Power decoupling control circuit of inverter system, inverter system and control device

Abstract

The invention provides a power decoupling control circuit of an inverter system, the inverter system and a control device, the power decoupling control circuit comprises a pre-stage conversion circuit, a post-stage converter, a filter circuit and a load which are connected in sequence, and the power decoupling control circuit further comprises an alternating current side power decoupling circuit, the alternating current side power decoupling circuit is arranged between the post-stage converter and the filter circuit, the alternating current side power decoupling circuit comprises a switch module, and the switch module comprises a first switch tube, a second switch tube, a third switch tube and a fourth switch tube; wherein the alternating current side power decoupling circuit is switched among a Boost mode, a Buck mode and a Buck-Boost mode in different working states in a switching period. According to the embodiment of the invention, the circuit structure is simple, and the decoupling capability of the AC side power decoupling circuit is higher.

Description

Technical Field

[0001] The present invention relates to the technical field of inverters, and in particular to a power decoupling control circuit of an inverter system, an inverter system and a control device. Background Art

[0002] Inverter systems are widely used in photovoltaic power generation, single-phase motor drive systems, and traction network power quality management. The inherent two-fold frequency power pulsation problem will greatly affect the performance of the system, such as reducing the maximum power tracking efficiency of the photovoltaic array, causing motor overheating, or shortening the service life of the motor. Placing a large-capacity electrolytic capacitor on the DC side is a traditional solution to achieve two-fold frequency pulsating power decoupling. However, this solution not only causes inconvenience in size and use, but also greatly limits the service life of the inverter. Therefore, it is of great theoretical significance and practical value to study the electrolytic capacitor-free inverter system, suppress its inherent two-fold frequency pulsating power, and achieve power decoupling.

[0003] At present, there are three main types of mainstream power decoupling solutions, namely three-port power decoupling technology, DC-link power decoupling technology and AC side power decoupling technology. The three-port power decoupling technology contains a high-frequency transformer and has the advantage of input and output electrical isolation; the entry point of the DC-link power decoupling technology is the DC voltage, and then the transfer or compensation of the double frequency pulsating power is realized from the DC side; the three-port and DC-link power decoupling technologies are essentially to separate the double frequency pulsating power from the DC side, which can suppress the low-frequency ripple on the DC side to a certain extent, but the secondary voltage ripple peak on the decoupling capacitor is limited, so the total capacitance of the system capacitor remains high. The AC side decoupling technology is based on the characteristics of the inverter bridge arm output voltage with high output voltage and fast voltage change frequency. It starts from the voltage average value on the decoupling capacitor and its coupled secondary voltage ripple, and uses the bridge arm output voltage as the input of the decoupling circuit. In addition, the bridge arm output voltage with high output voltage and fast voltage change frequency also greatly reduces the bus capacitance and decoupling capacitor capacitance. Therefore, AC side power decoupling has a high research value. However, the AC side power decoupling solution in the related art usually requires a complex circuit structure and has poor decoupling capability. Summary of the invention

[0004] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art, and to provide a power decoupling control circuit of an inverter system, an inverter system and a control device, which not only have a simple circuit structure, but also have a stronger decoupling capability of the AC side power decoupling circuit.

[0005] In a first aspect, an embodiment of the present invention provides a power decoupling control circuit of an inverter system, characterized in that it includes: a front-stage conversion circuit, a rear-stage converter, a filter circuit and a load connected in sequence, the power decoupling control circuit also includes an AC side power decoupling circuit, the AC side power decoupling circuit is arranged between the rear-stage converter and the filter circuit, the AC side power decoupling circuit includes a switch module, and the switch module includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube;

[0006] The AC side power decoupling circuit switches between the Boost mode, the Buck mode, and the Buck-Boost mode in different working states within a switching cycle.

[0007] The power decoupling control circuit of the inverter system provided according to the embodiment of the present invention has at least the following beneficial effects: in the power decoupling control circuit of the inverter system, only the first switch tube, the second switch tube, the third switch tube and the fourth switch tube are provided to constitute the AC side power decoupling circuit, the circuit structure is simpler and the cost is lower, and the AC side power decoupling circuit can be switched between Boost mode, Buck mode and Buck-Boost mode. Compared with the AC side power decoupling circuit that only works in a single Buck mode, the AC side power decoupling circuit in the embodiment of the present application has a stronger decoupling capability.

[0008] The above-mentioned power decoupling control circuit also includes a control device, which is respectively connected to the front-stage conversion circuit, the rear-stage converter, the filter circuit, the load and the AC side power decoupling circuit, and the control device is used to obtain the instantaneous power at both ends of the load, the first output voltage of the rear-stage converter and the active power; determine the working state of the AC side power decoupling circuit within the switching cycle according to the instantaneous power, the first output voltage and the active power, wherein the working state includes a first working state, a second working state, a third working state and a fourth working state; control the switching state of the switch module according to the working state, and control the charging and discharging state of the AC side power decoupling circuit according to the switching state, so that the AC side power decoupling circuit switches between Boost mode, Buck mode and Buck-Boost mode.

[0009] In the above power decoupling control circuit, determining the working state of the AC side power decoupling circuit in a switching cycle according to the instantaneous power, the first output voltage and the active power includes:

[0010] When the first output voltage is greater than a preset value and the active power is greater than the instantaneous power, it is determined that the AC side power decoupling circuit is in a first working state during a switching cycle, and in the first working state, the AC side power decoupling circuit is in a Buck-Boost mode;

[0011] When the first output voltage is greater than a preset value and the active power is less than the instantaneous power, it is determined that the AC side power decoupling circuit is in a second working state during a switching cycle, and in the second working state, the AC side power decoupling circuit is in a Buck-Boost mode;

[0012] When the first output voltage is less than a preset value and the active power is greater than the instantaneous power, it is determined that the AC side power decoupling circuit is in a third working state during a switching cycle, and in the third working state, the AC side power decoupling circuit is in a Boost mode;

[0013] When the first output voltage is less than a preset value and the active power is less than the instantaneous power, it is determined that the AC side power decoupling circuit is in a fourth working state during a switching cycle, and in the fourth working state, the AC side power decoupling circuit is in Buck mode;

[0014] The active power is obtained according to the first output voltage and the first output current of the subsequent converter.

[0015] In the above power decoupling control circuit, the AC side power decoupling circuit further includes a decoupling capacitor and a decoupling inductor, the decoupling capacitor is respectively connected to the first switch tube, the second switch tube, the third switch tube and the fourth switch tube, the decoupling inductor is respectively connected to the first switch tube, the second switch tube, the third switch tube and the fourth switch tube, the positive electrode of the first output voltage is connected to the first switch tube, and the negative electrode of the first output voltage is connected to the fourth switch tube;

[0016] The controlling the switch state of the switch module according to the working state, and controlling the charge and discharge state of the AC side power decoupling circuit according to the switch state, includes:

[0017] The corresponding main control switch tube is determined according to the working state, and the main control switch tube is controlled to be in a PWM control state to control the charging and discharging state of the AC side power decoupling circuit.

[0018] In the above power decoupling control circuit, the main control switch tube is the fourth switch tube, and the corresponding main control switch tube is determined according to the working state, and the main control switch tube is controlled to be in a PWM control state to control the charge and discharge state of the AC side power decoupling circuit, including:

[0019] In the first working state, the fourth switch tube is controlled to be in a PWM control state and the first switch tube, the second switch tube and the third switch tube are controlled to be in an off state, so as to control the charging of the AC side power decoupling circuit.

[0020] In the above power decoupling control circuit, the main control switch tube is the third switch tube, and the corresponding main control switch tube is determined according to the working state, and the main control switch tube is controlled to be in a PWM control state to control the charge and discharge state of the AC side power decoupling circuit, including:

[0021] In the second working state, the third switch tube is controlled to be in a PWM control state, the first switch tube is controlled to be in an on state, and the second switch tube and the fourth switch tube are controlled to be in an off state, so as to control the discharge of the AC side power decoupling circuit.

[0022] In the above power decoupling control circuit, the main control switch tube is the first switch tube, and the corresponding main control switch tube is determined according to the working state, and the main control switch tube is controlled to be in a PWM control state to control the charge and discharge state of the AC side power decoupling circuit, including:

[0023] In the third working state, the first switch tube is controlled to be in a PWM control state and the second switch tube, the third switch tube and the fourth switch tube are controlled to be in an off state, so as to control the charging of the AC side power decoupling circuit.

[0024] In the above power decoupling control circuit, the main control switch tube is the second switch tube, and the corresponding main control switch tube is determined according to the working state, and the main control switch tube is controlled to be in a PWM control state to control the charge and discharge state of the AC side power decoupling circuit, including:

[0025] In the fourth working state, the second switch tube is controlled to be in a PWM control state, the fourth switch tube is controlled to be in a conducting state, and the first switch tube and the third switch tube are controlled to be in an off state, so as to control the discharge of the AC side power decoupling circuit.

[0026] In a second aspect, an embodiment of the present invention provides an inverter system, comprising the power decoupling control circuit as described in the embodiment of the first aspect above.

[0027] In a third aspect, an embodiment of the present invention provides a control device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the AC side power decoupling circuit is switched between Boost mode, Buck mode, and Buck-Boost mode as in the embodiment of the first aspect above.

[0028] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention is further described below in conjunction with the accompanying drawings and embodiments;

[0030] Figure 1 is a schematic diagram of a power decoupling control circuit of an inverter system provided by an embodiment of the present invention;

[0031] Figure 2 is a schematic diagram of an AC side power decoupling circuit provided by an embodiment of the present invention;

[0032] Figure 3 A flow chart of a power decoupling control method for an inverter system provided by an embodiment of the present invention;

[0033] Figure 4 A timing diagram of the AC side power decoupling circuit operation within one cycle provided by an embodiment of the present invention;

[0034] Figure 5 A system energy flow diagram of an inverter system in different working states provided by an embodiment of the present invention;

[0035] Figure 6 A system energy flow diagram of another inverter system in different working states provided by an embodiment of the present invention;

[0036] Figure 7 A schematic diagram of the working mode of a single-capacitor four-switch AC-side power decoupling circuit in a first working state provided by an embodiment of the present invention;

[0037] Figure 8 A schematic diagram of the working mode of the single-capacitor four-switch AC-side power decoupling circuit in the second working state provided by an embodiment of the present invention;

[0038] Fig. 9 A schematic diagram of the working mode of the single-capacitor four-switch AC-side power decoupling circuit in the third working state provided by an embodiment of the present invention;

[0039] Fig.10 A schematic diagram of the working mode of the single-capacitor four-switch AC-side power decoupling circuit in the fourth working state provided by an embodiment of the present invention;

[0040] Fig.11 A driving signal diagram of a single capacitor four-switch AC side power decoupling circuit provided in an embodiment of the present invention;

[0041] Fig.12 A DC bus capacitor voltage simulation waveform diagram provided by an embodiment of the present invention;

[0042] Fig.13 The inductor current waveform of the front-stage conversion circuit provided by the embodiment of the present invention

[0043] Fig.14 An output voltage waveform diagram of the inverter system provided by an embodiment of the present invention;

[0044] Fig.15 An output current waveform diagram of the inverter system provided by an embodiment of the present invention;

[0045] Fig.16 A fast Fourier transform spectrum analysis diagram of the bus capacitor voltage before decoupling provided by an embodiment of the present invention;

[0046] Fig.17 A fast Fourier transform spectrum analysis diagram of the AC side output voltage before decoupling provided by an embodiment of the present invention;

[0047] Fig.18 A simulation waveform diagram of the DC bus voltage after the single-capacitor four-switch AC-side power decoupling circuit provided by an embodiment of the present invention starts working;

[0048] Fig.19 A waveform diagram of the front-stage inductor current of the inverter system provided by an embodiment of the present invention;

[0049] Fig. 20 A voltage waveform diagram of the AC output side after decoupling provided by an embodiment of the present invention;

[0050] Fig.21 A current waveform diagram of the AC output side after decoupling provided by an embodiment of the present invention;

[0051] Fig. 22 A spectrum analysis diagram of the bus capacitor voltage after the AC side power decoupling circuit of the single capacitor and four switches is added provided in an embodiment of the present invention;

[0052] Fig.23 A spectrum analysis diagram of the AC side output voltage after the AC side power decoupling circuit of the single capacitor and four switches provided in the embodiment of the present invention is added;

[0053] Fig.24It is a schematic diagram of the structure of a control device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0054] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be understood as a limitation on the scope of protection of the present invention.

[0055] It should be understood that in the description of the embodiments of the present invention, if there is a description of "first", "second", etc., it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features. "At least one" means one or more, "more than" means more than two, greater than, less than, exceeding, etc. are understood to not include the number itself, above, below, within, etc. are understood to include the number itself, and "several" means one or more, unless otherwise clearly and specifically limited. "And / or" describes the association relationship of associated objects, indicating that three relationships can exist. It can be understood that A and / or B can represent the situation where A exists alone, A and B exist at the same time, or B exists alone. Among them, A and B can be singular or plural.

[0056] In addition, unless otherwise clearly specified and limited, the term "connected / connected" should be understood in a broad sense, for example, it can be a fixed connection or a movable connection, a detachable connection or a non-detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or can communicate with each other; it can be directly connected or indirectly connected through an intermediate medium. It should be noted that although the logical order is shown in the flowchart, in some cases, the steps shown or described can be performed in a different order from that in the flowchart. It should be noted that the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0057] The embodiments of the present invention are further described below in conjunction with the accompanying drawings.

[0058] like Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a schematic diagram of a power decoupling control circuit of an inverter system, wherein the power decoupling control circuit includes a front-stage conversion circuit, a rear-stage converter, a filter circuit and a load R connected in sequence.

[0059] The front-stage conversion circuit includes input power supply, DC-DC converter and bus capacitor C b Among them, the input power supply can be connected to the input DC voltage U in and input DC current Ib . Bus capacitance C b It is the DC bus support capacitor. It is mainly used to smooth the voltage fluctuation on the DC bus, absorb the high pulse current generated by the switching action of the power device, and prevent the voltage overcharge and transient voltage from affecting the equipment. The voltage across it is U b The DC-DC converter may be a Boost converter for achieving maximum power point tracking and boosting.

[0060] The subsequent converter is a DC-AC converter, which usually adopts a full-bridge or multi-level inverter to convert DC power into AC power with the same frequency and phase as the power grid. inv is the first output voltage of the bridge arm of the subsequent converter before filtering, I O is the first output current of the subsequent converter.

[0061] The front-stage conversion circuit and the rear-stage converter constitute a two-stage inverter, which includes higher efficiency and better power quality, because the DC-DC stage can optimize the working point of the photovoltaic panel, and the DC-AC stage can provide high-quality AC output. In addition, the two-stage inverter usually has good modularity and scalability, and is suitable for medium to high power photovoltaic systems. g and i g They are respectively the second output voltage and the second output current after filtering on the AC side.

[0062] The filter circuit is an LC filter circuit.

[0063] In addition, the power decoupling control circuit also includes an AC side power decoupling circuit, which is arranged between the subsequent converter and the filter circuit. By arranging the AC side power decoupling circuit in the inverter system, the secondary pulsating power generated by the AC side of the inverter system can be completely eliminated, thereby improving the life of the inverter system. Moreover, the AC side power decoupling technology is to achieve on-site elimination of secondary ripples on the AC side of the inverter, shortening the loop of secondary pulsating power in the system, and greatly reducing the loss of the inverter system. Among them, on-site elimination of secondary ripples refers to directly suppressing the ripples on the AC side of the power electronic converter to reduce the impact of the ripples on system performance.

[0064] In some embodiments, Figure 2 As shown, an embodiment of the present invention provides a schematic diagram of an AC side power decoupling circuit, wherein the AC side power decoupling circuit includes a switch module, and the switch module includes a first switch tube S1, a second switch tube S2, a third switch tube S3 and a fourth switch tube S4. The AC side power decoupling circuit also includes a decoupling capacitor C d and decoupling inductor L d , decoupling capacitor C dThe first switch tube S1, the second switch tube S2, the third switch tube S3 and the fourth switch tube S4 are connected to the decoupling inductor L d The first output voltage U inv The positive electrode is connected to the first switch tube S1, and the first output voltage U inv The negative electrode of is connected to the fourth switch tube S4. The AC side power decoupling circuit also includes four anti-parallel diodes, namely a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4.

[0065] It is understandable that the AC side power decoupling circuit can work in multiple modes, including Boost, Buck and Buck-Boost, under different working conditions in the switching cycle, which makes it more flexible and decoupling than the decoupling circuit in a single working mode. The AC side power decoupling circuit including the first switch tube, the second switch tube, the third switch tube and the fourth switch tube is an effective way. It is composed of four switch tubes and corresponding diodes, inductors and capacitors, and can realize different working modes in different grid cycles, thereby absorbing or releasing energy. The design of this circuit allows the inverter to process average power in each switching cycle, and achieves precise energy compensation through the pulse energy modulation (PEM) strategy, which improves the waveform quality of the AC and DC sides of the inverter.

[0066] According to the power decoupling control circuit of the inverter system provided in the embodiment of the present invention, in the power decoupling control circuit of the inverter system, only the first switch tube, the second switch tube, the third switch tube and the fourth switch tube are set to form the AC side power decoupling circuit, the circuit structure is simpler and the cost is lower, and the AC side power decoupling circuit can be switched between Boost mode, Buck mode and Buck-Boost mode. Compared with the AC side power decoupling circuit that only works in a single Buck mode, the AC side power decoupling circuit in the embodiment of the present application has a stronger decoupling capability.

[0067] In the above power decoupling control circuit, a control device (not shown) is also included, and the control device is respectively connected to the front-stage conversion circuit, the rear-stage converter, the filter circuit, the load and the AC side power decoupling circuit, and the control device is used to execute the power decoupling control method, so as to switch the AC side power decoupling circuit between the Boost mode, the Buck mode and the Buck-Boost mode. Specifically, Figure 3 is a flow chart of a power decoupling control method performed by a control device according to an embodiment of the present invention. The power decoupling control method can be applied to Figure 1The power decoupling control circuit in the illustrated embodiment and the power decoupling control method may include but are not limited to steps S110 to S130.

[0068] Step S110: Obtain the instantaneous power at both ends of the load, the first output voltage of the subsequent converter, and the active power.

[0069] Among them, the instantaneous power P across the load ac (t) is calculated from the active power P n and the double frequency pulsating power P to be eliminated d (t) Composition; U inv is the first output voltage of the subsequent converter; the determination of active power usually involves the output voltage, output current and power factor of the inverter system, the power factor represents the phase difference between voltage and current, and the power factor can be set according to actual conditions. In some embodiments, the active power can be calculated by multiplying the first output voltage, the first output current and the power factor of the subsequent converter.

[0070] Step S120: determining the working state of the AC-side power decoupling circuit within the switching cycle according to the instantaneous power, the first output voltage and the active power.

[0071] The working states include a first working state, a second working state, a third working state and a fourth working state.

[0072] It can be understood that in order to better analyze the energy conversion relationship of the AC side power decoupling circuit, the instantaneous power P at both ends of the AC side load is ac (t) is divided into four working state intervals, namely state I, state II, state III and state IV. The working state intervals correspond to the working states one by one. Through these four working state intervals, the working timing of the power decoupling circuit within a switching cycle T can be obtained, such as Figure 4 shown.

[0073] Step S130: controlling the switch state of the switch module according to the working state, and controlling the charge and discharge state of the AC side power decoupling circuit according to the switch state, so that the AC side power decoupling circuit switches between the Boost mode, the Buck mode, and the Buck-Boost mode.

[0074] Among them, the switching state of the switch module includes the on state, the off state and the PWM control state. The on state means that the switch tube is driven to be in a low impedance state, and the current can flow through the switch tube. At this stage, the switch tube is basically a closed switch, allowing current to flow; the off state means that the switch tube is driven to be in a high impedance state, blocking the flow of current. At this stage, the switch tube is basically a disconnected switch, and current is not allowed to flow; the PWM (Pulse Width Modulation) control state is a modulation state, and the switch tube switches quickly between on and off to achieve precise control of the output voltage or current.

[0075] Among them, Boost means voltage increase, and Boost mode means that the output voltage is higher than the input voltage; Buck means voltage reduction, and Buck mode means that the output voltage is lower than the input voltage; Buck-Boost means voltage increase and decrease, and Buck-Boost mode means that the output voltage is higher or lower than the input voltage, depending on the control method. It combines the characteristics of Boost and Buck.

[0076] In the embodiment of the present application, compared with the AC side power decoupling circuit in the related art that requires more than six switching tubes to form, in the inverter system of the embodiment of the present application, only the first switching tube, the second switching tube, the third switching tube and the fourth switching tube are set to form the AC side power decoupling circuit, the circuit structure is simpler and the cost is lower, and the AC side power decoupling circuit can be switched between Boost mode, Buck mode, and Buck-Boost mode. Compared with the AC side power decoupling circuit that only works in a single mode, the AC side power decoupling circuit in the embodiment of the present application has a stronger decoupling capability.

[0077] In some embodiments, step S120 may include but is not limited to steps S210 to S240.

[0078] Step S210: When the first output voltage is greater than a preset value and the active power is greater than the instantaneous power, it is determined that the AC side power decoupling circuit is in a first working state during the switching cycle. In the first working state, the AC side power decoupling circuit is in Buck-Boost mode.

[0079] The preset value can be 0V or other voltage values. In addition, in the first working state, the instantaneous power value is less than 0, and the AC side power decoupling circuit needs to absorb excess energy. The energy can be transmitted from the DC side to the AC side power decoupling circuit and the load circuit, which is equivalent to a Buck-Boost circuit. Figure 5 shown.

[0080] Step S220: when the first output voltage is greater than a preset value and the active power is less than the instantaneous power, it is determined that the AC side power decoupling circuit is in a second working state during the switching cycle, and in the second working state, the AC side power decoupling circuit is in a Buck-Boost mode;

[0081] The preset value can be 0V or other voltage values. In addition, in the second working state, the instantaneous power value is greater than 0, and the AC side power decoupling circuit needs to release excess energy. The energy can be delivered to the load circuit by the DC side and the AC side power decoupling circuit, which is equivalent to a Buck-Boost circuit. Figure 6 shown.

[0082] Step S230: when the first output voltage is less than a preset value and the active power is greater than the instantaneous power, it is determined that the AC side power decoupling circuit is in a third working state during the switching cycle, and in the third working state, the AC side power decoupling circuit is in a Boost mode;

[0083] The preset value can be 0V or other voltage values. In addition, in the third working state, the instantaneous power value is less than 0, and the AC side power decoupling circuit needs to absorb excess energy. The energy can be transmitted from the DC side to the AC side power decoupling circuit and the load circuit, which is equivalent to a Boost circuit. Figure 5 Shown

[0084] Step S240: When the first output voltage is less than the preset value and the active power is less than the instantaneous power, it is determined that the AC side power decoupling circuit is in the fourth working state during the switching cycle. In the fourth working state, the AC side power decoupling circuit is in Buck mode.

[0085] The preset value can be 0V or other voltage values. In addition, in the fourth working state, the instantaneous power value is greater than 0, and the AC side power decoupling circuit needs to release excess energy. The energy can be delivered to the load circuit by the DC side and the AC side power decoupling circuit, which is equivalent to a Buck circuit. Figure 6 shown.

[0086] In addition, the active power is obtained according to the first output voltage and the first output current of the subsequent converter. Specifically, the active power can be calculated by multiplying the first output voltage, the first output current and the power factor.

[0087] In the embodiment of the present application, the switching period T of the AC side power decoupling circuit is the same as the switching period Ts of the power decoupling control circuit of the inverter system. In one switching period T, the AC side power decoupling circuit is also divided into four working state intervals, which correspond to the four working state intervals of the inverter system. When the AC side power decoupling circuit works in the first working state and the third working state, the decoupling capacitor C d Used to absorb energy; when the AC side power decoupling circuit works in the second working state and the fourth working state, the decoupling capacitor C d Used to release energy. Therefore, the AC side power decoupling circuit can work in multiple modes such as Boost, Buck and Buck-Boost, which makes it more flexible and has a greater decoupling capability than the decoupling circuit in only a single working mode.

[0088] In some embodiments, step S130 may include but is not limited to step S310.

[0089] Step S310: determining the corresponding main control switch tube according to the working state, and controlling the main control switch tube to be in a PWM control state to control the charge and discharge state of the AC side power decoupling circuit.

[0090] Among them, the main control switch tube can be the first switch tube, the second switch tube, the third switch tube or the fourth switch tube, which can be determined specifically according to the working state. For example, the main control switch tube corresponding to the first working state is the fourth switch tube, the main control switch tube corresponding to the second working state is the third switch tube, the main control switch tube corresponding to the third working state is the first switch tube, and the main control switch tube corresponding to the fourth working state is the second switch tube.

[0091] In an embodiment of the present application, the corresponding main control switch tube is determined by the working state, and the main control switch tube can be controlled to be in a PWM control state, so that each switch tube can be quickly switched between on and off to control the charging and discharging state of the AC side power decoupling circuit, thereby achieving precise control of the output voltage or current.

[0092] It is understandable that when the AC side power decoupling circuit needs to absorb energy, this energy comes from the output of the inverter system, that is, after the inverter system converts the energy on the DC side into AC power, it stores or releases instantaneous energy through the decoupling circuit. This process involves the control strategy of the inverter system to ensure that at any given time, the output of the inverter system can meet the load demand and synchronize with the power grid.

[0093] In the embodiment of the present application, the AC side power decoupling circuit can operate in three modes: Boost, Buck or Buck-Boost. Such a design provides greater flexibility and decoupling capability.

[0094] In some embodiments, when the main control switch is the fourth switch, step S310 may include but is not limited to step S410.

[0095] Step S410: in the first working state, the fourth switch tube is controlled to be in a PWM control state and the first switch tube, the second switch tube and the third switch tube are controlled to be in an off state, so as to control the charging of the AC side power decoupling circuit.

[0096] It should be noted that, in the first working state, a PWM signal is output to control the fourth switch tube to be in this state, and the fourth switch tube is continuously switched in this state. The PWM control state is a modulation state, and the fourth switch tube switches quickly between on and off to achieve precise control of the output voltage or current. PWM (pulse width modulation) control is a commonly used power electronic control technology that controls the output voltage or current by adjusting the ratio of the switch tube conduction time (i.e., pulse width) to the period.

[0097] In addition, the off state (ie, cut-off) refers to the switch being driven to a high impedance state, blocking the flow of current. At this stage, the switch is basically a disconnected switch, not allowing current to flow.

[0098] Specifically, Figure 7 As shown, the solid line with an arrow indicates the current flow direction in the circuit when the main control switch is closed, and the dotted line with an arrow indicates the current flow direction in the circuit when the main control switch is disconnected. When the first output voltage is greater than the preset value, and the active power is greater than the instantaneous power, it is determined that the AC side power decoupling circuit is in the first working state during the switching cycle. In the first working state, the fourth switch is determined to be the main control switch, and the fourth switch is controlled to be in the PWM control state and the first switch, the second switch and the third switch are controlled to be in the off state. When the fourth switch is closed, the current flow path is Uinv+→D1→L d →S4→Uinv-; when the fourth switch is turned off, the current flow path is L d →D3→C d →D1→L d At this time, the circuit absorbs energy through the decoupling capacitor Cd, and the AC side power decoupling circuit is charged, which is equivalent to a Buck-Boost circuit. Among them, Uinv+ is the positive electrode of the first output voltage, and Uinv- is the negative electrode of the first output voltage.

[0099] In some embodiments, when the main control switch is the third switch, step S310 may include but is not limited to step S510.

[0100] Step S510: in the second working state, the third switch tube is controlled to be in a PWM control state, the first switch tube is controlled to be in an on state, and the second switch tube and the fourth switch tube are controlled to be in an off state, so as to control the discharge of the AC side power decoupling circuit.

[0101] It should be noted that, in the second working state, a PWM signal is output to control the third switch tube to be in this state, and in this state the third switch tube is continuously switched.

[0102] Specifically, Figure 8 As shown, the solid line with an arrow indicates the current flow direction in the circuit when the main control switch is closed, and the dotted line with an arrow indicates the current flow direction in the circuit when the main control switch is disconnected. When the first output voltage is greater than the preset value and the active power is less than the instantaneous power, it is determined that the AC side power decoupling circuit is in the second working state during the switching cycle. In the second working state, the third switch is determined to be the main control switch, and the third switch is controlled to be in the PWM control state, the first switch is controlled to be in the on state, and the second switch and the fourth switch are controlled to be in the off state. When the third switch is closed, the current flow path is C d →S3→L d →S1→C d ; When the third switch is turned off, the current flow path is L d →S1→U inv+ →U inv- →D4→L d At this time, the circuit releases energy through the decoupling capacitor Cd, and the AC side power decoupling circuit discharges, which is equivalent to a Buck-Boost circuit.

[0103] In some embodiments, when the main control switch is the first switch, step S310 may include but is not limited to step S610.

[0104] Step S610: in the third working state, the first switch tube is controlled to be in the PWM control state and the second switch tube, the third switch tube and the fourth switch tube are controlled to be in the off state, so as to control the charging of the AC side power decoupling circuit.

[0105] It should be noted that, in the third working state, a PWM signal is output to control the first switch tube to be in this state, and in this state, the first switch tube is continuously switched.

[0106] Specifically, Fig. 9As shown, the solid line with an arrow indicates the current flow direction in the circuit when the main control switch is closed, and the dotted line with an arrow indicates the current flow direction in the circuit when the main control switch is disconnected. When the first output voltage is less than the preset value, and the active power is greater than the instantaneous power, it is determined that the AC side power decoupling circuit is in the third working state during the switching cycle. In the third working state, the first switch is determined to be the main control switch, and the first switch is controlled to be in the PWM control state and the second switch, the third switch and the fourth switch are controlled to be in the off state. When the first switch is closed, the current flow path is U inv+ →D4→L d →S1→U inv -; When the fourth switch tube is turned off, the current flow path is U inv+ →D4→L d →D2→C d →U inv -, at this time, the circuit absorbs energy through the decoupling capacitor Cd, and the AC side power decoupling circuit is charged, which is equivalent to a Boost circuit.

[0107] In some embodiments, when the main control switch is the second switch, step S310 may include but is not limited to step S710.

[0108] Step S710: In the fourth working state, the second switch tube is controlled to be in a PWM control state, the fourth switch tube is controlled to be in a conducting state, and the first switch tube and the third switch tube are controlled to be in an off state, so as to control the discharge of the AC side power decoupling circuit.

[0109] It should be noted that, in the fourth working state, a PWM signal is output to control the second switch tube to be in this state, and in this state the second switch tube is continuously switched.

[0110] Specifically, Fig.10 As shown, the solid line with an arrow indicates the current flow direction in the circuit when the main control switch is closed, and the dotted line with an arrow indicates the current flow direction in the circuit when the main control switch is disconnected. When the first output voltage is less than the preset value, and the active power is less than the instantaneous power, it is determined that the AC side power decoupling circuit is in the fourth working state during the switching cycle. In the fourth working state, the second switch is determined to be the main control switch, and the second switch is controlled to be in the PWM control state, the fourth switch is controlled to be in the on state, and the first switch and the third switch are controlled to be in the off state. When the second switch is closed, the current flow path is C d →S2→L d →S4→U inv+ →U inv -→C d ; When the second switch is turned off, the current flow path is L d →S4→U inv+ →Uinv -→D1→L d At this time, the circuit releases energy through the decoupling capacitor Cd, and the AC side power decoupling circuit discharges, which is equivalent to a Buck circuit.

[0111] In summary, the AC side power decoupling circuit with a single capacitor and four switches has three different working modes: Boost, Buck, and Buck-Boost in four working ranges. According to the switch state and energy relationship of the AC side power decoupling circuit in different working ranges, a table of four switch states of the AC side power decoupling circuit can be made, as shown in Table 1.

[0112] Table 1 Switching status of AC side power decoupling circuit

[0113] Interval I Interval II Interval III Interval IV Energy Relationship Charge Discharge Charge Discharge normal signal none S1 none S4 Drive signal S4 S3 S1 S2 Equivalent Circuit Buck-Boost Buck-Boost Boost Buck

[0114] like Fig.11 As shown, in order to more intuitively see the driving timing in the circuit, the driving signals of the first switch tube S1, the second switch tube S2, the third switch tube S3 and the fourth switch tube S4 in the circuit are represented graphically. The switch tube has three states, namely, on, off, and PWM control. The second switch tube S2 and the third switch tube S3 have only two states, PWM control and off, which can control the discharge of the AC side power decoupling circuit; the first switch tube S1 and the fourth switch tube S4 have three states, which can control the charging of the AC side power decoupling circuit and the discharge of the AC side power decoupling circuit.

[0115] In order to verify the decoupling effect and function of the AC side power decoupling circuit of single capacitor and four switches, a simulation model with a power of 200W was built through the Simulink module in Matlab. The specific simulation parameters of the main circuit two-stage inverter system topology are shown in Table 2 below.

[0116] Table 2 Specific simulation parameters of the main circuit two-stage inverter system topology

[0117]

[0118] <![CDATA[DC side inductor L x > 1.5mH Carrier frequency fs 20kHz Modulation frequency f 50Hz <![CDATA[Inverter output voltage U g > 100V <![CDATA[Bus capacitor C b > 50μF Load R 25Ω

[0119] Before adding the power decoupling circuit, the simulation results of the main circuit are as follows Fig.12 , 13 , 14 and 15 shown. Specifically, Fig.12 is the DC bus capacitor voltage simulation waveform. At this time, the bus capacitor C b The capacitance is 50μF, the bus voltage fluctuates between 160V and 240V, the voltage fluctuation range is 80V, and the secondary ripple content in the voltage waveform is relatively large. Fig.13This is the inductor current waveform of the previous DC-DC circuit. The input current fluctuates between 1A and 3.5A. Fig.14 and Fig.15 They are the output voltage and output current waveforms of the two-stage inverter. It can be seen from the figure that due to the existence of secondary ripple power, the inverter output voltage and current waveforms are obviously distorted, and the output waveform quality is poor.

[0120] Fig.16 and Fig.17 The bus capacitor voltage u dc And the AC side output voltage u g FFT (Fast Fourier Transform) spectrum analysis was performed. Fig.16 It can be seen that before the decoupling circuit is put into use, the bus capacitor voltage contains a large amount of 100Hz ripple components, and its content is 18.29%. It can be seen that the secondary ripple is the most important factor affecting the bus capacitor voltage waveform. Fig.17 The THD in the output voltage on the AC side is 9.54%. There are a lot of third-order ripple components in the voltage waveform. This low-frequency ripple component distorts the waveform of the output voltage, and the voltage waveform needs to be improved urgently.

[0121] The AC side power decoupling circuit with a single capacitor and four switches is added to the AC side of the two-stage inverter system to conduct simulation results research to verify the decoupling function of the newly constructed decoupling topology. The simulation parameter settings of the AC side power decoupling circuit are shown in Table 3 below.

[0122] Table 3 Simulation parameters of decoupling main circuit

[0123] Circuit parameters Reference value <![CDATA[Rated power P n > 200W <![CDATA[Decoupling circuit inductor L d > 100μH <![CDATA[Decoupling capacitor C d > 20μF Decoupling circuit switching frequency fs 20kHz

[0124] Maintain rated output power P n The power output is 200W, the capacitor in the AC side power decoupling circuit is set to 20μF, and the simulation decoupling effect of the single capacitor four-switch AC side power decoupling circuit in MATLAB / Simulink is as follows Fig.18 , Fig.19 , Fig. 20 and Fig.21 shown.

[0125] Fig.18 This is the simulated waveform of the DC bus voltage after the single capacitor four-switch AC side power decoupling circuit starts working. It can be seen from the figure that the bus voltage fluctuates between 194 and 206V, and the maximum range of the fluctuating voltage is 12V. Compared with the fluctuating voltage before decoupling, the voltage fluctuation range is significantly reduced. Fig.19 This is the current waveform of the front-stage inductor of the two-stage inverter. The current waveform is smoother than before decoupling.

[0126] Fig. 20 and Fig.21 They are the voltage and current waveforms on the AC output side after decoupling. It can be seen from the figure that the quality of the output waveform is good, the second harmonic component in the circuit is suppressed, and the output waveform is close to a sine wave. The proposed circuit realizes the power decoupling function.

[0127] Fig. 22 is the bus capacitor voltage u dc The spectrum analysis diagram after adding the AC side power decoupling circuit of the single capacitor and four switches, Fig.23 is the AC side output voltage u g The spectrum analysis diagram after adding the AC side power decoupling circuit of the single capacitor and four switches. It can be seen that the 100Hz ripple component is significantly reduced, with a content of only 2.98%. For the AC side output voltage, the harmonics are suppressed, the THD content is 1.52%, and the AC side output voltage u g The waveform is significantly improved and is close to a sine wave.

[0128] The simulation results show that after adding a single-capacitor four-switch AC side power decoupling circuit to the single-phase inverter, the DC side capacitor voltage secondary ripple is reduced from 18.29% to 2.98%, and the AC side output voltage harmonics are reduced from 9.54% to 1.52%, which proves the effectiveness of the power decoupling circuit.

[0129] like Fig.24 As shown, an embodiment of the present invention provides a control device 1000, including a memory 1010, a processor 1020, and a computer program stored in the memory 1010 and executable on the processor 1020, wherein the processor 1020 and the memory 1010 may be connected via a bus or other means. Fig.24 An example of a bus connection is shown in the figure. When the processor executes the computer program, the power decoupling control method of the first aspect embodiment is implemented, that is, the AC side power decoupling circuit is switched between Boost mode, Buck mode, and Buck-Boost mode.

[0130] The control device provided in the embodiment of the present invention, in the power decoupling control circuit of the inverter system, only needs to set the first switch tube, the second switch tube, the third switch tube and the fourth switch tube to form the AC side power decoupling circuit, the circuit structure is simpler and the cost is lower, and the AC side power decoupling circuit can be switched between Boost mode, Buck mode and Buck-Boost mode. Compared with the AC side power decoupling circuit that only works in a single mode, the AC side power decoupling circuit in the embodiment of the present application has a stronger decoupling capability.

[0131] An embodiment of the present invention provides an inverter system, comprising the power decoupling control circuit as described in the above embodiment.

[0132] According to the inverter system provided by the embodiment of the present invention, in the inverter system, only the first switch tube, the second switch tube, the third switch tube and the fourth switch tube are set to form an AC side power decoupling circuit, the circuit structure is simpler and the cost is lower, and the AC side power decoupling circuit can be switched between Boost mode, Buck mode and Buck-Boost mode. Compared with the AC side power decoupling circuit that only works in a single mode, the AC side power decoupling circuit in the embodiment of the present application has a stronger decoupling capability.

[0133] It will be appreciated by those skilled in the art that all or some of the steps and systems in the methods disclosed above may be implemented as software, firmware, hardware, and appropriate combinations thereof. Some physical components or all physical components may be implemented as software executed by a processor, such as a central processing unit, a digital signal processor, or a microprocessor, or may be implemented as hardware, or may be implemented as an integrated circuit, such as an application specific integrated circuit. Such software may be distributed on a computer-readable medium, which may include a computer storage medium or a non-transitory medium and a communication medium or a temporary medium. As known to those skilled in the art, the term computer storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information such as computer-readable instructions, data structures, program modules, or other data. Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disk DVD or other optical disk storage, magnetic cassettes, magnetic tapes, disk storage or other magnetic storage devices, or any other medium that may be used to store desired information and may be accessed by a computer. Furthermore, it is well known to those skilled in the art that communication media typically embodies computer readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.

[0134] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present invention.

Claims

1. A power decoupling control circuit of an inverter system, characterized in that: include: A front-stage conversion circuit, a rear-stage converter, a filter circuit and a load are sequentially connected, the power decoupling control circuit also includes an AC side power decoupling circuit, the AC side power decoupling circuit is arranged between the rear-stage converter and the filter circuit, the AC side power decoupling circuit includes a switch module, and the switch module includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube; The AC side power decoupling circuit switches between the Boost mode, the Buck mode, and the Buck-Boost mode in different working states within a switching cycle.

2. The power decoupling control circuit according to claim 1, characterized in that: The system also includes a control device, which is respectively connected to the front-stage conversion circuit, the rear-stage converter, the filter circuit, the load and the AC side power decoupling circuit, and is used to obtain the instantaneous power at both ends of the load, the first output voltage of the rear-stage converter and the active power; determine the working state of the AC side power decoupling circuit within the switching cycle according to the instantaneous power, the first output voltage and the active power, wherein the working state includes a first working state, a second working state, a third working state and a fourth working state; control the switching state of the switch module according to the working state, and control the charging and discharging state of the AC side power decoupling circuit according to the switching state, so that the AC side power decoupling circuit switches between Boost mode, Buck mode and Buck-Boost mode.

3. The power decoupling control circuit according to claim 2, characterized in that: The determining the working state of the AC side power decoupling circuit in a switching cycle according to the instantaneous power, the first output voltage and the active power includes: When the first output voltage is greater than a preset value and the active power is greater than the instantaneous power, it is determined that the AC side power decoupling circuit is in a first working state during a switching cycle, and in the first working state, the AC side power decoupling circuit is in a Buck-Boost mode; When the first output voltage is greater than a preset value and the active power is less than the instantaneous power, it is determined that the AC side power decoupling circuit is in a second working state during a switching cycle, and in the second working state, the AC side power decoupling circuit is in a Buck-Boost mode; When the first output voltage is less than a preset value and the active power is greater than the instantaneous power, it is determined that the AC side power decoupling circuit is in a third working state during a switching cycle, and in the third working state, the AC side power decoupling circuit is in a Boost mode; When the first output voltage is less than a preset value and the active power is less than the instantaneous power, it is determined that the AC side power decoupling circuit is in a fourth working state during a switching cycle, and in the fourth working state, the AC side power decoupling circuit is in Buck mode; The active power is obtained according to the first output voltage and the first output current of the subsequent converter.

4. The power decoupling control circuit according to claim 3, characterized in that: The AC side power decoupling circuit further includes a decoupling capacitor and a decoupling inductor, wherein the decoupling capacitor is connected to the first switch tube, the second switch tube, the third switch tube and the fourth switch tube respectively, and the decoupling inductor is connected to the first switch tube, the second switch tube, the third switch tube and the fourth switch tube respectively, the positive electrode of the first output voltage is connected to the first switch tube, and the negative electrode of the first output voltage is connected to the fourth switch tube; The controlling the switch state of the switch module according to the working state, and controlling the charge and discharge state of the AC side power decoupling circuit according to the switch state, includes: The corresponding main control switch tube is determined according to the working state, and the main control switch tube is controlled to be in a PWM control state to control the charging and discharging state of the AC side power decoupling circuit.

5. The power decoupling control circuit according to claim 4, characterized in that: The main control switch tube is the fourth switch tube, and the corresponding main control switch tube is determined according to the working state, and the main control switch tube is controlled to be in a PWM control state to control the charge and discharge state of the AC side power decoupling circuit, including: In the first working state, the fourth switch tube is controlled to be in a PWM control state and the first switch tube, the second switch tube and the third switch tube are controlled to be in an off state, so as to control the charging of the AC side power decoupling circuit.

6. The power decoupling control circuit according to claim 4, characterized in that: The main control switch tube is the third switch tube, and the corresponding main control switch tube is determined according to the working state, and the main control switch tube is controlled to be in a PWM control state to control the charge and discharge state of the AC side power decoupling circuit, including: In the second working state, the third switch tube is controlled to be in a PWM control state, the first switch tube is controlled to be in an on state, and the second switch tube and the fourth switch tube are controlled to be in an off state, so as to control the discharge of the AC side power decoupling circuit.

7. The power decoupling control circuit according to claim 4, characterized in that: The main control switch tube is the first switch tube, and the corresponding main control switch tube is determined according to the working state, and the main control switch tube is controlled to be in a PWM control state to control the charge and discharge state of the AC side power decoupling circuit, including: In the third working state, the first switch tube is controlled to be in a PWM control state and the second switch tube, the third switch tube and the fourth switch tube are controlled to be in an off state, so as to control the charging of the AC side power decoupling circuit.

8. The power decoupling control circuit according to claim 4, characterized in that: The main control switch tube is the second switch tube, and the corresponding main control switch tube is determined according to the working state, and the main control switch tube is controlled to be in a PWM control state to control the charge and discharge state of the AC side power decoupling circuit, including: In the fourth working state, the second switch tube is controlled to be in a PWM control state, the fourth switch tube is controlled to be in a conducting state, and the first switch tube and the third switch tube are controlled to be in an off state, so as to control the discharge of the AC side power decoupling circuit.

9. An inverter system, characterized in that: The invention comprises a power decoupling control circuit as claimed in any one of claims 1 to 8.

10. A control device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the AC side power decoupling circuit is switched between Boost mode, Buck mode, and Buck-Boost mode as claimed in any one of claims 1 to 8.

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