CN218549507U

CN218549507U - Voltage differential feedback active damping control system of filter capacitor

Info

Publication number: CN218549507U
Application number: CN202222149215.2U
Authority: CN
Inventors: 钱开荣; 牛晨晖; 张宝君; 张宇; 周小兵; 迟小锋; 严祺慧; 孙捷; 肖华锋; 李明明
Original assignee: Huaneng Guanyun Clean Energy Power Generation Co ltd; Southeast University; Clean Energy Branch of Huaneng International Power Jiangsu Energy Development Co Ltd Clean Energy Branch; Huaneng International Power Jiangsu Energy Development Co Ltd
Current assignee: Huaneng Guanyun Clean Energy Power Generation Co ltd; Southeast University; Clean Energy Branch of Huaneng International Power Jiangsu Energy Development Co Ltd Clean Energy Branch; Huaneng International Power Jiangsu Energy Development Co Ltd
Priority date: 2022-08-16
Filing date: 2022-08-16
Publication date: 2023-02-28
Anticipated expiration: 2032-08-16

Abstract

The utility model relates to a filter capacitor voltage differential feedback active damping control system relates to grid-connected inverter control field. The system comprises: the device comprises a first proportional regulator, a second proportional regulator, a third proportional regulator, a delay module, a first subtractor module and a damping branch feedback coefficient module; the measured voltage of the filter capacitor is connected with the input ends of the first proportional regulator, the second proportional regulator and the third proportional regulator, the output end of the second proportional regulator is connected with the input end of the delay module, the output ends of the delay module, the first proportional regulator and the third proportional regulator are connected with the input end of the first subtracter module, the output end of the first subtracter module is connected with the input end of the damping branch feedback coefficient module, and the output end of the damping branch feedback coefficient module is connected into a filter current loop main control loop.

Description

Voltage differential feedback active damping control system of filter capacitor

Technical Field

The utility model relates to a grid-connected inverter control field, concretely relates to filter capacitor voltage differential feedback active damping control system.

Background

On the premise of realizing the same filtering effect, the LCL filter has the advantages of small volume and low cost compared with a single L filter, but resonance is easy to occur to cause grid-connected system instability. Common methods for suppressing the resonance of the LCL filter can be divided into passive damping and active damping, wherein the passive damping is simple to realize and is not limited by switching frequency, but increases system loss.

The active damping is realized by feeding back the state quantity of the LCL filter, and the method has the advantages of simplicity in realization, flexibility in control and strong robustness. In the existing method, the filter capacitor current proportional feedback active damping is widely applied due to simple algorithm, but the practical application has the defect of difficult accurate sampling due to large capacitor current pulsation. Theoretical derivation can know that the same damping effect can be obtained by filtering capacitor voltage differential feedback, but the existing filtering capacitor voltage differential feedback active damping method is to regard the filtering capacitor voltage as the power grid voltage, sample the filtering capacitor voltage to carry out phase locking, feedforward and differential feedback, and indirectly control the network inlet current by controlling the side inductance current of the inverter. Although stable control can be achieved, steady-state errors exist in the network current, and the dynamic characteristics of the system are poor. Meanwhile, the measured filter capacitor voltage is directly fed back by a conventional differential method, and the equivalent proportion of the filter capacitor leakage current is fed back, so that the gain of the LCL filter at the fundamental wave is reduced.

SUMMERY OF THE UTILITY MODEL

Not enough to prior art, the utility model provides a filter capacitor voltage differential feedback active damping control system.

The purpose of the utility model can be realized by the following technical scheme:

a filter capacitor voltage differential feedback active damping control system, comprising: the device comprises a first proportion regulator, a second proportion regulator, a third proportion regulator, a delay module, a first subtracter module and a damping branch feedback coefficient module;

the measured voltage of the filter capacitor is connected with the input ends of the first proportional regulator, the second proportional regulator and the third proportional regulator, the output end of the second proportional regulator is connected with the input end of the delay module, the output ends of the delay module, the first proportional regulator and the third proportional regulator are connected with the input end of the first subtracter, the output end of the first subtracter is connected with the input end of the damping branch feedback coefficient module, and the output end of the damping branch feedback coefficient module is connected into a filter current loop main control loop.

Optionally, the filter capacitor voltage is negatively fed back to the filter current loop main control loop through the first proportional regulator, the second proportional regulator, the delay module and the third proportional regulator, respectively, through subtraction by the first subtractor and through the feedback coefficient regulation module.

Optionally, an SPWM module is connected in series between the feedback coefficient adjusting module and the filter current loop main control loop.

On the other hand, the technical scheme of the utility model still include the application of foretell filter capacitor voltage differential feedback active damping control system in grid-connected inverter control.

The first proportional regulator, the second proportional regulator and the third proportional regulator fully consider the influence of filter capacitor leakage current in an actual system in parameter design. According to the vector relation among the capacitor voltage, the insulation resistance voltage and corresponding differential quantities thereof, parameters of the first proportional regulator, the second proportional regulator and the third proportional regulator are designed, so that the final differential feedback of the filter capacitor voltage is realized, the proportional feedback of the filter capacitor current can be equivalent, and the problem that the conventional differential feeds back the filter capacitor leakage current together to influence the low-frequency performance of the LCL filter is solved.

The first proportional regulator, the second proportional regulator and the delay module fully consider digital control delay existing in an actual system when parameter design is carried out, and ensure that the damping effect is not influenced by control delay;

the damping feedback branch coefficient module reasonably designs a feedback coefficient on the basis of considering the digital control delay of an actual system, ensures that the system obtains the optimal damping ratio and realizes the optimal control;

the utility model has the advantages that:

compared with the prior art, the utility model discloses on the basis of effectively restraining LCL filter resonance, fully consider the influence of filter capacitor leakage current, according to the vector relation between electric capacity electric current, leakage current and its corresponding differential quantity, design first proportional control ware, second proportional control ware and third proportional control ware parameter, can solve the problem that conventional differential implementation method reduces LCL filter low-frequency band gain and reduces; the first proportional regulator, the second proportional regulator and the delay module fully consider the influence of the digital control delay of an actual system during parameter design and adopt an effective method to solve the problem; designing a damping branch feedback coefficient according to the optimal damping ratio to ensure that the system realizes optimal control; the method is directly applied to a direct control system of the network access current, and can ensure that the network access current has higher control precision and better dynamic characteristics.

Drawings

The present invention will be further described with reference to the accompanying drawings.

Fig. 1 is a control block diagram of the control system of the present invention.

Fig. 2 is a schematic diagram illustrating the connection between the power circuit and the control circuit of the LCL grid-connected inverter.

Fig. 3 is a schematic diagram of the conventional method for reducing the suppression capability of the LCL filter to the low-frequency harmonic by implementing active damping of the voltage of the feedback filter capacitor of the differential link.

FIG. 4 is a schematic diagram of the optimal control of the system to achieve the optimal damping ratio.

Fig. 5 is a schematic view of the damping effect of the present invention.

Fig. 6 is a schematic diagram illustrating the effectiveness of suppressing resonance according to the present invention.

Fig. 7 is a steady waveform of the current of the power grid when the utility model is used.

Fig. 8 is a dynamic waveform of the current of the power grid when the utility model is used.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative efforts belong to the protection scope of the present invention.

In some examples of the present invention, as shown in fig. 1, a filter capacitor voltage differential feedback active damping method is disclosed, involving a control system consisting of a differential feedback filter capacitor voltage active damping branch and an LCL filter current loop main control loop. The feedback filter capacitor voltage active damping branch circuit comprises a first proportional regulator 1, a second proportional regulator 2, a third proportional regulator 3, a delay module 4, a first subtracter module 5 and a damping branch circuit feedback coefficient module 6; the LCL filter current loop main control loop comprises a second subtracter module 7, a current loop controller module 8, an adder module 9 and a third subtracter module 10.

Based on the differential feedback filter capacitor voltage active damping method, the method specifically comprises the following steps: for the differential feedback filter capacitor voltage active damping branch circuit, the detected filter capacitor voltage is respectively subjected to proportional adjustment through a first proportional regulator, a second proportional regulator and a third proportional regulator, wherein the output of the second proportional regulator is delayed through a delay module, the outputs of the first proportional regulator, the third proportional regulator and the delay module are subjected to operation through a first subtracter module, and the output of the first subtracter is modulated through a damping branch circuit regulating coefficient and fed back to a main control loop; for the LCL filter current loop main control loop, a reference current and a network access current are subtracted through the second subtracter module 7, the obtained current deviation passes through the current loop controller 8, the output of the current loop controller 8 is added with a feedforward power grid voltage through the adder module 9, and is subtracted from the output of the damping branch through the third subtracter module 10, and finally a modulation wave is obtained. The active damping branch circuit of the voltage of the differential feedback filter capacitor can effectively realize active damping and obtain the optimal damping effect, the main control loop of the current loop of the LCL filter and the active damping branch circuit of the voltage of the differential feedback filter capacitor can control the current of the network to stably track the reference current under the combined action, and the inverter operates stably.

In some specific embodiments of the present invention, as shown in fig. 2, a schematic diagram of the LCL type grid-connected inverter power circuit and the control circuit connection is shown. It can be seen that the current of the network is directly controlled, so that the current of the network can be ensured to have better control precision and dynamic characteristic; the differential feedback of the voltage of the filter capacitor is essentially to calculate the current of the filter capacitor and then perform proportional feedback, but in an actual system, a branch circuit of the filter capacitor contains leakage current, and if a conventional differential implementation method is adopted, the differential feedback is directly performed on the measured voltage of the filter capacitor, the leakage current is fed back together, and the suppression capability of the LCL filter on harmonic waves in a low frequency band is reduced, as shown in fig. 3. Adopt the utility model provides a strategy is realized to differential method to according to electric capacity voltage, insulation resistance voltage and differential vector relation to consider that digital control postpones, design first proportional control ware parameter K ₁ A second proportional control parameter K ₂ A third ratio adjustment parameter K ₃ And delay module parameter e ^-Δt And the differential feedback capacitor voltage is ensured, and only the equivalent proportional feedback filter capacitor current is ensured. Meanwhile, the feedback parameters of the damping branch are designed, so that the system can obtain the optimal damping ratio while effectively inhibiting resonance, as shown in fig. 4.

Fig. 5 is adding the utility model discloses the bode diagram of back system can be seen, the utility model discloses can restrain LCL resonance peak well, and do not influence the low frequency of LCL wave filter, high frequency characteristic. Fig. 6 shows that the validity of the present invention can be verified, and after the switching, the current resonance is rapidly suppressed, which proves the validity of the present invention. Fig. 7 is the steady state current waveform, can see, will the utility model discloses be applied to into net electric current direct control scheme, advance the net electric current can be synchronous with the electric wire netting well, have better control accuracy. Fig. 8 is a reference current sudden change, and a dynamic waveform of the incoming network current shows that the system has better dynamic characteristics by adopting the utility model.

In the description herein, references to the description of "one embodiment," "an example," "a specific example," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the above embodiments, and that the foregoing embodiments and descriptions are provided only to illustrate the principles of the present invention without departing from the spirit and scope of the present invention.

Claims

1. A filter capacitor voltage differential feedback active damping control system, comprising: the device comprises a first proportional regulator, a second proportional regulator, a third proportional regulator, a delay module, a first subtractor module and a damping branch feedback coefficient module;

the measured voltage of the filter capacitor is connected with the input ends of the first proportional regulator, the second proportional regulator and the third proportional regulator, the output end of the second proportional regulator is connected with the input end of the delay module, the output ends of the delay module, the first proportional regulator and the third proportional regulator are connected with the input end of the first subtracter module, the output end of the first subtracter module is connected with the input end of the damping branch feedback coefficient module, and the output end of the damping branch feedback coefficient module is connected into a filter current loop main control loop.

2. The filter capacitor voltage differential feedback active damping control system according to claim 1, wherein the filter capacitor voltage is negatively fed back to the filter current loop main control loop through the first proportional regulator, the second proportional regulator, the delay module and the third proportional regulator, respectively, through subtraction by the first subtractor and through the feedback coefficient regulation module.

3. The filter capacitor voltage differential feedback active damping control system of claim 2, wherein the filter current loop main control loop comprises a second subtractor module, a current loop controller module, an adder module, and a third subtractor module; the reference current and the network access current are subtracted through the second subtracter module, the obtained current deviation passes through the current loop controller, the output of the current loop controller is added with the feedforward power grid voltage through the adder module, and the output of the current loop controller is subtracted from the output of the damping branch through the third subtracter module, and the modulation wave is obtained.

4. The filter capacitor voltage differential feedback active damping control system of claim 3, wherein an SPWM module is connected in series between the feedback coefficient adjustment module and the filter current loop main control loop.