CN1697303A - Power amplifier of magnetic bearing switch possessing multiple routes of output, and control method - Google Patents

Abstract

The switch power amplifier includes signal-conditioning circuit, current controller, drive circuit, power-switch circuit with four pieces of bridge arm, and current testing circuit. Through controlling potentials at nodes in each bridge arm, the power-switch circuit with four pieces of bridge arm realizes three routes of independent output in order to drive windings of magnetic bearing in three degree of freedom. The said three routes of output are connected to a common bridge arm so as to reduce number of power valve and switching loss as well as reduce complex degree. The control method is easy to be implemented, and possesses large economic and practical value.

Description

The power amplifier of magnetic bearing switch and the control method of multichannel output

One, technical field

Multichannel output power amplifier of magnetic bearing switch of the present invention and controlling party switch power amplifier owned by France thereof.

Two, technical background

Magnetic bearing system extensively adopts switch power amplifier at present, and the circuit for power conversion of these close power amplifiers mostly is half-bridge, improves half-bridge or full bridge structure, and every cover power amplifier all needs control circuit independently, and can only drive the coil of magnetic bearing one degree of freedom.If make a rotating shaft realize that the suspension of five degree of freedom then needs this power amplifier of five covers, such five overlap independently, and control circuit and circuit for power conversion will make the volume of power amplifier part become huger, the complexity height, and reliability is low, and power tube is more, and loss is bigger.

Three, summary of the invention

The present invention is directed to that the deficiencies in the prior art develop that a kind of volume is little, simple in structure, reliability is high, loss is little and each road output of power amplifier is separate, non-interfering multichannel output power amplifier of magnetic bearing switch.

Realize above-mentioned purpose multichannel output power amplifier of magnetic bearing switch, comprise that modulate circuit is connected in current controller, the output of current controller is connected in four brachium pontis circuit for power conversion through drive circuit, and the output of four brachium pontis circuit for power conversion links to each other with three tunnel loads through current detection circuit.

Wherein, each brachium pontis that is connected in the four brachium pontis circuit for power conversion between the dc bus is composed in series by two switching tubes, anti-and the fast recovery diode of each switching tube, first brachium pontis is as public brachium pontis, its node links to each other with an end of three tunnel loads, and the node of three brachium pontis in back connects the other end with three tunnel loads.Three road output voltages of this four brachium pontis circuit for power conversion are to realize by the node potential of controlling four brachium pontis, and can directly obtain the duty ratio of each path switching signal by the current potential of each node, to generate switching signal.Just can control the current tracking variation of given signal separately of three tunnel loads by constantly changing three road output voltages.

Because four node potentials are not well-determined, brought very big space therefore for the optimization of power amplifier output performance.If the both sides (mean value that is both is 1/2 DC bus-bar voltage) that make maximum in each node potential and minimum value be symmetrically distributed in 1/2 DC bus-bar voltage just can make the ripple minimum of each road output current; And if the maximum that makes each node potential is that DC bus-bar voltage or the minimum value that makes each current potential are 0, so total switch number of times will reduce 1/3, and the master switch number of times is minimum under the variety of way.

Multichannel of the present invention is exported power amplifier of magnetic bearing switch compared with prior art, and employed switching tube number is few, and switching loss is little, and efficient and reliability are higher, also have the control algolithm simple, intuitive simultaneously, are easy to advantages such as realization.

Four, description of drawings

Fig. 1 is the power amplifier of magnetic bearing switch theory diagram of multichannel output.

Designation among Fig. 1.Ixr, Iyr, Izr: three given electric currents; PWM1, PWM2 ..., the PWM8:8 path switching signal; X, Y, Z: the winding of magnetic bearing three degree of freedom.

Fig. 2 is four brachium pontis circuit for power conversion schematic diagrams.

Designation among Fig. 2.Udc: DC bus-bar voltage; S ₁-S ₈: switching tube; D ₁-D ₈: anti-and fast recovery diode; N, x, y, z: the node of each brachium pontis; X, Y, Z: the winding of magnetic bearing three degree of freedom.

Five, specific implementation method

Fig. 1 is a composition frame chart of the present invention, among the figure with given signal Ixr, modulate circuit that Iyr, Izr link to each other 1 is barricaded as by operational amplifier, and current control circuit adopts digital signal processor DSP, drive circuit 3 is the special driving chip of switching tube, current detection circuit 5 comprises three current sensors and the signal conditioning circuit that is made of amplifier, and above circuit is prior art, and load 6 is winding X of 3 degrees of freedom of magnetic bearing, Y, Z.Four brachium pontis circuit for power conversion also are prior art as shown in Figure 2.

The course of work of the present invention is: modulate circuit 1 is with three tunnel load X, Y, the given signal Ixr of Z, after handling, Iyr and Izr give current controller 2, current controller 2 is again to being obtained output current signal sampling of each road by current detection circuit 5, and relatively calculates the voltage U x that needs output, Uy with separately given signal, Uz, determine the current potential Vn of each brachium pontis node then as required, Vx, Vy, Vz, generate switching signal PWM1, PWM2 ..., PWM8 controls each switching tube S makes output current follow given electric current I xr all the time, the variation of Iyr and Izr.

For four brachium pontis circuit for power conversion in the accompanying drawing 2 a lot of control methods is arranged at present, as space vector of voltage (SVPWM) control and maximum current ERROR CONTROL etc., these control algolithms or implement more complicated, otherwise the ripple of output current is bigger.And the present invention has adopted a kind of simple controlling schemes in the novel power amplifier of sort circuit topology, is exactly by four node n of control, x, y, the current potential Vn of z, Vx, Vy, Vz obtains required output voltage U x, Uy, Uz, this is because Vx-Vn=Ux, Vy-Vn=Uy, Vz-Vn=Uz can obtain following equation after the arrangement

$\left[\begin{array}{cccc}-1& 0& 0& 1\\ 0& -1& 0& 1\\ 0& 0& -1& 1\end{array}\right]\left[\begin{array}{c}\mathrm{Vx}\\ \mathrm{Vy}\\ \mathrm{Vz}\\ \mathrm{Vn}\end{array}\right]=\left[\begin{array}{c}\mathrm{Ux}\\ \mathrm{Uy}\\ \mathrm{Uz}\end{array}\right]$

Vi=Udc*Di in the formula (i=n, x, y, z), wherein Udc is a DC bus-bar voltage, Di is the duty ratio of pipe switching signal on the i brachium pontis.

If reasonably choose Di then can make each node potential Vi in interval [0, Udc], so just can control output voltage Ux, Uy, Uz makes output current Ix, and Iy, Iz be the tracing preset signal well.

Top equation must be separated not unique, if make Vn, and Vx, Vy, maximum potential and minimum level are symmetrically distributed in the Udc/2 both sides among the Vz, even

$\frac{\min \left(V_i\right)+\max \left(V_i\right)}{2}=\frac{\mathrm{Udc}}{2},$

Just can make the ripple minimum of each road output current, at this moment the current potential of each node can be expressed as

$\left\{\begin{array}{c}{V}_n=\frac{1}{2}(\mathrm{Udc}-\min \left(V_i^{*}\right)-\max \left(V_i^{*}\right))\\ V_x=\mathrm{Ux}+\frac{1}{2}(\mathrm{Udc}-\min \left(V_i^{*}\right)-\max \left(V_i^{*}\right))\\ V_y=\mathrm{Uy}+\frac{1}{2}(\mathrm{Udc}-\min \left(V_i^{*}\right)-\max \left(V_i^{*}\right))\\ V_z=\mathrm{Uz}+\frac{1}{2}(\mathrm{Udc}-\min \left(V_i^{*}\right)-\max \left(V_i^{*}\right))\end{array}\right..$

If minimum level is equalled zero (or maximum potential is a DC bus-bar voltage), in each control cycle, always there is the switching tube of a brachium pontis to be failure to actuate so, switching loss is reduced once more.Four node potentials under these two kinds of situations are respectively

$\left\{\begin{array}{c}{V}_n=-\min \left(V_i^{*}\right)\\ V_x=\mathrm{Ux}-\min \left(V_i^{*}\right)\\ V_y=\mathrm{Uy}-\min \left(V_i^{*}\right)\\ V_z=\mathrm{Uz}-\min \left(V_i^{*}\right)\end{array}\right.$ With $\left\{\begin{array}{c}{V}_n=\mathrm{Udc}-\max \left(V_i^{*}\right)\\ V_x=\mathrm{Ux}+(\mathrm{Udc}-\max \left(V_i^{*}\right))\\ V_y=\mathrm{Uy}+(\mathrm{Udc}-\max \left(V_i^{*}\right))\\ V_z=\mathrm{Uz}+(\mathrm{Udc}-\max \left(V_i^{*}\right))\end{array}\right..$

This four brachium pontis power amplifier can have Udc, 0 and-output of three kinds of level of Udc, therefore the same with common three-state (or three level) close power amplifier, have the little advantage of output current ripple.This novel node potential control strategy equally also can be used for the control of three brachium pontis close power amplifiers, but also can be generalized in the middle of the control of power inverter of more brachium pontis.Under the prerequisite that the controller arithmetic speed allows, can adopt the main power circuit of 6 brachium pontis (one of them brachium pontis is as public brachium pontis) to drive the winding of 5 degrees of freedom of magnetic bearing simultaneously.

Among the present invention, because this novel power amplifier has public brachium pontis, therefore the number of employed switching tube will greatly reduce, and correspondingly also reduce switching loss, and the efficient of power amplifier improves greatly.For the magnetic bearing switch power amplifier of three full bridge structures, the total number of master switch pipe has reduced 1/3; Under the identical situation of switching frequency, total switching loss also will reduce 1/3, and volume also reduces a lot.

Though this novel close power amplifier has public brachium pontis,, do not disturb mutually, and can directly generate switching signal owing to adopted the control method of controlling each brachium pontis node voltage can make each road output of power amplifier separate.

Claims (2)

1, a kind of power amplifier of magnetic bearing switch of multichannel output, it is characterized in that, comprise that the modulate circuit (1) that links to each other with given signal is connected in current controller (2), the output of current controller (2) is connected in four brachium pontis circuit for power conversion (4) through drive circuit (3), the output of four brachium pontis circuit for power conversion (4) links to each other with three tunnel loads (6) through current detection circuit (5), and the output of current detection circuit links to each other with current controller (2).

2, a kind of control method of power amplifier of magnetic bearing switch of multichannel output, it is characterized in that, the control method of four brachium pontis circuit for power conversion is, by controlling the some position of two switching tube series connection nodes of each brachium pontis, directly obtain three required output voltages, make the variation of output current tracing preset signal, directly generate switching signal.