Control method and device of Z-source bidirectional AC / DC converter

Abstract

The invention discloses a control method and device for a Z-source bidirectional AC / DC converter in the technical field of flexible AC / DC interconnection, and the method comprises the steps: obtaining a DC side voltage # imgabs0 # of the converter, and calculating a current reference value # imgabs1 # based on a PI regulator; obtaining an alternating current side phase of the converter, and obtaining current reference values # imgabs3 # and # imgabs4 # through reverse Park conversion by combining the current reference value # imgabs2 #; obtaining an alternating current side current of the converter, and obtaining a current # imgabs 5 # and a current # imgabs 6 # through Clarke conversion; based on the current reference value # imgabs7 # and the current reference value # imgabs8 # and the current # imgabs9 # and the current # imgabs10 #, the voltage # imgabs11 # and the voltage # imgabs12 # are calculated through a fuzzy PR controller; based on the voltage # imgabs13 # and the voltage # imgabs14 #, a switching control signal is generated through an SVPWM modulation module, and on-off control is carried out on a switching tube of the converter through the switching control signal; according to the Z-source bidirectional AC / DC converter, the Z-source bidirectional AC / DC converter is constructed through the advantages brought by the unique topological structure of the Z-source impedance network. Meanwhile, fuzzy control and PR control are combined, a parameter self-tuning fuzzy PR control system is constructed, and high-precision control is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible AC / DC interconnection, and in particular to a control method and device for a Z-source bidirectional AC / DC converter. Background Art

[0002] As the last link from electricity production to users, the distribution network plays an extremely important role in the power system. In recent years, the large-scale access of various distributed energy sources (DG) and new loads such as electric vehicles is profoundly changing the structure and operation characteristics of the traditional distribution network. The existing distribution network has problems such as unbalanced distribution line load, increased short-circuit current due to ring closing, uncontrollable power flow, and large inrush current.

[0003] Flexible interconnection technology combines power electronics flexible control technology with distribution network optimization design, and can provide fast and accurate active and reactive power control, power failure support and power quality management functions between distribution network lines and between substations, providing an effective technical means to tap the power supply potential of distribution networks and improve power supply reliability. At the same time, the DC side of the flexible interconnection system can be more flexibly connected to distributed power sources and charging facilities, data centers and other DC sources and loads. The DC system based on DC voltage control can achieve photovoltaic grid connection, local source and load balance, etc. more quickly and efficiently, and there are no harmonics, terminal overvoltage and three-phase imbalance and other power quality problems. Therefore, the multi-level access of large-scale distributed power sources by flexible interconnection of low-voltage distribution networks can maximize the energy supply potential of distributed renewable energy, effectively improve the reliability, economy and environmental protection of the overall operation of the distribution system, and is an important technical route to solve the problem of high-proportion consumption of distributed power sources in distribution networks.

[0004] Conventional flexible converters are based on two traditional converter topologies: voltage source (or voltage-fed) and current source (or current-fed) converters (or inverters, depending on the direction of power flow). Voltage source converters have the following drawbacks: (1) The AC load must be inductive or the AC source must be connected in series with an inductor for the voltage source converter to work. (2) The AC output voltage is limited to being lower than but not higher than the DC bus voltage, or the DC bus voltage can only be higher than the AC input voltage. (3) The upper and lower devices of each bridge arm cannot be turned on at the same time, otherwise a direct short circuit will occur, damaging the device. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a control method and device for a Z-source bidirectional AC / DC converter to solve the defects of the voltage source converter mentioned in the background technology.

[0006] To achieve the above object, the present invention is implemented by adopting the following technical solutions: In a first aspect, the present invention provides a control method for a Z-source bidirectional AC / DC converter, comprising: Get the DC side voltage of the converter , and calculate the current reference value based on the PI regulator , the current reference value is the reference value of the d-axis component of the AC side current of the converter; Get the AC side phase of the converter and combine it with the current reference value The current reference value is obtained by inverse Park transformation and , the current reference value and is the current reference value of Axis component; Obtain the AC side current of the converter and obtain the current through Clarke transformation and , the current and is the AC side current of the converter Axis component; Based on the current reference value and and the current and , the voltage is calculated by the fuzzy PR controller and , the voltage and is the AC side voltage of the converter target values ​​of axis components; Based on the voltage and , a switch control signal is generated through the SVPWM modulation module, and the switch tube of the converter is controlled on and off through the switch control signal.

[0007] Optionally, the Z-source bidirectional AC / DC converter includes a Z-source impedance network and a three-phase inverter, the Z-source impedance network includes a capacitor C1, a capacitor C2, an inductor L1 and an inductor L2, one end of the capacitor C1 and the inductor L1 are both connected to the positive electrode of the DC voltage source, one end of the capacitor C2 and the inductor L2 are both connected to the negative electrode of the DC voltage source, the other end of the capacitor C1 and the inductor L2 are both connected to the positive electrode of the DC side of the three-phase inverter, and the other end of the capacitor C2 and the inductor L1 are both connected to the negative electrode of the DC side of the three-phase inverter; the three-phase inverter includes three bridge arms, each of the bridge arms includes two switching tubes connected in series, and the common end of the two switching tubes is recorded as the midpoint of the bridge arm; the midpoints of the three bridge arms are respectively connected to the AC voltage source.

[0008] Optionally, the Z-source bidirectional AC / DC converter further includes a capacitor C0 connected in parallel to the DC voltage source and a line resistor R and a filter inductor L connected in series between the three-phase inverter and the AC voltage source.

[0009] Optionally, the current reference value is calculated based on the PI regulator The expression is: ; In the formula, is the DC side voltage of the converter and its reference value, are the proportional coefficient and the integral coefficient, is the complex variable of the Laplace transform.

[0010] Optionally, the fuzzy PR controller includes a fuzzy controller and a PR controller; By calculating the current reference value and and the current and Error and the error change rate ; The error and the error change rate Input the fuzzy controller and output the parameter variables of the PR controller through the preset fuzzy rules ; The parameter variable Enter the PR controller and adjust the parameters: ; ; In the formula, are the proportional gains of the current sampling period and the previous sampling period respectively, are the resonant term gains of the current sampling period and the previous sampling period respectively; According to the proportional gain and the resonant gain Determine the transfer function of the PR controller and convert the error The input PR controller calculates the voltage and : ; ; In the formula, is the fundamental angular frequency.

[0011] Optionally, the voltage based and , the switch control signal generated by the SVPWM modulation module includes: Based on the voltage and Get the voltage space vector required for modulation : ; Based on SVPWM modulation technology, the voltage space vector is combined through 15 basic vectors. : ; In the formula, , For the The action time of the basic vectors, For the The basic vectors, is the 0th basic vector and its action time, is the 7th basic vector; , For the A direct vector, is the direct vector action time, is the switching cycle of the switch tube; The 0th and 7th basic vectors synthesize the zero vector, and the 1st to 6th basic vectors divide the plane into 6 sectors. In each sector, the action time of the corresponding basic vector and the through vector is calculated; According to the action time of the basic vector and the through vector and the on-off form of the corresponding switch tube, a switch control signal is formed on each switch tube.

[0012] In a second aspect, the present invention provides a control device for a Z-source bidirectional AC / DC converter, comprising: The first processing module is configured to obtain the DC side voltage of the converter , and calculate the current reference value based on the PI regulator , the current reference value is the reference value of the d-axis component of the AC side current of the converter; The second processing module is configured to obtain the AC side phase of the converter and combine the current reference value The current reference value is obtained by inverse Park transformation and , the current reference value and is the current reference value of Axis component; The third processing module is configured to obtain the AC side current of the converter and obtain the current through Clarke transformation and , the current and is the AC side current of the converter Axis component; A fourth processing module is configured to process the current reference value based on the current reference value. and and the current and , the voltage is calculated by the fuzzy PR controller and , the voltage and is the voltage on the AC side of the converter target values ​​of axis components; A fifth processing module is configured to and , a switch control signal is generated through the SVPWM modulation module, and the switch tube of the converter is controlled on and off through the switch control signal.

[0013] In a third aspect, the present invention provides an electronic device, including a processor and a storage medium; The storage medium is used to store instructions; The processor is used to operate according to the instructions to execute the steps according to the above method.

[0014] In a fourth aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, characterized in that the program implements the steps of the above method when executed by a processor.

[0015] In a fifth aspect, the present invention provides a computer program product, comprising a computer program / instruction, which implements the steps of the above method when executed by a processor.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a control method and device for a Z-source bidirectional AC / DC converter. Aiming at the problems existing in traditional interconnected converters, the Z-source bidirectional AC / DC converter is constructed by taking advantage of the unique topological structure of the Z-source impedance network. Aiming at the special structure of the Z-source bidirectional AC / DC converter, fuzzy control and PR control are combined to construct a parameter self-tuning fuzzy PR control system to realize fuzzy PR control, and an SVPWM strategy based on the Z-source topology is designed to realize high-precision control. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a circuit diagram of a Z-source bidirectional AC / DC converter provided by an embodiment of the present invention; Figure 2 1 is a flow chart of a control method for a Z-source bidirectional AC / DC converter provided by an embodiment of the present invention; Figure 3 is a logic schematic diagram of a control method for a Z-source bidirectional AC / DC converter provided by an embodiment of the present invention; Figure 4 is a schematic diagram of dividing a plane into six sectors using basic vectors provided in an embodiment of the present invention; Figure 5 is a waveform diagram of a Z-source-based SVPWM control signal provided in an embodiment of the present invention; Figure 6 It is a structural schematic diagram of a control device for a Z-source bidirectional AC / DC converter provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0019] Embodiment 1: The embodiment of the present invention provides a control method for a Z-source bidirectional AC / DC converter, such as Figure 1As shown, the Z-source bidirectional AC / DC converter proposed in this embodiment includes a Z-source impedance network and a three-phase inverter, the Z-source impedance network includes a capacitor C1, a capacitor C2, an inductor L1 and an inductor L2, one end of the capacitor C1 and the inductor L1 are both connected to the positive electrode of the DC voltage source Udc, one end of the capacitor C2 and the inductor L2 are both connected to the negative electrode of the DC voltage source Udc, the other end of the capacitor C1 and the inductor L2 are both connected to the positive electrode of the DC side of the three-phase inverter, and the other end of the capacitor C2 and the inductor L1 are both connected to the negative electrode of the DC side of the three-phase inverter; the three-phase inverter includes three bridge arms, each bridge arm includes two switch tubes (Sap, San, Sbp, Sbn, Scp, Scn) connected in series, and the common end of the two switch tubes is recorded as the midpoint of the bridge arm; the midpoints of the three bridge arms are respectively connected to the AC voltage source (ea, eb, ec). The Z-source bidirectional AC / DC converter also includes a capacitor C0 connected in parallel to the DC voltage source and a line resistor R and a filter inductor L connected in series between the three-phase inverter and the AC voltage source.

[0020] Based on the above Z-source bidirectional AC / DC converter, Figure 2 and 3 As shown, the control method includes the following steps: Step S1: Obtain the DC side voltage of the converter , and calculate the current reference value based on the PI regulator , current reference value is the reference value of the d-axis component of the AC side current of the converter.

[0021] Calculation of current reference value based on PI regulator The expression is: ; In the formula, is the DC side voltage of the converter and its reference value, are the proportional coefficient and the integral coefficient, is the complex variable of the Laplace transform.

[0022] Step S2: Obtain the AC side phase of the converter and combine it with the current reference value The current reference value is obtained by inverse Park transformation and , current reference value and is the current reference value of Axis component.

[0023] Step S3: Obtain the AC side current of the converter and obtain the current by Clarke transformation and , current and is the AC side current of the converter Axis component.

[0024] Step S4: Based on the current reference value and and current and , the voltage is calculated by the fuzzy PR controller and ,Voltage and is the voltage on the AC side of the converter Target value of the axis component.

[0025] The fuzzy PR controller includes a fuzzy controller and a PR controller; (1) By calculating the current reference value and and current and Error and the error rate of change ;error The basic domain is , error change rate The basic domain is ; The fuzzy subsets are (NB, Z, PB) which represent (negative large, zero, positive large) respectively; (2) The error and error rate of change Input the fuzzy controller and output the parameter variables of the PR controller through the preset fuzzy rules ; Parameter variables The basic domain is , the fuzzy subsets are (NB, NM, Z, PM, PB) representing (negative large, negative medium, zero, positive medium, positive large) respectively; the trigonometric function is selected as the membership function, which has two parameters, one is the peak value and the other is the width. The fuzzy rules are shown in Table 1; Table 1: Fuzzy rule table

[0026] The weighted average method is used to solve the fuzziness and the control quantity query table is made through offline calculation to realize online self-tuning of parameters.

[0027] (3) Set the parameter variable Enter the PR controller and adjust the parameters: ; ; In the formula, are the proportional gains of the current sampling period and the previous sampling period respectively, are the resonant term gains of the current sampling period and the previous sampling period respectively; (4) According to the proportional gain and the resonant gain Determine the transfer function of the PR controller and convert the error Input PR controller calculates voltage and : ; ; In the formula, is the fundamental angular frequency.

[0028] Step S5: Based on voltage and , a switch control signal is generated through the SVPWM modulation module, and the switch tube of the converter is controlled on and off through the switch control signal.

[0029] Specifically in this embodiment, generating a switch control signal through the SVPWM modulation module includes: Based on voltage and Get the voltage space vector required for modulation : ; The SVPWM modulation idea of ​​the Z-source inverter is to select some of the basic vectors including the direct zero vector and use the parallelogram rule to synthesize the reference voltage vector. Since the Z-source inverter needs a direct state to achieve boost, a direct zero vector is added. Table 2 shows the switching state of the Z-source inverter and its corresponding output phase voltage amplitude.

[0030] Table 2: Switching state and output phase voltage amplitude of Z-source inverter

[0031] The SVPWM modulation technology applied to the Z-source inverter is to adjust the action sequence and action time of the effective vector, traditional zero vector and direct zero vector by controlling the opening and closing of the inverter bridge switch tube to obtain the expected voltage. The voltage space vector is combined by 15 basic vectors : ; In the formula, , For the The action time of the basic vectors, For the The basic vectors, is the 0th basic vector and its action time, is the 7th basic vector; , For the A direct vector, is the direct vector action time, is the switching cycle of the switch tube; The 0th and 7th basic vectors synthesize the zero vector, and the 1st to 6th basic vectors divide the plane into 6 sectors. In each sector, the action time of the corresponding basic vector and the through vector is calculated; like Figure 4 As shown, taking the first sector as an example: Since the direct vector does not affect the output voltage, we can get: ; ; In the formula, is the modulation factor of the inverter; The sum of the time of the traditional zero vector and the direct zero vector is: ; Similarly, the action time of each vector in the other five sectors can be calculated.

[0032] According to the action time of the basic vector and the through vector and the on-off form of the corresponding switch tube, a switch control signal is formed on each switch tube, such as Figure 5 shown.

[0033] Embodiment 2:

[0034] like Figure 6 As shown, an embodiment of the present invention provides a control device for a Z-source bidirectional AC / DC converter, comprising: The first processing module is configured to obtain the DC side voltage of the converter , and calculate the current reference value based on the PI regulator , current reference value is the reference value of the d-axis component of the AC side current of the converter; The second processing module is configured to obtain the AC side phase of the converter and combine it with the current reference value The current reference value is obtained by inverse Park transformation and , current reference value and is the current reference value of Axis component; The third processing module is configured to obtain the AC side current of the converter and obtain the current through Clarke transformation and , current and is the AC side current of the converter Axis component; The fourth processing module is configured to and and current and , the voltage is calculated by the fuzzy PR controller and ,Voltage and is the AC side voltage of the converter target values ​​of axis components; A fifth processing module is configured to and , a switch control signal is generated through the SVPWM modulation module, and the switch tube of the converter is controlled on and off through the switch control signal.

[0035] Embodiment three:

[0036] Based on a control method of a Z-source bidirectional AC / DC converter provided in Embodiment 1, an embodiment of the present invention provides an electronic device, including a processor and a storage medium; The storage medium is used to store instructions; The processor is used to operate according to the instructions to execute the steps according to the above method.

[0037] Embodiment 4:

[0038] Based on a control method for a Z-source bidirectional AC / DC converter provided in Example 1, an embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon, characterized in that the program implements the steps of the above method when executed by a processor.

[0039] Embodiment five:

[0040] Based on the control method of a Z-source bidirectional AC / DC converter provided in Example 1, an embodiment of the present invention provides a computer program product, including a computer program / instruction, which implements the steps of the above method when executed by a processor.

[0041] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0042] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0043] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0044] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0045] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A control method for a Z-source bidirectional AC / DC converter, characterized in that: include: Get the DC side voltage of the converter , and calculate the current reference value based on the PI regulator , the current reference value is the reference value of the d-axis component of the AC side current of the converter; Get the AC side phase of the converter and combine it with the current reference value The current reference value is obtained by inverse Park transformation and , the current reference value and is the current reference value of Axis component; Obtain the AC side current of the converter and obtain the current through Clarke transformation and , the current and is the AC side current of the converter Axis component; Based on the current reference value and and the current and , the voltage is calculated by the fuzzy PR controller and , the voltage and is the AC side voltage of the converter target values ​​of axis components; Based on the voltage and , a switch control signal is generated through the SVPWM modulation module, and the switch tube of the converter is controlled on and off through the switch control signal.

2. The control method of the Z-source bidirectional AC / DC converter according to claim 1, characterized in that: The Z-source bidirectional AC / DC converter includes a Z-source impedance network and a three-phase inverter. The Z-source impedance network includes a capacitor C1, a capacitor C2, an inductor L1 and an inductor L2. One end of the capacitor C1 and the inductor L1 are both connected to the positive electrode of the DC voltage source, one end of the capacitor C2 and the inductor L2 are both connected to the negative electrode of the DC voltage source, the other end of the capacitor C1 and the inductor L2 are both connected to the DC side positive electrode of the three-phase inverter, and the other end of the capacitor C2 and the inductor L1 are both connected to the DC side negative electrode of the three-phase inverter; the three-phase inverter includes three bridge arms, each of the bridge arms includes two switch tubes connected in series, and the common end of the two switch tubes is recorded as the midpoint of the bridge arm; the midpoints of the three bridge arms are respectively connected to the AC voltage source.

3. The control method of the Z-source bidirectional AC / DC converter according to claim 2, characterized in that: The Z-source bidirectional AC / DC converter further includes a capacitor C0 connected in parallel to the DC voltage source and a line resistor R and a filter inductor L connected in series between the three-phase inverter and the AC voltage source.

4. The control method of the Z-source bidirectional AC / DC converter according to claim 1, characterized in that: The current reference value is calculated based on the PI regulator The expression is: ； In the formula, is the DC side voltage of the converter and its reference value, are the proportional coefficient and the integral coefficient, is the complex variable of the Laplace transform.

5. The control method of a Z-source bidirectional AC / DC converter according to claim 1, characterized in that: The fuzzy PR controller includes a fuzzy controller and a PR controller; By calculating the current reference value and and the current and Error and the error change rate ; The error and the error change rate Input the fuzzy controller and output the parameter variables of the PR controller through the preset fuzzy rules ; The parameter variable Enter the PR controller and adjust the parameters: ； ； In the formula, are the proportional gains of the current sampling period and the previous sampling period respectively, are the resonant term gains of the current sampling period and the previous sampling period respectively; According to the proportional gain and the resonant gain Determine the transfer function of the PR controller and convert the error The input PR controller calculates the voltage and : ； ； In the formula, is the fundamental angular frequency.

6. The control method of a Z-source bidirectional AC / DC converter according to claim 1, characterized in that: Based on the voltage and , the switch control signal generated by the SVPWM modulation module includes: Based on the voltage and Get the voltage space vector required for modulation : ； Based on SVPWM modulation technology, the voltage space vector is combined through 15 basic vectors. : ； In the formula, , For the The action time of the basic vectors, For the The basic vectors, is the 0th basic vector and its action time, is the 7th basic vector; , For the A direct vector, is the direct vector action time, is the switching cycle of the switch tube; The 0th and 7th basic vectors synthesize the zero vector, and the 1st to 6th basic vectors divide the plane into 6 sectors. In each sector, the action time of the corresponding basic vector and the through vector is calculated; According to the action time of the basic vector and the through vector and the on-off form of the corresponding switch tube, a switch control signal is formed on each switch tube.

7. A control device for a Z-source bidirectional AC / DC converter, characterized in that: include: The first processing module is configured to obtain the DC side voltage of the converter , and calculate the current reference value based on the PI regulator , the current reference value is the reference value of the d-axis component of the AC side current of the converter; The second processing module is configured to obtain the AC side phase of the converter and combine the current reference value The current reference value is obtained by inverse Park transformation and , the current reference value and is the current reference value of Axis component; The third processing module is configured to obtain the AC side current of the converter and obtain the current through Clarke transformation and , the current and is the AC side current of the converter Axis component; A fourth processing module is configured to process the current reference value based on the current reference value. and and the current and , the voltage is calculated by the fuzzy PR controller and , the voltage and is the AC side voltage of the converter target values ​​of axis components; A fifth processing module is configured to and , a switch control signal is generated through the SVPWM modulation module, and the switch tube of the converter is controlled on and off through the switch control signal.

8. An electronic device, characterized in that: including processor and storage medium; The storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the steps of the method according to any one of claims 1-6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

10. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

Images