A dual half-wave high-frequency chain micro inverter

Abstract

The technical problem this invention aims to solve is that in traditional half-wave high-frequency chain inverters, only the positive half-cycle of the high-frequency AC square wave generated on the primary side is transferred to the output side. The technical solution of this invention is to provide a dual half-wave high-frequency chain micro-inverter, whose circuit topology includes a primary-side transformation topology. The high-frequency AC square wave generated by the primary-side transformation topology is loaded onto the primary side of a transformer. The transformer's secondary side has two windings, each connected to a half-wave converter, or two transformers each connected to a half-wave converter. The positive and negative half-cycles of the high-frequency square wave on the primary side are transferred to the output side through these two half-wave converters. Compared to traditional half-wave high-frequency chain inverters, this invention has higher voltage utilization; the circuit topology provided by this invention is applicable to both grid-connected and off-grid applications; and this invention features a split-phase output structure, with automatic voltage balancing between the two phases.

Description

Technical Field

[0001] This invention relates to a high-frequency chain-type micro-inverter, belonging to the field of photovoltaic power generation, and particularly to a photovoltaic power generation system composed of micro-inverters, which uses inverters for power conversion. Background Technology

[0002] The circuit topology of a traditional half-wave high-frequency chain inverter is as follows: Figure 1 As shown, it includes a high-frequency transformer. The primary side of the high-frequency transformer is connected to a full-bridge converter topology circuit, and the secondary side of the high-frequency transformer is connected to a rectifier circuit, which then outputs the power through an LC filter circuit. In... Figure 1 In the half-wave high-frequency chain inverter shown, only the positive half-cycle of the high-frequency AC square wave generated on the primary side is transferred to the output side, thereby reducing the voltage utilization rate. Summary of the Invention

[0003] The technical problem to be solved by this invention is that in traditional half-wave high-frequency chain inverters, only the positive half-cycle of the high-frequency AC square wave generated on the primary side is transferred to the output side.

[0004] To solve the above-mentioned technical problems, the technical solution of the present invention is to provide a dual half-wave high-frequency chain micro inverter. The circuit topology of the dual half-wave high-frequency chain micro inverter includes a primary-side transformation topology. The signal waveform generated by the primary-side transformation topology is loaded on the primary side of the transformer. The transformer has two windings on the secondary side, and each winding is connected to a half-wave frequency converter. The energy of the positive and negative half-cycles of the primary-side signal waveform is transferred to the output side through the two half-wave frequency converters.

[0005] Alternatively, there are two independent transformers. The signal waveform generated by the primary-side transformation topology is simultaneously loaded onto the primary sides of both transformers. Each of the secondary sides of the two transformers is connected to a half-wave converter. The energy of the positive and negative half-cycles of the primary-side signal waveform is transferred to the output side through the two half-wave converters.

[0006] Preferably, the two half-wave converters can drive the load individually or together.

[0007] Preferably, the two half-wave converters transfer the energy of the positive and negative half-cycles of the primary high-frequency square wave to the output side through their respective filter circuits, and the two filter circuits can drive the load separately or together.

[0008] Preferably, when a single transformer is used, the two windings on the secondary side of the transformer have the same number of turns.

[0009] Preferably, when using a single transformer, the two windings on the secondary side of the transformer are defined as winding one and winding two, respectively:

[0010] During the positive half-cycle of the grid voltage: During the positive half-cycle of the switching cycle, when the primary voltage is positive, energy is output from winding one; when the primary voltage is zero, the secondary current freewheels along the loop formed by the two half-wave converters and winding one. During the negative half-cycle of the switching cycle, when the primary voltage is negative, energy is output from winding two; when the primary voltage is zero, the secondary current freewheels along the loop formed by the two half-wave converters and winding two.

[0011] During the negative half-cycle of the grid voltage: During the positive half-cycle of the switching cycle, when the primary voltage is positive, energy is output from winding two. When the primary voltage is zero, the secondary current freewheels along the loop formed by the two half-wave converters and winding two. During the negative half-cycle of the switching cycle, when the primary voltage is negative, energy is output from winding one. When the primary voltage is zero, the secondary current freewheels along the loop formed by the two half-wave converters and winding one.

[0012] Preferably, one end of winding one and one end of winding two are short-circuited together, and the other end of winding one is the same name as one of the pins of the primary side.

[0013] Preferably, the half-wave converter connected to the first winding includes switching transistors Q1, Q2, Q3, and Q4. The same-name terminals of the first winding are connected to the switching transistors Q1, Q2, Q3, and Q4 in sequence, and then the switching transistor Q4 is connected to the short-circuit terminal of the first winding. The two ends of the series-connected switching transistors Q3 and Q4 are the output of the half-wave converter.

[0014] The half-wave converter connected to the second winding includes switching transistors Q5, Q6, Q7, and Q8. The same-name terminals of the second winding are connected to the switching transistors Q5, Q6, Q7, and Q8 in sequence. Then, the switching transistor Q8 is connected to the short-circuit terminal of the second winding. The two ends of the series-connected switching transistors Q7 and Q8 are the output of the half-wave converter.

[0015] Preferably, during the positive half-cycle of the grid voltage, switching transistors Q1 and Q6 are kept on and switching transistors Q2 and Q5 are kept off; during the positive half-cycle of the switching cycle, a turn-off command is sent to switching transistors Q3 and Q4, and a turn-on command is sent to switching transistors Q7 and Q8; during the negative half-cycle of the switching cycle, a turn-off command is sent to switching transistors Q7 and Q8, and a turn-on command is sent to switching transistors Q3 and Q4.

[0016] During the negative half-cycle of the grid voltage, keep switching transistors Q1 and Q6 normally off and keep switching transistors Q2 and Q5 normally on; during the positive half-cycle of the switching cycle, send a turn-off command to switching transistors Q7 and Q8 and a turn-on command to switching transistors Q3 and Q4; during the negative half-cycle of the switching cycle, send a turn-off command to switching transistors Q3 and Q4 and a turn-on command to switching transistors Q7 and Q8.

[0017] Preferably, during the positive half-cycle of the grid voltage: during the positive half-cycle of the switching cycle, when the primary voltage is zero, the secondary current freewheels along the anti-parallel diodes of switching transistors Q1 and Q2, switching transistors Q8 and Q7, and winding one; during the negative half-cycle of the switching cycle, when the primary voltage is zero, the secondary current freewheels along the anti-parallel diodes of switching transistors Q4, Q3, Q6, and Q5, and winding two.

[0018] During the negative half-cycle of the grid voltage: During the positive half-cycle of the switching cycle, when the primary voltage is zero, the secondary current freewheels along the anti-parallel diodes of switching transistors Q5 and Q6, switching transistors Q3 and Q4, and winding 2; During the negative half-cycle of the switching cycle, when the primary voltage is zero, the secondary current freewheels along the anti-parallel diodes of switching transistors Q7, Q8, Q2, and Q1, and winding 1.

[0019] Preferably, the primary-side transformation topology is a full-bridge transformation topology circuit, a half-bridge transformation topology circuit, or a push-pull topology circuit.

[0020] Compared with existing half-wave high-frequency chain inverters, the advantages of this invention are:

[0021] 1. Compared with traditional half-wave high-frequency chain inverters, this invention has higher voltage utilization;

[0022] 2. The circuit topology provided by this invention is applicable to both grid-connected and off-grid applications;

[0023] 3. This invention has a phase-splitting output structure, and the two-phase output voltages can achieve automatic balancing. Attached Figure Description

[0024] Figure 1 The circuit topology of a traditional half-wave high-frequency chain inverter is illustrated.

[0025] Figure 2 The circuit topology of the first type of dual half-wave high-frequency chain micro inverter in Embodiment 1 of the present invention is illustrated.

[0026] Figure 3 It indicated Figure 2 The circuit topology shown is in its grid-connected state.

[0027] Figure 4 It indicated Figure 2 The circuit topology shown is in its off-grid, phase-by-phase load state.

[0028] Figure 5 The circuit topology of the second type of dual half-wave high-frequency chain microinverter in Embodiment 1 of the present invention is illustrated.

[0029] Figure 6The circuit topology of the dual half-wave high-frequency chain micro inverter in Embodiment 2 of the present invention is illustrated. Detailed Implementation

[0030] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0031] Example 1

[0032] like Figure 2 As shown, the circuit topology of the dual half-wave high-frequency chain micro-inverter disclosed in this embodiment is a single-stage inverter topology. The solar panel input is connected to an H-type full-bridge converter topology after passing through capacitor C3, and the output is connected to a high-frequency transformer Tra1 for voltage boosting. The secondary side of the high-frequency transformer Tra1 uses two winding outputs, defined as winding S1 and winding S2 respectively. One end of the two windings is shorted together, and the other end is the same-name terminal as pin 1 of the primary side. Each winding output is connected to a set of half-wave converter circuit topologies, filtered by LC, and then connected to the power grid or to a load. In this embodiment, the two windings on the secondary side have the same number of turns. The output of the high-frequency transformer Tra1 uses a combination of two half-wave frequency converters, so that the energy of the positive and negative half cycles of the high-frequency square wave on the primary side (it should be noted that in addition to high-frequency square waves, triangular waves, sine waves, and other AC waveforms can also be used) can be transferred to the output side, thereby improving voltage utilization.

[0033] Meanwhile, the two half-wave converters on the secondary side form a novel phase-splitting output structure. The output capacitors C1 and C2 of the LC filter can drive the load individually or together, and the output voltage can be naturally balanced. In traditional full-bridge high-frequency chain inverters, to achieve balanced phase-splitting voltage output, an additional third bridge arm is needed to control the neutral current, increasing the complexity and cost of the topology. In the proposed topology, no additional switching devices are needed; the neutral current can be controlled using switching transistors Q3, Q4, and Q7, Q8, thereby achieving two-phase output voltage balance.

[0034] During the positive half-cycle of the grid voltage, turn-on commands are sent to switches Q1 and Q6 to keep them normally on, and turn-off commands are sent to switches Q2 and Q5 to keep them normally off. During the positive half-cycle of the switching cycle, turn-off commands are sent to switches Q3 and Q4, and turn-on commands are sent to switches Q7 and Q8. When the primary voltage V... AB Timing, V ab When the voltage is positive, energy is output to the power grid through winding S1. When the primary voltage V... ABWhen the voltage is zero, the secondary current freewheels along the anti-parallel diodes of switching transistors Q1 and Q2, switching transistors Q8 and Q7, and winding S1. During the negative half-cycle of the switching cycle, turn-off commands are sent to switching transistors Q7 and Q8, and turn-on commands are sent to switching transistors Q3 and Q4. When the primary voltage V... AB When it is negative, V bc The voltage is positive, and energy is output to the power grid through winding S2. When the primary voltage V... AB When the current is zero, the secondary current freewheels along the anti-parallel diodes of switching transistors Q4, Q3, Q6, and Q5, and winding S2.

[0035] During the negative half-cycle of the grid voltage, turn-off commands are sent to switches Q1 and Q6, keeping them normally off; turn-on commands are sent to switches Q2 and Q5, keeping them normally open. During the positive half-cycle of the switching cycle, turn-off commands are sent to switches Q7 and Q8, and turn-on commands are sent to switches Q3 and Q4. When the primary voltage V... AB Timing, V bc When the voltage is negative, energy is output to the power grid through winding S2. When the primary voltage V... AB When the voltage is zero, the secondary current freewheels along the anti-parallel diodes of switching transistors Q5 and Q6, switching transistors Q3 and Q4, and winding S2. During the negative half-cycle of the switching cycle, turn-off commands are sent to switching transistors Q3 and Q4, and turn-on commands are sent to switching transistors Q7 and Q8. When the primary voltage V... AB When negative, V ab The voltage is negative, and energy is output to the power grid through winding S1. When the primary voltage V... AB When the current is zero, the secondary current freewheels along the anti-parallel diodes of switching transistors Q7, Q8, Q2, and Q1, and winding S1.

[0036] It should be noted that the transformation topology of the primary edge, in addition to using methods such as... Figure 2 Besides the H-type full-bridge transform topology shown, other forms of transform topologies can also be used, such as half-bridge topologies, or... Figure 5 The push-pull circuit shown.

[0037] Example 2

[0038] like Figure 6As shown, the circuit topology of the dual half-wave high-frequency chain microinverter disclosed in this embodiment differs from that of Embodiment 1 in that this embodiment uses two independent high-frequency transformers Tra1 and Tra2. The high-frequency square wave output from the primary-side transformation topology is simultaneously loaded onto the primary sides of both high-frequency transformers Tra1 and Tra2. One end of the secondary winding of high-frequency transformer Tra1 is short-circuited with one end of the secondary winding of high-frequency transformer Tra2. The other ends of the secondary windings of high-frequency transformers Tra1 and Tra2 are respectively pin 1 of the primary side of high-frequency transformer Tra1 and pin 2 of the primary side of high-frequency transformer Tra2. The secondary windings of high-frequency transformers Tra1 and Tra2 are connected to a half-wave transformation circuit topology and then filtered by LC before being connected to the power grid or to a load. Other structures and working principles of this embodiment are the same as in Embodiment 1 and will not be repeated here.

Claims

1. A dual half-wave high-frequency chain-type microinverter, wherein the circuit topology of the dual half-wave high-frequency chain-type microinverter includes a primary-side transformation topology, and the signal waveform generated by the primary-side transformation topology is loaded onto the primary side of the transformer, characterized in that, The secondary side of the transformer has two windings, each of which is connected to a half-wave converter. The positive and negative half-cycles of the primary signal waveform are transferred to the output side through the two half-wave converters. Define the two windings on the secondary side of the transformer as winding one and winding two, respectively. Short-circuit one end of winding one and winding two together, and make the other end of winding one the same name as one pin on the primary side. Then: During the positive half-cycle of the grid voltage: During the positive half-cycle of the switching cycle, when the primary voltage is positive, energy is output from winding one; when the primary voltage is zero, the secondary current freewheels along the loop formed by the two half-wave converters and winding one. During the negative half-cycle of the switching cycle, when the primary voltage is negative, energy is output from winding two; when the primary voltage is zero, the secondary current freewheels along the loop formed by the two half-wave converters and winding two. The half-wave converter connected to the first winding includes switching transistors Q1, Q2, Q3, and Q4. The same-name terminals of the first winding are connected to the switching transistors Q1, Q2, Q3, and Q4 in sequence. Then, the switching transistor Q4 is connected to the short-circuit terminal of the first winding. The two ends of the series-connected switching transistors Q3 and Q4 are the output of the half-wave converter. During the negative half-cycle of the grid voltage: During the positive half-cycle of the switching cycle, when the primary voltage is positive, energy is output from winding two; when the primary voltage is zero, the secondary current freewheels along the loop formed by the two half-wave converters and winding two. During the negative half-cycle of the switching cycle, when the primary voltage is negative, energy is output from winding one; when the primary voltage is zero, the secondary current freewheels along the loop formed by the two half-wave converters and winding one. The half-wave converter connected to the second winding includes switching transistors Q5, Q6, Q7, and Q8. The same-name terminals of the second winding are connected to the switching transistors Q5, Q6, Q7, and Q8 in sequence. Then, the switching transistor Q8 is connected to the short-circuit terminal of the second winding. The two ends of the series-connected switching transistors Q7 and Q8 are the output of the half-wave converter.

2. The dual half-wave high-frequency chain-type micro inverter as described in claim 1, characterized in that, The two half-wave converters can drive loads individually or together.

3. The dual half-wave high-frequency chain-type micro inverter as described in claim 2, characterized in that, The two half-wave converters transfer the energy of the positive and negative half-cycles of the primary high-frequency square wave to the output side through their respective filter circuits. The two filter circuits can drive the load separately or together.

4. The dual half-wave high-frequency chain-type micro inverter as described in claim 1, characterized in that, When a single transformer is used, the two windings on the secondary side of the transformer have the same number of turns.

5. A dual half-wave high-frequency chain-type micro inverter as described in claim 1, characterized in that, During the positive half-cycle of the grid voltage, keep switching transistors Q1 and Q6 normally on and keep switching transistors Q2 and Q5 normally off; during the positive half-cycle of the switching cycle, send a turn-off command to switching transistors Q3 and Q4 and a turn-on command to switching transistors Q7 and Q8; during the negative half-cycle of the switching cycle, send a turn-off command to switching transistors Q7 and Q8 and a turn-on command to switching transistors Q3 and Q4. During the negative half-cycle of the grid voltage, keep switching transistors Q1 and Q6 normally off and keep switching transistors Q2 and Q5 normally on; during the positive half-cycle of the switching cycle, send a turn-off command to switching transistors Q7 and Q8 and a turn-on command to switching transistors Q3 and Q4; during the negative half-cycle of the switching cycle, send a turn-off command to switching transistors Q3 and Q4 and a turn-on command to switching transistors Q7 and Q8.

6. The dual half-wave high-frequency chain-type micro inverter as described in claim 5, characterized in that, During the positive half-cycle of the grid voltage: During the positive half-cycle of the switching cycle, when the primary voltage is zero, the secondary current freewheels along the anti-parallel diodes of switching transistors Q1 and Q2, switching transistors Q8 and Q7, and winding one; During the negative half-cycle of the switching cycle, when the primary voltage is zero, the secondary current freewheels along the anti-parallel diodes of switching transistors Q4, Q3, Q6, and Q5, and winding two. During the negative half-cycle of the grid voltage: During the positive half-cycle of the switching cycle, when the primary voltage is zero, the secondary current freewheels along the anti-parallel diodes of switching transistors Q5 and Q6, switching transistors Q3 and Q4, and winding 2; During the negative half-cycle of the switching cycle, when the primary voltage is zero, the secondary current freewheels along the anti-parallel diodes of switching transistors Q7, Q8, Q2, and Q1, and winding 1.

7. A dual half-wave high-frequency chain-type micro inverter as described in claim 1, characterized in that, The primary-side transformation topology can be a full-bridge transformation topology, a half-bridge transformation topology, or a push-pull topology.

Images