JP2004180452A - Load current estimation device of pwm converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem in providing a current detector, as a hard ware, which directly detects a load current with sure but is not favorable in cost. <P>SOLUTION: A load current estimating device operates stably, without providing a load current detector. A first means detects a filter reactor current (I<SB>L</SB>), and a second means detects a filter capacitor voltage (V<SB>C</SB>). A third means uses the filter reactor current (I<SB>L</SB>), the filter capacitor voltage (V<SB>C</SB>) acquired by the first and second means and a filter capacitor capacitance (C), to provide a load current estimated value based on the observer theory with these as inputs. Gains H<SB>1</SB>and H<SB>2</SB>of the observer which is stably designed provide a desired convergence characteristics when selected as an equation (7). <P>COPYRIGHT: (C)2004,JPO

Description

を負荷電流の推定値とする。
【０００９】
【発明の実施の形態】
以下、本発明の負荷電流推定の原理を詳述する。
本発明は安定な負荷電流推定方法を得るために、オブザーバー理論に基づいて、負荷電流推定器を構成している。
【００１０】
図１は本発明の負荷電流の推定装置の構成を示す図である。同図において、１は本発明の第１の手段であり、フィルタリアクトル電流値（Ｉ_Ｌ）を検出する。２は本発明の第２の手段であり、フィルタコンデンサ電圧値（Ｖ_Ｃ）を検出する。３は本発明の第３の手段で、本発明の中心となる負荷電流オブザーバーである。ただし、Ｈ_１、Ｈ_２はオブザーバのゲイン定数であり、Ｃはフィルタコンデンサの容量値、＾符号の付いたものはその推定値を表している。
【００１１】
以下、第３の手段を中心に詳述する。
まず、オブザーバを構成するために、フィルタ回路のコンデンサ８の特性に注目し、そのダイナミックス方程式は（１）式のよう表すことができる。
ただし、Ｖ_Ｃはフィルタコンデンサ電圧、Ｖ_Ｃはコンデンサ電圧の微分値を表す。また、Ｉ_Ｌはフィルタリアクトル電流、Ｉｏは出力負荷電流を表す。
【００１２】

オブザーバの応答速度を負荷電流Ｉｏの変化速度と比べて十分速く設定できれば、負荷電流の変化は無視しても差し支えないので、（２）式が成立する。
【００１３】

以上の（１）、（２）式をまとめて、オブザーバの基本モデルとし、（３）式で表される。
【００１４】

【００１５】
（３）式のモデルに基づいて、オブザーバーを（４）式のように構成する。
【００１６】

【００１７】
（４）式において、Ｈ_１、Ｈ_２はオブザーバのゲイン定数で、推定値の安定化および真値への追従速度の決定に選定される。Ｉ_Ｌ、Ｖ_Ｃは本発明のオブザーバの入力であり、ぞれぞれ第１手段、第２手段の出力のフィルタリアクトル電流、フィルタコンデンサ電圧の検出値である。
（４）式のオブザーバの構成は本発明の第３の手段であり、Ｈ_１、Ｈ_２の選定でオブザーバを安定に設計すれば、オブザーバの出力の負荷電流推定値

はその真値に収束することが理論的に保証される。（４）式の推定装置は本発明請求項の第２項で請求する内容である。
【００１８】
以下、（４）式のオブザーバにあるゲイン定数Ｈ_１、Ｈ_２の一選択例を紹介する。設計目標は推定誤差をダンピング率がζ、減衰率がωｎとしよう。
【００１９】
（４）式のオブザーバーの特性はその特性方程式Ｐ（ｓ）の（５）式の根で決められる。ただし、ｓはラプラス演算子を表す。
【００２０】

【００２１】
上記特性方程式を希望通りに（６）式のようになるために、
【００２２】

【００２３】
オブザーバのゲインＨ_１、Ｈ_２を（７）式のように選択すると、所望の収束特性を得ることができる。
【００２４】

【００２５】
したがって、本発明によれば、負荷電流推定値を安定に負荷電流の真値に追従させることができ、また、オブザーバのゲインを適切に調整すれば、任意の収束率で収束させることが指定できる。
以上は本発明請求項に請求した内容である。
【００２６】
【発明の効果】
以上説明したようにＰＷＭ変換器の負荷電流推定装置において、本発明の請求項によれば、負荷電流を誤差無しで安定に推定することができる。また、推定装置の特性はゲイン定数を適切に選定により任意に設定することができる。本発明の推定装置を利用すれば、負荷電流センサを設けなくても、推定装置出力の推定値を利用すればよいので、安価な電力変換システムを構成することができる。
【００２７】
【図面の簡単な説明】
【図１】本発明の構成を示すブロック図である。
【図２】従来の技術を説明するための変換器主回路を示す図である。
【符号説明】
１ 本発明の第１の手段のフィルタリアクトル電流検出器
２ 本発明の第２の手段のフィルタコンデンサ電圧検出手段
３ 本発明の第３の手段の負荷電流算出手段
４ ＰＷＭ変換器を構成するＰＷＭ変換ブリッジ
５ 電力を供給する電源
６ 電力を供給される負荷
７ フィルタリアクトル
８ フィルタコンデンサ
９ リアクトル電流検出器
１０ コンデンサ電圧検出器
１１ 負荷電流検出器[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device for a PWM converter, and more particularly to a device for estimating a load current.
[0002]
[Prior art]
A PWM converter that performs power conversion by a switching action is known.
FIG. 2 is a diagram showing a circuit configuration of a PWM converter for performing power conversion for explaining a conventional technique. In FIG. 2, reference numeral 4 denotes a PWM conversion bridge constituting the converter, and reference numeral 5 denotes a power supply for supplying power. , 6 is a load, 7 is a filter reactor for smoothing the converter output current, 8 is a filter capacitor for smoothing the output voltage, 9 is a current detector for detecting the converter output current, and 10 filter capacitor voltages ( A voltage detector 11 for detecting the output voltage), and a current detector 11 for detecting the load current.
[0003]
The purpose of the converter control is mainly to stabilize the output voltage to a predetermined voltage command value. However, in order to secure the stability of the system, the converter output current (filter reactor current) detector 9 and the output voltage ( It is common to provide a (filter capacitor voltage) detector 10. In addition, in order to cope with a sudden change in load, it is necessary to directly or indirectly obtain a load current value and feed it back to the controller of the converter.
[0004]
For this reason, in the related art, the current detector 11 is often provided as hardware to directly detect the load current. (For example, refer to Patent Document 1).
[0005]
However, it is most reliable to directly detect and obtain the load current in terms of hardware, but this is not preferable in terms of cost.
[0006]
[Patent Document 1]
JP-A-2002-272117 (FIG. 1, 7 DC voltage detector, 11 current detector)
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above points, and an object of the present invention is to provide a load current estimating apparatus that operates stably without providing a load current detector. It is in.
[0008]
[Means for Solving the Problems]
That is, in order to achieve the object, a first means for detecting a current (I _L ) flowing through the filter reactor, a second means for detecting a filter capacitor voltage (V _C ), and a first and a second means And a third means for obtaining an estimated value of the current ( _IO ) flowing through the load using the filter reactor current value, the filter capacitor voltage value, and the filter capacitor capacitance value (C) obtained in Load current estimated value obtained by means of 4

Is the estimated value of the load current.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the principle of the load current estimation of the present invention will be described in detail.
The present invention configures a load current estimator based on the observer theory in order to obtain a stable load current estimation method.
[0010]
FIG. 1 is a diagram showing a configuration of a load current estimating device of the present invention. In the figure, reference numeral 1 denotes a first means of the present invention, which detects a filter reactor current value (I _L ). Reference numeral 2 denotes a second means of the present invention, which detects a filter capacitor voltage value (V _C ). Reference numeral 3 denotes a third means of the present invention, which is a load current observer at the center of the present invention. Here, H ₁ and H ₂ are the gain constants of the observer, C is the capacitance value of the filter capacitor, and the symbol with a ＾ sign indicates the estimated value.
[0011]
Hereinafter, the third means will be mainly described in detail.
First, in order to form an observer, attention is paid to the characteristics of the capacitor 8 of the filter circuit, and the dynamics equation thereof can be expressed as equation (1).
However, V _C filter capacitor voltage, V _C represents the differential value of the capacitor voltage. Also, _{I L} is the filter reactor current, the Io represents the output load current.
[0012]

If the response speed of the observer can be set sufficiently faster than the change speed of the load current Io, the change in the load current can be ignored, and the equation (2) holds.
[0013]

The above equations (1) and (2) are put together to form a basic observer model, which is expressed by equation (3).
[0014]

[0015]
The observer is configured as shown in equation (4) based on the model of equation (3).
[0016]

[0017]
In the equation (4), H ₁ and H ₂ are gain constants of the observer and are selected for stabilizing the estimated value and determining the speed of following the true value. I _L, V _C is the input of the observer of the present invention, Zorezo Re first means, filter reactor current of the output of the second means is a detection value of the filter capacitor voltage.
The structure of the observer in the expression (4) is the third means of the present invention. If the observer is designed stably by selecting H ₁ and H ₂ , the load current estimated value of the output of the observer is obtained.

Is theoretically guaranteed to converge to its true value. The estimating device of equation (4) is the content claimed in claim 2 of the present invention.
[0018]
Hereinafter, an example of selecting _one of the gain constants H ₁ and H _{2 in} the observer of Expression (4) will be introduced. Let the design error be the estimation error with a damping rate of ζ and a damping rate of ωn.
[0019]
The characteristic of the observer in the equation (4) is determined by the root of the equation (5) of the characteristic equation P (s). Here, s represents a Laplace operator.
[0020]

[0021]
In order for the above characteristic equation to become as desired in equation (6),
[0022]

[0023]
When the gains H ₁ and H ₂ of the observer are selected as in the equation (7), desired convergence characteristics can be obtained.
[0024]

[0025]
Therefore, according to the present invention, the load current estimated value can be made to follow the true value of the load current stably, and if the gain of the observer is appropriately adjusted, it is possible to designate to converge at an arbitrary convergence rate. .
The above is the contents claimed in the claims of the present invention.
[0026]
【The invention's effect】
As described above, in the load current estimating apparatus for a PWM converter, according to the present invention, the load current can be stably estimated without errors. Further, the characteristics of the estimating device can be arbitrarily set by appropriately selecting the gain constant. If the estimation device of the present invention is used, an inexpensive power conversion system can be configured because the estimated value of the output of the estimation device may be used without providing a load current sensor.
[0027]
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of the present invention.
FIG. 2 is a diagram showing a converter main circuit for explaining a conventional technique.
[Description of sign]
1 Filter reactor current detector 1 of the first means of the present invention 2 Filter capacitor voltage detecting means 3 of the second means of the present invention Load current calculating means 4 of the third means of the present invention 4 PWM conversion constituting the PWM converter Bridge 5 Power supply 6 that supplies power Load 7 that is supplied with power 7 Filter reactor 8 Filter capacitor 9 Reactor current detector 10 Capacitor voltage detector 11 Load current detector

Claims (2)

An apparatus for estimating a load current of a PWM converter that converts power supply power to a load through a semiconductor switching bridge, a filter reactor, and a filter capacitor,
First means for detecting a current (I _L ) flowing through the filter reactor, second means for detecting a filter capacitor voltage (V _C ), and a filter reactor current value obtained by the first and second means Third means for obtaining an estimated value of the current (I _O ) flowing to the load using the filter capacitor voltage value and the filter capacitor capacitance value (C), and a load current estimating device

And a load current estimated value obtained by the third means.

A load current estimating device for a PWM converter, wherein is used as an estimated value of the load current. In claim 1, as the third means,

Here, H1 and H2 are gain constants,

Is the filter capacitor voltage

Estimate and its derivative,

A load current estimating device for a PWM converter, wherein a differential value of the load current estimated value is used.

Images