which will easily lead to phase failed. The occurrence of commutation failure severely limits the transmission power of the DC system, causing the transmission power to suddenly drop from a normal value to a very small value or even zero, which brings huge disturbances to the entire AC-DC-AC system.

AC system failure is one of the important factors leading to commutation failure, and the key to prevent commutation failure is to detect the failure as early as possible and make the control system react quickly. In the existing power system protection, the protection range of the circuit breaker is strictly limited, and its action setting value usually needs to match the protection setting value of the adjacent line, which ensures selectivity and quick action. However, in HVDC transmission, a fault in the vicinity of the commutation bus may lead to commutation failure. The fault detection is not for this section of the line, but to detect whether there is a fault near the commutation bus. If the setting principle of the general circuit breaker action in the power system is followed, there will be problems such as the fault detection range is not wide enough, and the detection time is long. Moreover, HVDC is used as a harmonic source, and its bus voltage is not completely symmetrical, which makes the voltage output fluctuate to a certain extent. If only the voltage is used as the fault criterion, the quickness has to be sacrificed in order to ensure the reliability of the judgment. Similarly, harmonic currents and asymmetrical currents will affect the amplitude, slope, and curvature of the current waveform, and the same problem exists when only using current as a fault criterion.

Contents of the invention

In order to overcome the shortcomings of the above-mentioned prior art, the present invention provides an AC fault detection method for high-voltage direct current transmission, which has a wide range of detection faults and a short time for identifying faults, and meets the fault detection requirements of high-voltage direct current transmission. Control system defenses against commutation failures provide valuable information.

The solution adopted to achieve the above purpose is:

An AC fault detection method for high-voltage direct current transmission, the improvement of which is that the method includes the following steps:

1. Obtain the three-phase voltage of the commutation bus and the three-phase currents on each outgoing line of the commutation bus;

II. According to the three-phase voltage of the converter bus and the three-phase current on each outlet of the converter bus, the voltage zero-sequence component value and voltage rotation vector amplitude of the converter bus and the voltage of each outlet of the converter bus are respectively obtained. Current zero-sequence component value and current rotation vector magnitude;

III. Obtain the power zero-sequence component value and power rotation vector magnitude of each outgoing line of the converter bus;

IV. The voltage zero-sequence component value and voltage rotation vector magnitude of the commutation bus, the current zero-sequence component value and current rotation vector magnitude of each outlet of the commutation bus, and the power of each outlet of the commutation bus The zero-sequence component value and the magnitude of the power rotation vector are compared with their respective set values to obtain the fault detection result.

Further, in the step I, a voltage real-time monitoring device is provided on the commutation bus, and a current real-time monitoring device is provided on each outgoing line of the commutation bus, and the voltage real-time monitoring device and the current real-time monitoring device are used. The monitoring device obtains the three-phase voltage of the converter bus and the three-phase current of each outgoing line of the converter bus in real time.

Further, in the step II, the instantaneous values of the A, B, and C three-phase voltages of the converter bus are obtained, and the Voltage zero-sequence component value and the voltage rotation vector magnitude:

u ₀ =u _a +u _b +u _c (1)

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}& <span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}& <span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \frac{\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}}{\mathrm{<span\; class="notranslate">\; 3</span>}}& <span\; class="notranslate">\; -</span>\frac{\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\end{array}\right]\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}\end{array}\right]<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; h</span>}}<span\; class="notranslate">\; =</span>\sqrt{{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

In the formula, u _a , u _b and u _c are the instantaneous values of three-phase voltages A, B and C obtained in real time on the converter bus, respectively, u _α and u _β are the rotation vectors of the converter bus voltage on the α-β plane α The corresponding components on the axis and the β axis, u ₀ and u _th are the voltage zero-sequence component value and the voltage rotation vector amplitude of the commutation bus, respectively.

Further, in the step II, the instantaneous values of the A, B, and C three-phase currents on each outgoing line of the commutation bus are obtained in real time, and the commutation voltage is obtained according to the following formulas (4), (5), and (6). The current zero-sequence component value and the current rotation vector magnitude on each outgoing line of the bus:

i _0n ＝i _an +i _bn +i _cn (4)

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}& <span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}& <span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \frac{\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}}{\mathrm{<span\; class="notranslate">\; 3</span>}}& <span\; class="notranslate">\; -</span>\frac{\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\end{array}\right]\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\end{array}\right]<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; =</span>\sqrt{{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; no</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}\mathrm{<span\; class="notranslate">\; no</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

In the formula, i _an , i _bn and i _cn are the instantaneous values of the three-phase currents A, B and C on the outgoing line of the nth outgoing line of the commutation bus measured in real time by the current transformer respectively, and i _αn and i _βn are respectively the The corresponding components of the current rotation vector on the outgoing line on the α-axis and the β-axis of the α-β plane, i _0n and _ithn are the current zero-sequence component value and the current rotation vector magnitude on the outgoing line, respectively.

Further, in the step III, the absolute value of the voltage zero-sequence component value of the commutation bus bar is multiplied by the absolute value of the current zero-sequence component value of each outgoing line of the commutation bus bar in the following formula (7): Obtain the zero-sequence component value p _0n of the power on each outgoing line of the converter bus:

p _0n ＝|u ₀ |*|i _0n |(7)

In the formula, u ₀ is the voltage zero-sequence component value, and i _0n is the current zero-sequence component value.

Further, in the step III, the offset of the voltage rotation vector magnitude of the commutation bus is multiplied by the current rotation vector magnitude on each outgoing line of the commutation bus according to the following formula (8): Offset, to obtain the power rotation vector magnitude p _thn on each outgoing line of the commutation bus:

p _thn ＝(u _Nth -u _th )*(i _{thn -i Mthn )} (8)

In the formula, u _th is the magnitude of the voltage rotation vector; _ithn is the magnitude of the current rotation vector, u _Nth is the rated voltage rotation vector magnitude of the commutation bus three-phase voltage ratings u _aN , u _bN and u _cN , i _Mthn is the rotation vector magnitude of the maximum current of the three-phase current maximum values i _Man , i _Mbn and i _Mcn .

Further, said step IV includes the following steps:

S401. In combination with high-voltage direct current transmission, according to the setting principle, obtain the set value of the voltage zero-sequence component of the commutation bus, the set value of the voltage rotation vector amplitude of the commutation bus, and the set value of each commutation bus The set value of the current zero-sequence component on the outgoing line, the set value of the current rotation vector amplitude of each outgoing line of the commutation bus, the set value of the power zero-sequence component of each outgoing line of the commutation bus, and the The setting value of the power rotation vector amplitude of each outgoing line of the flow bus;

S402. Calculate the voltage zero-sequence component value and voltage rotation vector magnitude of the commutation bus, the current zero-sequence component value and current rotation vector magnitude of each outlet of the commutation bus, and the power of each outlet of the commutation bus The zero-sequence component value and the magnitude of the power rotation vector are compared with their respective set values and logically integrated to obtain rapid fault detection results;

S403. If the zero-sequence components of current, voltage, and power in a certain outgoing line of the commutation bus all exceed their respective set values, a judgment is made that a single-phase fault has occurred;

S404. If the rotation vector amplitudes of the above physical quantities in a certain outgoing line all exceed the set value, then make a judgment that a three-phase fault occurs;

Further, the setting principles include the following rules:

A. The set value of the current zero-sequence component of the nth outgoing line must be greater than the maximum unbalanced current of the outgoing line under normal conditions, and the set value of the current rotation vector amplitude of each outgoing line of the commutation bus must be greater than the maximum current The magnitude of the rotation vector;

B. The set value of the zero-sequence component of the commutation bus voltage must be greater than the maximum asymmetric voltage of the commutation bus, and the set value of the voltage rotation vector amplitude of the commutation bus must be smaller than the minimum operating voltage rotation vector amplitude.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The present invention measures the instantaneous value of the three-phase voltage of the commutation busbar and the three-phase current of each outgoing line of the commutation busbar in real time, and performs a certain operation to obtain the voltage zero-sequence component value of the commutation busbar and its rotation vector amplitude, The current zero-sequence component value and its rotation vector amplitude on each outgoing line of the converter bus, and further determine the power zero-sequence component value and its rotation vector amplitude; according to the requirements of high-voltage direct current transmission for fault detection, reasonably set the settings of the above physical quantities Set the value, and compare each physical quantity with its own set value, and carry out logical integration, and finally get the fault fast detection result; the obtained detection result is fast and accurate, and meets the requirements of high-voltage direct current transmission for fault detection , can provide valuable information for HVDC control system to defend against commutation failure.

(2) The present invention refers to three different physical quantities of the voltage of the commutation bus, the current on each outgoing line of the commutation bus, and the power of the outgoing lines at the same time. Compared with detecting a fault solely by relying on one physical quantity of voltage, the amount of information is more It reflects the real-time operating status near the commutation bus more comprehensively, and provides more space for the rapidity and reliability of fault detection and better cooperation between the two.

(3) The measurement of the voltage and current zero-sequence component and the rotation vector involved in the present invention and the calculation process of the power component are all relatively simple, the calculation speed is fast and the result is accurate, and the calculation delay is very small and can be ignored; improve work efficiency, reduce Small computing space.

(4) The method of the present invention performs fault detection with reference to three different physical quantities of the voltage of the commutation bus, the current on each outlet of the commutation bus, and the power of the outlets. The fault detection range is wide, and the time used for identifying the fault is short, satisfying The fault detection requirements of HVDC transmission provide valuable information for the control system of HVDC transmission to prevent commutation failure.

Description of drawings

Fig. 1 is a logic diagram of AC fault detection and judgment for HVDC transmission.

detailed description

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

As shown in Figure 1, Figure 1 is a judgment logic diagram for AC fault detection of HVDC transmission; a real-time voltage monitoring device is installed on the commutation bus, and a real-time current monitoring device is installed on each outgoing line of the commutation bus. The three-phase voltage value and three-phase current value are obtained in real time.

An AC fault detection method for HVDC transmission includes the following:

Step 1. Obtain the three-phase voltage and three-phase current of the commutation bus respectively;

Step 2. According to the instantaneous value of the three-phase voltage of the commutation bus and the instantaneous value of the three-phase current of each outgoing line of the commutation bus, respectively obtain the voltage zero-sequence component value of the commutation bus, the amplitude of the rotation vector and the value of the commutation bus Current zero-sequence component value and rotation vector magnitude of each outgoing line;

Step 3. Obtain the power zero-sequence component value and power rotation vector magnitude of each outgoing line of the commutation bus;

Step 4: Calculate the voltage zero-sequence component value and rotation vector magnitude of the commutation bus, the current zero-sequence component value and rotation vector magnitude of each outlet of the commutation bus, and the power zero of each outlet of the commutation bus The sequence component value and the magnitude of the power rotation vector are compared with their respective set values to obtain fast fault detection results.

In step 1, the three-phase voltage of the commutation bus and the three-phase current of each outgoing line of the commutation bus are acquired respectively.

In order to obtain the three-phase voltage of the commutation bus, a voltage real-time monitoring device, such as a voltage sensor, is installed on the commutation bus; in order to obtain the instantaneous value of the three-phase current commutation, each outgoing line of the commutation bus is equipped with a current real-time monitoring device, For example a current sensor.

Use the voltage real-time monitoring device to obtain the instantaneous voltage values of the three phases A, B, and C of the commutation bus, and use the current real-time monitoring device to obtain the instantaneous current values of the three phases A, B, and C on each outgoing line of the commutation bus.

In step 2, the voltage zero-sequence component value and rotation vector magnitude of the commutation bus are obtained according to the three-phase voltage.

The commutation failure prediction control module in the Sanguang DC project can be used to obtain the voltage zero-sequence component value and rotation vector amplitude of the commutation bus.

The fault detection method used in the Sanguang DC project is an AC fault detection method that utilizes the characteristics of the fault voltage. The execution cycle is short and meets the real-time requirements.

In the present invention, the commutation failure prediction control module in the Sanguang DC project respectively obtains the instantaneous values of the A, B, and C three-phase voltages of the commutation bus, and uses the method of the commutation failure prediction control module in the Sanguang DC project, that is, according to the following Formulas (1), (2) and (3) obtain the voltage zero-sequence component value and rotation vector amplitude of the commutation bus:

u ₀ =u _a +u _b +u _c (1)

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}& <span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}& <span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \frac{\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}}{\mathrm{<span\; class="notranslate">\; 3</span>}}& <span\; class="notranslate">\; -</span>\frac{\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\end{array}\right]\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}\end{array}\right]<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; h</span>}}<span\; class="notranslate">\; =</span>\sqrt{{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

In the formula, u _a , u _b and u _c are the instantaneous values of three-phase voltages A, B and C measured by the voltage transformers on the commutation bus in real time respectively, u _α and u _β are the rotation vectors of the commutation bus voltage at The corresponding components on the α-axis and β-axis of the α-β plane, u ₀ and u _th are the voltage zero-sequence component value and the rotation vector amplitude of the commutation bus, respectively.

In step 2, refer to the calculation method of the zero-sequence component value of the commutation bus voltage and the magnitude of the rotation vector in the commutation failure prediction control module of the Sanguang DC project, and obtain the zero-sequence component of the current on each outgoing line of the commutation bus according to the three-phase current value and rotation vector magnitude.

In the method of the present invention, on the basis of the commutation failure prediction control module in the Sanguang DC project, the current flowing through each outgoing line of the commutation bus is increased, and the three-phase voltage and the three-phase current are constructed It is a logical method to detect AC faults by using three physical quantities at the same time to output power components. details as follows;

To obtain the instantaneous values of the A, B, and C three-phase currents on each outgoing line of the commutation bus, refer to the method of the commutation failure prediction control module in the Sanguang DC project, that is, according to the following formulas (4), (5), and (6) to obtain Current zero-sequence component value and rotation vector magnitude on each outgoing line of the commutation bus:

i _0n ＝i _an +i _bn +i _cn (4)

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}& <span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}& <span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \frac{\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}}{\mathrm{<span\; class="notranslate">\; 3</span>}}& <span\; class="notranslate">\; -</span>\frac{\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\end{array}\right]\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\end{array}\right]<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; =</span>\sqrt{{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; no</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}\mathrm{<span\; class="notranslate">\; no</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

In the formula, i _an , i _bn and i _cn are the instantaneous current values of A, B and C three-phase currents on the nth outgoing line of the commutation bus obtained by the current real-time monitoring device of the nth outgoing line respectively, and i _αn and i _βn are respectively the The corresponding components of the current rotation vector on the outgoing line on the α-axis and the β-axis of the α-β plane, i _0n and _ithn are the current zero-sequence component value and the rotation vector magnitude on the outgoing line, respectively.

In step 3, the zero-sequence component value of the power of each outgoing line of the converter bus is obtained as follows:

The absolute value of the voltage zero-sequence component of the commutation bus is multiplied by the absolute value of the current zero-sequence component of each outgoing line of the commutation bus in the following formula (7) to obtain the The power zero-sequence component value p _0n :

p _0n ＝|u ₀ |*|i _0n |(7)

In the formula, u ₀ is the voltage zero-sequence component value of the commutation bus; i _0n is the current zero-sequence component value of the outgoing line on the commutation bus.

In step 3, the power rotation vector amplitude of each outgoing line of the commutation bus is obtained as follows:

The following equation (8) multiplies the offset of the voltage rotation vector amplitude of the commutation bus by the offset of the current rotation vector amplitude on each outgoing line of the commutation bus to obtain each Outline the power rotation vector magnitude p _thn :

p _thn ＝(u _Nth -u _th )*(i _{thn -i Mthn )} (8)

In the formula, u _th is the magnitude of the rotation vector; _ithn is the magnitude of the rotation vector; u _Nth is the rated voltage rotation vector magnitude of the three-phase voltage ratings u _aN , u _bN and u _cN of the commutation bus, and the formula (2 ) in u _a , u _b and u _c are replaced by the three-phase voltage ratings u _aN , u _bN and u _cN of the converter buses A, B and C respectively, which can be calculated from formulas (2) and (3); i _Mthn is the rotation vector amplitude of the maximum current of the three-phase currents i _Man , i _Mbn and i _Mcn , and i _an , i _bn and i _cn in formula (5) are replaced by the nth commutation bus The maximum values i _Man , i _Mbn and i _Mcn of the three-phase currents of A, B and C on the outgoing line can be calculated from formulas (5) and (6).

In step 4, the voltage zero-sequence component value and rotation vector magnitude of the commutation bus, the current zero-sequence component value and rotation vector magnitude of each outlet of the commutation bus, and the power of each outlet of the commutation bus The zero-sequence component value and the magnitude of the power rotation vector are compared with their respective set values to obtain fast fault detection results.

Specifically include the following steps:

(1) Perform tuning in combination with the characteristics of HVDC transmission. According to the tuning principles, the set value of the voltage zero-sequence component of the commutator bus, the set value of the voltage rotation vector amplitude of the commutator bus, and the set value of each commutator bus The set value of the current zero-sequence component on the outgoing line, the set value of the current rotation vector amplitude on each outgoing line of the commutation bus, the set value of the fault power zero-sequence component on each outgoing line of the commutation bus, and the commutation The setting value of the power rotation vector magnitude on each outgoing line of the bus.

Since a fault occurs within a certain distance from the commutation bus, it may cause commutation failure in the DC transmission system, and the specific value of this distance is related to many factors and is difficult to determine. Therefore, it is necessary to ensure that CFPREP (commutation failure prediction control module in Sanguang DC project) has sufficient sensitivity to detect all possible failures that may lead to commutation failure.

For this reason, it is only necessary to ensure that CFPREP will not misjudge under normal circumstances, and the setting principles of each physical quantity setting value in CFPREP are similar to the setting principles of definite time overcurrent protection in relay protection.

The above setting principles are as follows:

A. For the current of the nth outgoing line, its zero-sequence component setting value i _{0n_set} only needs to avoid the maximum unbalanced current of the outgoing line under normal conditions, and the αβ component setting value i _{thn_set} only needs to avoid the rotation vector of the maximum current The magnitude, i _{thn_set} is approximately 30% of the magnitude of the maximum current rotation vector.

B. For the commutation bus voltage, the set value u _{0_set} of the zero-sequence component only needs to avoid the maximum asymmetric voltage of the commutation bus, and the set value u _{th_set} of the αβ component only needs to avoid the minimum operating voltage rotation vector amplitude, that is, u _{th_set} is approximately 95% of the magnitude of the rated voltage rotation vector.

C. If the two are multiplied correspondingly, the CFPREP power zero-sequence component set value p _{0n_set} and the αβ component set value p _{thn_set} are respectively obtained, then the power component set values are small, the sensitivity is high, and the fault can be detected quickly .

D. In order to improve the reliability and ensure the correctness of the judgment, the set value of the CFPREP power component can be appropriately increased on this basis.

"Dodge" means not to move by mistake in the following situations. which is:

Setting principle A means that the set value of the zero-sequence component of the current needs to be greater than the maximum unbalanced current of the outgoing line under normal conditions, and the set value of the current rotation vector amplitude must be greater than the maximum current rotation vector amplitude.

Setting principle B means that the set value of the zero-sequence component of the commutation bus voltage must be greater than the maximum asymmetric voltage of the commutation bus, and the set value of the voltage rotation vector amplitude of the commutation bus must be smaller than the minimum operating voltage rotation vector amplitude value.

(2) The voltage zero-sequence component value and rotation vector amplitude of the commutation bus, the current zero-sequence component value and rotation vector amplitude of each outgoing line of the commutation bus, the power zero-sequence component value and power of each outgoing line of the commutation bus The magnitude of the rotation vector is compared with its respective set value, and logic integration is carried out to obtain rapid fault detection results;

If the zero-sequence components of current, voltage, and power (the voltage zero-sequence components are shared by each outgoing line, the same below) in a certain outgoing line of the commutation bus exceed their respective set values, then a single-phase fault will be declared judge;

If the rotation vector amplitudes of the above physical quantities in a certain outgoing line all exceed the set value, it will be judged that a three-phase fault has occurred.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application rather than limit the scope of protection thereof. Although the present application has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: After reading this application, those skilled in the art can still make various changes, modifications or equivalent replacements to the specific implementation methods of the application, but these changes, modifications or equivalent replacements are all within the protection scope of the pending claims of the application.

Claims (7)

1. An AC fault detection method for HVDC transmission, characterized in that: the method may further comprise the steps: 1. Obtain the three-phase voltage of the commutation bus and the three-phase currents on each outgoing line of the commutation bus; II. According to the three-phase voltage of the converter bus and the three-phase current on each outlet of the converter bus, the voltage zero-sequence component value and voltage rotation vector amplitude of the converter bus and the voltage of each outlet of the converter bus are respectively obtained. Current zero-sequence component value and current rotation vector magnitude; III. Obtain the power zero-sequence component value and power rotation vector magnitude of each outgoing line of the converter bus; In the step III, the absolute value of the voltage zero-sequence component value of the commutation bus is multiplied by the absolute value of the current zero-sequence component value of each outgoing line of the commutation bus in the following formula (7) to obtain the The zero-sequence component value p _0n of the power on each outgoing line of the above-mentioned commutation bus: p _0n ＝|u ₀ |*|i _0n |(7) In the formula, u ₀ is the voltage zero-sequence component value, i _0n is the current zero-sequence component value; IV. The voltage zero-sequence component value and voltage rotation vector magnitude of the commutation bus, the current zero-sequence component value and current rotation vector magnitude of each outlet of the commutation bus, and the power of each outlet of the commutation bus The zero-sequence component value and the magnitude of the power rotation vector are compared with their respective set values to obtain the fault detection result. 2. A kind of AC fault detection method for high-voltage direct current transmission as claimed in claim 1, is characterized in that: in described step 1, voltage real-time monitoring device is provided on the described commutation bus, and described commutation bus A real-time current monitoring device is installed on each outgoing line of the commutation bus, and the three-phase voltage of the commutation bus and the three-phase current of each outgoing line of the commutation bus are obtained in real time by using the real-time voltage monitoring device and the real-time current monitoring device. 3. A kind of AC fault detection method for high-voltage direct current transmission as claimed in claim 1, is characterized in that: in described step II, obtain the A, B, C three-phase voltage instantaneous value of described converter bus, The voltage zero-sequence component value and the voltage rotation vector magnitude of the commutation bus are obtained according to the following formulas (1), (2) and (3): u ₀ =u _a +u _b +u _c (1) $\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}& <span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}& <span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \frac{\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}}{\mathrm{<span\; class="notranslate">\; 3</span>}}& <span\; class="notranslate">\; -</span>\frac{\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\end{array}\right]\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}\end{array}\right]<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$ ${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; h</span>}}<span\; class="notranslate">\; =</span>\sqrt{{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$ In the formula, u _a , u _b and u _c are the instantaneous values of three-phase voltages A, B and C obtained in real time on the converter bus, respectively, u _α and u _β are the rotation vectors of the converter bus voltage on the α-β plane α The corresponding components on the axis and the β axis, u ₀ and u _th are the voltage zero-sequence component value and the voltage rotation vector amplitude of the commutation bus, respectively. 4. A kind of AC fault detection method for high-voltage direct current transmission as claimed in claim 1, is characterized in that: in described step II, obtain the A, B, C three-phase on each outgoing line of described converter bus bar in real time The current instantaneous value is obtained according to the following formulas (4), (5), and (6) to obtain the current zero-sequence component value and the current rotation vector magnitude on each outgoing line of the commutation bus: i _0n ＝i _an +i _bn +i _cn (4) $\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}& <span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}& <span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \frac{\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}}{\mathrm{<span\; class="notranslate">\; 3</span>}}& <span\; class="notranslate">\; -</span>\frac{\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\end{array}\right]\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; no</span>}}\end{array}\right]<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$ ${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; =</span>\sqrt{{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; no</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}\mathrm{<span\; class="notranslate">\; no</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$ In the formula, i _an , i _bn and i _cn are the instantaneous values of the three-phase currents A, B and C on the outgoing line of the nth outgoing line of the commutation bus measured in real time by the current transformer respectively, and i _αn and i _βn are respectively the The corresponding components of the current rotation vector on the outgoing line on the α-axis and the β-axis of the α-β plane, i _0n and _ithn are the current zero-sequence component value and the current rotation vector magnitude on the outgoing line, respectively. 5. A kind of AC fault detection method for high voltage direct current transmission as claimed in claim 1, is characterized in that: in described step III, the described voltage rotation vector amplitude of described commutation bus bar is as follows formula (8) The offset of the value is multiplied by the current rotation vector amplitude offset on each outgoing line of the commutation bus to obtain the power rotation vector amplitude p _thn on each outgoing line of the commutation bus: p _thn ＝(u _Nth -u _th )*(i _{thn -i Mthn )} (8) In the formula, u _th is the magnitude of the voltage rotation vector; _ithn is the magnitude of the current rotation vector, u _Nth is the rated voltage rotation vector magnitude of the commutation bus three-phase voltage ratings u _aN , u _bN and u _cN , i _Mthn is the rotation vector magnitude of the maximum current of the three-phase current maximum values i _Man , i _Mbn and i _Mcn . 6. A kind of AC fault detection method for high voltage direct current transmission as claimed in claim 1, is characterized in that: described step IV comprises the following steps: S401. Combining with the setting principle of HVDC transmission, obtain the set value of the voltage zero-sequence component of the commutation bus, the set value of the voltage rotation vector amplitude of the commutation bus, and each outgoing line of the commutation bus The set value of the zero-sequence component of the current above, the set value of the current rotation vector amplitude of each outgoing line of the commutation bus, the set value of the zero-sequence component of the power of each outgoing line of the commutation bus, and the set value of the commutation bus The setting value of the power rotation vector amplitude of each outgoing line of the bus; S402. Calculate the voltage zero-sequence component value and voltage rotation vector magnitude of the commutation bus, the current zero-sequence component value and current rotation vector magnitude of each outgoing line of the commutation bus, and the power of each outgoing line of the commutation bus The zero-sequence component value and the magnitude of the power rotation vector are compared with their respective set values and logically integrated to obtain rapid fault detection results; S403. If the zero-sequence component values of current, voltage, and power in a certain outgoing line of the commutation bus all exceed their respective set values, it is judged that a single-phase fault occurs; S404. If the amplitudes of the rotation vectors of the current, voltage, and power in a certain outgoing line all exceed the set values, it is judged that a three-phase fault occurs. 7. A kind of AC fault detection method for high-voltage direct current transmission as claimed in claim 6, is characterized in that: described setting principle comprises the following rules: A. The set value of the current zero-sequence component of the nth outgoing line must be greater than the maximum unbalanced current of the outgoing line under normal conditions, and the set value of the current rotation vector amplitude of each outgoing line of the commutation bus must be greater than the maximum current The magnitude of the rotation vector; B. The set value of the zero-sequence component of the commutation bus voltage must be greater than the maximum asymmetric voltage of the commutation bus, and the set value of the voltage rotation vector amplitude of the commutation bus must be smaller than the minimum operating voltage rotation vector amplitude.