Control method of ac-dc hybrid multi-port converter

Abstract

The application provides a control method of AC-DC hybrid multi-port converter, n converter units are connected in series on the DC side and n+1 DC terminals are led out to form n DC ports; a multi-winding transformer leads out 1 AC port to construct a multi-port converter system; the n+1th DC terminal d n+1 The n DC ports are sequentially ordered from low to high voltage level, the current reference value of the converter unit is calculated, the current inner loop control is constructed, the outer loop control is constructed according to the current inner loop control, the power and current of the DC and AC ports are controlled, and the transmission power of the DC and AC ports and the conversion power of the n converter units are determined. Through the electrical decoupling and flexible control among the DC and AC ports, diversified current, power control, AC or DC voltage control are realized, the multi-port converter device with any port number can be applied, and local flexible control and flexible DC and AC conversion, control and transmission and distribution between different places are realized.

Description

Technical Field

[0001] This invention belongs to the field of power system transmission and distribution technology, and particularly relates to a control method for AC / DC hybrid multi-port converter. Background Technology

[0002] In recent years, with economic development and social progress, electricity load has increased rapidly, and the demand for electricity and power quality has continued to grow. More and more distributed energy sources are being connected to the grid, such as photovoltaic energy, wind energy, and electric vehicles. Some of these are connected to the grid in the form of direct current (DC). With the popularization of various DC loads, the diversification of loads has made the current energy system complex, and the stability and efficiency of energy supply face enormous challenges.

[0003] Therefore, under the trend of power electronics in power distribution networks, AC / DC hybrid flexible power distribution has become a popular research direction. However, at present, when using AC / DC hybrid flexible power distribution technology to realize AC-DC conversion and DC-DC conversion, due to the defects of many power electronic devices, complex control methods and high overall cost, it is still impossible to achieve flexible and efficient power transmission and distribution control.

[0004] The above content is only used to help understand the technical solution of the present invention and does not represent an admission that the above content is prior art. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a control method for AC / DC hybrid multi-port converters. This method is mainly used to solve the problems of numerous power electronic devices, complex control methods, and high overall costs in the prior art when performing AC / DC conversion and DC / DC conversion, and to overcome the defects of insufficient flexibility and efficiency in power transmission and distribution control.

[0006] To achieve the above objectives, the present invention provides a control method for a hybrid AC / DC multiport converter, comprising the following steps:

[0007] Connect the DC sides of n converter units in series and draw n+1 DC terminals from the DC bus of the converter units, where the (n+1)th DC terminal d n+1 Defined as a common DC terminal, the other n DC terminals and the common DC terminal form n DC ports; one or more transformers are combined to form a multi-winding transformer with n+1 windings, the AC side of the n converter units is connected to the n windings of the multi-winding transformer, and the multi-winding transformer leads out one AC port from the n+1 winding to construct a multi-port converter system;

[0008] The (n+1)th DC terminal d n+1Defined as a common DC terminal, n DC ports are sorted in descending order of voltage level. The voltage of a DC port with a higher voltage level is formed by superimposing the voltage of a DC port with a lower voltage level and the DC voltage of the converter unit between them, thereby significantly reducing the number of power electronic devices required and improving cost performance.

[0009] Calculate the current reference value of the converter unit, construct the inner current loop control, construct the outer current loop control based on the inner current loop control, control the power and current of the DC and AC ports, and determine the transmission power of the AC and DC ports and the conversion power of n converter units.

[0010] In some embodiments, whether the converter unit performs power or current control on the corresponding port is used as a coupling condition. The coupling relationship between the DC port and the converter unit is constructed according to the coupling condition, and one or more of the multi-port independent control mode and multi-port cooperative control mode are formed according to the coupling relationship.

[0011] In some embodiments, the voltage, input current, and input power of the DC port are defined as V, respectively. dt k I dt k P dt k The DC voltage, DC input current, and DC input power of the converter unit are respectively V du k I du k P c k Where k = 1, 2, ..., n is the DC port number, and the d-th port is the d-th port number. n+1 The DC terminal is a common terminal with a reference potential, V dt k It is DC terminal d k With common DC terminal d n+1 The voltage at the resulting DC port k is then:

[0012]

[0013] Further calculations yield the following:

[0014]

[0015] By using the correspondence between the power of the converter unit and the power of the DC port in formula (2), the power and current of any converter unit can be controlled, thereby controlling the transmission power and current of n DC ports and 1 AC port.

[0016] In some embodiments, when power / current control is performed on n DC ports, the power / current reference value of the corresponding converter unit is calculated according to formula (2); when power control is performed on other DC ports and AC ports besides the kth DC port, the power / current reference value of DC port k is calculated according to the following formula:

[0017]

[0018] Where P at The input power at the AC port, calculated from formulas (2) and (3), is also limited by the rated power of each converter unit: -P cN k ≤P c k ≤P cN k k = 1, 2, ..., n, where the subscript N represents the rated value;

[0019] The result is obtained from formula (2):

[0020]

[0021] The power / current of converter unit k is affected by the power / current of DC port k, and also by the power / current of converter unit k-1. The power or current control between converter unit k and DC port k, and converter unit k-1 is used as the DC-side coupling relationship.

[0022] In some embodiments, the converter unit k provides a DC current path for each of its DC ports and converter units, the DC current path is kept constant according to the current rating, and this DC-side coupling relationship is corresponding to a multi-port independent control mode.

[0023] From formula (2), the transmission power of each DC port can be further derived as follows:

[0024]

[0025] The current at each DC port is expressed by the following formula:

[0026]

[0027] The superscript "*" indicates a control reference value;

[0028] According to formulas (4) and (6), except for the first converter unit, the DC current of the other converter units is equal to the difference between the input DC current of the previous converter unit and the input current of the corresponding DC port. The relationship between the rated currents of each converter unit is determined as follows:

[0029] I duN k =IduN k-1 +I dtN k k = 1, 2, ..., n, I duN 0 =0 (7)

[0030] The subscript N indicates the rated value;

[0031] In multi-port independent control mode, since the power / current of each port varies within its set rated value range and is not affected by the power / current of other ports, we can conclude that:

[0032] I dt k ≤I dtN k ,P dt k ≤P dtN k ,k=1,2,…n, (8)

[0033] Except for the first converter unit, the current of other converter units consists of two parts: the current of the upstream converter unit and the current of the DC port of this unit. These two currents vary independently within their rated ranges and do not affect each other. Under independent control, the maximum power transmitted through each DC port is its rated power.

[0034] P dtmax k =P dtN k =V dtN k I dtN k =V dtN k (P cN k / V duN k -P cN k-1 / V duN k-1 (9)

[0035] Where k = 1, 2, ..., n, I duN 0 =P cN 0 / V duN 0 =0

[0036] In some embodiments, the converter unit k provides a DC current path for each of its DC ports and converter units. The size of the DC current path varies according to the power conversion requirements of each DC port and converter unit to complete the power or current control of the corresponding port. This is called the multi-port cooperative control mode.

[0037] In the multi-port cooperative control mode, the maximum transmission power of each port can be calculated from formula (5):

[0038]

[0039] According to the relationship in formula (7), calculate the rated current and rated power of each converter unit. Set the exchange power of one of the adjacent converter units to a positive rated value and the exchange power of the other to a negative rated value. The maximum and minimum input power of the DC port can be obtained as follows:

[0040]

[0041] In some embodiments, in a multi-port cooperative control mode, the maximum power of each port is cooperatively controlled using a priority control method, including the following steps:

[0042] The n DC ports are prioritized, with each priority represented by a priority number R. The priority numbers of the n DC ports are arranged in order as R1, R2, ..., Rn. n The higher the value of R, the higher the priority. The power / current control of the DC port will give priority to the DC port with the higher priority number.

[0043] Taking the k-th DC port as an example, let the priority number of the k-th port be R. k When k is not equal to 1 or n, we can obtain from (5):

[0044] P dt k =P c k-1 V dt k / V du k-1 -P c k V dt k / V du k k = 1, 2, ..., n, P c 0 V dt 1 / V du 0 =0 (12)

[0045] Based on priority, there are four possible scenarios:

[0046] (1)R k >R k-1 R k >R k+1

[0047] At this time P c k-1 The range of values ​​will be affected by P dt k The influence of this will prioritize meeting the DC port k output power requirement, and from (12), its value range is limited to:

[0048] P dt k V du k-1 / V dt k -P cN k V du k-1 / V du k ≤P c k-1 ≤P dt k V du k-1 / V dt k +P cN k V du k-1 / V du k (13)

[0049] P dt k+1 The range of values ​​will also be affected by P c k The influence of this will prioritize satisfying the output power requirement of port k. From (12), its value range is limited to:

[0050] P c k V dt k+1 / V du k -P cN k+1 V dt k+1 / V du k+1 ≤P dt k+1 ≤P c k V dtk+1 / V du k +P cN k+1 V dt k+1 / V du k+1 ,k≠1,n (14)

[0051] Furthermore, when R k-1 >R k+1 P is preferred. c k-1 Adjust to meet the output power requirement of DC port k; otherwise, prioritize P. dt k+1 Adjustments;

[0052] (2)R k >R k-1 R k <R k+1

[0053] At this time P c k-1 The range of values ​​will be affected by P dt k The value of P is affected, so as to prioritize meeting the output power requirement of port k, and its value range is limited as shown in (13); in addition, P c k The range of values ​​will also be affected by P dt k+1 The influence of the value of P is considered, so that the output power requirement of port k+1 is satisfied first. From (12), P is obtained. c k The range of values ​​is limited to:

[0054] P dt k+1 V du k / V dt k+1 -P cN k+1 V du k / V du k+1 ≤P c k ≤P dt k+1 V du k / V dt k+1 +P cN k+1 V du k / V duk+1 (15)

[0055] (3)R k <R k-1 R k >R k+1

[0056] P dt k The range of values ​​will also be affected by P c k-1 The influence of the value is to prioritize meeting the output power requirement of port k-1. From (12), its value range is limited to:

[0057] P c k-1 V dt k / V du k-1 -P cN k V dt k / V du k ≤P dt k ≤P c k-1 V dt k / V du k-1 +P cN k V dt k / V du k ,k≠1,n (16)

[0058] P dt k+1 The range of values ​​will also be affected by P c k The influence of the value is to prioritize the output power requirement of port k, so its value range is limited as shown in (14);

[0059] (4)R k <R k-1 R k <R k+1

[0060] P dt k The range of values ​​will be affected by P c k-1 The value of P is affected, so as to prioritize meeting the output power requirements of port k-1, and its value range is limited as shown in (16); in addition, P c k The range of values ​​will also be affected by Pdt k+1 The value of the value is determined to prioritize the output power requirement of port k+1, and its range is limited as shown in (15).

[0061] When R k-1 >R k+1 And the above are respectively satisfying P c k-1 and P dt k+1 P regulating demand dt k and P c k If the values ​​conflict, P is determined first based on priority, satisfying the adjustment requirement of the former. dt k If a value is not specified, then the latter adjustment requirement should be satisfied first, and P should be determined preferentially. c k Values;

[0062] When k=1, the following two cases are included: R k >R k+1 or R k <R k+1 Based on the above situations (1) and (2), P is processed according to formulas (14) and (15) respectively. dt k+1 P c k The range of values ​​is limited;

[0063] When k = n, the following two cases are included: R k >R k-1 or R k <R k-1 Based on the above situations (1) and (3), P is processed according to formulas (13) and (16) respectively. c k-1 P dt k The range of values ​​is limited.

[0064] In some embodiments, when using a priority control method for collaborative control:

[0065] Power control is performed on all DC ports except the AC port and the k-th DC port, where the priority number for AC port power control is R. k The power that can be converted is equivalent to the power at DC port k according to P. dt k Control is performed, and its priority number is R. k Control is performed according to the aforementioned priority control method, where P dt k The formula for calculating the reference value is as follows:

[0066]

[0067] Among them, P dtmin k ,P dtmax k These are the converter unit k with priority number R. k The minimum and maximum values ​​that can be obtained under certain conditions.

[0068] In some embodiments, the multi-port cooperative control mode includes using a peer control method to cooperatively control the power of each port, including the following steps:

[0069] The control priority of each port is regarded as the same level. Each converter unit prioritizes completing its own specified transmission task. If there is still power / current margin beyond the specified transmission task, it will assist other related ports in completing the excess power / current transmission demand.

[0070] If AC and DC ports are controlled at the same level, then:

[0071]

[0072] Where k = 1, 2, ..., n, k ≠ 1;

[0073] When k = 1, then:

[0074]

[0075] in

[0076] In some embodiments, based on the above-mentioned multi-port power / current relationship, an inner current loop control is constructed, and a corresponding outer loop control is completed according to the control objective, including AC voltage control, DC voltage control, Droop control, and AC frequency control; independent control or collaborative control is completed by combining the inner current loop control and the outer loop control.

[0077] In the priority control mode, after obtaining the current reference value through the outer loop calculation, the inner loop of the current of different ports can still be controlled according to the priority number mentioned above. That is, the port with the higher priority number will be given priority to meet its current control requirements. If the outer loop is DC voltage control, considering that DC voltage stability is the basis for the stable operation of the corresponding DC circuit, it is generally advisable to assign a higher priority number. Moreover, the higher the voltage level, the greater the range of voltage stability and the power supply / load power. In this case, the priority number can be arranged from high to low voltage level.

[0078] In the same-level control mode, after obtaining the current reference values ​​of different ports through the outer loop calculation, the current inner loop of these ports completes the control adjustment according to the above same-level control principle. That is, each converter unit prioritizes to complete the current control requirements of the corresponding DC port. On this basis, if there is still current margin, it can assist other ports in completing their excess power / current transmission requirements.

[0079] In the hybrid control mode, some ports adopt priority control mode and some ports adopt peer control mode, so as to realize diversified operation control mode of multi-port converter.

[0080] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0081] Through electrical decoupling and flexible control between AC and DC ports, diverse current and power control, AC or DC voltage control can be achieved. It is applicable to multi-port converters with any number of ports, enabling flexible local control and flexible AC / DC conversion, control and distribution between different locations.

[0082] The novel multi-port converter device applied to this control method requires fewer power electronic devices, the control method is simple and effective, the overall cost is low, the power transmission and distribution control is flexible and efficient, and it can simultaneously realize AC-DC conversion and DC-DC conversion. Attached Figure Description

[0083] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0084] Figure 1 This is a schematic diagram of a multi-port converter system constructed in one embodiment.

[0085] Figure 2 This is a schematic diagram of the basic structure for current control at the k-th DC port in one embodiment.

[0086] Figure 3 This is a schematic diagram of the basic structure for power control at the k-th DC port in one embodiment.

[0087] Figure 4 This is a schematic diagram of the basic structure for voltage control of the k-th DC port in one embodiment.

[0088] Figure 5 This is a schematic diagram of independently controlled port power in one embodiment.

[0089] Figure 6 This is a schematic diagram of independently controlled port current in one embodiment.

[0090] Figure 7This is a schematic diagram of the port power that is prioritized for control in one embodiment.

[0091] Figure 8 This is a schematic diagram of the port current that is preferentially controlled in one embodiment.

[0092] Figure 9 This is a schematic diagram of port power control at the same level in one embodiment.

[0093] Figure 10 This is a schematic diagram of the port current under peer control in one embodiment. Detailed Implementation

[0094] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0095] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0096] This invention provides a control method for a hybrid AC / DC multiport converter, comprising the following steps:

[0097] Reference Figure 1 The DC sides of n converter units are connected in series and n+1 DC terminals are led out from the DC bus of the converter units. Each converter unit has independent control and regulation capabilities. The (n+1)th DC terminal d... n+1 Defined as a common DC terminal, the other n DC terminals and the common DC terminal form n DC ports; one or more transformers are combined to form a multi-winding transformer with n+1 windings. The n+1 windings are divided into two parts, one part consisting of n windings and the other part consisting of 1 winding. The AC side of the n converter units is connected to the n windings of the multi-winding transformer. The multi-winding transformer leads out 1 AC port from the n+1th winding to construct a multi-port converter system. This multi-port converter system has n DC ports and 1 AC port externally.

[0098] n converter units are used for AC / DC power conversion, AC / DC current conversion, and AC / DC voltage conversion, and are connected to have direct DC-DC conversion function; multi-winding transformers are used for electrical isolation, AC voltage transformation and power exchange between the first part consisting of n windings and the second part consisting of 1 winding, realizing AC voltage transformation and power transmission functions.

[0099] The (n+1)th DC terminal d n+1 Defined as a common DC terminal, n DC ports are arranged in descending order of voltage level. The voltage of a higher voltage level DC port is formed by superimposing the voltage of a lower voltage level DC port and the DC voltage of the converter unit between them. That is, from top to bottom, the voltage of the (n+1)th DC port is higher than the voltage of the nth DC port. This fully utilizes the lower voltage level converter unit and its corresponding DC port to play a role in the AC-DC conversion and corresponding DC port at the higher voltage level, forming a cost-effective multi-port converter topology. This allows the converter unit and power electronic devices in each DC port to be reused in the higher voltage level DC port, significantly reducing the number of power electronic devices required. At the same time, it enables direct DC-DC conversion between different DC ports, and the number of devices through which the current flows during direct DC-DC conversion is reduced, improving DC-DC conversion efficiency. It has the advantages of significantly reducing the number of power electronic devices required and improving cost-effectiveness.

[0100] Any of the above-mentioned converter units can be formed by connecting one or two or more bridge converter circuits in series and parallel, thereby increasing the rated voltage / rated power of the converter unit; different converter units can adopt different AC / DC conversion topologies, including modular multilevel bridge circuits, two-level voltage source bridge circuits, three-level and multilevel voltage source bridge circuits, current source bridge circuits, H-bridge converter circuits, etc.

[0101] Furthermore, for the aforementioned multi-port converter topology, the current reference value of the converter unit is calculated, an inner current loop control is constructed, and an outer loop control is constructed based on the inner current loop control to control the power and current of the DC and AC ports, determine the transmission power of the AC and DC ports and the conversion power of the n converter units, thereby meeting the diverse converter control requirements under different conditions.

[0102] In this embodiment, since the converter unit has two functions, one is to provide a DC current path for each of its DC ports and converter units, and the other is to perform power or current control on the corresponding ports; therefore, whether the converter unit performs power or current control on the corresponding ports is used as a coupling condition. The coupling relationship between the DC ports and the converter units is constructed according to the coupling condition. The coupling relationship between the DC ports and the converter units is also a DC-side coupling relationship. Based on the coupling relationship, one or more of the following can be formed: multi-port independent control mode and multi-port collaborative control mode.

[0103] In this AC / DC hybrid multiport converter control method, the voltage, input current, and input power of the DC port are defined as V, respectively. dt k I dt k P dt k The DC voltage, DC input current, and DC input power of the converter unit are respectively V du k I du k P c k Where k = 1, 2, ..., n is the DC port number, and the d-th port is the d-th port number. n+1 The DC terminal is a common terminal with a reference potential, V dt k It is DC terminal d k With common DC terminal d n+1 The voltage at the resulting DC port k is then:

[0104]

[0105] Further calculations yield the following:

[0106]

[0107] From formula (2), the current reference value of the converter unit can be further obtained, thereby completing the corresponding current regulation or current inner loop control. Based on the current inner loop, corresponding outer loop control can be further constructed as needed, such as AC power control outer loop, DC voltage control outer loop, AC voltage control outer loop, etc., so as to meet the diverse control needs under different conditions.

[0108] Taking a three-phase bridge converter unit as an example, the formula for calculating the D-axis reference current of the converter unit can be derived as follows:

[0109]

[0110] Among them, V m k Let be the D-axis voltage amplitude of the AC winding connected to converter unit k. For the k-th DC port, the basic block diagrams for DC current control, DC power control, and DC voltage control are as follows: Figure 2 , Figure 3 and Figure 4 As shown.

[0111] Using the correspondence between the power of the converter unit and the power of the DC port in formula (2), the power and current of any converter unit are controlled, thereby controlling the transmission power and current of n DC ports and 1 AC port. This determines the transmission power of n+1 AC and DC ports and the conversion power of n converter units, thus establishing the operating mode and status of the multi-port converter device. Furthermore, the power / current of n-1 DC ports and 1 AC port can also be controlled.

[0112] In this embodiment, when power / current control is performed on n DC ports, the power / current reference value of the corresponding converter unit is calculated according to formula (2); when power control is performed on other DC ports and AC ports other than the kth DC port, the power / current reference value of DC port k is calculated according to the following formula:

[0113]

[0114] Where P at The input power at the AC port, calculated from formulas (2) and (3), is also limited by the rated power of each converter unit: -P cN k ≤P c k ≤P cN k k = 1, 2, ..., n, where the subscript N represents the rated value;

[0115] The result is obtained from formula (2):

[0116]

[0117] The power / current of converter unit k is affected by the power / current of DC port k, and also by the power / current of converter unit k-1. The power or current control between converter unit k and DC port k, and converter unit k-1 is used as the DC-side coupling relationship.

[0118] In one implementation, the converter unit k provides a DC current path for each of its DC ports and converter units. The DC current path remains constant according to the current rating, that is, the converter unit k does not affect the current / power reference value of its corresponding port and its operation control, and this DC-side coupling relationship corresponds to a multi-port independent control mode.

[0119] From formula (2), the transmission power of each DC port can be further derived as follows:

[0120]

[0121] The current at each DC port is expressed by the following formula:

[0122]

[0123] The superscript "*" indicates a control reference value;

[0124] According to formulas (4) and (6), except for the first converter unit, the DC current of the other converter units is equal to the difference between the input DC current of the previous converter unit and the input current of the corresponding DC port. The relationship between the rated currents of each converter unit is determined as follows:

[0125] I duN k =I duN k-1 +I dtN k k = 1, 2, ..., n, I duN 0 =0 (7)

[0126] The subscript N indicates the rated value;

[0127] In multi-port independent control mode, since the power / current of each port varies within its set rated value range and is not affected by the power / current of other ports, we can conclude that:

[0128] I dt k ≤I dtN k ,P dt k ≤P dtN k ,k=1,2,…n, (8)

[0129] Except for the first converter unit, the current of other converter units consists of two parts: the current of the upstream converter unit and the current of the DC port of this unit. These two currents vary independently within their rated ranges and do not affect each other. Under independent control, the maximum power transmitted through each DC port is its rated power.

[0130] P dtmax k =P dtN k =V dtN k I dtN k =V dtN k (P cN k / V duN k -P cN k-1 / V duN k-1 (9)

[0131] Where k = 1, 2, ..., n, I duN 0 =P cN 0 / V duN 0 =0

[0132] In one implementation, the converter unit k provides a DC current path for each of its DC ports and converter units. The size of the DC current path can be flexibly changed according to the power conversion requirements of each DC port and converter unit, thereby realizing the coordinated cooperation between each converter unit / DC port to complete the power or current control of the corresponding port. This is called the multi-port coordinated control mode.

[0133] In the multi-port cooperative control mode, the output power / current control of port k can take into account the power / current changes and influences of k and above each converter unit, and carry out corresponding control coordination, thereby realizing the mutual assistance of power and capacity of each port to a certain extent. This is called multi-port cooperative control. The maximum transmission power of each port can be calculated from formula (5):

[0134]

[0135] According to the relationship in formula (7), calculate the rated current and rated power of each converter unit. With the front and rear ports working together, set the exchange power of one of the adjacent converter units to a positive rated value and the exchange power of the other to a negative rated value. The maximum and minimum input power of the DC port can be obtained as follows:

[0136]

[0137] From formula (11), it can be seen that in the multi-port cooperative control mode, the transmission power of the DC port exceeds the rated value specified by independent control, thereby greatly improving the transmission power (except for the first DC port). However, reaching the maximum power requires the control coordination of adjacent converter units, so it is not possible for each port to obtain the maximum power simultaneously. Therefore, according to different coordination methods, in this embodiment, the multi-port cooperative control mode includes at least two cooperative control methods: one is to use a priority control method to coordinate the maximum power of each port, and the other is to use a peer control method to coordinate the power of each port. The following explains these two methods:

[0138] Example 1:

[0139] In Example 1, a priority control method is used to coordinate the maximum power of each port. For a DC / AC port to reach its maximum transmission power, the cooperation of other DC / AC ports and their corresponding converter units is required. It is impossible for all DC / AC ports to achieve maximum transmission power simultaneously. The process includes the following steps:

[0140] The n DC ports are prioritized, and different priorities are assigned to different ports, with the power transmission demand of the higher priority ports being given priority. The priority is represented by a priority number R, and the priority numbers of the n DC ports are arranged in order as R1, R2, ..., Rn. n The higher the value of R, the higher the priority. Power / current control at DC ports prioritizes DC ports with higher priority numbers, i.e., R1, R2, ..., R2. n It only represents the order of arrangement, not the order of priority. Instead, the priority is represented by the value of R.

[0141] Taking the k-th DC port as an example, let the priority number of the k-th port be R. k When k is not equal to 1 or n, we can obtain from (5):

[0142] P dt k =P c k-1 V dt k / V du k-1 -P c k V dt k / V du k k = 1, 2, ..., n, P c 0 V dt 1 / V du 0 =0 (12)

[0143] Based on priority, there are four possible scenarios:

[0144] (1)R k >R k-1 R k >R k+1

[0145] At this time P c k-1 The range of values ​​will be affected by P dt k The influence of this will prioritize meeting the DC port k output power requirement, and from (12), its value range is limited to:

[0146] P dt k V du k-1 / V dt k -P cN k V du k-1 / V du k ≤P c k-1 ≤P dt k V du k-1 / V dt k +P cN k V du k-1 / V du k (13)

[0147] P dt k+1 The range of values ​​will also be affected by P c k The influence of this will prioritize satisfying the output power requirement of port k. From (12), its value range is limited to:

[0148] P c k V dt k+1 / V du k -P cN k+1 V dt k+1 / V du k+1 ≤P dt k+1 ≤P c k V dt k+1 / V du k +P cN k+1 V dt k+1 / V du k+1 ,k≠1,n (14)

[0149] Furthermore, when R k-1 >R k+1 P is preferred. c k-1Adjust to meet the output power requirement of DC port k; otherwise, prioritize P. dt k+1 Adjustments.

[0150] (2)R k >R k-1 R k <R k+1

[0151] At this time P c k-1 The range of values ​​will be affected by P dt k The value of P is influenced by the fact that the output power requirement of port k is prioritized, and its range is limited as shown in (13). In addition, P c k The range of values ​​will also be affected by P dt k+1 The influence of the value of P is considered, so that the output power requirement of port k+1 is satisfied first. From (12), P is obtained. c k The range of values ​​is limited to:

[0152] P dt k+1 V du k / V dt k+1 -P cN k+1 V du k / V du k+1 ≤P c k ≤P dt k+1 V du k / V dt k+1 +P cN k+1 V du k / V du k+1 (15)

[0153] (3)R k <R k-1 R k >R k+1

[0154] P dt k The range of values ​​will also be affected by P c k-1 The influence of the value is to prioritize meeting the output power requirement of port k-1. From (12), its value range is limited to:

[0155] P c k-1 V dt k / V du k-1 -P cN k V dt k / V du k ≤P dt k ≤P c k-1 V dt k / V du k-1 +P cN k V dt k / V du k ,k≠1,n (16)

[0156] P dt k+1 The range of values ​​will also be affected by P c k The influence of the value is to prioritize the output power requirement of port k, so its value range is limited as shown in (14).

[0157] (4)R k <R k-1 R k <R k+1

[0158] P dt k The range of values ​​will be affected by P c k-1 The value of P is affected, so as to prioritize meeting the output power requirements of port k-1, and its value range is limited as shown in (16); in addition, P c k The range of values ​​will also be affected by P dt k+1 The value of the value is affected so that the output power requirement of port k+1 is satisfied first, and its value range is limited as shown in (15).

[0159] When R k-1 >R k+1 And the above are respectively satisfying P c k-1 and P dt k+1 P regulating demand dt k and P ck If the values ​​conflict, P is determined first based on priority, satisfying the adjustment requirement of the former. dt k If a value is not specified, then the latter adjustment requirement should be satisfied first, and P should be determined preferentially. c k Values.

[0160] Furthermore, when using a priority control approach for coordinated control:

[0161] When k=1, the following two cases are included: R k >R k+1 or R k <R k+1 Based on the above situations (1) and (2), P is processed according to formulas (14) and (15) respectively. dt k+1 P c k The range of values ​​is limited;

[0162] When k = n, the following two cases are included: R k >R k-1 or R k <R k-1 Based on the above situations (1) and (3), P is processed according to formulas (13) and (16) respectively. c k-1 P dt k The range of values ​​is limited.

[0163] Furthermore, when using a priority control approach for collaborative control:

[0164] Power control is performed on all DC ports except the AC port and the k-th DC port, where the priority number for AC port power control is R. k The power that can be converted is equivalent to the power at DC port k according to P. dt k Control is performed, and its priority number is R. k Control is performed according to the aforementioned priority control method, where P dt k The formula for calculating the reference value is as follows:

[0165]

[0166] Among them, P dtmin k ,P dtmax k These are the converter unit k with priority number R. k The minimum and maximum values ​​that can be obtained under certain conditions. When P dtk P has reached its limit. at If the requirements are still not met, the output must be adjusted sequentially from the lowest priority unit to the highest priority unit until the AC port output meets the requirements, or until the priority number is less than R. k All converter units were adjusted until the AC port output was as close as possible to the reference value.

[0167] Based on the aforementioned principle of prioritizing power from high to low, the output power range of the relevant converter units affecting the power of each DC port is sequentially limited, thereby ensuring that the output power of each port is equal to or close to the specified power output according to the principle of prioritizing power from high to low. The current control and its reference value are derived accordingly based on the aforementioned power control equation.

[0168] Example 2:

[0169] In Example 2, a peer control method is used to coordinate the power control of each port, including the following steps:

[0170] The control priority of each port is considered to be the same. Each converter unit prioritizes completing its own specified transmission task. If there is still power / current margin beyond the specified transmission task, it will assist other related ports in completing the excess power / current transmission demand. For example, if the rated current of converter unit k is P... cN k When the conversion power of converter unit k-1 is P c k-1 >0, the input power of DC port k can exceed the rated power P shown in equation (9). dtN k Conversely, if the conversion power of converter unit k-1 is P c k-1 <0, the output power of DC port k can exceed the rated power P shown in equation (9). dtN k This achieves the goal of exceeding transmission requirements. By employing peer control, the power / current transmission needs of each port can be guaranteed as much as possible, while fully utilizing the power / current margin of each converter unit to assist the corresponding port in increasing its transmission power / current, thereby maximizing the overall conversion / transmission capacity of the multi-port converter.

[0171] Furthermore, if AC and DC ports are controlled at the same level, then:

[0172]

[0173] Where k = 1, 2, ..., n, k ≠ 1;

[0174] When k=1, the power / current control is relatively simple, as follows:

[0175]

[0176] in

[0177] If the n-1 DC ports other than DC port k and 1 AC port are to be controlled at the same level, it is only necessary to obtain the power / current reference value of DC port k from the reference power / current of these ports, and then control the power / current of the n DC ports in the manner described above.

[0178] It should be noted that, based on the aforementioned multi-port power / current relationship, a current inner loop control is constructed using current control as the inner loop. Different outer loop controls are then designed to achieve the corresponding control objectives, such as AC voltage control, DC voltage control, drop control, and AC frequency control. These control methods can be combined with the current inner loop to achieve independent or coordinated control based on different outer loop controls.

[0179] For priority control, after obtaining the current reference value through outer loop calculation, the inner loop of current at different ports can still be controlled according to the priority number mentioned above. That is, the port with the higher priority number will have its current control requirements met first. If the outer loop is DC voltage control, considering that DC voltage stability is the basis for the stable operation of the corresponding DC circuit, it is generally advisable to assign a higher priority number. Moreover, the higher the voltage level, the greater the impact of voltage stability and the larger the power supply / load power. In this case, the priority number can be arranged from high to low voltage level.

[0180] For the same-level control method, after obtaining the current reference values ​​of different ports through the outer loop calculation, the current inner loop of these ports completes the control and adjustment according to the above same-level control principle. That is, each converter unit prioritizes to complete the current control requirements of the corresponding DC port. On this basis, if there is still current margin, it can assist other ports in completing their excess power / current transmission requirements.

[0181] Of course, a hybrid control mode can also be adopted, that is, by establishing a coupling relationship between the DC port and the converter unit, some ports adopt priority control mode and some ports adopt peer control mode, thereby meeting the diverse operation control mode requirements of multi-port converters.

[0182] Example 3:

[0183] In this embodiment 3, the control method of a three-port converter system is used as an example. The constructed three-port converter system has two converter units and one multi-winding transformer, with a total of two DC ports and one AC port. From formula (2), the power control of each converter in constant power mode of each DC port can be obtained as follows:

[0184]

[0185] The corresponding active current control for the converter is as follows:

[0186]

[0187] 1) Priority control

[0188] (1) Medium-voltage DC port priority

[0189] If the power / current transmission of the medium-voltage DC port is controlled first, and the power / current of the low-voltage DC port is adjusted, then the reference value of the converter power can be obtained from (20) as shown in (22):

[0190]

[0191] -P cN k ≤P c k* ≤P cN k k = 1, 2

[0192] Considering that the power / current control priority of the low-voltage DC port is lower than that of the medium-voltage DC port, the output power range of the low-voltage DC port is affected and limited by the power / current supplied by the medium-voltage DC port, thus:

[0193] -P dt 1 V dt 2 / V dt 1 -P cN 2 ≤P dt ≤-P dt 1 V dt 2 / V dt 1 +P cN 2 (twenty three)

[0194] Alternatively, the corresponding power of the converter unit can be limited, from (20)

[0195] -P cN 1 V du 2 / V du 1 -P dt 2 V du 2 / V dt 2 ≤Pc 2 ≤P cN 1 V du 2 / V du 1 -P dt 2 V du 2 / V dt 2 (twenty four)

[0196] If the power / current of the medium-voltage DC port is prioritized, and the power / current of the AC port is adjusted, the reference values ​​for the conversion power of each converter unit, i.e., its limiting conditions, are as follows:

[0197]

[0198] Considering that the power / current control priority of the AC port is lower than that of the medium-voltage DC port, meaning that the output power range of the AC port is affected and limited by the power / current supplied by the medium-voltage DC port, this can be achieved through the following constraints.

[0199]

[0200] (2) Low-voltage DC port power / current priority

[0201] If the power / current transmission of the low-voltage DC port is prioritized for control, and the power / current of the medium-voltage DC port is adjusted, the reference value of the converter unit's conversion power can be obtained from (20), i.e., its limiting conditions are as follows:

[0202]

[0203] Considering that the power / current control priority of the medium-voltage DC port is lower than that of the low-voltage DC port, the output power range of the medium-voltage DC port is affected and limited by the power / current supplied by the low-voltage DC port. This can be achieved through the following constraints.

[0204]

[0205] If the low-voltage DC port adopts a constant power / current priority mode, and the power / current of the AC port is adjusted, the power reference value of each converter unit, i.e., its limiting conditions, is as follows:

[0206]

[0207] Considering that the power / current control priority of the AC port is lower than that of the low-voltage DC port, the input power range of the AC port is affected and limited by the power / current supplied by the low-voltage DC port. This can be achieved through the following constraints.

[0208]

[0209] In addition, the power adjustment range of the AC port can also be considered as follows:

[0210] P dt 2 V du 1 / V dt 2 -P cN 2 V dt 1 / V dt 2 ≤P at ≤P dt 2 V du 1 / V dt 2 +P cN 2 V dt 1 / V dt 2 (31)

[0211] (3) AC port power / current priority

[0212] If the power / current control of the AC port is prioritized and the power / current of the medium-voltage DC port is adjusted, then from (1) we can obtain

[0213]

[0214] because

[0215] P dt 1 =(P c 2 -P at V dt 1 / V du 1 (33)

[0216] Therefore, the power adjustment range of the medium-voltage DC port is affected and limited by the power / current transmitted from the AC port, as expressed as:

[0217] (-P cN 2 -Pat V dt 1 / V du 1 ≤P dt 1 ≤(P cN 2 -P at V dt 1 / V du 1 (34)

[0218] If the power / current control of the AC port is prioritized and the power / current of the low-voltage DC port is adjusted, then from (29) we can obtain

[0219]

[0220] The power adjustment range of the low-voltage DC port is also affected and limited by the power / current transmitted from the AC port, as follows:

[0221]

[0222] At the same time, P must also be considered c1 / P dt1 It does not exceed the standard, therefore there is still

[0223] -P at -P dtN 1 ≤P dt 2 ≤-P at +P dtN 1 (37)

[0224] 2) Peer control

[0225] In the same-level control mode, if the two DC ports are to be controlled, they can be directly controlled according to (18) and (19), thus:

[0226]

[0227] If a DC port and an AC port are to be controlled, the reference value of the other DC port is obtained based on the reference values ​​of these two ports, and then the same level control is completed according to (38).

[0228] The above describes different multi-port control methods for power / current control purposes. Similarly, other control modes besides power / current generally use current control as the inner loop and achieve corresponding control objectives through the design of different outer loop controls, such as AC voltage control, DC voltage control, and drop-off control. The control method proposed in this invention can obtain the current inner loop reference value based on different outer loop controls, thereby combining the current inner loop to complete the above-mentioned independent or coordinated control.

[0229] Furthermore, in this embodiment 3, a three-port converter system was actually constructed, and the parameters of its control process were measured and set. The rated power of the AC port of the three-port converter system is 11MW, the rated power of the first DC port and the second DC port are 10.48MW and 0.62MW respectively, and the rated power of the first converter unit and the second converter unit are 10MW and 1MW respectively. The PU value is calculated based on a total power of 11MW, therefore the rated power of the first DC port and the second DC port are 0.946pu and 0.056pu respectively. During the three time periods of 0.8s-1.0s, 1.0s-1.6s, and 1.6s-1.8s, the input power of the second DC port is set to 0.075pu, 0.056pu, and -0.075pu respectively, while the input power of the first DC port remains unchanged at 0.76pu. Now, under the same power setting, different control methods are applied to this three-port converter system, and the specific control effects are as follows:

[0230] 1) Multi-port independent control mode

[0231] like Figure 5 , 6 As shown, although the power of the second DC port is set to 0.075 pu during the period of 0.8s-1.0s, its transmission power is limited to 0.056 pu because the rated power of the second DC port is 0.056 pu. Similarly, during the period of 1.6s-1.8s, although the power of the second DC port is set to -0.075 pu, its transmission power is limited to -0.056 pu.

[0232] 2) Priority control method

[0233] like Figure 7 , 8As shown, although the power of the first DC port is set to 0.76 pu, because the power priority of the second DC port is the highest, the input power of the first DC port drops to 0.43 pu during the period of 0.8s-1.0s to ensure that the output of the second DC port meets the requirements. During the periods of 1.0s-1.6s and 1.6s-1.8s, the power requirements of the second DC port can be met according to the preset power settings, so the input power of the first DC port recovers to 0.76 pu. The input power of the second DC port meets its set requirements in all three time periods, which are 0.075, 0.056, and -0.075 pu respectively.

[0234] 3) Same-level control method

[0235] like Figure 9 , 10 As shown, the output power of the first DC port remains at its set value of 0.76 pu. During the period of 0.8s-1.0s, although the input power of the second DC port is set at 0.075 pu, the input power drops to 0.064 pu due to the power limitation of the converter unit. During the periods of 1.0s-1.6s and 1.6s-1.8s, the second DC port inputs 0.056 pu and -0.075 pu respectively, as required by the predetermined parameters. It can be seen that during the periods of 0.8s-1.0s and 1.6s-1.8s, by employing same-level control and fully utilizing the power margin of the converter unit, over-rated power output is achieved.

[0236] Compared with the prior art, the present invention provides a control method for AC / DC hybrid multiport converters. Through electrical decoupling and flexible control between AC / DC ports, it realizes diverse current, power control, AC or DC voltage control, etc. It can be applied to multiport converters with any number of ports, realizing flexible local control and flexible AC / DC conversion, control and transmission between different locations.

[0237] The novel multi-port converter device applied to this control method requires fewer power electronic devices, the control method is simple and effective, the overall cost is low, the power transmission and distribution control is flexible and efficient, and it can simultaneously realize AC-DC conversion and DC-DC conversion.

[0238] Finally, it should be emphasized that the present invention is not limited to the above-described embodiments. The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0239] The above description outlines the main process steps of the invention. Other functional steps may be interspersed within this process, and the logical order and process steps may be disrupted. If the data processing method follows this process step format or the core idea of ​​the data processing is similar or identical, it should be protected.

Claims

1. A control method for a hybrid AC / DC multiport converter, characterized in that, Includes the following steps: Connect the DC sides of n converter units in series and draw n+1 DC terminals from the DC bus of the converter units, where the (n+1)th DC terminal d n+1 Defined as a common DC terminal, the other n DC terminals and the common DC terminal form n DC ports; one or more transformers are combined to form a multi-winding transformer with n+1 windings, the AC side of the n converter units is connected to the n windings of the multi-winding transformer, and the multi-winding transformer leads out one AC port from the n+1 winding to construct a multi-port converter system; The (n+1)th DC terminal d n+1 Defined as a common DC terminal, n DC ports are sorted in descending order of voltage level. The voltage of a DC port with a higher voltage level is formed by superimposing the voltage of a DC port with a lower voltage level and the DC voltage of the converter unit between them. Calculate the current reference value of the converter unit, construct the inner current control loop, construct the outer current control loop based on the inner current control loop, control the power and current of the DC and AC ports, and determine the transmission power of the AC and DC ports and the conversion power of n converter units; Define the voltage, input current, and input power of the DC port as follows: V dt k , I dt k , P dt k The DC voltage, DC input current, and DC input power of the converter unit are respectively V du k , I du k , P c k ,in k =1,2,…, n , represents the DC port number, dth. n+1 The DC terminal is a common terminal with a reference potential. V dt k It is DC terminal d k With common DC terminal d n+1 The voltage at the resulting DC port k is then: （1） Further calculations yielded: （2） Using the correspondence between the power of the converter unit and the power of the DC port in formula (2), the power and current of any converter unit are controlled to control the transmission power and current of n DC ports and 1 AC port. When power / current control is applied to n DC ports, the power / current reference value of the corresponding converter unit is calculated according to formula (2); when power / current control is applied to the nth DC port, the power / current reference value of the corresponding converter unit is calculated according to formula (2); k When using power control for DC ports other than the DC port and AC ports, the DC port number is calculated using the following formula. k Power / current reference values: （3） in P at The input power at the AC port, calculated from formulas (2) and (3), is also limited by the rated power of each converter unit: subscript N Indicates the rated value; The result is obtained from formula (2): （4） Converter unit k Power / current controlled by DC port k The power / current ratio is also affected by the converter unit. k -1 The effect of power / current, with converter unit k With DC port k、 Converter unit k The power or current control between -1 is considered as a DC-side coupling relationship.

2. The control method for a hybrid AC / DC multiport converter as described in claim 1, characterized in that, The coupling condition is whether the converter unit performs power or current control on the corresponding port. The coupling relationship between the DC port and the converter unit is constructed according to the coupling condition. One or more of the following modes are formed: multi-port independent control mode and multi-port cooperative control mode.

3. The control method for a hybrid AC / DC multiport converter as described in claim 2, characterized in that, The converter unit k A DC current path is provided for each of its DC ports and converter units. The DC current path is kept constant according to the current rating, and this DC-side coupling relationship is corresponding to a multi-port independent control mode. From formula (2), the transmission power of each DC port can be further derived as follows: （5） The current at each DC port is expressed by the following formula: （6） The superscript "*" indicates a control reference value; According to formulas (4) and (6), except for the first converter unit, the DC current of the other converter units is equal to the difference between the input DC current of the previous converter unit and the input current of the corresponding DC port. The relationship between the rated currents of each converter unit is determined as follows: （7） The subscript N indicates the rated value; In multi-port independent control mode, since the power / current of each port varies within its set rated range and is not affected by the power / current of other ports, we get: （8） Except for the first converter unit, the current of other converter units consists of two parts: the channel current of the previous converter unit and the DC port current of this unit. Both the channel current of the previous converter unit and the DC port current of this unit vary independently within their rated ranges and do not affect each other. Under independent control, the maximum power transmitted by each DC port is its rated power. （9） 。 4. The control method for a hybrid AC / DC multiport converter as described in claim 3, characterized in that, The converter unit k provides a DC current path for each of its DC ports and converter units. The size of the DC current path varies according to the power conversion requirements of each DC port and converter unit in order to complete the power or current control of the corresponding port. This is called the multi-port cooperative control mode. In the multi-port cooperative control mode, the maximum transmission power of each port can be calculated from formula (5): （10） According to the relationship in formula (7), calculate the rated current and rated power of each converter unit. Set the exchange power of one of the adjacent converter units to a positive rated value and the exchange power of the other to a negative rated value. The maximum and minimum input power of the DC port are then obtained as follows: （11）。 5. The control method for a hybrid AC / DC multiport converter as described in claim 4, characterized in that, In the multi-port cooperative control mode, the maximum power of each port is controlled in a cooperative manner using a priority control method, including the following steps: Prioritize the n DC ports, with priority based on priority number. R This indicates that the priority numbers of the n DC ports are arranged in order, namely: R 1. R 2··· R n , R The higher the value, the higher the priority. The power / current control of the DC port will give priority to the DC port with the higher priority number. Taking the k-th DC port as an example, the priority number of the k-th port is set as follows: R k When k is not equal to 1 or n, we can obtain from formula (5): （12） Based on priority, there are four possible scenarios: (1) R k > R k-1 ， R k > R k+1 at this time P c k-1 The range of values ​​will be affected P dt k The impact of this will prioritize satisfying the DC port. k The output power requirement, derived from formula (12), is limited to the following range: （13） P dt k+1 The range of values ​​will also be affected P c k The impact of this, thus prioritizing port satisfaction. k The output power requirement, derived from formula (12), is limited to the following range: （14） In addition, when R k-1 > R k+1 Prioritize P c k-1 Adjustment to meet DC port requirements k Output power requirements, otherwise prioritize P dt k +1 Adjustments; (2) R k > R k-1 ， R k < R k+1 at this time P c k-1 The range of values ​​will be affected P dt k The influence of the value selection, thus prioritizing the satisfaction of the port. k The output power requirement is limited to the range shown in formula (13); in addition, P c k The range of values ​​will also be affected P dt k+1 The influence of the value, thus prioritizing the satisfaction. k The output power requirement for port +1 is obtained from formula (12). P c k The range of values ​​is limited to: （15） (3) R k < R k-1 ， R k > R k+1 P dt k The range of values ​​will also be affected P c k-1 The influence of the value is considered, so that the output power requirement of port k-1 is satisfied first. From formula (12), its value range is limited to: （16） P dt k+1 The range of values ​​will also be affected P c k The impact of the value selection prioritizes port number satisfaction. k The output power requirement is such that its range is limited as shown in formula (14); (4) R k < R k-1 ， R k < R k+1 P dt k The range of values ​​will be affected P c k-1 The influence of the value, thus prioritizing the satisfaction. k The output power requirement for port -1 is limited to the range shown in formula (16); in addition... P c k The range of values ​​will also be affected P dt k+1 The influence of the value selection, thus prioritizing the satisfaction of the port. k +1 output power requirement, the range of which is limited as shown in formula (15); when R k-1 > R k+1 And the above respectively satisfy P c k-1 and P dt k+1 Regulating demand P dt k and P c k If the values ​​conflict, the value with the highest priority number will be determined first to satisfy the adjustment requirement of the former. P dt k If a value is not selected, then the latter adjustment requirement should be prioritized and determined first. P c k Values; When k=1, there are two cases: R k > R k+1 or R k < R k+1 Based on the above situations (1) and (2), respectively, apply formulas (14) and (15) to... P dt k+1 , P c k The range of values ​​is limited; When k=n, the following two cases are included: R k > R k-1 or R k < R k-1 Based on the above situations (1) and (3), apply formulas (13) and (16) respectively. P c k-1 , P dt k The range of values ​​is limited.

6. The control method for a hybrid AC / DC multiport converter as described in claim 5, characterized in that, When using a priority control approach for coordinated control: For the communication port and the k Power control is performed on DC ports other than the DC port. When the priority number of AC port power control is... R k The conversion is equivalent to the conversion of the DC port. k Power according to P dt k Control is implemented, and its priority number is... R k Control will be implemented according to the aforementioned priority control method, wherein... P dt k The formula for calculating the reference value is as follows: （17) in, P dtmin k , P dtmax k These are converter units k Having priority number R k The minimum and maximum values ​​that can be obtained under certain conditions.

7. The control method for a hybrid AC / DC multiport converter as described in claim 6, characterized in that, In the multi-port cooperative control mode, including the use of a peer control method to coordinate the power control of each port, the following steps are included: The control priority of each port is regarded as the same level. Each converter unit prioritizes completing its own specified transmission task. If there is still power / current margin beyond the specified transmission task, it will assist other related ports in completing the excess power / current transmission demand. If AC and DC ports are controlled at the same level, then: （18) Where k = 1, 2, ..., n, k ≠ 1; When k=1, then: （19) in .

8. The control method for a hybrid AC / DC multiport converter as described in claim 7, characterized in that, Based on the above multi-port power / current relationship, an inner current control loop is constructed, and corresponding outer current control loops are completed according to the control objectives, including AC voltage control, DC voltage control, drop control, and AC frequency control; independent or coordinated control is completed by combining the inner and outer current control loops. In the priority control mode, after obtaining the current reference value through the outer loop calculation, the inner loop of the current of different ports is still controlled according to the priority number mentioned above. That is, the port with the higher priority number will be given priority to meet its current control requirements. If the outer loop is DC voltage control, considering that DC voltage stability is the basis for the stable operation of the corresponding DC circuit, a higher priority number is assigned. Moreover, the higher the voltage level, the greater the voltage stability influence range and the power supply / load power. In this case, the priority number is arranged from high to low according to the voltage level. In the same-level control mode, after obtaining the current reference values ​​of different ports through the outer loop calculation, the current inner loop of these ports completes the control adjustment according to the same-level control principle. That is, each converter unit prioritizes to complete the current control requirements of the corresponding DC port. On this basis, if there is still current margin, it assists other ports to complete their excess power / current transmission requirements. In the hybrid control mode, some ports adopt priority control mode and some ports adopt peer control mode, so as to realize diversified operation control mode of multi-port converter.

Images