A decoupling circuit and method

Abstract

The present invention relates to a decoupling circuit and method, and to the field of solar photovoltaic power generation technology. The decoupling circuit includes: one end of a decoupling inductor is connected to a first end of an inverter AC output side, the other end of the decoupling inductor is connected to an emitter of a first switch tube, a collector of the first switch tube is connected to an emitter of a second switch tube, and a collector of the second switch tube is connected to a positive electrode of a first decoupling capacitor; a collector of a third switch tube is connected to a collector of the first switch tube, and an emitter of the third switch tube is connected to a negative electrode of a second decoupling capacitor; a collector of a fourth switch tube is connected to a collector of the first switch tube, and an emitter of the fourth switch tube is connected to an emitter of a fifth switch tube, and the negative electrode of the first decoupling capacitor, the positive electrode of the second decoupling capacitor, and the collector of the fifth switch tube are all connected to a second end of the inverter AC output side. The decoupling circuit of the present invention is an independent decoupling, and is connected in parallel to the AC side of the inverter, and only five switch tubes are used, simplifying the double frequency power decoupling circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of solar photovoltaic power generation, and in particular to a decoupling circuit and method. Background Art

[0002] Single-phase inverters are commonly used in small and medium power applications, but the secondary pulsating power generated on the AC side will cause secondary ripples on the DC side. The existence of secondary ripples, especially in photovoltaic (PV) systems, will affect the working efficiency of PV panels and reduce the effect of maximum power point tracking (MPPT). In order to solve the problem of secondary ripple decoupling, the academic community generally proposes two methods, active power decoupling method and passive power decoupling method. The passive power decoupling method mainly adds passive devices to the photovoltaic system, such as adding large electrolytic capacitors on the DC side. Large electrolytic capacitors are used to buffer the secondary ripple energy. The large capacitance provided by large electrolytic capacitors is indeed very effective, but usually large electrolytic capacitors have a short service life, which affects the average service life of single-phase inverters. The situation of single-phase inverters is even more unsatisfactory under high temperature conditions. In addition, large electrolytic capacitors will cause the entire photovoltaic system to be too large, the cost will be relatively high, and the power density will be reduced.

[0003] In this regard, people have explored several active decoupling methods. Generally, active decoupling is to transfer the pulsating ripple on the DC side to other energy storage elements, making the voltage and current on the DC side more stable, so that long-life film capacitors can be used instead of electrolytic capacitors. This method mainly consists of new topological decoupling and control algorithms. For example, the AC side voltage is introduced into a low-frequency transformer and connected to a decoupling capacitor after rectification, but the entire system is complex and has large losses. Therefore, the active decoupling circuit of the existing single-phase inverter has the problem of complex decoupling circuit. Summary of the invention

[0004] The purpose of the present invention is to provide a decoupling circuit and method, which solves the problem of complex decoupling loop of the active decoupling circuit of the existing single-phase inverter.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A decoupling circuit includes: a decoupling inductor, a first switch tube, a second switch tube, a first decoupling capacitor, a third switch tube, a second decoupling capacitor, a fourth switch tube and a fifth switch tube;

[0007] One end of the decoupling inductor is connected to a first end of the AC output side of the inverter in the photovoltaic system, the other end of the decoupling inductor is connected to the emitter of the first switch tube, the collector of the first switch tube is connected to the emitter of the second switch tube, the collector of the second switch tube is connected to the positive electrode of the first decoupling capacitor, and the negative electrode of the first decoupling capacitor is connected to the second end of the AC output side of the inverter;

[0008] The collector of the third switch tube is connected to the collector of the first switch tube, the emitter of the third switch tube is connected to the negative electrode of the second decoupling capacitor, and the positive electrode of the second decoupling capacitor is connected to the second end of the AC output side of the inverter;

[0009] The collector of the fourth switch tube is connected to the collector of the first switch tube, the emitter of the fourth switch tube is connected to the emitter of the fifth switch tube, and the collector of the fifth switch tube is connected to the second end of the AC output side of the inverter.

[0010] Optionally, the decoupling circuit further includes: a first diode, a second diode, a third diode, a fourth diode and a fifth diode;

[0011] The anode of the first diode is connected to the emitter of the first switch tube, and the cathode of the first diode is connected to the collector of the first switch tube;

[0012] The anode of the second diode is connected to the emitter of the second switch tube, and the cathode of the second diode is connected to the collector of the second switch tube;

[0013] The anode of the third diode is connected to the emitter of the third switch tube, and the cathode of the third diode is connected to the collector of the third switch tube;

[0014] The anode of the fourth diode is connected to the emitter of the fourth switch tube, and the cathode of the fourth diode is connected to the collector of the fourth switch tube;

[0015] The anode of the fifth diode is connected to the emitter of the fifth switch tube, and the cathode of the fifth diode is connected to the collector of the fifth switch tube.

[0016] Optionally, the decoupling circuit further includes: a control device;

[0017] The control device is respectively connected to the base of the first switch tube, the base of the second switch tube, the base of the third switch tube, the base of the fourth switch tube and the base of the fifth switch tube;

[0018] The control device is used to determine a pulse energy modulation control signal according to the bus voltage of the inverter and the decoupling inductance value of the decoupling inductor using a pulse energy modulation technique, and to control the on and off of the first switch tube, the second switch tube, the third switch tube, the fourth switch tube and the fifth switch tube according to the pulse energy modulation control signal.

[0019] Optionally, the control device specifically includes:

[0020] An acquisition module, used to acquire the AC side output voltage amplitude, AC side output current amplitude and bus voltage of the inverter, as well as the decoupling inductance value of the decoupling inductor and the decoupling capacitor voltage of the decoupling capacitor; the decoupling capacitor is a first decoupling capacitor or a second decoupling capacitor;

[0021] A power coupling relationship determination module, used to determine the power coupling relationship of the decoupling circuit by using the AC side output voltage amplitude and the AC side output current amplitude;

[0022] A pulse energy modulation control signal determination module, used to obtain a pulse energy modulation control signal by using a pulse energy modulation technology according to the bus voltage, the decoupling inductance value, the decoupling capacitor voltage and the power coupling relationship;

[0023] A switch tube state determination module is used to determine the switch state of the switch tube in the decoupling circuit according to the pulse energy modulation control signal, the polarity of the AC side output voltage of the inverter and the operating state of the decoupling capacitor; the switch tube includes a first switch tube, a second switch tube, a third switch tube, a fourth switch tube and a fifth switch tube.

[0024] Optionally, the power coupling relationship determining module specifically includes:

[0025] A power calculation unit, used to obtain the AC side instantaneous power and the DC side input constant power of the inverter by using the AC side output voltage amplitude and the AC side output current amplitude respectively through the following formulas;

[0026]

[0027]

[0028] Where P ac (t) represents the instantaneous power on the AC side of the inverter at time t; U g Indicates the output voltage amplitude of the inverter on the AC side; I g represents the output current amplitude of the inverter on the AC side; ω represents the fundamental angular frequency; t represents time; P PV Indicates that the DC side of the inverter inputs a constant power;

[0029] A power coupling relationship determination unit is used to compare the instantaneous power on the AC side with the constant power input on the DC side to determine the power coupling relationship of the decoupling circuit; the power coupling relationship includes: when the instantaneous power on the AC side is greater than the constant power input on the DC side, the photovoltaic system is in an energy release process, and the decoupling capacitor is in a voltage reduction state; when the instantaneous power on the AC side is less than the constant power input on the DC side, the photovoltaic system is in an energy absorption process, and the decoupling capacitor is in a voltage increase state.

[0030] Optionally, the pulse energy modulation control signal determination module specifically includes:

[0031] A rising decoupling inductor peak reference current determination unit is used to determine the bus voltage, the decoupling inductance value and the power coupling relationship through a formula Obtaining a decoupling inductor peak reference current corresponding to a rise in a decoupling inductor current of the decoupling inductor;

[0032] The decoupling inductor peak reference current determination unit is used to determine the decoupling inductor peak reference current according to the bus voltage, the decoupling inductor value, the decoupling capacitor voltage and the power coupling relationship through the formula Obtaining a decoupling inductor peak reference current corresponding to when the decoupling inductor current decreases;

[0033] Where U DC Indicates bus voltage; L d represents the decoupling inductance value; d represents the duty cycle of the pulse drive switch; T s represents the switching cycle; i dref Indicates the peak reference current of the decoupling inductor; U d represents the decoupling capacitor voltage; d' represents the time proportion of the decoupling inductor current dropping from the peak value to 0 in a single switching cycle;

[0034] A decoupling inductor peak reference current determination unit is used to determine the decoupling inductor peak reference current corresponding to the decoupling inductor current when the decoupling inductor current rises and the decoupling inductor peak reference current corresponding to the decoupling inductor current when the decoupling inductor current falls, using the formula and energy conservation relationship, the decoupling inductor peak reference current of the decoupling circuit in each working mode is obtained; where W in Represents the energy absorbed by the decoupling circuit in a single switching cycle;

[0035] The pulse energy modulation control signal determination unit is used to determine the decoupling inductor peak reference current corresponding to each working mode through the formula The duty cycle of the pulse-driven switch corresponding to each of the working modes is determined; the pulse energy modulation control signal includes the decoupling inductor peak reference current and the duty cycle of the pulse-driven switch corresponding to each of the working modes.

[0036] A decoupling method is applied to the above-mentioned decoupling circuit, and the decoupling method comprises:

[0037] Acquire the AC side output voltage amplitude, AC side output current amplitude and bus voltage of the inverter, as well as the decoupling inductance value of the decoupling inductor and the decoupling capacitor voltage of the decoupling capacitor; the decoupling capacitor is a first decoupling capacitor or a second decoupling capacitor;

[0038] Determining the power coupling relationship of the decoupling circuit by using the AC side output voltage amplitude and the AC side output current amplitude;

[0039] According to the bus voltage, the decoupling inductance value, the decoupling capacitor voltage and the power coupling relationship, a pulse energy modulation control signal is obtained by using a pulse energy modulation technology;

[0040] The switching state of the switch tube in the decoupling circuit is determined according to the pulse energy modulation control signal, the polarity of the AC side output voltage of the inverter and the operating state of the decoupling capacitor; the switch tube includes a first switch tube, a second switch tube, a third switch tube, a fourth switch tube and a fifth switch tube.

[0041] Optionally, the determining the power coupling relationship of the decoupling circuit by using the AC side output voltage amplitude and the AC side output current amplitude specifically includes:

[0042] Using the AC side output voltage amplitude and the AC side output current amplitude, the AC side instantaneous power and the DC side input constant power of the inverter are obtained respectively through the following formulas;

[0043]

[0044]

[0045] Where P ac (t) represents the instantaneous power on the AC side of the inverter at time t; U g Indicates the output voltage amplitude of the inverter on the AC side; I g represents the output current amplitude of the inverter on the AC side; ω represents the fundamental angular frequency; t represents time; P PV Indicates that the DC side of the inverter inputs a constant power;

[0046] The instantaneous power on the AC side is compared with the constant power input on the DC side to determine the power coupling relationship of the decoupling circuit; the power coupling relationship includes: when the instantaneous power on the AC side is greater than the constant power input on the DC side, the photovoltaic system is in an energy release process, and the decoupling capacitor is in a voltage reduction state; when the instantaneous power on the AC side is less than the constant power input on the DC side, the photovoltaic system is in an energy absorption process, and the decoupling capacitor is in a voltage increase state.

[0047] Optionally, obtaining a pulse energy modulation control signal by using a pulse energy modulation technology according to the bus voltage, the decoupling inductance value, the decoupling capacitor voltage and the power coupling relationship specifically includes:

[0048] According to the bus voltage, the decoupling inductance value and the power coupling relationship, the formula Obtaining a decoupling inductor peak reference current corresponding to a rise in a decoupling inductor current of the decoupling inductor;

[0049] According to the bus voltage, the decoupling inductance value, the decoupling capacitor voltage and the power coupling relationship, the formula Obtaining a decoupling inductor peak reference current corresponding to when the decoupling inductor current decreases;

[0050] Where U DC Indicates bus voltage; L d represents the decoupling inductance value; d represents the duty cycle of the pulse drive switch; T s represents the switching cycle; i dref Indicates the peak reference current of the decoupling inductor; U d represents the decoupling capacitor voltage; d' represents the time proportion of the decoupling inductor current dropping from the peak value to 0 in a single switching cycle;

[0051] According to the decoupling inductor peak reference current corresponding to the decoupling inductor current when the decoupling inductor current rises and the decoupling inductor peak reference current corresponding to the decoupling inductor current when the decoupling inductor current decreases, the formula is used. and energy conservation relationship, the decoupling inductor peak reference current of the decoupling circuit in each working mode is obtained; where W in Represents the energy absorbed by the decoupling circuit in a single switching cycle;

[0052] According to the decoupling inductor peak reference current corresponding to each working mode, the formula The duty cycle of the pulse-driven switch corresponding to each of the working modes is determined; the pulse energy modulation control signal includes the decoupling inductor peak reference current and the duty cycle of the pulse-driven switch corresponding to each of the working modes.

[0053] Optionally, determining the switching state of the switch tube in the decoupling circuit according to the pulse energy modulation control signal, the polarity of the AC side output voltage of the inverter and the operating state of the decoupling capacitor specifically includes:

[0054] According to the pulse energy modulation control signal, the polarity of the AC side output voltage of the inverter and the operating state of the decoupling capacitor, the logical relationship formula Determining the switching state of the switch tube in the decoupling circuit;

[0055] In the formula, S1 represents the switching state of the first switch tube; A represents the polarity of the AC side output voltage of the inverter; B represents the operating state of the decoupling capacitor; S2 represents the switching state of the second switch tube; PEM represents the pulse energy modulation control signal; S3 represents the switching state of the third switch tube; S4 represents the switching state of the fourth switch tube; S5 represents the switching state of the fifth switch tube.

[0056] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0057] The present invention provides a decoupling circuit and method. The decoupling circuit includes: a decoupling inductor, a first switch tube, a second switch tube, a first decoupling capacitor, a third switch tube, a second decoupling capacitor, a fourth switch tube and a fifth switch tube; one end of the decoupling inductor is connected to the first end of the AC output side of the inverter in the photovoltaic system, the other end of the decoupling inductor is connected to the emitter of the first switch tube, the collector of the first switch tube is connected to the emitter of the second switch tube, the collector of the second switch tube is connected to the positive electrode of the first decoupling capacitor, and the negative electrode of the first decoupling capacitor is connected to the second end of the AC output side of the inverter; the collector of the third switch tube is connected to the collector of the first switch tube, the emitter of the third switch tube is connected to the negative electrode of the second decoupling capacitor, and the positive electrode of the second decoupling capacitor is connected to the second end of the AC output side of the inverter; the collector of the fourth switch tube is connected to the collector of the first switch tube, the emitter of the fourth switch tube is connected to the emitter of the fifth switch tube, and the collector of the fifth switch tube is connected to the second end of the AC output side of the inverter. The decoupling circuit of the present invention is an independent decoupling, that is, the decoupling circuit has no shared switch with the original inverter circuit part, and is connected in parallel to the AC side of the inverter. Only five switching tubes are used. Compared with the decoupling method of a single-phase inverter connected in parallel to the DC side, the double frequency power decoupling circuit is simplified. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0059] Figure 1 A structural diagram of a decoupling circuit provided by an embodiment of the present invention;

[0060] Figure 2 A power decoupling and energy coupling relationship curve diagram provided by an embodiment of the present invention;

[0061] Figure 3 A schematic diagram of the circuit structure of mode 1 provided in an embodiment of the present invention;

[0062] Figure 4 A schematic diagram of the circuit structure of mode 2 provided by an embodiment of the present invention;

[0063] Figure 5 A schematic diagram of the circuit structure of mode 3 provided in an embodiment of the present invention;

[0064] Figure 6 A schematic diagram of the circuit structure of mode 4 provided in an embodiment of the present invention;

[0065] Figure 7 A flow chart of a decoupling method provided by an embodiment of the present invention;

[0066] Figure 8 A schematic diagram of the PEM signal generation principle provided by an embodiment of the present invention; Figure 8 (a) is the waveform diagram of the inverter output voltage and output current; Figure 8 (b) is a schematic diagram of decoupling inductor current and PEM signal;

[0067] Fig. 9 A schematic diagram of a DC side input current waveform provided by an embodiment of the present invention;

[0068] Fig.10 A schematic diagram of a DC bus voltage waveform provided by an embodiment of the present invention;

[0069] Fig.11 A schematic diagram of a first decoupling capacitor voltage waveform provided by an embodiment of the present invention;

[0070] Fig.12 A schematic diagram of a second decoupling capacitor voltage waveform provided by an embodiment of the present invention;

[0071] Fig.13 A schematic diagram of a decoupling inductor current waveform provided by an embodiment of the present invention;

[0072] Fig.14 A schematic diagram of an AC side load output voltage waveform provided by an embodiment of the present invention;

[0073] Fig.15A schematic diagram of an AC side load output current waveform provided by an embodiment of the present invention.

[0074] Symbol Description: L d , decoupling inductor; D1, first diode; S1, first switch tube; S2, second switch tube; D2, second diode; C d1 , first decoupling capacitor; S3, third switch tube; D3, third diode; C d2 , a second decoupling capacitor; D4, a fourth diode; S4, a fourth switch tube; D5, a fifth diode; S5, a fifth switch tube. DETAILED DESCRIPTION

[0075] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0076] The purpose of the present invention is to provide a decoupling circuit and method, which solves the problem of complex decoupling loops in existing active decoupling circuits.

[0077] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0078] This embodiment provides a decoupling circuit. Figure 1 For a structural diagram of a decoupling circuit provided by an embodiment of the present invention, see Figure 1 , the decoupling circuit includes: decoupling inductor L d , the first switch tube S1, the second switch tube S2, the first decoupling capacitor C d1 , the third switch tube S3, the second decoupling capacitor C d2 , a fourth switch tube S4 and a fifth switch tube S5.

[0079] Decoupling inductor L d One end of the decoupling inductor L is connected to the first end of the AC output side of the inverter in the photovoltaic system. d The other end is connected to the emitter of the first switch tube S1, the collector of the first switch tube S1 is connected to the emitter of the second switch tube S2, and the collector of the second switch tube S2 is connected to the first decoupling capacitor C d1 The positive electrode of the first decoupling capacitor C d1 The negative pole is connected to the second end of the AC output side of the inverter.

[0080] The collector of the third switch tube S3 is connected to the collector of the first switch tube S1, and the emitter of the third switch tube S3 is connected to the second decoupling capacitor C d2 The negative terminal of the second decoupling capacitor C d2 The positive pole is connected to the second end of the AC output side of the inverter.

[0081] The collector of the fourth switch tube S4 is connected to the collector of the first switch tube S1 , the emitter of the fourth switch tube S4 is connected to the emitter of the fifth switch tube S5 , and the collector of the fifth switch tube S5 is connected to the second end of the AC output side of the inverter.

[0082] The decoupling circuit further includes: a first diode D1 , a second diode D2 , a third diode D3 , a fourth diode D4 and a fifth diode D5 .

[0083] An anode of the first diode D1 is connected to the emitter of the first switch tube S1 , and a cathode of the first diode D1 is connected to the collector of the first switch tube S1 .

[0084] The anode of the second diode D2 is connected to the emitter of the second switch tube S2 , and the cathode of the second diode D2 is connected to the collector of the second switch tube S2 .

[0085] An anode of the third diode D3 is connected to the emitter of the third switch tube S3 , and a cathode of the third diode D3 is connected to the collector of the third switch tube S3 .

[0086] An anode of the fourth diode D4 is connected to the emitter of the fourth switch tube S4 , and a cathode of the fourth diode D4 is connected to the collector of the fourth switch tube S4 .

[0087] An anode of the fifth diode D5 is connected to the emitter of the fifth switch tube S5 , and a cathode of the fifth diode D5 is connected to the collector of the fifth switch tube S5 .

[0088] The decoupling circuit is directly connected in parallel to the AC output side of the inverter. The entire decoupling circuit presents a π-shaped structure. The left branch of the decoupling circuit is the output voltage U of the AC output side of the inverter. inv , decoupling inductor L d The right branch of the decoupling circuit is composed of a fourth switch tube S4 and a fifth switch tube S5. The emitter of S4 is connected to the emitter of S5. The collector of the second switch tube S2 is connected to the first decoupling capacitor C d1 The positive series connection forms a closed loop with the left branch, wherein the emitter of S2 is connected to the collector of S1, and the emitter of the third switch tube S3 is connected to the second decoupling capacitor C d2 The negative direction is connected in series and forms a loop with the right branch, in which the collector of S3 is connected to the collector of S4.

[0089] The decoupling circuit also includes: a control device.

[0090] The control device is respectively connected to the base of the first switch tube, the base of the second switch tube, the base of the third switch tube, the base of the fourth switch tube and the base of the fifth switch tube.

[0091] The control device is used to determine the pulse energy modulation control signal according to the switching cycle of the inverter using the pulse energy modulation technology, and control the conduction and shutdown of the first switch tube, the second switch tube, the third switch tube, the fourth switch tube and the fifth switch tube according to the pulse energy modulation control signal.

[0092] The decoupling circuit of this embodiment is a power decoupling circuit, and the working principle of the power decoupling circuit is:

[0093] The AC output voltage u of the inverter g and the output current i g Usually it is a sinusoidal function, as shown below:

[0094] u g (t) = U g sin(ωt) (1)

[0095]

[0096] In the above formula, u g (t) is the AC side output voltage of the inverter at time t, U g is the output voltage amplitude on the AC side, ω is the fundamental angular frequency, t represents time, i g (t) is the AC side output current of the inverter at time t, I g is the output current amplitude on the AC side, is the power factor angle. To analyze the coupling relationship, let is 0. According to formulas (1) and (2), the instantaneous power P on the AC side is obtained: ac , DC side input constant power P PV They are:

[0097]

[0098]

[0099]

[0100] In the above formula, P ac (t) represents the instantaneous power on the AC side of the inverter at time t; U g Indicates the output voltage amplitude of the inverter on the AC side; I g represents the output current amplitude of the inverter on the AC side; ω represents the fundamental angular frequency; t represents time; P PVThe DC side input constant power, P r It is the periodically changing double frequency pulsating power.

[0101] Compare the instantaneous power on the AC side with the constant power input on the DC side to determine the power decoupling energy relationship. That is, when the instantaneous power on the AC side is greater than the constant power input on the DC side, the photovoltaic system is in the process of releasing energy and the decoupling capacitor is in a voltage-reducing state; when the instantaneous power on the AC side is less than the constant power input on the DC side, the photovoltaic system is in the process of absorbing energy and the decoupling capacitor is in a voltage-reducing state. At the same time, according to formulas (1)-(5), the power decoupling energy coupling relationship curve can be obtained. The power decoupling energy coupling relationship curve is as follows: Figure 2 shown. Figure 2 Where T is the period of the output voltage.

[0102] The decoupling circuit has four working modes, mode 1 and mode 2 correspond to the positive half cycle of the inverter output voltage, and mode 3 and mode 4 correspond to the negative half cycle of the inverter output voltage. Mode 1 and mode 3 can be equivalent to boost circuits, and mode 2 and mode 4 can be equivalent to buck circuits.

[0103] The circuit loop corresponding to mode 1 is as follows Figure 3 As shown, the inverter output voltage is positive at this time. Figure 2 It can be seen that in the time period [0, T / 8] and [3T / 8, 4T / 8], the instantaneous power on the AC side is less than the constant input power on the DC side. S4 is driven by the control device (Formula 9) and is in the open state. The circuit loop is U inv+ -L d -D1-S4-D5-U inv- , the decoupling inductor current gradually increases. When the decoupling inductor current peak reaches the decoupling inductor peak reference current i dref (Formula 10), at this time, switch S4 is disconnected, and the circuit loop is U inv+ -L d -D1-D2-C d1 -U inv- The circuit loop corresponding to mode 1 is specifically as follows: when the fourth switch tube is turned on and the first switch tube, the second switch tube, the third switch tube and the fifth switch tube are turned off, the current flows out from the first end of the AC output side of the inverter, passes through the decoupling inductor, the first diode, the fourth switch tube and the fifth diode in sequence, and then flows back to the second end of the AC output side of the inverter; when the fourth switch tube, the first switch tube, the second switch tube, the third switch tube and the fifth switch tube are all turned off, the current flows out from the first end of the AC output side of the inverter, passes through the decoupling inductor, the first diode, the second diode and the first decoupling capacitor in sequence, and then flows back to the second end of the AC output side of the inverter.

[0104] The circuit loop corresponding to mode 2 is as follows Figure 4As shown, the inverter output voltage is positive. In the [T / 8, 3T / 8] time period, the instantaneous power on the AC side is greater than the constant power on the DC side. S5 and S1 remain on, and S2 is controlled by the drive pulse. When S2 is on, the circuit loop is C d1 -S2-S1-L d -U inv -C d1 , the decoupling inductor current gradually increases, and when the current peak reaches the reference value i dref (Formula 7), switch S2 is disconnected, and the circuit loop is U inv- -S5-D4-S1-L d -U inv+ The circuit loop corresponding to mode 2 is specifically as follows: when the second switch tube, the first switch tube and the fifth switch tube are turned on, and the third switch tube and the fourth switch tube are turned off, the current flows out from the second end of the AC output side of the inverter, passes through the first decoupling capacitor, the second switch tube, the first switch tube and the decoupling inductor in sequence, and then flows back to the first end of the AC output side of the inverter; when the second switch tube is turned off, the first switch tube and the fifth switch tube are turned on, and the third switch tube and the fourth switch tube are turned off, the current flows out from the second end of the AC output side of the inverter, passes through the fifth switch tube, the fourth diode, the first switch tube and the decoupling inductor in sequence, and then flows back to the first end of the AC output side of the inverter.

[0105] The circuit loop corresponding to mode three is as follows Figure 5 As shown, the inverter output voltage is negative at this time. In the time period of [4T / 8, 5T / 8] and [7T / 8, T], the instantaneous power on the AC side is less than the constant power on the DC side. S5 is controlled by the drive pulse. When S5 is in the on state, the circuit loop is U inv+ -S5-D4-S1-L d -U inv- , the decoupling inductor current gradually increases, and when the current peak reaches the reference value i dref (Formula 11), switch S5 is disconnected, and the circuit loop is U inv+ -C d2 -D3-S1-L d -U inv- The circuit loop corresponding to mode three is specifically as follows: when the fifth switch tube and the first switch tube are turned on, and the second switch tube, the third switch tube and the fourth switch tube are turned off, the current flows out from the first end of the AC output side of the inverter, passes through the fifth switch tube, the fourth diode, the first switch tube and the decoupling inductor in sequence, and then flows back to the second end of the AC output side of the inverter; when the fifth switch tube is turned off, the first switch tube is turned on, and the second switch tube, the third switch tube and the fourth switch tube are turned off, the current flows out from the first end of the AC output side of the inverter, passes through the second decoupling capacitor, the third diode, the first switch tube and the decoupling inductor in sequence, and then flows back to the second end of the AC output side of the inverter.

[0106] The circuit loop corresponding to mode 4 is as follows Figure 6 As shown, the inverter output voltage is negative at this time. In the [5T / 8, 7T / 8] time period, the instantaneous power on the AC side is greater than the constant power on the DC side. S3 is controlled by the drive pulse. When S3 is turned on, the circuit loop is C d2 -U inv -L d -D1-S3-C d2 , decoupling inductor peak current i dref When (Formula 13) reaches the reference value, switch S3 is disconnected, and the circuit loop is U inv -L d -D1-S4-D5-U inv The circuit loop corresponding to mode 4 is specifically as follows: when the third switch tube and the fourth switch tube are turned on, and the first switch tube, the second switch tube and the fifth switch tube are turned off, the current flows out from the second end of the AC output side of the inverter, and flows back to the first end of the AC output side of the inverter after passing through the decoupling inductor, the first diode, the third switch tube and the second decoupling capacitor in sequence; when the third switch tube is turned off, the fourth switch tube is turned on, and the first switch tube, the second switch tube and the fifth switch tube are turned off, the current flows out from the second end of the AC output side of the inverter, and flows back to the first end of the AC output side of the inverter after passing through the decoupling inductor, the first diode, the fourth switch tube and the fifth diode in sequence.

[0107] The control device specifically includes:

[0108] The acquisition module is used to obtain the AC side output voltage amplitude, AC side output current amplitude and bus voltage of the inverter, as well as the decoupling inductance value of the decoupling inductor and the decoupling capacitor voltage of the decoupling capacitor; the decoupling capacitor is the first decoupling capacitor or the second decoupling capacitor.

[0109] The power coupling relationship determination module is used to determine the power coupling relationship of the decoupling circuit by using the AC side output voltage amplitude and the AC side output current amplitude.

[0110] The power coupling relationship determination module specifically includes:

[0111] The power calculation unit is used to use the AC side output voltage amplitude and the AC side output current amplitude to obtain the AC side instantaneous power and the DC side input constant power of the inverter through the following formulas respectively.

[0112]

[0113]

[0114] Where P ac (t) represents the instantaneous power on the AC side of the inverter at time t; U gIndicates the output voltage amplitude of the inverter on the AC side; I g represents the output current amplitude of the inverter on the AC side; ω represents the fundamental angular frequency; t represents time; P PV Indicates that the DC side of the inverter inputs a constant power.

[0115] The power coupling relationship determination unit is used to compare the instantaneous power on the AC side with the constant power input on the DC side to determine the power coupling relationship of the decoupling circuit; the power coupling relationship includes: when the instantaneous power on the AC side is greater than the constant power input on the DC side, the photovoltaic system is in the process of releasing energy and the decoupling capacitor is in a step-down state; when the instantaneous power on the AC side is less than the constant power input on the DC side, the photovoltaic system is in the process of absorbing energy and the decoupling capacitor is in a step-up state.

[0116] The pulse energy modulation control signal determination module is used to obtain the pulse energy modulation control signal by using the pulse energy modulation technology according to the bus voltage, the decoupling inductance value, the decoupling capacitor voltage and the power coupling relationship.

[0117] The pulse energy modulation control signal determination module specifically includes:

[0118] The rising decoupling inductor peak reference current determination unit is used to determine the peak current of the decoupling inductor according to the bus voltage, decoupling inductance value and power coupling relationship through the formula A decoupling inductor peak reference current corresponding to the decoupling inductor current rising is obtained.

[0119] The decoupling inductor peak reference current determination unit is used to determine the decoupling inductor peak current according to the bus voltage, decoupling inductance value, decoupling capacitor voltage and power coupling relationship through the formula The decoupling inductor peak reference current corresponding to the decoupling inductor current decreases is obtained.

[0120] Where U DC Indicates bus voltage; L d represents the decoupling inductance value; d represents the duty cycle of the pulse drive switch; T s represents the switching cycle; i dref Indicates the peak reference current of the decoupling inductor; U d represents the decoupling capacitor voltage; d' represents the time proportion of the decoupling inductor current dropping from the peak value to 0 in a single switching cycle.

[0121] The decoupling inductor peak reference current determination unit is used to determine the decoupling inductor peak reference current corresponding to the decoupling inductor current when the decoupling inductor current rises and the decoupling inductor peak reference current corresponding to the decoupling inductor current when the decoupling inductor current decreases, using the formula And the energy conservation relationship, the decoupling inductor peak reference current of the decoupling circuit in each working mode is obtained. In the formula, W in Represents the energy absorbed by the decoupling circuit during a single switching cycle.

[0122] The pulse energy modulation control signal determination unit is used to determine the peak reference current of the decoupling inductor corresponding to each working mode through the formula The duty cycle of the pulse drive switch corresponding to each working mode is determined; the pulse energy modulation control signal includes the decoupling inductor peak reference current and the duty cycle of the pulse drive switch corresponding to each working mode.

[0123] The switch tube state determination module is used to determine the switch state of the switch tube in the decoupling circuit according to the pulse energy modulation control signal, the polarity of the AC side output voltage of the inverter and the operating state of the decoupling capacitor; the switch tube includes a first switch tube, a second switch tube, a third switch tube, a fourth switch tube and a fifth switch tube.

[0124] The switch tube state determination module specifically includes:

[0125] The switch state determination unit is used to determine the state of the switch tube according to the pulse energy modulation control signal, the polarity of the AC side output voltage of the inverter and the operating state of the decoupling capacitor through a logical relationship formula Determine the switching state of the switch tube in the decoupling circuit.

[0126] In the formula, S1 represents the switching state of the first switch tube; A represents the polarity of the AC side output voltage of the inverter; B represents the operating state of the decoupling capacitor; S2 represents the switching state of the second switch tube; PEM represents the pulse energy modulation control signal; S3 represents the switching state of the third switch tube; S4 represents the switching state of the fourth switch tube; S5 represents the switching state of the fifth switch tube. It indicates that the output voltage on the AC side is negative, and when the decoupling capacitor voltage increases, the AND gate logic relationship between the three is added with the PEM signal.

[0127] This embodiment further provides a decoupling method, which is applied to the above-mentioned decoupling circuit. The decoupling method is performed by a control device. Figure 7 This is a flow chart of the decoupling method provided by an embodiment of the present invention. Figure 7 , decoupling methods include:

[0128] Step 101, obtaining an AC side output voltage amplitude, an AC side output current amplitude and a bus voltage of the inverter, as well as a decoupling inductance value of a decoupling inductor and a decoupling capacitor voltage of a decoupling capacitor; the decoupling capacitor is a first decoupling capacitor or a second decoupling capacitor.

[0129] Step 102: Determine the power coupling relationship of the decoupling circuit by using the AC side output voltage amplitude and the AC side output current amplitude.

[0130] Step 102 specifically includes:

[0131] Using the AC side output voltage amplitude and the AC side output current amplitude, the AC side instantaneous power and the DC side input constant power of the inverter are obtained through formulas (3) and (4) respectively.

[0132] In formulas (3) and (4), P ac (t) represents the instantaneous power on the AC side of the inverter at time t; U g Indicates the output voltage amplitude of the inverter on the AC side; I g represents the output current amplitude of the inverter on the AC side; ω represents the fundamental angular frequency; t represents time; P PV Indicates that the DC side of the inverter inputs a constant power.

[0133] The instantaneous power on the AC side is compared with the constant power input on the DC side to determine the power coupling relationship of the decoupling circuit; the power coupling relationship includes: when the instantaneous power on the AC side is greater than the constant power input on the DC side, the photovoltaic system is in the process of releasing energy and the decoupling capacitor is in a step-down state; when the instantaneous power on the AC side is less than the constant power input on the DC side, the photovoltaic system is in the process of absorbing energy and the decoupling capacitor is in a step-up state.

[0134] Step 103, according to the bus voltage, the decoupling inductance value, the decoupling capacitor voltage and the power coupling relationship, a pulse energy modulation control signal is obtained by using a pulse energy modulation technology.

[0135] Step 103 specifically includes:

[0136] According to the relationship between the bus voltage, the decoupling inductance value and the power coupling, the decoupling inductance peak reference current corresponding to the decoupling inductance current rising is obtained by formula (6).

[0137]

[0138] According to the bus voltage, decoupling inductance value, decoupling capacitor voltage and power coupling relationship, the decoupling inductor peak reference current corresponding to the decoupling inductor current decreases is obtained by formula (7).

[0139]

[0140] Where U DC Indicates bus voltage; L d represents the decoupling inductance value; d represents the duty cycle of the pulse drive switch; T s represents the switching cycle; i dref Indicates the peak reference current of the decoupling inductor; U d represents the decoupling capacitor voltage; d' represents the time proportion of the decoupling inductor current dropping from the peak value to 0 in a single switching cycle.

[0141] According to the decoupling inductor peak reference current corresponding to the decoupling inductor current rising and the decoupling inductor peak reference current corresponding to the decoupling inductor current falling, the decoupling inductor peak reference current of the decoupling circuit in each working mode is obtained by using formula (8) and the energy conservation relationship. In formula (8), W in Represents the energy absorbed by the decoupling circuit during a single switching cycle.

[0142]

[0143] According to the decoupling inductor peak reference current corresponding to each working mode, the duty cycle of the pulse drive switch corresponding to each working mode is determined by formula (6); the pulse energy modulation control signal includes the decoupling inductor peak reference current corresponding to each working mode and the duty cycle of the pulse drive switch.

[0144] Step 104, according to the pulse energy modulation control signal, the polarity of the AC side output voltage of the inverter and the operating state of the decoupling capacitor, the switch state of the switch tube in the decoupling circuit is determined; the switch tube includes a first switch tube, a second switch tube, a third switch tube, a fourth switch tube and a fifth switch tube. The switch tube control drive signal is formed by a logical combination of the PEM control signal, the output voltage polarity and the decoupling energy coupling relationship (the operating state of the decoupling capacitor), and the expression of the logical combination is formula (9).

[0145] Step 104 specifically includes:

[0146] According to the pulse energy modulation control signal, the polarity of the AC side output voltage of the inverter and the operating state of the decoupling capacitor, the switching state of the switch tube in the decoupling circuit is determined through the logical relationship formula (9).

[0147]

[0148] In the formula, S1 represents the switching state of the first switch tube; A represents the polarity of the AC side output voltage of the inverter; B represents the operating state of the decoupling capacitor; S2 represents the switching state of the second switch tube; PEM represents the pulse energy modulation control signal; S3 represents the switching state of the third switch tube; S4 represents the switching state of the fourth switch tube; S5 represents the switching state of the fifth switch tube. It indicates that the output voltage on the AC side is negative, and when the decoupling capacitor voltage increases, the AND gate logic relationship between the three is added with the PEM signal.

[0149] Voltage polarity: A indicates the output voltage polarity on the AC side. When the output voltage is positive, A=0; when the output voltage is negative, A=1. Operation status of the decoupling capacitor: B indicates the operation status of the decoupling capacitor. When the decoupling capacitor voltage increases, that is, the photovoltaic system is in the process of absorbing energy, B=0; when the decoupling capacitor voltage decreases, that is, the photovoltaic system is in the process of releasing energy, B=1. Table 1 shows the switching status of the switch tube in different working modes. In Table 1, the 0 corresponding to the switch tube indicates that the switch tube is in the disconnected state, and the 1 corresponding to the switch tube indicates that the switch tube is in the on state.

[0150] Table 1 Switching status of the four modes

[0151]

[0152]

[0153] According to the switching conditions of the switch tubes in the four working modes in Table 1, the logic expression formula (9) of each switch tube can be obtained.

[0154] Pulse Energy Modulation (PEM) technology can determine the instantaneous driving pulse duty cycle according to the instantaneous two-frequency pulsating power. From the four working modes of the above-mentioned decoupling circuit, it can be seen that each mode can be regarded as a single switch control circuit, which can determine the switch driving pulse width according to the energy coupling relationship at different times, thereby obtaining a PEM control signal.

[0155] The principle of PEM signal generation can be found in Figure 8 , where U inv is the inverter output voltage, U DC is the bus voltage, i dref is the decoupling inductor peak reference current, i d is the decoupling inductor current, PEM is the PEM control signal, t0 represents the starting time of each switching cycle, t1 represents the time when the decoupling inductor current starts to rise, t2 represents the time when the decoupling inductor current rises to the peak value, t3 represents the time when the decoupling inductor current drops from the peak value to 0, and t4 represents the corresponding time on the right side of the PWM wave output by the inverter; Figure 8 (a) is the inverter output voltage and output current waveform. Figure 8 (b) is a schematic diagram of the decoupled inductor current and PEM signal.

[0156] Since the inverter adopts unipolar pulse width modulation, the output U invIt is a series of PWM square waves with equal height but unequal width. Within a single square wave, the decoupling circuit completes the decoupling process for a single switching cycle. Arbitrarily select a single square wave for analysis. As Figure 8 (b) shows, t1 - t4 is the interval of a single square wave output by the square wave inverter. At t1, the decoupling inductor current I d rises linearly. When I d rises to i dref at the moment, the power decoupling circuit drives the switch to turn off. This is the moment of t2. After that, the decoupling inductor current I d begins to gradually decrease linearly and drops to 0 at t3.

[0157] Let the time period during which the decoupling current decreases be d’T S = t3 - t2, and T s is the output voltage period. Since the working mode is discontinuous, t3 < t4. During dT s = t2 - t1, it is the conduction time of the pulse-driven switch, and its magnitude is determined by i dref . The duty cycle d can be set as d = (t2 - t1) / T s . This stage is the PEM pulse interval, and the drive switch tube is maintained in the on state, as shown by the shaded part in Figure 8 (b).

[0158] According to formula (4) and formula (5), the pulsating power P that the photovoltaic system needs the decoupling circuit to buffer can be obtained d :

[0159] P d = P PV cos(2ωt) (10)

[0160] In the formula, P PV is the constant power input on the DC side, ω is the fundamental angular frequency, and t is the time.

[0161] Formula (5) represents the output instantaneous power. Formula (7) is the power expression after removing the negative sign. Formulas (5) and (7) are actually the same power form.

[0162] According to the power decoupling energy coupling relationship, i dref under four working modes can be deduced, and further the duty cycle d of the PEM signal can be deduced, specifically including:

[0163] According to the volt-second balance principle combined with Figure 8 it can be known that within the time period t1 - t2, the decoupling inductor current rises, and the decoupling inductor current rises from 0 to i dref , and formula (6) can be obtained.

[0164] At time t2, the switch tube is turned off. After d'Ts, the decoupling inductor current drops from the peak value to 0, and formula (7) can be obtained.

[0165] In the time period t1-t3, according to the law of conservation of energy and formula (8), the energy absorbed by the decoupling circuit can be obtained as W in .

[0166] According to the output voltage cycle T S In, get P r The corresponding photovoltaic system needs decoupling buffer energy, and according to equations (6) and (7), dTs and d'Ts are converted into dref Replace, and then substitute into formula (8), and deduce i in each working mode according to the energy conservation relationship dref , the obtained i dref Substituting into (6) we can get the duty cycle d of the pulse drive switch. The decoupling inductor peak reference current i corresponding to each working mode is dref The expression of the duty cycle d of the pulse drive switch is as follows:

[0167] Mode 1:

[0168]

[0169]

[0170] Mode 2:

[0171]

[0172]

[0173] Mode 3:

[0174]

[0175]

[0176] Mode 4:

[0177]

[0178]

[0179] During the operation of the decoupling circuit, the operation process of the decoupling circuit is divided into four working modes according to the periodic change law of the pulsating power. Therefore, in a single working mode, the polarity of the pulsating power does not change, and is always positive or always negative. The pulsating power can be written as P PV |cos(2ωt)|. Therefore, according to the instantaneous pulsating power to be buffered, the present invention only needs to measure the bus voltage and the decoupling capacitor voltage in real time to achieve real-time control.dref , thereby achieving the purpose of controlling the PEM duty cycle. Further, through the logical expression of formula (9), the logical combination signal of the PWM waveform can be obtained. The logic drive signal is transmitted to the base of the switch tube to control the on and off of the switch tube. Under normal circumstances, controlling the PEM state can control the on and off state of each switch tube, and then the operation process of the four working modes of the switching decoupling circuit is controlled in real time. The circuit loop of the four working modes is formed by the combination of different components in the decoupling circuit, so that each working mode can operate independently, and the double frequency power is buffered by the decoupling capacitor, so that the secondary ripple on the DC side of the inverter is suppressed.

[0180] The present invention maintains a relatively independent structure with the original inverter, increases the flexibility of the decoupling circuit control algorithm, can independently control the decoupling circuit, and the decoupling method of the present invention is simple. Compared with the DC side decoupling, the decoupling circuit of the present invention is connected in parallel to the AC side. Compared with other types of decoupling methods, this decoupling method can avoid the double frequency power passing through an additional loop, such as a DC side loop, thereby reducing the double frequency power compensation loop and achieving the effect of on-site compensation of the double frequency power, thereby reducing loop losses. The independent type means that the decoupling circuit and the original inverter circuit part have no shared switches, and the non-independent type often has switch sharing with the original inverter.

[0181] According to the above discussion on the voltage and current of the decoupling circuit, the five-switch power decoupling circuit (decoupling circuit) is simulated and verified by simulink using matlab software, which proves that the decoupling effect of the present invention is good. The simulation parameter settings of the decoupling circuit are shown in Table 2.

[0182] Table 2 Simulation parameters

[0183]

[0184] Fig. 9 and Fig.10 The waveforms of the DC side input current and bus voltage are shown respectively. When the decoupling circuit is put into operation at 0.4s, it can be observed that the pulsation amplitude of the input current decreases at the moment of input. Before the decoupling circuit is put into operation, the maximum value of the input current is about 5.45A, the minimum value is about 4.6A, and the pulsation amplitude is about 0.85A; after the decoupling circuit is put into operation, the maximum value of the input current is 5.28A, the minimum value is 4.94A, and the pulsation amplitude is about 0.34A. The pulsation amplitude of the input current is reduced by about 60% before and after the decoupling circuit is put into operation, and the dynamic response of the entire decoupling circuit is rapid. Similar to the input current, after the decoupling circuit is put into operation, the DC side bus voltage drops from a pulsation amplitude of about 42V to a pulsation amplitude of about 19V at 0.4s, indicating that the decoupling effect of the present invention is good.

[0185] Fig.11 and Fig.12The voltage waveforms of the first decoupling capacitor and the second decoupling capacitor are shown respectively. The two decoupling capacitors operate complementary to each other in the working cycle, and the voltage waveform during the working period is exactly 0.01s, which is a pulsating secondary ripple. The first decoupling capacitor C d1 The average voltage is about 477V, the highest voltage is about 513V, the lowest voltage is about 457V, and the pulsation amplitude is about 56V; the second decoupling capacitor C d2 The average voltage is about 462V, the maximum voltage is about 495V, the minimum voltage is about 435V, the pulsation amplitude is about 60V, the pulsation energy and C d1 This is because the equivalent circuits of the two decoupling capacitors corresponding to the working modes are the same, both are boost and buck circuits, so the decoupling effects are also the same.

[0186] Fig.13 The figure shows the decoupled inductor current waveform. In mode 1, the decoupled inductor current amplitude is about 12A, in mode 2, the current amplitude is about 8A, in mode 3, the current amplitude is about 12A, and in mode 4, the current amplitude is about 8A. Modes 1 and 3 both work in boost mode, and modes 2 and 4 both work in buck mode. When working under the same equivalent circuit state, the decoupled inductor currents are close.

[0187] Fig.14 and Fig.15 The figures show the output voltage and current waveforms of the AC side load respectively. After the decoupling circuit is put into use for 0.4s, it can be seen that the load output voltage and current have almost no obvious changes, the voltage amplitude is still stable at about 300V, and the current amplitude is stable at about 3A. It can be concluded that the control of the decoupling circuit has no obvious effect on the output voltage.

[0188] For the case where the power decoupling circuit is not added, if the bus voltage ripple is reduced from the original 42V to 19V, the DC side voltage pulsation needs to be reduced to 23V, then a 200μf large capacitor needs to be connected in parallel on the DC side; after adding the decoupling circuit, if the bus voltage ripple is reduced from 42V to 19V, only a 100μf capacitor needs to be connected in parallel. Therefore, through simulation verification of the decoupling circuit, it is found that the present invention can effectively suppress the secondary ripple in the bus voltage, and the decoupling circuit can achieve the effect of reducing the DC side capacitance, while extending the service life of the power supply.

[0189] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0190] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A decoupling circuit, characterized in that: include: A decoupling inductor, a first switch tube, a second switch tube, a first decoupling capacitor, a third switch tube, a second decoupling capacitor, a fourth switch tube and a fifth switch tube; One end of the decoupling inductor is connected to a first end of the AC output side of the inverter in the photovoltaic system, the other end of the decoupling inductor is connected to the emitter of the first switch tube, the collector of the first switch tube is connected to the emitter of the second switch tube, the collector of the second switch tube is connected to the positive electrode of the first decoupling capacitor, and the negative electrode of the first decoupling capacitor is connected to the second end of the AC output side of the inverter; The collector of the third switch tube is connected to the collector of the first switch tube, the emitter of the third switch tube is connected to the negative electrode of the second decoupling capacitor, and the positive electrode of the second decoupling capacitor is connected to the second end of the AC output side of the inverter; The collector of the fourth switch tube is connected to the collector of the first switch tube, the emitter of the fourth switch tube is connected to the emitter of the fifth switch tube, and the collector of the fifth switch tube is connected to the second end of the AC output side of the inverter; The decoupling circuit further includes: a control device; The control device is respectively connected to the base of the first switch tube, the base of the second switch tube, the base of the third switch tube, the base of the fourth switch tube and the base of the fifth switch tube; The control device is used to determine a pulse energy modulation control signal according to the bus voltage of the inverter and the decoupling inductance value of the decoupling inductor using a pulse energy modulation technique, and to control the on and off of the first switch tube, the second switch tube, the third switch tube, the fourth switch tube and the fifth switch tube according to the pulse energy modulation control signal.

2. The decoupling circuit according to claim 1, characterized in that: The decoupling circuit further includes: a first diode, a second diode, a third diode, a fourth diode and a fifth diode; The anode of the first diode is connected to the emitter of the first switch tube, and the cathode of the first diode is connected to the collector of the first switch tube; The anode of the second diode is connected to the emitter of the second switch tube, and the cathode of the second diode is connected to the collector of the second switch tube; The anode of the third diode is connected to the emitter of the third switch tube, and the cathode of the third diode is connected to the collector of the third switch tube; The anode of the fourth diode is connected to the emitter of the fourth switch tube, and the cathode of the fourth diode is connected to the collector of the fourth switch tube; The anode of the fifth diode is connected to the emitter of the fifth switch tube, and the cathode of the fifth diode is connected to the collector of the fifth switch tube.

3. The decoupling circuit according to claim 1, characterized in that: The control device specifically comprises: An acquisition module, used to acquire the AC side output voltage amplitude, AC side output current amplitude and bus voltage of the inverter, as well as the decoupling inductance value of the decoupling inductor and the decoupling capacitor voltage of the decoupling capacitor; the decoupling capacitor is a first decoupling capacitor or a second decoupling capacitor; A power coupling relationship determination module, used to determine the power coupling relationship of the decoupling circuit by using the AC side output voltage amplitude and the AC side output current amplitude; A pulse energy modulation control signal determination module, used to obtain a pulse energy modulation control signal by using a pulse energy modulation technology according to the bus voltage, the decoupling inductance value, the decoupling capacitor voltage and the power coupling relationship; A switch tube state determination module is used to determine the switch state of the switch tube in the decoupling circuit according to the pulse energy modulation control signal, the polarity of the AC side output voltage of the inverter and the operating state of the decoupling capacitor; the switch tube includes a first switch tube, a second switch tube, a third switch tube, a fourth switch tube and a fifth switch tube.

4. The decoupling circuit according to claim 3, characterized in that: The power coupling relationship determination module specifically includes: A power calculation unit, used to obtain the AC side instantaneous power and the DC side input constant power of the inverter by using the AC side output voltage amplitude and the AC side output current amplitude respectively through the following formulas; ； ； Where P ac (t) represents the instantaneous power on the AC side of the inverter at time t; U g Indicates the output voltage amplitude of the inverter on the AC side; I g represents the output current amplitude of the inverter on the AC side; ω represents the fundamental angular frequency; t represents time; P PV Indicates that the DC side of the inverter inputs a constant power; A power coupling relationship determination unit is used to compare the instantaneous power on the AC side with the constant power input on the DC side to determine the power coupling relationship of the decoupling circuit; the power coupling relationship includes: when the instantaneous power on the AC side is greater than the constant power input on the DC side, the photovoltaic system is in an energy release process, and the decoupling capacitor is in a voltage reduction state; when the instantaneous power on the AC side is less than the constant power input on the DC side, the photovoltaic system is in an energy absorption process, and the decoupling capacitor is in a voltage increase state.

5. The decoupling circuit according to claim 4, characterized in that: The pulse energy modulation control signal determination module specifically includes: A rising decoupling inductor peak reference current determination unit is used to determine the bus voltage, the decoupling inductor value and the power coupling relationship through a formula Obtaining a decoupling inductor peak reference current corresponding to a rise in a decoupling inductor current of the decoupling inductor; The decoupling inductor peak reference current determination unit is used to determine the decoupling inductor peak reference current according to the bus voltage, the decoupling inductor value, the decoupling capacitor voltage and the power coupling relationship through the formula Obtaining a decoupling inductor peak reference current corresponding to when the decoupling inductor current decreases; Where U DC Indicates bus voltage; L d represents the decoupling inductance value; d represents the duty cycle of the pulse drive switch; T s represents the switching cycle; i dref Indicates the peak reference current of the decoupling inductor; U d represents the decoupling capacitor voltage; d' represents the time proportion of the decoupling inductor current dropping from the peak value to 0 in a single switching cycle; A decoupling inductor peak reference current determination unit is used to determine the decoupling inductor peak reference current corresponding to the decoupling inductor current when the decoupling inductor current rises and the decoupling inductor peak reference current corresponding to the decoupling inductor current when the decoupling inductor current falls, using the formula and energy conservation relationship, the decoupling inductor peak reference current of the decoupling circuit in each working mode is obtained; where W in Represents the energy absorbed by the decoupling circuit in a single switching cycle; The pulse energy modulation control signal determination unit is used to determine the decoupling inductor peak reference current corresponding to each working mode through the formula , determining the duty cycle of the pulse-driven switch corresponding to each of the working modes; the pulse energy modulation control signal includes the decoupling inductor peak reference current and the duty cycle of the pulse-driven switch corresponding to each of the working modes.

6. A decoupling method, characterized in that: Applied to the decoupling circuit according to any one of claims 1 to 5, the decoupling method comprises: Acquire the AC side output voltage amplitude, AC side output current amplitude and bus voltage of the inverter, as well as the decoupling inductance value of the decoupling inductor and the decoupling capacitor voltage of the decoupling capacitor; the decoupling capacitor is a first decoupling capacitor or a second decoupling capacitor; Determining the power coupling relationship of the decoupling circuit by using the AC side output voltage amplitude and the AC side output current amplitude; According to the bus voltage, the decoupling inductance value, the decoupling capacitor voltage and the power coupling relationship, a pulse energy modulation control signal is obtained by using a pulse energy modulation technology; The switching state of the switch tube in the decoupling circuit is determined according to the pulse energy modulation control signal, the polarity of the AC side output voltage of the inverter and the operating state of the decoupling capacitor; the switch tube includes a first switch tube, a second switch tube, a third switch tube, a fourth switch tube and a fifth switch tube.

7. The decoupling method according to claim 6, characterized in that: The determining the power coupling relationship of the decoupling circuit by using the AC side output voltage amplitude and the AC side output current amplitude specifically includes: Using the AC side output voltage amplitude and the AC side output current amplitude, the AC side instantaneous power and the DC side input constant power of the inverter are obtained respectively through the following formulas; ； ； Where P ac (t) represents the instantaneous power on the AC side of the inverter at time t; U g Indicates the output voltage amplitude of the inverter on the AC side; I g represents the output current amplitude of the inverter on the AC side; ω represents the fundamental angular frequency; t represents time; P PV Indicates that the DC side of the inverter inputs a constant power; The instantaneous power on the AC side is compared with the constant power input on the DC side to determine the power coupling relationship of the decoupling circuit; the power coupling relationship includes: when the instantaneous power on the AC side is greater than the constant power input on the DC side, the photovoltaic system is in an energy release process, and the decoupling capacitor is in a voltage reduction state; when the instantaneous power on the AC side is less than the constant power input on the DC side, the photovoltaic system is in an energy absorption process, and the decoupling capacitor is in a voltage increase state.

8. The decoupling method according to claim 7, characterized in that: The step of obtaining a pulse energy modulation control signal by using a pulse energy modulation technique according to the bus voltage, the decoupling inductance value, the decoupling capacitor voltage and the power coupling relationship specifically includes: According to the bus voltage, the decoupling inductance value and the power coupling relationship, the formula Obtaining a decoupling inductor peak reference current corresponding to a rise in a decoupling inductor current of the decoupling inductor; According to the bus voltage, the decoupling inductance value, the decoupling capacitor voltage and the power coupling relationship, the formula Obtaining a decoupling inductor peak reference current corresponding to when the decoupling inductor current decreases; Where U DC Indicates bus voltage; L d represents the decoupling inductance value; d represents the duty cycle of the pulse drive switch; T s represents the switching cycle; i dref Indicates the peak reference current of the decoupling inductor; U d represents the decoupling capacitor voltage; d' represents the time proportion of the decoupling inductor current dropping from the peak value to 0 in a single switching cycle; According to the decoupling inductor peak reference current corresponding to the decoupling inductor current when the decoupling inductor current rises and the decoupling inductor peak reference current corresponding to the decoupling inductor current when the decoupling inductor current decreases, the formula is used. and energy conservation relationship, the decoupling inductor peak reference current of the decoupling circuit in each working mode is obtained; where W in Represents the energy absorbed by the decoupling circuit in a single switching cycle; According to the decoupling inductor peak reference current corresponding to each working mode, the formula , determining the duty cycle of the pulse-driven switch corresponding to each of the working modes; the pulse energy modulation control signal includes the decoupling inductor peak reference current and the duty cycle of the pulse-driven switch corresponding to each of the working modes.

9. The decoupling method according to claim 8, characterized in that: The step of determining the switching state of the switch tube in the decoupling circuit according to the pulse energy modulation control signal, the polarity of the AC side output voltage of the inverter and the operating state of the decoupling capacitor specifically includes: According to the pulse energy modulation control signal, the polarity of the AC side output voltage of the inverter and the operating state of the decoupling capacitor, the logical relationship formula , determining the switching state of the switch tube in the decoupling circuit; In the formula, S1 represents the switching state of the first switch tube; A represents the polarity of the AC side output voltage of the inverter; B represents the operating state of the decoupling capacitor; S2 represents the switching state of the second switch tube; PEM represents the pulse energy modulation control signal; S3 represents the switching state of the third switch tube; S4 represents the switching state of the fourth switch tube; S5 represents the switching state of the fifth switch tube.

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