Photovoltaic air conditioner and direct current component suppression method thereof, electronic equipment and medium

Abstract

The invention discloses a photovoltaic air conditioner and a direct current component suppression method thereof, electronic equipment and a medium, and the suppression method comprises the steps: building a bus ripple detection circuit at the direct current side of a single-phase inverter, and obtaining a bus ripple sampling result; carrying out primary compensation on a direct current component, and generating a current for compensation based on the direct current bus voltage; subtracting the acquired actual grid-connected current to obtain a grid-connected current error value, compounding the grid-connected current error value with a power grid voltage feed-forward signal and a capacitance current feedback signal to generate a duty ratio signal, and driving an inverter in an SPWM (sinusoidal pulse width modulation) mode; carrying out secondary compensation on the direct current component, carrying out phase tracking on the voltage of the power grid through SOGI-PLL with FLL, and generating a phase-synchronous current modulation signal; and adding the compensation signal with the current difference to obtain a compensation signal, and adjusting the duty ratio of the inverter. According to the invention, the grid-connected direct-current component of the photovoltaic household air conditioner is effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of air conditioners, and more particularly relates to a photovoltaic air conditioner and a direct current component suppression method thereof, an electronic device and a medium. BACKGROUND

[0002] Combining the single-phase full-bridge topology structure of LCL filtering and the second-order generalized phase-locked loop strategy is the mainstream method for realizing stable photovoltaic grid-connected inversion of the current photovoltaic household split unit. However, the single-phase full-bridge topology structure of the photovoltaic household split unit has the problem of direct current component grid connection. The topology structure lacks isolation of the direct current part circuit, and a large amount of direct current component will be generated in the process of grid connection of the photovoltaic household air conditioner inverter. When the grid voltage contains a direct current component or a harmonic component, the quadrature signal output by the second-order generalized phase-locked loop will still have a significant direct current offset, resulting in fluctuations in the obtained grid voltage frequency and phase information, and affecting the measurement accuracy.

[0003] The solution in the prior art is, for example but not limited to, a direct current component suppression method for inverter grid-connected output current and a photovoltaic system, but this method can only be applied to the problem of output current direct current component control failure caused by bus voltage imbalance; the prior art document also provides a control method and circuit for fast phase tracking compensation, but cannot compensate for the output current direct current component problem caused by bus voltage imbalance, and can only cope with the grid connection function under the ideal state of the direct current bus voltage; the solution of the prior art document also includes a direct current component detection method, suppression method, device and power converter, but this method needs to rely on a multi-stage sampling circuit to realize, which increases the cost and also increases the electromagnetic interference of the system. SUMMARY

[0004] To solve the problems in the prior art, the present application provides a photovoltaic air conditioner and a direct current component suppression method thereof, an electronic device and a medium, which comprehensively considers the influence of direct current bus ripple variation and frequency fluctuation on phase-locked accuracy by detecting the direct current bus ripple variation, and improves the hardware circuit and software algorithm of the photovoltaic household air conditioner.

[0005] The present application adopts the following technical solutions.

[0006] The first aspect of the present application provides a direct current component suppression method, comprising the following steps: building a bus ripple detection circuit on the direct current side of the single-phase inverter to obtain bus ripple sampling results ; performing a first compensation of the direct current component in the grid-connected voltage, including generating a current for compensation through error calculation and PI regulation based on the bus ripple sampling results and the collected direct current bus voltage , and ; The current The actual grid-connected current collected Subtract and get the grid-connected current error value , the grid-connected current error value After PI regulation and compounding with the grid voltage feedforward signal and capacitor current feedback signal, a duty cycle signal is generated, which drives the inverter through SPWM modulation; The DC component is compensated twice, including the grid voltage through a second-order generalized integrator phase-locked loop with a frequency adaptive phase-locked loop. Perform phase tracking to obtain the sine value of the grid voltage phase; multiply the sine value by the AC current signal output by the inverter to the grid to generate a phase-synchronized current modulation signal; and multiply it by the current The actual grid current The difference between the two is added to obtain a compensation signal, and the duty cycle of the inverter is adjusted to achieve secondary compensation of the DC component.

[0007] Preferably, the bus ripple sampling result is based on The DC bus voltage is collected , generates current for compensation through error calculation and PI regulation include: According to the bus ripple sampling results Calculate the DC component reference value and through the DC bus voltage Calculate the grid-connected DC component ; The DC component reference value With the grid-connected DC component Subtract the DC component tracking error, and the DC component tracking error is passed through the PI controller Processing, generating current for compensation .

[0008] Preferably, the grid-connected current error value After PI regulation and compounding with the grid voltage feedforward signal and capacitor current feedback signal, the duty cycle signal is generated, including: The grid-connected current error value Current PI controller The first control value output, grid voltage Feedforward function The second control value of the output, and the capacitor current The third control values ​​multiplied by the feedback coefficient are added to generate a duty cycle control signal.

[0009] Preferably, the DC bus voltage Calculate the grid-connected DC component include: The theoretical value of bus ripple voltage is expressed as follows:

[0010] Where: is the theoretical value of bus ripple voltage; is the peak value of the grid voltage; is the peak value of the grid-connected current; is the grid angular frequency; is the grid-connected DC component; is the bus capacitance; is the steady-state value of the DC bus voltage; set up , ; The theoretical value of the bus ripple voltage The average DC bus voltage can be obtained by integrating the AC power cycle T of the grid :

[0011] Based on the above formula, we get and grid-connected DC component The proportionality factor , expressed as follows:

[0012] The average voltage of the DC bus and the proportionality coefficient The grid-connected DC component is obtained .

[0013] Preferably, the second-order generalized integrator phase-locked loop with frequency adaptive phase-locked loop dynamically adjusts the center frequency by real-time detection of the orthogonal signal components output by the second-order generalized integrator.

[0014] A second aspect of the present invention provides a photovoltaic air conditioner, comprising: an inverter, a photovoltaic module, and executing a DC component suppression method as described in the first aspect of the present invention; The inverter includes: a full-bridge circuit, an LCL filter circuit, a bus ripple detection circuit, and a second-order generalized integral phase-locked loop circuit. The DC side of the full-bridge circuit is connected to the bus ripple detection circuit, and the AC side is connected to the LCL filter circuit. The inverter converts the DC power generated by the photovoltaic module into AC power.

[0015] Preferably, the bus ripple detection circuit includes: a high-frequency transformer, a high-pass filter, and an operational amplifier; The high-frequency transformer is used for electrical isolation and voltage division of the bus voltage; The high-pass filter is connected with the output end of the high-frequency transformer, and is used for passing a set frequency ripple signal; The operational amplifier is connected with the output end of the high-pass filter, and is used for amplifying the set frequency ripple signal and outputting a bus ripple sampling result.

[0016] Preferably, the second-order generalized integrator phase-locked loop circuit comprises: a second-order generalized integrator, a frequency-locked controller; The output end of the frequency-locked controller is connected with the center frequency adjustment end of the second-order generalized integrator, and is used for adjusting the center frequency of the second-order generalized integrator to realize frequency self-adaptive tracking.

[0017] The third aspect of the present application provides an electronic device, comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the computer program realizes the direct current component suppression method according to the first aspect when loaded into the processor. The fourth aspect of the present application provides a computer readable storage medium, wherein the computer readable storage medium stores a computer program, and the computer program realizes the direct current component suppression method according to the second aspect when executed by a processor.

[0018] Compared with the prior art, the present application realizes the direct current component preliminary criterion by means of bus ripple detection, compensates the component once in the control system of the original circuit topology, and compensates the direct current component twice by using the improved phase-locked loop structure with frequency self-adaptation. The present application has at least the following beneficial effects: by collecting the change of the direct current bus ripple, the direct current component problem caused by the unstable bus voltage is solved, the frequency self-adaptive phase-locked loop technology is used to realize the fast phase locking of the power grid, and then the grid-connected operation control is switched to, the direct current component of the grid-connected photovoltaic household split machine is reduced, and the system harmonic suppression capability is enhanced. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a single-phase photovoltaic direct current component suppression structure diagram of bus ripple detection according to the embodiment of the present application; Figure 2 It is a full-bridge topology structure diagram of single-phase LCL filtering according to the embodiment of the present application; Figure 3 It is a conventional single-phase phase-locked loop structure diagram according to the embodiment of the present application; Figure 4 It is an improved single-phase phase-locked loop structure block diagram according to the embodiment of the present application. DETAILED DESCRIPTION

[0020] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described clearly and completely below in conjunction with the accompanying drawings of the embodiments of the present application. The described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the spirit of the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the protection scope of the present application.

[0021] Embodiment 1 of the present application provides a direct current component suppression method, comprising primary compensation of a direct current component in grid-connected voltage and secondary compensation of the direct current component.

[0022] The primary compensation of the direct current component comprises, as shown in the figure, Figure 1 a bus ripple detection circuit is built on the DC side of a single-phase inverter to obtain bus ripple sampling results ; As shown in the figure, Figure 2 the direct current component reference value is calculated from the bus ripple sampling results ; the grid-connected direct current component is calculated from the DC bus voltage ; the direct current component reference value is subtracted from the grid-connected direct current component to obtain a direct current component tracking error, and the direct current component tracking error is subjected to PI controller to obtain a current for compensation ; the reference current is subtracted from the actual grid-connected current to obtain a grid-connected current error value ; the grid-connected current error value is subjected to current PI controller to obtain an output value, the grid voltage is subjected to a feedforward function to obtain an output value, and the capacitor current is multiplied by a feedback coefficient to obtain a duty cycle of the control signal, and the SPWM is subjected to inverter control to realize the primary compensation of the direct current component.

[0023] Preferably but not limitatively, in a single-phase LCL filtered full-bridge topology, the grid-connected current peak value and the grid voltage peak value are sampled, and the grid-connected inverter output current is expressed by the following formula:

[0024] In the formula, is the grid-connected inverter output current, is the direct current component contained in the grid-connected current, AC component contained in grid current; The fundamental component of grid current can be expressed as The grid voltage can be expressed as Combining the above equations, the instantaneous power of grid-connected inverter can be expressed as

[0025] In steady state condition, and are fixed values, and remains unchanged in one power frequency cycle, and is replaced, then the pulsating power of grid-connected inverter output can be expressed as

[0026] If the pulsating power is completely absorbed by bus capacitance , the steady-state value of DC bus voltage is , and the theoretical value of bus voltage ripple is , then the pulsating power can be expressed by the bus voltage ripple as

[0027] The integral of the bus voltage ripple is:

[0028] In the formula: ; ; As can be seen, the DC component of grid current is only related to in ideal conditions, and through integral processing, the 2 times frequency ripple component in the DC bus can be eliminated, and the 1 times frequency ripple component can be extracted, and further the theoretical value of bus voltage ripple is obtained by integrating the grid AC power cycle T to obtain the average voltage of the DC bus :

[0029] Substituting the above into the above formula, the proportional coefficient can be calculated as

[0030] The value of grid DC component is calculated by and . Those skilled in the art can know that using the same algorithm, the measured value Get the grid-connected direct current component reference value , combined Figure 1 The system block diagram, can realize once reject part direct current component purpose.

[0031] The secondary compensation of the direct current component includes phase tracking of the grid voltage by the second-order generalized integrator phase-locked loop with frequency adaptive phase-locked loop, obtaining the sine value of the grid voltage phase;The sine value is multiplied by the alternating current signal output by the inverter to the grid to generate a phase-synchronous current modulation signal;The difference between the current and the actual grid-connected current is added to obtain a compensation signal, and the duty cycle of the inverter is adjusted to realize secondary compensation of the direct current component.

[0032] As Figure 2 shown, the grid voltage The sine value of the grid voltage phase is obtained by SOGI-PLL with frequency adaptive phase-locked loop (FLL), multiplied by the alternating current, and added to the reference current and the actual grid-connected current The difference between the grid current error value is obtained, and the secondary compensation of the direct current component is realized.

[0033] Embodiment 2 of the application provides a photovoltaic air conditioner, which runs a direct current component suppression method as described in embodiment 1, comprising: an inverter, a photovoltaic module.

[0034] As Figure 1 shown, the inverter converts the direct current generated by the photovoltaic module into alternating current required by the air conditioner, comprising: full-bridge circuit, LCL filter circuit, bus ripple detection circuit, second-order generalized integral phase-locked loop circuit;The direct current side of the full-bridge circuit is connected with the bus ripple detection circuit, and the alternating current side is connected with the LCL filter circuit. Preferably but not limitedly, the upper bridge arm power switch tube S1, power switch tube S3 and lower bridge arm power switch tube S2, power switch tube S4 of the full-bridge circuit are alternately turned on, and the bus voltage The positive and negative alternating voltage is generated on the output side of the full-bridge circuit. When the voltage output by the full-bridge circuit passes through the LCL filter circuit, according to Kirchhoff's current law, the output current of the full-bridge circuit will be shunted to the filter capacitor branch where the filter capacitor C of the LCL filter circuit is located to obtain and the grid-side inductor L2 branch where the grid-side inductor L2 of the LCL filter circuit is located to obtain , where the high-frequency harmonic components preferentially pass through the filter capacitor branch due to the low impedance characteristics of the capacitor, thereby achieving effective filtering of the high-frequency harmonics.

[0035] As one of the outstanding essential features of the present invention, the bus ripple detection circuit is connected to the full-bridge circuit, and the bus ripple detection circuit includes: a high-frequency transformer, a high-pass filter, and an operational amplifier. Specifically, the high-frequency transformer can not only play an isolation role but also perform a voltage divider role. The high-pass filter passes the high-frequency ripple signal and suppresses the interference of the low-frequency signal. The high-frequency ripple signal outputs the sampling result of the bus ripple through the operational amplifier.

[0036] The second-order generalized integrator phase-locked loop circuit includes a second-order generalized integrator (SOGI), a frequency-locked controller (FLL), and a phase-locked controller (PLL). The output of the frequency-locked controller is connected to the center frequency adjustment terminal of the second-order generalized integrator to adjust the center frequency of the second-order generalized integrator for frequency adaptive tracking.

[0037] like Figure 3 The figure shows the structure of a traditional single-phase phase-locked loop (PLL). In a grid-connected inverter system, the inverter output current and the grid voltage must always maintain the same phase. The PLL needs to quickly and accurately detect the phase and frequency information of the grid voltage and generate a reference signal synchronized with it. The traditional single-phase PLL includes a phase detector (PD), a loop filter (LF), and a voltage-controlled oscillator (VCO). The phase detector is used to compare the phase difference between the input signal (i.e., the grid voltage) and the output signal (i.e., the PLL feedback signal) in real time, and output a signal containing phase error information. , Usually contains high frequency AC components. The loop filter uses a low-pass filter or proportional integral (PI) controller to effectively filter out the output signal by setting the cut-off frequency or control parameters. The voltage-controlled oscillator adjusts the output frequency according to the filtered error signal, and ultimately generates an AC signal that is phase-synchronized with the grid voltage, thereby achieving accurate tracking of the inverter output current and the grid voltage.

[0038] like Figure 4 As shown, a filtering process is added to the phase detector of the traditional phase-locked loop to achieve the purpose of eliminating DC components and enhancing harmonic components. As one of the outstanding essential features of the present invention, in order to tune the center frequency of the second-order generalized integrator and avoid the influence of frequency deviation on the output frequency and phase of the phase-locked controller, the frequency-locked controller is added in the later stage to realize the frequency adaptation function.

[0039] Preferably, but not limited to, the input signal in the conventional second-order generalized integrator is To two output signals 、 The transfer function is:

[0040] Where: s is the Laplace operator; 、 、 is the set system gain; is the grid angular frequency.

[0041] When the grid frequency fluctuates, in order to avoid the influence of frequency deviation on the phase-locked output frequency and phase, the frequency-locked controller is added on this basis to realize the frequency adaptive function of the phase-locked loop and adjust the input signal. To the error signal Write the transfer function:

[0042] Defining the Error Signal With output signal The ratio is ,make ,but , so we can get that when hour, , the error signal is in phase with the output signal, and vice versa, so by introducing a negative gain coefficient , after a finite time, the error signal can be adjusted to zero.

[0043] Embodiment 3 of the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is loaded into the processor, a DC component suppression method according to embodiment 1 is implemented.

[0044] Embodiment 4 of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the method for suppressing a DC component according to embodiment 1 is implemented.

[0045] It is worth noting that in the embodiments of the present invention, "steps + numbers" are only a way of expressing a photovoltaic air conditioner and its DC component suppression method, electronic device, and medium specific implementation method, rather than an absolute restriction on the sequence of each step. Under the guidance of the core concept of the present invention, changing the order of implementing these steps to obtain the same or similar technical effects falls within the scope of the present invention.

[0046] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application but not to limit it, and although the present application has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that the specific embodiments of the present application can be modified or replaced equivalently without departing from the spirit and scope of the present application, and any modification or equivalent replacement without departing from the spirit and scope of the present application should be covered in the protection scope of the claims of the present application.

Claims

1. A DC component suppression method, characterized in that: The following steps are involved: Build a bus ripple detection circuit on the DC side of the single-phase inverter to obtain the bus ripple sampling results ; Perform primary compensation of the DC component in the grid-connected voltage, including based on the bus ripple sampling result The DC bus voltage is collected , generates current for compensation through error calculation and PI regulation ; The current The actual grid-connected current collected Subtract and get the grid-connected current error value , the grid-connected current error value After PI regulation and compounding with the grid voltage feedforward signal and capacitor current feedback signal, a duty cycle signal is generated, which drives the inverter through SPWM modulation; The secondary compensation of the DC component is performed, including the grid voltage is compensated by a second-order generalized integrator phase-locked loop with a frequency adaptive phase-locked loop. Perform phase tracking to obtain a sine value of the grid voltage phase; multiply the sine value by the AC current signal output by the inverter to the grid to generate a phase-synchronized current modulation signal; Compare it with the current The actual grid current The difference between the two is added to obtain a compensation signal, and the duty cycle of the inverter is adjusted to achieve secondary compensation of the DC component.

2. A DC component suppression method according to claim 1, It is characterized by: Based on the bus ripple sampling result The DC bus voltage is collected , generates current for compensation through error calculation and PI regulation include: According to the bus ripple sampling results Calculate the DC component reference value and through the DC bus voltage Calculate the grid-connected DC component ; The DC component reference value With the grid-connected DC component Subtract the DC component tracking error, and the DC component tracking error is passed through the PI controller Processing, generating current for compensation .

3. A DC component suppression method according to claim 1, It is characterized by: The grid-connected current error value After PI regulation and compounding with the grid voltage feedforward signal and capacitor current feedback signal, the duty cycle signal is generated, including: The grid-connected current error value Current PI controller The first control value output, grid voltage Feedforward function The second control value of the output, and the capacitor current The third control values ​​multiplied by the feedback coefficient are added to generate a duty cycle control signal.

4. A DC component suppression method according to claim 2, It is characterized by: The DC bus voltage Calculate the grid-connected DC component include: The theoretical value of bus ripple voltage is expressed as follows: Where: is the theoretical value of bus ripple voltage; is the peak value of the grid voltage; is the peak value of the grid-connected current; is the grid angular frequency; is the grid-connected DC component; is the bus capacitance; is the steady-state value of the DC bus voltage; set up , ; The theoretical value of the bus ripple voltage The average DC bus voltage is obtained by integrating the AC power cycle T of the grid : Based on the above formula, we can get and grid-connected DC component The proportionality factor , expressed as follows: The average voltage of the DC bus and the proportionality coefficient The grid-connected DC component is obtained .

5. A DC component suppression method according to claim 1, characterized in that ； The second-order generalized integrator phase-locked loop with a frequency adaptive phase-locked loop dynamically adjusts the center frequency by real-time detection of the orthogonal signal components output by the second-order generalized integrator.

6. A photovoltaic air conditioner, characterized in that: include: An inverter and a photovoltaic module, performing a DC component suppression method according to any one of claims 1 to 5; The inverter includes: a full-bridge circuit, an LCL filter circuit, a bus ripple detection circuit, and a second-order generalized integral phase-locked loop circuit. The DC side of the full-bridge circuit is connected to the bus ripple detection circuit, and the AC side is connected to the LCL filter circuit. The inverter converts the DC power generated by the photovoltaic module into AC power.

7. A photovoltaic air conditioner according to claim 6, characterized in that ； The bus ripple detection circuit includes: a high-frequency transformer, a high-pass filter, and an operational amplifier; The high-frequency transformer is used for electrical isolation and voltage division of the bus voltage; The high-pass filter is connected to the output end of the high-frequency transformer and is used to pass the ripple signal of the set frequency; The operational amplifier is connected to the output end of the high-pass filter and is used to amplify the ripple signal of the set frequency and output the bus ripple sampling result.

8. The photovoltaic air conditioner according to claim 6, characterized in that: The second-order generalized integrator phase-locked loop circuit includes: a second-order generalized integrator and a frequency-locked controller; The output end of the frequency-locked controller is connected to the center frequency adjustment end of the second-order generalized integrator, and is used to adjust the center frequency of the second-order generalized integrator to achieve frequency adaptive tracking.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the computer program is loaded into a processor, the DC component suppression method according to any one of claims 1 to 5 is implemented.

10. A computer-readable storage medium storing a computer program, wherein: When the computer program is executed by a processor, the DC component suppression method according to any one of claims 1 to 5 is implemented.

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