Single-phase dual-active bridge micro-inverse controller with preset internal phase shift and external phase shift

Abstract

The invention discloses a single-phase dual-active bridge micro-inverse controller with preset internal phase shift and external phase shift in the technical field of power electronics and electricians. A power grid voltage phase-locked loop obtains a phase signal of power grid voltage; generating an inner phase shift angle and an outer phase shift angle preset quantity by the inner phase shift preset law and the outer phase shift preset law; a grid-connected current peak value output by the MPPT voltage loop is multiplied by a power grid voltage phase signal generated by the power grid voltage phase-locked loop to obtain a grid-connected current given value, a current PI regulator of the grid-connected current loop generates an external phase-shift angle compensation amount of a corresponding switch tube, and the external phase-shift angle compensation amount is superposed with an external phase-shift angle preset amount to obtain an external phase-shift angle of the corresponding switch tube; the internal phase shift angle and the external phase shift angle are sent to a phase shift controller to generate phase shift pulse control signals corresponding to on-off of a switching tube in the single-phase dual-active bridge micro inverter, power generation of photovoltaic energy to a power grid is realized, stable adjustment of the single-phase dual-active bridge micro inverter is facilitated, and the response speed of the system is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power electronics and electrical engineering, and particularly relates to a single-phase dual active bridge micro-inverter. BACKGROUND

[0002] Micro-inverter is a kind of grid-connected power generation device for a single photovoltaic module, which has the ability of maximum power point tracking at the module level and can effectively solve the hot spot effect, so it is more and more applied in distributed power generation systems. At present, according to the type of bus, the main circuit topology of micro-inverter is roughly divided into three types: DC bus, no DC bus and pseudo-DC bus structure. The DC bus type micro-inverter is usually composed of two-stage DC / DC and DC / AC converters, the former DC / DC converter not only undertakes the MPPT task but also needs to boost the voltage of the latter DC / AC to provide a high enough DC bus voltage, and the grid connection is realized by the latter DC / AC inverter. The former converter of the pseudo-DC bus structure not only needs to realize MPPT control and voltage boost, but also needs to convert the DC of the PV module into a steamed bun wave with a double power frequency period through high-frequency PWM modulation, so the latter needs to flip the steamed bun wave to a sine grid current through a power frequency polarity conversion circuit. The first two circuits are two-stage circuits, which are difficult to further improve the efficiency, therefore, the micro-inverter without DC bus appears, which is a single-stage micro-inverter. The most significant advantage of the single-stage micro-inverter is that it does not need a large DC capacitor for energy storage and decoupling, which simplifies the micro-inverter structure and obtains higher power density. At the same time, it saves the process of DC / DC voltage boost, realizes single-stage energy conversion, reduces the complexity compared with two-stage micro-inverter, and improves the energy conversion efficiency.

[0003] Dual active bridge micro-inverter is a micro-inverter without DC bus structure, which inherits many advantages of DAB circuit, such as high power density, high transformer utilization rate and good soft switching characteristics. At present, there are two main topologies of dual active bridge micro-inverter, which are single-phase full-bridge dual active micro-inverter and single-phase half-bridge dual active bridge micro-inverter. The research on dual active bridge micro-inverter in China mainly focuses on single-phase half-bridge. For the control of single-phase half-bridge dual active bridge micro-inverter, one method is to establish the expression of instantaneous transmission power about phase shift angle under single phase shift modulation mode. This method simplifies the control process, but the problem of high backflow power exists. In order to solve this problem, the modulation mode is divided into two modes, i.e. inner mode and outer mode. The outer mode is selected when the high power is transmitted, and the inner mode is selected when the low power is transmitted. However, the switching frequency range in the power frequency cycle is too large, which leads to the increase of the calculation amount of the control algorithm. Another method is to apply triple phase shift control to single-phase full-bridge dual active bridge micro-inverter, which introduces three control degrees of freedom, and the control process is complex and not easy to implement. At the same time, the single-phase half-bridge dual active bridge micro-inverter is affected by the grid-side capacitor, and its mathematical model is complex and not easy to control. For this problem, some scholars take the way of capacitor parallel virtual resistance active damping controller, but the effect is general. Compared with the single-phase half-bridge dual active bridge micro-inverter, the single-phase full-bridge dual active micro-inverter is closer to the traditional dual active circuit topology, and its mathematical model is simple and can meet higher power level. Up to now, the stability of single-phase dual active bridge micro-inverter still needs to be further improved. SUMMARY

[0004] In view of the deficiencies in the prior art, the present application provides a single-phase dual active bridge micro-inverter control with preset inner phase shift and outer phase shift to solve the problems in the background art.

[0005] The purpose of the present application is achieved by a single-phase dual active bridge micro-inverter control with preset inner phase shift and outer phase shift, comprising:

[0006] A grid voltage phase-locked loop unit is used to phase-lock according to the sampling value of the grid voltage to obtain the phase signal of the grid voltage;

[0007] An inner phase shift and outer phase shift preset law unit is used to generate the inner phase shift angle of the full-bridge circuit on the photovoltaic module side of the single-phase dual active bridge micro-inverter and the outer phase shift angle preset value of the corresponding switch tube in the bridge circuit on both sides of the high-frequency transformer in the single-phase dual active bridge micro-inverter according to the sampling value of the output voltage and output current of the photovoltaic module and the phase signal of the grid;

[0008] An MPPT voltage loop unit is used to generate the voltage or current given value of the photovoltaic module by disturbance. The error formed by the sampling value of the output voltage or output current of the photovoltaic module and the voltage or current given value is generated by the MPPT voltage PI regulator to generate the grid-connected current peak value. The grid-connected current peak value is multiplied by the grid voltage phase signal generated by the grid voltage phase-locked loop to obtain the grid-connected current given value.

[0009] a grid-connected current loop unit, which is configured to subtract a grid-connected current given value from a grid-connected current sample value to obtain a grid-connected current error, and to generate, by a grid-connected current PI regulator, an outward phase angle compensation amount of a corresponding switch tube in the single-phase dual active bridge micro-inverter, and to superimpose the outward phase angle compensation amount on the outward phase angle preset amount to obtain an outward phase angle of the corresponding switch tube in the single-phase dual active bridge micro-inverter;

[0010] a phase-shifting controller unit, to which the inward phase angle and the outward phase angle are sent to generate a phase-shifting pulse control signal for on-off of the switch tube in the corresponding single-phase dual active bridge micro-inverter.

[0011] Further, the output voltage and current of the photovoltaic module of the single-phase dual active bridge micro-inverter and the grid voltage and grid-connected current on the grid side are sent to a sampling and conditioning circuit to obtain corresponding output voltage and current sample signals of the photovoltaic module and sample signals of the grid voltage and grid-connected current; the output voltage and current sample signals of the photovoltaic module and the sample signals of the grid voltage and grid-connected current are sent back to the single-phase dual active bridge micro-inverter to generate the phase-shifting pulse control signal, which is then sent to a driving circuit to control on-off of the switch tube in the single-phase dual active bridge micro-inverter, so that the single-phase dual active bridge micro-inverter outputs a stable sinusoidal alternating current waveform.

[0012] Further, the inward phase angle calculation method in the inward phase angle and outward phase angle preset law unit is as follows:

[0013]

[0014] wherein k is a voltage gain, and k = V , D1 is the inward phase angle, V g is the amplitude of the grid voltage, V in is the output voltage of the full-bridge circuit on the photovoltaic module side in the single-phase dual active bridge micro-inverter, and n is the turns ratio of the grid side winding to the photovoltaic module side winding of the high-frequency transformer in the single-phase dual active bridge micro-inverter, is the phase signal of the grid voltage;

[0015] In the above formula, when <0, the inward phase angle D1 is 0; otherwise, D1 = .

[0016] Further, the inward phase angle and outward phase angle preset law unit based on the voltage gain and the power transmission ratio to implement the outward phase angle preset amount is implemented by the following formula:

[0017]

[0018] wherein m is the power transmission ratio, and , D1 is the internal phase shift angle calculated in step 1, is the external phase angle preset value under modulation mode A, is the external phase angle preset value under modulation mode B, sgn is the sign function, which means when P ac ≥0 hours Take the positive, P ac <0 hours Take the negative;

[0019] P ac is the transmission power of the single-phase dual active bridge micro-inverter in one switching cycle, which can be regarded as the instantaneous output power on the grid side, P N is the rated peak power of the single-phase dual active bridge microinverter; the transmission power in one switching cycle is calculated by the following formula:

[0020]

[0021] Where, is the grid voltage amplitude, I gm is the grid current amplitude, is the angular frequency of the grid, It is the phase difference between the grid voltage and the grid current, reflecting the reactive power situation.

[0022] Furthermore, in the modulation mode A, a portion of the positive voltage on the photovoltaic module side winding of the high-frequency transformer overlaps with the positive voltage on the grid side winding; and in the modulation mode B, the positive voltage on the photovoltaic module side winding of the high-frequency transformer is completely contained within the positive voltage on the grid side winding.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] In order to achieve effective control, the modulation strategy of the present invention constructs the internal phase shift angle of the full-bridge circuit on the photovoltaic module side through the voltage gain ratio, that is, the internal phase shift angle D1 based on the voltage gain is used on the photovoltaic module side to realize the phase shift control of the diagonal switch tube, thereby forming a voltage square wave with an equivalent duty cycle change on the photovoltaic module side winding, and on this basis, the external phase shift angle preset value D is constructed according to the power transmission ratio corresponding to the modulation mode A and the modulation mode B. 2,cal This external phase-shift preset value, combined with the external phase-shift compensation ΔD2 output by the current regulator in the grid-connected current loop, forms an external phase-shift angle D2. The phase-shift controller generates control signals for the switches in the single-phase dual-active-bridge microinverter. This control signal, after passing through the drive circuit, controls the on / off switching of the switches, thereby achieving grid-connected power generation. This external phase-shift preset value can mitigate the nonlinear relationship between control and grid-connected current, helping the controller designed based on small-signal modeling achieve stable regulation and improving system response speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only aim at the embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative effort based on the provided drawings.

[0026] Figure 1 The schematic diagram of the single-phase dual-active-bridge micro-inverter controller of the present application.

[0027] Figure 2 The control structure diagram of the single-phase dual-active-bridge micro-inverter of the present application.

[0028] Figure 3 The main circuit diagram of the single-phase dual-active-bridge micro-inverter in the embodiment of the present application.

[0029] Figure 4 The typical waveform and driving signal schematic diagram of the single-phase dual-active-bridge micro-inverter in the embodiment of the present application.

[0030] Figure 5 The modulation mode division schematic diagram of the forward power transmission of the present application.

[0031] Figure 6 The main program and interrupt flowchart in the embodiment of the present application.

[0032] Figure 7 The simulation waveform of the grid voltage and grid-connected current in the embodiment of the present application.

[0033] Figure 8 The outer phase angle driving waveform when the transmission power is large in the embodiment of the present application.

[0034] Figure 9 The outer phase angle driving waveform when the transmission power is small in the embodiment of the present application.

[0035] Figure 10 The grid voltage and grid-connected current waveform of the test prototype in the embodiment of the present application.

[0036] Figure 1 The symbol name in

[0037]

[0038] Figure 2 The symbol name in is same as Figure 1 ;

[0039] Figure 3 The symbol name in

[0040]

[0041] Other symbols Figure 1 in the description.

[0042] Figure 4 Other symbols Figure 1 and Figure 3 ;

[0043] Figure 5 Other symbols Figure 1 ;

[0044] Figure 7 Other symbols Figure 1 ;

[0045] Figure 8 Other symbols Figure 3 ;

[0046] Figure 9 Other symbols Figure 3 ;

[0047] Figure 10 Other symbols Figure 1 ; DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of the present application;

[0049] As Figure 1 , the components of the present application: single-phase dual-active bridge micro-inverter controller 1, drive circuit 7, single-phase dual-active bridge micro-inverter circuit 8 and sampling conditioning circuit 9, wherein the single-phase dual-active bridge micro-inverter controller 1 is composed of six links of internal phase shift and external phase shift preset law 2, MPPT voltage loop 3, grid voltage phase-locked loop 4, grid-connected current loop 5 and phase shift controller 6; the single-phase dual-active bridge micro-inverter controller 1 is realized by programming a digital control chip;

[0050] As Figure 1 and Figure 2 , a single-phase dual-active bridge micro-inverter controller 1 with internal phase shift and external phase shift preset, characterized in that the controller is composed of six links of grid voltage phase-locked loop 4, internal phase shift and external phase shift preset law 2, MPPT voltage loop 3, grid-connected current loop 5 and phase shift controller 6: the grid voltage phase-locked loop 4 is phase-locked according to the sampling value v g of the grid voltage, so as to obtain the phase signal sin(θ) of the grid voltage; the internal phase shift and external phase shift preset law 2 is preset according to the sampling values Vin and I in and the phase signal sin(θ) of the grid generates the inner phase angle D1 of the full-bridge circuit on the photovoltaic module side of the single-phase dual-active-bridge micro-inverter circuit 8 and the outer phase angle preset D of the corresponding switch tube in the high-frequency transformer two-side bridge circuit of the single-phase dual-active-bridge micro-inverter circuit 8 2,cal ; the error formed by the voltage or current given value (V in,ref or I in,ref ) of the photovoltaic module and the output voltage or output current sampling value (V in or I in ) of the photovoltaic module through the disturbance of the MPPT voltage PI regulator generates the grid-connected current peak value I m,ref , the grid-connected current peak value I m,ref is multiplied by the grid voltage phase signal sin(θ) generated by the grid voltage phase-locked loop to obtain the grid-connected current given value i g,ref , the grid-connected current given value i g,ref is subtracted from the grid-connected current sampling value i g to obtain the grid-connected current error, and the grid-connected current error generates the outer phase angle compensation amount ΔD2 of the corresponding switch tube in the single-phase dual-active-bridge micro-inverter through the grid-connected current PI regulator, and the outer phase angle compensation amount ΔD2 is superimposed on the outer phase angle preset D 2,cal to obtain the outer phase angle D2 of the corresponding switch tube in the single-phase dual-active-bridge micro-inverter; the inner phase angle D1 and the outer phase angle D2 are sent to the phase-shifting controller 6 to generate the phase-shifting pulse control signal (v c1 ~v c12 ); the phase-shifting pulse control signal is sent to the drive circuit 7 to generate the drive signal v dr that drives the on-off of the corresponding switch tube in the single-phase dual-active-bridge inverter 8. The phase-shifting pulse control signal (v c1 ~v c12 ) generates the corresponding Figure 3 switch tube drive signal v dr =[v drvS1 , v drvS2 , v drvS3 , v drvS4 , v drvS5 , v drvS6 , v drvS7 , v drvS8 , v drvS9 , v drvS10 , v drvS11 , v drvS12 ].

[0051] The application discloses a single-phase dual-active-bridge micro-inverter controller with preset inner phase shift and outer phase shift, characterized in that the output voltage and current of a photovoltaic module of the single-phase dual-active-bridge micro-inverter and the grid voltage and grid current at the grid side are subjected to sampling and conditioning, so as to obtain corresponding output voltage and current sampling signals of the photovoltaic module and sampling signals of the grid voltage and grid current, the output voltage and current sampling signals of the photovoltaic module and the sampling signals of the grid voltage and grid current are sent to the single-phase dual-active-bridge micro-inverter controller, and a phase shift pulse control signal is generated and is used to control the on-off of a switch tube in the single-phase dual-active-bridge micro-inverter through a driving circuit, so that the single-phase dual-active-bridge micro-inverter outputs a stable sinusoidal alternating current waveform.

[0052] The application discloses a preset law 2 of inner phase shift and outer phase shift, characterized in that the preset law is realized by the following three formulas.

[0053] (1)

[0054] In the formula, k is a voltage gain, k = V , D1 is an inner phase shift angle, V g is an amplitude of the grid voltage, V in is an output voltage of a full-bridge circuit at the photovoltaic module side in the single-phase dual-active-bridge micro-inverter, and n is a turns ratio of a grid side winding to a photovoltaic module side winding of a high-frequency transformer in the single-phase dual-active-bridge micro-inverter, is a phase signal of the grid voltage;

[0055] In the above formula, when D1 = 0 when V <0, the inner phase shift angle D1 is 0; otherwise, D1 = V ;

[0056] In the single-phase dual-active-bridge micro-inverter, the control freedom of the inner phase shift angle D1 is introduced because the grid side voltage changes in a sinusoidal manner, the voltage gain and the power transmission change in real time, and a single phase shift control cannot respond to the real-time changing voltage gain.

[0057] The calculated inner phase shift angle D1 is used to control the conduction of the photovoltaic module side skew symmetrical switch tube, and the calculation of the outer phase shift angle preset amount D 2,cal of the application is realized based on the inner phase shift angle of the voltage gain and the power transmission ratio, as shown in the following formula.

[0058] (2)

[0059] In the formula, m is a power transmission ratio, m = n , D1 is the inner phase shift angle calculated in step one, is the outer phase shift angle preset amount under the modulation mode A, is the outer phase shift angle preset amount under the modulation mode B, and sgn is a sign function, indicating that when Pac ≥0 positive, P ac <0 negative

[0060] P ac is the transmission power of the single-phase dual active bridge micro-inverter in one switching cycle, P N is the rated peak power of the single-phase dual active bridge micro-inverter; the transmission power in one switching cycle is calculated by the following formula:

[0061] (3)

[0062] wherein, is the grid voltage amplitude, I gm is the grid current amplitude, is the angular frequency of the grid, is the phase difference between the grid voltage and the grid current, reflecting the reactive power.

[0063] The modulation mode A: a part of the positive voltage on the photovoltaic module side winding of the high-frequency transformer coincides with the positive voltage part of the grid side winding; the modulation mode B: the positive voltage on the photovoltaic module side winding of the high-frequency transformer is completely contained in the positive voltage of the grid side winding.

[0064] When , the single-phase dual active bridge micro-inverter works in the modulation mode A, at this time, the mode A out-shift phase angle calculation formula is selected; when , the single-phase dual active bridge micro-inverter works in the modulation mode B, at this time, the mode B out-shift phase angle calculation formula is selected.

[0065] Wherein: the value range of the in-shift phase angle D1 is 0≤D1≤0.5; the value range of the out-shift phase angle D2 is -0.5≤D2≤0.5; the modulation mode of the transmission power is divided into the mode A and the mode B according to two control freedoms, including: when the out-shift phase angle D2 satisfies 0.5 D1<D2≤0.5(1-D1), the corresponding modulation mode is the mode A; when the out-shift phase angle D2 satisfies 0≤D2≤0.5 D1, the corresponding modulation mode is the mode B.

[0066] One specific embodiment of the present application is as follows:

[0067] The present application is applied to the single-phase dual active bridge micro-inverter, and the power is 1kW. The embodiment system is as shown in Figure 2 , and the single-phase dual active bridge micro-inverter circuit 8 in Figure 2 is as shown in Figure 3 , Figure 3The middle dual active bridge micro-inverter circuit 8 is composed of a photovoltaic module side full-bridge circuit 10, a grid side full-bridge circuit 12 and a high-frequency transformer 11.

[0068] The photovoltaic module side full-bridge circuit 10 is composed of four switching tubes S1-S4, a photovoltaic module PV and a DC side filter capacitor C in are connected in parallel at the DC input port, and the bridge arm midpoint is connected to the photovoltaic module side of the high-frequency transformer 11. The grid side of the high-frequency transformer 11 is connected to the bridge arm midpoint of the grid side full-bridge circuit 12. The grid side full-bridge circuit 12 is composed of four groups of bidirectional switches, each group of bidirectional switches is composed of two switching tubes connected in common source, and a total of eight switching tubes S5-S 12 are needed. The output of the grid side full-bridge circuit 12 is connected to the grid through LC filtering. The photovoltaic module side and the grid side of the high-frequency transformer 11 have a turn ratio of 1:n, and the resonant inductance converted to the grid side is denoted as L k . The photovoltaic module side full-bridge circuit 10 is used to invert the DC voltage generated by the photovoltaic module into a high-frequency AC voltage, and then the high-frequency transformer 11 is used for voltage boosting. The grid side full-bridge circuit 12 is used to convert the high-frequency voltage into a power frequency AC voltage required by the grid side.

[0069] Referring to FIG. 1, Figure 4 In the embodiment of the present application, the micro-inverter based on the preset method of the inner phase shift angle of the voltage gain and the outer phase shift angle of the power transmission ratio has two control degrees of freedom, which are the inner phase shift angle D1 of the photovoltaic module side circuit and the outer phase shift angle D2 of the original grid side circuit, respectively. The ratio of the time difference between the driving signal of S1 and the driving signal of S4 to the switching period is denoted as the inner phase shift angle D1, and the ratio of the time difference between the photovoltaic module side voltage midpoint and the grid side voltage midpoint to the switching period is denoted as the outer phase shift angle D2. The value range of the inner phase shift angle D1 is 0≤D1≤0.5, and the value range of the outer phase shift angle D2 is -0.5≤D2≤0.5. The output power can be adjusted by adjusting the inner phase shift angle and the outer phase shift angle.

[0070] Figure 4 The driving waveforms of the switching tubes S1-S 12 and the voltage and current waveforms of the photovoltaic module side and the grid side of the high-frequency transformer in the two modulation modes in the embodiment of the present application are shown in FIG. 2 and FIG. 3. The photovoltaic module side full-bridge circuit 10 adds the inner phase shift control, S1 and S2 form the leading bridge arm, S3 and S4 form the lagging bridge arm, and the duty cycle of the photovoltaic module side voltage can be changed by controlling the size of the inner phase shift angle D1. Figure 4 The driving waveforms when the grid side voltage is positive are shown in FIG. 4, at this time, the body diodes of S6, S8, S 10 and S 12 are in forward conduction, so in order to reduce the switching loss, when the grid voltage is positive, the four switching tubes are always on, S5 and S7 are high-frequency complementary conduction, and S 11The driving signal of S9 is the same as that of S7. Similarly, when the grid voltage is negative, S5, S7, S9 and S 11 The four switching tubes are always on to reduce switching loss, S6 and S8 are high-frequency complementary on, S 12 The driving signal of S9 is the same as that of S7. Similarly, when the grid voltage is negative, S5, S7, S9 and S 10 The driving signal of S9 is the same as that of S7. Similarly, when the grid voltage is negative, S5, S7, S9 and S

[0071] Figure 5 The modulation mode of the forward power transmission in the embodiment of the application is divided into a schematic diagram. Referring to Figure 5 When the inner phase shift angle D1 and the outer phase shift angle D2 change in the value range, the modulation mode switches between mode A and mode B.

[0072] Figure 1 The algorithm of the single-phase dual-active bridge micro-inverter controller preset with inner phase shift and outer phase shift is realized by software code programming in a digital signal processor (DSP), and the DSP uses a TMS320F28035 chip of TI Company as a control chip of the single-phase dual-active bridge micro-inverter. The CPU is the core of the control circuit, and the ADC sampling, the drive configuration and the interrupt setting are all developed around the CPU. The single-phase dual-active bridge micro-inverter circuit 8 mainly consists of a photovoltaic module side full-bridge circuit 10, a high-frequency transformer 11 and a grid side full-bridge circuit 12. There are 12 power switching tubes S1-S 12 , a resonant inductor L k =22uH, a photovoltaic module PV and a filter capacitor C in , a grid side filter capacitor C o and a filter inductor L o , the photovoltaic module side and the grid side of the high-frequency transformer 11 have a turn ratio of 1:4, the direct current input voltage range is 30V-100V, the rated alternating current voltage is 220V, the switching frequency f s =100kHz, and the power is 1kW.

[0073] According to the performance index, the maximum direct current input voltage is 100V, according to the simulation calculated photovoltaic module side winding current effective value is 53.35A, the peak current is 81.93A; the voltage stress of the photovoltaic module side switching tube is the input maximum voltage 100V. The photovoltaic module side switching tube should meet the requirements of the effective value current, the peak current and the maximum withstand voltage, considering a certain margin, the finally selected photovoltaic module side switching tube (S1-S4) is the AGM15T03LL of the core control source, the drain-source voltage V DS of the switching tube is 150V, and the continuous drain current I dThe maximum operating temperature is 175°C. The effective value of the grid-side winding current is 7.6A, the peak current is 20.48A, and the voltage stress is the maximum output voltage of the grid side, 373.352V. Therefore, the grid-side switch tube (S5-S 12 ) is Infineon's 60R102G7, whose drain-source voltage V DS At 600V, the continuous drain current I d The current is 32A (150℃), and the maximum operating temperature is 150℃.

[0074] The DC input voltage range of the embodiment is 30V~100V. In actual working engineering, the rated voltage design is based on the best performance of the inverter. The high-frequency transformer uses the PM62 / 46.8 / 32H-LP10 core of Xin Kangda Company, and the number of turns of the photovoltaic module side winding of the high-frequency transformer is N. p =2 turns, the number of turns of the grid-side winding of the high-frequency transformer is N s =8 turns. The resonant inductance L of the single-phase dual active bridge micro-inverter circuit 8 converted to the grid side k The design value is , resonant inductor L k The PQ32 / 22 / 10.5 magnetic core of Xinkangda Company is selected, and the LP10 material is used. The saturation magnetic flux density of the magnetic core is , the initial magnetic permeability is 3300, and the number of turns is 13. The DC side filter capacitor C in Select 12 Electrolytic capacitors are connected in parallel, and 14 more are configured 2 non-polarized capacitors in parallel Non-polarized capacitors. TI's TMS320F28035 was selected as the CPU for the single-phase dual-active bridge micro-inverter. Code Composer Studio 12.2 was selected to write the program to implement the algorithm. The program mainly includes a main program and an interrupt program. The corresponding control flow charts are shown below. Figure 6 shown.

[0075] The chip TMS320F28035 is used to collect signal amount, and system initialization is carried out, including phase-locked loop, watchdog, peripheral clock enable, closing interrupt, initializing PIE interrupt vector table and the like. After algorithm calculation, MPPT voltage ring and grid-connected current ring output values and inner and outer phase-shifting angle preset values are obtained, an EPWM module is configured, then PWM waves output by the ePWM module are used to control the turn-on and turn-off of power switch tubes, and a trigger EPWMxSOCA signal is set, so that power conversion of the topology is realized. The ADC module is configured to sample input channels, trigger sources (receiving EPWMxSOCA) and the size of a sampling window, and SOCx is selected to perform ADC conversion and trigger interrupt ADCINTx. When the ADC interrupt occurs, the ADC interrupt service function is entered.

[0076] The first event of EPWM7 counting to zero triggers AD sampling (EPwm7Regs.ETPS.all = 0x0500), and an interrupt occurs after AD sampling is completed. The EPWM7 is configured in a continuous increment mode, a function ADC_INT_Control() is called in the AD interrupt service program Vgid ADCINT1_ISR (Vgid), and the control algorithm of the inverter phase-locked loop, grid-connected current and MPPT voltage ring is executed, and the control algorithm of the single-phase dual-active-bridge micro-inverter is also executed.

[0077] The interrupt vector table initializes the EPWM1_TZINT_ISR interrupt, and the interrupt is allowed during initialization, and the interrupt entry points to Vgid EPWM1_TZINT_ISR (Vgid). When the Tz1 pin is low, the TripZone interrupt is triggered. In the Tz1 interrupt, the PWM control pulse signals of EPWM1 and EPWM2 are blocked, so as to realize overcurrent protection of the inverter.

[0078] The embodiment of the application builds a simulation model by means of PSIM software, and realizes dynamic link library based on Visual Studio software, so as to realize digital simulation. In PSIM, the rated input voltage of the photovoltaic assembly side is configured as 80V, the effective value of the grid side alternating voltage is 220V, the control strategy is realized by means of the DLL dynamic link library program to realize simulation, and the simulation waveform is as shown in Figure 7 The grid voltage is v g , the given value of the grid-connected current is i g,ref , and the grid-connected current is i g . As shown in the figure, the unit power factor grid-connected function of the grid side current is realized, and the given current is tracked by the grid-connected current.

[0079] The 1kW single-phase dual-active-bridge micro-inverter is experimented. As Figure 8 and Figure 9The driving waveform with the added preset amount of outward phase shift angle is shown. Figure 8 The equivalent time for the outward phase shift angle when the transmission power is large is ; Figure 9 The equivalent time for the outward phase shift when the transmission power is small is It can be seen that the larger the transmission power is, the larger the outward phase shift angle is. Figure 10 The grid voltage and grid-connected current waveform are given, and it can be seen that the unit power factor grid-connected power generation at the grid side is realized by using the method of the application.

[0080] The simulation and experiment prove that the single-phase dual-active-bridge micro-inverter effective control is realized by using the single-phase dual-active-bridge micro-inverter controller with the preset inward phase shift and outward phase shift according to the application.

[0081] (1) According to the voltage gain, the appropriate inward phase shift angle D1 in the current state is obtained by using the application technology, and then the preset value D of the outward phase shift angle at this time is obtained by the quantitative relationship between the inward phase shift angle and the transmission power. 2,cal The addition of the preset control can effectively reduce the control difficulty, improve the dynamic response speed of the control, and make the design of the grid-connected current loop parameters more simple.

[0082] (2) Compared with the existing scheme, the efficiency of the micro-inverter can be improved, especially the efficiency under light load. The power response speed of the micro-inverter can also be improved, and the influence of the nonlinearity of the circuit model on the closed-loop control can be weakened, thereby reducing the difficulty of the closed-loop design.

[0083] The above description of the embodiments is only used to help understand the method of the application and its core idea. It should be pointed out that for ordinary skilled persons in the art, without departing from the principles of the application, some improvements and modifications can be made to the application, and these improvements and modifications also fall within the protection scope of the claims of the application.

Claims

1. A single-phase dual-active bridge micro-inverter controller with preset inner phase shift and outer phase shift, characterized in that: include: A grid voltage phase-locked loop unit, used to perform phase locking according to the sampling value of the grid voltage to obtain a phase signal of the grid voltage; The internal phase shift and external phase shift preset law unit is used to generate the internal phase shift angle of the full-bridge circuit on the photovoltaic module side of the single-phase dual-active bridge microinverter and the external phase shift angle preset value of the corresponding switch tube in the bridge circuit on both sides of the high-frequency transformer in the single-phase dual-active bridge microinverter according to the sampled values ​​of the output voltage and output current of the photovoltaic module and the phase signal of the power grid; The MPPT voltage loop unit is used to generate a voltage or current set value of the photovoltaic module through disturbance. The error formed by the output voltage or output current sampling value of the photovoltaic module generates a grid-connected current peak value through the MPPT voltage PI regulator. The grid-connected current peak value is multiplied by the grid voltage phase signal generated by the grid voltage phase-locked loop to obtain the grid-connected current set value; A grid-connected current loop unit is used to subtract a grid-connected current given value from a grid current sampling value to obtain a grid-connected current error. The grid-connected current error is used to generate an external phase shift angle compensation value for a corresponding switch tube in a single-phase dual-active bridge micro-inverter via a grid-connected current PI regulator. The external phase shift angle compensation value is added to the external phase shift angle preset value to obtain an external phase shift angle for a corresponding switch tube in a single-phase dual-active bridge micro-inverter. Phase shift controller unit, the inner phase shift angle and the outer phase shift angle are sent to the phase shift controller to generate a phase shift pulse control signal corresponding to the on-off switching of the switch tube in the single-phase dual active bridge micro-inverter.

2. The single-phase dual-active bridge micro-inverter controller with preset inner phase shift and outer phase shift according to claim 1, characterized in that: The output voltage and current of the photovoltaic module of the single-phase dual-active bridge micro-inverter and the grid voltage and grid-connected current on the grid side are sampled and conditioned by a sampling and conditioning circuit to obtain corresponding output voltage and current sampling signals of the photovoltaic module and sampling signals of the grid voltage and grid-connected current; the output voltage and current sampling signals of the photovoltaic module and the sampling signals of the grid voltage and grid-connected current are sent back to the single-phase dual-active bridge micro-inverter controller to generate a phase-shifted pulse control signal, which is then used to control the on and off of the switch tube in the single-phase dual-active bridge micro-inverter after passing through a drive circuit, so that the single-phase dual-active bridge micro-inverter outputs a stable sinusoidal AC current waveform.

3. A single-phase dual-active bridge micro-inverter controller with preset inner phase shift and outer phase shift according to claim 1 or 2, characterized in that: The calculation method of the inner phase shift angle in the inner phase shift and outer phase shift preset law unit is: ； Where k is the voltage gain, and k= , D1 is the internal phase shift angle, V g is the amplitude of the grid voltage, V in is the output voltage of the full-bridge circuit on the photovoltaic module side in the single-phase dual-active bridge microinverter, n is the turns ratio of the grid-side winding and the photovoltaic module-side winding of the high-frequency transformer in the single-phase dual-active bridge microinverter, is the phase signal of the grid voltage; In the above formula, <0, the internal phase angle D1 is 0; otherwise D1= .

4. A single-phase dual-active bridge micro-inverter controller with preset inner phase shift and outer phase shift according to claim 1 or 2, characterized in that: The method for implementing the internal phase shift angle and external phase shift preset law unit to jointly build the external phase shift angle preset value based on the voltage gain and the power transfer ratio is implemented by the following formula: ； Where m is the power transfer ratio, and , D1 is the internal phase shift angle calculated in step 1, is the external phase angle preset value under modulation mode A, is the external phase angle preset value under modulation mode B, sgn is the sign function, which means when P ac ≥0 hours Take the positive, P ac <0 hours Take the negative; P ac is the transmission power of the single-phase dual active bridge micro-inverter in one switching cycle, which can be regarded as the instantaneous output power on the grid side, P N is the rated peak power of the single-phase dual active bridge microinverter; the transmission power in one switching cycle is calculated by the following formula: ； Where, is the grid voltage amplitude, I gm is the grid current amplitude, is the angular frequency of the grid, It is the phase difference between the grid voltage and the grid current, reflecting the reactive power situation.

5. The single-phase dual-active bridge micro-inverter controller with preset inner phase shift and outer phase shift according to claim 4, characterized in that: In the modulation mode A, a portion of the positive voltage on the photovoltaic module side winding of the high-frequency transformer overlaps with the positive voltage on the grid side winding. In the modulation mode B, the positive voltage on the photovoltaic module side winding of the high-frequency transformer is completely contained within the positive voltage on the grid side winding.

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