Photovoltaic inverter device and photovoltaic inverter control method based on voltage fluctuation

Abstract

The application relates to a photovoltaic inverter device and a photovoltaic inverter control method based on voltage fluctuation, wherein the device comprises an input circuit, an inverter circuit and a filter circuit connected in sequence, the input circuit comprises a capacitor, a switching sub-circuit and an auxiliary power supply sub-circuit, the capacitor is connected with an external power grid, a sampling circuit comprises a capacitor voltage sampling sub-circuit and an output current sampling sub-circuit, the capacitor voltage sampling sub-circuit comprises a capacitor sampling operational amplifier, a microcontroller is connected with the above-mentioned circuits, the capacitor sampling operational amplifier is connected with the capacitor, an output sampling operational amplifier is connected with the inverter circuit, and the microcontroller is connected with the inverter circuit. The method comprises sampling obtained capacitor voltage and output current, obtaining fluctuation energy of input voltage and output voltage, and obtaining a corrected output voltage angle. According to the photovoltaic inverter device and the control method, photovoltaic cells and external capacitors are fused, the service life is improved, and the use cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of test circuit technology, and in particular to photovoltaic inverter devices and photovoltaic inverter control methods based on voltage fluctuations. Background Technology

[0002] Photovoltaic inverters are widely used in photovoltaic (PV) power generation, converting the direct current (DC) output from PV solar panels into alternating current (AC) for power grid connection or storage. With the significant decrease in the overall cost of PV systems, demand for PV systems in the residential sector is constantly rising. However, existing PV systems require expensive battery banks, and integration with the local grid necessitates specialized electrical components or hard switching, leading to inconvenience and increased operating costs, thus hindering the development of residential PV systems. Furthermore, existing PV inverter systems are prone to inconsistencies between the input and output voltage phase angles, resulting in energy fluctuations that reduce system lifespan and further increase operating costs. Summary of the Invention

[0003] This invention provides a photovoltaic inverter device and a photovoltaic inverter control method based on voltage fluctuations, aiming to solve at least one of the technical problems existing in the prior art. To this end, the photovoltaic inverter device and the photovoltaic inverter control method based on voltage fluctuations proposed in this invention do not require hard switching with the local power grid, are compatible with household appliances, and do not require battery packs, thus reducing operating costs.

[0004] The technical solution of this invention relates to a photovoltaic inverter device, which includes an input circuit, an inverter circuit, and a filter circuit connected in sequence. The input circuit includes a capacitor, a switching sub-circuit, and an auxiliary power supply sub-circuit. The capacitor is connected to the external power grid through an input rectifier. The capacitor is connected to the photovoltaic cell, the switching sub-circuit, the auxiliary power supply sub-circuit, and the inverter circuit. The inverter circuit is connected to the auxiliary power supply sub-circuit and the filter circuit. The output terminal of the filter circuit is connected to an external electrical appliance and a sampling circuit. The sampling circuit includes a capacitor voltage sampling sub-circuit and an output current sampling sub-circuit. The capacitor voltage sampling sub-circuit includes a capacitor sampling operational amplifier, and the output current sampling sub-circuit includes an output sampling operational amplifier. Both the capacitor sampling operational amplifier and the output sampling operational amplifier are connected to a microcontroller. The capacitor sampling operational amplifier is connected to the capacitor, and the output sampling operational amplifier is connected to the inverter circuit. The microcontroller is connected to the inverter circuit.

[0005] Furthermore, the inverter circuit includes four sets of inverter sub-circuits. Each set of inverter sub-circuits includes an inverter driver and an inverter MOS transistor. The inverter driver is connected to the main controller, the auxiliary sub-circuit, and the inverter MOS transistor, respectively. The inverter MOS transistor is connected to the capacitor, the auxiliary sub-circuit, and external electrical appliances, respectively.

[0006] Furthermore, the output current sampling sub-circuit includes an output sampling operational amplifier, wherein the drain of one of the inverter MOS transistors is connected to the SPWM_N terminal of an external electrical appliance and the source is connected to the inverting input terminal of the output sampling operational amplifier and the microcontroller, and the output terminal of the output sampling operational amplifier is connected to the microcontroller.

[0007] Furthermore, the capacitor voltage sampling sub-circuit includes a capacitor sampling operational amplifier, the photovoltaic cell and the capacitor are respectively connected to the input terminal of the capacitor sampling operational amplifier, and the output terminal of the capacitor sampling operational amplifier is connected to the microcontroller.

[0008] Furthermore, it also includes a voltage detection circuit, which is connected to the photovoltaic cell, the capacitor and the main controller.

[0009] Furthermore, the capacitor includes multiple input capacitors connected in parallel. One end of the capacitor is connected to the negative terminal of the photovoltaic cell and the L terminal of the external power grid, and the other end of the capacitor is connected to the switching sub-circuit through an input inductor.

[0010] Furthermore, the switching sub-circuit includes a switching transistor and an electromagnetic relay. The base (B) of the switching transistor is connected to the microcontroller, and the collector (C) of the switching transistor is connected to the electromagnetic relay. The electromagnetic relay is connected to both the capacitor and the photovoltaic cell.

[0011] Furthermore, it also includes a temperature detection circuit. The temperature detection module includes a temperature sensing transistor and a temperature rheostat. The C terminal of the temperature sensing transistor is connected to the temperature rheostat, and the B terminal of the temperature sensing transistor is connected to the microcontroller.

[0012] Another aspect of the technical solution of the present invention relates to a control method for a photovoltaic inverter system based on input voltage fluctuation feedback, applied to the aforementioned photovoltaic inverter device, the method comprising the following steps: S100. Obtain the capacitor voltage through the capacitor voltage sampling sub-circuit, obtain the output current through the output current sampling sub-circuit, and input the obtained sampling data into the microcontroller. S200: Using the microcontroller and based on the sampled capacitor voltage and output current, obtain the output vector voltage magnitude, operation cycle frequency, and capacitor energy; Using the microcontroller and based on the capacitor energy, obtain the correction angle between the initial input voltage and the initial output voltage; Using the microcontroller and based on the operation cycle frequency and the correction angle, obtain the corrected output voltage angle. S300: The microcontroller obtains a voltage scalar based on the vector voltage magnitude and the corrected output voltage angle; and obtains the PWM duty cycle based on the voltage scalar and the capacitor voltage.

[0013] Furthermore, in step S200, the correction angle is determined based on energy fluctuations. The energy fluctuations are obtained. The capacitor energy is calculated using the following method: In the formula, The energy of the capacitor at time t is represented by the integral function of dP; This represents the average energy of the capacitor, which is the average value of the capacitor's energy; where, In the formula, dP represents the difference between the input power and the output power; P0 represents the average value of the input power and the output power when the input power and the output power are equal; dP represents a complex function. The real part; Indicates the phase angle of the input voltage; This indicates the phase angle of the output voltage.

[0014] The photovoltaic inverter device and the photovoltaic inverter control method based on voltage fluctuations of the present invention have at least the following beneficial effects: The photovoltaic inverter device of this invention does not require hard switching with the local power grid, is compatible with household appliances, and does not require a battery bank, thus reducing operating costs. By sampling capacitor voltage and output current to obtain a voltage scalar, and then using this voltage scalar and capacitor voltage to obtain the PWM duty cycle of the inverter H-bridge, it achieves integration with the external power grid, enabling compatibility with household appliances and avoiding reliance on batteries and dedicated hard switching equipment. When the photovoltaic cell output is sufficient, it can achieve 100% utilization of photovoltaic energy. By adding a transformer winding to the power transformer in the auxiliary power supply sub-circuit, grid voltage detection is achieved. A differential amplifier circuit is connected to the output of the newly added transformer winding to achieve data sampling by the main control unit. By extracting the frequency and phase angle from the sampled data, correction between the phase angle and the output phase angle is obtained, avoiding the phenomenon where the output voltage is lower than the input voltage due to the inconsistency between the output and input voltage phase angles. This effectively reduces the capacity fluctuation of the system capacitors and helps to improve the system's lifespan. By using software in the main control unit, the phase angle is corrected based on the capability fluctuation between the input and output voltages, thereby achieving phase angle correction, avoiding inconsistencies between the output and input voltage phase angles, reducing the capability fluctuations of the system capacitors, and also helping to reduce product manufacturing costs. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of a photovoltaic inverter device according to an embodiment of the present invention.

[0016] Figure 2 This is a circuit schematic diagram of the main control unit according to an embodiment of the present invention.

[0017] Figure 3 This is a circuit schematic diagram of the input circuit according to an embodiment of the present invention.

[0018] Figure 4 This is a circuit diagram of the capacitor voltage sampling sub-path according to an embodiment of the present invention.

[0019] Figure 5 This is a circuit diagram of an auxiliary power supply sub-circuit according to an embodiment of the present invention.

[0020] Figure 6 This is a circuit schematic diagram of a phase angle operational amplifier and a transformer winding according to an embodiment of the present invention.

[0021] Figure 7 This is a circuit schematic diagram of an inverter circuit according to an embodiment of the present invention.

[0022] Figure 8 This is a circuit diagram of the output current sampling sub-circuit according to an embodiment of the present invention.

[0023] Figure 9This is a circuit diagram of the input terminal of the auxiliary power supply sub-circuit according to an embodiment of the present invention.

[0024] Figure 10 This is a circuit diagram of a voltage detection circuit according to an embodiment of the present invention.

[0025] Figure 11 This is a circuit diagram of a temperature detection circuit according to an embodiment of the present invention.

[0026] Figure 12 This is a flowchart illustrating the sampling correction angle control method according to an embodiment of the present invention.

[0027] Figure 13 This is a schematic diagram of the overall process for obtaining the correction angle sampling according to an embodiment of the present invention.

[0028] Figure 14 This is a schematic diagram of the frequency extraction process based on the sampling correction angle control method according to an embodiment of the present invention.

[0029] Figure 15 This is a schematic diagram of the overall process of the voltage fluctuation control method according to an embodiment of the present invention.

[0030] Figure 16 This is a schematic diagram of the process of obtaining the correction angle software according to an embodiment of the present invention.

[0031] Figure 17 This is a schematic diagram showing the phase angle relationship between the input voltage and the output voltage according to the method of the present invention.

[0032] Figure 18 This is a schematic diagram of the frequency extraction process based on the voltage fluctuation control method according to an embodiment of the present invention.

[0033] Figure 19 This is a first schematic diagram of the capability waveform of a photovoltaic inverter device and system according to an embodiment of the present invention.

[0034] Figure 20 This is a second schematic diagram of the capability waveform of a photovoltaic inverter device and system according to an embodiment of the present invention. Detailed Implementation

[0035] The following will provide a clear and complete description of the concept, specific structure, and technical effects of the present invention in conjunction with the embodiments and accompanying drawings, so as to fully understand the purpose, solution, and effects of the present invention. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0036] It should be noted that, unless otherwise specified, when a feature is referred to as "fixed" or "connected" to another feature, it can be directly fixed or connected to the other feature, or it can be indirectly fixed or connected to the other feature, simulating a grounding terminal. Furthermore, the descriptions of "upper," "lower," "left," "right," "top," and "bottom" used in this invention are only relative to the relative positional relationships of the various components of the invention in the accompanying drawings.

[0037] Furthermore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing particular embodiments only and not for limiting the invention. The term "and / or" as used herein includes any combination of one or more of the associated listed items.

[0038] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various elements, these elements should not be limited to these terms. These terms are only used to distinguish elements of the same type from one another. For example, without departing from the scope of this disclosure, a first element may also be referred to as a second element, and similarly, a second element may also be referred to as a first element.

[0039] Reference Figures 1 to 5 In some embodiments, the photovoltaic inverter device according to the present invention includes an input circuit, an inverter circuit, and a filter circuit connected in sequence. The input circuit includes a capacitor, a switching sub-circuit, and an auxiliary power supply sub-circuit. The capacitor is connected to the external power grid through an input rectifier. The capacitor is connected to the photovoltaic cell, the switching sub-circuit, the auxiliary power supply sub-circuit, and the inverter circuit respectively. The inverter circuit is connected to the auxiliary power supply sub-circuit and the filter circuit respectively. The output terminal of the filter circuit is connected to an external electrical appliance and a sampling circuit respectively. The sampling circuit includes a capacitor voltage sampling sub-circuit and an output current sampling sub-circuit. Both the capacitor voltage sampling sub-circuit and the output current sampling sub-circuit are connected to a microcontroller. The capacitor voltage sampling sub-circuit is connected to the capacitor, and the output current sampling sub-circuit is connected to the inverter circuit. The microcontroller is connected to both the inverter circuit and the output circuit. The input circuit includes a phase angle operational amplifier, and the auxiliary power supply sub-circuit includes a power transformer. The power transformer includes two transformer windings. The two ends of one transformer winding are connected to the non-inverting input terminal of the phase angle operational amplifier and the live wire of the external power grid, respectively. The two ends of the other transformer winding are connected to the inverting input terminal of the phase angle operational amplifier and the neutral wire of the external power grid, respectively. The output terminal of the phase angle operational amplifier is connected to the microcontroller.

[0040] Specifically, the direct current (DC) power supplied by the photovoltaic cells is converted into alternating current (AC) power by an inverter circuit to supply power to external electrical appliances. The current and voltage are fed back to the main control unit via a sampling circuit, and the main control unit outputs the PWM duty cycle based on the feedback. The photovoltaic inverter device of this embodiment does not require a storage battery, and no hard switching is needed between the photovoltaic cells and the local power grid. It is compatible with all residential power needs, and when the photovoltaic cell output is sufficiently high, 100% of the photovoltaic energy can be utilized. See also... Figure 2 In this embodiment of the invention, the main control unit includes a microcontroller, and more specifically, the microcontroller is a GD32E230C8T6 chip. The microcontroller's pins 42 and 43 (RXD0 and TXD0) are connected to an LCD screen used for displaying the user interface.

[0041] In some specific embodiments of the present invention, the input circuit of the present invention includes a capacitor, see [link to relevant documentation]. Figure 3 The capacitor consists of four capacitors connected in parallel: a second input capacitor C2, a third input capacitor C3, a fourth input capacitor C4, and a fifth input capacitor C5. The DC- terminal of the capacitor is connected to the negative terminal (DC-in) of the photovoltaic cell and the live wire (L terminal) of the external power grid. The neutral wire (N terminal) of the external power grid is connected to the positive terminal (DC+in) of the photovoltaic cell. The DC+ terminal of the capacitor is connected to the switching sub-circuit through the second input inductor L2. Furthermore, two resistors, a first resistor R1 and a second resistor R2, are connected in parallel between the negative terminal (DC-in) of the photovoltaic cell and the capacitor.

[0042] In some specific embodiments of the present invention, the external power grid is connected to the positive terminal DC+in of the photovoltaic cell and the capacitor through the input grid rectifier BRIDGE1, see [link]. Figure 3 The V+ terminal of the input rectifier is connected to the positive terminal DC+in of the photovoltaic cell, the V- terminal of the input rectifier is connected to the DC- terminal of the capacitor, and the two AC terminals of the input rectifier are connected to the L and N terminals of the external power grid, respectively. A seventh capacitor C7 is connected in parallel between the V+ and V- terminals of the input rectifier, and a sixth capacitor C6 is connected in parallel between the two AC terminals of the input rectifier.

[0043] Furthermore, a reactor circuit is installed between the external power grid and the power grid rectifier, see [link to relevant documentation]. Figure 3 The reactor includes two grid inductors L1. One end of each grid inductor L1 is connected to the two AC terminals of the grid rectifier BRIDGE1, and the other end of each grid inductor L1 is connected to the L and N terminals of the external grid, respectively. Terminal 3 of grid inductor L1 is connected to the E terminal of the external grid through grid capacitor C9, and terminal 2 of grid inductor L1 is connected to the E terminal of the external grid through grid capacitor C8.

[0044] In some specific embodiments of the present invention, the switching sub-circuit includes a switching transistor Q1 and an electromagnetic relay RL1. The emitter (E) of the switching transistor is grounded, the base (B) of the switching transistor is connected to pin 22 of the microcontroller, and the collector (C) of the switching transistor is connected to the coil side of the electromagnetic relay (see...). Figure 3 Connecting (reference numbers 1 and 2), a fifth diode D5 is connected in parallel across the two ends of the electromagnetic relay, and the two ends of the switching side of the electromagnetic relay (see...) Figure 3 (Refs. 3 and 4) are connected to the DC+in terminal of the photovoltaic cell and the DC- terminal of the capacitor. Furthermore, a circuit consisting of two thermistors, the fifth thermistor R5 and the eighth thermistor R8, is connected in parallel on the switching side of the battery relay.

[0045] In some specific embodiments of the present invention, see Figure 4 The capacitor voltage sampling sub-circuit of this embodiment includes a capacitor sampling operational amplifier (op-amp). A photovoltaic cell and a capacitor are connected to the input terminal of the op-amp, and the output terminal of the op-amp is connected to the main control unit. Specifically, the DC- terminal of the capacitor is connected to the non-inverting input terminal of the op-amp U2, the negative terminal (DC+in) of the photovoltaic cell is connected to the inverting input terminal of the op-amp U2, and the output terminal of the op-amp U2 is connected to pin 10 of the microcontroller. Further, the non-inverting input terminal of the op-amp U2 is connected to a circuit consisting of a fourth resistor R4 and a first six-capacitor C16 connected in parallel. A current consisting of a second two-capacitor C22 and a first one resistor R11 connected in parallel is connected between the negative input terminal and the output terminal of the op-amp U2. The output terminal of the op-amp U2 is connected to a second one-capacitor C21, and the other end of the second one-capacitor C21 is grounded. This embodiment of the invention samples the capacitor voltage through the capacitor voltage sampling sub-circuit and sends the sampled data to the microcontroller.

[0046] Furthermore, the capacitor voltage sampling sub-circuit also includes a capacitor sampling diode assembly, which comprises two third switching diodes D3 and two first switching diodes D11. The anode of one third switching diode D3 is connected to the DC- terminal of the capacitor and the cathode of the other third switching diode D3, with the cathode connected to +3.3V, while the anode of the other third switching diode D3 is grounded. Similarly, the anode of one first switching diode D11 is connected to the DC-in terminal of the photovoltaic cell and the cathode of the other first switching diode D11, with the cathode connected to +3.3V, while the anode of the other first switching diode D11 is grounded.

[0047] In some specific embodiments of the present invention, the auxiliary power supply sub-circuit includes a switching power supply chip and a power transformer. The switching power supply chip is connected to a capacitor and to the primary side of the power transformer. Further, the auxiliary power supply sub-circuit also includes a voltage regulator chip connected to the power transformer. The power transformer includes a first primary winding N1 and a second primary winding N2, as well as a third secondary winding N3 and a fourth secondary winding N4. The third secondary winding N3 consists of three coils stacked together, and the fourth secondary winding N4 consists of three coils arranged in parallel.

[0048] See Figure 5 The two output terminals of the voltage regulator chip U1 are connected to the X and F terminals of the switching power supply chip U3, respectively. The V terminal of the switching power supply chip is connected to the DC+ terminal of the capacitor through two series resistors (i.e., the first two resistors R12 and the first six resistors R16). One end of the second primary winding N2 is connected to the DC+ terminal of the capacitor, and the other end is connected to the D terminal of the switching power supply chip. Furthermore, a circuit consisting of the seventh diode D7 and the second and third capacitors C23 connected in series is connected in parallel across the two ends of the second primary winding N2. The seventh zero capacitor C70 is connected in parallel across the two ends of the second and third capacitors C23, and the first zero resistor R10 is also connected in parallel.

[0049] Furthermore, one end of the primary winding N2 of the power transformer is grounded, and the other end is connected to the C terminal of the switching voltage chip U3 through the ninth diode D9 and terminal PC3. A third capacitor C32 with electrolyte is connected in parallel across the circuit consisting of the ninth diode D9 and the second primary winding N2. Light-emitting diodes are connected across terminal PC3.

[0050] Furthermore, phase 11 of the third secondary winding N3 of the power transformer is connected to the +24V power supply via diode D8, and phase 12 of the third secondary winding N3 is connected to the +5V power supply. A circuit consisting of resistor R17 (number of resistors) and capacitor C29 (number of capacitors) connected in series is connected between phase 12 and the +5V power supply. Diode D10 (number of diodes) is connected in parallel across this circuit. Phase 13 of the third secondary winding N3 is grounded, and a third tripolar capacitor C33 and a third tetrapolar capacitor C34 connected in parallel are connected between phase 13 and the +5V power supply.

[0051] Furthermore, the three coils of the fourth secondary winding N4 of the power transformer are connected to three sets of rectifier and filter sub-circuits, which in turn are connected to the PN+, PN-, PV+, PV-, PU+, and PU- terminals of the inverter circuit, as well as the PNE, PVE, and PUE terminals of the inverter circuit. An example of one set of rectifier and filter sub-circuits is provided here; see [link to example]. Figure 5 In the first rectifier filter circuit, the positive terminal of the second diode D2 is connected to one end of the first coil of the third secondary winding N3, and the negative terminal of the second diode D2 is connected to the PN+ terminal of the inverter circuit. The other end of the first coil of the third secondary winding N3 is connected to the PN- terminal of the inverter circuit. An electrode capacitor C13 is placed between the negative terminal of the second diode D2 and the PN- terminal of the inverter circuit. The negative terminal of the second diode D2 is connected to the PNE terminal of the inverter circuit through the third resistor R3. A circuit consisting of the first Zener diode ZD1, the first four electrolytic capacitors C14 and C15 connected in parallel is connected between the third resistor R3 and the PN- terminal of the inverter circuit. It should be noted that... (See also...) Figure 4 The connection method of the other two coils of the third secondary winding N3 to the rectifier filter sub-circuit is similar.

[0052] In some specific embodiments of the present invention, see Figure 3 and Figure 6 The output circuit of this embodiment further includes a phase angle operational amplifier. The power transformer includes two transformer windings. The two ends of one transformer winding are connected to the non-inverting input of the phase angle operational amplifier and the L terminal of the external power grid, respectively. The two ends of the other transformer winding are connected to the inverting input of the phase angle operational amplifier and the N terminal of the external power grid, respectively. The output of the phase angle operational amplifier is connected to the main control unit. This allows the main control unit to detect the grid voltage through the transformer windings and input the transformer windings to the phase angle operational amplifier. This enables the amplifier to be programmed to extract the main frequency and phase angle from the sampled data to obtain the correction angle. By obtaining the correction between the phase angle and the output phase angle, the output voltage is prevented from being lower than the input voltage due to a mismatch between the output and input voltage phase angles. Further, the phase angle operational amplifier in this embodiment is a differential amplifier, and both transformer windings include multiple resistors connected in series. This embodiment obtains the correction angle through the phase angle operational amplifier and transformer windings and sends the correction angle to the microcontroller.

[0053] Further, see Figure 6The non-inverting input of the eighth phase-angle op-amp U8 is connected to the +1.65V power supply, and a 95th resistor R95 and a 71st capacitor C71 are connected in parallel between them. The inverting input and output of the eighth phase-angle op-amp U8 are connected in series with a 70th resistor R70 and a 71st resistor R71, and a 8th capacitor C38 is connected in parallel across the circuit formed by the 70th resistor R70 and the 71st resistor R71. Further, the output of the ninth op-amp U9 is connected to the +1.65V power supply and the non-inverting input of the eighth phase-angle op-amp U8 through a 92nd resistor R92. The non-inverting input of the ninth op-amp U9 is connected to a 91st resistor R91, the other end of which is connected to the +3.3V power supply. The non-inverting input of the ninth op-amp U9 is connected to a 94th resistor R94, the other end of which is grounded. The inverting input of the ninth op-amp U9 is connected to the +1.65V power supply, and the inverting input of the ninth op-amp U9 is connected to its output through the sixth capacitor C66.

[0054] In some specific embodiments of the present invention, see Figure 7 and Figure 9 The inverter circuit of this embodiment includes four sets of inverter sub-circuits. The input terminals of the four sets of inverter sub-circuits are respectively connected to the U+ terminal, U- terminal, V+ terminal and V- terminal. The U+ terminal, U- terminal, V+ terminal and V- terminal are all connected to the microcontroller's 29th terminal, 26th terminal, 30th terminal and 27th terminal respectively through the seventh CMOS device U7. The number of seventh CMOS devices U7 is 3.

[0055] This section uses one set of inverter circuits as an example; see [link to example]. Figure 7 The first set of inverter sub-circuits includes an inverter driver PC1 and an inverter MOSFET. In this embodiment, the drivers (PC1 / PC2 / PC4 / PC5) are isolated gate drivers, specifically FOD8342TR2 drivers. The C terminal of inverter driver PC1 is connected to the microcontroller (U+ / 29 terminal), the A terminal of inverter driver PC1 is connected to the +5V power supply, and the VCC terminal (i.e., PU+ terminal) of inverter driver PC1 is connected to the auxiliary power supply sub-circuit. The VCC terminal of inverter driver PC1 is connected to the PU+ terminal of the auxiliary power supply sub-circuit, and is also connected to the PU- terminal of the auxiliary power supply sub-circuit through a third zero-capacitor C30. The VEE terminal of inverter driver PC1 is connected to the PU- terminal of the auxiliary power supply sub-circuit. The VO terminal of inverter driver PC1 is connected to the gate (G) of the inverter diode (MOS1) through a first eight-resistor R18. The PUG terminal of the auxiliary power supply sub-circuit is connected between the first eight-resistor R18 and the gate of the inverter diode. The gate (G) of the inverter diode is connected to the source (S) of the inverter diode through resistor R20. The auxiliary power supply (PUE) terminal of the power supply sub-circuit is connected between the second zero-resistance R20 and the source of the inverter diode. It should be noted that... (See also...) Figure 6The connection method between the other two sets of inverter drivers and inverter MOSFETs is similar.

[0056] Furthermore, in the inverter circuit, the source (S) of the first inverter MOSFET MOS1 is connected to the drain (D) of the second MOSFET MOS2. The midpoint between the S of the first MOSFET MOS1 and the D of the second MOSFET MOS2 is connected to the SPWM_L terminal of the external device via a fourth inductor L4. The D of the first MOSFET MOS1 is connected to the DC+ terminal of the capacitor and also to the DC- terminal of the capacitor via a second capacitor C28. The source (S) of the third MOSFET MOS3 is connected to the drain (D) of the fourth MOSFET MOS4. The midpoint between the S of the third MOSFET MOS3 and the D of the fourth MOSFET MOS4 is connected to the SPWM_N terminal of the external device. The D of the third MOSFET MOS3 is connected to the DC+ terminal of the capacitor. A third capacitor C39 is connected between the SPWM_L and SPWM_N terminals of the external device.

[0057] In some specific embodiments of the present invention, the output current sampling sub-circuit includes an output sampling operational amplifier. In this sub-circuit, the drain of an inverter MOSFET is connected to the SPWM_N terminal of an external electrical appliance, and its source is connected to the inverting input terminal of the output sampling operational amplifier and the main control unit. The output terminal of the output sampling operational amplifier is connected to the main control unit. See also... Figure 8 The inverting input of the fifth sampling operational amplifier U5 is connected to the source (S) terminal of the fourth inverter MOS transistor 4, and also to pin 16 (IFB) of the microcontroller. The output of the fifth sampling operational amplifier U5 is connected to pin 25 (OC) of the microcontroller. The non-inverting input of the fifth sampling operational amplifier U5 is connected to the +5V power supply through resistor R68, to ground through resistor R75, and to the OC terminal of the microcontroller through resistor R76. This embodiment of the invention samples the output current through an output current sampling sub-circuit and sends the sampled data to the microcontroller.

[0058] In some specific embodiments of the present invention, the filter circuit of the present invention is connected to the SPWM_L terminal of an external electrical appliance and is also connected to the main control unit. See [link to related documentation]. Figure 7 The filter circuit is connected to the SPWM_L terminal of an external device through one end of resistor R57 (the seventh resistor), and the other end of resistor R57 is connected to one end of resistor R60 (the zero resistor). The other end of resistor R60 is connected to pin 15 (VFB) of the microcontroller, and is also connected to the +3.3V power supply through diode D14 (the fourth diode). A circuit consisting of resistors R65 (the fifth resistor), R66 (the sixth resistor), and capacitor C51 (the first capacitor) connected in parallel is connected between resistors R57 and R60.

[0059] In some specific embodiments of the present invention, the photovoltaic inverter device of the present invention further includes a voltage detection circuit, which is connected to the photovoltaic cell, the capacitor, and the main controller. See also Figure 10 The voltage detection circuit includes a first input sub-circuit composed of multiple resistors (R22 / R23 / R24 / R25) connected in series. One end of the first input sub-circuit is connected to the DC+in terminal of the photovoltaic cell, and the other end is connected to the DC- terminal of the capacitor. A circuit composed of a second nine resistor (R29) and a third five resistor (R35) connected in series is connected between the second five resistor (R29) and the DC- terminal of the capacitor. A third two resistor (R32) is connected in parallel to the circuit composed of the second nine resistor (R29) and the third five resistor (R35). The second five resistor (R25) is connected to the +3.3V voltage through the first five diode (D15) and to the microcontroller's pin 11 (GFDV) through the second six resistor (R26).

[0060] Furthermore, the voltage detection circuit also includes a second input sub-circuit composed of multiple resistors (R44 / R45 / R46 / R47) connected in series. One end of the second input sub-circuit is connected to the DC+ terminal of the capacitor, and the other end is connected to the DC- terminal of the capacitor. A circuit composed of a fifth zero-resistance R50 and a fifth fourth-resistance R54 connected in series is connected between the fourth seven resistor R47 and the DC- terminal of the capacitor. A fifth second resistor R52 is connected in parallel to the circuit composed of the fifth zero-resistance R50 and the fifth fourth-resistance R54. The fourth seven resistor R47 is connected to the +3.3V voltage through the first two diode D12 and to pin 14 (BUSDV) of the microcontroller through the fourth eight resistor R48.

[0061] In some specific embodiments of the present invention, the photovoltaic inverter device of the present invention further includes a temperature detection circuit. The temperature detection module includes a temperature-sensing transistor and a temperature-sensing rheostat. The C terminal of the eighth temperature-sensing transistor is connected to the temperature-sensing rheostat, and the B terminal of the eighth temperature-sensing transistor is connected to the main control unit. See also Figure 11 The base (B) of the eighth temperature-sensing transistor Q8 is connected to pin 21 (FANCTR) of the microcontroller via resistor R73. The collector (C) of the eighth temperature-sensing transistor is connected to one end of the temperature-controlled rheostat PTC1, and the other end of the rheostat is connected to the +24V power supply. The base (B) and emitter (E) of the eighth temperature-sensing transistor are connected via resistor R77, and the emitter (E) of the eighth temperature-sensing transistor is grounded.

[0062] See Figures 1 to 11 , Figure 12 The photovoltaic inverter system control method based on sampling correction angle of the present invention is applied to the photovoltaic inverter device of the present invention embodiment. The photovoltaic inverter device includes a phase angle operational amplifier and a transformer winding for acquiring the correction angle. The method includes at least the following steps: S100: Obtain the capacitor voltage through the capacitor voltage sampling sub-circuit, obtain the output current through the output current sampling sub-circuit, and input the obtained sampling data to the microcontroller; obtain the correction angle through the phase angle operational amplifier and transformer winding; wherein, the correction angle is the phase angle difference between the output voltage and the input voltage.

[0063] S200: The microcontroller obtains the output vector voltage magnitude and operation cycle frequency based on the sampled capacitor voltage and output current; the microcontroller also obtains the corrected output voltage angle based on the operation cycle frequency and correction angle. The output vector voltage magnitude is the system-allowed output vector voltage magnitude.

[0064] S300: The microcontroller obtains the voltage scalar based on the vector voltage magnitude and the corrected output voltage angle; the PWM duty cycle is obtained based on the voltage scalar and the capacitor voltage. Further, Vout = Vmod * sin(Φ), where Vout represents the calculated voltage scalar, Vmod represents the vector voltage magnitude, and Φ represents the corrected output voltage angle.

[0065] See Figure 13 In the photovoltaic inverter system based on sampling correction angle of this invention embodiment, according to the commonly used power grid of 50Hz 220AC and under the condition of 100% power factor, see [reference needed]. Figure 14 The relationship between input power and time can be obtained as: P1 = U1 * I1 * sin 2 (θ(t)) = U1*I1*(1 - cos(2θ(t))) / 2, where P1 represents the input power, θ(t) = 100π*t+θ0, θ0 is the initial input voltage phase angle, and the relationship between output power and time is: P2= U2*I2*sin 2 (Φ(t)) = U2*I2*(1 - cos(2Φ(t))) / 2, where P2 represents the output power, Φ(t) = 100π*t+Φ0, and Φ0 is the initial output voltage phase angle. Existing photovoltaic inverter systems are prone to inconsistencies between the output and input voltage phase angles, i.e., θ0≠Φ0. This generates energy fluctuations with a period of 100Hz on the internal capacitors, burdening the system. Furthermore, since the maximum voltage of the energy storage capacitor is the grid peak voltage, different phase angles will cause the output voltage to be lower than the input voltage. In the photovoltaic inverter system control method of this invention, a voltage scalar is calculated based on the sampled capacitor voltage, output current, and correction angle. This scalar is then used to calculate the PWM duty cycle of the inverter H-bridge, eliminating the phase angle difference between the input and output voltages, minimizing energy fluctuations in the system capacitors, and improving system lifespan.

[0066] Furthermore, the frequency statistics and extraction in this embodiment of the invention are obtained through the following DFT / FFT calculations: In the formula, X k x represents the frequency domain component of the output. n The input represents the time-domain component, N represents the total number of computation points, k represents the current output being the k-th component, n represents the input being the n-th component, and i represents the imaginary unit.

[0067] Specifically, the corrected output voltage angle in this embodiment of the invention It is obtained through the following calculations: In the formula, This indicates the output voltage angle of the previous cycle. Indicates the correction angle for the current cycle. Indicates angular error. Indicates the output frequency of the current cycle. Indicates the output angle of the current cycle. Indicates the sampling time. These represent the three gains of the PID controller.

[0068] See Figures 1 to 11 , Figure 15 The photovoltaic inverter system control method based on input voltage fluctuation feedback of the present invention is applied to the photovoltaic inverter device of the present invention embodiment, and the method includes at least the following steps: S100: Obtain the capacitor voltage through the capacitor voltage sampling sub-circuit, obtain the output current through the output current sampling sub-circuit, and input the obtained sampling data to the microcontroller.

[0069] S200: Using a microcontroller and based on the sampled capacitor voltage and output current, the output vector voltage magnitude, operation cycle frequency, and capacitor energy are obtained; using the microcontroller and based on the capacitor energy, the correction angle between the initial input voltage and the initial output voltage is obtained; using the microcontroller and based on the operation cycle frequency and the correction angle, the corrected output voltage angle is obtained. The output vector voltage magnitude is the system-allowed output vector voltage magnitude.

[0070] S300: The microcontroller obtains the voltage scalar based on the vector voltage magnitude and the corrected output voltage angle; the PWM duty cycle is obtained based on the voltage scalar and the capacitor voltage. Further, Vout = Vmod * sin(Φ), where Vout represents the calculated voltage scalar, Vmod represents the vector voltage magnitude, and Φ represents the corrected output voltage angle.

[0071] See Figures 16 to 18 In the photovoltaic inverter system based on input voltage fluctuation feedback in this embodiment of the invention, according to the commonly used 50Hz 220AC power grid, the fluctuation function is dP = P1 – P2 = U1*I1*(1 - cos(2θ(t))) / 2 - U2*I2*(1 - cos(2Φ(t))) / 2, where P1 represents the input power, θ(t) = 100π*t+θ0, θ0 is the initial input voltage phase angle, P2 represents the output power, Φ(t) = 100π*t+Φ0, Φ0 is the initial output voltage phase angle. Therefore, when both the input and output power factors are 100%, and the input power = output power, i.e., U1*I1 = U2*I2, (see...) Figure 18 Let P0 = U1*I1 / 2. The above equation simplifies to: dP = P0*(cos(2θ(t)) - cos(2Φ(t))).

[0072] See Figure 17 Let dP, P1, P2 be several complex functions (denoted as ). The real part of ) then the energy fluctuation in the embodiments of the present invention The energy difference between the input voltage and the output voltage is calculated using the following software method: Integrating dP, we obtain the energy fluctuation as a function of time: In the formula, This indicates the capacitor's energy at any given moment. This represents the average energy of the capacitor. Therefore, based on the current period... If these are internal calculation parameters of the system, then it is only necessary to calculate them. The angle can be used to calculate the angle difference between the input voltage and the output voltage, i.e., the correction angle.

[0073] Furthermore, the frequency statistics and extraction in this embodiment of the invention are obtained through the following DFT / FFT calculations: In the formula, X k x represents the frequency domain component of the output. n The input represents the time-domain component, N represents the total number of computation points, k represents the current output being the k-th component, n represents the input being the n-th component, and i represents the imaginary unit.

[0074] Specifically, the corrected output voltage angle in this embodiment of the invention It is obtained through the following calculations: In the formula, This indicates the output voltage angle of the previous cycle. Indicates the correction angle for the current cycle. Indicates angular error. Indicates the output frequency of the current cycle. Indicates the output angle of the current cycle. Indicates the sampling time. These represent the three gains of the PID controller.

[0075] The photovoltaic inverter device, system, and method of the present invention are verified. When the photovoltaic cell voltage is greater than the peak voltage of the external power grid, see [link to relevant documentation]. Figure 19 From the theoretical waveforms of the photovoltaic cell and its output terminal, we can obtain the following: the external grid current is zero, and all energy is provided by the photovoltaic cell; when the photovoltaic cell voltage is less than the peak voltage of the external grid, see... Figure 20 From the theoretical waveforms of the photovoltaic cells and their output terminals, we can see that near the peak value of the waveform in the figure, energy is provided by the external power grid, while in other waveform portions, energy is provided by the photovoltaic cells themselves; both jointly provide energy. Therefore, the photovoltaic inverter device, system, and method of this invention can effectively integrate photovoltaic cells with the local power grid, and, when the photovoltaic cell output is sufficient, can achieve 100% utilization of photovoltaic energy.

[0076] The above description is merely a preferred embodiment of the present invention. The present invention is not limited to the above-described embodiments. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this disclosure, as long as they achieve the same technical effects, should be included within the scope of protection of this disclosure and fall under the protection scope of the present invention. Within the protection scope of the present invention, the technical solutions and / or implementation methods can have various modifications and variations.

Claims

1. A photovoltaic inverter device, characterized in that, include: The system comprises an input circuit, an inverter circuit, and a filter circuit connected in sequence. The input circuit includes a capacitor, a switching sub-circuit, and an auxiliary power supply sub-circuit. The capacitor is connected to the external power grid via an input rectifier. The capacitor is connected to the photovoltaic cell, the switching sub-circuit, the auxiliary power supply sub-circuit, and the inverter circuit. The inverter circuit is connected to the auxiliary power supply sub-circuit and the filter circuit. The output of the filter circuit is connected to external electrical appliances and a sampling circuit. The sampling circuit includes a capacitor voltage sampling sub-circuit and an output current sampling sub-circuit. The capacitor voltage sampling sub-circuit includes a capacitor sampling operational amplifier, and the output current sampling sub-circuit includes an output sampling operational amplifier. Both the capacitor sampling operational amplifier and the output sampling operational amplifier are connected to a microcontroller. The capacitor sampling operational amplifier is connected to the capacitor, and the output sampling operational amplifier is connected to the inverter circuit. The microcontroller is connected to the inverter circuit. The capacitor includes multiple input capacitors connected in parallel. One end of the capacitor is connected to the negative terminal of the photovoltaic cell and the L terminal of the external power grid, and the other end of the capacitor is connected to the switching sub-circuit through an input inductor. The switching sub-circuit includes a switching transistor and an electromagnetic relay. The base (B) of the switching transistor is connected to the microcontroller, and the collector (C) of the switching transistor is connected to the electromagnetic relay. The electromagnetic relay is connected to both the capacitor and the photovoltaic cell.

2. The photovoltaic inverter device according to claim 1, characterized in that, The inverter circuit includes four sets of inverter sub-circuits. Each set of inverter sub-circuits includes an inverter driver and an inverter MOS transistor. The inverter driver is connected to the main controller, the auxiliary sub-circuit and the inverter MOS transistor respectively. The inverter MOS transistor is connected to the capacitor, the auxiliary sub-circuit and the external electrical appliance respectively.

3. The photovoltaic inverter device according to claim 2, characterized in that, The output current sampling sub-circuit includes an output sampling operational amplifier, wherein the drain of one of the inverter MOS transistors is connected to the SPWM_N terminal of an external electrical appliance and the source is connected to the inverting input terminal of the output sampling operational amplifier and the microcontroller, and the output terminal of the output sampling operational amplifier is connected to the microcontroller.

4. The photovoltaic inverter device according to claim 1, characterized in that, The capacitor voltage sampling sub-circuit includes a capacitor sampling operational amplifier. The photovoltaic cell and the capacitor are respectively connected to the input terminal of the capacitor sampling operational amplifier, and the output terminal of the capacitor sampling operational amplifier is connected to the microcontroller.

5. The photovoltaic inverter device according to claim 2, characterized in that, It also includes a voltage detection circuit, which is connected to the photovoltaic cell, the capacitor, and the main controller; wherein, The voltage detection circuit includes a first input sub-circuit composed of multiple resistors connected in series. One end of the first input sub-circuit is connected to the DC+in terminal of the photovoltaic cell, and the other end of the first input sub-circuit is connected to the DC- terminal of the capacitor. The first input sub-circuit includes a second five-resistor R25. A circuit composed of a second nine-resistor R29 and a third five-resistor R35 connected in series is connected between the second five-resistor R25 and the DC- terminal of the capacitor. A third two-resistor R32 is connected in parallel to the circuit composed of the second nine-resistor R29 and the third five-resistor R35. The second five-resistor R25 is connected to a voltage of +3.3V through a first five-diode D15 and is connected to the GFDV terminal of the microcontroller through a second six-resistor R26. The voltage detection circuit further includes a second input sub-circuit composed of multiple resistors connected in series. One end of the second input sub-circuit is connected to the DC+ terminal of the capacitor, and the other end of the second input sub-circuit is connected to the DC- terminal of the capacitor. The second input sub-circuit includes a fourth seven-resistor R47 and a fourth seven-resistor R47. A circuit composed of a fifth zero-resistor R50 and a fifth four-resistor R54 connected in series is connected between the fourth seven-resistor R47 and the DC- terminal of the capacitor. A fifth two-resistor R52 is connected in parallel to the circuit composed of the fifth zero-resistor R50 and the fifth four-resistor R54. The fourth seven-resistor R47 is connected to the voltage +3.3V through a first two-diode D12 and is connected to the BUSDV terminal of the microcontroller through a fourth eight-resistor R48.

6. The photovoltaic inverter device according to claim 1, characterized in that, It also includes a temperature detection circuit, which includes a temperature sensing transistor and a temperature rheostat. The C terminal of the temperature sensing transistor is connected to the temperature rheostat, and the B terminal of the temperature sensing transistor is connected to the microcontroller.

7. A photovoltaic inverter system control method based on input voltage fluctuation feedback, applied to the photovoltaic inverter device according to any one of claims 1 to 6, the method comprising the following steps: S100. Obtain the capacitor voltage through the capacitor voltage sampling sub-circuit, obtain the output current through the output current sampling sub-circuit, and input the obtained sampling data into the microcontroller. S200: Using the microcontroller and based on the sampled capacitor voltage and output current, obtain the output vector voltage magnitude, operation cycle frequency, and capacitor energy; Using the microcontroller and based on the capacitor energy, obtain the correction angle between the initial input voltage and the initial output voltage; Using the microcontroller and based on the operation cycle frequency and the correction angle, obtain the corrected output voltage angle. S300: The microcontroller obtains a voltage scalar based on the vector voltage magnitude and the corrected output voltage angle; and obtains the PWM duty cycle based on the voltage scalar and the capacitor voltage.

8. The method according to claim 7, characterized in that, In step S200, the correction angle is based on energy fluctuations. The energy fluctuations are obtained. The capacitor energy is calculated using the following method: In the formula, The energy of the capacitor at time t is represented by the integral function of dP; This represents the average energy of the capacitor, which is the average value of the capacitor's energy; where, In the formula, dP represents the difference between the input power and the output power; P0 represents the average value of the input power and the output power when the input power and the output power are equal; dP represents a complex function. The real part; Indicates the phase angle of the input voltage; This indicates the phase angle of the output voltage.

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