CN209767391U

CN209767391U - high-gain bidirectional DC/DC converter suitable for energy storage system

Info

Publication number: CN209767391U
Application number: CN201920695507.1U
Authority: CN
Inventors: 曾君; 严志星; 刘俊峰; 林尉杰
Original assignee: South China University of Technology SCUT
Current assignee: Guangdong Suixin Energy Technology Co ltd
Priority date: 2019-05-15
Filing date: 2019-05-15
Publication date: 2019-12-10
Anticipated expiration: 2029-05-15

Abstract

The utility model discloses a high-gain bidirectional DC/DC converter suitable for an energy storage system, which comprises a first DC power supply, a second DC power supply, a first inductor, a second inductor, a first switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a seventh switch tube, an eighth switch tube, a first capacitor, a second capacitor, a third capacitor and a transformer; the first direct current power supply is connected with the first inductor and the second inductor; the first inductor is connected with the first switching tube, the second switching tube and the transformer; the second inductor is connected with the third switching tube, the fourth switching tube and the transformer; the first switching tube is connected with the third switching tube and the first capacitor; the second switching tube is connected with the fourth switching tube and the first capacitor; the transformer is connected with the fifth, sixth and seventh switching tubes; the transformer is connected with the eighth switching tube, the second capacitor and the third capacitor; the seventh switching tube is connected with the eighth switching tube; the fifth switching tube is connected with the second capacitor and the second direct-current power supply; and the sixth switching tube is connected with the third capacitor and the second direct-current power supply. The utility model has the advantages of high voltage gain, low current ripple, wide voltage range.

Description

High-gain bidirectional DC/DC converter suitable for energy storage system

Technical Field

The utility model relates to a technical field of two-way transform of direct current high-gain especially relates to a two-way DC converter of high-gain suitable for energy storage system, belongs to the high frequency switching power supply direction in power electronics field.

Background

renewable new energy in China has entered the rapid development period, and direct-current micro-grids formed by new energy power generation systems based on energy storage systems, photovoltaic power generation, wind power generation and the like are concerned by more and more scholars. Renewable energy power generation such as photovoltaic power generation, wind power generation and the like has randomness of power generation time and power generation amount, and the randomness can impact the access of a large power grid, so that an energy storage system is required to be arranged in a direct-current micro-grid to realize peak clipping and valley filling of renewable energy. Because the DC bus voltage in the DC microgrid is usually 400V or more, the voltage rating of the energy storage elements is generally low, and the reliability is reduced due to the series connection of the energy storage units, a DC/DC converter with high voltage gain is required. The traditional isolated bidirectional full-bridge DC/DC converter realizes high gain by adjusting the turn ratio of the transformer, and has the defects of narrow voltage variable range, large current ripple at the energy storage side and complex control. The isolated current type bidirectional DC/DC converter has been proposed by some researchers, which widens the voltage range and reduces the current ripple by interleaving, but it still has the problem of complicated control due to the coupling of a plurality of control variables in the control. Therefore, the research on the high-gain bidirectional DC/DC converter suitable for the energy storage system has great significance on the energy storage system in the DC micro-grid.

SUMMERY OF THE UTILITY MODEL

The utility model aims to solve the problem that the wide voltage range soft switch can not be realized to the current two-way DC converter of isolated that is applicable to energy storage system, the current ripple is big, a plurality of control variable coupling leads to control complicacy, provide a two-way DC converter of high-gain suitable for energy storage system.

In order to achieve the above object, the present invention provides a technical solution: a high-gain bidirectional DC/DC converter suitable for an energy storage system comprises a first direct-current power supply, a first inductor, a second inductor, a first switch tube, an anti-parallel diode and a parasitic capacitor of the first switch tube, a second switch tube, an anti-parallel diode and a parasitic capacitor of the second switch tube, a third switch tube, an anti-parallel diode and a parasitic capacitor of the third switch tube, a fourth switch tube, an anti-parallel diode and a parasitic capacitor of the fourth switch tube, a first capacitor, a leakage inductance of an equivalent dotted terminal of a transformer and a primary side of the transformer which are connected in series, and an excitation inductance of a secondary side of the transformer which are connected in parallel, a fifth switch tube, an anti-parallel diode and a parasitic capacitor of the fifth switch tube, a sixth switch tube, an anti-parallel diode and a parasitic capacitor of the sixth switch tube, a seventh switch tube, an anti-parallel diode and a parasitic capacitor of the seventh switch tube, an anti-; the positive electrode of the first direct-current power supply is respectively connected with one end of a first inductor and one end of a second inductor, the other end of the first inductor is respectively connected with a source electrode of a first switching tube, a drain electrode of a second switching tube and an equivalent homonymy end leakage inductor connected in series with a primary side of a transformer, the other end of the second inductor is respectively connected with a source electrode of a third switching tube, a drain electrode of a fourth switching tube and a heteronymy end of a primary side of the transformer, a drain electrode of the first switching tube is respectively connected with a drain electrode of the third switching tube and a positive electrode of a first capacitor, a source electrode of the second switching tube is respectively connected with a source electrode of the fourth switching tube and a negative electrode of the first capacitor, a homonymy end of a secondary side of the transformer is respectively connected with a source electrode of a fifth switching tube, a drain electrode of a sixth switching tube and a drain electrode of a seventh switching tube, and a heteronymy end of a secondary side of the transformer is respectively connected with a drain, The negative electrode of the second capacitor is connected with the positive electrode of the third capacitor, the source electrode of the seventh switching tube is connected with the source electrode of the eighth switching tube, the drain electrode of the fifth switching tube is respectively connected with the positive electrode of the second capacitor and the positive electrode of the second direct-current power supply, and the source electrode of the sixth switching tube is respectively connected with the negative electrode of the third capacitor and the negative electrode of the second direct-current power supply.

Further, the first switch tube and the second switch tube, the third switch tube and the fourth switch tube, the fifth switch tube and the seventh switch tube, and the sixth switch tube and the eighth switch tube are respectively complementarily conducted, and the first switch tube and the fourth switch tube, the fifth switch tube and the sixth switch tube are mutually conductedThe phase difference is 180 degrees, and the phase difference of the first switching tube and the fifth switching tube is a phase shift angleAnd between-90 degrees and 90 degrees, the duty ratios D of the second switching tube, the fourth switching tube, the seventh switching tube and the eighth switching tube are the same and are more than 0.5.

Further, the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, the sixth switch tube, the seventh switch tube and the eighth switch tube are power switch tubes with reverse conducting characteristics.

Further, the turn ratio of the primary side and the secondary side of the transformer is n:1, wherein n is the quotient of the number of primary turns of the transformer divided by the number of secondary turns.

Compared with the prior art, the utility model, have following advantage and beneficial effect:

1. Voltage steady state gain ofThe transformer turns ratio can be adjusted reasonably to make the converter have the required high voltage gain.

2. The first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, the sixth switch tube, the seventh switch tube and the eighth switch tube can all realize zero voltage switching-on, and switching loss and electromagnetic interference can be reduced.

3. The voltage stress of the seventh switching tube and the eighth switching tube is only half of that of the second direct current power supply, so that the cost of the circuit is reduced, and the high-voltage direct current power supply is suitable for high-voltage occasions.

4. The current of the first inductor is staggered with that of the second inductor, so that the current source ripple of the first direct current power supply can be reduced, and the service life of an energy storage battery serving as the first direct current power supply is prolonged.

Drawings

Fig. 1 is a circuit diagram of a high-gain bidirectional DC/DC converter suitable for an energy storage system according to the present invention.

Fig. 2 is a voltage-current waveform diagram of main components in a circuit in one switching period.

fig. 3a is a schematic diagram of a circuit in one switching cycle.

Fig. 3b is a second circuit mode diagram of the circuit in one switching cycle.

Fig. 3c is a third schematic diagram of the circuit in one switching cycle.

FIG. 3d is a diagram of the circuit mode within one switching cycle.

Fig. 3e is a diagram of the circuit mode of the circuit in one switching cycle.

Fig. 3f is a diagram of the circuit mode in one switching cycle.

Fig. 3g is a seventh schematic diagram of the circuit in one switching cycle.

Fig. 3h is an eighth schematic diagram of the circuit during one switching cycle.

FIG. 3i is a diagram of a circuit mode of the circuit in one switching cycle.

Fig. 3j is a diagram showing the circuit mode of the circuit in one switching cycle.

Detailed Description

The present invention is further described with reference to specific embodiments below with reference to a high-gain bidirectional DC/DC converter for an energy storage system.

Referring to fig. 1, the high-gain bidirectional DC/DC converter for an energy storage system according to the present embodiment includes a first DC power source V₁First inductance L₁Second inductance L₂A first switch tube Q_1aAnd its anti-parallel diode D_1aAnd parasitic capacitance C_1aA second switch tube Q₁And its anti-parallel diode D₁And parasitic capacitance C₁A third switching tube Q_2aAnd its anti-parallel diode D_2aAnd parasitic capacitance C_2aFourth switch tube Q₂And its anti-parallel diode D₂And parasitic capacitance C₂First capacitor C_CEquivalent homonymous end leakage inductance L of transformer T and primary side series connection thereof_rExcitation L parallel to secondary side_mFifth switching tube S₁And anti-parallel connection thereofDiode D_s1And parasitic capacitance C_s1The sixth switching tube S₂And its anti-parallel diode D_s2And parasitic capacitance C_s2Seventh switching tube S₃And its anti-parallel diode D_s3And parasitic capacitance C_s3The eighth switching tube S₄And its anti-parallel diode D_s4And parasitic capacitance C_s4A second capacitor C_uThird capacitor C_dA second DC power supply V₂(ii) a Wherein the first DC power supply V₁Respectively with the first inductor L₁One terminal of (1), a second inductance L₂Is connected to the first inductor L₁The other end of the first switch tube Q is respectively connected with the first switch tube Q_1aSource electrode of, the second switching tube Q₁equivalent homonymous terminal leakage inductance L of the series connection of the drain electrode and the primary side of the transformer T_rConnected to a second inductance L₂The other end of the first and second switching tubes Q are respectively connected with a third switching tube Q_2aSource electrode and fourth switching tube Q₂The drain electrode of the first switching tube Q is connected with the synonym end of the primary side of the transformer T_1aRespectively with the third switch tube Q_2aDrain electrode of, first capacitor C_CIs connected to the positive pole of a second switching tube Q₁With the fourth switching tube Q respectively₂Source electrode, first capacitor C_CIs connected with the negative pole of the transformer T, and the homonymous ends of the secondary side of the transformer T are respectively connected with the fifth switch tube S₁Source electrode of (1), sixth switching tube S₂Drain electrode of (1), seventh switching tube S₃Is connected with the drain electrode of the transformer T, and the different name ends of the secondary side of the transformer T are respectively connected with the eighth switching tube S₄Drain electrode of the first capacitor C_uNegative electrode of (1), third capacitor C_dIs connected to the positive pole of a seventh switching tube S₃Source electrode of and the eighth switching tube S₄Is connected to the source of the fifth switching tube S₁Respectively with the second capacitor C_uPositive electrode of the first DC power supply₂Is connected to the positive pole of the sixth switching tube S₂Respectively with the third capacitor C_dNegative electrode of (1), second DC power supply V₂Is connected to the negative electrode of (1).

The specific conditions of the high-gain bidirectional DC/DC converter suitable for the energy storage system in this embodiment are as follows:

1) Modal analysis

Fig. 2 is a waveform diagram of the main components in the case of stable operation of the circuit.

The operation of the circuit will be analyzed in detail with reference to fig. 3a to 3 j:

a. Stage theta₀Referring to FIG. 3a, the second switch Q is shown in this stage₁And a third switching tube Q_2aThe sixth switching tube S₂and a seventh switching tube S₃Maintaining the conducting state under the action of the driving signal; first switch tube Q_1aAnd a fourth switching tube Q₂The fifth switch tube S₁And an eighth switching tube S₄Maintaining an off state under the action of the driving signal; the primary voltage of the transformer T is controlled by the first capacitor C_CClamped to-V_C(ii) a The secondary side voltage of the transformer T is controlled by a third capacitor C_dClamped to-V₂2; excitation inductance L of transformer T secondary side in parallel_mCurrent i of_LmChange from negative to positive; equivalent homonymous terminal leakage inductance L of transformer T primary side series connection_rCurrent i of_LrKeeping the original shape; power is supplied from a first source V₁To a second power supply V₂(ii) a When the third switch tube Q_2aWhen the drive signal disappears, this phase ends.

b. Stage theta₀～θ₁Referring to FIG. 3b, the third switch Q at this stage_2aThe switch-off is carried out under the action of a driving signal; second inductance L₂Current i of_L2Equivalent homonymous terminal leakage inductance L connected in series with primary side of transformer T_rCurrent i of_LrFor the third switch tube Q_2aParasitic capacitance C of_2aCharging while supplying the fourth switch tube Q₂Parasitic capacitance C of₂Discharging till the fourth switch tube Q₂Is connected in parallel with the diode D₂Conducting; when the fourth switch tube Q₂This phase ends when the drive signal arrives.

c. Stage theta₁～θ₂Referring to FIG. 3c, the fourth switch Q is shown in this stage₂Realizing zero voltage conduction under the action of a driving signal; primary side voltage of transformer T is-V_CBecomes 0; the secondary side voltage of the transformer T is controlled by a third capacitor C_dClamping is maintained at-V₂2; with transformers T in parallelExcitation sensation L_mCurrent i of_LmContinuously rising; equivalent homonymous terminal leakage inductance L of transformer T primary side series connection_rCurrent i of_LrRising; when the sixth switch tube S₂When the drive signal disappears, this phase ends. At this stage, the equivalent homonymous end leakage inductance L of the series connection of the primary sides of the transformer T_rCurrent i of_LrThe expression is as follows:

d. Stage theta₂～θ₃As shown in fig. 3d, the sixth switch tube S at this stage₂The switch-off is carried out under the action of a driving signal; excitation inductance L of transformer T secondary side in parallel_mCurrent i of_LmFor the sixth switching tube S₂Parasitic capacitance C of_s2Charging while supplying the eighth switch tube S₄Parasitic capacitance C of_s4Discharging until the eighth switching tube S₄Is connected in parallel with the diode D_s4Conducting; when the eighth switch tube S₄This phase ends when the drive signal arrives.

e. Stage theta₃～θ₄As shown in fig. 3e, the eighth switch tube S at this stage₄Realizing zero voltage conduction under the action of a driving signal; the primary voltage of the transformer T is maintained to be 0; the secondary side voltage of the transformer T is from-V₂2 to 0; excitation inductance L of transformer T secondary side in parallel_mCurrent i of_LmKeeping the original shape; equivalent homonymous terminal leakage inductance L of transformer T primary side series connection_rcurrent i of_LrIs 0; when the second switch tube Q₁When the drive signal disappears, this phase ends. At this stage, the equivalent homonymous end leakage inductance L of the series connection of the primary sides of the transformer T_rCurrent i of_LrThe expression is as follows:

i_Lr(θ)＝0(θ₂＜θ≤θ₄) (2)

f. Stage theta₄～θ₅As shown in fig. 3f, the second switch tube Q at this stage₁The switch-off is carried out under the action of a driving signal; first inductance L₁Current i of_L1Equivalent homonymous terminal leakage inductance L connected in series with primary side of transformer T_rCurrent i of_LrFor the second switch tube Q₁Parasitic capacitance C of₁Charging while supplying the first switch tube Q_1aParasitic capacitance C of_1aDischarging until the first switch tube Q_1aIs connected in parallel with the diode D_1aConducting; when the first switch tube Q_1aThis phase ends when the drive signal arrives.

g. Stage theta₅～θ₆Referring to FIG. 3g, the first switch Q is at this stage_1aRealizing zero voltage conduction under the action of a driving signal; the primary voltage of the transformer T is controlled by the first capacitor C_Cclamping from 0 to V_C(ii) a The voltage of the secondary side of the transformer T is maintained to be 0; excitation inductance L of transformer T secondary side in parallel_mCurrent i of_LmKeeping the original shape; equivalent homonymous terminal leakage inductance L of transformer T primary side series connection_rCurrent i of_LrRising; when the seventh switch tube S₃When the drive signal disappears, this phase ends. At this stage, the equivalent homonymous end leakage inductance L of the series connection of the primary sides of the transformer T_rCurrent i of_Lrthe expression is as follows:

h. Stage theta₆～θ₇As shown in fig. 3h, the seventh switch tube S at this stage₃The switch-off is carried out under the action of a driving signal; equivalent homonymous terminal leakage inductance L of transformer T primary side series connection_rCurrent i of_LrEquivalent to the secondary side to the seventh switch tube S₃Parasitic capacitance C of_s3Charging while supplying the fifth switch tube S₁Parasitic capacitance C of_s1Discharging until the fifth switch tube S₁Is connected in parallel with the diode D_s1Conducting; when the fifth switch tube S₁This phase ends when the drive signal arrives.

i. Stage theta₇～θ₈As shown in fig. 3i, the fifth switch tube S at this stage₁Realizing zero voltage conduction under the action of a driving signal; the primary voltage of the transformer T is controlled by the first capacitor C_CClamped to V_C(ii) a The secondary side voltage of the transformer T is controlled by a third capacitor C_dClamping from 0 to V₂2; excitation inductance with parallel T secondary sides of transformerL_mCurrent i of_LmChanging from positive to negative; equivalent homonymous terminal leakage inductance L of transformer T primary side series connection_rCurrent i of_LrKeeping the original shape; power is supplied from a first source V₁To a second power supply V₂(ii) a When the first switch tube Q_1aWhen the drive signal disappears, this phase ends. At this stage, the equivalent homonymous end leakage inductance L of the series connection of the primary sides of the transformer T_rCurrent i of_LrThe expression is as follows:

i_Lr(θ)＝i_Lr(θ₆)(θ₆＜θ≤θ₈) (4)

j. Stage theta₈Then, as shown in FIG. 3j, the first switch tube Q at this stage_1athe switch-off is carried out under the action of a driving signal; first inductance L₁Current i of_L1Equivalent homonymous terminal leakage inductance L connected in series with primary side of transformer T_rCurrent i of_LrFor the first switch tube Q_1aParasitic capacitance C of_1aCharging while supplying the second switch tube Q₁Parasitic capacitance C of₁discharging until the second switch tube Q₁Is connected in parallel with the diode D₁And conducting.

Since the original secondary side structures are symmetrical, the latter half period will be cyclic, and the remaining states will not be described in detail.

2) Steady state gain

Under the action of the interleaved Boost circuit, the primary voltage amplitude u of the transformer T_abComprises the following steps:

The secondary side is a T-shaped neutral point clamping circuit, so the voltage amplitude u of the secondary side is_cdComprises the following steps:

Since the transformation ratio of the transformer T is n, and the topology has the function of voltage matching on two sides of the transformer, the following steps are carried out:

u_ab＝nu_cd (7)

According to the formulas (5), (6) and (7), the steady-state gain M is:

3) A first power supply V₁Current ripple of

Due to the first inductance L₁And a second inductance L₂The parameters are consistent, and a symmetrical double Boost topology with staggered parallel connection is adopted, so that the first inductor L₁And a second inductance L₂The real-time current waveforms of (1) are two waveforms 180 ° out of phase. The second inductance L is used below₂For example, the average current has an effective value of:

when the fourth switch tube Q₂When conducting, the second inductor L₂Is supplied by a first power supply V₁Clamping, during which the current starts to rise, during which the second inductance L₂The instantaneous value of the current is:

When the fourth switch tube Q₂When turned off, the second inductor L₂The voltage on both sides is-V₁The current begins to decrease, during which the second inductance L₂the instantaneous value of the current is:

Obtained by the volt-second balance principle, the first inductance L₁And a second inductance L₂Current ripple Δ i of_L1、Δi_L2And the total input current ripple Δ i is:

Wherein T is_sIs a switching cycle.

From this, it can be found that when D is 0.5, the current ripple of the total input current is 0. When D is not 0.5, the ripple frequency of the input current is 2 times of the switching frequency, and the amplitude is much smaller than that of the single-inductor boost converter, so that the first power supply V can be supplied to the second power supply V₁The service life of the energy storage element on the side plays a very good role in protection.

The above-mentioned embodiments are only preferred embodiments of the present invention, and the scope of the present invention is not limited thereto, so that all the changes made according to the shape and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A high-gain bi-directional DC/DC converter suitable for use in an energy storage system, comprising: comprises a first DC power supply (V)₁) First inductance (L)₁) Second inductance (L)₂) First switch tube (Q)_1a) And its anti-parallel diode (D)_1a) And parasitic capacitance (C)_1a) Second switch tube (Q)₁) And its anti-parallel diode (D)₁) And parasitic capacitance (C)₁) A third switching tube (Q)_2a) And its anti-parallel diode (D)_2a) And parasitic capacitance (C)_2a) Fourth switch tube (Q)₂) And its anti-parallel diode (D)₂) And parasitic capacitance (C)₂) First capacitance (C)_C) Transformer (T) and its primary side series equivalent homonymous terminal leakage inductance (L)_r) Excitation inductance (L) in parallel with secondary side_m) Fifth switching tube (S)₁) And its anti-parallel diode (D)_s1) And parasitic capacitance (C)_s1) Sixth switching tube (S)₂) And its anti-parallel diode (D)_s2) And parasitic capacitance (C)_s2) Seventh switching tube (S)₃) And its anti-parallel diode (D)_s3) And parasitic capacitance (C)_s3) The eighth switching tube (S)₄) And its anti-parallel diode (D)_s4) And parasitic capacitance (C)_s4) A second capacitance (C)_u) Third capacitance (C)_d) Second direct current power supply (V)₂) (ii) a Wherein the first DC power supply (V)₁) Is turning toThe poles are respectively connected with the first inductor (L)₁) One terminal of (a), a second inductance (L)₂) Is connected to said first inductor (L)₁) Respectively with the first switching tube (Q)_1a) Source electrode, second switch tube (Q)₁) Equivalent homonymous terminal leakage inductance (L) of the drain electrode and the primary side of the transformer (T) in series connection_r) Connected, the second inductance (L)₂) The other end of the first and second switching tubes (Q) are respectively connected with a third switching tube (Q)_2a) Source electrode, fourth switching tube (Q)₂) Is connected with the different name end of the primary side of the transformer (T), and the first switching tube (Q)_1a) Respectively with a third switching tube (Q)_2a) Drain electrode, first capacitor (C)_C) The positive pole of the second switching tube (Q)₁) With the fourth switching tube (Q) respectively₂) Source electrode, first capacitor (C)_C) Is connected with the negative pole of the transformer (T), and the homonymous ends of the secondary side of the transformer (T) are respectively connected with the fifth switch tube (S)₁) Source electrode of (1), sixth switching tube (S)₂) Drain electrode of (1), seventh switching tube (S)₃) Is connected with the drain electrode of the transformer (T), and the different name ends of the secondary side of the transformer (T) are respectively connected with the eighth switching tube (S)₄) Drain electrode of (1), second capacitor (C)_u) Negative electrode of (2), third capacitor (C)_d) The positive pole of the seventh switching tube (S)₃) Source electrode of (1) and eighth switching tube (S)₄) Is connected to the source of the fifth switching tube (S)₁) Respectively with a second capacitor (C)_u) Positive electrode of (2), second direct current power supply (V)₂) The positive pole of the sixth switching tube (S)₂) Respectively with a third capacitor (C)_d) Negative pole of (2), second direct current power supply (V)₂) Is connected to the negative electrode of (1).

2. A high gain bi-directional DC/DC converter suitable for use in an energy storage system as claimed in claim 1, wherein: the first switch tube (Q)_1a) And a second switching tube (Q)₁) And a third switching tube (Q)_2a) And a fourth switching tube (Q)₂) And a fifth switching tube (S)₁) And a seventh switching tube (S)₃) And a sixth switching tube (S)₂) And an eighth switching tube (S)₄) Respectively complementarily turned on, and the first switching tube (Q)_1a) And a fourth switching tube (Q)₂) And a fifth switching tube (S)₁) And a sixth switching tube (S)₂) 180 DEG phase difference, the first switch tube (Q)_1a) And a fifth switching tube (S)₁) Is phase shift angleAnd between-90 DEG and 90 DEG, the second switching tube (Q)₁) And a fourth switching tube (Q)₂) And a seventh switching tube (S)₃) And the eighth switching tube (S)₄) Is the same and greater than 0.5.

3. A high gain bi-directional DC/DC converter suitable for use in an energy storage system as claimed in claim 1, wherein: the first switch tube (Q)_1a) A second switch tube (Q)₁) And a third switching tube (Q)_2a) And a fourth switching tube (Q)₂) And a fifth switching tube (S)₁) And a sixth switching tube (S)₂) And a seventh switching tube (S)₃) And an eighth switching tube (S)₄) The power switch tube has reverse conducting characteristic.

4. A high gain bi-directional DC/DC converter suitable for use in an energy storage system as claimed in claim 1, wherein: the turn ratio of the primary side and the secondary side of the transformer (T) is n:1, wherein n is the quotient of the number of primary turns of the transformer (T) divided by the number of secondary turns.