CN112803804B - Single-phase three-level rectifier parameter compensation temperature balance control method and system - Google Patents
Single-phase three-level rectifier parameter compensation temperature balance control method and system Download PDFInfo
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- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M7/219—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
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Abstract
The invention relates to the technical field of electronics, and discloses a parameter compensation temperature balance control method and system for a single-phase three-level rectifier, which can ensure the control performance and realize the temperature balance control of an IGBT. The method comprises the following steps: establishing an active power prediction model and a reactive power prediction model of a next period respectively corresponding to a single-phase three-level rectifier under the normal state and the three states of the equivalent resistance and the equivalent inductance of the network side; respectively establishing a midpoint potential balance prediction model and an IGBT energy loss prediction model of the next period of the single-phase three-level rectifier; establishing four objective functions of an active power error, a reactive power error, a midpoint potential difference and an energy loss variance among IGBTs, configuring weight coefficients for the four objective functions, and establishing an evaluation function; and (4) performing finite set optimization on the minimum value of the evaluation function, and controlling the control performance of the single-phase three-level rectifier and the junction temperature balance among the IGBTs by taking the found optimal switching state as the control output of the next period.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to a parameter compensation temperature balance control method and system for a single-phase three-level rectifier.
Background
The single-phase three-level rectifier has the advantages of less current harmonic waves, high response speed, high power conversion efficiency and the like, and is widely applied to the field of rail transit such as electric locomotives, high-speed trains and the like. Statistical analysis of operation fault data of the single-phase three-level rectifier in the CRH2 motor train unit shows that the fault of the power device is one of high-speed train high-speed faults. IGBTs are considered to be one of the most vulnerable devices in single-phase three-level rectifiers. In the use process of the single-phase three-level rectifier, the difference of the IGBT manufacturing process and the asymmetry of the working state enable uneven thermal stress to be generated among the IGBTs on each bridge arm, so that the phenomenon of unbalanced temperature occurs, and finally the service lives of the IGBTs are inconsistent. When temperature imbalance occurs between the power devices, if the temperature imbalance cannot be handled in time, the heat loss borne by the power devices is larger than that of the power devices around the power devices, so that the power devices are easy to malfunction. When one IGBT breaks down, the whole bridge arm or the IGBT assembly module of the system is replaced, and the service cycle of the rest power devices of the bridge arm is reduced, so that the service life of the whole bridge arm or the system module is shortened, and the use cost of the system is increased.
In the operation process of the single-phase three-level rectifier, electronic components can age along with time and severe environment, so that the electrical parameters of the electronic components are changed to cause uncertainty of model parameters, and the control performance is reduced. Therefore, how to reasonably design online identification model parameters and further perform parameter compensation on the model under the condition that the model parameters are uncertain and realize the balance control of the temperature of each IGBT on the single-phase three-level rectifier bridge arm is a problem to be solved urgently.
Disclosure of Invention
The invention aims to disclose a parameter compensation temperature balance control method and system for a single-phase three-level rectifier, which realize temperature balance control of an IGBT on the basis of ensuring control performance.
In order to achieve the above object, the present invention discloses a parameter compensation temperature balance control method for a single-phase three-level rectifier, comprising the following steps:
s1: establishing an active power prediction model and a reactive power prediction model of the next period respectively corresponding to the single-phase three-level rectifier under the following three states;
state A, normal state;
state B, under the state that the equivalent resistance of the rectifier network side circuit changes;
the state C is in a state that the equivalent inductance of the rectifier network side circuit changes;
the active power prediction model and the reactive power prediction model corresponding to the state B and the state C are respectively an active power model and a reactive power prediction model after parameter compensation;
s2: respectively establishing a midpoint potential balance prediction model and an IGBT energy loss prediction model of the next period of the single-phase three-level rectifier;
s3: establishing four objective functions of an active power error, a reactive power error, a midpoint potential difference and an energy loss variance among IGBTs, configuring weight coefficients for the four objective functions, and establishing an evaluation function;
s4: and (4) performing finite set optimization on the minimum value of the evaluation function, and controlling the control performance of the single-phase three-level rectifier and the junction temperature balance among the IGBTs by taking the found optimal switching state as the control output of the next period.
Preferably, the S1 specifically includes the following steps:
s11: respectively establishing an active power and reactive power prediction model of the next period of the single-phase three-level rectifier, wherein the formula is as follows:
wherein P (k +1) and Q (k +1) are the active power and reactive power at time k +1, P (k) and Q (k) are the active power and reactive power at time k, k represents the current cycle, k +1 represents the next cycle, k is 0,1,2, …; t is s Represents a sampling period; u shape sm Is the peak value of the grid side voltage; l and R are equivalent inductance and equivalent resistance of the system network side respectively, and omega is the fundamental wave angular frequency of the network side voltage; u. of sα (k)、u sβ (k) Is the grid side voltage vector u at time k s (k) Alpha, beta components, u, in a two-phase stationary alpha beta coordinate system abα (k)、u abβ (k) Is the input voltage vector u of the H-bridge rectifier at the moment k ab (k) Alpha, beta components in a two-phase stationary alpha beta coordinate system;
the network side voltage u under the three-phase static coordinate system is converted in the s domain s (s), input voltage u of H-bridge rectifier ab (s) conversion to u in a two-phase stationary α β coordinate system sα (s) and u sβ (s)、u abα (s) and u abβ (s), the formula is as follows:
wherein γ is a damping coefficient;
transforming equations (2) and (3) from the s-domain to the time domain, respectively:
discretizing the formula (4) and the formula (5), wherein the formulas are respectively as follows:
wherein u is sα (k-1)、u sβ (k-1) is the net side voltage vector u at time k-1 s (k-1) alpha, beta components, u, in a two-phase stationary alpha beta coordinate system sα (k-2)、u sβ (k-2) is the grid-side voltage vector u at time k-2 s (k-2) alpha, beta components in a two-phase stationary alpha beta coordinate system; u. of abα (k-1)、u abβ (k-1) is the H-bridge rectifier input voltage vector u at time k-1 ab (k-1) alpha, beta components, u, in a two-phase stationary alpha beta coordinate system abα (k-2)、u abβ (k-2) is the H-bridge rectifier input voltage vector u at time k-2 ab (k-2) alpha, beta components in a two-phase stationary alpha beta coordinate system;
input voltage vector u of H-bridge rectifier at moment k-1 ab (k) And intermediate DC link voltage vectorQuantity U dc (k-1) a relation model between IGBT driving control signals of the power device of the single-phase three-level rectifier is expressed as follows:
wherein S is x As a power device T xn The subscript x represents a bridge arm, x belongs to { a, b }, n is the serial number of the power device IGBT on the x bridge arm, and n belongs to {1,2,3,4 }; s a ∈{-1,0,1}，S b ∈{-1,0,1}；
S12: establishing the relationship between the voltage on the equivalent inductor at the network side of the system in the single-phase three-level rectifier, the voltage on the network side, the voltage on the equivalent resistor and the input voltage of the H-bridge rectifier, wherein the formula is as follows:
in the formula i s (t) is the net side current;
discretizing an equation (9) as follows:
wherein, R (k), L (k) are equivalent resistance and equivalent inductance of the system network side at time k;
when the equivalent resistance parameter and the inductance parameter of the system network side in the single-phase three-level rectifier respectively change, the formulas are respectively as follows:
wherein, R (k +1) and L (k +1) are equivalent resistance values and equivalent inductance values of the system network side at the moment of k + 1;
when the equivalent resistance parameter of the system network side in the single-phase three-level rectifier changes, the active power and reactive power formula of the system at the k +1 moment is as follows:
when the equivalent inductance parameter of the system network side in the single-phase three-level rectifier changes, the active power and reactive power formula of the system at the k +1 moment is as follows:
when the system reaches a steady state, the active power and the reactive power of the system have
From equations (13) and (14) there are:
and (15) and (16) are respectively substituted into the step (1) to obtain an active power and reactive power prediction model after parameter compensation in the next period:
wherein, P R (k +1) and Q R (k +1) represents that at the k +1 moment, the resistance parameter is compensatedPower and reactive power, P L (k +1) and Q L And (k +1) represents the active power and the reactive power after the k +1 moment is compensated by the inductance parameter.
Preferably, the S2 specifically includes the following steps:
s21: establishing a midpoint potential balance prediction model of the next period;
when the dc-side capacitance C1 is equal to C2 is equal to C, the midpoint balance current formula is:
wherein i o (t) is the midpoint balance current, U dc1 (t) and U dc2 (t) is the voltage of capacitors C1 and C2, respectively;
the difference between the upper and lower capacitance voltages is obtained from equation (19):
wherein u is diff (t) is the difference between the upper and lower capacitor voltages;
discretizing the formula (20), wherein the midpoint potential balance prediction model at the k +1 moment is as follows:
s22: establishing an IGBT energy loss prediction model of the next period;
specifically, a relation model between the energy loss of each IGBT on the x bridge arm of the next period and the current and the polarity flag bit of each bridge arm, the switching state and the on-state voltage drop of a power device and the on-off power consumption of each bridge arm power device is established, namely the IGBT energy loss prediction model at the moment of k +1 has the following formula:
wherein, in the formula, E x1 (k+1)、E x2 (k+1)、E x3 (k+1)、E x4 (k +1) represents the power device T on the bridge arm at the moment of k +1 x respectively x1 、T x2 、T x3 、T x4 Energy loss of (a), symbol ^ represents AND operation, i x (k) Representing the current of the x leg at time k,
representing x bridge arm current i at time k x A flag bit of a polarity of the signal,
representing x bridge arm current i at time k x Negation operation of polarity flag bits, s x1 (k)、s x2 (k)、s x3 (k)、s x4 (k) Respectively representing power devices T on x bridge arms at k time x1 、T x2 、T x3 、T x4 On/off state of u ce_x1 (k)、u ce_x2 (k)、u ce_x3 (k)、u ce_x4 (k) Respectively representing power devices T on x bridge arms at k time x1 、T x2 、T x3 、T x4 On-state voltage drop of gamma x1 (k)、γ x2 (k)、γ x3 (k)、γ x4 (k) Respectively represents a power device T on a bridge arm at k time x x1 、T x2 、T x3 、T x4 The on-off power consumption of (1).
Preferably, the S3 specifically includes the following steps:
s31: establishing four objective functions of active power error, reactive power error, midpoint potential difference and energy loss variance of each bridge arm IGBT in the next period; the following are distinguished:
constructing a system active power error and reactive power error objective function, wherein the formulas are respectively as follows:
wherein E is P (k+1)、E Q (k +1) is the system active power at the moment of k +1 respectivelyRate error, reactive power error objective function, P _ref 、Q _ref The set values of active power and reactive power are set;
constructing an objective function of the midpoint potential difference, wherein the formula is as follows:
wherein, U' diff (k +1) is an objective function of the midpoint potential difference at the time k + 1;
constructing an objective function of energy loss among four IGBTs on an x bridge arm, wherein the formula is as follows:
wherein E is xn (k +1) represents the power device T on the bridge arm at the time x of k +1 xn X-a, b,
represents the energy loss average value E 'of four IGBTs on an x arm at the moment k + 1' totx (k +1) represents the energy loss variance of four IGBTs on the x bridge arm at the time of k + 1;
s32: configuring weight coefficients for the four objective functions, and establishing an evaluation function as follows:
g(k+1)＝λ 1 *E P (k+1)+λ 2 *E Q (k+1)+λ 3 *U′ diff (k+1)+λ 4 *E’ totx (k+1) (26)
wherein g (k +1) is the system evaluation function at time k +1, λ 1 ,λ 2 ,λ 3 ,λ 4 And respectively representing the weight coefficients configured by the active power error, the reactive power error, the midpoint potential difference and the loss variances of the four IGBTs of the x bridge arm.
Preferably, the S4 is specifically controlled by a value with the minimum evaluation function, and is represented as:
wherein S is a ∈{-1,0,1}，S b ∈{-1,0,1}，
Representing a power device IGBT driving control signal corresponding to the minimum value of an evaluation function in the single-phase three-level rectifier at the moment of k + 1;
the evaluation function comprises four target functions of active power error, reactive power error, midpoint potential difference and energy loss variance among IGBTs, the minimum value of the evaluation function is taken to carry out finite set optimization, the found optimal switching state is taken as the control output of the next period, and the control on the control performance of the single-phase three-level rectifier and the control on the junction temperature balance of the A and B bridge arm IGBTs are realized.
In order to achieve the above object, the present invention further discloses a parameter compensation temperature balance control system for a single-phase three-level rectifier, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the corresponding steps of the above method when executing the computer program.
The invention has the following beneficial effects:
the invention adopts a method and a system for parameter compensation temperature balance control of a single-phase three-level rectifier, and the method and the system can compensate the degradation of the system performance caused by uncertain parameters, thereby not only improving the unit power factor, but also reducing the junction temperature among the IGBTs of the rectifier, balancing the loss among the IGBTs and achieving the effect of prolonging the service life of the whole system of the rectifier.
The present invention will be described in further detail below with reference to the accompanying drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic diagram of a single phase three level rectifier circuit of an exemplary traction system to which the preferred embodiment of the present invention is applicable;
FIG. 2 is a schematic flow chart of a parameter compensation temperature balance control method for a single-phase three-level rectifier for rail train traction according to a preferred embodiment of the invention;
FIGS. 3a-d are graphs comparing distortion, power factor, active power error and reactive power error before and after parameter compensation without determining resistance parameters, respectively;
FIGS. 4a-d are graphs comparing distortion, power factor, active power error and reactive power error before and after parameter compensation without determining inductance parameters, respectively;
FIG. 5 is a graph of temperature distribution of four IGBTs of the a-bridge arm under transient current control;
fig. 6 is a graph of temperature distribution of four IGBTs of the a-arm under parameter compensation.
Detailed Description
The embodiments of the invention will be described in detail below with reference to the drawings, but the invention can be implemented in many different ways as defined and covered by the claims.
Example 1
As shown in fig. 2, the present embodiment provides a method for controlling parameter compensation temperature balance of a single-phase three-level rectifier, which includes the following steps:
s1: establishing an active power prediction model and a reactive power prediction model of the next period respectively corresponding to the single-phase three-level rectifier under the following three states; state A, normal state; state B, under the state that the equivalent resistance of the rectifier network side circuit changes; the state C is in a state that the equivalent inductance of the rectifier network side circuit changes; and the active power prediction model and the reactive power prediction model corresponding to the state B and the state C are respectively an active power model and a reactive power prediction model after parameter compensation.
S2: and respectively establishing a midpoint potential balance prediction model and an IGBT energy loss prediction model of the single-phase three-level rectifier in the next period.
S3: four objective functions of active power error, reactive power error, midpoint potential difference and energy loss variance among IGBTs are established, weight coefficients are configured for the four objective functions, and evaluation functions are established.
S4: and (4) performing finite set optimization on the minimum value of the evaluation function, and controlling the control performance of the single-phase three-level rectifier and the junction temperature balance among the IGBTs by taking the found optimal switching state as the control output of the next period.
The embodiment of the invention provides a parameter compensation temperature balance control method for a single-phase three-level rectifier, which takes a single-phase three-level rectifier system as a research object, deeply analyzes the application of a finite control set model prediction control (FCS-MPC) method on the single-phase three-level rectifier, analyzes the influence of parameters before and after change on the system temperature balance by constructing a power prediction model and an IGBT power loss prediction model under the condition that the model parameters in the FCS-MPC method are uncertain, and improves the performance of the system by researching a temperature balance control method based on parameter online identification and a sliding mode disturbance observer. From the qualitative and quantitative perspective, the control targets of realizing neutral point potential balance, unit power factor and temperature balance among the IGBTs are analyzed through various indexes, and the temperature balance control of the IGBTs is realized on the basis of ensuring the control performance.
The simulation method is performed in a Simulink environment based on a virtual simulation platform, and the simulation platform comprises a voltage signal generation module, a rectifier control module, an oscilloscope and the like. The simulation platform is a common prior art in the field, and is not described herein in detail. Wherein, the parameters used in the simulation experiment are shown in table 1;
TABLE 1 simulation experiment parameters
| Parameter item | Parameter(s) |
| Magnitude of net side voltage | 212V |
| Network side resistor | 0.2Ω |
| Network side inductor | 2mH |
| Frequency of network side voltage | 50Hz |
| Sampling frequency | 100kHz |
| DC side capacitor | 16mF |
| Voltage on the direct current side | 1500V |
Referring to fig. 2, a method for controlling parameter compensation and temperature balance of a single-phase three-level rectifier according to an embodiment of the present invention includes the following steps:
s1: respectively establishing an active power prediction model and a reactive power prediction model of the single-phase three-level rectifier in the next period; when the parameters of the resistance and the inductance of the circuit at the network side of the rectifier change, an active power prediction model and a reactive power prediction model which are compensated by the parameters in the next period are respectively established.
Specifically, the active power prediction model and the reactive power prediction model before and after the parameter compensation established in this embodiment include:
s11: respectively establishing an active power prediction model and a reactive power prediction model of the single-phase three-level rectifier in the next period, wherein the models are prediction models in a normal state, and the formula is as follows:
where P (k +1) and Q (k +1) are the active power and reactive power at time k + 1, P (k) and Q (k) are the active power and reactive power at time k, k denotes the current cycle, k +1 denotes the next cycle, k is 0,1,2, …; t is s Represents a sampling period; u shape sm Is the peak value of the grid side voltage; l and R are equivalent inductance and equivalent resistance of the system network side respectively, and omega is the fundamental wave angular frequency of the network side voltage; u. of sα (k)、u sβ (k) Is the grid side voltage vector u at time k s (k) Alpha, beta components, u, in a two-phase stationary alpha beta coordinate system abα (k)、u abβ (k) Is the input voltage vector u of the H-bridge rectifier at the moment k ab (k) Alpha, beta components in a two-phase stationary alpha beta coordinate system.
Converting the network side voltage u under the three-phase static coordinate system in a plurality of fields (s field) s (s), input voltage u of H bridge rectifier ab (s) conversion to u in a two-phase stationary α β coordinate system sα (s) and u sβ (s)、u abα (s) and u abβ (s), the formula is as follows:
wherein gamma is a damping coefficient;
transforming equations (2) and (3) from the s-domain to the time domain, respectively:
discretizing the formula (4) and the formula (5), wherein the formulas are respectively as follows:
in the formula u sα (k-1)、u sβ (k-1) is the net side voltage vector u at time k-1 s (k-1) alpha, beta components, u, in a two-phase stationary alpha beta coordinate system sα (k-2)、u sβ (k-2) is the grid-side voltage vector u at time k-2 s (k-2) alpha, beta components in a two-phase stationary alpha beta coordinate system; u. of abα (k-1)、u abβ (k-1) is the H-bridge rectifier input voltage vector u at time k-1 ab (k-1) alpha, beta components, u, in a two-phase stationary alpha beta coordinate system abα (k-2)、u abβ (k-2) is the H-bridge rectifier input voltage vector u at time k-2 ab (k-2) alpha, beta components in a two-phase stationary alpha beta coordinate system.
Input voltage vector u of H-bridge rectifier at moment k-1 ab (k) Voltage vector U with intermediate dc link dc (k-1) a relation model between IGBT driving control signals of the power device of the single-phase three-level rectifier is expressed as follows:
in the formula S x As a power device T xn The subscript x represents a bridge arm, x belongs to { a, b }, n is the number (from top to bottom) of the power device IGBT on the x bridge arm, and n belongs to {1,2,3,4 }; s a ∈{-1,0,1}，S b ∈{-1,0,1}。
S12: establishing the relationship between the voltage on the equivalent inductor at the network side of the system in the single-phase three-level rectifier, the voltage on the network side, the voltage on the equivalent resistor and the input voltage of the H-bridge rectifier, wherein the formula is as follows:
in the formula i s (t) is the net side current;
discretizing an equation (9) as follows:
wherein R (k), L (k) are equivalent resistance and equivalent inductance of the system network at time k.
When the equivalent resistance parameter and the inductance parameter of the system network side in the single-phase three-level rectifier respectively change, the formula respectively is as follows:
in the formula, R (k +1) and L (k +1) are equivalent resistance values and equivalent inductance values on the system network side at the time k + 1.
When the equivalent resistance parameter of the system network side in the single-phase three-level rectifier changes, the active power and reactive power formula of the system at the k +1 moment is as follows:
when the equivalent inductance parameter of the system network side in the single-phase three-level rectifier changes, the active power and reactive power formula of the system at the k +1 moment is as follows:
when the system reaches a steady state, the active power and the reactive power of the system are zeroWork power has
From equations (13) and (14) there are:
respectively substituting (15) and (16) into (1) to obtain an active power and reactive power prediction model after parameter compensation in the next period:
wherein, P R (k +1) and Q R (k +1) represents the active power and the reactive power after the resistance parameter compensation at the k +1 moment, P L (k +1) and Q L And (k +1) represents the active power and the reactive power after the k +1 moment is compensated by the inductance parameter.
It is worth mentioning that: in the embodiment of the invention, an equivalent resistance and equivalent inductance parameter compensation mechanism is parallel to the temperature balance control of the embodiment, and the embodiment is compatible with various parameter compensation methods only by utilizing the result that when the system reaches a steady state, the active power and the reactive power sampled by the system at present are respectively approximately equal to the active power and the reactive power sampled by the next period; optionally, the specific parameter compensation may be performed by reasonably designing the online identification model parameters to further implement the parameter compensation on the model, which is not the focus of the present invention and is not described in detail.
S2: and respectively establishing a midpoint potential balance prediction model and an IGBT energy loss prediction model of the next period. It is worth mentioning that: the "midpoint" described in this step refers to a period midpoint not on the time concept, but refers to a position O point in the circuit topology structure shown in fig. 1, and is not described in detail later.
Specifically, the midpoint potential balance prediction model and the IGBT energy loss prediction model for the next cycle, which are established in this embodiment, include:
s21: and establishing a midpoint potential balance prediction model of the next period.
When the dc-side capacitance C1 is equal to C2 is equal to C, the midpoint balance current formula is:
in the formula i o (t) is the midpoint balance current, U dc1 (t) and U dc2 (t) is the voltage of capacitors C1 and C2, respectively;
the difference between the upper and lower capacitance voltages is obtained from equation (19):
in the formula u diff And (t) is the difference between the upper and lower capacitor voltages.
Discretizing the formula (20), wherein the midpoint potential balance prediction model at the k +1 moment is as follows:
s22: and establishing an IGBT energy loss prediction model of the next period.
Establishing a relation model among the energy loss of each IGBT on the x bridge arm of the next period, the current and the polarity flag bit of each bridge arm, the switching state and the on-state voltage drop of the power device and the on-off power consumption of each bridge arm power device, namely establishing a prediction model formula of the energy loss of the IGBT at the moment of k +1 as follows:
wherein, in the formula, E x1 (k+1)、E x2 (k+1)、E x3 (k+1)、E x4 (k +1) represents the power device T on the bridge arm at the moment of k +1 x respectively x1 、T x2 、T x3 、T x4 Energy loss of (a), symbol ^ represents AND operation, i x (k) Representing the current of the x leg at time k,
bridge arm current i representing k time x x A flag bit of a polarity of the signal,
bridge arm current i representing k time x x Negation operation of polarity flag bits, s x1 (k)、s x2 (k)、s x3 (k)、s x4 (k) Respectively representing power devices T on x bridge arms at k time x1 、T x2 、T x3 、T x4 On/off state of (u) ce_x1 (k)、u ce_x2 (k)、u ce_x3 (k)、u ce_x4 (k) Respectively representing power devices T on x bridge arms at k time x1 、T x2 、T x3 、T x4 On-state voltage drop of gamma x1 (k)、γ x2 (k)、γ x3 (k)、γ x4 (k) Respectively representing power devices T on x bridge arms at k time x1 、T x2 、T x3 、T x4 The on-off power consumption of (1).
S3: four objective functions of active power error, reactive power error, midpoint potential difference and energy loss variance among IGBTs are established, weight coefficients are configured for the four objective functions, and evaluation functions are established.
Specifically, the four objective functions of the active power error, the reactive power error, the midpoint potential difference, and the energy loss variance between IGBTs, which are established in this embodiment, configure weight coefficients for the four objective functions, and establish an evaluation function, which includes:
constructing a system active power error and reactive power error objective function, wherein the formulas are respectively as follows:
in the formula, E P (k+1)、E Q (k +1) is a target function of active power error and reactive power error of the system at the moment of k +1, P _ref 、Q _ref The given values of active power and reactive power are given.
Constructing an objective function of the midpoint potential difference, wherein the formula is as follows:
in formula (II) U' diff (k +1) is an objective function of the potential difference at the point in time k + 1.
Constructing an objective function of energy loss among four IGBTs on an x bridge arm, wherein the formula is as follows:
in the formula, E xn (k +1) represents the power device T on the bridge arm at the time x of k +1 xn X is a, b, E x (k +1) represents the energy loss average value, E 'of the four IGBTs on the arm at the time x of k + 1' totx (k +1) represents energy loss variance of four IGBTs on an arm at the time x of k +1, and is used for describing the difference of energy loss among the four IGBTs on the arm, E' totx The smaller (k +1) indicates the closer the energy loss values of the four IGBTs on the x-arm.
Configuring weight coefficients for the four objective functions, and establishing an evaluation function as follows:
g(k+1)＝λ 1 *E P (k+1)+λ 2 *E Q (k+1)+λ 3 *U′ diff (k+1)+λ 4 *E’ totx (k+1) (26)
wherein g (k +1) is a system evaluation function at the time of k +1, and λ 1 ,λ 2 ,λ 3 ,λ 4 And respectively representing the weight coefficients configured by the active power error, the reactive power error, the midpoint potential difference and the loss variances of the four IGBTs of the x bridge arm.
S4: and (4) performing finite set optimization on the minimum value of the evaluation function, and controlling the control performance of the single-phase three-level rectifier and the junction temperature balance among the IGBTs by taking the found optimal switching state as the control output of the next period.
Specifically, the present embodiment takes the minimum value of the evaluation function to perform finite set optimization, and uses the found optimal switching state as the control output of the next period to control the control performance of the single-phase three-level rectifier and the junction temperature balance between the IGBTs, including:
the control is performed with the minimum value of the merit function, which is expressed as:
g (Sa,Sb) (k+1)＝min{g(k+1)} (27)
in the formula, S a ∈{-1,0,1}，S b ∈{-1,0,1}，
And the power device IGBT driving control signal corresponding to the minimum value of the evaluation function in the single-phase three-level rectifier at the moment of k +1 is represented.
The evaluation function comprises four objective functions of active power error, reactive power error, midpoint potential difference and energy loss variance among IGBTs, the minimum value of the evaluation function is taken for finite set optimization, the found optimal switching state is taken as the control output of the next period, and the control on the control performance of the single-phase three-level rectifier and the control on the junction temperature balance of the a bridge arm IGBT and the b bridge arm IGBT are realized. The output switch states of the corresponding bridge arms of the single-phase three-level rectifier are shown in table 2.
TABLE 2 output switch states of corresponding bridge arms of single-phase three-level rectifier
Specifically, a comparison graph before and after parameter compensation with uncertain resistance parameters in the present embodiment is shown in fig. 3; a comparison graph before and after parameter compensation under the condition of uncertain inductance parameters is shown in fig. 4; when the single-phase three-level rectifier adopts the traditional transient current control method, the temperature distribution difference of 4 IGBTs of the a bridge arm is large, and the temperature distribution condition of four IGBTs of the a bridge arm under the transient current control is shown in figure 5; the temperature distribution of the four IGBTs of the a-bridge arm under parameter compensation is shown in fig. 6.
Example 2
Corresponding to the above method embodiments, the present embodiment provides a single-phase three-level rectifier parameter compensation temperature balance control system, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method when executing the computer program.
In summary, the embodiments of the present invention disclose a method and a system for parameter compensation and temperature balance control of a single-phase three-level rectifier, which can compensate the degradation of system performance caused by uncertain parameters, thereby not only improving the unit power factor, but also reducing the junction temperature between the IGBTs of the rectifier, balancing the loss between the IGBTs, and prolonging the service life of the whole system of the rectifier.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. A single-phase three-level rectifier parameter compensation temperature balance control method is characterized by comprising the following steps:
s1: establishing an active power prediction model and a reactive power prediction model of the next period respectively corresponding to the single-phase three-level rectifier under the following three states;
state A, normal state;
state B, under the state that the equivalent resistance of the rectifier network side circuit changes;
the state C is in a state that the equivalent inductance of the rectifier network side circuit changes;
the active power prediction model and the reactive power prediction model corresponding to the state B and the state C are respectively an active power model and a reactive power prediction model after parameter compensation;
s2: respectively establishing a midpoint potential balance prediction model and an IGBT energy loss prediction model of the next period of the single-phase three-level rectifier;
s3: establishing four objective functions of an active power error, a reactive power error, a midpoint potential difference and an energy loss variance among IGBTs, configuring weight coefficients for the four objective functions, and establishing an evaluation function;
s4: and (4) performing finite set optimization on the minimum value of the evaluation function, and controlling the control performance of the single-phase three-level rectifier and the junction temperature balance among the IGBTs by taking the found optimal switching state as the control output of the next period.
2. The method as claimed in claim 1, wherein the step S1 comprises the steps of:
s11: respectively establishing an active power and reactive power prediction model of the next period of the single-phase three-level rectifier, wherein the formula is as follows:
wherein P (k +1) and Q (k +1) are the active power and reactive power at time k +1, P (k) and Q (k) are the active power and reactive power at time k, k represents the current cycle, k +1 represents the next cycle, k is 0,1,2, …; t is s Represents a sampling period; u shape sm Is the peak value of the grid side voltage; l and R are equivalent inductance and equivalent resistance of the system network side respectively, and omega is the fundamental wave angular frequency of the network side voltage; u. of sα (k)、u sβ (k) Is the grid side voltage vector u at time k s (k) Alpha, beta components, u, in a two-phase stationary alpha beta coordinate system abα (k)、u abβ (k) Is the input voltage vector u of the k-time single-phase three-level rectifier ab (k) Alpha, beta components in a two-phase stationary alpha beta coordinate system;
the network side voltage u under the three-phase static coordinate system is converted in the s domain s (s) single-phase three-level rectifier input voltage u ab (s) conversion to u in a two-phase stationary α β coordinate system sα (s) and u sβ (s)、u abα (s) and u abβ (s), the formula is as follows:
wherein γ is a damping coefficient;
transforming equations (2) and (3) from the s-domain to the time domain, respectively:
discretizing the formula (4) and the formula (5), wherein the formulas are respectively as follows:
wherein u is sα (k-1)、u sβ (k-1) is the net side voltage vector u at time k-1 s (k-1) alpha, beta components, u, in a two-phase stationary alpha beta coordinate system sα (k-2)、u sβ (k-2) is the grid-side voltage vector u at time k-2 s (k-2) alpha, beta components in a two-phase stationary alpha beta coordinate system; u. of abα (k-1)、u abβ (k-1) is the input voltage vector u of the single-phase three-level rectifier at the moment of k-1 ab (k-1) alpha, beta components, u, in a two-phase stationary alpha beta coordinate system abα (k-2)、u abβ (k-2) is the input voltage vector u of the single-phase three-level rectifier at the moment k-2 ab (k-2) alpha, beta components in a two-phase stationary alpha beta coordinate system;
input voltage vector u of k-1 time single-phase three-level rectifier ab (k) With intermediate DC link voltage vector U dc (k-1) a relation model between IGBT driving control signals of the power device of the single-phase three-level rectifier is expressed as follows:
wherein S is x As a power device T xn The subscript x represents a bridge arm, x belongs to { a, b }, a represents a bridge arm, b represents b bridge arm, n is the IGBT serial number of the power device on the x bridge arm, and n belongs to {1,2,3,4 }; s a ∈{-1,0,1}，S b ∈{-1,0,1}；
S12: establishing the relationship between the voltage on the equivalent inductor at the system network side in the single-phase three-level rectifier and the voltage at the network side, the voltage on the equivalent resistor and the input voltage of the single-phase three-level rectifier, wherein the formula is as follows:
in the formula i s (t) is the net side current;
discretizing an equation (9) as follows:
wherein, R (k), L (k) are equivalent resistance and equivalent inductance of the system network side at time k;
when the equivalent resistance parameter and the inductance parameter of the system network side in the single-phase three-level rectifier respectively change, the formula respectively is as follows:
wherein, R (k +1) and L (k +1) are equivalent resistance values and equivalent inductance values of the system network side at the moment of k + 1;
when the equivalent resistance parameter of the system network side in the single-phase three-level rectifier changes, the active power and reactive power formula of the system at the k +1 moment is as follows:
when the equivalent inductance parameter of the system network side in the single-phase three-level rectifier changes, the active power and reactive power formula of the system at the k +1 moment is as follows:
when the system reaches a steady state, the active power and the reactive power of the system have
From equations (13) and (14) there are:
respectively substituting (15) and (16) into (1) to obtain an active power and reactive power prediction model after parameter compensation in the next period:
wherein, P R (k +1) and Q R (k +1) represents the active power and the reactive power after the resistance parameter compensation at the k +1 moment, P L (k +1) and Q L And (k +1) represents the active power and the reactive power after the k +1 moment is compensated by the inductance parameter.
3. The method as claimed in claim 2, wherein the step S2 comprises the steps of:
s21: establishing a midpoint potential balance prediction model of the next period;
when the dc-side capacitance C1 is equal to C2 is equal to C, the midpoint balance current formula is:
wherein i o (t) is the midpoint balance current, U dc1 (t) and U dc2 (t) is the voltage of capacitors C1 and C2, respectively;
the difference between the upper and lower capacitance voltages is obtained from equation (19):
wherein u is diff (t) is the difference between the upper and lower capacitor voltages;
discretizing the formula (20), wherein the midpoint potential balance prediction model at the k +1 moment is as follows:
s22: establishing an IGBT energy loss prediction model of the next period;
specifically, a relation model between the energy loss of each IGBT on the x bridge arm of the next period and the current and the polarity flag bit of each bridge arm, the switching state and the on-state voltage drop of a power device and the on-off power consumption of each bridge arm power device is established, namely the IGBT energy loss prediction model at the moment of k +1 has the following formula:
wherein, in the formula, E x1 (k+1)、E x2 (k+1)、E x3 (k+1)、E x4 (k +1) respectively represents the power device T on the x bridge arm at the k +1 moment x1 、T x2 、T x3 、T x4 Energy loss of (a), symbol ^ represents AND operation, i x (k) Representing the current of the x leg at time k,
representing x bridge arm current i at time k x A flag bit of a polarity of the signal,
representing x bridge arm current i at time k x Negation operation of polarity flag bits, s x1 (k)、s x2 (k)、s x3 (k)、s x4 (k) Respectively representing power devices T on x bridge arms at k time x1 、T x2 、T x3 、T x4 On/off state of u ce_x1 (k)、u ce_x2 (k)、u ce_x3 (k)、u ce_x4 (k) Respectively representing power devices T on x bridge arms at k time x1 、T x2 、T x3 、T x4 On-state voltage drop of gamma x1 (k)、γ x2 (k)、γ x3 (k)、γ x4 (k) Respectively representing power devices T on x bridge arms at k time x1 、T x2 、T x3 、T x4 The on-off power consumption of (1).
4. The method as claimed in claim 3, wherein the step S3 comprises the steps of:
s31: establishing four objective functions of an active power error, a reactive power error, a midpoint potential difference and an energy loss variance of each bridge arm IGBT in the next period; the following are distinguished:
constructing a system active power error and reactive power error objective function, wherein the formulas are respectively as follows:
wherein E is P (k+1)、E Q (k +1) is a target function of active power error and reactive power error of the system at the moment of k +1, P _ref 、Q _ref The set values of active power and reactive power are set;
constructing an objective function of the midpoint potential difference, wherein the formula is as follows:
wherein, U' diff (k +1) is an objective function of the midpoint potential difference at the time k + 1;
constructing an objective function of energy loss among four IGBTs on an x bridge arm, wherein the formula is as follows:
wherein E is xn (k +1) represents the power device T on the bridge arm at the time x of k +1 xn The energy loss of (2) is reduced,
represents the energy loss average value E 'of four IGBTs on an x arm at the moment k + 1' totx (k +1) represents the energy loss variance of four IGBTs on the x bridge arm at the time of k + 1;
s32: configuring weight coefficients for the four objective functions, and establishing an evaluation function as follows:
g(k+1)＝λ 1 *E P (k+1)+λ 2 *E Q (k+1)+λ 3 *U′ diff (k+1)+λ 4 *E′ totx (k+1) (26)
wherein g (k +1) is the system evaluation function at time k +1, λ 1 ,λ 2 ,λ 3 ,λ 4 And respectively representing the weight coefficients configured by the active power error, the reactive power error, the midpoint potential difference and the loss variances of the four IGBTs of the x bridge arm.
5. The method as claimed in claim 4, wherein the S4 is specifically controlled by the value with the minimum evaluation function, and is represented as:
wherein S is a ∈{-1,0,1}，S b ∈{-1,0,1}，
Representing a power device IGBT driving control signal corresponding to the minimum value of an evaluation function in the single-phase three-level rectifier at the moment of k + 1;
the evaluation function comprises four target functions of active power error, reactive power error, midpoint potential difference and energy loss variance among IGBTs, the minimum value of the evaluation function is taken to carry out finite set optimization, the found optimal switching state is taken as the control output of the next period, and the control on the control performance of the single-phase three-level rectifier and the control on the junction temperature balance of the A and B bridge arm IGBTs are realized.
6. A single phase three level rectifier parameter compensating temperature balance control system comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor when executing the computer program performs the steps of the method of any of claims 1 to 5.
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