High-voltage direct-hanging type network configuration hybrid energy storage converter based on modular multilevel converter and control method thereof

Abstract

The application provides a high-voltage direct-hanging network type hybrid energy storage converter based on a modular multilevel converter, wherein the upper bridge arm converter unit and the lower bridge arm converter unit each comprise N sub-converter modules with the same structure, the N sub-converter modules of the upper bridge arm converter unit and the lower bridge arm converter module are sequentially cascaded, the positive terminals of the first sub-converter modules of the upper bridge arm converter unit and the lower bridge arm converter module are respectively connected to corresponding phase lines through an inductor, and the negative terminals of the tail sub-converter modules of the upper bridge arm converter unit and the lower bridge arm converter module are connected to a neutral point; the sub-converter module comprises an H-bridge circuit, a capacitor C, an energy storage battery module and a super capacitor module, the midpoint of the upper bridge arm of the H-bridge circuit is used as the positive terminal of the sub-converter module, the midpoint of the lower bridge arm of the H-bridge circuit is used as the negative terminal of the sub-converter module, and the capacitor C is connected in parallel with the H-bridge circuit; the positive terminals of the energy storage battery module and the super capacitor module are connected to the positive terminal of the capacitor C, and the negative terminals of the energy storage battery module and the super capacitor module are connected to the negative terminal of the capacitor C.

Description

Technical Field

[0001] This invention relates to a power equipment and its control method, and more particularly to a high-voltage direct-connected grid-type hybrid energy storage converter based on a modular multilevel converter and its control method. Background Technology

[0002] The green and low-carbon transformation of the energy sector is accelerating, with the proportion of new energy installed capacity continuing to increase. The large-scale integration of power electronic equipment has led to a decrease in the proportion of traditional synchronous units, a reduction in system rotational inertia, a weakening of reactive power support capacity, and a narrowing of voltage and frequency stability margins. This poses new challenges to the safety and stability of the power grid. Consequently, grid-connected converters have been proposed to address these issues.

[0003] In the existing technology, the main circuit topologies commonly used in grid-type converters are two / three-level topologies, cascaded full-bridge topologies, and modular multi-level topologies. Two / three-level topologies are limited by the voltage withstand level of power devices and are difficult to apply directly to high-voltage applications. Although cascaded full-bridge topologies can achieve high-voltage output through cascading, they require precise voltage balance control, which makes the circuit more complex and the control process more complicated, making it difficult to meet the requirements of actual operating conditions.

[0004] Therefore, in order to solve the above-mentioned technical problems, it is urgent to propose a new technical approach. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a high-voltage direct-connected grid-type hybrid energy storage converter based on a modular multilevel converter and its control method. By adopting a modular multilevel converter structure, it can provide support for high-voltage grid connection and large-capacity power output. Moreover, it adopts a hybrid energy storage method combining supercapacitors and energy storage batteries, thereby providing the power grid with short-term rapid inertia support and long-term frequency support, thus effectively ensuring the operational stability of the power grid system.

[0006] The present invention provides a high-voltage direct-connected grid-type hybrid energy storage converter based on a modular multilevel converter, comprising three converter modules, the three converter modules respectively corresponding to the three phases of the power grid;

[0007] The three converter modules have the same structure, and each converter module includes an upper bridge arm converter unit and a lower bridge arm converter unit.

[0008] Both the upper bridge arm converter unit and the lower bridge arm converter unit include N sub-converter modules with the same structure. The N sub-converter modules of the upper bridge arm converter unit and the lower bridge arm converter unit are cascaded in sequence. The positive terminals of the first terminal converter modules of the upper bridge arm converter unit and the lower bridge arm converter unit are respectively connected to the corresponding phase lines through an inductor. The negative terminals of the tail terminal converter modules of the upper bridge arm converter unit and the lower bridge arm converter unit are connected to the neutral point.

[0009] The sub-converter module includes an H-bridge circuit, a capacitor C, an energy storage battery module, and a supercapacitor module. The midpoint of the upper arm of the H-bridge circuit serves as the positive terminal of the sub-converter module, and the midpoint of the lower arm of the H-bridge circuit serves as the negative terminal of the sub-converter module. The capacitor C is connected in parallel with the H-bridge circuit. The positive terminals of the energy storage battery module and the supercapacitor module are connected to the positive terminal of the capacitor C, and the negative terminals of the energy storage battery module and the supercapacitor module are connected to the negative terminal of the capacitor C.

[0010] Furthermore, the supercapacitor module includes a supercapacitor, IGBT Q7, IGBT Q8, and inductor L. SC ;

[0011] The collector of IGBT Q7 is connected to the positive terminal of capacitor C, serving as the positive terminal of the supercapacitor module. The emitter of IGBT Q7 is connected to the collector of IGBT Q8. The emitter of IGBT Q8 is connected to the negative terminal of the supercapacitor and the negative terminal of capacitor C. The positive terminal of the supercapacitor is connected through inductor L. SC The collector of IGBT Q8 is connected; the gates of IGBT Q7 and IGBT Q8 respectively receive PWM control signals.

[0012] Furthermore, the energy storage battery module includes an energy storage battery, IGBT Q5, IGBT Q6, and inductor L. B ;

[0013] The collector of IGBT Q5 is connected to the positive terminal of capacitor C, serving as the positive terminal of the energy storage battery module. The emitter of IGBT Q5 is connected to the collector of IGBT Q6. The emitter of IGBT Q6 is connected to the negative terminal of the energy storage battery and the negative terminal of capacitor C. The positive terminal of the energy storage battery is connected through inductor L. B The collector of IGBT Q6 is connected to IGBT Q5 and IGBT Q6 respectively, and PWM control signals are input to them.

[0014] Accordingly, the present invention also provides a control method based on the above-described grid-type hybrid energy storage converter, comprising the following steps:

[0015] S1. Determine the operating parameters of the grid-type hybrid energy storage converter;

[0016] S2. Determine the phase angle and amplitude of the virtual internal potential based on the operating parameters of the grid-type hybrid energy storage converter;

[0017] S3. Determine the voltage modulation signal of the H-bridge circuit based on the phase angle and amplitude of the virtual internal potential, and use unipolar frequency doubling carrier phase shift modulation to modulate the voltage modulation signal of the H-bridge circuit to generate the PWM control signal of the H-bridge circuit.

[0018] S4. Determine the voltage control signal u of the supercapacitor module based on the supercapacitor's voltage reference value and actual voltage value. cmod Based on the voltage control signal u cmod Generate complementary PWM control signals to control the operation of the supercapacitor module;

[0019] S5. Determine the voltage control signal u of the energy storage battery module based on the reference value of the active power of the energy storage battery and the actual voltage value of the port. bmod Based on the voltage control signal u bmod Complementary PWM control signals are generated to control the operation of the energy storage battery module.

[0020] Furthermore, determining the phase angle θ of the virtual internal potential specifically includes:

[0021] Where: ω is the virtual angular velocity, and s represents the complex frequency domain;

[0022] ;

[0023] ;

[0024] Where: P ref P represents the active power reference value for a grid-type converter. e ω represents the actual output power of the grid-type converter, D represents the damping coefficient, J represents the virtual moment of inertia, and ω0 represents the rated angular velocity.

[0025] Furthermore, the amplitude E of the virtual internal potential is determined. ref Specifically, it includes:

[0026] ;

[0027] ;

[0028] Among them: U ref Q represents the voltage reference value of a grid-connected hybrid energy storage converter. ref Q represents the reactive power reference value of a grid-type hybrid energy storage converter. e k represents the actual output reactive power of the grid-type hybrid energy storage converter. q This represents the droop coefficient.

[0029] Furthermore, step S3 specifically includes:

[0030] Obtain the phase line voltage and transform it into the dq coordinate system to determine the direct-axis component u of the phase line voltage. d With cross-axis component u q ;

[0031] Determine the direct axis component ud With the amplitude E of the virtual internal potential ref Making a difference:

[0032] Δu d =E ref -u d ;

[0033] The difference Δu d The direct-axis current reference value i is obtained by inputting it into the PI controller. dref :

[0034] ;

[0035] Where: K p.d and K i.d These are the proportional and integral coefficients of the PI controller, respectively.

[0036] Intersect the axis component u with 0 q Determine the quadrature-axis voltage deviation Δu by subtraction. q ;

[0037] The quadrature-axis voltage deviation is input to the PI controller to obtain the quadrature-axis current reference value i. qref :

[0038] ;

[0039] Determine the voltage control commands s for the d-axis and q-axis d and s q :

[0040] ;

[0041] Where: i d with i q These are the direct-axis and quadrature-axis components of the actual phase line current value, respectively, K. p,id K i,id The proportional and integral coefficients of the PI controller are respectively; ωL represents the feedforward compensation coefficient.

[0042] Voltage control command s d and s q Transform to a three-phase stationary coordinate system:

[0043] ;

[0044] Obtain the circulating currents of the upper and lower bridge arm converter units, and transform them to the dq coordinate system to determine the direct-axis and quadrature-axis components of the circulating currents, denoted as i. td andi tq ;

[0045] The direct-axis and quadrature-axis components are input to the PI controller to obtain the command value u. d,PI and u q,PI :

[0046] ;

[0047] , , , These are the proportional and integral coefficients of the PI controller, respectively.

[0048] Determine the circulation suppression component s td andi tq :

[0049] ;

[0050] Transform the circulation suppression component to the three-phase stationary coordinate system:

[0051] ;

[0052] [v] ta ,v tb ,v tc ] T and [s a ,s b ,s c ] T The final three-phase modulation voltage [v] is obtained by summing the results. sa ,v sb ,v sc ] T ;

[0053] For three-phase modulated voltage [v sa ,v sb ,v sc ] T The PWM control signal for the H-bridge circuit is generated by unipolar frequency doubling carrier phase shift modulation.

[0054] Furthermore, step S4 specifically includes:

[0055] The voltage reference value u of the i-th sub-converter module supercapacitor module cref The actual voltage u of the supercapacitor module ci The difference is used to obtain the supercapacitor voltage deviation ∆u ci :

[0056] ;

[0057] The supercapacitor voltage deviation ∆u ci The current reference value i is obtained by inputting it into the PI controller. sciref :

[0058] ;

[0059] Where: K p,sc K is the proportional gain of the PI controller. i,sc The integral coefficient of the PI controller;

[0060] Determine the actual output current i of the supercapacitor in the i-th sub-converter module. sci Calculate the current deviation value ∆i sc :

[0061] ;

[0062] The current deviation value ∆i sc The control signal u is obtained by inputting it into the PI controller. cmod :

[0063] ;K p,b K i,b These are the proportional and integral coefficients of the PI controller, respectively.

[0064] Furthermore, step S5 specifically includes:

[0065] The active power reference value P of the energy storage battery module brefi With the port voltage V of the energy storage battery bi Determine the current reference value i bref :

[0066] ;

[0067] Determine the current deviation Δi bi :

[0068] ; where: i bi This indicates the actual output current of the energy storage battery;

[0069] The current deviation Δi bi The voltage control signal u is obtained by inputting it into the PI controller. bmod :

[0070] ;

[0071] Where: K p,b K i,b These are the proportional and integral coefficients of the PI controller, respectively.

[0072] The beneficial effects of this invention are as follows: By adopting a modular multilevel converter structure, this invention can provide support for high-voltage grid connection and large-capacity power output. Moreover, by using a hybrid energy storage method that combines supercapacitors and energy storage batteries, it can provide short-term rapid inertia support and long-term frequency support for the power grid, thereby effectively ensuring the operational stability of the power grid system.

[0073] By using bidirectional Buck / Boost converters in the energy storage battery module and the supercapacitor module to isolate the supercapacitor and the energy storage battery, it is possible to ensure deep discharge of the supercapacitor and avoid the impact of capacitor frequency double-frequency fluctuations on the cycle life of the energy storage battery. Attached Figure Description

[0074] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0075] Figure 1 This is a topological diagram of the present invention.

[0076] Figure 2 This is a topology diagram of the submodules of the present invention.

[0077] Figure 3 This is a schematic diagram of the process of the present invention.

[0078] Figure 4 This is a schematic diagram of the H-bridge circuit control of the present invention.

[0079] Figure 5 This is a schematic diagram of the control of the supercapacitor module and energy storage battery module of the present invention. Detailed Implementation

[0080] The present invention will be further described in detail below:

[0081] This invention provides a high-voltage direct-connected grid-type hybrid energy storage converter based on a modular multilevel converter, comprising three converter modules, which correspond to the three phases of the power grid, namely phases A, B, and C.

[0082] The three converter modules have the same structure, and each converter module includes an upper bridge arm converter unit and a lower bridge arm converter unit.

[0083] Both the upper and lower bridge arm converter units include N sub-converter modules with identical structures. These N sub-converter modules are cascaded sequentially. The positive terminals of the first terminal converter modules of both the upper and lower bridge arm converter units are connected to the corresponding phase lines via an inductor, and the negative terminals of the last terminal converter modules of both the upper and lower bridge arm converter units are connected to the neutral point. Figure 1As shown, the upper arm converter unit and the lower arm converter unit form a symmetrical structure;

[0084] The sub-converter module includes an H-bridge circuit, capacitor C, an energy storage battery module, and a supercapacitor module. The midpoint of the upper arm of the H-bridge circuit serves as the positive terminal of the sub-converter module, and the midpoint of the lower arm serves as the negative terminal. Capacitor C is connected in parallel with the H-bridge circuit. The positive terminals of the energy storage battery module and the supercapacitor module are connected to the positive terminal of capacitor C, and the negative terminals of the energy storage battery module and the supercapacitor module are connected to the negative terminal of capacitor C. In the above description, the midpoint of the upper arm of the H-bridge circuit is the common connection point between the emitter of IGBT Q1 and the collector of IGBT Q3, and the midpoint of the lower arm of the H-bridge circuit is the common connection point between the emitter of IGBT Q2 and the collector of IGBT Q4. The sequential cascading described above is illustrated with an example:

[0085] Taking the upper bridge arm as an example: the upper bridge arm has 3 sub-modules. The positive terminal of sub-converter module 1 is connected to the corresponding phase line through an inductor (or reactor). The negative terminal of sub-converter module 1 is connected to the positive terminal of sub-converter module 2. The negative terminal of sub-converter module 2 is connected to the positive terminal of sub-converter module 3. The negative terminal of sub-converter module 3 is connected to the neutral point.

[0086] Through the above structure, by adopting a modular multilevel converter structure, it is possible to provide support for high-voltage grid connection and large-capacity power output. Moreover, by adopting a hybrid energy storage method that combines supercapacitors and energy storage batteries, it can provide short-term rapid inertia support and long-term frequency support for the power grid, thereby effectively ensuring the operational stability of the power grid system.

[0087] By using bidirectional Buck / Boost converters in the energy storage battery module and the supercapacitor module to isolate the supercapacitor and the energy storage battery, it is possible to ensure deep discharge of the supercapacitor and avoid the impact of capacitor frequency double-frequency fluctuations on the cycle life of the energy storage battery.

[0088] In this embodiment, the supercapacitor module includes a supercapacitor, IGBT Q7, IGBT Q8, and inductor L. SC ;

[0089] The collector of IGBT Q7 is connected to the positive terminal of capacitor C, serving as the positive terminal of the supercapacitor module. The emitter of IGBT Q7 is connected to the collector of IGBT Q8. The emitter of IGBT Q8 is connected to the negative terminal of the supercapacitor and the negative terminal of capacitor C. The positive terminal of the supercapacitor is connected through inductor L. SC The collector of IGBT Q8 is connected; the gates of IGBT Q7 and IGBT Q8 respectively receive PWM control signals.

[0090] The energy storage battery module includes an energy storage battery, IGBT Q5, IGBT Q6, and inductor L. B ;

[0091] The collector of IGBT Q5 is connected to the positive terminal of capacitor C, serving as the positive terminal of the energy storage battery module. The emitter of IGBT Q5 is connected to the collector of IGBT Q6. The emitter of IGBT Q6 is connected to the negative terminal of the energy storage battery and the negative terminal of capacitor C. The positive terminal of the energy storage battery is connected through inductor L. B The collector of IGBT Q6 is connected to IGBT Q5, and PWM control signals are input to IGBT Q6 respectively. Figure 2 As can be seen from this: IGBT Q7, IGBT Q8, and inductor L SC This forms a bidirectional Buck / Boost converter, consisting of IGBT Q5, IGBT Q6, and inductor L. B Similarly, it forms a bidirectional Buck / Boost converter, thereby isolating the supercapacitor and energy storage battery from the H-bridge circuit and the supercapacitor and energy storage battery. This can ensure the deep discharge of the supercapacitor and avoid the impact of the capacitor's second harmonic frequency fluctuation on the cycle life of the energy storage battery. At the same time, it provides greater inertia, frequency and voltage support capabilities, making its active support technology advantages for new energy power plants more obvious.

[0092] Accordingly, the present invention also provides a control method based on the above-described grid-type hybrid energy storage converter, comprising the following steps:

[0093] S1. Determine the operating parameters of the grid-type hybrid energy storage converter;

[0094] S2. Determine the phase angle and amplitude of the virtual internal potential based on the operating parameters of the grid-type hybrid energy storage converter;

[0095] S3. The voltage modulation signal of the H-bridge circuit is determined based on the phase angle and amplitude of the virtual internal potential, and the voltage modulation signal of the H-bridge circuit is modulated by unipolar frequency doubling carrier phase shift modulation to generate the PWM control signal of the H-bridge circuit; the PWM control signal is used to control the operation of each IGBT in the H-bridge circuit; among them, unipolar frequency doubling carrier phase shift modulation (abbreviated as CPS-SPWM) is also an existing technology, which will not be described in detail here;

[0096] S4. Determine the voltage control signal u of the supercapacitor module based on the supercapacitor's voltage reference value and actual voltage value. cmod Based on the voltage control signal u cmod Generate complementary PWM control signals to control the operation of the supercapacitor module;

[0097] S5. Determine the voltage control signal u of the energy storage battery module based on the reference value of the active power of the energy storage battery and the actual voltage value of the port. bmod Based on the voltage control signal u bmod Complementary PWM control signals are generated to control the operation of the energy storage battery module. In the above, the voltage control signal u is used as the basis. cmod Generate complementary PWM control signals and voltage-based control signals u bmod The complementary PWM control signal is generated using the existing modulation method. Complementarity means that the phase difference between the upper and lower IGBTs in the supercapacitor module and the energy storage battery module is 180°, and they alternately conduct. Taking the supercapacitor module as an example, when the PWM control signal is generated to control Q7 and Q8, when Q7 is on, Q8 is off, and when Q8 is on, Q7 is off, thus forming a complementary conduction mechanism.

[0098] Specifically, such as Figures 4-5 As shown: Determining the phase angle θ of the virtual internal potential specifically includes:

[0099] Where: ω is the virtual angular velocity, and s represents the complex frequency domain;

[0100] ;

[0101] ;

[0102] Where: P ref P represents the active power reference value for a grid-type converter. e ω represents the actual output power of the grid-type converter, D represents the damping coefficient, J represents the virtual moment of inertia, and ω0 represents the rated angular velocity.

[0103] Furthermore, the amplitude E of the virtual internal potential is determined. ref Specifically, it includes:

[0104] ;

[0105] ;

[0106] Among them: U ref Q represents the voltage reference value of a grid-connected hybrid energy storage converter. ref Q represents the reactive power reference value of a grid-type hybrid energy storage converter. e k represents the actual output reactive power of the grid-type hybrid energy storage converter. q This represents the droop coefficient.

[0107] Furthermore, step S3 specifically includes:

[0108] Obtain the phase line voltage and transform it into the dq coordinate system to determine the direct-axis component u of the phase line voltage. d With cross-axis component u q ;

[0109] Determine the direct axis component u d With the amplitude E of the virtual internal potential ref Making a difference:

[0110] Δu d =E ref -u d ;

[0111] The difference Δu d The direct-axis current reference value i is obtained by inputting it into the PI controller. dref :

[0112] ;

[0113] Where: K p.d and K i.d These are the proportional and integral coefficients of the PI controller, respectively.

[0114] Intersect the axis component u with 0 q Determine the quadrature-axis voltage deviation Δu by subtraction. q ;

[0115] The quadrature-axis voltage deviation is input to the PI controller to obtain the quadrature-axis current reference value i. qref :

[0116] ;

[0117] Determine the voltage control commands s for the d-axis and q-axis d and s q :

[0118] ;

[0119] Where: i d with i q These are the direct-axis and quadrature-axis components of the actual phase line current value, respectively, K. p,id K i,id The proportional and integral coefficients of the PI controller are respectively; ωL represents the feedforward compensation coefficient.

[0120] Voltage control command s d and s q Transform to a three-phase stationary coordinate system:

[0121] ;

[0122] Obtain the circulating currents of the upper and lower bridge arm converter units, and transform them to the dq coordinate system to determine the direct-axis and quadrature-axis components of the circulating currents, denoted as i. td andi tq ;

[0123] The direct-axis and quadrature-axis components are input to the PI controller to obtain the command value u. d,PI and u q,PI :

[0124] ;

[0125] , , , These are the proportional and integral coefficients of the PI controller, respectively.

[0126] Determine the circulation suppression component s td andi tq :

[0127] ;

[0128] Transform the circulation suppression component to the three-phase stationary coordinate system:

[0129] ;

[0130] [v] ta ,v tb ,v tc ] T and [s a ,s b ,s c ] T The final three-phase modulation voltage [v] is obtained by summing the results. sa ,v sb ,v sc ] T ;

[0131] For three-phase modulated voltage [v sa ,v sb ,v sc ] T The PWM control signal for the H-bridge circuit is generated using unipolar frequency-doubled carrier phase-shift modulation. This means that after modulating three voltage sensors (corresponding to the three phases), the corresponding converter modules in each phase are controlled. Within the same phase, the PWM control signal for the H-bridge circuit of each sub-converter module is identical. Through this method, relying on the inertia and voltage frequency support provided by the network-type control, and in conjunction with circulating current suppression and compensation control mechanisms, reasonable power distribution is achieved, ensuring stable system operation.

[0132] In this embodiment, step S4 specifically includes:

[0133] The voltage reference value u of the i-th sub-converter module supercapacitor module cref The actual voltage u of the supercapacitor module ci The difference is used to obtain the supercapacitor voltage deviation ∆u ci :

[0134] ;

[0135] The supercapacitor voltage deviation ∆u ci The current reference value i is obtained by inputting it into the PI controller. sciref :

[0136] ;

[0137] Where: K p,sc K is the proportional gain of the PI controller. i,sc The integral coefficient of the PI controller;

[0138] Determine the actual output current i of the supercapacitor in the i-th sub-converter module. sci Calculate the current deviation value ∆i sc :

[0139] ;

[0140] The current deviation value ∆i sc The control signal u is obtained by inputting it into the PI controller. cmod :

[0141] ;K p,b K i,b These are the proportional and integral coefficients of the PI controller, respectively.

[0142] Step S5 specifically includes:

[0143] The active power reference value P of the energy storage battery module brefi With the port voltage V of the energy storage battery bi Determine the current reference value i bref :

[0144] ;

[0145] Determine the current deviation Δi bi :

[0146] ; where: i bi This indicates the actual output current of the energy storage battery;

[0147] The current deviation Δibi The voltage control signal u is obtained by inputting it into the PI controller. bmod :

[0148] ;

[0149] Where: K p,b K i,b These are the proportional and integral coefficients of the PI controller, respectively.

[0150] Finally, it should be noted that 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 preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high-voltage direct-connected grid-type hybrid energy storage converter based on a modular multilevel converter, characterized in that: It includes three converter modules, each corresponding to one of the three phases of the power grid; The three converter modules have the same structure, and each converter module includes an upper bridge arm converter unit and a lower bridge arm converter unit. Both the upper bridge arm converter unit and the lower bridge arm converter unit include N sub-converter modules with the same structure. The N sub-converter modules of the upper bridge arm converter unit and the lower bridge arm converter unit are cascaded in sequence. The positive terminals of the first terminal converter modules of the upper bridge arm converter unit and the lower bridge arm converter unit are respectively connected to the corresponding phase lines through an inductor. The negative terminals of the tail terminal converter modules of the upper bridge arm converter unit and the lower bridge arm converter unit are connected to the neutral point. The sub-converter module includes an H-bridge circuit, a capacitor C, an energy storage battery module, and a supercapacitor module. The midpoint of the upper arm of the H-bridge circuit serves as the positive terminal of the sub-converter module, and the midpoint of the lower arm of the H-bridge circuit serves as the negative terminal of the sub-converter module. The capacitor C is connected in parallel with the H-bridge circuit. The positive terminals of the energy storage battery module and the supercapacitor module are connected to the positive terminal of the capacitor C, and the negative terminals of the energy storage battery module and the supercapacitor module are connected to the negative terminal of the capacitor C.

2. The high-voltage direct-connected grid-type hybrid energy storage converter based on a modular multilevel converter according to claim 1, characterized in that: The supercapacitor module includes a supercapacitor, an IGBT Q7, an IGBT Q8, and an inductor L. SC ; The collector of IGBT Q7 is connected to the positive terminal of capacitor C, serving as the positive terminal of the supercapacitor module. The emitter of IGBT Q7 is connected to the collector of IGBT Q8. The emitter of IGBT Q8 is connected to the negative terminal of the supercapacitor and the negative terminal of capacitor C. The positive terminal of the supercapacitor is connected through inductor L. SC The collector of IGBT Q8 is connected; the gates of IGBT Q7 and IGBT Q8 respectively receive PWM control signals.

3. The high-voltage direct-connected grid-type hybrid energy storage converter based on a modular multilevel converter according to claim 1, characterized in that: The energy storage battery module includes an energy storage battery, IGBT Q5, IGBT Q6, and inductor L. B ; The collector of IGBT Q5 is connected to the positive terminal of capacitor C, serving as the positive terminal of the energy storage battery module. The emitter of IGBT Q5 is connected to the collector of IGBT Q6. The emitter of IGBT Q6 is connected to the negative terminal of the energy storage battery and the negative terminal of capacitor C. The positive terminal of the energy storage battery is connected through inductor L. B The collector of IGBT Q6 is connected to IGBT Q5 and IGBT Q6 respectively, and PWM control signals are input to them.

4. A control method for a grid-type hybrid energy storage converter based on any one of claims 1-3, characterized in that: Includes the following steps: S1. Determine the operating parameters of the grid-type hybrid energy storage converter; S2. Determine the phase angle and amplitude of the virtual internal potential based on the operating parameters of the grid-type hybrid energy storage converter; S3. Determine the voltage modulation signal of the H-bridge circuit based on the phase angle and amplitude of the virtual internal potential, and use unipolar frequency doubling carrier phase shift modulation to modulate the voltage modulation signal of the H-bridge circuit to generate the PWM control signal of the H-bridge circuit. S4. Determine the voltage control signal u of the supercapacitor module based on the supercapacitor's voltage reference value and actual voltage value. cmod Based on the voltage control signal u cmod Generate complementary PWM control signals to control the operation of the supercapacitor module; S5. Determine the voltage control signal u of the energy storage battery module based on the reference value of the active power of the energy storage battery and the actual voltage value of the port. bmod Based on the voltage control signal u bmod Complementary PWM control signals are generated to control the operation of the energy storage battery module.

5. The control method for a grid-type hybrid energy storage converter according to claim 4, characterized in that: Determining the phase angle θ of the virtual internal potential specifically includes: Where: ω is the virtual angular velocity, and s represents the complex frequency domain; ； ； Where: P ref P represents the active power reference value for a grid-type converter. e ω represents the actual output power of the grid-type converter, D represents the damping coefficient, J represents the virtual moment of inertia, and ω0 represents the rated angular velocity.

6. The control method for a grid-type hybrid energy storage converter according to claim 5, characterized in that: Determine the amplitude E of the virtual internal potential. ref Specifically, it includes: ； ； Among them: U ref Q represents the voltage reference value of a grid-connected hybrid energy storage converter. ref Q represents the reactive power reference value of a grid-type hybrid energy storage converter. e k represents the actual output reactive power of the grid-type hybrid energy storage converter. q This represents the droop coefficient.

7. The control method for a grid-type hybrid energy storage converter according to claim 6, characterized in that: Step S3 specifically includes: Obtain the phase line voltage and transform it into the dq coordinate system to determine the direct-axis component u of the phase line voltage. d With cross-axis component u q ; Determine the direct axis component u d With the amplitude E of the virtual internal potential ref Making a difference: Δu d =E ref −u d ; The difference Δu d The direct-axis current reference value i is obtained by inputting it into the PI controller. dref : ； Where: K p.d and K i.d These are the proportional and integral coefficients of the PI controller, respectively. Intersect the axis component u with 0 q Determine the quadrature-axis voltage deviation Δu by subtraction. q ; The quadrature-axis voltage deviation is input to the PI controller to obtain the quadrature-axis current reference value i. qref : ； Determine the voltage control commands s for the d-axis and q-axis d and s q : ； Where: i d with i q These are the direct-axis and quadrature-axis components of the actual phase line current value, respectively, K. p,id K i,id The proportional and integral coefficients of the PI controller are respectively; ωL represents the feedforward compensation coefficient. Voltage control command s d and s q Transform to a three-phase stationary coordinate system: ； Obtain the circulating currents of the upper and lower bridge arm converter units, and transform them to the dq coordinate system to determine the direct-axis and quadrature-axis components of the circulating currents, denoted as i. td andi tq ; The direct-axis and quadrature-axis components are input to the PI controller to obtain the command value u. d,PI and u q,PI : ； , , , These are the proportional and integral coefficients of the PI controller, respectively. Determine the circulation suppression component s td andi tq : ； Transform the circulation suppression component to the three-phase stationary coordinate system: ； [v] ta ,v tb ,v tc ] T and [s a ,s b ,s c ] T The final three-phase modulation voltage [v] is obtained by summing the results. sa ,v sb ,v sc ] T ; For three-phase modulated voltage [v sa ,v sb ,v sc ] T The PWM control signal for the H-bridge circuit is generated by unipolar frequency doubling carrier phase shift modulation.

8. The control method for a grid-type hybrid energy storage converter according to claim 4, characterized in that: Step S4 specifically includes: The voltage reference value u of the i-th sub-converter module supercapacitor module cref The actual voltage u of the supercapacitor module ci The difference is used to obtain the supercapacitor voltage deviation ∆u ci : ； The supercapacitor voltage deviation ∆u ci The current reference value i is obtained by inputting it into the PI controller. sciref : ； Where: K p,sc K is the proportional gain of the PI controller. i,sc The integral coefficient of the PI controller; Determine the actual output current i of the supercapacitor in the i-th sub-converter module. sci Calculate the current deviation value ∆i sc : ； The current deviation value ∆i sc The control signal u is obtained by inputting it into the PI controller. cmod : ;K p,b K i,b These are the proportional and integral coefficients of the PI controller, respectively.

9. The control method for a grid-type hybrid energy storage converter according to claim 4, characterized in that: Step S5 specifically includes: The active power reference value P of the energy storage battery module brefi With the port voltage V of the energy storage battery bi Determine the current reference value i bref : ； Determine the current deviation Δi bi : ; where: i bi This indicates the actual output current of the energy storage battery; The current deviation Δi bi The voltage control signal u is obtained by inputting it into the PI controller. bmod : ； Where: K p,b K i,b These are the proportional and integral coefficients of the PI controller, respectively.

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