CN113938012B - Power balance control method for two-phase staggered parallel three-level bidirectional direct current converter - Google Patents

Power balance control method for two-phase staggered parallel three-level bidirectional direct current converter Download PDF

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Publication number
CN113938012B
CN113938012B CN202111227349.5A CN202111227349A CN113938012B CN 113938012 B CN113938012 B CN 113938012B CN 202111227349 A CN202111227349 A CN 202111227349A CN 113938012 B CN113938012 B CN 113938012B
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current
switch tube
tube
switch
switching tube
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CN113938012A (en
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毕恺韬
卢禹卓
吕华阳
庄煜
张志伟
朱一昕
樊启高
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Jiangnan University
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Jiangnan University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H02M3/1584—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load with a plurality of power processing stages connected in parallel

Abstract

The invention relates to a power balance control method, in particular to a power balance control method of a two-phase staggered parallel three-level bidirectional direct current converter. It is atDetermining a switching tube S a1 Duty ratio D of (2) 1 Switch tube S b1 Duty ratio D of (2) 2 Switch tube S a4 Duty ratio D of (2) 3 Switch tube S b4 Duty ratio D of (2) 4 When using the main duty cycle D PI The voltage stabilizing control of the direct current converter can be realized; controlling duty cycle D with current balancing PI,B12 And current balance control duty ratio D PI,B34 The inter-phase inductance current deviation can be eliminated, and the power balance can be realized; equalizing duty cycle D with support capacitor voltage V Can eliminate the supporting capacitor C h1 And a supporting capacitor C h2 Voltage deviation between them. The invention can effectively realize power balance, reduce complexity and improve reliability when being applied to an energy storage system.

Description

Power balance control method for two-phase staggered parallel three-level bidirectional direct current converter
Technical Field
The invention relates to a power balance control method, in particular to a power balance control method of a two-phase staggered parallel three-level bidirectional direct current converter.
Background
Under the carbon neutralization prospect target, new energy represented by photovoltaic and wind power becomes the future dominant energy, and energy storage becomes a key technical support for solving the problems of stable grid connection and the absorption of the new energy. The energy storage system is to realize the bidirectional flow of energy between the power grid and the energy storage equipment, and the bidirectional direct current power converter is the core equipment of the system.
Compared with a two-level direct current converter, the three-level bidirectional direct current converter can reduce the voltage stress of a switching tube, and the non-isolated direct current converter has the advantages of high efficiency, low cost and small volume, so that the direct current converter can be widely applied to a high-power energy storage system. Under the high-power working condition, a staggered parallel connection mode is generally adopted to improve the system capacity; however, due to errors of component parameters and different local design structures, the problem of unbalanced inter-phase power exists under the staggered parallel working condition, so that the current stress of the switching device is increased, and the reliability of the system is affected.
At present, methods for realizing power balance of each phase are mainly divided into a droop control method and an active control method. The droop method requires adding an analog resistor to the output of each phase, and power balance is achieved by using the load regulation characteristic slope of each phase. The active control method is based on a sensor, and realizes the purpose of power balance by detecting phase current. However, the current power balancing method mainly has the following problems:
1) The droop control method cannot be considered in terms of load adjustment rate and balance performance, so that the droop control method is applicable to low-power occasions only;
2) The traditional active control method adopts a large number of current sensors, and the system has higher cost and larger volume.
Therefore, how to realize effective power balance of the direct current converter is a technical problem which needs to be solved urgently.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a power balance control method of a two-phase staggered parallel three-level bidirectional direct current converter, which can effectively realize power balance, reduce complexity and improve reliability when being applied to an energy storage system.
According to the technical scheme provided by the invention, the power balance control method of the two-phase staggered parallel three-level bidirectional direct current converter comprises a converter switch main body part, an inductance unit group and a supporting capacitor group, wherein the inductance unit group is connected with the converter switch main body part in an adapting mode, the supporting capacitor group is connected with the converter switch main body part in an adapting mode, the converter switch main body part comprises a plurality of controllable switching tubes, and the inductance unit group comprises an inductance L which is connected with the corresponding switching tube in the converter switch main body part in an adapting mode 1 Inductance L 2 Inductance L 3 Inductance L 4 The support electricityThe capacitor group comprises a supporting capacitor C h1 The method comprises the steps of carrying out a first treatment on the surface of the The power balance control method comprises the following steps:
step 1, obtaining output load voltage V out Output load voltage given reference valueAnd according to the output load voltage V out Output load voltage given reference value +.>Determining a main duty cycle D at closed loop regulation of an output voltage PI ；
Step 2, obtaining a supporting capacitor C h1 Is a supporting capacitance voltage value V h1 Support capacitor C h1 Is given a reference valueAnd according to the voltage value V of the supporting capacitor h1 A reference value is given to the supporting capacitor voltage +.>Determining a support capacitor voltage balance duty ratio D during support capacitor voltage closed-loop adjustment V ；
Step 3, configuring the working state of the direct current converter, and regarding the total current i when the direct current converter works D1 Total current i D2 Sampling; at the total current i D1 When sampling, to obtain the flowing inductance L 1 Is the sampled average current I of (1) 1 And flows through inductance L 2 Is the sampled average current I of (1) 2 The method comprises the steps of carrying out a first treatment on the surface of the At the total current i D2 Sampling to obtain the flowing inductance L 3 Is the sampled average current I of (1) 3 And flows through inductance L 4 Is the sampled average current I of (1) 4 ；
Step 4, sampling average current I 1 As a reference current value and to sample the average current I 2 Is the feedback current value to utilize the sampling average current I 1 Sampling average current I 2 Determining currentCurrent balance control duty ratio D in closed loop regulation PI,B12 ；
At the same time, the average current I will be sampled 3 As a reference current value and to sample the average current I 4 Is the feedback current value to utilize the sampling average current I 3 Sampling average current I 4 Determining a current balance control duty cycle D in closed-loop current regulation PI,B34 ；
Step 5, according to the main duty ratio D PI Duty ratio D of voltage equalization of supporting capacitor V Duty ratio D for current balance control PI,B12 Current balance control duty cycle D PI,B34 The duty ratios of all switching tubes in the inverter switch main body are configured.
The converter switch main body part comprises a switch tube S a1 Switch tube S b1 Wherein the switching tube S a1 Is a first end of a switching tube S b1 And a supporting capacitor C h1 Is connected with the first end of the switch tube S a1 Second end of (2) and switch tube S a2 Is connected with the first end of the switch tube S b1 Second end of (2) and switch tube S b2 Is connected with the first end of the switch tube S a2 Second end of (2) and switch tube S a3 Is connected with the first end of the switch tube S b2 Second end of (a) and switching tube S b3 Is connected with the first end of the switch tube S a3 Second end of (2) and switch tube S a4 Is connected with the first end of the switch tube S b3 Second end of (2) and switch tube S b4 Is connected with the first end of the switch tube S a4 Second end of (S) switch tube b4 Second end of (C) and supporting capacitor C in the supporting capacitor group h2 Is connected with the second end of the first connecting piece;
support capacitor C h2 Is connected with the supporting capacitor C h1 Second end of (S) switch tube a2 Second end of (S) switch tube a3 Is a first end of a switching tube S b2 Second end of (a) and switching tube S b3 Is a first end of (2);
switch tube S a1 And a switch tube S a2 Complementary conduction and switch tube S a3 And a switch tube S a4 Complementary conduction and switch tube S a1 Carrier and switch of (a)Tube S a4 Is 180 deg. different from the carrier wave of (a); switch tube S b1 And a switch tube S b2 Complementary conduction and switch tube S b3 And a switch tube S b4 Complementary conduction and switch tube S b1 Carrier wave of (a) and switching tube S b4 Is 180 deg. different from the carrier wave of (c).
The inductance L 1 One end of (2) is connected with a switch tube S a1 Second end of (a) and switching tube S a2 Is connected with the first end of the inductor L 2 One end of (2) is connected with a switch tube S b1 Second end of (a) and switching tube S b2 Is connected with the first end of the inductor L 3 One end of (2) is connected with a switch tube S a3 Second end of (a) and switching tube S a4 Is connected with the first end of the inductor L 4 One end of (2) is connected with a switch tube S b3 Second end of (a) and switching tube S b4 Is connected to the first end of the housing;
inductance L 1 Is connected to the other end of the inductor L 2 And the other end of the filter capacitor C L One end of the filter capacitor C is connected with L And the other end of (2) is connected with inductance L 3 Is connected to the other end of the inductor L 4 Is connected with the other end of the connecting rod.
In step 1, the output load voltage V is obtained out Output load voltage given reference valueAfter that, by giving the output load voltage a reference value +.>And output load voltage V out PI operation is carried out on the difference value to obtain a main duty ratio D during the closed-loop regulation of the output voltage PI 。
In step 2, the supporting capacitor C is obtained h1 Is a supporting capacitance voltage value V h1 The support capacitor C h1 Is given a reference valueAfter that, by giving the reference value +.>And the voltage value V of the supporting capacitor h1 PI operation is carried out on the difference value to obtain the voltage balance duty ratio D of the supporting capacitor V 。
By supporting the capacitor C h1 Is a first end of a switching tube S a1 Is connected with the first end of the switch tube S b2 The current of the first end combination part is sampled to be capable of measuring the total current i D1 Sampling; by means of a pair of supporting capacitors C h2 Second end of (S) switch tube a4 Second end of (a) and switching tube S b4 The current of the second end combination part is sampled to be capable of carrying out the total current i D2 Sampling.
For the total current i D1 During sampling, a switching tube S is configured a1 On and switch tube S b1 Off, then sampling the average current I 1 The method comprises the following steps: i 1 ＝<i L1 > TS1 Wherein TS1 is a switch tube S a1 Is a switching period of (a);
for the total current i D1 During sampling, a switching tube S is configured a1 Switch-off and switch tube S b1 On, the average current I is sampled 2 The method comprises the following steps: i 2 ＝<i L2 > TS2 Wherein TS2 is a switch tube S b1 Is provided.
In step 4, the average current I is calculated 1 And sample average current I 2 And average current I for the sample 1 And sample average current I 2 PI operation is carried out on the difference value of the current to obtain the current balance control duty ratio D during the current closed-loop adjustment PI,B12 。
In step 4, a sampled average current I is calculated 3 And sample average current I 4 Difference between them, and average current I for the sample 3 And sample average current I 4 PI operation is carried out on the difference value to obtain a current balance control duty ratio D during current closed-loop adjustment PI,B34 。
In the step 5, the duty ratio of the corresponding switching tube in the converter switch main body part is:
wherein D is 1 Is a switching tube S a1 Duty cycle of D 2 Is a switching tube S b1 Duty cycle of D 3 Is a switching tube S a4 Duty cycle of D 4 Is a switching tube S b4 Is a duty cycle of (c).
The invention has the advantages that: in determining the switching tube S a1 Duty ratio D of (2) 1 Switch tube S b1 Duty ratio D of (2) 2 Switch tube S a4 Duty ratio D of (2) 3 Switch tube S b4 Duty ratio D of (2) 4 When using the main duty cycle D PI The voltage stabilizing control of the direct current converter can be realized; controlling duty cycle D with current balancing PI,B12 And current balance control duty ratio D PI,B34 The inter-phase inductance current deviation can be eliminated, and the power balance can be realized; equalizing duty cycle D with support capacitor voltage V Can eliminate the supporting capacitor C h1 And a supporting capacitor C h2 Voltage deviation between them.
By at least one of the total currents i D1 Sampling to obtain the flowing inductance L 1 Is the sampled average current I of (1) 1 And flows through inductance L 2 Is the sampled average current I of (1) 2 The method comprises the steps of carrying out a first treatment on the surface of the For the total current i D2 Sampling to obtain the flowing inductance L 3 Is the sampled average current I of (1) 3 And flows through inductance L 4 Is the sampled average current I of (1) 4 Thus, the use of the current sensor can be reduced, and the volume and cost of the system can be further reduced. Determining the main duty cycle D PI Duty ratio D of voltage equalization of supporting capacitor V Duty ratio D for current balance control PI,B12 Current balance control duty cycle D PI,B34 The processes of the system are independent of each other and do not affect each other, so that the safety of the system operation is enhanced.
Drawings
Fig. 1 is a system block diagram of the present invention.
Fig. 2 is a schematic diagram of the phase current and the total current corresponding to the duty cycle according to the present invention.
FIG. 3 is a schematic diagram showing another correspondence relationship between phase current and total current and duty cycle according to the present invention.
Reference numerals illustrate: a 1-first current closed-loop regulator, a 2-first voltage closed-loop regulator, a 3-first sampling strategy module, a 4-second voltage closed-loop regulator, a 5-second current closed-loop regulator, and a 6-second sampling strategy module.
Detailed Description
The invention will be further described with reference to the following specific drawings and examples.
As shown in fig. 1: in order to effectively realize power balance, reduce complexity and improve reliability when being applied to an energy storage system, the power balance control method of the two-phase staggered parallel three-level bidirectional direct current converter comprises a converter switch main body part, an inductance unit group and a supporting capacitor group, wherein the inductance unit group is connected with the converter switch main body part in an adapting way, the supporting capacitor group is connected with the converter switch main body part in an adapting way, the converter switch main body part comprises a plurality of controllable switching tubes, and the inductance unit group comprises an inductance L which is connected with a corresponding switching tube in the converter switch main body part in an adapting way 1 Inductance L 2 Inductance L 3 Inductance L 4 The supporting capacitor group comprises a supporting capacitor C h1 ；
In an embodiment of the present invention, the converter switch main body includes a switch tube S a1 Switch tube S b1 Wherein the switching tube S a1 Is a first end of a switching tube S b1 And a supporting capacitor C h1 Is connected with the first end of the switch tube S a1 Second end of (2) and switch tube S a2 Is connected with the first end of the switch tube S b1 Second end of (2) and switch tube S b2 Is connected with the first end of the switch tube S a2 Second end of (2) and switch tube S a3 Is connected with the first end of the switch tube S b2 Second end of (a) and switching tube S b3 Is connected with the first end of the switch tube S a3 Second end of (2) and switch tube S a4 Is connected with the first end of the switch tube S b3 Second end of (2) and switch tube S b4 Is connected with the first end of the switch tube S a4 Second end of (S) switch tube b4 Second end of (2) and support electricitySupport capacitor C in capacitor bank h2 Is connected with the second end of the first connecting piece;
support capacitor C h2 Is connected with the supporting capacitor C h1 Second end of (S) switch tube a2 Second end of (S) switch tube a3 Is a first end of a switching tube S b2 Second end of (a) and switching tube S b3 Is a first end of (2);
switch tube S a1 And a switch tube S a2 Complementary conduction and switch tube S a3 And a switch tube S a4 Complementary conduction and switch tube S a1 Carrier wave of (a) and switching tube S a4 Is 180 deg. different from the carrier wave of (a); switch tube S b1 And a switch tube S b2 Complementary conduction and switch tube S b3 And a switch tube S b4 Complementary conduction and switch tube S b1 Carrier wave of (a) and switching tube S b4 Is 180 deg. different from the carrier wave of (c).
Specifically, a switching tube S a1 Switch tube S a2 Switch tube S a3 Switch tube S a4 Switch tube S b1 Switch tube S b2 Switch tube S b3 Switch tube S b4 The conventional controllable switch tube can be adopted, for example, a IGBT (Insulated Gate Bipolar Transistor) device or a Metal-Oxide-Semiconductor Field-Effect Transistor device can be adopted, and specific types can be selected according to actual needs, and are not repeated here. The first end of the switching tube is a drain end or a source end, the second end of the switching tube is a source end or a drain end, the switching tube is specifically related to the type selected by the switching tube, the switching tube can be controlled to be turned on or off by loading the gate end voltage on the gate end of the switching tube, and the switching tube is specifically consistent with the prior art, and is well known to those skilled in the art and is not repeated herein.
Generally, in the switching tube S a1 Switch tube S a2 Switch tube S a3 Switch tube S a4 Switch tube S b1 Switch tube S b2 Switch tube S b3 Switch tube S b4 The upper parts are connected in anti-parallel with a freewheeling diode to meet the requirement that the DC converter works in different states and freewheels by using the freewheeling diode, and particularly, a switching tube and the freewheels connected in anti-parallel with the switching tube are used for currentThe flow-through mode is consistent with the working process of the existing dc converter, and is well known to those skilled in the art, and will not be described here.
The supporting capacitor group comprises a supporting capacitor C h1 Support capacitor C h2 . When the inductance unit group is connected with the main body part of the converter switch in an adapting way, the inductance L 1 One end of (2) is connected with a switch tube S a1 Second end of (a) and switching tube S a2 Is connected with the first end of the inductor L 2 One end of (2) is connected with a switch tube S b1 Second end of (a) and switching tube S b2 Is connected with the first end of the inductor L 3 One end of (2) is connected with a switch tube S a3 Second end of (a) and switching tube S a4 Is connected with the first end of the inductor L 4 One end of (2) is connected with a switch tube S b3 Second end of (a) and switching tube S b4 Is connected to the first end of the housing;
inductance L 1 Is connected to the other end of the inductor L 2 And the other end of the filter capacitor C L One end of the filter capacitor C is connected with L And the other end of (2) is connected with inductance L 3 Is connected to the other end of the inductor L 4 Is connected with the other end of the connecting rod.
Specifically, in FIG. 1, r L1 Is the inductance L 1 Equivalent resistance of r L2 Is the inductance L 2 Equivalent resistance of r L3 Is the inductance L 3 Equivalent resistance of r L4 Is the inductance L 4 Is a constant current source. In particular, the DC converter has a terminal voltage V L Terminal voltage V H Wherein the terminal voltage V L Is the filter capacitor C L Corresponding terminal voltage, terminal voltage V H To support the voltage corresponding to the capacitor set, the terminal voltage V L Terminal voltage V H The details of which are related to the operation mode of the dc converter, are well known to those skilled in the art, and will not be described herein.
In the embodiment of the invention, the power balance control method comprises the following steps:
step 1, obtaining output load voltage V out Output load voltage given reference valueAnd according to the output load voltage V out Output load voltage given reference value +.>Determining a main duty cycle D at closed loop regulation of an output voltage PI ；
Specifically, the output load voltage V can be obtained by voltage sampling or the like out From the above description, it is apparent that the load voltage V is output out In general, according to the common-mode dependence of DC converters, i.e. the output load voltage V out Is the terminal voltage V L Or terminal voltage V H Obtaining output load voltage V out The specific process of (2) may be selected according to actual needs, and will not be described herein. Depending on the mode of operation of the dc converter and the condition of the load of said dc converter, a given reference value of the output load voltage may be configuredOutput load voltage given reference value->The specific given situation of (a) may be related to an actual application scenario, etc., and is well known to those skilled in the art, and will not be described herein.
In particular, when the output load voltage V is obtained out Output load voltage given reference valueAfter that, by giving the output load voltage a reference value +.>And output load voltage V out PI operation is carried out on the difference value to obtain a main duty ratio D during the closed-loop regulation of the output voltage PI I.e. +.>Wherein K is P 、K I The ratio coefficient and the integral coefficient are respectively the ratio coefficient K P Integral coefficient K I Is generally an empirical value or is determined by multiple adjustments, as is well known to those skilled in the art, and is not described in detail herein. In the embodiment of the invention, the main duty ratio D is regulated in a closed loop through the output voltage PI When the duty ratio control is performed, the method can be used for realizing the voltage stabilizing control of the output of the direct current converter.
Step 2, obtaining a supporting capacitor C h1 Is a supporting capacitance voltage value V h1 Support capacitor C h1 Is given a reference valueAnd according to the voltage value V of the supporting capacitor h1 A reference value is given to the supporting capacitor voltage +.>Determining a support capacitor voltage balance duty ratio D during support capacitor voltage closed-loop adjustment v ；
In specific implementation, the supporting capacitor C can be obtained by the conventional common voltage sampling technique means h1 Is a supporting capacitance voltage value V h1 Support capacitor C h1 Is given a reference valueTypically half the input voltage of the dc converter; of course, in practical application, the supporting capacitor C can be selected h2 Is a supporting capacitance voltage value V h2 The specific selection may be according to actual needs, and will not be described herein.
In the embodiment of the invention, the supporting capacitor C is obtained h1 Is a supporting capacitance voltage value V h1 The support capacitor C h1 Is given a reference valueAfter that, by giving the reference value +.>And the voltage value V of the supporting capacitor h1 PI operation is carried out on the difference value to obtain the voltage balance duty ratio D of the supporting capacitor V The method comprises the steps of carrying out a first treatment on the surface of the I.e. there is->Wherein K is PV 、K IV Respectively a proportional coefficient and an integral coefficient, s represents integral operation, and the coefficient is K PV Integral coefficient K IV Is generally an empirical value or is determined by multiple adjustments, as is well known to those skilled in the art, and is not described in detail herein. Specifically, the duty cycle D is balanced by the support capacitance voltage V Can eliminate the supporting capacitor C h1 And a supporting capacitor C h2 Voltage deviation between them.
Step 3, configuring the working state of the direct current converter, and regarding the total current i when the direct current converter works D1 Total current i D2 Sampling; at the total current i D1 When sampling, to obtain the flowing inductance L 1 Is the sampled average current I of (1) 1 And flows through inductance L 2 Is the sampled average current I of (1) 2 The method comprises the steps of carrying out a first treatment on the surface of the At the total current i D2 Sampling to obtain the flowing inductance L 3 Is the sampled average current I of (1) 3 And flows through inductance L 4 Is the sampled average current I of (1) 4 ；
Specifically, by supporting the capacitor C h1 Is a first end of a switching tube S a1 Is connected with the first end of the switch tube S b2 The current of the first end combination part is sampled to be capable of measuring the total current i D1 Sampling; by means of a pair of supporting capacitors C h2 Second end of (S) switch tube a4 Second end of (a) and switching tube S b4 The current of the second end combination part is sampled to be capable of carrying out the total current i D2 Sampling.
In practice, to the total current i D1 Sampling is taken as an example, and according to the relation of the duty ratio of the equivalent circuit, the current of each phase and the total current i in the equivalent circuit can be obtained D1 The correspondence with the duty cycle is shown in fig. 2 and 3. In fig. 2 and 3, D 1 Is a switching tube S a1 Duty cycle of D 2 Is a switching tube S b1 Duty cycle, I 1 I.e. the flow-through inductance L 1 Is the average current of the samples I 2 I.e. the flow-through inductance L 2 Is provided for the average current.
In fig. 2 and 3, i L1 And i L2 Respectively represent inductance L 1 And L 2 Is set in the above-described range). Due to the switching tube S a1 And a switch tube S b1 180 deg. out of phase, interleaved sampling is required. At the triangular wave V tri1 For the total current i at zero point D1 Sampling is performed since at t 2 ～t 3 Switch tube S in time period a1 On, switch tube S b1 Off, so the total current i D1 And current i L1 At this time, the average current I is sampled 1 Can be expressed as:
wherein TS1 is a switch tube S a1 Is used for the switching cycle of (a),<> Ts representing the current i L1 Is a periodic average value of (2); switch tube S a1 The switching period TS1 of (1) refers to the switching tube S a1 Is switched on and switched off by the switching tube S a1 The specific case of the switching period TS1 is well known to those skilled in the art, and will not be described here.
Similarly, at t 4 ～t 5 Time period switching tube S b1 On, switch tube S a1 Turn off, total current i D1 And current i L2 Equal in value, then at triangular wave V tri2 Is sampled at zero point to obtain the total current i D1 The value of (2) and i L2 Are equal. Current I 2 Can be expressed as:wherein TS2 is a switch tube S b1 Is provided.
As the characteristics of the dc converter can be seen,<i L3 > Ts and<i L4 > Ts also by the method ofTotal current i D2 Phase-shifting sampling to obtain sampling average current I 3 And sampling the average current I 4 . In specific implementation, the controller is triggered to sample according to the trough of the triangular wave, and under the phase-shifting control mode, the trough of the two triangular waves is contained in a single period, so that the relation of the sampling frequency to the switching frequency is as follows: f (f) samp ＝2f s The method comprises the steps of carrying out a first treatment on the surface of the Wherein f samp For sampling frequency f s Is the switching frequency of the switching tube.
In fig. 1, the sampled average current I is obtained by the first sampling strategy module 3 1 Sampling average current I 2 The method comprises the steps of carrying out a first treatment on the surface of the At the same time, the sampling average current I can be obtained through the second sampling strategy module 6 3 Sampling average current I 4 . The first sampling strategy module 3 and the second sampling strategy module 6 are generally realized through FPGA (Field Programmable Gate Array) programming, triangular waves in fig. 2 and 3 are generated by an FPGA, the triangular waves are carrier waves, the specific waveform of the generated triangular waves and the zero point of the triangular waves can be determined by the FPGA, and the conditions are consistent with the prior art, and are well known to those skilled in the art and are not repeated herein.
To sum up, the mode of the invention is adopted to determine the sampling average current I 1 Average current I is sampled 2 Average current I is sampled 3 Sampling average current I 4 And in addition, the use of the current sensor can be effectively reduced, and the volume and the cost are reduced. Of course, in practice, the sampled average current I may be obtained in other ways 1 Average current I is sampled 2 Average current I is sampled 3 Sampling average current I 4 The specific sampling or measuring mode can be selected according to actual needs, and will not be described herein.
Step 4, sampling average current I 1 As a reference current value and to sample the average current I 2 Is the feedback current value to utilize the sampling average current I 1 Sampling average current I 2 Determining a current balance control duty cycle D in closed-loop current regulation PI,B12 ；
At the same time, the average current I will be sampled 3 As a referenceCurrent value and average current I will be sampled 4 Is the feedback current value to utilize the sampling average current I 3 Sampling average current I 4 Determining a current balance control duty cycle D in closed-loop current regulation PI,B34 ；
In particular, the average current I is calculated 1 And sample average current I 2 And average current I for the sample 1 And sample average current I 2 PI operation is carried out on the difference value of the current to obtain the current balance control duty ratio D during the current closed-loop adjustment PI,B12 I.e.Wherein K is P,B1 、K I,B1 Respectively a proportional coefficient and an integral coefficient, a coefficient K P,B1 Integral coefficient K I,B1 Is generally an empirical value or is determined by multiple adjustments, as is well known to those skilled in the art, and is not described in detail herein.
Furthermore, a sampled average current I is calculated 3 And sample average current I 4 Difference between them, and average current I for the sample 3 And sample average current I 4 PI operation is carried out on the difference value to obtain a current balance control duty ratio D during current closed-loop adjustment PI,B34 I.e.Wherein K is P,B2 、K I,B2 Respectively a proportional coefficient and an integral coefficient, a coefficient K P,B2 Integral coefficient K I,B2 Is generally an empirical value or is determined by multiple adjustments, as is well known to those skilled in the art, and is not described in detail herein.
In order to achieve the above object, it is generally necessary to provide a first current closed-loop regulator 1, a first voltage closed-loop regulator 2, a second voltage closed-loop regulator 4, and a second current closed-loop regulator 5 in the FPGA, that is, the average current I can be sampled by the first current closed-loop regulator 1 1 And sample average current I 2 Performing PI operation on the difference value of the two values; by a first electricityThe closed-loop regulator 2 gives a reference value to the output load voltageAnd output load voltage V out And performing PI operation on the difference value. The reference value is given to the support capacitor voltage by the second voltage closed-loop regulator 4>And the voltage value V of the supporting capacitor h1 And performing PI operation on the difference value. The sampled average current I is regulated by a second current closed loop regulator 5 3 And sample average current I 4 And performing PI operation on the difference value.
Step 5, according to the main duty ratio D PI Duty ratio D of voltage equalization of supporting capacitor V Duty ratio D for current balance control PI,B12 Current balance control duty cycle D PI,B34 The duty ratios of all switching tubes in the inverter switch main body are configured.
Specifically, the duty ratio of the corresponding switching tube in the converter switch main body part is as follows:
wherein D is 1 Is a switching tube S a1 Duty cycle of D 2 Is a switching tube S b1 Duty cycle of D 3 Is a switching tube S a4 Duty cycle of D 4 Is a switching tube S b4 Is a duty cycle of (c).
In the embodiment of the present invention, due to the switch tube S a1 Switch tube S a2 Switch tube S a3 Switch tube S a4 Switch tube S b1 Switch tube S b2 Switch tube S b3 Switch tube S b4 The conduction relation between the two is known, and the switching tube S is determined a1 Duty ratio D of (2) 1 Switch tube S b1 Duty ratio D of (2) 2 Switch tube S b3 Duty ratio D of (2) 3 Switch tube S b4 Duty ratio D of (2) 4 In the time-course of which the first and second contact surfaces,i.e. to determine the switching tube S simultaneously a2 Switch tube S a3 Switch tube S b2 Switch tube S b3 The corresponding duty cycle is well known to those skilled in the art, and will not be described in detail herein. According to the switching tube S a1 Switch tube S b1 Switch tube S a2 Switch tube S a3 Switch tube S a4 Switch tube S b1 Switch tube S b2 Switch tube S b3 Switch tube S b4 The corresponding duty cycle can specifically control or configure the working state of the whole direct current converter, which is well known in the art, and is not described herein.
In the embodiment of the invention, the switching tube S is determined a1 Duty ratio D of (2) 1 Switch tube S b1 Duty ratio D of (2) 2 Is a switching tube S a4 Duty ratio D of (2) 3 Switch tube S b4 Duty ratio D of (2) 4 When using the main duty cycle D PI The voltage stabilizing control of the direct current converter can be realized; controlling duty cycle D with current balancing PI,B12 And current balance control duty ratio D PI,B34 The inter-phase inductance current deviation can be eliminated, and the power balance can be realized; equalizing duty cycle D with support capacitor voltage v Can eliminate the supporting capacitor C h1 And a supporting capacitor C h2 Voltage deviation between them.
By at least one of the total currents i D1 Sampling to obtain the flowing inductance L 1 Is the sampled average current I of (1) 1 And flows through inductance L 2 Is the sampled average current I of (1) 2 The method comprises the steps of carrying out a first treatment on the surface of the For the total current i D2 Sampling to obtain the flowing inductance L 3 Is the sampled average current I of (1) 3 And flows through inductance L 4 Is the sampled average current I of (1) 4 Thus, the use of the current sensor can be reduced, and the volume and cost of the system can be further reduced. Determining the main duty cycle D PI Duty ratio D of voltage equalization of supporting capacitor V Duty ratio D for current balance control PI,B12 Current balance control duty cycle D PI,B34 The processes of the two are independent of each other and do not affect each other, so that the working safety is enhanced.

Claims (5)

1. The power balance control method of the two-phase staggered parallel three-level bidirectional direct current converter comprises a converter switch main body part, an inductance unit group and a supporting capacitor group, wherein the inductance unit group is connected with the converter switch main body part in an adapting mode, the supporting capacitor group is connected with the converter switch main body part in an adapting mode, the converter switch main body part comprises a plurality of controllable switching tubes, and the inductance unit group comprises an inductance L which is connected with the corresponding switching tube in the converter switch main body part in an adapting mode 1 Inductance L 2 Inductance L 3 Inductance L 4 The supporting capacitor group comprises a supporting capacitor C h1 And C h2 The method comprises the steps of carrying out a first treatment on the surface of the The power balance control method is characterized by comprising the following steps of:
step 1, obtaining output load voltage V out Output load voltage given reference valueAnd according to the output load voltage V out Output load voltage given reference value +.>Determining a main duty cycle D at closed loop regulation of an output voltage PI ；
Step 2, obtaining a supporting capacitor C h1 Is a supporting capacitance voltage value V h1 Support capacitor C h1 Is given a reference valueAnd according to the voltage value V of the supporting capacitor h1 A reference value is given to the supporting capacitor voltage +.>Determining a support capacitor voltage balance duty ratio D during support capacitor voltage closed-loop adjustment V ；
Step 3, configuring the working state of the direct current converter, and regarding the total current i when the direct current converter works D1 Total current i D2 Sampling; for the total current i D1 Sampling to obtain the flowing inductance L 1 Is the sampled average current I of (1) 1 And flows through inductance L 2 Is the sampled average current I of (1) 2 The method comprises the steps of carrying out a first treatment on the surface of the For the total current i D2 Sampling to obtain the flowing inductance L 3 Is the sampled average current I of (1) 3 And flows through inductance L 4 Is the sampled average current I of (1) 4 ；
Step 4, sampling average current I 1 As a reference current value and to sample the average current I 2 Is the feedback current value to utilize the sampling average current I 1 Sampling average current I 2 Determining a current balance control duty cycle D in closed-loop current regulation PI,B12 ；
At the same time, the average current I will be sampled 3 As a reference current value and to sample the average current I 4 Is the feedback current value to utilize the sampling average current I 3 Sampling average current I 4 Determining a current balance control duty cycle D in closed-loop current regulation PI,B34 ；
Step 5, according to the main duty ratio D PI Duty ratio D of voltage equalization of supporting capacitor V Duty ratio D for current balance control PI,B12 Current balance control duty cycle D PI,B34 The duty ratio of all switching tubes in the main body part of the converter switch is configured;
the converter switch main body part comprises a switch tube S a1 To a switching tube S a4 Switch tube S b1 To a switching tube S b4 Wherein the switching tube S a1 Is a first end of a switching tube S b1 And a supporting capacitor C h1 Is connected with the first end of the switch tube S a1 Second end of (2) and switch tube S a2 Is connected with the first end of the switch tube S b11 Second end of (2) and switch tube S b2 Is connected with the first end of the switch tube S a2 Second end of (2) and switch tube S a3 Is connected with the first end of the switch tube S b2 Second end of (a) and switching tube S b3 Is connected with the first end of the switch tube S a3 Second end of (2) and switch tube S a4 Is connected with the first end of the switch tube S b3 Is connected to the second end of (2)Switch tube S b4 Is connected with the first end of the switch tube S a4 Second end of (S) switch tube b4 Second end of (C) and supporting capacitor C in the supporting capacitor group h2 Is connected with the second end of the first connecting piece; support capacitor C h22 Is connected with the supporting capacitor C h1 Second end of (S) switch tube a2 Second end of (S) switch tube a3 Is a first end of a switching tube S b2 Second end of (a) and switching tube S b3 Is a first end of (2);
switch tube S a1 And a switch tube S a2 Complementary conduction and switch tube S a3 And a switch tube S a4 Complementary conduction and switch tube S a1 Carrier wave of (a) and switching tube S a4 Is 180 deg. different from the carrier wave of (a); switch tube S b1 And a switch tube S b2 Complementary conduction and switch tube S b3 And a switch tube S b4 Complementary conduction and switch tube S b1 Carrier wave of (a) and switching tube S b4 Is 180 deg. different from the carrier wave of (a);
the inductance L 1 One end of (2) is connected with a switch tube S a1 Second end of (a) and switching tube S a2 Is connected with the first end of the inductor L 2 One end of (2) is connected with a switch tube S b1 Second end of (a) and switching tube S b2 Is connected with the first end of the inductor L 33 One end of (2) is connected with a switch tube S a3 Second end of (a) and switching tube S a4 Is connected with the first end of the inductor L 4 One end of (2) is connected with a switch tube S b3 Second end of (a) and switching tube S b4 Is connected to the first end of the housing;
inductance L 1 Is connected to the other end of the inductor L 2 And the other end of the filter capacitor C L One end of the filter capacitor C is connected with L And the other end of (2) is connected with inductance L 3 Is connected to the other end of the inductor L 4 Is connected with the other end of the connecting rod;
by supporting the capacitor C h1 Is a first end of a switching tube S a1 Is connected with the first end of the switch tube S b1 The current of the first end combination part is sampled to be capable of measuring the total current i D1 Sampling; by means of a pair of supporting capacitors C h2 Second end of (S) switch tube a4 Second end of (a) and switching tube S b4 The current of the second end combination part is sampled to be capable of carrying out the total current i DD2 Sampling;
in the step 5, the duty ratio of the corresponding switching tube in the converter switch main body part is:
wherein D is 1 Is a switching tube S a1 Duty cycle of D 2 Is a switching tube S b1 Duty cycle of D 3 Is a switching tube S a4 Duty cycle of D 4 Is a switching tube S b4 Is a duty cycle of (c).
2. The power equalization control method of two-phase interleaved parallel three-level bi-directional DC converter of claim 1 wherein in step 1, the output load voltage V is obtained out Output load voltage given reference valueAfter that, by giving the output load voltage a reference value +.>And output load voltage V out PI operation is carried out on the difference value to obtain a main duty ratio D during the closed-loop regulation of the output voltage PI 。
3. The power equalization control method of a two-phase interleaved parallel three-level bi-directional DC converter of claim 1, wherein in step 2, a supporting capacitor C is obtained h1 Is a supporting capacitance voltage value V h1 The support capacitor C h1 Is given a reference valueAfter that, by giving the reference value +.>And the voltage value V of the supporting capacitor h1 PI operation is carried out on the difference value to obtain the voltage balance duty ratio D of the supporting capacitor V 。
4. The power equalization control method of a two-phase interleaved parallel three-level bidirectional dc converter according to claim 1, wherein: in step 4, a sampled average current I is calculated 1 And sample average current I 2 And average current I for the sample 1 And sample average current I 2 PI operation is carried out on the difference value of the current to obtain the current balance control duty ratio D during the current closed-loop adjustment PI,B12 。
5. The power equalization control method of a two-phase interleaved parallel three-level bidirectional dc converter according to claim 1, wherein: in step 4, a sampled average current I is calculated 3 And sample average current I 4 Difference between them, and average current I for the sample 3 And sample average current I 4 PI operation is carried out on the difference value to obtain a current balance control duty ratio D during current closed-loop adjustment PI,B34 。
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CN104506040A (en) * 2014-09-22 2015-04-08 北京理工大学 Dual-PWM and phase-shifting control method with the same duty ratio
CN109728717A (en) * 2018-12-29 2019-05-07 国网天津市电力公司电力科学研究院 Based on direct current micro-grid system crisscross parallel two-way DC converter control method
CN110868068A (en) * 2019-11-28 2020-03-06 重庆理工大学 Multiphase staggered parallel direct current converter and current sharing control method thereof

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104467005A (en) * 2014-01-02 2015-03-25 艾伏新能源科技(上海)股份有限公司 T-type three-level three-phase four-bridge-arm grid-connected photovoltaic power generation system and control method thereof
CN104506040A (en) * 2014-09-22 2015-04-08 北京理工大学 Dual-PWM and phase-shifting control method with the same duty ratio
CN109728717A (en) * 2018-12-29 2019-05-07 国网天津市电力公司电力科学研究院 Based on direct current micro-grid system crisscross parallel two-way DC converter control method
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