CN117154676A - Power decoupling device and method for three-phase inverter - Google Patents

Abstract

The application belongs to the technical field of power electronics, and in particular relates to a power decoupling device and method for a three-phase inverter, comprising the following steps: the power decoupling circuit comprises an anode input end and a cathode input end, wherein the anode input end is connected with an anode on a direct current bus of the three-phase inverter, the cathode input end is connected with a cathode on the direct current bus of the three-phase inverter, a first capacitor is arranged in the power decoupling circuit, one end of the first capacitor is connected with the anode input end, the other end of the first capacitor is connected with the cathode input end, the first capacitor is used for absorbing the secondary pulsating current so as to inhibit the pulsation of voltage and current on the direct current bus of the three-phase inverter, and a PWM control law is obtained according to the current and the voltage on the direct current bus, the voltage of the first capacitor and the reference voltage of the first capacitor so as to control the working state of the power decoupling circuit.

Description

Power decoupling device and method for three-phase inverter

Technical Field

The application belongs to the technical field of power electronics, and particularly relates to a power decoupling device and method for a three-phase inverter.

Background

The three-phase inverter is a power electronic device which converts direct current into three-phase alternating current by controlling a power semiconductor device to turn on and off regularly, and is widely applied to occasions such as distributed power generation, locomotive auxiliary power supply and uninterruptible power supply, but the three-phase inverter operates under the condition of unbalanced load, the negative sequence current component in the output current can enable the power of an alternating current side to contain secondary pulsation power, the secondary pulsation power also exists on a direct current side according to the law of conservation of power, the power supply quality can be influenced by the secondary pulsation power existing in a system, and when the secondary pulsation power is transmitted to the direct current side in a coupling way, voltage and current fluctuation of the direct current side can be caused, so that the service life of the direct current side power supply can be influenced, and the stability of a front-stage device can be influenced.

Disclosure of Invention

The technical problems to be solved by the application are as follows: how to solve the problem of secondary current pulsation on the direct current side caused by coupling of secondary pulsation power generated on the alternating current side to the direct current side without changing the original three-phase inverter structure.

The application achieves the aim through the following technical scheme:

in a first aspect, a power decoupling apparatus for a three-phase inverter is provided, comprising: the power decoupling circuit and the control module are connected with the power decoupling circuit;

the power decoupling circuit comprises an anode input end and a cathode input end, wherein the anode input end is connected with an anode on a direct current bus of the three-phase inverter, and the cathode input end is connected with a cathode on the direct current bus of the three-phase inverter;

the power decoupling circuit is internally provided with a first capacitor, one end of the first capacitor is connected with the positive electrode input end, the other end of the first capacitor is connected with the negative electrode input end, and the first capacitor is used for absorbing secondary pulsating current in the three-phase inverter so as to inhibit the pulsation of voltage and current on a direct current bus of the three-phase inverter;

the control module is used for obtaining the current and the voltage on the direct current bus, the voltage of the first capacitor and the reference voltage of the first capacitor, and obtaining a PWM control law according to the current and the voltage on the direct current bus, the voltage of the first capacitor and the reference voltage of the first capacitor so as to control the working state of the power decoupling circuit.

Preferably, the power decoupling circuit further comprises a first voltage division point, an inductor and a half bridge arm, wherein the first voltage division point is connected with the positive electrode input end, one end of the inductor is connected with the first voltage division point, and the other end of the inductor is connected with the half bridge arm;

and the inductor and the half bridge arm form a bidirectional buck-boost circuit to provide a path for the secondary pulsating current.

Preferably, the other end of the inductor is connected with the half bridge arm, specifically:

the half bridge arm comprises a first switching tube and a second switching tube, a source electrode of the first switching tube is connected with a drain electrode of the second switching tube, a second voltage division point is arranged between the source electrode of the first switching tube and the drain electrode of the second switching tube, and the other end of the inductor is connected with the second voltage division point.

Preferably, one end of the first capacitor is connected with the drain electrode of the first switching tube, and the other end of the first capacitor is connected with the source electrode of the second switching tube.

Preferably, the power decoupling circuit further comprises a second capacitor, one end of the second capacitor is connected with the positive electrode input end, and the other end of the second capacitor is connected with the negative electrode input end;

the inductor and the second capacitor form a high-frequency filter for absorbing high-frequency current ripples generated when the first switching tube and the second switching tube work.

Preferably, the control module comprises an acquisition unit and a signal processing unit, and the acquisition unit is connected with the signal processing unit;

the acquisition unit is used for acquiring current and voltage on the direct current bus, voltage of the first capacitor and reference voltage of the first capacitor, and transmitting the current and voltage on the direct current bus, the voltage of the first capacitor and the reference voltage of the first capacitor to the signal processing unit;

the signal processing unit is used for obtaining a processing signal according to the current and the voltage on the direct current bus, the voltage of the first capacitor and the reference voltage of the first capacitor.

Preferably, the control module further includes a pulse width modulation (Pulse Width Modulation, abbreviated as PWM) unit, a signal input end of the PWM unit is connected to the signal processing unit, and a signal output end of the PWM unit is connected to gates of the first switching tube and the second switching tube respectively;

the PWM unit is used for generating a PWM control law according to the processing signal, and controlling the on and off of the first switching tube and the second switching tube according to the PWM control law, so that the working state of the power decoupling circuit is controlled.

Preferably, the signal processing unit includes a high-pass filter, a voltage controller and a Proportional-Integral (PI) controller, where the high-pass filter is connected to the voltage controller, and is configured to receive a voltage on the dc bus and transmit the voltage on the dc bus to the voltage controller to obtain a first reference current, where the first reference current is a component of a secondary pulsating current that needs to be compensated by the power decoupling circuit;

the PI controller is used for receiving the voltage of the first capacitor and the reference voltage of the first capacitor and obtaining a second reference current through PI control, and the second reference current is used for controlling the working stability of the first capacitor.

Preferably, the signal processing unit further includes a current controller, where the current controller is connected to a signal input end of the PWM unit, and the current controller is configured to compare the current on the dc bus with the first reference current and the second reference current, generate a processing signal, and send the processing signal to the PWM unit.

In a second aspect, a power decoupling method for a three-phase inverter is provided, comprising:

connecting the positive input end of the power decoupling circuit with the positive electrode on the direct current bus of the three-phase inverter, and connecting the negative input end with the negative electrode on the direct current bus of the three-phase inverter;

the first capacitor absorbs secondary pulsating current in the three-phase inverter so as to inhibit the pulsation of voltage and current on a direct current bus of the three-phase inverter;

the control module obtains the current and the voltage on the direct current bus, the voltage of the first capacitor and the reference voltage of the first capacitor, and obtains a PWM control law according to the current and the voltage on the direct current bus, the voltage of the first capacitor and the reference voltage of the first capacitor so as to control the working state of the power decoupling circuit.

The beneficial effects of the application are as follows: according to the application, the positive electrode input end and the negative electrode input end of the power decoupling circuit are connected in parallel to the direct current bus of the three-phase inverter, the power decoupling circuit provides a current path for the secondary pulsating current on the direct current bus and transmits the current path to the first capacitor in the power decoupling circuit, the first capacitor absorbs the secondary pulsating current, so that the problem of the secondary pulsating current on the direct current bus is restrained, the power decoupling circuit is connected in parallel to the direct current bus for use, plug and play can be realized, normal use of the original three-phase inverter is not influenced, and meanwhile, the normal work of the power decoupling circuit is controlled through the control module, and the stability of the power decoupling circuit to the work of the three-phase inverter is improved.

Drawings

In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art. The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification, illustrate the disclosure and together with the description serve to explain, but do not limit the disclosure. In the drawings:

fig. 1 is a schematic structural diagram of a power decoupling device for a three-phase inverter according to an embodiment of the present application;

fig. 2 is a schematic diagram of a power decoupling circuit of a power decoupling device for a three-phase inverter according to an embodiment of the present application;

fig. 3 is a schematic structural diagram of a control module of a power decoupling device for a three-phase inverter according to an embodiment of the present application;

fig. 4 is a schematic diagram of a connection structure between a control module of a power decoupling device and a power decoupling circuit for a three-phase inverter according to an embodiment of the present application;

fig. 5 is a schematic structural diagram of a signal processing unit in a control module of a power decoupling device for a three-phase inverter according to an embodiment of the present application;

fig. 6 is a schematic flow chart of a power decoupling method for a three-phase inverter according to an embodiment of the present application;

fig. 7 is a schematic structural diagram of a control module of a power decoupling device for a three-phase inverter according to an embodiment of the present application;

fig. 8 is a schematic diagram of simulation results of a power decoupling device for a three-phase inverter according to an embodiment of the present application;

fig. 9 is a schematic diagram of another simulation result of a power decoupling device for a three-phase inverter according to an embodiment of the present application.

Detailed Description

The present application will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present application more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.

In addition, the technical features of the embodiments of the present application described below may be combined with each other as long as they do not collide with each other. The application will be described in detail below with reference to the drawings and examples.

It should also be noted that in this specification, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

Example 1

In order to solve the problem of secondary pulsation of the dc side caused by coupling of secondary pulsation power generated on the ac side of the three-phase inverter to the dc side, as shown in fig. 1, a power decoupling apparatus for a three-phase inverter is proposed in the present embodiment, including: the power decoupling circuit comprises a power decoupling circuit and a control module, wherein the control module is connected with the power decoupling circuit, the power decoupling circuit comprises an anode input end and a cathode input end, the anode input end is connected with an anode on a direct current bus of a three-phase inverter, the cathode input end is connected with a cathode on the direct current bus of the three-phase inverter, a first capacitor C1 is arranged in the power decoupling circuit, one end of the first capacitor C1 is connected with the anode input end, the other end of the first capacitor C1 is connected with the cathode input end, the first capacitor C1 is used for absorbing secondary pulsating current in the three-phase inverter so as to inhibit pulsation of voltage and current on the direct current bus of the three-phase inverter, and the control module is used for acquiring current and voltage on the direct current bus, voltage of the first capacitor C1 and reference voltage of the first capacitor C1, and controlling the work state of the power decoupling circuit according to the current and the voltage on the direct current bus, the voltage of the first capacitor C1 and the reference voltage of the first capacitor C1.

The voltage of the first capacitor C1, that is, the instantaneous voltage of the first capacitor C1, is obtained by a voltage sensor, and the reference voltage of the first capacitor C1 is preset, but there is also a certain requirement, for example, the dc bus voltage of the three-phase inverter is set to 600V (this is determined), and the ripple requirement of the first capacitor C1 (this is selected according to the actual capacitor and is also determined) is below 50V, at this time, the reference voltage must be greater than 650V, but cannot be infinite, because this reference voltage cannot be greater than the maximum withstand voltage value of the capacitor C1.

The first capacitor C1 may smooth the current variation on the dc bus by providing a low impedance path, thereby reducing the influence of the secondary ripple current, in particular, the first capacitor C1 may be connected to the dc bus of the three-phase inverter, in parallel with the power supply of the three-phase inverter, and when the three-phase inverter operates, a certain ripple current may be generated, which is mainly caused by the instantaneous power unbalance of the dc bus side and the ac output, and in order to satisfy the rule of the power balance, the ripple power and the ripple current may necessarily occur on the dc bus, the first capacitor C1 may absorb the ripple current by providing a low impedance path, and stabilize the current on the dc bus, and when the ripple current occurs, the first capacitor C1 may release the stored electric energy, smooth the variation of the current, and when the ripple current decreases or disappears, the first capacitor C1 may be recharged to prepare for the next ripple current absorption.

The capacitance and characteristics of the first capacitor C1 need to be selected according to specific design and requirements, and it should be noted that the capacitance, voltage level, temperature and other factors of the first capacitor C1 need to be taken into consideration, so as to ensure that the first capacitor C1 can bear the current and voltage requirements of the inverter during operation, and has enough life and stability to provide the best decoupling effect.

Meanwhile, a control module is arranged to control the working state of the power decoupling circuit, a PWM control law is obtained according to the current and the voltage on the direct current bus, the voltage of the first capacitor C1 and the reference voltage of the first capacitor C1, and the working state of the power decoupling circuit is controlled through the PWM control law, wherein the specific structures of the power decoupling circuit and the control module are described below.

Next, a specific structure of the power decoupling circuit is described, and fig. 2 is a schematic diagram of the specific structure of the power decoupling circuit.

In a preferred embodiment, the power decoupling circuit further includes a first voltage division point a, an inductor L and a half bridge arm, the first voltage division point a is connected with the positive input end, one end of the inductor L is connected with the first voltage division point a, the other end of the inductor L is connected with the half bridge arm, and the inductor L and the half bridge arm form a bidirectional buck-boost circuit to provide a path for the secondary pulsating current.

In the bidirectional Buck-Boost circuit, the inductor L is an important component, the inductor L realizes control and smoothing of current by storing and releasing energy, and when a switching tube in the half bridge arm is conducted, the current passes through the inductor L, and the inductor L stores the energy; when the switching tube is turned off, the inductor L discharges the stored energy, maintains the continuity of the current, and provides a path for the secondary pulsating current.

The half bridge arm consists of two switching tubes and an inductor L, the half bridge arm comprises a first switching tube T1 and a second switching tube T2, a source electrode of the first switching tube T1 is connected with a drain electrode of the second switching tube T2, a second voltage division point B is arranged between the source electrode of the first switching tube T1 and the drain electrode of the second switching tube T2, and the other end of the inductor is connected with the second voltage division point B.

One end of the first capacitor C1 is connected to the drain of the first switching tube T1, and the other end of the first capacitor C1 is connected to the source of the second switching tube T2.

The current of the direct current bus of the three-phase inverter is pulsed, so that the current is high or low, and when the pulsed current is at a high side (positive half shaft), the current flows to an output side; when the pulsating current is at the low side (negative half-axis), the current flows to the input side to achieve a smoothing effect; by controlling the on and off of the first switching tube T1 and the second switching tube T2, the forward and reverse flow of the current can be realized, and when the voltage needs to be boosted, the current flows from the input side to the output side, so that the voltage is boosted; when the voltage needs to be reduced, current can flow from the output side to the input side, voltage reduction is achieved, and the bidirectional Buck-Boost circuit can achieve bidirectional adjustment of current and voltage through the combination of the inductor L and the half bridge arm.

When the first switching tube T1 and the second switching tube T2 operate normally, a high-frequency current ripple is generated, and the first switching tube T1 and the second switching tube T2 are switching devices, typically MOSFETs or Insulated Gate Bipolar Transistors (IGBT) and are not particularly limited in type in this embodiment, and the flow path of the current is controlled by periodically switching and off.

Due to the fast switching of the switching actions, current ripples are generated when the two switching tubes work, which is caused by current changes in the on and off processes of the switching tubes, the amplitude and the frequency of the high-frequency current ripples depend on the switching frequency and the characteristics of the switching tubes, and the switching frequency of the switching tubes is usually between tens of kHz and hundreds of kHz, so that the frequency of the high-frequency current ripples is also in a corresponding range.

In order to reduce the influence of the high-frequency current ripple, in a preferred embodiment, the power decoupling circuit further includes a second capacitor C2, one end of the second capacitor C2 is connected to the positive input terminal, the other end of the second capacitor C2 is connected to the negative input terminal, and the inductor L and the second capacitor C2 form a high-frequency filter, so as to absorb the high-frequency current ripple generated when the first switching tube T1 and the second switching tube T2 operate.

The high frequency filter composed of the inductor L and the second capacitor C2 may provide a low impedance path for filtering and absorbing the high frequency current, because the inductor L has an impedance characteristic, has a higher impedance for the high frequency signal, and the second capacitor C2 has a lower impedance, when the first switching tube T1 and the second switching tube T2 operate, their switching actions may cause a change and pulsation of the current, these high frequency current ripples may be transferred to the inductor L and the second capacitor C2, the inductor L blocks the high frequency signal by its high impedance characteristic, and the second capacitor C2 absorbs and smoothes the high frequency current ripples by its low impedance characteristic.

The above is an overall description of the structure of the power decoupling circuit, and a specific structure of the control module will be described next.

In a preferred embodiment, as shown in fig. 3 and 4, the control module includes an acquisition unit and a signal processing unit, where the acquisition unit is connected to the signal processing unit, and the acquisition unit is configured to acquire a current and a voltage on the dc bus, a voltage of the first capacitor C1, and a reference voltage of the first capacitor C1, and transmit the current and the voltage on the dc bus, the voltage of the first capacitor C1, and the reference voltage of the first capacitor C1 to the signal processing unit, and the signal processing unit is configured to obtain a processing signal according to the current and the voltage on the dc bus, the voltage of the first capacitor C1, and the reference voltage of the first capacitor C1.

In a preferred embodiment, referring to fig. 4, the control module further includes a PWM unit, a signal input end of the PWM unit is connected to the signal processing unit, a signal output end of the PWM unit is respectively connected to gates of the first switching tube T1 and the second switching tube T2, and the PWM unit is configured to generate a PWM control law according to the processing signal, and control on and off of the first switching tube T1 and the second switching tube T2 according to the PWM control law, so as to implement control on an operating state of the power decoupling circuit.

In the control module, the acquisition unit is the module responsible for acquiring the relevant current and voltage information from the dc bus and the first capacitor C1, which can measure and acquire these signals by means of sensors or other circuits and transmit them to a signal processing unit.

The signal processing unit is a module for processing the obtained current and voltage information, and performs operations such as filtering, amplifying, mathematical operation and the like on the signals to obtain required processing signals, where the processing signals include power on the dc bus, errors of current and voltage, and states of the first capacitor C1, and these signals can be used for subsequent control and adjustment.

Through cooperation of the acquisition unit and the signal processing unit, the control module can acquire current and voltage on the direct-current bus, voltage of the first capacitor C1 and reference voltage in real time, process the signals to obtain required processing signals, and the processing signals can be used for generating a PWM control law so as to control the working state of the power decoupling circuit, so that accurate control and optimization operation of the whole power decoupling device are realized.

Finally, a specific structural composition of the signal processing unit will be described, in a preferred embodiment, as shown in fig. 5, the signal processing unit includes a high-pass filter HPF, a voltage controller Gv and a PI controller, where the high-pass filter HPF is connected to the voltage controller Gv, the high-pass filter HPF is configured to receive a voltage on the dc bus, and transmit the voltage on the dc bus to the voltage controller Gv to obtain a first reference current I1, the first reference current I1 is a component of a secondary pulsating current that needs to be compensated by the power decoupling circuit, and the PI controller is configured to receive the voltage of the first capacitor C1 and a reference voltage of the first capacitor C1 and obtain a second reference current I2 through PI control, where the second reference current I2 is configured to control stability of operation of the first capacitor C1.

In a preferred embodiment, the signal processing unit further includes a current controller Gi, where the current controller Gi is connected to the signal input terminal of the PWM unit, and the current controller Gi is configured to compare the current on the dc bus, the first reference current I1, and the second reference current I2, generate a processing signal, and send the processing signal to the PWM unit.

Wherein the signal processing unit comprises a high pass filter HPF (High Pass Filter), a voltage controller Gv, a PI controller and a current controller Gi, which are connected to each other to realize control and regulation of the power decoupling circuit.

The high-pass filter HPF is used for receiving the voltage on the direct current bus and transmitting the voltage to the voltage controller Gv, and has the function of filtering out low-frequency components and transmitting only high-frequency components so as to obtain a high-frequency voltage signal on the direct current bus, wherein the high-frequency voltage signal is used for calculating and obtaining a first reference current I1, and the first reference current I1 is a component of the secondary pulsating current which needs to be compensated by the power decoupling circuit.

The voltage controller Gv receives the high-frequency voltage signal transmitted by the high-pass filter HPF and calculates to obtain a first reference current I1 according to a control strategy, the voltage controller Gv adjusts the magnitude of the first reference current I1 according to the high-frequency voltage signal on the direct-current bus, the PI controller receives the voltage of the first capacitor C1 and the reference voltage of the first capacitor C1 and calculates to obtain a second reference current I2 according to the PI control strategy, and the second reference current I2 is used for controlling the operation of the first capacitor C1 to maintain the stability of the first reference current I1, so that detailed PI control strategies will not be repeated in this embodiment.

The current controller Gi is connected with the signal input end of the PWM unit, and is used for comparing the current on the direct current bus, the first reference current I1 and the second reference current I2 at each moment, namely, the first reference current I1 and the second reference current I2 are added to obtain a comprehensive reference current; by comparing the current on the direct current bus with the integrated reference current, the duty cycle of the PWM signal is reduced when the current on the direct current bus is greater than the integrated reference current; when the current on the direct current bus is smaller than the integrated reference current, the duty cycle of the PWM signal increases.

The current controller Gi also generates a processing signal according to the comparison result, and sends the processing signal to the PWM unit, so as to control the duty ratio of the PWM signal in the PWM unit, and further generate a square wave signal (i.e. PWM wave) with a corresponding duty ratio, so as to control the on-off of the first switching tube T1 and the second switching tube T2 in the power decoupling circuit.

According to the application, the positive electrode input end and the negative electrode input end of the power decoupling circuit are connected in parallel to the direct current bus of the three-phase inverter, the power decoupling circuit provides a current path for the secondary pulsating current on the direct current bus and transmits the current path to the first capacitor C1 in the power decoupling circuit, the first capacitor C1 absorbs the secondary pulsating current, and further the problem of the secondary pulsating current on the direct current bus is restrained, the power decoupling circuit is connected in parallel to the direct current bus for use, so that plug and play can be realized, normal use of the original three-phase inverter is not influenced, and meanwhile, the normal operation of the power decoupling circuit is controlled through the control module, and the stability of the power decoupling circuit to the three-phase inverter is improved.

Example 2

In embodiment 1, a power decoupling device for a three-phase inverter is proposed, and as shown in fig. 6, in this embodiment, a power decoupling method for a three-phase inverter is proposed, including:

step 101: and the positive electrode input end of the power decoupling circuit is connected with the positive electrode on the direct current bus of the three-phase inverter, and the negative electrode input end is connected with the negative electrode on the direct current bus of the three-phase inverter.

The power decoupling circuit is connected in parallel to the direct current bus of the three-phase inverter, namely, a first capacitor C1 in the power decoupling circuit is connected to the direct current bus of the three-phase inverter and is connected in parallel with a power supply of the three-phase inverter.

Step 102: the first capacitor absorbs secondary pulsating current in the three-phase inverter to inhibit pulsation of voltage and current on a direct current bus of the three-phase inverter.

When the three-phase inverter is operated, a certain pulsating current is generated due to imperfect properties of the circuit, and is mainly caused by switching action of the switching device and variation of inductance, the first capacitor C1 absorbs the pulsating current by providing a low impedance path and stabilizes the current on the dc bus, when the pulsating current occurs, the first capacitor C1 releases the stored electric energy, smoothes the variation of the current, and when the pulsating current decreases or disappears, the first capacitor C1 is recharged to prepare for the next pulsating current absorption.

Step 103: the control module obtains the current and the voltage on the direct current bus, the voltage of the first capacitor and the reference voltage of the first capacitor, and obtains a PWM control law according to the current and the voltage on the direct current bus, the voltage of the first capacitor and the reference voltage of the first capacitor so as to control the working state of the power decoupling circuit.

The acquisition unit in the control module acquires current and voltage on the direct current bus, voltage of the first capacitor and reference voltage of the first capacitor in real time, the signals can be acquired through a sensor, a sampling circuit and the like and transmitted to the signal processing unit, and the signal processing unit performs signal processing according to the current and voltage on the direct current bus, the voltage of the first capacitor and the reference voltage of the first capacitor, and calculates to obtain a PWM control law through a proper algorithm and logic according to the input signals.

The PWM control law is a control method based on a pulse width modulation technology, according to the obtained PWM control law, a control module can adjust the duty ratio of PWM signals so as to control the working state of a power decoupling circuit, and by adjusting the duty ratio of the PWM signals, the on time and the off time of switching devices, namely a first switching tube T1 and a second switching tube T2, in the power decoupling circuit can be controlled so as to control the opening or closing of a working channel of a first capacitor C1, thereby realizing the accurate control of the decoupling of the secondary pulsating current in the three-phase inverter.

The specific structural composition of the power decoupling circuit is shown in embodiment 1, and will not be described in detail in this embodiment.

Example 3

In the power decoupling device for a three-phase inverter set forth in embodiment 1, in which the control module is implemented by a complex combination circuit, in a preferred embodiment, as shown in fig. 7, the function of the control module may also be implemented in a controller, which may be a microcontroller (Microcontroller Unit, abbreviated as MCU) or a digital signal processor (Digital Signal Processor, abbreviated as DSP), and implemented inside the MCU or DSP by combining the module circuits therein, so that the size of the power decoupling device and the precise control of the control module may be greatly reduced.

The specific control flow inside the controller refers to embodiment 2, and in this embodiment, too much description is omitted.

Example 4

For further explanation of the embodiments of the present application, a specific example will be provided in the embodiments of the present application to further explain the present application.

Simulation results of a power decoupling circuit when a certain 18KW three-phase four-wire system inverter is provided with an unbalanced load are shown in fig. 8 and 9:

when the three-phase four-wire system inverter works under the load condition (such as fig. 8) lacking the A phase and the load condition (such as fig. 9) lacking the A phase and the B phase, the measured direct current bus voltages all contain secondary ripple voltages, wherein the peak value of the secondary ripple voltages is about 80V, and the secondary ripple currents contained in the direct current bus currents are about 15A.

The power decoupling device for a three-phase inverter according to embodiment 1 is connected to the dc bus of the three-phase four-wire inverter (see embodiment 1 for a specific connection mode), the power decoupling device works normally after 0.1S, after transient adjustment, the three-phase four-wire inverter is stabilized (as shown in fig. 8 and 9), at this time, the peak value of the secondary ripple voltage contained in the dc bus voltage is only about 8V, and the secondary ripple current contained in the dc bus current is only about 1.5A.

The specific structure and implementation method of the power decoupling device are respectively referred to embodiment 1 and embodiment 2, and are not described in detail in this embodiment.

It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the application and is not intended to limit the application, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the application are intended to be included within the scope of the application.

Claims (10)

1. A power decoupling device for a three-phase inverter, comprising: the power decoupling circuit and the control module are connected with the power decoupling circuit;

the power decoupling circuit comprises an anode input end and a cathode input end, wherein the anode input end is connected with an anode on a direct current bus of the three-phase inverter, and the cathode input end is connected with a cathode on the direct current bus of the three-phase inverter;

the power decoupling circuit is internally provided with a first capacitor, one end of the first capacitor is connected with the positive electrode input end, the other end of the first capacitor is connected with the negative electrode input end, and the first capacitor is used for absorbing secondary pulsating current in the three-phase inverter so as to inhibit the pulsation of voltage and current on a direct current bus of the three-phase inverter;

the control module is used for obtaining the current and the voltage on the direct current bus, the voltage of the first capacitor and the reference voltage of the first capacitor, and obtaining a PWM control law according to the current and the voltage on the direct current bus, the voltage of the first capacitor and the reference voltage of the first capacitor so as to control the working state of the power decoupling circuit.

2. The power decoupling device for a three-phase inverter of claim 1, wherein the power decoupling circuit further comprises a first voltage division point, an inductor, and a half bridge arm, the first voltage division point being connected to the positive input terminal, one end of the inductor being connected to the first voltage division point, and the other end of the inductor being connected to the half bridge arm;

and the inductor and the half bridge arm form a bidirectional buck-boost circuit to provide a path for the secondary pulsating current.

3. The power decoupling device for a three-phase inverter of claim 2, wherein the other end of the inductor is connected to the half bridge arm, in particular:

the half bridge arm comprises a first switching tube and a second switching tube, a source electrode of the first switching tube is connected with a drain electrode of the second switching tube, a second voltage division point is arranged between the source electrode of the first switching tube and the drain electrode of the second switching tube, and the other end of the inductor is connected with the second voltage division point.

4. A power decoupling apparatus for a three-phase inverter as claimed in claim 3, wherein one end of the first capacitor is connected to the drain of the first switching tube and the other end of the first capacitor is connected to the source of the second switching tube.

5. A power decoupling apparatus for a three-phase inverter as claimed in claim 3, wherein the power decoupling circuit further comprises a second capacitor, one end of the second capacitor being connected to the positive input terminal, the other end of the second capacitor being connected to the negative input terminal;

the inductor and the second capacitor form a high-frequency filter for absorbing high-frequency current ripples generated when the first switching tube and the second switching tube work.

6. The power decoupling device for three-phase inverters of claim 3, wherein said control module comprises an acquisition unit and a signal processing unit, said acquisition unit being connected to said signal processing unit;

the acquisition unit is used for acquiring current and voltage on the direct current bus, voltage of the first capacitor and reference voltage of the first capacitor, and transmitting the current and voltage on the direct current bus, the voltage of the first capacitor and the reference voltage of the first capacitor to the signal processing unit;

the signal processing unit is used for obtaining a processing signal according to the current and the voltage on the direct current bus, the voltage of the first capacitor and the reference voltage of the first capacitor.

7. The power decoupling device for three-phase inverter of claim 6, wherein the control module further comprises a PWM unit, a signal input of the PWM unit is connected to the signal processing unit, and a signal output of the PWM unit is connected to gates of the first switching tube and the second switching tube, respectively;

the PWM unit is used for generating a PWM control law according to the processing signal, and controlling the on and off of the first switching tube and the second switching tube according to the PWM control law, so that the working state of the power decoupling circuit is controlled.

8. The power decoupling device for three-phase inverter of claim 7, wherein the signal processing unit comprises a high pass filter, a voltage controller and a PI controller, the high pass filter is connected with the voltage controller, the high pass filter is used for receiving the voltage on the dc bus and transmitting the voltage on the dc bus to the voltage controller to obtain a first reference current, and the first reference current is a component of a secondary pulsating current that the power decoupling circuit needs to compensate;

the PI controller is used for receiving the voltage of the first capacitor and the reference voltage of the first capacitor and obtaining a second reference current through PI control, and the second reference current is used for controlling the working stability of the first capacitor.

9. The power decoupling device for three-phase inverters of claim 8 wherein said signal processing unit further comprises a current controller connected to a signal input of said PWM unit, said current controller for comparing a current on said dc bus, said first reference current and said second reference current to generate a processed signal and transmitting said processed signal to said PWM unit.

10. A power decoupling method for a three-phase inverter, characterized in that the method is suitable for use in a power decoupling apparatus for a three-phase inverter as claimed in any one of claims 1 to 9, comprising:

connecting the positive input end of the power decoupling circuit with the positive electrode on the direct current bus of the three-phase inverter, and connecting the negative input end with the negative electrode on the direct current bus of the three-phase inverter;

the first capacitor absorbs secondary pulsating current in the three-phase inverter so as to inhibit the pulsation of voltage and current on a direct current bus of the three-phase inverter;

the control module obtains the current and the voltage on the direct current bus, the voltage of the first capacitor and the reference voltage of the first capacitor, and obtains a PWM control law according to the current and the voltage on the direct current bus, the voltage of the first capacitor and the reference voltage of the first capacitor so as to control the working state of the power decoupling circuit.