阅读说明：本技术 适宜于h桥串联并网逆变链lcl滤波器的参数快速整定方法 (Parameter quick setting method suitable for H-bridge series connection grid-connected inverter chain LCL filter ) 是由 杨维满 *** 朱亚娜 王兴贵 祁霄鹏 郭永吉 王琢玲 *** 郭群 于 2020-06-04 设计创作，主要内容包括：适宜于H桥串联并网逆变链LCL滤波器的参数快速整定方法,涉及的单相并网逆变链中H桥微源逆变器单元(1)、(2)、(3)、(4)交流输出侧依次通过串联方式连接。涉及一种多H桥单元串联连接型单相并网逆变链的LCL滤波器参数快速设计方法,前后依次包括五个步骤：确定LCL滤波器中逆变链侧电感和网侧电感取值总和；确定LCL滤波器中逆变链侧电感取值；确定单相并网逆变链等效载波频率；确定网侧电感取值；确定LCL滤波器中滤波电容取值。所涉及LCL滤波器参数设计方法对促进LCL型滤波器在串联连接型单相并网逆变链中的便捷应用具有重要用途。(The method is suitable for the parameter rapid setting method of the LCL filter of the H-bridge series-connection grid-connected inverter chain, and alternating current output sides of H-bridge micro-source inverter units (1), (2), (3) and (4) in the single-phase grid-connected inverter chain are connected in series in sequence. Relates to a method for rapidly designing parameters of an LCL filter of a multi-H-bridge unit series connection type single-phase grid-connected inverter chain, which sequentially comprises the following five steps: determining the value sum of the inverter chain side inductance and the network side inductance in the LCL filter; determining the value of the inductance on the side of an inverter chain in the LCL filter; determining the equivalent carrier frequency of a single-phase grid-connected inverter chain; determining the value of the network side inductance; and determining the value of the filter capacitor in the LCL filter. The LCL filter parameter design method has important application in promoting convenient application of the LCL type filter in a series connection type single-phase grid-connected inverter chain.)

1. The parameter rapid setting method suitable for the H-bridge series connection grid-connected inverter chain LCL filter is characterized by comprising the following steps of:

step (1): according to the limit of reactive power introduced by a filter capacitor C in the LCL filter, the value of the filter capacitor C is calculated as:

lambda in the formula (1)₁The percentage of capacitive reactive power consumed by a filter capacitor C in the LCL filter and rated active power output by the grid-connected inverter is 3% -8%;

step (2): according to the normal work of a multi-H-bridge unit series connection type single-phase grid-connected inverter chain, the side inductance L of the inverter chain in the LCL filter needs to be enabled₁And network side inductance L₂The sum of which satisfies the formula (2):

to make the inductance L on the side of the inverter chain in the LCL filter₁And network side inductance L₂The total voltage drop of the inductor does not exceed lambda% of the effective value of the network voltage, and the inductor L on the side of an inversion chain in the LCL filter is also enabled to be₁And network side inductance L₂The sum of which satisfies the formula (3):

u in formula (2) and formula (3)_dcjIs H-bridge micro-source inverter unit j (j is 1, 2, 3, 4) direct current bus voltage, Ug is effective value of fundamental component of grid voltage, Ig is effective value of grid-connected current fundamental component, fs is grid-connected point grid voltage fundamental component frequency, lambda₂The percentage of the effective value of the grid voltage is 5-10%, and the calculated inductance L at the side of the inverter chain in the LCL filter₁And network side inductance L₂The smaller of the sum is taken as an upper limit limiting value, and the larger is taken as a lower limit limiting value, so as to obtain a formula (4):

0＜L₁+L₂≤min(L₁₂,L'₁₂) (4)

the inductor L on the side of an inversion chain in the LCL filter is taken as the inductor L of the equation (4)₁And network side inductance L₂The value range of the sum;

and (3): determining the equivalent switching frequency f of the single-phase grid-connected inverter chain according to the carrier frequency of the H-bridge unit in the series connection structure_cN：

f_cN＝N×f_c(5)

In the formula (5) f_cThe carrier frequency of a single H-bridge inversion unit SPWM in a series connection type single-phase grid-connected inverter chain is adopted, and N is the number of the H-bridge inversion units in the series connection type single-phase grid-connected inverter chain;

and (4): determining the side inductance L of the inverter chain₁According to the current flowing through the side inductance L of the inverter chain₁Ripple factor limit L of current₁Minimum value, when the multi-H bridge unit series connection type single-phase grid-connected inverter chain adopts bipolar CPS-SPWM, the inverter chain side inductance L is calculated by using a formula (6)₁Lower limit value:

when the multi-H-bridge unit series connection type single-phase grid-connected inverter chain adopts unipolar CPS-SPWM, the inverter chain side inductance L is calculated by using a formula (7)₁Lower limit value:

lambda in formula (6) or formula (7)₂Is the inverter chain side inductance current ripple coefficient, and lambda₃＝Δi_L1max/I_L1Wherein Δ i_L1maxAnd I_L1Respectively, the side inductance L of the current-through inversion chain₁The maximum instantaneous value and the effective value of the current are 15 to 30 percent in the engineering, f_cNIs a single phaseEquivalent switching frequency of grid-connected inverter chain and side inductance L of inverter chain₁The upper limit value is determined by using a limiting condition of the voltage drop of the fundamental wave at the two ends:

λ in the formula (8)₄Is an inductance L₁The percentage of the fundamental voltage drop at the two ends to the voltage at the two ends of the capacitor C is usually 5%, so that the inductance L at the side of the inverter chain can be determined₁Value of L_1minAnd L_1maxAny positive number between, to reduce the LCL filter volume, take L_1minAnd L_1maxIs closest to L_1minA positive number of;

and (5): according to the side inductance L of the inverter chain₁And network side inductance L₂Is used to determine the inductance L₂Taking values:

in the formula (9), a is an inverter chain side inductor L₁And network side inductance L₂The ratio of values, a, is usually 1-3, L₂Finally at zero and min (L)₁₂,L'₁₂) The value between the/(1 + a) is obtained;

after the step (1) or the step (2) or the step (3) is adjusted, but before the step (4) and the step (5), the step (1) needs to ensure that LCL filter parameters meeting basic requirements can be quickly designed through the five steps, and the multi-H-bridge unit series connection type single-phase grid-connected inverter chain can output current meeting the grid-connected quality requirements of the distributed power supply by combining an active damping or passive damping method and a grid-connected current controller.

Technical Field

The invention relates to a LCL filter parameter design method, in particular to a LCL filter parameter rapid design method applied to a multi-H-bridge unit series connection type single-phase grid-connected inverter chain, which realizes rapid design of main circuit parameters of the LCL filter type multi-H-bridge unit series connection type single-phase grid-connected inverter chain and promotes related scientific problem research and application in photovoltaic, wind power and other clean energy practical projects.

Background

Wind power generation and photovoltaic power generation become main means for utilizing wind energy and solar energy, the topological structure types of the existing distributed power supply and electric energy converters such as wind power, light power and the like are various, particularly the forms of the electric energy converters of the distributed photovoltaic power generation system are various, and the wind-light storage grid-connected power generation system is provided with a multi-stage, single-stage, staggered parallel connection type, cascade connection type and H-bridge inversion unit series connection structure. In the wind-solar energy storage grid-connected power generation system with the cascade and H-bridge inversion unit series structure, the equivalent carrier frequency of a multi-H-bridge unit series connection type single-phase grid-connected inversion chain is high and is N times of the carrier frequency of a single H-bridge inversion unit, wherein N is the number of the H-bridge inversion units in the series connection type single-phase grid-connected inversion chain.

At present, an L-type filter and an LCL-type filter are mostly adopted at a grid-connected end of a distributed grid-connected power generation system, the suppression capacities of the L-type filter and the LCL-type filter to harmonic waves at a low frequency band are almost the same, but the suppression capacity of the L-type filter to high frequency harmonic waves at a high frequency band is much weaker than that of the LCL-type filter, namely the suppression capacity of the LCL-type filter to high frequency harmonic waves is better. The equivalent carrier frequency of the multi-H-bridge unit series connection type single-phase grid-connected inverter chain is increased by N times relative to the carrier frequency of a single H-bridge inverter unit, so that the frequency band in which the harmonic waves are mainly concentrated is correspondingly increased by N times, which indicates that the LCL type filter is more suitable for being adopted in the multi-H-bridge unit series connection type single-phase grid-connected distributed power generation system. Therefore, the invention relates to a method for rapidly designing parameters of an LCL filter of a multi-H-bridge unit series connection type single-phase grid-connected inverter chain.

Disclosure of Invention

The invention aims to apply an LCL filter to a wind-solar storage grid-connected power generation system with a cascade and H-bridge inversion unit series structure, and sequentially determines the sum L of inversion chain side inductance and grid side inductance₁+L₂Multiple H bridge units series connection type single-phase grid-connected inverter chain equivalent carrier frequency, inverter chain side inductance L₁Network side inductor L₂And the filter capacitor C is used for finishing the rapid design of the LCL filter parameters.

The invention relates to a parameter rapid setting method suitable for an H-bridge series grid-connected inverter chain LCL filter, which comprises the following steps:

step (1): according to the limit of reactive power introduced by a filter capacitor C in the LCL filter, the value of the filter capacitor C is calculated as:

lambda in the formula (1)₁The percentage of capacitive reactive power consumed by a filter capacitor C in the LCL filter and rated active power output by the grid-connected inverter is 3% -8%;

step (2): according to the normal work of a multi-H-bridge unit series connection type single-phase grid-connected inverter chain, the side inductance L of the inverter chain in the LCL filter needs to be enabled₁And network side inductance L₂The sum of which satisfies the formula (2):

to make the inductance L on the side of the inverter chain in the LCL filter₁And network side inductance L₂The total voltage drop of the inductor does not exceed lambda% of the effective value of the network voltage, and the inductor L on the side of an inversion chain in the LCL filter is also enabled to be₁And network side inductance L₂The sum of which satisfies the formula (3):

u in formula (2) and formula (3)_dcjIs H-bridge micro-source inverter unit j (j is 1, 2, 3, 4) direct current bus voltage, Ug is effective value of fundamental component of grid voltage, Ig is effective value of grid-connected current fundamental component, fs is grid-connected point grid voltage fundamental component frequency, lambda₂The percentage of the effective value of the grid voltage is 5-10%, and the calculated inductance L at the side of the inverter chain in the LCL filter₁And network side inductance L₂The smaller of the sum is taken as an upper limit limiting value, and the larger is taken as a lower limit limiting value, so as to obtain a formula (4):

0＜L₁+L₂≤min(L₁₂,L'₁₂) (4)

the inductor L on the side of an inversion chain in the LCL filter is taken as the inductor L of the equation (4)₁And network side inductance L₂The value range of the sum;

and (3): determining the equivalent switching frequency f of the single-phase grid-connected inverter chain according to the carrier frequency of the H-bridge unit in the series connection structure_cN：

f_cN＝N×f_c(5)

In the formula (5) f_cThe carrier frequency of a single H-bridge inversion unit SPWM in a series connection type single-phase grid-connected inverter chain is adopted, and N is the number of the H-bridge inversion units in the series connection type single-phase grid-connected inverter chain;

and (4): determining the side inductance L of the inverter chain₁According to the current flowing through the side inductance L of the inverter chain₁Ripple factor limit L of current₁Minimum value, when the multi-H bridge unit series connection type single-phase grid-connected inverter chain adopts bipolar CPS-SPWM, the inverter chain side inductance L is calculated by using a formula (6)₁Lower limit value:

when the multi-H-bridge unit series connection type single-phase grid-connected inverter chain adopts the unipolar CPS-SPWM, the lower limit value of the inverter chain side inductance L1 is calculated by using the formula (7):

lambda in formula (6) or formula (7)₂Is the inverter chain side inductance current ripple coefficient, and lambda₃＝Δi_L1max/I_L1Wherein Δ i_L1maxAnd I_L1Respectively, the side inductance L of the current-through inversion chain₁The maximum instantaneous value and the effective value of the current are 15 to 30 percent in the engineering, f_cNThe equivalent switching frequency of a single-phase grid-connected inverter chain and the side inductance L of the inverter chain₁The upper limit value is determined by using a limiting condition of the voltage drop of the fundamental wave at the two ends:

λ in the formula (8)₄Is an inductance L₁The percentage of the fundamental voltage drop at the two ends and the voltage at the two ends of the capacitor C is usually 5%, so that the inductance L at the side of the inverter chain can be determined₁Value of L_1minAnd L_1maxAny positive number between, to reduce the LCL filter volume, take L_1minAnd L_1maxIs closest to L_1minA positive number of;

and (5): according to the side inductance L of the inverter chain₁And network side inductance L₂Is used to determine the inductance L₂Taking values:

in the formula (9), a is an inverter chain side inductor L₁And network side inductance L₂The ratio of values, a, is usually 1-3, L₂Finally at zero and min (L)₁₂,L'₁₂) The value between the/(1 + a) is obtained;

after the step (1) or the step (2) or the step (3) is adjusted, but before the step (4) and the step (5), the step (1) needs to ensure that LCL filter parameters meeting basic requirements can be quickly designed through the five steps, and the multi-H-bridge unit series connection type single-phase grid-connected inverter chain can output current meeting the grid-connected quality requirements of the distributed power supply by combining an active damping or passive damping method and a grid-connected current controller.

The invention has the advantages that: the LCL filter is applied to a wind-solar energy storage grid-connected power generation system with a cascade and H-bridge inversion unit series structure, the equivalent carrier frequency of an internal multi-H-bridge unit series connection type single-phase grid-connected inversion chain is high and is N times of the carrier frequency of a single H-bridge inversion unit, and N is the number of H-bridge inversion units in the series connection type single-phase grid-connected inversion chain. At present, an L-type filter and an LCL-type filter are mostly adopted at a grid-connected end of a distributed grid-connected power generation system, the suppression capacities of the L-type filter and the LCL-type filter to harmonic waves at a low frequency band are almost the same, but the suppression capacity of the L-type filter to high frequency harmonic waves at a high frequency band is much weaker than that of the LCL-type filter, namely the suppression capacity of the LCL-type filter to high frequency harmonic waves is better. The equivalent carrier frequency of the multi-H-bridge unit series connection type single-phase grid-connected inverter chain is increased by N times relative to the carrier frequency of a single H-bridge inverter unit, so that the frequency band in which the harmonic waves are mainly concentrated is correspondingly increased by N times, which indicates that the LCL type filter is more suitable for being adopted in the multi-H-bridge unit series connection type single-phase grid-connected distributed power generation system. According to the method for quickly designing the parameters of the LCL filter of the multi-H-bridge unit series connection type single-phase grid-connected inverter chain, the specific values of the parameters of the LCL filter meeting the requirements of basic conditions can be quickly determined through a fixing step. The multi-H-bridge unit series connection type single-phase grid-connected inverter chain can output current meeting the grid-connected requirement of the distributed power supply by combining an active damping method or a passive damping method and a grid-connected current controller.

Drawings

Fig. 1 is a structural diagram of a multi-H-bridge unit series connection type single-phase grid-connected inverter chain and an LCL filter system, and fig. 2 is a connection diagram of a dc side power supply of each H-bridge unit in the series connection type single-phase grid-connected inverter chain.

Detailed Description

As shown in figure 1, in a multi-H-bridge unit series connection type single-phase grid-connected inverter chain, the alternating current output sides of H-bridge micro-source inverter units (1), (2), (3) and (4) are sequentially connected in series, micro-sources are subjected to splitting/recovery operation through bypass switches ((9), (10), (11) and (12)), the H-bridge micro-source inverter units (1), (2), (3) and (4) input side direct current power supplies (5), (6), (7) and (8) are photovoltaic cell components, or direct current energy storage batteries, or an alternating current generator and an AC/DC rectifier circuit combined unit (14), or an alternating current generator, an AC/DC rectifier circuit and a direct current energy storage battery combined unit (15), or a direct current generator and a DC/DC chopper circuit combined unit (16), or a direct current generator, a DC generator, The invention discloses a DC/DC direct current chopper circuit and direct current energy storage battery combined unit (17), wherein an H bridge unit is connected in series with the output end of a single-phase grid-connected inverter chain and the left side of an LCL filter (13) in parallel, and the right side of the LCL filter (13) is connected in parallel with a power grid bus through a grid-connected switch S1.

Step (1): according to the limit of reactive power introduced by a filter capacitor C in the LCL filter, the value of the filter capacitor C is calculated as:

lambda in the formula (1)₁The percentage of capacitive reactive power consumed by a filter capacitor C in the LCL filter and rated active power output by the grid-connected inverter is 3% -8%;

step (2): according to the normal work of a multi-H-bridge unit series connection type single-phase grid-connected inverter chain, the side inductance L of the inverter chain in the LCL filter needs to be enabled₁And network side inductance L₂The sum of which satisfies the formula (2):

to make the inductance L on the side of the inverter chain in the LCL filter₁And network side inductance L₂The total voltage drop of the inductor does not exceed lambda% of the effective value of the network voltage, and the inductor L on the side of an inversion chain in the LCL filter is also enabled to be₁And network side inductance L₂The sum of which satisfies the formula (3):

a formula(2) U in the formula (3)_dcjIs H-bridge micro-source inverter unit j (j is 1, 2, 3, 4) direct current bus voltage, Ug is effective value of fundamental component of grid voltage, Ig is effective value of grid-connected current fundamental component, fs is grid-connected point grid voltage fundamental component frequency, lambda₂The percentage of the effective value of the grid voltage is 5-10%, and the calculated inductance L at the side of the inverter chain in the LCL filter₁And network side inductance L₂The smaller of the sum is taken as an upper limit limiting value, and the larger is taken as a lower limit limiting value, so as to obtain a formula (4):

0＜L₁+L₂≤min(L₁₂,L'₁₂) (4)

the inductor L on the side of an inversion chain in the LCL filter is taken as the inductor L of the equation (4)₁And network side inductance L₂The value range of the sum;

and (3): determining the equivalent switching frequency f of the single-phase grid-connected inverter chain according to the carrier frequency of the H-bridge unit in the series connection structure_cN：

f_cN＝N×f_c(5)

In the formula (5) f_cThe carrier frequency of a single H-bridge inversion unit SPWM in a series connection type single-phase grid-connected inverter chain is adopted, and N is the number of the H-bridge inversion units in the series connection type single-phase grid-connected inverter chain;

and (4): determining the side inductance L of the inverter chain₁According to the current flowing through the side inductance L of the inverter chain₁Ripple factor limit L of current₁Minimum value, when the multi-H bridge unit series connection type single-phase grid-connected inverter chain adopts bipolar CPS-SPWM, the inverter chain side inductance L is calculated by using a formula (6)₁Lower limit value:

when the multi-H-bridge unit series connection type single-phase grid-connected inverter chain adopts unipolar CPS-SPWM, the inverter chain side inductance L is calculated by using a formula (7)₁Lower limit value:

lambda in formula (6) or formula (7)₂Is the inverter chain side inductance current ripple coefficient, and lambda₃＝Δi_L1max/I_L1Wherein Δ i_L1maxAnd I_L1Respectively, the side inductance L of the current-through inversion chain₁The maximum instantaneous value and the effective value of the current are 15 to 30 percent in the engineering, f_cNThe equivalent switching frequency of a single-phase grid-connected inverter chain and the side inductance L of the inverter chain₁The upper limit value is determined by using a limiting condition of the voltage drop of the fundamental wave at the two ends:

λ in the formula (8)₄Is an inductance L₁The percentage of the fundamental voltage drop at the two ends and the voltage at the two ends of the capacitor C is usually 5%, so that the inductance L at the side of the inverter chain can be determined₁Value of L_1minAnd L_1maxAny positive number between, to reduce the LCL filter volume, take L_1minAnd L_1maxIs closest to L_1minA positive number of;

and (5): according to the side inductance L of the inverter chain₁And network side inductance L₂Is used to determine the inductance L₂Taking values:

in the formula (9), a is an inverter chain side inductor L₁And network side inductance L₂The ratio of values, a, is usually 1-3, L₂Finally at zero and min (L)₁₂,L'₁₂) And/or (1+ a).