CN116191482A - Control system and method for unbalanced load of three-level voltage restorer - Google Patents
Control system and method for unbalanced load of three-level voltage restorer Download PDFInfo
- Publication number
- CN116191482A CN116191482A CN202310238321.4A CN202310238321A CN116191482A CN 116191482 A CN116191482 A CN 116191482A CN 202310238321 A CN202310238321 A CN 202310238321A CN 116191482 A CN116191482 A CN 116191482A
- Authority
- CN
- China
- Prior art keywords
- load
- voltage
- phase
- current
- cal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks
Abstract
The invention discloses a control system with unbalanced load for a three-level voltage restorer, which comprises a bypass unit, a power conversion unit and an energy storage unit, wherein the bypass unit is connected with the power conversion unit; the power conversion unit consists of a DC/AC converter and a DC/DC converter, wherein the DC/AC converter consists of three groups of RC filters, three groups of filter inductors and a three-phase three-level half-bridge; the DC/DC converter consists of two direct current inductors and two symmetrical half-bridges, wherein the two symmetrical half-bridges are connected in series, one ends of the two direct current inductors are respectively connected to the two symmetrical half-bridges, and the other ends of the two direct current inductors are respectively connected to two sides of the energy storage unit; the DC/DC converter shares two sets of bus support capacitances with the DC/AC converter. The invention can ensure that the phase voltage and the line voltage are simultaneously balanced to be output when the load unbalance is subjected to voltage compensation, and ensure the quality of the power supply voltage of the equipment.
Description
Technical Field
The invention belongs to the technical field of three-level voltage recoverers, and particularly relates to a control system and method for a three-level voltage recoverer with an unbalanced load.
Background
The proportion of the power electronic device in the load of the power system is higher and higher, the higher requirements are set for the reliability and stability of power supply, the load is down due to short-time interruption of the power grid voltage, the industrial production is influenced, the restarting to the normal production generally needs a longer time under the condition of down of large-scale equipment, the production plan and the task are influenced seriously, even the equipment is damaged, and the great economic loss is caused;
the dynamic voltage restorer (dynamic voltage restore) is simply DVR. The main problem solved by the current DVR is a short-time fault (generally indicated as load supply voltage sag, interruption and sag within 3 seconds) problem of the equipment supply voltage, when the load supply voltage is normal, the power supply of the load is provided by a bypass unit, and the power conversion unit is in a standby state or a charging state; when the short-time voltage fault occurs in the load power supply voltage, the bypass power supply loop is cut, and a power conversion unit and an energy storage element are put into operation, so that the load voltage is kept stable; when the supply voltage returns to normal, the power conversion and energy storage unit flexibly exits (phase synchronization, amplitude tracking, smooth power drop to 0), bypass is put in, and the power conversion and energy storage unit enters a charging state until the energy storage unit is full. As DVR systems are increasingly applied, a single DVR tends to perform high-power centralized management (MW level), but not low-power single-load management, so that the types of important loads protected by the DVR are more and more, and various load power supply modes (three-phase three-wire system equipment, three-phase four-wire system equipment, two-phase power supply equipment and single-phase power supply equipment) exist, and the load current imbalance is caused by the variety of the load power supply modes. Because of the limitation of the cost and the cost of the DVR, the capacity corresponding to the load is generally selected, when the voltage compensation is carried out, the DVR is equivalent to a weak current network system, the inversion output voltage is greatly influenced by the load, under the traditional control strategy, the unbalance of the output voltage can be caused to influence the load power supply, and the equipment is down when the situation is serious.
Disclosure of Invention
The technical problems to be solved are as follows: aiming at the technical problem that the single existence or the mixed existence of three-phase three-wire system equipment, three-phase four-wire system equipment, two-phase power supply equipment and single-phase power supply equipment can cause the unbalance of the whole load, the invention discloses a control system and a control method of a three-level voltage restorer with an unbalanced load, which can ensure that the phase voltage and the line voltage are simultaneously balanced and output when the voltage compensation is carried out by the unbalanced load, and ensure the quality of the power supply voltage of the equipment; in addition, the topological structure does not need to be provided with an isolation transformer to provide an N loop, so that the cost is saved and the volume space is reduced.
The technical scheme is as follows:
a control system with unbalanced load of a three-level voltage restorer comprises a bypass unit, a power conversion unit and an energy storage unit;
the bypass unit comprises 6 thyristors which are respectively connected with a load, and the 6 thyristors are connected in pairs in positive and negative parallel to form a three-phase power supply loop; the load power supply is provided by the grid voltage through a silicon controlled rectifier;
the power conversion unit consists of a DC/AC converter and a DC/DC converter, wherein the DC/AC converter consists of three groups of RC filters, three groups of filter inductors and a three-phase three-level half-bridge; three groups of RC filters, three groups of filter inductors and three-phase three-level half-bridges respectively correspond to three-phase power supply loops of the bypass unit, each filter inductor is connected with one phase of three-level half-bridge in series and then connected with the corresponding RC filter in parallel, and each RC filter is connected with two ends of a load in parallel; the DC/DC converter consists of two direct current inductors and two symmetrical half-bridges, wherein the two symmetrical half-bridges are connected in series, one ends of the two direct current inductors are respectively connected to the two symmetrical half-bridges, and the other ends of the two direct current inductors are respectively connected to two sides of the energy storage unit; the DC/DC converter and the DC/AC converter share two groups of bus supporting capacitors;
the energy storage unit adopts a super capacitor.
Further, the three-phase three-level half-bridge comprises an A-phase three-level half-bridge, a B-phase three-level half-bridge and a C-phase three-level half-bridge;
the A-phase three-level half-bridge, the B-phase three-level half-bridge and the C-phase three-level half-bridge are respectively composed of four IGBT, four anti-parallel diodes and two clamping diodes; the four IGBTs are sequentially connected in series and correspond to the four anti-parallel diodes one by one, and the two clamping diodes are connected at two ends of the two IGBTs in the middle after being connected in series.
Further, the control process of the DC/AC converter includes:
let the load side phase voltage measurement signals be u a_load 、u b_load And u c_load Positive and negative sequence separation is carried out on the three-phase voltage signal, and positive sequence component u is corrected ap_load 、u bp_load And u cp_load Performing coordinate transformation to obtain a voltage component u under a synchronous rotation coordinate system d And u q Will u d And u q Respectively sum to a given value u dref And u qref Making difference, and feeding the difference into regulator to obtain u d_out And u q_out Obtaining the given value i of the current loop dref And i qref ；
Collecting a three-level converter bridge arm output current signal i through a current Hall La 、i Lb And i Lc Coordinate transformation is carried out on the three-phase bridge arm current to obtain a current component i under a synchronous rotation coordinate system d And i q ，i d And i q Feedback quantity as current loop and current loop set point i dref And i qref Making difference, and respectively obtaining i by the difference value entering the regulator d_out And i q_out The method comprises the steps of carrying out a first treatment on the surface of the The phases of all coordinate transformations are obtained through given value integration;
the load side AC voltage is based on the voltage component u of the synchronous rotation coordinate system d And u q Through feedforward coefficient H i2 Respectively and the output i of the current loop d_out And i q_out Adding to obtain u d_cal And u q_cal ，u d_cal And u q_cal Inverse transformation from rotating to stationary to u a_cal 、u b_cal And u c_cal 。
Further, inControl loop G 1 The(s) output end is added with current feedforward, the feedforward quantity of the current is directly overlapped with the voltage duty ratio output end by multiplying G2(s), the self-adaptive controller is a PIR regulator, G 2 The transfer function of(s) is
The feedforward transfer function is +.>
Load current i a_load 、i b_load And i c_load Negative sequence component u of load voltage an_load 、u bn_load And u cn_load The respective compensation coefficient k is obtained through the self-adaptive controller a 、k b And k c The method comprises the steps of carrying out a first treatment on the surface of the Load current i a_load 、i b_load And i c_load Multiplying by respective compensation coefficients k a 、k b And k c G 2 (s), finally and u a_cal 、u b_cal And u c_cal Adding to obtain u a1_cal 、u b1_cal And u c1_cal The final PWM modulation wave is used as a trigger signal of a three-phase three-level half-bridge, and 12 paths of PWM are generated by comparing the final PWM modulation wave with a triangular wave.
Further, for a three-phase three-wire system without N wires, the neutral point potential of the three levels is balanced and controlled by injecting zero sequence components.
Further, the control process of the DC/DC converter includes:
the bus voltage is half voltage u dc1 And lower half voltage u dc2 The sum is used as the feedback value of the voltage outer loop, and the feedback value of the voltage outer loop is compared with the given value u dcref The difference value of the two is led into a regulator, the output of the regulator is taken as the input of a current loop, and the current sampling value i of the super capacitor is given cap For the feedback value of the current loop, the difference value between the feedback value of the current loop and the input given by the current loop is led into a current inner loop regulator;
super capacitor voltage sampling value u cap Through feedforward coefficient H i3 Is in loop regulation with currentThe output of the knots is added to obtain u dcl_cal By means of the upper half voltage u of the bus voltage dc1 And lower half voltage u dc2 The difference is output by the regulator to obtain u dc2_cal ，u dcl_cal And u is equal to dc2_cal Respectively subtracting and adding to obtain u dc3_cal And u is equal to dc4_cal The PWM control signal of the DC/DC converter is obtained by comparing the PWM modulated wave with the triangular wave as the PWM modulated wave of the DC/DC converter.
The invention also discloses a control method of the three-level voltage restorer with the unbalanced load, which is executed based on the control system of the three-level voltage restorer with the unbalanced load in the claim 4; the control method comprises the following steps:
s1, determining G according to a current loop control system 2 (s) a transfer function and control parameters, determining a body feed-forward function of the current feed-forward;
s2, collecting load three-phase alternating current and three-phase voltage, performing positive and negative sequence separation on the three-phase voltage, determining the maximum value and the minimum value of the three-phase current by comparing the sizes of the three-phase current, enabling the voltages of the three-phase current and the negative sequence component to enter the self-adaptive controller, determining the compensation coefficient of the minimum current to be 0, and adjusting the voltage of the negative sequence component of the output voltage to be 0;
s3, the three-level midpoint potential is controlled in the DC/DC controller, and zero sequence components are not required to be injected into PWM modulation waves of the DC/AC controller.
The beneficial effects are that:
first, the control system with unbalanced load of the three-level voltage restorer is applicable to various power supply modes, is not limited by the power supply modes of the load, and has higher practical significance.
Secondly, the control system with unbalanced load of the three-level voltage restorer does not need to increase more acquisition signal quantity and various complex hardware designs, and the topological structure is a general I-shaped or T-shaped three-level DC/AC converter and a three-level DC/DC converter, but does not need to add a transformer, thereby saving space and cost and improving efficiency.
Thirdly, the control method of the three-level voltage restorer with unbalanced load is realized through micro CPU or FPGA software, and the control method can be realized without a large number of processors with high calculation and performance.
Fourth, the control system with unbalanced load of the three-level voltage restorer of the invention has good phase voltage compensation effect, and the output voltage is not affected by unbalanced current.
Drawings
FIG. 1 is a topology diagram of a control system with unbalanced load for a three-level voltage restorer according to an embodiment of the present invention;
FIG. 2 a A control block diagram for the DC/AC converter;
FIG. 2b is a flow chart of the adaptive controller of the DC/AC converter;
FIG. 3 is an inverse measurement control block diagram;
fig. 4 is an inversion-side equivalent control block diagram;
FIG. 5 is a control block diagram of a DC/DC converter;
FIG. 6 is a graph of load phase voltage and current waveforms for a control system employing an embodiment of the present invention;
FIG. 7 is a graph of load phase voltage and current waveforms without a voltage compensation controller;
FIG. 8 is a graph of load phase voltage and current waveforms without employing full voltage feedforward control;
fig. 9 is a graph of load phase voltage and line voltage waveforms of the DC/AC control section injecting zero sequence component to control midpoint potential.
Detailed Description
The following examples will provide those skilled in the art with a more complete understanding of the invention, but are not intended to limit the invention in any way.
Fig. 1 is a topology diagram of a control system with unbalanced load for a three-level voltage restorer according to an embodiment of the present invention. The control system comprises a bypass unit, a power conversion unit and an energy storage unit; the bypass unit comprises 6 thyristors which are respectively connected with a load, and the 6 thyristors are connected in pairs in positive and negative parallel to form a three-phase power supply loop; the load power supply is provided by the grid voltage through a silicon controlled rectifier; the power conversion unit consists of a DC/AC converter and a DC/DC converter, wherein the DC/AC converter consists of three groups of RC filters, three groups of filter inductors and a three-phase three-level half-bridge; three groups of RC filters, three groups of filter inductors and three-phase three-level half-bridges respectively correspond to three-phase power supply loops of the bypass unit, each filter inductor is connected with one phase of three-level half-bridge in series and then connected with the corresponding RC filter in parallel, and each RC filter is connected with two ends of a load in parallel; the DC/DC converter consists of two direct current inductors and two symmetrical half-bridges, wherein the two symmetrical half-bridges are connected in series, one ends of the two direct current inductors are respectively connected to the two symmetrical half-bridges, and the other ends of the two direct current inductors are respectively connected to two sides of the energy storage unit; the DC/DC converter and the DC/AC converter share two groups of bus supporting capacitors; the energy storage unit adopts a super capacitor.
In a three-phase three-wire system device, a three-phase four-wire system device, a two-phase power supply device and a single-phase power supply device, the overall load unbalance is caused by single existence or mixed existence, and when the load unbalance performs voltage compensation, the phase voltage and the line voltage are simultaneously kept to be balanced and output, so that the quality of the power supply voltage of the device is ensured.
The topology structure of the control system of the embodiment does not need to add an isolation transformer to provide an N loop, saves cost and reduces volume space, utilizes the midpoint of three levels to provide the N loop, and because the super capacitor is required to be fully utilized as energy of an energy storage unit, a DC/DC converter is required to be added, the DC bus voltage is stabilized in a compensation state, meanwhile, the injected zero sequence voltage component is prevented from affecting a phase voltage waveform when a three-phase four-wire system is loaded, and the midpoint potential of the three-level converter is required to be controlled by the DC/DC converter.
The topology structure of a control system (see fig. 1) with unbalanced load of a three-level Dynamic Voltage Restorer (DVR) of the embodiment comprises the following components:
grid through silicon controlled rectifier (S) cr1 ～S crb ) And each phase is composed of two thyristors which are connected in positive and negative parallel, and when the power grid voltage is normal, the load power supply is provided by the power grid voltage through the thyristors, which is also called a bypass unit. The power conversion unit is composed of a DC/AC and a DC/DC converter, wherein the DC/AC converter is composed of an RC filter (R 1 ～R 3 ，C 1 ～C 3 ) Filter inductor (L) A ～L C ) Three-phase three-level half bridge (phase a is defined by the IGBTS a1 ～S a4 Anti-parallel diode D a1 ～D a4 Clamping diode D a5 ～D a6 Composition, other two phases, and so on), two sets of bus bar support capacitors (C 4 ～C 5 Two groups may contain multiple capacitors in parallel or in series). Wherein three-phase three-level half bridge S a1 ～S a4 The trigger signals of (a) are PWM 1-PWM 4 in figure 2a, S b1 ～S b4 The trigger signals of (a) are PWM 5-PWM 8 in figure 2, S b1 ～S b4 The trigger signals of (a) are PWM 9-PWM 12 in figure 2 a. The DC/DC converter is formed by a direct current inductor (L DC1 ～L DC2 ) Two symmetrical half-bridges (by IGBTS d1 ～S d4 Anti-parallel diode D d1 ～D d4 ) And sharing two sets of bus capacitances (C 4 ～C 5 ) Composition is prepared. The energy storage unit is the super capacitor C in figure 1 bank 。
A control strategy and an implementation method for a three-level Dynamic Voltage Restorer (DVR) with unbalanced load are as follows:
fig. 2a is a control block diagram of the DCAC converter. The load side phase voltage measurement signals are u respectively a_load 、u b_load And u c_load Positive and negative sequence separation is carried out on the three-phase voltage signal, and positive sequence component u ap_load 、u bp_load And u cp_load Performing coordinate transformation to obtain a voltage component u under a synchronous rotation coordinate system d And u q Will u d And u q Respectively sum to a given value u dref And u qref Making difference, and feeding the difference into regulator to obtain u d_out And u q_out I.e. the given value i of the current loop dref And i qreref . Collecting a three-level converter bridge arm output current signal i through a current Hall La 、i Lb And i Lc Coordinate transformation is carried out on the three-phase bridge arm current to obtain a current component i under a synchronous rotation coordinate system d And i q ，i d And i q Feedback quantity as current loop and current loop set point i dref And i qref Making difference, and respectively obtaining i by the difference value entering the regulator d_out And i q_out . The phases of all coordinate transformations are obtained by integration of given values.
The load side AC voltage is based on the voltage component u of the synchronous rotation coordinate system d And u q Through feedforward coefficient H i2 Respectively and the output i of the current loop d_out And i q_out Adding to obtain u d_cal And u q_cal ，u d_cal And u q_cal Inverse transformation from rotating to stationary to u a_ca l、u b_cal And u c_cal In order to increase the response speed of the compensation voltage, the control loop G is generally provided with 1 The(s) output plus current feed forward is shown in FIG. 3, but since the load is an unbalanced load, the load current i load The inclusion of the secondary component after dq conversion further affects the output of the compensation voltage by multiplying the feedforward amount of current by G after conversion of fig. 4 2 (s) directly superimposing the voltage duty cycle outputs and, due to load imbalance, the feedforward amount of each phase current can be adaptively generated by the compensation controller to the respective required control parameters. The controller used in this patent is a PIR regulator, so the typical transfer function of G2(s) is
Wherein the integral term is negligible and the feedforward transfer function can be written as +.>
Load current i a_load 、i b_load And i c_load Negative sequence component u of load voltage an_load 、u bn_load And u cn_load The respective compensation coefficient k is obtained through the self-adaptive controller a 、k b And k c The adaptive controller workflow is shown in fig. 2 b. Load current i a_load 、i b_load And i c_load Multiplying by respective compensation coefficients k a 、k b And k c G 2 (s), finally and u a_cal 、u b_cal And u c_cal Adding to obtain u a1_ca l、u b1_cal And u c1_cal The final PWM modulation wave is compared with the triangular wave to generate 12 paths of PWM. Note that the balance control of the three-level neutral point potential is not performed here, because the balance control of the neutral point potential is performed by injecting a zero sequence voltage control strategy, the control strategy is generally used in a three-phase three-wire system without an N-wire, the line voltage is ensured to have no zero sequence component, but the control strategy is unsuitable for the three-phase four-wire system, and the injection of the zero sequence component can cause the phase voltage waveform to contain harmonic components, and can also cause the imbalance of the three-phase voltage, so that the power supply quality of the phase voltage is affected.
Fig. 5 is a control block diagram of a DC/DC converter. Bus voltage upper half voltage u dc1 And lower half voltage u dc2 The sum is taken as the feedback value of the voltage outer loop, and the given value is u dcref The difference value of the two is entered into a regulator, the output of the regulator is given as the input of a current loop, and the current sampling value i of the super capacitor cap The feedback value of the current loop is the difference value of the feedback value and the feedback value of the current loop, and the difference value enters the current inner loop regulator. Super capacitor voltage sampling value u cap Through feedforward coefficient H i3 Added to the current inner loop regulator output to obtain u dc1_cal To balance the midpoint potential of the three levels, the upper half voltage u of the bus voltage is used dc1 And lower half voltage u dc2 The difference is output by the regulator to obtain u dc2_cal ，u dc1_cal And u is equal to dc2_cal Respectively subtracting and adding to obtain u dc3_cal And u is equal to dc4_cal That is, the PWM modulation wave of the DC/DC converter is compared with the triangular wave to obtain the PWM control signal of the DC/DC converter.
Based on the foregoing control system, the embodiment also discloses a workflow of a three-level Dynamic Voltage Restorer (DVR) with unbalanced load, which is as follows:
first, determining a main feedforward function of current feedforward according to a transfer function and control parameters of G2(s) determined by a current loop control system.
Secondly, collecting load three-phase alternating current and three-phase voltage, wherein the three-phase voltage needs to be subjected to positive and negative sequence separation, determining the maximum value and the minimum value of the three-phase current by comparing the sizes of the three-phase current, then enabling the three-phase current and the voltage of the negative sequence component to enter an adaptive controller, generally determining the compensation coefficient of the minimum current to be 0, obtaining the other two parameters through the flow of the figure 2b, and finally adjusting the voltage of the negative sequence component of the output voltage to be 0.
Third, the control of the three-level neutral point potential must be handled in a DC/DC controller, and no zero sequence component needs to be injected into the PWM modulated wave of the DC/AC controller, otherwise the phase voltage waveform is affected (line voltage is not affected).
The control system with unbalanced load of the three-level voltage restorer of the embodiment has good phase voltage compensation effect, and the output voltage is not affected by unbalanced current, as shown in fig. 6; the output voltage of the adaptive controller and current feed forward scheme not employing this scheme is affected by unbalanced current as shown in fig. 7; the full feedforward control mode of load voltage and current is not adopted, and the voltage response effect is shown in figure 8; the midpoint potential is in the DC/AC controller and the output voltage lines are voltage balanced, with phase voltage distortion as shown in fig. 9. These voltage qualities can lead to downtime of the load and even damage to the load.
The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above examples, and all technical solutions belonging to the concept of the present invention belong to the protection scope of the present invention. It should be noted that modifications and adaptations to the invention without departing from the principles thereof are intended to be within the scope of the invention as set forth in the following claims.
Claims (7)
1. The control system with the unbalanced load of the three-level voltage restorer is characterized by comprising a bypass unit, a power conversion unit and an energy storage unit;
the bypass unit comprises 6 thyristors which are respectively connected with a load, and the 6 thyristors are connected in pairs in positive and negative parallel to form a three-phase power supply loop; the load power supply is provided by the grid voltage through a silicon controlled rectifier;
the power conversion unit consists of a DC/AC converter and a DC/DC converter, wherein the DC/AC converter consists of three groups of RC filters, three groups of filter inductors and a three-phase three-level half-bridge; three groups of RC filters, three groups of filter inductors and three-phase three-level half-bridges respectively correspond to three-phase power supply loops of the bypass unit, each filter inductor is connected with one phase of three-level half-bridge in series and then connected with the corresponding RC filter in parallel, and each RC filter is connected with two ends of a load in parallel; the DC/DC converter consists of two direct current inductors and two symmetrical half-bridges, wherein the two symmetrical half-bridges are connected in series, one ends of the two direct current inductors are respectively connected to the two symmetrical half-bridges, and the other ends of the two direct current inductors are respectively connected to two sides of the energy storage unit; the DC/DC converter and the DC/AC converter share two groups of bus supporting capacitors;
the energy storage unit adopts a super capacitor.
2. The control system with unbalanced load of the three-level voltage restorer of claim 1, wherein the three-phase three-level half bridge comprises an a-phase three-level half bridge, a B-phase three-level half bridge and a C-phase three-level half bridge;
the A-phase three-level half-bridge, the B-phase three-level half-bridge and the C-phase three-level half-bridge are respectively composed of four IGBT, four anti-parallel diodes and two clamping diodes; the four IGBTs are sequentially connected in series and correspond to the four anti-parallel diodes one by one, and the two clamping diodes are connected at two ends of the two IGBTs in the middle after being connected in series.
3. The control system with unbalanced load of the three-level voltage restorer according to claim 1, wherein the control process of the DC/AC converter comprises:
let the load side phase voltage measurement signals be u a_load 、u b_load And u c_load Positive and negative sequence separation is carried out on the three-phase voltage signal, and positive sequence component u is corrected ap_load 、u bp_load And u cp_load Performing coordinate transformation to obtain a voltage component u under a synchronous rotation coordinate system d And u q Will u d And u q Respectively sum to a given value u dref And u qref Making difference, and feeding the difference into regulator to obtain u d_out And u q_out Obtaining the given value i of the current loop dref And i qref ；
Collecting a three-level converter bridge arm output current signal i through a current Hall La 、i Lb And i Lc Coordinate transformation is carried out on the three-phase bridge arm current to obtain a current component i under a synchronous rotation coordinate system d And i q ，i d And i q Feedback quantity as current loop and current loop set point i dref And i qref Making difference, and respectively obtaining i by the difference value entering the regulator d_out And i q_out The method comprises the steps of carrying out a first treatment on the surface of the The phases of all coordinate transformations are obtained through given value integration;
the load side AC voltage is based on the voltage component u of the synchronous rotation coordinate system d And u q Through feedforward coefficient H i2 Respectively and the output i of the current loop d_out And i q_out Adding to obtain u d_cal And u q_cal ，u d_cal And u q_cal Inverse transformation from rotating to stationary to u a_cal 、u b_cal And u c_cal 。
4. A control system with unbalanced load for a three-level voltage restorer according to claim 3, wherein in the control loop G 1 (s) adding current feedforward to the output terminal, multiplying the feedforward amount of the current by G 2 (s) directly superposing a voltage duty ratio output end, wherein the self-adaptive controller is a PIR regulator, G 2 The transfer function of(s) is
The feedforward transfer function is
Load current i a_load 、i b_load And i c_load Negative sequence component u of load voltage an_load 、u bn_load And u cn_load The respective compensation coefficient k is obtained through the self-adaptive controller a 、k b And k c The method comprises the steps of carrying out a first treatment on the surface of the Load current i a_load 、i b_load And i c_load Multiplying by respective compensation coefficients k a 、k b And k c G 2 (s), finally and u a_cal 、u b_cal And u c_cal Adding to obtain u a1_cal 、u b1_cal And u c1_cal The final PWM modulation wave is used as a trigger signal of a three-phase three-level half-bridge, and 12 paths of PWM are generated by comparing the final PWM modulation wave with a triangular wave.
5. The control system with unbalanced load of the three-level voltage restorer of claim 4, wherein for a three-phase three-wire system without N-wires, the three-level midpoint potential is balanced by injecting zero sequence components.
6. The control system with unbalanced load of the three-level voltage restorer according to claim 1, wherein the control process of the DC/DC converter comprises:
the bus voltage is half voltage u dc1 And lower half voltage u dc2 The sum is used as the feedback value of the voltage outer loop, and the feedback value of the voltage outer loop is compared with the given value u dcref The difference value of the two is led into a regulator, the output of the regulator is taken as the input of a current loop, and the current sampling value i of the super capacitor is given cap For the feedback value of the current loop, the difference value between the feedback value of the current loop and the input given by the current loop is led into a current inner loop regulator;
super capacitor voltage sampling value u cap Through feedforward coefficient H i3 Added to the current inner loop regulator output to obtain u dc1_cal By means of the upper half voltage u of the bus voltage dc1 And lower half voltage u dc2 The difference is output by the regulator to obtain u dc2_cal ，u dc1_cal And u is equal to dc2_cal Respectively subtracting and adding to obtain u dc3_cal And u is equal to dc4_cal The PWM control signal of the DC/DC converter is obtained by comparing the PWM modulated wave with the triangular wave as the PWM modulated wave of the DC/DC converter.
7. A control method of a three-level voltage restorer with an unbalanced load, characterized in that the control method is performed based on the control system of a three-level voltage restorer with an unbalanced load of claim 4; the control method comprises the following steps:
s1, determining G according to a current loop control system 2 (s) a transfer function and control parameters, determining a body feed-forward function of the current feed-forward;
s2, collecting load three-phase alternating current and three-phase voltage, performing positive and negative sequence separation on the three-phase voltage, determining the maximum value and the minimum value of the three-phase current by comparing the sizes of the three-phase current, enabling the voltages of the three-phase current and the negative sequence component to enter the self-adaptive controller, determining the compensation coefficient of the minimum current to be 0, and adjusting the voltage of the negative sequence component of the output voltage to be 0;
s3, the three-level midpoint potential is controlled in the DC/DC controller, and zero sequence components are not required to be injected into PWM modulation waves of the DC/AC controller.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310238321.4A CN116191482A (en) | 2023-03-13 | 2023-03-13 | Control system and method for unbalanced load of three-level voltage restorer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310238321.4A CN116191482A (en) | 2023-03-13 | 2023-03-13 | Control system and method for unbalanced load of three-level voltage restorer |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN116191482A true CN116191482A (en) | 2023-05-30 |
Family
ID=86442394
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202310238321.4A Pending CN116191482A (en) | 2023-03-13 | 2023-03-13 | Control system and method for unbalanced load of three-level voltage restorer |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116191482A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116760042A (en) * | 2023-08-15 | 2023-09-15 | 锦浪科技股份有限公司 | Bus voltage balance control system and method |
-
2023
- 2023-03-13 CN CN202310238321.4A patent/CN116191482A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116760042A (en) * | 2023-08-15 | 2023-09-15 | 锦浪科技股份有限公司 | Bus voltage balance control system and method |
| CN116760042B (en) * | 2023-08-15 | 2023-11-03 | 锦浪科技股份有限公司 | Bus voltage balance control system and method |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US10418916B2 (en) | Circuits of voltage source DC/AC converter with LCCL or LCC filter and other modified forms, and operation of microgrid with such circuits | |
| Peng et al. | A multilevel voltage-source inverter with separate DC sources for static var generation | |
| CN105553304B (en) | A kind of modular multilevel type solid-state transformer and its internal model control method | |
| Cheng et al. | A comparison of diode-clamped and cascaded multilevel converters for a STATCOM with energy storage | |
| CN102832841A (en) | Modularized multi-level converter with auxiliary diode | |
| CN105406748B (en) | A kind of control method of suppression module Multilevel Inverters output current harmonics | |
| CN108808710B (en) | Non-linear control-based UPFC three-phase imbalance optimization method | |
| CN112290567B (en) | Three-phase power quality compensation device and method based on half-bridge converter | |
| CN101291057B (en) | Dynamic voltage compensator adopting 3 phase structure | |
| CN205389177U (en) | Novel many level of modularization type solid -state transformer | |
| CN116191482A (en) | Control system and method for unbalanced load of three-level voltage restorer | |
| Babaei et al. | Voltage unbalance compensation based on optimal current injection by SSTs | |
| CN111952995B (en) | Direct-current capacitor voltage balance control method under single-phase fault of power grid | |
| CN114465515A (en) | Energy storage type MMC topology capable of avoiding battery microcirculation and control method thereof | |
| CN110011322B (en) | Diode clamping three-level inverter hybrid passive control system and method | |
| Wu et al. | Compound control strategy of active power filter based on modular multilevel converter | |
| CN111800028A (en) | Novel method for restraining power fluctuation and circulation of railway traction power supply system | |
| CN110912130A (en) | Circuit structure of double-alternating-current bus grid-connected converter and harmonic compensation method thereof | |
| Kumar et al. | Design and implementation of three-winding coupled inductor and switched capacitor-based DC–DC converter fed PV-TDVR | |
| CN104836465B (en) | LC serial-type three-phase PWM rectifier current iterative learning control method | |
| Afkar et al. | Complete Load Compensation in a Distribution Network with a Single-Stage PV Grid Interface Converter | |
| CN211830228U (en) | Capacitor split type static compensator circuit with zero sequence voltage-sharing bridge arm | |
| Zhong et al. | Control strategy of three-phase T-type three-level converter with reactive power compensation function | |
| CN114301066A (en) | Intelligent power distribution station combined system | |
| Fu et al. | Suppression Method of DC-side Voltage Fluctuation of SNOP Based on Energy Storage |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |