CN102904458B - Control method and device for inverter - Google Patents
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Abstract
The embodiment of the invention discloses a voltage sag generation device and a control method and a control device for an inverter. The generation device comprises a modular multi-level rectifier and a modular multi-level inverter, wherein the modular multi-level rectifier is connected with the modular multi-level inverter in a back-to-back power transmission connection manner, and the structures of the modular multi-level rectifier and the modular multi-level inverter are the same; each of the modular multi-level rectifier and the modular multi-level inverter comprises three phase units which are connected in parallel with one another; each phase unit consists of two bridge arms which are connected in series with each other; any bridge arm consists of N sub modules SM and a valve reactor which are connected in series; and each SM consists of two insulated gate bipolar transistor (IGBT) switching devices and a direct current energy storage capacitor which are connected in parallel. The device can precisely control a voltage sag depth, lasting time, a phase and a sag type and can be easily expanded to high voltage and high power grade; requirements on high voltage and high power are met; a requirement on the switching devices is low, and the switching devices are easy to purchase; the price is low; an output waveform is relatively high in quality; and the number of filters on an alternating current side is reduced.
Description
Technical Field
The invention relates to the field of mobile power grids, in particular to a voltage drop generation device, and a control method and device of an inverter.
Background
Wind power generation has attracted attention as a green renewable energy source. With the increasing of the proportion of the installation capacity of the wind turbine generator to the power grid, the wind power generation system is connected with the power grid in parallel through the grid-connected inverter, and when the power grid fails and voltage drops to a certain degree, the grid-connected inverter is disconnected with the power grid; as the penetration power of wind power generation increases continuously, if a large number of wind power generation systems are disconnected from the power grid when the power grid fails, the voltage and frequency of the power grid are seriously affected, even the failure degree may be aggravated, and finally, the system units are completely disconnected. Therefore, the operation capability of the fan under the condition of grid fault appears to be extremely important. The new grid operation rule in China clearly requires that the grid-connected wind turbine generator cannot be disconnected within a certain time after Voltage drops, and must have a certain Low Voltage Ride Through (LVRT).
The LVRT of a wind power generation system under the grid fault is researched, and a grid voltage drop generating device suitable for wind power generation research is needed firstly. The voltage drop is the most common power grid fault type, and only various types of voltage drop can be accurately simulated, namely, only the types of voltage drop depth, duration, phase and drop can be accurately controlled, any waveform voltage required is generated to meet the requirements of wind power system tests under different fault conditions, and the research on the low-voltage ride-through control strategy of the wind power generation system has practical significance.
While the Voltage Sag of the grid-connected point of the wind power plant caused by the grid fault or disturbance is uncontrollable, in order to develop and test the low Voltage ride through capability of the wind turbine, special equipment is necessary to simulate various types of Voltage Sag, and the equipment is called a Voltage Sag Generator (VSG).
The prior art uses VSGs based on two-level voltage source converters. The converter adopts a two-level voltage source, the power grid voltage supplies power to the tested equipment through AC-DC-AC conversion, the rectifier controls the input power factor and keeps the voltage at the DC side stable, and various required voltage drop waveforms can be generated through controlling the inverter. The feasible voltage drop generator scheme has to meet the requirements of three aspects: high voltage and high power level, simple realization and low cost.
In the VSG in the prior art, when high-voltage high-power output needs to be supported, the grade must be expanded, a large number of switching devices need to be directly connected in series, and the direct series connection mode has a high requirement on the consistency of the on and off of each device, and meanwhile, the stress borne by the switching devices is large. Therefore, this is also demanding on the manufacturing process of the switching device, and the currently available switching devices are very expensive to purchase, and can be sold for hundreds of thousands of dollars, resulting in high cost of VSG production.
Disclosure of Invention
In order to solve the above problems, an object of the present invention is to provide a voltage drop generation apparatus, a control method and a control apparatus for an inverter, which can precisely control a voltage drop depth, a duration, a phase and a drop type, can be easily expanded to a high voltage and a high power level, meet a requirement for high voltage and high power, have low requirement for a switching device, are easy to purchase, are low in price, have high quality of an output waveform, and reduce a filter on an ac side.
The invention provides a voltage drop generating device, comprising:
a modular multilevel rectifier and a modular multilevel inverter;
the modular multilevel inverter and the modular multilevel inverter are connected in a back-to-back power transmission connection mode, and the modular multilevel inverter have the same structure; wherein,
the modular multi-level rectifier includes: a first phase unit formed by connecting a first bridge arm and a second bridge arm in series, a second phase unit formed by connecting a third bridge arm and a fourth bridge arm in series, and a third phase unit formed by connecting a fifth bridge arm and a sixth bridge arm in series, wherein the three phase units are connected in parallel;
the six bridge arms are formed by connecting N sub-modules SM and a valve reactor in series, wherein N is a natural number greater than or equal to 1;
the SM comprises two IGBT switchgears and a direct-current energy storage capacitor, wherein the two IGBT switchgears are connected in series and then connected in parallel with the direct-current energy storage capacitor.
A control method of an inverter for controlling a modular multilevel inverter in the device comprises the following steps:
detecting three-phase actual current, three-phase actual voltage and three-phase reference voltage of an alternating current bus at the side of the modular multilevel inverter;
respectively carrying out coordinate conversion on the three-phase actual current, the three-phase actual voltage and the three-phase reference voltage to obtain a d-axis component and a q-axis component of the actual current, a d-axis component and a q-axis component of the actual voltage and a d-axis component and a q-axis component of the reference voltage;
calculating difference values between reference voltages of the d-axis component and the q-axis component and actual voltages respectively, and performing voltage regulation on the difference values respectively to obtain a d-axis voltage regulation value and a q-axis voltage regulation value;
respectively carrying out current regulation on an actual current q-axis component and an actual current d-axis component to obtain a first modulation voltage and a second modulation voltage;
calculating the d-axis voltage regulating value and the first modulation voltage sum value to obtain d-axis output voltage, and calculating the difference value of the q-axis voltage regulating value and the second modulation voltage to obtain q-axis output voltage;
respectively calculating d-axis and q-axis output voltages and respective voltage and value delayed by T/4 to respectively obtain d-axis control voltage and q-axis control voltage, wherein T is 2 pi/w, and w is angular frequency of preset current;
performing coordinate conversion on the d-axis control voltage and the q-axis control voltage to obtain an alpha-axis control voltage and a beta-axis control voltage;
and performing trigger pulse generation processing on the alpha axis control voltage and the beta axis control voltage to obtain a pulse signal for controlling the modular multilevel inverter.
Preferably, the calculating the difference between the reference voltage and the actual voltage of the d-axis component and the q-axis component, and performing voltage regulation control on the difference to obtain a d-axis voltage regulation value and a q-axis voltage regulation value respectively includes:
adjusting a controller through PI proportional integral according to a formula: calculating a d-axis voltage regulation value by Vd ═ k1(Udref-Ud) + k2 ^ (Uref-Ud) dt, wherein Vd is the d-axis voltage regulation value, k1 and k2 are respectively regulation control coefficients, Udref is a d-axis reference voltage, and Ud is a d-axis actual voltage; and are
According to the formula: vq ═ k3(Udref-Uq) + k4 · (Uqref-Uq) dt, a q-axis voltage adjustment value is calculated, where Vq is the q-axis voltage adjustment value, k3 and k4 are adjustment control coefficients, Uqref is a q-axis reference voltage, and Uq is a q-axis actual voltage.
Preferably, the current adjusting the actual current value of the q axis and the actual current value of the d axis respectively to obtain a first modulation voltage and a second modulation voltage includes:
according to the formula: v1 ═ ω LiqPerforming current regulation on the actual current value of the q axis, and calculating to obtain a first modulation voltage, wherein V1 is the first modulation voltage, omega is a preset current angular frequency, L is a half of the series reactance value of a single bridge arm in the modular multilevel inverter, and i isqIs the q-axis actual current value;
according to the formula: v2 ═ ω LidAnd carrying out current regulation on the actual current value of the d axis, and calculating to obtain a second modulation voltage, wherein V2 is the second modulation voltage, omega is the preset current angular frequency, L is half of the series reactance value of a single bridge arm in the modular multilevel inverter, i isdIs the d-axis actual current value.
Preferably, the calculating the d-axis voltage adjustment value and the first modulation voltage sum value to obtain a d-axis output voltage, and calculating a difference between the q-axis voltage adjustment value and the second modulation voltage to obtain a q-axis output voltage includes:
according to the formula: v1(t) ═ k1(Udref-Ud) + k2 ^ k ^ (Udref-Ud) dt + ω LiqAnd calculating to obtain d-axis output voltage, wherein V1(t) is the d-axis output voltage, k1(Udref-Ud) + k2 ^ (Udref-Ud) dt is the d-axis voltage regulation value, and omega LiqIs a first modulation voltage, k1 and k2 are respectively adjustment control coefficients, Udref and Ud are respectively a reference voltage and an actual voltage of a d axis, omega is a preset current angular frequency, L is a half of a series reactance value of a single bridge arm, i is a single bridge arm series reactance valueqIs the actual current q-axis value;
according to the formula: v2(t) ═ k3(Uqref-Uq) + k4 ═ q ═ Uqref-Uq) dt- ω LidAnd calculating a q-axis output voltage, wherein V2(t) is the q-axis output voltage, k3(Uqref-Uq) + k4 ^ (Uqref-Uq) dt is the q-axis voltage regulation value, and omega LidIs a second modulation voltage, k3 and k4 are respectively regulating control coefficients, Uqref and Uq are respectively a reference voltage and an actual voltage of a q axis, omega is a preset current angular frequency, L is a half of a series reactance value of a single bridge arm, i is a single bridge arm series reactance valuedIs the d-axis value of the actual current.
Preferably, the calculating the d-axis output voltage and the q-axis output voltage and the voltage sum value of the respective delay T/4 to obtain the d-axis control voltage and the q-axis control voltage respectively includes:
according to the formula: vd (T) ═ V1(T) + V1(T-T/4), and the voltage sum of the d-axis output voltage and the delay T/4 is calculated to obtain a d-axis control voltage, where vd (T) is the d-axis control voltage, V1(T) is the d-axis output voltage, and V1(T-T/4) is the delay T/4 voltage;
according to the formula: and vq (T) ═ V2(T) + V2(T-T/4), and the sum of the q-axis output voltage and the delay T/4 is calculated to obtain a q-axis control voltage, wherein vq (T) is the q-axis control voltage, V2(T) is the q-axis output voltage, and V2(T-T/4) is the delay T/4.
Preferably, the method further comprises the following steps:
and controlling the on-off of an insulated gate bipolar transistor IGBT in each sub-module SM of the modular multilevel inverter by using the obtained pulse signal for controlling the modular multilevel inverter to generate output voltage at the AC side of the modular multilevel inverter.
A control apparatus for an inverter, which controls a modular multilevel inverter in the apparatus, comprising:
the detection module is used for detecting three-phase actual current, three-phase actual voltage and three-phase reference phase voltage of an alternating current bus at the side of the multi-level inverter;
the first coordinate conversion module is used for respectively carrying out coordinate conversion on the detected three-phase actual current, three-phase actual voltage and three-phase reference phase voltage to obtain a d-axis component and a q-axis component of the actual current, a d-axis component and a q-axis component of the actual voltage and a d-axis component and a q-axis component of the reference voltage;
the first calculation module is used for calculating difference values between reference voltages of d-axis and q-axis components and actual voltages respectively and performing voltage regulation control on the difference values respectively to obtain a d-axis voltage regulation value and a q-axis voltage regulation value;
the first adjusting module is used for respectively adjusting the current of the q axis and the current of the d axis to obtain a first modulating voltage and a second modulating voltage;
the second calculation module is used for calculating the d-axis voltage regulating value and the first regulating voltage sum value to obtain d-axis output voltage, and calculating the difference value between the q-axis voltage regulating value and the second regulating voltage to obtain q-axis output voltage;
the delay processing module is used for respectively calculating d-axis and q-axis output voltages and respective delay T/4 voltage and value to respectively obtain d-axis control voltage and q-axis control voltage;
the second coordinate conversion module is used for carrying out coordinate conversion on the d-axis control voltage and the q-axis control voltage to obtain an alpha-axis control voltage and a beta-axis control voltage;
and the pulse signal generation module is used for generating trigger pulses for the alpha-axis control voltage and the beta-axis control voltage to obtain pulse signals for controlling the inverter.
Preferably, the first calculation module includes:
the d-axis voltage regulation submodule is used for regulating the controller through PI proportional integral according to a formula:
Vd=k1(Udref-Ud)+k2∫(Uref-Ud)dt
calculating a d-axis voltage regulating value, wherein Vd is the d-axis voltage regulating value, k1 and k2 are respectively regulating control coefficients, Udref is a d-axis reference voltage, and Ud is a d-axis actual voltage; and are
q-axis voltage regulator submodule: for generating, according to the formula: vq ═ k3(Udref-Uq) + k4 · (Uqref-Uq) dt, a q-axis voltage adjustment value is calculated, where Vq is the q-axis voltage adjustment value, k3 and k4 are adjustment control coefficients, Uqref is a q-axis reference voltage, and Uq is a q-axis actual voltage.
Preferably, the first adjusting module includes:
a q-axis current regulation submodule for: v1 ═ ω LiqCurrent regulation is carried out on the actual current value of the q axis, a first modulation voltage is obtained through calculation, wherein V1 is the first modulation voltage, omega is a preset current angular frequency, L is a half of the series reactance value of a single bridge arm in the modular multilevel inverter, and i isqIs the q-axis actual current value;
a d-axis current regulation submodule for: v2 ═ ω LidAnd carrying out current regulation on the actual current value of the d axis, and calculating to obtain a second modulation voltage, wherein V2 is the second modulation voltage, omega is the preset current angular frequency, L is half of the series reactance value of a single bridge arm in the modular multilevel inverter, i isdIs the d-axis actual current value.
Preferably, the second calculation module includes:
the d-axis output voltage calculation submodule is used for calculating the output voltage according to the formula:
V1(t)=k1(Udref-Ud)+k2∫(Udref-Ud)dt+ωLiqand calculating to obtain d-axis output voltage, wherein V1(t) is the d-axis output voltage, k1(Udref-Ud) + k2 ^ (Udref-Ud) dt is the d-axis voltage regulation value, and omega LiqIs a first modulation voltage, k1 and k2 are respectively adjustment control coefficients, Udref and Ud are respectively a reference voltage and an actual voltage of a d axis, omega is a preset current angular frequency, L is a half of a series reactance value of a single bridge arm, i is a single bridge arm series reactance valueqIs the actual current q-axis value;
a q-axis output voltage calculation submodule for calculating the q-axis output voltage according to the formula:
V2(t)=k3(Uqref-Uq)+k4∫(Uqref-Uq)dt-ωLidand calculating a q-axis output voltage, wherein V2(t) is the q-axis output voltage, k3(Uqref-Uq) + k4 ^ (Uqref-Uq) dt is the q-axis voltage regulation value, and omega LidIs a second modulation voltage, k3 and k4 are respectively regulating control coefficients, Uqref and Uq are respectively a reference voltage and an actual voltage of a q axis, omega is a preset current angular frequency, L is a half of a series reactance value of a single bridge arm, i is a single bridge arm series reactance valuedIs the d-axis value of the actual current.
Preferably, the delay processing module includes:
a d-axis delay submodule for: vd (T) ═ V1(T) + V1(T-T/4), and the voltage sum of the d-axis output voltage and the delay T/4 is calculated to obtain a d-axis control voltage, where vd (T) is the d-axis control voltage, V1(T) is the d-axis output voltage, and V1(T-T/4) is the delay T/4 voltage;
a q-axis delay submodule for: and vq (T) ═ V2(T) + V2(T-T/4), and the sum of the q-axis output voltage and the delay T/4 is calculated to obtain a q-axis control voltage, wherein vq (T) is the q-axis control voltage, V2(T) is the q-axis output voltage, and V2(T-T/4) is the delay T/4.
Preferably, the device also comprises a trigger pulse module,
the trigger module is used for controlling the on-off of Insulated Gate Bipolar Transistors (IGBTs) in each sub-module of the modular multi-level inverter according to the pulse signals generated by the pulse signal generation module so as to generate output voltage on the alternating current side of the modular multi-level inverter.
The voltage drop generating device provided by the invention adopts a modularized circuit structure, the number of sub-modules SM can be increased or reduced according to actual requirements to support the voltage test engineering requirements of high voltage and high power, the process requirements on the switching device are reduced, the generation cost and the integration difficulty of the device are reduced, the performance of the whole system is improved, the inverter in the voltage drop generating device is controlled by the provided control method, the problem of double-frequency alternating current component is eliminated by adopting a delay processing method, the control voltage is generated more accurately, the pulse signal of the control modularized multi-level inverter is obtained through trigger pulse generation processing, the switching device in the neutron inverter module SM is controlled by the pulse signal, and various waveform voltages are generated.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a voltage sag generator according to an embodiment of the present invention;
fig. 2 is a flowchart of a control method of an inverter according to a second embodiment of the present invention;
fig. 3 is a flowchart illustrating another inverter control method according to a third embodiment of the present invention;
fig. 4 is a schematic structural diagram of a control device of an inverter according to a fourth embodiment of the present invention;
fig. 5 is a schematic structural diagram of another inverter control device according to a fifth embodiment of the present invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
Example one
The present invention provides a voltage drop generator, which is described below by taking an embodiment as an example, and specifically refer to fig. 1, which is a schematic structural diagram of a voltage drop generator disclosed in an embodiment of the present invention, and specifically includes:
a modular multilevel rectifier and a modular multilevel inverter;
the modular multilevel inverter and the modular multilevel inverter are connected in a back-to-back power transmission connection mode, and the modular multilevel inverter have the same structure; wherein,
the modular multi-level rectifier includes: a first phase unit formed by connecting a first bridge arm and a second bridge arm in series, a second phase unit formed by connecting a third bridge arm and a fourth bridge arm in series, and a third phase unit formed by connecting a fifth bridge arm and a sixth bridge arm in series, wherein the three phase units are connected in parallel;
the six bridge arms are formed by connecting N sub-modules SM and a valve reactor in series, wherein N is a natural number greater than or equal to 1;
the SM comprises two IGBT switchgears and a direct-current energy storage capacitor, wherein the two IGBT switchgears are connected in series and then connected in parallel with the direct-current energy storage capacitor.
The device adopts a modular circuit structure, the number of the sub-modules SM can be increased or reduced according to actual requirements, the high-voltage high-power voltage test engineering requirements are supported, the technological requirements on the switch device are reduced, the generation cost and the integration difficulty of the device are reduced, and the performance of the whole system is improved.
Example two
For the device described in the above embodiment, because there are problems of static state, dynamic voltage equalization, electromagnetic interference, too high switching loss due to too high switching frequency, and the like, the voltage drop waveform quality output by the VSG is not high, the harmonic content is large, and especially when the number of sub-modules is large, these problems are more serious. In the prior art, a method of mounting a filter on an alternating current side for filtering is generally adopted, so that the problems are eliminated to a certain extent, and the influence on the performance of the whole VSG circuit is avoided. However, when the filter is installed on the ac side to completely eliminate the frequency-doubled ac component, the filtering effect is greatly affected by the frequency, and the performance of the filter is deteriorated due to the frequency fluctuation, resulting in a certain delay, so that the quality of the generated waveform is poor, and the test requirements cannot be met.
In view of the above technical problems, the present invention provides a method for controlling an inverter, which controls a modular multilevel inverter in the above apparatus, thereby solving the problem of thoroughly eliminating the frequency-doubled ac component, and also solving the cost problem and technical problem caused by the ac side-scheme sub-filter.
To better explain the method proposed by the present invention, the following embodiment is taken as an example to explain, and specifically, the flowchart of the method for controlling the inverter disclosed in fig. 2 specifically includes the following steps:
step 201: detecting three-phase actual current, three-phase actual voltage and three-phase reference voltage of an alternating current bus at the side of the modular multilevel inverter;
step 202: respectively carrying out coordinate conversion on the three-phase actual current, the three-phase actual voltage and the three-phase reference voltage to obtain a d-axis component and a q-axis component of the actual current, a d-axis component and a q-axis component of the actual voltage and a d-axis component and a q-axis component of the reference voltage;
step 203: calculating difference values between reference voltages of the d-axis component and the q-axis component and actual voltages respectively, and performing voltage regulation on the difference values respectively to obtain a d-axis voltage regulation value and a q-axis voltage regulation value;
step 204: respectively carrying out current regulation on an actual current q-axis component and an actual current d-axis component to obtain a first modulation voltage and a second modulation voltage;
step 205: calculating the d-axis voltage regulating value and the first modulation voltage sum value to obtain d-axis output voltage, and calculating the difference value of the q-axis voltage regulating value and the second modulation voltage to obtain q-axis output voltage;
step 207: respectively calculating d-axis and q-axis output voltages and respective voltage and value delayed by T/4 to respectively obtain d-axis control voltage and q-axis control voltage, wherein T is 2 pi/w, and w is angular frequency of preset current;
step 208: performing coordinate conversion on the d-axis control voltage and the q-axis control voltage to obtain an alpha-axis control voltage and a beta-axis control voltage;
step 209: and performing trigger pulse generation processing on the alpha axis control voltage and the beta axis control voltage to obtain a pulse signal for controlling the modular multilevel inverter.
By the method described in the above embodiment, a delay processing method can be adopted to eliminate the problem of frequency doubling alternating current component, control voltage can be generated more accurately, a pulse signal for controlling the modular multilevel inverter can be obtained through trigger pulse generation processing, and the pulse signal controls the on and off of a switching device in the submodule SM of the inverter, so that various waveform voltages can be generated.
EXAMPLE III
To describe the method of the present invention more specifically, the following description is given by taking the third embodiment as an example, and specifically please refer to a flowchart of another inverter control method provided in fig. 3, which specifically includes the following steps:
step 301: detecting three-phase actual current, three-phase actual voltage and three-phase reference voltage of an alternating current bus at the side of the modular multilevel inverter;
step 302: respectively carrying out coordinate conversion on the three-phase actual current, the three-phase actual voltage and the three-phase reference voltage to obtain a d-axis component and a q-axis component of the actual current, a d-axis component and a q-axis component of the actual voltage and a d-axis component and a q-axis component of the reference voltage;
step 303: calculating difference values between reference voltages of the d-axis component and the q-axis component and actual voltages respectively, and performing voltage regulation on the difference values respectively to obtain a d-axis voltage regulation value and a q-axis voltage regulation value;
the step 303 may specifically be: step 303A, by means of the PI proportional-integral adjustment controller,
according to the formula: calculating a d-axis voltage regulation value by Vd being k1(Udref-Ud) + k2 ^ (Uref-Ud) dt, wherein Vd is the d-axis voltage regulation value, k1 and k2 are respectively regulation control coefficients, Udref is a d-axis reference voltage, and Ud is a d-axis actual voltage; and are
Step 303B, by the PI proportional integral adjustment controller, according to the formula: vq ═ k3(Udref-Uq) + k4 · (Uqref-Uq) dt, a q-axis voltage adjustment value is calculated, where Vq is the q-axis voltage adjustment value, k3 and k4 are adjustment control coefficients, Uqref is a q-axis reference voltage, and Uq is a q-axis actual voltage.
The steps 303A and 303B do not have a requirement on the order, and any one of the steps may be performed first, or both of the steps may be performed simultaneously, and fig. 3 shows only one of the cases.
Step 304: respectively carrying out current regulation on an actual current q-axis component and an actual current d-axis component to obtain a first modulation voltage and a second modulation voltage;
the step 304 may specifically be, for example: step 304A, according to the formula: v1 ═ ω LiqPerforming current regulation on the actual current value of the q axis, and calculating to obtain a first modulation voltage, wherein V1 is the first modulation voltage, omega is a preset current angular frequency, L is a half of the series reactance value of a single bridge arm in the modular multilevel inverter, and i isqIs the q-axis actual current value;
step 304B follows the formula: v2 ═ ω LidAnd carrying out current regulation on the actual current value of the d axis, and calculating to obtain a second modulation voltage, wherein V2 is the second modulation voltage, omega is the preset current angular frequency, L is half of the series reactance value of a single bridge arm in the modular multilevel inverter, i isdIs the d-axis actual current value.
The steps 304A and 304B are not required to be in sequence, and any one of the steps may be performed first, or both of the steps may be performed simultaneously, and fig. 3 shows only one of the cases.
Step 305: calculating the d-axis voltage regulating value and the first modulation voltage sum value to obtain d-axis output voltage, and calculating the difference value of the q-axis voltage regulating value and the second modulation voltage to obtain q-axis output voltage;
the step 305 may specifically be, for example: step 305A follows the formula: v1(t) ═ k1(Udref-Ud) + k2 ^ k ^ (Udref-Ud) dt + ω LiqAnd calculating to obtain d-axis output voltage, wherein V1(t) is the d-axis output voltage, k1(Udref-Ud) + k2 ^ (Udref-Ud) dt is the d-axis voltage regulation value, and omega LiqIs a first modulation voltage, k1 and k2 are respectively adjustment control coefficients, Udref and Ud are respectively a reference voltage and an actual voltage of a d axis, omega is a preset current angular frequency, L is a half of a series reactance value of a single bridge arm, i is a single bridge arm series reactance valueqIs the actual current q-axis value;
step 305B, according to the formula: v2(t) ═ k3(Uqref-Uq) + k4 ═ q ═ Uqref-Uq) dt- ω LidAnd calculating a q-axis output voltage, wherein V2(t) is the q-axis output voltage, k3(Uqref-Uq) + k4 ^ (Uqref-Uq) dt is the q-axis voltage regulation value, and omega LidIs a second modulation voltage, k3 and k4 are respectively regulating control coefficients, Uqref and Uq are respectively a reference voltage and an actual voltage of a q axis, omega is a preset current angular frequency, L is a half of a series reactance value of a single bridge arm, i is a single bridge arm series reactance valuedIs the d-axis value of the actual current.
The steps 305A and 305B have no requirement of a sequential order, and any one of the steps may be performed first, or both of the steps may be performed simultaneously, and fig. 3 shows only one of the cases.
Step 306: respectively calculating d-axis and q-axis output voltages and respective voltage and value delayed by T/4 to respectively obtain d-axis control voltage and q-axis control voltage, wherein T is 2 pi/w, and w is angular frequency of preset current;
the step 306 may specifically be: step 306A, according to the formula: vd (T) ═ V1(T) + V1(T-T/4), and the voltage sum of the d-axis output voltage and the delay T/4 is calculated to obtain a d-axis control voltage, where vd (T) is the d-axis control voltage, V1(T) is the d-axis output voltage, and V1(T-T/4) is the delay T/4 voltage;
step 306B, according to the formula: and vq (T) ═ V2(T) + V2(T-T/4), and the sum of the q-axis output voltage and the delay T/4 is calculated to obtain a q-axis control voltage, wherein vq (T) is the q-axis control voltage, V2(T) is the q-axis output voltage, and V2(T-T/4) is the delay T/4.
The steps 306A and 306B are not required to be in sequence, and any one of the steps may be performed first, or both of the steps may be performed simultaneously, and fig. 3 shows only one of the cases.
Step 307: performing coordinate conversion on the d-axis control voltage and the q-axis control voltage to obtain an alpha-axis control voltage and a beta-axis control voltage;
step 308: and performing trigger pulse generation processing on the alpha axis control voltage and the beta axis control voltage to obtain a pulse signal for controlling the modular multilevel inverter.
The method further includes, in step 309: and controlling the on-off of an insulated gate bipolar transistor IGBT in each sub-module SM of the modular multilevel inverter by using the obtained pulse signal for controlling the modular multilevel inverter to generate output voltage at the AC side of the modular multilevel inverter.
By the method described in the above embodiment, the voltage and current can be adjusted and controlled by specific calculation, the problem of double frequency ac component is solved by a delay processing method, the control voltage is generated more accurately, and the pulse signal for controlling the modular multilevel inverter is obtained by trigger pulse generation processing, so that the pulse signal controls the on and off of the switching device in the submodule SM in the inverter, and thus, various waveform voltages are generated.
Example four
The present invention also provides a control device for an inverter, which controls a modular multilevel inverter in the device described in the above embodiment 1, and the following describes a fourth embodiment as an example, specifically referring to a structural schematic diagram of a control device for an inverter shown in fig. 4, specifically including:
the detection module 401 is configured to detect a three-phase actual current, a three-phase actual voltage, and a three-phase reference phase voltage of an ac bus on a multilevel inverter side;
a first coordinate conversion module 402, configured to perform coordinate conversion on the detected three-phase actual current, three-phase actual voltage, and three-phase reference phase voltage, respectively, to obtain a d-axis component and a q-axis component of the actual current, a d-axis component and a q-axis component of the actual voltage, and a d-axis component and a q-axis component of the reference voltage;
a first calculating module 403, configured to calculate difference values between reference voltages of d-axis and q-axis components and actual voltages, respectively, and perform voltage regulation control on the difference values, to obtain a d-axis voltage regulation value and a q-axis voltage regulation value;
a first adjusting module 404, configured to perform current adjustment on the q-axis current value and the d-axis current value respectively to obtain a first modulation voltage and a second modulation voltage;
a second calculating module 405, configured to calculate the d-axis voltage adjustment value and the first adjustment voltage sum value to obtain a d-axis output voltage, and calculate a difference between the q-axis voltage adjustment value and the second adjustment voltage to obtain a q-axis output voltage;
a delay processing module 406, configured to calculate d-axis and q-axis output voltages and voltage and value of respective delay T/4, respectively, to obtain a d-axis control voltage and a q-axis control voltage, respectively;
a second coordinate conversion module 407, configured to perform coordinate conversion on the d-axis control voltage and the q-axis control voltage to obtain an α -axis control voltage and a β -axis control voltage;
and a pulse signal generation module 408, which performs trigger pulse generation processing on the α axis control voltage and the β axis control voltage to obtain a pulse signal for controlling the inverter.
Preferably, the above apparatus further comprises: and the trigger module is used for controlling the on-off of Insulated Gate Bipolar Transistors (IGBT) in each sub-module of the modular multilevel inverter according to the pulse signals generated by the pulse signal generation module so as to generate the output voltage at the AC side of the modular multilevel inverter.
Through the device, the problem of double-frequency alternating current component can be eliminated by the aid of the delay processing module, the whole device can generate control voltage more accurately, pulse signals of the control modular multilevel inverter are generated through processing of the trigger pulse module, and the pulse signals control on and off of a switching device in the sub module SM of the inverter, so that various waveform voltages are generated.
EXAMPLE five
In the following, a control device provided by the present invention is described in more detail with reference to the fifth embodiment, specifically, referring to fig. 5, another control device of an inverter disclosed in the present invention specifically includes:
the detection module 501 is configured to detect three-phase actual current, three-phase actual voltage, and three-phase reference phase voltage of an ac bus on a multilevel inverter side;
a first coordinate conversion module 502, configured to perform coordinate conversion on the detected three-phase actual current, three-phase actual voltage, and three-phase reference phase voltage, respectively, to obtain a d-axis component and a q-axis component of the actual current, a d-axis component and a q-axis component of the actual voltage, and a d-axis component and a q-axis component of the reference voltage;
a first calculating module 503, configured to calculate difference values between the reference voltages of the d-axis component and the q-axis component and the actual voltage, and perform voltage regulation control on the difference values, respectively, to obtain a d-axis voltage regulation value and a q-axis voltage regulation value;
preferably, the first calculating module 503 includes: a d-axis voltage regulation submodule 503A and a q-axis voltage regulation submodule 503B, wherein the d-axis voltage regulation submodule 503A is configured to regulate, by a PI proportional-integral controller, according to a formula: vd ═ k1(Udref-Ud) + k2 ^ (Uref-Ud) dt
Calculating a d-axis voltage regulating value, wherein Vd is the d-axis voltage regulating value, k1 and k2 are respectively regulating control coefficients, Udref is a d-axis reference voltage, and Ud is a d-axis actual voltage; and are
q-axis voltage regulation submodule 503B: for generating, according to the formula: vq ═ k3(Udref-Uq) + k4 · (Uqref-Uq) dt, a q-axis voltage adjustment value is calculated, where Vq is the q-axis voltage adjustment value, k3 and k4 are adjustment control coefficients, Uqref is a q-axis reference voltage, and Uq is a q-axis actual voltage.
A first adjusting module 504, configured to perform current adjustment on the q-axis current value and the d-axis current value respectively to obtain a first modulation voltage and a second modulation voltage;
preferably, the first adjusting module 504 includes: a q-axis current regulation submodule 504A and a d-axis current regulation submodule 504B, wherein,
a q-axis current regulator submodule 504A for: v1 ═ ω LiqPerforming current regulation on the actual current value of the q axis, and calculating to obtain a first modulation voltage, wherein V1 is the first modulation voltage, omega is a preset current angular frequency, L is a half of the series reactance value of a single bridge arm in the modular multilevel inverter, and i isqIs the q-axis actual current value;
a d-axis current regulator submodule 504B for: v2 ═ ω LidAnd carrying out current regulation on the actual current value of the d axis, and calculating to obtain a second modulation voltage, wherein V2 is the second modulation voltage, omega is the preset current angular frequency, L is half of the series reactance value of a single bridge arm in the modular multilevel inverter, i isdIs the d-axis actual current value.
A second calculating module 505, configured to calculate the d-axis voltage adjustment value and the first adjustment voltage sum value to obtain a d-axis output voltage, and calculate a difference between the q-axis voltage adjustment value and the second adjustment voltage to obtain a q-axis output voltage;
preferably, the second calculating module 505 includes: a d-axis output voltage calculation submodule 505A and a q-axis output voltage calculation submodule 505B, wherein,
the d-axis output voltage calculation submodule 505A is configured to:
V1(t)=k1(Udref-Ud)+k2∫(Udref-Ud)dt+ωLiqand calculating to obtain d-axis output voltage, wherein V1(t) is the d-axis output voltage, k1(Udref-Ud) + k2 ^ (Udref-Ud) dt is the d-axis voltage regulation value, and omega LiqIs a first modulation voltage, k1 and k2 are respectively adjustment control coefficients, Udref and Ud are respectively a reference voltage and an actual voltage of a d axis, omega is a preset current angular frequency, L is a half of a series reactance value of a single bridge arm, i is a single bridge arm series reactance valueqIs the actual current q-axis value;
q-axis output voltage calculation submodule 505B for calculating a q-axis output voltage according to the formula: v2(t) ═ k3(Uqref-Uq) + k4 ═ q ═ Uqref-Uq) dt- ω LidAnd calculating a q-axis output voltage, wherein V2(t) is the q-axis output voltage, k3(Uqref-Uq) + k4 ^ (Uqref-Uq) dt is the q-axis voltage regulation value, and omega LidIs a second modulation voltage, k3 and k4 are respectively regulating control coefficients, Uqref and Uq are respectively a reference voltage and an actual voltage of a q axis, omega is a preset current angular frequency, L is a half of a series reactance value of a single bridge arm, i is a single bridge arm series reactance valuedIs the d-axis value of the actual current.
A delay processing module 506, configured to calculate d-axis and q-axis output voltages and voltage and value of respective delay T/4, respectively to obtain a d-axis control voltage and a q-axis control voltage;
preferably, the delay processing module 506 includes: a d-axis delay sub-module 506A and a q-axis delay sub-module 506B,
a d-axis delay submodule 506A for: vd (T) ═ V1(T) + V1(T-T/4), and the voltage sum of the d-axis output voltage and the delay T/4 is calculated to obtain a d-axis control voltage, where vd (T) is the d-axis control voltage, V1(T) is the d-axis output voltage, and V1(T-T/4) is the delay T/4 voltage;
a q-axis delay submodule 506B for: and vq (T) ═ V2(T) + V2(T-T/4), and the sum of the q-axis output voltage and the delay T/4 is calculated to obtain a q-axis control voltage, wherein vq (T) is the q-axis control voltage, V2(T) is the q-axis output voltage, and V2(T-T/4) is the delay T/4.
A second coordinate conversion module 507, configured to perform coordinate conversion on the d-axis control voltage and the q-axis control voltage to obtain an α -axis control voltage and a β -axis control voltage;
and a pulse signal generation module 508, which performs trigger pulse generation processing on the α axis control voltage and the β axis control voltage to obtain a pulse signal for controlling the inverter.
Preferably, the above apparatus further comprises: and a triggering module 509, configured to control, according to the pulse signal generated by the pulse signal generating module, on or off of the insulated gate bipolar transistor IGBT in each sub-module of the modular multilevel inverter, so as to generate an output voltage on the ac side of the modular multilevel inverter.
The voltage sag generator, the inverter control method and the inverter control device provided by the invention are described in detail, and the principle and the implementation mode of the invention are explained by applying specific embodiments in the text, and the description of the embodiments is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
Claims (12)
1. The control method of an inverter is characterized in that a modular multilevel inverter in a voltage sag generator is controlled, and the voltage sag generator comprises a modular multilevel current converter and a modular multilevel inverter; the modular multilevel inverter and the modular multilevel inverter are connected in a back-to-back power transmission connection mode, and the modular multilevel inverter have the same structure; wherein the modular multi-level rectifier includes: a first phase unit formed by connecting a first bridge arm and a second bridge arm in series, a second phase unit formed by connecting a third bridge arm and a fourth bridge arm in series, and a third phase unit formed by connecting a fifth bridge arm and a sixth bridge arm in series, wherein the three phase units are connected in parallel; the six bridge arms are formed by connecting N sub-modules SM and a valve reactor in series, wherein N is a natural number greater than or equal to 1; the SM comprises two IGBT switchers and a direct-current energy storage capacitor, the two IGBT switchers are connected in series and then connected in parallel with the direct-current energy storage capacitor, and the method comprises the following steps:
detecting three-phase actual current, three-phase actual voltage and three-phase reference voltage of an alternating current bus at the side of the modular multilevel inverter;
respectively carrying out coordinate conversion on the three-phase actual current, the three-phase actual voltage and the three-phase reference voltage to obtain a d-axis component and a q-axis component of the actual current, a d-axis component and a q-axis component of the actual voltage and a d-axis component and a q-axis component of the reference voltage;
calculating difference values between reference voltages of the d-axis component and the q-axis component and actual voltages respectively, and performing voltage regulation on the difference values respectively to obtain a d-axis voltage regulation value and a q-axis voltage regulation value;
respectively carrying out current regulation on an actual current q-axis component and an actual current d-axis component to obtain a first modulation voltage and a second modulation voltage;
calculating the d-axis voltage regulating value and the first modulation voltage sum value to obtain d-axis output voltage, and calculating the difference value of the q-axis voltage regulating value and the second modulation voltage to obtain q-axis output voltage;
respectively calculating d-axis and q-axis output voltages and respective voltage and value delayed by T/4 to respectively obtain d-axis control voltage and q-axis control voltage, wherein T is 2 pi/w, and w is angular frequency of preset current;
performing coordinate conversion on the d-axis control voltage and the q-axis control voltage to obtain an alpha-axis control voltage and a beta-axis control voltage;
and performing trigger pulse generation processing on the alpha axis control voltage and the beta axis control voltage to obtain a pulse signal for controlling the modular multilevel inverter.
2. The method of claim 1, wherein the calculating the difference between the reference voltage and the actual voltage of the d-axis component and the q-axis component, respectively, and performing voltage regulation control on the difference to obtain a d-axis voltage regulation value and a q-axis voltage regulation value, respectively, comprises:
adjusting a controller through PI proportional integral according to a formula:
calculating a d-axis voltage regulation value by using Vd as k1(Udref-Ud) + k2 ^ (Udref-Ud) dt, wherein Vd is the d-axis voltage regulation value, k1 and k2 are respectively regulation control coefficients, Udref is a d-axis reference voltage, and Ud is a d-axis actual voltage; and are
According to the formula: vq ═ k3(Uqref-Uq) + k4 · (Uqref-Uq) dt, a q-axis voltage adjustment value is calculated, where Vq is the q-axis voltage adjustment value, k3 and k4 are adjustment control coefficients, Uqref is a q-axis reference voltage, and Uq is a q-axis actual voltage.
3. The method of claim 1, wherein the current adjusting the q-axis actual current value and the d-axis actual current value to obtain the first modulation voltage and the second modulation voltage comprises:
according to the formula: v1 ═ ω LiqPerforming current regulation on the actual current value of the q axis, and calculating to obtain a first modulation voltage, wherein V1 is the first modulation voltage, omega is a preset current angular frequency, L is a half of the series reactance value of a single bridge arm in the modular multilevel inverter, and i isqIs the q-axis actual current value;
according to the formula: v2 ═ ω LidAnd carrying out current regulation on the actual current value of the d axis, and calculating to obtain a second modulation voltage, wherein V2 is the second modulation voltage, omega is the preset current angular frequency, L is half of the series reactance value of a single bridge arm in the modular multilevel inverter, i isdIs the d-axis actual current value.
4. The method of claim 1, wherein calculating the d-axis voltage adjustment value and the first modulation voltage sum to obtain a d-axis output voltage, and calculating the difference between the q-axis voltage adjustment value and the second modulation voltage to obtain a q-axis output voltage comprises:
according to the formula: v1(t) ═ k1(Udref-Ud) + k2 ^ k ^ (Udref-Ud) dt + ω LiqAnd calculating to obtain d-axis output voltage, wherein V1(t) is the d-axis output voltage, k1(Udref-Ud) + k2 ^ (Udref-Ud) dt is the d-axis voltage regulation value, and omega LiqIs a first modulation voltage, k1 and k2 are respectively adjustment control coefficients, Udref and Ud are respectively a reference voltage and an actual voltage of a d axis, omega is a preset current angular frequency, L is a half of a series reactance value of a single bridge arm, i is a single bridge arm series reactance valueqIs the actual current q-axis value;
according to the formula: v2(t) ═ k3(Uqref-Uq) + k4 ═ q ═ Uqref-Uq) dt- ω LidAnd calculating a q-axis output voltage, wherein V2(t) is the q-axis output voltage, k3(Uqref-Uq) + k4 ^ (Uqref-Uq) dt is the q-axis voltage regulation value, and omega LidIs a second modulation voltage, k3 and k4 are respectively regulating control coefficients, Uqref and Uq are respectively a reference voltage and an actual voltage of a q axis, omega is a preset current angular frequency, L is a half of a series reactance value of a single bridge arm, i is a single bridge arm series reactance valuedIs the d-axis value of the actual current.
5. The method of claim 1, wherein calculating the d-axis and q-axis output voltages and the voltage sum value of the respective delays T/4 to obtain a d-axis control voltage and a q-axis control voltage, respectively, comprises:
according to the formula: vd (T) ═ V1(T) + V1(T-T/4), and the voltage sum of the d-axis output voltage and the delay T/4 is calculated to obtain a d-axis control voltage, where vd (T) is the d-axis control voltage, V1(T) is the d-axis output voltage, and V1(T-T/4) is the delay T/4 voltage;
according to the formula: and vq (T) ═ V2(T) + V2(T-T/4), and the sum of the q-axis output voltage and the delay T/4 is calculated to obtain a q-axis control voltage, wherein vq (T) is the q-axis control voltage, V2(T) is the q-axis output voltage, and V2(T-T/4) is the delay T/4.
6. The method of claim 1, further comprising:
and controlling the on-off of an insulated gate bipolar transistor IGBT in each sub-module SM of the modular multilevel inverter by using the obtained pulse signal for controlling the modular multilevel inverter to generate output voltage at the AC side of the modular multilevel inverter.
7. A control apparatus for an inverter, which controls a modular multilevel inverter in a voltage sag generator, comprising:
the detection module is used for detecting three-phase actual current, three-phase actual voltage and three-phase reference phase voltage of an alternating current bus at the side of the multi-level inverter;
the first coordinate conversion module is used for respectively carrying out coordinate conversion on the detected three-phase actual current, three-phase actual voltage and three-phase reference phase voltage to obtain a d-axis component and a q-axis component of the actual current, a d-axis component and a q-axis component of the actual voltage and a d-axis component and a q-axis component of the reference voltage;
the first calculation module is used for calculating difference values between reference voltages of d-axis and q-axis components and actual voltages respectively and performing voltage regulation control on the difference values respectively to obtain a d-axis voltage regulation value and a q-axis voltage regulation value;
the first adjusting module is used for respectively adjusting the current of the q axis and the current of the d axis to obtain a first modulating voltage and a second modulating voltage;
the second calculation module is used for calculating the d-axis voltage regulating value and the first regulating voltage sum value to obtain d-axis output voltage, and calculating the difference value between the q-axis voltage regulating value and the second regulating voltage to obtain q-axis output voltage;
the delay processing module is used for respectively calculating d-axis and q-axis output voltages and respective delay T/4 voltage and value to respectively obtain d-axis control voltage and q-axis control voltage;
the second coordinate conversion module is used for carrying out coordinate conversion on the d-axis control voltage and the q-axis control voltage to obtain an alpha-axis control voltage and a beta-axis control voltage;
and the pulse signal generation module is used for generating trigger pulses for the alpha-axis control voltage and the beta-axis control voltage to obtain pulse signals for controlling the inverter.
8. The apparatus of claim 7, wherein the first computing module comprises:
the d-axis voltage regulation submodule is used for regulating the controller through PI proportional integral according to a formula: calculating a d-axis voltage regulation value by Vd ═ k1(Udref-Ud) + k2 ^ (Udref-Ud) dt, wherein Vd is the d-axis voltage regulation value, k1 and k2 are respectively regulation control coefficients, Udref is a d-axis reference voltage, and Ud is a d-axis actual voltage;
a q-axis voltage regulation submodule for: vq ═ k3(Uqref-Uq) + k4 · (Uqref-Uq) dt, a q-axis voltage adjustment value is calculated, where Vq is the q-axis voltage adjustment value, k3 and k4 are adjustment control coefficients, Uqref is a q-axis reference voltage, and Uq is a q-axis actual voltage.
9. The apparatus of claim 7, wherein the first adjustment module comprises:
a q-axis current regulation submodule for: v1 ═ ω LiqPerforming current regulation on the actual current value of the q axis, and calculating to obtain a first modulation voltage, wherein V1 is the first modulation voltage, omega is a preset current angular frequency, L is a half of the series reactance value of a single bridge arm in the modular multilevel inverter, and i isqIs the q-axis actual current value;
a d-axis current regulation submodule for: v2 ═ ω LidAnd carrying out current regulation on the actual current value of the d axis, and calculating to obtain a second modulation voltage, wherein V2 is the second modulation voltage, omega is the preset current angular frequency, L is half of the series reactance value of a single bridge arm in the modular multilevel inverter, i isdIs the d-axis actual current value.
10. The apparatus of claim 7, wherein the second computing module comprises:
the d-axis output voltage calculation submodule is used for calculating the output voltage according to the formula: v1(t) ═ k1(Udref-Ud) + k2 ^ k ^ (Udref-Ud) dt + ω LiqAnd d-axis output voltage is calculated, wherein V1(t) is the d-axis output voltage, k1 (Udr)ef-Ud) + k2 ^ (Udref-Ud) dt is the d-axis voltage regulation value, ω LiqIs a first modulation voltage, k1 and k2 are respectively adjustment control coefficients, Udref and Ud are respectively a reference voltage and an actual voltage of a d axis, omega is a preset current angular frequency, L is a half of a series reactance value of a single bridge arm, i is a single bridge arm series reactance valueqIs the actual current q-axis value;
a q-axis output voltage calculation submodule for calculating the q-axis output voltage according to the formula: v2(t) ═ k3(Uqref-Uq) + k4 ═ q ═ Uqref-Uq) dt- ω LidAnd calculating a q-axis output voltage, wherein V2(t) is the q-axis output voltage, k3(Uqref-Uq) + k4 ^ (Uqref-Uq) dt is the q-axis voltage regulation value, and omega LidIs a second modulation voltage, k3 and k4 are respectively regulating control coefficients, Uqref and Uq are respectively a reference voltage and an actual voltage of a q axis, omega is a preset current angular frequency, L is a half of a series reactance value of a single bridge arm, i is a single bridge arm series reactance valuedIs the d-axis value of the actual current.
11. The apparatus of claim 7, wherein the delay processing module comprises:
a d-axis delay submodule for: vd (T) ═ V1(T) + V1(T-T/4), and the voltage sum of the d-axis output voltage and the delay T/4 is calculated to obtain a d-axis control voltage, where vd (T) is the d-axis control voltage, V1(T) is the d-axis output voltage, and V1(T-T/4) is the delay T/4 voltage;
a q-axis delay submodule for: and vq (T) ═ V2(T) + V2(T-T/4), and the sum of the q-axis output voltage and the delay T/4 is calculated to obtain a q-axis control voltage, wherein vq (T) is the q-axis control voltage, V2(T) is the q-axis output voltage, and V2(T-T/4) is the delay T/4.
12. The apparatus of claim 7, further comprising a trigger pulse module,
the trigger module is used for controlling the on-off of Insulated Gate Bipolar Transistors (IGBTs) in each sub-module of the modular multilevel inverter according to the pulse signals generated by the pulse signal generation module so as to generate output voltage on the alternating current side of the modular multilevel inverter.
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Performance evaluation of half-bridge cascaded multilevel converters operated with multicarrier sinusoidal PWM techniques;Georgios S.Konstantinou et al.;《IEEE Industrial Electronics and Applications Conference》;20090527(第4期);第3399-3404页 * |
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