CN111624457A - Simulation test method for thyristor module action characteristics - Google Patents

Abstract

The invention relates to a power electronic technology, in particular to a simulation test method for the action characteristics of a thyristor module, which is used for providing a set of simulation power supply and corresponding load for the thyristor module in order to simulate the working condition of the thyristor module in a hybrid OLTC (online stability test). The power supply adopts two-state hysteresis control, and output current provides voltage support through a capacitor C and is applied to the gun model and the thyristor module. The test method adopts a current source controlled by two-state hysteresis current to obtain good current waveform output, and the harmonic content of the output current is small; fault signals pass through the photoelectric coupler, so that the analog circuit and the control circuit are isolated, and the anti-interference capability of the control circuit is enhanced; the scheme has the advantages of reasonable and detailed design, convenient operation, good effect, high efficiency and low cost.

Description

Simulation test method for thyristor module action characteristics

Technical Field

The invention belongs to the technical field of power electronics, and particularly relates to a simulation test method for the action characteristics of a thyristor module.

Background

Deep experimental research is carried out on the characteristics of triggering and arc extinguishing of the thyristor module of the hybrid OLTC, the mode of adopting the switch integral test is obviously uneconomical, on one hand, the test point arrangement in the test is difficult, and on the other hand, the test power supply has great dependence. Therefore, research on simulation test methods of the thyristor module is required.

Disclosure of Invention

The invention aims to provide a simulation test method for the action characteristics of a thyristor module.

In order to achieve the purpose, the invention adopts the technical scheme that: a simulation experiment method for the action characteristics of a thyristor module comprises the following steps:

step 1, a power supply is controlled by adopting a two-state hysteresis loop, and output current provides voltage support through a capacitor C and is applied to a gun model and a thyristor module;

step 2, designing a simulation test loop;

2.1, a main circuit adopts an AC-DC-AC circuit structure, a rectifying circuit adopts a three-phase full-wave rectifying circuit, an inverter circuit adopts a single-phase full-bridge inverter circuit, a plurality of IGBTs are selected to be connected in parallel by a switch device, and a pre-charging circuit is arranged;

step 2.2, the control circuit adopts a two-state hysteresis current control mode, and the protection circuit comprises overcurrent, overvoltage and overheat protection and current limiting circuits in a PEBB module of a power supply;

step 3, the electromagnetic compatibility technology and measures comprise: the circuit and the device are adopted to suppress voltage spikes, the filtering and reasonable wiring are adopted to resist interference, and the shielding and grounding mode is adopted to prevent magnetic circuit coupling.

In the above simulation experiment method for the thyristor module operation characteristics, the design of the main circuit specifically includes: after the three-phase power supply is input, the three-phase power supply is connected with a three-phase isolation transformer through a three-phase isolation switch and then connected with a three-phase air switch, and the air switch is controlled by a control circuit; after the air switch, the direct current is obtained through a three-phase full-wave rectifying circuit consisting of rectifying diodes D1-D6, filtered by a first capacitor and a first inductor and then generated into single-phase alternating current output through a full-bridge inverter circuit consisting of IGBTs 1-4;

step 2.1.1, selecting a three-phase isolating switch: the three-phase isolating switch is arranged at the access end of the three-phase power supply and is used for controlling the power supply of the device;

step 2.1.2, selecting a rectifier diode according to the actual condition of the voltage of the power grid;

step 2.1.3, selecting a power switch device: selecting a PEBB module SKM400GAL12T4 produced by Semikron as a power switch device, and forming a single-phase full-bridge inverter circuit by connecting a plurality of PEBB modules in parallel to form a bridge arm;

2.1.4, selecting a single-phase alternating current filter by an alternating current side filter circuit, and calculating the value of the element parameter of the alternating current filter to be an equivalent value of star connection;

a. the filter capacitance calculation formula is as follows:

wherein C is a filter capacitor, f is a cut-off frequency, and L is a series inductor;

b. the inductor design during current fast tracking is met; considering a current tracking transient process in a PWM switching period Ts near a current zero crossing wt-0, under a steady state condition, considering that a requirement of current fast tracking is met, when a maximum current change rate is obtained:

wherein L is a series inductor, v_dcIs the magnitude of the DC voltage source voltage, I_mIs the maximum current value, and omega is the angular frequency of the system;

c. designing an inductor when harmonic current is suppressed; considering the current tracking transient in one PWM switching period Ts around the current peak wt ═ p/2, under steady state conditions:

wherein L is a series inductor, v_dcIs the magnitude of the DC voltage source, E_mIs the peak voltage of the AC voltage source, T_sFor one PWM switching period, Δ i_maxThe current is the maximum value of the current variation;

step 2.1.5, selecting an inductance and a capacitance at the direct current side;

a. the filter inductor L is selected to ensure the continuity of the current and simultaneously consider the current ripple requirement;

wherein L is a filter inductor and U_dcIs the magnitude of the DC voltage source voltage, f_sIs the system frequency, r_iIs a resistance value, I_dcIs direct current, d is duty cycle;

b. the capacity of the filter capacitor C is determined according to the requirement of the filter capacitor C on the output voltage ripple, and the capacity value of the capacitor C is as follows:

wherein C is a battery side output filter capacitor, U_dcIs the voltage of DC voltage source, L is filter inductor, f_sIs the system frequency, Δ U_dcD is the voltage variation of the direct-current voltage source, and D is the voltage duty ratio;

and 2.1.6, the pre-charging circuit comprises an alternating current contactor, a first current-limiting resistor and a second current-limiting resistor.

In the above simulation experiment method for the operation characteristics of the thyristor module, the design of the control circuit includes:

2.2.1, the main controller adopts TMS320F series DSP of TI company to realize the output control of system voltage and current; the FPGA is EP1C6Q240I7 of a cylon series of Altera company, and realizes PWM waveform phase shift, protection signal processing, state signal acquisition and external IO control of a DC/DC module;

step 2.2.2, designing a power supply circuit and a power supply monitoring circuit; the power supply circuit adopts a dual power supply chip TPS73HD301 of TI company to supply power for the DSP; the power supply monitoring circuit adopts a TPS3823 chip to realize DSP reset and power supply voltage monitoring;

2.2.3, adopting an RS232 communication circuit as a communication circuit; the RXD, the TXD and the GND realize a serial communication function, the DSP signal input and output end converts the 3.3VTTL level into a 5VCOM level through a level conversion chip MAX3221E, and is connected with an upper computer communication port through a DB port; the second inductor, the third inductor, the second capacitor and the third capacitor are adopted to realize the filtering and jitter elimination of signals; the electrostatic discharge protection device ESDA14V2L limits the electrostatic overvoltage;

step 2.2.4, a voltage and current sampling circuit; respectively selecting a space wave Hall voltage sensor and a space wave Hall current sensor to measure voltage and current signals of each path;

2.2.5, adopting a linear optical coupling isolation circuit for optical coupling isolation to isolate the signal sampling circuit and the control circuit;

step 2.2.6, designing a driving circuit; the PWM output is boosted through a level conversion chip SN74LVC2T45 and is sent to an HCPL-2630 optical coupling isolation chip after passing through a third current limiting resistor; PWM is input into a SG2626M high-speed driving chip after passing through the optical coupling isolation chip;

step 2.2.7, designing a protection circuit; the pull-up resistor at the input end inputs current at the positive time of the input end, so that the driving capability of an input signal is enhanced; the fourth capacitor at the input end plays a role in voltage stabilization; the fault signal passes through the photoelectric coupler TLP521 and then is sent to the two-way schmidt trigger buffer SN74LVC2G17 through the fourth current limiting resistor, the pull-down resistor plays a role in limiting current, and the fifth capacitor plays a role in stabilizing voltage.

The invention has the beneficial effects that: 1. the current source controlled by the two-state hysteresis current can obtain good current waveform output, and the harmonic content of the output current is smaller; 2. fault signals pass through the photoelectric coupler, so that the analog circuit and the control circuit are isolated, and the anti-interference capability of the control circuit is enhanced; 3. the scheme has the advantages of reasonable and detailed design, convenient operation, good effect, high efficiency and low cost.

Drawings

FIG. 1 is a schematic diagram of a simulation test loop according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a main circuit topology of a hysteresis control current according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of the main circuit of one embodiment of the present invention;

FIG. 4 is a schematic diagram of a control circuit according to an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of a PEBB module according to an embodiment of the present invention;

FIG. 6 is an equivalent circuit of an SKM400GAL12T4 module according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of an AC-side filter according to an embodiment of the present invention;

FIG. 8 is a diagram illustrating a precharge circuit according to an embodiment of the present invention;

FIG. 9 is a schematic diagram of a circuit structure of a dual power supply chip according to an embodiment of the invention;

FIG. 10 is a schematic diagram of a power monitoring circuit according to an embodiment of the present invention;

FIG. 11 is a schematic diagram of an RS232 communication circuit according to an embodiment of the invention;

FIG. 12(a) is a schematic diagram of a voltage sampling circuit according to an embodiment of the present invention;

FIG. 12(b) is a schematic diagram of a current sampling circuit according to an embodiment of the present invention;

FIG. 13 is a schematic diagram of a linear optocoupler isolation circuit according to an embodiment of the invention;

FIG. 14 is a diagram illustrating a driving circuit according to an embodiment of the present invention;

fig. 15 is a schematic structural diagram of a protection circuit of a control system according to an embodiment of the present invention.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

In order to simulate the working condition of the thyristor module in the hybrid OLTC, a set of simulation power supply and corresponding load need to be provided for the thyristor module, and in consideration of the power supply voltage and capacity requirements for carrying out tests, the embodiment provides a hysteresis control current source, which is matched with a capacitor to provide voltage and current for the thyristor module in the switching process. The power supply adopts two-state hysteresis control, and output current provides voltage support through a capacitor C and is applied to the gun model and the thyristor module.

In the present embodiment, as shown in fig. 1, in a simulation test loop of the action characteristics of a thyristor module, a power supply adopts two-state hysteresis control, and an output current provides voltage support through a capacitor C and is applied to a gun model and the thyristor module.

A two-state hysteresis control principle; the working principle of hysteresis current two-state control is as follows: subtracting the inductive current from the current reference (voltage error signal) to obtain a current error signal i_e，i_eAnd then a PWM signal is obtained through a hysteresis comparator, and the current of the inductor is controlled within a set positive and negative ring width (+/-h) through an isolation amplification driving power tube. When i is shown in FIG. 2_eWhen the output voltage is larger than the positive ring width (+ h), the output voltage of the hysteresis comparator is low level u_AB＝-u_dcThe inverter bridge outputs a-1 state, and the inductive current is reduced; when i is_eWhen the output voltage is lower than the negative ring width (-h), the hysteresis comparator outputs a high level u_AB＝u_dcInverter outputs +1 state, inductor current rises, thereby holding i_aIs always limited in the width of the positive ring and the negative ring. Wherein: h is the width of the hysteresis loop, delta I is the variation of the inductance current, T is the control period of the hysteresis loop, T is₁Is the current rise time.

Controlling two-state hysteresis current; when the circuit works in the +1 state, the switching tubes S1 and S4 are turned on, the switching tubes S2 and S3 are turned off, and the circuit is in the +1 state, where the circuit equation is as follows:

wherein u is_dcIs the voltage of the DC voltage source, L is the inductance value,

is the instantaneous rate of change of the inductor current, R is the magnitude of the resistance value, i_LIs the current flowing through the inductor.

When the switching tube S1, S4 is turned off and the switching tube S2, S3 is turned on in the-1 state, the circuit equation can be obtained as follows:

u_dcis the voltage of the DC voltage source, L is the inductance value,

is the instantaneous rate of change of the inductor current, R is the resistance value, i_LIs the current flowing through the inductor.

Determining key parameters; the analysis is carried out by taking the controllable current source to output sine wave current as an example:

wherein I is a controllable current source outputting sine wave current, I_NIs a rated current value.

The current source output current change rate can be obtained as follows:

wherein k is_iThe current change rate is output for the current source, I is the current output current of the current source, omega is the angular frequency of the system, I_NIs a rated current value.

The maximum value of the rate of change of the current is obtained according to the formula:

wherein k is_imaxThe maximum value of the current change rate is output by the current source, omega is the angular frequency of the system, I_NIs a rated current value.

According to the current change rate in the actual circuit, the current change rate is as follows:

where k is the rate of change of current in the actual circuit,

is the instantaneous rate of change of the inductor current, u_dcIs the voltage of the DC voltage source, L is the inductance, R is the resistance, i_LIs the current flowing through the inductor.

To ensure good current tracking performance, it is necessary to require that the actual current change rate be greater than the change rate of the required output current, i.e.:

wherein u is_dcIs the voltage of the DC voltage source, L is the inductance, R is the resistance, i_LIs the current flowing through the inductor, omega is the angular frequency of the system, I_NIs a rated current value.

Generally, the current change rate is small when the output current is close to the peak value, that is, as long as the requirement is met at the peak value, the requirement can be met in the whole period, and the inductance parameter can be obtained:

wherein L is an inductance value, u_dcIs the voltage of the DC voltage source, R is the resistance value, i_LIs the current flowing through the inductor, omega is the angular frequency of the system, I_NIs a rated current value.

Because of the limitation of hysteresis loop current control switching frequency, there are:

wherein, Δ t is a certain time interval in the control process of the hysteresis current, L is an inductance value, Δ i is a variation of the inductance current, u_dcIs the voltage of the DC voltage source, R is the resistance value, i_LFor the current flowing through the inductor, T_maxThe longest period is controlled for the hysteresis current.

Another constraint can be found, namely:

L＞T_min(u_dc-Ri_L)/(2Δi) (8)

wherein L is inductance value, T_minFor controlling the minimum period of hysteresis current u_dcIs the voltage of the DC voltage source, R is the resistance value, i_LΔ i is the amount of change in the inductor current.

According to the formulas (6) and (8), the main parameters (frequency 50Hz, direct side current U) of the hysteresis current source are combined_dc530V, load Z1.5 Ω, I_N300A, maximum switching frequency 6kHz) may determine the leakage reactance parameter range of the isolation transformer of the current source, and finally L is 0.6 mH.

Simulating a simulation test loop and determining main loop parameters; and (3) building a simulation model of the hysteresis control current source in a Simulink environment.

The technical parameters of the main loop are as follows: (1) rated capacity: 120 kVA; (2) rated output voltage: 0-400V; (3) output frequency: 50 Hz; (4) outputting a waveform: a standard sine wave; (5) rated output current: 300A; (6) maximum switching frequency: 6 kHz; (7) leakage inductance of the isolation transformer: 0.6 mH; (8) a capacitor: 1190 uF/450V; (9) overload capacity: can bear short-time impact current 600A; (10) the output and the input are electrically isolated, and the overvoltage and current protection device for instantaneously cutting off the output current is provided.

Simulation results show that the current source controlled by the two-state hysteresis current can obtain good current waveform output, the harmonic content of the output current is small, but the simulation link cannot consider the time response influence of an actual control circuit, so that a good hysteresis tracking control effect can be ensured.

The design of the simulation test loop is as follows;

(1) main circuit

1) Circuit structure

The circuit structure needs to adopt an AC-DC-AC scheme according to the parameter requirements of the variable frequency power supply. After the three-phase alternating current input is rectified by a diode and filtered by a large capacitor, the average value of the rectified voltage is 1.3-1.35 times of the line voltage. The inversion adopts a single-phase full-bridge inverter circuit structure. The input voltage is 380V, and the effective value of the fundamental voltage output by the inverter bridge is 530V.

2) Switching device

Because the maximum direct-current voltage 530V of the bus of the inverter bridge, considering the additional voltage and the required safety margin caused by line inductance and the like, a switching device with the rated voltage of 1200V can be selected.

According to the rated power of 120kW, the output voltage of 400V,

the current is calculated.

Rated value of output current of I_outOutput current amplitude 375A

According to the current amplitude during overload, considering additional current caused by impact load, a buffer circuit and the like and a safety factor, a plurality of IGBTs need to be selected to be connected in parallel.

3) Pre-charging circuit

After rectification, the maximum voltage of 530V can be obtained on the direct current side, and because the direct current side needs to be connected with a bus capacitor and a filter capacitor, in order to prevent instantaneous current impact caused by charging of a large-capacity capacitor at the moment of power-on, the capacitor needs to be pre-charged before the rectification module is powered on.

4) Principle of operation of main circuit

As shown in fig. 3, after the three-phase power is input, the three-phase power passes through the three-phase isolation switch, and is connected with the three-phase isolation transformer, and then is connected with the three-phase air switch, and the air switch is controlled by the control circuit. After the air switch comes out, direct current is obtained through a three-phase full-wave rectifying circuit composed of D1-D6, and after the direct current is filtered through a first capacitor and a first inductor, a full-bridge inverter circuit composed of IGBTs 1-4 generates single-phase alternating current to be output.

(2) Control circuit

1) Control mode

A two-state hysteresis current control mode is adopted.

2) Protective circuit

The switch device of the power supply adopts an integrated PEBB module, the interior of the power supply comprises complete overcurrent, overvoltage and overheat protection, and the signal can be sent to the control chip while the device is protected. In addition to this, to prevent the load from short-circuiting and damaging the power supply, current limiting measures are taken, and if the fault time exceeds 2s, the control pulse of the switching device is turned off to protect the device.

3) Control circuit schematic diagram

As shown in fig. 4, the main controller is a TMS320F series DSP of TI company, which implements system voltage and current output control; the FPGA is EP1C6Q240I7 of a cylon series of Altera corporation, and mainly realizes the functions of PWM waveform phase shift, protection signal processing, state signal acquisition, external IO control and the like of a DC/DC module.

The DSP establishes two-way communication with the upper computer through the RS232, and can set the working state and working parameters of the system and receive system feedback information through the upper computer in real time; the DSP is internally provided with 16 AD conversion channels for sampling voltage and current signals of the converter analog circuit, the sampling signals are processed to form feedback and compared with a system set value, the set value is a voltage value in a constant voltage mode of the converter, and the current value in a constant current mode of the converter. And feeding back and a result of PI operation of a given value to an event manager, changing the PWM output duty ratio, directly transmitting a PWM control signal of the AC/DC module to the PEBB driving circuit after the jitter elimination and deburring of the FPGA, and controlling the on-off action of the power tube. The active rectifier module PWM driving signal of the embodiment is generated by an event manager A; FGPA real-time acquisition system working state signal, and control the analog circuit switch action; when the PEBB module generates an overcurrent or overtemperature protection signal, the protection signal is firstly sent to the FPGA, a low-level trigger signal is generated after the protection signal is processed by the FPGA and sent to the DSP, the PDP is interrupted and triggered, and the DSP locks PWM output to play a role in protecting devices.

(3) Selection of main circuit elements

1) Three-phase isolating switch selection

A three-phase isolating switch is required to be arranged at the access end of the three-phase power supply and used for controlling the power supply of the device.

2) Rectifier diode selection

According to the actual condition of the power grid voltage, the fluctuation coefficient is 1.1, the safety factor alpha is 2, and the rated voltage of the diode is as follows:

wherein, U_RRMRated voltage of diode, U_INFor the rated voltage of the grid, α is a safety factor.

The input voltage of this embodiment is three-phase AC380V, so U_RRMThe voltage grade of the diode is more than or equal to 1182V, and is 1600V. And calculating the rated current of the diode by considering the impact current and the safety factor, wherein the rated current of the diode is 2000A.

3) Selection of power switches

The power device selects a power electronic function module (PEBB), the general PEBB consists of a power semiconductor device, a gate driving circuit, a level conversion circuit, a protection circuit, a sensor, a power supply and a passive device, the power device has the biggest characteristic of universality, and a plurality of PEBB can be cascaded through an energy interface and a communication interface to form a high-power and high-capacity power electronic system. The schematic diagram of the PEBB module is shown in fig. 5.

Considering that the rated voltage and the current of the variable frequency power supply designed by the embodiment are both relatively large and the working switching frequency is also relatively high, the IGBT module is considered to be selected as the main power device. In order to meet the requirement of the maximum voltage and current when the variable frequency power supply normally works and to reserve sufficient margin, in the embodiment, a PEBB module SKM400GAL12T4 produced by Semikron is selected as a power switch device, the module has a withstand voltage of 1200V and a rated current of 400A, and a single-phase full-bridge inverter circuit is formed by connecting a plurality of modules in parallel to form a bridge arm. The highest switching frequency of the module reaches 20kHz, and the requirement of the embodiment can be met. Fig. 6 shows an equivalent circuit diagram of the module.

4) AC side filter circuit design

The ac-side filter mainly functions to suppress ac harmonics, and is a single-phase ac filter schematic diagram in which the values of the computing elements are star-connected equivalent values, as shown in fig. 7. In the figure, the series inductor L is used to limit the peak-to-peak value of the ripple current, and the cut-off frequency f is first selected, and usually to meet the requirement of voltage harmonic distortion rate, the cut-off frequency is 10% of the PWM carrier frequency, and the formula is calculated according to the filter capacitor:

wherein C is a filter capacitor, f is a cut-off frequency, and L is a series inductor.

After the filter capacitor C is obtained, calculating the parameters of the high-pass filter element:

wherein L is_dampIs a high-pass filter inductance value, C_dampIs a high pass filter capacitance value, R_dampIs the high pass filter resistance value.

When the line has no obvious load or line harmonic, the three-phase damping resistance power is usually 0.1% of the rated power of the converter, the rated power of the converter is 120KW in this embodiment, and therefore the damping resistance is selected to be 120W.

The AC side inductor can filter the harmonic current at the AC side, so that the current at the AC side tends to a sine wave, the current waveform control is realized within a certain frequency band range, and the DC/AC module obtains certain damping characteristic, thereby being beneficial to the stable operation of a system.

Firstly, the inductor design meeting the requirement of current fast tracking is analyzed. Considering the current tracking transient in a PWM switching period Ts near the current zero crossing (wt ═ 0), and considering the need to meet the fast tracking of current under steady state conditions, when the maximum current change rate is obtained:

wherein L is a series inductor, v_dcIs the magnitude of the DC voltage source voltage, I_mIs the current maximum and ω is the system angular frequency.

And secondly, analyzing the design of the inductor when harmonic current is suppressed. Considering the current tracking transient in one PWM switching period Ts around the current peak (wt ═ p/2), under steady state conditions:

wherein L is a series inductor, v_dcIs the magnitude of the DC voltage source, E_mIs the peak voltage of the AC voltage source, T_sFor one PWM switching period, Δ i_maxAnd the current variation is the maximum value.

5) Selection of inductance and capacitance on DC side

(a) Selection of filter inductance

The current flowing through the filter inductor L cannot change abruptly, but can only rise or fall approximately linearly, and the fluctuation of the current becomes smoother as the inductance is larger, and becomes steeper as the inductance is smaller. If the inductance is too small, the inductor current will be discontinuous, so the selection of the inductor on the dc side should ensure the continuity of the current, and the current ripple requirement should be considered when selecting the inductor parameters.

Wherein L is a filter inductor and U_dcIs the magnitude of the DC voltage source voltage, f_sIs the system frequency, r_iIs a resistance value, I_dcD is the duty cycle.

(b) Selection of capacitance

The selection of the battery side output filter capacitor C is directly related to the output voltage ripple of the bidirectional energy storage converter DC/DC module, and in the design, the capacity of the filter capacitor C is mainly determined according to the requirement of the filter capacitor C on the output voltage ripple. Therefore, the capacity value of C:

wherein C is a battery side output filter capacitor, U_dcIs the voltage of DC voltage source, L is filter inductor, f_sIs the system frequency, Δ U_dcD is the voltage duty ratio of the dc voltage source.

6) Pre-charge circuit design

In order to prevent instantaneous current impact caused by charging of a large-capacity capacitor at the power-on time of the converter system, the capacitor needs to be precharged before the system is powered on, the converter system is powered on and the precharging alternating-current contactor is disconnected after the precharging is finished, the first and second current limiting resistors R1 and R2 play a role in current limiting, and a precharging circuit diagram is shown in FIG. 8.

(4) Control circuit design

1) Power supply circuit design

FIG. 9 is a circuit diagram of a DSP dual power supply chip, and the system selects a dual power supply chip TPS73HD301 of TI company to supply power for DSP. Because the DSP needs to be powered on by 3.3V and 1.9V according to a certain time sequence to ensure that each module of the system is normally started, the power supply system firstly powers on all the pins of the 3.3V power supply and then is connected with the core power supply of the 1.9V chip. In the figure, Vout2 outputs 3.3V of stable voltage, Vout1 outputs 1.2-9.75V of adjustable voltage, and the output voltage can be controlled by the configuration of resistors R1 and R2.

Fig. 10 shows a system power supply monitoring circuit, and the TPS3823 chip mainly implements DSP reset and power supply voltage monitoring functions. The DSP reset pin samples the power supply voltage through the resistor R, and triggers the DSP chip to reset if the power supply voltage is too small, and in addition, the DSP reset can also be realized through a manual reset switch; the WDI pin of the chip generates a watchdog reset signal periodically, and if the chip does not output a trigger signal within the timeout time of the watchdog circuit, the DSP is reset.

2) Communication circuit design

Fig. 11 is a communication circuit design of the control circuit. To complete the most basic serial communication function, only three pins of RXD, TXD and GND are needed, and the DSP signal input and output end converts the 3.3VTTL level into the 5VCOM level through the level conversion chip MAX3221E and is connected with an upper computer communication port through a DB port. In the figure, the second inductor L1, the third inductor L2, the second capacitor C1 and the third capacitor C2 realize the filtering and jitter elimination of signals and prevent interference signals from being connected in series; the ESDA14V2L is an electrostatic discharge protection device, and limits electrostatic overvoltage, thereby ensuring the reliability of communication.

3) Voltage and current sampling circuit

Fig. 12(a) shows a voltage sampling circuit, and fig. 12(b) shows a current sampling circuit. And a space wave Hall voltage sensor and a space wave Hall current sensor are respectively selected to measure voltage and current signals of each path.

4) Optical coupling isolation circuit

Fig. 13 is a linear opto-isolator circuit. The optical coupling isolation circuit is used for isolating the signal sampling circuit and the control circuit and preventing noise in the sampling circuit from interfering with the acquisition of the control system. The sampling voltage flows through the conditioning circuit and then outputs 0-3V voltage to an input end Vin of the isolation circuit, and the sampling voltage is isolated by the optical coupler and then outputs voltage Vout.

5) Drive circuit design

Fig. 14 is a driving circuit. The system control system is constructed based on a DSP and an FPGA, a PWM signal sent by the DSP is subjected to jitter elimination and filtering processing by the FPGA, the PWM output processed by the FPGA is insufficient to drive a lower-level IGBT switching tube circuit, and the PWM needs to be subjected to power amplification by a power amplification circuit.

The PWM output is first boosted via a level shift chip SN74LVC2T45 (a dual-bit dual-power transceiver with configurable voltage shifts and 3-state outputs), as shown in the DIR as a direction control pin, with a high level configured in the input-output direction as shown. VccA is input end reference voltage, VccB is output end reference voltage, PWM output voltage is raised to about 5V, and the PWM output voltage is sent to the HCPL-2630 optical coupling isolation chip after passing through a third current limiting resistor. The optocoupler mainly plays a role in isolating the main loop from the control circuit in the circuit, prevents the control circuit from being influenced by the main loop, and increases the anti-interference capacity of the control circuit.

PWM is input into SG2626M high-speed drive chip after optical coupling isolation, and the chip maximum output voltage can reach 18V, and the maximum output peak current can reach 3A, and PWM can be directly driven the disconnection of IGBT switch tube after power amplification.

6) Protection circuit design

Fig. 15 is a control system protection circuit. The IGBT module outputs four paths of protection signals, namely an over-current protection signal and an over-temperature protection signal of three bridge arms. The four signals need to be processed and sent to the DSP. The fault signal passes through the photoelectric coupler TLP521, so as to isolate the analog circuit from the control circuit and enhance the anti-interference capability of the control circuit. The pull-up resistor at the input end inputs current at the positive time of the input end, so that the driving capability of an input signal is enhanced; the fourth capacitor at the input end plays a role in voltage stabilization. The fault signal is sent to the double-circuit Schmidt trigger buffer SN74LVC2G17 from the photoelectric coupler through the fourth current limiting resistor, the pull-down resistor plays a current limiting role, and the fifth capacitor plays a voltage stabilizing role.

(5) Electromagnetic compatibility techniques and measures

1) Controlled by circuits and devices

The occurrence of voltage spikes is easy to cause electromagnetic interference signals, and the suppression of the voltage spikes is one of the methods for suppressing noise sources. Measures for suppressing voltage spikes are many, and for example, by means of freewheeling with a parallel diode or by connecting an RC circuit, counter-electromotive force generated when an inductive load such as a relay or a coil in the circuit is interrupted can be suppressed. And surge absorbers, voltage dependent resistors, transient suppression diodes, etc. can suppress voltage spikes. To prevent interference signals from passing through the circuit, electrical isolation of the circuit may be performed in some circuits using photo-couplers, transformers, etc.

2) Filtering

Various power supplies in a switch mode are connected to a line, are not only subjected to various interferences in the line, but also are large interference sources, and can be transmitted to an alternating current power supply and a space in a conduction and radiation mode, so that not only is a power grid polluted, but also the work of communication equipment and electronic instruments can be influenced. The interference is mainly generated by the sharp rise and fall of the voltage and current on the devices such as a switching tube, a diode, an energy storage inductor, a transformer and the like of the power supply. This interference is usually overcome by means of line filters.

The filter is a circuit network consisting of a resistor, an inductor and a capacitor, and can separate noise superposed on a useful signal by utilizing the relation between the impedance and the frequency of the inductor and the capacitor. The interference signal is divided into differential mode interference and common mode interference according to different flow paths of the interference signal. The differential mode refers to a difference interference signal between two lines, and the common mode refers to an interference signal from the two lines to the shell ground. Differential mode filtering and common mode filtering are the blocking or absorption of the two signals, respectively. The differential mode filter capacitor is bridged between the line and the shell ground to bypass differential mode current, and the common mode filter capacitor is bridged between the line and the shell ground to bypass common mode current. The common mode choke and the differential mode inductance may also play a role in filtering. And the trap filter for the low-frequency differential mode interference is reasonable.

3) Shielding

Shielding refers to preventing noise intrusion through the absorption or emission of electromagnetic interference from various shielding objects or, conversely, confining radiated electromagnetic energy generated inside the device to prevent interference with other devices. The shield made of good conductor is suitable for electric field shielding, and the shield made of magnetic conductive material is suitable for magnetic field shielding. The shielding body is divided into an electromagnetic shielding body and an electrostatic shielding body, the electromagnetic shielding body is mainly used for inhibiting high-frequency switch interference, an electromagnetic field is utilized to generate eddy current in the shielding body to play a shielding role, the electromagnetic field and the electrostatic shielding body are made of the same material, and the electromagnetic field and the electrostatic shielding body are only effective when the electromagnetic field is grounded; the electromagnetic shield is effective for suppressing high-frequency electromagnetic interference even if it is not grounded, but the induction of interference voltage is increased due to the electrostatic coupling effect because the conductor is not grounded. So to prevent the magnetic circuit coupling, a material of high magnetic permeability is applied to isolate the relevant portions.

4) Wiring

Rational wiring is another method in anti-interference measures, and the type of the wire, the thickness of the wire diameter, the wiring mode, the distance between the wires, the symmetry of the wiring, the shielding method, the length of the wire, the bundling or twisting mode and the like all have direct influence on the coupling of the inductance, the resistance and the noise of the wire.

When wiring, the large-current positive and negative direct-current buses should be close to each other as much as possible so as to reduce the emission area of the strong magnetic field. The driving wire of each switch tube is preferably twisted independently to avoid the interference of the driving signals of other switch tubes, and if the driving signals of the same bridge arm interfere with each other, the circuit can generate the short-circuit fault of the bridge arm direct connection. If the connecting wire of the detection circuit passes through the strong magnetic field area, the wire should be stranded.

5) Ground connection

The grounding wires of all levels of circuits and structural members in the device need to be classified into a signal ground, a control ground, a power ground, a safety ground and the like according to the types, and the modes of one-point grounding, multi-point grounding or mixed grounding are determined according to the design target of specific equipment. To avoid ground loops, isolation techniques are also used, if necessary.

It should be understood that parts of the specification not set forth in detail are well within the prior art.

Although specific embodiments of the present invention have been described above with reference to the accompanying drawings, it will be appreciated by those skilled in the art that these are merely illustrative and that various changes or modifications may be made to these embodiments without departing from the principles and spirit of the invention. The scope of the invention is only limited by the appended claims.

Claims (3)

1. A simulation experiment method for the action characteristics of a thyristor module is characterized by comprising the following steps:

step 1, a power supply is controlled by adopting a two-state hysteresis loop, and output current provides voltage support through a capacitor C and is applied to a gun model and a thyristor module;

step 2, designing a simulation test loop;

2.1, a main circuit adopts an AC-DC-AC circuit structure, a rectifying circuit adopts a three-phase full-wave rectifying circuit, an inverter circuit adopts a single-phase full-bridge inverter circuit, a plurality of IGBTs are selected to be connected in parallel by a switch device, and a pre-charging circuit is arranged;

step 2.2, the control circuit adopts a two-state hysteresis current control mode, and the protection circuit comprises overcurrent, overvoltage and overheat protection and current limiting circuits in a PEBB module of a power supply;

step 3, the electromagnetic compatibility technology and measures comprise: the circuit and the device are adopted to suppress voltage spikes, the filtering and reasonable wiring are adopted to resist interference, and the shielding and grounding mode is adopted to prevent magnetic circuit coupling.

2. A simulation experiment method of an operation characteristic of a thyristor module according to claim 1, wherein the design of the main circuit specifically comprises: after the three-phase power supply is input, the three-phase power supply is connected with a three-phase isolation transformer through a three-phase isolation switch and then connected with a three-phase air switch, and the air switch is controlled by a control circuit; after the air switch, the direct current is obtained through a three-phase full-wave rectifying circuit consisting of rectifying diodes D1-D6, filtered by a first capacitor and a first inductor and then generated into single-phase alternating current output through a full-bridge inverter circuit consisting of IGBTs 1-4;

step 2.1.1, selecting a three-phase isolating switch: the three-phase isolating switch is arranged at the access end of the three-phase power supply and is used for controlling the power supply of the device;

step 2.1.2, selecting a rectifier diode according to the actual condition of the voltage of the power grid;

step 2.1.3, selecting a power switch device: selecting a PEBB module SKM400GAL12T4 produced by Semikron as a power switch device, and forming a single-phase full-bridge inverter circuit by connecting a plurality of PEBB modules in parallel to form a bridge arm;

2.1.4, selecting a single-phase alternating current filter by an alternating current side filter circuit, and calculating the value of the element parameter of the alternating current filter to be an equivalent value of star connection;

a. the filter capacitance calculation formula is as follows:

wherein C is a filter capacitor, f is a cut-off frequency, and L is a series inductor;

b. the inductor design during current fast tracking is met; considering a current tracking transient process in a PWM switching period Ts near a current zero crossing wt-0, under a steady state condition, considering that a requirement of current fast tracking is met, when a maximum current change rate is obtained:

wherein L is a series inductor, v_dcIs the magnitude of the DC voltage source voltage, I_mIs the maximum current value, and omega is the angular frequency of the system;

c. designing an inductor when harmonic current is suppressed; considering the current tracking transient in one PWM switching period Ts around the current peak wt ═ p/2, under steady state conditions:

wherein L is a series inductor, v_dcIs the magnitude of the DC voltage source, E_mIs the peak voltage of the AC voltage source, T_sFor one PWM switching period, Δ i_maxThe current is the maximum value of the current variation;

step 2.1.5, selecting an inductance and a capacitance at the direct current side;

a. the filter inductor L is selected to ensure the continuity of the current and simultaneously consider the current ripple requirement;

wherein L is a filter inductor and U_dcIs the magnitude of the DC voltage source voltage, f_sIs the system frequency, r_iIs a resistance value, I_dcIs direct current, d is duty cycle;

b. the capacity of the filter capacitor C is determined according to the requirement of the filter capacitor C on the output voltage ripple, and the capacity value of the capacitor C is as follows:

wherein C is a battery side output filter capacitor, U_dcIs the voltage of DC voltage source, L is filter inductor, f_sIs the system frequency, Δ U_dcD is the voltage variation of the direct-current voltage source, and D is the voltage duty ratio;

and 2.1.6, the pre-charging circuit comprises an alternating current contactor, a first current-limiting resistor and a second current-limiting resistor.

3. The method for simulating an operation characteristic of a thyristor module according to claim 1, wherein the design of the control circuit comprises:

2.2.1, the main controller adopts TMS320F series DSP of TI company to realize the output control of system voltage and current; the FPGA is EP1C6Q240I7 of a cylon series of Altera company, and realizes PWM waveform phase shift, protection signal processing, state signal acquisition and external IO control of a DC/DC module;

step 2.2.2, designing a power supply circuit and a power supply monitoring circuit; the power supply circuit adopts a dual power supply chip TPS73HD301 of TI company to supply power for the DSP; the power supply monitoring circuit adopts a TPS3823 chip to realize DSP reset and power supply voltage monitoring;

2.2.3, adopting an RS232 communication circuit as a communication circuit; the RXD, the TXD and the GND realize a serial communication function, the DSP signal input and output end converts the 3.3VTTL level into a 5VCOM level through a level conversion chip MAX3221E, and is connected with an upper computer communication port through a DB port; the second inductor, the third inductor, the second capacitor and the third capacitor are adopted to realize the filtering and jitter elimination of signals; the electrostatic discharge protection device ESDA14V2L limits the electrostatic overvoltage;

step 2.2.4, a voltage and current sampling circuit; respectively selecting a space wave Hall voltage sensor and a space wave Hall current sensor to measure voltage and current signals of each path;

2.2.5, adopting a linear optical coupling isolation circuit for optical coupling isolation to isolate the signal sampling circuit and the control circuit;

step 2.2.6, designing a driving circuit; the PWM output is boosted through a level conversion chip SN74LVC2T45 and is sent to an HCPL-2630 optical coupling isolation chip after passing through a third current limiting resistor; PWM is input into a SG2626M high-speed driving chip after passing through the optical coupling isolation chip;

step 2.2.7, designing a protection circuit; the pull-up resistor at the input end inputs current at the positive time of the input end, so that the driving capability of an input signal is enhanced; the fourth capacitor at the input end plays a role in voltage stabilization; the fault signal passes through the photoelectric coupler TLP521 and then is sent to the two-way schmidt trigger buffer SN74LVC2G17 through the fourth current limiting resistor, the pull-down resistor plays a role in limiting current, and the fifth capacitor plays a role in stabilizing voltage.

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