JP6175946B2 - Resonant inverter device - Google Patents

Description

  The present invention relates to a resonant inverter device of soft switching control that converts direct current to alternating current.

  A distributed power source such as a photovoltaic power generation system or a fuel cell system is connected to a power distribution system via a grid interconnection inverter. Grid-connected inverters used for these distributed power sources are required to have small size, high efficiency, and low noise performance. For this reason, a resonance type inverter device is used in which resonance is generated by a resonance reactor and a resonance capacitor to turn on the switching element to zero voltage switching (soft switching), thereby reducing the switching loss of the switching element.

  FIG. 6 is a circuit diagram showing an example of a conventional resonant inverter device (Patent Document 1). In the resonance type inverter device shown in FIG. 6, each of the booster circuit 10, the auxiliary circuit 20, and the inverter circuit 30 is connected between the positive input line P and the negative input line N, and the inverter circuit 30 and the distribution system are connected. A soft switching circuit system linked by the filter circuit 40 is employed.

At the timing when the switching elements Q0, S1 to S4 provided in the booster circuit 10 and the inverter circuit 30 are turned on, the auxiliary circuit 20 is operated to turn on the switching elements Q0, S1 to S4. The turn-off of the switching elements Q0, S1 to S4 is a soft turn-off because the rise of the voltage is delayed by the capacitors C0 to C4 connected in parallel to the switching elements Q0, S1 to S4.
According to this resonance type inverter device, since the switching loss generated in the switching elements Q0, S1 to S4 is reduced, the efficiency can be greatly improved. Further, since the voltage change of the switching elements Q0, S1 to S4 becomes gentle due to resonance, noise can be greatly reduced.

  However, the resonance type inverter device shown in FIG. 6 only reduces the switching element loss, and the loss in the other filter circuit 40 and the like is not reduced. Since the voltage applied to the filter circuit 40 changes from + Vpn / 2 to −Vpn / 2 every switching, the filter circuit 40 is enlarged. For this reason, there has been a problem that the loss generated in the filter circuit 40 is large. As an apparatus for solving this problem, for example, an inverter apparatus shown in FIG. 7 has been conventionally used.

  The inverter device shown in FIG. 7 connects each of the booster circuit 10 and the three-level inverter circuit 31 between the positive input line P and the negative input line N, and connects the three-level inverter circuit 31 and the distribution system to the filter circuit. The circuit system which connects with 40 is adopted. Since this method does not add a resonance circuit, a hard switching operation is performed.

  In this system, the voltage applied to the switching elements Tru1, Tru4, Trw1, and Trw4 is halved as compared with the two-level inverter circuit 30, so that the filter circuit 40 can be reduced in size and loss. Since this method can reduce the switching loss generated in the switching element and the loss generated in the filter circuit 40, the efficiency can be greatly improved.

  A similar three-level inverter device is described in Patent Document 2.

JP 2012-23831 A JP 2010-288415 A

  However, since the inverter device shown in FIG. 7 is hard switching, the noise suppression effect is small. Further, when the switching frequency is increased, the switching loss increases. Further, when the switching frequency is lowered, there are problems such as deterioration of noise characteristics.

  An object of the present invention is to provide a resonant inverter device that can reduce switching loss, noise, and loss of a filter circuit.

  In order to solve the above problems, the present invention is a resonant inverter device that converts a DC voltage of a DC power source supplied from between a positive input line and a negative input line into an AC voltage and outputs the AC voltage, A first series circuit including a positive first capacitor and a negative second capacitor, connected between the positive input line and the negative input line, and the positive input line and the negative input. A second series circuit including a first switch on the positive side and a second switch on the negative side, a first resonance capacitor connected in parallel to the first switch and the second switch, A second resonance capacitor; a third series circuit connected to both ends of the first capacitor and including a first diode and a first resonance switch; a connection point between the first capacitor and the second capacitor; and the first switch. And said A fourth series circuit composed of a second diode and a third switch, a connection point between the first diode and the resonant switch, the second diode, and the third diode. And a first resonance reactor connected between a connection point with the switch.

  According to the present invention, when the inverter reactor current is in the inverter-> system direction, the first resonance switch is operated to turn on the first switch, so that the switching loss and noise can be reduced. An inverter device can be provided.

It is a figure which shows the structure for 1 phase of the resonance type inverter apparatus of Example 1. FIG. It is a circuit diagram which shows the resonance type inverter apparatus of Example 1 of this invention. 3 is a timing chart for explaining the operation of each part of the resonant inverter device according to the first embodiment. It is a figure which shows the operation mode transition of the resonance type inverter apparatus of Example 1. FIG. It is a figure which shows the operation mode transition of the resonance type inverter apparatus of Example 1. FIG. It is a circuit diagram which shows an example of the conventional resonance type inverter apparatus. It is a circuit diagram which shows another example of the conventional 3 level inverter apparatus.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a resonant inverter device of the present invention will be described in detail with reference to the drawings. The present invention is characterized in that a three-level inverter circuit is improved and an auxiliary circuit 2 (auxiliary resonance circuit) is added to the conventional resonant inverter device shown in FIG. The auxiliary circuit 2 added to each inverter arm is operated only when the polarity of the inverter reactor current is the same as that of the inverter reactor current.

  FIG. 1 is a diagram illustrating a configuration of one phase of the resonant inverter device according to the first embodiment. The mid-point clamp switch of the three-level inverter circuit 3 is not a general IGBT series configuration, but a series circuit of a diode Dnpcp and a switching element Tr2 for limiting the current polarity to one direction, and a diode Dnpcn and a switching A series circuit with the element Tr3 is connected in parallel. During PWM control of the switch Tr1 and the switch Tr3, when the inverter reactor current is in the inverter → system direction, the upper resonance circuit (resonance switch Tr5) is operated to turn on the switch Tr1 with zero voltage. Further, during the PWM control of the switch Tr4 and the switch Tr2, when the inverter reactor current is in the system → inverter direction, the lower resonance circuit (resonance switch Tr6) is operated to turn on the switch Tr4 with zero voltage. Other than the above, that is, during a period in which the polarities of the output voltage and the output current are different, the resonance circuit is stopped.

  FIG. 1 shows a configuration for one phase, for example, a configuration for the U phase. A series circuit of a capacitor C1 (first capacitor) and a capacitor C2 (second capacitor) is connected, one end of the capacitor C1 is connected to the positive input line P, and one end of the capacitor C2 is connected to the negative input line N. The The connection point between the capacitor C1 and the capacitor C2 is a midpoint potential O.

  The auxiliary circuit 2Au for the positive input line P side is connected to both ends of the capacitor C1, and the auxiliary circuit 2Bu for the negative input line N side is connected to both ends of the capacitor C2.

In the auxiliary circuit 2Au, between the positive input line P and the negative input line N, a first series circuit including a positive capacitor C1 (first capacitor) and a negative capacitor C2 (second capacitor). Is connected. Between the positive input line P and the negative input line N, a positive switch Tr1 (first switch) and a negative switch Tr4 are provided.
A second series circuit comprising (second switch) is connected.

  A resonant capacitor Crp1 (first resonant capacitor) and a resonant capacitor Crn1 (second resonant capacitor) are connected in parallel to the switch Tr1 and the switch Tr4. A third series circuit including a diode Drp3 (first diode), a diode Drp2, and a resonance switch Tr5 (first resonance switch) is connected to both ends of the capacitor C1.

  A fourth series circuit including a diode Dnpcp (second diode) and a switch Tr2 (third switch) is connected between a connection point between the capacitor C1 and the capacitor C2 and a connection point between the switch Tr1 and the switch Tr2. The A series circuit of a resonance reactor Lrup (first resonance reactor) and a diode Drp1 is connected between a connection point between the diode Drp2 and the resonance switch Tr5 and a connection point between the diode Dnpcp and the switch Tr2.

  Between the connection point between the capacitor C1 and the capacitor C2, and the connection point between the diode Dnpcp and the switch Tr2, a diode Drp3, a diode Drp2 (fifth diode), a resonance reactor Lrup, and a diode Drp1 (sixth diode) are formed. A seventh series circuit is connected. A capacitor Crp2 (first snubber capacitor) is connected to both ends of a series circuit of the diode Drp2, the resonant reactor Lrup, and the diode Drp1.

  A diode Drp4 (seventh diode) is connected to both ends of the series circuit of the diode Drp3, the diode Drp2, and the resonant reactor Lrup. A diode Drp5 (eighth diode) is connected in parallel with a series circuit composed of the resonant switch Tr5 and the resonant reactor Lrup.

  In the auxiliary circuit 2Bu, a fifth series circuit including a diode Drn3 (third diode), a diode Drn2, and a resonance switch Tr6 (second resonance switch) is connected to both ends of the capacitor C2. A sixth series circuit including a diode Dnpcn (fourth diode) and a switch Tr3 (fourth switch) is connected between a connection point between the capacitor C1 and the capacitor C2 and a connection point between the switch Tr1 and the switch Tr4. The

  A series circuit of a resonance reactor Lrun (second resonance reactor) and a diode Drn1 is connected between a connection point between the diode Drn2 and the resonance switch Tr6 and a connection point between the diode Dnpcn and the switch Tr3.

  Between the connection point between the capacitor C1 and the capacitor C2, and the connection point between the diode Drn2 and the resonance switch Tr6, a diode Drn3, a diode Drn2 (9th diode), a resonance reactor Lrun, and a diode Drn1 (tenth diode) are formed. An eighth series circuit is connected.

  A capacitor Crn2 (second snubber capacitor) is connected to both ends of a series circuit of the diode Drn2, the resonant reactor Lrun, and the diode Drn1. A diode Drn4 (an eleventh diode) is connected to both ends of a series circuit of the diode Drn3, the diode Drn2, and the resonant reactor Lrun. A diode Drn5 (a twelfth diode) is connected in parallel with a series circuit including the resonance switch Tr6 and the resonance reactor Lrun.

  The switches Tr1, Tr2, Tr3, Tr4 are made of insulated gate bipolar transistors (IGBT), and the resonance switches Tr5, Tr6 are made of MOSFETs.

  Next, the operation of the resonance type inverter apparatus according to the first embodiment configured as described above will be described with reference to the timing chart shown in FIG. 3 and the operation mode transition diagrams shown in FIGS. 4 and 5, the current fluctuation in the switching period is assumed to be small, and the inverter reactor current is illustrated as an equivalent current source. 4 and 5 show a case where the polarities of the inverter reactor current and the output voltage command value are positive, the switch Tr1 and the switch Tr3 perform PWM control, the switch Tr2 is always on, and the switch Tr4 Is always off, and the upper resonance circuit operates.

  When the polarity of the inverter reactor current and the output voltage command value is negative, the switch Tr2 and the switch Tr4 perform PWM control, the switch Tr3 is always on, the switch Tr1 is always off, and the lower resonance circuit is Operate. Since the operation of the lower resonance circuit is basically the same as the operation of the upper resonance circuit, the description thereof is omitted here.

  In FIG. 3, iLrp is the current flowing through the resonant reactor Lrp (Lrup, Lrwp), iTr1 is the current flowing through the main switch Tr1 (Tru1, Trw1), VTr1 is the voltage across the main switch Tr1 (Tru1, Trw1), and VTr5 is The voltage across the resonance switch Tr5, Tr5 indicates the gate voltage of the resonance switch Tr5. Moreover, in FIG.4 and FIG.5, the code | symbol of each part has displayed the U phase and the W phase collectively. For example, Tr2 represents a U-phase switch Tru2 and a W-phase switch Trw2, and the symbol u and the symbol w are deleted.

  First, in mode 0 shown in FIG. 4A, the switch Tr2 is turned on, and all the switches other than the switch Tr2 are in the dead time DT period. The inverter reactor current IL circulates from Dnpcp → Tr2. For this reason, the output voltage is zero. The resonance capacitor Crp1 connected in parallel with the main switch is charged to the intermediate link voltage Vdcp, and the resonance capacitor Crn1 is charged to the voltage Vdcn.

  Next, in mode 1 shown in FIG. 4B, the resonance switch Tr5 is turned on. Then, the inverter reactor current IL flowing back through the diode Dnpcp is commutated to the resonant reactor Lrup. At this time, the reactor current iLrp flows through a path of C1 (voltage Vdcp) → Tr5 → Lrup → Drp1 → Tr2. Since the upper link voltage is applied to the resonant reactor Lrup, the slope of the resonant reactor current iLrp increases at Vdcp / Lrup. When the resonant reactor current iLrp coincides with the inverter reactor current IL, commutation is completed and the clamp diode Dnpcp is turned off.

  The resonance switch Tr5 is turned on because the rising of the current is suppressed by the resonance reactor Lrup, so that the zero current is turned on.

  Next, mode 2 shown in FIG. 4C is a mode in which series resonance is performed by the resonant reactor Lrup, the resonant capacitors Crp1 and Crn1 of each arm, and the DC link voltage. In this case, the first resonance path of Crp1 → Tr5 → Lrup → Drp1 → Tr2 → Crp1 and the second of C2 (voltage Vdcn) → C1 (voltage Vdcp) → Tr5 → Lrup → Drp1 → Tr2 → Crn1 → C2 Current flows through the resonance path.

  When the clamp diode Dnpcp is turned off, energy transitions from the resonance capacitor Crp1 to the resonance reactor Lrup in the first resonance path, and energy transitions from the DC link to the resonance capacitor Crp1 and the resonance reactor Lrup in the second resonance path. To do. This resonance continues until the terminal voltage of the main switch Tr1 starts to decrease from the upper DC link voltage Vdcp and becomes zero.

  Next, in mode 3 shown in FIG. 4D, when the terminal voltage of the main switch Tr1 becomes zero, the main switch Tr1 is turned on (zero voltage switching of the main switch Tr1), and then the resonance switch Tr5 is turned on. Is a mode in which the zero voltage is turned off. At the end of mode 2, when the terminal voltage of the main switch Tr1 becomes zero, the AC amplitude component Δ | iLr | of the resonant reactor current conducts the diode Drp5, so that the main switch Tr1 is turned on and the output voltage is zero. Change to Vdcp. That is, the amount of change in output voltage is halved compared to a two-level inverter.

  In this state, when the resonance switch Tr5 is turned off, the inverter reactor current IL and the resonance current AC amplitude Δ | iLr | accumulated in the resonance reactor Lr start to charge the snubber capacitor Crp2. As a result, the rise of the voltage of the resonance switch Tr5 is suppressed, so that the resonance switch Tr5 is turned off to zero voltage. In mode 3, current flows in the first path through which the inverter reactor current flows through the capacitor C1 and the main switch Tr1, and the second path from Lrup → Drp1 → Crp2 → Drp2 → Lrup, and the voltage of the snubber capacitor Crp2 is the voltage of the capacitor C1. Continue until the voltage reaches Vdcp.

  Next, in mode 4 shown in FIG. 5A, the diode Drp5 is turned on when the voltage of the snubber capacitor Crp2 becomes the voltage Vdcp of the capacitor C1, and the current of the resonant reactor Lrup is regenerated to the P-side DC link. The current flows through the route of Lrup → Drp5 → C1 → Drp3 → Drp2 → Lrup.

  That is, when the diode Drp5 is turned on, the upper link voltage Vdcp is applied to the resonant reactor Lrup, so that the resonant reactor current iLr starts to decrease with a slope −Vdcp / Lrup. Mode 4 ends when the energy stored in the resonance reactor is regenerated in the DC link.

  Next, in the mode 5 shown in FIG. 5B, the main switch Tr1 is turned on and the inverter reactor current IL is supplied to the load.

  Next, in mode 6 shown in FIG. 5C, the main switch Tr1 is turned off, and the resonant capacitors Crp1 and Crn1 and the snubber capacitor Crp2 are charged and discharged. When the main switch Tr1 is turned off, the inverter reactor current IL charges and discharges the resonant capacitors Crp1 and Crn1 and the snubber capacitor Crp2. In mode 6, it continues until the voltage of the resonant capacitor Crp1 becomes equal to the intermediate link voltage Vdcp. The turn-off of the main switch Tr1 is zero voltage switching because the rise of the voltage is suppressed by each capacitor.

  Next, mode 7 shown in FIG. 5D is a mode in which the switch Tr3 is turned on in a state where the inverter reactor current IL circulates through the clamp diode Dnpcp and the switch Tr2. At the end of mode 6, when the voltage of the resonant capacitor Crp1 becomes equal to the intermediate link voltage Vdcp, the clamp diode Dnpcp becomes conductive, and the inverter reactor current IL circulates through the clamp diode Dnpcp. Since the clamp diode Dnpcp and the switch Tr2 are conductive, the switch Tr3 is turned on to perform zero voltage switching.

  As described above, according to the resonance type inverter device of the first embodiment, when the inverter reactor current is positive in the PWM control in which the switches Tr1 and Tr3 are alternately turned on and off, the upper resonance circuit (resonance switch Tr5 ) To turn on the switch Tr1 with zero voltage. Also, during PWM control to alternately turn on and off the switch Tr4 and the switch Tr2, when the inverter reactor current is negative, the lower resonance circuit (resonance switch Tr6) is operated to turn on the switch Tr4 with zero voltage .

  Therefore, the switching loss and the loss in the filter circuit are reduced, and the efficiency can be greatly improved. Moreover, since the voltage change of the switching element becomes gentle due to resonance, noise can be reduced. Furthermore, since the switching loss is reduced, the switching frequency can be increased. For this reason, noise characteristics can also be improved.

  In the first embodiment shown in FIG. 1, the configuration for one phase (for example, the U phase) is shown, but in the second embodiment shown in FIG. 2, the configuration is applied to the configuration for three phases. The resonant inverter device according to the second embodiment includes a booster circuit 1, auxiliary circuits 2a and 2b, a three-level inverter circuit 3, and a filter circuit 4.

  In FIG. 2, a booster circuit 1 is connected to both ends of the DC power supply E. This booster circuit 1 has a series circuit of a boost reactor L1 connected to both ends of a DC power source E and a switch Qo composed of an insulated gate bipolar transistor (IGBT), and an anode at a connection point between the boost reactor L1 and the switch Qo. It is composed of a connected diode Dc and boosts the voltage of the DC power supply E.

  The auxiliary circuit 2a has a U-phase auxiliary circuit 2Au and a W-phase auxiliary circuit 2Aw, and the auxiliary circuit 2b has a U-phase auxiliary circuit 2Bu and a W-phase auxiliary circuit 2Bw. The auxiliary circuit 2Au for U phase and the auxiliary circuit 2Bu for U phase have been described in the first embodiment shown in FIG. Since the W-phase auxiliary circuit 2Aw and the W-phase auxiliary circuit 2Bw are also configured in the same manner as the U-phase auxiliary circuit 2Au and the U-phase auxiliary circuit 2Bu, description thereof will be omitted.

  A three-level inverter circuit 3 is connected between the positive input line P and the negative input line N. In the three-level inverter circuit 3, a series circuit (half bridge circuit) of a main switch Tru1 and a main switch Tru4 is connected between the positive input line P and the negative input line N, and the main switch Trw1 A series circuit (half bridge circuit) with the main switch Trw4 is connected.

  Diodes and resonant capacitors Crp1, Crn1, Crp4, Crn4 are connected between collectors and emitters of main switches Tru1, Tru4, Trw1, Trw4 made of IGBT. Between the connection point of the main switch Tru1 and the main switch Tru4 and the midpoint potential O, a series circuit of the diode Dnpcp and the switch Tru2 and a series circuit of the diode Dnpcn and the switch Tru3 are connected in antiparallel. . Between the connection point of the main switch Trw1 and the main switch Trw4 and the midpoint potential O, a series circuit of the diode Dnpcp and the switch Trw2 and a series circuit of the diode Dnpcn and the switch Trw3 are connected in antiparallel. .

  The connection point between the main switch Trw1 and the main switch Trw4 is connected to the AC output terminal W via the reactor Lw, and the connection point between the main switch Tru1 and the main switch Tru4 is connected to the AC output terminal U via the reactor Lu. The connection point between the capacitor Cacu and the capacitor Cacw is connected to the AC output terminal V and the neutral point O. Here, the filter circuit 4 is composed of reactors Lu and Lw and capacitors Cacu and Cacw, and is a filter that removes high frequency components and outputs sine wave components.

  The control circuit 10 performs on / off control of the switch Qo, the resonance switches Tr5, Tr6, Tr7, Tr8, the main switches Tru1, Tru4, Trw1, Trw4, and the switches Tru2, Tru3, Trw2, Trw3, and the main switches Tru1, Tru4, Trw1 and Trw4 are zero-voltage switched, and sinusoidal three-phase AC voltage is output to the AC output terminals U, V, and W.

  Thus, also in the resonance type inverter device of the second embodiment, the same effect as that of the resonance type inverter device of the first embodiment can be obtained.

  The present invention is applicable to a DC-AC power converter and a grid interconnection inverter.

E DC power supply L1 Boost reactor Qo switch
Tr5 to Tr8 resonant switch
Tru1, Tru4, Trw1, Trw4 main switch
Lrup, Lrwp, Lrun, Lrwn Resonant reactor
Crp1, Crn1, Crp4, Crn4 Resonant capacitors Lu, Lw Reactor 1 Booster circuits 2a, 2b, 2Au, 2Bu, 2Aw, 2Bw Auxiliary circuit 3 3-level inverter circuit 4 Filter circuit 10 Control circuit

Claims (6)

A resonance type inverter device that converts a DC voltage of a DC power source supplied from between a positive side input line and a negative side input line into an AC voltage,
A first series circuit connected between the positive input line and the negative input line and comprising a first capacitor on the positive side and a second capacitor on the negative side;
A second series circuit connected between the positive input line and the negative input line and comprising a positive first switch and a negative second switch;
A first resonant capacitor and a second resonant capacitor connected in parallel to the first switch and the second switch;
A third series circuit connected to both ends of the first capacitor and comprising a first diode and a first resonant switch;
A fourth series circuit comprising a second diode and a third switch connected between a connection point of the first capacitor and the second capacitor and a connection point of the first switch and the second switch;
A first resonance reactor connected between a connection point between the first diode and the resonance switch and a connection point between the second diode and the third switch;
A resonance type inverter device comprising: A fifth series circuit connected to both ends of the second capacitor and comprising a third diode and a second resonant switch;
A sixth series circuit comprising a fourth diode and a fourth switch connected between a connection point of the first capacitor and the second capacitor and a connection point of the first switch and the second switch;
A second resonance reactor connected between a connection point between the third diode and the second resonance switch and a connection point between the fourth diode and the fourth switch;
The resonance type inverter apparatus according to claim 1, further comprising: A filter circuit for extracting an output from a connection point between the first switch and the second switch;
The filter circuit includes a reactor,
When the current flowing through the reactor is in the first direction, the second switch is turned off, the third switch is turned on, the first resonance switch is operated, the first switch is turned on with a zero voltage, and the first switch is turned on. 1 switch and the fourth switch are alternately turned on and off to output a voltage in the first direction,
When the current flowing through the reactor is in a second direction opposite to the first direction, the first switch is turned off, the fourth switch is turned on, and the second resonance switch is operated to operate the second switch. The resonant inverter apparatus according to claim 2, further comprising a control circuit that turns on a zero voltage and alternately turns on and off the second switch and the third switch to output a voltage in a second direction. And connected between a connection point of the first capacitor and the second capacitor and a connection point of the second diode and the third switch, the first diode, the fifth diode, the first resonant reactor, A seventh series circuit composed of six diodes;
A first snubber capacitor connected to both ends of a series circuit of the fifth diode, the first resonant reactor, and the sixth diode;
A seventh diode connected to both ends of a series circuit of the first diode, the fifth diode, and the first resonant reactor;
An eighth diode connected in parallel with a series circuit comprising the first resonant switch and the first resonant reactor;
Resonant inverter according to claim 3, wherein you comprising: a. Connected between a connection point of the first capacitor and the second capacitor, and a connection point of the fourth diode and the fourth switch, the third diode, the ninth diode, the second resonance reactor, and the second An eighth series circuit composed of 10 diodes;
A second snubber capacitor connected to both ends of a series circuit of the ninth diode, the second resonant reactor, and the tenth diode;
An eleventh diode connected to both ends of a series circuit of the third diode, the ninth diode, and the second resonant reactor;
A twelfth diode connected in parallel with a series circuit composed of the second resonant switch and the second resonant reactor;
5. The resonant inverter device according to claim 2, further comprising:   A resonant inverter device according to any one of claims 2 to 5 is used as a resonant inverter unit for one phase, the resonant inverter unit for a plurality of phases is provided, and multiphase AC power is output. A resonance type inverter device.

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