Resonant inverter

Abstract

The auxiliary resonance circuit (2) is provided with: a positive-side resonance path (rp) that is opened and closed by a switching element (Tr3), the current polarity of which is defined in the direction from the neutral point (A) to the resonance inductor (Lr); a negative-side resonance path rn that is opened and closed by a switching element Tr4, the current polarity of the negative-side resonance path rn being defined in a direction from the resonance inductor Lr toward the neutral point A; a positive-side regeneration path (D3 + Dsp) whose current polarity is defined in a direction from the resonant inductor Lr toward the positive-side DC line P; and a negative-side regeneration path (D4 + Dsn), the current polarity of which is defined in a direction from the negative-side DC line N toward the resonant inductor Lr.

Description

TECHNICAL FIELD

[0001] The present application relates to a resonance inverter having an auxiliary resonance circuit. BACKGROUND

[0002] A power storage system such as an uninterruptible power supply device is provided with a power storage device and a PCS (Power Conditioner System) in which an inverter that performs conversion between alternating current and direct current between an external power system and the power storage device is built in. The power storage device is configured to have, for example, a plurality of power storage modules each having a plurality of power storage elements. In recent years, the power storage device is being promoted to be higher in voltage and larger in capacity.

[0003] With the higher voltage and larger capacity of the power storage device, an increase in switching loss and electromagnetic interference (EMI) noise in the inverter becomes a large problem. As a method of reducing the switching loss and the EMI noise, a resonance inverter is used (for example, refer to Patent Documents 1, 2, 3).

[0004] PRIOR ART DOCUMENTS

[0005] PATENT DOCUMENTS

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

[0007] Patent Document 2: Japanese Patent No. 5569204 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] The resonance inverter of Patent Document 2 ensures a path of the energy accumulated in the resonance inductor at the time of all switch turn-off by a snubber circuit, but the efficiency is reduced due to snubber loss.

[0010] The resonance inverter of Patent Document 3 regenerates the energy accumulated in the resonance inductor to the direct current link without loss by an auxiliary resonance circuit at the time of all switch turn-off. The auxiliary resonance circuit becomes a path of the energy accumulated in the resonance inductor, and snubber loss is not generated. However, the auxiliary circuit needs the same high voltage resistant elements as the main circuit. The high voltage resistant elements are few in kind, and slow in switching speed, and there is a concern that the efficiency is deteriorated.

[0011] One embodiment of the present application provides a resonance inverter that can be configured by elements lower in voltage resistance than the main circuit to become a lossless auxiliary resonance circuit of a path of the energy accumulated in the resonance inductor.

[0012] MEANS FOR SOLVING THE 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 consists of an upper arm switch and a lower arm switch connected in series between the positive and negative DC lines. The connection point of the upper arm switch and the lower arm switch, which are alternately controlled with a dead time interval, serves as the input / output point of the inverter current. The resonant inverter includes a first resonant capacitor and a second resonant capacitor, which are connected in parallel with the upper arm switch and the lower arm switch. 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 arm switch and the lower arm switch. The resonant inverter includes an auxiliary resonant circuit comprising a resonant inductor connected at one end to the input / output point of the main bridge arm. The auxiliary resonant circuit has a positive resonant path in which the current polarity is defined from the neutral point towards the resonant inductor, and is switched on and off by a positive resonant switch. The auxiliary resonant circuit also has a negative resonant path in which the current polarity is defined from the resonant inductor towards the neutral point, and is switched on and off by a negative resonant switch. Furthermore, the auxiliary resonant circuit has a positive regenerative path in which the current polarity is defined from the resonant inductor towards the positive DC line. Finally, the auxiliary resonant circuit has a negative regenerative path in which the current polarity is defined from the negative DC line towards the resonant inductor.

[0014] Invention Effects

[0015] According to one aspect of the invention, the lossless auxiliary resonant circuit, which serves as the path for energy stored in the resonant inductor, is clamped to the voltage at the neutral point via the positive and negative resonant paths. Therefore, the components constituting the auxiliary resonant circuit can be made of components with lower voltage ratings than the main circuit. Attached Figure Description

[0016] Figure 1 This is a diagram showing the circuit structure of one phase of an implementation of a resonant inverter.

[0017] Figure 2 It means Figure 1 The timing chart shown is for the operation of a resonant inverter.

[0018] Figure 3 It means Figure 2The diagram shows the actions of each mode.

[0019] Figure 4 This is a timing diagram representing the positive direction of the clamp snubber action.

[0020] Figure 5 It means Figure 4 The diagram shows the action of mode 3A.

[0021] Figure 6 It means Figure 1 The timing diagram shown is for the operation of a resonant inverter.

[0022] Figure 7 It means Figure 6 The diagram shows the actions of each mode.

[0023] Figure 8 This is a timing diagram representing the clamping and buffering action in the negative direction.

[0024] Figure 9 It means Figure 8 The diagram shows the action of mode 13A.

[0025] Figure 10 It means Figure 1 The diagram shows a first application example of a resonant inverter.

[0026] Figure 11 It means Figure 1 The diagram shows a second application example of the resonant inverter.

[0027] Figure 12 It means Figure 11 The diagram shows the operation of a resonant inverter.

[0028] Figure 13 It means Figure 1 The diagram shows a third application example of the resonant inverter.

[0029] Figure 14 It means Figure 13 The diagram shows the operation of a resonant inverter.

[0030] Figure 15 It means Figure 1 The diagram shows the fourth application example of the resonant inverter. Detailed Implementation

[0031] 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.

[0032] Reference Figure 1The resonant inverter 1 in this embodiment is a two-level inverter with an auxiliary resonant circuit 2 having an ARCP (auxiliary resonant commutated pole) topology of the NPC (neutral point clamped) type.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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 Tr3 (acting as the positive resonant switch) and the diode Drp. The switching element Tr3 is, for example, an insulated-gate bipolar transistor (IGBT). The switching element Tr3 can also be a MOSFET.

[0039] 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 Tr3. The collector of the switching 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.

[0040] 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 Tr3 switches the positive resonant path rp on and off.

[0041] The switching element Tr3 includes an anti-parallel diode D3, wherein the cathode and anode are connected to the collector and emitter of the switching element Tr3, respectively. The anti-parallel diode D3 is, for example, formed by the body diode of the switching element Tr3.

[0042] The auxiliary resonant circuit 2 has a connection point connecting the collector of the switching element Tr3 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 Tr3 and the cathode of the diode Drp, and the cathode is connected to the positive DC line P.

[0043] The anti-parallel diode D3 of the switching element Tr3 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).

[0044] 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 Tr4 (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 Tr4 is, for example, an insulated-gate bipolar transistor (IGBT). The switching element Tr4 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 collector of the switching element Tr4. The emitter of the switching 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.

[0046] Diode Drn restricts the current polarity of the negative resonant path rn to one direction (from input / output point B to neutral point A). Switching element Tr4 switches the negative resonant path rn on and off.

[0047] The switching element Tr4 includes an anti-parallel diode D4, wherein the cathode and anode are connected to the collector and emitter of the switching element Tr4, respectively. The anti-parallel diode D4 is, for example, formed by the body diode of the switching element Tr4.

[0048] The auxiliary resonant circuit 2 includes a lossless regenerative clamping buffer diode Dsn, which connects the emitter of the switching element Tr4 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 Tr4 and the anode of the diode Drn, and the anode is connected to the negative DC line N.

[0049] The anti-parallel diode D4 of the switching element Tr4 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).

[0050] The resonant inverter 1 has a control circuit 5 that controls the on / off state of each of the switching elements Tm1, Tm2, ​​Tr3, and Tr4. The control circuit 5 performs PWM control on the switching elements Tm1 and Tm2 of the main bridge arm 4 to enable zero-voltage turn-on.

[0051] Reference Figure 2 and Figure 3 Explain the 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.

[0052] When the output voltage Vo and inverter current Iinv are positive, the object of the zero-voltage (ZV) turn-on control based on resonance is the on timing of the switching element Tm1. When the inverter current Iinv is positive, in order to enable the positive side to resonate, the control circuit 5 controls the switching element Tr3 of the positive side resonant path rp before and after the switching element Tm1 is turned on.

[0053] In mode 0, at time t0, switching element Tm2 is turned off, and all switching elements Tm1, Tm2, ​​Tr3, and Tr4 are in the off state. In mode 0, as follows... Figure 3 As shown in (a), the inverter current Iinv is in the freewheeling state of the anti-parallel diode D2 of the switching element Tm2 in the lower arm.

[0054] In mode 0, the collector-emitter voltage Vce of switching element Tm1 is Vdc. Regarding the terminal voltages (Vce, reverse voltage VR) of each component in auxiliary resonant circuit 2, Tr3, Drn, and Dsp are Vdc / 2, while the voltages of other components are 0V.

[0055] In Mode 1, at time t1 during the dead time DT, the switching element Tr3 of the positive resonant path rp is controlled to turn on with zero current (ZC), as follows: Figure 3 As shown in (b), the inverter current Iinv is commutated to the resonant inductor Lr (positive resonant path rp). Mode 1 continues until the anti-parallel diode D2 of the switching element Tm2 is turned off.

[0056] In mode 1, regarding the terminal voltages of each component in the auxiliary resonant circuit 2, Dsp is Vdc / 2, Tr4, Drn, and Dsn are Vdc / 4, and the voltages of other components are 0V.

[0057] Mode 2 completes the commutation to the resonant inductor Lr at time t2, through... Figure 3 (c) 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 2, the Vce of switching element Tm1 changes from Vdc to 0V, and the Vce of switching element Tm2 changes from 0V to Vdc.

[0058] In mode 2, the voltage between the terminals of each component of the auxiliary resonant circuit 2 is the same as in mode 1.

[0059] The period of mode 1+2 is the time obtained by adding the first commutation time Tcom1[Lr÷Vdcn×Iinv] and 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)).

[0060] In other words, the switching element Tr3 of the positive resonant path rp is turned on before the turn-on timing of the switching element Tm1 (first commutation time Tcom1 + resonant time Tres).

[0061] Mode 3 timing at the moment t3 when Vce of switching element Tm1 becomes 0V, such as Figure 3 As shown in (d), zero-voltage turn-on control is applied to the switching element Tm1 to commutate the current ILr of the resonant inductor to the switching element Tm1.

[0062] In mode 3, the voltage between the terminals of each component in the auxiliary resonant circuit 2 is the same as in mode 1.

[0063] The period of Mode 3 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.

[0064] In other words, the switching element Tr3 of the positive resonant path rp is turned off after (the second commutation time Tcom2) compared to the turn-on timing of the switching element Tm1.

[0065] In mode 4, as the commutation of the resonant inductor current ILr to the switching element Tm1 is completed, the switching element Tr3 is turned off at time t4, as follows: Figure 3 As shown in (e), power is output from the DC bus (positive DC line P) to the load (AC system).

[0066] In mode 4, the terminal voltages of each component in the auxiliary resonant circuit 2 are Vdc / 2 for Drp, Tr4, and Dsn, and 0V for the other components.

[0067] Mode 5 controls the switching element Tm1 of the upper arm to turn off at time t5, such as... Figure 3As shown in (f), the inverter current Iinv is commutated by the anti-parallel diode D2 of the switching element Tm2 in the lower arm. The Vce of switching elements Tm1 and Tm2 changes due to the charging of resonant capacitor C1 and the discharging of resonant capacitor C2. In mode 5, the Vce of switching element Tm1 changes from 0V to Vdc, and the Vce of switching element Tm2 changes from Vdc to 0V.

[0068] In mode 5, the terminal voltages of each component in 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.

[0069] Mode 6 is the period until the commutation to the anti-parallel diode D2 of switching element Tm2 is completed at time t6, up to the dead time DT after the turn-off control of switching element Tm1. At time t7, after the dead time DT after the turn-off control of switching element Tm1, as... Figure 3 As shown in (g), the switching element Tm2 is controlled to turn on at zero voltage.

[0070] In mode 6, the terminal voltages of each component in the auxiliary resonant circuit 2 are Vdc / 2 for Tr3, Dsp, and Drn, and 0V for the other components.

[0071] When the output voltage Vo and inverter current Iinv are positive, the resonant inverter 1 operates by repeatedly switching between modes 0 to 6, and the switching elements Tm1 and Tm2 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 will not exceed Vdc / 2 in any mode.

[0072] The operation of the resonant inverter 1 when the switching element Tr3 is turned off midway through Mode 3 described above is taken as Mode 3A. Figure 4 as well as 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 3A.

[0073] Mode 3A occurs at moment t3A, midway through the commutation of the resonant inductor current ILr to the switching element Tm1, where the switching element Tr3 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 D4 of the switching element Tr4 are regenerated losslessly to the DC bus. 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 Tr3 (diode Drn, lossless regenerative clamping buffer diode Disp), are clamped at Vdc / 2.

[0074] Figure 6 and Figure 7 This shows the operation of the resonant inverter 1 when the output voltage Vo and the inverter current Iinv are negative. Figure 6 This is a timing diagram representing the operation of resonant inverter 1. Figure 7 Represented using the equivalent circuit of resonant inverter 1 Figure 6 The actions in each of the shown modes.

[0075] When the output voltage Vo and inverter current Iinv are negative, the target of the ZV (zero voltage) turn-on control based on resonance is the turn-on timing of the switching element Tm2. When the inverter current Iinv is negative, in order to enable the negative side to resonate, the control circuit 5 controls the switching element Tr4 of the negative side resonant path rn before and after the switching element Tm2 is turned on.

[0076] In mode 10, at time t10, switching element Tm1 is turned off, and all switching elements Tm1, Tm2, ​​Tr3, and Tr4 are in the off state. In mode 10, as... Figure 7 As shown in (a), the inverter current Iinv is in the freewheeling state of the anti-parallel diode D1 of the switching element Tm1 in the upper arm.

[0077] In mode 10, the collector-emitter voltage Vce of the switching element Tm2 is Vdc. Regarding the terminal voltages of each component in the auxiliary resonant circuit 2, Tr4, Drp, and Dsn are Vdc / 2, while the voltages of other components are 0V.

[0078] In mode 11, at time t11 during the dead time DT, the switching element Tr4 of the negative resonant path rn is controlled to turn on with zero current, while switching elements Tm1, Tm2, ​​and Tr3 are in the off state. For example... Figure 7 As shown in (b), mode 11 commutates the inverter current Iinv to the resonant inductor Lr (negative-side resonant path rn). Mode 11 continues until the anti-parallel diode D1 of the switching element Tm1 is turned off.

[0079] In mode 11, regarding the terminal voltages of each component in the auxiliary resonant circuit 2, Dsn is Vdc / 2, Tr3, Drp, and Dsp are Vdc / 4, and the voltages of other components are 0V.

[0080] Mode 12 completes commutation to the resonant inductor Lr at time t12, through... Figure 7 (c) 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 12, the Vce of switching element Tm1 changes from 0V to Vdc, and the Vce of switching element Tm2 changes from Vdc to 0V.

[0081] In mode 12, the voltage between the terminals of each component of the auxiliary resonant circuit 2 is the same as in mode 11.

[0082] The period of mode 11+12 is the time obtained by adding the first commutation time Tcom1[Lr÷Vdcp×Iinv] and 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)).

[0083] In other words, the switching element Tr4 of the negative resonant path rn is turned on before the turn-on timing of the switching element Tm2 (first commutation time Tcom1 + resonant time Tres).

[0084] Mode 13 is the timing of t13 when Vce of switching element Tm2 becomes 0V, as follows: Figure 7 As shown in (d), zero-voltage turn-on control is applied to the switching element Tm2 to commutate the current ILr of the resonant inductor to the switching element Tm2.

[0085] In mode 13, the voltage between the terminals of each component of the auxiliary resonant circuit 2 is the same as in mode 11.

[0086] The period of mode 13 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.

[0087] In other words, the switching element Tr4 of the negative resonant path rn is turned off after (the second commutation time Tcom2) compared to the turn-on timing of the switching element Tm1.

[0088] In mode 14, as the commutation of the resonant inductor current ILr to the switching element Tm2 is completed, the switching element Tr4 is turned off at time t14. For example... Figure 7 As shown in (e), mode 14 outputs power from the DC bus (positive DC line P, negative DC line N) to the load (AC system).

[0089] In mode 14, the terminal voltages of each component in the auxiliary resonant circuit 2 are Vdc / 2 for Drn, Tr3, and Dsp, and 0V for the other components.

[0090] Mode 15 controls the switching element Tm2 of the lower arm to turn off at time t15, such as... Figure 7 As shown in (f), the inverter current Iinv is commutated by the anti-parallel diode D1 of the switching element Tm1 in the upper arm. The Vce of switching elements Tm2 and Tm1 changes due to the charging of resonant capacitor C2 and the discharging of resonant capacitor C1. In mode 15, the Vce of switching element Tm2 changes from 0V to Vdc, and the Vce of switching element Tm1 changes from Vdc to 0V.

[0091] In mode 15, the terminal voltages of each component in 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.

[0092] Mode 16 is the period until the commutation to the anti-parallel diode D1 of switching element Tm1 is completed at time t16, up to the dead time DT after the turn-off control of switching element Tm2. At time t17, after the dead time DT following the turn-off control of switching element Tm2, ​​as... Figure 8 As shown in (g), the switching element Tm1 is controlled to turn on at zero voltage.

[0093] In mode 16, the terminal voltages of each component in the auxiliary resonant circuit 2 are Vdc / 2 for Tr4, Dsn, and Drp, and 0V for the other components.

[0094] When the output voltage Vo and inverter current Iinv are negative, the resonant inverter 1 operates by repeatedly switching between modes 10 to 16, and the switching elements Tm1 and Tm2 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 will not exceed Vdc / 2 in any mode.

[0095] The operation of the resonant inverter 1 when the switching element Tr4 is turned off midway through mode 13 is defined as mode 13A. Figure 9 and Figure 8As shown in the image. Figure 9 This is a timing diagram representing the operation of resonant inverter 1. Figure 8 The equivalent circuit of resonant inverter 1 is used to represent it. Figure 8 The actions shown are under mode 13A.

[0096] Mode 13A occurs at moment t13A, during the commutation of the resonant inductor current ILr to the switching element Tm2, ​​where the switching element Tr4 is turned off due to component deviation, calculation error, or malfunction. For example... Figure 10 As 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 D3 of the switching element Tr3 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 Tr4 (diode Drp, lossless regenerative clamping buffer diode Dsn), are clamped at Vdc / 2.

[0097] Figure 11 This represents a half-bridge inverter circuit 11 that utilizes a resonant inverter 1. The half-bridge inverter circuit 11 supplies AC voltage to the load 6 connected between the neutral point A and the input / output point B.

[0098] Figure 12 This represents a full-bridge inverter circuit 12 employing a resonant inverter 1. The full-bridge inverter circuit 12 includes a commercial cycle bridge arm 7 connected in parallel with the main bridge arm 4. In the commercial cycle bridge arm 7, switching elements Ts5 and Ts6 are connected in series between the positive DC line P and the negative DC line N. A load 6 is connected between the input / output point C of switching elements Ts5 and Ts6 and the input / output point B of the main bridge arm 4. Switching elements Ts5 and Ts6 are composed of IGBTs and MOSFETs.

[0099] The control circuit 5a switches the switching elements Ts5 and Ts6 on and off according to half a cycle of each commercial cycle. Figure 12 This indicates the operating mode of the full-bridge inverter circuit 12 during the positive half-cycle. Switching element Ts6 is always on, and switching element Ts5 is always off.

[0100] Figure 12 (a) The mode 20 shown is a state in which the switching element Tm2 is turned off and the inverter current Iinv freewheels in the anti-parallel diode D2 and the switching element Ts6 of the lower arm switching element Tm2.

[0101] Mode 21 performs zero-current turn-on control on the switching element Tr3 of the positive resonant path rp during the dead time DT, enabling... Figure 12(b) shows the inverter current Iinv commutating to the resonant inductor Lr (positive resonant path rp).

[0102] In mode 22, commutation to the resonant inductor Lr is completed, through... Figure 12 (c) 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 22, the Vce of switching element Tm1 changes from Vdc to 0V, and the Vce of switching element Tm2 changes from 0V to Vdc.

[0103] Mode 23 occurs when Vce of switching element Tm1 becomes 0V, such as... Figure 12 As shown in (d), zero-voltage turn-on control is applied to the switching element Tm1 to commutate the current ILr of the resonant inductor to the switching element Tm1.

[0104] In mode 24, as the commutation of the resonant inductor current ILr to the switching element Tm1 is completed, the switching element Tr3 is turned off, as follows: Figure 13 As shown in (e), power is output from the DC bus (positive DC line P, negative DC line N) to the load (AC system).

[0105] Figure 12 It is a full-bridge inverter circuit 13 that uses a resonant inverter 1. The full-bridge inverter circuit 13 sets the resonant inverter 1 as a full-bridge structure, and has a U-phase main bridge arm 4u, a W-phase main bridge arm 4w, an auxiliary resonant circuit 2u for the main bridge arm 4u, and an auxiliary resonant circuit 2w for the main bridge arm 4w.

[0106] Independently, at different timings, control circuit 5u controls auxiliary resonant circuit 2u, and control circuit 5w controls auxiliary resonant circuit 2w. The control of auxiliary resonant circuits 2u and 2w varies depending on the switching state of the opposite phase.

[0107] This describes the zero-voltage turn-on control operation of the upper arm (switching element Tm1) in the main bridge arm 4u of phase U. When the lower arm (switching element Tm2) in the main bridge arm 4w of phase W is turned on, it becomes... Figure 14 The full-bridge inverter circuit 12 shown operates in the same way.

[0108] Figure 14 This indicates the action when the upper arm (switching element Tm1) of the main bridge arm 4w of phase W is turned on during zero-voltage turn-on control of the upper arm (switching element Tm1) of the main bridge arm 4u of phase U.

[0109] Figure 14(a) The mode 30 shown is a state in which the switching element Tm2 of the main bridge arm 4u is turned off, and the inverter current Iinv freewheels in the anti-parallel diode D2 of the switching element Tm2 of the lower arm and the anti-parallel diode D1 of the switching element Tm1 of the main bridge arm 4w.

[0110] Mode 31 performs zero-current turn-on control on the switching element Tr3 of the auxiliary resonant circuit 2u during the dead time DT, making Figure 14 (b) shows the inverter current Iinv commutating to the resonant inductor Lr (the positive resonant path rp of the auxiliary resonant circuit 2u).

[0111] In mode 32, commutation to the resonant inductor Lr (the positive resonant path rp of the auxiliary resonant circuit 2u) is completed, through... Figure 14 (c) shows the resonance of resonant capacitors C1 and C2 (shown by dashed lines). The Vce of switching elements Tm1 and Tm2 in main bridge arm 4u changes in a sinusoidal waveform. In mode 22, the Vce of switching element Tm1 in main bridge arm 4u changes from Vdc to 0V, and the Vce of switching element Tm2 in main bridge arm 4u changes from 0V to Vdc.

[0112] In mode 33, when the Vce of the switching element Tm1 of the main bridge arm 4u becomes 0V, such as... Figure 14 As shown in (d), zero-voltage turn-on control is applied to the switching element Tm1 to commutate the current ILr of the resonant inductor to the switching element Tm1 of the main bridge arm 4u.

[0113] In mode 34, as the commutation of the resonant inductor current ILr to the switching element Tm1 of the main bridge arm 4u is completed, the switching element Tr3 of the auxiliary resonant circuit 2u is turned off. In mode 34, as... Figure 15 As shown in (e), the inverter current freewheels between the input and output points of phase U and phase W.

[0114] ​ This indicates a bidirectional chopper circuit 14 that utilizes a resonant inverter 1. The bidirectional chopper circuit 14 includes a filter circuit 8. The filter circuit 8 consists of an inductor L1 and a capacitor Cn, and the series circuit consisting of the inductor L1 and the capacitor Cn is connected between the input / output point B and the negative DC line N.

[0115] (1) In one embodiment of this invention, the resonant inverter 1 includes a neutral point clamping circuit 3. The neutral point clamping circuit 3 consists 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 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). The connection point of the switching elements Tm1 and Tm2, ​​whose dead time DT is alternately controlled, is called the 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 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 an auxiliary resonant circuit 2 comprising a resonant inductor Lr, one end of which is connected to the input / output point B of the main bridge arm 4. The auxiliary resonant circuit 2 has a positive resonant path rp whose current polarity is defined as flowing from the neutral point A towards the resonant inductor Lr and is switched on and off via a switching element Tr3 (positive resonant switch). The auxiliary resonant circuit 2 also has a negative resonant path rn whose current polarity is defined as flowing from the resonant inductor Lr towards the neutral point A and is switched on and off via a switching element Tr4 (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) whose current polarity is defined as flowing from the resonant inductor Lr towards the positive DC line P. The auxiliary resonant circuit 2 has a negative regeneration path whose current polarity is limited to the direction from the negative DC line N to the resonant inductor Lr (the anti-parallel diode D4 of the switching element Tr4 + the lossless regeneration clamping buffer diode Dsn).

[0116] According to the resonant inverter 1 described above (1), the lossless auxiliary resonant circuit 2, which serves as the path for the energy stored in the resonant inductor Lr, is clamped at the voltage of the neutral point A through the positive resonant path rp and the negative resonant path rn. Therefore, the components constituting the auxiliary resonant circuit 2 can be composed of components with lower withstand voltages than the components of the main bridge arm 4, which serves as the main circuit. The range of component selection for the auxiliary resonant circuit 2 is widened, and it can be constructed inexpensively. The lossless regenerative clamping buffer diodes Dsp and Dsn serve as the regeneration path for the energy of the resonant inductor Lr, enabling highly efficient overvoltage protection countermeasures.

[0117] (2) In the resonant inverter 1 described in (1) above, the control circuit 5 can also control the switching element Tr3 to turn on during the dead time DT before the turn-on control of the switching element Tm1, and control the switching element Tr3 to turn off after the turn-on control of the switching element Tm1. The control circuit 5 can also control the switching element Tr4 to turn on during the dead time DT before the turn-on control of the switching element Tm2, ​​and control the switching element Tr4 to turn off after the turn-on control of the switching element Tm2.

[0118] According to the resonant inverter 1 described in (2) above, the inverter current Iinv can be commutated to the auxiliary resonant circuit 2, causing a resonant action.

[0119] (3) In the resonant inverter 1 described in (2) above, the control circuit 5 can also control the switching element Tr3 to turn on at a time before the timing of the turn-on control of the switching element 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 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 Tr3. The resonant time Tres is based on half a cycle of the resonance of the resonant inductor Lr, the resonant capacitor C1, and the resonant capacitor C2. The control circuit 5 can also control the switching element Tr4 to turn on at a time before the timing of the turn-on control of the switching element Tm2, ​​which is the time obtained by adding the first commutation time Tcom1 (first commutation time on the load side) and the resonant time Tres.

[0120] According to the resonant inverter 1 described in (3) above, zero-voltage turn-on control of switching elements Tm1 and Tm2 can be realized.

[0121] (4) In the resonant inverter 1 described in (2) above, the control circuit 5 may also turn off the switching element Tr3 at a time after the second commutation time Tcom2 (positive side second commutation time) of the timing of the turn-on control of the switching 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 switching element Tm1 is completed through the turn-on control of the switching element Tm1. The control circuit 5 may also turn off the switching element Tr4 at a time after the second commutation time Tcom2 (negative side second commutation time) of the timing of the turn-on control of the switching 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 switching element Tm2 is completed through the turn-on control of the switching element Tm2.

[0122] 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 switching elements Tm1 and Tm2.

[0123] The present invention has been described above through specific embodiments, but the above embodiments are examples, and of course, modifications can be made to implement the invention without departing from the spirit of the invention.

[0124] Explanation of reference numerals in the attached figures

[0125] 1 Resonant inverter; 2, 2u, 2w Auxiliary resonant circuits; 3 Neutral point clamping circuit; 4, 4u, 4w Main bridge arms; 5, 5a, 5u, 5w Control circuits; 6 Load; 7 Commercial cycle bridge arm; 8 Filter circuit; 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 capacitors; D1, D2, D3, D4 Anti-parallel diodes; Drn, Drp diodes; Dsn Lossless regenerative clamping buffer diode; Dsp Lossless regenerative clamping buffer diode; Lr Resonant inductor; N Negative DC line; P Positive DC line; Tm1, Tm2, ​​Tr3, Tr4, Ts5, Ts6 Switching elements; rn Negative resonant path; rp Positive resonant path.

Claims

1. A resonant inverter comprising: a neutral point clamped circuit composed of a positive side capacitor and a negative side capacitor connected in series between a positive side DC line and a negative side DC line, a connection point of the positive side capacitor and the negative side capacitor becoming a neutral point; a main bridge arm composed of an upper arm switch and a lower arm switch connected in series between the positive side DC line and the negative side DC line, a connection point of the upper arm switch and the lower arm switch being alternately controlled with an interval of a dead time becoming an input / output point of an inverter current; a first resonant capacitor and a second resonant capacitor connected in parallel with the upper arm switch and the lower arm switch; a first anti-parallel diode and a second anti-parallel diode connected in anti-parallel with the upper arm switch and the lower arm switch; and an auxiliary resonant circuit including a resonant inductor connected at one end to the input / output point of the main bridge arm, the auxiliary resonant circuit comprising: a positive side resonant path in which a current polarity is defined as a direction from the neutral point to the resonant inductor, and in which opening and closing are performed by a positive side resonant switch; a negative side resonant path in which a current polarity is defined as a direction from the resonant inductor to the neutral point, and in which opening and closing are performed by a negative side resonant switch; a positive side regeneration path in which a current polarity is defined as a direction from the resonant inductor to the positive side DC line; and a negative side regeneration path in which a current polarity is defined as a direction from the negative side DC line to the resonant inductor.

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

3. The resonant inverter according to claim 2, wherein the positive side resonant switch is turned on at a timing before a positive side first commutation time until commutation of the inverter current to the resonant inductor is completed by turning on of the positive side resonant switch, and a time obtained by adding a resonant time based on 1 / 2 period of resonance of the resonant inductor and the first resonant capacitor and the second resonant capacitor to the timing of turning on of the upper arm switch, the negative side resonant switch is turned on at a timing before a negative side first commutation time until commutation of the inverter current to the resonant inductor is completed by turning on of the negative side resonant switch, and a time obtained by adding the resonant time to the timing of turning on of the lower arm switch.

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

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