CN100521491C - Inverter control method and apparatus - Google Patents

Abstract

A control method and control device for an inverter, the method is to subtract the feedback voltage of the output voltage from the voltage reference value to obtain the difference, process it into the basic inductor current reference current through the voltage control loop adjustment link, and then combine it with the The output generated by the nonlinear control link processing is added to obtain the inductor current reference current, and then the feedback current of the inductor current is subtracted from it to become the inductor current error, and finally the inverter is controlled after being processed by the inductor current control loop adjustment link . The device is composed of a subtraction part, a voltage control loop adjustment part, a subtraction part, and an inductance current control loop adjustment part connected in sequence, an addition part is set between the voltage control loop adjustment part and the subtraction part, and a nonlinear control mechanism is set to connect with the addition part . The invention can effectively improve the steady-state and dynamic performance of the inverter under the condition of instantaneous sudden change load and periodic nonlinear load, without affecting the normal operation of the inverter under the condition of linear load.

Description

A control method and control device for an inverter

technical field

The invention relates to an inverter, in particular to a control method and a control device which can effectively improve the dynamic and static performance of the inverter under nonlinear load conditions.

Background technique

With the increase of electrical equipment, the type, quantity and proportion of non-linear loads also increase rapidly, and the pollution of harmonics to the power supply system is becoming more and more serious. As a main AC power supply, inverters are increasingly faced with nonlinear loads in the application field (including instantaneous loads such as equivalent loads when gas discharge lamps are started and periodic nonlinear loads such as rectifier loads) The problem. When the inverter has a nonlinear load, its output waveform will be distorted. The common phenomenon is that the output voltage will drop instantaneously and top off. In severe cases, the output waveform will oscillate and cannot work stably. The sinusoidal output waveform will affect the normal operation of other loads of the inverter, and even cause equipment damage.

At present, the inverter's related control technology solutions for nonlinear load problems mainly include PID (proportional-integral-derivative) control, internal model control, deadbeat control, sliding mode variable structure control and intelligent control. PID control generally adopts a double-loop PID structure, which can obtain relatively good dynamic performance; but under nonlinear load conditions, the current inner loop needs a fast speed, so this form of controller has a certain ability to suppress nonlinear disturbances. limits. Internal model control mainly includes repetitive control and coordinate axis transformation (Reference frame) control, which can effectively improve the output waveform under steady-state conditions, but sacrifices dynamic performance. Deadbeat control can theoretically track the reference waveform within one control cycle, but it requires accurate inverter and load models, and an excessively high gain makes the system prone to oscillations or even unable to work stably. Sliding mode variable structure control uses a discontinuous switch control strategy to force the state variables of the system to move along a pre-designed "sliding mode" trajectory in the phase plane, which is insensitive to parameter changes and external disturbances. advantage. But it is difficult to choose the ideal sliding mode switching surface of the inverter; secondly, the sliding mode variable structure control has great application value only when it is realized in a digital form with a sufficiently high sampling frequency. Intelligent control has strong robustness and adaptability, but due to the limitations of the current technical level, intelligent control is still in the research stage.

Contents of the invention

The object of the present invention is to provide a control method and a control device for improving the steady-state and dynamic performance of the inverter under the condition of instantaneous sudden change load and periodic nonlinear load. At the same time, it does not affect the normal operation of the inverter under linear load conditions.

The object of the present invention is achieved by the following scheme:

Inverter Control Method

1) Subtract the feedback amount of the output voltage from the preset voltage reference value through the subtraction link to obtain the voltage error;

2) The voltage error is processed through the voltage control loop adjustment link to generate a basic inductor current reference quantity;

3) Add the output generated by the nonlinear control link to the basic inductor current reference quantity through the addition link to obtain the inductor current reference quantity as the circuit control quantity, and the output quantity is adjusted by the error adjustment link of the nonlinear control link. The voltage error is processed to generate the variable of the voltage error, and the feedback amount of the output current is sequentially processed through the output current adjustment link and the absolute value conversion link of the nonlinear control link, and the output current feedback amount after processing is compared with the voltage error The variable is multiplied by the multiplication link, and the product output obtained is obtained after being processed by the limiter control link;

4) subtracting the inductance current feedback amount from the inductance current reference amount through a subtraction link to obtain the inductance current error;

5) The inductance current error is processed by the inductance current control loop adjustment link to obtain the inverter control quantity;

6) Using the inverter control quantity to control the main circuit of the inverter.

While subtracting the inductor current feedback amount from the inductor current reference amount through the subtraction link, the output current feedback amount is added through the addition link to obtain the inductor current error.

The control device specially designed for implementing the control method of the inverter, including the control device of the inverter composed of the first subtraction part, the voltage control loop adjustment part, the second subtraction part, and the inductor current control loop adjustment part connected in sequence, The first subtraction component and the second subtraction component are respectively connected to the main circuit of the inverter, an addition component is set between the voltage control loop adjustment component and the second subtraction component, and a nonlinear control mechanism is set, and the two inputs of the nonlinear control mechanism The terminals are respectively connected with the first subtraction component and the voltage control loop adjustment component and the main circuit of the inverter, and the output terminal is connected with the addition component.

The second subtraction unit is replaced by an addition and subtraction synthesis unit, and the addition input end of the addition and subtraction synthesis unit is connected to the main circuit of the inverter. The non-linear control mechanism is composed of an error adjustment unit, a multiplication unit, an absolute value conversion unit, an output current adjustment unit, and a limiting control unit arranged between the multiplication unit and the addition unit in sequence.

The main features of the present invention are: since the control amount of the nonlinear control link is equal to the product of the load current and the voltage error, under the linear load condition, the current is very small, and the voltage error is also small. This control amount has a reference value for the inductor current Quantitative effects can be ignored. So the existence of the nonlinear control link will not affect the work of the inverter under the linear load. However, under nonlinear load conditions, for example, for instantaneous sudden change loads, the voltage error signal suddenly increases due to voltage drop, and the control amount of the nonlinear control link also increases accordingly, thereby increasing the inductor current reference value, which is equivalent to The gain of the inductor current control loop is increased, and the control bandwidth of the inverter is improved, so the dynamic performance of the inverter can be improved. Under the condition of periodic nonlinear load such as rectifying load, the output current is in the form of pulse current, and the current is much larger than the current in the case of linear load, so the control amount of the nonlinear control link is correspondingly larger. Therefore, increasing the reference value of the inductor current is equivalent to increasing the gain of the inductor current control loop, which can improve the steady-state performance of the inverter and reduce the distortion of the output waveform of the inverter.

Another feature of the present invention is that the voltage control loop adjustment link and the inductor current control loop adjustment link in the control method can be realized by various control methods, such as voltage control loop, inductor current control loop, error regulator and output current adjustment Links can adopt PID control, internal model control, intelligent control, etc., so the control method can have a wide range of applications.

Description of drawings

Fig. 1 is a schematic diagram of the principle of the inverter control method and the structure of the control device of the present invention;

Fig. 2 is a principle schematic diagram of another embodiment of the structure of the inverter control method and the control device of the present invention.

Fig. 3 is a schematic diagram of an inverter;

FIG. 4 is a schematic diagram of the principle of an existing inverter control method;

Detailed ways

Referring to Figure 1, Figure 2, Figure 3, and Figure 4, the control method is as follows:

The first subtraction link 6 subtracts the feedback voltage V _of the output voltage from the preset voltage reference value Vr to obtain the voltage error e;

The voltage error e is processed by the voltage control loop adjustment link 7 to generate the basic inductor current reference value I _Lr1 ;

On the other hand, the voltage error e is processed by the error adjustment link 16 of the nonlinear control link 11 to generate a variable e ₁ of the voltage error. Error adjustment link 16 can be a PID control link, also can be other control links, such as can adopt proportional adjustment link, at this moment its expression is:

e ₁ =k ₁ ×e

k ₁ is a preset constant.

The output current _regulation link 12 can be a PID control, also can be other control links, it processes the feedback current _{Iof of} the output current to generate the current _Io1 ; process to obtain _the current I _o2 ; then the variable e ₁ of the voltage error and the current I _o2 are multiplied by the multiplication link 14 to obtain the product C ₁ ; After processing, the output C _n of the nonlinear control link 11 is obtained.

The basic inductance current reference quantity I _Lrl is added to the output _Cn of the nonlinear control link 11 by the addition link 10 to obtain the inductance current reference quantity I _Lr ;

The feedback current I _Lf of the inductor current is subtracted from the inductor current reference value I _Lr by the second subtraction link 8 to obtain the inductor current error ei;

The inductance current error ei is processed by the inductance current control loop adjustment link 9 to generate an inverter control signal V _c ;

The main circuit of the inverter can be controlled according to the conventional inverter control method by using the inverter control signal Vc.

Another example of the present invention is shown in FIG. 2 , which is an extended form of FIG. 1 . It can be seen from the comparison between Fig. 2 and Fig. 1 that it introduces the feedback current _Iof of the output current on the basis of Fig. 1 . The specific improvement is as follows, the second subtraction link 8 is replaced by the addition and subtraction link 17, the feedback current _Iof of the output current is added to the inductor current reference value I _Lr by the addition and subtraction link 17, and the feedback current of the inductor current is subtracted I _Lf , get the inductor current error ei. Other steps are the same as in Figure 1.

The inverter is composed of a main circuit 1 and a control device 5 , and the main circuit is composed of a drive unit 2 , a detection unit 3 and a power unit 4 .

The control device 5 is composed of the first subtraction unit 6, the voltage control loop adjustment unit 7, the addition unit 10, the second subtraction unit 8, the inductance current control loop adjustment unit 9 and the nonlinear control mechanism 11, and the first subtraction unit 6, The second subtraction part 8 is respectively connected with the feedback voltage V _of line of the output voltage of the main circuit 1 and the feedback current I _Lf line of the inductance current, and one of the two input ends of the nonlinear control mechanism 11 is connected with the first subtraction part 6 and the voltage control The other is connected with the feedback current _Iof line of the output current of the main circuit 1, and the output end is connected with the addition unit 10.

The nonlinear control mechanism 11 is composed of an error adjustment unit 16 , a multiplication unit 14 , an absolute value conversion unit 13 , an output current adjustment unit 12 , and a limiter control unit 15 connected with the multiplication unit 14 connected in sequence.

Claims (5)

1, a kind of control method of inverter:

1) in default voltage reference value, deducts the feedback quantity of output voltage, obtain voltage error through the subtraction link;

2) described voltage error is handled through the voltage control loop governing loop, generates basic inductive current reference quantity;

3) in basic inductive current reference quantity, add the output variable that generates by the nonlinear Control link through the addition link, obtain the inductive current reference quantity as the circuit controlled quentity controlled variable, described output variable is by the error governing loop of nonlinear Control link described voltage error to be handled, the variable of formation voltage error, output current governing loop and absolute value transform part through the nonlinear Control link are handled successively to the feedback quantity of output current, the feedback quantity of the output current after handling and the variable of voltage error are carried out multiplying through the multiplication link, the product output variable that obtains obtains after the amplitude limit controlling unit is handled;

4) in described inductive current reference quantity, deduct the inductor current feedback amount, obtain the inductive current error through the subtraction link;

5) described inductive current error is handled through inductive current control ring governing loop, obtains the inverter controlled quentity controlled variable;

6) with described inverter controlled quentity controlled variable the main circuit of inverter is controlled.

2, the control method of inverter according to claim 1 is characterized in that: when the subtraction link deducts the inductor current feedback amount, add the output current feedback quantity through the addition link in described inductive current reference quantity, obtain the inductive current error.

3, for implementing the custom-designed control device of claim 1, comprise inverter by the first subtraction parts (6), voltage control loop is regulated parts (7), the second subtraction parts (8), the inductive current control ring is regulated the control device that parts (9) connect to form successively, the first subtraction parts (6), the second subtraction parts (8) are connected with the main circuit (1) of inverter respectively, it is characterized in that: regulate between the parts (7) and the second subtraction parts (8) that at voltage control loop adding unit (10) being set, nonlinear Control mechanism (11) is set, two inputs of nonlinear Control mechanism regulate between the parts (7) with the first subtraction parts (6) and voltage control loop respectively and the main circuit (1) of inverter is connected, and output is connected with adding unit (10).

4, control device according to claim 4 is characterized in that: the described second subtraction parts (8) are replaced to addition and subtraction compound component (17), and the addition input that the addition and subtraction compound component increases is connected with the main circuit (1) of inverter.

5. control device according to claim 4 is characterized in that: described nonlinear Control mechanism (11) regulates parts (16), multiplying unit (14), absolute value transform component (13), output current by error to regulate the amplitude limit control assembly (15) of parts (12) and setting between multiplying unit (14) and adding unit (10) and connect to form successively.

Images