Analog multiplier substitution circuit suitable for photovoltaic module power calculation

Abstract

The invention relates to the field of distributed photovoltaic power generation, and aims to provide an analog multiplier replacement circuit suitable for photovoltaic module power calculation. The circuit comprises a carrier generation circuit, a sampling voltage and current modulation circuit and a power calculation demodulation circuit, the carrier generation circuit comprises a direct-current voltage source, a second capacitor, a second resistor and a first analog switch, the sampling voltage and current modulation circuit comprises a first comparator and a second comparator, and the power calculation demodulation circuit comprises a first capacitor, a second analog switch, a third analog switch, a fourth analog switch and two resistors with the same resistance value; and the non-grounding end of the first capacitor outputs a voltage-to-ground signal, and the voltage-to-ground signal is transmitted to the MPPT analog control circuit as an equivalent value for calculating the current power of the photovoltaic module. According to the invention, an expensive analog multiplier chip in an existing control mode can be omitted, and the system cost is reduced; the method is not influenced by zero drift, temperature drift and the like of an active device, is higher in sampling calculation precision, and facilitates the improvement of control stability.

Description

Technical Field

[0001] The present invention relates to the field of distributed photovoltaic power generation, and more particularly to an analog multiplier replacement circuit suitable for photovoltaic module power calculation. Background Art

[0002] PV module-level power electronic converters, represented by microinverters and power optimizers, have become a vital component of distributed photovoltaic power generation systems due to their advantages of refined power management, ease of installation and maintenance, and safety and reliability. With increasingly stringent safety regulations for distributed photovoltaic power generation and the accelerated promotion of the photovoltaic building industry, their application is becoming increasingly widespread. However, the high per-watt power generation cost of existing distributed photovoltaic power generation equipment remains a major constraint to its large-scale deployment. In addition to optimizing the device's circuit structure, control strategy, power switching devices, and magnetic components, reducing the high price and functional redundancy associated with general-purpose CNC chips and their peripheral circuits is also an important way to reduce costs and increase efficiency.

[0003] Dedicated analog chips are the product of analog circuit design and integration based on specific application scenarios. Due to their limited process constraints and ability to maximize the use of hardware resources, they can effectively reduce system costs. Maximum power point tracking (MPPT) is an important part of improving power generation revenue for power electronic converters at the photovoltaic module level, and the technology is currently relatively mature. If analog circuits are used for control, analog multipliers are required to implement photovoltaic module power sampling. In existing technologies, analog multipliers are usually implemented based on Gilbert cells and their improved structures. Such solutions are expensive due to their extremely high process requirements, which limits the promotion and application of analog multipliers in photovoltaic maximum power tracking analog control solutions.

[0004] Therefore, the present invention proposes a newly designed analog multiplier replacement circuit to meet the demand for developing high-performance, low-cost dedicated analog chips for photovoltaic converters. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide an analog multiplier replacement circuit suitable for photovoltaic module power calculation.

[0006] To solve the technical problem, the solution of the present invention is:

[0007] Provided is an analog multiplier replacement circuit suitable for photovoltaic module power calculation, comprising a carrier generation circuit, a sampling voltage and current modulation circuit, and a power calculation and demodulation circuit; wherein,

[0008] The carrier generating circuit includes a DC voltage source V d , a second capacitor C2, a second resistor R2 and a first analog switch S1; a DC voltage source Vd The negative electrode of the capacitor is grounded, and the positive electrode thereof is connected to one end of the first analog switch S1; a second capacitor C2 is connected in parallel with the second resistor R2, one end of which is grounded, and the other end is connected to the other end of the first analog switch S1; a narrow pulse signal from the timer acts on the first analog switch S1 to control the charging and discharging of the second capacitor C2, and the voltage signal relative to the ground at the upper end of the second capacitor C2 is used as the output carrier waveform;

[0009] The sampling voltage and current modulation circuit includes a first comparator OPA1 and a second comparator OPA2; wherein the comparator OPA1 has a non-inverting input terminal connected to the output carrier waveform, an inverting input terminal connected to the sampled voltage at the output terminal of the photovoltaic cell, and a voltage signal relative to the ground at its output terminal as a first modulation waveform; the second comparator OPA2 has a non-inverting input terminal connected to the sampled current at the output terminal of the photovoltaic cell, an inverting input terminal connected to the output carrier waveform, and a voltage signal relative to the ground at its output terminal as a second modulation waveform;

[0010] The power calculation and demodulation circuit includes a first capacitor C1, a second analog switch S2, a third analog switch S3, and a fourth analog switch S4, as well as a first resistor R1 and a third resistor R3 with the same resistance value; wherein the third analog switch S3 and the first resistor R1, and the fourth analog switch S4 and the third resistor R3 respectively form a series branch, which are then arranged in parallel; one end of the first capacitor C1, the third analog switch S3, and the fourth analog switch S4 are connected to the ground, the other ends of the first capacitor C1, the first resistor R1, and the third resistor R3 are connected in parallel to the second analog switch S2, and the other end of the second analog switch S2 is connected to the DC voltage source V in the carrier generation circuit. d The positive electrode of the first capacitor C1 is connected to the positive electrode of the second analog switch S2; the second analog switch S3 and the fourth analog switch S4 are respectively connected to the narrow pulse signal, the first modulated waveform and the second modulated waveform also from the timer to realize switch control; the non-grounded end of the first capacitor C1 outputs a voltage signal to the ground, which is transmitted to the external MPPT analog control circuit as the equivalent value of the current power calculation of the photovoltaic module.

[0011] As a preferred solution of the present invention, the first capacitor C1 and the second capacitor C2 are ceramic chip capacitors or film capacitors.

[0012] As a preferred solution of the present invention, the first analog switch S1 , the second analog switch S2 , the third analog switch S3 and the fourth analog switch S4 are transistors or MOSFET switches.

[0013] As a preferred solution of the present invention, the first resistor R1, the second resistor R2 and the third resistor R3 are chip resistors or metal film resistors.

[0014] As a preferred solution of the present invention, the first comparator OPA1 and the second comparator OPA2 are voltage comparators.

[0015] The present invention further provides a photovoltaic power generation system that uses an analog multiplier replacement circuit to realize photovoltaic module power calculation, the system includes a photovoltaic cell, a power electronic converter and a load, as well as a peripheral sampling circuit, an MPPT analog control circuit and the aforementioned analog multiplier replacement circuit; wherein,

[0016] The sampling port of the peripheral sampling circuit is set at the output end of the photovoltaic cell, and its output end is connected to the analog multiplier replacement circuit to transmit the voltage and current signals obtained by sampling; the output end of the analog multiplier replacement circuit is connected to the MPPT analog control circuit to transmit the equivalent value used for calculating the current power of the photovoltaic component; the output end of the MPPT analog control circuit is connected to the switching tube of the power circuit in the power electronic converter to transmit the driving signal used to adjust the working state of the converter, and then control the power circuit to achieve maximum power point tracking of the photovoltaic component.

[0017] As a preferred solution of the present invention, the photovoltaic cell includes at least one group of photovoltaic power generation units.

[0018] As a preferred solution of the present invention, the power circuit is a DC-DC power circuit or a DC-AC power circuit.

[0019] As a preferred solution of the present invention, the MPPT analog control circuit is composed of a basic logic gate circuit and an operational amplifier circuit.

[0020] Description of the invention principle:

[0021] The Gilbert cell is a four-port circuit widely used in modulation, demodulation, mixer design, and other fields for its ability to perform analog multiplication. Existing analog multiplier chips based on traditional Gilbert cells require a large number of transistors to amplify, modulate, and calculate sampled analog signals. This leads to the risk of zero-point drift and temperature drift during the transistor-based signal feedback process. Improvements to the Gilbert cell, designed to achieve high linearity and low temperature drift, are limited by the manufacturing process, resulting in high modification costs.

[0022] Unlike existing technologies, this invention innovatively modulates the sampled analog signal into a digital signal and then demodulates it back into an analog output signal. A narrow pulse signal from a timer, a first modulation waveform, and a second modulation waveform are used to control the three switches in the demodulation circuit. Furthermore, the ground voltage signal output from the non-grounded terminal of the first capacitor C1 in the demodulation circuit is transmitted to the external MPPT analog control circuit as the equivalent value for calculating the current power of the photovoltaic module. This process eliminates the need for a large number of transistors, making the entire calculation process significantly less susceptible to interference.

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

[0024] 1. The present invention realizes the calculation of photovoltaic module output power in the analog control scheme of photovoltaic power electronic converter, which can eliminate the expensive analog multiplier chip in the existing control method and reduce the system control cost;

[0025] 2. The circuit unit used in the present invention is not affected by zero-point drift and temperature drift of active devices, and has higher sampling and calculation accuracy, which is conducive to improving control stability;

[0026] 3. The present invention lays the foundation for further integration of analog control solutions into dedicated control chips, which is conducive to further reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the photovoltaic module structure and its control using power electronic converter.

[0028] Figure 2 The specific topology of the analog multiplier replacement circuit used for photovoltaic power calculation in the present invention.

[0029] Figure 3 Schematic diagram of the working timing of the analog multiplier replacement circuit in the present invention.

[0030] Figure 1 Description of reference numerals: 100 is a photovoltaic module and a power electronic converter structure; 200 is a photovoltaic power calculation circuit; 300 is an MPPT simulation control circuit; DETAILED DESCRIPTION

[0031] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0032] like Figure 1As shown, the photovoltaic power generation system in the present invention includes a photovoltaic cell, a power electronic converter and a load, as well as a peripheral sampling circuit, an MPPT analog control circuit, and an analog multiplier replacement circuit; wherein, the sampling port of the peripheral sampling circuit is arranged at the output end of the photovoltaic cell, and its output end is connected to the analog multiplier replacement circuit to transmit the voltage and current signals obtained by sampling; the output end of the analog multiplier replacement circuit is connected to the MPPT analog control circuit to transmit the equivalent value used for calculating the current power of the photovoltaic component; the output end of the MPPT analog control circuit is connected to the switch tube of the power circuit in the power electronic converter to transmit the drive signal for adjusting the working state of the converter, thereby controlling the power circuit to achieve maximum power point tracking of the photovoltaic component.

[0033] As an optional solution, the photovoltaic cell includes at least one group of photovoltaic power generation units; the power circuit can be a DC-DC power circuit or a DC-AC power circuit. The MPPT analog control circuit is composed of a basic logic gate circuit and an operational amplifier circuit.

[0034] In a photovoltaic power generation system based on the aforementioned topology, photovoltaic cells convert DC power to DC or AC power through a power electronic converter, which then supplies power to the load. A peripheral sampling circuit samples the voltage and current at the photovoltaic cell's output port, which serves as the input to an analog multiplier replacement circuit. The equivalent value calculated from the current power of the photovoltaic module output by this circuit serves as the input to the MPPT analog control circuit. The MPPT analog control circuit generates drive signals for each switch in the power electronic converter based on logical judgment and closed-loop control, enabling the power electronic converter to track the maximum power of the photovoltaic module.

[0035] like Figure 2 As shown, the analog multiplier replacement circuit proposed in the present invention specifically includes: a carrier generation circuit, a sampling voltage and current modulation circuit, and a power calculation demodulation circuit. The design idea is that first, the carrier generation circuit generates an exponentially changing carrier signal by charging and discharging the capacitor, and then compares the carrier signal with the sampled photovoltaic voltage and current to generate two modulation signals. Finally, the modulation signal acts on the two analog switches of the demodulation circuit, and the voltage value across the internal capacitor is equivalent to the power value of the photovoltaic module. This equivalent value is used as the input of the maximum power point tracking (MPPT) control circuit, and then the DC-DC circuit or DC-AC circuit is controlled to achieve maximum power point tracking of the photovoltaic module. Specifically, it refers to

[0036] The carrier generation circuit includes: a DC voltage source V d , a second capacitor C2, a second resistor R2 and a first analog switch S1; wherein the DC voltage source V dThe negative terminal is grounded, and its positive terminal is connected to one end of the first analog switch S1; the second capacitor C2 and the second resistor R2 are grounded at one end, and the other end is connected to the other end of the first analog switch S1. The narrow pulse from the timer acts on the first analog switch S1 to control the charging and discharging of the second capacitor C2. The voltage waveform of the upper end of the second capacitor C2 to ground serves as the output carrier waveform. The specific parameters of the narrow pulse are determined by the rise speed of the modulation signal, and its positive pulse width is controlled in the range of 0.01 to 0.1T. mpp , T mpp Refers to the disturbance period of the MPPT analog control circuit.

[0037] The sampling voltage and current modulation circuit includes: a first comparator OPA1 and a second comparator OPA2; wherein the first comparator OPA1 receives the output carrier waveform of the carrier generation circuit at the same direction end, and receives the photovoltaic cell sampling voltage V from the peripheral sampling circuit at the reverse direction end. pv The output terminal of the first comparator OPA1 uses the ground voltage signal as the first modulation waveform, which acts on the third analog switch S3 of the demodulation circuit. The same-direction terminal of the second comparator OPA2 receives the photovoltaic cell sampling current I from the peripheral sampling circuit. pv The reverse end receives the output carrier waveform of the carrier generation circuit. The output end of the second comparator OPA2 uses the ground voltage signal as the second modulation waveform to act on the fourth analog switch S4 of the demodulation circuit.

[0038] The power calculation and demodulation circuit includes: two first resistors R1 and third resistors R3 with the same resistance value, as well as a first capacitor C1, a second analog switch S2, a third analog switch S3, and a fourth analog switch S4; wherein, one end of the first capacitor C1, the third analog switch S3, and the fourth analog switch S4 are connected to the ground, and the other ends of the third analog switch S3 and the fourth analog switch S4 are connected to one end of the first resistor R1 and the third resistor R3 respectively. The other end of the first capacitor C1 and the other ends of the first resistor R1 and the third resistor R3 are simultaneously connected to one end of the second analog switch S2, and the other end of the second analog switch S2 is connected to the DC voltage source V in the carrier generation circuit. d The third analog switch S3 and the fourth analog switch S4 are controlled by the signals output by comparators OPA1 and OPA2 in the modulation circuit, respectively. The second analog switch S2 is controlled by the same narrow pulse signal in the carrier generation circuit. The non-grounded terminal of the first capacitor C1 outputs a voltage signal relative to ground, which is used as the equivalent value of the current power calculation of the photovoltaic module and output to the next-level MPPT analog control circuit.

[0039] Figure 3The figure shows the changes in the signals of each analog switch and the voltage waveform across the first capacitor C1 during the normal operation of the analog multiplier replacement circuit. The following describes how the analog multiplier replacement circuit specifically implements the photovoltaic module power calculation process in conjunction with this figure:

[0040] The first analog switch S1 and the second analog switch S2 are driven by the same narrow pulse signal from the timer, and are used to periodically control the reset of the first capacitor C1 and the charge and discharge of the second capacitor C2. Therefore, when the first analog switch S1 and the second analog switch S2 are closed during the time [t0, t1], the first capacitor C1 and the second capacitor C2 reach the steady-state voltage value V d When the first analog switch S1 and the second analog switch S2 are disconnected during the time [t1, t4], the second capacitor C2 is discharged through the second resistor R2. The voltage across the second capacitor C2 is u c2 (t), the voltage signal to ground (also called carrier signal) as the output carrier waveform can be expressed as:

[0041]

[0042] Wherein, τ2=R2C2 represents the charge and discharge time constant; R2 and C2 respectively represent the resistance value of the second resistor R2 and the capacitance value of the second capacitor C2; and e represents the natural logarithm.

[0043] In the sampling voltage and current modulation circuit, the voltage and current signals of the sampled photovoltaic module output end are compared with the carrier signal. If they are lower than the carrier signal, they are set to a high level, otherwise they are set to a low level, and the pulse widths are T r1 +t1 and T r2 The modulated signal of +t1 acts on the third analog switch S3 and the fourth analog switch S4 respectively.

[0044] Then we have:

[0045]

[0046] Among them, T r1 and T r2 Refers to the modulation signal amplitude dropping to V pv , I pv Time required. pv Refers to the photovoltaic cell sampling voltage; I pv Refers to the photovoltaic cell sampling current.

[0047] During the time [t1, t2], the third analog switch S3 is turned on, and during the time [t1, t3], the fourth analog switch S4 is turned on, and the first capacitor C1 is discharged through the first resistor R1; during the time [t3, t4], the third analog switch S3 and the fourth analog switch S4 are turned off, and the voltage across the first capacitor C1 remains unchanged. The steady-state voltage u c1 (t) can be expressed as:

[0048]

[0049] Among them, τ1=R1C1, which represents the charge and discharge time constant.

[0050] Design the circuit parameters so that τ1=τ2, and change the T r1 and T r2 Substituting the above formula, we can get the voltage value u of the first capacitor C1 in steady state: c1 (t):

[0051]

[0052] Among them, P pv Refers to the sampled PV module power value.

[0053] From the above expression, we can see that the steady-state voltage value u c1 (t) is proportional to the power of the photovoltaic module, so the voltage signal can be output as the power calculation value to the MPPT circuit to achieve maximum power point tracking.

[0054] In summary, the present invention calculates the power of photovoltaic modules by modulating and then demodulating the sampled signal, avoiding the use of expensive analog multiplier chips, and thus helping to further reduce the cost of photovoltaic systems.

[0055] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. An analog multiplier replacement circuit suitable for photovoltaic module power calculation, characterized in that: It includes a carrier generation circuit, a sampling voltage and current modulation circuit and a power calculation and demodulation circuit; wherein, The carrier generating circuit includes a DC voltage source V d , a second capacitor C2, a second resistor R2 and a first analog switch S1; a DC voltage source V d The negative electrode of the capacitor is grounded, and the positive electrode thereof is connected to one end of the first analog switch S1; a second capacitor C2 is connected in parallel with the second resistor R2, one end of which is grounded, and the other end is connected to the other end of the first analog switch S1; a narrow pulse signal from the timer acts on the first analog switch S1 to control the charging and discharging of the second capacitor C2, and the voltage signal relative to the ground at the upper end of the second capacitor C2 is used as the output carrier waveform; The sampling voltage and current modulation circuit includes a first comparator OPA1 and a second comparator OPA2; wherein the comparator OPA1 has a non-inverting input terminal connected to the output carrier waveform, an inverting input terminal connected to the sampled voltage at the output terminal of the photovoltaic cell, and a voltage signal relative to the ground at its output terminal as a first modulation waveform; the second comparator OPA2 has a non-inverting input terminal connected to the sampled current at the output terminal of the photovoltaic cell, an inverting input terminal connected to the output carrier waveform, and a voltage signal relative to the ground at its output terminal as a second modulation waveform; The power calculation and demodulation circuit includes a first capacitor C1, a second analog switch S2, a third analog switch S3, and a fourth analog switch S4, as well as a first resistor R1 and a third resistor R3 with the same resistance value; wherein the third analog switch S3 and the first resistor R1, and the fourth analog switch S4 and the third resistor R3 respectively form a series branch, which are then arranged in parallel; one end of the first capacitor C1, the third analog switch S3, and the fourth analog switch S4 are connected to the ground, the other ends of the first capacitor C1, the first resistor R1, and the third resistor R3 are connected in parallel to the second analog switch S2, and the other end of the second analog switch S2 is connected to the DC voltage source V in the carrier generation circuit. d The positive electrode of the first capacitor C1 is connected to the positive electrode of the second analog switch S2; the second analog switch S3 and the fourth analog switch S4 are respectively connected to the narrow pulse signal, the first modulated waveform and the second modulated waveform also from the timer to realize switch control; the non-grounded end of the first capacitor C1 outputs a voltage signal to the ground, which is transmitted to the external MPPT analog control circuit as the equivalent value of the current power calculation of the photovoltaic module.

2. The analog multiplier replacement circuit according to claim 1, wherein: The first capacitor C1 and the second capacitor C2 are ceramic chip capacitors or film capacitors.

3. The analog multiplier replacement circuit according to claim 1, wherein: The first analog switch S1 , the second analog switch S2 , the third analog switch S3 and the fourth analog switch S4 are transistors or MOSFET switches.

4. The analog multiplier replacement circuit according to claim 1, wherein: The first resistor R1 , the second resistor R2 and the third resistor R3 are chip resistors or metal film resistors.

5. The analog multiplier replacement circuit according to claim 1, wherein: The first comparator OPA1 and the second comparator OPA2 are voltage comparators.

6. A photovoltaic power generation system that uses an analog multiplier to replace a circuit to realize photovoltaic module power calculation, the system includes a photovoltaic cell, a power electronic converter and a load, characterized in that: The system further comprises a peripheral sampling circuit, an MPPT analog control circuit, and the analog multiplier replacement circuit as described in any one of claims 1 to 5; wherein, The sampling port of the peripheral sampling circuit is set at the output end of the photovoltaic cell, and its output end is connected to the analog multiplier replacement circuit to transmit the voltage and current signals obtained by sampling; the output end of the analog multiplier replacement circuit is connected to the MPPT analog control circuit to transmit the equivalent value used for calculating the current power of the photovoltaic component; the output end of the MPPT analog control circuit is connected to the switching tube of the power circuit in the power electronic converter to transmit the driving signal used to adjust the working state of the converter, and then control the power circuit to achieve maximum power point tracking of the photovoltaic component.

7. The system according to claim 6, characterized in that The photovoltaic cell includes at least one group of photovoltaic power generation units.

8. The system according to claim 6, wherein: The power circuit is a DC-DC power circuit or a DC-AC power circuit.

9. The system according to claim 6, wherein: The MPPT analog control circuit is composed of a basic logic gate circuit and an operational amplifier circuit.

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