High-gain bidirectional converter and control method thereof

Abstract

This invention discloses a high-gain bidirectional converter and its control method, belonging to the field of converter technology, including: a first inductor L1, a second inductor L2, first to fifth switching transistors S1 to S5, and first to M+1 diodes D. B1～ D Bm+1 The invention comprises first to Mth SM1 (sub-module) units and first to Nth SM2 units, wherein the SM1 unit is a half-bridge MMC (Modular Multilevel Converter) module, and the SM2 unit is a rechargeable and bidirectional discharge MMC sub-module; it also includes an output voltage step amplitude sampling stage, a transfer function calculation stage, a carrier stage, a comparison stage, a delay stage, and a drive signal generation stage. This invention can significantly increase voltage gain while suppressing charging current peaks and reducing charging losses, and achieves closed-loop control of bipolar voltage with a single voltage sensor.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of converters, and particularly relates to a high-gain bidirectional converter and a control method thereof. BACKGROUND

[0002] The high-gain bidirectional converter can be applied to energy storage systems, new energy power generation systems and industrial water treatment systems. High-voltage pulse converters are currently mainly divided into two categories: traditional pulse converters and solid-state pulse converters. The types of traditional pulse converters that are widely used include single-switch chopping type, Marx type, magnetic pulse compression and pulse forming line. Solid-state pulse generators are mainly divided into three types: one is a non-modular multilevel converter (MMC) based pulse converter, one is an MMC based pulse converter and one is a hybrid pulse converter. Patent application number (201710019493.7) discloses a non-MMC topology that improves the structure of the Marx pulse generator by using fewer switching tubes and more controls, but the current rating of the switching tubes is not the same, so it lacks modularity; at the same time, if bipolar pulses are needed, two identical topologies are needed when the loads are connected in differential, so it lacks versatility. Mohamed A.Elgenedy et al. published an article A Modular Multilevel Voltage-Boosting Marx Pulse-Waveform Generator for Electroporation Applications in IEEE Transactions on Power Electronics in 2019, which proposes a hybrid topology. The module capacitor voltage value can be higher than the low-voltage DC input, so when generating high-voltage pulses, it is no longer through single module stacking, but the boost circuit gain and the number of modules are realized together. In addition, the hybrid pulse converter has high integration of the front and rear stages, and the charging elements, such as inductors, can be replaced by inductor elements in the boost circuit, effectively reducing the number of elements. However, two groups of SM modules are needed to generate positive and negative pulses. D.Malviya et al. published an article A Boost Converter-Based High-Voltage Pulsed-Power Supply in IEEE Transactions on Industry Applications in 2020, which proposes a topology structure that uses a single group of SM modules to realize bipolar high-voltage pulses, reduces the number of passive devices and improves the circuit gain, but under the condition of the same DC voltage input, the boost circuit needs to provide higher voltage gain. SUMMARY

[0003] The technical problem to be solved by the present application is to provide a topology structure capable of doubling voltage gain, while suppressing the peak value of charging current and reducing charging loss, and realizing closed-loop control to generate bipolar high-voltage pulses under a single voltage sensor.

[0004] To solve the above technical problems, the technical scheme adopted by the present application is:

[0005] A high-gain bidirectional converter, comprising a first inductor L1, a second inductor L2, first to fifth switch tubes S, first to (M+1) diodes DB, first to M SM1 units, and first to N SM2 units, wherein the SM1 unit is a half-bridge MMC module, and the SM2 unit is a chargeable and bidirectional discharging MMC sub-module.

[0006] The first inductor L1 has a first end connected to a positive pole of an input direct current voltage V in , and a second end simultaneously connected to a first end of a first diode D B1 and a first end of a first switch tube S1; a second end of the first switch tube S1 is simultaneously connected to a connection point B1 of a first SM1 unit, a connection point E1 of a first SM2 unit, and a second end of a third switch tube S3; a second end of the first diode D B1 is simultaneously connected to a first end of a second diode D B2 and a connection point C1 of the first SM1 unit; a first end of the second inductor L2 is connected to a connection point A m of the Mth SM1 unit; a second end of the second inductor L2 is connected to a first end of a (M+1) diode D Bm+1 ; a second end of the (M+1) diode D Bm+1 is connected to a connection point D1 of the first SM2 unit; a first end of a fourth switch tube S4 is simultaneously connected to a second end of a fifth switch tube S5 and a negative pole of an output pulse voltage V o ; a second end of a second switch tube S2 is simultaneously connected to a first end of the third switch tube S3 and a positive pole of V o .

[0007] Further improvement of the technical scheme of the present application is that: the connection point A1 of the first SM1 unit is connected to the connection point B2 of the second SM1 unit; the connection point B1 of the first SM1 unit is simultaneously connected to the second end of the first switch tube S1, the connection point E1 of the first SM2 unit is connected to the second end of the third switch tube S3; the connection point A2 of the second SM1 unit is connected to the connection point B m of the Mth SM1 unit; the second end of the second diode D B2 is simultaneously connected to the first end of the Mth diode D Bm and the connection point C2 of the second SM1 unit; the second end of the Mth diode D Bm is connected to the connection point C of the Mth SM1 module. mConnection point A of module M SM1 m Simultaneously connect the first terminal of the second switch S2 and the first terminal of the second inductor.

[0008] A further improvement to the technical solution of the present invention is that the tail end of the second inductor L2 is connected to the (M+1)th diode D. Bm+1 The first end; the (M+1)th diode D Bm+1 The tail end is connected to the connection point D1 of the first SM2 unit; the connection point F of the Nth SM2 unit n Connected to the start end of the fifth switch S5; connection point G of the Nth SM2 unit. n Connect to the tail end of the fourth switch S4; the connection point F1 of the first SM2 unit is connected to the connection point D2 of the second SM2 unit; the connection point G1 of the first SM2 unit is connected to the connection point E2 of the second SM2 unit; the connection point F2 of the second SM2 unit is connected to the connection point D of the Nth SM2 unit. n The connection point G2 of the second SM2 unit is connected to the connection point E of the Nth SM2 unit. n .

[0009] A further improvement of the technical solution of the present invention is that: the first ends of capacitors CA1 to CAm in the first to M SM1 units are simultaneously connected to connection points Ci (=1, 2, …, m) and the first end of the first switch Tx; the tail end of capacitor CA is simultaneously connected to connection point Bm and the tail end of the second switch Tm; the connection point between the first switch Tx and the second switch Tm is connected to connection point An.

[0010] A further improvement of the technical solution of the present invention is that: the first ends of capacitors CB1 to CBn in the first to Nth SM2 units are simultaneously connected to connection point Fj (j = 1, 2, ..., n); the tail end of the first switch Qa is connected to the first end of the third switch Qc; the tail end of capacitor CB is simultaneously connected to connection point Gn; the first end of the second switch Qb is connected to the first end of the fourth switch Qd; the first end of the first switch Qa is simultaneously connected to the tail end of the fourth switch Qd and connection point Dn; and the tail end of the third switch Qc is simultaneously connected to the tail end of the second switch Qb and connection point En.

[0011] The control method for a high-gain bidirectional converter described above includes an output voltage step amplitude sampling stage, an error calculation stage, a transfer function calculation stage, a carrier stage, a comparison stage, a delay stage, and a drive signal generation stage.

[0012] A further improvement of the technical solution of the present invention is that: the carrier stage and the comparison stage both adopt the DSP internal PWM module register, the delay stage adopts the DSP internal time base module register, and the drive signal adopts the DSP internal PWM module.

[0013] The further improvement of the technical scheme of the present application is that the driving signals for controlling the switching tubes are simultaneously sent by using the internal PWM module register, the internal time base module register and the internal EPWM module of the DSP.

[0014] Thanks to the above technical scheme, the present application has the following technical progress:

[0015] The topology can multiply the voltage gain, suppress the peak value of the charging current and reduce the charging loss, and can realize the closed-loop control to generate bipolar high-voltage pulses under a single voltage sensor. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is the circuit topology structure diagram of the high-gain bidirectional converter of the present application;

[0017] Figure 2 is the SM1 unit module circuit topology structure diagram of the present application;

[0018] Figure 3 is the SM2 unit module circuit topology structure diagram of the present application

[0019] Figure 4 is the control method principle diagram of the high-gain bidirectional converter of the present application;

[0020] Figure 5 is the input voltage and output high-voltage pulse waveform diagram when the control method of the high-gain bidirectional converter of the present application is used. DETAILED DESCRIPTION

[0021] The present application will be further described in detail below in combination with embodiments:

[0022] According to Figure 1 , the present application is a high-gain bidirectional converter, the first inductor, the second inductor, the first to fifth switching tubes, the first to (M+1) diodes, the first to M SM1 units and the first to N SM2 units, the SM1 unit is a half-bridge MMC module, and the SM2 unit is a chargeable and bidirectional discharging MMC sub-module.

[0023] The first inductor L1 has a first end connected to the positive pole of the input DC voltage V in , and a second end simultaneously connected to the first end of the first diode D B1 and the first end of the first switching tube S1; the second end of the first switching tube S1 is simultaneously connected to the connection point B1 of the first SM1 unit, the connection point E1 of the first SM2 unit and the second end of the third switching tube S3; the second end of the first diode D B1 is simultaneously connected to the second diode D B2the first end of the first SM1 unit and the connection point C1; the second end of the second inductor L2 is connected to the connection point A of the Mth SM1 unit m ; the first end of the (M+1)th diode D Bm+1 is connected to the second end of the fourth switch S4; the second end of the (M+1)th diode D Bm+1 is connected to the connection point D1 of the first SM2 unit; the first end of the fourth switch S4 is connected to the second end of the fifth switch S5 and the negative pole of the output pulse voltage V o ; the second end of the second switch S2 is connected to the first end of the third switch S3 and the positive pole of the output pulse voltage V o .

[0024] The connection point A1 of the first SM1 unit is connected to the connection point B2 of the second SM1 unit; the connection point B1 of the first SM1 unit is connected to the second end of the first switch S1, the connection point E1 of the first SM2 unit and the second end of the third switch S3; the connection point A2 of the second SM1 unit is connected to the connection point B m of the Mth SM1 unit; the second end of the second diode D B2 is connected to the first end of the Mth diode D Bm and the connection point C2 of the second SM1 unit; the second end of the Mth diode D Bm is connected to the connection point C m of the Mth SM1 module; the connection point A m of the Mth SM1 module is connected to the first end of the second switch S2 and the first end of the second inductor.

[0025] The second end of the second inductor L2 is connected to the first end of the (M+1)th diode D Bm+1 ; the second end of the (M+1)th diode D Bm+1 is connected to the connection point D1 of the first SM2 unit; the connection point F n of the Nth SM2 unit is connected to the first end of the fifth switch S5; the connection point G n of the Nth SM2 unit is connected to the second end of the fourth switch S4; the connection point F1 of the first SM2 unit is connected to the connection point D2 of the second SM2 unit; the connection point G1 of the first SM2 unit is connected to the connection point E2 of the second SM2 unit; the connection point F2 of the second SM2 unit is connected to the connection point D n of the Nth SM2 unit; the connection point G2 of the second SM2 unit is connected to the connection point E n of the Nth SM2 unit.

[0026] The high-voltage pulse modular converter proposed in the present application is experimentally verified below, wherein M=2 and N=2, i.e., 2 SM1 units and 2 SM2 units are used.

[0027] As Figure 2The SM1 unit shown includes two DC input filter capacitors, C1 and C2. A1 C A2 The two switching devices are T and T respectively. x ,T m ;

[0028] like Figure 3 The SM2 unit shown includes two DC input filter capacitors, C. B1 C B2 The four switching devices are Q... a Q b Q c Q d ;

[0029] (M+1) diodes are respectively D B1 ~D Bm+1 ;

[0030] The two charging inductors are L1 and L2;

[0031] M SM1 units are respectively SM 11 ~SM 1m , in specific forms such as Figure 1 As shown;

[0032] N SM2 units are respectively SM 21 ~SM 2n , in specific forms such as Figure 1 As shown;

[0033] like Figure 2 The DC input filter capacitors of the SM1 unit shown are C A1 C A2 With two switching devices T x ,T m The connection method is:

[0034] Capacitor C in the first to the M SM1 units A The first end is simultaneously connected to connection point C. i (i = 1, 2) and the first switch T x The first end; the capacitor C A The tail end is simultaneously connected to connection point B2 and the second switch transistor T. m The tail end; the first switch transistor T x With the second switching transistor T m The connection point is connected to the connection point A2.

[0035] like Figure 3 The DC input filter capacitor of the SM2 unit shown is C. B1 C B2 With four switching devices Q a Qb Q c Q d The connection method is:

[0036] Capacitor C in the first and second SM2 units A The first end is simultaneously connected to connection point F. j (j = 1, 2), first switch Q a The tail end and the third switch Q c The first end; the capacitor C A The tail end is simultaneously connected to connection point G2, and the second switch Q b The first end and the fourth switch Q d The first end; the first switch Q a The first end is simultaneously connected to the fourth switch Q. d The tail end is connected to connection point D2. The third switch Q c The tail end is simultaneously connected to the second switching transistor Q. b The tail end and connection point E2.

[0037] Diode D B1 ~D Bm+1 The specific connection method of the charging inductors L1, L2, SM1, and SM2 is as follows:

[0038] The first inductor L1 is connected to the input DC voltage V. in The positive terminal of the first diode is connected to the beginning of the first diode and the beginning of the first switch S1. The end of the first switch S1 is connected to the connection point B1 of the first SM1 unit, the connection point E1 of the first SM2 unit, and the end of the third switch S3. The end of the first diode D1 is connected to the beginning of the second diode D2 and the connection point C1 of the first unit.

[0039] Connection point A1 of the first SM1 unit is connected to connection point B2 of the second SM1 unit; connection point B1 of the first SM1 unit is also connected to the tail end of the first switch S1, connection point E1 of the first SM2 unit, and the tail end of the third switch S3; connection point A2 of the second SM1 unit is connected to connection point B2 of the Mth SM1 unit. M The two diodes are connected in series; the tail end of the second diode is simultaneously connected to the head end of the Mth diode and the connection point C2 of the second SM1 unit; the tail end of the Mth diode is connected to the connection point C of the M SM1 module. m The connection point A of the M SM1 module m Simultaneously connect the first terminal of the second switch S2 and the second inductor. L2 The beginning.

[0040] The tail end of the second inductor L2 is connected to the head end of the (M+1)th diode; the tail end of the (M+1)th diode is connected to the connection point D1 of the first SM2 unit; the tail end of the second switch S2 is simultaneously connected to the head end of the third switch S3 and the output pulse voltage V. o The positive electrode; the connection point F of the Nth SM2 unit. n Connected to the first end of the fifth switching transistor S5; the connection point G of the NSM2 unit. n Connected to the tail end of the fourth switch S4; the head end of the fourth switch S4 is simultaneously connected to the tail end of the fifth switch S5 and V. o The negative terminal; the connection point F1 of the first SM2 unit is connected to the connection point D2 of the second SM2 unit; the connection point G1 of the first SM2 unit is connected to the connection point E2 of the second SM2 unit; the connection point F2 of the second SM2 unit is connected to the connection point D of the Nth SM2 unit. n The connection point G2 of the second SM2 unit is connected to the connection point E of the Nth SM2. n .

[0041] like Figure 4 As shown, the present invention provides a control method for a high-gain bidirectional converter. The control method includes an output voltage step amplitude sampling stage, a transfer function calculation stage, a carrier stage, a comparison stage, a delay stage, and a drive signal generation stage.

[0042] The amplitude of the sampled output voltage pulse is compared with the reference voltage. The error signal is passed through a PI controller to obtain a modulated wave, which is then compared with the carrier wave to obtain the pre-stage drive signal.

[0043] Provides the converter controller with the output voltage amplitude measured at a constant sampling frequency. This can be achieved using... Figure 3 The voltage sampling method samples the amplitude of the positive pulse in each pulse repetition cycle. During each charge / discharge switch switching, when state s changes, V... o Indirect measurement can be achieved through the following methods:

[0044]

[0045] Where v′ and s′ are the quantities before the transition (output voltage step), and v″ and s″ are the values ​​after the transition. The proposed strategy does not rely on direct measurement. It monitors the voltage step on the output voltage and therefore measures the voltage of the capacitor that generated the step. This strategy provides a measurement method for modular converters (e.g., cascaded H-bridge converters) with equal capacitor voltages at each switching moment. However, a drawback of this strategy is that it cannot provide accurate measurement results when multiple capacitors do not switch simultaneously to sample a step with a voltage below the magnitude. Figure 3It can be seen that this situation will occur in most cases in MMC converter, because the simultaneous switching of two adjacent capacitors will produce a voltage step. Therefore, in this strategy, voltage sampling needs to be carried out after a small period of time when the voltage step occurs, so as to achieve the measurement value closest to the actual value. The calculation formula of the voltage error calculation link is formula (2);

[0046] Δu o = V o * -V o …………………………………………(2)

[0047] Wherein, Δu o is the output voltage error, V o is the output voltage reference, V o * is the output voltage feedback, which can be obtained by the voltage sensor.

[0048] The transfer function in the transfer function operation link is formula (2);

[0049]

[0050] The output quantity of the output voltage error Δu c after the transfer function , the modulation ratio δ can be obtained, and the calculation formula of the modulation ratio δ is formula (3);

[0051]

[0052] Wherein, k1, k2, λ are all coefficients, s is the Laplace operator, k1=0.0001, k2=0.2, and λ=1 in the voltage control loop.

[0053] The generation module in the carrier link and the generation module in the comparison link are both DSP (Digital Signal Processing) internal PWM module registers;

[0054] The generation module in the delay link is a DSP internal time base module register;

[0055] The generation module in the drive signal is the EPWM module of the DSP.

[0056] M takes 2, N takes 2, the input voltage is 50V, and the output high voltage pulse waveform diagram when the control method is controlled is shown in Figure 5 .

[0057] The above examples are merely intended to describe the preferred embodiments of the present application, and are not intended to limit the scope of the present application. Any modifications and improvements made by those skilled in the art to the technical solutions of the present application without departing from the design spirit of the present application shall fall within the protection scope of the present application.

Claims

1. A high-gain bidirectional converter characterized by The application relates to a control method of a high-gain bidirectional converter, which comprises an output voltage step amplitude sampling link, an error calculation link, a transfer function operation link, a carrier link, a comparison link, a delay link and a driving signal generation link. The first inductor L1, the second inductor L2, the first to fifth switch tubes S1 to S5, the first to (M+1) diodes D B1 ~D Bm+1 , the first to M SM1 units, the first to N SM2 units, the SM1 unit is a half-bridge MMC module, and the SM2 unit is a chargeable and bidirectional discharging MMC submodule; The first inductor L1 has a first end connected to a positive pole of an input DC voltage V in and a second end connected to a first end of a first diode D B1 and a first end of a first switch S1; a second end of the first switch S1 is connected to a connection point B1 of a first SM1 unit, a connection point E1 of a first SM2 unit and a second end of a third switch S3; a second end of the first diode D B1 is connected to a first end of a second diode D B2 and the connection point C1 of the first SM1 unit; a first end of a second inductor L2 is connected to a connection point A m of an Mth SM1 unit; a second end of the second inductor L2 is connected to a first end of an (M+1)th diode D Bm+1 ; a second end of the (M+1)th diode D Bm+1 is connected to a connection point D1 of the first SM2 unit; a first end of a fourth switch S4 is connected to a second end of a fifth switch S5 and a negative pole of an output pulse voltage V o ; a second end of the second switch S2 is connected to a first end of the third switch S3 and a positive pole of V o . The connection point A1 of the first SM1 unit is connected with the connection point B2 of the second SM1 unit; the connection point B1 of the first SM1 unit is connected with the tail end of the first switch tube S1, the connection point E1 of the first SM2 unit and the tail end of the third switch tube S3 are connected; the connection point A2 of the second SM1 unit is connected with the connection point B m of the Mth SM1 unit; the tail end of the second diode D B2 is connected with the tail end of the Mth diode D Bm ; the tail end of the Mth diode D Bm is connected with the connection point C m of the Mth SM1 module; the connection point A m of the Mth SM1 module is connected with the tail end of the second switch tube S2 and the tail end of the second inductor. The tail end of the second inductor L2 is connected to the head end of the (M+1)th diode D Bm+1 The tail end of the (M+1)th diode D Bm+1 is connected to the connection point D1 of the first SM2 unit; the connection point F of the Nth SM2 unit n is connected to the head end of the fifth switch tube S5; the connection point G of the Nth SM2 unit n is connected to the tail end of the fourth switch tube S4; the connection point F1 of the first SM2 unit is connected to the connection point D2 of the second SM2 unit; the connection point G1 of the first SM2 unit is connected to the connection point E2 of the second SM2; the connection point F2 of the second SM2 unit is connected to the connection point D of the Nth SM2 unit n ; the connection point G2 of the second SM2 unit is connected to the connection point E n of the Nth SM2 unit; The calculation formula of the voltage error calculation link is formula (2); The transfer function in the transfer function operation link is formula (2); （2） wherein, is an output voltage error quantity, is an output voltage reference, is an output voltage feedback, which can be obtained by a voltage sensor; Wherein, k1, k2 and lambda are coefficients, s is a Laplace operator, k1=0.0001, k2=0.2 and lambda=1 in the voltage control loop; （3） Output voltage error amount Δu c After the transfer function The output quantity, the modulation ratio The calculation formula of the modulation ratio is formula (3); （4） The carrier link and the comparison link adopt a DSP internal PWM module register, the delay link adopts a DSP internal time base module register, and the driving signal adopts a DSP internal PWM module; the driving signals of the control switch tubes are simultaneously sent by using the DSP internal PWM module register, the DSP internal time base module register and the DSP internal EPWM module. ​ 2. A high-gain bidirectional converter according to claim 1, characterized in that: Capacitor C in the first to the M SM1 units A1 ~C Am The first end is simultaneously connected to connection point C. i (=1, 2, ..., m) and the first switch T x The first end; capacitor C A The tail end is simultaneously connected to connection point B. m Second switch T m The tail end; the first switching transistor T x With the second switching transistor T m Connection point and connection point A m Connected.

3. A high-gain bidirectional converter according to claim 1, characterized in that: the first to the Nth SM2 unit B1 C Bn the head end of simultaneously connecting the connection point F j (j=1, 2, …, n), the first switch tube Q a the tail end of and the third switch tube Q c the head end of simultaneously connecting F n ; the tail end of the capacitor C B the head end of simultaneously connecting the connection point G n , the second switch tube Q b the head end of and the fourth switch tube Q d the head end of simultaneously connecting G n ; the first switch tube Q a the head end of simultaneously connecting to the tail end of the fourth switch tube Q d and the connection point D n ; the tail end of the third switch tube Q c the head end of simultaneously connecting to the tail end of the second switch tube Q b and the connection point E n .

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