Resonant inverter

Abstract

The resonant inverter (1) is a three-level converter, and the resonant operation can be easily controlled as a two-level converter during charging. And the action is performed by zero-voltage turn-on control. The auxiliary resonance circuit (2) is provided with a negative-side resonance path (rn in which the current polarity is limited in a direction from the resonance inductor (Lr) toward the neutral point (A), and which is opened and closed by a switching element (Tr6). The auxiliary resonance circuit (2) is provided with a positive-side regeneration path (D5 + Dsp) in which the current polarity is defined in the direction from the resonance inductor (Lr) to the positive-side DC line (P). The auxiliary resonant circuit (2) is provided with a negative-side regeneration path (D6 + Dsn) in which the current polarity is defined in the direction from the negative-side DC line (N) to the resonant inductor (Lr).

Description

Technical Field

[0001] This invention relates to a resonance inverter with an auxiliary resonant circuit. Background Technology

[0002] Uninterruptible power supply (UPS) devices and other energy storage systems include energy storage devices and a power regulation unit (PCS). The PCS incorporates an inverter that converts AC to DC power between the external power system and the energy storage device. The energy storage device, for example, is configured as a multi-module containing multiple energy storage elements. In recent years, energy storage devices have been trending towards higher voltage and larger capacity.

[0003] With the increasing voltage and capacity of energy storage devices, the increase in switching losses and electromagnetic interference (EMI) noise in inverters has become a major problem. As a method to reduce switching losses and EMI noise, resonant inverters are used (for example, see Patent Documents 1, 2, and 3).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 5195161

[0007] Patent Document 2: Japanese Patent No. 5569204 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] In the resonant inverter of Patent Document 1, when all switches are off, the path of energy stored in the resonant inductor is ensured by a snubber circuit, but efficiency is reduced due to snubber losses.

[0010] The resonant inverter in Patent Document 2 regenerates the energy stored in the resonant inductor to the DC link without loss through an auxiliary resonant circuit when all switches are off. The auxiliary resonant circuit becomes the path for the energy stored in the resonant inductor and does not generate buffer losses. However, the auxiliary circuit requires high-voltage components identical to those in the main circuit. High-voltage components are limited in variety and have slow switching speeds, raising concerns about efficiency degradation.

[0011] One aspect of the present invention provides a resonant inverter that can be configured with a lossless auxiliary resonant circuit, consisting of components with lower voltage ratings than the main circuit, which serve as a path for energy stored in the resonant inductor.

[0012] Methods for solving problems

[0013] One aspect of the present invention is a resonant inverter with a neutral point clamping circuit. This neutral point clamping circuit comprises a positive-side capacitor and a negative-side capacitor connected in series between the positive and negative DC lines, with the connection point of the positive and negative capacitors forming the neutral point. The resonant inverter has a main arm, which comprises an upper arm switch and a lower arm switch connected in series between the positive and negative DC lines, with the connection point of the upper and lower arm switches forming the inverter current input / output point. The resonant inverter includes a first resonant capacitor and a second resonant capacitor, which are connected in parallel with the upper and lower arm switches. The resonant inverter also includes a first anti-parallel diode and a second anti-parallel diode, which are connected in anti-parallel with the upper and lower arm switches. The resonant inverter includes a neutral phase bridge arm with a positive-side neutral phase switch and a negative-side neutral phase switch for opening and closing a positive-side polarity path (defined as a current polarity from the neutral point to the input / output point) and a negative-side polarity path (defined as a current polarity from the input / output point to the neutral point), respectively. The resonant inverter also includes an auxiliary resonant circuit comprising a resonant inductor connected at one end to the input / output point. The auxiliary resonant circuit has a positive-side resonant path in which the current polarity is defined as a current polarity from the neutral point to the resonant inductor, and is opened and closed by a positive-side resonant switch. The auxiliary resonant circuit also has a negative-side resonant path in which the current polarity is defined as a current polarity from the resonant inductor to the neutral point, and is opened and closed by a negative-side resonant switch. Finally, the auxiliary resonant circuit has a positive-side regenerative path in which the current polarity is defined as a current polarity from the resonant inductor to the positive DC line. The auxiliary resonant circuit has a negative-side regeneration path, in which the current polarity is defined as flowing from the negative-side DC line towards the resonant inductor. During the charging operation, which alternately controls the upper arm switch and the negative-side neutral phase switch at dead-time intervals, the positive-side neutral phase switch and the upper arm switch are simultaneously turned off. The negative-side resonant switch is turned on during the dead-time before the negative-side neutral phase switch is turned on.

[0014] One aspect of the present invention is a resonant inverter with a neutral point clamping circuit. This neutral point clamping circuit comprises a positive-side capacitor and a negative-side capacitor connected in series between the positive and negative DC lines, with the connection point of the positive and negative capacitors forming the neutral point. The resonant inverter has a main arm, which comprises an upper arm switch and a lower arm switch connected in series between the positive and negative DC lines, with the connection point of the upper and lower arm switches forming the inverter current input / output point. The resonant inverter includes a first resonant capacitor and a second resonant capacitor, which are connected in parallel with the upper and lower arm switches. The resonant inverter also includes a first anti-parallel diode and a second anti-parallel diode, which are connected in anti-parallel with the upper and lower arm switches. The resonant inverter includes a neutral phase bridge arm with a positive-side neutral phase switch and a negative-side neutral phase switch for opening and closing a positive-side polarity path (defined as a current polarity from the neutral point to the input / output point) and a negative-side polarity path (defined as a current polarity from the input / output point to the neutral point), respectively. The resonant inverter also includes an auxiliary resonant circuit comprising a resonant inductor connected at one end to the input / output point. The auxiliary resonant circuit has a positive-side resonant path in which the current polarity is defined as a current polarity from the neutral point to the resonant inductor, and is opened and closed by a positive-side resonant switch. The auxiliary resonant circuit also has a negative-side resonant path in which the current polarity is defined as a current polarity from the resonant inductor to the neutral point, and is opened and closed by a negative-side resonant switch. Finally, the auxiliary resonant circuit has a positive-side regenerative path in which the current polarity is defined as a current polarity from the resonant inductor to the positive DC line. The auxiliary resonant circuit has a negative-side regeneration path, in which the current polarity is defined as flowing from the negative-side DC line towards the resonant inductor. During the charging operation, which alternately controls the lower arm switch and the positive-side neutral phase switch at dead-time intervals, the negative-side neutral phase switch and the lower arm switch are simultaneously turned off, and the positive-side resonant switch is turned on during the dead-time before the positive-side neutral phase switch is turned on.

[0015] Invention Effects

[0016] According to one aspect of the present invention, the lossless auxiliary resonant circuit, which serves as the path for energy stored in the resonant inductor, is clamped to the neutral point voltage via the positive and negative resonant paths. Therefore, the components constituting the auxiliary resonant circuit can be composed of components with lower voltage ratings than the components of the main bridge arm 4, which serves as the main circuit. During charging, the resonant inverter 1 can be treated as a two-level converter, and the resonant operation can be easily controlled. Attached Figure Description

[0017] Figure 1 This is a diagram showing the circuit structure of one phase of an implementation of a resonant inverter.

[0018] Figure 2 It means Figure 1 The timing chart shown is for the discharge operation of a resonant inverter.

[0019] Figure 3 It means Figure 2 The diagram shows the actions for each mode.

[0020] Figure 4 This is a timing diagram representing the positive direction of the clamp snubber action.

[0021] Figure 5 It means Figure 4 The diagram shows the action of mode 5A.

[0022] Figure 6 It means Figure 1 The timing diagram of the discharge operation of the resonant inverter is shown.

[0023] Figure 7 It means Figure 6 The diagram shows the actions for each mode.

[0024] Figure 8 This is a timing diagram representing the clamping and buffering action in the negative direction.

[0025] Figure 9 It means Figure 8 The diagram shows the action of mode 15A.

[0026] Figure 10 It means Figure 1 The timing diagram shown is for the charging operation of a resonant inverter.

[0027] Figure 11 It means Figure 10 The diagram shows the actions for each mode.

[0028] Figure 12 It means Figure 1The timing diagram of the discharge operation of the resonant inverter is shown.

[0029] Figure 13 It means Figure 12 The diagram shows the actions for each mode.

[0030] Figure 14 It means Figure 1 The diagram shows a first application example of the auxiliary resonant circuit.

[0031] Figure 15 It means Figure 1 The diagram shows a second application example of the resonant inverter.

[0032] Figure 16 It means Figure 1 The diagram shows a third application example of the resonant inverter.

[0033] Figure 17 It means Figure 16 The diagram shows the operation of a resonant inverter. Detailed Implementation

[0034] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following embodiments, structures that represent the same function will be labeled with the same reference numerals and descriptions will be omitted as appropriate.

[0035] Reference Figure 1 The resonant inverter 1 in this embodiment is a three-level inverter with an auxiliary resonant circuit 2 having an ARCP (auxiliary resonant commutated pole) topology of the NPC (neutral point clamped) type.

[0036] The resonant inverter 1 includes a neutral point clamping circuit 3 with a positive-side capacitor Cp and a negative-side capacitor Cn connected in series. The neutral point clamping circuit 3 is connected between the positive-side DC line P and the negative-side DC line N. The capacitors Cp and Cn have the same capacitance. The connection point of the capacitors Cp and Cn is the neutral point A, which generates half of the input DC voltage Vdc between the positive-side DC line P and the negative-side DC line N, called Vdc / 2.

[0037] The resonant inverter 1 includes a main bridge arm 4 consisting of a series circuit comprising a switching element Tm1 (an upper arm switch) and a switching element Tm2 (a lower arm switch) as a lower arm switch. Switching elements Tm1 and Tm2 are, for example, insulated-gate bipolar transistors (IGBTs). Switching elements Tm1 and Tm2 may also be MOSFETs. The main bridge arm 4 is connected between the positive DC line P and the negative DC line N. For switching element Tm1, its collector is connected to the positive DC line P, and its emitter is connected to the collector of switching element Tm2. For switching element Tm2, ​​its emitter is connected to the negative DC line N. The connection point between the emitter of switching element Tm1 and the collector of switching element Tm2 becomes the input / output point B of the inverter current Iinv, which is connected to the AC input / output terminals via inductor L1.

[0038] The switching element Tm1 includes an anti-parallel diode D1, wherein the cathode and anode are connected in anti-parallel to the collector and emitter of the switching element Tm1, respectively. The anti-parallel diode D1 is, for example, formed by the body diode of the switching element Tm1. The switching element Tm1 also includes a resonant capacitor C1 connected in parallel. The resonant capacitor C1 is formed by the parasitic capacitance of the switching element Tm1 and an external capacitor.

[0039] The switching element Tm2 includes an anti-parallel diode D2, wherein the cathode and anode are connected in anti-parallel to the collector and emitter of the switching element Tm2, ​​respectively. The anti-parallel diode D2 is, for example, formed by the body diode of the switching element Tm2. The switching element Tm2 also includes a resonant capacitor C2 connected in parallel. The resonant capacitor C2 is formed by the parasitic capacitance of the switching element Tm2 and an external capacitor.

[0040] The resonant inverter 1 has a neutral phase bridge arm 5. The neutral phase bridge arm 5 has a positive polarity path np and a negative polarity path nn. The positive polarity path np and the negative polarity path nn connect the neutral point A of the neutral point clamping circuit 3 in parallel with the input / output point B of the main bridge arm 4.

[0041] The positive polarity path np is a series circuit consisting of diode Dnp and switching element Tn3, which limits the current polarity in one direction (from neutral point A to input / output point B), and switches it on and off via switching element Tn3. Switching element Tn3 can be either an IGBT or a MOSFET. For diode Dnp, the anode is connected to neutral point A, and the cathode is connected to the collector of switching element Tn3. For switching element Tn3, the emitter is connected to input / output point B.

[0042] The negative polarity path nn is a series circuit consisting of diode Dnn and switching element Tn4, which limits the current polarity in one direction (from input / output point B to neutral point A), and is switched on and off by switching element Tn4. Switching element Tn4 is composed of IGBT and MOSFET. For switching element Tn4, the collector is connected to input / output point B, and the emitter is connected to the anode of diode Dnn. For diode Dnn, the cathode is connected to neutral point A.

[0043] The auxiliary resonant circuit 2 has a resonant inductor Lr, a positive resonant path rp and a negative resonant path rn connected in parallel between the input / output point B of the main bridge arm 4 and the neutral point A of the neutral point clamping circuit 3.

[0044] The positive resonant path rp starts from the other end of the resonant inductor Lr, which is connected to the input / output point B, and forms a series circuit in the order of the switching element Tr5 (acting as the positive resonant switch) and the diode Drp. The switching element Tr5 is, for example, an insulated-gate bipolar transistor (IGBT). The switching element Tr5 can also be a MOSFET.

[0045] For the resonant inductor Lr, one end is connected to the input / output point B, and the other end is connected to the emitter of the switching element Tr5. The collector of the switching element Tr5 is connected to the cathode of the diode Drp, and the anode of the diode Drp is connected to the neutral point A.

[0046] Diode Drp limits the current polarity of the positive resonant path rp to one direction (from neutral point A to input / output point B). Switching element Tr5 switches the positive resonant path rp on and off.

[0047] The switching element Tr5 includes an anti-parallel diode D5, wherein the cathode and anode are connected to the collector and emitter of the switching element Tr5, respectively. The anti-parallel diode D5 is, for example, formed by the body diode of the switching element Tr5.

[0048] The auxiliary resonant circuit 2 has a connection point connecting the collector of the switching element Tr5 and the cathode of the diode Drp, and a lossless regenerative clamping buffer diode Dsp on the positive DC line P. For the lossless regenerative clamping buffer diode Dsp, the anode is connected to the connection point between the collector of the switching element Tr5 and the cathode of the diode Drp, and the cathode is connected to the positive DC line P.

[0049] The anti-parallel diode D5 of the switching element Tr5 and the lossless regenerative clamping buffer diode Dsp constitute a positive regenerative path in which the current polarity is limited to one direction (from the resonant inductor Lr to the positive DC line P).

[0050] The negative-side resonant path rn starts from the other end of the resonant inductor Lr, which is connected to the input / output point B, and forms a series circuit in the order of the switching element Tr6 (acting as the negative-side resonant switch) and the diode Drn. The resonant inductor Lr is shared with the positive-side resonant path rp. The switching element Tr6 is, for example, an insulated-gate bipolar transistor (IGBT). The switching element Tr6 can also be a MOSFET.

[0051] For the resonant inductor Lr, one end is connected to the input / output point B, and the other end is connected to the collector of the switching element Tr6. The emitter of the switching element Tr6 is connected to the anode of the diode Drn, and the cathode of the diode Drn is connected to the neutral point A.

[0052] Diode Drn limits the current polarity of the negative resonant path rn to one direction (from input / output point B to neutral point A). Switching element Tr6 switches the negative resonant path rn on and off.

[0053] The switching element Tr6 includes an anti-parallel diode D6, wherein the cathode and anode are connected to the collector and emitter of the switching element Tr6, respectively. The anti-parallel diode D6 is, for example, formed by the body diode of the switching element Tr6.

[0054] The auxiliary resonant circuit 2 includes a lossless regenerative clamping buffer diode Dsn, which connects the emitter of the switching element Tr6 to the anode of the diode Drn, and the negative DC line N. For the lossless regenerative clamping buffer diode Dsn, the cathode is connected to the connection point between the emitter of the switching element Tr6 and the anode of the diode Drn, and the anode is connected to the negative DC line N.

[0055] The anti-parallel diode D6 of the switching element Tr6 and the lossless regenerative clamping buffer diode Dsn constitute a negative regenerative path in which the current polarity is limited to one direction (from the negative DC line N to the resonant inductor Lr).

[0056] The resonant inverter 1 includes a control circuit 6 that controls the on / off state of each of the switching elements Tm1, Tm2, ​​Tn3, Tn4, Tr5, and Tr6. When performing PWM control on the switching element Tm1 of the main bridge arm 4 and the switching element Tn4 of the neutral phase bridge arm 5, the control circuit 6 turns Tm1 on at zero voltage. When performing PWM control on the switching element Tm2 of the main bridge arm 4 and the switching element Tn3 of the neutral phase bridge arm 5, the control circuit 6 turns Tm2 on at zero voltage.

[0057] Reference Figure 2 and Figure 3Explain the discharge operation of resonant inverter 1 when the output voltage Vo and inverter current Iinv are positive. Figure 2 This is a timing diagram representing the operation of resonant inverter 1. Figure 3 The equivalent circuit of resonant inverter 1 is used to represent it. Figure 2 The actions in each of the shown modes.

[0058] Since the output voltage Vo is positive, the switching elements Tm1 and Tn4 alternately perform PWM operations. When the inverter current Iinv is positive, the object of the resonant zero-voltage (ZV) turn-on control is the on-time of the switching element Tm1.

[0059] Control circuit 6 turns off switching element Tn3 before resonant operation, thereby enabling resonant inverter 1 to operate as a two-level inverter, forming a mode in which the anti-parallel diode D2 of switching element Tm2 is turned on. When the inverter current Iinv is positive, in order to enable resonant operation on the positive side, control circuit 6 controls switching element Tr5 of the positive resonant path rp before and after the conduction of switching element Tm1.

[0060] Figure 3 (a) shows mode 0, which is the state in which the inverter current Iinv freewheels in the positive polarity path np of the neutral phase bridge arm 5.

[0061] In mode 0, the collector-emitter voltage Vce of switching elements Tm1 and Tm2 is Vdc / 2. Regarding the inter-terminal voltages (Vce, reverse voltage VR) of each element in auxiliary resonant circuit 2, Tr5, Tr6, Dsp, Dsn, Drp, and Drn are Vdc / 4. The inter-terminal voltage of each element in neutral phase bridge arm 5 is 0V.

[0062] In Mode 1, at time t1, switching elements Tn3 and Tn4 are simultaneously turned off, causing the inverter current Iinv to commutate through the anti-parallel diode D2 of the downstream switching element Tm2. All other switching elements Tm1, Tm2, ​​Tr5, and Tr6 are in the off state. In Mode 1, as... Figure 3 As shown in (b), the resonant capacitor C1 of switching element Tm1 is charged, and the resonant capacitor C2 of switching element Tm2 is discharged. Therefore, switching element Tn3 becomes a zero-voltage turn-off control based on lossless snubber.

[0063] In mode 1, the Vce of switching element Tm1 changes from Vdc / 2 to Vdc, and the Vce of switching element Tm2 changes from Vdc / 2 to 0V. Regarding the inter-terminal voltages of the components in auxiliary resonant circuit 2, Tr5, Dsp, and Drn change from Vdc / 4 to Vdc / 2, and Tr6, Dsn, and Drp change from Vdc / 4 to 0V. Regarding the inter-terminal voltages of the components in neutral phase bridge arm 5, Tn3 and Dnn change from 0V to Vdc / 2.

[0064] Mode 2 is as follows: at time t2, the Vce of switching element Tm1 changes to Vdc, and the Vce of switching element Tm2 changes to 0V, as shown below. Figure 3 As shown in (c), the inverter current Iinv freewheels in the anti-parallel diode D2 of the switching element Tm2 in the lower arm.

[0065] In mode 2, the terminal voltages of each component in the auxiliary resonant circuit 2 are Vdc / 2 for Tr5, Drn, and Dsp, and 0V for the other components. Similarly, the terminal voltages of each component in the neutral phase bridge arm 5 are Vdc / 2 for Tn3 and Dnn, and 0V for the other components.

[0066] In mode 3, at time t3 during the dead time DT, the switching element Tr5 of the positive resonant path rp is controlled to turn on with zero current (ZC), as follows: Figure 3 As shown in (d), the inverter current Iinv is commutated to the resonant inductor Lr (positive resonant path rp). Mode 3 continues until the anti-parallel diode D2 of the switching element Tm2 is turned off.

[0067] In mode 3, the terminal voltages of each component in the auxiliary resonant circuit 2 are as follows: Dsp is Vdc / 2, Tr6, Drn, and Dsn are Vdc / 4, and the voltages of other components are 0V. The terminal voltages of each component in the neutral phase bridge arm 5 are the same as in mode 2.

[0068] Mode 4 completes commutation to the resonant inductor Lr at time t4, through... Figure 3 (e) shows the resonance of resonant capacitors C1 and C2 (shown by dashed lines), and the Vce of switching elements Tm1 and Tm2 changes in a sinusoidal waveform. In mode 4, the Vce of switching element Tm1 changes from Vdc to 0V, and the Vce of switching element Tm2 changes from 0V to Vdc.

[0069] In mode 4, the terminal voltages of each component in the auxiliary resonant circuit 2 are the same as in mode 3. Regarding the terminal voltages of each component in the neutral phase bridge arm 5, Tn4 and Dnp change from 0V to Vdc / 2, while Tn3 and Dnn change from Vdc / 2 to 0V.

[0070] The period of mode 3+4 is the time obtained by adding the first commutation time Tcom1[Lr÷Vdcn×Iinv] to the resonant time Tres[π×√(Lr×2Cr)]. Lr is the inductance of the resonant inductor Lr, and Cr is the capacitance of the resonant capacitors C1 and C2. Vdcn is the voltage across capacitor Cn in the neutral point clamping circuit 3. The first commutation time Tcom1 is the time until the commutation of the inverter current Iinv to the resonant inductor Lr is completed. The resonant time Tres is half a period of the resonance with a resonant frequency of (1 / 2π√(Lr×2Cr)).

[0071] In other words, the switching element Tr5 of the positive resonant path rp is turned on before the turn-on timing of the switching elements Tm1 and Tn3 (first commutation time Tcom1 + resonant time Tres).

[0072] Mode 5 is the timing of t5 when Vce of switching element Tm1 becomes 0V, such as... Figure 3 As shown in (f), the switching elements Tm1 and Tn3 are controlled to turn on at zero voltage, so that the current ILr of the resonant inductor is commutated to the switching element Tm1.

[0073] In mode 5, the inter-terminal voltages of the components in auxiliary resonant circuit 2 are the same as in mode 3. Regarding the inter-terminal voltages of the components in neutral phase bridge arm 5, Tn3 and Dnn are 0V, and the voltages of the other components are Vdc / 2.

[0074] The period of mode 5 is called the second commutation time Tcom2[Lr÷Vdcp×Iinv]. Vdcp is the voltage across capacitor Cp in neutral point clamping circuit 3. The second commutation time Tcom2 is the time until the commutation of inverter current Iinv to switching element Tm1 is completed.

[0075] In other words, the switching element Tr5 of the positive resonant path rp is turned off after the second commutation time Tcom2, compared with the turn-on timing of switching elements Tm1 and Tn3.

[0076] In mode 6, as the commutation of the resonant inductor current ILr to the switching element Tm1 is completed, the switching element Tr5 is turned off at time t6, as follows: Figure 3 As shown in (g), power is discharged from the DC bus (positive DC line P) to the load (AC system).

[0077] In mode 6, the terminal voltages of each component in the auxiliary resonant circuit 2 are Vdc / 2 for Drp, Tr6, and Dsn, and 0V for the other components. The terminal voltages of each component in the neutral phase bridge arm 5 are the same as in mode 5.

[0078] Mode 7 involves turning off the upper arm's switching element Tm1 at time t7, causing the inverter current Iinv to commutate to the positive polarity path np of the neutral phase bridge arm 5, until the dead time DT following the turn-off control of switching element Tm1. In Mode 7, as... Figure 3 As shown in (h), the resonant capacitor C1 of switching element Tm1 is charged, and the resonant capacitor C2 of switching element Tm2 is discharged. Therefore, switching element Tm1 becomes a zero-voltage turn-off control based on lossless buffering.

[0079] At time t8, after the dead time DT following the turn-off control of switching element Tm1, switching element Tn4 is turned on at zero voltage and returns to mode 0.

[0080] In mode 7, the Vce of switching element Tm1 changes from 0V to Vdc / 2, and the Vce of switching element Tm2 changes from Vdc to Vdc / 2. Regarding the inter-terminal voltages of each component in auxiliary resonant circuit 2, Drp, Tr6, and Dsn change from Vdc / 2 to Vdc / 4, and Drn, Tr5, and Disp change from 0V to Vdc / 4. Regarding the inter-terminal voltages of each component in neutral phase bridge arm 5, Tn4 and Dnp change from Vdc / 2 to 0V.

[0081] Repeating modes 0 through 7, switching elements Tm1 and Tn3 are controlled to turn on at zero voltage. The auxiliary resonant circuit 2 becomes the path for the energy stored in the resonant inductor Lr. The voltage between the terminals of each element in the auxiliary resonant circuit 2 and the neutral phase bridge arm 5 will not exceed Vdc / 2 in any mode.

[0082] The operation of the resonant inverter 1 when the switching element Tr5 is turned off midway through Mode 5 described above is taken as Mode 5A. Figure 4 and Figure 5 As shown in the image. Figure 4 This is a timing diagram representing the operation of resonant inverter 1. Figure 5 The equivalent circuit of resonant inverter 1 is used to represent it. Figure 4 The actions shown are under mode 5A.

[0083] Mode 5A occurs at moment t5A, midway through the commutation of the resonant inductor current ILr to the switching element Tm1, where the switching element Tr5 is turned off due to component deviation, calculation error, or malfunction. For example... Figure 5As shown by the dashed line, for the energy excited in the resonant inductor Lr in the positive direction, the lossless regenerative clamping buffer diode Dsn and the anti-parallel diode D6 of the switching element Tr6 are regenerated to the DC bus without loss. During this regeneration, since the auxiliary resonant circuit 2 is clamped at the neutral point A of the DC bus, the components of the auxiliary resonant circuit 2, including the switching element Tr5 (diode Drn, lossless regenerative clamping buffer diode Dsp), are clamped at Vdc / 2.

[0084] Reference Figure 6 and Figure 7 The discharge operation of the resonant inverter 1 when the output voltage Vo and the inverter current Iinv are negative is explained. Figure 6 This is a timing diagram representing the operation of resonant inverter 1. Figure 7 The equivalent circuit of resonant inverter 1 is used to represent it. Figure 6 The actions in each of the shown modes.

[0085] Since the output voltage Vo is negative, switching elements Tm2 and Tn3 alternately perform PWM operations. When the inverter current Iinv is negative, the target of the resonant zero-voltage turn-on control is the turn-on timing of switching element Tm2.

[0086] Control circuit 6 turns off switching element Tn4 before resonant operation, thereby enabling resonant inverter 1 to operate as a two-level inverter, forming a mode in which the anti-parallel diode D1 of switching element Tm1 is turned on. When the inverter current Iinv is negative, in order to enable resonant operation on the negative side, control circuit 6 controls the switching element Tr6 of the negative side resonant path rn before and after the switching element Tm2 is turned on.

[0087] Figure 7 (a) shows mode 10, which is the state in which the inverter current Iinv freewheels in the negative polarity path nn of the neutral phase bridge arm 5.

[0088] In mode 10, the collector-emitter voltage Vce of switching elements Tm1 and Tm2 is Vdc / 2. Regarding the inter-terminal voltages (Vce, reverse voltage VR) of each element in auxiliary resonant circuit 2, Tr5, Tr6, Dsp, Dsn, Drp, and Drn are Vdc / 4. The inter-terminal voltage of each element in neutral phase bridge arm 5 is 0V.

[0089] In Mode 11, at time t11, switching elements Tn3 and Tn4 are simultaneously turned off, causing the inverter current Iinv to commutate through the anti-parallel diode D1 of the upper arm switching element Tm1. All other switching elements Tm1, Tm2, ​​Tr5, and Tr6 are in the off state. In Mode 11, as... Figure 7As shown in (b), the resonant capacitor C2 of switching element Tm2 is charged, and the resonant capacitor C1 of switching element Tm1 is discharged. Therefore, switching element Tn4 becomes a zero-voltage turn-off control based on lossless buffering.

[0090] In mode 11, the Vce of switching element Tm2 changes from Vdc / 2 to Vdc, and the Vce of switching element Tm1 changes from Vdc / 2 to 0V. Regarding the inter-terminal voltages of the components in auxiliary resonant circuit 2, Tr6, Dsn, and Drp change from Vdc / 4 to Vdc / 2, and Tr5, Dsp, and Drn change from Vdc / 4 to 0V. Regarding the inter-terminal voltages of the components in neutral phase bridge arm 5, Tn4 and Dnp change from 0V to Vdc / 2.

[0091] Mode 12 is as follows: at time t12, the Vce of switching element Tm2 changes to Vdc, and the Vce of switching element Tm1 changes to 0V. Figure 7 As shown in (c), the inverter current Iinv freewheels in the anti-parallel diode D1 of the switching element Tm1 in the upper arm.

[0092] In mode 12, the terminal voltages of each component in the auxiliary resonant circuit 2 are Vdc / 2 for Tr6, Drp, and Dsn, and 0V for the other components. The terminal voltages of each component in the neutral phase bridge arm 5 are Vdc / 2 for Tn4 and Dnp, and 0V for the other components.

[0093] In mode 13, at time t13 during the dead time DT, the switching element Tr6 of the negative resonant path rn is controlled to turn on with zero current, as follows: Figure 7 As shown in (d), the inverter current Iinv is commutated to the resonant inductor Lr (negative-side resonant path rn). Mode 13 continues until the anti-parallel diode D1 of the switching element Tm1 is turned off.

[0094] In mode 13, the terminal voltages of each component in the auxiliary resonant circuit 2 are as follows: Dsn is Vdc / 2, Tr5, Drp, and Dsp are Vdc / 4, and the voltages of other components are 0V. The terminal voltages of each component in the neutral phase bridge arm 5 are the same as in mode 12.

[0095] Mode 14 completes commutation to the resonant inductor Lr at time t14, through... Figure 7 In (e), the resonant capacitors C1 and C2, indicated by the dashed lines, resonate, and the Vce of switching elements Tm1 and Tm2 changes in a sinusoidal waveform. In mode 14, the Vce of switching element Tm2 changes from Vdc to 0V, and the Vce of switching element Tm1 changes from 0V to Vdc.

[0096] In mode 14, the terminal voltages of each component in the auxiliary resonant circuit 2 are the same as in mode 13. Regarding the terminal voltages of each component in the neutral phase bridge arm 5, Tn3 and Dnn change from 0V to Vdc / 2, while Tn4 and Dnp change from Vdc / 2 to 0V.

[0097] The period of mode 13+14 is the time obtained by adding the first commutation time Tcom1[Lr÷Vdcp×Iinv] to the resonant time Tres[π×√(Lr×2Cr)]. The first commutation time Tcom1 is the time until the commutation of the inverter current Iinv to the resonant inductor Lr is completed. The resonant time Tres is half a period of the resonance with a resonant frequency of (1 / 2π√(Lr×2Cr)).

[0098] In other words, the switching element Tr6 of the negative resonant path rn is turned on before the turn-on timing of switching elements Tm2 and Tn4 (first commutation time Tcom1 + resonant time Tres).

[0099] Mode 15 is the timing of t15 when Vce of the switching element Tm2 becomes 0V, such as... Figure 7 As shown in (f), the switching elements Tm2 and Tn4 are controlled to turn on at zero voltage, so that the current ILr of the resonant inductor is commutated to the switching element Tm2.

[0100] In mode 15, the inter-terminal voltages of the components in the auxiliary resonant circuit 2 are the same as in mode 13. Regarding the inter-terminal voltages of the components in the neutral phase bridge arm 5, Tn4 and Dnp are 0V, and the voltages of the other components are Vdc / 2.

[0101] The period of Mode 15 is called the 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.

[0102] In other words, the switching element Tr6 of the negative resonant path rn is turned off after (the second commutation time Tcom2) compared with the turn-on timing of switching elements Tm2 and Tn4.

[0103] In mode 16, as the commutation of the resonant inductor current ILr to the switching element Tm2 is completed, the switching element Tr6 is turned off at time t16. For example... Figure 7 As shown in (g), in mode 16, power is discharged from the DC bus (negative DC line N) to the load (AC system).

[0104] In mode 16, the terminal voltages of each component in the auxiliary resonant circuit 2 are Vdc / 2 for Drn, Tr5, and Dsp, and 0V for the other components. The terminal voltages of each component in the neutral phase bridge arm 5 are the same as in mode 15.

[0105] Mode 17 involves turning off the lower arm's switching element Tm2 at time t17, causing the inverter current Iinv to commutate to the negative polarity path nn of the neutral phase bridge arm 5, until the dead time DT following the turn-off control of switching element Tm1. In Mode 17, as... Figure 7 As shown in (h), the resonant capacitor C2 of switching element Tm2 is charged, and the resonant capacitor C1 of switching element Tm1 is discharged. Therefore, switching element Tm2 becomes a zero-voltage turn-off control based on lossless buffering.

[0106] At time t18, after the dead time DT following the turn-off control of switching element Tm2, ​​switching element Tn3 is turned on at zero voltage, returning to mode 10.

[0107] In mode 17, the Vce of switching element Tm2 changes from 0V to Vdc / 2, and the Vce of switching element Tm1 changes from Vdc to Vdc / 2. Regarding the terminal voltages of each component in auxiliary resonant circuit 2, Drn, Tr5, and Dsp change from Vdc / 2 to Vdc / 4, and Drp, Tr4, and Dsn change from 0V to Vdc / 4. Regarding the terminal voltages of each component in neutral phase bridge arm 5, Tn4 and Dnp change from Vdc / 2 to 0V.

[0108] Repeating modes 10 to 17, switching elements Tm2 and Tn3 are controlled to turn on at zero voltage. The auxiliary resonant circuit 2 becomes the path for the energy stored in the resonant inductor Lr. The voltage between the terminals of each element in the auxiliary resonant circuit 2 and the neutral phase bridge arm 5 will not exceed Vdc / 2 in any mode.

[0109] The operation of the resonant inverter 1 when the switching element Tr6 is turned off midway through the above-mentioned mode 15 is defined as mode 15A. Figure 8 and Figure 9 As shown in the image. Figure 8 This is a timing diagram representing the operation of resonant inverter 1. Figure 9 The equivalent circuit of resonant inverter 1 is used to represent it. Figure 8 The actions shown are under mode 15A.

[0110] Mode 15A refers to the state where, at moment t15A, during the commutation of the resonant inductor current ILr to the switching element Tm2, ​​the switching element Tr6 is turned off due to component deviation, calculation error, malfunction, etc. For example... Figure 9As shown by the dashed line, for the energy excited in the resonant inductor Lr in the negative direction, the lossless regenerative clamping buffer diode Dsp and the anti-parallel diode D5 of the switching element Tr5 are regenerated to the DC bus without loss. During this regeneration, since the auxiliary resonant circuit 2 is clamped at the neutral point A of the DC bus, the components of the auxiliary resonant circuit 2, including the switching element Tr6 (diode Drp, lossless regenerative clamping buffer diode Dsn), are clamped at Vdc / 2.

[0111] Reference Figure 10 and Figure 11 The charging operation of the resonant inverter 1 is explained when the output voltage Vo is positive and the inverter current Iinv is negative. Figure 10 This is a timing diagram representing the operation of resonant inverter 1. Figure 11 The equivalent circuit of resonant inverter 1 is used to represent it. Figure 10 The actions in each of the shown modes.

[0112] Since the output voltage Vo is positive, the switching elements Tm1 and Tn4 alternately perform PWM operations. When the inverter current Iinv is negative, the zero-voltage turn-on control based on resonance targets the turn-on timing of the switching element Tn4.

[0113] Figure 11 (a) shows mode 20, where the inverter current Iinv freewheels in the anti-parallel diode D1 of the switching element Tm1. Figure 11 As shown in (a), power is charged from the load (AC system) to the DC bus (positive DC line P).

[0114] In mode 20, the Vce of switching element Tm2 is Vdc. Regarding the terminal voltages of each component in auxiliary resonant circuit 2, Tr6, Drp, and Dsn are each Vdc / 2, while the voltages of other components are 0V. Regarding the terminal voltages of each component in neutral phase bridge arm 5, Tn3 and Dnn are each 0V, while the voltages of other components are Vdc / 2.

[0115] In mode 21, such as Figure 11 As shown in (b), at time t21, switching elements Tm1 and Tn3 are simultaneously turned off. The state of mode 21 is unchanged compared to mode 20.

[0116] In mode 22, at time t22 during the dead time DT, the switching element Tr6 of the negative resonant path rn is controlled to turn on with zero current, as follows: Figure 11 As shown in (c), the inverter current Iinv is commutated to the resonant inductor Lr (negative resonant path rn). Mode 22 continues until the anti-parallel diode D1 of the switching element Tm1 is turned off.

[0117] In mode 22, the terminal voltages of each component in the auxiliary resonant circuit 2 are as follows: Dsn is Vdc / 2, Tr5, Drp, and Dsp are Vdc / 4, and the voltages of other components are 0V. The terminal voltages of each component in the neutral phase bridge arm 5 are the same as in mode 21.

[0118] Mode 23 completes commutation to the resonant inductor Lr at time t23, through... Figure 11 (d) shows the resonance of resonant capacitors C1 and C2 (shown by dashed lines), and the Vce of switching elements Tm1 and Tm2 changes in a sinusoidal waveform. In mode 23, the Vce of switching element Tm2 changes from Vdc to 0V, and the Vce of switching element Tm1 changes from 0V to Vdc.

[0119] In mode 23, the inter-terminal voltages of each component in the auxiliary resonant circuit 2 are the same as in mode 22. Regarding the inter-terminal voltages of each component in the neutral phase bridge arm 5, Tn3 and Dnn change from 0V to Vdc / 2, while Tn4 and Dnp change from Vdc / 2 to 0V.

[0120] The period of mode 22+23 is the time obtained by adding the first commutation time Tcom1[Lr÷Vdcp×Iinv] to the resonant time Tres[π×√(Lr×2Cr)]. The first commutation time Tcom1 is the time until the commutation of the inverter current Iinv to the resonant inductor Lr is completed. The resonant time Tres is half a period of the resonance with a resonant frequency of (1 / 2π√(Lr×2Cr)).

[0121] In other words, the switching element Tr6 of the negative resonant path rn is turned on before the turn-on timing of the switching elements Tm2 and Tn4 (first commutation time Tcom1 + resonant time Tres).

[0122] Mode 24 is the timing of t24 when Vce of the switching element Tm2 becomes 0V, such as Figure 11 As shown in (e), switching elements Tm2 and Tn4 are controlled to turn on at zero voltage. In mode 24, the resonant inductor current ILr is not commutated to the neutral phase bridge arm 5, but is commutated to the switching element Tm2.

[0123] In mode 24, the inter-terminal voltages of the components in the auxiliary resonant circuit 2 are the same as in mode 23. Regarding the inter-terminal voltages of the components in the neutral phase bridge arm 5, Tn4 and Dnp are 0V, and the voltages of the other components are Vdc / 2.

[0124] The period of mode 24 is called the 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.

[0125] In other words, the switching element Tr6 of the negative resonant path rn is turned off after (the second commutation time Tcom2) compared with the turn-on timing of switching elements Tm2 and Tn4.

[0126] In mode 25, as the commutation of the resonant inductor current ILr to the switching element Tm2 is completed, the switching element Tr6 is turned off at time t25.

[0127] In mode 25, the terminal voltages of each component in the auxiliary resonant circuit 2 are Vdc / 2 for Drn, Tr5, and Dsp, and 0V for the other components. The terminal voltages of each component in the neutral phase bridge arm 5 are the same as in mode 24.

[0128] Mode 26 commutates the inverter current Iinv to the negative polarity path nn of the neutral phase bridge arm 5 by turning off the switching element Tm2 of the lower arm at time t26. In mode 26, as... Figure 11 As shown in (g), the resonant capacitor C2 of switching element Tm2 is charged, and the resonant capacitor C1 of switching element Tm1 is discharged. Therefore, switching element Tm2 becomes a zero-voltage turn-off control based on lossless buffering.

[0129] In mode 26, the Vce of switching element Tm2 changes from 0V to Vdc / 2, and the Vce of switching element Tm1 changes from Vdc to Vdc / 2. Regarding the inter-terminal voltages of each element in the auxiliary resonant circuit 2, Drn, Tr5, and Dsp change from Vdc / 2 to Vdc / 4, and Drp, Tr4, and Dsn change from 0V to Vdc / 4. Regarding the inter-terminal voltages of each element in the neutral phase bridge arm 5, Tn3 and Dnn change from Vdc / 2 to 0V.

[0130] Mode 27 is the state where commutation is complete and the inverter current Iinv freewheels in the negative polarity path nn of the neutral phase bridge arm 5. In Mode 27 after commutation to the negative polarity path nn of the neutral phase bridge arm 5 is completed, a series of zero-voltage turn-on operations are completed by performing zero-current turn-on control on the switching element Tn3.

[0131] In mode 27, the collector-emitter voltage Vce of switching elements Tm1 and Tm2 is Vdc / 2. Regarding the inter-terminal voltages (Vce, reverse voltage VR) of each element in auxiliary resonant circuit 2, Tr5, Tr6, Dsp, Dsn, Drp, and Drn are Vdc / 4. The inter-terminal voltage of each element in neutral phase bridge arm 5 is 0V.

[0132] In mode 28, at time t28, switching element Tn4 is turned off, causing inverter current Iinv to commutate to switching element Tm1. In mode 28, as... Figure 11 As shown in (i), the resonant capacitor C2 of switching element Tm2 is charged, and the resonant capacitor C1 of switching element Tm1 is discharged. Therefore, switching element Tn4 becomes a zero-voltage turn-off control based on lossless buffering.

[0133] In mode 28, the Vce of switching element Tm2 changes from Vdc / 2 to Vdc, and the Vce of switching element Tm1 changes from Vdc / 2 to 0V. Regarding the inter-terminal voltages of each component in auxiliary resonant circuit 2, Tr6, Dsn, and Drp change from Vdc / 4 to Vdc / 2, and Tr5, Dsp, and Drn change from Vdc / 4 to 0V. Regarding the inter-terminal voltages of each component in neutral phase bridge arm 5, Tn4 and Dnp change from 0V to Vdc / 2.

[0134] At time t29, after the dead time DT following the turn-off control of switching element Tn4, switching element Tm1 is turned on at zero voltage and returns to mode 20.

[0135] Repeating modes 20 to 28, switching elements Tm1 and Tn4 are controlled to turn on at zero voltage. The auxiliary resonant circuit 2 becomes the path for the energy stored in the resonant inductor Lr. The voltage between the terminals of each element in the auxiliary resonant circuit 2 and the neutral phase bridge arm 5 will not exceed Vdc / 2 in any mode.

[0136] In the middle of mode 24 described above, when the switching element Tr6 is turned off, the energy of the resonant inductor Lr excited in the negative direction is... Figure 9 Similarly, in mode 15A, lossless regeneration is performed on the DC bus. The lossless regeneration clamping buffer diode Dsp and the anti-parallel diode D5 of the switching element Tr5 are turned on. During this regeneration, since the auxiliary resonant circuit 2 is clamped at the neutral point A of the DC bus, the components of the auxiliary resonant circuit 2, including the switching element Tr6 (diode Drp, lossless regeneration clamping buffer diode Dsn), are clamped at Vdc / 2.

[0137] Reference Figure 12 and Figure 13The charging operation of the resonant inverter 1 is explained when the output voltage Vo is negative and the inverter current Iinv is positive. Figure 12 This is a timing diagram representing the operation of resonant inverter 1. Figure 13 The equivalent circuit of resonant inverter 1 is used to represent it. Figure 12 The actions in each of the shown modes.

[0138] Since the output voltage Vo is negative, switching elements Tm2 and Tn3 alternately perform PWM operations. When the inverter current Iinv is positive, the target of the resonant zero-voltage turn-on control is the turn-on timing of switching element Tn3.

[0139] Figure 13 (a) shows mode 30, where the inverter current Iinv freewheels in the anti-parallel diode D2 of the switching element Tm2. For example... Figure 13 As shown in (a), power is charged from the load (AC system) to the DC bus (negative DC line N).

[0140] In mode 30, the Vce of switching element Tm1 is Vdc. Regarding the terminal voltages of each component in the auxiliary resonant circuit 2, Tr5, Drn, and Dsp are each Vdc / 2, while the voltages of other components are 0V. Regarding the terminal voltages of each component in the neutral phase bridge arm 5, Tn4 and Dnp are each 0V, while the voltages of other components are Vdc / 2.

[0141] In mode 31, such as Figure 13 As shown in (b), at time t31, switching elements Tm2 and Tn4 are simultaneously turned off. The state of mode 31 is unchanged compared to mode 30.

[0142] In mode 32, at time t32 during the dead time DT, the switching element Tr5 of the positive resonant path rp is controlled to turn on with zero current, as follows: Figure 13 As shown in (c), the inverter current Iinv is commutated to the resonant inductor Lr (positive resonant path rp). Mode 32 continues until the anti-parallel diode D2 of the switching element Tm2 is turned off.

[0143] In mode 32, the terminal voltages of each component in the auxiliary resonant circuit 2 are as follows: Dsp is Vdc / 2, Tr6, Drn, and Dsn are Vdc / 4, and the voltages of other components are 0V. The terminal voltages of each component in the neutral phase bridge arm 5 are the same as in mode 31.

[0144] Mode 33 completes commutation to the resonant inductor Lr at time t33, through... Figure 13(d) shows the resonance of resonant capacitors C1 and C2 (shown by dashed lines), and the Vce of switching elements Tm1 and Tm2 changes in a sinusoidal waveform. In mode 33, the Vce of switching element Tm1 changes from Vdc to 0V, and the Vce of switching element Tm2 changes from 0V to Vdc.

[0145] In mode 33, the terminal voltages of each component in the auxiliary resonant circuit 2 are the same as in mode 32. Regarding the terminal voltages of each component in the neutral phase bridge arm 5, Tn4 and Dnp change from 0V to Vdc / 2, while Tn3 and Dnn change from Vdc / 2 to 0V.

[0146] The period of mode 32+33 is the time obtained by adding the first commutation time Tcom1[Lr÷Vdcn×Iinv] to the resonant time Tres[π×√(Lr×2Cr)]. The first commutation time Tcom1 is the time until the commutation of the inverter current Iinv to the resonant inductor Lr is completed. The resonant time Tres is half a period of the resonance with a resonant frequency of (1 / 2π√(Lr×2Cr)).

[0147] In other words, the switching element Tr5 of the positive resonant path rp is turned on before the turn-on timing of the switching elements Tm1 and Tn3 (first commutation time Tcom1 + resonant time Tres).

[0148] Mode 34 is the timing of t34 when Vce of switching element Tm1 becomes 0V, such as Figure 13 As shown in (e), switching elements Tm1 and Tn3 are controlled to turn on at zero voltage. In mode 34, the resonant inductor current ILr is not commutated to the neutral phase bridge arm 5, but is commutated to the switching element Tm1.

[0149] In mode 34, the inter-terminal voltages of the components in the auxiliary resonant circuit 2 are the same as in mode 33. Regarding the inter-terminal voltages of the components in the neutral phase bridge arm 5, Tn3 and Dnn are 0V, and the voltages of the other components are Vdc / 2.

[0150] The period of mode 34 is called the second commutation time Tcom2[Lr÷Vdcp×Iinv]. The second commutation time Tcom2 is the time until the commutation of the inverter current Iinv to the switching element Tm1 is completed.

[0151] In other words, the switching element Tr5 of the positive resonant path rp is turned off after the second commutation time Tcom2, compared with the turn-on timing of switching elements Tm1 and Tn3.

[0152] In mode 35, as the commutation of the resonant inductor current ILr to the switching element Tm1 is completed, the switching element Tr5 is turned off at time t35.

[0153] In mode 35, the terminal voltages of each component in the auxiliary resonant circuit 2 are Vdc / 2 for Drp, Tr6, and Dsn, and 0V for the other components. The terminal voltages of each component in the neutral phase bridge arm 5 are the same as in mode 34.

[0154] Mode 36 commutates the inverter current Iinv to the positive polarity path np of the neutral phase bridge arm 5 by turning off the switching element Tm1 of the upper arm at time t36. In mode 36, as... Figure 13 As shown in (g), the resonant capacitor C1 of switching element Tm1 is charged, and the resonant capacitor C2 of switching element Tm2 is discharged. Therefore, switching element Tm1 becomes a zero-voltage turn-off control based on lossless buffering.

[0155] In mode 36, the Vce of switching element Tm1 changes from 0V to Vdc / 2, and the Vce of switching element Tm2 changes from Vdc to Vdc / 2. Regarding the inter-terminal voltages of each component in the auxiliary resonant circuit 2, Drp, Tr6, and Dsn change from Vdc / 2 to Vdc / 4, and Drn, Tr5, and Dsp change from 0V to Vdc / 4. Regarding the inter-terminal voltages of each component in the neutral phase bridge arm 5, Tn4 and Dnp change from Vdc / 2 to 0V.

[0156] Mode 37 is the state where commutation is complete and the inverter current Iinv freewheels in the positive polarity path np of the neutral phase bridge arm 5. In Mode 37 after commutation to the positive polarity path np of the neutral phase bridge arm 5 is completed, a series of zero-voltage turn-on operations are completed by performing zero-current turn-on control on the switching element Tn4.

[0157] In mode 37, the collector-emitter voltage Vce of switching elements Tm1 and Tm2 is Vdc / 2. Regarding the inter-terminal voltages (Vce, reverse voltage VR) of each element in auxiliary resonant circuit 2, Tr5, Tr6, Dsp, Dsn, Drp, and Drn are Vdc / 4. The inter-terminal voltage of each element in neutral phase bridge arm 5 is 0V.

[0158] In mode 38, at time t38, the switching element Tn3 is turned off, causing the inverter current Iinv to be switched to the switching element Tm2. In mode 38, as... Figure 13 As shown in (i), the resonant capacitor C1 of switching element Tm1 is charged, and the resonant capacitor C2 of switching element Tm2 is discharged. Therefore, switching element Tn3 becomes a zero-voltage turn-off control based on lossless buffering.

[0159] In mode 38, the Vce of switching element Tm1 changes from Vdc / 2 to Vdc, and the Vce of switching element Tm2 changes from Vdc / 2 to 0V. Regarding the inter-terminal voltages of the components in auxiliary resonant circuit 2, Tr5, Dsp, and Drn change from Vdc / 4 to Vdc / 2, and Tr6, Dsn, and Drp change from Vdc / 4 to 0V. Regarding the inter-terminal voltages of the components in neutral phase bridge arm 5, Tn3 and Dnn change from 0V to Vdc / 2.

[0160] At time t39, after the dead time DT following the turn-off control of switching element Tn3, switching element Tm2 is turned on at zero voltage and returns to mode 30.

[0161] Repeating modes 30 to 38, switching elements Tm2 and Tn3 are controlled to turn on at zero voltage. The auxiliary resonant circuit 2 becomes the path for the energy stored in the resonant inductor Lr. The voltage between the terminals of each element in the auxiliary resonant circuit 2 and the neutral phase bridge arm 5 will not exceed Vdc / 2 in any mode.

[0162] In the middle of mode 34 described above, when the switching element Tr5 is turned off, the energy excited in the resonant inductor Lr in the positive direction is... Figure 5 Similarly, in Mode 5A, lossless regeneration is performed on the DC bus. The lossless regeneration buffer diode Dsn and the anti-parallel diode D6 of the switching element Tr6 are turned on. During this regeneration, since the auxiliary resonant circuit 2 is clamped at the neutral point A of the DC bus, the components of the auxiliary resonant circuit 2, including the switching element Tr5 (diode Drn, lossless regeneration clamping buffer diode Disp), are clamped at Vdc / 2.

[0163] Figure 14 This represents a T-NPC type inverter circuit 10 that utilizes an auxiliary resonant circuit 2. In the T-NPC type inverter circuit 10, switching elements Tn3 and Tn4 are connected in series in a direction that allows control in opposite withstand voltage directions, serving as a neutral phase bridge arm 5a connecting the neutral point A and the input / output point B. For switching element Tn3, its collector is connected to the neutral point A, and its emitter is connected to the emitter of switching element Tn4. For switching element Tn4, its collector is connected to the input / output point B.

[0164] In the neutral phase bridge arm 5a, the anti-parallel diode D4 of switching elements Tn3 and Tn4 functions as the positive polarity path np, which is switched on and off by switching element Tn3. The anti-parallel diode D3 of switching elements Tn4 and Tn3 functions as the negative polarity path nn, which is switched on and off by switching element Tn4.

[0165] Figure 15 This is a full-bridge inverter circuit 11 that utilizes a resonant inverter 1. The full-bridge inverter circuit 11 sets the resonant inverter 1 into a full-bridge structure. The full-bridge inverter circuit 11 includes a U-phase main bridge arm 4u, a U-phase neutral phase bridge arm 5au of the U-phase main bridge arm 4u, and a U-phase auxiliary resonant circuit 2u. The full-bridge inverter circuit 11 also includes a W-phase main bridge arm 4w, a W-phase neutral phase bridge arm 5aw of the W-phase main bridge arm 4w, and a W-phase auxiliary resonant circuit 2w.

[0166] The U-phase control circuit 6u and the W-phase control circuit 6w control the U-phase auxiliary resonant circuit 2u and the W-phase auxiliary resonant circuit 2w separately at different timings. The control of the U-phase auxiliary resonant circuit 2u varies depending on the switching state of the W-phase circuit. The control of the W-phase auxiliary resonant circuit 2w varies depending on the switching state of the U-phase circuit.

[0167] Figure 16 This is a three-phase inverter circuit 12 that utilizes a resonant inverter 1. The three-phase inverter circuit 12 configures the resonant inverter 1 as a three-phase structure. The three-phase inverter circuit 12 includes a U-phase main bridge arm 4u, a U-phase neutral phase bridge arm 5au of the U-phase main bridge arm 4u, and a U-phase auxiliary resonant circuit 2u. The three-phase inverter circuit 12 also includes a V-phase main bridge arm 4v, a V-phase neutral phase bridge arm 5av of the V-phase main bridge arm 4v, and a V-phase auxiliary resonant circuit 2v. Finally, the three-phase inverter circuit 12 includes a W-phase main bridge arm 4w, a W-phase neutral phase bridge arm 5aw of the W-phase main bridge arm 4w, and a W-phase auxiliary resonant circuit 2w.

[0168] The U-phase control circuit 6u, V-phase control circuit 6v, and W-phase control circuit 6w each independently control the U-phase auxiliary resonant circuit 2u, V-phase auxiliary resonant circuit 2v, and W-phase auxiliary resonant circuit 2w via timing mechanisms. The control of the U-phase auxiliary resonant circuit 2u varies depending on the switching states of the V-phase and W-phase circuits. The control of the V-phase auxiliary resonant circuit 2v varies depending on the switching states of the U-phase and W-phase circuits. The control of the W-phase auxiliary resonant circuit 2w varies depending on the switching states of the U-phase and V-phase circuits.

[0169] Reference Figure 17 This section describes the case where the switching element Tm1 of the U-phase main bridge arm 4u is controlled to turn on at zero voltage when both the V-phase main bridge arm 4v and the W-phase main bridge arm 4w are conducting. Assume the U-phase current is positive, and the V-phase and W-phase currents are both negative.

[0170] Figure 17 (a) shows the mode 40, which is the state in which the inverter current Iinv freewheels in the anti-parallel diode D2 of the switching element Tm2 of the U-phase main bridge arm 4u, the anti-parallel diode D1 of the switching element Tm1 of the V-phase main bridge arm 4v and the W-phase main bridge arm 4w.

[0171] Mode 41 controls the switching element Tr5 in the U-phase auxiliary resonant circuit 2u of the U-phase main bridge arm 4u to turn on, such as... Figure 17 As shown in (b), the inverter current Iinv is commutated to the positive resonant path rp (resonant inductor Lr) of the U-phase auxiliary resonant circuit 2u.

[0172] In mode 42, commutation is completed by the resonant inductor Lr in the U-phase auxiliary resonant circuit 2u. Mode 42 is achieved through... Figure 17 (c) shows the resonance of resonant capacitors C1 and C2 in the U-phase main bridge arm 4u (shown by the dashed line). The Vce of switching elements Tm1 and Tm2 in the U-phase main bridge arm 4u changes in a sinusoidal waveform. In mode 42, the Vce of switching element Tm1 in the U-phase main bridge arm 4u changes from Vdc to 0V, and the Vce of switching element Tm2 in the U-phase main bridge arm 4u changes from 0V to Vdc.

[0173] In mode 43, when the Vce of the switching element Tm1 in the U-phase main bridge arm 4u becomes 0V, such as... Figure 17 As shown in (d), the switching element Tm1 of the U-phase main bridge arm 4u is controlled to turn on at zero voltage. Mode 43 causes the resonant inductor current ILr to commutate to the switching element Tm1 of the U-phase main bridge arm 4u.

[0174] In mode 44, as the commutation of the resonant inductor current ILr to the switching element Tm1 is completed, the switching element Tr5 is turned off, as shown below. Figure 17 As shown in (e), the current freewheels between the inverter input and output points.

[0175] The above describes the operation of phase U of the U-phase control circuit 6u. Similarly, phase V control circuit 6v and phase W control circuit 6w control phase V and W respectively at separate timings, just like phase U.

[0176] (Summarize)

[0177] The resonant inverters involved in the various embodiments of the present invention can also be described as follows.

[0178] (1) In one embodiment of this invention, the resonant inverter 1 includes a neutral point clamping circuit 3 consisting of a capacitor Cp (positive capacitor) and a capacitor Cn (negative capacitor) connected in series between the positive DC line P and the negative DC line N. The connection point of the capacitors Cp and Cn in the neutral point clamping circuit 3 is called the neutral point A. The resonant inverter 1 includes a main bridge arm 4 connected in series between the positive DC line P and the negative DC line N. The main bridge arm 4 consists of a switching element Tm1 (upper arm switch) and a switching element Tm2 (lower arm switch), and the connection point of the switching elements Tm1 and Tm2 is called the input / output point B of the inverter current. The resonant inverter 1 includes a resonant capacitor C1 (first resonant capacitor) and a resonant capacitor C2 (second resonant capacitor) connected in parallel with the switching 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 switching elements Tm1 and Tm2. The resonant inverter 1 also includes a neutral phase bridge arm 5, which has a positive polarity path np defined as the current polarity from neutral point A to input / output point B, and a negative polarity path nn defined as the current polarity from input / output point B to neutral point A. The neutral phase bridge arm 5 includes a switching element Tn3 (positive neutral phase switch) and a switching element Tn4 (negative neutral phase switch) that open and close the positive polarity path np and the negative polarity path nn, respectively. The resonant inverter 1 further includes an auxiliary resonant circuit 2 containing a resonant inductor Lr connected at one end to input / output point B. The auxiliary resonant circuit 2 has a positive resonant path rp, where the current polarity is defined as flowing from the neutral point A towards the resonant inductor Lr, and is switched on and off via the switching element Tr5 (positive resonant switch). The auxiliary resonant circuit 2 also has a negative resonant path rn, where the current polarity is defined as flowing from the resonant inductor Lr towards the neutral point A, and is switched on and off via the switching element Tr6 (negative resonant switch). The auxiliary resonant circuit 2 also has a positive regenerative path (the anti-parallel diode D3 of the switching element Tr3 + the lossless regenerative clamping buffer diode Dsp) where the current polarity is defined as flowing from the resonant inductor Lr towards the positive DC line P. Finally, the auxiliary resonant circuit 2 has a negative regenerative path (the anti-parallel diode D4 of the switching element Tr4 + the lossless regenerative clamping buffer diode Dsn) where the current polarity is defined as flowing from the negative DC line N towards the resonant inductor Lr. During the charging operation where switching elements Tm1 and Tn4 are alternately controlled by the dead time DT, switching elements Tn3 and Tm1 are simultaneously turned off, and switching element Tr6 is turned on during the dead time DT before the turn-on control of switching element Tn4.

[0179] According to the resonant inverter 1 described in (1) above, the auxiliary resonant circuit 2 becomes a lossless regeneration path for the energy stored in the resonant inductor Lr. The auxiliary resonant circuit 2 is clamped to the voltage of the neutral point A through the positive resonant path rp and the negative resonant path rn. The components constituting the auxiliary resonant circuit 2 can be composed of components with lower withstand voltage than the components of the main bridge arm 4, which is the main circuit. The range of component selection for the auxiliary resonant circuit 2 is widened, and it can be constructed inexpensively. The lossless regeneration clamping buffer diodes Dsp and Dsn become the regeneration path for the energy of the resonant inductor Lr, enabling highly efficient overvoltage protection measures. By applying the auxiliary resonant circuit 2 to the resonant inverter 1, which is a three-level inverter, the resonant inverter 1 can be further improved in efficiency. The resonant inverter 1 can perform soft switching even when the power factor is less than 1, so it is most suitable for charging and discharging applications. The resonant inverter 1 can achieve heat dissipation by setting the auxiliary resonant circuit 2, so the heat dissipation mechanism becomes inexpensive. During the charging operation where the switching elements Tm1 and Tn4 are alternately controlled by the dead time DT, the resonant inverter 1 can be treated as a two-level converter, and the resonant operation can be easily controlled.

[0180] (2) In the resonant inverter 1 described in (1) above, the switching element Tm2 and the switching element Tn4 can be turned on simultaneously, and the switching element Tr6 can be turned off after the switching elements Tn4 and Tm2 are turned on.

[0181] According to the resonant inverter 1 described above (2), when the switching elements Tm1 and Tn4 are alternately controlled during the dead time DT, the inverter current Iinv can be commutated to the auxiliary resonant circuit 2, causing the resonant action.

[0182] (3) In the resonant inverter 1 described in (2) above, the switching element Tr6 may be turned on at a time before the timing of the turn-on control of the switching elements Tn4 and Tm2, ​​which is the time obtained by adding the first commutation time Tcom1 (the first commutation time on the negative side) to the resonant time Tres. The first commutation time Tcom1 (the first commutation time on the negative side) is the time until the commutation of the inverter current Iinv to the resonant inductor Lr is completed through the turn-on control of the switching element Tr6. The resonant time Tres is based on half a cycle of the resonance between the resonant inductor Lr and the resonant capacitors C1 and C2.

[0183] According to the resonant inverter 1 described above (3), when the switching element Tm1 and the switching element Tn4 are alternately controlled during the charging operation of the dead time DT, the zero-voltage turn-on control of the switching element Tn4 can be realized.

[0184] (4) In the resonant inverter 1 described in (2) or (3) above, the switching element Tr6 may also be turned off at a timed interval after the second commutation time Tcom2 (negative-side second commutation time) of the turn-on control of switching elements Tn4 and Tm2. The second commutation time Tcom2 (negative-side second commutation time) is the time until the commutation of the resonant inductor current ILr from the resonant inductor Lr to the switching element Tm2 is completed through the turn-on control of switching elements Tn4 and Tn2.

[0185] According to the resonant inverter 1 described above (4), when the switching elements Tm1 and Tn4 are alternately controlled during the charging operation of the dead time DT, the resonant operation can be quickly ended after the zero voltage turn-on control of the switching element Tn4.

[0186] (5) In any one of (2) to (4) above, the resonant inverter 1 may be controlled to turn off after the switching element Tm2 is turned off, and the switching element Tn3 is turned on after the inverter current Iinv is commutated to the negative polarity path nn of the neutral phase bridge arm 5 by the turn-off control of the switching element Tm2.

[0187] According to the resonant inverter 1 described above (5), when the switching elements Tm1 and Tn4 are alternately controlled during the charging operation of the dead time DT, it can be processed as a three-level converter at the end of the resonant operation, thereby achieving high efficiency.

[0188] (6) In the resonant inverter 1 described in (1) above, a neutral point clamping circuit 3 is provided, consisting of a capacitor Cp (positive capacitor) and a capacitor Cn (negative capacitor) connected in series between the positive DC line P and the negative DC line N. In the neutral point clamping circuit 3, the connection point of the capacitor Cp and the capacitor Cn is called the neutral point A. The resonant inverter 1 is provided with a main bridge arm 4 connected in series between the positive DC line P and the negative DC line N. The main bridge arm 4 is composed of a switching element Tm1 (upper arm switch) and a switching element Tm2 (lower arm switch), and the connection point of the switching element Tm1 and the switching element Tm2 is called the input / output point B of the inverter current. The resonant inverter 1 is provided with a resonant capacitor C1 (first resonant capacitor) and a resonant capacitor C2 (second resonant capacitor) connected in parallel with the switching 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 switching elements Tm1 and Tm2. The resonant inverter 1 also includes a neutral phase bridge arm 5, which has a positive polarity path np defined as the current polarity from neutral point A to input / output point B, and a negative polarity path nn defined as the current polarity from input / output point B to neutral point A. The neutral phase bridge arm 5 includes a switching element Tn3 (positive neutral phase switch) and a switching element Tn4 (negative neutral phase switch) that open and close the positive polarity path np and the negative polarity path nn, respectively. The resonant inverter 1 further includes an auxiliary resonant circuit 2 comprising a resonant inductor Lr connected at one end to input / output point B. The auxiliary resonant circuit 2 has a positive resonant path rp, where the current polarity is defined as flowing from the neutral point A towards the resonant inductor Lr, and is switched on and off via the switching element Tr5 (positive resonant switch). The auxiliary resonant circuit 2 also has a negative resonant path rn, where the current polarity is defined as flowing from the resonant inductor Lr towards the neutral point A, and is switched on and off via the switching element Tr6 (negative resonant switch). The auxiliary resonant circuit 2 also has a positive regenerative path (the anti-parallel diode D3 of the switching element Tr3 + the lossless regenerative clamping buffer diode Dsp) where the current polarity is defined as flowing from the resonant inductor Lr towards the positive DC line P. Finally, the auxiliary resonant circuit 2 has a negative regenerative path (the anti-parallel diode D4 of the switching element Tr4 + the lossless regenerative clamping buffer diode Dsn) where the current polarity is defined as flowing from the negative DC line N towards the resonant inductor Lr. During the charging operation where switching elements Tm2 and Tn3 are alternately controlled at intervals of dead time, switching elements Tn4 and Tm2 are simultaneously turned off, and switching element Tr5 is turned on during the dead time before the turn-on control of switching element Tn3.

[0189] According to the resonant inverter 1 described above (6), in addition to the effects of (1) above, when the switching elements Tm2 and Tn3 are alternately controlled during the charging operation with the dead time DT, the resonant inverter 1 can be treated as a two-level converter, and the resonant operation can be easily controlled.

[0190] (7) In the resonant inverter 1 described in (6) above, the switching element Tm1 and the switching element Tn3 can be turned on simultaneously, and the switching element Tr5 can be turned off after the switching element Tn3 and the switching element Tm1 are turned on.

[0191] According to the resonant inverter 1 described above (7), when the switching elements Tm2 and Tn3 are alternately controlled during the charging operation with the interval dead time, the inverter current Iinv can be commutated to the auxiliary resonant circuit 2, causing the resonant operation.

[0192] (8) In the resonant inverter 1 described in (6) or (7) above, the switching element Tr5 may be turned on at a time before the timing of the turn-on control of the switching elements Tn3 and Tm1, which is the time obtained by adding the first commutation time Tcom1 (first commutation time on the positive side) and the resonant time Tres. The first commutation time Tcom1 (first commutation time on the positive side) is the time until the commutation of the inverter current Iinv to the resonant inductor Lr is completed through the turn-on control of the switching element Tr5. The resonant time Tres is based on half a cycle of the resonance between the resonant inductor Lr and the resonant capacitors C1 and C2.

[0193] According to the resonant inverter 1 described above (8), when the switching element Tm2 and the switching element Tn3 are alternately controlled during the charging operation with the dead time interval, the zero voltage turn-on control of the switching element Tn3 can be realized.

[0194] (9) In any of the resonant inverters 1 described in (6) to (8) above, the switching element Tr5 may be turned off at a time after the second commutation time Tcom2 (positive side second commutation time), which is the timing of the turn-on control of the switching elements Tn3 and Tm1. The second commutation time Tcom2 (positive side second commutation time) is the time until the commutation of the resonant inductor current ILr from the resonant inductor Lr to the switching element Tm1 is completed through the turn-on control of the switching elements Tn3 and Tm1.

[0195] According to the resonant inverter 1 described above (9), when the switching element Tm2 and the switching element Tn3 are alternately controlled during the charging operation with the interval dead time, the resonant operation can be quickly ended after the zero voltage turn-on control of the switching element Tn3.

[0196] (10) In any of the resonant inverters 1 described in (6) to (9) above, the switching element Tm1 may be turned off after the switching element Tr5 is turned off, and the switching element Tn4 may be turned on after the inverter current Iinv is commutated to the positive polarity path np of the neutral phase bridge arm 5 by the turn-off control of the switching element Tm1.

[0197] According to the resonant inverter 1 described above (10), when the switching elements Tm2 and Tn3 are alternately controlled during the charging operation with the interval dead time, it can be processed as a three-level converter at the end of the resonant operation, thereby achieving high efficiency.

[0198] The present invention has been described above through specific embodiments. However, the above embodiments are examples, and it is self-evident that modifications can be made without departing from the spirit of the present invention.

[0199] Explanation of reference numerals in the attached figures

[0200] 1. Resonant inverter; 2. Auxiliary resonant circuits: 2u, 2v, 2w; 3. Neutral point clamping circuit; 4. Main bridge arm: 4u (U-phase main bridge arm); 4v (V-phase main bridge arm); 4w (W-phase main bridge arm); 5. Neutral phase bridge arm: 5a (neutral phase bridge arm); 5au (U-phase neutral phase bridge arm); 5av (V-phase neutral phase bridge arm); 5aw (W-phase neutral phase bridge arm); 5u (U-phase neutral phase bridge arm); 5w (W-phase neutral phase bridge arm); 6. Control circuit: 6u (U-phase control circuit); 6v (V-phase control circuit); 6w (W-phase control circuit); 10. T-NPC inverter circuit; 11. Full-bridge inverter circuit; 12. Three-phase inverter circuit; C1, C2 resonant capacitors; Cn, Cp capacitors; D1, D2, D3, D4, D5, D6 anti-parallel diodes; Dnn, Dnp, Drn, Drp diodes; Dsn, Dsp diodes. Lossless regenerative clamping buffer diode; L1 inductor; Lr resonant inductor; N negative DC line; P positive DC line; Tm1, Tm2, ​​Tn3, Tn4, Tr5, Tr6 switching elements; nn negative polarity path; np positive polarity path; rn negative resonant path; rp positive resonant path.

Claims

1. A resonant inverter, comprising: A neutral point clamping circuit consists of a positive capacitor and a negative capacitor connected in series between the positive DC line and the negative DC line, and the connection point between the positive capacitor and the negative capacitor is called the neutral point. The main bridge arm consists of an upper arm switch and a lower arm switch connected in series between the positive DC line and the negative DC line. The connection point between the upper arm switch and the lower arm switch becomes the input and output point of the inverter current. The first resonant capacitor and the second resonant capacitor are connected in parallel with the upper arm switch and the lower arm switch; The first anti-parallel diode and the second anti-parallel diode are connected in anti-parallel to the upper arm switch and the lower arm switch; A neutral phase bridge arm, connected between the neutral point and the input / output point, has a positive-side neutral phase switch and a negative-side neutral phase switch that respectively open and close a positive polarity path whose current polarity is defined as the direction from the neutral point to the input / output point and a negative polarity path whose current polarity is defined as the direction from the input / output point to the neutral point. as well as The auxiliary resonant circuit includes a resonant inductor, one end of which is connected to the input / output point of the main bridge arm. The auxiliary resonant circuit includes: In the positive resonant path, the current polarity is defined as being from the neutral point toward the resonant inductor, and is switched on and off by a positive resonant switch. In the negative-side resonant path, the current polarity is defined as being from the resonant inductor toward the neutral point, and is switched on and off by a negative-side resonant switch. In the positive regeneration path, the current polarity is defined as being from the resonant inductor toward the positive DC line; as well as In the negative-side regeneration path, the current polarity is defined as flowing from the negative-side DC line towards the resonant inductor. During the charging operation, which alternately controls the upper arm switch and the negative-side neutral phase switch at dead time intervals, The positive-side neutral phase switch and the upper arm switch are simultaneously turned off, and the negative-side resonant switch is turned on during the dead time before the negative-side neutral phase switch is turned on.

2. The resonant inverter according to claim 1, wherein, The lower arm switch and the negative side neutral phase switch are simultaneously turned on, and the negative side resonant switch is turned off after the negative side neutral phase switch and the lower arm switch are turned on.

3. The resonant inverter according to claim 2, wherein, The negative-side resonant switch is turned on at a timed interval between the turn-on control of the negative-side neutral phase switch and the lower arm switch, including the first negative-side commutation time until the inverter current is commutated to the resonant inductor by the turn-on control of the negative-side resonant switch, and the time before the time obtained by adding the resonant time based on half a cycle of the resonance of the resonant inductor with the first resonant capacitor and the second resonant capacitor.

4. The resonant inverter according to claim 2, wherein, The negative-side resonant switch is turned off after the second negative-side commutation time following the timing of the turn-on control of the negative-side neutral phase switch and the lower arm switch, which is until the commutation of the resonant inductor current from the resonant inductor to the lower arm switch is completed through the turn-on control of the negative-side neutral phase switch.

5. The resonant inverter according to claim 4, wherein, The lower arm switch is turned off after the negative resonant switch is turned off, and the positive neutral phase switch is turned on after the inverter current is switched to the negative polarity path of the neutral phase bridge arm by the turn-off control of the lower arm switch.

6. A resonant inverter, comprising: A neutral point clamping circuit consists of a positive capacitor and a negative capacitor connected in series between the positive DC line and the negative DC line, and the connection point between the positive capacitor and the negative capacitor is called the neutral point. The main bridge arm consists of an upper arm switch and a lower arm switch connected in series between the positive DC line and the negative DC line. The connection point between the upper arm switch and the lower arm switch becomes the input and output point of the inverter current. The first resonant capacitor and the second resonant capacitor are connected in parallel with the upper arm switch and the lower arm switch; The first anti-parallel diode and the second anti-parallel diode are connected in anti-parallel to the upper arm switch and the lower arm switch; A neutral phase bridge arm, connected between the neutral point and the input / output point, has a positive-side neutral phase switch and a negative-side neutral phase switch that respectively open and close a positive polarity path whose current polarity is defined as the direction from the neutral point to the input / output point and a negative polarity path whose current polarity is defined as the direction from the input / output point to the neutral point. as well as The auxiliary resonant circuit includes a resonant inductor, one end of which is connected to the input / output point of the main bridge arm. The auxiliary resonant circuit includes: In the positive resonant path, the current polarity is defined as being from the neutral point toward the resonant inductor, and is switched on and off by a positive resonant switch. In the negative-side resonant path, the current polarity is defined as being from the resonant inductor toward the neutral point, and is switched on and off by a negative-side resonant switch. In the positive regeneration path, the current polarity is defined as being from the resonant inductor toward the positive DC line; as well as In the negative-side regeneration path, the current polarity is defined as flowing from the negative-side DC line towards the resonant inductor. During the charging operation, which alternately controls the lower arm switch and the positive side neutral phase switch during the dead time interval, The negative-side neutral phase switch and the lower arm switch are simultaneously turned off, and the positive-side resonant switch is turned on during the dead time before the positive-side neutral phase switch is turned on.

7. The resonant inverter according to claim 6, wherein, The upper arm switch and the positive side neutral phase switch are simultaneously turned on, and after the positive side neutral phase switch and the upper arm switch are turned on, the positive side resonant switch is turned off.

8. The resonant inverter according to claim 7, wherein, The positive resonant switch is turned on at a timed manner, including the first positive commutation time until the inverter current is commutated to the resonant inductor by the turn-on control of the positive resonant switch, and the time before the time obtained by adding the resonant time based on half a cycle of the resonance of the resonant inductor with the first resonant capacitor and the second resonant capacitor.

9. The resonant inverter according to claim 7, wherein, The positive resonant switch is turned off after the second positive commutation time following the timing of the turn-on control of the positive neutral phase switch and the upper arm switch, which is 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 positive neutral phase switch.

10. The resonant inverter according to claim 9, wherein, The upper arm switch is turned off after the positive resonant switch is turned off, and the negative neutral phase switch is turned on after the inverter current is switched to the positive polarity path of the neutral phase bridge arm by the turn-off control of the upper arm switch.

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