Topological structure of inverter
By combining the MPPT cascaded circuit with the DC voltage conversion circuit, the inverter topology achieves independent maximum power point tracking and reactive power dispatch for each photovoltaic module string, solving the power generation efficiency problem of string inverters and expanding the operating range of the inverter.
Patent Information
- Application Number
- CN202423040279.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-10
- Publication Date
- 2025-11-25
- Estimated Expiration
- 2034-12-10
AI Technical Summary
Existing string inverters cannot perform independent maximum power point tracking for each photovoltaic panel, resulting in inconsistent aging levels or the entire string of photovoltaic panels not operating at its maximum power point when shaded, affecting power generation efficiency; micro inverters cannot provide reactive power output or AC off-grid power supply.
The inverter topology adopts a combination of MPPT cascaded circuit and DC voltage conversion circuit. Each photovoltaic module string independently performs maximum power point tracking, and reactive power dispatch is achieved through the inverter circuit to meet the grid demand.
It achieves independent maximum power point tracking for each photovoltaic module string, solves the bottleneck effect of photovoltaic module strings, meets the voltage source requirements for single module operation, and has reactive power dispatch function.
Smart Images
Figure CN223599518U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to photovoltaic power generation technical field, concretely relates to a kind of inverter topological structure. BACKGROUND
[0002] As Figure 1 As shown in the prior art, the high-voltage boost circuit is generally used in the existing string-type inverter, and the inverter conversion circuit is connected in the rear stage. This scheme has a simple architecture and relatively low system cost. However, the maximum power tracking of the photovoltaic panel can only track the entire string of photovoltaic panels. If the aging degree of individual blocks in the entire string of photovoltaic panels is inconsistent or part of the photovoltaic panels is shaded, the entire string of photovoltaic panels cannot work at the maximum power point, which seriously affects the power generation efficiency.
[0003] As Figure 2 As shown in the prior art, the existing micro inverter architecture generally uses a multi-channel flyback circuit connected to an inverter switching bridge in the rear stage. This scheme architecture can independently track the maximum power point of each photovoltaic panel and perfectly solve the problem of inconsistent aging degree of the system photovoltaic panel or partial shading of the photovoltaic panel. However, this architecture scheme cannot perform reactive power output and AC off-grid power supply output. SUMMARY
[0004] Therefore, the utility model provides an inverter topological structure to solve the problem of the entire string of photovoltaic panels connected to the inverter that cannot perform individual photovoltaic panel maximum power tracking and the problem of being unable to perform reactive power output.
[0005] The utility model provides an inverter topological structure, comprising: an MPPT cascade circuit, a direct-current voltage conversion circuit, and an inverter circuit. Each input end of the MPPT cascade circuit is connected to a photovoltaic module string. The two output ends of each output end of the MPPT cascade circuit connected in cascade are connected to the input end of the direct-current voltage conversion circuit. The output end of the direct-current voltage conversion circuit is connected to the direct-current side of the inverter circuit. The AC side of the inverter circuit is connected to a load.
[0006] The MPPT cascade circuit can independently track the maximum power point of each photovoltaic module string and adjust the output current and output voltage of each photovoltaic module string to adapt to the output of other photovoltaic module strings, thereby solving the problem of the inverter photovoltaic module string's "barrel effect". The combination of the MPPT cascade circuit and the direct-current voltage conversion circuit realizes the full-range adaptive component-level maximum power tracking within a single inverter and can meet the voltage source requirements of the rear-stage circuit when a single component works. The inverter circuit can meet the functional requirements of grid reactive power dispatching.
[0007] In an alternative embodiment, the MPPT cascade circuit comprises at least one first DC-DC circuit, wherein the input terminal of each first DC-DC circuit is connected with one photovoltaic module string; when the MPPT cascade circuit comprises one first DC-DC circuit, the output terminal of the first DC-DC circuit is connected with the input terminal of the DC voltage conversion circuit; when the MPPT cascade circuit comprises at least two first DC-DC circuits, the output terminal of each first DC-DC circuit is connected with the two output terminals after cascading.
[0008] In an alternative embodiment, the first DC-DC circuit is a step-down circuit or a step-up / step-down circuit.
[0009] In an alternative embodiment, the step-down circuit comprises a first switch, a second switch, a first diode, a second diode, a first inductor and a first capacitor, wherein the first terminal of the first switch is connected with the photovoltaic module string, the second terminal of the first switch is connected with the first terminal of the first inductor and the first terminal of the second switch; the second terminal of the second switch is connected with the photovoltaic module string; the second terminal of the first inductor is connected with the first terminal of the first capacitor; the second terminal of the first capacitor is connected with the second terminal of the second switch, the second terminal of the first capacitor is the first output terminal of the step-down circuit, and the second terminal of the first capacitor is the second output terminal of the step-down circuit; the cathode of the first diode is connected with the first terminal of the first switch, and the anode of the first diode is connected with the second terminal of the first switch; the cathode of the second diode is connected with the first terminal of the second switch, and the anode of the second diode is connected with the second terminal of the second switch.
[0010] In an alternative embodiment, the DC voltage conversion circuit is a step-down circuit or a step-up / step-down circuit.
[0011] In an alternative embodiment, the step-down circuit comprises a third switch, a fourth switch, a third diode, a fourth diode, a second inductor and a second capacitor, wherein the first terminal of the second inductor is connected with one output terminal of the MPPT cascade circuit, the second terminal of the second inductor is connected with the first terminal of the third switch and the first terminal of the fourth switch, the second terminal of the third switch is connected with the other output terminal of the MPPT cascade circuit; the second terminal of the fourth switch is connected with the first terminal of the second capacitor and one end of the DC side of the inverter circuit; the second terminal of the second capacitor is connected with the second terminal of the third switch and the other end of the DC side of the inverter circuit; the cathode of the third diode is connected with the first terminal of the third switch, and the anode of the third diode is connected with the second terminal of the third switch; the anode of the fourth diode is connected with the first terminal of the fourth switch, and the pin of the fourth diode is connected with the second terminal of the fourth switch.
[0012] In an alternative embodiment, the inverter circuit comprises: a first bridge arm, a second bridge arm and a filter circuit, wherein the two ends of the first bridge arm and the second bridge arm connected in parallel are connected to the output end of the direct-current voltage conversion circuit; the first end of the filter circuit is connected to the bridge arm midpoint of the first bridge arm, the second end of the filter circuit is connected to the midpoint of the second bridge arm, and the third end and the fourth end of the filter circuit are connected to the load; the first bridge arm and the second bridge arm are both connected in series by two controllable switches.
[0013] In an alternative embodiment, the filter circuit comprises: a third inductor, a fourth inductor and a third capacitor, wherein the first end of the third inductor is connected to the midpoint of the first bridge arm, and the second end of the third inductor is connected to the first end of the third capacitor; the first end of the fourth inductor is connected to the midpoint of the second bridge arm, and the second end of the fourth inductor is connected to the second end of the third capacitor; and the two ends of the third capacitor are connected to the load.
[0014] In an alternative embodiment, the inverter circuit further comprises: a fifth switch, a sixth switch, a fifth diode and a sixth diode, wherein the first end of the fifth switch is connected to one output end of the direct-current voltage conversion circuit, the second end of the fifth switch is connected to one end of the first bridge arm and the second bridge arm connected in parallel; the first end of the sixth switch is connected to the other output end of the direct-current voltage conversion circuit, the second end of the sixth switch is connected to the other end of the first bridge arm and the second bridge arm connected in parallel; the cathode of the fifth diode is connected to the first end of the fifth switch, and the anode of the fifth diode is connected to the second end of the fifth switch; the anode of the sixth diode is connected to the first end of the sixth switch, and the cathode of the sixth diode is connected to the second end of the sixth switch. BRIEF DESCRIPTION OF DRAWINGS
[0015] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings described below are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.
[0016] Figure 1 is a structure diagram of a string type inverter in the related art;
[0017] Figure 2 is a structure diagram of a micro inverter in the related art;
[0018] Figure 3 is a topology structure diagram of an inverter according to an embodiment of the present application;
[0019] Fig. 4(a) and Fig. 4(b) are both another topology structure diagram of an inverter according to an embodiment of the present application;
[0020] Figure 5 is a specific inverter topology structure diagram of the embodiment of the utility model. DETAILED DESCRIPTION
[0021] In order to make the purpose, technical scheme and advantage of the embodiment of the utility model more clear, the technical scheme in the embodiment of the utility model will be clearly and completely described below in combination with the drawings in the embodiment of the utility model, obviously, the described embodiment is a part of the embodiment of the utility model, rather than all the embodiment. Based on the embodiment in the utility model, all other embodiments obtained by the person skilled in the art without making creative labor are within the protection scope of the utility model.
[0022] An inverter topology structure is provided in the embodiment, as shown in Figure 3 Including: MPPT cascade circuit, DC voltage conversion circuit, inverter circuit.
[0023] As shown in Figure 3 Each input end of the MPPT cascade circuit is connected with a photovoltaic module string, and the two output ends of each output end of the MPTT cascade circuit after cascade connection are connected with the input end of the DC voltage conversion circuit. The output end of the DC voltage conversion circuit is connected with the DC side of the inverter circuit. The AC side of the inverter circuit is connected with the load.
[0024] Specifically, the MPPT cascade circuit is built-in with multiple DC-DC circuits, the DC-DC circuit can be connected with at least one photovoltaic module, or at least two photovoltaic module strings are connected in series and then connected with one DC-DC circuit, and one DC-DC circuit is connected with one photovoltaic module string, so as to track the maximum power of the photovoltaic module string by controlling the DC-DC circuit. The output ends of the DC-DC circuits are connected with the DC voltage conversion circuit after cascade connection, the DC voltage conversion circuit adjusts the total voltage output by the DC-DC circuit, so as to meet the bus voltage required by the inverter circuit, thereby meeting the use of respective working conditions.
[0025] Specifically, the inverter circuit converts the DC into AC, realizes the leading or lagging reactive power by controlling the phase difference of voltage and current, and meets the reactive power scheduling demand of the power grid.
[0026] In some optional embodiments, as shown in Figures 4(a) and 4(b), the MPPT cascade circuit includes: at least one first DC-DC circuit, wherein the input terminal of each first DC-DC circuit is connected in series with a photovoltaic module; when the MPPT cascade circuit includes one first DC-DC circuit, the output terminal of the first DC-DC circuit is connected to the input terminal of the DC-DC converter circuit; when the MPPT cascade circuit includes at least two first DC-DC circuits, the two output terminals of the cascaded first DC-DC circuit are connected to the input terminal of the DC-DC converter circuit.
[0027] Specifically, in Figure 4(a), the MPPT cascade circuit is connected to at least two photovoltaic module strings, and in Figure 4(b), the MPPT cascade circuit is connected to one photovoltaic module string. The input terminal of each first DC-DC circuit is connected to one photovoltaic module string, and the output terminal of each first DC-DC circuit is cascaded and connected to a DC-DC voltage conversion circuit. The connection methods in Figures 4(a) and 4(b) ensure that each photovoltaic module string has an independent MPPT maximum power point tracking circuit module, which can accurately track the maximum power output and adjust the output current and output voltage of each photovoltaic module string to adapt to the output of other photovoltaic module strings, thus solving the bottleneck effect of the inverter photovoltaic module string.
[0028] Optionally, the first DC-DC circuit is a buck converter or a buck-boost converter. For example... Figure 5 As shown, the step-down circuit includes: a first switch S1, a second switch S2, a first diode D1, a second diode D2, a first inductor L1, and a first capacitor C1. The first terminal of the first switch S1 is connected in series with the photovoltaic module; the second terminal of the first switch S1 is connected to the first terminals of the first inductor L1 and the second switch S2; the second terminal of the second switch S2 is connected in series with the photovoltaic module; the second terminal of the first inductor L1 is connected to the first terminal of the first capacitor C1; the second terminal of the first capacitor C1 is connected to the second terminal of the second switch S2, serving as both the first and second output terminals of the step-down circuit; the cathode of the first diode D1 is connected to the first terminal of the first switch S1, and the anode of the first diode D1 is connected to the second terminal of the first switch S1; the cathode of the second diode D2 is connected to the first terminal of the second switch S2, and the anode of the second diode D2 is connected to the second terminal of the second switch S2.
[0029] Specifically, the output voltage amplitude and maximum power tracking are controlled by the on and off timing of the first switch S1 and the second switch S2. The specific control method is the existing mature maximum power tracking method, which will not be elaborated here.
[0030] In some alternative implementations, the DC-DC voltage conversion circuit is a buck circuit or a buck-boost circuit.
[0031] Specifically, when the first DC-DC circuit is a step-down circuit, although the step-down circuit is low in cost and good in effect, when multiple battery panels are abnormal or shaded, the problem of insufficient inverter bus voltage occurs; in order to solve this problem, the direct current voltage conversion circuit should be a step-up circuit, and due to the existence of the step-up circuit, the inverter system can be ensured to normally inverter output to the power grid even if only one photovoltaic component string is normal, which greatly expands the working range of the inverter.
[0032] Optionally, as shown in Figure 5 , the step-down circuit comprises a third switch K3, a fourth switch K4, a third diode D3, a fourth diode D4, a second inductor L2 and a second capacitor C2, wherein a first end of the second inductor L2 is connected with one output end of the MPPT cascade circuit, a second end of the second inductor L2 is connected with a first end of the third switch K3 and a first end of the fourth switch K4, a second end of the third switch K3 is connected with another output end of the MPPT cascade circuit; a second end of the fourth switch K4 is connected with a first end of the second capacitor C2 and one end of the direct current side of the inverter circuit; a second end of the second capacitor C2 is connected with the second end of the third switch K3 and another end of the direct current side of the inverter circuit; a cathode of the third diode D3 is connected with the first end of the third switch K3, and an anode of the third diode D3 is connected with the second end of the third switch K3; an anode of the fourth diode D4 is connected with the first end of the fourth switch K4, and a pin of the fourth diode D4 is connected with the second end of the fourth switch K4.
[0033] Specifically, the input voltage amplitude is controlled by the duty cycle of the third switch K3 and the fourth switch K4.
[0034] In some optional embodiments, the inverter circuit comprises a first bridge arm, a second bridge arm and a filter circuit, wherein two ends of the first bridge arm and the second bridge arm connected in parallel are connected with the output end of the direct current voltage conversion circuit; a first end of the filter circuit is connected with the bridge arm midpoint of the first bridge arm, a second end of the filter circuit is connected with the midpoint of the second bridge arm, and a third end and a fourth end of the filter circuit are connected with the load; the first bridge arm and the second bridge arm are both connected in series by two controllable switches.
[0035] Specifically, as shown in Figure 5 , the first bridge arm is composed of Q1 and Q2 connected in series, and the second bridge arm is composed of Q3 and Q4 connected in series. Q1-Q4 constitute a full-bridge inverter circuit, and the full-bridge inverter circuit can realize reactive power regulation, which greatly expands the applicability of the product.
[0036] It should be noted that the full-bridge inverter circuit can also be other full-bridge circuit structures except Figure 5 , which is not limited here.
[0037] Optionally, as shown in Figure 5 The filter circuit comprises a third inductor L3, a fourth inductor L4 and a third capacitor C3, wherein a first end of the third inductor L3 is connected to the midpoint of the first bridge arm, a second end of the third inductor L3 is connected to a first end of the third capacitor C3; a first end of the fourth inductor L4 is connected to the midpoint of the second bridge arm, a second end of the fourth inductor L4 is connected to a second end of the third capacitor C3; and the two ends of the third capacitor C3 are connected to the load.
[0038] Specifically, the third inductor L3, the fourth inductor L4 and the third capacitor C3 constitute an LCL filter circuit to filter out the clutter, and the filter circuit can also be other structures, which are not limited herein.
[0039] In some optional embodiments, as shown in Figure 5 The inverter circuit further comprises a fifth switch K5, a sixth switch K6, a fifth diode D5 and a sixth diode D6, wherein a first end of the fifth switch K5 is connected to one output end of the direct-current voltage conversion circuit, a second end of the fifth switch K5 is connected to one end of the first bridge arm and the second bridge arm connected in parallel; a first end of the sixth switch K6 is connected to the other output end of the direct-current voltage conversion circuit, a second end of the sixth switch K6 is connected to the other end of the first bridge arm and the second bridge arm connected in parallel; a cathode of the fifth diode D5 is connected to the first end of the fifth switch K5, an anode of the fifth diode D5 is connected to the second end of the fifth switch K5; an anode of the sixth diode D6 is connected to the first end of the sixth switch K6, a cathode of the sixth diode D6 is connected to the second end of the sixth switch K6.
[0040] Specifically, the fifth switch K5 and the sixth switch K6 are controlled to be turned on or turned off to realize the input or output of the inverter circuit.
[0041] Although the embodiments of the present application are described in conjunction with the drawings, various modifications and changes can be made by those skilled in the art without departing from the spirit and scope of the present application, and such modifications and changes fall within the scope defined by the appended claims.
Claims
1. An inverter topology, characterized by, The application relates to a photovoltaic power generation system, which comprises an MPPT cascade circuit, a direct-current voltage conversion circuit and an inverter circuit, wherein, each input end of the MPPT cascade circuit is connected with a photovoltaic component string, and two output ends of each output end of the MPPT cascade circuit after cascade connection are connected with an input end of the direct-current voltage conversion circuit; an output end of the direct-current voltage conversion circuit is connected with a direct-current side of the inverter circuit; an alternating-current side of the inverter circuit is connected with a load. The MPPT cascade circuit comprises at least one first DC-DC circuit, wherein, 2. The inverter topology of claim 1, wherein, each input end of the first DC-DC circuit is connected with a photovoltaic component string; when the MPPT cascade circuit comprises one first DC-DC circuit, an output end of the first DC-DC circuit is connected with an input end of the direct-current voltage conversion circuit; when the MPPT cascade circuit comprises at least two first DC-DC circuits, two output ends of each output end of the first DC-DC circuit after cascade connection are connected with an input end of the direct-current voltage conversion circuit. The first DC-DC circuit is a step-down circuit or a step-up and step-down circuit.
3. The inverter topology of claim 2, wherein, The step-down circuit comprises a first switch, a second switch, a first diode, a second diode, a first inductor and a first capacitor, wherein, 4. The inverter topology of claim 3, wherein, a first end of the first switch is connected with the photovoltaic component string, and a second end of the first switch is connected with a first end of the first inductor and a first end of the second switch; a second end of the second switch is connected with the photovoltaic component string; a second end of the first inductor is connected with a first end of the first capacitor; a second end of the first capacitor is connected with a second end of the second switch, and the second end of the first capacitor is a first output end of the step-down circuit and a second output end of the step-down circuit; a cathode of the first diode is connected with the first end of the first switch, and an anode of the first diode is connected with the second end of the first switch; a cathode of the second diode is connected with the first end of the second switch, and an anode of the second diode is connected with the second end of the second switch. The direct-current voltage conversion circuit is a step-down circuit or a step-up and step-down circuit.
5. The inverter topology of claim 1, wherein, The step-down circuit comprises a third switch, a fourth switch, a third diode, a fourth diode, a second inductor and a second capacitor, wherein, 6. The inverter topology of claim 5, wherein, a first end of the second inductor is connected with one output end of the MPPT cascade circuit, and a second end of the second inductor is connected with a first end of the third switch and a first end of the fourth switch; a second end of the third switch is connected with another output end of the MPPT cascade circuit; a second end of the fourth switch is connected with a first end of the second capacitor and one end of a direct-current side of the inverter circuit; a second end of the second capacitor is connected with a second end of the third switch and another end of the direct-current side of the inverter circuit; a cathode of the third diode is connected with the first end of the third switch, and an anode of the third diode is connected with the second end of the third switch; an anode of the fourth diode is connected with the first end of the fourth switch, and a pin of the fourth diode is connected with the second end of the fourth switch. 7. The inverter topology of claim 1, wherein, The inverter circuit comprises a first bridge arm, a second bridge arm and a filter circuit, wherein The two ends of the first bridge arm and the second bridge arm connected in parallel are connected with the output end of the direct-current voltage conversion circuit; The first end of the filter circuit is connected with the bridge arm midpoint of the first bridge arm, the second end of the filter circuit is connected with the midpoint of the second bridge arm, and the third end and the fourth end of the filter circuit are connected with the load; The first bridge arm and the second bridge arm are both connected in series by two controllable switches.
8. The inverter topology of claim 7, wherein, The filter circuit comprises a third inductor, a fourth inductor and a third capacitor, wherein The first end of the third inductor is connected with the midpoint of the first bridge arm, and the second end of the third inductor is connected with the first end of the third capacitor; The first end of the fourth inductor is connected with the midpoint of the second bridge arm, and the second end of the fourth inductor is connected with the second end of the third capacitor; The two ends of the third capacitor are connected with the load.
9. The inverter topology of claim 7, wherein, The inverter circuit further comprises a fifth switch, a sixth switch, a fifth diode and a sixth diode, wherein The first end of the fifth switch is connected with one output end of the direct-current voltage conversion circuit, and the second end of the fifth switch is connected with one end of the first bridge arm and the second bridge arm connected in parallel; The first end of the sixth switch is connected with the other output end of the direct-current voltage conversion circuit, and the second end of the sixth switch is connected with the other end of the first bridge arm and the second bridge arm connected in parallel; The cathode of the fifth diode is connected with the first end of the fifth switch, and the anode of the fifth diode is connected with the second end of the fifth switch; The anode of the sixth diode is connected with the first end of the sixth switch, and the cathode of the sixth diode is connected with the second end of the sixth switch.