CN105242139B - A kind of static frequency changer triggering state detection method - Google Patents

Abstract

The invention discloses a kind of static frequency changer triggering state detection method, when static frequency changer loop current reference value is more than startup threshold values, special time section after trigger pulse output, biphase current feature according to commutation is participated in judges the conducting state of IGCT, and using three-phase current relation as locking criterion, quick turn on thyristors state-detection is realized, while detectable current measurement circuit is abnormal.The Current Waveform Characteristics when present invention utilize commutation, can Quick static frequency changer IGCT open exception, current measurement circuit exception.The detection speed of this method is fast, can well adapt to the frequency conversion operating mode of static frequency changer pusher side current transformer, and operand is small, is easy to software realization.

Description

A trigger state detection method of static frequency converter

technical field

The invention relates to a method for detecting the trigger state of a static frequency converter.

Background technique

As shown in Figure 1 and Figure 2, as a self-controlled current source type synchronous motor variable frequency drive system, the static frequency converter uses phase-controlled thyristors as power components, and the reliable conduction and phase commutation of the thyristors are the working premise of the static frequency converter.

Failure of thyristor components, abnormality of the trigger circuit, failure of bridge commutation, etc. will lead to the failure of the static inverter system to work normally, and even cause consequences such as bridge arm through-through, over-current, and unit start-up failure. Therefore, fast and accurate detection of the conduction state of the thyristor is of great significance to the static frequency converter system.

In order to realize thyristor trigger state detection, the conventional method usually requires additional circuits, and does not consider the working condition of a static frequency converter with a wide range of output frequency.

Contents of the invention

The object of the present invention is to propose a trigger state detection method for a static frequency converter. The trigger state detection method for a static frequency converter is suitable for frequency conversion working conditions of a static frequency converter and can detect abnormality of a current measurement circuit at the same time.

The technical solution adopted by the present invention is: a method for detecting the trigger state of a static frequency converter. As shown in Figure 2, when the loop current reference value is greater than the threshold value I _{ref_min} , at the rising edge of the thyristor trigger pulse of the static frequency converter, the start-up time is t _μ The timer, t _μ is calculated according to formula ①, and the threshold I _{ref_min} can be set at a fixed value.

If the current of the thyristor is not greater than the threshold IT within the time _{t μ} , it is determined that the current waveform is abnormal. For common anode thyristors, if the time t _μ is not less than the threshold _-IT , it is determined that the current waveform is abnormal.

In order to prevent misjudgment caused by abnormality of the current measurement circuit (such as CT disconnection), when it is determined that the current waveform of the triggered thyristor is abnormal, the anti-misjudgment criterion described in formula ② is started:

In formula ②, i _n is the current of another phase that participates in the commutation, and i _m is the current value that does not participate in the commutation.

If the criterion of formula ② is met, it is considered that the triggered thyristor is abnormally conducted, and the action can be selected to alarm or trip by setting the value; otherwise, it is judged to be a fault in the current measurement circuit.

The beneficial effects of the invention are: by using the characteristics of the current waveform during phase commutation, it is possible to quickly judge the abnormal opening of the thyristor of the static frequency converter and the abnormality of the current measurement circuit. The detection speed of the method is fast, and it can better adapt to the frequency conversion working condition of the machine-side converter of the static frequency converter. The calculation amount is small, and it is easy to realize by software.

Description of drawings

Figure 1 shows the common topology of static inverters:

ICB is the input circuit breaker;

TLS is the input transformer;

DS is the output switch;

G is the dragged generator;

Ld is a smoothing reactor;

CLS is a 6-pulse grid-side thyristor converter;

CMS is a 6-pulse thyristor converter on the machine side;

PT1 is the grid-side voltage transformer group;

PT2 is the machine side voltage transformer group;

CT1 is the grid-side converter current transformer group;

CT2 is the current transformer group of the machine-side converter;

i _A , i _B , and i _C are the line currents of ABC three-phases respectively.

Figure 2 is the three-phase current waveform of the thyristor full-control bridge:

CP1, CP2, CP3, CP4, CP5, CP6 are 6 trigger pulses.

VT1, VT2, VT3, VT4, VT5, VT6 are 6 thyristors of the three-phase fully controlled bridge.

Fig. 3 is a schematic diagram of the principle of trigger pulse detection.

detailed description

Below in conjunction with accompanying drawing, describe this method in detail. Install current sensors on the three phases of the AC side of the static frequency converter converter bridge respectively. Taking the A-phase current value i _A as an example, as shown in FIG. 2 , when the loop current reference value is greater than the threshold value I _{ref_min} , the timer is started at the rising edge of the trigger pulse CP1 of the thyristor VT1 . If i _A >IT is not satisfied within the entire timing time _{t μ} , it is judged that the current waveform is abnormal, and _IT is the judgment threshold, and factors such as sampling zero drift have been considered during the setting. At the rising edge of the trigger pulse CP4 of the thyristor VT4, the timer is started, and if i _A <-IT is not satisfied within _{t μ} , it is determined that the current waveform is abnormal. Timing time t _μ can be calculated according to the common formula shown in formula ①:

In formula ①, α is the firing angle, I _d is the loop current value, L _c is the commutation inductance value, E is the commutation voltage amplitude, and ω _m is the angular frequency of the AC voltage. T _Δ is the margin time. Similar processing is done when the thyristors VT2, VT3, VT5, and VT6 are triggered.

In order to prevent misjudgment caused by the abnormality of the current measurement circuit, the following blocking criteria are added. As shown in Figure 3, when it is determined that the current waveform of the triggered thyristor is abnormal, the judgment described in formula ② is carried out:

If the criterion of formula ② is satisfied, it is considered that the triggered thyristor is abnormally conducted, and the action is an alarm or trip; otherwise, it is determined that the current measurement circuit is faulty.

The trigger state detection method of the static frequency converter proposed by the present invention utilizes the transient characteristics of the current waveform during the commutation period of the static frequency converter, and can quickly judge whether the thyristor has been reliably triggered and whether the current sensor is abnormal, the protection speed is faster, and the algorithm does not rely on Based on the frequency of the current fundamental wave, it can better adapt to the frequency conversion working condition of the static frequency converter, the calculation amount is small, and it is easy to realize by software.

Claims (4)

1. A kind of 1. static frequency changer triggering state detection method, it is characterized in that comprising the following steps：

   Sample the AC three-phase current of static frequency changer unsteady flow bridge；

   Judge whether static frequency changer loop current reference value is more than startup threshold values I_{ref_min}；If static frequency changer loop current Reference value is more than startup threshold values I_{ref_min}, then in the t using thyristor triggering impulse rising edge as starting_μIn time interval, according to ginseng Judge the conducting state of IGCT with the biphase current measured value of commutation：

   If the current amplitude for the phase that is triggered is respectively less than threshold values I_T, start formula 1. shown criterion；As 1. formula is set up, it is determined as IGCT Conducting is abnormal, otherwise it is assumed that current measurement circuit is abnormal；

   Formula 1. in, i_nParticipate in another phase current of commutation, i_mTo have neither part nor lot in the current value of commutation.
2. 2. static frequency changer triggering state detection method according to claim 1, it is characterized in that：Time interval t_μBy formula 2. Calculate：

   Formula 2. in, α is Trigger Angle, I_dFor loop current value, L_cFor commutation inductance value, E is commutation voltage amplitude, ω_mFor alternating current The angular frequency of pressure, T_ΔFor the allowance time.
3. 3. static frequency changer triggering state detection method according to claim 1, it is characterized in that：Threshold values I_{ref_min}By fixed Value is adjusted.
4. 4. static frequency changer triggering state detection method according to claim 1, it is characterized in that：Threshold values I_TIt is whole by definite value It is fixed.