CN105402152A - Device for cooling controlling of fans - Google Patents

Abstract

The invention relates to a device for fan cooling control, comprising: a temperature detection sensor, several fans, and a PLC module connected with the temperature detection sensor and suitable for controlling the operation of a corresponding number of fans and the corresponding speed of the fans according to the external temperature. The present invention uses the PLC module to replace the traditional relay circuit, which avoids the defects of cumbersome wiring and high relay failure rate; controls the number of fans and the number of rotations according to the temperature, and does not start the fan or a small number of fans in the winter when the temperature is low. The number of revolutions is slow, and in summer when the temperature is high, all the fans need to be started to dissipate heat and the number of revolutions should be increased according to the specific temperature, so the device saves a lot of electric energy and prolongs the life of the motor.

Description

A device for fan cooling control

This application is a divisional application of the invention patent application with the application number: 201210370398.9, the invention name is "Fan Cooling Control Device and Its Working Method", and the application date is: September 28, 2012.

technical field

The invention relates to a device for fan cooling control and a working method thereof.

Background technique

In the prior art, transformers with a voltage level of 110kV and below often use a cooling fan to cool the transformer, and the working condition of the cooling fan directly affects the load capacity of the transformer; and the fan cooling control device often fails, according to statistics , the failure of the fan cooling control device is mainly divided into control loop and component failure, and the main reason for the control loop failure is that the control component uses an electromagnetic relay. Poor capacity causes these components to be often burned and damaged, which affects the operation of the air-cooled system. Therefore, how to design a replacement electromagnetic relay to control the entire fan cooling control device is a technical problem in this field.

Contents of the invention

The technical problem to be solved by the present invention is to provide a control device suitable for detecting ambient temperature to control fan cooling.

In order to solve the above technical problems, the present invention provides a device for fan cooling control, including: a temperature detection sensor, a number of fans, connected to the temperature detection sensor and suitable for controlling the corresponding number of fans according to the external temperature and The PLC module of the corresponding speed of the fan.

Furthermore, because the motor is an inductive load, it will increase the reactive power of the grid during use and reduce the power factor. Therefore, it is necessary to use chained SVG (static var generator, also known as Static synchronous compensator) control device to improve the power factor in the grid, so the device for fan cooling control also includes: a chained SVG control device suitable for correcting power factor, the chained SVG control device is connected to The input terminal of the three-phase power supply of the device for fan cooling control.

Further, in order to automatically bypass the failed H-bridge unit circuit, to ensure the normal operation of the H-bridge multi-connected multi-level inverter, so that the chained SVG control device can continue to achieve the purpose of correcting the power factor, the The chain-type SVG control device includes: H-bridge multi-connected multi-level inverter, automatic bypass circuit, sampling circuit, phase-splitting current independent control circuit and pulse width modulation circuit.

H-bridge multi-connected multi-level inverter, which is composed of three-phase H-bridge power modules connected to the three-phase power supply, wherein, at least one spare H-bridge unit circuit is added to each phase H-bridge power module ; The automatic bypass circuit is located at the output end of each H bridge unit circuit, and when an H bridge unit circuit is damaged, the H bridge unit circuit is bypassed; the sampling circuit is suitable for collecting the three-phase The instantaneous value of the voltage and current of the power supply; the phase-separated current independent control circuit, which is connected with the sampling circuit, is suitable for calculating the required voltage of the pulse width modulation circuit according to the instantaneous value of the voltage and current of the three-phase power supply The modulation ratio M and the phase angle δ of the sinusoidal modulation wave; the pulse width modulation circuit is connected with the independent control circuit of the split-phase current, and is used to control each H-bridge unit according to the modulation ratio M and the phase angle δ of the sinusoidal modulation wave The carrier triangular wave phase shifting SPWM used between the circuits is controlled; that is, after the damaged H bridge unit circuit is bypassed, the pulse width modulation circuit is suitable for changing the sampling period of the sampling circuit on the basis of keeping the sampling period unchanged. The carrier frequency of the carrier triangular wave phase-shifting SPWM of a phase H bridge power module where the damaged H bridge unit circuit is located, to obtain a carrier corresponding to the number of remaining H bridge unit circuits in the phase H bridge power module Triangular phase-shifted SPWM pulse modulation waveform.

Further, the phase-splitting current independent control circuit includes:

A phase-locked loop, tracking the voltage phase of the three-phase power supply according to the instantaneous value of the voltage of the three-phase power supply; a reactive current given module, adapted to calculate the voltage according to the voltage phase obtained by the phase-locked loop The cosine of the phase is multiplied by a reactive current reference value to obtain the actual reactive current output; the active current given module is suitable for calculating the sine of the voltage phase according to the voltage phase obtained by the phase-locked loop At the same time, according to the average voltage of the DC side capacitors of the H-bridge power modules of each phase, the voltage reference value of a DC side capacitor is subtracted and then multiplied by the sine quantity after PI control to obtain the actual active power Current output; an instantaneous current tracking module, used to first superimpose the currents output by the reactive current given module and the active current given module, then subtract the instantaneous current in the three-phase power supply, and use the controller to calculate The modulation ratio M and the phase angle δ of the sinusoidal modulation wave required by the pulse width modulation circuit are obtained.

Compared with the prior art, the device for fan cooling control of the present invention has the following advantages: (1) utilize the PLC module to replace the traditional relay circuit, avoiding the defects of cumbersome wiring and high failure rate of the relay; (2) according to The temperature controls the number of fans and the number of revolutions. In the winter when the temperature is low, you can not start the fan or a small number of fans and the number of revolutions is slow. In the summer when the temperature is high, you need to start all the fans to dissipate heat and increase the number of revolutions according to the specific temperature. , so this device has saved a large amount of electric energy, has also prolonged the life-span of motor; (3) utilizes described chain type SVG control device, rectifies the problem that the power factor of power grid is dropped because of motor operation, has improved the utilization ratio of transformer; ( 4) A standby H bridge unit circuit is provided in the chained SVG control device, and when another H bridge unit circuit fails, the faulty H bridge unit circuit is automatically bypassed, and the H bridge multi-connected type is guaranteed. The multilevel inverter works normally, that is, the power factor of the power grid is corrected; (5) and when the H-bridge power module is damaged, there is no need to stop for maintenance, which ensures the stability of the power grid; (6) the pulse width modulation circuit is damaged The modulated wave of the one-phase H-bridge power module effectively avoids the generation of harmonics; (7) The compensation problem of the unbalanced output of the three-phase power supply is realized through independent control of the phase-separated current.

The technical problem to be solved by the present invention is to provide a kind of H-bridge unit circuit suitable for automatic bypass fault on the basis of the device for fan cooling control, so as to ensure that the H-bridge multi-connected multi-level inverter How the chained SVG controls work for the transformer to work properly.

In order to solve the above problems, the working method of the device for fan cooling control includes:

The working method of described chain type SVG control device, it comprises the steps:

A: When an H bridge unit circuit is damaged, the corresponding automatic bypass circuit bypasses the H bridge unit circuit;

B: On the basis of keeping the sampling period of the sampling circuit unchanged, the pulse width modulation circuit changes the carrier triangular wave phase-shifting SPWM of the one-phase H-bridge power module where the damaged H-bridge unit circuit is located Carrier frequency, to obtain the pulse modulation waveform of the carrier triangular wave phase-shifting SPWM corresponding to the remaining H bridge unit circuit quantity in the phase H bridge power module;

The working method of the phase-splitting current independent control circuit comprises the following steps:

(1) tracking the voltage phase of the three-phase power supply according to the instantaneous value of the input voltage of the three-phase power supply through a phase-locked loop;

(2) Calculate the cosine of the voltage phase according to the voltage phase obtained by the phase-locked loop and multiply it with a reactive current reference value to obtain the actual reactive current output;

(3) Calculate the sine quantity of the voltage phase according to the voltage phase obtained by the phase-locked loop, and at the same time, according to the average voltage of the DC side capacitor of the H-bridge power module of each phase and the voltage reference value of a DC side capacitor After subtraction and multiplication with the sine quantity after PI control, to obtain the actual active current output;

(4) It is used to first superimpose the output currents of the reactive current given module and the active current given module, then subtract the instantaneous current in the three-phase power supply, and calculate the pulse width through the controller The modulation ratio M and phase angle δ of the sinusoidal modulation wave required by the modulation circuit.

Compared with the prior art, the working method of the chained SVG control device in the working method of the device for fan cooling control of the present invention has the following advantages: (1) through the addition of each phase H bridge power module At least one spare H-bridge unit circuit, so that when the H-bridge power module is damaged, the faulty module will be automatically bypassed without shutting down for maintenance; (2) The pulse width modulation circuit adjusts the modulated wave of the damaged one-phase H-bridge power module, effectively (3) The compensation problem of the unbalanced output of the three-phase power supply is realized through independent control of the phase-separated current.

Description of drawings

In order to make the content of the present invention more easily understood, the present invention will be described in further detail below in conjunction with the specific embodiments according to the accompanying drawings, wherein

Fig. 1 is the structural block diagram of the device for fan cooling control of the present invention;

Fig. 2 chained SVG control device structural block diagram of the present invention;

The circuit structure diagram of the multi-level inverter of the multi-connection type of H electric bridge of the present invention of Fig. 3;

The block diagram of the structure of the independent control circuit of phase-splitting current of Fig. 4 of the present invention;

The oscillogram of carrier triangular wave in-phase single-layer laminated SPWM modulation of Fig. 5 of the present invention;

The timing sequence of pulse generation before the failure of the H bridge unit module of the present invention occurs in Fig. 6;

The timing sequence of pulse generation after the first fault H bridge unit module of the present invention is bypassed in Fig. 7;

FIG. 8 is the timing sequence of pulse generation after the second faulty H-bridge unit module of the present invention is bypassed.

detailed description

Below in conjunction with accompanying drawing and embodiment the present invention is described in detail:

(Example 1)

As shown in Figure 1, a device for fan cooling control, including: a temperature detection sensor, a number of fans, connected to the temperature detection sensor and suitable for controlling the operation of a corresponding number of fans and the corresponding speed of the fans according to the external temperature. PLC module. In the summer when the temperature of the fan is high, the heat generated by the transformer is huge, so when the temperature detected by the sensor reaches 60 degrees Celsius, all the fans are working, and the fan speed can be increased according to the ambient temperature; in winter with a low temperature, due to the ambient temperature Low, so when the calorific value of the transformer is not high, the fan can be turned on less or not, and the rotation speed of the fan can be appropriately reduced.

As shown in Figure 2, the device for fan cooling control also includes: a chained SVG control device suitable for power factor correction, the chained SVG control device is connected to the three-phase power supply of the device for fan cooling control input terminal.

As shown in Figures 2 and 3, the chained SVG control device includes:

H-bridge multi-connected multi-level inverter, which is composed of three-phase H-bridge power modules connected to the three-phase power supply, wherein, at least one spare H-bridge unit circuit is added to each phase H-bridge power module ;

An automatic bypass circuit is set at the output end of each H-bridge unit circuit, and when an H-bridge unit circuit is damaged, the H-bridge unit circuit is bypassed;

The sampling circuit is suitable for collecting the instantaneous value of the voltage and current of the three-phase power supply, the instantaneous value includes the amplitude and period of the voltage and current;

Separate phase current independent control circuit, which is connected to the sampling circuit and is suitable for calculating the modulation ratio M and phase of the sinusoidal modulation wave required by the pulse width modulation circuit according to the instantaneous value of the voltage and current of the three-phase power supply angle δ;

The pulse width modulation circuit is connected with the phase-splitting current independent control circuit, and is used to control the carrier triangular wave phase-shifting SPWM adopted between the H bridge unit circuits according to the modulation ratio M and the phase angle δ of the sinusoidal modulation wave ; That is, after the damaged H-bridge unit circuit is bypassed, the pulse width modulation circuit is suitable for changing a phase where the damaged H-bridge unit circuit is located on the basis of keeping the sampling period of the sampling circuit unchanged. The carrier frequency of the phase-shifted SPWM of the carrier triangular wave of the H-bridge power module is used to obtain the pulse modulation waveform of the carrier triangular wave phase-shifted SPWM corresponding to the number of remaining H-bridge unit circuits in the phase H-bridge power module.

As shown in Fig. 4, the independent control circuit of the split-phase current includes:

a phase-locked loop, tracking the voltage phase of the three-phase power supply according to the instantaneous value of the voltage of the three-phase power supply;

The reactive current given module is adapted to calculate the cosine of the voltage phase according to the voltage phase obtained by the phase-locked loop and multiply it with a reactive current reference value to obtain the actual reactive current output;

The active current given module is adapted to calculate the sine quantity of the voltage phase according to the voltage phase obtained by the phase-locked loop, and at the same time according to the average voltage and a DC side capacitance of the H-bridge power module of each phase The voltage reference value of the capacitor is subtracted and then multiplied by the sine quantity after PI control to obtain the actual active current output;

The instantaneous current tracking module is used to superimpose the output currents of the given reactive current module and the given active current module, then subtract the instantaneous current in the three-phase power supply, and calculate the The modulation ratio M and phase angle δ of the sinusoidal modulation wave required by the pulse width modulation circuit.

Wherein the reference current is an expected compensation current, and the DC voltage reference value is an expected compensation voltage.

The pulse width modulation circuit relates to the SPWM pulse width modulation method. The SPWM pulse width modulation method uses a sine wave as a modulation wave, and uses a triangular wave with F times the frequency of the sine modulation wave as a carrier wave to perform waveform comparison. Equal, the rectangular pulse train whose width is proportional to the sinusoidal modulation wave is equivalent to the sine wave, thereby controlling the on-off of the switching device (that is, the switching device in the multi-level inverter).

The present invention adopts the hybrid control algorithm of carrier triangular wave phase-shifting SPWM control and carrier triangular wave stacked SPWM control: on the whole, carrier triangular wave phase-shifting SPWM control is adopted between each H bridge unit circuit, and a single H bridge unit circuit adopts The stacked SPWM control method, this modulation method has small output harmonic content, low switching frequency, and can well solve the problem of low inverter efficiency.

Carrier triangular wave phase-shifting SPWM control method means that for N H-bridge unit circuits, N sets of SPWM control pulses are generated by comparing N carrier triangular waves with the same frequency and amplitude with the same sine modulating wave. The waveforms are used to control the N H-bridges, so that each H-bridge unit circuit outputs the SPWM voltage waveform with the same fundamental voltage, and then the SPWM voltage waveforms output by the N H-bridge unit circuits are superimposed to synthesize a multi-SPWM level voltage waveform.

The initial phase angles of the N carrier triangular waves should be shifted by an angle. If a bipolar carrier triangular wave is used, the angle is α=π/N; if a unipolar carrier triangular wave is used, the angle is α=2π/N.

Carrier triangular wave stacked SPWM control method is a kind of SPWM modulation method of multi-level inverter that was applied relatively early. The carrier triangular wave stacked SPWM modulation method can be divided into two types, that is, a single-layer stacked SPWM modulation method and a multi-layer stacked SPWM modulation method, both of which can achieve the technical effect of this patent.

Carrier triangular wave single-layer stacked SPWM modulation method can be divided into carrier triangular wave anti-phase single-layer stacked SPWM modulation method (the phase of the two carrier triangular waves is opposite) and carrier triangular wave in-phase single-layer stacked SPWM modulation method according to the phase relationship of the two triangular carrier waves (The two carrier triangle waves have the same phase). Carrier triangular wave anti-phase single-layer stacked SPWM modulation method and carrier triangular wave in-phase single-layer stacked SPWM modulation method have no advantages or disadvantages. The present invention adopts carrier triangular wave in-phase single-layer stacked SPWM modulation method.

In the carrier triangular wave in-phase single-layer stacked SPWM modulation method, the phases of the two carrier triangular waves u _C1 and u _C2 are the same, and their working waveforms are shown in Figure 5. Among them, u _C1 and u _C2 are the upper and lower carrier triangular waves on the horizontal axis, and u _S is the sine modulation wave. Comparing the sine wave with the triangular wave, the output SPWM pulse will be generated in the part where the sine wave u _S is greater than the triangular wave, and the zero pulse of the output voltage will be generated in the part where the sine wave u _S is smaller than the triangular wave. Since u _C1 and u _C2 are in the same phase, that is to say, u _C1 and u _C2 are asymmetrical to the horizontal axis of the coordinates, so by comparing the sine wave and the triangular wave, the positive half cycle and the negative half axis of the output voltage SPWM waveform are different. of.

Take any H-bridge unit circuit for research, and analyze it from the perspective of power. Suppose U _rj is the output voltage of the H bridge unit circuit, I _s is the phase current, θ _j is the angle between the output voltage and the phase current, then the active power absorbed by the H bridge unit circuit is: P _ab = U _rj I _s ·cosθ _j , it can be seen that the active power absorbed by the H bridge can be changed by changing the output voltage of the H bridge unit circuit, the phase current and the angle between them. Because the magnitude and direction of the phase current I _s are fixed, only the magnitude and direction of the output voltage of the H bridge unit circuit can be changed, that is, the modulation ratio M and the phase shift angle θ corresponding to the output of the pulse width modulation circuit.

The control strategy of the chained SVG adopts a hierarchical control structure: the upper layer control mainly determines the total active and reactive power, and the lower layer control mainly adjusts the reasonable distribution of active power among the H-bridges of the phase to ensure the DC side capacitor voltage balance. The upper layer control method of the present invention adopts independent control of the phase-separated current, calculates the modulation ratio and phase angle of the expected modulation wave, quantizes the error of the DC side voltage of each bridge into a sinusoidal function and superimposes it on the modulation wave of the H-bridge unit circuit , to fine-tune the phase of the modulated wave of each H-bridge unit circuit, and adjust the distribution of active power among the H-bridge unit circuits.

There is no coupling relationship on the three-phase DC side of the chain-type SVG, so phase-separated control can be realized, and the three-phase system can be compensated separately, and it can have a better compensation effect on both balanced and unbalanced systems. In the control strategy proposed in the previous section, the upper layer control adopts the complete decoupling control of the current state, the transient response is fast, and the stability is good, but the controller design only considers the situation when the three-phase balance is not considered. A matter of balance. The investigation of the power grid quality shows that the grid voltage is more or less asymmetrical in phase or amplitude, that is to say, in actual situations, the three-phase system is mostly unbalanced.

The automatic bypass circuit adopts automatic bypass technology, which is to directly bypass the AC side of the faulty power module, so as to realize the separation of the faulty module and the device. Automatic bypass is realized by setting a bypass mechanism on the output side of each power unit module.

A relay can be provided at the output end of each H-bridge unit circuit, and the faulty H-bridge unit circuit can be separated from the H-bridge power module of the phase by controlling the normally open and normally closed states; a rectifier bridge and a thyristor can also be used, each The output of the H-bridge unit circuit is connected to the rectifier bridge composed of two pairs of diodes, so the thyristor is always under the forward voltage drop. When the monitoring system detects an internal fault in the power module, it immediately blocks the IGBT pulse and triggers the thyristor to conduct to realize bypass separation; or use a bidirectional thyristor.

When the faulty H bridge unit circuit in a certain phase H bridge power module is bypassed, if the pulse transmission of the sinusoidal modulation signal output by the pulse width modulation circuit is still transmitted according to normal operation, and the output of the chain SVG control system However, only N H bridge unit circuit output voltages are superimposed, and the harmonic content will increase. Therefore, for the remaining N non-faulty H-bridge unit circuits, the modulation strategy needs to be adjusted accordingly.

Because the carrier triangular wave stacked SPWM only works inside a single H-bridge unit circuit, the separation of the faulty module has no effect on the carrier triangular wave stacked SPWM modulation, and only affects the carrier triangular wave phase-shifting SPWM. Therefore, for the convenience of analysis, only the phase-shifted SPWM of the carrier triangular wave is analyzed. Assume that when N+1 H bridge unit circuits are connected in series, the carrier frequency of the chained SVG control system is 1/T _c , the sampling period is T _s , and when the carrier is unipolar, the sampling period T _s =T _c /[ 2(N+1)]. Two commonly used adjustment methods after the faulty H bridge unit circuit is separated are given below.

The first method: T _c does not change, T _s changes

In order to simplify the analysis, before selecting the fault, assuming that the number of multilevel inverters is n+1=6, then the sampling period of the H-bridge power module of each phase is T _s =T _c /12, at 0/6T _s , T _s /7T _s , 2T _s /8T _s , 3T _s /9T _s , 4T _s /10T _s , 5T _s /11T _s samples the modulated wave once, and compare them to generate corresponding trigger pulses, as shown in Figure 6.

If a certain H-bridge unit circuit is separated due to a fault (assuming that the first H-bridge unit circuit is separated), if the modulation strategy is not adjusted accordingly, the pulse generation of the remaining N non-faulty H-bridge unit circuits Timing is shown in Fig. 7(a). It can be seen from the figure that the sampling interval between H-bridge unit circuit 0 and H-bridge unit circuit 2 is 2T _s , but the sampling interval between other power H-bridge unit circuits is T _s , which obviously does not conform to the carrier The basic principle of phase shift SPWM modulation. The harmonic content of the output voltage of the SVG device necessarily increases.

Assuming that the carrier period remains unchanged, it is still T _c , but the sampling period is readjusted within T _c . As shown in FIG. 7( b ), since the number of multilevel inverters becomes 5 after a fault, the sampling period after modulation is T _s ′=T _c /10. This will generate N=5 complete carrier phase shifted output pulses.

The method adjusts the switching modulation strategy of the phase-carrier and phase-shifting SPWM by changing the sampling period of the faulty phase (one-phase H-bridge power module where the faulty H-bridge unit circuit is located). For this phase, it can play a very good regulating role.

The second method: T _c changes, T _s does not change

When the first H bridge unit circuit breaks down and is separated, keep the sampling period T _s unchanged, and adjust the carrier triangular wave period of this phase. As shown in Figure 8.

The carrier period of the faulty phase after adjustment is Tc', and the carrier period Tc of other non-faulty phases remains unchanged. The adjusted pulse timing is shown in Fig. 8(b): At the time of 0/5Ts, Ts/6Ts, 2Ts/7Ts, 3Ts/8Ts, 4Ts/9Ts, the trigger pulse of the H-bridge power module is generated by sampling the modulated wave once. In this way, a complete N=5 carrier phase-shifted SPWM pulse modulation waveform is obtained. Since the sampling period of the fault phase does not change before and after the fault module is separated, the synchronization of the three-phase current sampling can still be guaranteed after the fault is separated.

The working method of the phase-splitting current independent control circuit. See Figure 4, where v _ab , v _bc , and v _ca are the instantaneous values of the three-phase voltage collected by the acquisition circuit; is the voltage phase of the three-phase power tracked by the PLL; is the reference value of reactive current of each phase; is the average voltage of the DC side capacitors of the H-bridge power modules of each phase; u _ef is the voltage reference value of the DC side capacitors; i _ab , i _bc , and i _ca are the instantaneous values of the three-phase currents collected by the acquisition circuit; they are controlled by the corresponding PI The converter can calculate the reference signal of the SVG output voltage, and further calculate the corresponding reactive current reference value of each phase and the voltage reference value of the DC side capacitor according to the instantaneous reactive power theory. For the specific method of obtaining the reference value of the reactive current of each phase and the voltage reference value of the DC side capacitor, please refer to the literature: Yang Jun, Wang Zhaoan, Qiu Guanyuan. A detection method for single-phase circuit harmonics and reactive current [J], Electrician Journal of Technology, 1996(3), 11(3): 42-46; Jiang Bin, Yan Gangfeng, Zhao Guangzhou. A new method for real-time detection of instantaneous harmonics and reactive current in single-phase circuits [J]. Electric Power System Automation, 2000(11) :36-39.

(Example 2)

See Figures 2-4, on the basis of Embodiment 1, the working method of the device for fan cooling control includes:

The working method of the chained SVG control device provided at the three-phase power supply of the control device comprises the following steps:

A: When an H bridge unit circuit is damaged, the corresponding automatic bypass circuit bypasses the H bridge unit circuit;

B: On the basis of keeping the sampling period of the sampling circuit unchanged, the pulse width modulation circuit changes the carrier triangular wave phase-shifting SPWM of the one-phase H-bridge power module where the damaged H-bridge unit circuit is located Carrier frequency, to obtain the pulse modulation waveform of the carrier triangular wave phase-shifting SPWM corresponding to the remaining H bridge unit circuit quantity in the phase H bridge power module;

The working method of the phase-splitting current independent control circuit comprises the following steps:

(1) tracking the voltage phase of the three-phase power supply according to the instantaneous value of the input voltage of the three-phase power supply through a phase-locked loop;

(2) Calculate the cosine of the voltage phase according to the voltage phase obtained by the phase-locked loop and multiply it with a reactive current reference value to obtain the actual reactive current output;

(3) Calculate the sine quantity of the voltage phase according to the voltage phase obtained by the phase-locked loop, and at the same time, according to the average voltage of the DC side capacitor of the H-bridge power module of each phase and the voltage reference value of a DC side capacitor After subtraction and multiplication with the sine quantity after PI control, to obtain the actual active current output;

(4) It is used to first superimpose the output currents of the reactive current given module and the active current given module, then subtract the instantaneous current in the three-phase power supply, and calculate the pulse width through the controller The modulation ratio M and phase angle δ of the sinusoidal modulation wave required by the modulation circuit.

Apparently, the above-mentioned embodiments are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. And these obvious changes or modifications derived from the spirit of the present invention are still within the protection scope of the present invention.

Claims (1)

1. for the device that blower fan cooling controls, it is characterized in that comprising: temperature detection sensor, some blower fans, the PLC module, being suitable for the blower fan work and the corresponding rotating speed of blower fan controlling respective numbers according to external temperature height be connected to described temperature detection sensor are suitable for correcting the chain type SVG control gear of power factor; This chain type SVG control gear is connected to the input end of the three phase mains of the described device for blower fan cooling control;

Described chain type SVG control gear comprises: the multi-electrical level inverter of H electrical bridge multi-type, auto by pass circuit, sample circuit, point phase current independent controling circuit and pulse-width modulation circuit;

The multi-electrical level inverter of H electrical bridge multi-type, it is made up of the three-phase H bridge power model being connected to described three phase mains, wherein, sets up at least one H electrical bridge element circuit for subsequent use in every phase H bridge power model;

Auto by pass circuit, is located at the output terminal of each H electrical bridge element circuit, and when a H electrical bridge element circuit is damaged, by this H electrical bridge element circuit bypass;

Sample circuit, is suitable for the momentary value of the voltage and current gathering described three phase mains;

Divide phase current independent controling circuit, it is connected with described sample circuit, is suitable for the modulation ratio M and the phase angle δ that calculate the sinusoidal modulation wave needed for described pulse-width modulation circuit according to the momentary value of the voltage and current of described three phase mains;

Pulse-width modulation circuit, is connected with described point of phase current independent controling circuit, for controlling the carrier triangular wave phase shift SPWM adopted between each H electrical bridge element circuit according to the modulation ratio M of described sinusoidal modulation wave and phase angle δ; Namely, when after the H electrical bridge element circuit bypass damaged, this pulse-width modulation circuit is suitable on the basis keeping the sampling period of described sample circuit constant, change the carrier frequency of the described carrier triangular wave phase shift SPWM of a phase H bridge power model at the H electrical bridge element circuit place of this damage, to obtain the Sampling waveform of the carrier triangular wave phase shift SPWM corresponding with H electrical bridge element circuit quantity remaining in this phase H bridge power model;

The method of work of described chain type SVG control gear comprises the steps:

A: when a H electrical bridge element circuit damages, this H electrical bridge element circuit of corresponding auto by pass circuits bypass;

B: described pulse-width modulation circuit is on the basis keeping the sampling period of described sample circuit constant, change the carrier frequency of the described carrier triangular wave phase shift SPWM of a phase H bridge power model at the H electrical bridge element circuit place of described damage, to obtain the Sampling waveform of the carrier triangular wave phase shift SPWM corresponding with H electrical bridge element circuit quantity remaining in this phase H bridge power model.