Low-complexity full-simulation single-phase inversion alternating current parallel connection device

Abstract

The utility model relates to a low-complexity full-simulation single-phase inversion alternating current parallel connection device, which is used for improving the tracking and response speed of grid connection and reducing the complexity of a circuit at the same time. The device comprises a single-phase full-bridge voltage type inverter circuit and an alternating current real-time tracking feedback circuit, according to the circuit, an average current control method is adopted, an amplifier circuit is used for achieving differencing calculation and tracking through an II-type compensation feedback loop, and therefore the circuit is simplified, and stable and rapid single-phase inversion and parallel connection with an alternating current power grid can be achieved through reasonable loop compensation.

Description

Technical Field

[0001] The utility model relates to a low-complexity full-simulation single-phase inverter alternating current parallel connection device, which is used for improving the tracking and response speed of grid connection and reducing the circuit complexity. Background Art

[0002] Energy is an important pillar of the modern economy, and the development of society is inseparable from the efficient use of energy. How to develop and utilize renewable energy has become a major issue of concern to people. Solar energy and wind energy are currently the main renewable energy sources. Solar energy is mainly effectively utilized through photovoltaic power generation. Photovoltaic power generation usually includes a front-stage and a rear-stage circuit. The front-stage circuit converts the direct current output by photovoltaic power generation into direct current suitable for inversion through a DC-DC converter; the rear-stage circuit converts the direct current into alternating current matching the alternating current grid through a DC-AC inverter to achieve parallel connection. The front-stage DC-DC circuit is greatly affected by the photovoltaic power generation environment, and its dynamic range is wide, so the control strategy is relatively flexible. In contrast, the rear-stage DC-AC circuit needs to output rated alternating current matching the grid, and usually adopts a digital control method. However, the design of the digital control method is complex and is easily affected by quantization errors, which may cause the loop to produce limit cycle oscillations. To solve this problem, the utility model aims to design a low-complexity fully analog single-phase inverter alternating current parallel connection device. The device adopts a fully analog circuit to avoid the quantization error and limit cycle oscillation problems that may occur in digital control. It can invert direct current into rated alternating current matching the alternating current grid, and realize parallel connection with the grid. To solve this problem, the utility model aims to design a low-complexity full-analog single-phase inverter alternating current parallel connection device. The device adopts a full-analog circuit to avoid the quantization error and limit cycle oscillation problems that may occur in digital control. It can invert direct current into rated alternating current matching the alternating current grid, and realize parallel connection with the grid. Utility Model Content

[0003] In order to meet the requirements of voltage same frequency, same phase and same amplitude when connected in parallel with an AC power grid, and to achieve fast tracking and response, while reducing circuit complexity, the utility model provides a low-complexity full-analog single-phase inverter AC power parallel connection device. The circuit adopts an average current control method, and uses an amplifier circuit to achieve difference calculation and tracking through a type II compensation feedback loop, thereby simplifying the circuit. Through reasonable loop compensation, stable and fast single-phase inversion and parallel connection with an AC power grid can be achieved.

[0004] The technical solution adopted by the utility model to solve its technical problems is: a low-complexity full-analog single-phase inverter AC parallel connection device, including a single-phase full-bridge voltage-type inverter circuit and an AC real-time tracking feedback circuit, wherein the first input end of the single-phase full-bridge voltage-type inverter circuit is connected to a DC power supply, and is used to convert the DC power output by photovoltaic power generation into AC power; the input of the AC real-time tracking feedback circuit is connected to the first and second output ends of the single-phase full-bridge voltage-type inverter circuit, and is used to sample the output current of the first output end and the output voltage of the second output end of the single-phase full-bridge voltage-type inverter circuit, and is used to achieve a phase-locked and proportional relationship between the output current and the output voltage; the output of the AC real-time tracking feedback circuit is connected to the second input end of the single-phase full-bridge voltage-type inverter circuit, and is used for the single-phase full-bridge voltage-type inverter circuit to generate a sine wave with the same phase, frequency and amplitude when connected in parallel with the AC power grid, so as to achieve parallel connection with the grid;

[0005] The single-phase full-bridge voltage-type inverter circuit comprises: a full-bridge circuit, a filter circuit and a drive circuit, wherein the input end of the drive circuit is connected to the output of the AC real-time tracking feedback circuit, the output of the drive circuit is connected to one input end of the full-bridge circuit, the other input end of the full-bridge circuit is connected to the DC power supply as the first input end of the single-phase full-bridge voltage-type inverter circuit, the output of the full-bridge circuit is connected to the input of the filter circuit, the output of the filter circuit is used as the first and second output ends of the single-phase full-bridge voltage-type inverter circuit, the first output end is connected to the AC power grid, and the second output end is connected to the AC real-time tracking feedback circuit;

[0006] The AC real-time tracking feedback circuit comprises: an AC current sampling circuit, wherein the input of the AC current sampling circuit is connected to the first output end of the filter circuit, and is used to monitor and sample the inductor current in the filter circuit of the single-phase full-bridge voltage-type inverter circuit, generate a fluctuation signal with a DC bias, and send it to the signal processing circuit; an AC voltage sampling circuit, wherein the input of the AC voltage sampling circuit is connected to the second output end of the filter circuit, and is used to collect and condition the voltage signal of the connected AC power grid, and the voltage signal is used as a reference signal for the grid-connected current; a signal processing circuit, wherein the first input end of the signal processing circuit is connected to the output of the AC current sampling circuit, and the second input end is connected to the output of the AC voltage sampling circuit, and is used to generate a desired SPWM modulation wave, and input it into a sawtooth wave generation circuit based on TL494; a 2.5V reference voltage source, wherein the three output ends of the 2.5V reference voltage source are respectively connected to the The invention is connected to an AC current sampling circuit, an AC voltage sampling circuit and a signal processing circuit to provide a 2.5V reference voltage; a sawtooth wave generating circuit based on TL494, wherein the input of the sawtooth wave generating circuit based on TL494 is connected to the signal processing circuit to generate a high-frequency sawtooth carrier wave to support and transmit information; a comparator logic circuit, wherein the first input end of the comparator logic circuit is connected to the output of the signal processing circuit, and the second input end is connected to the output of the sawtooth wave generating circuit based on TL494, and the output end of the comparator logic circuit is connected to the driving circuit of a single-phase full-bridge voltage-type inverter circuit to generate a PWM switch control signal to convert the input DC power supply into a unidirectional pulse power, which is then filtered through a filtering circuit to generate AC power that can be connected in parallel with the AC power grid. Due to the negative feedback control technology adopted, the generated AC power has the same frequency, phase and amplitude as the AC power grid voltage, and can be smoothly connected in parallel with the AC power grid.

[0007] In the above-mentioned low-complexity full-analog single-phase inverter AC parallel connection device, the purpose of the signal processing circuit is to obtain a modulation signal based on average current control, which is used to generate a desired PWM wave. Specifically, the sampled inductor current signal and the sampled AC grid voltage signal are sent to the MCP6022T amplifier through the summing resistor, and a zero point and a pole are added to the loop through type II compensation to increase the gain of the loop at low frequency and reduce the gain at high frequency, reduce the steady-state error, obtain sufficient phase margin, and reduce the influence of high-frequency noise.

[0008] In the above-mentioned low-complexity fully analog single-phase inverter AC parallel connection device, the comparator logic circuit receives the modulation signal from the signal processing circuit and the sawtooth carrier generated by the sawtooth wave generation circuit based on TL494, generates a PWM switch control signal through comparison and digital logic, and sends it to the drive circuit. Through the full-bridge circuit, it generates AC power with the same frequency, phase and amplitude as the AC power grid to achieve parallel connection with the AC power grid.

[0009] The beneficial effects of the utility model are as follows: the utility model designs a low-complexity full-analog single-phase inverter AC parallel connection device, which realizes parallel connection with the AC power grid. Due to the adoption of a full-analog feedback control method, the quantization error and limit cycle oscillation problems that may occur in digital control are avoided, and the stability of the current loop is improved. Because the AC real-time tracking feedback circuit adds a low-frequency zero point and a high-frequency pole in the loop, the low-frequency gain of the current loop is improved and the high-frequency noise is reduced, so the average current change in the AC power grid can be tracked in real time, and the controlled switch signal is sent to the driver to control the output waveform of the full-bridge circuit, thereby ensuring a stable and fast dynamic response. At the same time, the designed feedback loop type II compensation makes the AC generated by the single-phase full-bridge voltage inverter circuit meet the parallel connection conditions of the same frequency, same phase and same amplitude as the power grid voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The utility model is further described below in conjunction with the accompanying drawings and embodiments.

[0011] Figure 1 It is a schematic diagram of the overall structure of the utility model;

[0012] Figure 2 It is a structural diagram of the AC real-time tracking feedback circuit of the utility model;

[0013] Figure 3 It is the schematic diagram of the full-bridge circuit with a green wave circuit in a single-phase full-bridge voltage-type inverter circuit;

[0014] Figure 4 It is the principle diagram of the driving circuit in the single-phase full-bridge voltage-type inverter circuit;

[0015] Figure 5 It is the schematic diagram of the current sampling circuit and the voltage sampling circuit in the AC real-time tracking feedback circuit;

[0016] Figure 6 It is the schematic diagram of the signal processing circuit in the AC real-time tracking feedback circuit;

[0017] Figure 7 This is the schematic diagram of the sawtooth wave generation circuit based on TL494 in the AC real-time tracking feedback circuit;

[0018] Figure 8 It is the schematic diagram of the comparator logic circuit in the AC real-time tracking feedback circuit;

[0019] Fig. 9 This is the overall circuit schematic diagram of the utility model. DETAILED DESCRIPTION

[0020] Figure 1The schematic diagram of the overall structure of the utility model. The utility model is composed of a single-phase full-bridge voltage-type inverter circuit and an AC real-time tracking feedback circuit. Among them, the single-phase full-bridge voltage-type inverter circuit is composed of a full-bridge circuit, a filter circuit, and a drive circuit, and is used to invert DC power into AC power that can be connected in parallel with the AC power grid. The AC real-time tracking feedback circuit and the single-phase full-bridge voltage-type inverter circuit form a negative feedback control system, which samples the output signal and generates a PWM switching signal to ensure that the AC power output by the single-phase full-bridge voltage-type inverter circuit is of the same frequency, phase, and amplitude as the AC power grid. The utility model adopts a full analog circuit to realize a negative feedback control system, which simplifies the circuit complexity and improves the grid-connected tracking and response speed.

[0021] Figure 2 The utility model is a structural schematic diagram of an alternating current real-time tracking feedback circuit. The alternating current real-time tracking feedback circuit is composed of an alternating current voltage sampling circuit, an alternating current sampling circuit, a signal processing circuit, a 2.5V reference voltage source, a sawtooth wave generating circuit based on TL494, and a comparator logic circuit. The alternating current voltage sampling circuit is responsible for collecting the voltage signals at both ends of the alternating current connection interface acp and acm, while the alternating current sampling circuit collects the current signals of the inductor L1 and the inductor L2 in the filter circuit. The voltage and current signals collected by these two channels are then sent to the signal processing circuit, and the signal processing circuit is responsible for generating a modulation signal for output. The modulation signal is sent to the comparator logic circuit together with the carrier signal generated by the sawtooth wave generating circuit based on TL494. In the comparator logic circuit, these signals are compared and processed, and finally a control signal for controlling a single-phase full-bridge voltage-type inverter circuit is generated. This process realizes negative feedback control of the inverter circuit, ensuring that the output alternating current has the same frequency, phase and amplitude as the grid voltage.

[0022] Figure 3 and Figure 4 They are the schematic diagram of the full-bridge circuit with a filter circuit in a single-phase full-bridge voltage inverter circuit and the schematic diagram of the drive circuit. The drive circuit takes the IR2104 half-bridge driver as an example. It is composed of two IR2104 driver chips with internal dead time. It controls the on and off of the full-bridge circuit. The full-bridge circuit consists of two groups of 4 IRF3205MOS tubes. Through the control of the drive circuit, the input DC power is inverted and converted to output a stable AC voltage. Specific parameters: DC power supply Vdc = 40; filter inductor L1 = L2 = 600μH, sampling resistor Rs = 0.01, and a stable AC voltage of 34V is generated at the acp and acm ports. The acp and acm terminals are AC parallel connection ports.

[0023] Figure 5The schematic diagram of the current sampling circuit and the voltage sampling circuit in the AC real-time tracking feedback circuit. The AC voltage sampling circuit is composed of a ZMPT101B voltage transformer and an MCP6022T amplifier. The AC parallel ports acp and acm provide AC grid voltage signals, and the signal scaling factor is adjusted by adjusting the values ​​of resistors Re0, Re1 and Re2. Similarly, the AC current sampling circuit is composed of a ZHTM104B current transformer and an MCP6022T amplifier. The ZHTM104B current transformer input is connected to acp and in-, and is connected across the sampling resistor Rs. The signal scaling factor can also be adjusted by adjusting the values ​​of Rd1 and Rd2. Here, Rd1=200Ω. Since the positive phase terminal of the amplifier MCP6022T is connected to a 2.5V bias voltage, the output of the AC voltage sampling circuit and the AC current acquisition circuit is a fluctuating voltage signal with a DC bias. Since the sampled AC grid voltage signal and inductor current signal inevitably have noise, the outputs of the AC voltage sampling circuit and the AC current sampling circuit are both connected to a first-order RC filter circuit.

[0024] Figure 6 This is the schematic diagram of the signal processing circuit in the AC real-time tracking feedback circuit. The signal processing circuit uses the amplifier MCP6022T for signal processing. In this circuit, the positive input terminal +INA of the amplifier MCP6022T receives the output signal C3 of the AC voltage sampling circuit and the output signal C4 of the AC current sampling circuit. These two signals are used to compare the difference between the sampled inductor current signal and the AC grid voltage signal. At the same time, the negative input terminal -INA of the amplifier MCP6022T receives a 2.5V bias voltage, which is also sent to the negative input terminal -INA of the amplifier after passing through a 100kΩ resistor. The purpose of this design is to achieve differential amplification of the signal to remove the unnecessary 2.5V DC level. A capacitor and a resistor are connected between the output terminal of the amplifier MCP6022T and the negative input terminal -INA to achieve type II compensation. The specific parameters include: Cb1 = 8.443pF, Cb2 = 73.88pF, Rb4 = 754k. The role of these components is to optimize the performance of the amplifier, ensuring its stability and linearity.

[0025] Figure 7This is the schematic diagram of the sawtooth wave generation circuit based on TL494 in the AC real-time tracking feedback circuit. The sawtooth wave generation circuit based on TL494 is used to receive the output adjustment signal of the signal processing circuit and generate a high-frequency carrier signal. The specific design is as follows: the output signal C5 of the signal processing circuit is sent to the feedback compensation pin (FeedBack) of the TL494 chip, and the power input pin Vcc is connected to the C1 and C2 pins through a 150Ω resistor Rc3. The timing capacitor terminal CT pin of the oscillator generates a sawtooth wave C6 with an amplitude of 3V. The oscillation frequency of this sawtooth wave is adjusted by the resistor Rc1 and capacitor Cc1 of the chip external circuit. In this example, Rc1=11.5kΩ and Cc1=1nF. According to the relevant calculation formula, it can be concluded that the oscillation frequency is close to 100kHz.

[0026] Figure 8 This is a schematic diagram of the comparator logic circuit in the AC real-time tracking feedback circuit. The comparator logic circuit generates a control signal for a single-phase full-bridge voltage-type inverter circuit by comparing the carrier and the sawtooth carrier. The specific operation is as follows: the output signal C5 of the signal processing circuit is sent to the positive input terminal of the comparator logic circuit, that is, the positive input terminal +INB of the MCP6561T comparator. The output signal C6 of the sawtooth wave generation circuit based on TL494 is sent to the negative input terminal of the comparator logic circuit, that is, the negative input terminal -INB of the MCP6561T comparator. The comparison output of the comparator MCP6561T passes through digital logic and finally generates a pair of complementary PWM switch control signals, namely, C1 and C2 signals. These two signals are sent to the drive circuit respectively to realize negative feedback control of the inverter circuit.

[0027] Fig. 9 This is the overall circuit schematic diagram of the utility model. The overall circuit schematic diagram includes two main modules: a single-phase full-bridge voltage-type inverter circuit and an AC real-time tracking feedback circuit. The two modules interact with each other to form a negative feedback control system. The main function of the system is to invert DC power into AC power and ensure that the output AC power has the same frequency, phase and amplitude as the AC power grid, thereby achieving parallel connection with the AC power grid. In addition, the figure also shows the connection relationship between modules and within the modules, as well as the implementation details of the circuit.

[0028] Although the present example has been described with respect to a relatively limited number of embodiments, those skilled in the art having benefit of this disclosure will appreciate numerous modifications and variations therefrom. The appended claims are intended to cover such modifications and variations as fall within the true spirit and scope of the present invention.

Claims

1. A low-complexity full-analog single-phase inverter AC power parallel connection device, characterized in that: It comprises a single-phase full-bridge voltage-type inverter circuit and an AC real-time tracking feedback circuit, wherein the first input end of the single-phase full-bridge voltage-type inverter circuit is connected to a DC power supply, and is used to convert the DC power outputted by photovoltaic power generation into AC power; the input of the AC real-time tracking feedback circuit is connected to the first and second output ends of the single-phase full-bridge voltage-type inverter circuit, and is used to sample the output current of the first output end and the output voltage of the second output end of the single-phase full-bridge voltage-type inverter circuit, and is used to achieve a phase-locked and proportional relationship between the output current and the output voltage; the output of the AC real-time tracking feedback circuit is connected to the second input end of the single-phase full-bridge voltage-type inverter circuit, and is used for the single-phase full-bridge voltage-type inverter circuit to generate a sine wave with the same phase, frequency and amplitude when connected in parallel with an AC power grid, and achieve parallel connection with the grid; The single-phase full-bridge voltage-type inverter circuit comprises a full-bridge circuit, a filter circuit and a drive circuit, the input end of the drive circuit is connected to the output of the AC real-time tracking feedback circuit, the output of the drive circuit is connected to one input end of the full-bridge circuit, the other input end of the full-bridge circuit is connected to the DC power supply as the first input end of the single-phase full-bridge voltage-type inverter circuit, the output of the full-bridge circuit is connected to the input of the filter circuit, the output of the filter circuit is used as the first and second output ends of the single-phase full-bridge voltage-type inverter circuit, the first output end is connected to the AC power grid, and the second output end is connected to the AC real-time tracking feedback circuit; The AC real-time tracking feedback circuit comprises: an AC current sampling circuit, wherein the input of the AC current sampling circuit is connected to the first output end of the filter circuit, and is used to monitor and sample the inductor current in the filter circuit of the single-phase full-bridge voltage-type inverter circuit, generate a fluctuation signal with a DC bias, and send it to the signal processing circuit; an AC voltage sampling circuit, wherein the input of the AC voltage sampling circuit is connected to the second output end of the filter circuit, and is used to collect and condition the voltage signal of the connected AC power grid, and the voltage signal is used as a reference signal for the grid-connected current; a signal processing circuit, wherein the first input end of the signal processing circuit is connected to the output of the AC current sampling circuit, and the second input end is connected to the output of the AC voltage sampling circuit, and is used to generate a desired SPWM modulation wave, and input the sawtooth wave generation circuit based on TL494; a 2.5V reference voltage source, wherein the three output ends of the 2.5V reference voltage source are respectively connected to the AC A current sampling circuit, an AC voltage sampling circuit and a signal processing circuit are used to provide a 2.5V reference voltage; a sawtooth wave generating circuit based on TL494, wherein the input of the sawtooth wave generating circuit based on TL494 is connected to the signal processing circuit, which is used to generate a high-frequency sawtooth carrier wave to support and transmit information; a comparator logic circuit, wherein the first input end of the comparator logic circuit is connected to the output of the signal processing circuit, and the second input end is connected to the output of the sawtooth wave generating circuit based on TL494, and the output end of the comparator logic circuit is connected to the driving circuit of the single-phase full-bridge voltage-type inverter circuit, which is used to generate a PWM switch control signal to convert the input DC power supply into a unidirectional pulse power, which is then filtered through a filtering circuit to generate AC power that can be connected in parallel with the AC power grid. Due to the negative feedback control technology adopted, the generated AC power has the same frequency, phase and amplitude as the AC power grid voltage, and can be smoothly connected in parallel with the AC power grid.

2. A low-complexity full-analog single-phase inverter AC parallel connection device according to claim 1, characterized in that: The purpose of the signal processing circuit is to obtain a modulation signal based on average current control, so as to generate a desired PWM wave.

3. A low-complexity full-analog single-phase inverter AC parallel connection device according to claim 2, characterized in that: The sampled inductor current signal and the sampled AC grid voltage signal are sent to the MCP6022T amplifier through the summing resistor. Through type II compensation, a zero point and a pole are added to the loop to increase the gain of the loop at low frequency and reduce the gain at high frequency, thereby reducing the steady-state error, obtaining sufficient phase margin and reducing the influence of high-frequency noise.

Images