A high-voltage high-power DC system broadband signal generating device and control method

Abstract

A kind of high-voltage high-power DC system broadband signal generating device and control method, belong to the field of power electronics, solve the problem of disturbance signal generation in DC system broadband impedance measurement, provide technical support for the measurement of DC system impedance characteristics;Including n sub-modules, filter inductance and corresponding control circuit, control circuit adopts voltage and current double closed loop control and voltage sharing control link of sub-module, wherein outer ring voltage adopts PI controller, current inner ring adopts adaptive PIR controller, current inner ring adopts adaptive PIR controller, controller adjusts PIR controller parameter according to the frequency of output current, realizes the no-static error tracking of sine signal in 1~1000Hz wide frequency range, improves the effect of output signal, meets the broadband demand of device, can be widely applied to the impedance measurement of various voltage grade DC systems.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology and relates to a broadband signal generation device and control method for high-voltage, high-power DC systems. Background Technology

[0002] The rapid development of power electronics technology has greatly facilitated the conversion of electrical energy, and thus it is widely used in industrial production, transportation, power systems, and daily life. With the development of new energy sources such as wind power and photovoltaic power generation in recent years, more and more power generation equipment is connected to the system through power electronic devices. The connection of these devices has brought some problems to the stability of the system, and has induced low-frequency oscillations in the system on several occasions.

[0003] The existing literature "Analysis of Output Impedance and Stability of Converter in Distributed Power System" (Tong Qiang et al., Proceedings of the CSEE, 2011) explores the cause of low-frequency oscillations in the system from a theoretical perspective. It finds that the low-frequency oscillations are caused by the negative impedance introduced by the power electronic equipment. Therefore, the stability problem of the system is transferred to the study of the system impedance characteristics.

[0004] Currently, most wideband impedance characteristic measurements are concentrated in low-voltage, low-power applications, while research on high-voltage, high-power applications is insufficient, and research is focused on AC systems, with a lack of research on medium- and high-voltage DC systems. As the core equipment for wideband impedance measurement, the performance of a wideband signal generator is crucial to the accuracy of the impedance measurement results; therefore, there is an urgent need to design a high-precision wideband signal generator. Summary of the Invention

[0005] The technical solution of this invention is used to solve the problem of disturbance signal generation in wideband impedance measurement of DC systems, and provides technical support for the measurement of impedance characteristics of DC systems.

[0006] The present invention solves the above-mentioned technical problems through the following technical solutions:

[0007] A high-voltage, high-power DC system broadband signal generator includes: a main circuit and a control circuit; the main circuit includes: n sub-modules SM1, SM2…SM n Filter inductor L, submodules SM1, SM2…SM nThe circuit is cascaded in series and then connected in series with the filter inductor L, and finally connected to the DC system. The control circuit includes: an outer loop PI control unit, an inner loop adaptive PIR control unit, a voltage equalization control unit, and a carrier phase shift modulator (19). The outer loop PI control unit includes: a subtractor (10), a proportional-integral controller (11), and an adder / subtractor (12). The inner loop adaptive PIR control unit includes: an adaptive PIR controller (13), an adder (14), and a feedforward calculation unit (15). The voltage equalization control unit includes: a direction detection unit (16) and n identical voltage equalization branches, each of which includes: a subtractor (10), an adder (14), a proportional controller (17), and a multiplier (18). The subtractor (10) in the outer loop PI control unit receives a reference voltage V at one input terminal. ref The average input voltage V at the other input terminal ave The output terminal is connected to the input terminal of the proportional-integral controller (11). The output terminal of the proportional-integral controller (11) is connected to the first input terminal of the adder-subtractor (12). The second input terminal of the adder-subtractor (12) receives the sine command signal. The third input terminal of the adder-subtractor (12) receives the current I1 of the filter inductor L. The output terminal of the adder-subtractor (12) is connected to the input terminal of the adaptive PIR controller (13). The output terminal of the adaptive PIR controller (13) is connected to one input terminal of the adder (14) in the inner loop adaptive PIR control unit. The output terminal of the feedforward calculation unit (15) is connected to the other input terminal of the adder (14) in the inner loop adaptive PIR control unit. The two input terminals of the feedforward calculation unit (15) respectively receive the voltage V of the DC system. dc and the sum of the submodule voltages V sum One input terminal of the subtractor (10) in each equalizing branch corresponds to the input capacitor voltage V. C1 V C2 …V Cn The other input terminal of the subtractor (10) in each equalizing branch is input with the average voltage V. aveThe output of the subtractor (10) in each voltage equalization branch is connected to the input of the proportional controller (17) in that voltage equalization branch. The output of the proportional controller (17) in each voltage equalization branch is connected to one input of the multiplier (18) in that voltage equalization branch. The other input of the multiplier (18) in each voltage equalization branch is connected to the output of the direction detection unit (16). The current I1 of the filter inductor L is input to the direction detection unit (16). The output of the multiplier (18) in each voltage equalization branch is connected to one input of the adder (14) in that voltage equalization branch. The other input of the adder (14) in each voltage equalization branch is connected to the output of the adder (14) in the inner loop adaptive PIR control unit. The output of the adder (14) in each voltage equalization branch is connected to the input of the carrier phase shift modulator (19). The output of the carrier phase shift modulator (19) is connected to the n sub-modules SM1, SM2...SM n connect.

[0008] Furthermore, the proportional-integral controller (11) includes a first PI controller (111) and a second PI controller (112). The first PI controller (111) and the second PI controller (112) are switched according to switching conditions. The switching conditions are: the first PI controller (111) is used when the output frequency is 1 to 10 Hz, and the second PI controller (112) is used when the output frequency is 10 to 1000 Hz.

[0009] Furthermore, the submodule adopts a half-bridge topology, which includes a first IGBT, a second IGBT, and a capacitor C. The collector of the first IGBT is connected to the positive terminal of the capacitor C, the emitter of the first IGBT is connected to the collector of the second IGBT, and serves as the positive output terminal of the half-bridge topology. The emitter of the second IGBT is connected to the negative terminal of the capacitor C, and serves as the negative output terminal of the submodule.

[0010] A control method for a broadband signal generator applied to a high-voltage, high-power DC system includes the following steps:

[0011] Step (1): Acquire the voltage V of the DC system dc n submodules SM1, SM2...SM n capacitor voltage V c1 V c2 …V cn And the current I1 of the filter inductor L;

[0012] Step (2): Calculate the average voltage V based on the capacitor voltages of each submodule collected in step (1). ave ;

[0013] Step (3): Set the reference voltage Vref With average voltage V ave The input subtractor (10) performs the difference and inputs the error signal into the proportional-integral controller (11);

[0014] Step (4): The output signal of the proportional-integral controller (11) is added to the sine command signal through the adder-subtractor (12) and the difference is taken with the current I1 of the filter inductor L as the input of the adaptive PIR controller (13);

[0015] Step (5): Convert the voltage V of the DC system dc The sum of the voltages of the sub-modules V sum The feedforward quantity C is calculated after inputting into the feedforward quantity calculation unit (15). ff ;

[0016] Step (6): Combine the output of the adaptive PIR controller (13) with the feedforward quantity C ff The sum is used as the control output component;

[0017] Step (7): Capacitor voltage V of each submodule C1 V C2 …V Cn With average voltage V ave The error signal is input into the corresponding subtractor (10) to calculate the difference. After passing through the proportional controller (17), the error signal is input into the corresponding multiplier (18) and then multiplied by the output of the direction detection unit (16) to become the module equalization component.

[0018] Step (8): The control output component from step (6) and the module voltage equalization component from step (7) are input together into the corresponding adder (14) and added to obtain the modulation signal. After passing through the carrier phase-shift modulator (19), the driving signals D1, D2, D3...D of each sub-module are obtained. n .

[0019] Furthermore, the transfer function of the adaptive PIR controller (13) is:

[0020]

[0021] Among them, K p For proportionality coefficient, K i For the integral coefficient, K r For resonant gain, ω c ω is the resonant bandwidth, and ω0 is the resonant frequency.

[0022] Furthermore, the feedforward calculation unit (15) calculates the feedforward quantity C. ff The formula is as follows:

[0023]

[0024] in:

[0025]

[0026] Among them, V cj This represents the capacitor voltage of the j-th submodule, where j = 1, 2, 3…n.

[0027] Furthermore, the output of the direction detection unit (16) is represented by the following formula:

[0028]

[0029] Where out represents the output of the direction detection unit (16).

[0030] The advantages of this invention are:

[0031] (1) The device of the present invention includes n sub-modules, a filter inductor and a corresponding control circuit. The control circuit adopts voltage and current dual closed-loop control and voltage equalization control of the sub-modules. The outer loop voltage adopts a PI controller, and the inner current loop adopts an adaptive PIR controller. The controller adaptively adjusts the PIR controller parameters according to the frequency of the output current, realizing sinusoidal signal tracking without steady-state error in a wide frequency range of 1 to 1000 Hz, improving the output signal effect, meeting the wide frequency requirement of the device, and can be widely used for impedance measurement of DC systems of various voltage levels.

[0032] (2) The sub-module adopts a half-bridge structure, which reduces the number of IGBTs used by half compared to the full-bridge structure, thus meeting the requirements while reducing costs.

[0033] (3) The feedforward calculation unit calculates the feedforward quantity C. ff The purpose is to improve the dynamic performance of the system by adjusting the feedforward quantity C. ff By incorporating an open-loop control mechanism, the burden on the controller's integral component is reduced. Attached Figure Description

[0034] Figure 1 This is a circuit diagram of the broadband signal generator for DC systems according to the present invention;

[0035] Figure 2 This is a schematic diagram of the control circuit of the broadband signal generator for DC systems according to the present invention;

[0036] Figures 3(a), 3(b), 3(c), 3(d), and 3(e) are the output current waveforms of the broadband signal generator of the present invention applied to a DC system under the conditions of 50A amplitude and 1Hz, 10Hz, 50Hz, 500Hz, and 1000Hz. Figures 3(f), 3(g), 3(h), 3(i), and 3(j) are the spectrum analysis diagrams of the corresponding output current waveforms. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0039] 1. Circuit structure of a broadband signal generator applied to a DC system

[0040] like Figure 1 As shown, the broadband signal generator for DC systems includes a main circuit and a control circuit; the main circuit includes n sub-modules SM1, SM2…SM n Filter inductor L, submodules SM1, SM2…SM n The components are cascaded in series and then connected in series with a filter inductor L, finally connected to the DC system; the submodule adopts a half-bridge topology; the control circuit is used to collect the capacitor voltage V of each submodule. C1 V C2 …V Cn And the current I1 flowing through the filter inductor L, and based on the collected data, the drive signals D1, D2...D required by each submodule are issued. n .

[0041] The half-bridge topology includes a first IGBT, a second IGBT, and a capacitor C. The collector of the first IGBT is connected to the positive terminal of the capacitor C, the emitter of the first IGBT is connected to the collector of the second IGBT, and serves as the positive output terminal of the half-bridge topology. The emitter of the second IGBT is connected to the negative terminal of the capacitor C, and serves as the negative output terminal of the submodule.

[0042] The reason why the submodule of this invention adopts a half-bridge topology is that, for a DC system, the bus voltage is DC. To achieve a sinusoidal signal output, it is only necessary to control (change) the magnitude of the device's output voltage to achieve the current signal output. During the positive half-cycle of current output, the device's output voltage needs to be greater than the DC system voltage; during the negative half-cycle of output current, it is only necessary to control the device's output voltage to be less than the DC system voltage level. Therefore, for this application scenario, it is not necessary to achieve a negative voltage output; only the magnitude of the output voltage needs to be controlled to achieve a sinusoidal current output. Compared to a full-bridge structure, the number of IGBTs used in the half-bridge structure is halved, meeting the requirements while also considering cost factors.

[0043] like Figure 2 As shown, the control circuit includes: an outer loop PI control unit, an inner loop adaptive PIR control unit, a voltage equalization control unit, and a carrier phase shift modulator (19); the outer loop PI control unit includes: a subtractor (10), a proportional-integral controller (11), and an adder-subtractor (12); the inner loop adaptive PIR control unit includes: an adaptive PIR controller (13), an adder (14), and a feedforward calculation unit (15); the voltage equalization control unit includes: a direction detection unit (16) and n identical voltage equalization branches, each voltage equalization branch including: a subtractor (10), an adder (14), a proportional controller (17), and a multiplier (18);

[0044] One input terminal of the subtractor (10) in the outer loop PI control unit receives a reference voltage V. ref The average value of the input voltage at the other input terminal is V. ave The output terminal is connected to the input terminal of the proportional-integral controller (11). The output terminal of the proportional-integral controller (11) is connected to the first input terminal of the adder-subtractor (12). The second input terminal of the adder-subtractor (12) receives the sine command signal. The third input terminal of the adder-subtractor (12) receives the current I1 of the filter inductor L. The output terminal of the adder-subtractor (12) is connected to the input terminal of the adaptive PIR controller (13). The output terminal of the adaptive PIR controller (13) is connected to one input terminal of the adder (14) in the inner loop adaptive PIR control unit. The output terminal of the feedforward calculation unit (15) is connected to the other input terminal of the adder (14) in the inner loop adaptive PIR control unit. The two input terminals of the feedforward calculation unit (15) respectively receive the voltage V of the DC system. dc and the sum of the submodule voltages V sum One input terminal of the subtractor (10) in each equalizing branch corresponds to the input capacitor voltage V. C1 V C2 …V CnThe other input terminal of the subtractor (10) in each equalizing branch is input with the average voltage V. ave The output of the subtractor (10) in each voltage equalization branch is connected to the input of the proportional controller (17) in that voltage equalization branch. The output of the proportional controller (17) in each voltage equalization branch is connected to one input of the multiplier (18) in that voltage equalization branch. The other input of the multiplier (18) in each voltage equalization branch is connected to the output of the direction detection unit (16). The input of the direction detection unit (16) is the current I1 of the filter inductor L. The output of the multiplier (18) in each voltage equalization branch is connected to one input of the adder (14) in that voltage equalization branch. The other input of the adder (14) in each voltage equalization branch is connected to the output of the adder (14) in the inner loop adaptive PIR control unit. The output of the adder (14) in each voltage equalization branch is connected to the input of the carrier phase shift modulator (19). The output of the carrier phase shift modulator (19) is connected to the n sub-modules SM1, SM2...SM n connect.

[0045] The proportional-integral controller (11) includes a first PI controller (111) and a second PI controller (112). The first PI controller (111) and the second PI controller (112) are switched according to the switching conditions. The switching conditions are: the first PI controller (111) is used when the output frequency is 1 to 10 Hz, and the second PI controller (112) is used when the output frequency is 10 to 1000 Hz. However, this embodiment is not limited to setting two sets of parameters. In order to pursue better results, the number of PI controllers can be selected by balancing the design complexity and the output effect.

[0046] The working principle of the control circuit is as follows:

[0047] Reference voltage V ref With average voltage V ave The input subtractor (10) performs the subtraction and inputs the error signal into the proportional-integral controller (11). The output signal of the proportional-integral controller (11) is added to the sine command signal by the adder / subtractor (12) and subtracted from the current I1 of the filter inductor L, and then used as the input of the adaptive PIR controller (13). The voltage V of the DC system is... dc The sum of the voltages of the sub-modules V sum The feedforward quantity C is calculated after inputting into the feedforward quantity calculation unit (15). ff The output of the adaptive PIR controller (13) is compared with the feedforward quantity C. ff The summation is used as the control output component; the capacitor voltage V of each submodule C1 V C2 …V CnWith average voltage V ave The inputs are respectively fed into the corresponding subtractors (10) to calculate the difference. The error signal passes through the proportional controller (17) and is then input into the corresponding multiplier (18). After being multiplied by the output of the direction detection unit (16), it becomes the module equalization component. The control output component and the module equalization component are input into the corresponding adders (14) and added together to become the modulation signal. After passing through the carrier phase shift modulator (19), the driving signals D1, D2, D3...D of each submodule are obtained. n .

[0048] 2. The control method for a broadband signal generator applied to a DC system includes the following steps:

[0049] Step (1): Acquire the voltage V of the DC system dc n submodules SM1, SM2...SM n capacitor voltage V c1 V c2 …V cn And the current I1 of the filter inductor L.

[0050] Step (2): Calculate the average voltage V based on the capacitor voltages of each submodule collected in step (1). ave ,Right now

[0051]

[0052] Step (3): Set the reference voltage V ref With average voltage V ave The input subtractor (10) performs the difference and inputs the error signal into the proportional-integral controller (11).

[0053] Step (4): The output signal of the proportional-integral controller (11) is added to the sine command signal through the adder-subtractor (12) and the difference is taken with the current I1 of the filter inductor L as the input of the adaptive PIR controller (13);

[0054] The transfer function of the adaptive PIR controller (13) is:

[0055]

[0056] Among them, K p For proportionality coefficient, K i For the integral coefficient, K r For resonant gain, ω c ω is the resonant bandwidth, and ω0 is the resonant frequency.

[0057] The use of an adaptive PIR controller (13) is determined by the operating characteristics of the device. Since the signal generating device needs to output a sine signal with a wide frequency range of 1 to 1000 Hz, the ordinary PI controller can only achieve zero steady-state error tracking of DC signals, but cannot achieve zero steady-state error tracking of sine signals. In order to improve the output signal effect, an R (i.e., a resonant controller) is added on the original basis. The resonant controller usually has a narrow bandwidth and can only achieve zero steady-state error tracking at the target frequency. However, the device of the present invention needs to achieve zero steady-state error tracking over a wide range. Therefore, the parameters of the controller need to be adaptively modified according to the operating conditions (output of sine signals at different frequencies) to meet the output effect at different frequencies.

[0058] Step (5): Convert the voltage V of the DC system dc The sum of the voltages of the sub-modules V sum The feedforward quantity C is calculated after inputting into the feedforward quantity calculation unit (15). ff ;

[0059] The feedforward calculation unit (15) calculates the feedforward quantity C. ff The formula is as follows:

[0060]

[0061] in:

[0062]

[0063] Among them, V cj This represents the capacitor voltage of the j-th submodule, where j = 1, 2, 3…n.

[0064] Feedforward quantity C ff The purpose is to improve the dynamic performance of the system by adjusting the feedforward quantity C. ff By adding a control loop in an open-loop manner, the burden on the integral element of the controller is reduced.

[0065] Step (6): Combine the output of the adaptive PIR controller (13) with the feedforward quantity C ff The sum is used as the control output component;

[0066] Step (7): Capacitor voltage V of each submodule C1 V C2 …V Cn With average voltage V ave The error signal is input into the corresponding subtractor (10) to calculate the difference. After passing through the proportional controller (17), the error signal is input into the corresponding multiplier (18) and then multiplied by the output of the direction detection unit (16) to become the module equalization component.

[0067] The output of the direction detection unit (16) is represented by the following formula:

[0068]

[0069] Where out represents the output of the direction detection unit (16).

[0070] Step (8): The control output component from step (6) and the module voltage equalization component from step (7) are input together into the corresponding adder (14) and added to obtain the modulation signal. After passing through the carrier phase-shift modulator (19), the driving signals D1, D2, D3...D of each sub-module are obtained. n .

[0071] 3. Simulation test verification

[0072] Figure 3 shows the output waveforms and corresponding waveform analysis of the broadband signal generator. Figures 3(a), 3(b), 3(c), 3(d), and 3(e) show the output current waveforms under operating conditions of 50A amplitude and frequencies of 1Hz, 10Hz, 50Hz, 500Hz, and 1000Hz, respectively. Figures 3(f), 3(g), 3(h), 3(i), and 3(j) show the corresponding waveform spectrum analysis. For the two operating conditions in Figures 3(a) and 3(b), the voltage outer loop control parameter corresponds to PI1, and for the three operating conditions in Figures 3(c), 3(d), and 3(e), the controller PI2 is used. The spectrum analysis shows that the THD remains below 2%, proving that the broadband signal generator of this invention, applied to DC systems, can output high-quality broadband sinusoidal current signals from 1 to 1000Hz.

[0073] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A broadband signal generator for a high-voltage, high-power DC system, characterized in that, include: The main circuit and control circuit; the main circuit includes: n sub-modules SM1, SM2…SM n Filter inductor L, submodules SM1, SM2…SM n The circuit is cascaded in series and then connected in series with the filter inductor L, and finally connected to the DC system. The control circuit includes an outer loop PI control unit, an inner loop adaptive PIR control unit, a voltage equalization control unit, and a carrier phase shift modulator (19). The outer loop PI control unit includes a subtractor (10), a proportional-integral controller (11), and an adder / subtractor (12). The inner loop adaptive PIR control unit includes an adaptive PIR controller (13), an adder (14), and a feedforward calculation unit (15). The voltage equalization control unit includes a direction detection unit (16) and n identical voltage equalization branches, each of which includes a subtractor (10), an adder (14), a proportional controller (17), and a multiplier (18). The subtractor (10) in the outer loop PI control unit receives a reference voltage V at one input terminal. ref The average value of the input voltage at the other input terminal is V. ave The output terminal is connected to the input terminal of the proportional-integral controller (11). The output terminal of the proportional-integral controller (11) is connected to the first input terminal of the adder / subtractor (12). The second input terminal of the adder / subtractor (12) receives the sine command signal. The third input terminal of the adder / subtractor (12) receives the current I1 of the filter inductor L. The output terminal of the adder / subtractor (12) is connected to the input terminal of the adaptive PIR controller (13). The output terminal of the adaptive PIR controller (13) is connected to one input terminal of the adder (14) in the inner loop adaptive PIR control unit. The output terminal of the feedforward calculation unit (15) is connected to the other input terminal of the adder (14) in the inner loop adaptive PIR control unit. The two input terminals of the feedforward calculation unit (15) respectively receive the voltage V of the DC system. dc and the sum of the submodule voltages V sum One input terminal of the subtractor (10) in each equalizing branch corresponds to the input capacitor voltage V. C1 V C2 …V Cn The other input terminal of the subtractor (10) in each equalizing branch receives the average voltage V. ave The output of the subtractor (10) in each voltage equalization branch is connected to the input of the proportional controller (17) in that voltage equalization branch. The output of the proportional controller (17) in each voltage equalization branch is connected to one input of the multiplier (18) in that voltage equalization branch. The other input of the multiplier (18) in each voltage equalization branch is connected to the output of the direction detection unit (16). The current I1 of the filter inductor L is input to the direction detection unit (16). The output of the multiplier (18) in each voltage equalization branch is connected to one input of the adder (14) in that voltage equalization branch. The other input of the adder (14) in each voltage equalization branch is connected to the output of the adder (14) in the inner loop adaptive PIR control unit. The output of the adder (14) in each voltage equalization branch is connected to the input of the carrier phase shift modulator (19). The output of the carrier phase shift modulator (19) is connected to the n sub-modules SM1, SM2...SM n connect.

2. The high-voltage, high-power DC system broadband signal generator according to claim 1, characterized in that, The submodule adopts a half-bridge topology, which includes a first IGBT, a second IGBT, and a capacitor C. The collector of the first IGBT is connected to the positive terminal of the capacitor C, the emitter of the first IGBT is connected to the collector of the second IGBT, and serves as the positive output terminal of the half-bridge topology. The emitter of the second IGBT is connected to the negative terminal of the capacitor C, and serves as the negative output terminal of the submodule.

3. A control method for a broadband signal generator for a high-voltage, high-power DC system as described in any one of claims 1 to 2, characterized in that, Includes the following steps: Step (1): Acquire the voltage V of the DC system dc n submodules SM1, SM2...SM n capacitor voltage V c1 V c2 …V cn And the current I1 of the filter inductor L; Step (2): Calculate the average voltage V based on the capacitor voltages of each submodule collected in step (1). ave ; Step (3): Set the reference voltage V ref With average voltage V ave The input subtractor (10) performs the difference operation and inputs the error signal into the proportional-integral controller (11); Step (4): The output signal of the proportional-integral controller (11) is added to the sine command signal by the adder-subtractor (12) and the difference is taken with the current I1 of the filter inductor L as the input of the adaptive PIR controller (13); Step (5): Convert the voltage V of the DC system dc The sum of the voltages of the sub-modules V sum The feedforward quantity C is calculated after inputting into the feedforward quantity calculation unit (15). ff ; Step (6): Combine the output of the adaptive PIR controller (13) with the feedforward quantity C ff The sum is used as the control output component; Step (7): Capacitor voltage V of each submodule C1 V C2 …V Cn With average voltage V ave The error signal is input into the corresponding subtractor (10) to calculate the difference. After passing through the proportional controller (17), the error signal is input into the corresponding multiplier (18) and then multiplied by the output of the direction detection unit (16) to become the module equalization component. Step (8): The control output component from step (6) and the module equalization component from step (7) are input together into the corresponding adder (14) and added to obtain the modulation signal. After passing through the carrier phase-shift modulator (19), the driving signals D1, D2, D3...D of each sub-module are obtained. n .

4. The control method according to claim 3, characterized in that, The transfer function of the adaptive PIR controller (13) is: Among them, K p For proportionality coefficient, K i For the integral coefficient, K r For resonant gain, ω c ω is the resonant bandwidth, and ω0 is the resonant frequency.

5. The control method according to claim 3, characterized in that, The feedforward calculation unit (15) calculates the feedforward quantity C. ff The formula is as follows: in: Among them, V cj This represents the capacitor voltage of the j-th submodule, where j = 1, 2, 3…n.

6. The control method according to claim 3, characterized in that, The output of the direction detection unit (16) is represented by the following formula: Where out represents the output of the direction detection unit (16).

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