Multivariable rapid identification and cooperative control method for modular medium-voltage DC converter

Abstract

The invention relates to a multivariable rapid identification and cooperative control method for a modular medium-voltage direct-current converter, and relates to the field of high-power power electronic conversion. The high-power modularized series-parallel medium-voltage direct-current converter control system comprises an integrated controller and a module controller, the centralized controller comprises an algorithm operation unit, a data processing unit and a photoelectric conversion unit, and the module controller comprises a data processing unit and a photoelectric conversion unit. The centralized controller algorithm operation unit calculates a plurality of control variables such as duty ratio, frequency, phase and the like, the control variables are sent to the plurality of module controller data processing units in parallel through the centralized data processing unit, and the module controllers latch the plurality of control variables and return latched data. And the centralized controller data processing unit rapidly identifies latch states of a plurality of modules and sends a plurality of paths of frequency conversion cooperative control signals in parallel, so that multivariable cooperative control of a plurality of power module units of the direct current converter is realized, and the output performance of the medium-voltage direct current converter is optimized.

Description

Technical Field

[0001] The present invention relates to the field of high-power electronic conversion, and in particular to a method for fast multi-variable identification and coordinated control of a modular medium-voltage direct current converter. Background Art

[0002] High-power medium-voltage DC converters in renewable energy power generation systems often adopt modular design. The medium-voltage DC converter achieves large-capacity and high-step-up ratio conversion through the input and output series-parallel connection of multiple power modules. The DC converter and power modules adopt a centralized-distributed control method, with the centralized controller sending multiple variables such as phase, frequency, and duty cycle to the module controller. If the power module directly executes the relevant control variables, due to the real-time frequency changes, the different clock sources of multiple power modules, and the lack of coordination in the relative execution time of multiple variables between modules, it will lead to problems such as unbalanced power module voltage and large output ripple of the DC converter.

[0003] The existing DC converter control method mainly uses algorithmic calculation of control variables, and the centralized / module multi-variable coordinated control implementation of modular DC converters is rarely considered. In addition, the existing centralized modular control architecture mainly considers the single control variable control method, and does not consider the coordinated control of multiple control variables under variable frequency conditions. Summary of the invention

[0004] In order to solve the problem of poor output characteristics of modular series-parallel high-power DC converters due to the lack of coordinated control of multiple variables, the present invention proposes a method for rapid identification and coordinated control of multiple variables of modular medium-voltage DC converters based on a centralized / modular control architecture. The method is a method for coordinated control between modules after rapid identification and latching of multiple variables. The method can keep the changes of multiple variables between multiple series-parallel modules relatively synchronized, maintain a fixed phase between power modules, and optimize the output performance of the DC converter.

[0005] A high-power modular series-parallel medium-voltage DC converter control system includes a centralized controller and a module controller; the centralized controller includes an algorithm operation unit, a data processing unit, and a photoelectric conversion unit; the module controller includes a data processing unit and a photoelectric conversion unit; the centralized controller algorithm operation unit calculates multiple control variables such as duty cycle, frequency, phase, etc., and sends them in parallel to the multiple module controller data processing units via the centralized data processing unit; the module controller latches multiple control variables and transmits back the latched data; the centralized controller data processing unit quickly identifies multiple module latch states, and sends multiple frequency conversion coordinated control signals in parallel, thereby realizing multi-variable coordinated control of multiple power module units of the DC converter and optimizing the output performance of the medium-voltage DC converter.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] The multi-variable rapid identification and coordinated control method of a modular medium voltage DC converter comprises the following steps:

[0008] Step 1: The algorithm operation unit of the centralized control unit calculates the frequency, duty cycle, and phase variable values ​​that the power module needs to execute in a closed loop, and then transmits multiple variable data to the data processing unit, which sends them to multiple module controllers in parallel;

[0009] Step 2: The module controller latches data according to the initial coordinated control signal, and then uploads the latched frequency data to the centralized controller;

[0010] Step 3: The centralized controller quickly identifies the frequency data of multiple module controllers to determine whether the data latch of each module is normal;

[0011] Step 4: When the initial coordination signal is executed, the central controller sends a coordination control signal with a duty cycle of 50% of the frequency to the module controller according to the frequency data uploaded by the module controller;

[0012] Step 5: The module controller executes its latched duty cycle and phase variables according to the coordinated control signal.

[0013] Furthermore, the step 1 includes: the algorithm operation unit of the centralized controller adopts closed-loop control to fix the control frequency, that is, the closed-loop calculation cycle calculates the frequency, duty cycle, and phase control variables.

[0014] Furthermore, step 2 includes: when the module controller detects that the initial coordination signal is a falling edge, the data packet sent by the centralized controller is captured. If a packet of data is being transmitted at this time, the previous packet of complete data is captured to prevent multiple variables from not being the same group of calculated values; after the data packet is captured, it is latched in the module controller, and then the frequency data in the data packet is re-encoded, packaged and uploaded to the centralized controller.

[0015] Furthermore, the steps 2 and 3 include: selecting frequency data as the identification basis, the modular DC converter adopts triangular wave counting and comparison to generate waves, and the frequency value, duty cycle value, and phase delay corresponding phase shift angle value calculation formula are:

[0016] ; ;

[0017] ;

[0018] Among them, T clk The module controller executes the wave clock, f is the frequency, f num is the frequency count value, D is the duty cycle, D numis the duty cycle comparison value of the module controller, p num Phase shift angle value, x is the phase shift number of the corresponding power module, counting from 0; the medium voltage DC converter includes multiple power modules, and n modules are used for staggered output between the power modules. The phase staggered angle is based on the first module and shifted to the corresponding angle in sequence;

[0019] According to the above calculation formula, if the frequency value is latched correctly, other variables will also be latched correctly; each module controller uploads the latched frequency value to the centralized controller through the collaborative control channel, and the centralized controller uses the frequency value to identify whether the latch is correct, thereby reducing the number of communications and optimizing the identification logic.

[0020] Furthermore, step 4 includes: after the centralized controller identifies, the frequency value of the cooperative signal is updated when the coordination signal executes the current frequency, and the centralized controller sends a cooperative control signal with a duty cycle of 50% of the frequency to n modules in parallel to complete the real-time update of the variable frequency cooperative signal.

[0021] Furthermore, step 5 includes: executing the module controller to latch the control variable data at the rising edge of the cooperative signal, wherein the cooperative signal frequency is the frequency value of the package data, and the cooperative control signal edge controls the increase and decrease switching of the triangular wave count to achieve variable frequency wave generation, and the duty cycle and phase values ​​are loaded at the rising edge of the cooperative control signal to execute the package data variable.

[0022] Furthermore, multiple module controllers simultaneously receive the coordinated control signal, and the rising edge of the coordinated signal triggers the execution of the latched duty cycle and phase variables, wherein the phase variable execution mechanism starts with the rising edge of the coordinated signal and begins the corresponding phase time delay to achieve phase control of multiple power modules.

[0023] Furthermore, the algorithm operation unit of the centralized controller performs closed-loop control to calculate the variable value of the next cycle and continues to repeat the above process.

[0024] Furthermore, to ensure coordination between collaborative control and data transmission timing requirements, data encoding and decoding speeds are more than five times faster than collaborative signals.

[0025] The present invention also includes a centralized / module control system, in which the centralized controller is connected to each module controller by two pairs of optical fibers, wherein one pair of optical fibers is a data transmission channel, which performs data transmission based on the Manchester Encoding communication protocol and is used for data interaction between the centralized controller and the module controller; one pair of optical fibers is a collaborative control channel, which is used for the module controller to upload centralized identification data and to centrally send collaborative signals to the modules, wherein the centralized controller is connected to multiple module controllers by optical fibers of equal length.

[0026] Beneficial effects:

[0027] The present invention has developed a centralized / module control system based on multi-channel parallel "algorithm operation + data processing", and proposed a modular DC converter multi-variable rapid identification and coordinated control method, the purpose of which is to make the changes of control variables between multiple modules relatively synchronized through the centralized / module controller multi-variable data latch rapid identification and coordinated control. The present invention can not only suppress the problems of power, voltage imbalance and large output ripple caused by the lack of coordination of control variables between modules, but also effectively improve the reliability of modular DC converters under actual operation conditions, and is suitable for renewable energy power generation scenarios such as wind power / photovoltaic power generation with high power and modular DC conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG1 is a schematic diagram of a centralized / module control system of the present invention;

[0029] FIG2 is a schematic diagram of the timing of data identification and collaborative control. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0031] like Figure 1 As shown, the centralized / module control system of the present invention includes a centralized controller and n module controllers ( Figure 1 The centralized controller includes an algorithm operation unit and a data processing unit. The algorithm operation unit calculates the frequency, duty cycle, and phase, and the data processing unit performs parallel processing and data identification. The centralized controller and the module controller are connected by two pairs of optical fibers. Figure 1 The medium gray represents the data transmission channel, which uses the Manchester Encoding communication protocol for data transmission. The centralized controller sends multiple control variables, start and stop instructions and other data to the module controller, and the module controller sends the module real-time operation status data to the centralized controller; the black represents the collaborative control channel, the module controller uploads the latch frequency data to the centralized controller, and the data processing unit of the centralized controller quickly identifies and sends the collaborative signal to the module controller. The centralized controller and multiple module controllers are connected by equal-length optical fibers to ensure equal physical link delays. The electrical signals of the centralized controller and the module controllers are converted into optical signals by the photoelectric conversion unit and transmitted as optical signals to prevent signal interference.

[0032] The modular medium voltage DC converter uses triangular wave counting and comparison to generate waves. The frequency value calculation formula is: , where T clk The module controller executes the wave clock, f is the actual frequency, f num is the frequency count value. The duty cycle is also implemented in the form of numerical comparison. The duty cycle comparison numerical calculation formula is: , where D is the actual duty cycle of the closed loop calculation, D num The output phases of multiple power modules in the medium voltage DC converter are staggered. The phase staggered angle is based on the first module. The delay corresponds to the phase shift angle value. , where p num Phase shift angle value, x is the phase shift number of the corresponding power module (counting from 0).

[0033] Based on the above formula, the frequency value is derived. If the latch is correct, other variables can be judged to be normal. Therefore, in the centralized controller, by identifying the frequency value of each module, it is judged whether each module has latched multiple variables correctly. Each module controller uploads the latched frequency value to the centralized controller through the collaborative control channel. Using the frequency value of each module to identify whether the latch is correct can not only reduce the communication time, but also optimize the identification and judgment logic.

[0034] like Figure 2 As shown, Figure 2 The core data and signal timing involved in identification and collaborative control include collaborative control signals, centralized data packets, module latch data packets, and module upload data packets, wherein the module upload data includes the data required by the method of the present invention, and other module upload data is completed by the uplink optical fiber of the data transmission channel.

[0035] The modular medium voltage DC converter multi-variable rapid identification and coordinated control method of the present invention is realized by decoupling the coordinated control signal sent by the centralized controller and the centralized data packet. Figure 2 In the data packet, data and idle time are included and sent regularly with a fixed communication cycle. The collaborative control signal initially sends a fixed frequency initial collaborative signal of 1 cycle. The first collaborative signal module controller only processes data and does not send a drive wave. When the medium-voltage DC converter is not running, the collaborative control signals are all 0. The initial collaborative signal starts with the first rising edge and ends with the next rising edge. The modular medium-voltage DC converter multi-variable rapid identification and collaborative control method includes the following steps:

[0036] Step 1: When the module controller detects that the initial coordination signal is a falling edge, it captures the centralized data packet. If a packet of data is being transmitted at this time, it chooses to capture the previous complete packet of data to prevent multiple variables from being calculated in the same group of values. After the data packet is captured, it is latched in the module controller, and then the frequency data in the data packet is re-encoded and packaged and uploaded to the centralized controller.

[0037] Step 2: The centralized controller identifies the frequency data uploaded by the n module controllers and determines whether all module latches are the same group of control variables. This process must be completed before the next rising edge of the coordination signal. After the identification is normal, the coordination signal frequency value is updated after the coordination signal executes the current frequency. The centralized controller sends a 50% duty cycle coordination control signal to the n modules in parallel. This operation completes the real-time update of the variable frequency coordination signal.

[0038] like Figure 1 , Figure 2 As shown, at the rising edge of the coordinated signal, the module controller latches the control variable data, where the coordinated signal is the frequency value of the data package, and the frequency conversion wave can be realized by switching the triangular wave increase and decrease count at the edge of the coordinated control signal, and the duty cycle and phase value can be loaded at the rising edge of the coordinated control signal to complete the execution of the data package. By looping the above process, the rapid identification and coordinated control of multiple variables are realized, so that multiple power modules in the medium voltage DC converter can achieve relatively fixed phases under the condition of variable frequency, and optimize the output performance.

Claims

1. A multi-variable rapid identification and coordinated control method for a modular medium voltage DC converter, characterized in that: The steps include: Step 1: The algorithm operation unit of the centralized control unit calculates the frequency, duty cycle, and phase variable values ​​that the power module needs to execute in a closed loop, and then transmits multiple variable data to the data processing unit, which sends them to multiple module controllers in parallel; Step 2: The module controller latches data according to the initial coordinated control signal, and then uploads the latched frequency data to the centralized controller; Step 3: The centralized controller quickly identifies the frequency data of multiple module controllers to determine whether the data latching of each module is normal; Step 4: When the initial coordination signal is executed, the central controller sends a coordination control signal with a duty cycle of 50% of the frequency to the module controller according to the frequency data uploaded by the module controller; Step 5: The module controller executes its latched duty cycle and phase variables according to the coordinated control signal.

2. The method for multi-variable rapid identification and coordinated control of a modular medium voltage DC converter according to claim 1, characterized in that: The step 1 includes: the algorithm operation unit of the centralized controller adopts closed-loop control to calculate the frequency, duty cycle, and phase control variables with a fixed control frequency.

3. The method for multi-variable rapid identification and coordinated control of a modular medium voltage DC converter according to claim 1, characterized in that: The step 2 includes: when the module controller detects that the initial coordination signal is a falling edge, the data packet sent by the centralized controller is captured. If a packet of data is being transmitted at this time, the previous packet of complete data is captured to prevent multiple variables from not being the same group of calculated values; after the data packet is captured, it is latched in the module controller, and then the frequency data in the data packet is re-encoded, packaged and uploaded to the centralized controller.

4. The method for multi-variable rapid identification and coordinated control of a modular medium voltage DC converter according to claim 1, characterized in that: The steps 2 and 3 include: selecting frequency data as the identification basis, the modular DC converter adopts triangular wave counting and comparison to generate waves, and the frequency value, duty cycle value, and phase delay corresponding phase shift angle value calculation formula are: ； ； ； Among them, T clk The module controller executes the wave clock, f is the frequency, f num is the frequency count value, D is the duty cycle, D num is the duty cycle comparison value of the module controller, p num Phase shift angle value, x is the phase shift number of the corresponding power module, counting from 0; the medium voltage DC converter includes multiple power modules, and n modules are used for staggered output between the power modules. The phase staggered angle is based on the first module and shifted to the corresponding angle in sequence; According to the above calculation formula, if the frequency value is latched correctly, other variables will also be latched correctly; each module controller uploads the latched frequency value to the centralized controller through the collaborative control channel, and the centralized controller uses the frequency value to identify whether the latch is correct, thereby reducing the number of communications and optimizing the identification logic.

5. The modular medium voltage DC converter multi-variable rapid identification and coordinated control method according to claim 1, characterized in that: The step 4 includes: after the centralized controller identifies, the frequency value of the coordinated signal is updated when the coordinated signal executes the current frequency, and the centralized controller sends a coordinated control signal with a duty cycle of 50% of the frequency to n modules in parallel to complete the real-time update of the variable frequency coordinated signal.

6. The modular medium voltage DC converter multi-variable rapid identification and coordinated control method according to claim 1, characterized in that: The step 5 includes: executing the module controller to latch the control variable data at the rising edge of the cooperative signal, wherein the cooperative signal frequency is the frequency value of the package data, and the cooperative control signal edge controls the increase and decrease switching of the triangular wave count to realize variable frequency wave generation, and the duty cycle and phase values ​​are loaded at the rising edge of the cooperative control signal to execute the package data variable.

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