CN107612409B - Simplified matrix converter model prediction control method with magnetic bias control - Google Patents

Simplified matrix converter model prediction control method with magnetic bias control Download PDF

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CN107612409B
CN107612409B CN201710891517.8A CN201710891517A CN107612409B CN 107612409 B CN107612409 B CN 107612409B CN 201710891517 A CN201710891517 A CN 201710891517A CN 107612409 B CN107612409 B CN 107612409B
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CN107612409A (en
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宋卫章
刘江
杜晓斌
高大庆
吴凤军
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Xi'an Singularity Energy Co ltd
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Xian University of Technology
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Abstract

The invention discloses a model prediction control method of a simplified matrix converter with magnetic bias control, which is based on an input filter, a preceding-stage converter of the simplified matrix converter, a transformer, a rear-stage controllable rectifier bridge and a load model, samples input voltage and current at a network side, input voltage and output current at a rectification stage of the simplified matrix converter, constructs a mathematical model of the simplified matrix converter system and discretizes the mathematical model, finds out an optimal switching state by taking input reactive power and output current errors as objective functions, solves the problem of magnetic bias of the transformer by adopting a positive-negative pulse alternating distribution mode, and realizes model prediction control with magnetic bias suppression of the simplified matrix converter. The method realizes the prediction control of the RMC model, so that the RMC can still obtain the control target performance even under the condition of power supply and load disturbance and improve the immunity of the RMC; the method can completely eliminate the magnetic biasing problem of the RMC transformer under model prediction control by using an algorithm only by adjusting the pulse sequence.

Description

Simplified matrix converter model prediction control method with magnetic bias control
Technical Field
The invention belongs to the technical field of power electronics, and particularly relates to a model prediction control method for a simplified matrix converter with magnetic bias control.
Background
The Reduced Matrix Converter (RMC) is a new type of power Converter, and the RMC topology is shown in fig. 1, and is composed of an input filter, an RMC rectifier stage, a high-frequency transformer, and a controllable rectifier bridge. The RMC rectifier stage completes the conversion from three-phase AC voltage to positive and negative alternating high-frequency pulse voltage, realizes the three-phase to single-phase intersection-AC conversion, and the front-stage positive and negative pulse voltage is coupled to the rear-stage through a high-frequency transformer and rectified into DC. Compared with the traditional AC/DC-DC/AC-AC/DC three-level converter, the RMC omits an intermediate DC/AC link, simplifies a hardware circuit and improves the conversion efficiency. The RMC also has the following properties: 1) the input current is sinusoidal, and the input unit power factor can be realized; 2) the device has the function of energy bidirectional flow, and can realize four-quadrant operation; 3) the front stage and the rear stage are isolated by a transformer, so that system integration is facilitated; 4) the direct current side does not need an energy storage capacitor, and the direct current side has small volume and simple and compact structure.
However, the conventional modulation strategy of the RMC is approximate open-loop control, power supply disturbance can be transmitted to the load side, and the load disturbance can affect the input performance. And the model prediction control takes the input and output performance as the constraint, so that the influence of input and output disturbance can be eliminated, and excellent input and output performance is always obtained. However, one of the defects of model predictive control is that the switching frequency is not fixed, and the RMC transformer under the strategy control has the problem of magnetic bias saturation due to random switching frequency.
Disclosure of Invention
The invention aims to provide a simplified matrix converter model prediction control method with magnetic bias control, which can not only improve the immunity of the simplified matrix converter, but also solve the problem of magnetic bias of a transformer.
The technical scheme adopted by the invention is as follows: a model prediction control method for a simplified matrix converter with magnetic bias control comprises the steps of sampling input voltage and current at a network side, input voltage and output current at a rectification stage of the simplified matrix converter, constructing a mathematical model of the simplified matrix converter system, discretizing the mathematical model, finding out an optimal switching state by taking input reactive power and output current errors as objective functions, solving the problem of magnetic bias of the transformer by adopting a positive and negative pulse alternative distribution mode, and realizing model prediction control with magnetic bias suppression of the simplified matrix converter based on an input filter, a preceding stage converter of the simplified matrix converter, the transformer, a subsequent stage controllable rectifier bridge and a load model
The present invention is also characterized in that,
the method is implemented according to the following steps:
step 1: establishing a mathematical model of front and rear switches of the simplified matrix converter;
step 2: establishing a state table of all switches at the front stage and the rear stage of the simplified matrix converter;
and step 3: on the basis of the step 1, discretizing and simplifying a matrix converter mathematical model;
and 4, step 4: on the basis of the steps 1 to 3, establishing a quality function taking the input reactive power and the output current error as objective functions;
and 5: on the basis of the steps 1 to 4, the pulse sequence distribution of the bias magnet of the transformer is considered: and a positive and negative pulse alternative distribution mode is adopted, so that the problem of transformer magnetic biasing caused by the prediction control of random switching states by a traditional model is solved.
The step 1 specifically comprises the following steps:
simplified matrix converter pre-converter mathematical model describes input side voltage current u of simplified matrix convertere，ieWith the voltage and current u on the DC sidedc，idcThe switching matrix model of (1) is as follows:
Figure BDA0001421269450000031
Figure BDA0001421269450000032
wherein S isap、San、Sbp、Sbn、Scp、ScnAll the switches are simplified matrix converter rectifier switches;
the switching mathematical model of the rear-stage controllable rectifier bridge is as follows:
u0＝u1(S1-S3) (3)
i0＝i1(S1-S3) (4)
wherein u is0And i0To output voltage and current u1And i1For secondary voltage and current of the transformer, S1、S3The on-off states of the rear-stage controllable rectifier bridge are all the on-off states.
The step 2 specifically comprises the following steps: according to the principle that the output side and the input side of the rectification stage of the simplified matrix converter cannot be in short circuit and open circuit, the three-phase bridge arm of the rectification stage of the simplified matrix converter has nine switch state combinations, three zero vectors are removed in order to increase the voltage transmission ratio, and only effective vectors are considered, such as six switch states shown in table 1:
table 1:
Figure BDA0001421269450000033
in table 1, 1 indicates on, 0 indicates off;
the rear-stage controllable rectifier bridge lists two switching states of the rear-stage full-bridge rectification, as shown in table 2:
table 2:
Figure BDA0001421269450000041
in Table 2, S1、S2、S3、S4All the switches are rear-stage controllable rectifier bridge switches, wherein 1 represents on, and 0 represents off.
The step 3 specifically comprises the following steps:
the discretization form of the phase current at the network side and the phase voltage at the input side of the rectification stage of the reduced matrix converter is as follows:
Figure BDA0001421269450000042
Figure BDA0001421269450000043
Figure BDA0001421269450000044
wherein,
Figure BDA0001421269450000045
and
Figure BDA0001421269450000046
respectively representing the input side phase voltage values of the rectification stage at the k-th moment and the k +1 moment,
Figure BDA0001421269450000047
and
Figure BDA0001421269450000048
respectively shows the grid side phase current values at the k-th time and the k +1 time,
Figure BDA0001421269450000049
indicating the current value of the input phase of the rectifier stage at time k,
Figure BDA00014212694500000410
representing the voltage value of the grid side phase at the k-th moment; cf、LfAnd RfRespectively representing the capacitance, inductance and equivalent resistance, T, of the input filtersIs a switching cycle; c and D are coefficient matrixes of a grid side phase voltage and an input side phase voltage of an RMC rectification stage in a discrete form; a and B are factor matrixes formed by input filter parameters; coefficient matrix Cij、DijThe method comprises the steps of calculating a predicted value (i is 1, 2; j is 1, 2) of a variable corresponding to a discrete system after one sampling period; i is2*2A unit matrix of two rows and two columns;
the discretized expression of the load model is as follows:
Figure BDA0001421269450000051
wherein,
Figure BDA0001421269450000052
and
Figure BDA0001421269450000053
respectively representing the system output current values at the k-th time and the k +1 time,
Figure BDA0001421269450000054
represents the system output voltage value, L, at the k-th moment1And R1Representing the inductance and resistance of the load.
The step 4 specifically comprises the following steps:
the error expression of the output current prediction reference value is as follows:
Figure BDA0001421269450000055
wherein the superscript "+" denotes a reference value,
Figure BDA0001421269450000056
predicting the current for the time k + 1;
the error expression of the network side instantaneous reactive power and the reference value thereof is as follows:
Figure BDA0001421269450000057
where 0 is the instantaneous reactive power reference value,
Figure BDA0001421269450000058
and
Figure BDA0001421269450000059
respectively inputting real parts and imaginary parts of voltage and current at the k +1 moment under a two-phase static coordinate system by sampling input three-phase voltage and current through input side discretization model prediction;
combining equation (7) and equation (8), the expression for the quality function is given as follows:
Figure BDA00014212694500000510
wherein λ is a weighting factor.
The specific process of considering the pulse sequence distribution of the bias magnet of the transformer in the step 5 is as follows: each switching period is divided into two equal half periods, when the switching period is the first half, a preceding-stage converter of the simplified matrix converter is a switching state vector selected by model prediction control, and when the switching period is the second half, a control vector is a vector with the opposite direction of the first half period, namely, the upper bridge arm and the lower bridge arm of the same bridge arm conduction switch are exchanged under the state of the first half period and the second half period, so that the output voltage of the rectification stage of the simplified matrix converter in each switching period is composed of two parts, the amplitudes of the two parts are equal and opposite, the primary voltage of the high-frequency transformer is ensured to be positive and negative alternating pulses all the time, and the.
The invention has the beneficial effects that:
1. the invention provides a model prediction control method for a simplified matrix converter, which realizes RMC model prediction control, enables RMC to obtain control target performance (input unit power factor and output current follow with high precision) even under the condition of power supply and load disturbance, and improves RMC immunity.
2. Compared with the traditional method for solving the magnetic biasing, the method for solving the magnetic biasing of the RMC transformer under model prediction control can completely eliminate the magnetic biasing problem of the RMC transformer under model prediction control by using an algorithm only by adjusting a pulse sequence without detecting a direct current component and increasing a hardware circuit.
Drawings
FIG. 1 is a block diagram of a topology of a reduced matrix converter;
FIG. 2 is a block diagram of an implementation of the reduced matrix converter model predictive control method with bias control of the present invention;
FIG. 3 is a flow chart of a reduced matrix converter model predictive control method with bias control in accordance with the present invention;
FIG. 4 is a block diagram of an input filter circuit for building a mathematical model according to the present invention;
FIG. 5 is a diagram of the RMC rectifier stage circuit structure during mathematical modeling of the present invention;
FIG. 6 is a diagram of a high frequency transformer circuit configuration for building a mathematical model according to the present invention;
FIG. 7 is a circuit diagram of a controllable rectifier bridge according to the present invention during mathematical modeling;
FIG. 8 is a diagram of a load circuit configuration for creating a mathematical model according to the present invention;
FIG. 9 is a diagram illustrating a sequence of turn-on of the output voltage of the rectifier stage during bias control according to the present invention;
FIG. 10 illustrates the current flow direction of the first half cycle during bias control in accordance with the present invention;
FIG. 11 shows the current flow in the second half cycle of the bias control according to the present invention;
FIG. 12 is a net side input voltage current simulated waveform of the present invention;
FIG. 13 is an output current simulation waveform of the present invention;
FIG. 14 is a simulated waveform of primary side current of a transformer with bias control added in accordance with the present invention;
FIG. 15 is a partial amplified simulation waveform of the primary side current of the transformer with bias control according to the present invention;
FIG. 16 is a simulated waveform of primary side current of a transformer without bias control according to the present invention;
FIG. 17 is a partial amplified simulation waveform of the primary side current of the transformer without bias control according to the present invention;
FIG. 18 is an input voltage sag waveform of the present invention;
FIG. 19 is an input current waveform with an instantaneous drop in input voltage according to the present invention;
FIG. 20 is a waveform of the a-phase voltage current at the instant of the drop in input voltage according to the present invention;
FIG. 21 is a waveform of the output current when the input voltage drops momentarily in accordance with the present invention;
FIG. 22 is an input voltage imbalance waveform of the present invention;
FIG. 23 is an input current waveform with an unbalanced input voltage according to the present invention;
FIG. 24 is a waveform of the a-phase voltage current when the input voltage is unbalanced according to the present invention;
FIG. 25 is a graph of the output current waveform when the input voltage is unbalanced according to the present invention.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
The invention provides a simplified matrix converter model prediction control method with magnetic bias control, which utilizes network side input voltage (u in figure 4)sa、usb、usc) Current (i in FIG. 4)sa、isb、isc) RMC rectifier stage input side voltage (u in FIG. 5)ea、ueb、uec) Primary and secondary side voltage and current of transformer (u in fig. 6)dc、idc、u1、i1) Output voltage current (u in FIG. 8)0、i0) And simplifying the matrix converter switch matrix model, establishing and discretizing the simplified matrix converter mathematical model, and performing discretization according to the discretizationThe mathematical model predicts the input reactive power and the output current, establishes a quality function of errors between the input reactive power and the output current at the next moment and respective reference values, optimizes the switching state of the simplified matrix converter by taking the quality function as constraint, and realizes the output following of the simplified matrix converter by utilizing the optimal switching state. A block diagram of an implementation of model predictive control is shown in fig. 2.
a. Establishment of mathematical model
The topology of the RMC is shown in FIG. 1, and Table 3 gives the voltage-current notation in the RMC system under the abc/αβ coordinate system.
TABLE 3 RMC Voltage-Current notation in the abc/αβ coordinate System
Figure BDA0001421269450000081
Assuming that the input three-phase voltage at the RMC network side and the carried load are symmetrical, any variable x is respectively as follows under an αβ coordinate system and an abc coordinate system:
Figure BDA0001421269450000082
Figure BDA0001421269450000083
the mathematical model of the rectifier stage describes the input side voltage and current u of the RMCe，ieWith the voltage and current u on the DC sidedc，idcThe switching matrix model of (1) is as follows:
Figure BDA0001421269450000084
Figure BDA0001421269450000085
wherein S isap、San、Sbp、Sbn、Scp、ScnAll of which are simplified matrix converter rectifier switches, 1 tableOn and 0 off.
The mathematical model of the input filter is as follows:
Figure BDA0001421269450000091
Figure BDA0001421269450000092
the switching mathematical model of the rear-stage controllable rectifier bridge is as follows:
u0＝u1(S1-S3) (3)
i0＝i1(S1-S3) (4)
wherein u is0And i0For outputting voltage and current u1And i1For secondary voltage and current of the transformer, S1、S2、S3、S4The on-off states of the rear-stage controllable rectifier bridge are all the on-off states, wherein 1 represents on, and 0 represents off;
similarly, a mathematical model of the load can be derived as follows:
Figure BDA0001421269450000093
b. establishing a switch state table
According to the principle that the output side and the input side of a rectification stage of a simplified matrix converter cannot be in short circuit and open circuit, nine switching state combinations are provided for a three-phase bridge arm of an RMC rectification stage, three zero vectors are removed here in order to increase the voltage transmission ratio, and only effective vectors are considered, namely six switching states shown in Table 1. A similar controllable rectifier bridge lists two switching states for the post full bridge rectification, as shown in table 2.
TABLE 1 rectifier stage switch states
Figure BDA0001421269450000101
TABLE 2 FULL-BRIDGE RECTIFICATION OPEN LIGHT STATE TABLE
Figure BDA0001421269450000102
c. Calculation of predicted values
And discretizing the established system mathematical model.
The calculation formula of the network side phase current and the input side phase voltage predicted value of the RMC rectification stage can be obtained by discretizing an input filter mathematical model:
Figure BDA0001421269450000103
Figure BDA0001421269450000104
wherein the coefficient Cij、DijThe method is used for calculating the predicted value of the variable corresponding to the discrete system after one sampling period. Cij、DijThe specific calculation result of (2) can be obtained by a state space expression of the mathematical model of the input filter.
Figure BDA0001421269450000105
The discrete form of which can be represented by the formula (5),
Figure BDA0001421269450000111
wherein,
Figure BDA0001421269450000112
Figure BDA0001421269450000113
wherein,
Figure BDA0001421269450000114
and
Figure BDA0001421269450000115
respectively representing the input side phase voltage values of the rectification stage at the k-th moment and the k +1 moment,
Figure BDA0001421269450000116
and
Figure BDA0001421269450000117
respectively shows the grid side phase current values at the k-th time and the k +1 time,
Figure BDA0001421269450000118
indicating the current value of the input phase of the rectifier stage at time k,
Figure BDA0001421269450000119
representing the grid-side phase voltage value, C, at the k-th timef、LfAnd RfRespectively representing the capacitance, inductance and equivalent resistance, T, of the input filtersFor the switching period, A and B are factor matrices formed by the input filter parameters, I2*2Is a unit matrix with two rows and two columns.
Similarly, the discretized form of the load model is shown in (6),
Figure BDA00014212694500001110
wherein,
Figure BDA00014212694500001111
and
Figure BDA00014212694500001112
respectively representing the system output current values at the k-th time and the k +1 time,
Figure BDA00014212694500001113
represents the system output voltage value, L, at the k-th moment1And R1Representing the inductance and resistance of the load.
d. Quality function
In a predictive control strategy, different quality functions have different control effects.
The error expression of the output current prediction reference value is as follows:
Figure BDA00014212694500001114
wherein the superscript "+" denotes a reference value,
Figure BDA00014212694500001115
the current is output at the moment k + 1.
The error expression of the network side instantaneous reactive power and the reference value thereof is as follows:
Figure BDA0001421269450000121
where 0 is the instantaneous reactive power reference value,
Figure BDA0001421269450000122
and
Figure BDA0001421269450000123
the real part and the imaginary part of the grid side input voltage and current under the k +1 moment static coordinate system are respectively used for inputting the voltage and the current at the k +1 moment under the two-phase static coordinate system, which are obtained by predicting the sampled three-phase voltage and the sampled current through an input side discretization model;
combining the above two equations, the expression of the quality function can be obtained as follows:
Figure BDA0001421269450000124
wherein λ is a weighting factor.
e. Pulse allocation taking into account magnetic bias
Each switching cycle is divided into two equal half cycles as shown in fig. 9, and during the first half of the switching cycle, the RMC pre-converter selects the switching state vector for model predictive control, assuming that S is on as shown in fig. 10bpAnd San(ii) a In the second half of the switching cycle, S is turned on as shown in FIG. 11bnAnd SapThe control vector is a vector with opposite directions in the first half cycle, namely, the upper bridge arm and the lower bridge arm of the same bridge arm conduction switch are interchanged in the state of the first half cycle and the second half cycle, so that the output voltage of the RMC rectifier stage in each switching cycle is composed of two parts, and the voltage amplitudes of the two parts are equal and opposite. Therefore, the primary voltage of the high-frequency transformer is ensured to be positive and negative alternating pulses all the time, and the problem of magnetic biasing of the transformer is solved.
Simulation verification:
in order to verify the effectiveness of the model prediction control method of the simplified matrix converter with bias control, simulation is carried out in an MATLAB/Simulink environment, the total simulation time is 0.4s, the output current is given to be increased from 25A to 50A in 0.2s, and the simulation parameters are as follows:
TABLE 4 simulation parameters
Figure BDA0001421269450000131
The simulation results are shown in fig. 12-15.
Fig. 12 shows waveforms of input phase voltage and input phase current of the RMC under the control method, and it is known from the waveforms that input voltage and current are in the same phase, so that a network-side unit power factor is realized, the current sine is still good when a load is suddenly applied for 0.2s, and it is verified that the RMC under the model predictive control of the reduced matrix converter with bias control has good input performance.
Fig. 13 is a waveform of the output current of the RMC under the control method, and it can be seen from the graph that the output current follows the given value, and can also follow the given value faster when the load is suddenly increased, and can operate stably, verifying that the system under the model predictive control of the reduced matrix converter with bias control of the present invention has good output following and load disturbance resistance.
Fig. 14 and 15 are voltage waveforms and partially amplified waveforms of an RMC transformer under a conventional MPC, respectively, and it is known that an MPC without transformer dc bias suppression will cause asymmetry between positive and negative voltages of a primary side of the transformer, thereby causing a problem of transformer bias.
Fig. 16 shows the primary voltage waveform of the RMC transformer under model predictive control with bias suppression, and fig. 17 shows the partial amplification of the primary voltage of the transformer (which amplifies the waveform of 0.15s to 0.152 s). as can be seen from fig. 17, the primary voltage of the transformer alternates between positive and negative, the transformer does not have the bias problem, and the output current change can be well responded when the load is suddenly added for 0.2s, thus verifying the effectiveness of the method for solving the bias problem by model predictive control of the reduced matrix converter with bias control of the present invention.
FIG. 18 is a graph showing a 50% drop in three-phase input voltage at 0.1s to simulate a voltage sag; FIG. 19 is a waveform of a three-phase input current with a dip in the input voltage, the input current still being a sine wave; FIG. 20 is a waveform of a-phase voltage current before and after an input voltage sag, where unity power factor is maintained on both the grid side and the grid side before and after the voltage sag; fig. 21 shows waveforms of output currents before and after an input voltage drop, and it can be seen from the diagram that the output currents before and after the input voltage drop can still better follow a reference, thereby indicating that the control method of the invention enables a system to have a characteristic of resisting power grid drop disturbance.
The inventive method was tested in the unbalanced condition of the grid, fig. 22 shows a three-phase unbalanced input voltage waveform, in which the a-phase voltage is unbalanced and the b-phase is unbalanced (U)s＝[150sin(100πt)311sin(100πt-90°)311sin(100πt+120°)]) (ii) a FIG. 23 is the input current waveform when the three phase input is unbalanced, it can be seen that the input current is still sinusoidal; FIG. 24 is a graph of the a-phase voltage current waveforms with an unbalanced input, the input still maintaining unity power factor; fig. 25 shows waveforms of the output current and the reference current, and it is known from the waveforms that the output current still keeps highly following the reference even under the three-phase input unbalanced working condition, thereby verifying that the system has strong power grid unbalanced disturbance rejection capability under the control method of the present invention.
According to the test waveforms of the instantaneous drop of the input voltage and the unbalanced working condition of the three-phase input voltage, the simplified matrix converter model with the bias control has stronger resistance to abnormal input (drop and unbalance), so that the system has stronger anti-interference property.

Claims (4)

1. The model prediction control method of the simplified matrix converter with the magnetic bias control is characterized in that input voltage and current on a network side, input voltage and output current on a rectification stage of the simplified matrix converter, voltage and current on an input side and output current on an output side are sampled on the basis of an input filter, a pre-stage converter of the simplified matrix converter, a transformer, a post-stage controllable rectifier bridge and a load model, a mathematical model of the simplified matrix converter system is constructed and discretized, an input reactive power error and an output current error are taken as objective functions, an optimal switching state is found, the problem of the magnetic bias of the transformer is solved by adopting a positive-negative pulse alternative distribution mode, and model prediction control with the magnetic bias suppression of the; the method is implemented according to the following steps:
step 1: establishing a mathematical model of front and rear switches of the simplified matrix converter;
step 2: establishing a state table of all switches at the front stage and the rear stage of the simplified matrix converter;
and step 3: on the basis of the step 1, discretizing and simplifying a matrix converter mathematical model;
and 4, step 4: on the basis of the steps 1 to 3, establishing a quality function taking the input reactive power and the output current error as objective functions; the method specifically comprises the following steps:
the error expression of the output current prediction reference value is as follows:
Figure FDA0002183999050000011
wherein the superscript "+" denotes a reference value,
Figure FDA0002183999050000012
predicting the current for the time k + 1;
the error expression of the network side instantaneous reactive power and the reference value thereof is as follows:
Figure FDA0002183999050000013
where 0 is the instantaneous reactive power reference value,
Figure FDA0002183999050000014
and
Figure FDA0002183999050000015
respectively inputting real parts and imaginary parts of voltage and current at the k +1 moment under a two-phase static coordinate system by sampling input three-phase voltage and current through input side discretization model prediction;
combining equation (7) and equation (8), the expression for the quality function is given as follows:
Figure FDA0002183999050000021
wherein λ is a weighting factor;
and 5: on the basis of the steps 1 to 4, the pulse sequence distribution of the bias magnet of the transformer is considered: a positive and negative pulse alternative distribution mode is adopted, so that the problem of transformer magnetic biasing caused by the prediction control of random switching states by a traditional model is solved; the specific process is as follows: each switching period is divided into two equal half periods, when the switching period is the first half, a preceding-stage converter of the simplified matrix converter is a switching state vector selected by model prediction control, and when the switching period is the second half, a control vector is a vector with the opposite direction of the first half period, namely, the upper bridge arm and the lower bridge arm of the same bridge arm conduction switch are exchanged under the state of the first half period and the second half period, so that the output voltage of the rectification stage of the simplified matrix converter in each switching period is composed of two parts, the amplitudes of the two parts are equal and opposite, the primary voltage of the high-frequency transformer is ensured to be positive and negative alternating pulses all the time, and the.
2. The method for model predictive control of a reduced matrix converter with bias control as claimed in claim 1, wherein said step 1 is specifically:
simplified matrix converter pre-converter mathematical model describes input side voltage current u of simplified matrix convertere，ieWith the voltage and current u on the DC sidedc，idcThe switching matrix model of (1) is as follows:
Figure FDA0002183999050000022
Figure FDA0002183999050000023
wherein S isap、San、Sbp、Sbn、Scp、ScnAll the switches are simplified matrix converter rectifier switches;
the switching mathematical model of the rear-stage controllable rectifier bridge is as follows:
u0＝u1(S1-S3) (3)
i0＝i1(S1-S3) (4)
wherein u is0And i0To output voltage and current u1And i1For secondary voltage and current of the transformer, S1、S3The on-off states of the rear-stage controllable rectifier bridge are all the on-off states.
3. The method for model predictive control of a reduced matrix converter with bias control as claimed in claim 2, wherein said step 2 is specifically: according to the principle that the output side and the input side of the rectification stage of the simplified matrix converter cannot be in short circuit and open circuit, the three-phase bridge arm of the rectification stage of the simplified matrix converter has nine switch state combinations, three zero vectors are removed in order to increase the voltage transmission ratio, and only effective vectors are considered, such as six switch states shown in table 1:
table 1:
Figure FDA0002183999050000031
in table 1, 1 indicates on, 0 indicates off;
the rear-stage controllable rectifier bridge lists two switching states of the rear-stage full-bridge rectification, as shown in table 2:
table 2:
Figure FDA0002183999050000032
in Table 2, S1、S2、S3、S4All the switches are rear-stage controllable rectifier bridge switches, wherein 1 represents on, and 0 represents off.
4. The method for model predictive control of a reduced matrix converter with bias control as claimed in claim 1, wherein said step 3 is specifically:
the discretization form of the phase current at the network side and the phase voltage at the input side of the rectification stage of the reduced matrix converter is as follows:
Figure FDA0002183999050000041
Figure FDA0002183999050000042
Figure FDA0002183999050000043
wherein,
Figure FDA0002183999050000044
and
Figure FDA0002183999050000045
respectively representing the input side phase voltage values of the rectification stage at the k-th moment and the k +1 moment,
Figure FDA0002183999050000046
and
Figure FDA0002183999050000047
respectively shows the grid side phase current values at the k-th time and the k +1 time,
Figure FDA0002183999050000048
indicating the current value of the input phase of the rectifier stage at time k,
Figure FDA0002183999050000049
representing the voltage value of the grid side phase at the k-th moment; cf、LfAnd RfRespectively representing the capacitance, inductance and equivalent resistance, T, of the input filtersIs a switching cycle; c and D are coefficient matrixes of a grid side phase voltage and an input side phase voltage of an RMC rectification stage in a discrete form; a and B are factor matrixes formed by input filter parameters; coefficient matrix Cij、DijThe method comprises the steps of calculating a predicted value (i is 1, 2; j is 1, 2) of a variable corresponding to a discrete system after one sampling period; i is2*2A unit matrix of two rows and two columns;
the discretized expression of the load model is as follows:
Figure FDA00021839990500000410
wherein,
Figure FDA00021839990500000411
and
Figure FDA00021839990500000412
respectively representing the system output current values at the k-th time and the k +1 time,
Figure FDA00021839990500000413
represents the system output voltage value, L, at the k-th moment1And R1Representing the inductance and resistance of the load.
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