Measure-valued processes for energy markets Christa CuchieroLuca Di PersioFrancesco Guida Sara Svaluto-Ferro

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Measure-valued processes for energy markets
Christa CuchieroLuca Di Persio Francesco Guida
Sara Svaluto-Ferro §
Abstract
We introduce a framework that allows to employ (non-negative) measure-valued
processes for energy market modeling, in particular for electricity and gas futures.
Interpreting the process’ spatial structure as time to maturity, we show how the
Heath-Jarrow-Morton approach (see Heath et al. (1992)) can be translated to this
framework, thus guaranteeing arbitrage free modeling in infinite dimensions. We
derive an analog to the HJM-drift condition and then treat in a Markovian set-
ting existence of non-negative measure-valued diffusions that satisfy this condition.
To analyze mathematically convenient classes we build on Cuchiero et al. (2021)
and consider measure-valued polynomial and affine diffusions, where we can pre-
cisely specify the diffusion part in terms of continuous functions satisfying certain
admissibility conditions. For calibration purposes these functions can then be pa-
rameterized by neural networks yielding measure-valued analogs of neural SPDEs.
By combining Fourier approaches or the moment formula with stochastic gradient
descent methods, this then allows for tractable calibration procedures which we
also test by way of example on market data. We also sketch how measure-valued
processes can be applied in the context of renewable energy production modeling.
Keywords: HJM term structure modeling; energy markets; (neural) measure-valued
processes, polynomial and affine diffusions; Dawson-Watanabe type superprocesses
AMS MSC 2020: 91B72, 91B74, 60J68
Contents
1 Introduction 2
1.1 Notation and basic definitions . . . . . . . . . . . . . . . . . . . . . . . . 6
2 The large financial market and the no-arbitrage condition 7
Vienna University, Department of Statistics and Operations Research, Data Science @ Uni Vienna,
Kolingasse 14-16, 1090 Wien, Austria, christa.cuchiero@univie.ac.at
University of Verona, Department of Computer Science, Strada le Grazie 15, 37134 Verona, Italy,
luca.dipersio@univr.it
University of Trento and University of Verona, Department of Mathematics, Via Sommarive 14,
38123 Povo, Italy, francesco.guida@unitn.it
§University of Verona, Department of Economics, Via Cantarane 24, 37129 Verona, Italy,
luca.dipersio@univr.it
The first author gratefully acknowledges financial support through grant Y 1235 of the START-program.
1
arXiv:2210.09331v1 [q-fin.MF] 17 Oct 2022
3 A Heath-Jarrow-Morton approach for measure-valued processes 8
4 Measure-valued diffusions satisfying the HJM condition 14
4.1 Cylindrical functions and polynomials . . . . . . . . . . . . . . . . . . . . 14
4.2 Directionalderivatives ............................ 14
4.3 Diffusion-type operators and martingale problems . . . . . . . . . . . . . 15
4.4 Existence of measure-valued diffusions satisfying the HJM drift-condition 15
5 Tractable examples of affine and polynomial type 18
5.1 Black-Scholes type measure-valued HJM-models . . . . . . . . . . . . . . 22
5.2 Affine measure-valued HJM-models . . . . . . . . . . . . . . . . . . . . . 25
5.3 Optionpricing................................. 27
5.3.1 Option pricing in Black-Scholes type measure-valued HJM-models 27
5.3.2 Option pricing in affine measure-valued HJM-models . . . . . . . 28
5.4 Calibration to market option prices . . . . . . . . . . . . . . . . . . . . . 30
6 Measure-valued processes for renewable energy production 32
A Auxiliary results 33
B Existence for martingale problems 35
1 Introduction
In this article we show how to employ non-negative measure-valued processes for energy
market modeling, in particular for electricity and gas futures. Before describing in detail
our approach we start by discussing some important features of these markets, following
Benth et al. (2008).
The most liquidly traded products in electricity, gas, and also temperature markets
are future contracts as well as options written on these. These future contracts deliver the
underlying commodity over a certain period rather than at one fixed instance of time. By
their nature, these contracts are often also called swaps, since they represent an exchange
between fixed and variable commodity prices. We shall however employ the terms future
or future contract throughout.
Our focus lies on these future markets as they exhibit higher liquidity than the spot
energy markets. Indeed, even though it is possible to trade power and gas commodities
on the spot market, one usually faces high storage and transaction costs, which in turn
explains the lack of liquidity on the spot market. As a consequence it is potentially
more difficult to recognize and model features or characteristic patterns of the spot price
behavior. Nevertheless stochastic models for the spot prices are widely applied and also
used to derive the dynamics of future prices based on no-arbitrage principles. Indeed,
this is one of the two main approaches how to to set up tractable mathematical models
for future contracts in power markets. The second approach consists in directly modeling
the complete forward curve by applying a Heath-Jarrow-Morton (HJM) type approach
(see Heath et al. (1992) and Benth and Kr¨uhner (2014) in the context of energy markets).
We shall adapt this second approach and model directly an analog of the forward curve,
2
however with non-negative measure-valued processes rather than function-valued ones.
In the sequel, we shall omit “non-negative” and only use “measure” for “non-negative
measure”.
There are many mathematical motivations to deal with this kind of processes. In
general, measure-valued processes are often used for modeling dynamical systems for
which the spatial structure plays a significant role. In the current setting, time to maturity
takes the role of the spatial structure. This is similar to common forward curve modeling
via stochastic partial differential equation (SPDE) as for instance in Benth and Kr¨uhner
(2014) or Benth et al. (2021b). The potential advantage of using measure-valued processes
instead of function-valued ones is that many spatial stochastic processes do not fall into
the framework of SPDEs. In addition, it is often easier to establish existence of a measure-
valued process rather than of an analogous SPDE, say in some Hilbert space, which would
for instance correspond to its Lebesgue density, but which does not necessarily exist.
The decisive economic reason for using measure-valued processes in electricity and
gas modeling however lies in the very nature of the future contracts, namely as products
that deliver the underlying commodity always over a certain period instead of one fixed
instance in time. To formulate this mathematically, denote the price of a future with
delivery over the time interval (τ1, τ2] at time 0 tτ1by F(t, τ1, τ2). Then, following
Benth et al. (2008), F(t, τ1, τ2) can be written as a weighted integral of instantaneous
forward prices f(t, u) with delivery at one fixed time τ1< u τ2, i.e.
F(t, τ1, τ2) = Zτ2
τ1
w(u, τ1, τ2)f(t, u)du, (1.1)
where w(u, τ1, τ2) denotes some weight function. The crucial motivation for measure-
valued process now comes from the fact that there is no trading with the instantaneous
forwards f(t, u) for obvious reasons. Thus, rather than using f(t, u)du in the expression
of the future prices, we can also use a measure.
An additional motivation stems from the empirically well documented fact that energy
spot prices can jump at predictable times, e.g. due to maintenance works in the power grid
or political decisions which currently influence these markets substantially. In the context
of such stochastic discontinuities we refer to the pioneering work Fontana et al. (2020)
in the setup of multiple yield curves. To illustrate why these predictable jumps lead to
measure-valued forward processes, consider the simple example where the spot price S
exhibits a jump at the deterministic time t. In this case we can write Su=e
Su+J{ut}
for some jump-size Jwhich is supposed to be Ft-measurable1and some process e
Sthat we
suppose for simplicity to be continuous. As the instantaneous forward price is according
to (Benth et al.,2008, equation (1.6)) given by
f(t, u) = EQ[Su|Ft] = EQ[e
Su+J{ut}|Ft] = EQ[e
Su|Ft] + EQ[J|Ft]{ut},
for each t < t< T and u[t, T ], this implies that u7→ f(t, u) is discontinuous at
u=t. As forward curve modeling requires to take derivatives with respect to u, the
corresponding SPDE contains a differential operator and we thus have to deal with dis-
tributional derivatives, leading naturally to measure-valued processes that can be treated
1Here, (Ft)0tTdenotes some filtration supporting the spot price process and T > 0 some finite
time horizon.
3
with the analysis presented in this paper. We also refer to Assefa and Harms (2022) where
stochastic discontinuities are also used as one motivation for term structure models based
on cylindrical measure-valued processes.
Due to these reasons one of the main goals of this article is to establish a Heath-Jarrow-
Morton (HJM) approach for measure-valued processes. To this end we pass to the Musiela
parametrization and thus consider time to maturity instead of time of maturity.
More precisely, fix a finite time horizon T, consider a filtered probability space (Ω,F,
(Ft)t[0,T ],P), and a measure-valued process (µt)t[0,T ]supported on the compact interval
E:= [0, T ]. The measure µtwill play the role of f(t, t+x)dx, meaning that if its Lebesgue
density µt(dx)/dx existed, it would correspond to instantaneous forward prices at time t
with time to maturity x. Then future prices at time tgiven by (1.1) become
F(t, τ1, τ2) = Z(τ1t,τ2t]
w(t+x;τ1, τ2)µt(dx), t [0, τ1].
Note that the integration domain does not include the left boundary point τ1tas we
suppose a delivery over the left-open interval (τ1, τ2]. Observe that the this choice permits
to cumulatively add delivery periods, meaning that,
F(t, τ1, τn) =
n1
X
k=1 Z(τkt,τk+1t]
w(t+x;τ1, τn)µt(dx), t [0, τ1]
for each τ1<· · · < τn.
The next step is now to specify a suitable no-arbitrage condition. As long as the future
contracts exist for potentially all delivery periods, it is natural to rely on no-arbitrage
conditions for large financial markets allowing for a continuum of assets. In this respect
the notion of no asymptotic free lunch with vanishing risk (NAFLVR), as introduced in
Cuchiero et al. (2016b), qualifies as an appropriate and economically meaningful condi-
tion. Mathematically, in our setting, this is equivalent to the existence of an equivalent
(local) martingale measure QPunder which the (discounted) price processes of these
contracts are (local) martingales. Modulo some technical conditions, this can then be
translated to the following HJM-drift condition on the measure-valued process (µt)t[0,T ]
(see Theorem 3.1): if there exists an equivalent measure QPsuch that
hφ, µi+Z·
0
hφ0
s, µsids,
is Q-martingale for all appropriate test functions φ, then NAFLVR holds. Here, the
brackets mean hφ, µi=REφ(x)µ(dx). Note that this is a weak formulation to make sense
out of
t(dx) = d
dxµt(dx)dt +dNt(dx)”,
where Ndenotes a measure-valued local martingale. Indeed, this would correspond
to a (non-existing) strong formulation, well-known from function-valued forward curve
modeling, see e.g. (Benth et al.,2021b, Section 2). Note that even though we here focus
on energy markets, a similar framework can be used for term structure models in interest
rate theory. The HJM-drift condition of course has to be adapted to guarantee that the
bond prices are (local) martingales.
4
Clearly the HJM-drift condition restricts the choice of the measure-valued process
since the drift part is completely determined, but we are free to specify the martingale
part as long as we do not leave the state space of (non-negative) measures. To establish
existence of measure-valued diffusion processes satisfying the drift condition, we rely on
the martingale problem formulation of Ethier and Kurtz (2005) in locally compact and
separable spaces which applies to our setting of measures on a compact set equipped with
the weak--topology. Based on the positive maximum principle we then give sufficient
conditions for the existence of such measure-valued diffusions (see Theorem 4.3). Addi-
tionally to these requirements we look for tractable specifications coming from the class
of affine and polynomial processes as introduced in Cuchiero et al. (2021), where we can
precisely specify the diffusion part due to sufficient and (partly) necessary conditions on
its form. This setup then allows for tractable pricing procedures via the moment formula
well-known from polynomial processes (see e.g. Cuchiero et al. (2012), Filipovi´c and Lars-
son (2016)) and Fourier approaches. This holds in particular true for the affine class as we
obtain explicit solutions for the Riccati PDEs. These pricing methods can then of course
be used for calibration purposes. To this end we parameterize the function valued charac-
teristics of polynomial models as neural networks to get neural measure-valued processes,
an analog to neural SDEs and SPDEs. In Section 5.4 we exemplify such a calibration
for the particular case of an affine measure-valued model which we calibrate to market
call options written on certain future contracts whose prices are obtained from the EEX
German Power data (see https://www.eex.com/en/market-data/power/options).
Apart from modeling energy futures via the described HJM approach, measure-valued
processes also qualify for modeling quantities related to renewable energy production. In
Section 6we exemplify this briefly by considering wind energy markets.
Finally, let us remark that the setting of cylindrical measures considered in Assefa and
Harms (2022) constitutes an interesting alternative approach to term structure modeling.
In contrast to our framework there cylindrical measure-valued processes arising from
SPDEs driven by some cylindrical Brownian motion are used to model the forwards.
Note that being merely a cylindrical measure-valued process is a weaker requirement
than being a measure-valued process. This weakening in turn allows to define SPDEs via
cylindrical integrals, which would to be possible in the current measure-valued Markov
process setup. One advantage of our approach is that we do not need Lipschitz conditions
on the volatility function (imposed in Assefa and Harms (2022)), which is essential in
order to accommodate affine and polynomial specifications. Another difference is that
we consider concrete model specifications, in particular conditions that guarantee to stay
in the state-space of non-negative measures, while the focus in Assefa and Harms (2022)
lies rather on the abstract framework of cylindrical stochastic integration. Moreover, in
the application to energy contracts, in Assefa and Harms (2022) the time of maturity
parametrization (in contrast to the Musiela parametrization) is considered, which does not
require to specify a HJM drift condition. Note that we could do this as well by specifying
a measure-valued (local) martingale. The disadvantage of this approach is that – in order
to keep the interpretation as forward process – the support of this measure-valued process
should be [t, T ] and thus depends on the running time which is difficult to achieve. We
therefore opted for the HJM approach with time to maturity where the support of the
measure-valued process is constant over time.
The remainder of the paper is organized as follows: in Section 1.1 we introduce
5
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Measure-valuedprocessesforenergymarketsChristaCuchiero*LucaDiPersio„FrancescoGuida…SaraSvaluto-Ferro§AbstractWeintroduceaframeworkthatallowstoemploy(non-negative)measure-valuedprocessesforenergymarketmodeling,inparticularforelectricityandgasfutures.Interpretingtheprocess'spatialstructureastimetomatu...

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