Active arc extinction and dimension reduction control method for converter

Abstract

The invention provides a converter active arc extinction dimension reduction control method, which is applied to a modular multilevel matrix converter, and comprises the following steps of: establishing a system state space equation of the modular multilevel matrix converter under dimension reduction transformation according to a topological structure and a Kirchhoff voltage law of the modular multilevel matrix converter; drawing an equivalent circuit model according to the system state space equation; deducing the system state space equation to obtain a power expression of each bridge arm of the modular multilevel matrix converter, and establishing a bridge arm capacitor voltage average value-power mathematical model according to the power expression of each bridge arm; controlling the modular multi-level matrix converter according to the equivalent circuit model and the bridge arm capacitor voltage average value-power mathematical model to obtain a dimension reduction control result of the modular multi-level matrix converter; the problem of serious coupling between control channel regulating variables is solved, and safe and reliable arc extinction of the single-phase earth fault of the power distribution network is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of converter stability control, and in particular to a converter active arc suppression and dimensionality reduction control method. Background Art

[0002] In recent years, the effective integration of traditional matrix converters with modular multilevel technology has driven the formation and development of modular multilevel matrix converters (M3Cs). The application of three-phase, single-phase, and frequency-matched M3Cs in active arc suppression for ground faults in distribution networks offers advantages such as the absence of an intermediate DC stage, low output harmonics, and enhanced flexibility, effectively reducing device size and improving reliability.

[0003] Currently, most research, both domestically and internationally, focuses on controlling the voltage ripple and balance of capacitors in MMC submodules. Research on direct, single-phase, and three-phase M3C control with the same frequency is still in its early stages. Module capacitor energy balance is key to M3C control and can typically be achieved through two approaches: modulation and control. Modulation methods primarily rely on capacitor voltage sequencing and its improved methods. While simple and effective, these methods often conflict with the submodule switching frequency. Based on the relationship between submodule power and output voltage, closed-loop feedback control is used to achieve capacitor voltage balancing. This approach ensures low switching frequencies and balanced capacitor voltages across submodules and has been widely adopted. Regarding the stable control of capacitor voltages in the bridge arms of three-phase-single-phase M3Cs, most existing literature focuses on input and output frequency mismatches. Given that the bridge arm power has no DC component and the submodule capacitor energy does not continuously increase or decrease, some researchers have proposed open-loop energy balance control strategies. However, these strategies suffer from weak interference immunity and system stability is sensitive to changes in physical model parameters. Other researchers have proposed closed-loop energy balance control strategies, which utilize only the circulating intermediate control variable to achieve bridge arm energy balance control, enhancing the robustness of the control system.

[0004] Because three-phase-to-single-phase direct co-frequency M3C applied in arc suppression scenarios has the characteristics of input-output co-frequency coupling and power mismatch, its bridge arm capacitor voltage stability control, ripple balance, and suppression have not yet been fully solved. Researchers further elaborated from the perspective of steady-state power models that co-frequency conversion has only a limited number of steady-state operating points. Under this premise, some researchers have achieved converter capacitor voltage stability control by adding a DC component to the circulating current and common-mode voltage. However, this method has the problem of high ripple amplitude of sub-module capacitor voltage. Other researchers have effectively solved the capacitor voltage stability control problem by introducing intermediate regulating variables such as circulating current and common-mode voltage, and setting a combination of base frequency and multiplier frequency in the circulating current and common-mode voltage. However, the asymmetric circulating current injection method produces sinusoidal components of unequal amplitude in the three-phase circulating current, making it difficult to achieve consistent balance of the bridge arm capacitor voltage. Summary of the Invention

[0005] The present invention provides a converter active arc suppression dimensionality reduction control method, the purpose of which is to solve the problem of severe coupling between adjustment quantities of various control channels and to achieve safe and reliable arc suppression for single-phase grounding faults in distribution networks.

[0006] In order to achieve the above object, the present invention provides a converter active arc suppression dimensionality reduction control method applied to a modular multi-level matrix converter, comprising:

[0007] Step 1: Based on the topological structure of the modular multilevel matrix converter and Kirchhoff's voltage law, a system state space equation of the modular multilevel matrix converter under dimensionality reduction transformation is established, and an equivalent circuit model is drawn according to the system state space equation;

[0008] Step 2: derive the system state space equation to obtain the power expression of each bridge arm of the modular multi-level matrix converter, and establish the bridge arm capacitor voltage average value-power mathematical model based on the power expression of each bridge arm;

[0009] Step 3: Control the modular multilevel matrix converter using the equivalent circuit model and the bridge arm capacitor voltage average value-power mathematical model to obtain a dimension reduction control result of the modular multilevel matrix converter.

[0010] Furthermore, the system state space equation of the modular multilevel matrix converter under dimensionality reduction transformation is:

[0011]

[0012] Among them, u o represents the output voltage of the modular multilevel matrix converter, represents the bridge arm voltage under the dimensionality reduction system, represents the circulation flow under the dimensionality reduction system, represents the output current of the dimensionality reduction system, represents the input current under the dimensionality reduction system, u R1 、u R2 Represents the input voltage under the dimensionality reduction system, u n Indicates the common-mode voltage.

[0013] More specifically, the equivalent circuit model includes:

[0014] The circulating system model includes the bridge arm inductance L and the bridge arm voltage under the reduced dimension system The first circulating system model is composed of the bridge arm inductance L and the bridge arm voltage under the reduced dimension system. The second circulation system model composed of

[0015] Common mode voltage model, including common mode voltage u n And the bridge arm voltage under the dimensionality reduction system

[0016] Input system model, including the input voltage u under the reduced dimension system R1 , bridge arm inductance L and bridge arm voltage under reduced dimension system The first input system model is composed of the input voltage u under the reduced dimension system R2 , bridge arm inductance L and bridge arm voltage under reduced dimension system The second input system model composed of

[0017] Output system model, including the output voltage u of the modular multilevel matrix converter o , bridge arm inductance L and bridge arm voltage under reduced dimension system

[0018] Furthermore, the power expression of each bridge arm of the modular multilevel matrix converter is:

[0019]

[0020] in, Both represent the bridge arm power, i o Indicates the output current.

[0021] Furthermore, the bridge arm capacitor voltage average value-power mathematical model is:

[0022]

[0023] in, Indicates the capacitor voltage reference value, C indicates the submodule capacitance, Represents the capacitor voltage in the abc coordinate system.

[0024] Furthermore, the modular multilevel matrix converter is controlled using the equivalent circuit model and the bridge arm capacitor voltage average value-power mathematical model, including:

[0025] The input current of the modular multi-level matrix converter is controlled using the equivalent circuit model and the average value-power mathematical model of the bridge arm capacitor voltage.

[0026] The injection loop current of the modular multi-level matrix converter is controlled using the equivalent circuit model and the average value-power mathematical model of the bridge arm capacitor voltage.

[0027] The output current of modular multi-level matrix converter is controlled using equivalent circuit model;

[0028] The common-mode voltage of a modular multilevel matrix converter is controlled using an equivalent circuit model.

[0029] Furthermore, the input current of the modular multilevel matrix converter is controlled using an equivalent circuit model and a bridge arm capacitor voltage average value-power mathematical model, including:

[0030] After performing dimensionality reduction transformation on the capacitor voltage in the abc coordinate system in the bridge arm capacitor voltage average value-power mathematical model, the total energy of the modular multi-level matrix converter is controlled to obtain the total energy control result;

[0031] Based on the total energy control results, the input current of the modular multilevel matrix converter is controlled using the input system model and PR controller.

[0032] Furthermore, the injection loop current of the modular multilevel matrix converter is controlled by using the equivalent circuit model and the average value-power mathematical model of the bridge arm capacitor voltage, including:

[0033] After performing dimensionality reduction transformation on the capacitor voltage in the abc coordinate system in the bridge arm capacitor voltage average value-power mathematical model, the bridge arm energy balance control of the modular multi-level matrix converter is performed to obtain the bridge arm energy balance control result;

[0034] Based on the bridge arm energy balance control results, the injected circulating current of the modular multilevel matrix converter is controlled using the circulating current system model and PR controller.

[0035] Furthermore, the output current of the modular multilevel matrix converter is controlled using an equivalent circuit model, including:

[0036] The output voltage of the modular multi-level matrix converter is controlled by using the PR controller to obtain the output voltage control result;

[0037] Based on the output voltage control results, the output current of the modular multilevel matrix converter is controlled using the output system model and PR controller.

[0038] Furthermore, the common-mode voltage of the modular multilevel matrix converter is controlled using an equivalent circuit model, including:

[0039] The common-mode voltage model is used to control the common-mode voltage of a modular multilevel matrix converter.

[0040] The above solution of the present invention has the following beneficial effects:

[0041] The present invention is applied to a modular multilevel matrix converter. Based on the topological structure of the modular multilevel matrix converter and Kirchhoff's voltage law, a system state space equation of the modular multilevel matrix converter under dimensionality reduction transformation is established, and an equivalent circuit model is drawn based on the system state space equation. The system state space equation is derived to obtain power expressions of each bridge arm of the modular multilevel matrix converter, and a bridge arm capacitor voltage average value-power mathematical model is established based on the power expressions of each bridge arm. The modular multilevel matrix converter is controlled based on the equivalent circuit model and the bridge arm capacitor voltage average value-power mathematical model to obtain a dimensionality reduction control result of the modular multilevel matrix converter. Compared with the prior art, the present invention can directly output alternating current with high power quality at the same frequency without an intermediate direct current stage. The modular multilevel matrix converter is controlled using the equivalent circuit model and the bridge arm capacitor voltage average value-power mathematical model, thereby solving the problem of severe coupling between adjustment variables of each control channel and achieving safe and reliable arc extinguishing in the event of a single-phase grounding fault in the distribution network.

[0042] Other beneficial effects of the present invention will be described in detail in the subsequent specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of a flow chart of an embodiment of the present invention;

[0044] Figure 2 A topological structure diagram of a modular multi-level matrix converter according to an embodiment of the present invention;

[0045] Figure 3 Schematic diagram of the structure of the equivalent circuit model in an embodiment of the present invention;

[0046] Figure 4 This is a control block diagram of input current control in an embodiment of the present invention;

[0047] Figure 5 This is a control block diagram of injection circulation control in an embodiment of the present invention;

[0048] Figure 6 This is a control block diagram of output current control in an embodiment of the present invention;

[0049] Figure 7 This is a control block diagram of common-mode voltage control in an embodiment of the present invention;

[0050] Figure 8 1 is a waveform diagram of the fault current under different working conditions in an embodiment of the present invention. DETAILED DESCRIPTION

[0051] To make the technical problems, technical solutions, and advantages to be solved by the present invention more clear, the following is a detailed description with reference to the accompanying drawings and specific embodiments. It is obvious that the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0052] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0053] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to a locking connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0054] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0055] In view of the existing problems, the present invention provides a converter active arc suppression and dimensionality reduction control method.

[0056] like Figure 1 As shown, an embodiment of the present invention provides a converter active arc suppression dimensionality reduction control method, which is applied to a modular multi-level matrix converter, including:

[0057] Step 1: Based on the topological structure of the modular multilevel matrix converter and Kirchhoff's voltage law, a system state space equation of the modular multilevel matrix converter under dimensionality reduction transformation is established, and an equivalent circuit model is drawn according to the system state space equation;

[0058] Step 2: derive the system state space equation to obtain the power expression of each bridge arm of the modular multi-level matrix converter, and establish the bridge arm capacitor voltage average value-power mathematical model based on the power expression of each bridge arm;

[0059] Step 3: Control the modular multilevel matrix converter using the equivalent circuit model and the bridge arm capacitor voltage average value-power mathematical model to obtain a dimension reduction control result of the modular multilevel matrix converter.

[0060] In the embodiment of the present invention, the modular multi-level matrix converter is an AC / AC modular multi-level matrix converter, and its topology is as follows: Figure 2 As shown, it consists of 6 bridge arms, each of which contains a bridge arm inductor L and N cascaded full-bridge sub-modules. The capacitance of the parallel capacitor on the DC side of each sub-module is C. Figure 2 in, u x is the x-phase input voltage, i x is the x-phase input current, u o is the output voltage, u p,nx is the voltage of the upper and lower bridge arms of phase x, i p,nx is the current of the upper and lower bridge arms of phase x, x=a, b, c; M and O are the neutral points of the input and output sides of M3C, and the potential difference between M and O is defined as the common mode voltage u n .

[0061] Specifically, step 1 includes:

[0062] According to Figure 2 Given the voltage and current reference directions of the modular multilevel matrix converter shown in FIG, the initial state space equation of the modular multilevel matrix converter can be obtained from Kirchhoff's voltage law as follows:

[0063]

[0064] Among them, the bridge arm current consists of output current, input current and circulating current, which is defined as:

[0065]

[0066]

[0067] Among them, i o Indicates the output current, i x Indicates the input current, i cir_X Indicates circulation;

[0068] The dimensionality reduction transformation formula shown below is introduced to perform dimensionality reduction transformation on the initial state space equation, and the system state space equation of the modular multi-level matrix converter under dimensionality reduction transformation is obtained as follows:

[0069]

[0070] Among them, u o represents the output voltage of the modular multilevel matrix converter, represents the bridge arm voltage under the dimensionality reduction system, represents the circulation flow under the dimensionality reduction system, represents the output current of the dimensionality reduction system, represents the input current under the dimensionality reduction system, u R1 、u R2 Represents the input voltage under the dimensionality reduction system, u n Indicates common mode voltage;

[0071] Without loss of generality, the expressions of the three-phase input side voltage and current, single-phase output side voltage and current, circulating current and common-mode voltage of the modular multilevel matrix converter are as follows:

[0072]

[0073] u n =U n cos(ω n t+φ n )

[0074] Among them, U s , I s are the phase voltage and phase current amplitudes on the input side respectively; U o , I o are the voltage and current amplitudes on the output side respectively; are the power factor angles of the input and output sides respectively; θ1 is the phase angle difference between the input and output voltages; ω1 is the frequency of the system input and output sides. z1 , I z2 、φ z1 、φ z2 are the positive and negative sequence circulating current amplitudes and their corresponding initial phase angles injected at frequency n, respectively; u n 、φ n are the amplitude of the injected n-frequency common-mode voltage and its corresponding initial phase angle respectively.

[0075] In the embodiment of the present invention, the dimensionality reduction transformation formula is:

[0076]

[0077] Among them, T R 、T ∑Δ represents the coordinate transformation matrix, H abc Represents the matrix composed of the components to be transformed in the abc coordinate system, Represents the matrix composed of the reduced-dimensional system components after dimensionality reduction transformation.

[0078] Specifically, if Figure 3 As shown, the equivalent circuit model includes:

[0079] The circulating system model includes the bridge arm inductance L and the bridge arm voltage under the reduced dimension system The first circulating system model is composed of the bridge arm inductance L and the bridge arm voltage under the reduced dimension system. The second circulation system model composed of

[0080] Common mode voltage model, including common mode voltage u n And the bridge arm voltage under the dimensionality reduction system

[0081] Input system model, including the input voltage u under the reduced dimension system R1 , bridge arm inductance L and bridge arm voltage under reduced dimension system The first input system model is composed of the input voltage u under the reduced dimension system R2 , bridge arm inductance L and bridge arm voltage under reduced dimension system The second input system model composed of

[0082] Output system model, including the output voltage u of the modular multilevel matrix converter o , bridge arm inductance L and bridge arm voltage under reduced dimension system

[0083] Since the analysis of the converter arm power is the premise of analyzing the bridge arm capacitor voltage, in order to fundamentally analyze the stability control problem of the modular multilevel matrix converter, we can first perform a power analysis of the modular multilevel matrix converter without considering circulating current injection and common mode voltage control. Combining the bridge arm voltage and current equations, we can derive the system state space equation and obtain the power expression of each bridge arm of the modular multilevel matrix converter, including:

[0084] First, combining the bridge arm voltage and current formulas, we can get the bridge arm power expression without considering the circulating current injection and common mode voltage control:

[0085]

[0086]

[0087] Analysis of the above formula shows that the DC power component in the six bridge arm powers is the power that must exist when the input and output ports of the converter system are at the same frequency. This DC power component is defined as the inherent DC power of the converter system. The existence of inherent DC power is the cause of the instability of the converter capacitor voltage and needs to be eliminated or offset to achieve stable control of the capacitor voltage.

[0088] By analyzing the capacitor voltage in the system's degrees of freedom, a dimensionality reduction transformation formula is proposed to reduce the system's degrees of freedom. The above-mentioned bridge arm power formula adopts dimensionality reduction transformation, and the bridge arm power expression without considering circulating current injection and common-mode voltage control under dimensionality reduction transformation is obtained as follows:

[0089]

[0090] In the embodiment of the present invention, when the loop injection is not considered, The DC power in the inherent power is zero, that is, at this time the objectives of capacitor voltage balance control are reduced from 6 to 3, and the dimension of system freedom is reduced from 9 to 6, realizing dimensionality reduction of system freedom.

[0091] Through dimensionality reduction transformation, the system degree of freedom dimension is reduced from 9 to 6, and the system control input has the following constraints due to the particularity of the modular multi-level matrix converter:

[0092]

[0093] The above equation can be simplified by combining the definition of the converter bridge arm current to obtain the following equality constraints:

[0094]

[0095] From the above equation, we can see that if no circulating current is injected for control, that is, the circulating currents of the three-phase bridge arms are all zero, then the output voltages of the three-phase bridge arms abc are equal, that is, the following equality constraint condition exists:

[0096]

[0097] The existence of this bridge arm voltage constraint reduces the control inputs of the modular multilevel matrix converter from six to four, worsening the system's underdriven characteristics. Therefore, in modular multilevel matrix converter control, controlling the circulating current is a way to increase the system's control inputs and achieve full system drive.

[0098] Different frequencies of injected circulating current will generate different power components in the system. Therefore, the injected circulating current should meet the following two requirements:

[0099] Injection circulation will not cause DC power is generated in the system, which makes the control of the system more difficult.

[0100] The injection circulation will Generate controllable DC power to offset its inherent DC power;

[0101] Therefore, combining the dimensionality reduction transformation, state space equation and bridge arm current formula, the power expression of each bridge arm of the modular multilevel matrix converter is obtained as follows:

[0102]

[0103] in, Both represent the bridge arm power, i o Indicates the output current.

[0104] The embodiment of the present invention ignores the inductor voltage drop and assumes that the capacitor voltage of all submodules is controlled to the capacitor voltage reference value through an appropriate control strategy. By listing the differential equations of the capacitor voltage of each bridge arm and performing dimensionality reduction transformation, the average capacitor voltage-power mathematical model of the modular multi-level matrix converter can be obtained as follows. It is used to characterize the relationship between the bridge arm power and the sub-module capacitor voltage. The average capacitor voltage-power mathematical model of the bridge arm is:

[0105]

[0106] in, Indicates the capacitor voltage reference value, C indicates the submodule capacitance, Represents the capacitor voltage in the abc coordinate system.

[0107] Specifically, the modular multilevel matrix converter is controlled using an equivalent circuit model and a bridge arm capacitor voltage average value-power mathematical model, including:

[0108] The input current of the modular multi-level matrix converter is controlled using the equivalent circuit model and the average value-power mathematical model of the bridge arm capacitor voltage.

[0109] The injection loop current of the modular multi-level matrix converter is controlled using the equivalent circuit model and the average value-power mathematical model of the bridge arm capacitor voltage.

[0110] The output current of modular multi-level matrix converter is controlled using equivalent circuit model;

[0111] The common-mode voltage of a modular multilevel matrix converter is controlled using an equivalent circuit model.

[0112] Most preferably, the input current of the modular multi-level matrix converter is controlled using an equivalent circuit model and a bridge arm capacitor voltage average value-power mathematical model, including:

[0113] After performing dimensionality reduction transformation on the capacitor voltage in the abc coordinate system in the bridge arm capacitor voltage average value-power mathematical model, the total energy of the modular multi-level matrix converter is controlled to obtain the total energy control result;

[0114] Based on the total energy control results, the input current of the modular multilevel matrix converter is controlled using the input system model and PR controller.

[0115] In the embodiment of the present invention, the control block diagram of the input current control is as follows: Figure 4 As shown, the capacitor voltage in the abc coordinate system is transformed into the total capacitor voltage by dimensionality reduction. The dimensionality reduction transformation expression is as follows:

[0116]

[0117] Among them, U Cpa 、U Cpb 、U Cpc 、U Cna 、U Cnb 、U Cnc Represents the bridge arm capacitor voltage in the abc coordinate system;

[0118] The ripple component in the total capacitor voltage is filtered out by a low-pass filter to obtain the average value of the total capacitor voltage;

[0119] The average value of the total capacitor voltage is differentiated to obtain the active current command value, which is used to track the average value of the total capacitor voltage in the modular multi-level matrix converter. The expression is:

[0120]

[0121] in, Represents the average value of the total capacitor voltage, i d Indicates the active current command value;

[0122] The active current command value and the reactive current command value are respectively subjected to dimensionality reduction transformation and compared with the input system model output After merging, the first PR controller and the second PR controller are used to control the input current control signal Used to control the input current of a modular multi-level matrix converter.

[0123] Most preferably, the injection circulating current of the modular multi-level matrix converter is controlled by using an equivalent circuit model and a bridge arm capacitor voltage average value-power mathematical model, including:

[0124] After performing dimensionality reduction transformation on the capacitor voltage in the abc coordinate system in the bridge arm capacitor voltage average value-power mathematical model, the bridge arm energy balance control of the modular multi-level matrix converter is performed to obtain the bridge arm energy balance control result;

[0125] Based on the bridge arm energy balance control results, the injected circulating current of the modular multilevel matrix converter is controlled using the circulating current system model and PR controller.

[0126] In the embodiment of the present invention, the control block diagram of the injection circulation control is as follows: Figure 5 As shown, the capacitor voltage in the abc coordinate system is transformed by dimensionality reduction to obtain the bridge arm capacitor voltage The dimensionality reduction transformation expression is as follows:

[0127]

[0128] Among them, U Cpa 、U Cpb 、U Cpc 、U Cna 、U Cnb 、U Cnc Represents the bridge arm capacitor voltage in the abc coordinate system;

[0129] The ripple component in the bridge arm capacitor voltage is filtered out by a low-pass filter to obtain the average value of the bridge arm capacitor voltage, which is expressed as:

[0130]

[0131] By analyzing the above formula, it is found that the bridge arm capacitor voltage balance control can be achieved by injecting the amplitude of the circulating current. The average value of the capacitor voltage of each bridge arm is input into the PI controller for adjustment, and the adjusted circulating current amplitude is obtained.

[0132] The adjusted circulation amplitude is input into the circulation expression for calculation to obtain the instruction value of the circulation amount under the dimensionality reduction transformation.

[0133] The command value of the circulation flow under the dimensionality reduction transformation is compared with the circulation flow output by the circulation system model. After merging, input into PR controller for adjustment to obtain circulation control quantity Used to control the injection loop current of a modular multi-level matrix converter.

[0134] In the embodiment of the present invention, in the bridge arm energy balance control, due to the presence of a certain degree of coupling between the two control channels, a feedforward decoupling method is adopted to superimpose the coupling term inversely in the controller of the corresponding channel to achieve decoupling between the control channels and improve the response speed of the system. The expression related to feedforward is as follows:

[0135]

[0136] in, represents the phase angle of the common-mode voltage, Represents the circulation in the reduced-dimensional system The phase angle, Represents the circulation in the reduced-dimensional system The phase angle, θm Indicates the phase angle difference between the input side a phase voltage and the output voltage, Indicates the power factor angle on the output side.

[0137] Most preferably, the output current of the modular multi-level matrix converter is controlled using an equivalent circuit model, comprising:

[0138] The output voltage of the modular multi-level matrix converter is controlled by using the PR controller to obtain the output voltage control result;

[0139] Based on the output voltage control results, the output current of the modular multilevel matrix converter is controlled using the output system model and PR controller.

[0140] In the embodiment of the present invention, the control block diagram of the output current control is as follows: Figure 6 As shown in the figure, the output voltage command value is obtained according to the active voltage arc suppression command value, and the expression is:

[0141]

[0142] in, Indicates the output voltage command value, e a Indicates the fault phase voltage;

[0143] The output voltage command value and the output voltage value u o After merging, the current command value is obtained by inputting the PR controller for adjustment.

[0144] The current command value The output of the system model is i o After merging, the PR controller is input to obtain the output current control signal. Used to control the output current of a modular multi-level matrix converter.

[0145] Most preferably, the common mode voltage of the modular multilevel matrix converter is controlled using an equivalent circuit model, comprising:

[0146] The common-mode voltage model is used to control the common-mode voltage of a modular multilevel matrix converter.

[0147] In the embodiment of the present invention, the control block diagram of the common mode voltage control is as follows: Figure 7 As shown, according to the common mode voltage model, the common mode voltage u n Combined with the common mode voltage expression, the intermediate variable between the common mode voltage and the bridge arm voltage is obtained By adjusting the intermediate variable of the bridge arm voltage Can achieve common mode voltage u n , and there is only a coefficient relationship between the two.

[0148] An embodiment of the present invention is applied to a modular multilevel matrix converter. Based on the topological structure of the modular multilevel matrix converter and Kirchhoff's voltage law, a system state space equation of the modular multilevel matrix converter under dimensionality reduction transformation is established, and an equivalent circuit model is drawn based on the system state space equation. The system state space equation is derived to obtain power expressions for each bridge arm of the modular multilevel matrix converter, and a mathematical model of the average value of the bridge arm capacitor voltage-power is established based on the power expressions for each bridge arm. The modular multilevel matrix converter is controlled based on the equivalent circuit model and the mathematical model of the average value of the bridge arm capacitor voltage-power, and a dimensionality reduction control result of the modular multilevel matrix converter is obtained. Compared with the prior art, the embodiment of the present invention can directly output high-power quality alternating current at the same frequency without an intermediate DC stage. The modular multilevel matrix converter is controlled using the equivalent circuit model and the mathematical model of the average value of the bridge arm capacitor voltage-power, thereby solving the problem of severe coupling between the adjustment variables of each control channel and achieving safe and reliable arc suppression for single-phase grounding faults in the distribution network.

[0149] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A converter active arc suppression dimensionality reduction control method, characterized in that: Applications in modular multi-level matrix converters, including: Step 1: establishing a system state space equation of the modular multilevel matrix converter under dimensionality reduction transformation according to the topological structure of the modular multilevel matrix converter and Kirchhoff's voltage law, and drawing an equivalent circuit model according to the system state space equation; Step 2: deriving the system state space equation to obtain each bridge arm power expression of the modular multi-level matrix converter, and establishing a bridge arm capacitor voltage average value-power mathematical model according to each bridge arm power expression; Step 3: Control the modular multi-level matrix converter using the equivalent circuit model and the bridge arm capacitor voltage average value-power mathematical model to obtain a dimension reduction control result of the modular multi-level matrix converter.

2. The converter active arc suppression dimensionality reduction control method according to claim 1, characterized in that: The system state space equation of the modular multi-level matrix converter under dimensionality reduction transformation is: Among them, u o represents the output voltage of the modular multilevel matrix converter, represents the bridge arm voltage under the dimensionality reduction system, represents the circulation flow under the dimensionality reduction system, represents the output current of the dimensionality reduction system, represents the input current under the dimensionality reduction system, u R1 、u R2 Represents the input voltage under the dimensionality reduction system, u n Indicates the common-mode voltage.

3. The converter active arc suppression dimensionality reduction control method according to claim 2, characterized in that: The equivalent circuit model includes: The circulating system model includes the bridge arm inductance L and the bridge arm voltage under the reduced dimension system The first circulating system model is composed of the bridge arm inductance L and the bridge arm voltage under the reduced dimension system. The second circulation system model composed of Common mode voltage model, including common mode voltage u n And the bridge arm voltage under the dimensionality reduction system Input system model, including the input voltage u under the reduced dimension system R1 , bridge arm inductance L and bridge arm voltage under reduced dimension system The first input system model is composed of the input voltage u under the reduced dimension system R2 , bridge arm inductance L and bridge arm voltage under reduced dimension system The second input system model composed of Output system model, including the output voltage u of the modular multilevel matrix converter o , bridge arm inductance L and bridge arm voltage under reduced dimension system 4. The converter active arc suppression dimensionality reduction control method according to claim 3, characterized in that: The power expression of each bridge arm of the modular multi-level matrix converter is: in, Both represent the bridge arm power, i o Indicates the output current.

5. The converter active arc suppression dimensionality reduction control method according to claim 4, characterized in that: The bridge arm capacitor voltage average value-power mathematical model is: in, Indicates the capacitor voltage reference value, C indicates the submodule capacitance, Represents the capacitor voltage in the abc coordinate system.

6. The converter active arc suppression dimensionality reduction control method according to claim 5, characterized in that: Controlling the modular multi-level matrix converter using the equivalent circuit model and the bridge arm capacitor voltage average value-power mathematical model includes: Controlling the input current of the modular multi-level matrix converter using the equivalent circuit model and the bridge arm capacitor voltage average-power mathematical model; Controlling the injected circulating current of the modular multi-level matrix converter by using the equivalent circuit model and the bridge arm capacitor voltage average value-power mathematical model; Controlling the output current of the modular multi-level matrix converter using the equivalent circuit model; The common-mode voltage of the modular multi-level matrix converter is controlled using the equivalent circuit model.

7. The converter active arc suppression dimensionality reduction control method according to claim 6, characterized in that: Controlling the input current of the modular multi-level matrix converter by using the equivalent circuit model and the bridge arm capacitor voltage average value-power mathematical model includes: After performing a dimensionality reduction transformation on the capacitor voltage in the abc coordinate system in the bridge arm capacitor voltage average value-power mathematical model, the total energy of the modular multi-level matrix converter is controlled to obtain a total energy control result; Based on the total energy control result, the input current of the modular multi-level matrix converter is controlled by using the input system model and the PR controller.

8. The converter active arc suppression dimensionality reduction control method according to claim 6, characterized in that: Controlling the injected circulating current of the modular multi-level matrix converter by using the equivalent circuit model and the bridge arm capacitor voltage average value-power mathematical model includes: After performing a dimensionality reduction transformation on the capacitor voltage in the abc coordinate system in the bridge arm capacitor voltage average value-power mathematical model, the bridge arm energy balance control of the modular multi-level matrix converter is performed to obtain a bridge arm energy balance control result; Based on the bridge arm energy balance control result, the injection circulating current of the modular multi-level matrix converter is controlled by utilizing the circulating current system model and the PR controller.

9. The converter active arc suppression dimensionality reduction control method according to claim 6, characterized in that: Controlling the output current of the modular multi-level matrix converter by using the equivalent circuit model includes: Using the PR controller to control the output voltage of the modular multi-level matrix converter to obtain an output voltage control result; Based on the output voltage control result, the output current of the modular multi-level matrix converter is controlled by using the output system model and a PR controller.

10. The converter active arc suppression dimensionality reduction control method according to claim 6, characterized in that: Controlling the common-mode voltage of the modular multi-level matrix converter using the equivalent circuit model includes: The common-mode voltage model is used to control the common-mode voltage of the modular multi-level matrix converter.

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