Abstract: Introduced with the IGBT rate of doing work component’s intermediate frequency inversion power source, has carried on the exhaustive analysis to electric circuit’s principle of work.
Key word: Insulation grid bipolar transistor; Intermediate frequency inversion power source; Actuation; Sine wave pulse-duration modulation
Introduction
the 400Hz intermediate frequency power source in domains and so on industry, national defense, navigation, aviation applies is widespread. At present in our country, the 400Hz intermediate frequency power supply system mostly is the intermediate frequency unit, the volume is big, chirp the pitch, the efficiency is low, the management is inconvenient. We developed one (IGBT) to make primarily the power switch component’s 400Hz sine wave intermediate frequency inversion power source with the insulation grid bipolar transistor, it had the volume to be young, the weight was light, the noise was low, the transfer efficiency was high, the operation reliable, merits and so on easy to operate, were the intermediate frequency unit’s ideal substitution new products.
IGBT is the new generation multi-skill electric power electronic device, its control level for insulation grid control field effect transistor, output stage for double pole power transistor, thus it had at the same time both’s merit to overcome both’s shortcoming, like high input impedance; High turn-on frequency; Very small driver power; Passes condition the pressure drop to be small; Current density big and so on.
Figure 1
1 system composition and principle of work
1.1 contravariant power source main circuit
Sine wave intermediate frequency inversion power source’s main circuit constitution like chart 1 the upper half branch shows, in the chart K1 is the air switch. L is the EMI filter, with filters out in electrical network’s disturbance and eliminates the contravariant power source to electrical network’s disturbance. K2, K3, K4 is the contact device, the K2 function is when the system initiation puts through the power source, when breakdown shuts off the main power source, its auxiliary contact K2 ‘ uses for when the engine off or the protection circuit movement causes the energy which on filter electric capacity C1 and C2 stores through resistance R2 to bleed off fast, the energy which with the aim of overhauling or avoiding when power failure in electric capacity C1 and C2 accumulates not putting, because inverts in the bridge the drive pulse level not to be indefinite with bridge arm high and low host power IGBT has at the same time the breakover to damage. Contact device K3 and the resistance R1 constitution soft start electric circuit, its function is when the system initiation, because through resistance R1 to electric capacity C1 and the C2 charge, prevents time the line start on capacitor C1 and C2 the initial voltage is zero slowly, causes the rectification bridge module withstanding oversized current surge to damage, when on electric capacity C1 and the C2 voltage imitates to certain value, contact device K3 movement, its electronic contact the resistance R1 pipe nipple. K4 uses in the power source outputting with the load separates, after and so on system initiation successfully, puts through again the load, guarantees the electrical power system smooth start and the protection current collector. Filter electric capacity C1 and C2 use for after the rectification the voltage to carry on the filter, guaranteed that provides for the contravariant bridge’s voltage for the straight DC voltage. R3 and the R4 distinction and in C1 and the C2 both sides, guarantees C1 and in the C2 each withstanding main circuit DC voltage half. S is the Hall electric current sensor, provides a sampled signal to contravariant power source’s going nonstop to and the short circuit protection. V1~V4 is 4 IGBT, the constitution bridge-type inversion electric circuit. C3 and C4 use for to suppress peak pulse voltage Ldi/dt which because in the IGBT make-and-break process in the electric circuit the inductance existence causes, guaranteed that main power switch component IGBT because of does not withstand the high peak pulse voltage to penetrate the damage. The L1, L2, C5 constitution output filter, output the contravariant bridge according to the sine wave rule change pulse width high frequency pulse wave reduction intermediate frequency sine wave output, and after the transformer T1 isolation provides the appropriate peak-to-peak value for the load the voltage.
The contravariant power source main circuit’s principle of work may induce as follows: Three-phase (or single-phase) exchanges the city electricity after the EMI filter filter, by the rectification bridge module U rectification, passes through the electric capacity filter again, adds to by the IGBT constitution bridge-type contravariant electric circuit, this direct-current high pressure inverts after the contravariant electric circuit for the pulse width according to the sine wave rule change high frequency pulse wave, by outputs the filter to filter out the high frequency overtone again, obtains the intermediate frequency sine wave, finally after transformer isolation, live pressure (pressure-rise or voltage dropping) provides for the load. The SPWM pulse wave produces by the master control electric circuit and changes the pulse wave according to the output feedback voltage and the feedback electric current the width, thus guarantee output voltage stability.
1.2 master control electric circuits
Master control part’s functional block diagram as shown in Figure 2. It uses INTEL Corporation’s 16 monolithic integrated circuit 87C196MC to take the control core. This monolithic integrated circuit mainly uses in controlling and the data processing, and has the pulse-duration modulation signal output port. Uses the fuzzy control algorithm in the control algorithm. The monolithic integrated circuit has the carrier frequency is the 20kHz SPWM signal impulse, outputs by the pulse-duration modulation signal output port, adds to IGBT through the driving circuit the electronics grid, the control inversion electric circuit works correctly, simultaneously, adjusts the SPWM signal impulse according to the voltage and the electric current feedback value the pulse width maintains the output signal scope the stability. For the guarantee system moves reliably safely, displays monolithic integrated circuit’s formidable control function fully, by the master control electric circuit to system’s essential component and the key parameter, for example the pressure, the undervoltage, the overflow, the overload, the output has short-circuited, overheated and so on to carry on the real-time monitoring, realizes carries on the corresponding acousto-optic warning to the system active status from the diagnosis and to the breakdown. Because used 16 monolithic integrated circuits to take system’s control core, control fast accurate, enabled the system to have responds quickly, movement stable, reliable characteristic.
1.3 driving circuits
The IGBT electronics grid slaving voltage may provide by the different driving circuit, when choice driving circuit, should consider that driving circuit’s power source request, the component shuts off the bias the request, the electronics grid electric charge request, bears soundness request, protects factors and so on function. Driving circuit’s performance not only direct relation IGBT component’s operating performance and movement security, moreover affects overall system’s performance and the security.
German west gate Kang (SEMIKRON) the company produces SKM the series IGBT power module, in chip aspects and so on fabrication technology, internal layout, foundation plate choice has the originality, does not need to use the RCD absorbing circuit, SOA (clear working place) the curve is the rectangle, does not need the negative pressure to shut off, is parallel when can automatic flow, short-circuits when the electric current suppresses automatically, the switching loss does not increase along with the temperature direct proportion, temperature characteristic curve. In view of this, selects west gate Kang company’s SKM series IGBT to take the contravariant power source’s main power switch component. To use IGBT fully the fine performance, the guarantee system can work reliably safely, the driving circuit also selects west gate Kang company’s SKHI series driver. This series driver only needs a non-isolation the 15V power source; Has the high dv/dt capacity; The protection function is perfect; The breakdown remembered that informs the control system through the ERROR signal; The high and low interlock, avoids identical bridge arm two IGBT also clearing; Outside grid resistor adjustable, causes the use different power capacity when IGBT can work Yu Jiaogao the turn-on frequency, and obtains the high transfer efficiency.
Does not need the electronics grid drive current as voltage control’s IGBT, but because the electronics grid input end has a big electric capacity, causes when the actuation forms very narrow pulse electronics grid drive current, and the IGBT capacity is bigger, this pulse current’s peak value is bigger, for example, the 200A/1200V IGBT clear electric current’s impulse peak approximately achieves 1.5A. The SKHI driver both can withstand this kind of crest value grid current and not to reduce VGE. For? The high clear and the shutdown speed, reduce the driver to lose, the SKHI driver’s output stage uses MOSFET to reduce on the connection line’s resistance to the tube. Influence shutter speed’s another important attribute is grid resistor RG, reduces RG to be possible to reduce IGBT the switching loss, but as a result of stray inductance’s existence, causes time the IGBT shutdown peak voltage between the collection emitter’s increases, the SKHI driver divides into RG RGON and RGOFF (see Figure 3), such two parameters may control separately, and may act according to the IGBT capacity the difference, adjusts RGON and RGOFF separately, obtains the best actuation effect.
The overflow protection is one which of important functions the driving circuit has, SKHI uses monitors IGBT collection emitter voltage VCE to observe and control the overflow, the schematic diagram see Figure 4. The VCE observation electric circuit simultaneously monitors the electronics grid input signal and the collection emitter voltage, when the input signal is the high electric potential, and after 3~5 μs, VCE normal saturation value (3.5~5.5V) high, then thinks the overflow, shuts off the signal impulse, gives the malfunction alert signal. This is one advanced overflow observation way.
The SKHI driver is aims at IGBT and the MOS characteristic designs, is a performance more perfect one kind of driver.
1.4 secondary control electric circuits
The secondary control electric circuit’s function is the control signal which sends out according to the master control electric circuit, controls contact device K2, K3, K4 to attract in turn gathers and breakes, guaranteed that the main circuit adds the electricity according to the correct order, when the protection circuit works shuts off main circuit’s electric power supply. The secondary control electric circuit also provides the power source for the ventilator.
1.5 demonstrations and pressed key control circuit
The demonstration and the pressed key control circuit’s function is under the master control electric circuit’s control, display system’s active status, like the voltage, the electric current, the frequency and so on, and may change the output voltage through the pressed key the scope (change scope to amount decide output voltage ±10%) and the output voltage frequency (400Hz±30Hz). When the system presents the breakdown carries on the demonstration and the warning to the breakdown, the alarm including the overflow, the overload, the short circuit, overheated, inputs has pressed the undervoltage, the actuation warning and so on.
1.6 software controls
Uses SPWMT and the PID algorithm as well as fuzzy control logic, the dynamic table look-up law in the algorithm, causes the system response to be quicker, protects the function to be stronger, the reliability enhances greatly.
1.7 other
Uses the essential component to fall the volume design, starts measures softly and so on design, automatic protection design, the guarantee circuit can work reliably in the environment stress big situation; Uses means and so on reliable hot design, NBC processing, structural element reinforcement processing, the guarantee product in the bad climatic stress and under the mechanical stress condition reliability; Regarding the ship-borne equipment necessary this product, uses the multi-skill shock absorber and the guidance structure, the guarantee product anti-impact, the vibration-proof mobility energy. The strengthened product’s insulation design, guarantees the product the security.
2 practical effects
According to above sine wave intermediate frequency inversion power source plan, has succeeded develops the series sine wave intermediate frequency inversion power source, after actual when rated load outputs the sine wave the degree of distortion <3%, MTBF>20000h, each technical specification achieves the design requirements. Has installed the expert appraisal which through the sea the Ministry of Electricity organizes, but also adopted China electronic products reliability and the environmental testing research institute quality detection center (i.e. information produces for five) reliable and the electromagnetic compatibility appraisal, the environmental testing examination. The power source after navy many armies and the base, the war industry unit, research institute’s actual use, has made the satisfying progress.
3 conclusions
because 1) high efficiency IGBT has the operating frequency to be high, the driving circuit power is small, loss of work small and so on merits, in addition has the special-purpose driving circuit to be possible to make driving circuit’s design simplification, the reliability to enhance, therefore, but uses in conveniently the frequency conversion power source.
2) applies 16 monolithic integrated circuit 87C196MC in the sine wave inversion electrical power system to produce the SPWM signal impulse which the system needs, is very convenient practical, may make the hardware circuit big simplification, the reliability to enhance, simultaneously may use monolithic integrated circuit’s formidable control function, real-time carries on the monitoring to system’s essential component and the key parameter, realizes to the system active status from the diagnosis.
3) the high efficiency IGBT invertor’s protection circuit design has the very vital role to its reliable work, should take seriously fully. IGBT module absorption electric capacity C3 and C4 must select the low feeling electric capacity, if the polypropylene electric capacity or similar low dielectric loss membrane’s electric capacity, installs time should approach the module as far as possible.
4) the sine wave inversion power source output sine wave’s degree of distortion with outputs filter’s parameter to have the close relation, in the design should select filter’s cut-off frequency reasonably, and considers the contravariant power source maximum output frequency the need, the filter inductance and the electric capacity should satisfy
In the formula: fc is filter’s cut-off frequency, the value for maximum output frequency 5~10 times.
5) the intermediate frequency inversion power source volume which constitutes by the IGBT acting rate switch component is small, the weight is light, the noise is low, the operation reliable, the use, the maintenance are convenient, in domains and so on industry, national defense, astronautics has the broad application prospect, is the intermediate frequency frequency conversion unit’s ideal substitution product.
