阅读说明：本技术 一种同相供电装置串联侧电压采样极性自动校正方法 (Method for automatically correcting voltage sampling polarity of series side of in-phase power supply device ) 是由 刘刚 陈旭东 高洪 宋晓梅 翟超 赵小虎 陈雪 许恩泽 黄辉 于 2021-07-20 设计创作，主要内容包括：本发明提出了一种同相供电串联侧电压采样极性自动校正方法。该方法操作同相供电装置进行预充电和输出开环电压流程,自动根据启动柜和进线开关柜的PT电压采样信号,将进线开关柜PT电压采样信号的极性进行自动校正,在控制中使用极性后的电压,确保同相供电装置的串联侧输出的电压极性与进线开关柜电压(T座电压)匹配,避免了变流器输出电压与进线电压相反造成的过流问题。本发明提出了在串联侧电压采样极性自动校正过程中,两次采样方向判断的方法,简单有效。本发明在两次进行极性判断的流程中,还可以发现采样系数设置错误等造成采样极性不是相反,也不相同的情况。(The invention provides a method for automatically correcting voltage sampling polarity of a series side of in-phase power supply. The method operates the in-phase power supply device to carry out the processes of pre-charging and outputting open-loop voltage, automatically corrects the polarity of the PT voltage sampling signal of the inlet wire switch cabinet according to the PT voltage sampling signals of the starting cabinet and the inlet wire switch cabinet, uses the voltage after the polarity in the control process, ensures that the voltage polarity output by the series side of the in-phase power supply device is matched with the voltage (T seat voltage) of the inlet wire switch cabinet, and avoids the overcurrent problem caused by the fact that the output voltage of a converter is opposite to the inlet wire voltage. The invention provides a method for judging the sampling direction twice in the process of automatically correcting the voltage sampling polarity on the serial side, which is simple and effective. In the process of judging the polarity twice, the invention can also find the condition that the sampling polarities are not opposite or different due to the setting error of the sampling coefficient and the like.)

1. A method for automatically correcting voltage sampling polarity of a same-phase power supply serial side is characterized by comprising the following steps:

the in-phase power supply device is pre-charged in an inlet wire through a circuit breaker at the serial side of an inlet wire switch cabinet and a starting circuit of a starting cabinet; during the pre-charging period, acquiring a voltage sampling signal of a PT (potential transformer) of the T-base incoming line switch cabinet and a voltage signal of a PT in a starting cabinet and judging, if the voltage sampling directions of the two positions are the same, recording that a first FLAG FLAG1 is invalid, otherwise, recording that the first FLAG FLAG1 is valid;

disconnecting a series side breaker in the T-base incoming line switch cabinet after the pre-charging is finished, generating an open-loop modulation wave according to a phase angle of PT voltage of the T-base incoming line switch cabinet, and outputting open-loop voltage at a series side;

comparing whether the phase of the open-loop voltage of the starting cabinet PT is the same as the direction of a PT signal of the T-seat incoming line switch cabinet or not, if so, recording that the second FLAG FLAG2 is invalid, otherwise, recording that the second FLAG FLAG2 is valid;

if one of the first FLAG1 and the second FLAG2 is valid or invalid, the voltage signal of the T-base incoming line switch cabinet sampling PT needs to be inverted and used as a signal for actual control, otherwise, the voltage sampling polarity does not need to be corrected.

2. The method according to claim 1, wherein the in-phase power supply device comprises a power cabinet, a starting cabinet, a T-base incoming line switch cabinet, a traction matching transformer and an outgoing line switch cabinet;

the power cabinet comprises a plurality of power units for power conversion, the serial side H bridge of each power unit is connected with the starting cabinet after being connected in series, and the parallel side of each power unit is connected with the outgoing line switch cabinet through a traction matching transformer;

the outgoing line switch cabinet is connected with the M base of the power grid transformer;

the starting cabinet comprises a soft starting contactor KM1, a soft starting resistor and a main contactor KM2, wherein the soft starting resistor and the soft starting contactor KM1 are connected in series and then connected in parallel with the main contactor;

the starting cabinet is connected with the T-seat incoming line switch cabinet, and the T-seat incoming line switch cabinet is connected with the T seat of the power grid transformer.

3. The method for automatically correcting the voltage sampling polarity of the in-phase power supply series side according to claim 2, wherein during the pre-charging period, acquiring and judging a voltage sampling signal of a PT (potential transformer) of a T-base incoming line switch cabinet and a voltage signal of a PT (potential transformer) in a starting cabinet comprises the following steps: defining the per unit value of PT sampling instantaneous voltage of T-seat incoming line switch cabinet as u_TPT sampling instantaneous voltage per unit value of u in starting cabinet_QCalculating the instantaneous difference value delta u ═ u between two voltage samples_T-u_QIf the effective value of Δ U is Δ U_RMSIf the voltage sampling direction is less than 0.3pu, the voltage sampling direction is considered to be the same, and the first FLAG1 is recorded as invalid; if the effective value of Δ U is Δ U_RMSIf the voltage sampling direction is larger than 1.6pu, the voltage sampling direction is different, and the first FLAG1 is recorded as effective; if the effective value of Δ U is Δ U_RMSBetween 0.3pu and 1.6pu, there is a downtime.

4. The method for automatically correcting the sampling polarity of the voltage on the series side of the in-phase power supply according to claim 2 or 3, wherein the pre-charging process comprises closing a soft-start contactor KM1 of a starting loop in the starting cabinet, then closing a breaker QF in the T-seat incoming line switch cabinet, closing a main contactor KM2 of the starting loop when the charging of a direct current bus capacitor of the power unit reaches a set value, and then opening the soft-start contactor KM 1.

5. The method for automatically correcting the sampling polarity of the voltage at the series side of the in-phase power supply according to claim 1, wherein after the pre-charging is completed and the breaker QF of the T-base incoming line switch cabinet is disconnected, an open-loop modulation wave is generated according to a phase angle of the PT voltage of the T-base incoming line switch cabinet, and the series side outputs an open-loop voltage, comprising:

PT voltage sampling u of T-base incoming line switch cabinet_TPhase locking is carried out, and the phase angle omega of the voltage of the T-base incoming line switch cabinet obtained by phase locking_Tt in u_mod＝U_opensin(ω_Tt) given as an open-loop modulation wave, where U_openAnd in order to set open-loop modulation degree, the open-loop pulse generation is carried out by utilizing the DC voltage pre-charged by the DC bus capacitor, and the voltage is output at the serial side port and the starting cabinet.

6. The method of claim 5, wherein comparing whether the phase of the open-loop voltage for starting the PT sampling of the cabinet is the same as the direction of the PT voltage signal of the T-base incoming line switch cabinet comprises:

the voltage for starting the PT sampling of the cabinet during the open-loop pulse generation is u_{Q_open}To u, to u_{Q_open}Phase locking is carried out to obtain a phase angle omega_Qot；

Phase angle omega of T seat voltage obtained by phase locking_Tt and phase angle omega_Qot is subtracted and the absolute value is taken: Δ θ ═ ω_Tt-ω_QoL, |; if Δ θ is greater than π, the process yields θ in the range of 0 to π_FLAG2(ii) a If theta is greater than theta_FLAG2Is less thanJudging that the open-loop voltage of the starting cabinet is in the same phase with the voltage of the T seat, and setting a second FLAG FLAG2 as invalid; if the difference, θ_FLAG2Is greater thanJudging that the open-loop voltage of the starting cabinet is opposite to the voltage of the T seat, and setting a second FLAG FLAG2 to be effective; if theta is greater than theta_FLAG2BetweenAndand then the machine is stopped in a fault mode.

7. The method as claimed in claim 6, wherein if no fault occurs, 0 indicates invalid and 1 indicates valid, the first FLAG1 and the second FLAG2 are xored, and the operation result is defined as FLAG 3:

if FLAG3 is 0, then the voltage sampling polarity does not need to be rectified; if FLAG3 is 1, PT voltage acquisition signal u of T-base incoming line switch cabinet is required_TMultiplied by (-1) and used as a signal for control.

8. The in-phase power supply series side voltage sampling polarity automatic correction method as claimed in claim 6, characterized in that if Δ θ is larger than π, the processing gets θ within the range of 0 to π_FLAG2The method comprises the following steps: if the angle is greater than π, θ_FLAG2＝2π-|Δθ|。

Technical Field

The invention relates to the technical field of power electronics, in particular to an automatic correction method for voltage sampling polarity of a series side of an in-phase power supply device.

Background

The electric locomotive is a single-phase power load, measures such as phase splitting and partitioning, phase sequence rotation and the like are adopted for power supply of a traction network in order to reduce the influence of negative sequence current on an electric power system, and an electric phase splitting link is added in a contact network. The automatic passing neutral section device not only has frequent action, short service life and low reliability, but also can cause the loss of train speed and traction force. The in-phase power supply device solves the problems of electric phase splitting, voltage fluctuation, low power factor, overproof negative sequence current and the like in the traction substation.

The in-phase power supply device mainly comprises a traction matching transformer and an in-phase power supply converter, wherein the traction matching transformer is a multi-winding transformer, and the in-phase power supply converter is formed by connecting a plurality of power units in series and in parallel and comprises a parallel side and a series side. The high-voltage side of the traction matching transformer is connected with a traction transformer M seat, the low-voltage side of the traction matching transformer is connected with the parallel side of the cophase power supply converter, and the serial side of the converter is connected into a traction transformer T seat through a starting cabinet.

The positive direction of voltage sampling of the T seat of the transformer is very important for controlling the serial side of the in-phase power supply device, if the voltage sampling direction of the T side is incorrect, the conditions that variables such as phase locking, feedforward and the like of the serial side are wrong, voltage and current cannot be effectively controlled can occur, even the situation that when the maximum positive voltage is output by the serial side, the T seat is just the maximum negative voltage, double voltage is added to a reactor of a starting cabinet, instantaneous large current occurs, and a power switch device of the serial side can be damaged.

At present, a current transformer is connected with an external incoming line, PT signals sent by a switch cabinet are used, generally, in a design stage, all parties communicate to stipulate a positive direction, in a field early stage installation and debugging stage, a line checking mode is adopted, and a channel relay protection tester adds signals to clearly sample the positive direction.

The prior art scheme can also determine the direction, but has the problem that manual line inspection is time-consuming and labor-consuming. In addition, although the relay protection tester is used for testing the sampling direction of the T seat voltage of the in-phase power supply device to be correct, the wiring error of a main loop can also occur, and the problem that the output voltage of the series side is opposite to the T seat voltage can also occur.

Disclosure of Invention

The method is used for operating the same-phase power supply device to carry out the processes of pre-charging and outputting open-loop voltage, automatically carrying out automatic correction on the polarity of a PT voltage sampling signal of an inlet wire switch cabinet according to the PT voltage sampling signals of a starting cabinet and the inlet wire switch cabinet, and using the voltage after polarity correction in control to ensure that the voltage polarity output by the series side of the same-phase power supply device is matched with the voltage of the T seat, thereby avoiding the overcurrent problem caused by the fact that the output voltage of a converter is opposite to the voltage of the inlet wire.

In order to achieve the purpose, the invention provides an automatic correction method for the sampling polarity of the voltage at the same-phase power supply serial side, which comprises the following steps:

the in-phase power supply device is pre-charged in an inlet wire through a circuit breaker at the serial side of an inlet wire switch cabinet and a starting circuit of a starting cabinet; during the pre-charging period, acquiring a voltage sampling signal of a PT (potential transformer) of the T-base incoming line switch cabinet and a voltage signal of a PT in a starting cabinet and judging, if the voltage sampling directions of the two positions are the same, recording that a first FLAG FLAG1 is invalid, otherwise, recording that the first FLAG FLAG1 is valid;

disconnecting a series side breaker in the T-base incoming line switch cabinet after the pre-charging is finished, generating an open-loop modulation wave according to a phase angle of PT voltage of the T-base incoming line switch cabinet, and outputting open-loop voltage at a series side;

comparing whether the phase of the open-loop voltage of the starting cabinet PT is the same as the direction of a PT signal of the T-seat incoming line switch cabinet or not, if so, recording that the second FLAG FLAG2 is invalid, otherwise, recording that the second FLAG FLAG2 is valid;

if one of the first FLAG1 and the second FLAG2 is valid or invalid, the voltage signal of the T-base incoming line switch cabinet sampling PT needs to be inverted and used as a signal for actual control, otherwise, the voltage sampling polarity does not need to be corrected.

Furthermore, the in-phase power supply device comprises a power cabinet, a starting cabinet, a T-base incoming line switch cabinet, a traction matching transformer and an outgoing line switch cabinet;

the power cabinet comprises a plurality of power units for power conversion, the serial side H bridge of each power unit is connected with the starting cabinet after being connected in series, and the parallel side of each power unit is connected with the outgoing line switch cabinet through a traction matching transformer;

the outgoing line switch cabinet is connected with the M base of the power grid transformer;

the starting cabinet comprises a soft starting contactor KM1, a soft starting resistor and a main contactor KM2, wherein the soft starting resistor and the soft starting contactor KM1 are connected in series and then connected in parallel with the main contactor;

the starting cabinet is connected with the T-seat incoming line switch cabinet, and the T-seat incoming line switch cabinet is connected with the T seat of the power grid transformer.

Further, during the precharge, gather the voltage sampling signal of T seat inlet wire cubical switchboard PT and start the voltage signal of PT in the cabinet and carry out the judgement, include: defining the per unit value of PT sampling instantaneous voltage of T-seat incoming line switch cabinet as u_TPT sampling instantaneous voltage per unit value of u in starting cabinet_QCalculating the instantaneous difference value delta u ═ u between two voltage samples_T-u_QIf, ifEffective value of Δ U Δ U_RMSIf the voltage sampling direction is less than 0.3pu, the voltage sampling direction is considered to be the same, and the first FLAG1 is recorded as invalid; if the effective value of Δ U is Δ U_RMSIf the voltage sampling direction is larger than 1.6pu, the voltage sampling direction is different, and the first FLAG1 is recorded as effective; if the effective value of Δ U is Δ U_RMSBetween 0.3pu and 1.6pu, there is a downtime.

Further, the pre-charging process comprises the steps of firstly closing the soft start contactor KM1 of the starting circuit in the starting cabinet, then closing the breaker QF in the T-base incoming line switch cabinet, when the charging of the direct current bus capacitor of the power unit reaches a set value, closing the main contactor KM2 of the starting circuit, and then opening the soft start contactor KM 1.

Further, precharge and accomplish to break off behind T seat inlet wire cubical switchboard circuit breaker QF, according to the phase angle generation open-loop modulation ripples of T seat inlet wire cubical switchboard PT voltage, open-loop voltage is exported to the series connection side, includes:

PT voltage sampling u of T-base incoming line switch cabinet_TPhase locking is carried out, and the phase angle omega of the voltage of the T-base incoming line switch cabinet obtained by phase locking_Tt in u_mod＝U_opensin(ω_Tt) given as an open-loop modulation wave, where U_openAnd in order to set open-loop modulation degree, the open-loop pulse generation is carried out by utilizing the DC voltage pre-charged by the DC bus capacitor, and the voltage is output at the serial side port and the starting cabinet.

Further, whether the phase place of the open loop voltage that the comparison starts cabinet PT sampling is the same with the direction of T seat inlet wire cubical switchboard PT voltage signal includes:

the voltage for starting the PT sampling of the cabinet during the open-loop pulse generation is u_{Q_open}To u, to u_{Q_open}Phase locking is carried out to obtain a phase angle omega_Qot；

Phase angle omega of T seat voltage obtained by phase locking_Tt and phase angle omega_Qot is subtracted and the absolute value is taken: Δ θ ═ ω_Tt-ω_QoL, |; if Δ θ is greater than π, the process yields θ in the range of 0 to π_FLAG2(ii) a If theta is greater than theta_FLAG2Is less thanThen judge it asThe open-loop voltage of the starting cabinet is in phase with the voltage of the T seat, and a second FLAG FLAG2 is set to be invalid; if the difference, θ_FLAG2Is greater thanJudging that the open-loop voltage of the starting cabinet is opposite to the voltage of the T seat, and setting a second FLAG FLAG2 to be effective; if theta is greater than theta_FLAG2BetweenAndand then the machine is stopped in a fault mode.

Further, if no fault occurs, 0 indicates invalid, 1 indicates valid, and the first FLAG1 and the second FLAG2 are xored, and the operation result is defined as FLAG 3:

if FLAG3 is 0, then the voltage sampling polarity does not need to be rectified; if FLAG3 is 1, PT voltage acquisition signal u of T-base incoming line switch cabinet is required_TMultiplied by (-1) and used as a signal for control.

Further, if Δ θ is greater than π, the process yields θ in the range of 0 to π_FLAG2The method comprises the following steps: if the angle is greater than π, θ_FLAG2＝2π-|Δθ|。

The technical scheme of the invention has the following beneficial technical effects:

(1) the method for automatically correcting the voltage sampling polarity of the series side of the in-phase power supply device can save the complicated line-checking step, quickly and reliably correct the sampling, and avoid the problem that the output voltage of the converter is opposite to the voltage of the incoming line due to the error voltage sampling direction.

(2) In the process of judging the polarity twice, the invention can also find the condition that the sampling polarities are not opposite or different due to the setting error of the sampling coefficient and the like.

Drawings

FIG. 1 is a block diagram of an in-phase power supply topology;

fig. 2 is a flow chart of a method for automatically correcting the polarity of the voltage on the series side of the in-phase power supply device.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings in conjunction with the following detailed description. It should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.

The invention provides a method for automatically correcting the voltage polarity of a series side of an in-phase power supply device, wherein the in-phase power supply device comprises a power cabinet, a starting cabinet, a T-base incoming line switch cabinet, a traction matching transformer and an outgoing line switch cabinet, which are shown in figure 1.

The power cabinet comprises n power units, one side of each power unit is connected in parallel, and the other side of each power unit is connected in series, and the serial side of each power unit is connected with the starting cabinet.

The starting cabinet comprises an output reactor L, a starting loop and a sampling PT in the starting cabinet. The other end of the starting cabinet is connected with the T-base incoming line switch cabinet.

The T-base incoming line switch cabinet comprises a series side breaker QF and a voltage sampling PT.

Furthermore, the power unit comprises a parallel side H bridge, a direct current bus capacitor and a series side H bridge, the parallel side is provided with a module grid-connected contactor KM3_ i (i is a power module serial number), the series side is provided with a bypass switch PLi (i is a power module serial number), and the series side H bridges of the plurality of power units are connected in series and then are connected to the starting cabinet.

Further, the starting cabinet comprises an output reactor L which is used for limiting the rapid change of current and filtering higher-order voltage harmonics. The starting circuit of the starting cabinet comprises a soft start contactor KM1, a soft start resistor and a main contactor KM2, the soft start contactor KM2 is used for limiting the charging current of a power unit through a soft start resistor and the soft start contactor KM1, the main contactor is connected with the soft start contactor KM1 and the soft start resistor which are connected in series in parallel, the soft start resistor is bypassed, and the purposes of avoiding energy consumption and voltage drop of the soft start resistor during operation are achieved.

In order to realize the purpose of automatic correction of the sampling polarity of the T-seat voltage, in combination with FIG. 2, the method of the invention comprises the following steps:

(1) the in-phase power supply device is pre-charged through the circuit breaker at the series side of the T-base incoming line switch cabinet and the incoming line of the starting circuit of the starting cabinet; during pre-charging, a voltage sampling signal from a T-base incoming line switch cabinet PT and a voltage signal from a start-up in-cabinet PT are collected simultaneously. And if the two voltage sampling directions are the same, recording the first mark 1 as invalid, otherwise, recording the first mark as valid.

Further, the pre-charging process comprises the steps of firstly closing the soft start contactor KM1 of the starting circuit in the starting cabinet, then closing the breaker QF in the T-base incoming line switch cabinet, when the charging of the direct current bus capacitor of the power unit reaches a set value, closing the main contactor KM2 of the starting circuit, and then opening the soft start contactor KM 1.

Further, comparing the sampling directions of the two voltages, the method is to make a difference between the sampling real-time values of the two locations and judge the effective value of the difference value of the two voltages, if the effective value of the difference value is small, the voltage sampling directions are considered to be the same, the setting flag1 is 0 (invalid), if the effective value of the difference value is large, the voltage sampling directions are considered to be opposite, and the setting flag1 is 1 (valid).

Defining the per unit value of PT sampling instantaneous voltage of T-seat incoming line switch cabinet as u_TPT sampling instantaneous voltage per unit value of u in starting cabinet_Q. When the T-base incoming line switch cabinet breaker is switched on, the main loop is connected, so that the amplitude of the voltage acquired by the two PTs is the same, and the phases are the same or opposite. Judging whether the directions of two sampling points are consistent, using a per-unit instantaneous value subtraction method to judge, and defining the instantaneous difference value delta u-u of two voltage sampling points_T-u_QIf the effective value of Δ U is Δ U_RMSIf the effective value of Δ u is greater than 1.6pu, FLAG1 is set to be invalid (1), and if the effective value of Δ u is between the two FLAGs, FLAG1 is set to be invalid (0) if the effective value of Δ u is greater than 1.6puMeanwhile, the PT or the sampling circuit or the gain of sampling is set to be wrong, and the machine is stopped due to fault alarm.

If a fail-down condition has not occurred, then step (2) continues.

In the pre-charging stage, the method not only completes the task of charging the direct-current bus of the power unit, but also compares the voltage directions of the T-base incoming line switch cabinet PT and the start cabinet PT when the main loop is communicated. This comparison is to record the difference in sampling direction when the same primary voltage is acquired by the PTs at the two locations.

(2) And disconnecting a circuit breaker on the series side in the T-base incoming line switch cabinet after the pre-charging is finished, generating a modulation wave according to a phase angle of a voltage sampling signal of a PT (potential transformer) of the T-base incoming line switch cabinet, and outputting open-loop voltage on the series side.

Further, the output open-loop voltage is the phase angle of a voltage phase lock sampled by using a T-base incoming line switch cabinet PT, the phase angle is used as the phase of an open-loop modulation wave, the amplitude value can be set, and a default 50% modulation degree is provided.

The circuit breaker of the series side in the disconnection T seat inlet wire cubical switchboard after the precharge, main contactor in the start cabinet keeps the combined floodgate state, and at this moment, T seat inlet wire cubical switchboard and start cabinet owner return circuit disconnection, the PT of start cabinet and the PT in the inlet wire cubical switchboard do not have the relevance.

PT voltage sampling u of T-base incoming line switch cabinet used in control_TPhase-locked using phase angle omega of phase-locked T-base voltage_Tt in u_mod＝U_opensin(ω_Tt) given as an open-loop modulation wave, where U_openAnd for the settable open-loop modulation degree, the open-loop pulse is generated by using the DC voltage pre-charged by the DC bus capacitor, and the voltage is output at the serial port.

The start-up cabinet PT is used to sample the voltage signal output when the open loop is pulsed. The voltage for starting the PT sampling of the cabinet during the pulse generation of the open loop is defined as u_{Q_open}To u, to u_{Q_open}Phase locking is carried out to obtain a phase angle omega_Qot。

(3) And comparing whether the phase of the open-loop voltage acquired by the starting cabinet PT is opposite to the direction of the PT signal of the T-seat incoming line switch cabinet. If the direction is the same, the second flag2 is recorded as invalid, otherwise it is valid.

When the open-loop voltage is output, because the actual values of the two voltages are different, the phase position cannot be judged by using a mode of calculating an effective value by making a difference. The phase locking is carried out on the PT sampling voltage of the starting cabinet, the phase locking angle of the PT sampling voltage of the starting cabinet and the phase locking angle of the sampling voltage of the PT base incoming line switch cabinet are differentiated, if the difference value is very small, the second setting mark 2 is 0 (invalid), and if the difference value is close to 180 degrees, the second setting mark 2 is 1 (valid).

During the period of outputting the open-loop voltage, because the open-loop voltage at the serial side is not equal to the voltage amplitude of the switch cabinet, the effective value of the voltage difference value can not be used as a basis. During the period, the voltage sampling direction is judged according to the phase angle difference of two voltage samples. If the phase angle difference is around 0 degrees, the sampling direction is considered to be the same, and if around 180 degrees, the direction is considered to be opposite. Because the range of the phase angle difference delta theta is +/-2 pi, an absolute value | delta theta | is firstly calculated, and the range is limited to be 0 to +2 pi; if the angle is greater than π, θ_FLAG22 pi-i Δ θ i, if the range is limited to 0 to pi, the angle difference θ is finally judged_FLAG2It is convenient to judge whether to approach pi or 0. If the angle difference is not close to 0 or pi, other faults are considered to occur, and shutdown inspection is needed.

In one embodiment, the phase angle ω of the voltage (T-base voltage) of the T-base incoming line switch cabinet obtained by sampling the PT voltage of the T-base incoming line switch cabinet_Tt and open loop pulse starting cabinet voltage phase angle omega_Qot is subtracted and the absolute value is taken: i Δ θ ═ ω_Tt-ω_QoThe difference range is translated to a range of 0 to 2 pi. If | Δ θ | is greater than π, the reprocessing is done to process the angular difference to be in the range of 0 to π. Theta_FLAG2Is less thanJudging that the open-loop voltage of the starting cabinet is in phase with the voltage of the T seat, and setting a set FLAG 2(FLAG2) as invalid; if the difference, θ_FLAG2Is greater thanThen the judgment is that the starting cabinet open loop voltage is consideredSetting a second FLAG 2(FLAG2) to be effective in a reverse phase of the T seat voltage; if the phase angle difference value is between the two, the problem is considered to occur in the output pulse or sampling link, and the machine is shut down by reporting the fault.

After the pre-charging is finished, the T-seat incoming line switch circuit breaker is disconnected, open-loop modulation waves are output by using a phase-locked angle of PT voltage sampling of the T-seat incoming line switch cabinet, and open-loop voltage output by a PT sampling series side of the cabinet is started. And comparing the voltage sampling direction of the current starting cabinet PT with the voltage sampling direction of the incoming line switch cabinet PT. This comparison is to determine the relationship between the output voltage on the series side and the switchgear voltage when the signal from the switchgear PT is used directly for control.

(4) If the first mark 1 and the second mark 2 are valid and invalid, the signal of the sampling PT of the T-base switch cabinet needs to be inverted as a signal used for actual control. Otherwise, the voltage sampling polarity does not need to be corrected.

Further, the first flag1 and the second flag2 obtained in steps 1 and 3 are subjected to exclusive or operation, if the exclusive or result 1 is valid, it is considered that the incoming cabinet PT sampling voltage is directly used for control, a voltage opposite to the incoming cabinet phase is output, and a signal of the T-base incoming switch cabinet voltage sampling PT needs to be inverted and used as a signal for actual control. If the exclusive or result is 0 (invalid), the signal of the voltage sampling PT of the T-seat incoming line switch cabinet can be directly used for control.

If no fault occurs, judging whether the FLAG 1(FLAG1) and the FLAG 2(FLAG2) are not uniform to be valid or not, namely performing exclusive-or operation, and defining the operation result as FLAG 3:

if FLAG3 is 0, there is no problem in using the voltage sampling signal of the switch cabinet PT as control; if FLAG3 is 1, PT voltage acquisition signal u of the incoming line switch cabinet is required_TMultiplied by (-1) and used as a signal for control.

In summary, the present invention provides an automatic calibration method for sampling polarity of voltage at the in-phase power supply serial side. The method operates the in-phase power supply device to carry out the processes of pre-charging and outputting open-loop voltage, automatically corrects the polarity of the PT voltage sampling signal of the inlet wire switch cabinet according to the PT voltage sampling signals of the starting cabinet and the inlet wire switch cabinet, uses the voltage after the polarity in the control process, ensures that the voltage polarity output by the series side of the in-phase power supply device is matched with the voltage (T seat voltage) of the inlet wire switch cabinet, and avoids the overcurrent problem caused by the fact that the output voltage of a converter is opposite to the inlet wire voltage. The invention provides a method for judging sampling directions in a pre-charging stage and an open-loop voltage output process in the process of automatically correcting the sampling polarity of a voltage on a serial side. During the in-phase power supply unit is precharged, because the sampled voltages are equal in size, the effective value of the sampled voltage instantaneous values of the start cabinet and the incoming line switch cabinet PT can be obtained after the difference is made, and whether the two sampling directions are consistent or not can be judged according to the effective value. The method is simple and effective. If the effective value of the difference value is very small, the two sampling directions are consistent; if the effective value of the difference value is near 2 times of the rated value, the sampling directions of the two positions are considered to be opposite; if the difference effective value does not meet the two conditions, the sampling or other faults are considered to occur, and the machine needs to be stopped to search for problems. And during the period of outputting the open-loop voltage, judging the voltage sampling direction according to the phase-locked phase angle difference between the open-loop voltage of the starting cabinet and the voltage of the incoming line switch cabinet. This method is suitable for the situation that the voltage amplitudes at two positions in the process of outputting the open-loop voltage are not consistent. If the angle difference is near 0 degree, the directions of the two voltage signals are consistent; if the angle difference is about 180 degrees, the two voltage signals are opposite in direction; if the angle difference does not meet the two conditions, the sampling or other faults are considered to occur, and the machine needs to be stopped to search for problems.

It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modification, equivalent replacement, improvement and the like made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. Further, it is intended that the appended claims cover all such variations and modifications as fall within the scope and boundaries of the appended claims or the equivalents of such scope and boundaries.