TWI451685B - Inverter - Google Patents

Description

Inverter

The present invention relates to a power conversion device, and more particularly to an inverter.

Please refer to Fig. 20, which is a circuit diagram of the first conventional inverter. The first conventional inverter 7 includes a first inductor L1, a capacitor C1, switches S1 to S4, and an isolation transformer TR1. The first inductor L1, the capacitor C1, the switches S1 to S4, and the isolation transformer TR1 convert the solar DC voltage generated by the solar power generation device 1 into a commercial power voltage required for the city grid circuit 3, and the solar power generation device 1 is, for example, a solar photovoltaic panel. However, since the first conventional inverter 7 requires the use of the isolation transformer TR1, it will result in a decrease in efficiency.

Please refer to Fig. 21, which is a circuit diagram of the second conventional inverter. The second conventional inverter 8 includes a first inductor L1, a second inductor L2, a capacitor C1, and switches S1 to S4. The first inductor L1, the second inductor L2, the capacitor C1, and the switches S1 to S4 convert the solar DC voltage generated by the solar power generation device 1 into a commercial power voltage required for the city grid circuit 3. Although the second conventional inverter 8 does not use an isolation transformer, it also causes a decrease in safety.

The invention relates to an inverter.

According to the invention, an inverter is proposed. The converter converts the DC voltage Switch to AC voltage and output to a load. The inverter includes a first inductor and a second inductor respectively electrically connected to both ends of the load; the first switch circuit, the first flywheel switch circuit and the second switch circuit connected in series; the third switch sequentially connected in series a circuit and a fourth switch circuit; the second flywheel switch circuit has one end electrically connected to a first node between the first switch circuit and the first flywheel switch circuit, and the other end of which is connected to the third switch A second node between the circuit and the fourth switching circuit. The first flywheel switch circuit, the second flywheel switch circuit, the first inductor, the load, and the second inductor are sequentially connected to each other when the first flywheel switch circuit and the second flywheel switch circuit are turned on. Current back path.

According to the invention, an inverter is proposed. The converter converts the DC voltage into an AC voltage output to a load. The inverter includes a first inductor, a second inductor, a first switch circuit, a second switch circuit, a third switch circuit, a fourth switch circuit, a first flywheel switch circuit, and a second flywheel switch circuit. The fourth switching circuit is in series with the third switching circuit. The first flywheel switching circuit is in series with the first switching circuit and the second switching circuit. One end of the second flywheel switch circuit is coupled to the first switch circuit, and the other end of the second flywheel switch circuit is coupled to the third switch circuit. One end of the third flywheel switch circuit is coupled to the first flywheel switch circuit and the second switch circuit, and the other end of the third flywheel switch circuit is coupled to the second flywheel switch circuit, the third switch circuit, and the fourth switch circuit.

In order to provide a better understanding of the above and other aspects of the present invention, the following detailed description of the embodiments and the accompanying drawings

First embodiment

Please refer to FIG. 1. FIG. 1 is a circuit diagram of an inverter according to the first embodiment and the second embodiment. The inverter 2 is configured to convert the solar DC voltage VDC generated by the solar power generation device 1 into a mains voltage VAC of the AC form and output it to the city grid road 3, and provide an output current Io to the city grid road 3, where the city grid road 3 is located. Can be regarded as a load. The solar power generation device 1 is, for example, a solar photovoltaic panel. The inverter 2 includes a capacitor C, a first inductor L1, a second inductor L2, a first switch circuit 21, a second switch circuit 22, a third switch circuit 23, a fourth switch circuit 24, and a first flywheel switch. Circuit 25 and second flywheel switch circuit 26. The fourth switching circuit 24 is connected in series with the third switching circuit 23, and the first flywheel switching circuit 25 is connected in series with the first switching circuit 21 and the second switching circuit 22. One end of the second flywheel switch circuit 26 is electrically connected to the first node N1 between the first shutoff circuit 21 and the first flywheel switch circuit 25, and the other end thereof is connected to the third switch circuit 23 and the fourth switch. A second node N2 between the circuits 24. When the first flywheel switch circuit 25 and the second flywheel switch circuit 26 are turned on, the first flywheel switch circuit 25, the second flywheel switch circuit 26, the first inductor L1, the load, and the second inductor L2 may be sequentially connected to form a Current back path. By controlling the above-mentioned switching circuit, the solar power generation device 1 and the city grid circuit 3 can be electrically connected or disconnected, and the current return path can be formed into a flywheel circuit.

Further, when the solar power generation device 1 and the mains voltage network 3 are not electrically connected, if the mains voltage VAC is in the positive half cycle and the mains voltage VAC is in phase with the output current Io, the first flywheel switch circuit 25 and the second flywheel switch The circuit 26, the city grid circuit 3, the first inductor L1 and the second inductor L2 may form a positive flywheel circuit PL; if the mains voltage VAC is in a negative half cycle and the mains voltage VAC is in phase with the output current Io, a negative flywheel circuit NL is formed. The positive flywheel circuit PL and the negative flywheel circuit NL are in the same path, and only the current directions are opposite.

In the embodiment illustrated in FIG. 1 , the first switch circuit 21 includes a first bypass diode TD1 and a first switch T1 ; the second switch circuit 22 includes a second bypass diode TD2 and a second switch T2; the third switching circuit 23 includes a third bypass diode TD3 and a third switch T3; the fourth switching circuit 24 includes a fourth bypass diode TD4 and a fourth switch T4; the first flywheel switch circuit 25 includes a flywheel diode TD5 and a first flywheel switch T5; the second flywheel switch circuit 26 includes a second flywheel diode TD6 and a second flywheel switch T6, wherein the switches T1~T4 and the flywheel switches T5 and T6 respectively correspond to The bypass diodes TD1~TD4 and the flywheel diodes TD5 and TD6 are connected in parallel, and the cathode of the second flywheel diode TD6 is coupled to the first node N1 between the first switch T1 and the first flywheel switch T5, and the first The anode of the second flywheel diode TD6 is coupled to the third switch T3, the fourth switch T4, and the second node N2 between the first inductors L1. The cathode of the first flywheel diode TD5 is coupled to the first node N1, and the anode of the first flywheel diode TD5 is coupled to the second switch T2 and the inductor L2. The first bypass diode TD1, the second bypass pole body TD2, and the first flywheel diode TD5 allow the same current direction. The first flywheel diode TD5 and the second flywheel diode TD6 allow opposite current directions in the flywheel circuit.

Please refer to Table 1, FIG. 1 , FIG. 2 and FIG. 7 at the same time. FIG. 2 is a timing diagram of a switching signal according to the first embodiment and the second embodiment, and FIG. 7 is a diagram showing Schematic diagram of pulse width modulation. When the mains voltage VAC is in the positive half cycle and the mains voltage VAC is in phase with the output current Io, the second switch T2 and the third switch T3 are switched at a high frequency, and the second flywheel switch T6 is turned on. When the mains voltage VAC is in the negative half cycle and the mains voltage VAC is in phase with the output current Io, the first switch T1 and the fourth switch T4 are switched at a high frequency, and the first flywheel switch T5 is turned on. The first flywheel switch T5 and the second flywheel switch T6 can be considered to be alternately switched at the mains frequency. However, it should be added that when the mains voltage VAC is at the switching instant of the positive half cycle and the negative half cycle, the first flywheel switch T5 and the second flywheel switch T6 can be simultaneously cut off to reduce the risk of circuit damage caused by the short circuit. The high frequency frequency referred to in the present specification means a load frequency higher than one hundred times, for example, when the commercial power voltage VAC whose operating frequency is generally 50 Hz or 60 Hz is a load, the high frequency frequency is exponential kHz, tens of kHz or higher.

It should be noted that the high frequency switching of the first switch T1, the second switch T2, the third switch T3, the fourth switch T4, the first flywheel switch T5, and the second flywheel switch T6 is, for example, a pulse width modulation signal. achieve. The pulse width modulation signal of the first switch T1, the second switch T2, the third switch T3, the fourth switch T4, the first flywheel switch T5 or the second flywheel switch T6 includes a plurality of pulse waves. The pulse widths of these pulse waves may be the same or different. For example, in the drawing of FIG. 7, the pulse width modulation signal is formed by pulse waves of different pulse widths.

Please refer to Table 1, FIG. 2 and FIG. 3 at the same time. FIG. 3 illustrates the first switch, the third switch and the second flywheel switch being turned on by the first switch in the first embodiment and the second embodiment, A schematic diagram of the fourth switch and the first flywheel switch being cut off. Further, when the mains voltage VAC is in the positive half cycle and the mains voltage VAC is in phase with the output current Io, the second switch T2, the third switch T3 and the second flywheel switch T6 are turned on, the first switch T1 and the fourth switch T4 and The first flywheel switch T5 is turned off. The inverter 2 will be charged as shown in FIG. 3, and the charging current charges the first inductor L1 and the second inductor L2 via the second switch T2 and the third switch T3.

Please refer to Table 1, FIG. 2 and FIG. 4 at the same time. FIG. 4 is a diagram showing the first switch, the second switch, and the third switch in the first embodiment and the second embodiment. A schematic diagram of the fourth switch and the first flywheel switch being cut off. When the mains voltage VAC is in the positive half cycle and the mains voltage VAC is in phase with the output current Io, the second flywheel switch T6 is turned on and the first switch T1, the second switch T2, the third switch T3, the fourth switch T4 and the first flywheel switch T5 By the end, the aforementioned flywheel circuit PL is formed. The converter 2 will be as shown in FIG. 4, and the discharge currents of the first inductor L1 and the second inductor L2 will flow into the mains grid 3 via the first flywheel diode TD5 and the second flywheel switch T6.

Please refer to Table 1, FIG. 2 and FIG. 5 simultaneously. FIG. 5 illustrates the first switch, the fourth switch and the first flywheel switch being turned on and the second switch in the first embodiment and the second embodiment. A schematic diagram of the cutoff of the third switch and the second flywheel switch. When the mains voltage VAC is in the negative half cycle and the mains voltage VAC is in phase with the output current Io, the first switch T1, the fourth switch T4 and the first flywheel switch T5 are turned on, the second switch T2, the third switch T3 and the second fly The wheel switch T6 is turned off. The inverter 2 will be charged as shown in FIG. 5, and the charging current is charged to the first inductor L1 and the second inductor L2 via the first switch T1, the fourth switch T4 and the first flywheel switch T5.

Please refer to Table 1, FIG. 2 and FIG. 6 at the same time. FIG. 6 illustrates that the first flywheel switch is turned on and the first switch, the second switch, and the third switch are in the first embodiment and the second embodiment. A schematic diagram of the fourth switch and the second flywheel switch being cut off. When the mains voltage VAC is in the negative half cycle and the mains voltage VAC is in phase with the output current Io, the first flywheel switch T5 is turned on and the first switch T1, the second switch T2, the third switch T3, the fourth switch T4, and the second flywheel switch T6 By the end, the aforementioned negative flywheel circuit NL is formed. The converter 2 will be shown in FIG. 6. The discharge currents of the first inductor L1 and the second inductor L2 will flow into the mains grid 3 via the second flywheel diode TD6 and the first flywheel switch T5.

The inverter 2 of the first embodiment described above can form the positive flywheel circuit PL and the negative flywheel circuit NL, respectively, when the commercial power voltage VAC is in the positive half cycle and the negative half cycle. As a result, the solar power generation device 1 and the commercial power grid circuit 3 can be disconnected and the fluctuation of the common mode voltage can be reduced, so that the leakage current can be reduced. The first switch T1, the second switch T2, the third switch T3, and the fourth switch T4 can be controlled using a unipolar width modulation switching method. In addition, the first flywheel switch T5 and the second flywheel switch T6 only need to switch once off and once in one mains cycle, the switching loss is less, and the operating frequency is lower than the first switch T1 and the second switch T2. The switching elements of the third switch T3 and the fourth switch T4, so that the designer has more switching elements with lower conduction loss, so that the inverter 2 can obtain higher efficiency.

Second embodiment

In the situation described in the first embodiment, the phase of the commercial power voltage VAC does not lead or lags behind the output current Io, but sometimes the inverter 2 also needs to perform virtual power compensation according to the indication from the city grid road 3, in this case, the utility power The phase of the voltage VAC may lead or lag behind the output current Io of the converter 2. The second embodiment of the present invention is an inverter that can perform a virtual power compensation function according to the instruction of the city power grid road 3.

The circuit diagram of the second embodiment is the same as the circuit diagram of the first embodiment. Since the output current Io is inverted from the mains voltage VAC (the polarity is different) when the virtual power compensation is performed, the two flywheel switches need to be switched with other switches to form an appropriate current. The path, the first flywheel switch T5, and the second flywheel switch T6 need to select a switching element that can operate at the same high frequency as the first switch T1, the second switch T2, the third switch T3, and the fourth switch T4. The switching signal timing of the second embodiment may be the same as that of the first embodiment in the case where the phase of the mains voltage VAC is not leading or lagging behind the output current Io, and details are not described herein again.

When the inverter 2 receives the indication of the mains grid 3 and switches to the virtual power compensation mode, there may be two cases where the mains voltage leads the output current and the output current leads the mains voltage. In these two cases, the first flywheel switch T5 and the second flywheel switch T6 need to perform high frequency switching respectively for the virtual power compensation during the period before and after the zero crossing point of the mains voltage VAC and the output current Io, and at the commercial power voltage. The VAC is at the peak and its vicinity to maintain the cut-off or conduction. The control timing of the switch is determined according to the zero-crossing point of the mains voltage, the virtual power compensation voltage range and the virtual power compensation current range. It is necessary to ensure that the inverter 2 will not be carried out. When the virtual power compensation is performed, the switching of the circuit is caused to malfunction and is damaged.

Mains voltage lead output current

Referring to Tables 2, 3, and 8, FIG. 8 is a timing diagram of a switching signal according to a voltage lead current according to the second embodiment. Taking the starting point of the positive half cycle of the mains voltage VAC as time point 0, the time point t ₂ and the time point t ₅ may depend on the zero crossing point of the mains voltage VAC. The time point t ₀ and the time point t ₃ may depend on the virtual work compensation current range | I [n]|<| Iac _ peak × sin θ _c | or the virtual work compensation current range | I [n]|<| Id |. I [ n ] is the current value of the instantaneous measured output current Io, and Iac _ peak is the peak value of the measured output current Io in the previous mains cycle. The time point t ₁ and the time point t ₄ may depend on the virtual work compensation voltage range | V [n]|<| Vac _ peak × sin θ _a | or the virtual work compensation voltage range | V [n]|<| V _b | . V [ n ] is the voltage value of the instantaneous measured mains voltage VAC, and Vac_peak is the peak value of the mains voltage VAC measured in the previous mains cycle. The angle θ _a and the angle θ _{c are set} according to the virtual work compensation amount transmitted from the commercial power grid 3 and the operating condition of the inverter (for example, the power level) to ensure that the output current Io is opposite to the commercial power voltage VAC (the polarity is different). One of the two flywheel switches performs high frequency switching, but does not cause the high frequency switching time to be too long to reduce the overall efficiency of the converter 2; the voltage V _b and the current I _d are based on the micro processing unit of the converter ( The accuracy of the figure is not shown), to avoid malfunction of the inverter switch when V [ n ], I [ n ] is too small.

Please refer to Table 2, FIG. 8, FIG. 9 and FIG. 10 at the same time. FIG. 9 illustrates the first switch and the second switch in the second embodiment, in which the first flywheel switch and the second flywheel switch are turned on. FIG. 10 is a schematic diagram showing the second switch, the third switch, and the second flywheel switch being turned on by the first switch, the fourth switch, and the first flywheel switch in the second embodiment. Schematic diagram of the cutoff.

When 0 ≦ t < t ₀ , the mains voltage VAC is in the positive half cycle and the output current Io is from the negative half cycle to the positive half cycle, the first switch T1 and the fourth switch T4 are turned off, and the second flywheel switch T6 is turned on. The second switch T2 is switched in high frequency in synchronization with the third switch T3, and the second switch T2 and the third switch T3 are complemented with the first flywheel switch T5 to perform high frequency switching for virtual work compensation.

Further, when the output current Io is still in the negative half cycle, at this time, the input The output current Io is inverted from the mains voltage VAC. When the second switch T2 and the third switch T3 are turned off, the first flywheel switch T5 is turned on. The charging current will flow through the second flywheel diode TD6 and the first flywheel switch T5 as shown in FIG. 9 to store the first inductor L1 and the second inductor L2. Conversely, if the second switch T2 and the third switch T3 are turned on, the first flywheel switch T5 is turned off. The discharge currents of the first inductor L1 and the second inductor L2 will flow into the capacitor C via the second bypass diode TD2 and the third bypass diode TD3 as shown in FIG.

Please refer to Table 2, FIG. 3, FIG. 8 and FIG. 11 at the same time. FIG. 11 illustrates the first switch and the second switch in the second embodiment, in which the first flywheel switch and the second flywheel switch are turned on. A schematic diagram of the third switch and the fourth switch being turned off. When 0≦t<t ₀ and the output current Io enters the positive half cycle, the output current Io is in phase with the mains voltage VAC, and if the second switch T2 and the third switch T3 are turned off, the first flywheel switch T5 is turned on. The discharge currents of the first inductor L1 and the second inductor L2 will flow into the mains grid path 3 via the first flywheel diode TD5 and the second flywheel switch T6 as shown in FIG. Conversely, if the second switch T2 and the third switch T3 are turned on, the first flywheel switch T5 is turned off, and the charging current is as shown in FIG. 3 via the second switch T2 and the third switch T3 to the first inductor L1 and the second Inductor L2 is charged.

Please refer to Table 2 and Figure 8 at the same time. When t ₀ ≦t<t ₁ , the mains voltage VAC is in the positive half cycle and the output current Io is in phase with the mains voltage VAC. At this time, the operation of the switching circuit and the first embodiment are the same in the case where the commercial power voltage VAC is in the positive half cycle and the commercial power voltage VAC is in phase with the output current Io, and will not be described again.

Please refer to Table 2, Figure 3, Figure 8 and Figure 11 at the same time. When t ₁ ≦t<t ₂ , the mains voltage VAC is in the positive half cycle, and the output current Io is in phase with the mains voltage VAC, but the virtual power compensation condition Triggered. At this time, the first switch T1 and the fourth switch T4 are turned off, T6 is kept on, the second switch T2 and the third switch T3 are synchronously switched at high frequency, and the first flywheel switch T5 is again complementarily high with the second switch T2 and the third switch T3. Frequency switching for virtual work compensation.

Further, if the second switch T2 and the third switch T3 are turned on, the first flywheel switch T5 is turned off. The charging current charges the first inductor L1 and the second inductor L2 via the second switch T2 and the third switch T3 as shown in FIG. Conversely, if the second switch T2 and the third switch T3 are turned off, the first flywheel switch T5 is turned on. The discharge currents of the first inductor L1 and the second inductor L2 will flow into the mains grid path 3 via the first flywheel diode TD5 and the second flywheel switch T6 as shown in FIG.

Please refer to Table 2, Figure 8, Figure 11, and Figure 12 at the same time. Figure 12 shows the second switch, the fourth switch and the first flywheel switch being turned on and the second switch in the second embodiment. Schematic diagram of the cutoff of the three switches and the second flywheel switch. When t ₂ ≦t<t ₃ , the mains voltage VAC is in the negative half cycle, the output current Io is from the positive half cycle to the negative half cycle, the second switch T2 and the third switch T3 are turned off, T5 is maintained on, and the first switch T1 is The fourth switch T4 is synchronously switched at a high frequency, and the first switch T1 and the fourth switch T4 are synchronized with the second flywheel switch T6 to perform high frequency switching to perform virtual work compensation.

Further, when t ₂ ≦t<t ₃ and the output current Io is still in the positive half cycle, the output current Io is inverted from the mains voltage VAC, and if the first switch T1 and the fourth switch T4 are turned off, the second flywheel switch T6 is turned on. The charging current flows through the first flywheel diode TD5 and the second flywheel switch T6 as shown in FIG. 11 to store the first inductor L1 and the second inductor L2. Conversely, if the first switch T1 and the fourth switch T4 are turned on, the second flywheel switch T6 is turned off, and the discharge currents of the first inductor L1 and the second inductor L2 are via the first bypass diode as shown in FIG. The TD1, the fourth bypass diode TD4, and the first flywheel diode TD5 flow into the capacitor C.

Please refer to Table 2, Figure 5, Figure 8 and Figure 9 at the same time. When t ₂ ≦t<t ₃ and the output current Io is in phase with the mains voltage VAC, if the first switch T1 and the fourth switch T4 are turned off, then The second flywheel switch T6 is turned on. The discharge currents of the first inductor L1 and the second inductor L2 flow into the mains grid path 3 via the second flywheel diode TD6 and the first flywheel switch T5 as shown in FIG. Conversely, if the first switch T1 and the fourth switch T4 are turned on, the second flywheel switch T6 is turned off, and the charging current will pass through the first switch T1 and the fourth switch T4 to the first inductor L1 and the second as shown in FIG. Inductor L2 is charged.

Please refer to Table 2 and Figure 8 at the same time. When t ₃ ≦t<t ₄ , the mains voltage VAC is in the negative half cycle and the output current Io is in phase with the mains voltage VAC. At this time, the operation of the switching circuit and the first embodiment are the same in the case where the commercial power voltage VAC is in the negative half cycle and the commercial power voltage VAC is in phase with the output current Io, and will not be described again.

Please refer to Table 2, Figure 5, Figure 8 and Figure 9 at the same time. When t ₄ ≦t<t ₅ , the mains voltage is still negative for half a week, and the output current Io is still in phase with the mains voltage VAC, but the virtual power compensation condition Triggered again. At this time, the second switch T2 and the third switch T3 are turned off, T5 is maintained to be turned on, the first switch T1 and the fourth switch T4 are synchronously switched at a high frequency, and the second flywheel switch T6 is complementary to the first switch T1 and the fourth switch T4. Switch to perform virtual work compensation.

Further, if the first switch T1 and the fourth switch T4 are turned on, the second flywheel switch T6 is turned off, and the charging current is as shown in FIG. 5 through the first switch T1 and the fourth switch T4 to the first inductor L1 and the second Inductor L2 is charged. Conversely, if the first switch T1 and the fourth switch T4 are turned off, the second flywheel switch T6 is turned on, and the discharge currents of the first inductor L1 and the second inductor L2 are via the second flywheel diode TD6 as shown in FIG. The first flywheel switch T5 flows into the city grid road 3. The next sequence returns to 0≦t<t ₀ and loops.

Output current leads the mains voltage

Please refer to Table 2, Table 4 and FIG. 13 at the same time. FIG. 13 is a timing diagram of the switching signal according to a current lead voltage according to the second embodiment. Taking the starting point of the positive half cycle of the mains voltage VAC as time point 0, the time point t ₂ and the time point t ₅ may depend on the zero crossing point of the mains voltage VAC. The time point t ₀ and the time point t ₃ may depend on the virtual work compensation voltage range | V [n]|<| Vac _ peak × sin θ _a ' | or the virtual work compensation voltage range | V [n]|<| V _b '|. V [ n ] is the voltage value of the instantaneous measured mains voltage VAC, and Vac_peak is the peak value of the mains voltage VAC measured in the previous mains cycle. The time point t ₁ and the time point t4 may depend on the virtual work compensation current range | I [n]|<| Iac _ peak ×sin θ _c ' | or the virtual work compensation current range | I [n]|<| Id '| . I [ n ] is the current value of the instantaneous measured output current Io, and Iac _ peak is the peak value of the output current Io measured in the previous mains cycle. The angle θ _a ', the voltage V _b ', the angle θ _c ', and the current I _d ' can be set by the amount of virtual work required to be compensated and the rule of thumb.

Please refer to Table 2, FIG. 3, FIG. 11 and FIG. 13 at the same time. FIG. 13 is a timing diagram of a switching signal according to a current lead voltage according to the second embodiment. When 0≦t<t ₀ , the mains voltage VAC is in the positive half cycle, and the output current Io is in phase with the mains voltage VAC, but the virtual work compensation condition has been triggered, the first switch T1 and the fourth switch T4 are cut off, and the second flywheel switch T6 Maintaining the conduction, the second switch T2 and the third switch T3 are synchronously switched in high frequency, and the second switch T2 and the third switch T3 are complemented with the first flywheel switch T5 to perform high frequency switching for virtual work compensation.

Further, if the second switch T2 and the third switch T3 are turned on, the first flywheel switch T5 is turned off. The charging current will flow through the second switch 2 and the third switch 3 as shown in FIG. 3 to store the first inductor L1 and the second inductor L2. Conversely, if the second switch T2 and the third switch T3 are turned off, the first flywheel switch T5 is turned on, and the discharge currents of the first inductor L1 and the second inductor L2 are via the first flywheel diode TD5 as shown in FIG. And the second flywheel switch T6 flows into the city grid road 3.

Please refer to Table 2 and Figure 13, at the same time, when t0≦t<t1, the mains voltage VAC is in the positive half cycle, the output current Io is in phase with the mains voltage VAC, and no virtual work compensation is needed at this time. At this time, the operation of the switching circuit and the first embodiment are the same in the case where the commercial power voltage VAC is in the positive half cycle and the commercial power voltage VAC is in phase with the output current Io, and will not be described again.

Please refer to Table 2, Figure 3, Figure 11 and Figure 13 at the same time. When t ₁ ≦t<t ₂ , the mains voltage VAC is in the positive half cycle, and the output current Io enters the negative half cycle from the positive half cycle. A switch T1 and a fourth switch T4 are turned off, the second flywheel switch T6 is kept conducting, the second switch T2 is synchronously switched with the third switch T3, and the first flywheel switch T5 is again complementary to the second switch T2 and the third switch T3. High frequency switching for virtual work compensation.

Further, when the output current Io is still in the positive half cycle, that is, still in phase with the mains voltage VAC, if the second switch T2 and the third switch T3 are turned on, the first flywheel switch T5 is turned off. The charging current charges the first inductor L1 and the second inductor L2 via the second switch T2 and the third switch T3 as shown in FIG. Conversely, if the second switch T2 and the third switch T3 are turned off, the first flywheel switch T5 is turned on. The discharge currents of the first inductor L1 and the second inductor L2 will flow into the mains grid path 3 via the first flywheel diode TD5 and the second flywheel switch T6 as shown in FIG.

Please refer to Table 2, Figure 9, Figure 10 and Figure 13, and further, when the output current Io enters the negative half cycle, that is, the output current Io is inverted from the mains voltage VAC, if the second switch T2 and the second When the three switches T3 are turned off, the first flywheel switch T5 is turned on, and the charging current will flow through the second flywheel diode TD6 and the first flywheel switch T5 as shown in FIG. 9 to store the first inductor L1 and the second inductor L2. Conversely, if the second switch T2 and the third switch T3 are turned on, the first flywheel switch T5 is turned off, and the discharge currents of the first inductor L1 and the second inductor L2 are shown in FIG. 10 via the second bypass diode TD2. And the third bypass diode TD3 flows into the capacitor C.

Please refer to Table 2, Figure 5, Figure 9 and Figure 13 at the same time. When t ₂ ≦t<t ₃ , the mains voltage VAC enters the negative half cycle, the second switch T2 and the third switch T3 are cut off, the first flywheel switch T5 is maintained on, the first switch T1 and the fourth switch T4 are synchronously switched in high frequency, and the first switch T1 and the fourth switch T4 are synchronized with the second flywheel switch T6 to perform high frequency switching to perform virtual work compensation.

Further, the output current Io at the time point t ₂ has been in phase with the mains voltage VAC, but the virtual work compensation condition has been triggered. If the first switch T1 and the fourth switch T4 are turned on, the second flywheel switch T6 is turned off, and the charging current flows through the first switch T1, the fourth switch T4, and the first flywheel switch T5 as shown in FIG. The inductor L1 and the second inductor L2 store energy. Conversely, if the first switch T1 and the fourth switch T4 are turned off, the second flywheel switch T6 is turned on, and the discharge currents of the first inductor L1 and the second inductor L2 are drawn as shown in FIG. It is shown that the second flywheel diode TD6 and the first flywheel switch T5 flow into the city grid road.

Please also refer to Table 2, Figure 5, Figure 6 and Figure 13. When t ₃ ≦t<t ₄ , the mains voltage VAC is in the negative half cycle, the output current Io is in phase with the mains voltage VAC, and no virtual work is needed. make up. At this time, the operation of the switching circuit and the first embodiment are the same in the case where the commercial power voltage VAC is in the negative half cycle and the commercial power voltage VAC is in phase with the output current Io, and will not be described again.

Please also refer to Table 2, Figure 5, Figure 9, Figure 11, Figure 12 and Figure 13. When t4≦t<t5, the mains voltage VAC is still negative for half a week, but the virtual power compensation condition is triggered again. At this time, the second switch T2 and the third switch T3 are turned off, the first flywheel switch T5 is kept turned on, the first switch T1 and the fourth switch T4 are synchronously switched with high frequency, and the second flywheel switch T6 is connected with the first switch T1 and the fourth switch. T4 complements high frequency switching for virtual work compensation.

Further, when the output current Io is still in phase with the mains voltage VAC, if the first switch T1 and the fourth switch T4 are turned on, the second flywheel switch When T6 is turned off, the charging current charges the first inductor L1 and the second inductor L2 via the first switch T1 and the fourth switch T4 as shown in FIG. Conversely, if the first switch T1 and the fourth switch T4 are turned off, the second flywheel switch T6 is turned on, and the discharge currents of the first inductor L1 and the second inductor L2 are shown in FIG. 9 via the second flywheel diode TD6 and The first flywheel switch T5 flows into the city grid road 3.

When the output current is opposite to the mains voltage, if the first switch T1 and the fourth switch T4 are turned off, the second flywheel switch T6 is turned on, and the charging current flows through the first flywheel diode TD5 and the second as shown in FIG. The flywheel switch TD6 charges the first inductor L1 and the second inductor L2. Conversely, if the first switch T1 and the fourth switch T4 are turned on, the second flywheel switch T6 is turned off, and the discharge currents of the first inductor L1 and the second inductor L2 are via the first bypass diode as shown in FIG. The TD1, the fourth bypass diode TD4 and the first flywheel diode TD5 flow into the capacitor C. The next sequence returns to 0≦t<t ₀ and loops.

Third embodiment

Please refer to Table 5, FIG. 14 and FIG. 15 at the same time. FIG. 14 is a circuit diagram of an inverter according to the third embodiment, and FIG. 15 is a diagram showing a switching signal according to the third embodiment. Timing diagram. Third implementation The main difference from the first embodiment is that one end of the second flywheel switch circuit 26' of the inverter 5 is coupled to the first switch circuit 21, and the other end of the second flywheel switch circuit 26' is coupled to the first Three switch circuit 23. One end of the third flywheel switch circuit 27' is coupled to the first flywheel switch circuit 25 and the second switch circuit 22, and the other end of the third flywheel switch circuit 27' is coupled to the second flywheel switch circuit 26', the third switch Circuit 23 and fourth switching circuit 24.

Further, the second flywheel switch circuit 26' of the inverter 5 includes only the second flywheel diode TD7, and the third flywheel switch circuit 27' includes the third flywheel diode TD8, the third flywheel switch T8, and the Four flywheel diode TD9. The anode of the second flywheel diode TD7 is coupled to the anode of the third bypass diode TD3, and the cathode of the second flywheel diode TD7 is coupled to the anode of the first bypass diode TD1. The third flywheel diode TD8 is connected in parallel with the third flywheel switch T8, and the fourth flywheel diode TD9 is connected in series with the third flywheel switch T8. The anode of the third flywheel diode TD8 is coupled to the anode of the fourth flywheel diode TD9, and the cathode of the third flywheel diode TD8 is coupled to the cathode of the second bypass diode TD2 and the first flywheel diode The anode of the body TD5, the cathode of the fourth flywheel diode TD9 is coupled to the anode of the second flywheel diode TD7 and the anode of the third bypass diode TD3.

In addition, in another embodiment, the cathode of the third flywheel diode TD8 can be coupled to the cathode of the fourth flywheel diode TD9, and the anode of the third flywheel diode TD8 can be coupled to the second bypass. The cathode of the diode TD4 and the anode of the second flywheel diode TD7 and the anode of the third bypass diode TD3, the anode of the fourth flywheel diode TD9 can be coupled to the anode of the first flywheel diode TD5 .

Please also refer to Table 5, Figure 15 and Figure 16, Figure 16 In the third embodiment, the second switch T2, the third switch T3, and the third flywheel switch T8 are turned on, and the first switch T1, the fourth switch T4, and the first flywheel switch T5 are turned off. The third flywheel switch T8, the second switch T2, and the third switch T3 are turned on during the positive half cycle of the mains voltage VAC, and the first flywheel switch T5, the first switch T1, and the fourth switch T4 are turned off at the positive half cycle of the mains voltage VAC. The inverter 5 will be charged as shown in FIG. 16, and the charging current charges the first inductor L1 and the second inductor L2 via the second switch T2 and the third switch T3.

Referring to Table 5, Figure 15, and Figure 17, FIG. 17 is a diagram showing the third switch, the second switch, the third switch, the fourth switch, and the third flywheel switch in the third embodiment. A schematic diagram of the cutoff of a flywheel switch. When the third flywheel switch T8 is in the positive half cycle of the mains voltage VAC, the first flywheel switch T5, the first switch T1, the second switch T2, the third switch T3 and the fourth switch T4 are in the positive half cycle at the mains voltage VAC. The converter 5 will be shown in FIG. 17, and the discharge currents of the first inductor L1 and the second inductor L2 flow into the mains grid 3 via the third flywheel switch T8 and the fourth flywheel diode TD9.

Please refer to Table 5, FIG. 15 and FIG. 18 simultaneously. FIG. 18 illustrates that in the third embodiment, the first switch, the fourth switch and the first flywheel switch are turned on, and the second switch, the third switch and the first Schematic diagram of the cutoff of the three flywheel switches. The first flywheel switch T5, the first switch T1 and the fourth switch T4 are turned on during the negative half cycle of the mains voltage VAC, and the third flywheel switch T8, the second switch T2 and the third switch T3 are turned off at the negative half cycle of the mains voltage VAC. The inverter 5 will be as shown in FIG. 18, and the charging current passes through the first flywheel switch T5, the first switch T1 and the fourth switch T4 to the first inductor L1 and the second inductor L2. Charging.

Referring to Table 5, FIG. 15 and FIG. 19 simultaneously, FIG. 19 illustrates the first switch, the second switch, the third switch, the fourth switch, and the first flywheel switch in the third embodiment. Schematic diagram of the cutoff of the three flywheel switches. The first flywheel switch T5 is turned on in the negative half cycle of the mains voltage VAC, and the third flywheel switch T8, the first switch T1, the second switch T2, the third switch T3 and the fourth switch T4 are cut off at the negative half cycle of the mains voltage VAC. The inverter 5 will be shown in FIG. 19, and the discharge currents of the first inductor L1 and the second inductor L2 flow into the mains grid 3 via the second flywheel diode TD7.

In conclusion, the present invention has been disclosed in the above embodiments, but it is not intended to limit the present invention. A person skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

1‧‧‧Solar power plant

2, 4, 5, 6‧‧‧ inverters

7‧‧‧The first traditional inverter

8‧‧‧Second traditional inverter

3‧‧‧ City Grid Road

21‧‧‧First switch circuit

22‧‧‧Second switch circuit

23‧‧‧ Third switch circuit

24‧‧‧fourth switch circuit

25‧‧‧First flywheel switch circuit

26, 26'‧‧‧Second flywheel switch circuit

27’‧‧‧ Third Flywheel Switch Circuit

VDC‧‧‧ solar DC voltage

VAC‧‧‧mains voltage

Io‧‧‧ output current

C, C1‧‧‧ capacitor

L1‧‧‧first inductance

L2‧‧‧second inductance

TD1‧‧‧ first bypass diode

TD2‧‧‧Second Bypass Diode

TD3‧‧‧ third bypass diode

TD4‧‧‧fourth bypass diode

TD5‧‧‧first flywheel diode

TD6, TD7‧‧‧ second flywheel diode

TD8‧‧‧ third flywheel diode

TD9‧‧‧Fourth flywheel diode

T1‧‧‧ first switch

T2‧‧‧ second switch

T3‧‧‧ third switch

T4‧‧‧fourth switch

T5‧‧‧First flywheel switch

T6‧‧‧second flywheel switch

T8‧‧‧ third flywheel switch

TR1‧‧‧Isolation transformer

PL‧‧‧Flywheel circuit

NL‧‧‧negative flywheel circuit

S1~S4‧‧‧ switch

t ₀ ~t ₅ ‧‧‧Time

N1‧‧‧ first node

N2‧‧‧ second node

Fig. 1 is a circuit diagram showing an inverter according to a first embodiment and a second embodiment.

FIG. 2 is a timing diagram of a switching signal according to the first embodiment and the second embodiment.

FIG. 3 is a schematic diagram showing the first switch, the fourth switch and the first flywheel switch being turned off when the second switch, the third switch and the second flywheel switch are turned on in the first embodiment and the second embodiment.

FIG. 4 is a diagram showing the first switch, the second switch, the third switch, and the fourth switch being turned on in the first embodiment and the second embodiment. A schematic diagram of the cutoff of the first flywheel switch.

FIG. 5 is a schematic diagram showing the first switch, the fourth switch, and the first flywheel switch being turned on and the second switch, the third switch, and the second flywheel switch being turned off in the first embodiment and the second embodiment.

FIG. 6 is a schematic diagram showing the first switch, the second switch, the third switch, the fourth switch, and the second flywheel switch being turned off when the first flywheel switch is turned on in the first embodiment and the second embodiment.

Figure 7 is a schematic diagram showing a pulse width modulation.

FIG. 8 is a timing diagram of a switching signal according to a voltage lead current according to the second embodiment.

FIG. 9 is a schematic diagram showing the first switch, the second switch, the third switch, and the fourth switch being turned off when the first flywheel switch and the second flywheel switch are turned on in the second embodiment.

FIG. 10 is a schematic diagram showing the second switch, the third switch and the second flywheel switch being turned on and the first switch, the fourth switch and the first flywheel switch being turned off in the second embodiment.

11 is a schematic diagram showing the first switch, the second switch, the third switch, and the fourth switch being turned off when the first flywheel switch and the second flywheel switch are turned on in the second embodiment.

FIG. 12 is a schematic diagram showing the first switch, the fourth switch, and the first flywheel switch being turned on and the second switch, the third switch, and the second flywheel switch being turned off in the second embodiment.

Fig. 13 is a timing chart showing the switching signal of a current lead voltage according to the second embodiment.

Figure 14 is a diagram showing the power of an inverter according to the third embodiment. Road map.

Figure 15 is a timing diagram of a switching signal according to the third embodiment.

FIG. 16 is a schematic diagram showing the first switch, the fourth switch, the first flywheel switch and the third flywheel switch being turned off when the second switch and the third switch are turned on in the third embodiment.

FIG. 17 is a schematic diagram showing the first switch, the second switch, the third switch, the fourth switch, and the first flywheel switch being turned off when the third flywheel switch is turned on in the third embodiment.

FIG. 18 is a schematic diagram showing the first switch, the fourth switch, and the first flywheel switch being turned on and the second switch, the third switch, and the third flywheel switch being turned off in the third embodiment.

FIG. 19 is a schematic diagram showing the first switch, the second switch, the third switch, the fourth switch, and the third flywheel switch being turned off when the first flywheel switch is turned on in the third embodiment.

Figure 20 is a circuit diagram of the first conventional inverter.

Figure 21 is a circuit diagram of a second conventional inverter.

1‧‧‧Solar power plant

2‧‧‧Inverter

3‧‧‧ City Grid Road

21‧‧‧First switch circuit

22‧‧‧Second switch circuit

23‧‧‧ Third switch circuit

24‧‧‧fourth switch circuit

25‧‧‧First flywheel switch circuit

26‧‧‧Second flywheel switch circuit

VDC‧‧‧ solar DC voltage

VAC‧‧‧mains voltage

Io‧‧‧ output current

C‧‧‧ capacitor

L1‧‧‧first inductance

L2‧‧‧second inductance

TD1‧‧‧ first bypass diode

TD2‧‧‧Second Bypass Diode

TD3‧‧‧ third bypass diode

TD4‧‧‧fourth bypass diode

TD5‧‧‧first flywheel diode

TD6‧‧‧second flywheel diode

T1‧‧‧ first switch

T2‧‧‧ second switch

T3‧‧‧ third switch

T4‧‧‧fourth switch

T5‧‧‧First flywheel switch

T6‧‧‧second flywheel switch

PL‧‧‧Flywheel circuit

NL‧‧‧negative flywheel circuit

N1‧‧‧ first node

N2‧‧‧ second node

Claims (13)

An inverter for converting a DC voltage to an AC voltage and outputting the AC voltage to a load, the converter comprising: a first inductor and a second inductor respectively connected to both ends of the load Electrical connection; a first switch circuit, a first flywheel switch circuit and a second switch circuit connected in series; a third switch circuit and a fourth switch circuit connected in series; a second flywheel switch circuit, One end is electrically connected to a first node between the first shut-off circuit and the first flywheel switch circuit, and the other end is connected to a second between the third switch circuit and the fourth switch circuit a node; wherein, when the first flywheel switch circuit and the second flywheel switch circuit are turned on, the first flywheel switch circuit, the second flywheel switch circuit, the first inductor, the load, and the second inductor are sequentially connected Forming a current return path; wherein the first switch circuit, the second switch circuit, the third switch circuit, the fourth switch circuit, the first flywheel switch circuit, and the second flywheel switch circuit respectively comprise a first a switch, a second switch, a third switch, a fourth switch, a first flywheel switch, and a second flywheel switch; wherein, when the inverter is in a virtual work compensation mode, the first flywheel switch is A partial period of one or a half of the positive half cycle or the negative half cycle of the alternating voltage is switched complementarily with the second switch, and the switching frequency is higher than the frequency of the alternating voltage. The inverter of claim 1, wherein the current return path forms a positive when the first switch circuit, the second switch circuit, the third switch circuit, and the fourth switch circuit are turned off. Flywheel loop or a negative flywheel loop. The inverter of claim 2, wherein the first switch circuit, the second switch circuit, the third switch circuit, the fourth switch circuit, the first flywheel switch circuit, and the second flywheel switch Each of the circuits further includes a first bypass diode and a first bypass diode respectively connected to the first switch, the second switch, the third switch, the fourth switch, the first flywheel switch and the second flywheel switch a second bypass diode, a third bypass diode, a fourth bypass diode, a first flywheel diode and a second flywheel diode. The inverter of claim 3, wherein the first bypass diode, the second bypass pole body and the first flywheel diode have the same current direction; and the first flywheel The diode and the second flywheel diode allow opposite current directions in the current return path. The inverter of claim 4, wherein when the inverter is in the virtual work compensation mode, the second flywheel switch is in a positive half cycle of the alternating voltage or a half cycle of the negative half cycle The period of time is switched complementary to the first switch, and the switching frequency is higher than the frequency of the alternating voltage. The inverter of claim 5, wherein the first flywheel switch and the second flywheel switch are respectively before and after the AC voltage zero crossing point when the inverter is in the virtual work compensation mode Switching is performed complementary to the second switching circuit and complementary to the first switching circuit, and the switching frequency is higher than the frequency of the alternating voltage. The inverter of claim 5, wherein the inverter supplies an output current to the load, and when the converter is in the virtual work compensation mode, a zero crossing point of the output current occurs. When the first flywheel switch circuit is complementary to the second switch circuit or when the second flywheel switch circuit is complementary to the first switch circuit. The inverter of claim 1, wherein when the AC voltage reaches a peak, one of the first flywheel switch circuit and the second flywheel switch circuit is turned off and the other is turned on. An inverter for converting a solar DC voltage into a mains voltage output to a city grid circuit, the converter comprising: a first inductor; a second inductor; a first switch circuit; and a second switch Circuit a third switching circuit; a fourth switching circuit is connected in series with the third switching circuit; a first flywheel (Free Wheeling) switching circuit is connected in series with the first switching circuit and the second switching circuit; a flywheel switch circuit, one end of the second flywheel switch circuit is coupled to the first switch circuit, and the other end of the second flywheel switch circuit is coupled to the third switch circuit; and a third flywheel switch circuit, the first One end of the three flywheel switch circuit is coupled to the first flywheel switch circuit and the second switch circuit, and the other end of the third flywheel switch circuit is coupled to the second flywheel switch circuit, the third switch circuit, and the first Four switch circuit. The inverter of claim 9, wherein the first switching circuit comprises a first bypass diode and a first switch, and the first bypass diode system is connected in parallel with the first switch. The second switching circuit includes a second bypass diode and a second switch. The second bypass diode system is connected in parallel with the second switch. The third switching circuit includes a third bypass diode and a third switch, the third bypass diode system is connected in parallel with the third switch, the fourth switch circuit includes a fourth bypass diode and a fourth switch, the fourth bypass diode system and the The fourth switch is connected in parallel, the first flywheel switch circuit includes a first flywheel diode and a first flywheel switch, the first flywheel diode system is connected in parallel with the first flywheel switch, and the second flywheel switch circuit includes only one a second flywheel diode, the third flywheel switch circuit comprising a third flywheel diode, a third flywheel switch and a fourth flywheel diode, the third flywheel diode system being connected in parallel with the third flywheel switch The fourth flywheel diode system is in series with the third flywheel switch. The inverter of claim 10, wherein the first flywheel switch circuit is coupled to the second inductor, and the second flywheel switch circuit is coupled to the first inductor. The inverter of claim 10, wherein when the mains voltage is in a positive half cycle and a negative half cycle, the second switch and the third open relationship are higher than a frequency of the mains frequency. Switching, and the third flywheel opening relationship is turned on. When the mains voltage is in the positive half cycle and the other half cycle of the negative half cycle, the first switch and the fourth open relationship are switched at a frequency higher than the mains frequency, and The first flywheel opening relationship is turned on. The inverter of claim 10, wherein an anode of the third flywheel diode is coupled to an anode of the fourth flywheel diode, and a cathode of the third flywheel diode is coupled to the anode a cathode of the second bypass diode and an anode of the first flywheel diode, a cathode of the fourth flywheel diode coupled to an anode of the second flywheel diode and the third bypass diode The anode of the body.