Resonance type inverter

Abstract

To provide a resonance type inverter capable of constructing an auxiliary resonance circuit of a lossless auxiliary resonance circuit that is a path of an energy accumulated to a resonance inductor with a breakdown element that is lower than that of a main circuit.SOLUTION: An auxiliary resonance circuit 2 comprises: a positive side resonance path rp in which a current polarity is limited to a direction of a resonance inductor Lr from a neutral point A, and is switched by a switch element Tr3; a negative side resonance path rn in which the current polarity is limited to a direction of the neutral point A from the resonance inductor Lr, and is switched by a switch element Tr4; a positive side regeneration route (D3+Dsp) in which the current polarity is limited to the direction of a positive side DC line P from the resonance inductor Lr; and a negative side regeneration route (D4+Dsn) in which the current polarity is limited to the direction of the resonance inductor Lr from a negative side DC line N.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a resonant inverter having an auxiliary resonant circuit. [Background technology]

[0002] An energy storage system such as an uninterruptible power supply includes an energy storage device and a PCS (power conditioner unit) with a built-in inverter that converts AC and DC between an external power system and the energy storage device. The energy storage device is configured with, for example, a plurality of energy storage modules each having a plurality of energy storage elements. In recent years, the energy storage device has become higher in voltage and larger in capacity.

[0003] As the voltage and capacity of power storage devices increase, the increase in switching loss and electromagnetic interference (EMI) noise in inverters becomes a major problem. Resonant inverters are used as a method for reducing switching loss and EMI noise (see, for example, Patent Documents 1, 2, and 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5195161 [Patent Document 2] Patent No. 5569204 Summary of the Invention [Problem to be solved by the invention]

[0005] In the resonant inverter of Patent Document 2, when all switches are off, a path for the energy stored in the resonant inductor is secured by the snubber circuit, but efficiency decreases due to snubber loss.

[0006] In the resonant inverter of Patent Document 3, when all switches are off, the energy stored in the resonant inductor is regenerated to the DC link without loss by the auxiliary resonant circuit. The auxiliary resonant circuit serves as a path for the energy stored in the resonant inductor, and no snubber loss occurs. However, the auxiliary circuit requires high-voltage elements, the same as the main circuit. There are only a few types of high-voltage elements, and their switching speed is slow, which raises concerns about a decrease in efficiency.

[0007] One aspect of the present invention provides a resonant inverter in which a loss-free auxiliary resonant circuit, which serves as a path for energy stored in a resonant inductor, can be configured using elements with a lower withstand voltage than the main circuit. [Means for solving the problem]

[0008] One aspect of the present invention is a resonant inverter including a positive-side capacitor and a negative-side capacitor connected in series between a positive-side DC line and a negative-side DC line, and a neutral point clamp circuit in which a connection point between the positive-side capacitor and the negative-side capacitor is a neutral point. The resonant inverter includes a main leg including an upper arm switch and a lower arm switch connected in series between the positive-side DC line and the negative-side DC line, and a connection point between the upper arm switch and the lower arm switch, which are alternately controlled with a dead time therebetween, is an input / output point of an inverter current. The resonant inverter includes a first resonant capacitor and a second resonant capacitor connected in parallel to the upper arm switch and the lower arm switch. The resonant inverter includes a first anti-parallel diode and a second anti-parallel diode connected in anti-parallel to the upper arm switch and the lower arm switch. The resonant inverter includes an auxiliary resonant circuit including a resonant inductor having one end connected to the input / output point of the main leg. The auxiliary resonant circuit includes a positive-side resonant path in which a current polarity is limited to a direction from the neutral point to the resonant inductor and opened / closed by a positive-side resonant switch. The auxiliary resonant circuit includes a negative-side resonant path whose current polarity is limited to a direction from the resonant inductor to the neutral point and which is opened and closed by a negative-side resonant switch. The auxiliary resonant circuit includes a positive-side regenerative path whose current polarity is limited to a direction from the resonant inductor to the positive-side DC line. The auxiliary resonant circuit includes a negative-side regenerative path whose current polarity is limited to a direction from the negative-side DC line to the resonant inductor. Effect of the Invention

[0009] According to one aspect of the present invention, the lossless auxiliary resonant circuit, which serves as a path for the energy stored in the resonant inductor, is clamped to the neutral voltage by the positive resonant path and the negative resonant path, so that the elements that make up the auxiliary resonant circuit can be constructed from elements with a lower voltage resistance than the main circuit. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a diagram showing a circuit configuration for one phase of an embodiment of a resonant inverter. [Diagram 2] 2 is a timing chart showing an operation of the resonant inverter shown in FIG. [Diagram 3] 3A to 3C are diagrams illustrating the operation of each mode shown in FIG. 2. [Figure 4] 11 is a timing chart showing a clamp snubber operation in a positive direction. [Diagram 5] FIG. 5 is a diagram illustrating the operation of mode 3A shown in FIG. [Figure 6] 2 is a timing chart showing an operation of the resonant inverter shown in FIG. [Figure 7] 7A to 7C are diagrams illustrating the operation of each mode shown in FIG. 6. [Figure 8] 11 is a timing chart showing a clamp snubber operation in the negative direction. [Figure 9] FIG. 9 is a diagram illustrating the operation of mode 13A shown in FIG. 8. [Figure 10] FIG. 2 is a diagram illustrating a first application example of the resonant inverter illustrated in FIG. [Figure 11] 1. FIG. 4 is a diagram illustrating a second application example of the resonant inverter illustrated in FIG. [Figure 12] 12 is a diagram illustrating an operation of the resonant inverter shown in FIG. [Figure 13] 1. FIG. 4 is a diagram illustrating a third application example of the resonant inverter illustrated in FIG. [Figure 14] FIG. 14 is a diagram illustrating an operation of the resonant inverter shown in FIG. [Figure 15] 1. FIG. 4 is a diagram illustrating a fourth application example of the resonant inverter illustrated in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, components having similar functions are given the same reference numerals and descriptions thereof will be omitted as appropriate.

[0012] Referring to FIG. 1, the resonant inverter 1 of this embodiment is a two-level inverter having an auxiliary resonant circuit 2 of an NPC (neutral point clamped) type ARCP (auxiliary resonant commutated pole) topology.

[0013] The resonant inverter 1 includes a neutral point clamp circuit 3 in which a positive side capacitor Cp and a negative side capacitor Cn are connected in series. The neutral point clamp circuit 3 is connected between a positive side DC line P and a negative side DC line N. The capacitors Cp and Cn are configured to have the same capacitance. The connection point between the capacitors Cp and Cn is a neutral point A where a voltage Vdc / 2, which is half the voltage of the input DC voltage Vdc input between the positive side DC line P and the negative side DC line N, is generated.

[0014] The resonant inverter 1 includes a main leg 4, which is a series circuit including a switch element Tm1, which is an upper arm switch arranged in an upper arm, and a switch element Tm2, ​​which is a lower arm switch arranged in a lower arm. The switch elements Tm1 and Tm2 are, for example, insulated gate bipolar transistors (IGBTs). The switch elements Tm1 and Tm2 may be MOSFETs. The main leg 4 is connected between a positive side DC line P and a negative side DC line N. The switch element Tm1 has a collector connected to the positive side DC line P and an emitter connected to the collector of the switch element Tm2. The switch element Tm2 has an emitter connected to the negative side DC line N. The connection point between the emitter of the switch element Tm1 and the collector of the switch element Tm2 becomes an input / output point B of the inverter current Iinv, and is connected to an AC input / output terminal via an inductor L1.

[0015] The switch element Tm1 includes an anti-parallel diode D1, the cathode of which is connected to the collector of the switch element Tm1, and the anode of which is connected to the emitter of the switch element Tm1. The anti-parallel diode D1 is, for example, a body diode of the switch element Tm1. The switch element Tm1 includes a resonant capacitor C1 connected in parallel. The resonant capacitor C1 is formed of a stray capacitance of the switch element Tm1 or an external capacitor.

[0016] The switch element Tm2 includes an anti-parallel diode D2, the cathode of which is connected to the collector of the switch element Tm2, ​​and the anode of which is connected to the emitter of the switch element Tm2. The anti-parallel diode D2 is, for example, a body diode of the switch element Tm2. The switch element Tm2 includes a resonant capacitor C2 connected in parallel. The resonant capacitor C2 is a stray capacitance of the switch element Tm2 or an external capacitor.

[0017] The auxiliary resonant circuit 2 includes a resonant inductor Lr, and a positive-side resonant path rp and a negative-side resonant path rn connected in parallel between an input / output point B of the main leg 4 and a neutral point A of the neutral point clamp circuit 3.

[0018] The positive-side resonant path rp is configured as a series circuit including, from the other end side of the resonant inductor Lr, one end of which is connected to the input / output point B, a switch element Tr3, which is a positive-side resonant switch, and a diode Drp. The switch element Tr3 is configured, for example, by an insulated gate bipolar transistor (IGBT). The switch element Tr3 may be configured by a MOSFET.

[0019] The resonant inductor Lr has one end connected to the input / output point B and the other end connected to the emitter of the switch element Tr3. The collector of the switch element Tr3 is connected to the cathode of the diode Drp, and the anode of the diode Drp is connected to the neutral point A.

[0020] The diode Drp limits the current polarity of the positive-side resonant path rp to one direction (from the neutral point A to the input / output point B). The switch element Tr3 opens and closes the positive-side resonant path rp.

[0021] The switch element Tr3 includes an anti-parallel diode D3 having a cathode and an anode connected to the collector and the emitter of the switch element Tr3, respectively. The anti-parallel diode D3 is formed, for example, by the body diode of the switch element Tr3.

[0022] The auxiliary resonant circuit 2 includes a lossless regenerative clamp snubber diode Dsp that connects a connection point between the collector of the switch element Tr3 and the cathode of the diode Drp, and the positive side DC line P. The lossless regenerative clamp snubber diode Dsp has an anode connected to the connection point between the collector of the switch element Tr3 and the cathode of the diode Drp, and a cathode connected to the positive side DC line P.

[0023] The anti-parallel diode D3 of the switch element Tr3 and the lossless regenerative clamp snubber diode Dsp form a positive-side regenerative path in which the current polarity is limited to one direction (from the resonance inductor Lr to the positive-side DC line P).

[0024] The negative-side resonant path rn is configured in series with a switch element Tr4, which is a negative-side resonant switch, and a diode Drn, in this order, from the other end side of a resonant inductor Lr, one end of which is connected to the input / output point B. The resonant inductor Lr is also used with the positive-side resonant path rp. The switch element Tr4 is configured, for example, by an insulated gate bipolar transistor (IGBT). The switch element Tr4 may be configured by a MOSFET.

[0025] The resonant inductor Lr has one end connected to the input / output point B and the other end connected to the collector of the switch element Tr4. The emitter of the switch element Tr4 is connected to the anode of the diode Drn, and the cathode of the diode Drn is connected to the neutral point A.

[0026] The diode Drn limits the current polarity of the negative-side resonant path rn to one direction (from the input / output point B to the neutral point A). The switch element Tr4 opens and closes the negative-side resonant path rn.

[0027] The switch element Tr4 includes an anti-parallel diode D4 having a cathode and an anode connected to the collector and the emitter of the switch element Tr4, respectively. The anti-parallel diode D4 is formed, for example, by the body diode of the switch element Tr4.

[0028] The auxiliary resonant circuit 2 includes a lossless regenerative clamp snubber diode Dsn that connects the connection point between the emitter of the switch element Tr4 and the anode of the diode Drn to the negative DC line N. The lossless regenerative clamp snubber diode Dsn has a cathode connected to the connection point between the emitter of the switch element Tr4 and the anode of the diode Drn, and an anode connected to the negative DC line N.

[0029] The anti-parallel diode D4 of the switch element Tr4 and the lossless regenerative clamp snubber diode Dsn form a negative side regenerative path in which the current polarity is limited to one direction (from the negative side DC line N to the resonant inductor Lr).

[0030] The resonant inverter 1 includes a control circuit 5 that controls the on / off of each of the switch elements Tm1, Tm2, ​​Tr3, and Tr4. The control circuit 5 performs PWM control on the switch elements Tm1 and Tm2 of the main leg 4 to perform zero voltage turn-on.

[0031] The operation of the resonant inverter 1 when the output voltage Vo and the inverter current Iinv are positive will be described with reference to Fig. 2 and Fig. 3. Fig. 2 is a timing chart showing the operation of the resonant inverter 1. Fig. 3 shows the operation in each mode shown in Fig. 2 using an equivalent circuit of the resonant inverter 1.

[0032] When the output voltage Vo and the inverter current Iinv are positive, the target of the zero voltage (ZV) turn-on control by resonance is the on-timing of the switch element Tm1. When the inverter current Iinv is positive, in order to perform a resonant operation on the positive side, the control circuit 5 controls the switch element Tr3 of the positive-side resonant path rp before and after the switch element Tm1 is turned on.

[0033] In mode 0, the switch element Tm2 is turned off at time t0, and all the switch elements Tm1, Tm2, ​​Tr3, and Tr4 are in the off state. In mode 0, the inverter current Iinv is circulating through the anti-parallel diode D2 of the switch element Tm2 in the lower arm, as shown in FIG.

[0034] In mode 0, the collector-emitter voltage Vce of the switch element Tm1 is Vdc. The inter-terminal voltages (Vce, reverse voltage VR) of the elements of the auxiliary resonant circuit 2 are Vdc / 2 for Tr3, Drn, and Dsp, and 0V for the other elements.

[0035] In mode 1, the switch element Tr3 in the positive-side resonant path rp is turned on under zero current (ZC) control at time t1 during the dead time DT, and the inverter current Iinv is commutated to the resonant inductor Lr (positive-side resonant path rp) as shown in Fig. 3(b). Mode 1 continues until the anti-parallel diode D2 of the switch element Tm2 is turned off.

[0036] In mode 1, the inter-terminal voltages of the elements of the auxiliary resonant circuit 2 are Vdc / 2 for Dsp, Vdc / 4 for Tr4, Drn, and Dsn, and 0V for the other elements.

[0037] In mode 2, the commutation to the resonant inductor Lr is completed at time t2, and Vce of the switch element Tm1 and the switch element Tm2 changes in a sinusoidal shape due to resonance with the resonant capacitors C1 and C2 shown by dotted lines in Fig. 3(c). In mode 2, Vce of the switch element Tm1 changes from Vdc to 0V, and Vce of the switch element Tm2 changes from 0V to Vdc.

[0038] In mode 2, the terminal voltages of each element of the auxiliary resonant circuit 2 are the same as in mode 1.

[0039] The period of mode 1+2 is the sum of the first commutation time Tcom1 [Lr÷Vdcn×Iinv] and the resonance time Tres [π×√(Lr×2Cr)]. Lr is the inductance of the resonance inductor Lr, and Cr is the capacitance of the resonance capacitors C1 and C2. Vdcn is the voltage across the capacitor Cn in the neutral point clamp circuit 3. The first commutation time Tcom1 is the time until the commutation of the inverter current Iinv to the resonance inductor Lr is completed. The resonance time Tres is 1 / 2 the period of resonance at which the resonance frequency is (1 / 2π√(Lr×2Cr)).

[0040] In other words, the switch element Tr3 in the positive-side resonant path rp is controlled to be turned on prior to the turn-on timing of the switch element Tm1 (first commutation time Tcom1+resonant time Tres).

[0041] In mode 3, at timing t3 when Vce of the switching element Tm1 becomes 0 V, as shown in FIG. 3(d), the switching element Tm1 is subjected to zero voltage turn-on control, and the resonant inductor current ILr is commutated to the switching element Tm1.

[0042] In mode 3, the terminal voltages of each element of the auxiliary resonant circuit 2 are the same as in mode 1.

[0043] The period of mode 3 is a second commutation time Tcom2 [Lr÷Vdcp×Iinv], where Vdcp is the voltage across the capacitor Cp in the neutral point clamp circuit 3. The second commutation time Tcom2 is the time until the commutation of the inverter current Iinv to the switch element Tm1 is completed.

[0044] In other words, the switch element Tr3 in the positive side resonant path rp is controlled to be turned off after (the second commutation time Tcom2) the turn-on timing of the switch element Tm1.

[0045] In mode 4, upon completion of the commutation of the resonant inductor current ILr to the switch element Tm1, the switch element Tr3 is turned off at time t4, and power is output from the DC bus (positive DC line P) to the load (AC system), as shown in Figure 3(e).

[0046] In mode 4, the terminal voltages of each element of the auxiliary resonant circuit 2 are Vdc / 2 for Drp, Tr4, and Dsn, and 0V for the other elements.

[0047] In mode 5, the upper arm switch element Tm1 is turned off at time t5, so that the inverter current Iinv is commutated to the anti-parallel diode D2 of the lower arm switch element Tm2, ​​as shown in FIG. 3(f). The Vce of the switch elements Tm1 and Tm2 changes due to charging of the resonant capacitor C1 and discharging of the resonant capacitor C2. In mode 5, the Vce of the switch element Tm1 changes from 0V to Vdc, and the Vce of the switch element Tm2 changes from Vdc to 0V.

[0048] In mode 5, the terminal voltages of the elements of the auxiliary resonant circuit 2 change from Vdc / 2 to 0V for Drp, Tr4, and Dsn, and from 0V to Vdc / 2 for Drn, Tr3, and Dsp.

[0049] Mode 6 is the period from when the commutation to the anti-parallel diode D2 of the switching element Tm2 is completed at time t6 until the dead time DT after the turn-off control of the switching element Tm1 has elapsed. At time t7 when the dead time DT after the turn-off control of the switching element Tm1 has elapsed, as shown in FIG. 3(g), the switching element Tm2 is subjected to zero-voltage turn-on control.

[0050] In mode 6, the terminal voltages of each element of the auxiliary resonant circuit 2 are Vdc / 2 for Tr3, Dsp, and Drn, and 0V for the other elements.

[0051] When the output voltage Vo and the inverter current Iinv are positive, the operation of the resonant inverter 1 repeats the above modes 0 to 6, and the switch elements Tm1 and Tm2 are zero-voltage turn-on controlled. The auxiliary resonant circuit 2 serves as a path for the energy stored in the resonant inductor Lr. The terminal voltage of each element of the auxiliary resonant circuit 2 does not exceed Vdc / 2 in any mode.

[0052] 4 and 5 show the operation of the resonant inverter 1 in a case where the switch element Tr3 turns off during the above-mentioned mode 3 as mode 3A. Fig. 4 is a timing chart showing the operation of the resonant inverter 1. Fig. 5 shows the operation in mode 3A shown in Fig. 4 using an equivalent circuit of the resonant inverter 1.

[0053] Mode 3A is a state in which the switch element Tr3 turns off due to element variations, calculation variations, malfunctions, etc. at time t3A while the resonant inductor current ILr is commutating to the switch element Tm1. The energy excited in the positive direction in the resonant inductor Lr is regenerated to the DC bus without loss as the lossless regenerative clamp snubber diode Dsn and the anti-parallel diode D4 of the switch element Tr4 conduct, as shown by the dotted line in Figure 5. During this regeneration, the auxiliary resonant circuit 2 is clamped to the neutral point A of the DC bus, so each element of the auxiliary resonant circuit 2 including the switch element Tr3 (diode Drn, lossless regenerative clamp snubber diode Dsp) is clamped at Vdc / 2.

[0054] The operation of the resonant inverter 1 when the output voltage Vo and the inverter current Iinv are negative is shown in Fig. 6 and Fig. 7. Fig. 6 is a timing chart showing the operation of the resonant inverter 1. Fig. 7 shows the operation in each mode shown in Fig. 6 using an equivalent circuit of the resonant inverter 1.

[0055] When the output voltage Vo and the inverter current Iinv are negative, the target of the ZV (zero voltage) turn-on control by resonance is the on-timing of the switch element Tm2. When the inverter current Iinv is negative, in order to perform a resonant operation on the negative side, the control circuit 5 controls the switch element Tr4 of the negative-side resonant path rn before and after turning on the switch element Tm2.

[0056] In mode 10, the switch element Tm1 is turned off at time t10, and all the switch elements Tm1, Tm2, ​​Tr3, and Tr4 are in the off state. In mode 10, the inverter current Iinv is circulating through the anti-parallel diode D1 of the switch element Tm1 in the upper arm, as shown in FIG.

[0057] In mode 10, the collector-emitter voltage Vce of the switch element Tm2 is Vdc. The inter-terminal voltages of the elements of the auxiliary resonant circuit 2 are Vdc / 2 for Tr4, Drp, and Dsn, and 0V for the other elements.

[0058] In mode 11, at time t11 during the dead time DT, the switch element Tr4 of the negative resonant path rn is turned on with zero current, and the switch elements Tm1, Tm2, ​​and Tr3 are in the off state. In mode 11, as shown in FIG. 7(b), the inverter current Iinv is commutated to the resonant inductor Lr (negative resonant path rn). Mode 11 continues until the anti-parallel diode D1 of the switch element Tm1 is turned off.

[0059] In mode 11, the terminal voltages of the elements of the auxiliary resonant circuit 2 are Vdc / 2 for Dsn, Vdc / 4 for Tr3, Drp, and Dsp, and 0V for the other elements.

[0060] In mode 12, the commutation to the resonant inductor Lr is completed at time t12, and Vce of the switch element Tm1 and the switch element Tm2 changes in a sinusoidal shape due to resonance with the resonant capacitors C1 and C2 shown by dotted lines in Fig. 7(c). In mode 12, Vce of the switch element Tm1 changes from 0V to Vdc, and Vce of the switch element Tm2 changes from Vdc to 0V.

[0061] In mode 12, the voltage across each element of the auxiliary resonant circuit 2 is the same as in mode 11.

[0062] The period of mode 11+12 is the sum of the first commutation time Tcom1 [Lr÷Vdcp×Iinv] and the resonance time Tres [π×√(Lr×2Cr)]. The first commutation time Tcom1 is the time until the commutation of the inverter current Iinv to the resonance inductor Lr is completed. The resonance time Tres is 1 / 2 the period of the resonance at which the resonance frequency is (1 / 2π√(Lr×2Cr)).

[0063] In other words, the switch element Tr4 of the negative side resonant path rn is controlled to be turned on before the turn-on timing of the switch element Tm2 (first commutation time Tcom1+resonant time Tres).

[0064] In mode 13, at timing t13 when Vce of the switching element Tm2 becomes 0 V, as shown in FIG. 7(d), the switching element Tm2 is subjected to zero voltage turn-on control to commutate the resonant inductor current ILr to the switching element Tm2.

[0065] In mode 13, the voltage across each element of the auxiliary resonant circuit 2 is the same as in mode 11.

[0066] The period of mode 13 is a second commutation time Tcom2 [Lr÷Vdcn×Iinv]. The second commutation time Tcom2 is the time until the commutation of the inverter current Iinv to the switching element Tm2 is completed.

[0067] In other words, the switch element Tr4 of the negative side resonant path rn is controlled to be turned off after (the second commutation time Tcom2) the turn-on timing of the switch element Tm1.

[0068] In mode 14, the switch element Tr4 is turned off at time t14 in response to the completion of commutation of the resonant inductor current ILr to the switch element Tm2. In mode 14, as shown in FIG 7(e), power is output from the DC bus (positive side DC line P, negative side DC line N) to the load (AC system).

[0069] In mode 14, the terminal voltages of the elements of the auxiliary resonant circuit 2 are Vdc / 2 for Drn, Tr3, and Dsp, and 0V for the other elements.

[0070] In mode 15, the lower arm switch element Tm2 is turned off at time t15, so that the inverter current Iinv is commutated to the anti-parallel diode D1 of the upper arm switch element Tm1, as shown in Fig. 7(f). The Vce of the switch elements Tm2 and Tm1 changes due to charging of the resonant capacitor C2 and discharging of the resonant capacitor C1. In mode 15, the Vce of the switch element Tm2 changes from 0V to Vdc, and the Vce of the switch element Tm1 changes from Vdc to 0V.

[0071] In mode 15, the terminal voltages of the elements of the auxiliary resonant circuit 2 change from Vdc / 2 to 0V for Drn, Tr3, and Dsp, and from 0V to Vdc / 2 for Drp, Tr4, and Dsn.

[0072] Mode 16 is a period from when the commutation to the anti-parallel diode D1 of the switching element Tm1 is completed at time t16 until the dead time DT after the turn-off control of the switching element Tm2 has elapsed. At time t17 when the dead time DT after the turn-off control of the switching element Tm2 has elapsed, as shown in FIG. 7(g), the switching element Tm1 is subjected to zero-voltage turn-on control.

[0073] In mode 16, the terminal voltages of each element of the auxiliary resonant circuit 2 are Vdc / 2 for Tr4, Dsn, and Drp, and 0V for the other elements.

[0074] When the output voltage Vo and the inverter current Iinv are negative, the operation of the resonant inverter 1 repeats the above modes 10 to 16, and the switch elements Tm1 and Tm2 are zero-voltage turn-on controlled. The auxiliary resonant circuit 2 serves as a path for the energy stored in the resonant inductor Lr. The terminal voltage of each element of the auxiliary resonant circuit 2 does not exceed Vdc / 2 in any mode.

[0075] 8 and 9 show the operation of the resonant inverter 1 in a case where the switch element Tr4 turns off during the above-mentioned mode 13 as mode 13A. Fig. 8 is a timing chart showing the operation of the resonant inverter 1. Fig. 9 shows the operation in mode 13A shown in Fig. 8 using an equivalent circuit of the resonant inverter 1.

[0076] Mode 13A is a state in which the switch element Tr4 is turned off due to element variations, calculation variations, malfunctions, etc. at time t13A while the resonant inductor current ILr is commutating to the switch element Tm2. The energy excited in the negative direction in the resonant inductor Lr is regenerated to the DC bus without loss as the lossless regenerative clamp snubber diode Dsp and the anti-parallel diode D3 of the switch element Tr3 conduct, as shown by the dotted line in Figure 8. During this regeneration, the auxiliary resonant circuit 2 is clamped to the neutral point A of the DC bus, so that each element of the auxiliary resonant circuit 2 including the switch element Tr4 (diode Drp, lossless regenerative clamp snubber diode Dsn) is clamped at Vdc / 2.

[0077] 10 shows a half-bridge inverter circuit 11 to which the resonant inverter 1 is applied. The half-bridge inverter circuit 11 supplies an AC voltage to a load 6 connected between a neutral point A and an input / output point B.

[0078] FIG. 11 shows a full-bridge inverter circuit 12 to which the resonant inverter 1 is applied. The full-bridge inverter circuit 12 includes a commercial cyclic leg 7 connected in parallel with the main leg 4. In the commercial cyclic leg 7, a switch element Ts5 and a switch element Ts6 are connected in series between a positive DC line P and a negative DC line N. A load 6 is connected between an input / output point C of the switch elements Ts5 and Ts6 and an input / output point B of the main leg 4. The switch elements Ts5 and Ts6 are configured by IGBTs or MOSFETs.

[0079] The control circuit 5a switches the switching elements Ts5 and Ts6 on and off every half cycle of the commercial power cycle. Fig. 12 shows an operation mode in a positive half cycle of the full-bridge inverter circuit 12. The switching element Ts6 is always on, and the switching element Ts5 is always off.

[0080] Mode 20 shown in FIG. 12(a) is a state in which the switch element Tm2 is turned off and the inverter current Iinv flows back through the anti-parallel diode D2 of the switch element Tm2 in the lower arm and the switch element Ts6.

[0081] In mode 21, the switch element Tr3 in the positive-side resonant path rp is subjected to zero-current turn-on control during the dead time DT, and the inverter current Iinv shown in FIG. 12(b) is commutated to the resonant inductor Lr (positive-side resonant path rp).

[0082] In mode 22, the commutation to the resonant inductor Lr is completed, and Vce of the switch element Tm1 and the switch element Tm2 changes in a sinusoidal shape due to resonance with the resonant capacitors C1 and C2 shown by dotted lines in Fig. 12(c). In mode 22, Vce of the switch element Tm1 changes from Vdc to 0V, and Vce of the switch element Tm2 changes from 0V to Vdc.

[0083] In mode 23, at the timing when Vce of the switching element Tm1 becomes 0 V, as shown in FIG. 12(d), the switching element Tm1 is subjected to zero voltage turn-on control, and the resonant inductor current ILr is commutated to the switching element Tm1.

[0084] In mode 24, upon completion of the commutation of the resonant inductor current ILr to the switch element Tm1, the switch element Tr3 is controlled to be turned off, and power is output from the DC bus (positive side DC line P, negative side DC line N) to the load (AC system), as shown in Figure 12 (e).

[0085] 13 shows a full-bridge inverter circuit 13 to which the resonant inverter 1 is applied. The full-bridge inverter circuit 13 is a full-bridge configuration of the resonant inverter 1, and includes a U-phase main leg 4u, a W-phase main leg 4w, an auxiliary resonant circuit 2u for the main leg 4u, and an auxiliary resonant circuit 2w for the main leg 4w.

[0086] The control circuit 5u controls the auxiliary resonant circuit 2u and the control circuit 5w controls the auxiliary resonant circuit 2w individually and at different timings. The control of the auxiliary resonant circuits 2u and 2w differs depending on the switching state of the other phase.

[0087] The operation of performing zero-voltage turn-on control on the upper arm (switch element Tm1) in the U-phase main leg 4u will be described. When the lower arm (switch element Tm2) in the W-phase main leg 4w is on, the operation is the same as that of the full-bridge inverter circuit 12 shown in FIG.

[0088] FIG. 14 shows an operation in which the upper arm (switch element Tm1) of the W-phase main leg 4w is on when the upper arm (switch element Tm1) of the U-phase main leg 4u is subjected to zero voltage turn-on control.

[0089] Mode 30 shown in FIG. 14(a) is a state in which the switch element Tm2 of the main leg 4u is turned off and the inverter current Iinv flows back through the anti-parallel diode D2 of the switch element Tm2 of the lower arm and the anti-parallel diode D1 of the switch element Tm1 of the main leg 4w.

[0090] In mode 31, the switch element Tr3 of the auxiliary resonant circuit 2u is subjected to zero-current turn-on control during the dead time DT, and the inverter current Iinv shown in FIG. 14(b) is commutated to the resonant inductor Lr (the positive-side resonant path rp of the auxiliary resonant circuit 2u).

[0091] In mode 32, commutation to the resonant inductor Lr (positive-side resonant path rp of the auxiliary resonant circuit 2u) is completed, and Vce of the switch elements Tm1 and Tm2 of the main leg 4u changes sinusoidally due to resonance with the resonant capacitors C1 and C2 shown by dotted lines in Fig. 14(c). In mode 22, Vce of the switch element Tm1 of the main leg 4u changes from Vdc to 0V, and Vce of the switch element Tm2 of the main leg 4u changes from 0V to Vdc.

[0092] In mode 33, when Vce of the switching element Tm1 of the main leg 4u becomes 0V, as shown in FIG. 14(d), the switching element Tm1 is subjected to zero-voltage turn-on control to commutate the resonant inductor current ILr to the switching element Tm1 of the main leg 4u.

[0093] In mode 34, the switch element Tr3 of the auxiliary resonant circuit 2u is turned off upon completion of commutation of the resonant inductor current ILr to the switch element Tm1 of the main leg 4u. In mode 34, as shown in FIG. 14(e), the inverter current circulates between the input and output points of the U phase and the W phase.

[0094] 15 shows a bidirectional chopper circuit 14 to which the resonant inverter 1 is applied. The bidirectional chopper circuit 14 includes a filter circuit 8. The filter circuit 8 includes an inductor L1 and a capacitor Cn, and a series circuit including the inductor L1 and the capacitor Cn is connected between an input / output point B and a negative DC line N.

[0095] (1) The resonant inverter 1 according to one embodiment of the present invention includes a neutral point clamp circuit 3. The neutral point clamp circuit 3 includes a capacitor Cp (positive side capacitor) and a capacitor Cn (negative side capacitor) connected in series between a positive side DC line P and a negative side DC line N, and a connection point between the capacitor Cp and the capacitor Cn is a neutral point A. The resonant inverter 1 includes a main leg 4 connected in series between the positive side DC line P and the negative side DC line N. The main leg 4 includes a switch element Tm1 (upper arm switch) and a switch element Tm2 (lower arm switch), and a connection point between the switch elements Tm1 and Tm2, ​​which are alternately controlled with a dead time DT in between, is an input / output point B of the inverter current Iinv. The resonant inverter 1 includes a resonant capacitor C1 (first resonant capacitor) and a resonant capacitor C2 (second resonant capacitor) connected in parallel to the switch elements Tm1 and Tm2. The resonant inverter 1 includes an anti-parallel diode D1 (first anti-parallel diode) and an anti-parallel diode D2 (second anti-parallel diode) connected in anti-parallel to the switch element Tm1 and the switch element Tm2. The resonant inverter 1 includes an auxiliary resonant circuit 2 including a resonant inductor Lr having one end connected to an input / output point B of a main leg 4. The auxiliary resonant circuit 2 includes a positive-side resonant path rp in which the current polarity is limited to the direction from the neutral point A to the resonant inductor Lr and is opened and closed by a switch element Tr3 (positive-side resonant switch). The auxiliary resonant circuit 2 includes a negative-side resonant path rn in which the current polarity is limited to the direction from the resonant inductor Lr to the neutral point A and is opened and closed by a switch element Tr4 (negative-side resonant switch). The auxiliary resonant circuit 2 includes a positive-side regenerative path (anti-parallel diode D3 of the switch element Tr3+lossless regenerative clamp snubber diode Dsp) in which the current polarity is limited to the direction from the resonant inductor Lr to the positive-side DC line P. The auxiliary resonant circuit 2 includes a negative-side regenerative path (anti-parallel diode D4 of switch element Tr4+lossless regenerative clamp snubber diode Dsn) in which the current polarity is limited to the direction from the negative-side DC line N to the resonant inductor Lr.

[0096] According to the resonant inverter 1 described in (1) above, the lossless auxiliary resonant circuit 2, which serves as a path for the energy stored in the resonant inductor Lr, is clamped to the voltage of the neutral point A by the positive side resonant path rp and the negative side resonant path rn, so that the elements constituting the auxiliary resonant circuit 2 can be constructed with elements having a lower withstand voltage than the elements of the main leg 4, which is the main circuit. This widens the range of elements to be selected for the auxiliary resonant circuit 2, allowing it to be constructed at low cost. The lossless regenerative clamp snubber diodes Dsp, Dsn serve as a regenerative path for the energy of the resonant inductor Lr, enabling highly efficient overvoltage protection measures.

[0097] (2) In the resonant inverter 1 described in (1) above, the control circuit 5 may turn on the switch element Tr3 during a dead time DT before the switch element Tm1 is turned on, and may turn off the switch element Tr3 after the switch element Tm1 is turned on. The control circuit 5 may turn on the switch element Tr4 during a dead time DT before the switch element Tm2 is turned on, and may turn off the switch element Tr4 after the switch element Tm2 is turned on.

[0098] According to the resonant inverter 1 described in (2) above, the inverter current Iinv can be commutated to the auxiliary resonant circuit 2 to cause a resonant operation.

[0099] (3) In the resonant inverter 1 described in (2) above, the control circuit 5 may turn on the switch element Tr3 at a timing before the timing of the turn-on control of the switch element Tm1, which is a time obtained by adding the first commutation time Tcom1 (first positive-side commutation time) and the resonance time Tres. The first commutation time Tcom1 is the time required for the commutation of the inverter current Iinv to the resonance inductor Lr to be completed by the turn-on control of the switch element Tr3. The resonance time Tres is a half period of the resonance of the resonance inductor Lr and the resonance capacitors C1 and C2. The control circuit 5 may turn on the switch element Tr4 at a timing before the timing of the turn-on control of the switch element Tm2, ​​which is a time obtained by adding the first commutation time Tcom1 (first load-side commutation time) and the resonance time Tres.

[0100] According to the resonant inverter 1 described in (3) above, it is possible to realize zero-voltage turn-on control of the switch elements Tm1 and Tm2.

[0101] (4) In the resonant inverter 1 described in (2) above, the control circuit 5 may turn off the switch element Tr3 at a timing after a second commutation time Tcom2 (second positive commutation time) of the timing of the turn-on control of the switch element Tm1. The second commutation time Tcom is the time until the commutation of the resonant inductor current ILr from the resonant inductor Lr to the switch element Tm1 is completed by the turn-on control of the switch element Tm1. The control circuit 5 may turn off the switch element Tr4 at a timing after a second commutation time Tcom2 (second negative commutation time) of the timing of the turn-on control of the switch element Tm2. In this case, the second commutation time Tcom2 is the time until the commutation of the resonant inductor current ILr from the resonant inductor Lr to the switch element Tm2 is completed by the turn-on control of the switch element Tm2.

[0102] According to the resonant inverter 1 described in (4) above, the resonant operation can be quickly terminated after the zero voltage turn-on control of the switch elements Tm1 and Tm2.

[0103] Although the present invention has been described above with reference to specific embodiments, it goes without saying that the above embodiments are merely examples and can be modified and implemented without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0104] 1 Resonant inverter 2, 2u, 2w auxiliary resonant circuit 3. Neutral Point Clamp Circuit 4, 4u, 4w main leg 5, 5a, 5u, 5w control circuit 6 Load 7 Commercial Cycle Leg 8 Filter Circuits 11 Half-bridge inverter circuit 12, 13 Full-bridge inverter circuit 14 Bidirectional chopper circuit A neutral point B, C input / output points C1, C2 Resonant capacitors Cn, Cp capacitor D1, D2, D3, D4 Anti-parallel diodes Drn, Drp diode Dsn Lossless regenerative clamp snubber diode DSP Lossless Regenerative Clamp Snubber Diode Lr Resonant inductor N Negative DC line P Positive DC line Tm1, Tm2, ​​Tr3, Tr4, Ts5, Ts6 Switch elements rn Negative resonance path rp Positive resonance path

Claims

1. a neutral point clamp circuit including a positive side capacitor and a negative side capacitor connected in series between a positive side DC line and a negative side DC line, the connection point between the positive side capacitor and the negative side capacitor being a neutral point; a main leg including an upper arm switch and a lower arm switch connected in series between the positive DC line and the negative DC line, the main leg being an input / output point of an inverter current at a connection point between the upper arm switch and the lower arm switch that are alternately controlled with a dead time therebetween; a first resonant capacitor and a second resonant capacitor connected in parallel to the upper arm switch and the lower arm switch; a first anti-parallel diode and a second anti-parallel diode connected in anti-parallel to the upper arm switch and the lower arm switch; an auxiliary resonant circuit including a resonant inductor having one end connected to the input / output point of the main leg; The auxiliary resonant circuit includes: a positive-side resonant path in which a current polarity is limited to a direction from the neutral point to the resonant inductor and which is opened and closed by a positive-side resonant switch; a negative-side resonant path in which a current polarity is limited to a direction from the resonant inductor to the neutral point and which is opened and closed by a negative-side resonant switch; a positive-side regenerative path in which a current polarity is limited to a direction from the resonant inductor to the positive-side DC line; a negative-side regenerative path whose current polarity is limited to a direction from the negative-side DC line to the resonant inductor.

2. The positive side resonant switch is turned on during the dead time before the upper arm switch is turned on, and the positive side resonant switch is turned off after the upper arm switch is turned on; 2. The resonant inverter according to claim 1, wherein the negative side resonant switch is turned on during the dead time before the lower arm switch is turned on, and the negative side resonant switch is turned off after the lower arm switch is turned on.

3. the positive side resonant switch is turned on at a timing before the timing of the turn-on control of the upper arm switch, the timing being a sum of a positive side first commutation time until the commutation of the inverter current to the resonant inductor is completed by the turn-on control of the positive side resonant switch and a resonance time which is a half period of resonance between the resonant inductor, the first resonant capacitor, and the second resonant capacitor; 3. The resonant inverter according to claim 2, wherein the negative side resonant switch is turned on at a timing before the timing of the turn-on control of the lower arm switch, the timing being a sum of a load side first commutation time until the commutation of the inverter current to the resonant inductor is completed by the turn-on control of the negative side resonant switch and the resonant time.

4. the positive side resonant switch is turned off at a timing after a positive side second commutation time until the commutation of the resonant inductor current from the resonant inductor to the upper arm switch is completed by the turn-on control of the upper arm switch, from the timing of the turn-on control of the upper arm switch; 3. The resonant inverter according to claim 2, wherein the negative side resonant switch is turned off at a timing that is a negative side second commutation time after the turn-on control of the lower arm switch, the time until the commutation of the resonant inductor current from the resonant inductor to the lower arm switch is completed by the turn-on control of the lower arm switch.

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