DE102017007037B4 - Network evaluation and setpoint generation procedures - Google Patents

Abstract

Method for network evaluation and setpoint generation with a generalized integrator (1) to which a mains voltage signal (u) is fed as a first input signal and to which a variable frequency coefficient (a) is fed as a second input signal, the frequency coefficient (a) being a first output signal from a Phase controller (2), the line voltage signal (u), a phase setpoint signal (w) and the output signals (y, y) of the generalized integrator (1) being fed to the phase controller at its inputs (E21, E22, E23, E24), and where the phase controller (2) forms a difference signal (rp) from the mains voltage signal (u) and one of the output signals (y) from the generalized integrator (1), the absolute value of which represents a mains quality index (r), characterized in that the method for operating a Charger is used, and that the value of the power quality index (r) when the charger starts the rate of change of the electrical The power consumption of the charger is affected.

Description

The invention relates to a method for the method for network evaluation and setpoint generation with a generalized integrator, to which a network voltage signal is supplied as a first input signal and to which a variable frequency coefficient is supplied as a second input signal, the frequency coefficient being a first output signal of a phase controller, the The phase voltage signal, a phase setpoint signal, and the output signals of the generalized integrator are fed to the phase controller at its inputs, and the phase controller forms a difference signal from the line voltage signal and one of the output signals of the generalized integrator, the absolute value of which represents a network quality index.

Such a method is in the document US 2010/0 213 925 A1 disclosed.

From the European patent application EP 2 354 800 A1 a method is known in which a generalized integrator is used to determine the fundamental frequency of a mains voltage.

Chargers in electric vehicles, so-called on-board chargers or on-board charge clients, are connected to the three-phase or alternating voltage network of the energy suppliers. Depending on the connection point, the connection to the power supply network can be defined by certain electrical parameters. The connection can have a particularly high resistance or a particularly high inductance. There may also be other consumers in the immediate vicinity of the connection location that have a strong influence on the voltage form of the connection point. Switching such consumers on and off can also lead to disturbances in the voltage form and phase position, and even voltage and phase jumps.

Since the chargers are installed in the vehicles, they can be confronted with all these types of malfunctions at various connection points. The chargers should therefore be able to deal with all of these problems. Whenever possible, the full charging capacity of the charger should be available. Depending on the type of fault, this is not always achievable; in any case, the charger should be able to provide at least part of the charging power.

Furthermore, high demands are made on the chargers with regard to the current consumption from the energy supply network. The charger should take up a possible sinusoidal current in phase with the mains voltage. This property can be assessed using the power factor ϕ, which describes the phase shift of voltage and current, and the total harmonic distortion THD, which quantifies the harmonic content of the current.

Two important tasks for the charger can be derived from this, firstly the determination of a current setpoint which corresponds to the fundamental wave of the mains voltage and secondly the determination of a quality index for evaluating the mains connection quality.

The method proposed here for network evaluation and setpoint generation for a charger is intended to improve the solution of both tasks compared to the current state of the art, in particular in a simple method that can be carried out for inexpensive microcontrollers.

This object is achieved by the combination of features of claim 1.

• 1 einen verallgemeinerten Integrator mit einem variablen Frequenzkoeffizienten als Eingangsgröße,
• 2 einen Phasenregler zur Regelung des Frequenzkoeffizienten,
• 3 zwei Diagramme zur Erläuterung der Detektion eines Phasensignals,
• 4 eine Implementierung des verallgemeinerten Integrators mit variablem Frequenzkoeffizienten,
• 5 eine erste Implementierung des Phasenreglers,
• 6 eine zweite Implementierung des Phasenreglers.

The invention will be illustrated and explained below with reference to the drawing. They show

• 1 a generalized integrator with a variable frequency coefficient as an input variable,
• 2nd a phase controller for regulating the frequency coefficient,
• 3rd two diagrams to explain the detection of a phase signal,
• 4th an implementation of the generalized integrator with variable frequency coefficient,
• 5 a first implementation of the phase controller,
• 6 a second implementation of the phase controller.

The method according to the invention uses a generalized integrator 1 with an adjustable frequency coefficient a. Such an integrator is from the literature, such as the European patent application mentioned at the beginning EP 2 354 800 A1 , known and is used in many places as a sine filter.

This generalized integrator 1 is now expanded by a phase controller 2. The entirety of the two parts forms a frequency-adaptive generalized integrator 1, 2, which implements the method according to the invention.

phasenverschobene Ausgangssignal y₂.The generalized integrator 1 with variable frequency coefficients a is in the 1 shown. It has two entrances E ₁₁ , E ₁₂ and two exits A11 , A12 . The input signal at the first input E ₁₁ is the measured mains voltage u. That at the second entrance E ₁₂ The input signal is the adjustable frequency coefficient a . The output signals y ₁ , y ₂ at the two exits A ₁₁ , A ₁₂ are firstly the fundamental wave of the input signal u, adjusted for interference, as the first output signal y ₁ , as well as the second one $90°=\frac{\pi }{\mathrm{2nd}}$

phase-shifted output signal y ₂ .

Hierin beschreibt der Parameter b die Filtergüte des verallgemeinerten Integrators 1.The temporal behavior of the generalized integrator 1 can be described by a set of two differential equations: $$\frac{d}{dt}\left(\begin{array}{c}{y}_1\left(t\right)\\ y_{\mathrm{2nd}}\left(t\right)\end{array}\right)=\left(\begin{array}{cc}-b& -a\left(t\right)\\ a\left(t\right)& 0\end{array}\right)\left(\begin{array}{c}{y}_1\left(t\right)\\ y_{\mathrm{2nd}}\left(t\right)\end{array}\right)+\left(\begin{array}{c}b\\ 0\end{array}\right)u\left(t\right)$$

Here parameter b describes the filter quality of the generalized integrator 1.

The phase controller 2 for regulating the frequency coefficient a of the generalized integrator is in the 2nd shown. The input signals of the four inputs E ₂₁ , E ₂₂ , E ₂₃ , E ₂₄ are in sequence the mains voltage signal u, the first output signal y ₁ and the second output signal y _{2 of} the generalized integrator 1, and a phase setpoint w. The output signals of the phase controller 2 are a so-called power quality index r at the output A ₂₁ , and at the output A ₂₂ the frequency coefficient a, which forms an input variable of the generalized integrator 1.

Both in the 1 and 2nd The control loops outlined together result in a frequency-adaptive generalized integrator 1, 2.

The operation of the frequency adaptive generalized integrator 1, 2 is as follows. The profile of the mains voltage is recorded by a suitable measuring device, not shown here, and is transmitted as a mains voltage signal u to the frequency-adaptive generalized integrator 1, 2. The course of the mains voltage signal u is in principle sinusoidal, but may well contain disturbances such as distortions, harmonics or gaps.

Then two things happen. The generalized integrator 1 records the course of the sinusoidal fundamental wave of the mains voltage signal u and oscillates with it. The quality and speed of this adaptation can be set using parameter b.

Simultaneously with the settling of the generalized integrator 1 is by the in the 2nd phase controller shown 2nd the parameter a of the generalized integrator 1 set so that this is the fundamental wave of the mains voltage signal u describes the underlying frequency. Is this frequency coefficient a incorrectly set, results between the signals u and y ₁ a phase shift p . This is from the phase controller 2nd detected and by changing the frequency coefficient a to a phase setpoint w regulated.

The detection of the phase shift p is shown by the two diagrams of the 3rd further clarified. Are listed in the 3a the time course of voltage signals and in the 3b the time course of the angle of the phase shift p , with the figures representing their courses purely qualitatively.

First, the mains voltage signal u the signal cleaned of interference y ₁ deducted. The resulting difference signal rp will with the signal y ₂ multiplied ( 3a) . This gives a phase signal p ( 3b) which is the phase shift between the signals u and y ₁ describes. Because of the always the same relation between the signals y ₁ and y ₂ which are 90 ° out of phase is the phase signal p always positive as soon as the signal y ₁ the signal u runs after, and always negative once the signal y ₁ before the mains voltage signal u runs here. The phase signal p oscillates at twice the frequency of the mains voltage signal u . The required phase information is found in the mean value of the phase signal p again.

This average of the phase signal p is now used by the I controller in the phase controller 2nd by adjusting the frequency coefficient a the phase setpoint w aligned. The control speed of the phase controller can be set by the parameter k can be set.

The network quality index r is generated from the signal by generating amounts rp generated. It describes the deviation of the measured mains voltage at all times u from the expected fundamental wave y ₁ the mains voltage. This is a real-time assessment of the network quality, the all possible disturbances of the network voltage u maps, given.

Further processing of the network quality index r is possible in many ways; At this point, a continuous evaluation, which directly influences the rate of change of the electrical power consumption, especially when the charger is started, and an evaluation by means of an absolute or variable limit value, which leads to a reduction in the performance of the charger, are to be proposed here. As a result, the charger can react efficiently to malfunctions that can occur at a poorly quality grid connection point or an island grid with a high power consumption by the charger.

In this case, a regulation can also take effect, the aim of which is the network quality index r to be kept exactly at the limit in order to keep the performance degradation of the charger as low as possible.

With the help of the phase setpoint w can give the charger any phase shift p for the mains voltage in the range of about - 20 ° to + 20 °. This can be used as a manipulated variable for grid stability regulations of the energy supplier.

You can also use the signal y ₁ the zero crossing of the mains voltage u can be recognized without having to implement complex, fault-prone detection. This works because of the signal y ₁ the fundamental wave of the mains voltage u filtered out as a strictly monotonously falling or rising signal at the zero point.

The method presented can be implemented on inexpensive microcontrollers and, in addition to generating a filtered sinusoidal current setpoint, also allows a phase shift curve to be set by the phase setpoint w and the assessment of the network quality using a single variable, namely the network quality index r . The response to the network quality index r is not subject to the enormous time requirements of network analysis and can therefore also be implemented on inexpensive microcontrollers.

Various designs are conceivable for implementing the described method. A preferred implementation for the generalized integrator 1 is in the 4th shown. This is obtained from the general definition in the 1 by transforming it into a discrete model with a defined sampling rate. The element Mem represents a buffer.

The implementation for the phase controller, shown in the 5 , as well as the implementation of the generalized integrator, can be discretized in the 2nd generate the model shown. The parameter kd is a time-discrete parameter here.

Alternatively it is possible instead of a direct multiplication with the signal y ₂ first determine its sign using a Signum function sgn and then simply multiply it with the sign. As a result, the value ranges of the subsequent signals become less large and are easier to handle for the microcontroller used. This version is in the 6 shown.

Reference list

1

generalized integrator

2nd

Phase controller

1, 2

frequency adaptive generalized integrator

A ₁₁ , A12, A21, A22

Exits

E11, E12, E21, E22, E23, E24

Entrances

Mem

Cache

a

second input signal (frequency coefficient)

b

Parameters (quality of the generalized integrator)

k

parameter

kd

Parameters (discrete-time)

p

Phase shift (swinkel)

r

Network quality index

rp

Differential signal

u

first input signal (mains voltage signal, mains voltage)

y ₁

first output signal of the generalized integrator

y ₂

second output signal of the generalized integrator

w

Phase setpoint

Claims (2)

Method for network evaluation and setpoint generation with a generalized integrator (1) to which a mains voltage signal (u) is fed as a first input signal and to which a variable frequency coefficient (a) is fed as a second input signal, the frequency coefficient (a) being a first output signal of a phase regulator (2), the phase regulator at its inputs (E21, E22, E23, E24) having the mains voltage signal (u), a phase setpoint signal (w) and the output signals (y ₁ , y ₂ ) of the generalized integrator (1) and the phase controller (2) forms a difference signal (rp) from the mains voltage signal (u) and one of the output signals (y ₁ ) of the generalized integrator (1), the absolute value of which represents a mains quality index ( r), characterized in that the method is used to operate a charger and that the value of the power quality index (r) influences the rate of change of the electrical power consumption of the charger when the charger is started. Procedure according to Claim 1 , characterized in that the phase setpoint (w) is used as a manipulated variable for grid stability control of the energy supplier.

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