CN109742963B - Single-phase pulse rectifier power grid voltage estimation method - Google Patents
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Abstract
The invention discloses a method for estimating the power grid voltage of a single-phase pulse rectifier, which belongs to the technical field of power electronics and specifically comprises the following steps: dividing active power and reactive power of a single-phase pulse rectifier system into two power parts respectively, and establishing an active power and reactive power mathematical model of a reference model in a model reference self-adaptive system; according to errors of active power and reactive power in the reference model and the adjustable model, power grid voltage fundamental wave estimated values are obtained through a PI controller in the model reference adaptive system respectively; a phase-locked loop is eliminated, and fundamental wave angle information and angular frequency of the grid voltage are estimated through the grid side current and the active and reactive power of a reference model; and designing the initial value of the modulation voltage of the rectifier to realize the smooth start of the control system. The method adopts a model reference self-adaptive control idea to establish a reference model and an adjustable model active and reactive power mathematical model, and realizes accurate estimation of the grid voltage of the single-phase pulse rectifier without a grid voltage sensor.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to a method for estimating the power grid voltage of a single-phase pulse rectifier.
Background
The single-phase pulse rectifier has the advantages of high power factor at the network side, small current harmonic wave, capability of realizing bidirectional energy flow and the like, and is widely applied to the fields of new energy power generation, uninterruptible power supplies, railway locomotive traction and the like. At present, control methods of single-phase pulse rectifiers are numerous and mature, and the control methods can be roughly divided into current control and power control. The current control takes the network side current as a control object, and accurately tracks the given network side current, so that the control target of network side unit power factor and direct current side voltage constancy is realized. Whereas the magnitude and phase of a given grid-side current is closely related to the grid voltage. The power control takes the active power and the reactive power of the network side as control objects, and indirectly realizes the decoupling control of the active component and the reactive component of the current of the network side. And the calculation of the system power needs to extract the amplitude, the phase and other information of the fundamental wave of the grid voltage. Therefore, the implementation of the pulse rectifier current control and power control depends on the extraction of grid voltage information.
The amplitude, phase and frequency information of the grid voltage is generally obtained by a Phase Locked Loop (PLL). The traditional PLL obtains the period and phase information by detecting the zero crossing point of the network voltage, and the method is simple, but has poor phase locking effect, weak harmonic interference resistance and slow phase tracking speed. In order to improve the anti-interference capability of the PLL, the phase locking of the network voltage is realized by constructing a virtual signal orthogonal to the network voltage by using the principle of a three-phase-locked loop. Although these PLL methods are effective in extracting phase, frequency, etc. information from the grid voltage, they all require the acquisition of the grid voltage by a rectifier grid side voltage sensor. In practical engineering application, under the condition that the rectifier equipment is far away from a power grid, when a grid voltage sensor is installed on the power grid side, a longer cable line can generate voltage drop, so that a voltage signal acquired by a system controller is influenced; when the grid pressure sensor is installed at the equipment, the wiring scheme between the sensor and the grid is complex in design. In addition, when the grid voltage sensor fails, it is a challenge to ensure that the rectifier system operates normally. For this reason, scholars at home and abroad have successively proposed a plurality of network-free pressure sensor control methods.
At present, the pulse rectifier network voltage sensor-free control method based on virtual power grid flux linkage orientation is widely applied in practice. By taking the ac motor flux linkage observation method as a reference, the rectifier grid side voltage is regarded as a virtual flux linkage differential quantity to replace the grid voltage as a directional vector, thereby omitting a grid voltage sensor. Although the virtual grid flux observer method achieves grid voltage-free sensor control of the pulse rectifier by estimating the amplitude and phase of the virtual flux, the grid voltage information is not estimated. In the field of railroad electric traction drives, the output power allowed by the traction system is closely related to the magnitude of the traction grid voltage, and therefore, in a railroad locomotive electric traction drive system, the grid voltage magnitude must be measured or estimated. The existing control method of the non-grid pressure sensor is bound to be limited in application.
Disclosure of Invention
Aiming at the problems, the invention aims to provide a method for estimating the power grid voltage of a single-phase pulse rectifier, which adopts a model reference self-adaptive control idea, establishes a reference model and an adjustable model active and reactive power mathematical model and can solve the problem of accurately estimating the power grid voltage without a power grid voltage sensor. The technical scheme is as follows:
s1: an active power and reactive power mathematical model of a reference model in the model reference self-adaptive system is constructed:
wherein, Pest_refAnd Qest_refRespectively the active power and the reactive power in the reference model; i.e. idAnd iqRespectively, the network side current isD and q axis components, u, in dq coordinate systemabdAnd uabqTo modulate the voltage uabD and q axis components under dq coordinate system; l issAnd RsRespectively, a network side equivalent inductor and a network side equivalent resistor, IsmAmplitude of fundamental wave of current on network side, omegaestThe estimation value of the angular frequency of the fundamental wave of the grid voltage is obtained.
Model parameterActive power estimated value P of adjustable model in adaptive systemestAnd the reactive power estimated value QestThe expression of (a) is:
wherein, UsmIs the amplitude of the fundamental wave of the grid voltage;
the included angle between the voltage of the power grid and the current of the grid side, namely a power factor angle;
s2: estimating the amplitude of the fundamental wave of the grid voltage:
the errors of the active power and the reactive power of the reference model and the adjustable model are respectively obtained by a PI controller in the model reference adaptive system to obtain the estimated value of the power grid voltage and the power factor angle trigonometric function
And
an estimate U of the amplitude of the fundamental wave of the grid voltagesm_estComprises the following steps:
s3: estimating the fundamental wave angle information of the grid voltage according to the grid side current, the active power and the reactive power of the reference model:
the trigonometric function of the grid voltage fundamental wave angle is:
wherein, thetauAnd thetaiRespectively is a grid voltage usNet side current isThe initial phase angle of (a);
and is also provided with
Wherein iαFor second-order generalized integral to actual net side current isFiltered current iβIs a SOGI structure and isA virtual current component in quadrature; the trigonometric function of the grid voltage fundamental angle is then expressed as follows:
the grid voltage fundamental wave angular frequency estimate ωestThe expression is as follows:
furthermore, when the control system is started, the voltage u is modulatedabInitial value u of axial component in dq coordinate systemabd_setup、uabq_setupThe following settings are set:
the initial estimation value of the trigonometric function of the net pressure fundamental wave angle is set as follows:
wherein u isdcIs a DC side voltage, sin (ω)0t) and cos (. omega.) of0t) sending out sine signal and cosine signal, omega, respectively for the controller by local clock0Is the angular frequency at nominal power frequency.
The invention has the beneficial effects that: the active power and the reactive power of a single-phase pulse rectifier system are divided into two power parts respectively, and an active power and reactive power mathematical model of a reference model in a model reference self-adaptive system is established; according to errors of active power and reactive power in the reference model and the adjustable model, power grid voltage fundamental wave estimated values are obtained through a PI controller in the model reference adaptive system respectively; a phase-locked loop is eliminated, and fundamental wave angle information and angular frequency of the grid voltage are estimated through the grid side current and the active and reactive power of a reference model; and designing the initial value of the modulation voltage of the rectifier to realize the smooth start of the control system.
Compared with the traditional algorithm, the method adopts the model reference self-adaptive control idea to establish the reference model and the adjustable model active and reactive power mathematical model, and realizes the accurate estimation of the single-phase pulse rectifier power grid voltage without the power grid voltage sensor.
Drawings
Fig. 1 is a topology structure diagram of a single-phase two-level pulse rectifier.
FIG. 2 is a schematic block diagram of a method for estimating the grid voltage of a single-phase pulse rectifier.
Fig. 3 is a block diagram of grid voltage magnitude estimation based on model reference adaptation.
Fig. 4 is a block diagram of grid voltage frequency estimation.
FIG. 5 is a simulation waveform of actual net pressure and estimated net pressure under steady state conditions.
FIG. 6 is a simulated waveform of estimated net pressure under different conditions; (a) the amplitude of the power grid voltage is suddenly changed; (b) the phase of the power grid voltage is suddenly changed; (c) the frequency of the grid voltage abruptly changes.
FIG. 7 is a graph of actual and estimated net compaction test waveforms at system start-up.
Fig. 8 is an experimental waveform of the actual grid voltage and the estimated voltage under the steady state condition.
Fig. 9 shows the experimental waveforms of the estimated grid voltage and the grid side current when the actual grid voltage is distorted.
Detailed Description
The invention is described in further detail below with reference to the figures and specific embodiments. According to one embodiment of the present application, referring to fig. 1, the present solution is directed to a single-phase two-level pulse rectifier topology. Fig. 2 shows a functional division block diagram of the single-phase pulse rectifier grid voltage estimation system of the scheme. The whole system can be divided into six parts, namely voltage PI outer loop control 01, second-order generalized integral 02, MRAS-based grid voltage estimation 03, direct power control 04, dq/alpha beta coordinate transformation 05 and pulse width modulation strategy PWM 06. The specific protection content of the invention is a MRAS-based power grid voltage estimation 03 module, and the specific content of the module is as follows:
input side active power P of rectifierinAnd reactive power QinThe expression of (a) is:
wherein idAnd iqRespectively, the network side current isD and q axis components, u, in dq coordinate systemabdAnd uabqTo modulate the voltage uabD-axis and q-axis components in a dq coordinate system.
Active power P of equivalent resistance at network sideRAnd reactive power Q of equivalent inductanceLThe calculation expression of (a) is:
wherein L issAnd RsRespectively, the equivalent inductance and resistance at the network side, IsmAmplitude of fundamental wave of current on network side, omegaestIs the estimated grid voltage fundamental angular frequency.
The system active power P of the reference model in the model reference adaptive systemest_refReactive power Qest_refThe mathematical model is as follows:
active power estimated value P of adjustable model in model reference adaptive systemestAnd the reactive power estimated value QestThe expression of (a) is:
wherein, UsmIs the amplitude of the fundamental wave of the grid voltage,
the included angle between the voltage of the power grid and the current of the grid side, namely the power factor angle.
The errors of the active power and the reactive power output by the reference model and the adjustable model are respectively obtained by the estimated values of the power grid voltage and the power factor angle trigonometric function through the PI controller
As shown in fig. 3, the estimated value U of the fundamental amplitude of the grid voltagesm_estComprises the following steps:
the trigonometric function of the grid voltage fundamental wave angle is:
wherein, thetauAnd thetaiRespectively is a grid voltage usNet side current isThe initial phase angle of (c). And is also provided with
Wherein iαFor second order generalized integral SOGI vs. actual net side current isFiltered current iβIs a SOGI structure and isThe orthogonal virtual current component. The trigonometric function of the grid voltage fundamental angle can be written as:
grid voltage fundamental wave angular frequency estimation value omegaestThe expression is as follows:
fig. 4 shows a block diagram of the implementation of the trigonometric function of the grid voltage fundamental angle and the frequency estimation.
In practical application, the starting process of the rectifier needs to be sequentially operated under the working conditions of uncontrolled rectification pre-charging and PWM rectification. The modulation voltage u obtained by the control system during the uncontrolled rectifying pre-charging phase, i.e. when the PWM pulse is blockedabdAnd uabqInvalid, the calculation of the reference values of the active power and the reactive power in the reference model is meaningless, so that the system is out of control when the control method operates. Therefore, in order to realize smooth startup of the rectifier, the system control parameters need to be initialized.
And setting the initial estimation value of the trigonometric function of the net pressure angle as follows:
wherein, ω is0Is the angular frequency at nominal power frequency, sin (ω)0t)、cos(ω0t) respectively sending out sine signals and cosine signals by a local clock for the controller.
Setting the initial estimated value of the modulation voltage as:
wherein u isdcIs the voltage across the dc side load.
Network voltage information estimated by a MRAS network voltage estimation 03 module is used for a direct power control 04 module to obtain coordinate components of d and q axes of modulation voltage, and an alpha axis component u of the modulation voltage is generated by a dq/alpha beta coordinate transformation 05 moduleabα. In the PWM06 module, u is modulatedabαAnd comparing the voltage with a triangular carrier, generating different pulse sequences based on a volt-second balance principle, and further driving a switching tube, thereby realizing the control of the single-phase pulse rectifier network-free voltage sensor.
FIG. 5 is a simulated waveform of the actual net voltage, the estimated net voltage and its voltage error under steady state conditions. FIG. 6 is a simulated waveform of estimated net pressure under different conditions. Fig. 7 is an experimental waveform of the actual grid voltage, the estimated grid voltage, the grid side current and the dc side voltage at the start of the system. FIG. 8 is an experimental waveform of the actual net voltage, the estimated voltage and its voltage error under steady state conditions. Fig. 9 shows the experimental waveforms of the estimated grid voltage and the grid side current when the actual grid voltage is distorted.
Claims (2)
1. A method for estimating the grid voltage of a single-phase pulse rectifier is characterized by comprising the following steps:
s1: an active power and reactive power mathematical model of a reference model in the model reference self-adaptive system is constructed:
wherein, Pest_refAnd Qest_refRespectively the active power and the reactive power in the reference model; i.e. idAnd iqRespectively, the network side current isD and q axis components, u, in dq coordinate systemabdAnd uabqTo modulate the voltage uabD and q axis components under dq coordinate system; l issAnd RsRespectively, a network side equivalent inductor and a network side equivalent resistor, IsmAmplitude of fundamental wave of current on network side, omegaestThe estimation value of the fundamental wave angular frequency of the grid voltage is obtained;
active power estimated value P of adjustable model in model reference adaptive systemestAnd the reactive power estimated value QestThe expression of (a) is:
wherein, UsmIs the amplitude of the fundamental wave of the grid voltage;
the included angle between the voltage of the power grid and the current of the grid side, namely a power factor angle;
s2: estimating the amplitude of the fundamental wave of the grid voltage:
the errors of the active power and the reactive power of the reference model and the adjustable model are respectively obtained by a PI controller in the model reference adaptive system to obtain the estimated value of the power grid voltage and the power factor angle trigonometric function
And
an estimate U of the amplitude of the fundamental wave of the grid voltagesm_estComprises the following steps:
s3: estimating the fundamental wave angle information of the grid voltage according to the grid side current, the active power and the reactive power of the reference model:
the trigonometric function of the grid voltage fundamental wave angle is:
wherein, thetauAnd thetaiRespectively is a grid voltage usNet side current isThe initial phase angle of (a);
and is also provided with
Wherein iαFor second-order generalized integral to actual net side current isFiltered current iβIs a SOGI structure and isA virtual current component in quadrature; the trigonometric function of the grid voltage fundamental angle is then expressed as follows:
the grid voltage fundamental wave angular frequency estimate ωestThe expression is as follows:
2. the method of claim 1, wherein the modulated voltage u is adjusted when the control system is activatedabInitial value u of axial component in dq coordinate systemabd_setup、uabq_setupThe following settings are set:
the initial estimation value of the trigonometric function of the net pressure fundamental wave angle is set as follows:
wherein u isdcIs a DC side voltage, sin (ω)0t) and cos (. omega.) of0t) sending out sine signal and cosine signal, omega, respectively for the controller by local clock0Is the angular frequency at nominal power frequency.
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| CN110855169B (en) * | 2019-12-06 | 2021-09-14 | 龙岩学院 | Single-phase inverter model prediction control method without voltage sensor |
| CN111711353B (en) * | 2020-06-17 | 2023-06-20 | 中国国家铁路集团有限公司 | Reactive component detection method, control method and device of single-phase rectifier |
| CN113098015B (en) * | 2021-04-20 | 2022-08-30 | 中国铁道科学研究院集团有限公司 | Method and device for suppressing low-order harmonic of network side current of single-phase rectifier |
| CN116633126B (en) * | 2023-07-24 | 2023-10-17 | 成都希望森兰智能制造有限公司 | Power factor control method for aging system of frequency converter without network voltage sensor |
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