阅读说明：本技术 一种控制电池储能系统的双向多电平变换器拓扑结构 (Bidirectional multilevel converter topological structure for controlling battery energy storage system ) 是由 胡毕华 闫晗 陈智勇 谭平安 盘宏斌 邓文浪 于 2021-09-23 设计创作，主要内容包括：本发明提出了一种控制电池储能系统的双向多电平变换器,其基础单元为三个开关管与一个电容组成的开关电容模块,以三电平基础拓扑为例具体分析,还提出了四电平、m电平扩展拓扑。该拓扑结构具有高电压增益且输出电压纹波小,其通过开关电容部分与滤波部分实现电池与直流母线之间的电压转换。电路主要通过开关电容部分实现升压功能,各功率开关工作在不同状态组合得到多电平输出,并通过调控相邻工作状态的占空比实现一定范围内的精确输出。(The invention provides a bidirectional multilevel converter for controlling a battery energy storage system, wherein a basic unit is a switched capacitor module consisting of three switching tubes and a capacitor, a three-level basic topology is taken as an example for specific analysis, and a four-level and m-level expansion topology is also provided. The topological structure has high voltage gain and small output voltage ripple, and realizes voltage conversion between the battery and the direct current bus through the switched capacitor part and the filtering part. The circuit mainly realizes a boosting function through a switched capacitor part, each power switch works in different states and is combined to obtain multi-level output, and accurate output within a certain range is realized by regulating and controlling the duty ratio of adjacent working states.)

1. A bidirectional multilevel converter for controlling a battery energy storage system is characterized in that a basic unit (figure 2) is a switched capacitor module consisting of three switching tubes and a capacitor. The battery is connected in series with the capacitor in the switched capacitor module to realize the boosting function. One more basic unit per topology structure, changeVoltage gain upper limit improvement U of converter_b. The voltage conversion between the battery and the direct current bus is realized through the switched capacitor part and the filtering part, and the switching tubes work in different states and are combined to obtain multi-level output.

2. A three-level base topology (fig. 3) using the base unit of claim 1, consisting of five switching tubes, two capacitors and an inductor, including a switched capacitor part and a filter part. Wherein the switched capacitor part is composed of a basic unit including S₁、S₃、S₄And C₁. The left side of the switched capacitor part is connected with the battery and passes through S₂Forming a capacitor C in a switched capacitor module₁Charging loop of (1), right side channel S₅And the filter part is connected with the direct current bus. When S is₁Off, S₂、S₃When conducting, the battery is coupled to the capacitor C₁Charging; when S is₁Conduction, S₂、S₃、S₄Off, at this time C₁Voltage at both ends is U_bBatteries and C₁The boosting function is realized by serial connection. S₅Is a high level path, S₂Is a low level path. The filter part is composed of L and C₂Is constructed to filter out high frequency voltage.

3. Three-level basic topology according to claim 2, characterized in that different driving signals are applied to the topology circuit such that the switching tube S₁～S₅The circuit works in different state combinations to obtain different output levels, and has three states in total. State 1: switch S₂、S₃、S₄Conduction, S₁、S₅And (6) cutting off. The current loop is shown in fig. 4. Battery warp S₂And S₃To C₁Charging, wherein the output of the direct current bus is 0V; state 2: switch S₂、S₃、S₅Conduction, S₁、S₄And cut off, and the current loop is as shown in figure 5. Battery warp S₂And S₃To C₁Charging while passing through S₃、S₅The filter circuit is connected with the DC busThe output of the current bus is U_b(ii) a State 3: switch S₁、S₅Conduction, S₂、S₃、S₄And is cut off, and the current loop is as shown in figure 6. Battery warp S₁、C₁、S₅The filter circuit is connected with the direct current bus, and the output of the direct current bus is 2U_b. Obtaining three output levels in total;

at 0, U obtained_b、2U_bOn the basis of three output levels, for other required 0-2U_bThe output voltage in the voltage regulating circuit can regulate the respective action time of two adjacent working states, namely the duty ratio is regulated to realize accurate output in each interval. From 0 to U_b、U_b～2U_bTwo intervals, which are divided into two combination modes:

the required voltage is between 0 and U_bThe circuit is operated in states 1 and 2, each of which is active for a period of time, mode 1. The action time of State 1 is T₁With a switching period of T_SDuty cycle D of state 1₁＝T₁/T_SOutput voltage U₀Comprises the following steps:

U₀＝(1-D₁)U_b (1-1)

required voltage at U_b～2U_bThe circuit is operated in states 2 and 3, with each of the two operating states being active for a period of time, mode 2. The action time of State 2 is T₂With a switching period of T_SDuty cycle D of state 2₂＝T₂/T_S，U₀Comprises the following steps:

U₀＝D₂U_b+(1-D₂)2U_b (1-2)

4. a four-level topology (fig. 7) using the basic unit of claim 1, consisting of eight switching transistors, three capacitors and an inductor, including a switched capacitor part and a filter part. Wherein the switched capacitor part is composed of two basic units including S₁、S₃、S₄、S₅、S₆、S₈、C₁、C₂. The left side of the switched capacitor part is connected with the battery and passes through S₂Forming a capacitor C in a switched capacitor module₁、C₂Charging loop of (1), right side channel S₇And the filter part is connected with the direct current bus. When the battery switches the capacitor C in the capacitor module₁、C₂After charging, each switch tube is combined in different states to make the battery and the C₁、C₂The boosting function is realized by serial connection. S₇Is a high level path, S₂Is a low level path. The filter part is composed of L and C₃Is constructed to filter out high frequency voltage.

5. The four-level expansion topology according to claim 4, wherein different driving signals are applied to the topology circuit to cause the switch tube S₁～S₈The circuit works in different state combinations to obtain different output levels, and has four states in total. State 1: switch S₂、S₃、S₄、S₆、S₈Conduction, S₁、S₅、S₇And when the circuit is cut off, the current loop is as shown in figure 8. Battery warp S₂And S₃To C₁Charging while passing through S₂、S₃、S₄、S₆To C₂Charging, wherein the output of the direct current bus is 0V; state 2: switch S₂、S₃、S₄、S₆、S₇Conduction, S₁、S₅、S₈And cut off, and the current loop is as shown in figure 9. Battery warp S₂And S₃To C₁Charging while passing through S₂、S₃、S₄、S₆To C₂Charging, and passing through S₃、S₆、S₇The filter circuit is connected with the DC bus, and the output of the DC bus is U_b(ii) a State 3: the circuit has two drive signals, a switch S in the first half period₂、S₃、S₅、S₇Conduction, S₁、S₄、S₆、S₈And when the circuit is cut off, the current loop is as shown in figure 10. Battery warp S₂And S₃To C₁Is charged with C₂Series warp of S₃、S₅、S₇The filter circuit is connected with the direct current bus, and the output of the direct current bus is 2U_b(ii) a Switch S in the second half period₁、S₄、S₆、S₇Conduction, S₂、S₃、S₅、S₈And when the circuit is cut off, the current loop is as shown in figure 11. Batteries and C₁Series warp of S₁、S₆、S₇The filter circuit is connected with the DC bus, and C is the same₁And C₂Are connected in parallel to C₂Charging, the output of the DC bus is 2U_b. And 4: switch S₁、S₅、S₇Conduction, S₂、S₃、S₄、S₆、S₈And cut off, and the current loop is as shown in figure 12. Batteries and C₁、C₂Series warp of S₁、S₅、S₇The filter circuit is connected with the direct current bus, and the output of the direct current bus is 3U_b. Obtaining four output levels in total;

at 0, U obtained_b、2U_b、3U_bOn the basis of four output levels, for other required 0-3U_bThe output voltage in the voltage regulating circuit can regulate the respective action time of two adjacent working states, namely the duty ratio is regulated to realize accurate output in each interval. From 0 to U_b、U_b～2U_b、2U_b～3U_bThree intervals are divided into three combined modes:

the required voltage is between 0 and U_bThe circuit is operated in states 1 and 2, each of which is active for a period of time, mode 1. The action time of State 1 is T₁With a switching period of T_SDuty cycle D of state 1₁＝T₁/T_SOutput voltage U₀Comprises the following steps:

U₀＝(1-D₁)U_b (1-3)

required voltage at U_b～2U_bThe circuit is operated in states 2 and 3, with each of the two operating states being active for a period of time, mode 2. The action time of State 2 is T₂With a switching period of T_SThen state ofDuty cycle D of 2₂＝T₂/T_S，U₀Comprises the following steps:

U₀＝D₂U_b+(1-D₂)2U_b (1-4)

the required voltage is 2U_b～3U_bThe circuit is operated in states 3 and 4, with each of the two operating states being active for a period of time, mode 3. The action time of State 3 is T₃With a switching period of T_SDuty cycle D of state 3₃＝T₃/T_S，U₀Comprises the following steps:

U₀＝2D₃U_b+(1-D₃)3U_b (1-5)

6. an m-level extension topology (fig. 13) using the basic unit of claim 1, which is composed of 3m-4 switching tubes, m-1 capacitors and an inductor, and comprises a switched capacitor part and a filter part. Wherein the switched capacitor part consists of m-2 basic units, the left side of which is connected with the battery and passes through S₂Forming a charging loop of each capacitor in the switched capacitor module by the battery, and passing through S on the right side_3m-4And the filter part is connected with the direct current bus. After the battery finishes charging each capacitor in the switch capacitor module, each switch tube is combined in different states, so that the battery is connected with each switch capacitor in series to realize the boosting function. S_3m-4Is a high level path, S₂Is a low level path. The filter part is composed of L and C_m-1Is constructed to filter out high frequency voltage.

7. The m-level spreading topology of claim 6, wherein every more base unit increases the voltage gain upper bound of the converter by U_bAnd m-2 basic units in m-level expansion topology, 0 and U can be obtained_b、2U_b、……、(m-1)U_bM output levels in total, and 0 to (m-1) U can be accurately adjusted by modulating the duty ratio of adjacent working states_bThe output voltage of the internal. The topological structure has high voltage gain and small output voltage ripple.

Technical Field

The invention relates to the field of DC-DC converters, in particular to a bidirectional multi-level converter for controlling a battery energy storage system.

Background

In a battery energy storage system, a DC-DC converter is a bridge for a DC bus to receive power from a battery or for the battery to transmit power to the DC bus, and the voltages between the DC bus and the battery are not matched. Therefore, a converter having a high voltage gain is required to solve this problem. In a conventional converter, there are only two output levels, and the high voltage gain also brings about an increase in output voltage ripple, which can be suppressed by increasing the output voltage level. Based on this, this patent proposes a bidirectional multilevel converter topology for controlling a battery energy storage system.

Disclosure of Invention

In order to achieve the above requirements, the present invention proposes a bidirectional multilevel converter for controlling a battery energy storage system. By taking three-level basic topology as an example for specific analysis, a four-level and m-level extended topology is also provided. The topological structure has high voltage gain and small output voltage ripple, the voltage at two ends of a capacitor in the switched capacitor circuit is automatically stabilized when the circuit works so as to realize stable output of the circuit, each power switch works in different states to be combined to obtain multi-level output, and the output voltage is accurately adjusted by regulating and controlling the duty ratio of adjacent working states.

The basic unit (fig. 2) of the multilevel converter is a switched capacitor module consisting of three switching tubes and one capacitor. The battery is connected in series with the capacitor in the switched capacitor module to realize the boosting function. The upper limit of the voltage gain of the converter is increased by U every more one basic unit in the topological structure_b. The converter realizes voltage conversion between the battery and the direct current bus through the filtering part of the switched capacitor, and each switching tube works in different states and is combined to obtain multi-level output.

The three-level basic topology (fig. 3) adopting the basic unit is composed of five switching tubes, two capacitors and an inductor, and comprises a switching capacitor part and a filtering part. Wherein the switched capacitor part is composed of a basic unit including S₁、S₃、S₄And C₁. The left side of the switched capacitor part is connected with the battery and passes through S₂Forming a capacitor C in a switched capacitor module₁Charging loop of (1), right side channel S₅And the filter part is connected with the direct current bus. When S is₁Off, S₂、S₃When conducting, the battery is coupled to the capacitor C₁Charging; when S is₁Conduction, S₂、S₃、S₄Off, at this time C₁Voltage at both ends is U_bBatteries and C₁The boosting function is realized by serial connection. S₅Is a high level path, S₂Is a low level path. The filter part is composed of L and C₂Is constructed to filter out high frequency voltage.

If "1" is defined as a high level driving signal of the switch and "0" represents a low level driving signal, the operating state of the circuit can be represented by a five-bit number. Different driving signals act on the topological circuit to enable the switch tube S₁～S₅The circuit works in different state combinations to obtain different output levels, and has three states in total. State 1: switch S₂、S₃、S₄Conduction, S₁、S₅Cutting off; state 2: switch S₂、S₃、S₅Conduction, S₁、S₄Cutting off; state 3: switch S₁、S₅Conduction, S₂、S₃、S₄And (6) cutting off. Resulting in three output levels.

Table 1 drive signal meter (three level base topology)

State 1:

at this time, the circuit driving signal is 01110, and the switch S₂、S₃、S₄Conduction, S₁、S₅And when the direct current bus is cut off, the output voltage of the direct current bus is 0V. When the battery is discharged (the discharge circuit is shown as a solid line in FIG. 4), the battery passes through S₂、S₃To C₁And charging, wherein no current flows to the direct current bus. When the battery is charged (the charging circuit is shown as a dotted line in FIG. 4), C₁Warp (S)₂、S₃The battery is charged with no current flowing from the dc bus to the battery.

State 2:

at this time, the circuit driving signal is 01101, and the switchS₂、S₃、S₅Conduction, S₁、S₄When the direct current bus is cut off, the output voltage of the direct current bus is U_b. When the battery is discharged (the discharge circuit is shown as a solid line in FIG. 5), the battery passes through S₂、S₃To C₁Charging and generating a current through S₃、S₅And the filter circuit flows to the direct current bus. When the battery is charged (the charging circuit is shown as a dotted line in FIG. 5), C₁Warp (S)₂、S₃Charging the battery, the current flowing out from the DC bus passes through S₃、S₅And the filter circuit charges the battery.

State 3:

at this time, the circuit driving signal is 10001, and the switch S₁、S₅Conduction, S₂、S₃、S₄When the direct current bus is cut off, the output voltage of the direct current bus is 2U_b. When the battery is discharged (the discharge circuit is shown as a solid line in FIG. 6), the battery is connected in series with C₁Generating a current through S₁、S₅And the filter circuit flows to the direct current bus. When the battery is charged (the charging circuit is shown as a dotted line in FIG. 6), the current flowing out from the DC bus passes through S₁、S₅And filter circuit pair C₁And charging the battery.

At 0, U obtained_b、2U_bOn the basis of three output levels, for other required 0-2U_bThe output voltage in the voltage regulating circuit can regulate the respective action time of two adjacent working states, namely the duty ratio is regulated to realize accurate output in each interval. From 0 to U_b、U_b～2U_bTwo intervals, which are divided into two combination modes:

the first mode is as follows: the required voltage is between 0 and U_bWhen the circuit works in states 1 and 2, the two driving signals are respectively acted for a period of time. When the action time of the state 1 is T₁With a switching period of T_SWhile, the duty ratio D of the state 1₁＝T₁/T_SAt this time, the output voltage U₀Comprises the following steps:

U₀＝(1-D₁)U_b (2-1)

if the battery voltage and output voltage are known, the duty cycle D of state 1 can be obtained from the above equation 2-1₁：

D₁＝1-U₀/U_b (2-2)

From D₁It can be seen that the time T of the action of state 1₁＝D₁T_STime T of action of State 2₂＝T_S-T₁。

And a second mode: required voltage at U_b～2U_bWhen the circuit works in states 2 and 3, the two driving signals are respectively acted for a period of time. When the action time of the state 2 is T₂With a switching period of T_SWhile, the duty cycle D of the state 2₂＝T₂/T_SAt this time, the output voltage U₀Comprises the following steps:

U₀＝D₂U_b+(1-D₂)2U_b (2-3)

if the battery voltage and output voltage are known, the duty cycle D of state 2 can be obtained from the above equation 2-3₂：

D₂＝2-U₀/U_b (2-4)

From D₂As can be seen, the time T of the action of State 2₂＝D₂T_STime T of action of State 3₃＝T_S-T₂。

The four-level expansion topology (fig. 7) adopting the basic unit is composed of eight switching tubes, three capacitors and an inductor, and comprises a switching capacitor part and a filtering part. Wherein the switched capacitor part is composed of two basic units including S₁、S₃、S₄、S₅、S₆、S₈、C₁、C₂. The left side of the switched capacitor part is connected with the battery and passes through S₂Forming a capacitor C in a switched capacitor module₁、C₂The right side of the charging loop is S₇And the filter part is connected with the direct current bus. When the battery switches the capacitor C in the capacitor module₁、C₂After charging, different on-off combinations of the switch tubes enable the battery and the C to be connected₁、C₂And the voltage boosting function is realized by series connection. S₇Is a high level path, S₂Is a low level path. Filter elementWave part consisting of L and C₃Is constructed to filter out high frequency voltage.

Different driving signals act on the topological circuit to enable the switch tube S₁～S₈The circuit works in different state combinations to obtain different output levels, and has four states in total. State 1: switch S₂、S₃、S₄、S₆、S₈Conduction, S₁、S₅、S₇Cutting off; state 2: switch S₂、S₃、S₄、S₆、S₇Conduction, S₁、S₅、S₈Cutting off; state 3: the circuit has two drive signals, a switch S in the first half period₂、S₃、S₅、S₇Conduction, S₁、S₄、S₆、S₈Cutting off; switch S in the second half period₁、S₄、S₆、S₇Conduction, S₂、S₃、S₅、S₈And (6) cutting off. And 4: switch S₁、S₅、S₇Conduction, S₂、S₃、S₄、S₆、S₈And (6) cutting off. Resulting in four output levels.

Table 2 driving signal meter (four-level expansion topology)

State 1:

at this time, the circuit driving signal is 01110101, switch S₂、S₃、S₄、S₆、S₈Conduction, S₁、S₅、S₇And when the direct current bus is cut off, the output voltage of the direct current bus is 0V. When the battery is discharged (the discharge circuit is shown by the solid line in FIG. 8), the battery passes through S₂、S₃To C₁Charging, through S₂、S₃、S₄、S₆To C₂And charging, wherein no current flows to the direct current bus. When the battery is charged (the charging circuit is shown as a dotted line in FIG. 8), C₁Warp (S)₂、S₃Charging the battery, C₂Warp (S)₂、S₃、S₄、S₆The battery is charged with no current flowing to the battery.

State 2:

at this time, the circuit driving signal is 01110110, switch S₂、S₃、S₄、S₆、S₇Conduction, S₁、S₅、S₈When the direct current bus is cut off, the output voltage of the direct current bus is U_b. When the battery is discharged (the discharge circuit is shown as a solid line in FIG. 9), the battery passes through S₂、S₃To C₁Charging, through S₂、S₃、S₄、S₆To C₂Charging, the battery generates current through S₃、S₆、S₇And the filter circuit flows to the direct current bus. When the battery is charged (the charging circuit is shown as a dotted line in FIG. 9), C₁Warp (S)₂、S₃Charging the battery, C₂Warp (S)₂、S₃、S₄、S₆Charging the battery, the current flowing out from the DC bus passes through S₃、S₆、S₇And the filter circuit charges the battery.

State 3:

the output voltage of the DC bus is 2U_bThe working state of the circuit is divided into a front half period and a rear half period. The first half period circuit driving signal is 01101010, switch S₂、S₃、S₅、S₇Conduction, S₁、S₄、S₆、S₈And (6) cutting off. When the battery is discharged (the discharge circuit is shown by the solid line in FIG. 10), the battery passes through S₂、S₃To C₁Charging while connecting in series C₂Generating a current through S₃、S₅、S₇And the filter circuit flows to the direct current bus. When the battery is charged (the charging circuit is shown as a dotted line in FIG. 10), C₁Warp (S)₂、S₃Charging the battery, the current flowing out from the DC bus passes through S₃、S₅、S₇And a filter circuit to C₂And charging the battery. The second half period circuit driving signal is 10010110, switch S₁、S₄、S₆、S₇Conduction, S₂、S₃、S₅、S₈And (6) cutting off. When the battery is discharged (the discharge circuit is shown as a solid line in FIG. 11), the battery is connected in series with C₁Generating a current through S₁、S₆、S₇And the filter circuit flow direction DC bus, C₁Warp (S)₄、S₆To C₂And (6) charging. When the battery is charged (the charging circuit is shown by a dotted line in FIG. 11), C₂Warp (S)₄、S₆To C₁Charging, the current flowing out of the DC bus passes through S₁、S₆、S₇And a filter circuit to C₁And charging the battery.

And 4:

at this time, the circuit driving signal is 10001010, and the switch S₁、S₅、S₇Conduction, S₂、S₃、S₄、S₆、S₈When the direct current bus is cut off, the output voltage of the direct current bus is 3U_b. When the battery is discharged (the discharge circuit is shown as a solid line in FIG. 12), the battery is connected in series with C₁And C₂Generating a current through S₁、S₅、S₇And the filter circuit flows to the direct current bus. When the battery is charged (the charging circuit is shown as a dotted line in FIG. 12), the current flowing out from the DC bus passes through S₁、S₅、S₇And filter circuit pair C₁、C₂And charging the battery.

At 0, U obtained_b、2U_b、3U_bOn the basis of four output levels, for other required 0-3U_bThe output voltage in the voltage regulating circuit can regulate the respective action time of two adjacent working states, namely the duty ratio is regulated to realize accurate output in each interval. From 0 to U_b、U_b～2U_b、2U_b～3U_bThree intervals are divided into three combined modes:

the first mode is as follows: the required voltage is between 0 and U_bWhen the circuit works in states 1 and 2, the two driving signals are respectively acted for a period of time. When the action time of the state 1 is T₁With a switching period of T_SWhile, the duty ratio D of the state 1₁＝T₁/T_SAt this time, the output voltage U₀Comprises the following steps:

U₀＝(1-D₁)U_b (2-5)

if the battery voltage and output voltage are known, the duty cycle D of state 1 can be obtained from the above equation 2-1₁：

D₁＝1-U₀/U_b (2-6)

From D₁It can be seen that the time T of the action of state 1₁＝D₁T_STime T of action of State 2₂＝T_S-T₁。

And a second mode: required voltage at U_b～2U_bWhen the circuit works in states 2 and 3, the two driving signals are respectively acted for a period of time. When the action time of the state 2 is T₂With a switching period of T_SWhile, the duty cycle D of the state 2₂＝T₂/T_SAt this time, the output voltage U₀Comprises the following steps:

U₀＝D₂U_b+(1-D₂)2U_b (2-7)

if the battery voltage and output voltage are known, the duty cycle D of state 2 can be obtained from the above equation 2-3₂：

D₂＝2-U₀/U_b (2-8)

From D₂As can be seen, the time T of the action of State 2₂＝D₂T_STime T of action of State 3₃＝T_S-T₂。

And a third mode: the required voltage is 2U_b～3U_bThe circuit is operated in states 3 and 4, with the two drive signals each active for a period of time. When the action time of state 3 is T₃With a switching period of T_SWhile, the duty cycle D of state 3₃＝T₃/T_SAt this time, the output voltage U₀Comprises the following steps:

U₀＝2D₃U_b+(1-D₃)3U_b (2-9)

if the battery voltage and output voltage are known, the duty cycle D of state 3 can be obtained from equations 2-5 above₃：

D₃＝3-U₀/U_b (2-10)

From D₃As can be seen, the time T of the action of State 3₃＝D₃T_STime T of action of State 4₄＝T_S-T₃。

The m-level expansion topology (figure 13) adopting the basic unit is composed of 3m-4 switching tubes, m-1 capacitors and an inductor, and comprises a switching capacitor part and a filtering part. Wherein the switched capacitor part consists of m-2 basic units, the left side of which is connected with the battery through S₂Forming a charging loop of each capacitor in the switched capacitor module by the battery, and passing through S on the right side_3m-4And the filter part is connected with the direct current bus. After the battery finishes charging each capacitor in the switch capacitor module, each switch tube is combined in different states, so that the battery is connected with each switch capacitor in series to realize the boosting function. S_3m-4Is a high level path, S₂Is a low level path. The filter part is composed of L and C_m-1Is constructed to filter out high frequency voltage.

For m-level expansion topology, the voltage gain upper limit of the converter is increased by U by one more basic unit_bAnd m-2 basic units in m-level expansion topology, 0 and U can be obtained_b、2U_b、……、(m-1)U_bM output levels in total, and 0 to (m-1) U can be accurately adjusted by modulating the duty ratio of adjacent working states_bThe output voltage of the internal. The topological structure has high voltage gain and small output voltage ripple.

Compared with the prior art, the method has the following advantages:

1. the non-isolated DC-DC converter has the advantages of low power consumption, simple structure and easiness in integration.

2. The converter topology provided by the application has high modularization degree and good expansibility, and can reduce the maintenance and installation cost.

3. The output voltage regulation range in the application is from 0 to U_bIncrease to 0-2U_b、0～3U_bAnd 0 to (m-1) U_bAnd has high voltage gain.

4. Output voltage ripple is suppressed by increasing the output voltage level in the present application.

5. The voltage automatic stabilization at electric capacity both ends among the switched capacitor circuit during operation in this application to realize the stable output of circuit.

Drawings

FIG. 1 is a bidirectional multilevel converter topology for controlling a battery energy storage system;

FIG. 2 a base unit;

FIG. 3 a three-level base topology;

fig. 4 shows a charge-discharge loop (three-level base topology) with an output of 0;

FIG. 5 output is U_bTime-varying charge-discharge loops (three-level base topology);

FIG. 6 output is 2U_bTime-varying charge-discharge loops (three-level base topology);

FIG. 7 a four-level expansion topology;

fig. 8 shows a charge-discharge loop (four-level expansion topology) when the output is 0;

FIG. 9 output is U_bTime-varying charge-discharge loops (four-level extended topology);

FIG. 10 output 2U_bA time-first half-cycle charge-discharge loop (four-level extension topology);

FIG. 11 output is 2U_bA time-half-cycle charge-discharge loop (four-level expansion topology);

FIG. 12 output is 3U_bTime-varying charge-discharge loops (four-level extended topology);

FIG. 13 m level expansion topology;

Detailed Description

The application provides a bidirectional multi-level converter topology for controlling a battery energy storage system, and the topology structure has the characteristics of high voltage gain and small output voltage ripple.

The basic unit (fig. 2) is a switched capacitor module consisting of three switching tubes and a capacitor. S₁Collector electrode of (1) and S₂Is connected to the emitter of S₂Collector and switch capacitor C₁Is connected to the anode C₁And S₁And S₃Are connected. The left side of the basic unit is connected with the battery, and the right side is continuously connected with the basic unit or is connected with the basic unit through a high-level path and filteringAnd part of the direct current bus is connected with the direct current bus. When S is₂Conduction, S₁When turned off, the battery is coupled to the capacitor C₁Charging; when S is₁Conduction, S₂、S₃When the switch is turned off, the capacitor C is switched on₁Voltage at both ends is U_bBattery and switch capacitor C₁Connected in series to achieve the boost function. The battery charges the capacitor in the switch capacitor module, and then is connected with the capacitor in series to realize the boosting function. The upper limit of the voltage gain of the converter is increased by U every more one basic unit in the topological structure_b。

The three-level basic topology (fig. 3) adopting the basic unit is composed of five switching tubes, two capacitors and an inductor, and comprises a switching capacitor part and a filtering part. Wherein the switched capacitor part is composed of a basic unit including S₁、S₃、S₄And C₁. The left side of the switched capacitor part is connected with the battery and passes through S₂Forming a capacitor C in a switched capacitor module₁Charging loop of (1), right side channel S₅And the filter part is connected with the direct current bus. When S is₁Off, S₂、S₃When conducting, the battery is coupled to the capacitor C₁Charging; when S is₁Conduction, S₂、S₃、S₄Off, at this time C₁Voltage at both ends is U_bBatteries and C₁The boosting function is realized by serial connection. S₅Is a high level path, S₂Is a low level path. The filter part is composed of L and C₂Is constructed to filter out high frequency voltage.

Three-level base topology, positive pole of battery and S₁Collector electrode of (1) and (S)₃Is connected to the emitter of S₃Collector electrode of (1) and (C)₁And S₅Is connected to the collector of S₅Emitter and S₄Is connected with the front end of the L, and the rear end of the L is connected with the C₂Is connected with the positive pole of the direct current bus, and the negative pole of the battery is connected with S₂Emitter electrode of, C₂Is connected to the negative pole of the direct current bus bar, S₁Emitter and S₂Collector electrode of (1), C₁And S₄Is connected to the emitter.

Different driving signals act on the topological circuit to enable the switch tube S₁～S₅The circuit works in different state combinations to obtain different output levels, and has three states in total. State 1: switch S₂、S₃、S₄Conduction, S₁、S₅Cutting off, wherein the output voltage is 0; state 2: switch S₂、S₃、S₅Conduction, S₁、S₄Cut-off when the output voltage is U_b(ii) a State 3: switch S₁、S₅Conduction, S₂、S₃、S₄Cut off when the output voltage is 2U_b. For other required 0-2U_bThe output voltage in each interval can realize accurate output in each interval by regulating and controlling the duty ratio of two adjacent working states. From 0 to U_b、U_b～2U_bTwo intervals are divided into two combined modes.

When the required output voltage U is reached₀In the range of 0 to U_bWhen the circuit is operated in states 1 and 2, the two states are each acted for a period of time, namely mode 1, and the duty ratios of the states 1 and 2 are modulated. The duty cycle D of state 1 can be obtained from equations 1-3₁If the switching period is T_SThen the time T of the state 1 action₁＝D₁T_STime T of action of State 2₂＝T_S-T₁。

When the required output voltage U is reached₀In U_b～2U_bWhen the circuit is in the states 2 and 3, the two states act for a period of time, namely the mode 2, and the duty ratios of the states 2 and 3 are modulated, and the duty ratio D of the state 2 is obtained by the formulas 1 to 4₂If the switching period is T_SThen time T of state 2 action₂＝D₂T_STime T of action of State 3₃＝T_S-T₂。

The four-level expansion topology (fig. 7) adopting the basic unit is composed of eight switching tubes, three capacitors and an inductor, and comprises a switching capacitor part and a filtering part. Wherein the switched capacitor part is composed of two basic units including S₁、S₃、S₄、S₅、S₆、S₈、C₁、C₂. The left side of the switched capacitor part is connected with the battery and passes through S₂Forming a capacitor C in a switched capacitor module₁、C₂Charging loop of (1), right side channel S₇And the filter part is connected with the direct current bus. When the battery switches the capacitor C in the capacitor module₁、C₂After charging, each switch tube is combined in different states to make the battery and the C₁、C₂The boosting function is realized by serial connection. S₇Is a high level path, S₂Is a low level path. The filter part is composed of L and C₃Is constructed to filter out high frequency voltage.

Positive pole and S of battery in four-level extended topology₁Collector electrode of (1) and (S)₃Is connected to the emitter of S₃Collector and switch capacitor C₁Anode of (2), S₅Collector electrode of (1) and (S)₆Is connected to the emitter of S₆Collector and switch capacitor C₂And S₇The collector electrodes are connected; s₁Emitter and S₂Collector electrode of (1), C₁And S₄Is connected to the emitter of S₄Collector electrode of (1) and S₅Emitter electrode of, C₂And S₈The emitting electrodes are connected; front end of L and S₇And S₈Is connected with the collector of the collector and the rear end is connected with the collector of the collector₃The anode of the direct current bus is connected with the anode of the direct current bus; negative electrode of battery and S₂Emitter electrode of, C₃Is connected with the negative pole of the direct current bus.

Different driving signals act on the topological circuit to enable the switch tube S₁～S₈The circuit works in different state combinations to obtain different output levels, and has four states in total. State 1: switch S₂、S₃、S₄、S₆、S₈Conduction, S₁、S₅、S₇Cutting off, wherein the output voltage is 0; state 2: switch S₂、S₃、S₄、S₆、S₇Conduction, S₁、S₅、S₈Cut-off when the output voltage is U_b(ii) a Status of state3: the circuit has two drive signals, a switch S in the first half period₂、S₃、S₅、S₇Conduction, S₁、S₄、S₆、S₈Cutting off; switch S in the second half period₁、S₄、S₆、S₇Conduction, S₂、S₃、S₅、S₈The output voltage is 2U when the power is off_b. And 4: switch S₁、S₅、S₇Conduction, S₂、S₃、S₄、S₆、S₈Cut off, at the moment, the output voltage is 3U_b. For other required 0-3U_bThe output voltage in each interval realizes the accurate output of each interval by regulating and controlling the duty ratio of the adjacent working states. From 0 to U_b、U_b～2U_b、2U_b～3U_bThree intervals are divided into three combined modes.

When the required output voltage U is reached₀In the range of 0 to U_bWhen the circuit is operated in states 1 and 2, the two states are each acted for a period of time, namely mode 1, and the duty ratios of the states 1 and 2 are modulated. The duty cycle D of state 1 can be obtained from equations 1-5₁If the switching period is T_SThen the time T of the state 1 action₁＝D₁T_STime T of action of State 2₂＝T_S-T₁。

When the required output voltage U is reached₀In U_b～2U_bWhen the circuit is operating in states 2 and 3, the two states each act for a period of time, i.e., mode 2, to modulate the duty cycles of states 2 and 3. The duty cycle D of state 2 can be derived from equations 1-6₂If the switching period is T_SThen time T of state 2 action₂＝D₂T_STime T of action of State 3₃＝T_S-T₂。

When the required output voltage U is reached₀In 2U_b～3U_bThe circuit is operated in states 3 and 4, each of which acts for a period of time, mode 3, to modulate the duty cycles of states 3 and 4. The duty cycle D of state 3 can be derived from equations 1-7₃If the switching period isIs T_SThen the time T of the state 3 action₃＝D₃T_STime T of action of State 4₄＝T_S-T₃。

The m-level expansion topology (figure 13) adopting the basic unit is composed of 3m-4 switching tubes, m-1 capacitors and an inductor, and comprises a switching capacitor part and a filtering part. Wherein the switched capacitor part consists of m-2 basic units, the left side of which is connected with the battery and passes through S₂Forming a charging loop of each capacitor in the switched capacitor module by the battery, and passing through S on the right side_3m-4And the filter part is connected with the direct current bus. After the battery finishes charging each capacitor in the switch capacitor module, each switch tube is combined in different states, so that the battery is connected with each switch capacitor in series to realize the boosting function. S_3m-4Is a high level path, S₂Is a low level path. The filter part is composed of L and C_m-1Is constructed to filter out high frequency voltage.

In m-level expansion topology, one more basic unit increases the voltage gain upper limit of the converter by U_bAnd m-2 basic units in m-level expansion topology, 0 and U can be obtained_b、2U_b、……、(m-1)U_bM output levels in total, and 0 to (m-1) U can be accurately adjusted by modulating the duty ratio of adjacent working states_bThe output voltage of the internal. The modulation strategy of the m-level expansion topology is similar to the modulation strategy of the three-level basic topology and the four-level expansion topology analyzed above.

The above method is a preferred embodiment of the present invention, but the embodiment is not exclusive and not limitative in any way, and several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.