DC polarity conversion circuit, control method, control device and equipment based on DC transformer

Abstract

The present application relates to a DC polarity conversion circuit based on a DC transformer, the circuit includes a preset number of cascaded sub-DC polarity conversion circuit modules, any sub-DC polarity conversion circuit module includes: a full-bridge circuit and a DAB DC transformer, the full-bridge circuit is used to act according to a control signal to convert a medium-voltage DC input signal with a fixed polarity into a medium-voltage DC output signal with a variable polarity; the DAB DC transformer is connected to the full-bridge circuit and is used to convert the medium-voltage DC output signal into a low-voltage DC signal. In the above-mentioned DC polarity conversion circuit based on a DC transformer, by setting a full-bridge circuit, the polarity reversal of the output DC signal is achieved according to the control signal action, the circuit structure is simple, the control method is convenient, and the technical solution is mature, so that the DC transformer can achieve the reversal of the DC voltage polarity on the medium voltage side only through the control method, which greatly facilitates the application of the DC transformer in the DC system based on LCC.

Description

Technical Field

[0001] The present application relates to the field of direct current power transmission technology, and in particular to a direct current polarity conversion circuit, control method, control device and equipment based on a direct current transformer. Background Art

[0002] Compared with AC transmission, high-voltage DC transmission has the characteristics of large transmission power capacity, low loss, long transmission distance, good stability, etc., and has broad application prospects. With the extension of DC technology from the transmission level to the distribution level, the DC distribution network, which is closely related to the future development of urban distribution networks, has gradually attracted people's attention. In the DC distribution network, the DC transformer is the key conversion equipment to complete power transmission and voltage conversion.

[0003] Since the output voltage polarity of traditional DC transformers is fixed and cannot be reversed between positive and negative polarities, they can only be applied to DC grids composed of voltage source converters (VSCs), but cannot be applied to DC systems based on line commutated converters (LCCs) where DC voltage polarity reversal may occur. In view of this, inventing a DC transformer circuit with variable DC polarity to promote the application of DC transformers in DC systems based on LCCs has become a research direction for DC transformers. Summary of the invention

[0004] Based on this, it is necessary to provide a DC polarity conversion circuit, control method, control device and equipment based on a DC transformer to solve the problem that the output voltage polarity of a traditional DC transformer cannot be changed.

[0005] On one hand, the present application provides a DC polarity conversion circuit based on a DC transformer, which is used to be connected between a medium-voltage DC distribution network and a low-voltage DC distribution network to provide a low-voltage DC signal with variable polarity for the low-voltage DC distribution network. The circuit includes a preset number of cascaded sub-DC polarity conversion circuit modules, and any of the sub-DC polarity conversion circuit modules includes: a full-bridge circuit and a DAB DC transformer, the full-bridge circuit is used to operate according to a control signal to convert a medium-voltage DC input signal with fixed polarity into a medium-voltage DC output signal with variable polarity; the DAB DC transformer is connected to the full-bridge circuit to convert the medium-voltage DC output signal into the low-voltage DC signal.

[0006] In the DC polarity conversion circuit based on the DC transformer in the above embodiment, on the one hand, by setting a full-bridge circuit, the polarity reversal of the output DC signal is realized according to the control signal action. The circuit structure is simple, the control method is convenient, and the technical solution is mature. The DC transformer can realize the reversal of the DC voltage polarity on the medium voltage side only through the control method, which greatly facilitates the application of the DC transformer in the DC system based on LCC. On the other hand, the conversion circuit continues the advantages of the DAB DC transformer such as modularity, high power density and large transmission capacity.

[0007] In one embodiment, the full bridge circuit comprises:

[0008] A first half-bridge comprises a first controllable switch unit and a second controllable switch unit connected in series, wherein a midpoint of the first half-bridge is set as a first input port of the sub-DC polarity conversion circuit module;

[0009] a second half-bridge connected in parallel with the first half-bridge, the second half-bridge comprising a third controllable switch unit and a fourth controllable switch unit connected in series, the third controllable switch unit being connected to the first controllable switch unit, the fourth controllable switch unit being connected to the second controllable switch unit, and the midpoint of the second half-bridge being set as the second input port of the sub-DC polarity conversion circuit module;

[0010] The full bridge circuit is configured as:

[0011] According to the control signal, the first controllable switch unit and the fourth controllable switch unit are controlled to be turned on, and the second controllable switch unit and the third controllable switch unit are controlled to be turned off, so as to output a positive medium voltage DC output signal; and

[0012] According to the control signal, the first controllable switch unit and the fourth controllable switch unit are controlled to be turned off, and the second controllable switch unit and the third controllable switch unit are controlled to be turned on, so as to output a reverse medium voltage DC output signal.

[0013] In one embodiment, the preset number is N, N is a positive integer, and the N sub-DC polarity conversion circuit modules are sequentially cascaded one by one to form N stages;

[0014] The first input port of the first-stage DC polarity conversion circuit module is connected to the medium-voltage DC distribution network, and the second input port of the N-th DC polarity conversion circuit module is connected to the medium-voltage DC distribution network;

[0015] The sub-DC polarity conversion circuit module of the i-th stage is configured as follows: the first input port is connected to the second input port of the sub-DC polarity conversion circuit module of the adjacent previous stage, and the second input port is connected to the first input port of the sub-DC polarity conversion circuit module of the adjacent next stage, i∈[2, N-1], and i is a positive integer;

[0016] The first output end of each sub-DC polarity conversion circuit module is connected to the first input end of the low-voltage DC distribution network, and the second output end of each sub-DC polarity conversion circuit module is connected to the second input end of the low-voltage DC distribution network.

[0017] A second aspect of the present application provides a DC polarity conversion control method based on a DC transformer, which is used to control the sub-DC polarity conversion circuit module described in any of the above embodiments, and the method includes:

[0018] Obtaining circuit parameters of any of the sub-DC polarity conversion circuit modules;

[0019] A switch control signal is generated according to the circuit parameter and the preset circuit parameter reference value to control the sub-DC polarity conversion circuit module to convert a medium-voltage DC input signal with a fixed polarity into a low-voltage DC signal with a variable polarity.

[0020] In the DC polarity conversion control method based on the DC transformer in the above embodiment, by sampling the circuit parameters on the medium and low voltage sides and using them together with the reference values ​​of the preset circuit parameters as the input of the circuit control, the switch control signal is obtained through pulse width modulation, so as to accurately control the conversion circuit to generate a DC signal with variable polarity as required. At the same time, the circuit control system can also expand its functions as required. For example, if there is a requirement for equalizing the voltage of the sub-DC polarity conversion circuit modules, equalizing voltage control can be added to the system to keep the output voltages of each sub-DC polarity conversion circuit module consistent.

[0021] In one embodiment, the circuit parameter includes at least one of a medium voltage DC output voltage measurement value, a low voltage DC current measurement value, a low voltage DC voltage measurement value, and low voltage DC voltage polarity information, the preset circuit parameter reference value includes a medium voltage DC output voltage reference value and a low voltage DC voltage reference value, and the step of generating a switch control signal according to the circuit parameter and the preset circuit parameter reference value includes:

[0022] Generate the shift phase information of the sub-DC polarity conversion circuit module through a PI regulator according to the medium voltage DC output voltage measurement value, the low voltage DC current measurement value, the low voltage DC voltage measurement value and the corresponding preset circuit parameter reference value;

[0023] generating full-bridge circuit switch state information according to the low-voltage DC voltage polarity information;

[0024] A switch control signal is generated by a PWM modulator according to the shift ratio information and the switch state information of the full-bridge circuit.

[0025] In one embodiment, the step of generating the shift ratio information of the sub-DC polarity conversion circuit module through a PI regulator according to the medium voltage DC output voltage measurement value, the low voltage DC current measurement value, the low voltage DC voltage measurement value and the corresponding preset circuit parameter reference value includes:

[0026] Generate a first low-voltage DC current reference compensation amount through a first PI regulator according to the low-voltage DC voltage measurement value and the low-voltage DC voltage reference value;

[0027] generating a second low-voltage DC current reference compensation amount through a second PI regulator according to the medium-voltage DC output voltage measurement value and the medium-voltage DC output voltage reference value;

[0028] generating a low-voltage direct current reference compensation amount according to the first low-voltage direct current reference compensation amount and the second low-voltage direct current reference compensation amount;

[0029] The shift ratio information is generated by a third PI regulator according to the low-voltage direct current measurement value and the low-voltage direct current reference compensation amount.

[0030] In one of the embodiments, the medium voltage DC output voltage reference value is an average value of N medium voltage DC output voltage measurement values.

[0031] A third aspect of the present application provides a DC polarity conversion control device based on a DC transformer, comprising:

[0032] A parameter acquisition module, used to acquire the circuit parameters;

[0033] The control module is used to generate a switch control signal according to the circuit parameter and a preset circuit parameter reference value to control the sub-DC polarity conversion circuit module to work normally.

[0034] In one embodiment, the control module includes:

[0035] A low-voltage DC voltage controller, used for generating a first low-voltage DC current reference compensation amount through a first PI regulator according to a low-voltage DC voltage measurement value and a low-voltage DC voltage reference value;

[0036] A voltage balancing controller, configured to generate a second low-voltage DC current reference compensation amount through a second PI regulator according to a medium-voltage DC output voltage measurement value and a medium-voltage DC output voltage reference value;

[0037] A current controller, used for generating a shift ratio information through a third PI regulator according to a low-voltage DC current measurement value and a low-voltage DC current reference compensation amount;

[0038] The PWM modulator is used to generate a switch control signal according to the shift phase information and the switch state information of the full-bridge circuit.

[0039] A fourth aspect of the present application provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the method described in any of the foregoing embodiments are implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 It is a circuit topology diagram of a DC transmission and distribution system including a DAB type DC transformer;

[0042] Figure 2 It is a circuit topology diagram of a DC transmission and distribution system including a SCDCT type DC transformer;

[0043] Figure 3 A circuit structure diagram of a DC polarity conversion circuit based on a DC transformer provided in one embodiment of the present application;

[0044] Figure 4 A circuit structure diagram of a full-bridge circuit provided in an embodiment of the present application;

[0045] Figure 5 A working principle diagram of a DC polarity conversion circuit based on a DC transformer provided in one embodiment of the present application;

[0046] Figure 6 A working principle diagram of a DC polarity conversion circuit based on a DC transformer provided in another embodiment of the present application;

[0047] Figure 7 This is a flowchart of a DC polarity conversion circuit control method based on a DC transformer provided in an embodiment of the present application;

[0048] Figure 8 This is a flowchart of a DC polarity conversion circuit control method based on a DC transformer provided in the second embodiment of the present application;

[0049] Fig. 9This is a flowchart of a DC polarity conversion circuit control method based on a DC transformer provided in the third embodiment of the present application;

[0050] Fig.10 This is a structural block diagram of a DC polarity conversion circuit control device based on a DC transformer provided in one embodiment of the present application;

[0051] Fig.11 A structural schematic diagram of a DC polarity conversion circuit control device based on a DC transformer provided in one embodiment of the present application;

[0052] Fig.12 This is a diagram of the internal structure of a computer device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0053] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0054] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0055] It can be understood that the terms "first", "second", etc. used in the present application can be used in this article to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from another element.

[0056] It should be noted that when an element is considered to be "connected" to another element, it can be directly connected to the other element, or connected to the other element through an intermediate element. In addition, the "connection" in the following embodiments should be understood as "electrical connection", "communication connection", etc. if there is transmission of electrical signals or data between the connected objects.

[0057] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" etc. specify the presence of stated features, wholes, steps, operations, components, parts or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts or combinations thereof.

[0058] In recent years, with the rapid growth of my country's power load, ultra-high voltage and ultra-high voltage transmission projects have also ushered in a golden period of rapid development. High-voltage direct current (HVDC) transmission has the advantages of ultra-high voltage, long distance, large capacity and low loss, and is the mainstream direction advocated by international large power grids. High-voltage direct current transmission mainly converts AC to DC at converter stations. The most common types of converter stations are grid-commutated converters (LCCs) and voltage source converters (VSCs). Since LCCs are slightly more efficient than VSCs and can transmit more power, most of the HVDC systems currently in operation use LCC topology. The characteristic of the LCC topology is that the DC voltage polarity will reverse when the power system power flow reverses.

[0059] In the DC transmission and distribution network, the DC transformer is a key device to complete power transmission and voltage conversion. Among them, the DC transformer based on dual-active-bridge (DAB) input series-output parallel is a research hotspot. Figure 1 The figure shows the topological structure of the DAB DC transformer. From the circuit structure, we can see that the DC power on the medium voltage side is converted into medium voltage AC power through the DAB DC transformer via the DC / AC on the medium voltage side, and then stepped down into low voltage AC power through the AC transformer, and finally outputs low voltage DC power with fixed polarity after AC / DC conversion. On the other hand, another type of switched capacitor based DC transformer (Switched Capacitor based DC Transformer, SCDCT) has higher power density, larger transmission capacity, and can realize redundant submodule design and medium voltage side DC fault blocking compared to the DAB type DC transformer, and has gradually become another research hotspot in the field of DC transformers. Figure 2 The figure shows the topological structure of the SCDCT type DC transformer. From the circuit diagram, it can be seen that the SCDCT is equivalent to adding a half-bridge circuit to the input front end of the DAB transformer. Since the half-bridge circuit does not have the function of reversing the polarity of DC current, the SCDCT also outputs low-voltage DC power with fixed polarity.

[0060] Since the above two DC transformer circuit topologies cannot achieve DC output polarity reversal, the application of DC transformers in DC grids based on line-commutated converters (LCCs) is seriously limited. Therefore, it is necessary to propose a new DC transformer circuit topology to meet the requirements of voltage polarity reversal in LCC DC grids.

[0061] In order to solve the above problems, the present application proposes a DC polarity conversion circuit, control method, control device and equipment based on a DC transformer, which will be explained through specific embodiments below.

[0062] In one embodiment of the present application, Figure 3As shown, a DC polarity conversion circuit based on a DC transformer is provided, which is used to be connected between a medium-voltage DC distribution network and a low-voltage DC distribution network to provide a low-voltage DC signal with variable polarity for the low-voltage DC distribution network. The DC polarity conversion circuit based on the DC transformer includes a preset number of cascaded sub-DC polarity conversion circuit modules, and any sub-DC polarity conversion circuit module includes: a full-bridge circuit 100 and a DAB DC transformer 200, wherein the full-bridge circuit 100 is used to act according to a control signal to convert a medium-voltage DC input signal with fixed polarity into a medium-voltage DC output signal with variable polarity; the DAB DC transformer 200 is connected to the full-bridge circuit 100, and is used to convert the medium-voltage DC output signal into a low-voltage DC signal.

[0063] Among them, N sub-DC polarity conversion circuit modules are cascaded one by one in sequence to form N levels; the first input port of the first-level sub-DC polarity conversion circuit module is connected to the medium-voltage DC distribution network, and the second input port of the N-th sub-DC polarity conversion circuit module is connected to the medium-voltage DC distribution network; the i-th sub-DC polarity conversion circuit module is configured as follows: the first input port is connected to the second input port of the adjacent previous-level sub-DC polarity conversion circuit module, and the second input port is connected to the first input port of the adjacent next-level sub-DC polarity conversion circuit module, i∈[2, N-1], and i is a positive integer; the first output end of each sub-DC polarity conversion circuit module is connected to the first input end of the low-voltage DC distribution network, and the second output end of each sub-DC polarity conversion circuit module is connected to the second input end of the low-voltage DC distribution network. From the above connection relationship, it can be seen that on the medium voltage side, the voltage of the medium voltage DC distribution network is the sum of the input voltages of the N sub-DC polarity conversion circuit modules, thereby reducing the withstand voltage of each sub-DC polarity conversion circuit module and improving the safety of the system. On the low voltage side, the current of the low voltage DC distribution network is the sum of the output currents of the N sub-DC polarity conversion circuit modules. Under the condition of the same number of sub-DC polarity conversion circuit modules, the maximum output current can be obtained, thereby maximizing the load capacity of the system.

[0064] Specifically, by controlling the on and off of the switch tube inside the full-bridge circuit 100, a DC power supply with variable polarity can be provided to the DAB DC transformer 200, thereby achieving the purpose of outputting variable polarity DC power to the downstream low-voltage DC distribution network.

[0065] In the DC polarity conversion circuit based on the DC transformer in the above embodiment, on the one hand, by setting a full-bridge circuit, the polarity reversal of the output DC signal is realized according to the control signal action. The circuit structure is simple, the control method is convenient, and the technical solution is mature. The DC transformer can realize the reversal of the DC voltage polarity on the medium voltage side only through the control method, which greatly facilitates the application of the DC transformer in the DC system based on LCC. On the other hand, the conversion circuit continues the advantages of the DAB DC transformer such as modularity, high power density and large transmission capacity.

[0066] In one embodiment of the present application, Figure 4 As shown, the full-bridge circuit 100 includes: a first half-bridge 110 and a second half-bridge 120, wherein the first half-bridge 110 includes a first controllable switch unit Q1 and a second controllable switch unit Q2 connected in series, and the midpoint of the first half-bridge is set as the first input port of the sub-DC polarity conversion circuit module; the second half-bridge 120 is connected in parallel with the first half-bridge 110, and the second half-bridge 120 includes a third controllable switch unit Q3 and a fourth controllable switch unit Q4 connected in series, the third controllable switch unit Q3 is connected to the first controllable switch unit Q1, the fourth controllable switch unit Q4 is connected to the second controllable switch unit Q2, and the midpoint of the second half-bridge 120 is set as the second input port of the sub-DC polarity conversion circuit module.

[0067] Specifically, by controlling the opening and closing sequence of the above four controllable switch units, a DC power supply with variable polarity can be obtained at the input end of the DAB DC transformer 200, which will be described below through specific embodiments.

[0068] In one embodiment of the present application, Figure 5 As shown, the first controllable switch unit Q1 and the fourth controllable switch unit Q4 are controlled to be turned on according to the control signal, and the second controllable switch unit Q2 and the third controllable switch unit Q3 are controlled to be turned off. From the flow path of the circuit in the figure, the current sequentially passes from the positive electrode of the medium-voltage DC distribution network through the first controllable switch unit Q1, the DAB DC transformer 200, the fourth controllable switch unit Q4 and the negative electrode of the medium-voltage DC distribution network to form a power-on loop. In this case, the DAB DC transformer 200 obtains a positive medium-voltage DC output signal, thereby outputting a positive low-voltage DC power to the downstream low-voltage DC distribution network.

[0069] In one embodiment of the present application, Figure 6As shown, the first controllable switch unit Q1 and the fourth controllable switch unit Q4 are controlled to be turned off according to the control signal, and the second controllable switch unit Q2 and the third controllable switch unit Q3 are controlled to be turned on. From the flow path of the circuit in the figure, the current sequentially passes from the positive electrode of the medium-voltage DC distribution network through the second controllable switch unit Q2, the DAB DC transformer 200, the fourth controllable switch unit Q3 and the negative electrode of the medium-voltage DC distribution network to form a power-on loop. In this case, the DAB DC transformer 200 obtains a reverse medium-voltage DC output signal, thereby outputting reverse low-voltage DC power to the downstream low-voltage DC distribution network.

[0070] In one embodiment of the present application, Figure 7 As shown, the present application provides a DC polarity conversion control method based on a DC transformer, which is used to control the DC polarity conversion circuit module of any of the above-mentioned embodiments, and the method includes:

[0071] Step 22, obtaining circuit parameters of any of the sub-DC polarity conversion circuit modules;

[0072] The circuit parameters include at least one of a medium voltage DC output voltage measurement value, a low voltage DC current measurement value, a low voltage DC voltage measurement value and low voltage DC voltage polarity information.

[0073] Step 24, generating a switch control signal according to the circuit parameter and a preset circuit parameter reference value to control the sub-DC polarity conversion circuit module to convert the medium voltage DC input signal with fixed polarity into a low voltage DC signal with variable polarity.

[0074] The preset circuit parameter reference values ​​include a medium voltage DC output voltage reference value and a low voltage DC voltage reference value.

[0075] Specifically, the medium voltage DC output voltage reference value is an average value of N medium voltage DC output voltage measurement values.

[0076] In the DC polarity conversion control method based on the DC transformer in the above embodiment, by sampling the circuit parameters on the medium and low voltage sides and using them together with the reference values ​​of the preset circuit parameters as the input of the circuit control, the switch control signal is obtained through pulse width modulation, so as to accurately control the conversion circuit to generate a DC signal with variable polarity as required. At the same time, the circuit control system can also expand its functions as required. For example, if there is a requirement for equalizing the voltage of the sub-DC polarity conversion circuit modules, equalizing voltage control can be added to the system to keep the output voltages of each sub-DC polarity conversion circuit module consistent.

[0077] In one embodiment of the present application, Figure 8 As shown, step 24, generating a switch control signal according to the circuit parameter and a preset circuit parameter reference value, includes:

[0078] Step 242, generating the shift ratio information of the sub-DC polarity conversion circuit module through a PI regulator according to the medium voltage DC output voltage measurement value, the low voltage DC current measurement value, the low voltage DC voltage measurement value and the corresponding preset circuit parameter reference values;

[0079] Specifically, a PI regulator is a linear controller that forms a control deviation based on a given value and an actual output value, and forms a control quantity through a linear combination of the proportion and integral of the deviation to control the controlled object. It has proportional regulation and integral regulation functions. In control engineering practice, it is mainly used to improve the steady-state performance of the control system. In this embodiment, the medium-voltage DC output voltage measurement value, the low-voltage DC current measurement value and the low-voltage DC voltage measurement value are used as input quantities of the actual output value of the PI regulator, and the medium-voltage DC output voltage reference value and the low-voltage DC voltage reference value are used as input quantities of the given value of the PI regulator. The two constitute a control deviation, and the shift ratio information of the sub-DC polarity conversion circuit module is generated by the PI regulator, thereby optimizing the output voltage waveform.

[0080] Step 244, generating full-bridge circuit switch state information according to the low-voltage DC voltage polarity information;

[0081] Specifically, it can be seen from the previous embodiments that different switching states of the full-bridge circuit will generate different DC voltage polarities. Therefore, the opening and closing information of the controllable switch unit inside the full-bridge circuit can also be obtained through the polarity of the DC voltage on the low-voltage side. This information is used as input information for generating a switch control signal to generate an accurate switch control signal, thereby realizing the change of the DC voltage polarity as required.

[0082] Step 246: Generate a switch control signal through a PWM modulator according to the shift ratio information and the switch state information of the full-bridge circuit.

[0083] Specifically, the circuit shift ratio information and the full-bridge circuit switch state information obtained according to the aforementioned embodiments are processed through a PWM modulator to obtain a trigger pulse control signal of a controllable switch unit of the circuit, thereby realizing functions such as variable polarity of the circuit output DC voltage and voltage balancing of each sub-DC polarity conversion circuit module.

[0084] In one embodiment of the present application, Fig. 9 As shown, step 242, according to the medium voltage DC output voltage measurement value, the low voltage DC current measurement value and the low voltage DC voltage measurement value and the corresponding preset circuit parameter reference value, generates the shift ratio information of the sub DC polarity conversion circuit module through the PI regulator, including:

[0085] Step 2422, generating a first low-voltage DC current reference compensation value through a first PI regulator according to the low-voltage DC voltage measurement value and the low-voltage DC voltage reference value;

[0086] Specifically, in order to obtain an ideal low-voltage DC voltage output waveform, the low-voltage DC voltage measurement value must be optimized and controlled. A first low-voltage DC current reference compensation amount can be generated through a first PI regulator based on the low-voltage DC voltage measurement value and the low-voltage DC voltage reference value, which serves as the first input control amount of the final reference current compensation amount, so that the final output voltage waveform can be optimized.

[0087] Step 2424, generating a second low-voltage DC current reference compensation value through a second PI regulator according to the medium-voltage DC output voltage measurement value and the medium-voltage DC output voltage reference value;

[0088] Specifically, since the conversion circuit system is composed of N sub-DC polarity conversion circuits cascaded, there must be a situation where the DC voltages on the medium-voltage side of each sub-module are different, which may cause circuit circulation, resulting in energy waste, and even burning of power equipment. Therefore, it is necessary to perform voltage balancing control on each sub-module. In this embodiment, the medium-voltage DC output voltage measurement value and the medium-voltage DC output voltage reference value are generated through the second PI regulator to generate a second low-voltage DC current reference compensation amount as the second input control amount of the final reference current compensation amount, so that the final output voltages of each sub-module remain consistent.

[0089] Step 2426, generating a low-voltage direct current reference compensation amount according to the first low-voltage direct current reference compensation amount and the second low-voltage direct current reference compensation amount;

[0090] Step 2428: Generate the shift ratio information through a third PI regulator according to the low-voltage DC current measurement value and the low-voltage DC current reference compensation amount.

[0091] Specifically, by using the low-voltage DC current reference compensation amount obtained by superimposing the various input control amounts in the aforementioned embodiments and the actual low-voltage DC current measurement value as the two input amounts of the third PI regulator, the shift ratio information of the final control signal can be obtained, so that the final switch control signal can control the conversion circuit to achieve low-voltage DC power with optimized output voltage waveform and equal voltage for each sub-module.

[0092] In one embodiment of the present application, Fig.10As shown, the present application provides a DC polarity conversion control device based on a DC transformer, including: a parameter acquisition module 1000 and a control module 2000, wherein the parameter acquisition module 1000 is used to obtain the circuit parameters; the control module 2000 is used to generate a switch control signal according to the circuit parameters and preset circuit parameter reference values ​​to control the sub-DC polarity conversion circuit module to work normally.

[0093] In one embodiment of the present application, Fig.11 As shown, the control module 2000 includes: a low-voltage DC voltage controller 2100, a voltage balance controller 2200, a current controller 2300 and a PWM modulator 2400, wherein the voltage controller 2100 is used to generate a first low-voltage DC current reference compensation amount through a first PI regulator according to the low-voltage DC voltage measurement value and the low-voltage DC voltage reference value; the voltage balance controller 2200 is used to generate a second low-voltage DC current reference compensation amount through a second PI regulator according to the medium-voltage DC output voltage measurement value and the medium-voltage DC output voltage reference value; the current controller 2300 is used to generate the shift ratio information through a third PI regulator according to the low-voltage DC current measurement value and the low-voltage DC current reference compensation amount; the PWM modulator 2400 is used to generate a switch control signal according to the shift ratio information and the full-bridge circuit switch state information.

[0094] In one embodiment of the present application, Fig.11 As shown, the present application further provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the method described in any of the above embodiments are implemented, and the specific steps include:

[0095] Step 22, obtaining circuit parameters of any of the sub-DC polarity conversion circuit modules;

[0096] Step 2422, generating a first low-voltage DC current reference compensation value through a first PI regulator according to the low-voltage DC voltage measurement value and the low-voltage DC voltage reference value;

[0097] Step 2424, generating a second low-voltage DC current reference compensation value through a second PI regulator according to the medium-voltage DC output voltage measurement value and the medium-voltage DC output voltage reference value;

[0098] Step 2426, generating a low-voltage direct current reference compensation amount according to the first low-voltage direct current reference compensation amount and the second low-voltage direct current reference compensation amount;

[0099] Step 2428, generating the shift ratio information through a third PI regulator according to the low-voltage DC current measurement value and the low-voltage DC current reference compensation amount;

[0100] Step 244, generating full-bridge circuit switch state information according to the low-voltage DC voltage polarity information;

[0101] Step 246: Generate a switch control signal through a PWM modulator according to the shift ratio information and the switch state information of the full-bridge circuit.

[0102] It should be noted that in the embodiments provided in the present application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the system embodiments described above are only schematic. For example, the division of the units can be a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of units or modules, which can be electrical or other forms.

[0103] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0104] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above integrated units may be implemented in the form of hardware.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A DC polarity conversion control method based on a DC transformer, characterized in that: Used to control a sub-DC polarity conversion circuit module, wherein the DC polarity conversion circuit based on a DC transformer is connected between a medium-voltage DC distribution network and a low-voltage DC distribution network to provide a low-voltage DC signal with variable polarity for the low-voltage DC distribution network, and the DC polarity conversion circuit based on a DC transformer includes a preset number of cascaded sub-DC polarity conversion circuit modules, and any of the sub-DC polarity conversion circuit modules includes: a full-bridge circuit, including a first half-bridge and a second half-bridge, the first half-bridge includes a first controllable switch unit and a second controllable switch unit connected in series, the midpoint of the first half-bridge is set as the first input port of the sub-DC polarity conversion circuit module, the second half-bridge is connected in parallel with the first half-bridge, the second half-bridge includes a third controllable switch unit and a fourth controllable switch unit connected in series, the third controllable switch unit and The first controllable switch unit is connected, the fourth controllable switch unit is connected to the second controllable switch unit, the midpoint of the second half bridge is set as the second input port of the sub-DC polarity conversion circuit module, and the full-bridge circuit is used to control the first controllable switch unit and the fourth controllable switch unit to be turned on according to the control signal, and control the second controllable switch unit and the third controllable switch unit to be turned off, and output a positive medium-voltage DC output signal; and control the first controllable switch unit and the fourth controllable switch unit to be turned off according to the control signal, and control the second controllable switch unit and the third controllable switch unit to be turned on, and output a reverse medium-voltage DC output signal; a DAB DC transformer is connected to the full-bridge circuit, and is used to convert the medium-voltage DC output signal into the low-voltage DC signal; the method includes; Obtaining circuit parameters of any of the sub-DC polarity conversion circuit modules, wherein the circuit parameters include at least one of a medium voltage DC output voltage measurement value, a low voltage DC current measurement value, a low voltage DC voltage measurement value, and low voltage DC voltage polarity information; Generate a switch control signal according to the circuit parameter and a preset circuit parameter reference value to control the sub-DC polarity conversion circuit module to convert a medium voltage DC input signal with a fixed polarity into a low voltage DC signal with a variable polarity, wherein the preset circuit parameter reference value includes a medium voltage DC output voltage reference value and a low voltage DC voltage reference value; Wherein, the step of generating a switch control signal according to the circuit parameter and a preset circuit parameter reference value includes: Generate the shift phase information of the sub-DC polarity conversion circuit module through a PI regulator according to the medium voltage DC output voltage measurement value, the low voltage DC current measurement value, the low voltage DC voltage measurement value and the corresponding preset circuit parameter reference value; generating full-bridge circuit switch state information according to the low-voltage DC voltage polarity information; Generate a switch control signal through a PWM modulator according to the shift phase information and the switch state information of the full-bridge circuit; Wherein, the step of generating the shift ratio information of the sub-DC polarity conversion circuit module through a PI regulator according to the medium voltage DC output voltage measurement value, the low voltage DC current measurement value, the low voltage DC voltage measurement value and the corresponding preset circuit parameter reference value includes: Generate a first low-voltage DC current reference compensation amount through a first PI regulator according to the low-voltage DC voltage measurement value and the low-voltage DC voltage reference value; generating a second low-voltage DC current reference compensation amount through a second PI regulator according to the medium-voltage DC output voltage measurement value and the medium-voltage DC output voltage reference value; generating a low-voltage direct current reference compensation amount according to the first low-voltage direct current reference compensation amount and the second low-voltage direct current reference compensation amount; The shift ratio information is generated by a third PI regulator according to the low-voltage direct current measurement value and the low-voltage direct current reference compensation amount.

2. The method according to claim 1, characterized in that The preset number is N, N is a positive integer, and the N sub-DC polarity conversion circuit modules are cascaded one by one in sequence to form N stages; The first input port of the first-stage DC polarity conversion circuit module is connected to the medium-voltage DC distribution network, and the second input port of the N-th DC polarity conversion circuit module is connected to the medium-voltage DC distribution network; The sub-DC polarity conversion circuit module of the i-th stage is configured as follows: the first input port is connected to the second input port of the sub-DC polarity conversion circuit module of the adjacent previous stage, and the second input port is connected to the first input port of the sub-DC polarity conversion circuit module of the adjacent next stage, i∈[2, N-1], and i is a positive integer; The first output end of each sub-DC polarity conversion circuit module is connected to the first input end of the low-voltage DC distribution network, and the second output end of each sub-DC polarity conversion circuit module is connected to the second input end of the low-voltage DC distribution network.

3. The method according to claim 2, characterized in that The medium voltage DC output voltage reference value is an average value of N medium voltage DC output voltage measurement values.

4. The method according to claim 1, characterized in that: The PI regulator is a linear controller.

5. A DC polarity conversion control device based on a DC transformer, characterized in that: The DC polarity conversion control method based on a DC transformer as described in any one of claims 1 to 4, wherein the device comprises: A parameter acquisition module, used to acquire circuit parameters; A control module, used to generate a switch control signal according to the circuit parameters and the preset circuit parameter reference value, so as to control the sub-DC polarity conversion circuit module to work normally; Wherein, the control module comprises: A low-voltage DC voltage controller, used for generating a first low-voltage DC current reference compensation amount through a first PI regulator according to a low-voltage DC voltage measurement value and a low-voltage DC voltage reference value; A voltage balancing controller, configured to generate a second low-voltage DC current reference compensation amount through a second PI regulator according to a medium-voltage DC output voltage measurement value and a medium-voltage DC output voltage reference value; A current controller, used for generating a shift ratio information through a third PI regulator according to a low-voltage DC current measurement value and a low-voltage DC current reference compensation amount; The PWM modulator is used to generate a switch control signal according to the shift phase information and the switch state information of the full-bridge circuit.

6. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 4 are implemented.

Images